WO2013099136A1 - 高強度熱延鋼板およびその製造方法 - Google Patents
高強度熱延鋼板およびその製造方法 Download PDFInfo
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- 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
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- 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
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- 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
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- 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
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- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0426—Hot rolling
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- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
- C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
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- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- 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
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- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
- C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
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- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12771—Transition metal-base component
- Y10T428/12785—Group IIB metal-base component
- Y10T428/12792—Zn-base component
- Y10T428/12799—Next to Fe-base component [e.g., galvanized]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12771—Transition metal-base component
- Y10T428/12861—Group VIII or IB metal-base component
- Y10T428/12951—Fe-base component
- Y10T428/12972—Containing 0.01-1.7% carbon [i.e., steel]
Definitions
- the present invention relates to a high-strength thin steel sheet having a yield strength of 530 MPa or more and excellent in stretch flangeability, and a method for producing the same, which are suitable as parts for transportation machinery including automobiles and structural members for construction.
- it relates to suppression of fluctuations in mechanical properties in the steel sheet (coil).
- the “steel plate” here includes a steel strip.
- the fluctuation of the steel sheet strength is generally caused by the fluctuation of the temperature history in the rolling direction and the width direction of the steel sheet during the production of the steel sheet, and further the fluctuation of the steel sheet structure caused by the difference in rolling conditions.
- Patent Document 1 discloses a ferrite crystal having a structure in which dislocation cell structures arranged in one direction intersect in two or more directions in the deformation region after deformation of 20% or more.
- a high-strength steel sheet having a tensile strength of 500 MPa or more and containing 60% or more of a ferrite structure containing 50% or more of grains is described.
- the amount of springback can be stably reduced, and the member is excellent in shape freezing property.
- Patent Document 2 describes a high workability high strength hot-rolled steel sheet with small anisotropy and excellent shape freezing property.
- ferrite or bainite is used as the phase with the largest volume fraction, or further contains 1 to 25% martensite or retained austenite, and the specific crystal orientation of the plate surface at 1/2 plate thickness
- the average value of the X-ray random intensity ratio of the group is 2.5 or more, and the average value of the X-ray random intensity ratio of the specific three crystal orientations is 3.5 or less, and the r value in the rolling direction and the r value in the direction perpendicular to the rolling direction.
- a thin steel sheet having a good press formability with a small amount of springback and excellent shape freezing properties and at the same time low anisotropy can be obtained.
- the texture of the steel sheet cannot be stably obtained in the longitudinal direction and the width direction of the coil, and moreover, actively contains martensite and retained austenite as the steel sheet structure. Therefore, there is a problem that the strength stability is remarkably lowered and it is quite difficult to obtain a stable shape freezing property.
- Patent Document 3 describes a high formability, high tension hot-rolled steel sheet having excellent material uniformity.
- C 0.1% or less
- Ti 0.02 to 0.2%, including one or two selected from Mo and W, specific relationship of Ti, Mo, W content Carbide containing Ti and one or more of Mo and W is substantially dispersed and precipitated in the ferrite structure by heat treatment after hot rolling and coiling so as to satisfy the formula It is said that a steel sheet having an excellent material uniformity in which the difference in yield stress between the central part and the end part in the steel sheet width direction is 39 MPa or less is obtained.
- Patent Document 3 can reduce the material fluctuation in the width direction to some extent, but due to segregation of Mn, the tensile strength fluctuates due to the difference in the position in the longitudinal direction of the steel plate (coil). There was a problem with uniformity.
- Patent Document 4 describes a high-formability high-tensile steel plate having excellent strength stability.
- C 0.03 to 0.15%, Mn: 0.2% or more, N: 0.01% or less, Ti: 0.05 to 0.35%, Mo: 0.6% or less, W: 1.5% or less 1 or more selected from the group consisting of Mo: 0.1% or more, W: 0.2% or more, Ex.C (C not bonded to Ti, Mo, W) is 0.015% or less,
- Patent Document 5 describes a high-stretch flangeable steel plate having excellent shape freezing properties.
- ferrite or bainite is the maximum phase in terms of area ratio, the occupation ratio of iron carbide at the grain boundary is 0.1 or less, and the maximum particle diameter of the iron carbide is 1 ⁇ m or less, and at least a plate A steel sheet having a texture in which crystals having a specific orientation are aligned parallel to the plate surface at the thickness center and having an r value in a specific range. Thereby, the amount of springback is reduced, and the shape freezing property is improved.
- the technique described in Patent Document 5 has a problem that it is difficult to stably secure a specific texture in the longitudinal direction and width direction of the coil, and it is difficult to obtain a steel plate having stable strength. .
- Patent Document 6 contains, in mass%, C: 0.02 to 0.08%, Si: 0.01 to 1.5%, Mn: 0.1 to 1.5%, Ti: 0.03 to 0.06%, and the ratio of Ti and C is Ti. / C: An alloy-saving high-strength hot-rolled steel sheet with a tensile strength of 540 to 650 MPa that is adjusted to 0.375 to 1.6, TiC is 0.8 to 3 nm, and the average number density is 1 ⁇ 10 17 / cm 3 or more is described. ing. In the technique described in Patent Document 6, TiC is finely dispersed by winding at a temperature of 600 ° C. or lower, and a high strength of tensile strength: 540 MPa or more is ensured.
- the yield strength which is more sensitive to changes in the size of the precipitate, varies more than the tensile strength.
- the coiling temperature 575 ° C. or lower, and containing 1% or higher Mn or 0.07% or higher C
- Patent Document 7 describes a high-strength steel sheet having an excellent balance of strength and ductility.
- the technology described in Patent Document 7 includes, in mass%, C: 0.01 to 0.2%, Mn: 0.20 to 3%, Ti: 0.03 to 0.2%, Nb: 0.01 to 0.2%, Mo: 0.01 to 0.2% V: Hard ferrite crystal grains A and soft ferrites containing one or more of 0.01 to 0.2% and having a ferrite single-phase structure with a different number density of precipitates or clusters of 8 nm or less in the crystal grains It is a hot-rolled steel sheet composed of two kinds of crystal grains B and having an excellent balance of strength ductility. By changing the hardness of each crystal grain, the work hardening behavior of DP steel is simulated.
- the present invention solves such problems of the prior art, enables high-strength hot-rolled steel sheets with excellent stretch flangeability, which can produce parts with small fluctuations in mechanical properties in the coil and stable dimensional accuracy, and the same.
- An object is to provide a manufacturing method.
- the “high-strength hot-rolled steel sheet” as used herein refers to a hot-rolled steel sheet having a high strength of yield strength YS: 530 MPa or more, preferably tensile strength TS: 590 MPa or more.
- “the fluctuation of the mechanical characteristics in the coil is small” means that the yield strength YS between the width center position and the width end side position in the steel strip made of the coil, as described in Examples below. It is assumed that the difference ⁇ YS is 20 MPa or less.
- the dimensional accuracy of press-formed parts is evaluated by the amount of spring back.
- a component having stable dimensional accuracy means a component in which the amount of springback is constant between the same types of components.
- the “spring back” amount is the amount of deformation when the processing is finished and the deformation stress is unloaded, but it depends on the yield strength of the material. Therefore, in order to obtain a component with stable dimensional accuracy, it is necessary to adjust the yield strength of the material to be constant.
- the present inventors diligently studied various factors affecting the strength fluctuation in the coil in a high-strength hot-rolled steel sheet having a yield strength of 530 MPa or more. As a result, it was thought that there was a variation in the size and distribution form of the hard phase as one of the factors of the strength variation, and in order to eliminate the formation of the hard phase, the metal structure was substantially made up of a collection of ferrite crystal grains. The ferrite phase was single phase.
- the steel sheet structure may contain a wide variety of phases, each phase fraction change, each phase hardness of Due to the change, the steel plate strength changes greatly. Therefore, the present inventors have thought that this change in strength cannot be easily suppressed if the metal structure is a composite structure containing a variety of phases, and thus the metal structure needs to be made into a single phase. .
- the present inventors have found that the tensile strength in the width direction changes when the amount of Mn in steel is large, and have come to think of reducing the amount of Mn. This is because if the amount of Mn in the steel is large, Mn segregates, and the precipitation timing of carbide is delayed at that part, and further, the part hardens abnormally due to solid solution strengthening by Mn. For this reason, it has been found that in conventional high-strength steel sheets, a large fluctuation in strength occurs due to the Mn content of 0.8% or more, which has been considered to be a normal content. In addition, it has been found that even with a Si content of 0.3% or more, which is considered to be a normal content, it causes a change in the steel sheet structure, that is, a strength fluctuation, similarly to Mn.
- the present inventors reduced the amounts of Si and Mn, made the structure substantially a single ferrite phase, and evenly dispersed ultrafine TiC in the ferrite crystal grains of the ferrite phase. If it is a structure, the size and precipitation amount of carbide can be kept constant at each position of the steel plate (coil), yield strength: strength within the steel plate (coil) while maintaining high strength of 530 MPa or more. It has been found that a high strength hot rolled steel sheet with extremely small fluctuations can be obtained.
- the “substantially ferrite phase single phase” in the present invention means that ferrite crystal grains occupy 95% or more of the metal structure when observed with an optical microscope and a scanning electron microscope at 500 to 5000 times. Refers to cases.
- the present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows. (1) By mass%, C: more than 0.010% and 0.06% or less, Si: 0.3% or less, Mn: 0.8% or less, P: 0.03% or less, S: 0.02% or less, Al: 0.1% or less, N: 0.01%
- Ti 0.05 to 0.10%, the composition composed of the balance Fe and inevitable impurities, the ferrite phase occupies 95% or more in area ratio, the ferrite crystal grains have an average grain size of 1 ⁇ m or more, and A high-strength hot-rolled steel sheet having a yield strength of 530 MPa or more, characterized by having a metal structure in which TiC having an average particle diameter of 7 nm or less is dispersed and precipitated in ferrite crystal grains.
- a method for producing a high-strength hot-rolled steel sheet comprising one or more selected from V, REM, Cs, Zr, and Zn in total of 1% or less.
- the present invention it is possible to easily produce a high-strength hot-rolled steel sheet that has a high yield strength of 530 MPa or more, has small fluctuations in mechanical properties in the coil, and has excellent stretch flangeability. Has an exceptional effect.
- the hot-rolled steel sheet of the present invention has C: more than 0.010% and 0.06% or less, Si: 0.3% or less, Mn: 0.8% or less, P: 0.03% or less, S: 0.02% or less, Al: 0.1% or less, N: 0.01%
- Ti: 0.05 to 0.10% is contained, and the composition is composed of the balance Fe and inevitable impurities.
- mass% is simply expressed as%.
- C more than 0.010% and 0.06% or less
- C is an element that combines with Ti and precipitates as carbide (TiC) and contributes to an increase in strength.
- TiC carbide
- the content exceeding 0.010% is required. If it is 0.010% or less, a high strength with a yield strength of 530 MPa or more cannot be secured.
- the content exceeds 0.06% pearlite is generated, the strength stability is lowered, and stretch flangeability is also lowered. For this reason, C was limited to the range of more than 0.010% and 0.06% or less.
- the content is preferably 0.010 to 0.025%.
- Si 0.3% or less
- Si is an element that has been conventionally contained as an element that increases the strength of the steel sheet but does not decrease the elongation.
- Si improves hardenability, facilitates the formation of hard phases such as martensite and bainite, and has a great influence on fluctuations in steel sheet strength. For this reason, in this invention, it is desirable to reduce as much as possible.
- Si is limited to 0.3% or less in the present invention.
- Mn 0.8% or less
- Mn is an element that increases the strength of a steel sheet by solid solution, and has been actively used in the past.
- Mn like Si
- Mn is easily segregated, and in the segregated part (segregated part), the transformation point is partially lowered in temperature, and the strength is partially increased by forming a hard phase. Fluctuates and the stability of strength decreases. For this reason, it is desirable to reduce Mn as much as possible, but it is acceptable up to 0.8%. For this reason, Mn was limited to 0.8% or less.
- the content is 0.15 to 0.55%.
- P 0.03% or less
- P is segregated at the ferrite grain boundary in the steel sheet and lowers the stretch flangeability, so it is desirable to reduce it as much as possible, but 0.03% is acceptable. For this reason, P was limited to 0.03% or less.
- S 0.02% or less Since S forms TiS and consumes Ti, it also causes fluctuations in strength. Such a thing becomes remarkable when it contains exceeding 0.02%. For this reason, S was limited to 0.02% or less. In addition, Preferably it is 0.005% or less, More preferably, it is 0.001% or less. There is no problem even if the S content is zero.
- Al 0.1% or less Al is an element that acts as a deoxidizer. In order to acquire such an effect, it is desirable to contain 0.005% or more. On the other hand, if it exceeds 0.1%, it remains as Al oxide and tends to aggregate and become coarse Al oxide (alumina). Coarse Al oxide becomes a starting point of destruction and the strength is likely to fluctuate. For this reason, Al was limited to 0.1% or less from the viewpoint of ensuring strength stability. Preferably, the content is 0.015 to 0.065%.
- N 0.01% or less N combines with Ti in steel to form TiN. Therefore, if N exceeds 0.01%, the amount of Ti that can become carbide decreases due to the presence of N, and the desired high strength Cannot be secured. Coarse TiN precipitation consumes Ti, reduces the amount of fine TiC that bears the strength, causes a change in strength, easily becomes a starting point of fracture during processing, and stretch flangeability also decreases. For this reason, it is desirable to reduce N as a harmful element in the present invention as much as possible. For these reasons, N is limited to 0.01% or less. In addition, Preferably it is 0.006% or less. There is no problem even if the N content is zero.
- Ti is an important element for securing a desired high strength in the present invention, and is an element that forms fine TiC to increase the strength of the steel sheet. In order to acquire such an effect, 0.05% or more of content is required. If Ti is less than 0.05%, the desired high strength, yield strength of 530 MPa or more cannot be secured. On the other hand, if the content exceeds 0.10%, the amount of solid solution Ti increases, and the coarsening of TiC cannot be suppressed, and a desired high strength cannot be ensured. For these reasons, Ti is preferably limited to a range of 0.05 to 0.10%. In the present invention, the added Ti is almost all Ti-containing precipitates, and the amount of Ti in a solid solution state is 0.001% or less.
- B 0.0020% or less may be contained as necessary as a selective element.
- B: 0.0020% or less B is present in a solid solution state in steel, and has the effect of delaying the austenite ( ⁇ ) ⁇ ferrite ( ⁇ ) transformation and precipitating TiC finely. In order to obtain such an effect, it is desirable to contain 0.0010% or more. However, if it exceeds 0.0020%, the ⁇ ⁇ ⁇ transformation is suppressed too much, and a bainite phase or the like is likely to be generated, and stretch flangeability is improved. It deteriorates and the strength stability in the width direction of the steel sheet decreases. For this reason, when it contains, it is preferable to limit B to 0.0020% or less.
- one of Cu, Ni, Cr, Co, Mo, Sb, W, As, Pb, Mg, Ca, Sn, Ta, Nb, V, REM, Cs, Zr, and Zn Or even when it contains 2 or more types, if these total content is 1% or less, since the influence on the effect of this invention is few, if it is 1% or less in total, it is permissible.
- the balance other than the above components is Fe and inevitable impurities.
- the hot-rolled steel sheet of the present invention has the above composition, the ferrite phase has a metal structure occupying 95% or more in area ratio, the ferrite crystal grains in the ferrite phase have an average crystal grain size of 1 ⁇ m or more, In addition, the ferrite crystal grains have a metal structure in which TiC having an average particle diameter of 7 nm or less is dispersed and precipitated.
- ferrite phase is 95% or more in area ratio
- it is important that the metal structure is substantially a ferrite phase single phase composed of ferrite crystal grains.
- the strength varies depending on the structure fraction. For this reason, in order to suppress the intensity
- substantially ferrite single phase means that the phase ratio is 95% or more, preferably 98%, based on the area ratio of the entire structure, except when the area ratio of the ferrite phase is 100% with respect to the entire structure. It means to include the case of being super.
- the term “metal structure” as used herein refers to a metal structure that is observed when observing at 500 to 5000 times with an optical microscope or a scanning electron microscope.
- Average grain size of ferrite crystal grains 1 ⁇ m or more
- the factor for changing the strength is eliminated as much as possible.
- the present invention does not actively refine crystal grains, which is an effective means for increasing the strength.
- the ferrite crystal grain size is less than 1 ⁇ m, the strengthening due to miniaturization rapidly increases, and the strength greatly depends on the ferrite crystal grain size. Therefore, the strength varies greatly due to a slight change in the crystal grain size in the coil (steel plate). For this reason, the average grain size of the ferrite crystal grains is limited to 1 ⁇ m or more.
- TiC fine Ti carbide
- the ferrite crystal grains to increase the yield strength: 530 MPa or more. Since the strength is increased by controlling only the precipitation of fine carbides, a desired strength can be secured stably.
- the average grain size of TiC exceeds 7 nm, it becomes difficult to secure a high yield strength of 530 MPa or more. For this reason, the average particle diameter of TiC was limited to 7 nm or less.
- the atomic ratio Ti / C of Ti and C in Ti carbide (TiC) is important in order to precipitate TiC finely.
- TiC Ti carbide
- trace amounts of Nb, V, Mo, and W may be dissolved in TiC.
- TiC including TiC in which such Nb, V, Mo, and W are dissolved is expressed as TiC.
- Ti is an element that can be added at a relatively low cost
- fine carbide forming elements other than Ti that is, among the selective elements, Mo, W, Nb, and V should not be added (content of an impurity level). This is preferable from the viewpoint of avoiding an increase in cost.
- a plating layer may be provided on the surface of the steel sheet in order to impart corrosion resistance to the steel sheet. Even if a hot-rolled steel sheet of the present invention forms a plating layer on the surface, the effect of the present invention is not impaired.
- the type of the plating layer formed on the surface is not particularly limited, and any method such as electroplating or hot dipping can be applied without any problem. Examples of the hot dip plating include hot dip galvanizing and hot dip aluminum plating. Moreover, there is no problem even if it is alloyed hot dip galvanization in which the hot dip galvanized layer is alloyed after hot dip galvanization. Although there is no particular upper limit for the strength of the hot-rolled steel sheet, it is preferable to use a steel sheet of TS: 750 MPa or less, or 725 MPa or less, as will be apparent from the examples described later.
- hot rolling consisting of rough rolling and finish rolling is performed on a steel material, and after finishing rolling, the steel material is cooled, wound, and made into a hot-rolled steel sheet.
- finish rolling finish temperature finish rolling to 1050 ° C. or less, average cooling rate of 30 ° C./s or more in the temperature range from the end of finish rolling to 750 ° C.
- the coil is wound in a coil shape at a winding temperature of 580 ° C. or higher and 700 ° C. or lower.
- the production method of the steel material is not particularly limited.
- the conventional melting furnace such as a converter or an electric furnace
- the molten steel having the above-described composition is melted, and a normal casting such as a continuous casting method is performed.
- a steel material such as a slab.
- a conventional casting method such as an ingot-bundling rolling method or a thin slab continuous casting method may be applied.
- the obtained steel material is subjected to rough rolling and finish rolling, and the steel material is heated to an austenite single phase region prior to rough rolling. If the steel material before rough rolling is not heated to the austenite single phase region, remelting of TiC existing in the steel material does not proceed, and fine precipitation of TiC is not achieved after rolling. Therefore, prior to rough rolling, the steel material is heated to the austenite single phase region.
- the heating temperature is preferably 1100 ° C. or higher.
- the heating temperature is excessively high, the surface is excessively oxidized to form TiO 2 , and Ti is consumed. When the steel sheet is formed, the hardness in the vicinity of the surface decreases. For this reason, it is preferable that heating temperature shall be 1300 degrees C or less.
- direct rolling may be performed without heating the steel material after casting.
- the conditions for rough rolling need not be particularly limited.
- Finish rolling end temperature 860 ° C. or higher and 1050 ° C. or lower
- the finish rolling end temperature exceeds 1050 ° C. and becomes a high temperature
- the ferrite crystal grains are likely to be coarsened, and the steel sheet strength is significantly reduced.
- the finish rolling end temperature is set to 1050 ° C. or less.
- the finish rolling finish temperature is less than 860 ° C.
- the finally obtained ferrite grains are less than 1 ⁇ m, and the effect of refining crystal grains becomes remarkable, so that the strength fluctuation in the steel sheet tends to increase.
- the finish rolling finish temperature was set to 860 ° C. or higher.
- it is 900 degreeC or more.
- Average cooling rate in the temperature range from the end of finish rolling to 750 ° C 30 ° C / s or more
- accelerated cooling after finish rolling is completed, and ⁇ ⁇ ⁇ transformation at the lowest possible temperature It is necessary to make this occur.
- the average cooling rate in the temperature range from the end of finish rolling to 750 ° C. was set to 30 ° C./s or more. It is preferably 50 ° C./s or more.
- the upper limit of the cooling rate is preferably set to 450 ° C./s or less because it tends to cause uneven cooling in the width direction.
- Coiling temperature 580 ° C. or more and 700 ° C. or less
- the coiling temperature was set to 580 ° C. or higher.
- it is 600 degreeC or more.
- the coiling temperature exceeds 700 ° C., pearlite and coarse TiC are generated, and the strength tends to decrease.
- the winding temperature was set to 700 ° C. or less.
- it is 680 degrees C or less.
- the type of the plating layer formed on the surface is not particularly limited, and any method such as electroplating or hot dipping can be applied without any problem.
- Examples of the hot dip plating include hot dip galvanizing and hot dip aluminum plating. Moreover, there is no problem even if it is alloyed hot dip galvanization in which the hot dip galvanized layer is alloyed after hot dip galvanization.
- the present invention will be described in more detail according to examples.
- Example 1 Molten steel having the composition shown in Table 1 was melted by a conventional melting method (converter), and a slab (steel material) (thickness: 270 mm) was formed by a continuous casting method. These slabs are heated to the heating temperature shown in Table 2, roughly rolled, then finish-rolled under the conditions shown in Table 2, and after finishing finish rolling, the temperature range up to 750 ° C. shows in Table 2. Accelerated cooling was performed at an average cooling rate, and the coil was wound into a coil shape at the winding temperature shown in Table 2 to obtain a hot rolled steel sheet having a plate thickness of 2.3 mm.
- Some hot-rolled steel plates (steel plates No.
- the plating layer was alloyed to form an alloyed hot-dip galvanized layer.
- the amount of plating applied was 45 g / m 2 .
- the obtained hot-rolled steel sheet was subjected to a structure observation, a tensile test, and a hole expansion test.
- the test method is as follows.
- (1) Microstructure observation A specimen for microstructural observation is collected from the obtained steel sheet, polished so that the cross section (L cross section) parallel to the rolling direction becomes the observation surface, and corroded with nital liquid.
- the tissue was observed and imaged with an optical microscope (magnification: 500 times) and a scanning electron microscope (magnification: 3000 times). From the obtained tissue photograph, the type of tissue and the area ratio thereof were calculated using an image analysis apparatus.
- a cross section parallel to the rolling direction was mirror-polished, corroded with a nital corrosive solution, ferrite grains were revealed, and the structure was imaged with an optical microscope (magnification: 100 times).
- 10 straight lines were drawn in the rolling direction and the plate thickness direction at intervals of 100 ⁇ m or more, and the number of intersections between the grain boundaries and the straight lines was counted.
- the total ferrite length divided by the number of intersections was taken as the length of one ferrite grain, and this was multiplied by 1.13 to determine the ASTM ferrite grain size.
- a specimen for transmission electron microscope observation was collected from the obtained steel sheet, and a thin film for transmission electron microscope observation was obtained by mechanical polishing and chemical polishing. Using the obtained thin film, the tissue was observed with a transmission electron microscope (magnification: 340000 times), and imaged with 5 fields of view.
- the maximum diameter d the diameter of the largest portion on the upper and lower surfaces of the disk
- the diameter (thickness) of the disk-like precipitates in the direction perpendicular to the upper and lower surfaces of the disk T) was measured, and their arithmetic average value (average particle size ddef (d + t) / 2) was defined as the average particle size of TiC in each steel plate.
- a test piece for electrolytic extraction was collected from the obtained steel plate, electrolyzed in an AA-based electrolytic solution (AA: acetylacetone), and the extraction residue was collected.
- the obtained electrolytic extraction residue is observed with a transmission electron microscope, and Ti concentration of TiC is determined with EDX (energy dispersive X-ray spectrometer), and C concentration is determined with EELS (electron energy loss spectrometer). The atomic ratio Ti / C of Ti and C in TiC was calculated.
- the difference in yield strength ⁇ YS between the width center position and the width end side position was determined and used as an index of strength fluctuation.
- the case where ⁇ YS was 20 MPa or less was evaluated as ⁇ when the intensity fluctuation was small, and the case other than that was evaluated as ⁇ .
- the yield strength YS maintaining high strength of 530 MPa or more, ⁇ YS is 20 MPa or less, there is little fluctuation in strength in the width direction, and fluctuation of mechanical characteristics in the coil is small. Moreover, it is a high-strength hot-rolled steel sheet having a hole expansion rate of 100% or more and excellent stretch flangeability.
- the comparative examples outside the scope of the present invention are yield strength YS: less than 530 MPa, the strength is reduced, ⁇ YS exceeds 20 MPa, the strength fluctuation in the width direction is large, or the hole expansion rate is 100%. If it is less than that, the stretch flangeability is lowered, or they are all lowered.
- Example 2 Molten steel having the compositions of steel No. H and No. M shown in Table 1 was melted in a converter, and was made into a slab (wall thickness: 270 mm) by a continuous casting method in the same manner as in Example 1. These slabs were heated under the same conditions as steel plates No. 8 and No. 12 shown in Table 2, subjected to rough rolling and finish rolling, further accelerated cooling, coiled into a coil thickness of 2.6 mm A hot-rolled steel sheet was obtained. About the obtained coil, at each position in the longitudinal direction shown in Table 4, a JIS No. 5 tensile test piece and a hole expansion test piece were collected from the central part in the plate width direction, and subjected to a tensile test under the same conditions as in Example 1. A hole expansion test was conducted. Table 4 shows the obtained results. In addition, the difference ⁇ YS in yield strength at each position in the longitudinal direction with reference to the 40 m position in the longitudinal direction is also shown.
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Abstract
Description
(1)質量%で、C:0.010%超0.06%以下、Si:0.3%以下、Mn:0.8%以下、P:0.03%以下、S:0.02%以下、Al:0.1%以下、N:0.01%以下、Ti:0.05~0.10%を含有し、残部Fe及び不可避不純物よりなる組成と、さらにフェライト相が面積率で95%以上を占め、フェライト結晶粒が1μm以上の平均粒径を有し、かつフェライト結晶粒内に平均粒径:7nm以下のTiCを分散析出させた金属組織とを、有することを特徴とする降伏強さ530MPa以上の高強度熱延鋼板。
まず、本発明熱延鋼板の組成限定理由について、説明する。以下、とくに断わらない限り、質量%は単に%で記す。
Cは、本発明では、Tiと結合し炭化物(TiC)として析出し、強度増加に寄与する元素である。このような効果を得るためには、0.010%を超える含有を必要とする。0.010%以下では、降伏強さ530MPa以上の高強度を確保することができない。一方、0.06%を超える含有は、パーライトが生成して強度の安定性が低下するうえ、伸びフランジ性も低下する。このため、Cは0.010%超0.06%以下の範囲に限定した。なお、好ましくは0.010~0.025%である。
Siは、鋼板強度を増加させるものの、伸びを低下させない元素として、従来から含有されてきた元素である。しかし、本発明では、Siは焼入れ性を向上させ、マルテンサイト、ベイナイト等の硬質相を形成しやすくし、鋼板強度の変動に大きな影響を与える。このため、本発明では、できるだけ低減することが望ましい。ただし、0.3%までは許容できることから、本発明では、Siは0.3%以下に限定した。なお、好ましくは0.2%以下、さらに好ましくは0.1%以下である。Si含有量はゼロであっても問題ない。
Mnは、Siと同様に、固溶して鋼板の強度を増加させる元素であり、従来は積極的に利用してきた。しかし、Mnは、Siと同様に、焼入れ性を向上させ、マルテンサイト、ベイナイト等の硬質相を生成しやすくし、鋼板強度の変動に大きな影響を及ぼす。また、Mnは、偏析しやすく、偏析した箇所(偏析部)では、部分的に変態点が低温化し、硬質相を形成して部分的に強度を高めるため、鋼板内(コイル内)で強度が変動し、強度の安定性が低下する。このようなことから、Mnはできるだけ低減することが望ましいが、0.8%までは許容できる。このため、Mnは0.8%以下に限定した。なお、好ましくは0.15~0.55%である。
Pは、鋼板中でフェライト粒界等に偏析して、伸びフランジ性を低下させるため、できるだけ低減することが望ましいが、0.03%までは許容できる。このため、Pは0.03%以下に限定した。なお、好ましくは、0.02%以下、さらに好ましくは0.01%以下である。P含有量はゼロであっても問題ない。
Sは、TiSを形成してTiを消費するため、強度変動の要因にもなる。このようなことは、0.02%を超えて含有した場合に顕著となる。このため、Sは0.02%以下に限定した。なお、好ましくは、0.005%以下、さらに好ましくは0.001%以下である。S含有量はゼロであっても問題ない。
Alは、脱酸剤として作用する元素である。このような効果を得るためには、0.005%以上含有することが望ましい。一方、0.1%を超えて含有すると、Al酸化物として残存し、凝集して粗大なAl酸化物(アルミナ)となりやすい。粗大なAl酸化物は、破壊の起点となり、強度が変動しやすくなる。このため、強度安定性の確保という観点から、Alは0.1%以下に限定した。なお、好ましくは0.015~0.065%である。
Nは、鋼中でTiと結合してTiNを形成するため、Nが0.01%を超えて多量になると、炭化物となりうるTi量がNの存在により低下し、所望の高強度を確保できなくなる。粗大なTiNの析出はTiを消費し、強度を担う微細TiCの析出量を低減し、強度変化の原因になるとともに、加工時の破壊の起点になりやすく、伸びフランジ加工性も低下する。このため、Nは本発明においては、有害な元素としてできるだけ低減することが望ましい。このようなことから、Nは0.01%以下に限定した。なお、好ましくは0.006%以下である。N含有量はゼロであっても問題ない。
Tiは、本発明において所望の高強度を確保するための重要な元素であり、微細なTiCを形成して鋼板を高強度化する元素である。このような効果を得るためには、0.05%以上の含有を必要とする。Tiが0.05%未満では、所望の高強度である、降伏強さ530MPa以上を確保できない。一方、0.10%を超える含有は、固溶Tiが多くなりTiCの粗大化(coarsening)が抑制できなくなり、所望の高強度を確保できなくなる。このようなことから、Tiは0.05~0.10%の範囲に限定することが好ましい。なお、本発明では、添加されたTiは、ほぼすべてTi含有析出物となっており、固溶状態にあるTi量は0.001%以下である。
B:0.0020%以下
Bは、鋼中で固溶状態で存在して、オーステナイト(γ)→フェライト(α)変態を遅延させ、TiCを微細に析出させる作用を有する。このような効果を得るためには、0.0010%以上含有することが望ましいが、0.0020%を超える含有は、γ→α変態が抑制されすぎて、ベイナイト相等が生成しやすくなり、伸びフランジ加工性が劣化し、また、鋼板幅方向の強度安定性が低下する。このため、含有する場合には、Bは0.0020%以下に限定することが好ましい。
本発明熱延鋼板は、上記した組成を有し、フェライト相が面積率で95%以上を占める金属組織を有し、フェライト相中のフェライト結晶粒が1μm以上の平均結晶粒径を有し、かつフェライト結晶粒内に平均粒径:7nm以下のTiCを分散析出させた金属組織を有する。
本発明では、金属組織をフェライト結晶粒からなる実質的にフェライト相単相とすることが重要である。フェライト相以外に、マルテンサイト相やベイナイト相などの硬質相を多量に含むと、その組織分率に依存して強度が変動する。このため、鋼板(コイル)内の強度変動を抑えるために、金属組織は実質的にフェライト相単相とした。ここでいう「実質的にフェライト単相」とは、組織全体に対するフェライト相の面積率で100%である場合以外に、当該相が、組織全体に対する面積率で、95%以上、好ましくは98%超である場合を含む意味である。ここでいう「金属組織」とは、光学顕微鏡や走査型電子顕微鏡で500~5000倍で観察するときに見られる金属組織をいう。
本発明では、コイル(鋼板)内の強度変動を少なくするため、強度を変動させる要因を極力排除する。このため、本発明では、強度増加の有効な手段である結晶粒の積極的な微細化は行わない。フェライト結晶粒径が1μm未満となると、微細化による強化が急激に増大する領域となり、強度がフェライト結晶粒径に大きく依存するようになる。そのため、コイル(鋼板)内の僅かな結晶粒径の変化により、強度が大きく変動するようになる。このようなことから、フェライト結晶粒の平均粒径を1μm以上に限定した。
本発明では、フェライト結晶粒内に微細なTi炭化物(TiC)を析出させて、降伏強さ:530MPa以上となる高強度化を図る。微細炭化物の析出のみを制御して高強度化するため、安定して所望の強度を確保できる。TiCの平均粒径が7nmを超えて大きくなると、降伏強さ:530MPa以上の高強度を確保しにくくなる。このため、TiCの平均粒径は7nm 以下に限定した。
Ti炭化物(TiC)中のTiとCの原子数比Ti/Cは、TiCを微細に析出させるために、重要となる。TiCが析出する際に炭化物中のTiがCよりも過剰に存在すると、Ti炭化物(TiC)が粗大化しやすくなる。このため、TiC中のTiとCの原子数比、Ti/Cを1未満に限定することが好ましい。また、微量なNb、V、Mo、WがTiCに固溶している場合があるが、本発明ではこのようなNb、V、Mo、Wが固溶したTiCを含めてTiCと表した。なお、Tiは比較的安価に添加できる元素であり、Ti以外の微細炭化物形成元素、すなわち前記選択元素のうち、Mo、W、Nb、Vは無添加(不純物程度の含有量)とすることがコストアップを回避する観点から好ましい。
本発明の製造方法では、鋼素材に、粗圧延、仕上圧延からなる熱間圧延を施し、仕上圧延終了後、冷却し、巻き取り、熱延鋼板とする。この際、オーステナイト単相域に加熱したのち、仕上圧延終了温度:1050℃以下となる仕上圧延を施し、該仕上圧延終了後から750℃までの温度域で、30℃/s以上の平均冷却速度で冷却し、巻取り温度:580℃以上700℃以下でコイル状に巻き取ることを特徴とする。
仕上圧延終了温度が1050℃を超えて高温となると、フェライト結晶粒が粗大化しやすくなり、鋼板強度が顕著に低下する。このため、仕上圧延終了温度は1050℃以下とした。一方、仕上圧延終了温度が860℃未満では、最終的に得られるフェライト粒が1μm未満となり、結晶粒の微細化効果が顕著となるため、鋼板内の強度変動が大きくなりやすい。このため、仕上圧延終了温度は860℃以上とした。なお、好ましくは、900℃以上である。
微細なTiCを得るためには、仕上圧延終了後、加速冷却し、可能な限り低い温度でγ→α変態が生じるようにすることが必要となる。冷却速度が30℃/s未満と遅くなると、γ→α変態が高温で生じるようになり、フェライト中に析出したTiCが粗大化しやすく、微細なTiCが得にくくなる。このようなことから、仕上圧延終了後から750℃までの温度域での平均冷却速度は30℃/s以上とした。なお好ましくは50℃/s以上である。また、冷却速度の上限は、幅方向の冷却の不均一を招きやすくなるため、450℃/s以下とすることが好ましい。
巻取り温度が580℃未満では、ベイニティックフェライトやベイナイトが生じるようになり、実質的にフェライト相単相組織が得にくくなる。このため、巻取り温度は580℃以上とした。なお、好ましくは600℃以上である。一方、700℃を超える巻取り温度では、パーライトや粗大なTiCが生成して、強度が低下しやすくなる。このため、巻取り温度は700℃以下とした。なお、好ましくは680℃以下である。
上記した工程で製造された熱延鋼板には、さらに鋼板表面にめっき層を形成する、めっき処理を行ってもよい。表面に形成するめっき層の種類は、特に限定する必要はなく、電気めっき、溶融めっき等、いずれであっても何ら問題はなく、適用できる。溶融めっきとしては、溶融亜鉛めっき、溶融アルミめっきなどが挙げられる。また、溶融亜鉛めっき後に、溶融亜鉛めっき層を合金化した合金化溶融亜鉛めっきとしても、何ら問題はない。
以下、さらに実施例にしたがって、本発明をさらに詳細に説明する。
表1に示す組成の溶鋼を常用の溶製方法(転炉)で溶製し、連続鋳造法でスラブ(鋼素材)(肉厚:270mm)とした。これらのスラブを、表2に示す加熱温度に加熱し、粗圧延して、ついで、表2に示す条件で仕上圧延を施し、仕上圧延終了後、750℃までの温度域で、表2に示す平均冷却速度で加速冷却し、表2に示す巻取り温度でコイル状に巻き取り、板厚:2.3mmの熱延鋼板とした。なお、一部の熱延鋼板(鋼板No.6~10)には、酸洗して表面スケールを除去したのち、溶融亜鉛めっき処理を施し、鋼板表面にめっき層を形成した。さらに一部の鋼板では、めっき層の合金化処理を行い、合金化溶融亜鉛めっき層とした。めっきの付着量は45g/m2とした。
(1)組織観察
得られた鋼板から、組織観察用試験片を採取して、圧延方向に平行な断面(L断面)が観察面となるように研磨し、ナイタール(nital)液で腐食し、光学顕微鏡(倍率:500倍)および走査型電子顕微鏡(倍率:3000倍)で組織を観察し、撮像した。得られた組織写真から、画像解析装置を用いて、組織の種類およびその面積率を算出した。また、圧延方向に平行な断面を鏡面研磨し、ナイタール腐食液で腐食し、フェライト粒を現出させて光学顕微鏡(倍率:100倍)で組織を撮像した。得られた組織写真について、圧延方向、板厚方向にそれぞれ10本の直線を、100μm以上の間隔で引き、粒界と直線との交点の数をかぞえた。全線長を交点の数で割ったものをフェライト粒一つの線分長として、これに1.13を乗じてASTMフェライト粒径を求めた。
得られた熱延鋼板から、引張方向が圧延方向と平行になるようにJIS 5号試験片(GW:25mm、GL:50mm)を採取した。採取位置は、鋼板長手方向で先端から150mの位置で、幅中央位置と、幅方向端から内側に50mmの幅端側位置の2箇所とし、各箇所各1本採取した。得られた引張試験片を用いて、JIS Z2241の規定に準拠して引張試験を行い、引張特性(降伏強さYS、引張強さTS)を測定した。幅中央位置と幅端側位置との降伏強さの差ΔYSを求め、強度変動の指標とした。なお、ΔYSが20MPa以下である場合を、強度変動が少ないとして○、それ以外の場合を×として評価した。
得られた熱延鋼板から、穴拡げ試験片(130×130mm)を切り出し、試験片の中央位置に、ポンチで10mmφの穴をクリアランス12.5%で打ち抜き、ポンチの打抜き方向に、頂角60度の円錐ポンチを挿入し、穴を拡げた。板厚を貫通する明瞭な亀裂が発生した段階で円錐ポンチの挿入を中止し、試験片を取り出してその穴の直径を測定した。穴拡げ後の穴径と穴拡げ前の穴径の差を穴拡げ前の値で割り、それに100を書けた数字を穴拡げ率(%)として算出し、伸びフランジ性の指標とした。なお、穴拡げ率100%以上の場合を伸びフランジ性に優れると評価した。
得られた結果を表3に示す。
表1に示す鋼No.H、No.Mの組成の溶鋼を転炉で溶製し、実施例1と同様に、連続鋳造法でスラブ(肉厚:270mm)とした。これらのスラブを、表2に示す鋼板No.8、No.12と同様の条件で、加熱し、粗圧延、仕上圧延を施し、さらに加速冷却し、コイル状に巻取り、板厚2.6mmの熱延鋼板とした。得られたコイルについて、表4に示す長手方向の各位置で、板幅方向中央部から、JIS 5号引張試験片、穴拡げ試験片を採取し、実施例1と同様の条件で引張試験、穴拡げ試験を実施した。得られた結果を表4に示す。なお、長手方向の40m位置を基準にして長手方向各位置での降伏強さの差ΔYSも併せて示す。
Claims (9)
- 質量%で、
C:0.010%超0.06%以下、 Si:0.3%以下、
Mn:0.8%以下、 P:0.03%以下、
S:0.02%、 Al:0.1%以下、
N:0.01%以下、 Ti:0.05~0.10%
を含有し、残部Fe及び不可避不純物よりなる組成と、さらにフェライト相が面積率で95%以上を占め、フェライト結晶粒が1μm以上の平均粒径を有し、かつ該フェライト結晶粒内に平均粒径:7nm以下のTiCを分散析出させた金属組織と、を有することを特徴とする降伏強さ530MPa以上の高強度熱延鋼板。 - 前記組成に加えてさらに、質量%で、B:0.0020%以下を含有することを特徴とする請求項1に記載の高強度熱延鋼板。
- 前記組成に加えてさらに、質量%で、Cu、Ni、Cr、Co、Mo、Sb、W、As、Pb、Mg、Ca、Sn、Ta、Nb、V、REM、Cs、Zr、Znのうちから選ばれた1種または2種以上を合計で、1%以下含有することを特徴とする請求項1または2に記載の高強度熱延鋼板。
- 前記TiCが、TとCとの原子数比、Ti/Cが1未満であることを特徴とする請求項1ないし3のいずれかに記載の高強度熱延鋼板。
- 表面にめっき層を有することを特徴とする請求項1ないし4のいずれかに記載の高強度熱延鋼板。
- 前記めっき層が、亜鉛めっきまたは亜鉛含有合金めっきであることを特徴とする請求項5に記載の高強度熱延鋼板。
- 鋼素材に、熱間圧延を施して熱延板とする熱延鋼板の製造方法であって、
前記鋼素材を、質量%で、
C:0.010%超0.06%以下、 Si:0.3%以下、
Mn:0.8%以下、 P:0.03%以下、
S:0.02%、 Al:0.1%以下、
N:0.01%以下、 Ti:0.05~0.10%
を含有し、残部Fe及び不可避不純物よりなる組成を有する鋼素材とし、
前記鋼素材に、オーステナイト単相域に加熱したのち、仕上圧延終了温度:860℃以上1050℃以下となる仕上圧延を施し、該仕上圧延終了後から750℃までの温度域で、30℃/s以上の平均冷却速度で冷却し、巻取り温度:580℃以上700℃以下でコイル状に巻き取り、熱延板とすることを特徴とする降伏強さ530MPa以上の高強度熱延鋼板の製造方法。 - 前記組成に加えてさらに、質量%で、B:0.0020%以下を含有することを特徴とする請求項7に記載の高強度熱延鋼板の製造方法。
- 前記組成に加えてさらに、質量%で、Cu、Ni、Cr、Co、Mo、Sb、W、As、Pb、Mg、Ca、Sn、Ta、Nb、V、REM、Cs、Zr、Znのうちから選ばれた1種または2種以上を合計で、1%以下含有することを特徴とする請求項7または8に記載の高強度熱延鋼板の製造方法。
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US9657382B2 (en) | 2017-05-23 |
EP2799578B1 (en) | 2017-11-22 |
US20140363696A1 (en) | 2014-12-11 |
US10533236B2 (en) | 2020-01-14 |
IN2014KN01189A (ja) | 2015-10-16 |
KR20140103339A (ko) | 2014-08-26 |
CN104024460A (zh) | 2014-09-03 |
JP5838796B2 (ja) | 2016-01-06 |
US20170218474A1 (en) | 2017-08-03 |
JP2013133497A (ja) | 2013-07-08 |
CN104024460B (zh) | 2016-06-22 |
EP2799578A4 (en) | 2016-01-27 |
EP2799578A1 (en) | 2014-11-05 |
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