WO2012128206A1 - プレス成形性に優れた熱延鋼板及びその製造方法 - Google Patents
プレス成形性に優れた熱延鋼板及びその製造方法 Download PDFInfo
- Publication number
- WO2012128206A1 WO2012128206A1 PCT/JP2012/056856 JP2012056856W WO2012128206A1 WO 2012128206 A1 WO2012128206 A1 WO 2012128206A1 JP 2012056856 W JP2012056856 W JP 2012056856W WO 2012128206 A1 WO2012128206 A1 WO 2012128206A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- less
- steel sheet
- cementite
- hot
- inclusions
- Prior art date
Links
Images
Classifications
-
- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing 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
- C22C38/04—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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- 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
-
- 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
- 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
- C21D2211/003—Cementite
-
- 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 hot-rolled steel sheet excellent in press formability suitable for automobiles and a method for producing the same.
- Automobile undercarriage members often have complicated shapes to ensure high rigidity.
- a plurality of types of processing such as burring, stretch flange processing, and stretch processing are performed. Therefore, workability corresponding to these processes is required for a hot-rolled steel sheet as a raw material.
- burring workability and stretch flange workability are considered to correlate with the hole expansion rate measured in the hole expansion test, and development of high-strength steel sheets with improved hole expansion has been promoted so far. .
- single-phase steel is ideal as a hot-rolled steel sheet excellent in hole expansibility, and it is preferable that the difference in plastic deformability between the phases constituting the composite structure is small in the composite steel. . That is, it is preferable that the difference in hardness between the phases is small.
- a hot-rolled steel sheet excellent in hole expansibility according to such a concept, a steel sheet mainly composed of bainite or bainitic ferrite has been proposed (for example, Patent Document 1).
- the present inventors diligently investigated the cause of cracking during actual press forming even in the case of a conventional hot-rolled steel sheet having excellent hole expandability. As a result, the inventors of the present invention are greatly different from the molding in the actual expansion flange processing, and even if the hole expansion performance is excellent, it cannot be said that the stretch flangeability is excellent. I found out.
- the hole expansion rate which indicates the hole expansion property, is an opening ratio until a punched end surface is widened with a punch and a crack generated on the punched end surface penetrates the plate thickness.
- the stretch flange process is a process of stretching a plate end portion cut by a shear or the like when the flange is erected.
- the molding in the hole expansion test is greatly different from the molding in the actual stretch flange processing.
- a difference will arise in the stress state and distortion state of a hot-rolled steel plate, and the amount of limit deformation which leads to a fracture will change. It is thought that the amount of limit deformation changes because the metal structure that greatly affects the fracture changes depending on the stress state and strain state.
- the present invention pays attention to actual stretch flange processing, can suppress cracking during stretch flange molding, and has a hot-rolled steel plate excellent in press formability that has good hole-expandability as in the past and It aims at providing the manufacturing method.
- the cracks generated at the end of the steel sheet progress due to ductile fracture. That is, when a strain is applied, a plurality of voids are generated and grown at the interface between martensite or the hard second phase and the soft phase, and the cracks are developed by connecting the voids to each other. Therefore, it is an important factor to improve the hole expandability and stretch flange workability by making the structure composed of phases having a small strength difference between adjacent phases.
- the present inventors investigated a structure factor that affects stretch flangeability by a side bend test simulating stretch flange processing.
- a side bend test simulating stretch flange processing.
- the side bend elongation is governed by the dispersion state of hard second phase particles such as martensite and / or retained austenite (hereinafter sometimes referred to as MA), cementite hard second phase, and inclusions.
- MA hard second phase particles
- cementite hard second phase cementite hard second phase
- the hole expanding process is a process of expanding a punched hole, and the stretch flange process is performed so that the edge of the steel plate extends when the end of the steel plate is bent to form a flange.
- the strain decreases from the end toward the inside of the workpiece. The reduction rate at this time is called a strain gradient.
- stretch flange processing is a process with a smaller strain gradient than hole expansion processing, so paying attention to strain gradient, stretch flange processing is more sensitive to internal cracks than the hole expansion processing. It becomes easy to progress to.
- a void generation connection index L (Equation 1) reflecting the dispersion state of MA, cementite and inclusions was proposed, and it was found that this index shows a strong correlation with side bend elongation indicating stretch flangeability. That is, a hot-rolled steel sheet with excellent press formability that satisfies both strength and hole expansibility, and has good hole expansibility by controlling the structure so that the void generation connection index L is a high numerical value. Can be obtained.
- n ⁇ , n i , n MA number density of cementite, inclusions and MA (pieces / ⁇ m 2 ), respectively D ⁇ , D i , D MA : cementite, inclusion, mean diameter of MA ( ⁇ m), respectively L ⁇ , L i , L MA : Mean distance ( ⁇ m) between cementite, inclusions and MA, respectively
- the void generation connection index L is 11.5 ( ⁇ m ⁇ 1 ) or more
- the slope of the side bend elongation increases and the elongation increases. It has been found that it has a more sensitive effect on flange workability. Therefore, it has been found that by controlling the structure so that the void generation connection index L is 11.5 ( ⁇ m ⁇ 1 ) or more, the generated voids are difficult to connect and higher stretch flangeability can be obtained.
- the present invention has been made based on these findings, and the gist of the present invention is as follows.
- the void formation connection index L (unit: ⁇ m ⁇ 1 ) represented by Formula 1 is A hot-rolled steel sheet excellent in press formability, characterized by being 11.5 ( ⁇ m ⁇ 1 ) or more.
- n ⁇ , n i, n MA each cementite, inclusions, martensite and one or both of the number density of residual austenite (pieces / [mu] m 2)
- D ⁇ , D i , D MA Average diameter ( ⁇ m) of one or both of cementite, inclusion, martensite, and retained austenite, respectively
- L ⁇ , L i , L MA Mean spacing ( ⁇ m) of one or both of cementite, inclusions, martensite and retained austenite, respectively
- the X-ray random intensity ratio of the ⁇ 211 ⁇ plane parallel to the surface at the 1/2 thickness position, 1/4 thickness position, and 1/8 thickness position is 1.5 or less, respectively.
- the balance consists of Fe and inevitable impurities,
- P 0.05% or less
- S 0.01% or less
- Al 0.30% or less
- N a step of reheating a slab made of steel limited to 0.01% or less to a temperature of 1150 ° C.
- a step of performing finish rolling so that the end temperature is Ae 3 ⁇ 30 ° C. or higher and Ae 3 + 30 ° C. or lower;
- a primary cooling step to a temperature of 510 ° C. to 700 ° C. at a cooling rate of 50 ° C./s or more, Next, air cooling for 2 to 5 seconds;
- a step of performing secondary cooling at a cooling rate of 30 ° C./s or more, Next, a step of winding at a temperature of 500 ° C. to 600 ° C., Next, a step of cooling to 200 ° C.
- a method for producing a hot-rolled steel sheet having excellent press formability comprising obtaining a steel sheet.
- Ae 3 937-477C + 56Si-20Mn-16Cu-15Ni-5Cr + 38Mo + 125V + 136Ti-19Nb + 198Al + 3315B ...
- C, Si, Mn, Cu, Ni, Cr, Mo, V, Ti, Nb, Al, and B in Formula 2 indicate the content (% by mass) of each element.
- the slab is further mass%, Nb: 0.08% or less, Ti: 0.2% or less, V: 0.2% or less, W: 0.5% or less, Mo: 0.4% or less, Cu: 1.2% or less Ni: 0.6% or less Cr: 1.0% or less B: 0.005% or less Ca: 0.01% or less, and REM: 0.01% or less,
- Void formation connection index L represented by Formula 1 regarding the average distance, average diameter, and number density of each or both of cementite, inclusions, and martensite and retained austenite in the metal structure of the steel sheet : ⁇ m ⁇ 1 ) of 11.5 ( ⁇ m ⁇ 1 ) or more, a method for producing a hot-rolled steel sheet having excellent press formability.
- n ⁇ , n i, n MA each cementite, inclusions, martensite and one or both of the number density of residual austenite (pieces / [mu] m 2)
- D ⁇ , D i , D MA Average diameter ( ⁇ m) of one or both of cementite, inclusion, martensite, and retained austenite, respectively
- L ⁇ , L i , L MA Mean spacing ( ⁇ m) of one or both of cementite, inclusions, martensite and retained austenite, respectively (8)
- Void formation connection index L (unit: in terms of the average interval, average diameter, and number density of each or both of cementite, inclusions, and martensite and retained austenite in the metal structure of the steel sheet A method for evaluating a hot-rolled steel sheet having excellent press formability, characterized by evaluating the stretch flangeability of the steel sheet at ⁇ m ⁇ 1 ).
- n ⁇ , n i, n MA each cementite, inclusions, martensite and one or both of the number density of residual austenite (pieces / [mu] m 2)
- D ⁇ , D i , D MA Average diameter ( ⁇ m) of one or both of cementite, inclusion, martensite, and retained austenite, respectively
- L ⁇ , L i , L MA Mean spacing ( ⁇ m) of one or both of cementite, inclusions, martensite and retained austenite, respectively (9)
- it is characterized by evaluating the stretch flangeability of the steel sheet in consideration of the area ratio of ferrite in the metal structure of the steel sheet, the area ratio of bainite, and the area ratio of either one or both of martensite and retained austenite.
- the method for evaluating a hot-rolled steel sheet having excellent press formability according to (8) (10) The steel sheet is (1) % By mass C: 0.03% to 0.10%, Si: 0.5% to 1.5% Mn: 0.5% to 2.0% And the balance consists of Fe and inevitable impurities, As an impurity, P: 0.05% or less, S: 0.01% or less, Al: 0.30% or less, N: The method for evaluating a hot-rolled steel sheet having excellent press formability according to (8) or (9), wherein the steel sheet is limited to 0.01% or less.
- a high-strength hot-rolled steel sheet having excellent ductility, hole expandability, and stretch flangeability can be obtained.
- FIG. 1 is a diagram showing a relationship between void generation connection index and side bend elongation. Data of TS (tensile strength) of 540 MPa or more, ⁇ 110% or more, and elongation at break of 30% or more are plotted.
- the present invention also pays attention to actual stretch flange processing, can suppress cracking during stretch flange molding, and has excellent press formability that has good hole expandability as in the past, and its manufacture It aims to provide a method. Therefore, with the exception of stretch flange workability, the goal is to have the same characteristics as conventional materials.
- a specific target mechanical property a numerical value equivalent to that of a conventional steel having a tensile strength of 540 MPa shown below was set as a target.
- the side bend elongation may be low even in the case of a hot-rolled steel sheet having improved hole expansibility as a structure composed of a phase having a small strength difference between the phases in the crystal structure.
- MA martensite and / or retained austenite
- hard second phase such as cementite
- hard second phase particles such as inclusions It was found to be dominated by the existence state (dispersed state).
- the present inventors have found the void generation connection index L shown in the above formula 1 as an index of the existence state (dispersion state) of these second phases and inclusions.
- index L used as the core of this invention is demonstrated.
- Hole expansion is a process that widens punched holes.
- the punched end is subjected to severe processing.
- Stretch flange processing is performed so that the edge of a steel plate extends when a flange is formed by bending a steel plate end.
- Stretch flange processing is processing with a small strain gradient compared to hole expansion processing. For this reason, in stretch flange processing, minute cracks generated in the punched end portion easily propagate to the inside, and breakage occurs with a strain amount lower than that in hole expansion processing.
- the progress of cracks is defined as the hard second phase such as MA and cementite, and the hard second particles such as inclusions (hereinafter referred to as “hard second phase etc.” unless otherwise specified).
- the hard second phase such as MA and cementite
- the hard second particles such as inclusions
- control of these hard second phases becomes more important than hole expansion processing. Therefore, even if a metal structure is composed of phases having a small strength difference between phases and high hole expandability is realized, high stretch flangeability can be obtained depending on the distribution of MA, cementite, and inclusions. I can't.
- the ease of void formation, the ease of connection of voids, that is, the ease of crack growth, is greatly influenced by the void generation connection index L obtained from the dispersion state of these hard second phases, etc.
- n ⁇ , n i, n MA cementite, inclusions, either or both of martensite and residual austenite, each number density (number / [mu] m 2)
- D ⁇ , D i , D MA Mean diameter ( ⁇ m) of one or both of cementite, inclusions, martensite and retained austenite
- L ⁇ , L i , L MA any one or both of cementite, inclusions, martensite, and retained austenite, average distance ( ⁇ m) of each
- Equation 1 the value obtained by dividing the average interval by the square of the average diameter for each of MA, cementite, and inclusions is the effective interval, and the weighted average of the effective intervals of MA, cementite, and inclusions is the void generation connection index L It is said.
- the void generation connection index L is qualitatively described as follows. The probability of void generation is proportional to the surface area (D 2 ) of the hard second phase, and the ease of connection of voids is inversely proportional to the distance between the phases (interval L 0 between the phases). Therefore, (D 2 / L 0 ) can be considered as an index for generating voids and easily connecting them.
- Equation 3 the subscripts of cementite, inclusions, and MA are ⁇ , i, and MA, and the average intervals L ⁇ , L i , and L MA can be obtained from Equation 3, for example.
- f ⁇ , f i , and f MA indicate the area ratios of cementite, inclusions, and MA, respectively
- D ⁇ , D i , and D MA indicate average diameters ( ⁇ m) of cementite, inclusions, and MA, respectively.
- the area ratio is the ratio of cementite, inclusions, and MA to the entire survey area.
- the average diameter is the average value of the major and minor diameters of cementite, inclusions, and MA, respectively, which were investigated.
- the measuring method of each area ratio, number density, and average interval will be described in Examples described later.
- Equation 3 an average interval ( ⁇ m) when an isotropic distribution is assumed is obtained.
- the ease of connection of voids generated from these depends on the effective interval. This is because voids are more difficult to connect as the effective interval is larger.
- the quotient obtained by dividing the average interval by the square of the average diameter is the effective interval (unit is ⁇ m ⁇ 1 ). This is because the ease of connecting the voids is not simply determined by the average interval, but the smaller the size of the hard second phase, etc., the smaller the voids generated from these and the more difficult it is to connect. is there.
- the ease of generating voids differs depending on the type of the hard second phase and the like, and the inclusions are more likely to generate voids than MA and cementite. This is the reason why the inclusion term is multiplied by a factor in the weighted average.
- the coefficient is the ratio of the number of voids generated per inclusion and the number of voids generated per MA and cementite, and was 2.1 from the observation results.
- FIG. 1 it was confirmed that there is a strong correlation between the void generation connection index L considering the ease of generation of voids and the side bend elongation. Further, it was found that the increase rate of the side bend elongation increases when the void generation connection index exceeds 11.5 ( ⁇ m ⁇ 1 ). That is, it was confirmed that the stretch flangeability can be greatly improved by setting the void generation connection index L to 11.5 ( ⁇ m ⁇ 1 ) or more.
- the amount of strain leading to fracture is due to the generation and connection of voids starting from the hard second phase present in the steel structure, and is determined by the type, amount and size of the hard second phase. Therefore, even if the composition of the steel material changes, the critical void generation connection index that can achieve the effect of the invention does not change.
- interval, and an average diameter are those whose area is 0.1 micrometer ⁇ 2 > or more in the cross section of a hot-rolled steel plate. This is because smaller MA and cementite are less likely to greatly affect the side bend elongation.
- interval, and an average diameter has an area of 0.05 micrometer ⁇ 2 > or more in the cross section of a hot-rolled steel plate. This is because inclusions smaller than this do not greatly affect the side bend elongation.
- the area ratio, average interval, and average diameter are determined by image analysis. Prepare sample for measurement by MA for repeller etching and cementite for picral etching.
- optical micrographs of these samples are binarized, and the area ratio and average diameter can be obtained using image analysis software (for example, Image Pro). Inclusions can be obtained using particle analysis software (for example, particle finder) in FE-SEM. From these values, an interval when an isotropic distribution is assumed can be obtained as an average interval.
- image analysis software for example, Image Pro
- particle analysis software for example, particle finder
- the stretch flangeability of the steel sheet can also be evaluated by the void generation connection index. Since the steel sheet can be evaluated by the void generation connection index without actually testing the steel sheet and confirming the stretch flangeability, the quality control efficiency of the steel sheet can be remarkably improved.
- C 0.03% to 0.10% C is an important component for securing strength.
- the C content is less than 0.03%, it is difficult to obtain sufficient strength, for example, strength of 540 MPa or more.
- the C content is more than 0.10%, the hard second phase such as cementite is excessively increased, and the hole expandability is deteriorated. Therefore, the C content is 0.03% to 0.10%.
- the C content is preferably 0.05% or more from the viewpoint of securing strength, and more preferably 0.06% or more.
- the C content is preferably 0.08% or less, and more preferably 0.07% or less.
- Si 0.5% to 1.5% Si is an important element for securing strength by solid solution strengthening.
- the Si content is less than 0.5%, it is difficult to obtain sufficient strength, for example, strength of 540 MPa or more.
- the Si content is more than 1.5%, the hole expandability deteriorates. This is because when a large amount of Si is added, the toughness is lowered, and the brittle fracture occurs before large deformation. Therefore, the Si content is 0.5% to 1.5%.
- the Si content is preferably 0.7% or more, and more preferably 0.8% or more.
- the Si content is preferably 1.4% or less, and more preferably 1.3% or less.
- Mn 0.5% to 2.0%
- Mn is an important element that ensures hardenability. If the Mn content is less than 0.5%, bainite cannot be generated sufficiently, and it is difficult to obtain sufficient strength, for example, strength of 540 MPa or more. This is because Mn is an austenite former and has an effect of suppressing ferrite transformation. That is, if Mn is small, ferrite transformation proceeds excessively and bainite cannot be obtained. On the other hand, if the Mn content is more than 2.0%, the transformation is remarkably delayed, making it difficult to produce ferrite, and the ductility deteriorates. This is because Mn, which is an austenite former, has the effect of lowering the Ae3 point. Therefore, the Mn content is 0.5% to 2.0%. Furthermore, the Mn content is preferably 1.0% or more, and preferably 1.6% or less.
- Al 0.30% or less
- Al functions as a deoxidizing element, but if the Al content exceeds 0.3%, many inclusions such as alumina are formed, and the hole expandability and stretch flangeability deteriorate. To do. Therefore, Al is an element to be excluded, but even if it is inevitably contained, the Al content is limited to 0.3% or less. Preferably, the content is 0.15% or less, and further limited to 0.10% or less. Although the lower limit of the Al content is not particularly defined, it is technically difficult to reduce it to less than 0.0005%.
- P 0.05% or less
- P is an impurity element, and when the P content is more than 0.05%, when the hot-rolled steel sheet is welded, embrittlement of the weld becomes significant. Therefore, the P content should be as low as possible, and is limited to 0.05% or less. Preferably, it is 0.01% or less. Although the lower limit of the P content is not particularly defined, it is economically disadvantageous to reduce it to less than 0.0001% in a dephosphorization (P) step or the like.
- S 0.01% or less
- S is an impurity element, and if the S content exceeds 0.01%, the adverse effect on weldability becomes significant. Therefore, the S content should be as low as possible, and is limited to 0.01% or less. Preferably, it is 0.005% or less. Moreover, when S is contained excessively, coarse MnS is formed, and the hole expandability and stretch flange workability tend to deteriorate. Although the lower limit of the S content is not particularly defined, it is economically disadvantageous to reduce it to less than 0.0001% in the desulfurization (S) step or the like.
- N 0.01% or less
- N is an impurity element, and if the N content exceeds 0.01%, coarse nitrides are formed, and the hole expandability and stretch flangeability deteriorate. Therefore, the N content should be as low as possible, and is limited to 0.01% or less. Preferably, it is 0.005% or less. Further, as the N content increases, blow holes are more likely to occur during welding.
- the lower limit of the N content is not particularly defined, but when it is reduced to less than 0.0005%, the production cost is remarkably increased.
- the balance of the hot-rolled steel sheet according to the present invention and the steel used for its production is Fe. However, it may contain at least one element selected from Nb, Ti, V, W, Mo, Cu, Ni, Cr, B, Ca, and REM (rare earth metal).
- Nb, Ti, V, W, and Mo are elements that contribute to further improvement in strength.
- the lower limit of the content of these elements is not particularly defined, in order to improve the strength effectively, the Nb content is 0.005% or more, the Ti content is 0.02% or more, and the V content is 0.00. 02% or more, W content is preferably 0.1% or more, and Mo content is preferably 0.05% or more.
- Nb content is 0.08% or less
- Ti content is 0.2% or less
- V content is 0.2% or less
- W content is 0.5% or less
- the Mo content is preferably 0.4% or less.
- Cu, Ni, Cr and B are also elements contributing to high strength. Although the lower limit is not particularly defined, it is preferable to add Cu: 0.1% or more, Ni: 0.01%, Cr: 0.01%, B: 0.0002% or more to obtain the effect of increasing the strength. . However, if excessively added, the formability may be deteriorated, so Cu: 1.2%, Ni: 0.6%, Cr: 1.0%, B: 0.005% are made the upper limit.
- Ca and REM are effective elements for controlling the form of oxides and sulfides.
- the lower limit of the content of these elements is not particularly defined, but in order to effectively control the form, the Ca content and the REM content are preferably 0.0005% or more.
- the Ca content and the REM content are both preferably 0.01% or less.
- REM in this invention shows the element of La and a lanthanoid series.
- misch metal can be added in the steelmaking stage.
- Misch metal contains a series of elements such as La and Ce.
- Metal La and / or metal Ce may be added.
- Ferrite area ratio 70% or more Ferrite is an extremely important structure for ensuring ductility. If the area ratio of ferrite is less than 70%, sufficiently high ductility cannot be obtained. Therefore, the area ratio of ferrite is 70% or more, further preferably 75% or more, and more preferably 80% or more. On the other hand, if the area ratio of ferrite is more than 90%, bainite may be insufficient and the strength may not be ensured. Moreover, C concentration to austenite progresses, and as a result, the strength of bainite increases excessively and the hole expandability may deteriorate. Therefore, the area ratio of ferrite is preferably 90% or less. If possible, it is more preferable that it is 88% or less, and if it is 85% or less, deterioration of hole expansibility is eliminated, which is better.
- Bainite area ratio 30% or less Bainite is an important structure that contributes to strengthening.
- the area ratio of bainite is less than 5%, it is difficult to ensure a sufficiently high tensile strength, for example, a tensile strength of 540 MPa or more. Therefore, the area ratio of bainite is preferably 5% or more, and more preferably 7% or more.
- the area ratio of bainite is preferably 30% or less, more preferably 27% or less from the viewpoint of securing ductility by ferrite, and even more preferably 25% or less.
- MA martensite-residual austenite area ratio: 2% or less MA is one or both of martensite and retained austenite, and is observed as a white part in an optical microscope image of a sample etched with a repeller reagent, for example. be able to. Further, the inclusions include oxides such as MnS and Al 2 O 3 , sulfides, and the like. These contain, for example, impurity components and components added for deoxidation. MA is a structure that forms voids with deformation and deteriorates hole expansibility. Therefore, when the area ratio of MA is more than 2%, such deterioration of hole expansibility becomes remarkable. Therefore, the area ratio of MA is 2% or less. The MA area ratio should be small, preferably 1% or less, more preferably 0.5% or less.
- a hot-rolled steel sheet excellent in press formability having high ductility, hole expansibility, and side bend elongation can be obtained. Therefore, for example, the application of high-strength steel sheets to automobile undercarriage parts is promoted, and the contribution to improvement of fuel consumption and reduction of carbon dioxide emissions is extremely remarkable. Furthermore, by controlling the texture as shown below, a hot-rolled steel sheet with small material anisotropy and excellent press formability can be obtained. That is, in steel having a predetermined component composition, by producing so that the void structure and connection index L is in a predetermined range (11.5 or more in the present invention) with a predetermined structure. It is possible to produce a hot-rolled steel sheet that is excellent not only in hole expandability but also in stretch flangeability.
- Texture is an important factor for material anisotropy. If there is a difference of 10% or more between the side bend elongation in the sheet width direction and the rolling direction, cracks may occur depending on the molding direction of the actual part.
- the X-ray random intensity ratio of the ⁇ 211 ⁇ plane parallel to the steel plate surface (rolled surface) at the 1/2 thickness position, 1/4 thickness position, and 1/8 thickness position of the steel sheet is 1.5 or less and 1.3 or less, respectively. 1.1 or less, the anisotropy of side bend elongation is reduced, and the difference can be 10% or less.
- the 1/2 thickness position, the 1/4 thickness position, and the 1/8 thickness position are positions where the distance in the thickness direction from the surface of the hot-rolled steel sheet is 1/2 of the thickness of the hot-rolled steel sheet, It means that the position is 1/4 and 1/8.
- the amount of strain until the generated crack penetrates in the thickness direction is measured. Therefore, in order to reduce the anisotropy, it is effective to reduce the X-ray random intensity ratio at all plate thickness positions.
- ⁇ Slabs (steel pieces) are obtained by melting and casting steel with the above components. As casting, it is preferable to perform continuous casting from the viewpoint of productivity.
- the slab is reheated to a temperature of 1150 ° C. or higher, held for 120 minutes or more, and then hot-rolled. By heating at 1150 ° C. or more for 120 minutes or more, inclusions such as MnS in the slab are dissolved, and even if inclusions are generated in the subsequent cooling process, the inclusions become fine. is there. If the reheating temperature is less than 1150 ° C., or if the time is less than 120 minutes, the coarse inclusions present in the slab remain without being sufficiently dissolved, and thus high stretch flangeability may not be obtained. is there.
- the upper limit of the reheating temperature is not particularly defined, but is preferably 1300 ° C. or less from the viewpoint of manufacturing cost.
- the upper limit of the reheating holding time is not particularly defined, but is preferably 180 minutes or less from the viewpoint of manufacturing cost. However, this is not the case when a slab cast by continuous casting is directly fed hot and rolled. In that case, what is necessary is just to be a temperature state of 1150 degreeC or more continuously for 120 minutes or more before rolling including the temperature after continuous casting.
- finish rolling In hot rolling, rough rolling is performed, and then finish rolling is performed. At this time, the finish rolling is preferably performed so that the end temperature (finish rolling temperature) is Ae 3 ⁇ 30 ° C. or higher and Ae 3 + 30 ° C. or lower.
- finish rolling temperature is higher than Ae 3 + 30 ° C.
- the austenite grains after recrystallization are coarsened, and ferrite transformation hardly occurs.
- finish rolling temperature is less than Ae 3 -30 ° C., recrystallization is remarkably delayed, and the anisotropy of side bend elongation increases.
- finish rolling is preferably performed so that the temperature is preferably Ae 3 ⁇ 25 ° C.
- Ae 3 937-477C + 56Si-20Mn-16Cu-15Ni-5Cr + 38Mo + 125V + 136Ti-19Nb + 198Al + 3315B (Formula 2)
- C, Si, Mn, Cu, Ni, Cr, Mo, V, Ti, Nb, Al, and B indicate the content (% by mass) of each element.
- the total time between passes of the last four stands in the case of a four-tandem tandem rolling mill, the total time passing between each stand (three sections)) be 3 seconds or less. If the total time between passes exceeds 3 seconds, recrystallization occurs between passes, and strain cannot be accumulated, so that the recrystallization rate after finish rolling becomes slow. As a result, the X-ray random intensity ratio of the ⁇ 211 ⁇ plane increases, and side bend anisotropy may increase.
- the rolled steel sheet is cooled in two stages. This two-stage cooling is called primary cooling and secondary cooling, respectively.
- the cooling rate of a steel plate shall be 50 degrees C / s or more. This is because if the cooling rate of the primary cooling is less than 50 ° C./s, ferrite grains grow greatly and the number of nucleation sites of cementite decreases. As a result, cementite is coarsened, and a void generation connection index L of 11.5 ( ⁇ m ⁇ 1 ) or more cannot be obtained.
- the lower limit of the cooling rate is preferably 60 ° C./s or higher, preferably 70 ° C./s or higher.
- the upper limit of the cooling rate in primary cooling is not specifically defined, it is good to make an upper limit into 300 degrees C / s or less in a practical range.
- Primary cooling is preferably started between 1.0 second and 2.0 seconds from the end of hot rolling. If it is started before the lapse of 1.0 second, recrystallization does not proceed sufficiently, so that the random strength ratio increases and the anisotropy of side bend elongation tends to increase. On the other hand, when cooling is started after 2.0 seconds have elapsed, the ⁇ grains after recrystallization are coarsened, making it difficult to ensure strength.
- the lower limit of the elapsed time from hot rolling to the start of primary cooling is preferably 1.2 seconds, more preferably 1.3 seconds, and the upper limit of the elapsed time is preferably It may be 1.9 seconds, more preferably 1.8 seconds.
- the primary cooling stop temperature is 510 ° C to 700 ° C.
- ferrite grain growth proceeds, and the number of nucleation sites of cementite decreases.
- a void generation connection index L 11.5 ( ⁇ m ⁇ 1 ) or more cannot be obtained.
- the primary cooling stop temperature is as low as possible. Therefore, the primary cooling stop temperature is preferably 650 ° C. or less, and more preferably 620 ° C. or less. More preferably, when the temperature is 600 ° C.
- the primary cooling stop temperature is desirably as low as possible, but it cannot be so low from the viewpoint of the ferrite transformation rate.
- the lower limit of the primary cooling stop temperature is preferably 520 ° C., more preferably 530 ° C. More preferably, if the primary cooling stop temperature is set to 550 ° C. or higher, the ferrite transformation also proceeds, and the subsequent air cooling effect can be obtained with a margin.
- Air cooling is performed for 2 to 5 seconds between primary cooling and secondary cooling. If the air cooling time is less than 2 seconds, the ferrite transformation does not proceed sufficiently and sufficient elongation cannot be obtained. On the other hand, when the air cooling time is longer than 5 seconds, pearlite is generated and bainite cannot be obtained, so that the strength is lowered.
- the air cooling is to leave in the atmosphere, that is, to let it cool, and its cooling rate is about 4 to 5 ° C./s.
- the cooling rate in the secondary cooling is 30 ° C./s or more. This is because when the cooling rate is less than 30 ° C./s, the growth of cementite is promoted, and a void generation connection index L of 11.5 ( ⁇ m ⁇ 1 ) or more cannot be obtained.
- the cooling rate is preferably 40 ° C./s or more, and more preferably 50 ° C./s or more.
- the upper limit of the cooling rate in secondary cooling is not specifically defined, it is good to make an upper limit into 300 degrees C / s or less in a practical range.
- the end point temperature of the secondary cooling is substantially the same as the winding start temperature.
- the winding start temperature is preferably 500 ° C. to 600 ° C.
- the upper limit of the winding start temperature is preferably 590 ° C, and more preferably 580 ° C.
- the winding start temperature is less than 500 ° C.
- bainite becomes excessive, and not only the hole expandability but also stretch flangeability deteriorate.
- the winding start temperature is a low temperature of less than 500 ° C.
- the formation of acicular ferrite is easily promoted.
- the needle-like ferrite easily generates a void as a starting point of the crack, deteriorates the stretch flangeability, and lowers the ductility.
- the winding start temperature is preferably 510 ° C.
- it is more preferable that it is 520 degreeC or more. If it is 530 degreeC or more, the production
- the average cooling rate until reaching 200 ° C. from the winding start temperature is 30 ° C./h or more.
- the method for controlling the cooling rate is not particularly limited.
- the coil obtained by winding may be directly water-cooled.
- the cooling rate decreases as the coil mass increases, the cooling rate can be increased by reducing the coil mass.
- the production method is based on the production method described above, and the void generation connection index L proposed in the present invention is within a predetermined range (11.5 or more in the present invention). In this way, it is advisable to finely modify the unique characteristics of the production line.
- the area ratio of ferrite and the area ratio of pearlite were measured from optical micrographs at 1/4 thickness positions of samples etched with a nital reagent.
- the area ratio (f MA ), average diameter (D MA ), and number density (n MA ) of MA were measured by image analysis of a 500-fold optical micrograph at a 1/4 thickness position of a sample etched with a repeller reagent. .
- the measurement field of view and 40000Myuemu 2 or more, area was measured to 0.1 [mu] m 2 or more MA.
- the area ratio of bainite was the area ratio of the remainder of ferrite, pearlite, and MA.
- the area ratio (f ⁇ ), average diameter (D ⁇ ), and number density (n ⁇ ) of cementite were measured by image analysis of a 1000 times optical micrograph at a 1/4 thickness position of a sample etched with a Picral reagent. did.
- the measurement field of view was 10,000 ⁇ m 2 or more, and two or more fields were measured per sample, and cementite having an area of 0.1 ⁇ m 2 or more was used as the measurement target.
- the area ratio (f i ), average diameter (D i ), and number density (n i ) of inclusions are 1 at the 1/4 thickness position of the plate thickness cross section in the rolling direction by particle analysis (particle finder method). Measured within an area of 0.0 mm ⁇ 2.0 mm. At this time, inclusions having an area of 0.05 ⁇ m 2 or more were measured.
- the measurement object of MA and cementite is set to have an area of 0.1 ⁇ m 2 or more because smaller MA and cementite do not significantly affect the side bend elongation.
- the inclusion was measured with an area of 0.05 ⁇ m 2 or more because inclusions are more likely to generate voids than MA and cementite and affect side bend elongation. is there.
- Tensile strength and elongation at break were measured according to JIS Z 2241 using a JIS Z 2201 No. 5 test piece taken perpendicularly to the rolling direction from the center in the sheet width direction.
- the hole expansion rate was evaluated according to the test method described in the Japan Iron and Steel Federation plan JFST 1001-1996, using a hole expansion test piece taken from the center in the plate width direction.
- Side bend elongation was evaluated by the method described in JP-A-2009-145138. In this method, strip-shaped steel slabs were collected from the hot-rolled steel sheet in two directions, ie, the rolling direction and the direction perpendicular to the rolling direction (sheet width direction). A ruled line was drawn on the surface of the steel slab.
- test no. In No. 1 since the C content was lower than the range of the present invention, a strength of 540 MPa or more could not be obtained.
- Test No. In No. 2 since the C content was higher than the range of the present invention, the area ratio of bainite was higher than the range of the present invention, and the ductility and the hole expansion rate were low.
- Test No. 3 since the Si content was lower than the range of the present invention, cementite was excessively generated, and the void generation connection index L became smaller than the range of the present invention. For this reason, although the hole expansion ratio was high, side bend elongation of 70% or more was not obtained. Test No. In No. 4, since the Si content was higher than the range of the present invention, 110% or more hole expandability was not obtained.
- the cooling rate of the primary cooling is lower than the range of the present invention, so that coarse carbides are generated, the void generation connection index L is smaller than the range of the present invention, and the side bend elongation is 70% or more. It was not obtained.
- Test No. 21 since the primary cooling stop temperature was lower than the range of the present invention, the ferrite transformation did not proceed and the elongation was low. That is, the ductility deteriorated. Test No. In No. 22, since the primary cooling stop temperature was higher than the range of the present invention, the second phase became coarse and the side bend elongation decreased.
- Test No. 23 since the air cooling time was shorter than the range of the present invention, the ferrite transformation did not proceed and the elongation was low. That is, the ductility was low. Test No. In No. 24, since the air cooling time was longer than the range of the present invention, pearlite was generated, and bainite was not obtained, so the strength was lowered. Test No. In No. 25, since the winding temperature was lower than the range of the present invention, bainite was excessive and the ductility was low. Test No. In No. 26, since the winding temperature was higher than the range of the present invention, a strength of 540 MPa or more could not be obtained. Further, the carbide was coarsened and the side bend elongation was low.
- FIG. 1 shows the measurement results obtained by these tests, those having a tensile strength of 540 MPa or more and a hole expansion ratio of 110% or more.
- a high-strength steel of 540 MPa class or higher can produce a steel sheet having not only hole expandability but also stretch flange workability and excellent workability and press formability. Therefore, the present invention is not limited to the steel industry but can be widely used in industries such as the automobile industry using steel plates.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
また、前述したように従来技術では、穴広げ性と伸びフランジ加工性が同一視されており、比較的良好な穴広げ性が得られているため、MA、セメンタイト、及び介在物の排除やそれらの存在状況についての検討は行われていなかった。
Dθ、Di、DMA:それぞれセメンタイト、介在物、MAの平均直径(μm)
Lθ、Li、LMA:それぞれセメンタイト、介在物、MAの平均間隔(μm)
本発明は、これら知見により成されたものであり、その主旨とするところは以下のとおりである。
質量%で、
C :0.03%~0.10%、
Si:0.5%~1.5%、
Mn:0.5%~2.0%、
を含有し、残部がFe及び不可避的不純物からなり、
不純物として
P :0.05%以下、
S :0.01%以下、
Al:0.30%以下、
N :0.01%以下に限定した鋼板であって、
前記鋼板の金属組織における、フェライトの面積率が70%以上、ベイナイトの面積率が30%以下、マルテンサイト及び残留オーステナイトのいずれか一方または両方の面積率が2%以下であり、
セメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標L(単位:μm-1)が11.5(μm-1)以上であることを特徴とするプレス成形性に優れた熱延鋼板。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径(μm)
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔(μm)
(2)
前記鋼板が、さらに質量%で、
Nb:0.08%以下、
Ti:0.2%以下、
V:0.2%以下、
W:0.5%以下、
Mo:0.4%以下、
Cu:1.2%以下
Ni:0.6%以下
Cr:1.0%以下
B:0.005%以下
Ca:0.01%以下、及び
REM:0.01%以下、
のうち一種または二種以上を含むことを特徴とする(1)に記載のプレス成形性に優れた熱延鋼板。
(3)
前記鋼板において、その表面から厚さ方向で、1/2厚位置、1/4厚位置、1/8厚位置における表面と平行な{211}面のX線ランダム強度比がそれぞれ1.5以下、1.3以下、1.1以下であることを特徴とする(1)または(2)に記載のプレス成形性に優れた熱延鋼板。
(4)
質量%で、
C :0.03%~0.10%、
Si:0.5%~1.5%、
Mn:0.5%~2.0%、
を含有し、残部がFe及び不可避的不純物からなり、
不純物として
P :0.05%以下、
S :0.01%以下、
Al:0.30%以下、
N :0.01%以下に限定した鋼からなるスラブを
1150℃以上の温度に再加熱し、120分間以上保持して、粗圧延を行う工程と、
次に、終了温度がAe3-30℃以上、Ae3+30℃以下となるように仕上圧延を行う工程と、
次に、50℃/s以上の冷却速度で510℃~700℃の温度まで一次冷却する工程と、
次に、2秒間~5秒間の空冷を行う工程と、
次に、30℃/s以上の冷却速度で二次冷却する工程と、
次に、500℃~600℃の温度で巻き取りを行う工程と、
次に、30℃/h以上の平均冷却速度で200℃以下まで冷却する工程と、
を有し鋼板を得ることを特徴とするプレス成形性に優れた熱延鋼板の製造方法。
ここで、Ae3=937-477C+56Si-20Mn-16Cu-15Ni-5Cr+38Mo+125V+136Ti-19Nb+198Al+3315B
・・・(式2)
式2中のC、Si、Mn、Cu、Ni、Cr、Mo、V、Ti、Nb、Al、Bは各元素の含有量(質量%)を示す。
(5)
前記仕上圧延における最終の4スタンドの合計パス間時間を3秒間以下とすることを特徴とする(4)に記載のプレス成形性に優れた熱延鋼板の製造方法。
(6)
前記スラブが、さらに質量%で、
Nb:0.08%以下、
Ti:0.2%以下、
V:0.2%以下、
W:0.5%以下、
Mo:0.4%以下、
Cu:1.2%以下
Ni:0.6%以下
Cr:1.0%以下
B:0.005%以下
Ca:0.01%以下、及び
REM:0.01%以下、
のうち一種または二種以上を含むことを特徴とする(4)又は(5)に記載のプレス成形性に優れた熱延鋼板の製造方法。
(7)
前記鋼板の金属組織におけるセメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標L(単位:μm-1)が11.5(μm-1)以上になることを特徴とするプレス成形性に優れた熱延鋼板の製造方法。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径(μm)
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔(μm)
(8)
鋼板の金属組織におけるセメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標L(単位:μm-1)で鋼板の伸びフランジ加工性を評価することを特徴とするプレス成形性に優れた熱延鋼板の評価方法。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径(μm)
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔(μm)
(9)
さらに、前記鋼板の金属組織におけるフェライトの面積率、ベイナイトの面積率、およびマルテンサイト及び残留オーステナイトのいずれか一方または両方の面積率で加味して鋼板の伸びフランジ加工性を評価することを特徴とする(8)に記載のプレス成形性に優れた熱延鋼板の評価方法。
(10)
前記鋼板が、(1)
質量%で、
C :0.03%~0.10%、
Si:0.5%~1.5%、
Mn:0.5%~2.0%、
を含有し、残部がFe及び不可避的不純物からなり、
不純物として
P :0.05%以下、
S :0.01%以下、
Al:0.30%以下、
N :0.01%以下に限定した鋼板であることを特徴とする(8)または(9)に記載のプレス成形性に優れた熱延鋼板の評価方法。
引張強度 540MPa
破断伸び 30%
穴広げ率 110%
伸びフランジ加工性についてはサイドベンド伸びで評価する。
以下本発明について詳細に説明する。
前述したように、結晶組織において各相間の強度差の小さい相からなる組織として穴広げ性を高めた熱延鋼板であっても、サイドベンド伸びが低い場合があることがある。その理由を究明する過程で、サイドベンド伸びが、マルテンサイト及び残留オーステナイトのいずれか一方または両方(以下、MAという)、セメンタイト等の硬質第二相、並びに介在物等の硬質第二相粒子の存在状態(分散状態)によって支配されていることが分かった。本発明者らは、これら第二相や介在物等の存在状態(分散状態)の指標として、前記式1に示すボイド生成連結指標Lを見出した。以下、本発明の中核となるボイド生成連結指標Lについて説明する。
Dθ、Di、DMA:セメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方、それぞれの平均直径(μm)
Lθ、Li、LMA:セメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方、それぞれの平均間隔(μm)
ここで、セメンタイト、介在物、MAの添字をθ、i、MAとし、各平均間隔Lθ、Li、LMAは、例えば、式3から求めることができる。式3において、fθ、fi、fMAは、それぞれセメンタイト、介在物、MAの面積率を示し、Dθ、Di、DMAは、それぞれセメンタイト、介在物、MAの平均直径(μm)を示す。 面積率は、調査範囲全体に対するセメンタイト、介在物、MAがそれぞれ占める割合である。平均直径は、調査対象となったそれぞれセメンタイト、介在物、MAの長径と短径の平均値とする。それぞれの面積率、個数密度、平均間隔の測定方法については、後述する実施例において説明する。
この式3では、等方分布を仮定した場合の平均間隔(μm)が求められる。
また、硬質第二相等が小さいと、ボイドが成長しづらくなるだけでなく、連結も起こりにくくなる。したがって破断に至るまでの歪量は硬質第二相等が小さい程、ボイド生成連結指標Lが大きいほど増加することになる。平均直径の2乗となる理由は、加工によって生まれる硬質第二相等の周りの応力は、サイズに比例する一方で、硬質第二相等の単位表面積当りの応力は小さくなってボイドが成長しづらくなるためだと考えられる。
図1に示すように、ボイドの生成しやすさを考慮したボイド生成連結指標Lとサイドベンド伸びとの間には強い相関関係が存在することが確認された。さらに、ボイド生成連結指標が11.5(μm-1)を境にそれ以上になると、サイドベンド伸びの増加率が増えることが分かった。つまり、ボイド生成連結指標Lが11.5(μm-1)以上とすることにより、伸びフランジ加工性を大きく改善することができることを確認した。
面積率、平均間隔、平均直径は画像解析によって求められる。MAはレペラーエッチング、セメンタイトはピクラールエッチングして計測用サンプルを準備する。これらサンプルの光学顕微鏡写真を二値化し、画像解析ソフト(例えばImage Pro)を用いて面積率と平均直径を求めることができる。介在物はFE-SEMにて粒子解析ソフト(例えばparticle finder)を用いて求めることができる。これらの値から、等方分布を仮定した場合の間隔を平均間隔として求めることができる。
次に、本発明に係る熱延鋼板及びその製造に用いる鋼の成分について詳細に説明する。なお、各成分の含有量の単位である「%」は「質量%」を意味する。
Cは強度を確保するために重要な成分である。C含有量が0.03%未満であると、十分な強度、例えば540MPa以上の強度を得ることが困難である。一方、C含有量が0.10%超であると、セメンタイト等の硬質第二相等が過剰に増加し、穴広げ性が劣化する。従って、C含有量は0.03%~0.10%とする。なお、C含有量は、強度確保の観点から0.05%以上であることが好ましく、さらに0.06%以上であると更に好ましい。また、セメンタイト等の硬質第二相等の過剰な増加を極力抑えるため、C含有量は0.08%以下であることが好ましく、更には0.07%以下であることがより好ましい。
Siは固溶強化により強度を確保するために重要な元素である。Si含有量が0.5%未満であると、十分な強度、例えば540MPa以上の強度を得ることが困難である。一方、Si含有量が1.5%超であると、穴広げ性が劣化する。Siを多量に添加すると靭性が低下し、大きく変形する前に脆性破壊してしまうからである。従って、Si含有量は0.5%~1.5%とする。
なお、強度確保の観点からSi含有量は0.7%以上であることが好ましく、さらには0.8%以上であるとより好ましい。また、硬質第二相等の過剰な増加を極力抑える観点からSi含有量は、1.4%以下であることが好ましく、さらには1.3%以下とするとより好ましい。
Mnは焼き入れ性を担保する重要な元素である。Mn含有量が0.5%未満であると、ベイナイトを十分に生成させることができず、十分な強度、例えば540MPa以上の強度を得ることが困難である。Mnはオーステナイトフォーマーであり、フェライト変態を抑制する効果があるからである。つまり、Mnが少ないとフェライト変態が過剰に進行し、ベイナイトを得ることができないからである。
一方、Mn含有量が2.0%超であると、変態が著しく遅延し、フェライトを生成させることが困難となって延性が劣化する。オーステナイトフォーマーであるMnはAe3点を低下させる効果があるからである。従って、Mn含有量は0.5%~2.0%とする。さらには、Mn含有量は1.0%以上であることが好ましく、1.6%以下であることが好ましい。
Alは脱酸元素として機能するが、Al含有量が0.3%超であると、アルミナ等の介在物が多く形成され、穴広げ性及び伸びフランジ加工性が劣化する。従って、Alは排除したい元素であるが、不可避的に含有されたとしてもAl含有量は0.3%以下に限定する。好ましくは0.15%以下とするとよく、さらには0.10%以下に限定するとよい。なお、Al含有量の下限は特に定めないが、技術的に、0.0005%未満まで低減させることは困難である。
Pは不純物元素であり、P含有量が0.05%超であると、熱延鋼板に溶接が施された場合に溶接部の脆化が顕著になる。従って、P含有量はできるだけ少ないほうがよく、0.05%以下に限定する。好ましくは、0.01%以下とするとよい。なお、P含有量の下限は特に定めないが、脱リン(P)工程などで0.0001%未満まで低減することは経済的に不利である。
Sは不純物元素であり、S含有量が0.01%超であると、溶接性への悪影響が顕著となる。従って、S含有量はできるだけ少ないほうがよく、0.01%以下に限定する。好ましくは、0.005%以下とするとよい。また、Sが過剰に含有されていると、粗大なMnSが形成され、穴広げ性及び伸びフランジ加工性が劣化しやすい。なお、S含有量の下限は特に定めないが、脱硫(S)工程などで0.0001%未満まで低減することは経済的に不利である。
Nは不純物元素であり、N含有量が0.01%超であると、粗大な窒化物が形成され、穴広げ性及び伸びフランジ加工性が劣化する。従って、N含有量はできるだけ少ないほうがよく、0.01%以下に限定する。好ましくは、0.005%以下とするとよい。また、N含有量が増加するほど、溶接時にブローホールが発生しやすくなる。N含有量の下限は特に定めないが、0.0005%未満まで低減すると、製造コストが著しく上昇する。
次に、本発明に係る熱延鋼板の組織について詳細に説明する。
フェライトは延性を確保するために極めて重要な組織である。フェライトの面積率が70%未満であると、十分に高い延性を得ることができない。従って、フェライトの面積率は70%以上とし、さらには75%以上が好ましく、80%以上であるとより好ましい。一方、フェライトの面積率が90%超であると、ベイナイトが不足して強度を確保できない可能性がある。また、オーステナイトへのC濃化が進み、その結果、ベイナイトの強度が過剰に高まって穴広げ性が劣化することもある。従って、フェライトの面積率は90%以下であることが好ましい。できれば88%以下であるとより好ましく、85%以下であれば、穴拡げ性の劣化がなくなるので、よりよい。
ベイナイトは強化に寄与する重要な組織である。ベイナイトの面積率が5%未満であると、十分に高い引張強度、例えば540MPa以上の引張強度を確保することが困難となる。従って、ベイナイトの面積率は5%以上であることが好ましく、7%以上あるとより好ましい。一方、ベイナイトの面積率が30%を超えると、フェライトの面積率が不足して十分な延性が得られない。従って、ベイナイトの面積率は30%以下とするとよく、フェライトによる延性確保の観点から27%以下がより好ましく、25%以下であればなお好ましい。
MAは、マルテンサイトと残留オーステナイトのいずれか一方または両方であり、例えば、レペラー試薬にてエッチングしたサンプルの光学顕微鏡像において白色部として観察することができる。また、介在物には、MnS、Al2O3等の酸化物、硫化物等が含まれる。これらは、例えば、不純物成分や脱酸のために添加される成分を含有している。
MAは変形に伴ってボイドを形成し、穴広げ性を劣化させる組織である。そのため、MAの面積率が2%超であると、このような穴広げ性の劣化が顕著となる。従って、MAの面積率は2%以下とする。MA面積率は少ないほうがよく、できれば1%以下、さらに0.5%以下であればより好ましい。
即ち、所定の成分組成を有する鋼において、所定の組織構造であってボイド生成連結指標Lが所定の範囲(本発明においては11.5以上)となるように製造することにより、
穴拡げ性だけでなく伸びフランジ加工性にも優れた熱延鋼板を製造することができるのである。
次に、本発明に係る熱延鋼板の製造方法について説明する。
Ae3=937-477C+56Si-20Mn-16Cu-15Ni-5Cr+38Mo+125V+136Ti-19Nb+198Al+3315B ・・・(式2)
ここで、C、Si、Mn、Cu、Ni、Cr、Mo、V、Ti、Nb、Al、Bは各元素の含有量(質量%)を示す。
セメンタイトやMAの微細化のためには、一次冷却停止温度はできるだけ低い方が望ましい。このため、一次冷却の停止温度は650℃以下とすることが好ましく、620℃以下であるとより好ましい。さらに好ましくは600℃以下とするとより微細なセメンタトやMAが得られる。
一方、510℃未満の温度で停止すると、フェライト変態が進まずにベイナイト体積率が増加するため、延性が劣化する。セメンタイトやMAの微細化のためには、一次冷却停止温度はできるだけ低い方が望ましいが、フェライト変態率の観点からはあまり低くすることはできない。このため、一次冷却の停止温度の下限は、好ましくは520℃、より好ましくは530℃とするとよい。さらに好ましくは一次冷却の停止温度を550℃以上とすれば、フェライト変態も進み、その後の空冷の効果が余裕をもって得ることができる。
以上、本発明について詳細に説明したが、本発明は前記した実施態様に限定されることはない。本発明の技術的特徴を備える態様であれば、特に限定されない。
また、製造ライン固有の特性もあるため、製造方法においては、前記した製造方法を機軸とし、本発明で提案するボイド生成連結指標Lが所定の範囲(本発明においては11.5以上)となるように製造ラインの固有の特性を微修正するとよい。
穴広げ率は板幅方向の中央から採取した穴広げ試験片を用い、日本鉄鋼連盟企画JFST 1001-1996に記載の試験方法に準拠して評価した。
サイドベンド伸びは、特開2009-145138号公報に記載された方法で評価した。この方法では、熱延鋼板から圧延方向及び圧延方向に対して垂直な方向(板幅方向)の2方向に短冊状の鋼片を採取した。そして、鋼片の表面に罫書き線を描いた。次いで、鋼片の長手方向の中央部における幅方向の端部を半円状に打ち抜いた。続いて、その打ち抜き端面に対して引張曲げを行い、板厚を貫通する亀裂を発生させた。そして、当該亀裂が発生までの歪量を、予め描いておいた罫書き線に基づいて測定した。
試験No.2では、C含有量が本発明範囲よりも高いため、ベイナイトの面積率が本発明範囲よりも高くなり、延性および穴広げ率が低かった。
試験No.4では、Si含有量が本発明範囲よりも高いため、110%以上の穴広げ性が得られなかった。
試験No.6では、Mn含有量が本発明範囲よりも高いため、硬質第二相が過剰に生成し、30%以上の伸びが得られなかった。つまり、延性が低かった。
試験No.22では、一次冷却の停止温度が本発明範囲よりも高いため、第二相が粗大化し、サイドベンド伸びが低下した。
試験No.24では、空冷時間が本発明範囲よりも長いため、パーライトが生成し、ベイナイトが得られなかったため、強度が低下した。
試験No.25では、巻き取り温度が本発明範囲よりも低いため、ベイナイトが過剰となり、延性が低かった。試験No.26では、巻き取り温度が本発明範囲よりも高いため、540MPa以上の強度が得られなかった。また炭化物が粗大化し、サイドベンド伸びも低かった。
Claims (8)
- 質量%で、
C :0.03%~0.10%、
Si:0.5%~1.5%、
Mn:0.5%~2.0%、
を含有し、残部がFe及び不可避的不純物からなり、
不純物として
P :0.05%以下、
S :0.01%以下、
Al:0.30%以下、
N :0.01%以下に限定した鋼板であって、
前記鋼板の金属組織における、フェライトの面積率が70%以上、ベイナイトの面積率が30%以下、マルテンサイト及び残留オーステナイトのいずれか一方または両方の面積率が2%以下であり、
セメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標Lが11.5以上であることを特徴とするプレス成形性に優れた熱延鋼板。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径であって、単位はμmである。
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔であって、単位はμmである。
- 前記鋼板が、さらに質量%で、
Nb:0.08%以下、
Ti:0.2%以下、
V:0.2%以下、
W:0.5%以下、
Mo:0.4%以下、
Cu:1.2%以下
Ni:0.6%以下
Cr:1.0%以下
B:0.005%以下
Ca:0.01%以下、及び
REM:0.01%以下、
のうち一種または二種以上を含むことを特徴とする請求項1に記載のプレス成形性に優れた熱延鋼板。
- 前記鋼板において、その表面から厚さ方向で、1/2厚位置、1/4厚位置、1/8厚位置における表面と平行な{211}面のX線ランダム強度比がそれぞれ1.5以下、1.3以下、1.1以下であることを特徴とする請求項1または2に記載のプレス成形性に優れた熱延鋼板。
- 質量%で、
C :0.03%~0.10%、
Si:0.5%~1.5%、
Mn:0.5%~2.0%、
を含有し、残部がFe及び不可避的不純物からなり、
不純物として
P :0.05%以下、
S :0.01%以下、
Al:0.30%以下、
N :0.01%以下に限定した鋼からなるスラブを
1150℃以上の温度に再加熱し、120分間以上保持して、粗圧延を行う工程と、
次に、終了温度がAe3-30℃以上、Ae3+30℃以下となるように仕上圧延を行う工程と、
次に、50℃/s以上の冷却速度で510℃~700℃の温度まで一次冷却する工程と、
次に、2秒間~5秒間の空冷を行う工程と、
次に、30℃/s以上の冷却速度で二次冷却する工程と、
次に、500℃~600℃の温度で巻き取りを行う工程と、
次に、30℃/h以上の平均冷却速度で200℃以下まで冷却する工程と、
を有し鋼板を得ることを特徴とするプレス成形性に優れた熱延鋼板の製造方法。
ここで、Ae3=937-477C+56Si-20Mn-16Cu-15Ni-5Cr+38Mo+125V+136Ti-19Nb+198Al+3315B
・・・(式2)
式2中のC、Si、Mn、Cu、Ni、Cr、Mo、V、Ti、Nb、Al、Bは各元素の含有量を示し、単位は質量%である。
- 前記仕上圧延における最終の4スタンドの合計パス間時間を3秒間以下とすることを特徴とする請求項4に記載のプレス成形性に優れた熱延鋼板の製造方法。
- 前記スラブが、さらに質量%で、
Nb:0.08%以下、
Ti:0.2%以下、
V:0.2%以下、
W:0.5%以下、
Mo:0.4%以下、
Cu:1.2%以下
Ni:0.6%以下
Cr:1.0%以下
B:0.005%以下
Ca:0.01%以下、及び
REM:0.01%以下、
のうち一種または二種以上を含むことを特徴とする請求項4又は5に記載のプレス成形性に優れた熱延鋼板の製造方法。
- 前記鋼板の金属組織におけるセメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標Lが11.5以上になることを特徴とする請求項4又は5に記載のプレス成形性に優れた熱延鋼板の製造方法。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径であって、単位はμmである。
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔であって、単位はμmである。
- 前記鋼板の金属組織におけるセメンタイト、介在物、並びに、マルテンサイト及び残留オーステナイトのいずれか一方または両方の各々の平均間隔、平均直径、及び個数密度に関し、式1で表わされるボイド生成連結指標Lが11.5以上になることを特徴とする請求項6に記載のプレス成形性に優れた熱延鋼板の製造方法。
Dθ、Di、DMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均直径であって、単位はμmである。
Lθ、Li、LMA:それぞれセメンタイト、介在物、マルテンサイト及び残留オーステナイトのいずれか一方または両方の平均間隔であって、単位はμmである。
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/005,408 US10428409B2 (en) | 2011-03-18 | 2012-03-16 | Hot-rolled steel sheet with excellent press formability and production method thereof |
MX2013009509A MX364430B (es) | 2011-03-18 | 2012-03-16 | Hoja de acero laminado en caliente con excelente formabilidad de prensa y metodo de produccion del mismo. |
BR112013023633A BR112013023633A2 (pt) | 2011-03-18 | 2012-03-16 | chapa de aço laminada a quente com excelente capacidade de conformação por prensagem e seu método de produção |
JP2013505944A JP5429429B2 (ja) | 2011-03-18 | 2012-03-16 | プレス成形性に優れた熱延鋼板及びその製造方法 |
KR1020137021326A KR101531778B1 (ko) | 2011-03-18 | 2012-03-16 | 프레스 성형성이 우수한 열연 강판 및 그 제조 방법 |
CN201280005592.5A CN103328671B (zh) | 2011-03-18 | 2012-03-16 | 冲压成形性优良的热轧钢板及其制造方法 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2011-061500 | 2011-03-18 | ||
JP2011061500 | 2011-03-18 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2012128206A1 true WO2012128206A1 (ja) | 2012-09-27 |
Family
ID=46879353
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2012/056856 WO2012128206A1 (ja) | 2011-03-18 | 2012-03-16 | プレス成形性に優れた熱延鋼板及びその製造方法 |
Country Status (7)
Country | Link |
---|---|
US (1) | US10428409B2 (ja) |
JP (1) | JP5429429B2 (ja) |
KR (1) | KR101531778B1 (ja) |
CN (1) | CN103328671B (ja) |
BR (1) | BR112013023633A2 (ja) |
MX (1) | MX364430B (ja) |
WO (1) | WO2012128206A1 (ja) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2014185359A (ja) * | 2013-03-22 | 2014-10-02 | Jfe Steel Corp | 高強度鋼板 |
JP2015203124A (ja) * | 2014-04-11 | 2015-11-16 | 新日鐵住金株式会社 | 熱延鋼板およびその製造方法 |
JP2019523828A (ja) * | 2016-06-21 | 2019-08-29 | 宝山鋼鉄股▲分▼有限公司 | 980MPa級の熱間圧延フェライトベイナイト二相鋼及びその製造方法 |
JP2019533082A (ja) * | 2016-09-22 | 2019-11-14 | タタ、スティール、アイモイデン、ベスローテン、フェンノートシャップTata Steel Ijmuiden Bv | 優れた伸びフランジ成形性及びエッジ疲労性能を有する熱間圧延高強度鋼の製造方法 |
JP2020509172A (ja) * | 2016-12-13 | 2020-03-26 | ポスコPosco | 低温域におけるバーリング性に優れた高強度複合組織鋼及びその製造方法 |
WO2022210220A1 (ja) * | 2021-03-30 | 2022-10-06 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103469079B (zh) * | 2013-10-08 | 2015-09-09 | 武汉钢铁(集团)公司 | 抗拉强度490MPa级具有高扩孔性能的铁素体贝氏体钢及其生产方法 |
KR101560944B1 (ko) * | 2013-12-24 | 2015-10-15 | 주식회사 포스코 | 표면 품질이 우수한 고강도 열연강판 및 그 제조방법 |
KR101630977B1 (ko) * | 2014-12-09 | 2016-06-16 | 주식회사 포스코 | 성형성이 우수한 고강도 열연강판 및 그 제조방법 |
WO2017006563A1 (ja) * | 2015-07-06 | 2017-01-12 | Jfeスチール株式会社 | 高強度薄鋼板およびその製造方法 |
KR101797383B1 (ko) * | 2016-08-09 | 2017-11-13 | 주식회사 포스코 | 재질편차가 적고 표면품질이 우수한 고강도 열연강판 및 그 제조방법 |
KR101899674B1 (ko) * | 2016-12-19 | 2018-09-17 | 주식회사 포스코 | 저온역 버링성이 우수한 고강도 강판 및 이의 제조방법 |
KR101917469B1 (ko) * | 2016-12-23 | 2018-11-09 | 주식회사 포스코 | 재질편차가 적고 표면품질이 우수한 고강도 열연강판 및 그 제조방법 |
KR101917466B1 (ko) * | 2016-12-23 | 2019-01-24 | 주식회사 포스코 | 재질편차와 굽힘가공성이 우수한 박물 열연 내후성강판 및 그 제조방법 |
CN106756517B (zh) * | 2017-02-17 | 2018-06-01 | 上海海事大学 | 一种用于极地船舶的钢板及其制造方法 |
CN110621794B (zh) * | 2017-04-20 | 2022-03-29 | 塔塔钢铁荷兰科技有限责任公司 | 具有优异延展性和可拉伸翻边性的高强度钢片 |
CN108796363B (zh) * | 2017-04-27 | 2020-10-27 | 宝山钢铁股份有限公司 | 适应大变形及冲压加工的高表面质量覆铝基板用钢及其生产方法 |
CN107747042A (zh) * | 2017-11-06 | 2018-03-02 | 攀钢集团攀枝花钢铁研究院有限公司 | 一种690MPa级经济型高表面质量高扩孔钢及其制备方法 |
CN107868909A (zh) * | 2017-11-06 | 2018-04-03 | 攀钢集团攀枝花钢铁研究院有限公司 | 一种580MPa级经济型高表面质量高扩孔钢及其制备方法 |
KR101988764B1 (ko) * | 2017-12-21 | 2019-06-12 | 주식회사 포스코 | 확관성이 우수한 열연강판 및 그 제조방법 |
KR102109271B1 (ko) * | 2018-10-01 | 2020-05-11 | 주식회사 포스코 | 표면 품질이 우수하고, 재질편차가 적은 초고강도 열연강판 및 그 제조방법 |
EP4079913A4 (en) * | 2019-12-20 | 2023-02-22 | Posco | STEEL FOR HOT FORMING, HOT FORMED ELEMENT AND METHOD OF MANUFACTURE THEREOF |
KR102468035B1 (ko) * | 2020-11-13 | 2022-11-18 | 주식회사 포스코 | 열적 안정성이 우수한 고항복비 고강도 강판 및 그 제조방법 |
CN113802065B (zh) * | 2021-11-18 | 2022-03-29 | 育材堂(苏州)材料科技有限公司 | 热冲压成形构件、热冲压成形用钢板以及热冲压工艺 |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH04276024A (ja) * | 1991-02-28 | 1992-10-01 | Nkk Corp | 伸びフランジ性に優れた高強度熱延鋼板の製造方法 |
JP2002180189A (ja) * | 2000-12-07 | 2002-06-26 | Nippon Steel Corp | 穴拡げ性と延性に優れた高強度熱延鋼板及びその製造方法 |
JP2007262487A (ja) * | 2006-03-28 | 2007-10-11 | Nippon Steel Corp | 伸びフランジ性に優れた高強度鋼板 |
JP2011012308A (ja) * | 2009-07-02 | 2011-01-20 | Nippon Steel Corp | バーリング性に優れた高降伏比型熱延鋼板及びその製造方法 |
Family Cites Families (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH09170048A (ja) | 1995-12-15 | 1997-06-30 | Kobe Steel Ltd | 疲労特性と穴拡げ性に優れた加工用高強度熱延鋼板 |
JP3684851B2 (ja) | 1997-07-10 | 2005-08-17 | Jfeスチール株式会社 | 耐衝撃特性および強度−伸びバランスに優れた高強度高加工性熱延鋼板およびその製造方法 |
WO2001023624A1 (en) * | 1999-09-29 | 2001-04-05 | Nkk Corporation | Sheet steel and method for producing sheet steel |
KR20090087129A (ko) | 2000-12-07 | 2009-08-14 | 니폰 스틸 코포레이션 | 구멍확장성과 연성(延性)이 뛰어난 고강도 열연강판 및 그 제조방법 |
TWI248977B (en) * | 2003-06-26 | 2006-02-11 | Nippon Steel Corp | High-strength hot-rolled steel sheet excellent in shape fixability and method of producing the same |
JP4469248B2 (ja) * | 2004-03-09 | 2010-05-26 | 新日本製鐵株式会社 | 耐摩耗性および延性に優れた高炭素鋼レールの製造方法 |
JP4333444B2 (ja) * | 2004-03-31 | 2009-09-16 | Jfeスチール株式会社 | 伸び特性、伸びフランジ特性、引張疲労特性および耐衝突特性に優れた高強度熱延鋼板およびその製造方法 |
JP4466196B2 (ja) * | 2004-05-24 | 2010-05-26 | 住友金属工業株式会社 | 耐疲労き裂進展性に優れた鋼板およびその製造方法 |
JP3889766B2 (ja) * | 2005-03-28 | 2007-03-07 | 株式会社神戸製鋼所 | 穴拡げ加工性に優れた高強度熱延鋼板およびその製造方法 |
JP5070732B2 (ja) | 2005-05-30 | 2012-11-14 | Jfeスチール株式会社 | 伸び特性、伸びフランジ特性および引張疲労特性に優れた高強度熱延鋼板およびその製造方法 |
KR20080110904A (ko) * | 2006-05-16 | 2008-12-19 | 제이에프이 스틸 가부시키가이샤 | 신장 특성, 신장 플랜지 특성 및 인장 피로 특성이 우수한 고강도 열연강판 및 그 제조 방법 |
JP5359296B2 (ja) * | 2008-01-17 | 2013-12-04 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
ES2526974T3 (es) * | 2008-04-10 | 2015-01-19 | Nippon Steel & Sumitomo Metal Corporation | Hojas de acero de alta resistencia que presentan un balance excelente entre capacidad de expansión de agujeros y ductilidad y también una resistencia a fatiga excelente, hojas de acero revestidas de zinc y procedimientos para producir las hojas de acero |
US8128762B2 (en) * | 2008-08-12 | 2012-03-06 | Kobe Steel, Ltd. | High-strength steel sheet superior in formability |
JP5370016B2 (ja) | 2008-09-11 | 2013-12-18 | 新日鐵住金株式会社 | 穴広げ性に優れた高強度熱延鋼板及びその製造方法 |
JP5630026B2 (ja) * | 2009-01-30 | 2014-11-26 | Jfeスチール株式会社 | 低温靭性に優れた厚肉高張力熱延鋼板およびその製造方法 |
JP5423191B2 (ja) * | 2009-07-10 | 2014-02-19 | Jfeスチール株式会社 | 高強度鋼板およびその製造方法 |
JP5482162B2 (ja) * | 2009-12-09 | 2014-04-23 | Jfeスチール株式会社 | 伸びおよび伸びフランジ特性に優れた引張強度が780MPa以上の高強度熱延鋼板およびその製造方法 |
JP5423737B2 (ja) * | 2010-08-10 | 2014-02-19 | Jfeスチール株式会社 | 加工性に優れた高強度熱延鋼板およびその製造方法 |
-
2012
- 2012-03-16 US US14/005,408 patent/US10428409B2/en active Active
- 2012-03-16 CN CN201280005592.5A patent/CN103328671B/zh active Active
- 2012-03-16 KR KR1020137021326A patent/KR101531778B1/ko active IP Right Grant
- 2012-03-16 WO PCT/JP2012/056856 patent/WO2012128206A1/ja active Application Filing
- 2012-03-16 BR BR112013023633A patent/BR112013023633A2/pt not_active IP Right Cessation
- 2012-03-16 MX MX2013009509A patent/MX364430B/es active IP Right Grant
- 2012-03-16 JP JP2013505944A patent/JP5429429B2/ja active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH04276024A (ja) * | 1991-02-28 | 1992-10-01 | Nkk Corp | 伸びフランジ性に優れた高強度熱延鋼板の製造方法 |
JP2002180189A (ja) * | 2000-12-07 | 2002-06-26 | Nippon Steel Corp | 穴拡げ性と延性に優れた高強度熱延鋼板及びその製造方法 |
JP2007262487A (ja) * | 2006-03-28 | 2007-10-11 | Nippon Steel Corp | 伸びフランジ性に優れた高強度鋼板 |
JP2011012308A (ja) * | 2009-07-02 | 2011-01-20 | Nippon Steel Corp | バーリング性に優れた高降伏比型熱延鋼板及びその製造方法 |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2014185359A (ja) * | 2013-03-22 | 2014-10-02 | Jfe Steel Corp | 高強度鋼板 |
JP2015203124A (ja) * | 2014-04-11 | 2015-11-16 | 新日鐵住金株式会社 | 熱延鋼板およびその製造方法 |
JP2019523828A (ja) * | 2016-06-21 | 2019-08-29 | 宝山鋼鉄股▲分▼有限公司 | 980MPa級の熱間圧延フェライトベイナイト二相鋼及びその製造方法 |
US11220724B2 (en) | 2016-06-21 | 2022-01-11 | Baoshan Iron & Steel Co., Ltd. | 980 MPa-grade hot-rolled ferritic bainite dual-phase steel and manufacturing method therefor |
JP2019533082A (ja) * | 2016-09-22 | 2019-11-14 | タタ、スティール、アイモイデン、ベスローテン、フェンノートシャップTata Steel Ijmuiden Bv | 優れた伸びフランジ成形性及びエッジ疲労性能を有する熱間圧延高強度鋼の製造方法 |
US11242579B2 (en) | 2016-09-22 | 2022-02-08 | Tata Steel Ijmuiden B.V. | Method of producing a hot-rolled high-strength steel with excellent stretch-flange formability and edge fatigue performance |
JP7077309B2 (ja) | 2016-09-22 | 2022-05-30 | タタ、スティール、アイモイデン、ベスローテン、フェンノートシャップ | 優れた伸びフランジ成形性及びエッジ疲労性能を有する熱間圧延高強度鋼の製造方法 |
JP2020509172A (ja) * | 2016-12-13 | 2020-03-26 | ポスコPosco | 低温域におけるバーリング性に優れた高強度複合組織鋼及びその製造方法 |
WO2022210220A1 (ja) * | 2021-03-30 | 2022-10-06 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
JPWO2022210220A1 (ja) * | 2021-03-30 | 2022-10-06 | ||
JP7435796B2 (ja) | 2021-03-30 | 2024-02-21 | Jfeスチール株式会社 | 熱延鋼板およびその製造方法 |
Also Published As
Publication number | Publication date |
---|---|
US20140000766A1 (en) | 2014-01-02 |
JPWO2012128206A1 (ja) | 2014-07-24 |
KR20130116329A (ko) | 2013-10-23 |
CN103328671B (zh) | 2015-06-03 |
BR112013023633A2 (pt) | 2016-12-13 |
CN103328671A (zh) | 2013-09-25 |
US10428409B2 (en) | 2019-10-01 |
JP5429429B2 (ja) | 2014-02-26 |
KR101531778B1 (ko) | 2015-06-25 |
MX364430B (es) | 2019-04-26 |
MX2013009509A (es) | 2013-09-26 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5429429B2 (ja) | プレス成形性に優れた熱延鋼板及びその製造方法 | |
RU2518830C1 (ru) | Горячекатаный стальной лист и способ его изготовления | |
JP6542249B2 (ja) | フェライト系ステンレス鋼板、鋼管およびその製造方法 | |
EP2799567B1 (en) | High-strength steel plate and high-strength steel pipe excellent in deformability and low-temperature toughness, and manufacturing method of the steel plate | |
JP5278188B2 (ja) | 耐水素誘起割れ性および脆性亀裂伝播停止特性に優れた厚鋼板 | |
KR101744429B1 (ko) | 열연 강판 및 그 제조 방법 | |
JP5741483B2 (ja) | 現地溶接性に優れるラインパイプ用高強度熱延鋼板およびその製造方法 | |
KR101737255B1 (ko) | 후 강판 및 후 강판의 제조 방법 | |
JP5476735B2 (ja) | 加工性に優れた高強度熱延鋼板およびその製造方法 | |
JP5353573B2 (ja) | 成形性及び疲労特性に優れた複合組織鋼板並びにその製造方法 | |
CA3001529A1 (en) | As-rolled type k55 electric resistance welded oil well pipe and hot-rolled steel sheet | |
JP6179604B2 (ja) | 電気抵抗溶接鋼管用鋼帯および電気抵抗溶接鋼管ならびに電気抵抗溶接鋼管用鋼帯の製造方法 | |
CN114599813B (zh) | 热轧钢板 | |
JP7448804B2 (ja) | ラインパイプ用電縫鋼管、及びラインパイプ用熱延鋼板 | |
JP2010236052A (ja) | 曲げ加工性に優れた高強度冷延鋼板 | |
JP2006037162A (ja) | 熱延鋼板及びその製造方法 | |
KR20090109571A (ko) | 저온 인성이 우수한 스파이럴 파이프용 고강도 열연 강판 및 그 제조 방법 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 12760369 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2013505944 Country of ref document: JP Kind code of ref document: A |
|
ENP | Entry into the national phase |
Ref document number: 20137021326 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: MX/A/2013/009509 Country of ref document: MX |
|
WWE | Wipo information: entry into national phase |
Ref document number: 14005408 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 1301005180 Country of ref document: TH |
|
REG | Reference to national code |
Ref country code: BR Ref legal event code: B01A Ref document number: 112013023633 Country of ref document: BR |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 12760369 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 112013023633 Country of ref document: BR Kind code of ref document: A2 Effective date: 20130916 |