WO2018117489A1 - Ferrite-based stainless steel having excellent strength and acid resistance and method for manufacturing same - Google Patents

Ferrite-based stainless steel having excellent strength and acid resistance and method for manufacturing same Download PDF

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Publication number
WO2018117489A1
WO2018117489A1 PCT/KR2017/014205 KR2017014205W WO2018117489A1 WO 2018117489 A1 WO2018117489 A1 WO 2018117489A1 KR 2017014205 W KR2017014205 W KR 2017014205W WO 2018117489 A1 WO2018117489 A1 WO 2018117489A1
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stainless steel
ferritic stainless
acid resistance
strength
less
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PCT/KR2017/014205
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French (fr)
Korean (ko)
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박지언
박미남
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주식회사 포스코
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Priority to MX2019007636A priority Critical patent/MX2019007636A/en
Priority to JP2019534678A priority patent/JP6894515B2/en
Priority to CN201780084405.XA priority patent/CN110199049B/en
Priority to US16/473,044 priority patent/US20200087745A1/en
Publication of WO2018117489A1 publication Critical patent/WO2018117489A1/en

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    • 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
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • 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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the present invention relates to a ferritic stainless steel and a method for producing the same, and more particularly to a ferritic stainless steel and its manufacturing method excellent in strength and acid resistance.
  • ferritic stainless steels are widely used in building materials, kitchen containers, home appliances, automobile exhaust systems, and the like.
  • Ferritic stainless steels have recently been applied to automotive battery cells, and automobile companies require higher strength and corrosion resistance than conventional ferritic stainless steels to guarantee long-term battery performance. We demand material of price.
  • the method of increasing the strength of ferritic stainless steel to satisfy the demands of such automobile companies includes methods such as work hardening, solid solution strengthening, and precipitation hardening. Due to the characteristics of ferritic stainless steel without phase transformation, there is a problem in that workability decreases rapidly during work hardening. Mo, Nb and the like which are excellent in effects are difficult to utilize as expensive elements.
  • C is an element that impairs the workability of ferritic stainless steel, and is managed to be lower than 0.02wt% unless it is a special use.
  • C is an element that impairs the workability of ferritic stainless steel, and is managed to be lower than 0.02wt% unless it is a special use.
  • the strength of ferritic stainless steel may be improved due to the precipitation of carbides, and if the ductility is secured to some extent through recent developments in processing technology, strength and processability may be simultaneously obtained.
  • Patent Document 0001 Japanese Laid-Open Patent Publication No. 2006-183081
  • Embodiments of the present invention are to provide an excellent ferritic stainless steel that can improve the strength and acid resistance through controlling the alloy components of the ferritic stainless steel by controlling the precipitates and grains of the ferritic stainless steel.
  • embodiments of the present invention to provide a method for producing a ferritic stainless steel that can improve the strength and acid resistance through the control of precipitates and grains by controlling the slab reheating temperature, reduction rate and winding temperature during hot rolling.
  • Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, containing the remaining iron (Fe) and other unavoidable impurities, the diameter of 100nm or more The number of branches is 50 to 200ea / 100 ⁇ m 2 per unit area of carbide.
  • the average grain diameter may be 10 ⁇ m or less.
  • the tensile strength may be 520MPa or more.
  • the elongation may be 20% or more.
  • the critical current density I crit may be 10 mA or less in a 5% sulfuric acid atmosphere.
  • Method for producing a ferritic stainless steel excellent in strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): Ferritic stainless steel containing 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, remaining iron (Fe) and other unavoidable impurities It includes the step of hot rolling and cold rolling the steel slab, the value of the following formula (1) at the time of hot rolling satisfies 1,000 or less.
  • RHT (°C) means the slab reheating temperature
  • R4 (%) means the reduction ratio of the R4 stand of rough rolling
  • CT (°C) means the winding temperature.
  • the value of the formula (1) may satisfy 800 to 1,000.
  • RHT is less than 1,250 °C
  • R4 is 40% or more
  • CT may be less than 650 °C.
  • the cold rolled sheet material may be 50 to 200ea / 100 ⁇ m 2 per unit area of the carbide having a diameter of 100nm or more, the average grain diameter may be 10 ⁇ m or less.
  • Embodiments of the present invention can improve the strength and acid resistance of the ferritic stainless steel through controlling the alloy components and hot rolling conditions of the ferritic stainless steel by controlling the precipitates and grains.
  • 1 is a graph for explaining the correlation between the hot rolling conditions of the ferritic stainless steel and the number of carbides of the cold rolled steel sheet.
  • TEM 2 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to an embodiment of the present invention.
  • TEM 3 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to a comparative example of the present invention.
  • Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, containing the remaining iron (Fe) and other unavoidable impurities, the diameter of 100nm or more The number of branches is 50 to 200ea / 100 ⁇ m 2 per unit area of carbide.
  • Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.50%, copper (Cu): 0.3 to 1.5%, remaining iron (Fe) and other unavoidable impurities.
  • the amount of carbon (C) is from 0.1 to 0.2%. If the amount of carbon (C) is less than 0.1%, there is a problem that the amount of austenite produced during hot rolling is reduced and the ferrite band structure is not destroyed and the grain size is increased, thus increasing the tensile strength of the final cold rolled product. There is a problem that the strength is lowered below 500 MPa. In addition, when the amount of carbon (C) is greater than 0.2%, the carbide of the material increases too much, the elongation of the final product is lowered, there is a problem that the surface quality and corrosion resistance is lowered by the dropping of carbides.
  • the amount of nitrogen (N) is 0.005 to 0.05%. If the amount of nitrogen (N) is less than 0.005%, the manufacturing cost increases due to the increase in refining time and the shortening of the refractory life, and also the low degree of supercooling during casting lowers the slab equiaxed crystal ratio, and the amount of nitrogen (N) is 0.05 If it is more than%, it is highly likely that pinholes by nitrogen occur during slab casting, and the number of Cr 2 N precipitates per unit area in the final cold rolled product increases, resulting in a chromium depleted zone formed around the Cr 2 N precipitates. The formation of multiple pits on the surface of the cold rolled product results in poor surface quality.
  • the amount of manganese (Mn) is 0.01 to 0.5%. If the amount of manganese (Mn) is less than 0.01%, there is a problem that the refining price is expensive, if the amount of manganese (Mn) is more than 0.5%, there is a problem that the elongation and corrosion resistance is inferior.
  • the amount of chromium (Cr) is 12.0 to 19.0%. If the amount of chromium (Cr) is less than 12.0%, there is a problem of poor corrosion resistance, and if the amount of chromium (Cr) is more than 19.0%, the elongation is lowered and there is a problem that a hot rolled sticking defect occurs.
  • the amount of nickel (Ni) is 0.01 to 0.50%. If the amount of nickel (Ni) is less than 0.01%, there is a problem that the refining price is expensive, if the amount of nickel (Ni) is more than 0.5%, there is a problem that the impurities of the material increases and the elongation is lowered.
  • the amount of copper (Cu) is 0.3 to 1.5%. If the amount of copper (Cu) is less than 0.3%, the critical current density (I crit ) is more than 10 mA in 5% sulfuric acid atmosphere and sufficient acid resistance cannot be secured. If the amount of copper (Cu) is more than 1.5% Not only does the price go too high, it also leads to a decrease in hot workability and a drop in elongation of the final product.
  • Ferritic stainless steel having excellent strength and acid resistance has a number of carbides having a diameter of 100 nm or more per unit area of 50ea / 100 ⁇ m 2 or more.
  • the carbide may be an M 23 C 6 type carbide based metal precipitate.
  • the slab reheating temperature, rough rolling reduction rate, and hot rolled coil winding temperature must be controlled during the hot rolling process, which will be described later.
  • the number of carbides having a diameter of 100 nm or more may be 50ea / 100 ⁇ m 2 or more through the control of the hot rolling process conditions, and by securing a large number of fine carbides, tensile strength of 520 MPa or more may be secured. If the above process conditions are exceeded, the carbides become coarse and the amount of carbides cannot be sufficiently obtained.
  • the amount of carbides is small, resulting in coarsening of grains and lowering tensile strength.
  • the ferritic stainless steel may have an average grain diameter of 10 ⁇ m or less.
  • the ferritic stainless steel according to an embodiment of the present invention may have a tensile strength of 520 MPa or more.
  • the ferritic stainless steel according to one embodiment of the present invention may have an elongation of 20% or more.
  • the ferritic stainless steel according to an embodiment of the present invention may have a critical current density I crit of 10 mA or less in a 5% sulfuric acid atmosphere.
  • RHT (°C) means the slab reheating temperature
  • R4 (%) means the reduction ratio of the R4 stand of rough rolling
  • CT (°C) means the winding temperature.
  • the slab reheat temperature (RHT) is less than 1,250 ° C
  • the rolling reduction R4 of the roughly rolled R4 stand is 40% or more
  • the coiling temperature (CT) is performed at less than 650 ° C, wherein hot Rolling conditions are performed so that the value of said Formula (1) may satisfy 1,000 or less.
  • 1 is a graph for explaining the correlation between the hot rolling conditions of the ferritic stainless steel and the number of carbides of the cold rolled steel sheet.
  • the coiling temperature is higher than 650 °C, the coarsening of the precipitate occurs, the desired number of carbides can not be obtained, thereby grains are coarse and the desired tensile strength in the final product is not obtained.
  • the value of Formula (1) may satisfy 800 to 1,000.
  • the value of the formula (1) is less than 800, the temperature during the hot rolling is too low can lead to plate-like defects.
  • the hot rolled sheet is subjected to an annealing process, in which the carbide is sufficiently precipitated through annealing heat treatment at a temperature of 700 to 900 ° C.
  • the annealing heat treatment may be performed by a BAF annealing process.
  • the cold rolled sheet material having a thickness of less than 2mm through cold rolling may be manufactured and the final heat treatment may be performed by heat treatment at a temperature of 800 to 900 °C.
  • the cold rolled sheet material may be 50ea / 100 ⁇ m 2 or more per unit area of the carbide having a diameter of 100nm or more, the average grain diameter may be 10 ⁇ m or less.
  • a TEM replica was made on the final produced cold rolled sheet to measure the number of carbide precipitates per unit area (100 ⁇ m 2 ).
  • TEM 2 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to an embodiment of the present invention.
  • 3 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to a comparative example of the present invention.
  • FIG. 2 is a photograph of a cold rolled steel sheet according to Example 2
  • FIG. 3 is a photograph of a cold rolled steel sheet according to Comparative Example 2.
  • the number of carbides and the tensile strength of the cold rolled steel sheets according to the embodiments and the comparative examples are shown in a graph. As the number of carbides increases, the tensile strength also tends to increase.
  • Ferritic stainless steel and its manufacturing method excellent in strength and acid resistance according to embodiments of the present invention is applicable to building materials, kitchen containers, home appliances, automotive exhaust system parts, automotive batteries and the like.

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Abstract

Disclosed are: a ferrite-based stainless steel having excellent strength and acid resistance; and a method for manufacturing the same. The ferrite-based stainless steel according to an embodiment of the present invention comprises, in terms of weight%, 0.1-0.2% of carbon (C), 0.005-0.05% of nitrogen (N), 0.01-0.5% of manganese (Mn), 12.0-19.0% of chrome (Cr), 0.01-0.5% of nickel (Ni), 0.3-1.5% of copper (Cu), and the remainder iron (Fe) and other unavoidable impurities, wherein the number of carbides having a diameter of 100nm or larger per unit area is 50-200 ea/100μm2.

Description

강도 및 내산성이 우수한 페라이트계 스테인리스강 및 이의 제조 방법Ferritic stainless steel with excellent strength and acid resistance and method for producing same
본 발명은 페라이트계 스테인리스강 및 이의 제조 방법에 관한 것으로, 보다 상세하게는 강도 및 내산성이 우수한 페라이트계 스테인리스강 및 이의 제조 방법에 관한 것이다.The present invention relates to a ferritic stainless steel and a method for producing the same, and more particularly to a ferritic stainless steel and its manufacturing method excellent in strength and acid resistance.
스테인리스강 중 특히 페라이트계 스테인리스강은 건축 자재, 주방 용기, 가전 제품, 자동차 배기계 부품 등에 널리 사용되고 있다.Among the stainless steels, in particular, ferritic stainless steels are widely used in building materials, kitchen containers, home appliances, automobile exhaust systems, and the like.
페라이트계 스테인리스강은 최근 자동차 배터리 셀용으로 일부 적용되고 있으며, 자동차사에서는 장기간의 배터리 성능을 보장하기 위해서 기존 페라이트계 스테인리스강 보다 더 높은 강도와 내식성을 요구하고 있으며, 배터리의 가격을 낮추기 위해서 더욱 낮은 가격의 소재도 요구하고 있다.Ferritic stainless steels have recently been applied to automotive battery cells, and automobile companies require higher strength and corrosion resistance than conventional ferritic stainless steels to guarantee long-term battery performance. We demand material of price.
이러한 자동차사의 요구를 만족하기 위한 페라이트계 스테인리스강의 고강도화 방법은 가공 경화, 고용 강화, 석출 경화 등의 방법이 있는데, 상변태가 없는 페라이트계 스테인리스강의 특성상 가공 경화 시 가공성이 급격히 떨어지는 문제가 있으며, 고용 강화 효과가 뛰어난 Mo, Nb 등은 고가의 원소로서 활용하기가 어렵다.The method of increasing the strength of ferritic stainless steel to satisfy the demands of such automobile companies includes methods such as work hardening, solid solution strengthening, and precipitation hardening. Due to the characteristics of ferritic stainless steel without phase transformation, there is a problem in that workability decreases rapidly during work hardening. Mo, Nb and the like which are excellent in effects are difficult to utilize as expensive elements.
기존에는 C는 페라이트계 스테인리스강의 가공성을 해치는 원소로서 특별한 용도가 아니면 대부분 0.02wt% 이하로 낮게 관리하였다. 하지만 반대로 다량의 C를 첨가하게 되면 탄화물(carbide)의 석출로 인해 페라이트계 스테인리스강의 강도를 향상시킬 수 있으며, 최근 가공 기술의 발달로 어느 정도의 연성만 확보되면 강도와 가공성을 동시에 확보 가능하다.Conventionally, C is an element that impairs the workability of ferritic stainless steel, and is managed to be lower than 0.02wt% unless it is a special use. On the contrary, when a large amount of C is added, the strength of ferritic stainless steel may be improved due to the precipitation of carbides, and if the ductility is secured to some extent through recent developments in processing technology, strength and processability may be simultaneously obtained.
하지만 C를 다량 넣더라도 고온에서 열연하거나 압하율이 낮고 권취 온도가 높게 되면, 탄화물들이 변형조직 내에 미세하게 석출되지 못하고 조대하게 되어 결정립 미세화가 어렵고 또한 원하는 강도를 확보하기가 어려운 문제점이 있다.However, even if a large amount of C is hot rolled at a high temperature, or if the rolling ratio is low and the winding temperature is high, carbides are not finely precipitated and coarse in the deformed tissue, so that grain refinement is difficult and it is difficult to secure desired strength.
(특허문헌 0001) 일본 공개특허문헌 제2006-183081호  (Patent Document 0001) Japanese Laid-Open Patent Publication No. 2006-183081
본 발명의 실시예들은 페라이트계 스테인리스강의 합금 성분을 제어하여 폐라이트계 스테인리스강의 석출물 및 결정립 제어를 통하여 강도 및 내산성을 향상시킬 수 있는 우수한 페라이트계 스테인리스강을 제공하고자 한다.Embodiments of the present invention are to provide an excellent ferritic stainless steel that can improve the strength and acid resistance through controlling the alloy components of the ferritic stainless steel by controlling the precipitates and grains of the ferritic stainless steel.
또한, 본 발명의 실시예들은 열간 압연시 슬라브 재가열 온도, 압하율 및 권취 온도를 제어하여 석출물 및 결정립 제어를 통하여 강도 및 내산성을 향상시킬 수 있는 페라이트계 스테인리스의 제조 방법을 제공하고자 한다.In addition, embodiments of the present invention to provide a method for producing a ferritic stainless steel that can improve the strength and acid resistance through the control of precipitates and grains by controlling the slab reheating temperature, reduction rate and winding temperature during hot rolling.
본 발명의 일 실시예에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강은, 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하며, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50 내지 200ea/100㎛2 이다.Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, containing the remaining iron (Fe) and other unavoidable impurities, the diameter of 100nm or more The number of branches is 50 to 200ea / 100㎛ 2 per unit area of carbide.
또한, 본 발명의 일 실시예에 따르면, 평균 결정립 지름이 10㎛ 이하 일 수 있다.In addition, according to an embodiment of the present invention, the average grain diameter may be 10㎛ or less.
또한, 본 발명의 일 실시예에 따르면, 인장강도가 520MPa 이상 일 수 있다.In addition, according to an embodiment of the present invention, the tensile strength may be 520MPa or more.
또한, 본 발명의 일 실시예에 따르면, 연신율이 20% 이상 일 수 있다.In addition, according to an embodiment of the present invention, the elongation may be 20% or more.
또한, 본 발명의 일 실시예에 따르면, 5% 황산 분위기에서 임계전류밀도(Icrit)가 10mA 이하 일 수 있다.Further, according to an embodiment of the present invention, the critical current density I crit may be 10 mA or less in a 5% sulfuric acid atmosphere.
본 발명의 일 실시예에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강의 제조 방법은, 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하는 페라이트계 스테인리스강 슬라브를 열간 압연하는 단계 및 냉간 압연하는 단계를 포함하며, 열간 압연시 하기 식 (1)의 값이 1,000 이하를 만족한다.Method for producing a ferritic stainless steel excellent in strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): Ferritic stainless steel containing 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, remaining iron (Fe) and other unavoidable impurities It includes the step of hot rolling and cold rolling the steel slab, the value of the following formula (1) at the time of hot rolling satisfies 1,000 or less.
15*RHT/R4+CT ------ 식 (1)15 * RHT / R4 + CT ------ Formula (1)
여기서, RHT(℃)는 슬라브 재가열 온도를 의미하며, R4(%)는 조압연의 R4 스탠드의 압하율을 의미하며, CT(℃)는 권취 온도를 의미한다.Here, RHT (℃) means the slab reheating temperature, R4 (%) means the reduction ratio of the R4 stand of rough rolling, CT (℃) means the winding temperature.
또한, 본 발명의 일 실시예에 따르면, 상기 식 (1)의 값은 800 내지 1,000을 만족할 수 있다.In addition, according to an embodiment of the present invention, the value of the formula (1) may satisfy 800 to 1,000.
또한, 본 발명의 일 실시예에 따르면, RHT는 1,250℃ 미만이며, R4는 40% 이상이며, CT는 650℃ 미만 일 수 있다.In addition, according to an embodiment of the present invention, RHT is less than 1,250 ℃, R4 is 40% or more, CT may be less than 650 ℃.
또한, 본 발명의 일 실시예에 따르면, 냉연 판재는 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50 내지 200ea/100㎛2이며, 평균 결정립 지름이 10㎛ 이하 일 수 있다.In addition, according to one embodiment of the present invention, the cold rolled sheet material may be 50 to 200ea / 100㎛ 2 per unit area of the carbide having a diameter of 100nm or more, the average grain diameter may be 10㎛ or less.
본 발명의 실시예들은 페라이트계 스테인리스강의 합금 성분 및 열간 압연 조건을 제어하여 석출물 및 결정립 제어를 통하여 페라이트계 스테인리스강의 강도 및 내산성을 향상시킬 수 있다.Embodiments of the present invention can improve the strength and acid resistance of the ferritic stainless steel through controlling the alloy components and hot rolling conditions of the ferritic stainless steel by controlling the precipitates and grains.
도 1은 페라이트계 스테인리스강의 열간압연 조건 및 냉연 강판의 탄화물 개수의 상관관계를 설명하기 위한 그래프이다.1 is a graph for explaining the correlation between the hot rolling conditions of the ferritic stainless steel and the number of carbides of the cold rolled steel sheet.
도 2는 본 발명의 일 실시예에 따른 페라이트계 스테인리스 냉연 강판의 석출물 분포 상태를 투과전자현미경(TEM)을 통하여 촬영한 사진이다.2 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to an embodiment of the present invention.
도 3은 본 발명의 비교예에 따른 페라이트계 스테인리스 냉연 강판의 석출물 분포 상태를 투과전자현미경(TEM)을 통하여 촬영한 사진이다.3 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to a comparative example of the present invention.
도 4는 페라이트계 스테인리스강의 냉연 강판의 탄화물 개수 및 인장강도의 상관관계를 설명하기 위한 그래프이다.4 is a graph for explaining the correlation between the number of carbides and the tensile strength of the cold-rolled steel sheet of ferritic stainless steel.
본 발명의 일 실시예에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강은, 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하며, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50 내지 200ea/100㎛2 이다.Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.5%, copper (Cu): 0.3 to 1.5%, containing the remaining iron (Fe) and other unavoidable impurities, the diameter of 100nm or more The number of branches is 50 to 200ea / 100㎛ 2 per unit area of carbide.
이하에서는 본 발명의 실시 예를 첨부 도면을 참조하여 상세히 설명한다. 이하의 실시 예는 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 본 발명의 사상을 충분히 전달하기 위해 제시하는 것이다. 본 발명은 여기서 제시한 실시 예만으로 한정되지 않고 다른 형태로 구체화될 수도 있다. 도면은 본 발명을 명확히 하기 위해 설명과 관계 없는 부분의 도시를 생략하고, 이해를 돕기 위해 구성요소의 크기를 다소 과장하여 표현할 수 있다.Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are presented to sufficiently convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein but may be embodied in other forms. The drawings may omit illustrations of parts not related to the description in order to clarify the present invention, and may be exaggerated to some extent in order to facilitate understanding.
본 발명의 일 실시예에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강은, 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.50%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함한다.Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention, in weight%, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05%, manganese (Mn): 0.01 to 0.5%, chromium (Cr): 12.0 to 19.0%, nickel (Ni): 0.01 to 0.50%, copper (Cu): 0.3 to 1.5%, remaining iron (Fe) and other unavoidable impurities.
탄소(C): 0.1 내지 0.2%Carbon (C): 0.1-0.2%
탄소(C)의 양은 0.1 내지 0.2%이다. 탄소(C)의 양이 0.1% 미만이면, 열연 중에 생성되는 오스테나이트의 양이 줄어들어 페라이트 밴드 조직이 파괴되지 않고 잔존하게 되어 결정립의 크기가 커지는 문제가 있으며, 이에 따라 최종 냉연 제품의 인장강도가 500MPa 미만으로 강도가 저하되는 문제점이 있다. 또한, 탄소(C)의 양이 0.2% 초과이면, 소재의 탄화물이 너무 많이 증가하여 최종 제품의 연신율이 떨어지고 탄화물들의 탈락으로 표면 품질 및 내식성이 저하되는 문제점이 있다.The amount of carbon (C) is from 0.1 to 0.2%. If the amount of carbon (C) is less than 0.1%, there is a problem that the amount of austenite produced during hot rolling is reduced and the ferrite band structure is not destroyed and the grain size is increased, thus increasing the tensile strength of the final cold rolled product. There is a problem that the strength is lowered below 500 MPa. In addition, when the amount of carbon (C) is greater than 0.2%, the carbide of the material increases too much, the elongation of the final product is lowered, there is a problem that the surface quality and corrosion resistance is lowered by the dropping of carbides.
질소(N): 0.005 내지 0.05%Nitrogen (N): 0.005 to 0.05%
질소(N)의 양은 0.005 내지 0.05%이다. 질소(N)의 양이 0.005% 미만이면, 정련 시간 증가 및 내화물 수명 단축으로 제조 원가가 상승하며, 또한 주조시의 과냉도가 낮아 슬라브의 등축정율이 낮아지고, 질소(N)의 양이 0.05% 초과이면, 슬라브 주조 중에 질소에 의한 핀홀이 발생할 가능성이 높으며, 최종 냉연 제품에서 Cr2N 석출물의 단위 면적당 개수가 증가하여 Cr2N 석출물 주변에 형성된 크롬 고갈 영역(Cr depleted zone)에 의해서 최종 냉연 제품의 표면에 다수의 피트(pit)를 형성하여 표면 품질이 떨어지게 된다.The amount of nitrogen (N) is 0.005 to 0.05%. If the amount of nitrogen (N) is less than 0.005%, the manufacturing cost increases due to the increase in refining time and the shortening of the refractory life, and also the low degree of supercooling during casting lowers the slab equiaxed crystal ratio, and the amount of nitrogen (N) is 0.05 If it is more than%, it is highly likely that pinholes by nitrogen occur during slab casting, and the number of Cr 2 N precipitates per unit area in the final cold rolled product increases, resulting in a chromium depleted zone formed around the Cr 2 N precipitates. The formation of multiple pits on the surface of the cold rolled product results in poor surface quality.
망간(Mn): 0.01 내지 0.5%Manganese (Mn): 0.01-0.5%
망간(Mn)의 양은 0.01 내지 0.5%이다. 망간(Mn)의 양이 0.01% 미만이면, 정련 가격이 비싸지는 문제가 있고, 망간(Mn)의 양이 0.5% 초과이면, 연신율과 내식성이 떨어지는 문제가 있다.The amount of manganese (Mn) is 0.01 to 0.5%. If the amount of manganese (Mn) is less than 0.01%, there is a problem that the refining price is expensive, if the amount of manganese (Mn) is more than 0.5%, there is a problem that the elongation and corrosion resistance is inferior.
크롬(Cr): 12.0 내지 19.0%Chromium (Cr): 12.0 to 19.0%
크롬(Cr)의 양은 12.0 내지 19.0%이다. 크롬(Cr)의 양이 12.0% 미만이면, 내식성이 나빠지는 문제가 있고, 크롬(Cr)의 양이 19.0% 초과이면, 연신율이 떨어지고 열연 스티킹(sticking) 결함이 발생하는 문제가 있다.The amount of chromium (Cr) is 12.0 to 19.0%. If the amount of chromium (Cr) is less than 12.0%, there is a problem of poor corrosion resistance, and if the amount of chromium (Cr) is more than 19.0%, the elongation is lowered and there is a problem that a hot rolled sticking defect occurs.
니켈(Ni): 0.01 내지 0.50%Nickel (Ni): 0.01 to 0.50%
니켈(Ni)의 양은 0.01 내지 0.50%이다. 니켈(Ni)의 양이 0.01% 미만이면, 정련 가격이 비싸지는 문제가 있고, 니켈(Ni)의 양이 0.5% 초과이면, 소재의 불순물이 증가하여 연신율이 떨어지는 문제가 있다.The amount of nickel (Ni) is 0.01 to 0.50%. If the amount of nickel (Ni) is less than 0.01%, there is a problem that the refining price is expensive, if the amount of nickel (Ni) is more than 0.5%, there is a problem that the impurities of the material increases and the elongation is lowered.
구리(Cu): 0.3 내지 1.5%Copper (Cu): 0.3-1.5%
구리(Cu)의 양은 0.3 내지 1.5%이다. 구리(Cu)의 양이 0.3% 미만이면, 5% 황산 분위기에서 임계전류밀도(Icrit)가 10mA를 초과하여 충분한 내산성을 확보할 수 없고, 구리(Cu)의 양이 1.5%를 초과하면 원료 가격이 너무 올라갈 뿐만 아니라, 열간 가공성의 하락과 최종 제품의 연신율 하락을 초래한다.The amount of copper (Cu) is 0.3 to 1.5%. If the amount of copper (Cu) is less than 0.3%, the critical current density (I crit ) is more than 10 mA in 5% sulfuric acid atmosphere and sufficient acid resistance cannot be secured. If the amount of copper (Cu) is more than 1.5% Not only does the price go too high, it also leads to a decrease in hot workability and a drop in elongation of the final product.
페라이트계 스테인리스강의 최종 냉연 제품에서 원하는 인장강도를 얻기 위하여는 미세한 탄화물을 다수 확보하는 것이 필요하며, 결정립의 미세화가 요구된다.In order to obtain a desired tensile strength in the final cold-rolled product of ferritic stainless steel, it is necessary to secure a large number of fine carbides, it is required to refine the grain.
본 발명의 일 실시예에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강은, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50ea/100㎛2 이상이다.Ferritic stainless steel having excellent strength and acid resistance according to an embodiment of the present invention has a number of carbides having a diameter of 100 nm or more per unit area of 50ea / 100 μm 2 or more.
예를 들어, 상기 탄화물은 M23C6형 탄화물계 금속 석출물일 수 있다.For example, the carbide may be an M 23 C 6 type carbide based metal precipitate.
상기 탄화물의 단위 면적당 개수를 증가시키기 위하여는 열연 공정 중에 열연 소재에 충분한 변형 조직을 형성하여야 한다. 변형 조직이 충분히 형성되지 않는 경우 탄화물 석출 사이트(site)가 충분하지 않아 탄화물의 양을 증가시키기 어렵다.In order to increase the number of carbides per unit area, sufficient deformation structure should be formed in the hot rolled material during the hot rolling process. If the deformed tissue is not sufficiently formed, it is difficult to increase the amount of carbide due to insufficient carbide precipitation sites.
열연 소재에 충분한 변형 조직을 형성하기 위하여는 열연 공정 중에 슬라브 재가열 온도, 조압연 압하율, 열연 코일 권취 온도를 제어하여야 하며 이의 상세한 내용은 후술하도록 한다.In order to form a sufficient deformation structure in the hot rolled material, the slab reheating temperature, rough rolling reduction rate, and hot rolled coil winding temperature must be controlled during the hot rolling process, which will be described later.
즉, 열연 공정 조건의 제어를 통하여 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50ea/100㎛2 이상을 달성할 수 있으며, 이에 미세한 탄화물을 다수 확보함으로써 520MPa 이상의 인장강도를 확보할 수 있다. 상기 공정 조건을 벗어나는 경우 탄화물이 조대해져 탄화물의 양을 충분히 얻을 수 없다.That is, the number of carbides having a diameter of 100 nm or more may be 50ea / 100 μm 2 or more through the control of the hot rolling process conditions, and by securing a large number of fine carbides, tensile strength of 520 MPa or more may be secured. If the above process conditions are exceeded, the carbides become coarse and the amount of carbides cannot be sufficiently obtained.
예를 들어, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50ea/100㎛2 미만인 경우, 탄화물의 양이 적어 결정립의 조대화가 발생하여 인장강도가 저하된다.For example, when the number of carbides having a diameter of 100 nm or more per unit area is less than 50ea / 100 µm 2 , the amount of carbides is small, resulting in coarsening of grains and lowering tensile strength.
예를 들어, 상기 페라이트계 스테인리스강은 평균 결정립 지름이 10㎛ 이하일 수 있다.For example, the ferritic stainless steel may have an average grain diameter of 10 μm or less.
예를 들어, 본 발명의 일 실시예에 따른 페라이트계 스테인리스강은 인장강도가 520MPa 이상 일 수 있다.For example, the ferritic stainless steel according to an embodiment of the present invention may have a tensile strength of 520 MPa or more.
예를 들어, 본 발명의 일 실시예에 따른 페라이트계 스테인리스강은 연신율이 20% 이상 일 수 있다.For example, the ferritic stainless steel according to one embodiment of the present invention may have an elongation of 20% or more.
예를 들어, 본 발명의 일 실시예에 따른 페라이트계 스테인리스강은 5% 황산 분위기에서 임계전류밀도(Icrit)가 10mA 이하 일 수 있다.For example, the ferritic stainless steel according to an embodiment of the present invention may have a critical current density I crit of 10 mA or less in a 5% sulfuric acid atmosphere.
상기 페라이트계 스테인리스강을 제조하기 위한, 본 발명의 일 실시예에 따른 페라이트계 스테인리스강의 제조 방법에 따르면, 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하는 페라이트계 스테인리스강 슬라브를 열간 압연하는 단계 및 냉간 압연하는 단계를 포함하며, 열간 압연시 하기 식 (1)의 값이 1,000 이하를 만족한다.According to the method for producing a ferritic stainless steel according to an embodiment of the present invention for producing the ferritic stainless steel, by weight, carbon (C): 0.1 to 0.2%, nitrogen (N): 0.005 to 0.05% , Manganese (Mn): 0.01-0.5%, chromium (Cr): 12.0-19.0%, nickel (Ni): 0.01-0.5%, copper (Cu): 0.3-1.5%, remaining iron (Fe) and other unavoidable impurities It includes a step of hot rolling and cold rolling a ferritic stainless steel slab comprising a, the value of the following formula (1) during hot rolling satisfies 1,000 or less.
15*RHT/R4+CT ------ 식 (1)15 * RHT / R4 + CT ------ Formula (1)
여기서, RHT(℃)는 슬라브 재가열 온도를 의미하며, R4(%)는 조압연의 R4 스탠드의 압하율을 의미하며, CT(℃)는 권취 온도를 의미한다.Here, RHT (℃) means the slab reheating temperature, R4 (%) means the reduction ratio of the R4 stand of rough rolling, CT (℃) means the winding temperature.
상기 성분을 포함하는 용강을 연속주조를 통하여 페라이트계 스테인리스강 슬라브를 제조한다. 이후, 상기 슬라브를 열간 압연하며, 열간 압연을 통해 2 내지 10mm 두께의 열연 코일을 제조한다.Through the continuous casting of molten steel containing the above components to produce a ferritic stainless steel slab. Thereafter, the slabs are hot rolled, and hot rolled coils having a thickness of 2 to 10 mm are manufactured by hot rolling.
예를 들어, 슬라브 재가열 온도(RHT)는 1,250℃ 미만이며, 조압연의 R4 스탠드의 압하율(R4)는 40% 이상이며, 권취 온도(CT)는 650℃ 미만으로 수행하는데, 이때에, 열간 압연 조건은 상기 식 (1)의 값이 1,000 이하를 만족하도록 수행된다.For example, the slab reheat temperature (RHT) is less than 1,250 ° C, the rolling reduction R4 of the roughly rolled R4 stand is 40% or more, and the coiling temperature (CT) is performed at less than 650 ° C, wherein hot Rolling conditions are performed so that the value of said Formula (1) may satisfy 1,000 or less.
도 1은 페라이트계 스테인리스강의 열간압연 조건 및 냉연 강판의 탄화물 개수의 상관관계를 설명하기 위한 그래프이다.1 is a graph for explaining the correlation between the hot rolling conditions of the ferritic stainless steel and the number of carbides of the cold rolled steel sheet.
도 1을 참조하면, 상기 식 (1)에 따른 값이 1,000 이하인 경우, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50ea/100㎛2 이상임을 알 수 있다.Referring to FIG. 1, when the value according to Equation (1) is 1,000 or less, it can be seen that the number per unit area of carbide having a diameter of 100 nm or more is 50ea / 100 μm 2 or more.
탄소 함량이 충분하더라도 상기 식 (1)의 열간 압연 조건을 벗어나는 경우에는 열연 소재에 충분한 변형조직이 형성되지 않아 탄화물 석출 사이트가 충분히 형성되지 않는다.Even if the carbon content is sufficient, when the temperature is out of the hot rolling condition of the formula (1), sufficient deformation structure is not formed in the hot rolled material, and carbide precipitation sites are not sufficiently formed.
특히, 권취 온도가 650℃ 이상으로 높으면 석출물의 조대화가 발생하여 원하는 탄화물 개수를 얻을 수 없으며, 이에 따라 결정립이 조대해지며 최종 제품에서 원하는 인장강도를 얻을 수 없게 된다.In particular, when the coiling temperature is higher than 650 ℃, the coarsening of the precipitate occurs, the desired number of carbides can not be obtained, thereby grains are coarse and the desired tensile strength in the final product is not obtained.
예를 들어, 상기 식 (1)의 값은 800 내지 1,000을 만족할 수 있다.For example, the value of Formula (1) may satisfy 800 to 1,000.
상기 식 (1)의 값이 800 미만인 경우, 열간 압연시 온도가 너무 낮아 판형상의 불량을 초래할 수 있다.If the value of the formula (1) is less than 800, the temperature during the hot rolling is too low can lead to plate-like defects.
열연 판재는 소둔 공정을 거치는데, 상기 소둔 공정에서 700 내지 900℃의 온도에서의 소둔 열처리를 통해 탄화물을 충분히 석출을 시킨다. 예를 들어, 상기 소둔 열처리는 BAF 소둔 공정으로 수행될 수 있다. 상기 소둔 열처리 이후, 냉간 압연을 통하여 2mm 두께 미만의 냉연 판재를 제조하고 800 내지 900℃의 온도의 열처리를 통해 최종 열처리를 수행할 수 있다.The hot rolled sheet is subjected to an annealing process, in which the carbide is sufficiently precipitated through annealing heat treatment at a temperature of 700 to 900 ° C. For example, the annealing heat treatment may be performed by a BAF annealing process. After the annealing heat treatment, the cold rolled sheet material having a thickness of less than 2mm through cold rolling may be manufactured and the final heat treatment may be performed by heat treatment at a temperature of 800 to 900 ℃.
예를 들어, 상기 냉연 판재는 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50ea/100㎛2 이상이며, 평균 결정립 지름이 10㎛ 이하일 수 있다.For example, the cold rolled sheet material may be 50ea / 100㎛ 2 or more per unit area of the carbide having a diameter of 100nm or more, the average grain diameter may be 10㎛ or less.
이하, 실시예들을 통하여 본 발명의 보다 상세하게 설명하고자 한다.Hereinafter, the present invention will be described in more detail with reference to the following examples.
실시예Example
연속주조를 통하여 하기 표 1의 성분을 만족하는 발명강 1 내지 4 그리고 비교강 1 내지 9의 슬라브를 제조하여 하기 표 2의 열간 압연 조건에 따라, 재가열한 후, 열간 압연을 통해 5mmt의 열연 코일을 제조하였다. 그리고, BAF 소둔 공정에서 900℃의 소둔 열처리를 수행하였다. 이후, 냉간 압연을 통해 1mmt의 냉연판을 제조하고 900℃의 열처리를 수행하였으며, 표면 숏볼처리 및 황산 및 과수를 포함하는 산세액으로 산세하여 최종 제품을 제조하였다.Slabs of the inventive steels 1 to 4 and the comparative steels 1 to 9 satisfying the components of Table 1 through continuous casting, according to the hot rolling conditions of Table 2, after reheating, 5mmt hot rolled coil through hot rolling Was prepared. Then, annealing heat treatment at 900 ° C. was performed in the BAF annealing process. Thereafter, a cold rolled sheet of 1 mmt was manufactured through cold rolling, heat treatment was performed at 900 ° C., and the final product was prepared by pickling a surface shotball and pickling with sulfuric acid and fruit water.
CC NN MnMn CrCr NiNi CuCu
발명강 1Inventive Steel 1 0.1030.103 0.0140.014 0.130.13 14.314.3 0.11 0.11 0.67 0.67
발명강 2Inventive Steel 2 0.1710.171 0.0160.016 0.110.11 17.217.2 0.09 0.09 0.45 0.45
발명강 3Inventive Steel 3 0.1220.122 0.0060.006 0.240.24 16.716.7 0.13 0.13 1.21 1.21
발명강 4Inventive Steel 4 0.1250.125 0.0080.008 0.190.19 16.516.5 0.12 0.12 1.05 1.05
비교강 1Comparative Steel 1 0.1330.133 0.0120.012 0.230.23 17.517.5 0.15 0.15 1.79 1.79
비교강 2Comparative Steel 2 0.1470.147 0.0150.015 0.240.24 16.916.9 0.17 0.17 0.14 0.14
비교강 3Comparative Steel 3 0.2270.227 0.0220.022 0.150.15 17.117.1 0.21 0.21 0.84 0.84
비교강 4Comparative Steel 4 0.2320.232 0.0170.017 0.140.14 17.617.6 0.11 0.11 0.66 0.66
비교강 5Comparative Steel 5 0.0420.042 0.0460.046 0.210.21 16.216.2 0.11 0.11 0.12 0.12
비교강 6Comparative Steel 6 0.0510.051 0.0420.042 0.150.15 15.215.2 0.13 0.13 0.23 0.23
비교강 7Comparative Steel 7 0.0470.047 0.0410.041 0.170.17 16.916.9 0.14 0.14 0.77 0.77
비교강 8Comparative Steel 8 0.0620.062 0.0150.015 0.160.16 17.317.3 0.13 0.13 0.81 0.81
비교강 9Comparative Steel 9 0.0850.085 0.0150.015 0.250.25 18.118.1 0.15 0.15 0.67 0.67
강종Steel grade RHT(℃)RHT (℃) CT(℃)CT (℃) R4(%)R4 (%) 15*RHT/R4+CT15 * RHT / R4 + CT
실시예 1Example 1 발명강 1Inventive Steel 1 1,1301,130 550550 4545 927927
실시예 2Example 2 발명강 2Inventive Steel 2 1,1301,130 550550 4545 927927
실시예 3Example 3 발명강 3Inventive Steel 3 1,1801,180 550550 4545 943943
실시예 4Example 4 발명강 4Inventive Steel 4 1,1801,180 580580 4545 973973
비교예 1Comparative Example 1 발명강 1Inventive Steel 1 1,2501,250 550550 3030 1,1751,175
비교예 2Comparative Example 2 발명강 2Inventive Steel 2 1,1801,180 650650 3030 1,2401,240
비교예 3Comparative Example 3 발명강 3Inventive Steel 3 1,1801,180 580580 3030 1,1701,170
비교예 4Comparative Example 4 발명강 4Inventive Steel 4 1,2501,250 550550 4040 1,0191,019
비교예 5Comparative Example 5 비교강 1Comparative Steel 1 1,1301,130 550550 4545 927927
비교예 6Comparative Example 6 비교강 2Comparative Steel 2 1,1301,130 580580 4545 957957
비교예 7Comparative Example 7 비교강 3Comparative Steel 3 1,1801,180 550550 4545 943943
비교예 8Comparative Example 8 비교강 4Comparative Steel 4 1,1801,180 580580 4545 973973
비교예 9Comparative Example 9 비교강 5Comparative Steel 5 1,1801,180 650650 3030 1,2401,240
비교예 10Comparative Example 10 비교강 6Comparative Steel 6 1,1301,130 550550 4545 927927
비교예 11Comparative Example 11 비교강 7Comparative Steel 7 1,1801,180 550550 4545 943943
비교예 12Comparative Example 12 비교강 8Comparative Steel 8 1,1801,180 650650 4545 1,0431,043
비교예 13Comparative Example 13 비교강 9Comparative Steel 9 1,2501,250 650650 3030 1,2751,275
이에 따라 최종 생산된 냉연 강판의 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수, 평균 결정립 지름, 인장강도, 연신율, 5% 황산 분위기에서 임계전류밀도를 측정하여 하기 표 3에 나타내었다.Accordingly, the number of units per unit area, average grain diameter, tensile strength, elongation, and critical current density of a carbide having a diameter of 100 nm or more of the final produced cold rolled steel sheet were measured and shown in Table 3 below.
최종 생산된 냉연 판재에 대하여 TEM Replica를 만들어 단위 면적당(100㎛2) 탄화물 석출물의 개수를 측정하였다.A TEM replica was made on the final produced cold rolled sheet to measure the number of carbide precipitates per unit area (100 μm 2 ).
탄화물의 개수 (ea/100㎛2)Number of Carbide (ea / 100㎛ 2 ) 평균 결정립 지름 (㎛)Average grain diameter (㎛) 연신율(%)Elongation (%) 인장강도 (MPa)Tensile Strength (MPa) 5% 황산 분위기에서 임계전류밀도 (mA)Critical current density (mA) in 5% sulfuric acid atmosphere
실시예 1Example 1 9191 6.86.8 25.725.7 529529 5.65.6
실시예 2Example 2 124124 5.95.9 23.923.9 531531 7.27.2
실시예 3Example 3 7272 7.47.4 25.325.3 542542 3.73.7
실시예 4Example 4 7575 8.18.1 26.726.7 537537 3.53.5
비교예 1Comparative Example 1 3232 10.810.8 27.627.6 498498 8.58.5
비교예 2Comparative Example 2 4545 11.611.6 25.325.3 508508 5.95.9
비교예 3Comparative Example 3 3737 10.510.5 26.726.7 515515 4.24.2
비교예 4Comparative Example 4 4141 12.112.1 27.227.2 498498 4.54.5
비교예 5Comparative Example 5 8181 6.56.5 18.818.8 554554 3.13.1
비교예 6Comparative Example 6 107107 5.45.4 25.725.7 527527 14.514.5
비교예 7Comparative Example 7 227227 4.84.8 18.518.5 567567 6.96.9
비교예 8Comparative Example 8 305305 5.35.3 19.219.2 572572 7.57.5
비교예 9Comparative Example 9 1313 18.118.1 30.130.1 457457 15.615.6
비교예 10Comparative Example 10 1919 17.317.3 29.829.8 453453 13.813.8
비교예 11Comparative Example 11 2828 20.620.6 28.928.9 476476 6.36.3
비교예 12Comparative Example 12 2121 14.114.1 27.727.7 481481 5.45.4
비교예 13Comparative Example 13 2626 12.012.0 26.326.3 491491 4.24.2
도 2는 본 발명의 일 실시예에 따른 페라이트계 스테인리스 냉연 강판의 석출물 분포 상태를 투과전자현미경(TEM)을 통하여 촬영한 사진이다. 도 3은 본 발명의 비교예에 따른 페라이트계 스테인리스 냉연 강판의 석출물 분포 상태를 투과전자현미경(TEM)을 통하여 촬영한 사진이다.2 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to an embodiment of the present invention. 3 is a photograph taken through the transmission electron microscope (TEM) of the precipitate distribution state of the ferritic stainless steel cold rolled steel sheet according to a comparative example of the present invention.
도 2는 상기 실시예 2에 따른 냉연 강판을 촬영한 사진이며, 도 3은 상기 비교예 2에 따른 냉연 강판을 촬영한 사진이다.FIG. 2 is a photograph of a cold rolled steel sheet according to Example 2, and FIG. 3 is a photograph of a cold rolled steel sheet according to Comparative Example 2.
도 2 및 3을 참조하면, 비교예 1 내지 4에서와 같이 열간 압연시 슬라브 재가열 온도, R4 압하율, 권취 온도에 관한 관계식에 따른 15*RHT/R4+CT의 값이 1,000을 초과하여 탄소 함량이 충분하더라도 열연 소재에 충분한 변형조직이 형성되지 않아 탄화물 석출 사이트가 충분치 않다.2 and 3, as in Comparative Examples 1 to 4, the value of 15 * RHT / R4 + CT in excess of 1,000 according to the relation relating to the slab reheating temperature, the R4 reduction ratio, and the coiling temperature during hot rolling is more than 1,000. Even if this is sufficient, there is not enough carbide deposition site because no sufficient deformed tissue is formed in the hot rolled material.
뿐만 아니라, 비교예 2에서와 같이 권취 온도가 높으면 석출물의 조대화가 발생하여 원하는 탄화물 개수를 얻을 수 없음을 알 수 있다.In addition, it can be seen that, as in Comparative Example 2, when the coiling temperature is high, coarsening of precipitates occurs, so that the desired number of carbides cannot be obtained.
비교예 5에서와 같이 구리의 함량이 과다한 경우, 최종 제품의 연신율이 18.8%를 가져 연신율이 저하됨을 알 수 있으며, 비교예 6에서와 같이 구리의 함량이 적은 경우, 5% 황산 분위기에서 임계전류밀도(Icrit)가 14.5mA를 나타내어 충분한 내산성을 확보할 수 없다.When the copper content is excessive as in Comparative Example 5, it can be seen that the elongation is reduced by having an elongation of 18.8% of the final product, the critical current in 5% sulfuric acid atmosphere when the copper content is low as in Comparative Example 6 The density I crit represents 14.5 mA, so that sufficient acid resistance cannot be obtained.
비교예 7 및 8에서와 같이 탄소의 함량이 과다한 경우, 탄화물의 개수가 증가하여 연신율이 떨어짐을 확인할 수 있다. 비교예 9 내지 13에서와 같이 탄소의 함량이 적은 경우, 결정립의 크기가 커지며, 인장강도가 500MPa 미만으로 강도가 저하됨을 확인할 수 있다.When the content of carbon is excessive as in Comparative Examples 7 and 8, it can be seen that the number of carbides is increased to reduce the elongation. When the content of carbon is small as in Comparative Examples 9 to 13, the size of the crystal grains is increased, it can be seen that the tensile strength is lowered to less than 500MPa.
도 4는 페라이트계 스테인리스강의 냉연 강판의 탄화물 개수 및 인장강도의 상관관계를 설명하기 위한 그래프이다.4 is a graph for explaining the correlation between the number of carbides and the tensile strength of the cold-rolled steel sheet of ferritic stainless steel.
도 4를 참조하면, 상기 실시예들 및 비교예들에 따른 냉연 강판의 탄화물 수와 인장강도를 그래프로 나타낸 것이며, 탄화물의 수가 증가할수록 인장강도 역시 증가하는 경향이 있음을 알 수 있다.Referring to FIG. 4, the number of carbides and the tensile strength of the cold rolled steel sheets according to the embodiments and the comparative examples are shown in a graph. As the number of carbides increases, the tensile strength also tends to increase.
상술한 바에 있어서, 본 발명의 예시적인 실시예들을 설명하였지만, 본 발명은 이에 한정되지 않으며 해당 기술 분야에서 통상의 지식을 가진 자라면 다음에 기재하는 특허청구범위의 개념과 범위를 벗어나지 않는 범위 내에서 다양한 변경 및 변형이 가능함을 이해할 수 있을 것이다.As described above, the exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and a person skilled in the art does not depart from the concept and scope of the following claims. It will be understood that various changes and modifications are possible in the following.
본 발명의 실시예들에 따른 강도 및 내산성이 우수한 페라이트계 스테인리스강 및 이의 제조 방법은 건축 자재, 주방 용기, 가전 제품, 자동차 배기계 부품, 자동차 베터리 등에 적용 가능하다.Ferritic stainless steel and its manufacturing method excellent in strength and acid resistance according to embodiments of the present invention is applicable to building materials, kitchen containers, home appliances, automotive exhaust system parts, automotive batteries and the like.

Claims (9)

  1. 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하며, 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50 내지 200ea/100㎛2인 강도 및 내산성이 우수한 페라이트계 스테인리스강.By weight, carbon (C): 0.1-0.2%, nitrogen (N): 0.005-0.05%, manganese (Mn): 0.01-0.5%, chromium (Cr): 12.0-19.0%, nickel (Ni): 0.01 To 0.5%, copper (Cu): 0.3 to 1.5%, the remaining iron (Fe) and other unavoidable impurities, strength and acid resistance of 50 to 200ea / 100㎛ 2 per unit area of carbide having a diameter of 100nm or more Excellent ferritic stainless steel.
  2. 제1항에 있어서, The method of claim 1,
    평균 결정립 지름이 10㎛ 이하인 강도 및 내산성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent strength and acid resistance with an average grain size of 10 µm or less.
  3. 제1항에 있어서, The method of claim 1,
    인장강도가 520MPa 이상인 강도 및 내산성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent tensile strength and 520 MPa strength and acid resistance.
  4. 제1항에 있어서, The method of claim 1,
    연신율이 20% 이상인 강도 및 내산성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent elongation and 20% elongation and high acid resistance.
  5. 제1항에 있어서, The method of claim 1,
    5% 황산 분위기에서 임계전류밀도(Icrit)가 10mA 이하인 강도 및 내산성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent strength and acid resistance with a critical current density (I crit ) of 10 mA or less in a 5% sulfuric acid atmosphere.
  6. 중량%로, 탄소(C): 0.1 내지 0.2%, 질소(N): 0.005 내지 0.05%, 망간(Mn): 0.01 내지 0.5%, 크롬(Cr): 12.0 내지 19.0%, 니켈(Ni): 0.01 내지 0.5%, 구리(Cu): 0.3 내지 1.5%, 나머지 철(Fe) 및 기타 불가피한 불순물을 포함하는 페라이트계 스테인리스강 슬라브를 열간 압연하는 단계 및 냉간 압연하는 단계를 포함하며, By weight, carbon (C): 0.1-0.2%, nitrogen (N): 0.005-0.05%, manganese (Mn): 0.01-0.5%, chromium (Cr): 12.0-19.0%, nickel (Ni): 0.01 To 0.5%, copper (Cu): 0.3 to 1.5%, hot rolling and cold rolling a ferritic stainless steel slab containing the remaining iron (Fe) and other unavoidable impurities,
    열간 압연시 하기 식 (1)의 값이 1,000 이하를 만족하는 강도 및 내산성이 우수한 페라이트계 스테인리스강의 제조 방법.The method of manufacturing ferritic stainless steel excellent in strength and acid resistance at which the value of the following formula (1) satisfies 1,000 or less during hot rolling.
    15*RHT/R4+CT ------ 식 (1)15 * RHT / R4 + CT ------ Formula (1)
    여기서, RHT(℃)는 슬라브 재가열 온도를 의미하며, R4(%)는 조압연의 R4 스탠드의 압하율을 의미하며, CT(℃)는 권취 온도를 의미한다.Here, RHT (℃) means the slab reheating temperature, R4 (%) means the reduction ratio of the R4 stand of rough rolling, CT (℃) means the winding temperature.
  7. 제6항에 있어서, The method of claim 6,
    상기 식 (1)의 값은 800 내지 1,000을 만족하는 강도 및 내산성이 우수한 페라이트계 스테인리스강의 제조 방법.The value of said Formula (1) is a manufacturing method of the ferritic stainless steel excellent in intensity | strength and acid resistance which satisfy | fill 800-1,000.
  8. 제6항에 있어서, The method of claim 6,
    RHT는 1,250℃ 미만이며, R4는 40% 이상이며, CT는 650℃ 미만인 강도 및 내산성이 우수한 페라이트계 스테인리스강의 제조 방법.RHT is less than 1,250 ° C, R4 is at least 40%, CT is less than 650 ° C, the method for producing ferritic stainless steel having excellent strength and acid resistance.
  9. 제6항에 있어서, The method of claim 6,
    냉연 판재는 100nm 이상의 지름을 가지는 탄화물의 단위 면적당 개수가 50 내지 200ea/100㎛2이며, 평균 결정립 지름이 10㎛ 이하인 강도 및 내산성이 우수한 페라이트계 스테인리스강의 제조 방법.The cold rolled sheet material has a number of carbides having a diameter of 100 nm or more per unit area of 50 to 200ea / 100㎛ 2 , the average grain diameter of 10㎛ or less manufacturing method of ferritic stainless steel excellent in strength and acid resistance.
PCT/KR2017/014205 2016-12-23 2017-12-06 Ferrite-based stainless steel having excellent strength and acid resistance and method for manufacturing same WO2018117489A1 (en)

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