WO2024043608A1 - Plated steel sheet for hot press forming having excellent impact resistance, hot press formed part, and manufacturing methods thereof - Google Patents

Plated steel sheet for hot press forming having excellent impact resistance, hot press formed part, and manufacturing methods thereof Download PDF

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WO2024043608A1
WO2024043608A1 PCT/KR2023/012157 KR2023012157W WO2024043608A1 WO 2024043608 A1 WO2024043608 A1 WO 2024043608A1 KR 2023012157 W KR2023012157 W KR 2023012157W WO 2024043608 A1 WO2024043608 A1 WO 2024043608A1
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steel sheet
less
content
present
carbon
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PCT/KR2023/012157
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French (fr)
Korean (ko)
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김상헌
오진근
김성우
이세웅
이상철
소슬기
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주식회사 포스코
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
    • B21C47/02—Winding-up or coiling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Definitions

  • the present invention relates to galvanized steel sheets for hot forming, hot forming members, and methods for manufacturing the same. More specifically, it relates to galvanized steel sheets for hot forming with excellent collision resistance, hot forming members, and methods for manufacturing them.
  • Hot forming members have recently been widely applied to structural members of automobiles for the purpose of improving fuel efficiency and protecting passengers by reducing the weight of automobiles.
  • they can be used in bumpers, doors, or pillar reinforcements that require ultra-high strength or energy absorption.
  • Patent Document 1 was proposed as a representative technology regarding this hot forming technology.
  • ultra-high strength with high tensile strength can be secured by heating Al-Si plated steel sheet to over 850°C and then forming the structure of the member into martensite by hot forming with a press and rapid cooling.
  • complex shapes can be easily formed because they are formed at high temperatures, and a weight reduction effect due to high strength can be expected through an increase in strength due to rapid cooling in the mold.
  • Patent Document 1 U.S. Patent Publication No. 6296805 (published on October 2, 2001)
  • it is intended to provide a galvanized steel sheet for hot forming with excellent collision resistance, a hot forming member, and a method for manufacturing the same.
  • One aspect of the present invention includes a base steel sheet containing, in weight percent, carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1%, and a plating layer formed on the surface of the base steel sheet,
  • the base steel plate includes an antimony (Sb) concentrated layer therein,
  • the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) It is possible to provide a plated steel sheet in which the carbon (C) content is 10 to 70% of the nominal carbon content (C 0 ) of the base steel sheet.
  • the decarburization rate ( ⁇ ) of carbon (C) in a region from the interface between the base steel sheet and the plating layer to a depth of 30 ⁇ m in the thickness direction may be 14 to 35%.
  • the plated steel sheet may have a point where the carbon (C) content is 50% of the nominal carbon content (C 0 ) at a depth of more than 1.5 ⁇ m and less than 6 ⁇ m in the thickness direction from the interface of the base steel sheet and the plating layer.
  • the plated steel sheet may have a point where the carbon (C) content is 80% of the nominal carbon content (C 0 ) at a depth of more than 6 ⁇ m and less than 15 ⁇ m in the thickness direction from the interface between the base steel sheet and the plating layer.
  • the plated steel sheet has an R value defined in equation 1 below of 1.2 or more
  • the B value defined in Equation 2 below may be 0.008 or more.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is ⁇ m.
  • the area from the interface between the base steel plate and the plating layer to a depth of 10 ⁇ m in the thickness direction may have a microstructure containing ferrite as the main phase and more than 1 area% of pearlite.
  • the base steel sheet contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
  • the plating layer may be made of aluminum or aluminum alloy.
  • Another aspect of the present invention includes base iron containing 0.06 to 0.5% of carbon (C) and 0.01 to 0.1% of antimony (Sb), in weight percent, and a plating layer formed on the surface of the base iron,
  • the base iron includes an antimony (Sb) enriched layer within it,
  • the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) It is possible to provide a member in which the carbon (C) content is 80% or less of the nominal carbon content (C 0 ) of the base iron.
  • the member may have a carbon (C) content of 15 to 80% of the nominal carbon content (C 0 ) of the base iron at a depth where the antimony (Sb) content reaches its maximum value (Sb max ).
  • the member has an R value defined in equation 1 below of 1.5 or more,
  • the B value defined in Equation 2 below may be 0.01 or more.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface where the plating layer and the base iron contact. It represents the straight line distance between one points, and the unit is ⁇ m.
  • a region with a depth of 45 to 100 ⁇ m in the thickness direction from the interface between the base iron and the plating layer may have a softening rate ( ⁇ ) of 2 to 7%.
  • the area from the interface between the base iron and the plating layer to a depth of 50 ⁇ m in the thickness direction may include less than 5 area% of ferrite as a microstructure.
  • the area from the interface of the base iron and the plating layer to a depth of 50 ⁇ m in the thickness direction may have martensite as the main phase as a microstructure, and may include less than 5 area% of ferrite and the remaining upper and lower bainite.
  • the base iron contains carbon (C): 0.06 to 0.5%, antimony (Sb): 0.01 to 0.1%, silicon (Si): 0.001 to 2%, manganese (Mn): 0.1 to 4%, and molybdenum (Mo): 1. % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
  • the plating layer may be made of aluminum or aluminum alloy.
  • the product of the tensile strength and bending angle of the member may be 80,000 MPa ⁇ ° or more.
  • the member may have a diffusible hydrogen content of 0.2ppm or less.
  • One aspect of the present invention includes preparing a cold-rolled steel sheet containing, in weight percent, carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1%;
  • the product of the annealing time and the absolute humidity is 10,000 to 80,000 s ⁇ g/m 3 .
  • the average temperature increase rate from room temperature to 500°C is 2.7 to 10.0°C/s
  • the average temperature increase rate in the 500 to 700°C section is 0.5 to 2.5°C/s
  • the annealing time is 100 to 200 seconds, and the absolute humidity may be 100 to 400 g/m 3 .
  • the steel slab contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
  • plating may be done with aluminum or aluminum alloy.
  • Another aspect of the present invention includes manufacturing one plated steel sheet as a blank
  • a method of manufacturing a member may be provided including the steps of forming and cooling the heated blank.
  • cooling can be performed at a cooling rate of 20°C/s or more.
  • a galvanized steel sheet for hot forming with excellent collision resistance, a hot forming member, and a method for manufacturing the same can be provided.
  • a plated steel sheet for hot forming with excellent fatigue resistance and collision resistance, a hot forming member, and a method for manufacturing the same.
  • Figure 1 schematically shows an exemplary change in Sb content of the present invention to represent a Sb enriched layer.
  • Figure 2 schematically shows the Sb and C content profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
  • Figure 3 schematically shows the decarburization rate ( ⁇ ) profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
  • Figure 4 schematically shows the Sb enriched layer profile of a plated steel sheet according to an embodiment of the present invention.
  • Figure 5 schematically shows the Sb and C content profile from the interface to the thickness direction in a member according to an embodiment of the present invention.
  • Figure 6 schematically shows the hardness softening rate ( ⁇ ) profile from the interface to the thickness direction in a member according to an embodiment of the present invention.
  • Figure 7 shows the C content profile in a plated steel sheet according to an embodiment of the present invention.
  • Figure 8 is a photograph of the microstructure of a plated steel sheet according to an embodiment of the present invention observed with a scanning electron microscope (SEM).
  • Figure 9 is a photograph observing the microstructure of a member according to an embodiment of the present invention.
  • One aspect of the present invention is directed to a plated steel sheet including a base steel sheet and a plating layer formed on the surface of the base steel sheet. Collision resistance and fatigue resistance can be greatly affected by the degree of decarburization of the steel sheet, and the effects of the present invention can be advantageously obtained when the decarburization rate is appropriately controlled using the thickened layer formed in the base steel sheet. That is, the plated steel sheet according to one aspect of the present invention includes a base steel plate and a plating layer formed on the surface of the base steel sheet (which may mean the interface between the base steel sheet and the plating layer), and the base steel sheet contains antimony (Sb) formed within the base steel sheet. ) may include a thickening layer.
  • the decarburization rate according to the depth in the thickness direction of the steel sheet can be appropriately controlled according to the formation of the Sb enriched layer.
  • Figure 1 schematically shows an exemplary change in Sb content of the present invention to express the Sb enriched layer.
  • the It represents the distance
  • the y-axis represents the Sb content measured using a glow discharge spectrometer (GDS).
  • GDS glow discharge spectrometer
  • the Sb enriched layer 2 may have an Sb content of 1.05 times or more than the nominal Sb content (Sb 0 ) of the base steel plate, and within the Sb enriched layer 2, there is a point (200) where the Sb content is at its maximum value. Sb max ) may exist.
  • the Sb enriched layer 2 has a Sb content increasing section 21 in which the Sb content increases to the point (200; Sb max ) where the Sb content is the maximum as it progresses in the x-axis direction, and a point where the Sb content is the maximum. It may include a Sb content lowering section 22 in which the Sb content decreases while proceeding from (200; Sb max ) in the x-axis direction.
  • the last contact point (11) can be used as the starting point of the Sb content increase section (21).
  • the Sb average content line 10 of the plating layer 1 is a point 15 ⁇ m away from the point (200, Sb max ) where the Sb content is the maximum in the Sb enriched layer 2 toward the plating layer 1. It may mean an extension line that extends horizontally the average Sb content of the section from point A to point B, which is 20 ⁇ m away.
  • the Sb average content line 30 of the base steel plate and the Sb content line The first contact point (31) in the x-axis (+) direction of (100) is regarded as the end point of the Sb enriched layer (2).
  • the average Sb content line 30 of the base steel sheet 3 excluding the Sb enriched layer is from the point 200 (Sb max ) where the Sb content is the maximum in the Sb enriched layer 2.
  • Sb max the Sb content is the maximum in the Sb enriched layer 2.
  • It can mean an extension line that extends the average Sb content of the section horizontally from point C, which is 15 ⁇ m away, to point D, which is 20 ⁇ m away.
  • the Sb enriched layer may be formed directly below the interface between the base steel sheet and the plating layer.
  • the Al content profile is analyzed from the surface of the plated steel sheet in the depth (thickness) direction using a glow discharge spectrometer (GDS), it can be defined as the point where the Al content is 15%.
  • the thickness of the concentrated layer may be 1 to 30 ⁇ m.
  • antimony (Sb) when analyzing the content of antimony (Sb) in the thickness direction of the base steel sheet using a glow discharge spectrometer (GDS), antimony (Sb) is present in the antimony (Sb) enriched layer.
  • the carbon (C) content at the depth where the content represents the maximum value (Sb max ) may be 10 to 70% of the nominal carbon content (C 0 ) of the base steel plate.
  • the nominal carbon content (C 0 ) may mean the average carbon content in the thickness 1/4 to 3/4 region based on the cross-section of the base steel plate, and specifically, glow discharge spectroscopy
  • the average carbon content can be obtained by analyzing the carbon profile at a distance of 50 ⁇ m or more from any point in the area of 1/4 to 3/4 of the thickness of the base steel plate using an analyzer (GDS).
  • Figure 2 schematically shows the profile of Sb and C contents from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
  • the x-axis of FIG. 2 represents the depth ( ⁇ m) from the interface between the base steel plate and the plating layer, and the y-axis may represent the element content (wt%).
  • 70% of the nominal carbon content (C 0 ) is 0.154%.
  • the nominal carbon content (C 0 ) is 0.22%, and as described above, a certain thickness (depth) is analyzed using a glow discharge spectrometer (GDS) in the 1/4 to 3/4 thickness area of the base steel plate. can be obtained. At this time, it can be confirmed that at the depth where the Sb content shows the maximum value (Sb max ), the carbon content is 70% or less of the nominal carbon content (C 0 ).
  • GDS glow discharge spectrometer
  • the ratio of the carbon content to the nominal carbon content (C 0 ) is 10 to 70. It is controlled by %, and the carbon content at this time affects the surface hardness softening rate and bendability of the member.
  • the carbon content in the Sb enriched layer exceeds 70% of the nominal carbon content (C 0 ) at the depth where the Sb content reaches its maximum value (Sb max )
  • the hardness of the surface layer may increase and the bendability may deteriorate.
  • the carbon content is less than 10% of the nominal carbon content (C 0 )
  • the hardness may be excessively lowered and the fatigue resistance may be inferior.
  • the ratio of the carbon content to the nominal carbon content (C 0 ) may be 10.0 to 70.0%.
  • the decarburization rate ( ⁇ ) of carbon (C) in the area from the interface between the base steel sheet and the plating layer to a depth of 30 ⁇ m in the thickness direction may be 14 to 35%.
  • Figure 3 schematically shows the decarburization rate ( ⁇ ) profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
  • the decarburization rate ( ⁇ ) can be obtained from the results of measuring the carbon of the plated steel sheet using a glow discharge spectrometer (GDS).
  • GDS glow discharge spectrometer
  • the y-axis represents the ratio (%) of the carbon content at the corresponding position to the nominal carbon content (C 0 )
  • the x-axis represents the distance ( ⁇ m) in the thickness (depth) direction from the interface of the base steel plate and the plating layer.
  • a rectangle can be drawn with a horizontal side corresponding to a length of 0 to 30 ⁇ m in depth from the interface to the base steel sheet thickness direction in the x-axis direction, and a vertical side corresponding to a length of 0 to 100% in the y-axis direction.
  • the carbon profile curve represents the ratio of the carbon content at that depth to the nominal carbon content (C 0 ) in the square, resulting in the ratio (%) of the area above the carbon profile curve within the square to the total area of the square.
  • the decarburization rate ( ⁇ ) of the present invention has the distance ( ⁇ m) in the thickness (depth) direction from the interface between the base steel sheet and the plating layer as the abscissa, and is calculated as the ratio of the carbon content at that position to the nominal carbon content (C 0 ).
  • ratio (%) as the vertical axis, it means the ratio (%) of the area above the carbon profile curve to the total area of the rectangle.
  • the carbon (C) decarburization rate ( ⁇ ) in the area from the interface to a depth of 30 ⁇ m in the thickness direction is less than 14%, the carbon concentration of the base steel plate excessively increases the hardness in the member after hot forming, so the bendability improvement effect is significantly reduced. It can be.
  • the decarburization rate exceeds 35%, the amount of carbon in the surface layer of the base steel sheet decreases, and the martensite hardness in the member significantly decreases, which may cause the member to have inferior fatigue resistance properties.
  • the decarburization rate ( ⁇ ) of carbon (C) in the area from the interface between the base steel sheet and the plating layer to a depth of 30.0 ⁇ m in the thickness direction may be 14.0 to 35.0%.
  • the carbon (C) content is 50% of the nominal carbon content (C 0 ) at a depth of more than 1.5 ⁇ m and less than 6 ⁇ m in the thickness direction from the interface between the base steel sheet and the plating layer. This can exist.
  • Controlling the ratio of carbon (C) content according to the nominal carbon content (C 0 ) at a depth of more than 1.5 ⁇ m to less than 6 ⁇ m in the thickness direction from the interface is to simultaneously secure fatigue resistance and crash resistance.
  • the carbon (C) content is 50% of the nominal carbon content (C 0 )
  • the 50% point is 6 ⁇ m or more. If present at depth, fatigue resistance may be deteriorated due to excessive decarburization.
  • the 50% point exists at a depth of 1.5 ⁇ m or less, there may be difficulty in securing the desired bendability due to insufficient decarburization.
  • the carbon (C) content at a depth of more than 1.50 ⁇ m and less than 6.0 ⁇ m in the thickness direction from the interface between the base steel sheet and the plating layer is 50.0% of the nominal carbon content (C 0 ). Branches may exist.
  • the carbon (C) content is 80% of the nominal carbon content (C 0 ) at a depth of more than 6 ⁇ m and less than 15 ⁇ m in the thickness direction from the interface between the base steel plate and the plating layer.
  • the ratio of carbon (C) content according to the nominal carbon content (C 0 ) is 80% at a depth of more than 6 ⁇ m to less than 15 ⁇ m in the thickness direction from the interface, appropriate bendability is secured and excessive fatigue resistance deterioration is suppressed. can be advantageous.
  • the 80% point is at a depth of 15 ⁇ m or more, the fatigue resistance may be reduced due to excessive decarburization, and if the 80% point is at a depth of 6 ⁇ m or less, the desired bendability may be lost due to insufficient decarburization. may be difficult to secure.
  • the carbon (C) content is 80.0% of the nominal carbon content (C 0 ) at a depth of more than 6.0 ⁇ m and less than 15.0 ⁇ m in the thickness direction from the interface between the base steel plate and the plating layer.
  • the R value defined in equation 1 below may be 1.2 or more, and the B value defined in equation 2 below may be 0.008 or more.
  • the R value defined in equation 1 below may be 1.20 or more, and the B value defined in equation 2 below may be 0.0080 or more.
  • the decarburization rate can be appropriately controlled by controlling the Sb content according to the thickness direction depth, and the present invention proposes the following relational equations 1 and 2.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is ⁇ m.
  • Figure 4 schematically shows the Sb enriched layer profile of a coated steel sheet according to an embodiment of the present invention.
  • the area corresponding to the B value of relational equation 2 is shown as a colored part, and the above-mentioned area represents the degree of Sb enrichment according to ⁇ t, which represents the distance between the point where Sb coat was measured and the point where Sb max was measured. You can.
  • the R value defined in Equation 1 may be limited to 1.5 or more.
  • the B value defined in Equation 2 above may be limited to 0.02 or more.
  • the upper limit of the R value can be limited to 6.5.
  • the upper limit of the B value may be limited to 0.15.
  • the R value defined in Equation 1 may be limited to 1.50 or more.
  • the B value defined in Equation 2 above may be limited to 0.020 or more.
  • the upper limit of the R value can be limited to 6.50.
  • the upper limit of the B value may be limited to 0.150.
  • the R value and B value of the plated steel sheet can be controlled to an appropriate range, thereby effectively suppressing the intrusion of hydrogen.
  • the plated steel sheet may have a microstructure containing ferrite as the main phase and more than 1 area% of pearlite in an area from the interface between the base steel sheet and the plating layer to a depth of 10 ⁇ m in the thickness direction.
  • a phase accounting for more than 50 area% of the total microstructure fraction can be regarded as the main phase.
  • the fatigue resistance characteristics of the member may be inferior.
  • pearlite In the area up to 10 ⁇ m in the thickness (depth) direction from the interface between the base steel sheet and the plating layer, pearlite provides carbon to the structure directly under the plating layer during heat treatment for hot forming, thereby preventing the hardness of the surface layer from deteriorating. It can play a role. Therefore, in the present invention, pearlite may be included in an amount of 1 area% or more.
  • the hardness of the surface layer may decrease excessively after hot forming, which may increase the hardness softening rate and cause the problem of inferior fatigue resistance of the member.
  • the area from the interface between the base steel sheet and the plating layer to a depth of 10.0 ⁇ m in the thickness direction may have ferrite as the main phase and contain pearlite in an amount of 1.0 area% or more.
  • the base steel plate according to one embodiment of the present invention may include carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1% by weight.
  • the base steel plate according to one embodiment of the present invention may include carbon (C): 0.060 to 0.50% and antimony (Sb): 0.010 to 0.10% by weight.
  • the % indicating the content of each element is based on weight.
  • Carbon (C) is an element that improves the strength of hot-formed members and improves hardenability. It is an essential element to control strength and must be added appropriately. If the carbon (C) content is less than 0.06%, hardenability is low, so when the cooling rate is reduced, sufficient martensite cannot be secured, and it may be difficult to secure the desired strength due to the formation of ferrite. In one embodiment of the present invention, the carbon (C) content may be 0.1% or more. On the other hand, if the content exceeds 0.5%, the strength may increase excessively, cause brittleness, and weldability may be poor. In one embodiment of the present invention, the upper limit of the carbon (C) content may be 0.45%.
  • carbon (C) may contain 0.060 to 0.50%.
  • carbon (C) may be 0.10% or more.
  • the upper limit may be 0.450%.
  • Antimony (Sb) can play a role in controlling the amount of carbon escaping when internal oxidation annealing is applied by concentrating within the base steel sheet and preventing excessive decline in hardness in the member. If the antimony (Sb) content is less than 0.01%, a sufficient thickening layer is not formed at the interface between the plating layer and the base steel plate, resulting in excessive decarburization, which may result in an excessive decrease in surface hardness and poor fatigue resistance properties. According to one embodiment of the present invention, the lower limit of antimony (sb) may be 0.02%. On the other hand, if the content exceeds 0.1%, excessive antimony (Sb) is precipitated at the grain boundaries, which may cause grain boundary destruction when stress occurs, thereby deteriorating the material. According to one embodiment, the upper limit of the antimony (Sb) content may be 0.08%.
  • antimony (Sb) may contain 0.010 to 0.10%.
  • antimony (Sb) may be 0.020% or more.
  • the upper limit may be 0.080%.
  • the type and content are not particularly limited as long as it is an element that can be added normally.
  • elements that can be added to the base steel sheet according to one embodiment of the present invention include silicon (Si), manganese (Mn), molybdenum (Mo), phosphorus (P), and sulfur (S). , aluminum (Al), chromium (Cr), nitrogen (N), titanium (Ti), boron (B), copper (Cu), nickel (Ni), vanadium (V), calcium (Ca), niobium (Nb).
  • tin (Sn), tungsten (W), magnesium (Mg), cobalt (Co), arsenic (As), zirconium (Zr), bismuth (Bi), and rare earth elements (REM), one or more of these More may be included.
  • the base steel plate contains, in weight percent, silicon (Si): 0.001 to 2%, manganese (Mn): 0.1 to 4%, molybdenum (Mo): 1.0% or less, phosphorus (P): 0.05% or less, Sulfur (S): 0.02% or less, Aluminum (Al): 0.001 to 1%, Chromium (Cr): 1.00% or less, Nitrogen (N): 0.02% or less, Titanium (Ti): 0.1% or less, Boron (B): 0.01% or less, may include remaining iron (Fe) and impurities.
  • Silicon (Si) can be added as a deoxidizer in steelmaking.
  • Si can be added as a solid solution strengthening element and an element that suppresses carbide formation, it is not only effective in uniforming the internal structure, but also contributes to increasing the strength of hot-formed members and is added as an effective element in material uniformity.
  • the content is less than 0.001%, the above effect cannot be expected, and if the silicon (Si) content exceeds 2%, the plating property may be greatly reduced due to excessive Si oxide generated on the surface of the steel sheet during annealing.
  • the lower limit of the silicon (Si) content may be 0.005%, and in some cases, 0.01%.
  • the upper limit of the silicon (Si) content may be 0.7%, and in some cases, 0.65%.
  • silicon (Si) may contain 0.001 to 2.0%.
  • silicon (Si) may be 0.0050% or more.
  • the upper limit may be ⁇ 0.70%.
  • silicon (Si) may be 0.010% or more.
  • the upper limit may be 0.650%.
  • Manganese (Mn) needs to be added to not only secure the desired strength due to the solid solution strengthening effect, but also to suppress ferrite formation during hot forming by improving hardenability. If the manganese (Mn) content is less than 0.1%, it is difficult to obtain sufficient hardenability effect, and other expensive alloy elements are excessively required for insufficient hardenability, which may lead to a significant increase in manufacturing cost. According to one embodiment of the present invention, it may contain 0.5% or more of manganese (Mn), and in another embodiment, it may contain 0.8% or more. However, if the content exceeds 4%, the band-like structure arranged in the microstructure rolling direction becomes deeper, causing non-uniformity of the internal structure, which may deteriorate the collision resistance. In one embodiment of the present invention, the upper limit of the manganese (Mn) content may be 3.5%.
  • manganese (Mn) may contain 0.010 to 4.0%.
  • manganese (Mn) may contain 0.050 to 4.0%.
  • manganese (Mn) may contain 0.080 to 4.0%.
  • manganese (Mn) may contain 0.050 to 3.50%.
  • manganese (Mn) may contain 0.080 to 3.50%.
  • Molybdenum (Mo) may be included as an element that can improve bendability by strengthening crystal grains. However, if the content exceeds 1.0%, the manufacturing cost may increase significantly. According to one embodiment of the present invention, the upper limit of molybdenum (Mo) content may be 0.5%, and in some cases, may be 0.45%.
  • molybdenum (Mo) may contain 1.0% or less.
  • the upper limit of molybdenum (Mo) content may be 0.50%, and in some cases, may be 0.450%.
  • Phosphorus (P) exists as an impurity in steel, and if its content exceeds 0.05%, the weldability of hot-formed members and material properties may be deteriorated due to high-temperature grain boundary segregation.
  • the upper limit may be limited to 0.015%.
  • the lower limit can be limited to 0.001%.
  • phosphorus (P) may contain 0.050% or less.
  • the upper limit may be limited to 0.0150%.
  • the lower limit can be limited to 0.0010%.
  • S is an impurity in steel and is an element that impairs the ductility, impact properties, and weldability of the member, so the upper limit can be limited to 0.02%. In one embodiment of the present invention, controlling the content to a very small amount may significantly increase manufacturing costs, so the lower limit may be limited to 0.0001%.
  • sulfur (S) may contain 0.020% or less. According to one embodiment, the lower limit may be limited to 0.00010%.
  • Aluminum (Al), along with Si, is an element that increases the cleanliness of steel by acting as a deoxidizer in steelmaking. If the aluminum (Al) content is less than 0.001%, it may be difficult to achieve the above effect. According to one embodiment of the present invention, the lower limit of aluminum (Al) may be 0.01%, and in some cases, 0.02%. On the other hand, if the content exceeds 1%, high-temperature ductility is reduced due to excessive AlN precipitates formed during the casting process, and slab cracks may occur, which may cause manufacturing problems. In one embodiment, the upper limit may be limited to 0.1%, and in some cases, it may be limited to 0.09%.
  • aluminum (Al) may contain 0.0010 to 1.0%.
  • aluminum (Al) may contain 0.010 to 1.0%.
  • aluminum (Al) may contain 0.020 to 1.0%.
  • aluminum (Al) may contain 0.010 to 0.10%.
  • aluminum (Al) may contain 0.010 to 0.090%.
  • aluminum (Al) may contain 0.020 to 0.10%.
  • aluminum (Al) may contain 0.020 to 0.090%.
  • the upper limit may be 0.8%.
  • the lower limit may be limited to 0.01%, and in some cases, may be limited to 0.05%.
  • chromium (Cr) may contain 1.0% or less.
  • chromium (Cr) may contain 0.80% or less.
  • chromium (Cr) may contain 0.01 to 1.0%.
  • chromium (Cr) may contain 0.01 to 0.8%.
  • chromium (Cr) may contain 0.05 to 1.0%.
  • chromium (Cr) may contain 0.05 to 0.8%.
  • Nitrogen (N) may be included as an impurity in steel. If the nitrogen (N) content exceeds 0.02%, there is a risk that AlN will be formed together with the added Al, resulting in slab cracks. On the other hand, since excessive manufacturing costs may be incurred to control the content to a very small amount, the lower limit of nitrogen (N) may be limited to 0.001% according to one embodiment of the present invention.
  • nitrogen (N) may contain 0.020% or less.
  • nitrogen (N) may contain 0.0010 to 0.02%.
  • nitrogen (N) may contain 0.0010 to 0.020%.
  • Titanium (Ti) combines with N remaining as an impurity in steel to create TiN, thereby protecting B from becoming a compound to ensure hardenability.
  • precipitation strengthening and grain refinement effects can be expected through the formation of TiC precipitates.
  • the content exceeds 0.1%, a large amount of coarse TiN is formed, which may deteriorate the steel material.
  • the upper limit of the content may be limited to 0.09%.
  • titanium (Ti) may contain 0.10% or less.
  • titanium (Ti) may contain 0.090% or less.
  • Boron (B) is an element that can effectively improve hardenability, and is an element that is segregated at the grain boundaries of old austenite and can suppress the embrittlement of hot-formed members due to grain boundary segregation of impurities P or S.
  • the content exceeds 0.01%, brittleness may occur during hot rolling due to the formation of Fe 23 CB 6 complex compounds.
  • the upper limit of the boron (B) content may be limited to 0.008%.
  • boron (B) may contain 0.010% or less.
  • boron (B) may contain 0.0080% or less.
  • Zr zirconium
  • Bi bismuth
  • REM rare earth elements
  • Zr zirconium
  • Bi bismuth
  • REM rare earth element
  • the base steel sheet of the present invention may contain remaining iron (Fe) and inevitable impurities in addition to the composition described above. Since unavoidable impurities may be unintentionally introduced during the normal manufacturing process, they cannot be excluded. Since these impurities are known to anyone skilled in the field of steel manufacturing, all of them are not specifically mentioned in this specification.
  • the plating layer of the plated steel sheet may be an aluminum or aluminum-based alloy plating layer.
  • the plating layer may be an alloyed aluminum-based plating layer.
  • the plating layer may include Si, Mg, and Fe in addition to Al, and in some cases, Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, and Sr. , Zn, etc. may be included.
  • the thickness of the plating layer is not particularly limited, and may have a plating layer thickness within a general range.
  • the plating layer contains one or two or more types selected from Si: 5-11%, Fe: 5% or less, and Mg: 5% or less, in weight percent, and the balance is Al and other impurities. may include. If necessary, the above-mentioned composition may further include elements such as Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, and Zn in a total amount of 30% or less.
  • the plating layer contains one or two or more types selected from Si: 5.0 to 11.0%, Fe: 5.0% or less, and Mg: 5.0% or less, in weight percent, and the balance is Al and other impurities. may include. If necessary, the above-mentioned composition may further include elements such as Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, and Zn in a total amount of 30.0% or less.
  • a member according to one embodiment of the present invention may include base iron and a plating layer formed on the surface of the base iron.
  • the base iron according to one aspect of the present invention may have the same alloy composition as the base steel sheet of the plated steel sheet proposed in the present invention.
  • the plating layer may be formed on at least one surface of the base iron.
  • the plating layer of the member may have an alloy composition in which the plating layer of the above-described plated steel sheet and components including Fe of the base steel sheet are diffused.
  • a member according to one embodiment of the present invention may include an antimony (Sb) enriched layer formed in the base iron.
  • Sb antimony
  • the Sb enriched layer of the present invention can be distinguished by analyzing the change in Sb content in the thickness direction of the base iron from any point of the plating layer using a glow discharge spectrometer (GDS).
  • GDS glow discharge spectrometer
  • the method for classifying the Sb enriched layer in the plated steel sheet proposed in the present invention can be applied in the same way.
  • an antimony (Sb) enriched layer may be formed directly below the interface where the base iron and the plating layer are in contact.
  • the interface between the base iron and the plating layer may mean a point where the Al content is 15%.
  • the antimony (Sb) content in the antimony (Sb) enriched layer is maximum.
  • the carbon (C) content at the depth representing the value (Sb max ) may be 80% or less of the nominal carbon content (C 0 ) of the base iron.
  • the antimony (Sb) content in the antimony (Sb) enriched layer is maximum.
  • the carbon (C) content at the depth representing the value (Sb max ) may be 80.0% or less of the nominal carbon content (C 0 ) of the base iron.
  • the carbon content at the depth where the Sb content in the Sb enriched layer reaches its maximum value (Sb max ) affects the hardness of the surface layer structure and bendability.
  • the carbon content at the depth where the Sb content reaches the maximum value (Sb max ) in the Sb enriched layer exceeds 80% of the nominal carbon content (C 0 )
  • the hardness of the surface layer may increase and the bendability may deteriorate.
  • the carbon content in the Sb enriched layer at the depth where the Sb content reaches its maximum value (Sb max ) is excessively low, there may be difficulty in securing fatigue resistance characteristics due to insufficient hardness of the surface layer. Therefore, in one embodiment of the present invention, the lower limit can be limited to 15%. In one embodiment of the present invention, the lower limit may be limited to 15.0%.
  • Figure 5 schematically shows the profile of Sb and C contents from the interface to the thickness direction in a member according to an embodiment of the present invention.
  • the x-axis of FIG. 5 may represent the depth ( ⁇ m) from the interface between the base iron and the plating layer, and the y-axis may represent the element content (wt%).
  • 80% of the nominal carbon content (C 0 ) is 0.176%.
  • the nominal carbon content (C 0 ) is 0.22%, and as previously explained, a certain thickness (depth) is analyzed using a glow discharge spectrometer (GDS) in the 1/4 to 3/4 thickness region of the base iron. can be obtained. At this time, it can be confirmed that at the depth where the Sb content reaches its maximum value, the carbon content is 80% or less of the nominal carbon content (C 0 ).
  • GDS glow discharge spectrometer
  • the member according to one embodiment of the present invention may have an R value defined in equation 1 below of 1.5 or more, and a B value defined in equation 2 below may be 0.01 or more.
  • the member according to one embodiment of the present invention may have an R value defined in equation 1 below of 1.50 or more, and a B value defined in equation 2 below may be 0.010 or more.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface between the plating layer and the base iron. It represents the straight line distance between one points, and the unit is ⁇ m.
  • the degree of Sb enrichment in the Sb enrichment layer may become more severe.
  • the Sb enriched layer effectively protects against infiltrating diffusible hydrogen, and since diffusible hydrogen promotes the occurrence of grain boundary cracks when stress occurs, bendability can be increased by reducing this. You can. That is, if the above relational equation is not satisfied, specifically, if the R value defined in relational equation 1 is less than 1.5 or the B value defined in relational equation 2 is less than 0.01, the diffusive hydrogen penetrating during hot forming is not sufficiently protected. There is a risk that crash resistance will be deteriorated.
  • the R value defined in Equation 1 may be 1.7 or more.
  • the B value defined in Equation 2 may be 0.014 or more.
  • the upper limit of the R value may be limited to 6.4.
  • the upper limit of the B value may be limited to 0.5.
  • the R value defined in Equation 1 may be 1.70 or more. Additionally, in one embodiment of the present invention, the B value defined in Equation 2 may be 0.0140 or more. In one embodiment of the present invention, the upper limit of the R value may be limited to 6.40. Additionally, in one embodiment of the present invention, the upper limit of the B value may be limited to 0.50.
  • the member according to one aspect of the present invention may have a softening rate ( ⁇ ) of 2 to 7% in a region with a depth of 45 to 100 ⁇ m in the thickness direction from the interface between the base iron and the plating layer.
  • An area with a depth of 45 to 100 ⁇ m in the thickness direction from the interface between the base iron and the plating layer affects the hardness of the surface layer of the member and may affect bendability.
  • the softening rate in the area from 45 to 100 ⁇ m in the thickness direction is less than 2%, the hardness of the surface layer may become too high, which may reduce the effect of improving bendability. On the other hand, if the softening rate exceeds 7%, the hardness of the surface layer becomes too low, which may cause the problem of deterioration in fatigue resistance properties.
  • the hardness softening rate can be measured as shown in Figure 6.
  • Figure 6 schematically shows the hardness softening rate ( ⁇ ) profile at a depth of 45 to 100 ⁇ m in the thickness direction from the interface in a member according to an embodiment of the present invention.
  • Vickers Hardness is measured and hardness is measured by applying a weight of 1 kg.
  • the hardness inside the base iron is taken as the standard hardness (H O ), and at this time, the standard hardness (H O ) can be measured at 1/5 of the thickness of the base iron.
  • the y-axis represents the ratio (%) of the hardness value (H) at the corresponding position to the reference hardness value (H 0 ), and the x-axis represents the distance ( ⁇ m) from the interface in the thickness direction.
  • a rectangle was drawn with 0 to 100% as the y-axis range and a depth of 45 to 100 ⁇ m from the interface as the x-axis range.
  • a hardness profile curve representing the ratio of hardness values according to the depth from the interface is shown, and the ratio of the area of the upper area within the rectangle of the hardness profile to the total area of the rectangle is defined as the hardness softening rate ( ⁇ , %). can do.
  • the hardness profile is determined at a depth of 45 to 100 ⁇ m. It was created and used for the hardness softening rate ( ⁇ ).
  • the hardness softening rate ( ⁇ ) of the present invention is the distance ( ⁇ m) in the thickness (depth) direction from the interface between the base steel sheet and the plating layer as the abscissa, and the hardness value at the corresponding position with respect to the reference hardness value (H 0 ).
  • the ratio (%) of (H) as the vertical axis it means the ratio (%) of the area above the hardness profile curve to the total area of the rectangle.
  • the member according to one aspect of the present invention may have a softening rate ( ⁇ ) of 2.0 to 7.0% in a region with a depth of 45.0 to 100.0 ⁇ m in the thickness direction from the interface between the base iron and the plating layer.
  • the member may include less than 5 area% of ferrite as a microstructure in a region from the interface between the base iron and the plating layer to a depth of 50 ⁇ m in the thickness direction.
  • Ferrite in an area up to a depth of 50 ⁇ m in the thickness direction from the interface between the base iron and the plating layer may cause the propagation of cracks.
  • ferrite is more than 5% in the corresponding area, when stress occurs in the surface layer, local stress is concentrated on the relatively soft ferrite, which promotes crack propagation, which may deteriorate bendability and fatigue resistance.
  • the member according to one embodiment of the present invention has martensite as the main phase in the area from the interface between the base iron and the plating layer to a depth of 50 ⁇ m in the thickness direction, and contains less than 5 area% of ferrite and the remaining upper and lower bainite. You can have an organization.
  • a phase having an area fraction of 50% or more of the total microstructure fraction can be regarded as the main phase.
  • the physical properties desired in the present invention may be insufficient.
  • the member may include less than 5.0 area% of ferrite as a microstructure in a region from the interface between the base iron and the plating layer to a depth of 50.0 ⁇ m in the thickness direction.
  • the member according to one embodiment of the present invention includes martensite as the main phase in the area from the interface between the base iron and the plating layer to a depth of 50.0 ⁇ m in the thickness direction, less than 5.0 area% of ferrite, and the remaining upper and lower bainite. It may have a fine structure.
  • a phase having an area fraction of 50.0% or more in the total microstructure fraction can be regarded as the main phase.
  • the plated steel sheet according to one aspect of the present invention can be manufactured by annealing and plating a cold rolled steel sheet satisfying the above-described alloy composition.
  • the cold rolled steel sheet can be manufactured by reheating, hot rolling, coiling, cooling, and cold rolling a steel slab that satisfies the above-described alloy composition.
  • Steel slabs satisfying the alloy composition according to one embodiment of the present invention can be reheated to a temperature range of 1050 to 1300°C.
  • the reheating temperature is less than 1050°C, the slab structure is not sufficiently homogenized, so it may be difficult to re-employ when using precipitated elements.
  • the temperature exceeds 1300°C, an excessive oxidation layer is formed, which increases manufacturing costs for removing the oxide layer and is likely to cause surface defects after hot rolling.
  • the reheated steel slab can be finish rolled at a temperature range of 800 to 950°C.
  • finish rolling temperature is less than 800°C, biphasic rolling occurs, ferrite is introduced into the surface layer of the steel sheet, and plate shape control may be difficult. On the other hand, if the temperature exceeds 950°C, grain coarsening may occur.
  • the rolled steel can be coiled and cooled in a temperature range of 500 to 700°C.
  • the coiling temperature is less than 500°C, tension may become excessively high during coiling, which may cause defects in the width shape of the hot rolled coil and equipment problems.
  • the temperature exceeds 700°C, coarse carbides are excessively formed and crack generation is promoted when stress is generated in the hot-formed member, which may lead to a problem of reduced collision resistance.
  • a cold rolled steel sheet can be manufactured by cold rolling the cooled steel at a reduction ratio of 30 to 80%.
  • the cold rolling reduction rate is not specifically limited, but may be implemented within the range of 30 to 80% to obtain a predetermined target thickness.
  • the cold rolled steel sheet can be annealed in a temperature range of Ac 1 to Ac 3 .
  • the annealing temperature is less than Ac 1 , recrystallization of the cold rolled structure is not sufficiently completed, so the plate shape may be poor, and antimony may not be sufficiently concentrated, making it difficult to fully demonstrate the effect of the invention in the final member.
  • the temperature exceeds Ac 3 , it may cause equipment problems in the annealing furnace and cause defects on the surface due to acceleration of surface oxide formation.
  • the lower limit of the annealing temperature may be 750°C.
  • the upper limit of the annealing temperature may be limited to 860°C.
  • the product of the annealing time and absolute humidity may be 10,000 to 80,000 s ⁇ g/m 3 .
  • the atmosphere and humidity can be adjusted using hydrogen gas, hydrogen-nitrogen mixed gas, etc. to create an oxidizing atmosphere, and the annealing time in the temperature range of Ac 1 to Ac 3 is used to obtain an appropriate decarburization rate of the steel sheet. and it is important to control absolute humidity.
  • the product of the annealing time and the absolute humidity may be 10,000 to 80,000 s ⁇ g/m 3 .
  • the annealing time may be 100 to 200 seconds.
  • the absolute humidity may be 100 to 400 g/m 3 .
  • the average temperature increase rate from room temperature to 500°C is 2.7 ⁇ 10.0°C/s
  • the average temperature increase rate between 500°C and 700°C is 0.5 ⁇ 2.5°C/s
  • the annealing temperature at 700°C The average temperature increase rate can be controlled to 0.01 ⁇ 0.4°C/s.
  • the average temperature increase rate from room temperature to 500°C is limited to 2.7 ⁇ 10.0°C/s to secure the Sb enriched layer. If the average temperature increase rate from room temperature to 500°C exceeds 2.7 to 10.0°C/s, specifically, if it is less than 2.7°C/s, there is a problem in which the concentrated layer is not sufficiently formed, and if it exceeds 10°C/s, Due to rapid heating, the temperature unevenness in the width direction of the steel sheet increases, which can lead to tissue differences and line trouble problems. In the section where the surface temperature of the steel plate is 500 ⁇ 700°C, Sb enrichment of base iron may be affected.
  • the temperature at which a Sb-enriched layer is sufficiently formed in the base iron is from 700°C to the desired annealing temperature of the steel sheet.
  • the average temperature increase rate is 0.01 ⁇ . It is preferably 0.4°C/s.
  • the annealed cold rolled steel sheet can be plated.
  • the plating bath according to one aspect of the present invention may be aluminum or an aluminum-based alloy.
  • the plating bath composition may include Si, Mg, and Fe in addition to Al, and in some cases, Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, It may also contain Zn and the like.
  • the adhesion amount is not particularly limited and may be within a general range.
  • the composition of the plating bath in weight percent, includes one or two or more selected from among Si: 5-11%, Fe: 5% or less, and Mg: 5% or less, with the balance being Al. and other impurities.
  • an alloying process may be included after plating, and the alloying process is not particularly limited and can be performed under normal conditions.
  • the member according to one aspect of the present invention can be manufactured by manufacturing, heating, maintaining, forming, and cooling the plated steel sheet manufactured by the above-described method into a blank.
  • the plated steel sheet proposed in the present invention can be manufactured as a blank for hot forming.
  • the prepared blank can be heated to a temperature range of Ac 3 to 975°C and maintained for 10 to 1000 seconds.
  • the blank heating temperature is less than Ac 3 , it may be difficult to secure strength and collision resistance due to the presence of untransformed ferrite in the ideal region.
  • the heating temperature exceeds 975°C, excessive oxides are generated on the surface of the member, making it difficult to secure spot weldability and manufacturing costs for maintaining the high temperature may increase.
  • the subsequently heated blank has a heat treatment residence time of 10 to 1000 seconds in the above temperature range. If the holding time is less than 10 seconds, it is difficult to achieve uniform temperature distribution throughout the blank, which may cause material deviation by location.
  • the holding time exceeds 1000 seconds, as when the heating temperature is exceeded, excessive oxide is generated on the surface of the member and an interdiffusion layer grows excessively, which not only makes it difficult to secure spot weldability but also causes an increase in the manufacturing cost of the member.
  • the heated blank can be molded and cooled.
  • the final member can be manufactured by transferring the heated blank to a press and performing hot forming and die quenching at a cooling rate of 20°C/s or more. At a cooling rate of less than 20°C/s, a ferrite phase may be introduced during cooling and formed at grain boundaries, which may deteriorate strength and collision resistance. According to one embodiment of the present invention, after forming the blank, it can be cooled to 25°C/s or more.
  • the coated steel sheet of the present invention manufactured in this way can maintain the surface hardness below a certain level and can maintain the blade life above a certain level when shearing for producing a blank for hot forming, thereby reducing the cost. It works.
  • the member of the present invention manufactured in this way has a product of tensile strength and bending angle of 80,000 MPa ⁇ ° or more, a diffusible hydrogen content of 0.2 ppm or less, and can have excellent fatigue resistance and bending properties.
  • tensile strength (TS) * bending angle (BA) was used as an indicator for measuring collision resistance.
  • the bending angle which is an indicator of crash resistance, is influenced by tensile strength, which tends to be inversely proportional. Therefore, as the product of tensile strength and bending angle (TS*BA) increases, crash resistance increases.
  • the BA value can be measured through bendability evaluation according to the VDA238-100 standard, and is expressed as the bending outer angle converted from the maximum bending strength.
  • a 40 mm thick slab containing Sb in the content shown in Table 1 below and having the composition of 0.22C-0.25Si-1.25Mn-0.2Cr-0.03Al-0.03Ti-0.0025B was manufactured by vacuum melting.
  • the slab was heated to 1200°C and held for 1 hour, then hot rolled at a hot rolling end temperature of 900°C and coiled at a temperature of 600°C. Afterwards, a pickling process was performed, and cold rolling was performed at a reduction ratio of 30 to 80% to manufacture cold rolled steel sheets.
  • the cold-rolled steel sheet was annealed at a temperature of Ac 1 to Ac 3 , but the annealing time (s) and absolute humidity (g/m 3 ) were adjusted, and the resulting value of the product of annealing time and absolute humidity is shown in Table 1.
  • plating was performed by immersing the steel sheet in a plating bath consisting of Al-9%Si-2%Fe and trace amounts of impurities.
  • Table 2 below shows the Sb enriched layer, microstructure, and decarburization rate of the manufactured plated steel sheet.
  • SEM scanning electron microscopy
  • the remaining fractions were observed to be ferrite.
  • GDS850A model name, manufactured by LECO
  • DC and RF equipment were used to measure the carbon decarburization rate in an area from the interface to a depth of 30 ⁇ m in the thickness direction of the base steel plate, and the decarburization rate ( ⁇ ) was determined through the carbon profile obtained through the equipment. ) and the depth according to the ratio of carbon content are shown in Table 2 below.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is ⁇ m.
  • a member was manufactured by hot forming using a plated steel sheet in which no unplated area was observed.
  • the heat treatment temperature and time for hot forming were 900°C and 360 seconds, and the transfer time from the heat treatment furnace to the forming press was 10 seconds.
  • Table 3 shows the structure and properties of the member manufactured through hot forming, measured in the same manner as described above.
  • Vickers hardness was measured by applying a load of 1.0 kg at a depth of 45 to 100 ⁇ m from the interface between the plating layer of the member and the base iron, and the hardness softening rate ( ⁇ ) was recorded using FIG. 6 and the method described above.
  • the amount of diffusible hydrogen was measured using TDA equipment (Thermal Desorption Analysis) (Bruker G8; model name). Specifically, the temperature was raised to 400°C at a rate of 20°C/min, and the diffusion hydrogen curve was measured by maintaining it for a certain period of time so that the diffusible hydrogen peak sufficiently appeared. This curve was integrated to determine diffusion in the steel. The amount of sexual hydrogen was obtained.
  • the ferrite area fraction within a depth of 30 ⁇ m from the interface between the base iron and the plating layer was measured using optical microscopy and is shown in Table 3. At this time, all specimens were observed to be martensite except for the ferrite area fraction.
  • more than 10,000,000 repetitive fatigue tests were performed to measure the measured fatigue limit strength. If the fatigue limit strength divided by the tensile strength is 0.25 or more, it is O, and if it is less than 0.25, it is X. Fatigue resistance characteristics were confirmed by marking.
  • crash resistance characteristics were expressed as the product of tensile strength and bending angle, and the tensile strength value was measured through a room temperature tensile test in accordance with the ISO6892 standard using a JIS-5 specimen.
  • the bending angle was recorded as the bending outer angle converted from the maximum bending strength specified in the standard according to the bendability evaluation method according to the VDA238-100 standard.
  • Sb max represents the maximum value of Sb content in the Sb enriched layer
  • Sb coat represents the average Sb content in the plating layer
  • ⁇ t measures Sb max from the interface between the plating layer and the base iron. It represents the straight line distance between one points, and the unit is ⁇ m.
  • Comparative Examples 1 and 2 were cases in which the product of annealing time and absolute humidity during annealing was below the range suggested by the present invention, and the decarburization rate of the coated steel sheet was outside the suggested range. As a result, the hardness softening rate of the member decreased, and the collision resistance deteriorated due to excessive carbon concentration in the surface layer.
  • Figure 7 shows a carbon profile in a plated steel sheet according to an embodiment of the present invention.
  • Invention Examples 1 and 3 of Figure 7 confirm that the decarburization control proposed in the present invention was sufficiently achieved, and as a result, the product of tensile strength and bending angle and fatigue resistance characteristics above a certain level were secured. On the other hand, it can be confirmed that in Comparative Example 1, decarburization according to depth was not sufficiently achieved, and in Comparative Example 3, excessive decarburization occurred due to insufficient production of the Sb enriched layer, resulting in inferior physical properties.
  • Figure 8 is a photograph of the structure directly below the interface of the plated steel sheets of Inventive Example 3 and Comparative Example 3 according to an embodiment of the present invention observed with an SEM. In the case of Inventive Example 3, 2.9% of pearlite was observed, but in the case of Comparative Example 3, it can be confirmed that less than 1% of pearlite was observed.
  • Figure 9 is an optical photograph of the interface between the plating layer and the base iron in the members of Inventive Example 3 and Comparative Example 3 of the present invention.
  • ferrite was observed to be less than 1%, but in Comparative Example 3, the ferrite content was 7.3%, which did not ensure the fatigue resistance desired in the present invention.
  • Comparative Example 4 the product of the Sb content in the steel, annealing time, and absolute humidity is outside the range proposed by the present invention, and the amount of diffusible hydrogen in the member is excessive, deteriorating bendability, and tensile strength, which is an index of collision resistance, The product value of the bending angle did not reach the desired level.

Abstract

The present invention relates to a plated steel sheet for hot press forming, a hot press formed part, and manufacturing methods thereof and, more specifically, a plated steel sheet for hot press forming having excellent impact resistance, a hot press formed part, and manufacturing methods thereof.

Description

내충돌성이 우수한 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법Coated steel sheets for hot forming with excellent collision resistance, hot forming members, and their manufacturing methods
본 발명은 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법에 관한 것으로, 보다 상세하게는 내충돌성이 우수한 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법에 관한 것이다.The present invention relates to galvanized steel sheets for hot forming, hot forming members, and methods for manufacturing the same. More specifically, it relates to galvanized steel sheets for hot forming with excellent collision resistance, hot forming members, and methods for manufacturing them.
열간 성형 부재는 최근 자동차 경량화를 통한 연비 향상 및 승객 보호 등의 목적으로 자동차의 구조 부재에 많이 적용되고 있으며, 특히 초고강도 또는 에너지 흡수능이 크게 요구되는 범퍼, 도어 또는 필러 보강재 등에 활용될 수 있다. Hot forming members have recently been widely applied to structural members of automobiles for the purpose of improving fuel efficiency and protecting passengers by reducing the weight of automobiles. In particular, they can be used in bumpers, doors, or pillar reinforcements that require ultra-high strength or energy absorption.
이러한 열간 성형 기술에 관한 대표적인 기술로서 특허문헌 1이 제안되었다. 상기 특허는 Al-Si 도금강판을 850℃ 이상 가열 후 프레스에 의한 열간 성형 및 급냉에 의해 부재의 조직을 마르텐사이트로 형성시킴으로써, 인장강도가 높은 초고강도를 확보할 수 있다. 이러한 열간 성형용 초고강도 강을 적용할 경우, 고온에서 성형하기 때문에 복잡한 형상도 쉽게 성형이 가능하며, 금형 내 급랭에 따른 강도 상승을 통해 고강도화에 따른 경량화 효과를 기대할 수 있다. Patent Document 1 was proposed as a representative technology regarding this hot forming technology. In the above patent, ultra-high strength with high tensile strength can be secured by heating Al-Si plated steel sheet to over 850°C and then forming the structure of the member into martensite by hot forming with a press and rapid cooling. When applying such ultra-high strength steel for hot forming, complex shapes can be easily formed because they are formed at high temperatures, and a weight reduction effect due to high strength can be expected through an increase in strength due to rapid cooling in the mold.
그러나, 이와 더불어, 자동차 사는 승객 안전을 위한 내충돌성 향상에 대한 요구 수준이 높아지고 있으나, 통상의 열간 성형용 강재는 마르텐사이트 조직으로 충돌 시, 강도는 높은 반면 내충돌성이 열위하기 때문에 개선이 필요하다. However, in addition to this, automobile companies are increasingly demanding improved crash resistance for passenger safety. However, regular hot forming steel materials have a martensitic structure and have high strength in the event of a collision, but are poor in crash resistance, so there is no need for improvement. need.
[선행기술문헌][Prior art literature]
(특허문헌 1) 미국 특허공보 제6296805호 (2001.10.02 공개)(Patent Document 1) U.S. Patent Publication No. 6296805 (published on October 2, 2001)
본 발명의 일 측면에 따르면 내충돌성이 우수한 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법을 제공하고자 하는 것이다.According to one aspect of the present invention, it is intended to provide a galvanized steel sheet for hot forming with excellent collision resistance, a hot forming member, and a method for manufacturing the same.
본 발명의 과제는 상술한 내용에 한정되지 않는다. 통상의 기술자라면 본 명세서의 전반적인 내용으로부터 본 발명의 추가적인 과제를 이해하는데 아무런 어려움이 없을 것이다.The object of the present invention is not limited to the above-described content. A person skilled in the art will have no difficulty in understanding the additional problems of the present invention from the overall content of the present specification.
본 발명의 일 측면은, 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 소지강판 및 상기 소지강판의 표면에 형성된 도금층을 포함하고,One aspect of the present invention includes a base steel sheet containing, in weight percent, carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1%, and a plating layer formed on the surface of the base steel sheet,
상기 소지강판은 내에 안티몬(Sb) 농화층을 포함하며,The base steel plate includes an antimony (Sb) concentrated layer therein,
글로우 방전 분광 분석기(Glow Discharge Spectrometer)를 이용하여 상기 소지강판의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지강판의 공칭 탄소 함량(C0)의 10~70%인 도금강판을 제공할 수 있다.When analyzing the element content in the thickness direction of the steel sheet using a glow discharge spectrometer, the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) It is possible to provide a plated steel sheet in which the carbon (C) content is 10 to 70% of the nominal carbon content (C 0 ) of the base steel sheet.
상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 30μm까지 영역의 탄소(C)의 탈탄율(α)이 14~35%일 수 있다.The decarburization rate (α) of carbon (C) in a region from the interface between the base steel sheet and the plating layer to a depth of 30 μm in the thickness direction may be 14 to 35%.
상기 도금강판은 상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 1.5μm 초과, 6μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 50%인 지점이 존재할 수 있다.The plated steel sheet may have a point where the carbon (C) content is 50% of the nominal carbon content (C 0 ) at a depth of more than 1.5 μm and less than 6 μm in the thickness direction from the interface of the base steel sheet and the plating layer.
상기 도금강판은 상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 6μm 초과, 15μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 80%인 지점이 존재할 수 있다.The plated steel sheet may have a point where the carbon (C) content is 80% of the nominal carbon content (C 0 ) at a depth of more than 6 μm and less than 15 μm in the thickness direction from the interface between the base steel sheet and the plating layer.
상기 도금강판은 하기 관계식 1에서 정의되는 R 값이 1.2 이상이고,The plated steel sheet has an R value defined in equation 1 below of 1.2 or more,
하기 관계식 2에서 정의되는 B 값이 0.008 이상일 수 있다.The B value defined in Equation 2 below may be 0.008 or more.
[관계식 1]
Figure PCTKR2023012157-appb-img-000001
[Relationship 1]
Figure PCTKR2023012157-appb-img-000001
[관계식 2]
Figure PCTKR2023012157-appb-img-000002
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000002
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지강판의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is μm.)
상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 10μm까지의 영역은 페라이트를 주상으로 하고, 1면적% 이상의 펄라이트를 포함하는 미세조직을 가질 수 있다.The area from the interface between the base steel plate and the plating layer to a depth of 10 μm in the thickness direction may have a microstructure containing ferrite as the main phase and more than 1 area% of pearlite.
상기 소지강판은 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함할 수 있다.The base steel sheet contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
상기 도금층은 알루미늄 또는 알루미늄 합금으로 이루어질 수 있다.The plating layer may be made of aluminum or aluminum alloy.
본 발명의 다른 일 측면은, 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 소지철 및 상기 소지철의 표면에 형성된 도금층을 포함하고,Another aspect of the present invention includes base iron containing 0.06 to 0.5% of carbon (C) and 0.01 to 0.1% of antimony (Sb), in weight percent, and a plating layer formed on the surface of the base iron,
상기 소지철은 내에 안티몬(Sb) 농화층을 포함하며,The base iron includes an antimony (Sb) enriched layer within it,
글로우 방전 분광 분석기(Glow Discharge Spectrometer)를 이용하여 상기 소지철의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 80% 이하인 부재를 제공할 수 있다.When analyzing the element content in the thickness direction of the base iron using a glow discharge spectrometer, the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) It is possible to provide a member in which the carbon (C) content is 80% or less of the nominal carbon content (C 0 ) of the base iron.
상기 부재는 상기 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 15~80%일 수 있다.The member may have a carbon (C) content of 15 to 80% of the nominal carbon content (C 0 ) of the base iron at a depth where the antimony (Sb) content reaches its maximum value (Sb max ).
상기 부재는 하기 관계식 1에서 정의되는 R 값이 1.5 이상이고,The member has an R value defined in equation 1 below of 1.5 or more,
하기 관계식 2에서 정의되는 B 값이 0.01 이상일 수 있다.The B value defined in Equation 2 below may be 0.01 or more.
[관계식 1]
Figure PCTKR2023012157-appb-img-000003
[Relationship 1]
Figure PCTKR2023012157-appb-img-000003
[관계식 2]
Figure PCTKR2023012157-appb-img-000004
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000004
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지철이 접하는 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface where the plating layer and the base iron contact. It represents the straight line distance between one points, and the unit is μm.)
상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 45~100μm의 영역은 연화율(β)이 2~7%일 수 있다.A region with a depth of 45 to 100 μm in the thickness direction from the interface between the base iron and the plating layer may have a softening rate (β) of 2 to 7%.
상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 50μm까지 영역은 미세조직으로 5면적% 미만의 페라이트를 포함할 수 있다.The area from the interface between the base iron and the plating layer to a depth of 50 μm in the thickness direction may include less than 5 area% of ferrite as a microstructure.
상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 50μm까지 영역은 미세조직으로 마르텐사이트를 주상으로 하고, 5면적% 미만의 페라이트, 잔부 상부 및 하부 베이나이트를 포함할 수 있다.The area from the interface of the base iron and the plating layer to a depth of 50 μm in the thickness direction may have martensite as the main phase as a microstructure, and may include less than 5 area% of ferrite and the remaining upper and lower bainite.
상기 소지철은 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함할 수 있다.The base iron contains carbon (C): 0.06 to 0.5%, antimony (Sb): 0.01 to 0.1%, silicon (Si): 0.001 to 2%, manganese (Mn): 0.1 to 4%, and molybdenum (Mo): 1. % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
상기 도금층은 알루미늄 또는 알루미늄 합금으로 이루어질 수 있다.The plating layer may be made of aluminum or aluminum alloy.
상기 부재는 인장강도 및 굽힘각도의 곱이 80,000MPa·° 이상일 수 있다.The product of the tensile strength and bending angle of the member may be 80,000 MPa·° or more.
상기 부재는 확산성 수소량이 0.2ppm 이하일 수 있다.The member may have a diffusible hydrogen content of 0.2ppm or less.
본 발명의 일 측면은, 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 냉연강판을 준비하는 단계; One aspect of the present invention includes preparing a cold-rolled steel sheet containing, in weight percent, carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1%;
상기 냉연강판을 Ac1~Ac3의 온도범위에서 소둔하는 단계; 및 Annealing the cold rolled steel sheet in a temperature range of Ac 1 to Ac 3 ; and
상기 소둔된 냉연강판을 도금하는 단계를 포함하고, Comprising the step of plating the annealed cold rolled steel sheet,
상기 소둔 시, 소둔 시간과 절대 습도의 곱이 10,000~80,000s·g/m3이고,During the annealing, the product of the annealing time and the absolute humidity is 10,000 to 80,000 s·g/m 3 ,
상기 소둔 시, 강판의 표면 온도를 기준으로, 상온에서 500℃까지 평균 승온 속도가 2.7~10.0℃/s이고, 500~700℃ 구간의 평균 승온 속도가 0.5~2.5℃/s이고, 700℃에서 소둔 온도까지 평균 승온 속도가 0.01~0.4℃/s인 도금강판 제조방법을 제공할 수 있다.During the annealing, based on the surface temperature of the steel sheet, the average temperature increase rate from room temperature to 500°C is 2.7 to 10.0°C/s, the average temperature increase rate in the 500 to 700°C section is 0.5 to 2.5°C/s, and at 700°C. It is possible to provide a method for manufacturing plated steel sheets with an average temperature increase rate of 0.01 to 0.4°C/s up to the annealing temperature.
상기 소둔 시, 소둔 시간은 100~200초이며, 절대 습도는 100~400g/m3일 수 있다.During the annealing, the annealing time is 100 to 200 seconds, and the absolute humidity may be 100 to 400 g/m 3 .
상기 냉연강판은,The cold rolled steel sheet,
강 슬라브를 1050~1300℃의 온도범위로 재가열하는 단계;Reheating the steel slab to a temperature range of 1050-1300°C;
상기 재가열된 강 슬라브를 800~950℃의 온도범위에서 마무리 압연하는 단계;Finish rolling the reheated steel slab at a temperature range of 800 to 950°C;
상기 압연된 강을 500~700℃의 온도범위에서 권취 및 냉각하는 단계; 및Winding and cooling the rolled steel at a temperature range of 500 to 700°C; and
상기 냉각된 강을 30~80%의 압하율로 냉간압연하는 단계를 포함할 수 있다.It may include cold rolling the cooled steel at a reduction rate of 30 to 80%.
상기 강 슬라브는 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함할 수 있다.The steel slab contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, and may include remaining iron (Fe) and impurities.
상기 도금 시, 알루미늄 또는 알루미늄 합금으로 도금하는 것일 수 있다.During the plating, plating may be done with aluminum or aluminum alloy.
본 발명의 다른 일 측면은, 어느 하나의 도금강판을 블랭크로 제조하는 단계; Another aspect of the present invention includes manufacturing one plated steel sheet as a blank;
상기 블랭크를 Ac3~975℃의 온도범위로 가열하고, 10~1000초 유지하는 단계; 및 Heating the blank to a temperature range of Ac 3 to 975°C and maintaining it for 10 to 1000 seconds; and
상기 가열된 블랭크를 성형 및 냉각하는 단계를 포함하는 부재 제조방법을 제공할 수 있다.A method of manufacturing a member may be provided including the steps of forming and cooling the heated blank.
상기 냉각 시, 20℃/s 이상의 냉각속도로 냉각할 수 있다.During the cooling, cooling can be performed at a cooling rate of 20°C/s or more.
본 발명의 일 측면에 따르면 내충돌성이 우수한 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법을 제공할 수 있다.According to one aspect of the present invention, a galvanized steel sheet for hot forming with excellent collision resistance, a hot forming member, and a method for manufacturing the same can be provided.
본 발명의 일 측면에 따르면 내피로특성 및 내충돌성이 우수한 열간 성형용 도금강판, 열간 성형 부재 및 이들의 제조방법을 제공할 수 있다.According to one aspect of the present invention, it is possible to provide a plated steel sheet for hot forming with excellent fatigue resistance and collision resistance, a hot forming member, and a method for manufacturing the same.
도 1은 Sb 농화층을 표현하기 위해 본 발명의 예시적인 Sb 함량 변화를 모식적으로 나타낸 것이다.Figure 1 schematically shows an exemplary change in Sb content of the present invention to represent a Sb enriched layer.
도 2는 본 발명의 일 실시예에 따른 도금강판에서, 계면으로부터 두께 방향으로의 Sb 및 C 함량 프로파일을 모식적으로 나타낸 것이다.Figure 2 schematically shows the Sb and C content profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
도 3은 본 발명의 일 실시예에 따른 도금강판에서, 계면으로부터 두께 방향으로의 탈탄율(α) 프로파일을 모식적으로 나타낸 것이다.Figure 3 schematically shows the decarburization rate (α) profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention.
도 4는 본 발명의 일 실시예에 따른 도금강판의 Sb 농화층 프로파일을 모식적으로 나타낸 것이다.Figure 4 schematically shows the Sb enriched layer profile of a plated steel sheet according to an embodiment of the present invention.
도 5는 본 발명의 일 실시예에 따른 부재에서, 계면으로부터 두께 방향으로의 Sb 및 C 함량 프로파일을 모식적으로 나타낸 것이다.Figure 5 schematically shows the Sb and C content profile from the interface to the thickness direction in a member according to an embodiment of the present invention.
도 6은 본 발명의 일 실시예에 따른 부재에서, 계면으로부터 두께 방향으로의 경도 연화율(β) 프로파일을 모식적으로 나타낸 것이다.Figure 6 schematically shows the hardness softening rate (β) profile from the interface to the thickness direction in a member according to an embodiment of the present invention.
도 7은 본 발명의 일 실시예에 따른 도금강판에서의 C 함량 프로파일을 나타낸 것이다.Figure 7 shows the C content profile in a plated steel sheet according to an embodiment of the present invention.
도 8은 본 발명의 일 실시예에 따른 도금강판의 미세조직을 주사전자현미경(SEM)으로 관찰한 사진이다.Figure 8 is a photograph of the microstructure of a plated steel sheet according to an embodiment of the present invention observed with a scanning electron microscope (SEM).
도 9는 본 발명의 일 실시예에 따른 부재의 미세조직을 관찰한 사진이다.Figure 9 is a photograph observing the microstructure of a member according to an embodiment of the present invention.
이하에서는 본 발명의 바람직한 실시예들을 설명하고자 한다. 본 발명의 실시예들은 여러 가지 형태로 변형될 수 있으며, 본 발명의 범위가 아래에서 설명되는 실시예들에 한정되는 것으로 해석되어서는 안된다. 본 실시예들은 당해 발명이 속하는 기술분야에서 통상의 기술자에게 본 발명을 더욱 상세하게 설명하기 위하여 제공되는 것이다.Below, preferred embodiments of the present invention will be described. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as limited to the embodiments described below. These embodiments are provided to explain the present invention in more detail to those skilled in the art.
종래 기술의 문제점을 해결하기 위하여, 탈탄 기술을 적용함으로써 굽힘성을 개선할 수 있는 방안을 생각해 볼 수 있으나, 국부적인 표층부 경도 저하로 인하여 피로 특성이 열위해질 수 있어, 자동차 부재의 적용이 제한될 수 있다. 이에, 본 발명자는 이와 같은 문제를 해결하기 위하여 깊이 연구한 결과, 소지강판에 안티몬(Sb) 농화층을 형성시키고 강판의 탈탄율을 적정 수준으로 유지할 경우에 피로 특성의 열화 문제를 해결하고, 내충돌특성 또한 개선할 수 있는 것을 발견하고, 본 발명에 이르게 되었다.In order to solve the problems of the prior art, a way to improve bendability by applying decarburization technology can be considered, but fatigue characteristics may be inferior due to localized decrease in surface hardness, which will limit application to automobile members. You can. Accordingly, the present inventor has conducted in-depth research to solve this problem, and as a result, when an antimony (Sb) enriched layer is formed on the base steel sheet and the decarburization rate of the steel sheet is maintained at an appropriate level, the problem of fatigue properties deterioration is solved, It was discovered that crash characteristics could also be improved, leading to the present invention.
이하, 본 발명에 대하여 보다 상세히 설명한다. Hereinafter, the present invention will be described in more detail.
본 발명의 일 측면은 소지강판 및 상기 소지강판의 표면에 형성된 도금층을 포함하는 도금강판을 대상으로 한다. 내충돌성 및 내피로특성은 강판의 탈탄 정도에 따라 크게 영향을 받을 수 있는데, 소지강판 내에 형성된 농화층을 이용하여 탈탄율을 적절하게 제어할 경우에는 본 발명의 효과를 유리하게 얻을 수 있다. 즉, 본 발명의 일 측면에 따르는 도금강판은 소지강판 및 상기 소지강판의 표면(소지강판과 도금층 사이의 계면을 의미할 수 있음)에 형성된 도금층을 포함하고, 상기 소지강판은 내에 형성된 안티몬(Sb) 농화층을 포함할 수 있다. One aspect of the present invention is directed to a plated steel sheet including a base steel sheet and a plating layer formed on the surface of the base steel sheet. Collision resistance and fatigue resistance can be greatly affected by the degree of decarburization of the steel sheet, and the effects of the present invention can be advantageously obtained when the decarburization rate is appropriately controlled using the thickened layer formed in the base steel sheet. That is, the plated steel sheet according to one aspect of the present invention includes a base steel plate and a plating layer formed on the surface of the base steel sheet (which may mean the interface between the base steel sheet and the plating layer), and the base steel sheet contains antimony (Sb) formed within the base steel sheet. ) may include a thickening layer.
본 발명의 한가지 실시예에 따르면, 강판 내에 안티몬(Sb)의 농화층이 형성될 경우, Sb 농화층 형성에 따라 강판의 두께 방향 깊이에 따른 탈탄율이 적절히 제어될 수 있다. According to one embodiment of the present invention, when an enriched layer of antimony (Sb) is formed in a steel sheet, the decarburization rate according to the depth in the thickness direction of the steel sheet can be appropriately controlled according to the formation of the Sb enriched layer.
이하에서는 도 1의 그래프를 참고하여 본 발명의 한가지 실시예에 따른 Sb 농화층과 그 역할에 대하여 상세히 설명한다. 도 1은 Sb 농화층을 표현하기 위해 본 발명의 예시적인 Sb 함량 변화를 모식적으로 나타낸 것으로, 도 1에서 x축은 도금강판 내의 임의의 위치에서 도금층으로부터 소지강판 측 방향, 즉 두께 방향으로의 직선 거리를 나타내고, y축은 글로우 방전 분광 분석기(Glow Discharge Spectrometer, GDS)를 활용하여 측정된 Sb 함량을 나타낸다. 도 1에는 도금층(1), Sb 농화층(2) 및 Sb 농화층(2)을 제외한 소지강판(3)의 Sb 함량 변화가 예시되어 있다. 여기서, 상기 Sb 농화층(2)은 소지강판의 공칭 Sb 함량(Sb0)의 1.05배 이상의 Sb 함량을 가질 수 있으며, 상기 Sb 농화층(2) 내에는 Sb 함량이 최대값인 지점(200; Sbmax)이 존재할 수 있다. 또한, 상기 Sb 농화층(2)은 x축 방향으로 진행하면서 Sb 함량이 최대값인 지점(200; Sbmax)까지 Sb 함량이 상승하는 Sb 함량 상승 구간(21)과 Sb 함량이 최대값인 지점(200; Sbmax)으로부터 x축 방향으로 진행하면서 Sb 함량이 감소하는 Sb 함량 하강 구간(22)을 포함할 수 있다. 도 1에서 상기 도금층(1)의 Sb 평균 함량선(10)과 Sb 함량이 최대값인 지점(200; Sbmax)에 도달하기 전 상기 Sb 함량선(100)의 x축 (+)방향으로의 마지막 접촉 지점(11)을 상기 Sb 함량 상승 구간(21)의 시작점으로 할 수 있다.Hereinafter, the Sb enriched layer and its role according to an embodiment of the present invention will be described in detail with reference to the graph in FIG. 1. Figure 1 schematically shows an exemplary change in Sb content of the present invention to express the Sb enriched layer. In Figure 1, the It represents the distance, and the y-axis represents the Sb content measured using a glow discharge spectrometer (GDS). Figure 1 illustrates the change in Sb content of the plated layer (1), the Sb-enriched layer (2), and the base steel sheet (3) excluding the Sb-enriched layer (2). Here, the Sb enriched layer 2 may have an Sb content of 1.05 times or more than the nominal Sb content (Sb 0 ) of the base steel plate, and within the Sb enriched layer 2, there is a point (200) where the Sb content is at its maximum value. Sb max ) may exist. In addition, the Sb enriched layer 2 has a Sb content increasing section 21 in which the Sb content increases to the point (200; Sb max ) where the Sb content is the maximum as it progresses in the x-axis direction, and a point where the Sb content is the maximum. It may include a Sb content lowering section 22 in which the Sb content decreases while proceeding from (200; Sb max ) in the x-axis direction. In Figure 1, the Sb average content line 10 of the plating layer 1 and the x-axis (+) direction of the Sb content line 100 before reaching the point (200; Sb max ) where the Sb content is the maximum value. The last contact point (11) can be used as the starting point of the Sb content increase section (21).
일 실시예에 있어서, 상기 도금층(1)의 Sb 평균 함량선(10)은, Sb 농화층(2)에서 Sb 함량이 최대값인 지점(200, Sbmax)으로부터 도금층(1)측으로 15μm 떨어진 지점인 A 지점에서 20μm 떨어진 지점인 B 지점까지 구간의 Sb 평균 함량을 수평으로 연장한 연장선을 의미할 수 있다.In one embodiment, the Sb average content line 10 of the plating layer 1 is a point 15 μm away from the point (200, Sb max ) where the Sb content is the maximum in the Sb enriched layer 2 toward the plating layer 1. It may mean an extension line that extends horizontally the average Sb content of the section from point A to point B, which is 20 μm away.
마찬가지로, 상기 Sb 함량이 최대값인 지점(200; Sbmax)으로부터 x축 (+)방향으로의 Sb 함량 하강 구간(22) 중에서, 상기 소지강판의 Sb 평균 함량선(30)과 상기 Sb 함량선(100)의 x축 (+)방향으로의 최초의 접촉 지점(31)을 Sb 농화층(2)의 종료점으로 본다. Likewise, in the Sb content decreasing section 22 in the x-axis (+) direction from the point 200 (Sb max ) where the Sb content is the maximum value, the Sb average content line 30 of the base steel plate and the Sb content line The first contact point (31) in the x-axis (+) direction of (100) is regarded as the end point of the Sb enriched layer (2).
일 실시예에 있어서, 상기 Sb 농화층을 제외한 소지강판(3)의 Sb 평균 함량선(30)은, Sb 농화층(2)에서 Sb 함량이 최대값인 지점(200; Sbmax)으로부터 소지강판(3)측으로 15μm 떨어진 지점인 C 지점에서 20μm 떨어진 지점인 D 지점까지 구간의 Sb 평균 함량을 수평으로 연장한 연장선을 의미할 수 있다.In one embodiment, the average Sb content line 30 of the base steel sheet 3 excluding the Sb enriched layer is from the point 200 (Sb max ) where the Sb content is the maximum in the Sb enriched layer 2. (3) It can mean an extension line that extends the average Sb content of the section horizontally from point C, which is 15 μm away, to point D, which is 20 μm away.
본 발명의 일 실시예에 있어서, Sb 농화층은 상기 소지강판과 상기 도금층의 계면 직하에 형성될 수 있다. 예를 들어, 글로우 방전 분광 분석기(GDS)를 이용하여 도금강판의 표면으로부터 깊이(두께) 방향으로 Al 함량의 프로파일을 분석하였을 때, Al 함량이 15%인 지점으로 정의할 수 있다. 또한, 예를 들어, 상기 농화층의 두께는 1~30μm일 수 있다.In one embodiment of the present invention, the Sb enriched layer may be formed directly below the interface between the base steel sheet and the plating layer. For example, when the Al content profile is analyzed from the surface of the plated steel sheet in the depth (thickness) direction using a glow discharge spectrometer (GDS), it can be defined as the point where the Al content is 15%. Additionally, for example, the thickness of the concentrated layer may be 1 to 30 μm.
또한, 본 발명의 한가지 실시예에 따르면, 글로우 방전 분광 분석기(GDS)를 이용하여 소지강판의 두께 방향으로 안티몬(Sb)의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지강판의 공칭 탄소 함량(C0)의 10~70%일 수 있다. 본 발명의 일 실시예에 있어서, 상기 공칭 탄소 함량(C0)은 소지강판 단면 기준으로, 두께 1/4~3/4 영역에서의 탄소 평균 함량을 의미할 수 있으며, 구체적으로, 글로우 방전 분광 분석기(GDS)를 이용하여 소지강판 두께 1/4~3/4 영역에서 임의의 지점으로부터 거리 50μm 이상에 대하여 탄소 프로파일을 분석하여 평균 탄소 함량일 수 있다.In addition, according to one embodiment of the present invention, when analyzing the content of antimony (Sb) in the thickness direction of the base steel sheet using a glow discharge spectrometer (GDS), antimony (Sb) is present in the antimony (Sb) enriched layer. The carbon (C) content at the depth where the content represents the maximum value (Sb max ) may be 10 to 70% of the nominal carbon content (C 0 ) of the base steel plate. In one embodiment of the present invention, the nominal carbon content (C 0 ) may mean the average carbon content in the thickness 1/4 to 3/4 region based on the cross-section of the base steel plate, and specifically, glow discharge spectroscopy The average carbon content can be obtained by analyzing the carbon profile at a distance of 50 μm or more from any point in the area of 1/4 to 3/4 of the thickness of the base steel plate using an analyzer (GDS).
도 2는 본 발명의 일 실시예에 따른 도금강판에서, 계면으로부터 두께 방향으로의 Sb 및 C 함량의 프로파일을 모식적으로 나타낸 것이다. 상기 도 2의 x축은 소지강판과 도금층의 계면으로부터의 깊이(μm)를 나타내며, y축은 원소의 함량(wt%)을 나타낼 수 있다. 도 2에서 나타난 바와 같이, 공칭 탄소 함량(C0)의 70%는 0.154%이다. 여기서, 공칭 탄소 함량(C0)은 0.22%로서, 앞서 설명한 바와 같이, 소지강판의 두께 1/4~3/4 영역에서 글로우 방전 분광 분석기(GDS)를 이용하여 일정 두께(깊이)를 분석하여 얻어질 수 있다. 이 때, Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서 탄소의 함량은 공칭 탄소 함량(C0)의 70% 이하인 탄소 함량을 나타내는 것을 확인할 수 있다.Figure 2 schematically shows the profile of Sb and C contents from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention. The x-axis of FIG. 2 represents the depth (μm) from the interface between the base steel plate and the plating layer, and the y-axis may represent the element content (wt%). As shown in Figure 2, 70% of the nominal carbon content (C 0 ) is 0.154%. Here, the nominal carbon content (C 0 ) is 0.22%, and as described above, a certain thickness (depth) is analyzed using a glow discharge spectrometer (GDS) in the 1/4 to 3/4 thickness area of the base steel plate. can be obtained. At this time, it can be confirmed that at the depth where the Sb content shows the maximum value (Sb max ), the carbon content is 70% or less of the nominal carbon content (C 0 ).
도 2에서 나타난 바와 같이, 본 발명의 일 실시예에 있어서, Sb 농화층 내에 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서, 공칭 탄소 함량(C0) 대비 탄소 함량의 비율을 10~70%로 제어하고 있으며, 이 때의 탄소 함량은 부재의 표층 경도 연화율 및 굽힘성에 영향을 미친다. As shown in Figure 2, in one embodiment of the present invention, at the depth where the Sb content in the Sb enriched layer shows the maximum value (Sb max ), the ratio of the carbon content to the nominal carbon content (C 0 ) is 10 to 70. It is controlled by %, and the carbon content at this time affects the surface hardness softening rate and bendability of the member.
한편, Sb 농화층 내에 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서 탄소 함량이 공칭 탄소 함량(C0)의 70%를 초과하면 표층부 경도가 높아져 굽힘성이 열화될 수 있다. 또한, 본 발명의 한가지 실시예에 따르면 탄소 함량이 공칭 탄소 함량(C0)의 10% 미만일 경우, 경도가 과도하게 낮아져 내피로특성이 열위될 수 있다. On the other hand, if the carbon content in the Sb enriched layer exceeds 70% of the nominal carbon content (C 0 ) at the depth where the Sb content reaches its maximum value (Sb max ), the hardness of the surface layer may increase and the bendability may deteriorate. In addition, according to one embodiment of the present invention, when the carbon content is less than 10% of the nominal carbon content (C 0 ), the hardness may be excessively lowered and the fatigue resistance may be inferior.
본 발명의 일 실시예에 있어서, Sb 농화층 내에 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서, 공칭 탄소 함량(C0) 대비 탄소 함량의 비율을 10.0~70.0% 일 수 있다.In one embodiment of the present invention, at the depth where the Sb content in the Sb enriched layer shows the maximum value (Sb max ), the ratio of the carbon content to the nominal carbon content (C 0 ) may be 10.0 to 70.0%.
본 발명의 한가지 실시예에 따르면, 소지강판과 도금층의 계면으로부터 두께 방향으로 깊이 30μm까지 영역의 탄소(C)의 탈탄율(α)이 14~35%일 수 있다.According to one embodiment of the present invention, the decarburization rate (α) of carbon (C) in the area from the interface between the base steel sheet and the plating layer to a depth of 30 μm in the thickness direction may be 14 to 35%.
도 3은 본 발명의 일 실시예에 따른 도금강판에서, 계면으로부터 두께 방향으로의 탈탄율(α) 프로파일을 모식적으로 나타낸 것이다. 도 3에서, 탈탄율(α)은 도금강판의 탄소를 글로우 방전 분광 분석기(GDS)로 측정한 결과로부터 얻어질 수 있다. 도면에서 y축은 공칭 탄소 함량(C0)에 대한 해당 위치의 탄소 함량의 비율(%)을 나타내고, x축은 소지강판과 도금층의 계면으로부터 두께(깊이) 방향으로의 거리(μm)를 의미한다. 도면과 같이, x축 방향으로 상기 계면으로부터 소지강판 두께 방향으로의 깊이 0~30μm의 길이에 대응되는 가로변과, y축 방향으로 0~100%의 길이에 대응되는 세로변을 가지는 사각형을 그릴 수 있다. 여기서, 상기 사각형에서 공칭 탄소 함량(C0)에 대한 해당 깊이의 탄소 함량의 비율을 나타내는 탄소 프로파일 곡선을 나타내어, 상기 사각형의 전체 면적에 대한 사각형 내 탄소 프로파일 곡선 위쪽 영역의 면적의 비율(%)을 탈탄율(α)로 정의할 수 있다.Figure 3 schematically shows the decarburization rate (α) profile from the interface to the thickness direction in a plated steel sheet according to an embodiment of the present invention. In Figure 3, the decarburization rate (α) can be obtained from the results of measuring the carbon of the plated steel sheet using a glow discharge spectrometer (GDS). In the drawing, the y-axis represents the ratio (%) of the carbon content at the corresponding position to the nominal carbon content (C 0 ), and the x-axis represents the distance (μm) in the thickness (depth) direction from the interface of the base steel plate and the plating layer. As shown in the drawing, a rectangle can be drawn with a horizontal side corresponding to a length of 0 to 30 μm in depth from the interface to the base steel sheet thickness direction in the x-axis direction, and a vertical side corresponding to a length of 0 to 100% in the y-axis direction. there is. wherein the carbon profile curve represents the ratio of the carbon content at that depth to the nominal carbon content (C 0 ) in the square, resulting in the ratio (%) of the area above the carbon profile curve within the square to the total area of the square. Can be defined as the decarburization rate (α).
다시 말해서, 본 발명의 탈탄율(α)은 소지강판과 도금층의 계면으로부터 두께(깊이) 방향으로의 거리(μm)를 가로축으로 하고, 공칭 탄소 함량(C0)에 대한 해당 위치의 탄소 함량의 비율(%)을 세로축으로 하는 사각형에서, 상기 사각형의 전체 면적에 대한 탄소 프로파일 곡선 위쪽 영역의 면적의 비율(%)을 의미한다.In other words, the decarburization rate (α) of the present invention has the distance (μm) in the thickness (depth) direction from the interface between the base steel sheet and the plating layer as the abscissa, and is calculated as the ratio of the carbon content at that position to the nominal carbon content (C 0 ). In a rectangle with ratio (%) as the vertical axis, it means the ratio (%) of the area above the carbon profile curve to the total area of the rectangle.
상기 계면으로부터 두께 방향으로 깊이 30μm까지 영역의 탄소(C) 탈탄율(α)이 14% 미만이면, 소지강판의 탄소 농화도가 열간 성형 후 부재에서 경도를 지나치게 높이므로 굽힘성 개선 효과가 현저히 감소될 수 있다. 반면, 탈탄율이 35%를 초과하면 소지강판 표층의 탄소량 감소로, 부재에서의 마르텐사이트 경도가 현저하게 감소하게 되어 부재의 내피로특성이 열위해지는 문제가 있을 수 있다. If the carbon (C) decarburization rate (α) in the area from the interface to a depth of 30 μm in the thickness direction is less than 14%, the carbon concentration of the base steel plate excessively increases the hardness in the member after hot forming, so the bendability improvement effect is significantly reduced. It can be. On the other hand, if the decarburization rate exceeds 35%, the amount of carbon in the surface layer of the base steel sheet decreases, and the martensite hardness in the member significantly decreases, which may cause the member to have inferior fatigue resistance properties.
본 발명의 한가지 실시예에 따르면, 소지강판과 도금층의 계면으로부터 두께 방향으로 깊이 30.0μm까지 영역의 탄소(C)의 탈탄율(α)이 14.0~35.0%일 수 있다.According to one embodiment of the present invention, the decarburization rate (α) of carbon (C) in the area from the interface between the base steel sheet and the plating layer to a depth of 30.0 μm in the thickness direction may be 14.0 to 35.0%.
본 발명의 다른 한가지 실시예에 따른 도금강판에서는, 소지강판과 도금층의 계면으로부터 두께 방향으로 1.5μm 초과, 6μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 50%인 지점이 존재할 수 있다. In the plated steel sheet according to another embodiment of the present invention, the carbon (C) content is 50% of the nominal carbon content (C 0 ) at a depth of more than 1.5 μm and less than 6 μm in the thickness direction from the interface between the base steel sheet and the plating layer. This can exist.
상기 계면으로부터 두께 방향으로 깊이 1.5μm 초과 내지 6μm 미만인 깊이에서, 공칭 탄소 함량(C0)에 따른 탄소(C) 함량의 비율을 제어하는 것은 내피로특성과 내충돌성을 동시에 확보하기 위한 것이다. 해당 범위의 깊이에, 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 50%인 지점이 존재할 경우, 내충돌성과 내피로특성을 동시에 확보하기에 유리하나, 50%인 지점이 6μm 이상의 깊이에 존재하는 경우 과도한 탈탄에 따른 내피로특성이 열화될 수 있다. 한편, 50%인 지점이 1.5μm 이하의 깊이에 존재하는 경우, 탈탄이 부족하여 목적하는 굽힘성을 확보하기에 어려움이 있을 수 있다.Controlling the ratio of carbon (C) content according to the nominal carbon content (C 0 ) at a depth of more than 1.5 μm to less than 6 μm in the thickness direction from the interface is to simultaneously secure fatigue resistance and crash resistance. In the depth of the range, if there is a point where the carbon (C) content is 50% of the nominal carbon content (C 0 ), it is advantageous to secure both crash resistance and fatigue resistance, but the 50% point is 6 μm or more. If present at depth, fatigue resistance may be deteriorated due to excessive decarburization. On the other hand, if the 50% point exists at a depth of 1.5 μm or less, there may be difficulty in securing the desired bendability due to insufficient decarburization.
본 발명의 다른 한가지 실시예에 따른 도금강판에서는, 소지강판과 도금층의 계면으로부터 두께 방향으로 1.50μm 초과, 6.0μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 50.0%인 지점이 존재할 수 있다. In the plated steel sheet according to another embodiment of the present invention, the carbon (C) content at a depth of more than 1.50 μm and less than 6.0 μm in the thickness direction from the interface between the base steel sheet and the plating layer is 50.0% of the nominal carbon content (C 0 ). Branches may exist.
또한, 본 발명의 한가지 실시예에서는 소지강판과 도금층의 계면으로부터 두께 방향으로 6μm 초과, 15μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 80%인 지점이 존재할 수 있다.In addition, in one embodiment of the present invention, there may be a point where the carbon (C) content is 80% of the nominal carbon content (C 0 ) at a depth of more than 6 μm and less than 15 μm in the thickness direction from the interface between the base steel plate and the plating layer.
상기 계면으로부터 두께 방향으로 6μm 초과 내지 15μm 미만인 깊이에 상기 공칭 탄소 함량(C0)에 따른 탄소(C) 함량의 비율이 80%인 지점이 존재할 경우, 적정한 굽힘성 확보 및 과도한 내피로특성 열화 억제에 유리할 수 있다. 한편, 80%인 지점이 15μm 이상의 깊이에 존재하는 경우, 과도한 탈탄에 의해 내피로특성이 저하될 수 있으며, 80%인 지점이 6μm 이하의 깊이에 존재하는 경우, 탈탄이 부족하여 목적하는 굽힘성을 확보하기 어려울 수 있다.If there is a point where the ratio of carbon (C) content according to the nominal carbon content (C 0 ) is 80% at a depth of more than 6 μm to less than 15 μm in the thickness direction from the interface, appropriate bendability is secured and excessive fatigue resistance deterioration is suppressed. can be advantageous. On the other hand, if the 80% point is at a depth of 15μm or more, the fatigue resistance may be reduced due to excessive decarburization, and if the 80% point is at a depth of 6μm or less, the desired bendability may be lost due to insufficient decarburization. may be difficult to secure.
본 발명의 한가지 실시예에서는 소지강판과 도금층의 계면으로부터 두께 방향으로 6.0μm 초과, 15.0μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 80.0%인 지점이 존재할 수 있다.In one embodiment of the present invention, there may be a point where the carbon (C) content is 80.0% of the nominal carbon content (C 0 ) at a depth of more than 6.0 μm and less than 15.0 μm in the thickness direction from the interface between the base steel plate and the plating layer.
본 발명의 한가지 실시예에서는 하기 관계식 1에서 정의되는 R 값이 1.2 이상이고, 하기 관계식 2에서 정의되는 B 값이 0.008 이상일 수 있다.In one embodiment of the present invention, the R value defined in equation 1 below may be 1.2 or more, and the B value defined in equation 2 below may be 0.008 or more.
본 발명의 한가지 실시예에서는 하기 관계식 1에서 정의되는 R 값이 1.20 이상이고, 하기 관계식 2에서 정의되는 B 값이 0.0080 이상일 수 있다.In one embodiment of the present invention, the R value defined in equation 1 below may be 1.20 or more, and the B value defined in equation 2 below may be 0.0080 or more.
상기 소지강판 내에 Sb 농화층이 형성되면, 소둔로 내 해리된 산소가 소지강판 내부로 침투하기 어려워 탈탄을 어렵게 하는 방어막 역할을 수행할 수 있다. 본 발명에서는, 두께 방향 깊이에 따른 Sb 함량을 제어함으로써 탈탄율을 적절히 제어할 수 있음을 확인하고, 본 발명에서는 하기 관계식 1 및 2를 제안한다. When the Sb enriched layer is formed in the base steel sheet, it is difficult for oxygen dissociated in the annealing furnace to penetrate into the base steel sheet, thereby serving as a shield that makes decarburization difficult. In the present invention, it has been confirmed that the decarburization rate can be appropriately controlled by controlling the Sb content according to the thickness direction depth, and the present invention proposes the following relational equations 1 and 2.
[관계식 1]
Figure PCTKR2023012157-appb-img-000005
[Relationship 1]
Figure PCTKR2023012157-appb-img-000005
[관계식 2]
Figure PCTKR2023012157-appb-img-000006
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000006
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지강판의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is μm.)
도 4는 본 발명의 일 실시예에 따른 도금강판의 Sb 농화층 프로파일을 모식적으로 나타낸 것이다. 도 4에는 상기 관계식 2의 B 값에 해당하는 면적을 색칠 부분으로 나타내었고, 전술한 면적은 Sbcoat를 측정한 지점과 Sbmax를 측정한 지점 사이의 거리를 나타내는 Δt에 따른 Sb 농화 정도를 나타낼 수 있다.Figure 4 schematically shows the Sb enriched layer profile of a coated steel sheet according to an embodiment of the present invention. In Figure 4, the area corresponding to the B value of relational equation 2 is shown as a colored part, and the above-mentioned area represents the degree of Sb enrichment according to Δt, which represents the distance between the point where Sb coat was measured and the point where Sb max was measured. You can.
상기 관계식 1에서 정의되는 R 값이 1.2 미만이거나, 상기 관계식 2에서 정의되는 B 값이 0.008 미만일 경우, 탈탄이 과도하게 발생하여 도금강판에서의 탈탄율이 지나치게 높아지게 되고, 열간 성형 이후 부재의 표층 경도가 크게 감소하여 부재의 내피로특성이 열화될 우려가 있다. If the R value defined in equation 1 is less than 1.2 or the B value defined in equation 2 is less than 0.008, excessive decarburization occurs, causing the decarburization rate in the plated steel sheet to become excessively high, and the surface hardness of the member after hot forming There is a risk that the fatigue resistance of the member may deteriorate due to a significant decrease.
본 발명의 한가지 실시예에서는 관계식 1에서 정의되는 R 값을 1.5 이상으로 제한할 수 있다. 또한, 본 발명의 다른 한가지 실시예에서는 상기 관계식 2에서 정의되는 B 값을 0.02 이상으로 제한할 수 있다. 다만, R 값이 과도하게 높거나, B 값이 과도하게 높을 경우에는 표면의 탄소가 거의 제거되지 않아, 열간 성형 이후 부재의 표층 경도가 과도하게 높아져 표층부의 굽힘성이 저하될 수 있다. 따라서, 본 발명의 한가지 실시예로, R 값의 상한을 6.5로 제한할 수 있다. 또한, 본 발명의 한가지 실시예로, B 값의 상한을 0.15으로 제한할 수 있다.In one embodiment of the present invention, the R value defined in Equation 1 may be limited to 1.5 or more. Additionally, in another embodiment of the present invention, the B value defined in Equation 2 above may be limited to 0.02 or more. However, if the R value is excessively high or the B value is excessively high, almost no surface carbon is removed, and the surface layer hardness of the member may increase excessively after hot forming, resulting in a decrease in the bendability of the surface layer portion. Therefore, in one embodiment of the present invention, the upper limit of the R value can be limited to 6.5. Additionally, in one embodiment of the present invention, the upper limit of the B value may be limited to 0.15.
본 발명의 한가지 실시예에서는 관계식 1에서 정의되는 R 값을 1.50 이상으로 제한할 수 있다. 또한, 본 발명의 다른 한가지 실시예에서는 상기 관계식 2에서 정의되는 B 값을 0.020 이상으로 제한할 수 있다. 다만, R 값이 과도하게 높거나, B 값이 과도하게 높을 경우에는 표면의 탄소가 거의 제거되지 않아, 열간 성형 이후 부재의 표층 경도가 과도하게 높아져 표층부의 굽힘성이 저하될 수 있다. 따라서, 본 발명의 한가지 실시예로, R 값의 상한을 6.50로 제한할 수 있다. 또한, 본 발명의 한가지 실시예로, B 값의 상한을 0.150으로 제한할 수 있다.In one embodiment of the present invention, the R value defined in Equation 1 may be limited to 1.50 or more. Additionally, in another embodiment of the present invention, the B value defined in Equation 2 above may be limited to 0.020 or more. However, if the R value is excessively high or the B value is excessively high, almost no surface carbon is removed, and the surface layer hardness of the member may increase excessively after hot forming, resulting in a decrease in the bendability of the surface layer portion. Therefore, in one embodiment of the present invention, the upper limit of the R value can be limited to 6.50. Additionally, in one embodiment of the present invention, the upper limit of the B value may be limited to 0.150.
상술한 바와 같이, 도금강판에서 R 값과 B 값을 제안하는 범위로 제어함으로써 부재의 R 값과 B 값을 적절한 범위로 제어할 수 있으며, 그에 따라 수소의 침입을 효과적으로 억제할 수 있다.As described above, by controlling the R value and B value of the plated steel sheet to the suggested range, the R value and B value of the member can be controlled to an appropriate range, thereby effectively suppressing the intrusion of hydrogen.
본 발명의 또 한가지 실시예에 따르면, 도금강판은 소지강판과 도금층의 계면으로부터 두께 방향으로 깊이 10μm까지 영역이 페라이트를 주상으로 하고, 1면적% 이상의 펄라이트를 포함하는 미세조직을 가질 수 있다. 본 발명에서는 미세조직 전체 분율에서 50면적% 이상인 상을 주상으로 간주할 수 있다.According to another embodiment of the present invention, the plated steel sheet may have a microstructure containing ferrite as the main phase and more than 1 area% of pearlite in an area from the interface between the base steel sheet and the plating layer to a depth of 10 μm in the thickness direction. In the present invention, a phase accounting for more than 50 area% of the total microstructure fraction can be regarded as the main phase.
본 발명의 도금강판은 소지강판과 도금층의 계면으로부터 두께 방향으로 깊이 10μm까지 영역의 페라이트의 분율이 부족할 경우, 부재의 내피로특성이 열위될 수 있다. In the plated steel sheet of the present invention, if the ferrite fraction in the area from the interface between the base steel sheet and the plating layer to a depth of 10 μm in the thickness direction is insufficient, the fatigue resistance characteristics of the member may be inferior.
상기 소지강판과 도금층의 계면으로부터 두께(깊이) 방향으로 거리 10μm까지의 영역에서 펄라이트는 열간 성형을 위한 열처리 시, 도금층 직하 조직에 탄소를 제공하여 표층부 경도가 열화되는 것을 막는 역할을 할 수 있다. 따라서, 본 발명에서는 펄라이트를 1면적% 이상 포함할 수 있다.In the area up to 10 μm in the thickness (depth) direction from the interface between the base steel sheet and the plating layer, pearlite provides carbon to the structure directly under the plating layer during heat treatment for hot forming, thereby preventing the hardness of the surface layer from deteriorating. It can play a role. Therefore, in the present invention, pearlite may be included in an amount of 1 area% or more.
한편, 펄라이트가 1면적% 미만이면 열간 성형 후 표층부 경도가 과도하게 감소하여 경도 연화율이 높아질 수 있으며, 부재의 내피로특성이 열위되는 문제가 발생할 수 있다.On the other hand, if pearlite is less than 1 area%, the hardness of the surface layer may decrease excessively after hot forming, which may increase the hardness softening rate and cause the problem of inferior fatigue resistance of the member.
본 발명의 다른 실시예에 따르면, 소지강판과 도금층의 계면으로부터 두께 방향으로 깊이 10.0μm까지의 영역은 페라이트를 주상으로 하고, 1.0면적% 이상의 펄라이트를 포함할 수 있다.According to another embodiment of the present invention, the area from the interface between the base steel sheet and the plating layer to a depth of 10.0 μm in the thickness direction may have ferrite as the main phase and contain pearlite in an amount of 1.0 area% or more.
이하에서는, 본 발명의 소지강판의 조성에 대해 자세히 설명한다.Below, the composition of the base steel sheet of the present invention will be described in detail.
본 발명의 한가지 실시예에 따르는 소지강판은 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함할 수 있다.The base steel plate according to one embodiment of the present invention may include carbon (C): 0.06 to 0.5% and antimony (Sb): 0.01 to 0.1% by weight.
본 발명의 한가지 실시예에 따르는 소지강판은 중량%로, 탄소(C): 0.060~0.50%, 안티몬(Sb): 0.010~0.10%를 포함할 수 있다.The base steel plate according to one embodiment of the present invention may include carbon (C): 0.060 to 0.50% and antimony (Sb): 0.010 to 0.10% by weight.
본 발명에서 특별히 달리 언급하지 않는 한 각 원소의 함량을 표시하는 %는 중량을 기준으로 한다.In the present invention, unless otherwise specified, the % indicating the content of each element is based on weight.
탄소(C): 0.06~0.5%Carbon (C): 0.06-0.5%
탄소(C)는 열간 성형 부재의 강도를 향상시키고 경화능을 향상시키는 원소로써 강도 조절을 위해 필수적인 원소로 적정하게 첨가되어야 한다. 탄소(C) 함량이 0.06% 미만일 경우, 경화능이 낮아 냉각속도 감소 시, 충분한 마르텐사이트를 확보하지 못하고, 페라이트 생성으로 원하는 강도를 확보하기 어려울 수 있다. 본 발명의 한가지 실시예에서는 탄소(C) 함량이 0.1% 이상일 수 있다. 반면, 그 함량이 0.5%를 초과할 경우, 강도가 과도하게 상승되고 취성을 유발 및 용접성이 열위해질 수 있다. 본 발명의 한가지 실시예에서는 상기 탄소(C) 함량의 상한이 0.45%일 수 있다.Carbon (C) is an element that improves the strength of hot-formed members and improves hardenability. It is an essential element to control strength and must be added appropriately. If the carbon (C) content is less than 0.06%, hardenability is low, so when the cooling rate is reduced, sufficient martensite cannot be secured, and it may be difficult to secure the desired strength due to the formation of ferrite. In one embodiment of the present invention, the carbon (C) content may be 0.1% or more. On the other hand, if the content exceeds 0.5%, the strength may increase excessively, cause brittleness, and weldability may be poor. In one embodiment of the present invention, the upper limit of the carbon (C) content may be 0.45%.
본 발명의 다른 실시예에 따르면, 탄소(C)는 0.060~0.50%를 포함할 수 있다. According to another embodiment of the present invention, carbon (C) may contain 0.060 to 0.50%.
본 발명의 다른 실시예에 따르면, 탄소(C)는 0.10% 이상일 수 있다. According to another embodiment of the present invention, carbon (C) may be 0.10% or more.
본 발명의 다른 실시예에 따르면 상한이 0.450%일 수 있다.According to another embodiment of the present invention, the upper limit may be 0.450%.
안티몬(Sb): 0.01~0.1%Antimony (Sb): 0.01~0.1%
안티몬(Sb)은 소지강판의 내에 농화됨으로써 내부산화 소둔 적용 시, 빠져나가는 탄소량을 제어하여, 부재에서의 과도한 경도 하락을 막아주는 역할을 할 수 있다. 안티몬(Sb)의 함량이 0.01% 미만이면 도금층과 소지강판 계면에 충분한 농화층이 형성되지 않아 탈탄이 과도하게 일어남으로써 과도한 표층 경도 하락으로 내피로특성이 열위될 수 있다. 본 발명의 한가지 실시예에 따르면 상기 안티몬(sb)의 하한은 0.02%일 수 있다. 반면, 그 함량이 0.1%를 초과하게 되면 입계에 안티몬(Sb)이 과다하게 석출되어 응력 발생 시, 입계 파괴를 유발하여 재질이 열화될 수 있다. 한가지 실시예에 따를 경우에 상기 안티몬(Sb) 함량의 상한은 0.08%일 수 있다.Antimony (Sb) can play a role in controlling the amount of carbon escaping when internal oxidation annealing is applied by concentrating within the base steel sheet and preventing excessive decline in hardness in the member. If the antimony (Sb) content is less than 0.01%, a sufficient thickening layer is not formed at the interface between the plating layer and the base steel plate, resulting in excessive decarburization, which may result in an excessive decrease in surface hardness and poor fatigue resistance properties. According to one embodiment of the present invention, the lower limit of antimony (sb) may be 0.02%. On the other hand, if the content exceeds 0.1%, excessive antimony (Sb) is precipitated at the grain boundaries, which may cause grain boundary destruction when stress occurs, thereby deteriorating the material. According to one embodiment, the upper limit of the antimony (Sb) content may be 0.08%.
본 발명의 다른 실시예에 따르면, 안티몬(Sb)은 0.010~0.10%를 포함할 수 있다. According to another embodiment of the present invention, antimony (Sb) may contain 0.010 to 0.10%.
본 발명의 다른 실시예에 따르면, 안티몬(Sb)은 0.020% 이상일 수 있다. According to another embodiment of the present invention, antimony (Sb) may be 0.020% or more.
본 발명의 다른 실시예에 따르면 그 상한은 0.080%일 수 있다. According to another embodiment of the present invention, the upper limit may be 0.080%.
본 발명의 열간 성형용 도금강판에 적용되는 소지강판의 첨가원소로서, 통상 첨가될 수 있는 원소라면 특별히 그 종류와 함량을 제한하지 아니한다. 다만, 본 발명의 한가지 실시예에 따라 소지강판에 첨가될 수 있는 원소들의 비제한적인 예를 든다면 실리콘(Si), 망간(Mn), 몰리브덴(Mo), 인(P), 황(S), 알루미늄(Al), 크롬(Cr), 질소(N), 티타늄(Ti), 보론(B), 구리(Cu), 니켈(Ni), 바나듐(V), 칼슘(Ca), 니오븀(Nb), 주석(Sn), 텅스텐(W), 마그네슘(Mg), 코발트(Co), 비소(As), 지르코늄(Zr), 비스무트(Bi), 희토류 원소(REM)가 있으며, 이들 중 1종 이상을 더 포함할 수 있다. As an added element to the base steel sheet applied to the plated steel sheet for hot forming of the present invention, the type and content are not particularly limited as long as it is an element that can be added normally. However, non-limiting examples of elements that can be added to the base steel sheet according to one embodiment of the present invention include silicon (Si), manganese (Mn), molybdenum (Mo), phosphorus (P), and sulfur (S). , aluminum (Al), chromium (Cr), nitrogen (N), titanium (Ti), boron (B), copper (Cu), nickel (Ni), vanadium (V), calcium (Ca), niobium (Nb). , tin (Sn), tungsten (W), magnesium (Mg), cobalt (Co), arsenic (As), zirconium (Zr), bismuth (Bi), and rare earth elements (REM), one or more of these More may be included.
본 발명의 한가지 실시예에 따르면, 소지강판은 중량%로, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1.0% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1.00% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함할 수 있다. According to one embodiment of the present invention, the base steel plate contains, in weight percent, silicon (Si): 0.001 to 2%, manganese (Mn): 0.1 to 4%, molybdenum (Mo): 1.0% or less, phosphorus (P): 0.05% or less, Sulfur (S): 0.02% or less, Aluminum (Al): 0.001 to 1%, Chromium (Cr): 1.00% or less, Nitrogen (N): 0.02% or less, Titanium (Ti): 0.1% or less, Boron (B): 0.01% or less, may include remaining iron (Fe) and impurities.
실리콘(Si): 0.001~2%Silicon (Si): 0.001~2%
실리콘(Si)은 제강에서 탈산제로 첨가될 수 있다. 또한, 고용강화 원소이자 탄화물 생성 억제 원소로써 내부 조직 균일화에 효과적일 뿐만 아니라, 열간 성형 부재의 강도 상승에 기여하며 재질 균일화에 효과적인 원소로써 첨가된다. 다만, 그 함량이 0.001% 미만에서는 상기 효과를 기대할 수 없고, 실리콘(Si)의 함량이 2% 초과하게 되면 소둔 중 강판 표면에 생성되는 과도한 Si 산화물로 인하여 도금성이 크게 저하될 수 있다. 본 발명의 한가지 실시예에 따르면 실리콘(Si) 함량의 하한은 0.005%일 수 있으며, 경우에 따라 0.01%일 수 있다. 또한, 본 발명의 일 실시예에 따르면 실리콘(Si) 함량의 상한은 0.7%일 수 있으며, 경우에 따라서는 0.65%일 수 있다.Silicon (Si) can be added as a deoxidizer in steelmaking. In addition, as a solid solution strengthening element and an element that suppresses carbide formation, it is not only effective in uniforming the internal structure, but also contributes to increasing the strength of hot-formed members and is added as an effective element in material uniformity. However, if the content is less than 0.001%, the above effect cannot be expected, and if the silicon (Si) content exceeds 2%, the plating property may be greatly reduced due to excessive Si oxide generated on the surface of the steel sheet during annealing. According to one embodiment of the present invention, the lower limit of the silicon (Si) content may be 0.005%, and in some cases, 0.01%. Additionally, according to one embodiment of the present invention, the upper limit of the silicon (Si) content may be 0.7%, and in some cases, 0.65%.
본 발명의 다른 실시예에 따르면, 실리콘(Si)은 0.001~2.0%를 포함할 수 있다. According to another embodiment of the present invention, silicon (Si) may contain 0.001 to 2.0%.
본 발명의 다른 실시예에 따르면, 실리콘(Si)은 0.0050% 이상일 수 있다. According to another embodiment of the present invention, silicon (Si) may be 0.0050% or more.
본 발명의 다른 실시예에 따르면 상한이~ 0.70%일 수 있다. According to another embodiment of the present invention, the upper limit may be ~0.70%.
본 발명의 다른 실시예에 따르면, 실리콘(Si)은 0.010% 이상일 수 있다. According to another embodiment of the present invention, silicon (Si) may be 0.010% or more.
본 발명의 다른 실시예에 따르면 상한이 0.650%일 수 있다. According to another embodiment of the present invention, the upper limit may be 0.650%.
망간(Mn): 0.1~4%Manganese (Mn): 0.1~4%
망간(Mn)은 고용강화 효과로 인하여 목적하는 강도를 확보할 수 있을 뿐만 아니라 경화능 향상을 통하여 열간 성형 시, 페라이트 형성을 억제하기 위하여 첨가될 필요가 있다. 망간(Mn) 함량이 0.1% 미만일 경우, 충분한 경화능 효과를 얻기 힘들고 부족한 경화능을 위해서 다른 고가의 합금원소가 과다하게 필요하여 제조원가가 크게 상승하는 문제가 발생할 수 있다. 본 발명의 일 실시예에 따르면 망간(Mn)을 0.5% 이상 포함할 수 있으며, 또 다른 실시예로는 0.8% 이상 포함할 수 있다. 다만, 그 함량이 4%를 초과하면 미세조직 압연방향으로 배열된 밴드(band)성 조직이 심화되어 내부 조직의 불균일성을 유발하게 되고 이에 따른 내충돌성을 열위시킬 수 있다. 본 발명의 한가지 실시예에서는 망간(Mn) 함량의 상한이 3.5%일 수 있다.Manganese (Mn) needs to be added to not only secure the desired strength due to the solid solution strengthening effect, but also to suppress ferrite formation during hot forming by improving hardenability. If the manganese (Mn) content is less than 0.1%, it is difficult to obtain sufficient hardenability effect, and other expensive alloy elements are excessively required for insufficient hardenability, which may lead to a significant increase in manufacturing cost. According to one embodiment of the present invention, it may contain 0.5% or more of manganese (Mn), and in another embodiment, it may contain 0.8% or more. However, if the content exceeds 4%, the band-like structure arranged in the microstructure rolling direction becomes deeper, causing non-uniformity of the internal structure, which may deteriorate the collision resistance. In one embodiment of the present invention, the upper limit of the manganese (Mn) content may be 3.5%.
본 발명의 다른 실시예에 따르면, 망간(Mn)은 0.010~4.0%를 포함할 수 있다. According to another embodiment of the present invention, manganese (Mn) may contain 0.010 to 4.0%.
본 발명의 다른 실시예에 따르면, 망간(Mn)은 0.050~4.0%를 포함할 수 있다. According to another embodiment of the present invention, manganese (Mn) may contain 0.050 to 4.0%.
본 발명의 다른 실시예에 따르면, 망간(Mn)은 0.080~4.0%를 포함할 수 있다.According to another embodiment of the present invention, manganese (Mn) may contain 0.080 to 4.0%.
본 발명의 다른 실시예에 따르면, 망간(Mn)은 0.050~3.50%를 포함할 수 있다. According to another embodiment of the present invention, manganese (Mn) may contain 0.050 to 3.50%.
본 발명의 다른 실시예에 따르면, 망간(Mn)은 0.080~3.50%를 포함할 수 있다.According to another embodiment of the present invention, manganese (Mn) may contain 0.080 to 3.50%.
몰리브덴(Mo): 1.0% 이하Molybdenum (Mo): 1.0% or less
몰리브덴(Mo)은 결정립을 강화하여 굽힘성을 개선시킬 수 있는 원소로 포함될 수 있다. 다만, 그 함량이 1.0%를 초과하면 원가 제조비용이 크게 상승할 수 있다. 본 발명의 일 실시예에 따르면 몰리브덴(Mo) 함량의 상한은 0.5%일 수 있으며, 경우에 따라서는 0.45%일 수도 있다.Molybdenum (Mo) may be included as an element that can improve bendability by strengthening crystal grains. However, if the content exceeds 1.0%, the manufacturing cost may increase significantly. According to one embodiment of the present invention, the upper limit of molybdenum (Mo) content may be 0.5%, and in some cases, may be 0.45%.
본 발명의 다른 실시예에 따르면, 몰리브덴(Mo)은 1.0% 이하를 포함할 수 있다. 본 발명의 일 실시예에 따르면 몰리브덴(Mo) 함량의 상한은 0.50%일 수 있으며, 경우에 따라서는 0.450%일 수도 있다.According to another embodiment of the present invention, molybdenum (Mo) may contain 1.0% or less. According to one embodiment of the present invention, the upper limit of molybdenum (Mo) content may be 0.50%, and in some cases, may be 0.450%.
인(P): 0.05% 이하Phosphorus (P): 0.05% or less
인(P)은 강 중 불순물로 존재하며, 그 함량이 0.05%를 초과하면 열간 성형 부재의 용접성 및 고온 입계 편석에 따른 재질 물성이 열화될 수 있다. 일 실시예에 따르면, 그 상한을 0.015%로 제한할 수 있다. 한편, 본 발명의 일 실시예에서는 그 함량을 극소량으로 제어하기 위해서 많은 제조비용이 들게 되므로, 그 하한을 0.001%로 제한할 수 있다.Phosphorus (P) exists as an impurity in steel, and if its content exceeds 0.05%, the weldability of hot-formed members and material properties may be deteriorated due to high-temperature grain boundary segregation. According to one embodiment, the upper limit may be limited to 0.015%. Meanwhile, in one embodiment of the present invention, since a lot of manufacturing costs are incurred to control the content to a very small amount, the lower limit can be limited to 0.001%.
본 발명의 다른 실시예에 따르면, 인(P)은 0.050% 이하를 포함할 수 있다. 일 실시예에 따르면, 그 상한을 0.0150%로 제한할 수 있다. 한편, 경우에 따라서는 그 하한을 0.0010%로 제한할 수 있다.According to another embodiment of the present invention, phosphorus (P) may contain 0.050% or less. According to one embodiment, the upper limit may be limited to 0.0150%. Meanwhile, in some cases, the lower limit can be limited to 0.0010%.
황(S): 0.02% 이하Sulfur (S): 0.02% or less
황(S)은 강 중 불순물로서, 부재의 연성, 충격특성 및 용접성을 저해하는 원소이기 때문에 상한을 0.02%로 제한할 수 있다. 본 발명의 일 실시예에서는 그 함량을 극소량으로 제어하기 위해서는 제조비용을 크게 상승시킬 수 있으므로, 그 하한을 0.0001%로 제한할 수 있다.Sulfur (S) is an impurity in steel and is an element that impairs the ductility, impact properties, and weldability of the member, so the upper limit can be limited to 0.02%. In one embodiment of the present invention, controlling the content to a very small amount may significantly increase manufacturing costs, so the lower limit may be limited to 0.0001%.
본 발명의 다른 실시예에 따르면, 황(S)은 0.020% 이하를 포함할 수 있다. 일 실시예에 따르면, 그 하한을 0.00010%로 제한할 수 있다.According to another embodiment of the present invention, sulfur (S) may contain 0.020% or less. According to one embodiment, the lower limit may be limited to 0.00010%.
알루미늄(Al): 0.001~1%Aluminum (Al): 0.001~1%
알루미늄(Al)은 Si과 더불어 제강에서 탈산 작용을 하여 강의 청정도를 높이는 원소이다. 알루미늄(Al) 함량이 0.001% 미만일 경우, 상기 효과를 얻기 어려울 수 있다. 본 발명의 일 실시예에 따르면 알루미늄(Al) 하한은 0.01%일 수 있으며, 경우에 따라 0.02%일 수 있다. 반면, 그 함량이 1%를 초과하게 되면 연주공정 중 형성되는 과다한 AlN 석출물로 인해 고온연성이 저하되어, 슬라브 크랙이 발생하여 제조상 문제를 유발할 수 있다. 일 실시예로는 그 상한을 0.1%로 제한할 수 있으며, 경우에 따라 0.09%로 제한할 수 있다.Aluminum (Al), along with Si, is an element that increases the cleanliness of steel by acting as a deoxidizer in steelmaking. If the aluminum (Al) content is less than 0.001%, it may be difficult to achieve the above effect. According to one embodiment of the present invention, the lower limit of aluminum (Al) may be 0.01%, and in some cases, 0.02%. On the other hand, if the content exceeds 1%, high-temperature ductility is reduced due to excessive AlN precipitates formed during the casting process, and slab cracks may occur, which may cause manufacturing problems. In one embodiment, the upper limit may be limited to 0.1%, and in some cases, it may be limited to 0.09%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.0010~1.0%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.0010 to 1.0%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.010~1.0%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.010 to 1.0%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.020~1.0%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.020 to 1.0%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.010~0.10%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.010 to 0.10%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.010~0.090%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.010 to 0.090%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.020~0.10%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.020 to 0.10%.
본 발명의 다른 실시예에 따르면, 알루미늄(Al)은 0.020~0.090%를 포함할 수 있다. According to another embodiment of the present invention, aluminum (Al) may contain 0.020 to 0.090%.
크롬(Cr): 1% 이하Chromium (Cr): 1% or less
크롬(Cr)은 Mn과 같이, 강의 경화능을 확보하여 열간 성형 후 페라이트 생성을 억제하기 위한 원소로써 첨가될 수 있다. 크롬(Cr) 함량이 1%를 초과하면 첨가량 대비 경화능 향상 효과가 미미할 뿐만 아니라, 조대한 철탄화물이 과다하게 형성되어 응력 작용 시 크랙이 유발되어 재질을 열위하게 할 수 있다. 본 발명의 한가지 실시예에서는 그 상한이 0.8%일 수 있다. 한편, 본 발명의 일 실시예로, 상술한 효과를 효과적으로 확보하기 위하여 그 하한을 0.01%로 제한할 수 있으며, 경우에 따라 0.05%로 제한할 수 있다.Chromium (Cr), like Mn, can be added as an element to secure the hardenability of steel and suppress ferrite formation after hot forming. If the chromium (Cr) content exceeds 1%, not only is the effect of improving hardenability compared to the amount added, but excessive formation of coarse iron carbides can cause cracks under stress, deteriorating the material. In one embodiment of the present invention, the upper limit may be 0.8%. Meanwhile, in one embodiment of the present invention, in order to effectively secure the above-described effect, the lower limit may be limited to 0.01%, and in some cases, may be limited to 0.05%.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 1.0% 이하를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 1.0% or less.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 0.80% 이하를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 0.80% or less.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 0.01~1.0%를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 0.01 to 1.0%.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 0.01~0.8%를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 0.01 to 0.8%.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 0.05~1.0%를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 0.05 to 1.0%.
본 발명의 다른 실시예에 따르면, 크롬(Cr)은 0.05~0.8%를 포함할 수 있다. According to another embodiment of the present invention, chromium (Cr) may contain 0.05 to 0.8%.
질소(N): 0.02% 이하Nitrogen (N): 0.02% or less
질소(N)는 강 중에 불순물로 포함될 수 있다. 질소(N) 함량이 0.02%를 초과하게 되면 첨가된 Al과 같이 AlN을 형성하여, 이에 따른 슬라브 크랙이 발생할 우려가 있다. 한편, 그 함량을 극소량으로 제어하기 위하여 과다한 제조비용이 수반될 수 있으므로, 본 발명의 한가지 실시예에 따라 질소(N)의 하한을 0.001%로 제한할 수 있다.Nitrogen (N) may be included as an impurity in steel. If the nitrogen (N) content exceeds 0.02%, there is a risk that AlN will be formed together with the added Al, resulting in slab cracks. On the other hand, since excessive manufacturing costs may be incurred to control the content to a very small amount, the lower limit of nitrogen (N) may be limited to 0.001% according to one embodiment of the present invention.
본 발명의 다른 실시예에 따르면, 질소(N)는 0.020% 이하를 포함할 수 있다. According to another embodiment of the present invention, nitrogen (N) may contain 0.020% or less.
본 발명의 다른 실시예에 따르면, 질소(N)는 0.0010~0.02%를 포함할 수 있다. According to another embodiment of the present invention, nitrogen (N) may contain 0.0010 to 0.02%.
본 발명의 다른 실시예에 따르면, 질소(N)는 0.0010~0.020%를 포함할 수 있다. According to another embodiment of the present invention, nitrogen (N) may contain 0.0010 to 0.020%.
티타늄(Ti): 0.1% 이하Titanium (Ti): 0.1% or less
티타늄(Ti)은 강에 불순물로 잔존하는 N와 결합하여 TiN을 생성시킴으로써, 경화능 확보를 위한 B가 화합물이 되지 않도록 보호해주는 역할을 할 수 있다. 또한, TiC 석출물 형성을 통하여 석출강화 및 결정립 미세화 효과를 기대할 수 있다. 다만, 그 함량이 0.1% 초과하면 오히려 조대한 TiN이 다량 형성되며 강의 재질을 열위하게 할 수 있다. 본 발명의 한가지 실시예에서는 그 함량의 상한을 0.09%로 제한할 수 있다.Titanium (Ti) combines with N remaining as an impurity in steel to create TiN, thereby protecting B from becoming a compound to ensure hardenability. In addition, precipitation strengthening and grain refinement effects can be expected through the formation of TiC precipitates. However, if the content exceeds 0.1%, a large amount of coarse TiN is formed, which may deteriorate the steel material. In one embodiment of the present invention, the upper limit of the content may be limited to 0.09%.
본 발명의 다른 실시예에 따르면, 티타늄(Ti)은 0.10% 이하를 포함할 수 있다. According to another embodiment of the present invention, titanium (Ti) may contain 0.10% or less.
본 발명의 다른 실시예에 따르면, 티타늄(Ti)은 0.090% 이하를 포함할 수 있다.According to another embodiment of the present invention, titanium (Ti) may contain 0.090% or less.
보론(B): 0.01% 이하Boron (B): 0.01% or less
보론(B)은 경화능을 효과적으로 향상시킬 수 있는 원소로써, 구 오스테나이트 결정립계에 편석되어 불순물인 P 또는 S의 입계편석에 따른 열간 성형 부재의 취성을 억제할 수 있는 원소이다. 한편, 그 함량이 0.01%를 초과하게 되면, Fe23CB6 복합화합물의 형성으로 열간압연 시, 취성을 야기시킬 수 있다. 본 발명의 한가지 실시예에서는 보론(B) 함량의 상한을 0.008%로 제한할 수 있다.Boron (B) is an element that can effectively improve hardenability, and is an element that is segregated at the grain boundaries of old austenite and can suppress the embrittlement of hot-formed members due to grain boundary segregation of impurities P or S. On the other hand, if the content exceeds 0.01%, brittleness may occur during hot rolling due to the formation of Fe 23 CB 6 complex compounds. In one embodiment of the present invention, the upper limit of the boron (B) content may be limited to 0.008%.
본 발명의 다른 실시예에 따르면, 보론(B)은 0.010% 이하를 포함할 수 있다.According to another embodiment of the present invention, boron (B) may contain 0.010% or less.
본 발명의 다른 실시예에 따르면, 보론(B)은 0.0080% 이하를 포함할 수 있다.According to another embodiment of the present invention, boron (B) may contain 0.0080% or less.
더하여, 본 발명의 한가지 실시예로, 구리(Cu): 1% 이하, 니켈(Ni): 1％ 이하, 바나듐(V): 1.0％ 이하, 칼슘(Ca): 0.01％ 이하, 니오븀(Nb): 0.1％ 이하, 주석(Sn): 1％ 이하, 텅스텐(W): 1％ 이하, 마그네슘(Mg): 0.1% 이하, 코발트(Co): 1% 이하, 비소(As): 1% 이하, 지르코늄(Zr): 1% 이하, 비스무트(Bi): 1% 이하, 희토류 원소(REM): 0.3％ 이하 중 1종 이상을 더 포함할 수 있다.In addition, in one embodiment of the present invention, copper (Cu): 1% or less, nickel (Ni): 1% or less, vanadium (V): 1.0% or less, calcium (Ca): 0.01% or less, niobium (Nb) : 0.1% or less, tin (Sn): 1% or less, tungsten (W): 1% or less, magnesium (Mg): 0.1% or less, cobalt (Co): 1% or less, arsenic (As): 1% or less, It may further include one or more of zirconium (Zr): 1% or less, bismuth (Bi): 1% or less, and rare earth elements (REM): 0.3% or less.
더하여, 본 발명의 한가지 실시예로, 구리(Cu): 1.0% 이하, 니켈(Ni): 1.0％ 이하, 바나듐(V): 1.0％ 이하, 칼슘(Ca): 0.010％ 이하, 니오븀(Nb): 0.10％ 이하, 주석(Sn): 1.0％ 이하, 텅스텐(W): 1.0％ 이하, 마그네슘(Mg): 0.10% 이하, 코발트(Co): 1.0% 이하, 비소(As): 1.0% 이하, 지르코늄(Zr): 1.0% 이하, 비스무트(Bi): 1.0% 이하, 희토류 원소(REM): 0.30％ 이하 중 1종 이상을 더 포함할 수 있다.In addition, in one embodiment of the present invention, copper (Cu): 1.0% or less, nickel (Ni): 1.0% or less, vanadium (V): 1.0% or less, calcium (Ca): 0.010% or less, niobium (Nb) : 0.10% or less, tin (Sn): 1.0% or less, tungsten (W): 1.0% or less, magnesium (Mg): 0.10% or less, cobalt (Co): 1.0% or less, arsenic (As): 1.0% or less, It may further include one or more of zirconium (Zr): 1.0% or less, bismuth (Bi): 1.0% or less, and rare earth element (REM): 0.30% or less.
본 발명의 소지강판은, 상술한 조성 이외에 나머지 철(Fe) 및 불가피한 불순물을 포함할 수 있다. 불가피한 불순물은 통상의 제조공정에서 의도되지 않게 혼입될 수 있으므로, 이를 배제할 수는 없다. 이러한 불순물들은 통상의 철강제조분야의 기술자라면 누구라도 알 수 있는 것이기 때문에 그 모든 내용을 특별히 본 명세서에서 언급하지는 않는다.The base steel sheet of the present invention may contain remaining iron (Fe) and inevitable impurities in addition to the composition described above. Since unavoidable impurities may be unintentionally introduced during the normal manufacturing process, they cannot be excluded. Since these impurities are known to anyone skilled in the field of steel manufacturing, all of them are not specifically mentioned in this specification.
본 발명의 한가지 실시예에 따르면, 도금강판의 도금층은 알루미늄 또는 알루미늄계 합금 도금층일 수 있다. 더하여, 일 실시예에 따르면, 상기 도금층은 합금화 알루미늄계 도금층일 수 있다. According to one embodiment of the present invention, the plating layer of the plated steel sheet may be an aluminum or aluminum-based alloy plating layer. In addition, according to one embodiment, the plating layer may be an alloyed aluminum-based plating layer.
또한, 본 발명의 일 실시예로, 상기 도금층에는 Al 외에 Si, Mg, Fe을 포함할 수 있으며, 경우에 따라서는, Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, Zn 등이 포함될 수 있다. 본 발명에서는 도금층의 두께는 특별히 제한하지 않으며, 일반적인 범위 내의 도금층 두께를 가질 수 있다.In addition, in one embodiment of the present invention, the plating layer may include Si, Mg, and Fe in addition to Al, and in some cases, Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, and Sr. , Zn, etc. may be included. In the present invention, the thickness of the plating layer is not particularly limited, and may have a plating layer thickness within a general range.
본 발명의 일 실시예로, 도금층은 중량%로, Si: 5~11%, Fe: 5% 이하, Mg: 5% 이하 중에서 선택되는 1종 또는 2종 이상을 포함하고, 잔부 Al 및 기타 불순물을 포함할 수 있다. 필요에 따라 상술한 조성에 Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, Zn 등의 원소들을 합계로 30% 이하 더 포함할 수 있다.In one embodiment of the present invention, the plating layer contains one or two or more types selected from Si: 5-11%, Fe: 5% or less, and Mg: 5% or less, in weight percent, and the balance is Al and other impurities. may include. If necessary, the above-mentioned composition may further include elements such as Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, and Zn in a total amount of 30% or less.
본 발명의 일 실시예로, 도금층은 중량%로, Si: 5.0~11.0%, Fe: 5.0% 이하, Mg: 5.0% 이하 중에서 선택되는 1종 또는 2종 이상을 포함하고, 잔부 Al 및 기타 불순물을 포함할 수 있다. 필요에 따라 상술한 조성에 Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, Zn 등의 원소들을 합계로 30.0% 이하 더 포함할 수 있다.In one embodiment of the present invention, the plating layer contains one or two or more types selected from Si: 5.0 to 11.0%, Fe: 5.0% or less, and Mg: 5.0% or less, in weight percent, and the balance is Al and other impurities. may include. If necessary, the above-mentioned composition may further include elements such as Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, and Zn in a total amount of 30.0% or less.
이하에서는, 본 발명의 부재에 대해 자세히 설명한다.Below, the elements of the present invention will be described in detail.
본 발명의 한가지 실시예에 따르는 부재는 소지철 및 상기 소지철의 표면에 형성된 도금층을 포함할 수 있다.A member according to one embodiment of the present invention may include base iron and a plating layer formed on the surface of the base iron.
본 발명의 일 측면에 따르는 소지철은 본 발명에서 제안하는 도금강판의 소지강판과 합금조성이 동일하게 적용될 수 있다.The base iron according to one aspect of the present invention may have the same alloy composition as the base steel sheet of the plated steel sheet proposed in the present invention.
또한, 본 발명의 한가지 실시예에 따르면, 상기 도금층은 상기 소지철의 적어도 일면에 형성될 수 있다. 상기 부재의 도금층은 상술한 도금강판의 도금층과 상기 소지강판의 Fe를 비롯한 성분이 확산되어 합금화된 조성을 가질 수 있다. Additionally, according to one embodiment of the present invention, the plating layer may be formed on at least one surface of the base iron. The plating layer of the member may have an alloy composition in which the plating layer of the above-described plated steel sheet and components including Fe of the base steel sheet are diffused.
본 발명의 한가지 실시예에 따르는 부재는 소지철 내에 형성된 안티몬(Sb) 농화층을 포함할 수 있다.A member according to one embodiment of the present invention may include an antimony (Sb) enriched layer formed in the base iron.
본 발명의 Sb 농화층은 글로우 방전 분광 분석기(GDS)을 활용하여 도금층의 어느 한 지점으로부터 소지철 측 두께 방향으로 Sb 함량 변화를 분석함으로써 구분 가능하다. 이에 대해서는, 본 발명에서 제안하는 도금강판에서의 Sb 농화층 구분 방법과 동일하게 적용될 수 있다. 본 발명의 일 실시예에서 안티몬(Sb) 농화층은 상기 소지철과 상기 도금층이 접하는 계면 직하에 형성될 수 있다. 본 발명의 한가지 실시예에 따르면, 본 발명에서 소지철과 도금층의 계면은 Al 함량이 15%인 지점을 의미할 수 있다.The Sb enriched layer of the present invention can be distinguished by analyzing the change in Sb content in the thickness direction of the base iron from any point of the plating layer using a glow discharge spectrometer (GDS). In this regard, the method for classifying the Sb enriched layer in the plated steel sheet proposed in the present invention can be applied in the same way. In one embodiment of the present invention, an antimony (Sb) enriched layer may be formed directly below the interface where the base iron and the plating layer are in contact. According to one embodiment of the present invention, in the present invention, the interface between the base iron and the plating layer may mean a point where the Al content is 15%.
본 발명의 한가지 실시예에 따르는 부재는, 글로우 방전 분광 분석기(GDS)를 이용하여 소지철의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 80% 이하일 수 있다.In the member according to one embodiment of the present invention, when the element content is analyzed in the thickness direction of the base iron using a glow discharge spectrometer (GDS), the antimony (Sb) content in the antimony (Sb) enriched layer is maximum. The carbon (C) content at the depth representing the value (Sb max ) may be 80% or less of the nominal carbon content (C 0 ) of the base iron.
본 발명의 한가지 실시예에 따르는 부재는, 글로우 방전 분광 분석기(GDS)를 이용하여 소지철의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 80.0% 이하일 수 있다.In the member according to one embodiment of the present invention, when the element content is analyzed in the thickness direction of the base iron using a glow discharge spectrometer (GDS), the antimony (Sb) content in the antimony (Sb) enriched layer is maximum. The carbon (C) content at the depth representing the value (Sb max ) may be 80.0% or less of the nominal carbon content (C 0 ) of the base iron.
Sb 농화층 내 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소 함량은 표층 조직의 경도에 영향을 미치며, 굽힘성에 영향을 미친다. 한편, Sb 농화층 내에 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소 함량이 공칭 탄소 함량(C0)의 80%를 초과하면 표층부 경도가 높아져 굽힘성이 열화될 수 있다. 다만, Sb 농화층 내에 Sb 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소 함량이 과도하게 낮을 경우, 표층부의 경도가 부족하여 내피로특성을 확보하기에 어려움이 있을 수 있다. 따라서, 본 발명의 한가지 실시예로, 그 하한을 15%로 제한할 수 있다. 본 발명의 한가지 실시예로, 그 하한을 15.0%로 제한할 수 있다.The carbon content at the depth where the Sb content in the Sb enriched layer reaches its maximum value (Sb max ) affects the hardness of the surface layer structure and bendability. On the other hand, if the carbon content at the depth where the Sb content reaches the maximum value (Sb max ) in the Sb enriched layer exceeds 80% of the nominal carbon content (C 0 ), the hardness of the surface layer may increase and the bendability may deteriorate. However, if the carbon content in the Sb enriched layer at the depth where the Sb content reaches its maximum value (Sb max ) is excessively low, there may be difficulty in securing fatigue resistance characteristics due to insufficient hardness of the surface layer. Therefore, in one embodiment of the present invention, the lower limit can be limited to 15%. In one embodiment of the present invention, the lower limit may be limited to 15.0%.
도 5는 본 발명의 일 실시예에 따른 부재에서, 계면으로부터 두께 방향으로의 Sb 및 C 함량의 프로파일을 모식적으로 나타낸 것이다. 상기 도 5의 x축은 소지철과 도금층의 계면으로부터의 깊이(μm)를 나타내고, y축은 원소의 함량(wt%)을 나타낼 수 있다. 도 5에서 나타난 바와 같이, 공칭 탄소 함량(C0)의 80%는 0.176%이다. 여기서, 공칭 탄소 함량(C0)은 0.22%로서, 앞서 설명한 바와 같이, 소지철의 두께 1/4~3/4 영역에서 글로우 방전 분광 분석기(GDS)를 이용하여 일정 두께(깊이)를 분석하여 얻어질 수 있다. 이 때, Sb 함량이 최대값을 나타내는 깊이에서 탄소의 함량은 공칭 탄소 함량(C0)의 80% 이하인 탄소 함량을 나타내는 것을 확인할 수 있다.Figure 5 schematically shows the profile of Sb and C contents from the interface to the thickness direction in a member according to an embodiment of the present invention. The x-axis of FIG. 5 may represent the depth (μm) from the interface between the base iron and the plating layer, and the y-axis may represent the element content (wt%). As shown in Figure 5, 80% of the nominal carbon content (C 0 ) is 0.176%. Here, the nominal carbon content (C 0 ) is 0.22%, and as previously explained, a certain thickness (depth) is analyzed using a glow discharge spectrometer (GDS) in the 1/4 to 3/4 thickness region of the base iron. can be obtained. At this time, it can be confirmed that at the depth where the Sb content reaches its maximum value, the carbon content is 80% or less of the nominal carbon content (C 0 ).
본 발명의 한가지 실시예에 따르는 부재는 하기 관계식 1에서 정의되는 R 값이 1.5 이상이고, 하기 관계식 2에서 정의되는 B 값이 0.01 이상일 수 있다.The member according to one embodiment of the present invention may have an R value defined in equation 1 below of 1.5 or more, and a B value defined in equation 2 below may be 0.01 or more.
본 발명의 한가지 실시예에 따르는 부재는 하기 관계식 1에서 정의되는 R 값이 1.50 이상이고, 하기 관계식 2에서 정의되는 B 값이 0.010 이상일 수 있다.The member according to one embodiment of the present invention may have an R value defined in equation 1 below of 1.50 or more, and a B value defined in equation 2 below may be 0.010 or more.
[관계식 1]
Figure PCTKR2023012157-appb-img-000007
[Relationship 1]
Figure PCTKR2023012157-appb-img-000007
[관계식 2]
Figure PCTKR2023012157-appb-img-000008
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000008
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지철의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the equation, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base iron. It represents the straight line distance between one points, and the unit is μm.)
열간 성형을 위해 도금강판을 가열하면 Sb 농화층의 Sb 농화 정도가 보다 심화될 수 있다. 열간 성형을 위한 열처리 시, Sb 농화층은 침투하는 확산성 수소를 효과적으로 방어하는 역할을 하며, 확산성 수소는 응력 발생 시, 결정립계 크랙 발생을 촉진하는 원인이 되므로, 이를 저감함으로써 굽힘성이 증가할 수 있다. 즉, 상기 관계식을 만족하지 못할 경우, 구체적으로, 관계식 1에서 정의되는 R 값이 1.5 미만이거나, 관계식 2에서 정의되는 B 값이 0.01 미만일 경우, 열간 성형 중 침투하는 확산성 수소를 충분히 방어하지 못하여 내충돌성이 열위해질 우려가 있다. 본 발명의 한가지 실시예에서 관계식 1에서 정의되는 R 값이 1.7 이상일 수 있다. 또한, 본 발명의 한가지 실시예에서 관계식 2에서 정의되는 B 값이 0.014 이상일 수 있다. 다만, R 값 또는 B 값이 과도하게 높을 경우, 부재 표층의 경도가 과도하게 높아져 굽힘성이 저하될 수 있으므로, 본 발명의 한가지 실시예에서 R 값의 상한을 6.4로 제한할 수 있다. 또한, 본 발명의 한가지 실시예로, B 값의 상한을 0.5로 제한할 수 있다. When the plated steel sheet is heated for hot forming, the degree of Sb enrichment in the Sb enrichment layer may become more severe. During heat treatment for hot forming, the Sb enriched layer effectively protects against infiltrating diffusible hydrogen, and since diffusible hydrogen promotes the occurrence of grain boundary cracks when stress occurs, bendability can be increased by reducing this. You can. That is, if the above relational equation is not satisfied, specifically, if the R value defined in relational equation 1 is less than 1.5 or the B value defined in relational equation 2 is less than 0.01, the diffusive hydrogen penetrating during hot forming is not sufficiently protected. There is a risk that crash resistance will be deteriorated. In one embodiment of the present invention, the R value defined in Equation 1 may be 1.7 or more. Additionally, in one embodiment of the present invention, the B value defined in Equation 2 may be 0.014 or more. However, if the R value or B value is excessively high, the hardness of the surface layer of the member may increase excessively and the bendability may decrease, so in one embodiment of the present invention, the upper limit of the R value may be limited to 6.4. Additionally, in one embodiment of the present invention, the upper limit of the B value may be limited to 0.5.
본 발명의 한가지 실시예에서 관계식 1에서 정의되는 R 값이 1.70 이상일 수 있다. 또한, 본 발명의 한가지 실시예에서 관계식 2에서 정의되는 B 값이 0.0140 이상일 수 있다. 본 발명의 한가지 실시예에서 R 값의 상한을 6.40로 제한할 수 있다. 또한, 본 발명의 한가지 실시예로, B 값의 상한을 0.50로 제한할 수 있다. In one embodiment of the present invention, the R value defined in Equation 1 may be 1.70 or more. Additionally, in one embodiment of the present invention, the B value defined in Equation 2 may be 0.0140 or more. In one embodiment of the present invention, the upper limit of the R value may be limited to 6.40. Additionally, in one embodiment of the present invention, the upper limit of the B value may be limited to 0.50.
본 발명의 일 측면에 따르는 부재는 상기 소지철과 상기 도금층의 계면으로부터 두께 방향으로 깊이 45~100μm의 영역은 연화율(β)이 2~7%일 수 있다.The member according to one aspect of the present invention may have a softening rate (β) of 2 to 7% in a region with a depth of 45 to 100 μm in the thickness direction from the interface between the base iron and the plating layer.
상기 소지철과 상기 도금층의 계면으로부터 두께 방향으로 깊이 45~100μm의 영역은 부재 표층부 경도에 영향이 있으며, 굽힘성에 영향을 미칠 수 있다.An area with a depth of 45 to 100 μm in the thickness direction from the interface between the base iron and the plating layer affects the hardness of the surface layer of the member and may affect bendability.
두께 방향으로 깊이 45~100μm까지 영역의 연화율이 2% 미만이면 표층부의 경도가 지나치게 높아져 굽힘성의 개선 효과가 낮아질 우려가 있다. 반면, 연화율이 7%를 초과하면 표층부의 경도가 지나치게 낮아지므로 내피로특성이 열화되는 문제가 발생할 수 있다.If the softening rate in the area from 45 to 100 μm in the thickness direction is less than 2%, the hardness of the surface layer may become too high, which may reduce the effect of improving bendability. On the other hand, if the softening rate exceeds 7%, the hardness of the surface layer becomes too low, which may cause the problem of deterioration in fatigue resistance properties.
본 발명에서 경도 연화율은 도 6에서 나타낸 바와 같이 측정할 수 있다. 도 6은 본 발명의 일 실시예에 따른 부재에서, 계면으로부터 두께 방향 깊이 45~100μm에서의 경도 연화율(β) 프로파일을 모식적으로 나타낸 것이다. 구체적으로, 비커스 경도(Vickers Hardness)를 측정하되 무게는 1kg를 적용하여 경도를 측정한다. 소지철 내부의 경도를 기준 경도(HO)로 하고, 이때, 기준 경도(HO)는 소지철의 두께 1/5 지점에서 측정할 수 있다. 도 6에서 y축은 기준 경도 값(H0)에 대한 해당 위치의 경도 값(H)의 비율(%)을 나타내고, x축은 계면으로부터 두께 방향으로의 거리(μm)를 의미한다. 도 6에서 볼 수 있듯이 0~100%를 y축의 범위로 하고, 계면으로부터 깊이 45~100μm를 x축의 범위로 한 사각형을 작도하였다. 상기 사각형에서 계면으로부터의 깊이에 따른 경도 값의 비율을 나타내는 경도 프로파일 곡선을 나타내어, 상기 사각형의 전체 면적에 대한 경도 프로파일의 사각형 내 위쪽 영역의 면적의 비율을 경도 연화율(β, %)로 정의할 수 있다. 계면에서 45μm 이내의 범위에서는 1kg를 적용한 비커스 경도(Vickers Hardness)의 압흔 혹은 영향 범위가 도금층 및 외부에 노출될 수 있어 정확한 경도 값을 얻기 힘들기 때문에 본 발명에서는 45~100μm의 깊이에서 경도 프로파일을 작성하고 이를 경도 연화율(β)에 활용하였다.In the present invention, the hardness softening rate can be measured as shown in Figure 6. Figure 6 schematically shows the hardness softening rate (β) profile at a depth of 45 to 100 μm in the thickness direction from the interface in a member according to an embodiment of the present invention. Specifically, Vickers Hardness is measured and hardness is measured by applying a weight of 1 kg. The hardness inside the base iron is taken as the standard hardness (H O ), and at this time, the standard hardness (H O ) can be measured at 1/5 of the thickness of the base iron. In Figure 6, the y-axis represents the ratio (%) of the hardness value (H) at the corresponding position to the reference hardness value (H 0 ), and the x-axis represents the distance (μm) from the interface in the thickness direction. As can be seen in Figure 6, a rectangle was drawn with 0 to 100% as the y-axis range and a depth of 45 to 100 μm from the interface as the x-axis range. In the rectangle, a hardness profile curve representing the ratio of hardness values according to the depth from the interface is shown, and the ratio of the area of the upper area within the rectangle of the hardness profile to the total area of the rectangle is defined as the hardness softening rate (β, %). can do. In the range within 45μm from the interface, the indentation or influence range of the Vickers Hardness applied at 1kg may be exposed to the plating layer and the outside, making it difficult to obtain an accurate hardness value. Therefore, in the present invention, the hardness profile is determined at a depth of 45 to 100μm. It was created and used for the hardness softening rate (β).
다시 말해서, 본 발명의 경도 연화율(β)은 소지강판과 도금층의 계면으로부터 두께(깊이) 방향으로의 거리(μm)를 가로축으로 하고, 기준 경도 값(H0)에 대한 해당 위치의 경도 값(H)의 비율(%)을 세로축으로 하는 사각형에서, 상기 사각형의 전체 면적에 대한 경도 프로파일 곡선 위쪽 영역의 면적의 비율(%)을 의미한다.In other words, the hardness softening rate (β) of the present invention is the distance (μm) in the thickness (depth) direction from the interface between the base steel sheet and the plating layer as the abscissa, and the hardness value at the corresponding position with respect to the reference hardness value (H 0 ). In a rectangle with the ratio (%) of (H) as the vertical axis, it means the ratio (%) of the area above the hardness profile curve to the total area of the rectangle.
본 발명의 일 측면에 따르는 부재는 상기 소지철과 상기 도금층의 계면으로부터 두께 방향으로 깊이 45.0~100.0μm의 영역은 연화율(β)이 2.0~7.0%일 수 있다.The member according to one aspect of the present invention may have a softening rate (β) of 2.0 to 7.0% in a region with a depth of 45.0 to 100.0 μm in the thickness direction from the interface between the base iron and the plating layer.
본 발명의 한가지 실시예에 따르면, 부재는 상기 소지철과 상기 도금층의 계면으로부터 두께 방향으로 깊이 50μm까지 영역은 미세조직으로 5면적% 미만의 페라이트를 포함할 수 있다.According to one embodiment of the present invention, the member may include less than 5 area% of ferrite as a microstructure in a region from the interface between the base iron and the plating layer to a depth of 50 μm in the thickness direction.
상기 소지철과 상기 도금층 계면으로부터 두께 방향으로 깊이 50μm까지 영역의 페라이트는 크랙의 전파를 촉진시키는 원인이 될 수 있다. 즉, 해당 영역에서 페라이트가 5% 이상이면 표층부 응력 발생 시, 상대적으로 연질인 페라이트에 국부적인 응력이 집중되며 크랙 전파를 촉진시켜 굽힘성 및 내피로특성이 열화될 수 있다. Ferrite in an area up to a depth of 50 μm in the thickness direction from the interface between the base iron and the plating layer may cause the propagation of cracks. In other words, if ferrite is more than 5% in the corresponding area, when stress occurs in the surface layer, local stress is concentrated on the relatively soft ferrite, which promotes crack propagation, which may deteriorate bendability and fatigue resistance.
본 발명의 한가지 실시예에 따르는 부재는 상기 소지철과 상기 도금층 계면으로부터 두께 방향으로 깊이 50μm까지 영역은 마르텐사이트를 주상으로 하고, 5면적% 미만의 페라이트, 잔부 상부 및 하부 베이나이트를 포함하는 미세조직을 가질 수 있다. 본 발명에서는 미세조직 전체 분율에서 50% 이상의 면적 분율을 가지는 상을 주상으로 간주할 수 있다.The member according to one embodiment of the present invention has martensite as the main phase in the area from the interface between the base iron and the plating layer to a depth of 50 μm in the thickness direction, and contains less than 5 area% of ferrite and the remaining upper and lower bainite. You can have an organization. In the present invention, a phase having an area fraction of 50% or more of the total microstructure fraction can be regarded as the main phase.
마르텐사이트의 분율이 부족할 경우, 본 발명에서 목적하는 물성이 미흡해질 수 있다. If the martensite fraction is insufficient, the physical properties desired in the present invention may be insufficient.
본 발명의 한가지 실시예에 따르면, 부재는 상기 소지철과 상기 도금층의 계면으로부터 두께 방향으로 깊이 50.0μm까지 영역은 미세조직으로 5.0면적% 미만의 페라이트를 포함할 수 있다.According to one embodiment of the present invention, the member may include less than 5.0 area% of ferrite as a microstructure in a region from the interface between the base iron and the plating layer to a depth of 50.0 μm in the thickness direction.
본 발명의 한가지 실시예에 따르는 부재는 상기 소지철과 상기 도금층 계면으로부터 두께 방향으로 깊이 50.0μm까지 영역은 마르텐사이트를 주상으로 하고, 5.0면적% 미만의 페라이트, 잔부 상부 및 하부 베이나이트를 포함하는 미세조직을 가질 수 있다. 본 발명에서는 미세조직 전체 분율에서 50.0% 이상의 면적 분율을 가지는 상을 주상으로 간주할 수 있다.The member according to one embodiment of the present invention includes martensite as the main phase in the area from the interface between the base iron and the plating layer to a depth of 50.0 μm in the thickness direction, less than 5.0 area% of ferrite, and the remaining upper and lower bainite. It may have a fine structure. In the present invention, a phase having an area fraction of 50.0% or more in the total microstructure fraction can be regarded as the main phase.
이하에서는, 본 발명의 도금강판 제조방법에 대해 자세히 설명한다.Below, the method for manufacturing a plated steel sheet of the present invention will be described in detail.
본 발명의 일 측면에 따르는 도금강판은 상술한 합금조성을 만족하는 냉연강판을 소둔 및 도금하여 제조될 수 있다. 여기서, 냉연강판은 상술한 합금조성을 만족하는 강 슬라브를 재가열, 열간압연, 권취, 냉각 및 냉간압연하여 제조될 수 있다.The plated steel sheet according to one aspect of the present invention can be manufactured by annealing and plating a cold rolled steel sheet satisfying the above-described alloy composition. Here, the cold rolled steel sheet can be manufactured by reheating, hot rolling, coiling, cooling, and cold rolling a steel slab that satisfies the above-described alloy composition.
재가열reheat
본 발명의 한가지 실시예에 따르는 합금조성을 만족하는 강 슬라브를 1050~1300℃의 온도범위로 재가열할 수 있다.Steel slabs satisfying the alloy composition according to one embodiment of the present invention can be reheated to a temperature range of 1050 to 1300°C.
재가열 온도가 1050℃ 미만일 경우, 슬라브 조직이 충분히 균질화되지 않으므로 석출원소를 활용할 경우 재고용 시키기 어려울 수 있다. 반면, 그 온도가 1300℃를 초과할 경우, 과다한 산화층이 형성되어 산화층 제거를 위한 제조비용 증가를 초래하고 열간압연 후 표면 결함이 발생할 가능성이 있다.If the reheating temperature is less than 1050℃, the slab structure is not sufficiently homogenized, so it may be difficult to re-employ when using precipitated elements. On the other hand, if the temperature exceeds 1300°C, an excessive oxidation layer is formed, which increases manufacturing costs for removing the oxide layer and is likely to cause surface defects after hot rolling.
열간압연hot rolling
상기 재가열된 강 슬라브를 800~950℃의 온도범위에서 마무리 압연할 수 있다.The reheated steel slab can be finish rolled at a temperature range of 800 to 950°C.
마무리 압연 온도가 800℃ 미만이면, 이상역 압연이 진행되어 강판 표층부에 페라이트가 도입되며 판형상 제어가 어려울 수 있다. 반면, 그 온도가 950℃를 초과하면 결정립 조대화가 발생할 수 있다.If the finish rolling temperature is less than 800°C, biphasic rolling occurs, ferrite is introduced into the surface layer of the steel sheet, and plate shape control may be difficult. On the other hand, if the temperature exceeds 950°C, grain coarsening may occur.
권취 및 냉각Winding and cooling
상기 압연된 강을 500~700℃의 온도범위에서 권취 및 냉각할 수 있다.The rolled steel can be coiled and cooled in a temperature range of 500 to 700°C.
권취온도가 500℃ 미만이면 권취 시, 장력이 지나치게 높아짐으로 인해 열연 코일의 폭 형상 불량 및 설비 문제를 유발할 수 있다. 반면, 그 온도가 700℃를 초과하면 조대한 탄화물이 과다하게 형성되어 열간 성형 부재의 응력 발생 시, 크랙 발생이 촉진되므로 내충돌성이 떨어지는 문제점이 있을 수 있다. If the coiling temperature is less than 500°C, tension may become excessively high during coiling, which may cause defects in the width shape of the hot rolled coil and equipment problems. On the other hand, if the temperature exceeds 700°C, coarse carbides are excessively formed and crack generation is promoted when stress is generated in the hot-formed member, which may lead to a problem of reduced collision resistance.
냉간압연cold rolling
상기 냉각된 강을 30~80%의 압하율로 냉간압연하여 냉연강판을 제조할 수 있다.A cold rolled steel sheet can be manufactured by cold rolling the cooled steel at a reduction ratio of 30 to 80%.
본 발명에서는 냉간 압하율을 특별히 한정하지는 않지만, 소정의 목표 두께를 얻기 위하여 30~80% 범위 내에서 실시될 수 있다.In the present invention, the cold rolling reduction rate is not specifically limited, but may be implemented within the range of 30 to 80% to obtain a predetermined target thickness.
소둔Annealing
상기 냉연강판을 Ac1~Ac3의 온도범위에서 소둔할 수 있다. The cold rolled steel sheet can be annealed in a temperature range of Ac 1 to Ac 3 .
상기 소둔 온도가 Ac1 미만일 경우, 냉간압연된 조직의 재결정이 충분히 완료되지 않으므로 판 형상이 불량할 수 있으며, 안티몬이 충분히 농화되지 않아 최종 부재에서 발명의 효과를 충분히 발현하기 어려울 수 있다. 반면, 그 온도가 Ac3을 초과할 경우, 소둔로 내 장비 문제를 유발하고, 표면 산화물 형성의 촉진으로 인해 표면에 결함을 유발할 수 있다. 본 발명의 한가지 실시예에 따르면 소둔 온도의 하한은 750℃일 수 있다. 또한, 본 발명의 다른 한가지 실시예에서는 소둔 온도의 상한을 860℃로 제한할 수 있다. If the annealing temperature is less than Ac 1 , recrystallization of the cold rolled structure is not sufficiently completed, so the plate shape may be poor, and antimony may not be sufficiently concentrated, making it difficult to fully demonstrate the effect of the invention in the final member. On the other hand, if the temperature exceeds Ac 3 , it may cause equipment problems in the annealing furnace and cause defects on the surface due to acceleration of surface oxide formation. According to one embodiment of the present invention, the lower limit of the annealing temperature may be 750°C. Additionally, in another embodiment of the present invention, the upper limit of the annealing temperature may be limited to 860°C.
상기 소둔 시, 소둔 시간과 절대 습도의 곱이 10,000~80,000s·g/m3일 수 있다.During the annealing, the product of the annealing time and absolute humidity may be 10,000 to 80,000 s·g/m 3 .
상기 소둔 시, 산화 분위기를 형성하기 위하여 수소 가스, 수소-질소 혼합가스 등을 사용하여 분위기 및 습도를 조절할 수 있으며, 적절한 강판의 탈탄율을 획득하기 위하여 Ac1~Ac3 온도범위에서의 소둔 시간 및 절대 습도를 제어하는 것이 중요하다.During the annealing, the atmosphere and humidity can be adjusted using hydrogen gas, hydrogen-nitrogen mixed gas, etc. to create an oxidizing atmosphere, and the annealing time in the temperature range of Ac 1 to Ac 3 is used to obtain an appropriate decarburization rate of the steel sheet. and it is important to control absolute humidity.
따라서, 상기 소둔 시, 소둔 시간과 절대 습도의 곱이 10,000~80,000s·g/m3일 수 있다.Therefore, during the annealing, the product of the annealing time and the absolute humidity may be 10,000 to 80,000 s·g/m 3 .
소둔 시간과 절대 습도의 곱이 10,000s·g/m3 미만일 경우, 내부 산화에 따른 탈탄 반응이 충분하게 일어나지 않아, 목적하는 탈탄율을 얻기 어려우며, 부재에서의 과도한 탄소 농화로 인하여 내충돌성 개선효과를 기대할 수 없다. 반면, 그 값이 80,000s·g/m3를 초과할 경우, 강판 표면의 과도한 산화로 인하여 표면 산화물이 생성될 수 있으므로, 도금 시, 표면 결함을 유발할 우려가 있다. 본 발명의 한가지 실시예에 따르면 소둔 시간이 100~200초일 수 있다. 또한, 본 발명의 한가지 실시예에 따르면 절대 습도는 100~400g/m3일 수 있다.If the product of annealing time and absolute humidity is less than 10,000 s·g/m 3 , the decarburization reaction due to internal oxidation does not sufficiently occur, making it difficult to obtain the desired decarburization rate, and the impact resistance improvement effect due to excessive carbon concentration in the member. cannot be expected. On the other hand, if the value exceeds 80,000 s·g/m 3 , surface oxide may be generated due to excessive oxidation of the surface of the steel sheet, and there is a risk of causing surface defects during plating. According to one embodiment of the present invention, the annealing time may be 100 to 200 seconds. Additionally, according to one embodiment of the present invention, the absolute humidity may be 100 to 400 g/m 3 .
또한, 강판의 표면 온도 기준으로, 상온에서 500℃까지의 평균 승온 속도를 2.7~10.0℃/s로, 500~700℃ 구간의 평균 승온 속도를 0.5~2.5℃/s로, 700℃에서 소둔 온도까지의 평균 승온 속도를 0.01~0.4℃/s로 제어할 수 있다.In addition, based on the surface temperature of the steel plate, the average temperature increase rate from room temperature to 500℃ is 2.7~10.0℃/s, the average temperature increase rate between 500℃ and 700℃ is 0.5~2.5℃/s, and the annealing temperature at 700℃ The average temperature increase rate can be controlled to 0.01~0.4℃/s.
강판의 표면 온도 기준으로, 상온에서 500℃까지의 평균 승온 속도를 2.7~10.0℃/s로 한정하는 것은 Sb 농화층을 확보하기 위한 것이다. 상온에서 500℃까지의 평균 승온 속도가 2.7~10.0℃/s를 벗어날 경우, 구체적으로, 2.7℃/s 미만이면, 농화층이 충분하게 형성되지 않는 문제점이 있으며, 10℃/s을 초과하면, 급속한 가열에 따른 강판의 폭 방향 온도 불균일도가 높아져 조직 차이 발생 및 라인 트러블 문제가 있을 수 있다. 강판의 표면 온도가 500~700℃인 구간에서는 소지철의 Sb 농화에 영향이 있을 수 있다. 즉, 해당 구간에서의 평균 승온 속도가 0.5~2.5℃/s를 벗어날 경우, Sb 농화층이 충분히 형성되지 않을 우려가 있다. 강판의 표면 온도가 700℃에서 목적하는 소둔 온도까지는 소지철에 Sb 농화층이 충분히 형성되는 온도로, 관계식 1, 2에 부합하는 Sb 농화층 및 강판 표면부 결함 방지를 위하여 평균 승온 속도가 0.01~0.4℃/s인 것이 바람직하다. Based on the surface temperature of the steel plate, the average temperature increase rate from room temperature to 500°C is limited to 2.7~10.0°C/s to secure the Sb enriched layer. If the average temperature increase rate from room temperature to 500°C exceeds 2.7 to 10.0°C/s, specifically, if it is less than 2.7°C/s, there is a problem in which the concentrated layer is not sufficiently formed, and if it exceeds 10°C/s, Due to rapid heating, the temperature unevenness in the width direction of the steel sheet increases, which can lead to tissue differences and line trouble problems. In the section where the surface temperature of the steel plate is 500~700℃, Sb enrichment of base iron may be affected. That is, if the average temperature increase rate in the corresponding section exceeds 0.5 to 2.5°C/s, there is a risk that the Sb enriched layer may not be sufficiently formed. The temperature at which a Sb-enriched layer is sufficiently formed in the base iron is from 700℃ to the desired annealing temperature of the steel sheet. In order to prevent defects in the Sb-enriched layer and the surface of the steel sheet that comply with equations 1 and 2, the average temperature increase rate is 0.01~. It is preferably 0.4°C/s.
도금Plated
상기 소둔된 냉연강판을 도금할 수 있다.The annealed cold rolled steel sheet can be plated.
본 발명의 일 측면에 따르는 도금욕은 알루미늄 또는 알루미늄계 합금일 수 있다. The plating bath according to one aspect of the present invention may be aluminum or an aluminum-based alloy.
본 발명의 한가지 실시예에 따르면, 도금욕 조성으로 Al 외에 Si, Mg, Fe을 포함할 수 있으며, 경우에 따라서는 Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, Zn 등을 포함할 수도 있다. 도금 시, 부착량은 특별히 제한하지 않고, 일반적인 범위 내의 부착량을 가질 수 있다.According to one embodiment of the present invention, the plating bath composition may include Si, Mg, and Fe in addition to Al, and in some cases, Mn, Cr, Cu, Mo, Ni, Sb, Sn, Ti, Ca, Sr, It may also contain Zn and the like. During plating, the adhesion amount is not particularly limited and may be within a general range.
본 발명의 일 실시예로, 도금욕의 조성은 중량%로, Si: 5~11%, Fe: 5% 이하, Mg: 5% 이하 중에서 선택되는 1종 또는 2종 이상을 포함하고, 잔부 Al 및 기타 불순물을 포함할 수 있다.In one embodiment of the present invention, the composition of the plating bath, in weight percent, includes one or two or more selected from among Si: 5-11%, Fe: 5% or less, and Mg: 5% or less, with the balance being Al. and other impurities.
본 발명의 일 실시예에 따르면, 도금 후 합금화 공정을 포함할 수 있으며, 합금화 공정은 특별히 한정하지 않으며, 통상의 조건으로 행할 수 있다.According to one embodiment of the present invention, an alloying process may be included after plating, and the alloying process is not particularly limited and can be performed under normal conditions.
이하에서는, 본 발명의 부재 제조방법에 대해 자세히 설명한다.Below, the member manufacturing method of the present invention will be described in detail.
본 발명의 일 측면에 따르는 부재는 상술한 방법으로 제조되는 도금강판을 블랭크로 제조, 가열, 유지, 성형 및 냉각하여 제조될 수 있다. The member according to one aspect of the present invention can be manufactured by manufacturing, heating, maintaining, forming, and cooling the plated steel sheet manufactured by the above-described method into a blank.
블랭크 제조blank manufacturing
본 발명에서 제안하는 도금강판을 열간 성형을 위한 블랭크로 제조할 수 있다.The plated steel sheet proposed in the present invention can be manufactured as a blank for hot forming.
가열 및 유지Heating and Maintaining
상기 제조된 블랭크를 Ac3~975℃의 온도범위로 가열하고, 10~1000초 유지할 수 있다.The prepared blank can be heated to a temperature range of Ac 3 to 975°C and maintained for 10 to 1000 seconds.
상기 블랭크 가열 온도가 Ac3 미만일 경우, 이상역 구간에 따른 미변태된 페라이트의 존재로 인하여 강도 및 내충돌성을 확보하기 어려울 수 있다. 반면, 가열 온도가 975℃를 초과할 경우, 부재 표면에 과다한 산화물이 생성되어 점용접성의 확보가 어렵고 높은 온도 유지를 위한 제조 비용이 상승할 수 있다. 이후 가열된 블랭크는 상기 온도범위에서 10~1000초의 열처리 체류시간을 가지는 것이 바람직하다. 유지 시간이 10초 미만일 경우, 블랭크 전체에서의 균일한 온도 분포가 힘들어 위치별 재질 편차를 유발할 수 있다. 한편, 유지 시간 1000초를 초과할 경우, 가열 온도 초과 시와 같이 부재 표면에 과다한 산화물 생성 및 상호 확산층이 과도하게 성장하여 점용접성 확보가 어려운 뿐만 아니라 부재의 제조 비용 증가를 유발할 수 있다.When the blank heating temperature is less than Ac 3 , it may be difficult to secure strength and collision resistance due to the presence of untransformed ferrite in the ideal region. On the other hand, if the heating temperature exceeds 975°C, excessive oxides are generated on the surface of the member, making it difficult to secure spot weldability and manufacturing costs for maintaining the high temperature may increase. It is preferable that the subsequently heated blank has a heat treatment residence time of 10 to 1000 seconds in the above temperature range. If the holding time is less than 10 seconds, it is difficult to achieve uniform temperature distribution throughout the blank, which may cause material deviation by location. On the other hand, if the holding time exceeds 1000 seconds, as when the heating temperature is exceeded, excessive oxide is generated on the surface of the member and an interdiffusion layer grows excessively, which not only makes it difficult to secure spot weldability but also causes an increase in the manufacturing cost of the member.
성형 및 냉각Forming and Cooling
상기 가열된 블랭크를 성형 및 냉각할 수 있다.The heated blank can be molded and cooled.
상기 가열된 블랭크를 프레스로 이송하여 20℃/s 이상의 냉각속도로 열간 성형 및 다이퀜칭을 진행하여 최종 부재를 제조할 수 있다. 20℃/s 미만의 냉각속도에서는 냉각 중 페라이트 상이 도입되어 결정립계에 생성될 수 있으며, 이로 인해 강도 및 내충돌성을 열화시킬 수 있다. 본 발명의 한가지 실시예에 따르면 블랭크를 성형한 후 25℃/s 이상으로 냉각할 수 있다.The final member can be manufactured by transferring the heated blank to a press and performing hot forming and die quenching at a cooling rate of 20°C/s or more. At a cooling rate of less than 20°C/s, a ferrite phase may be introduced during cooling and formed at grain boundaries, which may deteriorate strength and collision resistance. According to one embodiment of the present invention, after forming the blank, it can be cooled to 25°C/s or more.
이와 같이 제조된 본 발명의 도금강판은 표층 경도를 일정 수준 이하로 유지할 수 있으며, 열간 성형을 위한 블랭크 제작용 전단 시, 칼날 수명을 일정 수준 이상으로 유지시킬 수 있어 소모되는 비용을 감소시킬 수 있는 효과가 있다.The coated steel sheet of the present invention manufactured in this way can maintain the surface hardness below a certain level and can maintain the blade life above a certain level when shearing for producing a blank for hot forming, thereby reducing the cost. It works.
이와 같이 제조된 본 발명의 부재는 인장강도 및 굽힘각도의 곱이 80,000MPa·° 이상이고, 확산성 수소량이 0.2ppm 이하로, 내피로특성 및 굽힘성이 우수한 특성을 구비할 수 있다.The member of the present invention manufactured in this way has a product of tensile strength and bending angle of 80,000 MPa·° or more, a diffusible hydrogen content of 0.2 ppm or less, and can have excellent fatigue resistance and bending properties.
본 발명에서는 내충돌성을 측정하기 위한 지표로 인장강도(TS)*굽힘각도(Bending Angle, BA)를 사용하였다. 내충돌성의 지표가 되는 굽힘각도는 인장강도의 영향을 받으며, 이는 반비례 경향을 가진다. 따라서, 인장강도와 굽힘각도의 곱(TS*BA) 값이 증가하면 내충돌성이 증가하게 된다. BA 값은 VDA238-100 규격에 따른 굽힘성 평가를 통하여 측정될 수 있으며, 최대 굽힘 강도에서 환산된 굽힘 외각으로 표현된다.In the present invention, tensile strength (TS) * bending angle (BA) was used as an indicator for measuring collision resistance. The bending angle, which is an indicator of crash resistance, is influenced by tensile strength, which tends to be inversely proportional. Therefore, as the product of tensile strength and bending angle (TS*BA) increases, crash resistance increases. The BA value can be measured through bendability evaluation according to the VDA238-100 standard, and is expressed as the bending outer angle converted from the maximum bending strength.
이하, 실시예를 통하여 본 발명을 보다 구체적으로 설명한다. 다만, 아래의 실시예는 본 발명을 예시하여 보다 상세하게 설명하기 위한 것일 뿐, 본 발명의 권리범위를 제한하기 위한 것이 아니라는 점에 유의할 필요가 있다.Hereinafter, the present invention will be described in more detail through examples. However, it is important to note that the examples below are only for illustrating and explaining the present invention in more detail, and are not intended to limit the scope of the present invention.
(실시예)(Example)
하기 표 1에 개시된 함량의 Sb를 포함하고, 0.22C-0.25Si-1.25Mn-0.2Cr-0.03Al-0.03Ti-0.0025B의 조성을 가지는 두께 40mm의 슬라브를 진공 용해하여 제조하였다. 상기 슬라브를 1200℃로 가열하고 1시간 유지 후, 900℃의 열간 압연 종료 온도로 열간압연을 행하였으며, 600℃의 온도로 권취하였다. 이후 산세공정을 행하고, 30~80%의 압하율로 냉간압연을 행하여 냉연강판을 제조하였다. 상기 냉연강판을 Ac1~Ac3 온도에서 소둔하되, 소둔 시간(s) 및 절대습도(g/m3)를 조절하였고, 그에 따른 소둔 시간과 절대습도 곱의 값을 표 1에 나타내었다. 소둔 후, Al-9%Si-2%Fe 및 미량의 불순물로 이루어진 도금욕에 강판을 침지하여 도금을 수행하였다. A 40 mm thick slab containing Sb in the content shown in Table 1 below and having the composition of 0.22C-0.25Si-1.25Mn-0.2Cr-0.03Al-0.03Ti-0.0025B was manufactured by vacuum melting. The slab was heated to 1200°C and held for 1 hour, then hot rolled at a hot rolling end temperature of 900°C and coiled at a temperature of 600°C. Afterwards, a pickling process was performed, and cold rolling was performed at a reduction ratio of 30 to 80% to manufacture cold rolled steel sheets. The cold-rolled steel sheet was annealed at a temperature of Ac 1 to Ac 3 , but the annealing time (s) and absolute humidity (g/m 3 ) were adjusted, and the resulting value of the product of annealing time and absolute humidity is shown in Table 1. After annealing, plating was performed by immersing the steel sheet in a plating bath consisting of Al-9%Si-2%Fe and trace amounts of impurities.
시편
번호Psalter
number 		조성Furtherance 소둔Annealing
Sb(wt%)Sb(wt%) 소둔시간·절대습도
(s·g/m3)Annealing time/absolute humidity
(s·g/m 3 ) 		강판 표면 평균 승온 속도(℃/s)Steel plate surface average temperature increase rate (℃/s)
상온~500℃Room temperature ~ 500℃ 500~700℃500~700℃ 700℃~소둔온도700℃~annealing temperature
1One 0.0720.072 10,65410,654 2.92.9 2.02.0 0.030.03
22 0.0450.045 22,34722,347 6.76.7 1.61.6 0.100.10
33 0.0360.036 40,45140,451 4.54.5 1.01.0 0.160.16
44 0.0150.015 58,36358,363 9.49.4 1.11.1 0.080.08
55 0.0720.072 50,66750,667 7.97.9 0.60.6 0.320.32
66 0.0150.015 11,21011,210 2.82.8 2.42.4 0.180.18
77 0.0610.061 9,5189,518 3.03.0 1.91.9 0.210.21
88 0.0300.030 9,3579,357 4.54.5 2.02.0 0.100.10
99 0.0030.003 35,94035,940 10.610.6 3.03.0 0.430.43
1010 0.0020.002 5,5605,560 2.42.4 1.81.8 0.0080.008
1111 0.0900.090 85,41085,410 3.03.0 0.70.7 0.220.22
1212 0.0200.020 90,25090,250 2.12.1 0.30.3 0.0090.009
하기 표 2에는 제조된 도금강판에 대하여, Sb 농화층, 미세조직, 탈탄율을 측정하여 나타내었다. 먼저, 주사전자현미경(SEM, Scanning Electron Microscopy)을 이용하여 계면 직하 조직을 관찰하여 펄라이트를 면적 분율을 측정하였다. 이때 모든 시편은, 펄라이트 면적 분율을 제외한 나머지 분율이 페라이트로 관찰되었다. 또한, 계면에서부터 소지강판 두께 방향으로 깊이 30μm까지 영역의 탄소 탈탄율을 측정하기 위하여 GDS850A (모델명, LECO사제), DC 및 RF 장비를 활용하였으며, 해당 장비를 통하여 얻은 탄소 프로파일을 통하여 탈탄율(α) 및 탄소 함량의 비율에 따른 깊이를 하기 표 2에 나타내었다. 글로우 방전 분광 분석기(GDS)를 이용하여, 관계식 1 및 2의 값과 안티몬 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소 함량을 측정하여 나타내었다. 더하여, 도금강판을 육안으로 관찰하여 미도금 영역 여부를 나타내었으며, 미도금 영역의 평균 지름이 1mm 이상을 만족하는 미도금 영역이 2개/m2를 초과하면 O, 그 미만이면 X로 표기하였다.Table 2 below shows the Sb enriched layer, microstructure, and decarburization rate of the manufactured plated steel sheet. First, the area fraction of pearlite was measured by observing the structure directly below the interface using scanning electron microscopy (SEM). At this time, in all specimens, except for the pearlite area fraction, the remaining fractions were observed to be ferrite. In addition, GDS850A (model name, manufactured by LECO), DC and RF equipment were used to measure the carbon decarburization rate in an area from the interface to a depth of 30 μm in the thickness direction of the base steel plate, and the decarburization rate (α) was determined through the carbon profile obtained through the equipment. ) and the depth according to the ratio of carbon content are shown in Table 2 below. Using a glow discharge spectrometer (GDS), the values of equations 1 and 2 and the carbon content at the depth where the antimony content shows the maximum value (Sb max ) were measured and expressed. In addition, the presence of unplated areas was indicated by observing the plated steel sheet with the naked eye. If the average diameter of the unplated area exceeded 2/ m2 , it was marked as O, and if it was less than that, it was marked as X. .
시
편
번
호city
side
th
like 		Sb 농화층Sb enriched layer 미세조직microstructure 탈탄율Decarburization rate 탄소-공칭 탄소Carbon - nominal carbon 미도금 여부
(O,X)Unplated or not
(O,X) 		구분 division
관계식 1Relation 1 관계식 2 Relation 2 안티몬(Sb) 함량이 최대값
(Sbmax)을 나타내는 깊이에서 탄소(C)
함량(wt%)Antimony (Sb) content is maximum
Carbon (C) at a depth representing (Sb max )
Content (wt%) 		계면에서 10μm 내 펄라이트 분율
(면적%)Pearlite fraction within 10 μm from the interface
(area%) 		계면에서 30μm까지 영역의 탈탄율
(α,%)Decarburization rate in areas up to 30μm from the interface
(α,%) 		공칭 탄소 함량(C0)에 대한 탄소(C) 함량 비율이 50%인 지점
(μm)The point at which the ratio of carbon (C) content to the nominal carbon content (C 0 ) is 50%.
(μm) 		공칭 탄소 함량(C0)에 대한 탄소(C) 함량 비율이 80%인 지점
(μm)The point at which the ratio of carbon (C) content to the nominal carbon content (C 0 ) is 80%.
(μm)
1One 4.104.10 0.1020.102 68.868.8 4.34.3 14.6614.66 1.81.8 6.46.4 XX 발명예1Invention Example 1
22 3.033.03 0.0650.065 48.948.9 3.43.4 18.7718.77 2.82.8 9.39.3 XX 발명예2Invention Example 2
33 2.602.60 0.0530.053 31.431.4 2.92.9 24.9524.95 3.93.9 11.111.1 XX 발명예3Invention Example 3
44 1.661.66 0.0250.025 20.820.8 1.31.3 34.8034.80 4.74.7 13.013.0 XX 발명예4Invention Example 4
55 3.973.97 0.0970.097 47.247.2 2.82.8 17.0817.08 2.82.8 8.48.4 XX 발명예5Invention Example 5
66 1.721.72 0.0300.030 11.811.8 3.13.1 29.6729.67 5.95.9 14.714.7 XX 발명예6Invention Example 6
77 3.593.59 0.0880.088 76.376.3 5.15.1 11.3411.34 1.11.1 4.34.3 XX 비교예1Comparative Example 1
88 2.302.30 0.0490.049 75.575.5 5.35.3 13.1513.15 1.21.2 4.54.5 XX 비교예2Comparative example 2
99 1.101.10 0.0070.007 9.79.7 0.40.4 54.1554.15 7.17.1 24.124.1 XX 비교예3Comparative Example 3
1010 1.081.08 0.0050.005 72.872.8 1.61.6 10.7810.78 1.41.4 4.84.8 XX 비교예4Comparative example 4
1111 5.015.01 0.1270.127 9.89.8 1.21.2 25.7125.71 6.16.1 15.915.9 OO 비교예5Comparative Example 5
1212 1.941.94 0.0300.030 8.98.9 0.90.9 39.0739.07 6.86.8 16.816.8 OO 비교예6Comparative Example 6
[관계식 1]
Figure PCTKR2023012157-appb-img-000009
[Relationship 1]
Figure PCTKR2023012157-appb-img-000009
[관계식 2]
Figure PCTKR2023012157-appb-img-000010
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000010
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지강판의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is μm.)
미도금 영역이 관찰되지 않은 도금강판을 활용하여 열간 성형을 행함으로써 부재를 제조하였다. 열간 성형을 위한 열처리 온도 및 시간은 900℃, 360초이며, 열처리로에서 성형 프레스까지의 이송시간은 10초를 적용하였다.A member was manufactured by hot forming using a plated steel sheet in which no unplated area was observed. The heat treatment temperature and time for hot forming were 900°C and 360 seconds, and the transfer time from the heat treatment furnace to the forming press was 10 seconds.
하기 표 3에는 상기 열간 성형을 통하여 제조된 부재의 조직 및 특성을 상기 서술한 방법과 동일하게 측정하여 나타내었다. 부재의 도금층과 소지철의 계면으로부터 깊이 45~100μm 영역에서 1.0kg의 하중을 적용하여 Vickers 경도를 측정하였고, 도 6 및 전술한 방법을 이용하여 경도 연화율(β)을 기재하였다. 또한, TDA 장비(Thermal Desorption Analysis)(Bruker G8; 모델명)를 활용하여 확산성 수소량을 측정하였다. 구체적으로, 400℃까지 20℃/분의 속도로 승온하고, 확산성 수소 피크(peak)가 충분히 나오도록 일정 시간을 유지하여 확산 수소 커브(Curve)를 측정하였고, 이러한 커브를 적분하여 강 중 확산성 수소량을 구하였다.Table 3 below shows the structure and properties of the member manufactured through hot forming, measured in the same manner as described above. Vickers hardness was measured by applying a load of 1.0 kg at a depth of 45 to 100 μm from the interface between the plating layer of the member and the base iron, and the hardness softening rate (β) was recorded using FIG. 6 and the method described above. In addition, the amount of diffusible hydrogen was measured using TDA equipment (Thermal Desorption Analysis) (Bruker G8; model name). Specifically, the temperature was raised to 400°C at a rate of 20°C/min, and the diffusion hydrogen curve was measured by maintaining it for a certain period of time so that the diffusible hydrogen peak sufficiently appeared. This curve was integrated to determine diffusion in the steel. The amount of sexual hydrogen was obtained.
또한, 광학 현미경(Optical Microscopy)을 활용하여 소지철과 도금층의 계면으로부터 깊이 30μm 범위 내의 페라이트 면적 분율을 측정하여 표 3에 나타내었다. 이 때, 모든 시편들은 페라이트 면적 분율을 제외한 나머지 분율이 마르텐사이트로 관찰되었다. 더하여, JIS Z2275 규격을 적용하여 10,000,000회 이상의 반복 피로 실험을 진행하여 측정된 피로 한계(Fatigue limit) 강도를 측정하였고, 피로 한계 강도를 인장강도로 나눈 값이 0.25 이상이면 O, 0.25 미만이면 X로 표기하여 내피로특성을 확인하였다. 내충돌성 특성은 인장강도와 굽힘각도의 곱으로 나타내었으며, 인장강도 값은 JIS-5호 시편으로 ISO6892 규격에 의거 상온 인장시험을 통하여 측정하였다. 또한, 굽힘각도는 VDA238-100 규격에 따른 굽힘성 평가 방법에 따라 규격 내 명시되어 있는 최대 굽힘 강도에서 환산된 굽힘 외각으로 값을 기재하였다.In addition, the ferrite area fraction within a depth of 30 μm from the interface between the base iron and the plating layer was measured using optical microscopy and is shown in Table 3. At this time, all specimens were observed to be martensite except for the ferrite area fraction. In addition, by applying the JIS Z2275 standard, more than 10,000,000 repetitive fatigue tests were performed to measure the measured fatigue limit strength. If the fatigue limit strength divided by the tensile strength is 0.25 or more, it is O, and if it is less than 0.25, it is X. Fatigue resistance characteristics were confirmed by marking. The crash resistance characteristics were expressed as the product of tensile strength and bending angle, and the tensile strength value was measured through a room temperature tensile test in accordance with the ISO6892 standard using a JIS-5 specimen. In addition, the bending angle was recorded as the bending outer angle converted from the maximum bending strength specified in the standard according to the bendability evaluation method according to the VDA238-100 standard.
시
편
번
호city
side
th
like 		Sb농화층Sb enriched layer 미세조직microstructure 연화율softening rate 물성 Properties 구분division
관계식 1Relation 1 관계식 2 Relation 2 안티몬(Sb) 함량이 최대값(Sbmax)을 가지는 깊이에서 탄소(C) 함량(wt%)Carbon (C) content (wt%) at the depth where antimony (Sb) content reaches its maximum value (Sb max ) 계면에서 50μm 내 페라이트 분율
(면적%)Ferrite fraction within 50 μm from the interface
(area%) 		계면에서 45~100μm 영역의 연화율
(β,%)Softening rate in the 45-100μm region at the interface
(β,%) 		인장강도와
굽힘각도의
곱
(MP·°)tensile strength and
bending angle
product
(MP·°) 		내피로 특성
(O,X)Fatigue resistance properties
(O,X) 		확산성 수소량
(ppm)Diffusible hydrogen amount
(ppm)
1One 5.895.89 0.39670.3967 76.976.9 0.20.2 2.072.07 80,13480,134 OO 0.0490.049 발명예1Invention Example 1
22 4.094.09 0.15570.1557 58.758.7 0.50.5 2.672.67 81,51781,517 OO 0.0770.077 발명예2Invention Example 2
33 3.303.30 0.08340.0834 40.340.3 0.90.9 4.014.01 82,94182,941 OO 0.0980.098 발명예3Invention Example 3
44 1.861.86 0.01470.0147 24.524.5 1.91.9 6.886.88 83,05783,057 OO 0.1300.130 발명예4Invention Example 4
55 5.705.70 0.37060.3706 53.953.9 0.50.5 2.652.65 80,87680,876 OO 0.0690.069 발명예5Invention Example 5
66 1.951.95 0.01970.0197 16.216.2 1.31.3 6.076.07 82,16782,167 OO 0.1070.107 발명예6Invention Example 6
77 4.674.67 0.29770.2977 90.290.2 0.10.1 0.650.65 74,17974,179 OO 0.0600.060 비교예1Comparative Example 1
88 2.702.70 0.14070.1407 87.787.7 0.50.5 0.850.85 77,07977,079 OO 0.1060.106 비교예2Comparative example 2
99 1.151.15 0.00570.0057 13.213.2 7.37.3 15.7015.70 83,51083,510 XX 0.4070.407 비교예3Comparative Example 3
1010 1.101.10 0.00300.0030 80.680.6 1.81.8 1.751.75 75,48375,483 OO 0.3050.305 비교예4Comparative example 4
1111 미도금으로 인한 열간 성형 미실시No hot forming due to non-plating 비교예5Comparative Example 5
1212 미도금으로 인한 열간 성형 미실시No hot forming due to non-plating 비교예6Comparative Example 6
[관계식 1]
Figure PCTKR2023012157-appb-img-000011
[Relationship 1]
Figure PCTKR2023012157-appb-img-000011
[관계식 2]
Figure PCTKR2023012157-appb-img-000012
[Relational Expression 2]
Figure PCTKR2023012157-appb-img-000012
(식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지철의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the equation, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base iron. It represents the straight line distance between one points, and the unit is μm.)
표 2 및 3에 나타난 바와 같이, 본 발명의 합금조성 및 제조조건을 만족하는 발명예 1 내지 6의 경우, 본 발명에서 제안하는 특징을 만족하였으며, 본 발명에서 목적하는 물성 또한 확보하였다.As shown in Tables 2 and 3, in the case of Invention Examples 1 to 6 that satisfy the alloy composition and manufacturing conditions of the present invention, the characteristics proposed in the present invention were satisfied, and the physical properties desired in the present invention were also secured.
비교예 1 및 2는 소둔 시, 소둔 시간과 절대습도의 곱이 본 발명에서 제안하는 범위에 미달된 경우로, 도금강판의 탈탄율이 제안하는 범위를 벗어났다. 이로 인하여 부재의 경도 연화율이 낮아졌으며, 표층부의 과도한 탄소 농화로 인해 내충돌성이 열화되었다.Comparative Examples 1 and 2 were cases in which the product of annealing time and absolute humidity during annealing was below the range suggested by the present invention, and the decarburization rate of the coated steel sheet was outside the suggested range. As a result, the hardness softening rate of the member decreased, and the collision resistance deteriorated due to excessive carbon concentration in the surface layer.
비교예 3은 강 중 Sb 함량이 본 발명의 범위를 벗어나 Sb 농화층이 불충분하게 생성됨으로써 소둔 시, 과하게 내부산화가 발생하였고, 이로 인하여 열처리 후 부재에서의 경도 연화가 과하게 발생하고, 표층부에 페라이트가 다량 생성되면서 내피로특성이 열화되었다.In Comparative Example 3, the Sb content in the steel was outside the range of the present invention, and the Sb enriched layer was insufficiently generated, resulting in excessive internal oxidation during annealing. As a result, excessive hardness softening occurred in the member after heat treatment, and ferrite was formed in the surface layer. As a large amount of was produced, the fatigue resistance properties deteriorated.
도 7은 본 발명의 일 실시예에 따른 도금강판에서의 탄소 프로파일을 나타낸 것이다. 도 7의 발명예 1 및 3은 본 발명에서 제안하는 탈탄 제어가 충분히 이루어진 것을 확인할 수 있으며, 그 결과 인장강도와 굽힘각도의 곱 및 일정 수준 이상의 내피로특성이 확보되었다. 반면, 비교예 1은 깊이에 따른 탈탄이 충분히 이루어지지 않았으며, 비교예 3은 Sb 농화층의 불충분한 생성으로 인하여 과다한 탈탄이 발생하여 물성이 열위한 것을 확인할 수 있다. Figure 7 shows a carbon profile in a plated steel sheet according to an embodiment of the present invention. Invention Examples 1 and 3 of Figure 7 confirm that the decarburization control proposed in the present invention was sufficiently achieved, and as a result, the product of tensile strength and bending angle and fatigue resistance characteristics above a certain level were secured. On the other hand, it can be confirmed that in Comparative Example 1, decarburization according to depth was not sufficiently achieved, and in Comparative Example 3, excessive decarburization occurred due to insufficient production of the Sb enriched layer, resulting in inferior physical properties.
도 8은 본 발명의 일 실시예에 따른 발명예 3 및 비교예 3의 도금강판에서의 계면 직하 조직을 SEM으로 관찰한 사진이다. 발명예 3의 경우, 펄라이트가 2.9% 관찰되었으나, 비교예 3의 경우, 펄라이트가 1% 미만으로 관찰된 것을 확인할 수 있다.Figure 8 is a photograph of the structure directly below the interface of the plated steel sheets of Inventive Example 3 and Comparative Example 3 according to an embodiment of the present invention observed with an SEM. In the case of Inventive Example 3, 2.9% of pearlite was observed, but in the case of Comparative Example 3, it can be confirmed that less than 1% of pearlite was observed.
도 9는 본 발명의 발명예 3 및 비교예 3의 부재에서의 도금층 및 소지철 계면의 광학 사진이다. 발명예 3의 경우, 페라이트가 1% 미만으로 관찰되었으나, 비교예 3의 경우, 페라이트가 7.3%로 본 발명에서 목적하는 내피로특성을 확보하지 못하였다.Figure 9 is an optical photograph of the interface between the plating layer and the base iron in the members of Inventive Example 3 and Comparative Example 3 of the present invention. In the case of Inventive Example 3, ferrite was observed to be less than 1%, but in Comparative Example 3, the ferrite content was 7.3%, which did not ensure the fatigue resistance desired in the present invention.
비교예 4는 강 중 Sb 함량과 소둔 시간과 절대 습도의 곱이 본 발명에서 제안하는 범위를 벗어난 것으로, 부재에서의 확산성 수소량이 과도하여 굽힘성을 열화시킴으로써, 내충돌성 지표인 인장강도와 굽힘각도의 곱 값이 목적하는 수준에 미치지 못하였다.In Comparative Example 4, the product of the Sb content in the steel, annealing time, and absolute humidity is outside the range proposed by the present invention, and the amount of diffusible hydrogen in the member is excessive, deteriorating bendability, and tensile strength, which is an index of collision resistance, The product value of the bending angle did not reach the desired level.
비교예 5 및 6은 소둔 시, 소둔 시간과 절대 습도의 곱이 본 발명의 범위를 초과한 것으로, 소둔 시 표층부 산화가 심해져 Fe 산화물이 표층에 생성되었다. 그 결과, 도금 밀착성이 열화되어 미도금 현상이 발생하였다.In Comparative Examples 5 and 6, during annealing, the product of annealing time and absolute humidity exceeded the range of the present invention, and during annealing, oxidation of the surface layer became severe and Fe oxide was generated in the surface layer. As a result, plating adhesion deteriorated and non-plating phenomenon occurred.
이상에서 실시예를 통하여 본 발명을 상세하게 설명하였으나, 이와 다른 형태의 실시예들도 가능하다. 그러므로, 이하에 기재된 청구항들의 기술적 사상과 범위는 실시예들에 한정되지 않는다.Although the present invention has been described in detail through examples above, other forms of embodiments are also possible. Therefore, the technical spirit and scope of the claims set forth below are not limited to the embodiments.
[부호의 설명][Explanation of symbols]
1: 도금층1: Plating layer
2: Sb 농화층2: Sb enriched layer
21: Sb 농화층에 있어서, x축 (+)방향으로의 Sb 함량 상승 구간21: In the Sb enriched layer, the Sb content increase section in the x-axis (+) direction
22: Sb 농화층에 있어서, x축 (+)방향으로의 Sb 함량 하강 구간22: In the Sb enriched layer, the Sb content decreasing section in the x-axis (+) direction
3: Sb 농화층을 제외한 소지강판3: Base steel plate excluding Sb enriched layer
10: 도금층의 Sb 평균 함량선10: Sb average content line of plating layer
11: 도금층의 Sb 평균 함량선과, GDS에 의한 Sb 함량선의 x축 (+)방향으로의 마지막 접촉 지점11: Last point of contact between the average Sb content line of the plating layer and the Sb content line by GDS in the x-axis (+) direction
30: 소지강판의 Sb 평균 함량선30: Sb average content line of base steel plate
31: 소지강판의 Sb 평균 함량선과, GDS에 의한 Sb 함량선의 x축 (+)방향으로의 최초의 접촉 지점31: First contact point in the x-axis (+) direction between the Sb average content line of the base steel plate and the Sb content line by GDS
100: GDS에 의한 Sb 함량선100: Sb content line by GDS
200: Sb 농화층에서 Sb 함량 최대값인 지점200: Point at the maximum Sb content in the Sb enriched layer

Claims (25)

  1. 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 소지강판 및 상기 소지강판의 표면에 형성된 도금층을 포함하고,In weight percent, it includes a base steel sheet containing 0.06 to 0.5% of carbon (C) and 0.01 to 0.1% of antimony (Sb), and a plating layer formed on the surface of the base steel sheet,
    상기 소지강판은 내에 안티몬(Sb) 농화층을 포함하며,The base steel plate includes an antimony (Sb) concentrated layer therein,
    글로우 방전 분광 분석기(Glow Discharge Spectrometer)를 이용하여 상기 소지강판의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지강판의 공칭 탄소 함량(C0)의 10~70%인 도금강판.When analyzing the element content in the thickness direction of the steel sheet using a glow discharge spectrometer, the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) A coated steel sheet in which the carbon (C) content is 10 to 70% of the nominal carbon content (C 0 ) of the base steel sheet.
  2. 청구항 1에 있어서,In claim 1,
    상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 30μm까지 영역의 탄소(C)의 탈탄율(α)이 14~35%인 도금강판.A plated steel sheet having a decarburization rate (α) of carbon (C) of 14 to 35% in a region from the interface between the base steel sheet and the plating layer to a depth of 30 μm in the thickness direction.
  3. 청구항 1 또는 2에 있어서,In claim 1 or 2,
    상기 도금강판은 상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 1.5μm 초과, 6μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 50%인 지점이 존재하는 도금강판.The plated steel sheet has a point where the carbon (C) content is 50% of the nominal carbon content (C 0 ) at a depth of more than 1.5 μm and less than 6 μm in the thickness direction from the interface of the base steel sheet and the plating layer. A plated steel sheet.
  4. 청구항 1 내지 3 중 어느 한 항에 있어서,The method of any one of claims 1 to 3,
    상기 도금강판은 상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 6μm 초과, 15μm 미만인 깊이에 탄소(C) 함량이 상기 공칭 탄소 함량(C0)의 80%인 지점이 존재하는 도금강판.The plated steel sheet has a point where the carbon (C) content is 80% of the nominal carbon content (C 0 ) at a depth of more than 6 μm and less than 15 μm in the thickness direction from the interface of the base steel sheet and the plating layer. A plated steel sheet.
  5. 청구항 1 내지 4 중 어느 한 항에 있어서,The method of any one of claims 1 to 4,
    상기 도금강판은 하기 관계식 1에서 정의되는 R 값이 1.2 이상이고,The plated steel sheet has an R value defined in equation 1 below of 1.2 or more,
    하기 관계식 2에서 정의되는 B 값이 0.008 이상인 도금강판.A coated steel sheet with a B value of 0.008 or more, defined in equation 2 below.
    [관계식 1]
    Figure PCTKR2023012157-appb-img-000013
    [Relationship 1]
    Figure PCTKR2023012157-appb-img-000013
    [관계식 2]
    Figure PCTKR2023012157-appb-img-000014
    [Relational Expression 2]
    Figure PCTKR2023012157-appb-img-000014
    (식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지강판의 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface between the plating layer and the base steel sheet. It represents the straight line distance between one points, and the unit is μm.)
  6. 청구항 1 내지 5 중 어느 한 항에 있어서,The method of any one of claims 1 to 5,
    상기 소지강판과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 10μm까지의 영역은 페라이트를 주상으로 하고, 1면적% 이상의 펄라이트를 포함하는 미세조직을 가지는 도금강판.A plated steel sheet in which the area from the interface between the base steel sheet and the plating layer to a depth of 10 μm in the thickness direction has a microstructure containing ferrite as the main phase and pearlite in an amount of 1 area% or more.
  7. 청구항 1 내지 6 중 어느 한 항에 있어서,The method of any one of claims 1 to 6,
    상기 소지강판은 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함하는 도금강판.The base steel sheet contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, Boron (B): 0.01% or less, galvanized steel sheet containing remaining iron (Fe) and impurities.
  8. 청구항 1 내지 7 중 어느 한 항에 있어서,The method of any one of claims 1 to 7,
    상기 도금층은 알루미늄 또는 알루미늄 합금으로 이루어지는 도금강판.The plating layer is a plated steel sheet made of aluminum or aluminum alloy.
  9. 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 소지철 및 상기 소지철의 표면에 형성된 도금층을 포함하고,In weight percent, it includes base iron containing 0.06 to 0.5% of carbon (C) and 0.01 to 0.1% of antimony (Sb), and a plating layer formed on the surface of the base iron,
    상기 소지철은 내에 안티몬(Sb) 농화층을 포함하며,The base iron includes an antimony (Sb) enriched layer within it,
    글로우 방전 분광 분석기(Glow Discharge Spectrometer)를 이용하여 상기 소지철의 두께 방향으로 원소의 함량을 분석할 때, 상기 안티몬(Sb) 농화층 내에 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 80% 이하인 부재.When analyzing the element content in the thickness direction of the base iron using a glow discharge spectrometer, the depth at which the antimony (Sb) content in the antimony (Sb) enriched layer shows the maximum value (Sb max ) A member in which the carbon (C) content is 80% or less of the nominal carbon content (C 0 ) of the base iron.
  10. 청구항 9에 있어서,In claim 9,
    상기 부재는 상기 안티몬(Sb) 함량이 최대값(Sbmax)을 나타내는 깊이에서의 탄소(C) 함량이 상기 소지철의 공칭 탄소 함량(C0)의 15~80%인 부재.The member is a member in which the carbon (C) content at a depth where the antimony (Sb) content shows the maximum value (Sb max ) is 15 to 80% of the nominal carbon content (C 0 ) of the base iron.
  11. 청구항 9 또는 10에 있어서,The method of claim 9 or 10,
    상기 부재는 하기 관계식 1에서 정의되는 R 값이 1.5 이상이고,The member has an R value defined in equation 1 below of 1.5 or more,
    하기 관계식 2에서 정의되는 B 값이 0.01 이상인 부재.A member with a B value of 0.01 or more defined in the following relational equation 2.
    [관계식 1]
    Figure PCTKR2023012157-appb-img-000015
    [Relationship 1]
    Figure PCTKR2023012157-appb-img-000015
    [관계식 2]
    Figure PCTKR2023012157-appb-img-000016
    [Relational Expression 2]
    Figure PCTKR2023012157-appb-img-000016
    (식에서, Sbmax는 Sb 농화층의 Sb 함량의 최대값을 나타내고, Sbcoat는 도금층 내 평균 Sb 함량을 나타내며, 단위는 중량%이다. 더하여, Δt는 도금층과 소지철이 접하는 계면으로부터 Sbmax를 측정한 지점 사이의 직선 거리를 나타내며, 단위는 μm이다.)(In the formula, Sb max represents the maximum value of Sb content in the Sb enriched layer, and Sb coat represents the average Sb content in the plating layer, and the unit is weight%. In addition, Δt measures Sb max from the interface where the plating layer and the base iron contact. It represents the straight line distance between one points, and the unit is μm.)
  12. 청구항 9 내지 11 중 어느 한 항에 있어서,The method of any one of claims 9 to 11,
    상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 45~100μm의 영역은 연화율(β)이 2~7%인 부재.A member having a softening rate (β) of 2 to 7% in an area 45 to 100 μm deep in the thickness direction from the interface between the base iron and the plating layer.
  13. 청구항 9 내지 12 중 어느 한 항에 있어서,The method of any one of claims 9 to 12,
    상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 50μm까지 영역은 미세조직으로 5면적% 미만의 페라이트를 포함하는 부재.A member containing less than 5 area% of ferrite as a microstructure in an area from the interface between the base iron and the plating layer to a depth of 50 μm in the thickness direction.
  14. 청구항 9 내지 13 중 어느 한 항에 있어서,The method of any one of claims 9 to 13,
    상기 소지철과 상기 도금층의 계면으로부터 상기 두께 방향으로 깊이 50μm까지 영역은 미세조직으로 마르텐사이트를 주상으로 하고, 5면적% 미만의 페라이트, 잔부 상부 및 하부 베이나이트를 포함하는 부재.A member containing less than 5 area% of ferrite and the remaining upper and lower bainite in an area from the interface between the base iron and the plating layer to a depth of 50 μm in the thickness direction.
  15. 청구항 9 내지 14 중 어느 한 항에 있어서,The method of any one of claims 9 to 14,
    상기 소지철은 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함하는 부재.The base iron contains carbon (C): 0.06 to 0.5%, antimony (Sb): 0.01 to 0.1%, silicon (Si): 0.001 to 2%, manganese (Mn): 0.1 to 4%, and molybdenum (Mo): 1. % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, Boron (B): 0.01% or less, member containing remaining iron (Fe) and impurities.
  16. 청구항 9 내지 15 중 어느 한 항에 있어서,The method of any one of claims 9 to 15,
    상기 도금층은 알루미늄 또는 알루미늄 합금으로 이루어지는 부재.The plating layer is a member made of aluminum or aluminum alloy.
  17. 청구항 9 내지 16 중 어느 한 항에 있어서,The method of any one of claims 9 to 16,
    상기 부재는 인장강도 및 굽힘각도의 곱이 80,000MPa·° 이상인 부재.The member is a member whose product of tensile strength and bending angle is 80,000 MPa·° or more.
  18. 청구항 9 내지 17 중 어느 한 항에 있어서,The method of any one of claims 9 to 17,
    상기 부재는 확산성 수소량이 0.2ppm 이하인 부재.The member is a member in which the amount of diffusible hydrogen is 0.2ppm or less.
  19. 중량%로, 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%를 포함하는 냉연강판을 준비하는 단계; Preparing a cold-rolled steel sheet containing, in weight percent, carbon (C): 0.06-0.5% and antimony (Sb): 0.01-0.1%;
    상기 냉연강판을 Ac1~Ac3의 온도범위에서 소둔하는 단계; 및 Annealing the cold rolled steel sheet in a temperature range of Ac 1 to Ac 3 ; and
    상기 소둔된 냉연강판을 도금하는 단계를 포함하고, Comprising the step of plating the annealed cold rolled steel sheet,
    상기 소둔 시, 소둔 시간과 절대 습도의 곱이 10,000~80,000s·g/m3이고,During the annealing, the product of the annealing time and the absolute humidity is 10,000 to 80,000 s·g/m 3 ,
    상기 소둔 시, 강판의 표면 온도를 기준으로, 상온에서 500℃까지 평균 승온 속도가 2.7~10.0℃/s이고, 500~700℃ 구간의 평균 승온 속도가 0.5~2.5℃/s이고, 700℃에서 소둔 온도까지 평균 승온 속도가 0.01~0.4℃/s인 도금강판 제조방법.During the annealing, based on the surface temperature of the steel sheet, the average temperature increase rate from room temperature to 500°C is 2.7 to 10.0°C/s, the average temperature increase rate in the 500 to 700°C section is 0.5 to 2.5°C/s, and at 700°C. A method of manufacturing plated steel sheets with an average temperature increase rate of 0.01 to 0.4°C/s to the annealing temperature.
  20. 청구항 19에 있어서,In claim 19,
    상기 소둔 시, 소둔 시간은 100~200초이며, 절대 습도는 100~400g/m3인 도금강판 제조방법.During the annealing, the annealing time is 100 to 200 seconds, and the absolute humidity is 100 to 400 g/m 3 .
  21. 청구항 19 또는 20에 있어서,The method of claim 19 or 20,
    상기 냉연강판은,The cold rolled steel sheet,
    강 슬라브를 1050~1300℃의 온도범위로 재가열하는 단계;Reheating the steel slab to a temperature range of 1050-1300°C;
    상기 재가열된 강 슬라브를 800~950℃의 온도범위에서 마무리 압연하는 단계;Finish rolling the reheated steel slab at a temperature range of 800 to 950°C;
    상기 압연된 강을 500~700℃의 온도범위에서 권취 및 냉각하는 단계; 및Winding and cooling the rolled steel at a temperature range of 500 to 700°C; and
    상기 냉각된 강을 30~80%의 압하율로 냉간압연하는 단계를 포함하는 도금강판 제조방법.A method of manufacturing a plated steel sheet including the step of cold rolling the cooled steel at a reduction rate of 30 to 80%.
  22. 청구항 19 내지 21 중 어느 한 항에 있어서,The method of any one of claims 19 to 21,
    상기 강 슬라브는 탄소(C): 0.06~0.5%, 안티몬(Sb): 0.01~0.1%, 실리콘(Si): 0.001~2%, 망간(Mn): 0.1~4%, 몰리브덴(Mo): 1% 이하, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 알루미늄(Al): 0.001~1%, 크롬(Cr): 1% 이하, 질소(N): 0.02% 이하, 티타늄(Ti): 0.1% 이하, 보론(B): 0.01% 이하, 잔부 철(Fe) 및 불순물을 포함하는 도금강판 제조방법.The steel slab contains carbon (C): 0.06-0.5%, antimony (Sb): 0.01-0.1%, silicon (Si): 0.001-2%, manganese (Mn): 0.1-4%, molybdenum (Mo): 1 % or less, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, aluminum (Al): 0.001 to 1%, chromium (Cr): 1% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0.1% or less, boron (B): 0.01% or less, method of manufacturing a plated steel sheet containing the remainder of iron (Fe) and impurities.
  23. 청구항 19 내지 22 중 어느 한 항에 있어서,The method of any one of claims 19 to 22,
    상기 도금 시, 알루미늄 또는 알루미늄 합금으로 도금하는 것인 도금강판 제조방법.A method of manufacturing a plated steel sheet, wherein during the plating, plating is performed with aluminum or aluminum alloy.
  24. 청구항 19 내지 23 중 어느 하나의 도금강판을 블랭크로 제조하는 단계; Manufacturing the plated steel sheet of any one of claims 19 to 23 into a blank;
    상기 블랭크를 Ac3~975℃의 온도범위로 가열하고, 10~1000초 유지하는 단계; 및 Heating the blank to a temperature range of Ac 3 to 975°C and maintaining it for 10 to 1000 seconds; and
    상기 가열된 블랭크를 성형 및 냉각하는 단계를 포함하는 부재 제조방법.A member manufacturing method comprising forming and cooling the heated blank.
  25. 청구항 24에 있어서,In claim 24,
    상기 냉각 시, 20℃/s 이상의 냉각속도로 냉각하는 부재 제조방법.A method of manufacturing a member that cools at a cooling rate of 20°C/s or more during the cooling.
PCT/KR2023/012157 2022-08-26 2023-08-17 Plated steel sheet for hot press forming having excellent impact resistance, hot press formed part, and manufacturing methods thereof WO2024043608A1 (en)

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