WO2019187124A1 - 溶融亜鉛めっき鋼板及び合金化溶融亜鉛めっき鋼板 - Google Patents
溶融亜鉛めっき鋼板及び合金化溶融亜鉛めっき鋼板 Download PDFInfo
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- WO2019187124A1 WO2019187124A1 PCT/JP2018/013915 JP2018013915W WO2019187124A1 WO 2019187124 A1 WO2019187124 A1 WO 2019187124A1 JP 2018013915 W JP2018013915 W JP 2018013915W WO 2019187124 A1 WO2019187124 A1 WO 2019187124A1
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- steel sheet
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- C—CHEMISTRY; METALLURGY
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
- B32B15/013—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
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- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/043—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
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- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C21D8/0268—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment between cold rolling steps
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
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- C23C2/29—Cooling or quenching
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
- C23C28/025—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only with at least one zinc-based layer
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
- C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
- C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
- C23C28/3225—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only with at least one zinc-based layer
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
- C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates
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- 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
- C21D2211/001—Austenite
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- 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
- C21D2211/008—Martensite
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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
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- 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
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- 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
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- Y10T428/12771—Transition metal-base component
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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
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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
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- Y10T428/12965—Both containing 0.01-1.7% carbon [i.e., steel]
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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
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- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
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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
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- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
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- Y10T428/12951—Fe-base component
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- Y10T428/12979—Containing more than 10% nonferrous elements [e.g., high alloy, stainless]
Definitions
- the present invention relates to a high-strength hot-dip galvanized steel sheet and high-strength galvanized steel sheet suitable for press forming, and in particular, high-strength hot-dip galvanized steel sheet and high-strength alloyed hot-dip galvanized steel excellent in ductility and low-temperature impact properties. It relates to steel plates.
- the thin steel sheet for automobiles is also required to have excellent uniform ductility and local ductility.
- the steel sheet in order to improve the collision safety performance of automobiles, the steel sheet needs to have excellent shock absorption. From the viewpoint of impact absorption, the steel sheet for automobiles needs to be excellent in local ductility in order to suppress cracking during impact load loading in addition to higher strength.
- the steel sheet for automobiles has high strength for reducing the weight of the vehicle body and improving collision safety, high uniform ductility for improving formability, and improving formability and improving collision safety. Therefore, high local ductility is required. Furthermore, in order to ensure the collision safety even in a low temperature environment, the steel sheet for automobiles is also required to have excellent low temperature impact characteristics.
- a method for improving the ductility of a high-tensile cold-rolled steel sheet a method in which retained austenite is contained in a metal structure has been proposed.
- a steel sheet containing residual austenite exhibits a large elongation due to transformation-induced plasticity (TRIP) expressed by transformation of austenite to martensite during processing.
- TRIP transformation-induced plasticity
- Patent Documents 1 and 2 a steel sheet containing Si and Mn is annealed by heating to a ferrite-austenite two-phase region or an austenite single-phase region, and then cooled, and then held at 350 to 500 ° C.
- a manufacturing method of a high-strength cold-rolled steel sheet is disclosed in which austenite treatment is performed to stabilize austenite. According to these production methods, strength and ductility can be improved in a balanced manner in a cold-rolled steel sheet.
- Patent Document 3 by containing Si and Mn at a certain ratio or more with respect to the C amount, the transformation of austenite during alloying treatment is suppressed, and a metal structure in which residual austenite is mixed in ferrite is formed.
- a method for producing an alloyed hot-dip galvanized steel sheet is disclosed.
- Patent Document 4 discloses a high-tensile melt excellent in ductility, stretch flangeability, and fatigue resistance, in which retained austenite and low-temperature transformation product phase are dispersed in ferrite and tempered martensite having an average crystal grain size of 10 ⁇ m or less.
- a galvanized steel sheet is disclosed. It is disclosed that tempered martensite is an effective phase for improving stretch flangeability and fatigue resistance characteristics, and that the above characteristics are further improved when the tempered martensite is refined.
- JP 61-157625 A Japanese Patent Laid-Open No. Sho 61-217529 Japanese Patent Application Laid-Open No. 11-296991 JP 2001-192768 A
- Patent Document 3 no consideration is given to the deterioration of local ductility and low-temperature impact characteristics, which are problematic in steel sheets in which retained austenite is mixed in the metal structure.
- Patent Document 4 in order to obtain a metal structure containing tempered martensite and retained austenite, primary heat treatment for generating martensite, tempering martensite, and further, secondary heat treatment for obtaining retained austenite. Therefore, the productivity of the steel sheet manufacturing method of Patent Document 4 is significantly low. Moreover, in the manufacturing method of the steel plate of patent document 4, since secondary heat processing are performed at the high temperature of Ac 1 point or more, tempered martensite becomes soft too much and it is difficult to obtain high intensity
- the present invention provides a hot dip galvanized steel sheet and an alloyed hot dip galvanized steel sheet that are improved in all of uniform ductility and local ductility, low temperature impact properties, yield strength and tensile strength, and
- An object is to provide an alloyed hot-dip galvanized steel sheet.
- the present inventors diligently studied a method for solving the above problems. As a result, the following findings (A) to (D) were obtained.
- the present inventors Based on the knowledge of (A) to (D), the present inventors applied temper rolling to the hot dip galvanized steel sheet or the alloyed hot dip galvanized steel sheet, and then reheated by two-stage heating. If treated, it has a metal structure containing retained austenite with high C concentration and tempered martensite, excellent in uniform ductility, local ductility, and low temperature impact properties, and also has high yield strength and tensile strength. It has been found that galvanized steel sheets and galvannealed steel sheets can be manufactured.
- steel plate includes “steel strip”.
- a hot-dip galvanized steel sheet having a hot-dip galvanized layer on the surface of the steel sheet wherein the composition of the steel sheet is C: 0.03 to 0.70%, Si: 0.25 to 2 in mass%. .50%, Mn: 1.00 to 5.00%, P: 0.0005 to 0.100%, S: 0.010% or less, sol.
- the composition of the steel sheet is, by mass%, B: 0.0002 to 0.0200%, Ti: 0.001 to 0.30%, Nb: 0.001 to 0.30%, V: 0 0.001 to 0.30%, Cr: 0.001 to 2.00%, Mo: 0.001 to 2.00%, Cu: 0.001 to 2.00%, Ni: 0.001 to 2.00 %, Ca: 0.0001 to 0.010%, Mg: 0.0001 to 0.010%, REM: 0.0001 to 0.10%, and Bi: 0.0001 to 0.050% (1)
- B 0.0002 to 0.0200%
- Nb 0.001 to 0.30%
- V 0 0.001 to 0.30%
- Cr 0.001 to 2.00%
- Mo 0.001 to 2.00%
- Cu 0.001 to 2.00%
- Mg 0.0001 to 0.010%
- REM 0.0001 to 0.10%
- Bi
- the B content is 0.0002% or more, and the amount of B segregation (number of atoms / nm 2 ) at the prior austenite grain boundaries in the metal structure of the steel sheet: [B] ⁇ gb And the ratio of P segregation (number of atoms / nm 2 ): [P] ⁇ gb : [B] ⁇ gb / [P] ⁇ gb is 4.0 or more, wherein (1) or (2) Hot dip galvanized steel sheet.
- the annealing step for heating and annealing in the zone, the annealing step, the raw steel plate is cooled to 500 ° C. or less by setting the average cooling rate in the temperature range of 650 to 500 ° C. to 2 ° C./second or more and less than 100 ° C./second.
- the average cooling rate in the temperature range from the plating temperature to 300 ° C is set to 2 ° C / second or more after the plating step and the plating step of hot-dip galvanizing the material steel plate.
- the temper rolling step for subjecting the raw steel sheet to temper rolling with an elongation of 0.10% or more and the temper rolling step, Average addition in the temperature range up to 300 ° C Heating to 300 ° C. with a rate of less than 10 ° C./second, then heating to a temperature range of more than 300 ° C. to 600 ° C. with an average heating rate in the temperature region exceeding 300 ° C. exceeding 10 ° C./second, and heating
- a method for producing a hot-dip galvanized steel sheet comprising a two-stage heat treatment step for performing a heat treatment for holding at a temperature for 1 second or more.
- the plating process for hot-dip galvanizing on the material steel sheet after the plating process, the alloying process for alloying the material steel sheet, after the alloying process, Temper rolling with an elongation rate of 0.10% or more after the second cooling step, cooling to less than 300 ° C. with the average cooling rate in the temperature range of 300 ° C. being 2 ° C./second or higher, and the second cooling step.
- temper rolling process and temper rolling process The steel sheet is heated to 300 ° C. with an average heating rate in the temperature range up to 300 ° C. being less than 10 ° C./second, and then 300 ° C.
- a method for producing an alloyed hot-dip galvanized steel sheet comprising a two-stage heat treatment step in which heat treatment is performed in a temperature range of ultra-600 ° C or lower and the heat temperature is maintained for 1 second or longer.
- both uniform ductility and local ductility are good, press formability is excellent, yield strength and tensile strength are high, local ductility is good, shock absorption is excellent, and low temperature impact is achieved.
- a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet that are also excellent in properties can be provided.
- the steel sheet of the present invention the component composition, metal structure, and mechanical properties of the hot-dip galvanized steel sheet of the present invention and the alloyed hot-dip galvanized steel sheet (hereinafter collectively referred to as “the steel sheet of the present invention”) will be sequentially described.
- % relating to the component composition means “% by mass”.
- C is an element necessary for obtaining retained austenite. Furthermore, in the steel plate of this invention, it is an element which strengthens a grain boundary by segregating to a prior-austenite grain boundary. If C is less than 0.03%, it becomes difficult to obtain a metal structure containing retained austenite and tempered martensite, so C is made 0.03% or more. Preferably it is 0.10% or more, More preferably, it is 0.13% or more, More preferably, it is 0.16% or more.
- C if C exceeds 0.70%, the weldability of the steel sheet is remarkably lowered, so C is made 0.70% or less.
- it is 0.30% or less, More preferably, it is 0.26% or less, More preferably, it is 0.24% or less.
- Si 0.25 to 2.50%
- Si is an element that suppresses the precipitation of cementite and promotes the formation of retained austenite, and also suppresses excessive softening of tempered martensite and contributes to securing strength. It is.
- Si is less than 0.25%, the effect of addition cannot be sufficiently obtained, so Si is 0.25% or more, preferably more than 0.60%, more preferably more than 1.00%, and still more preferably. 1.45% or more.
- Si is made 2.50% or less.
- it is 2.30% or less, More preferably, it is 2.10% or less, More preferably, it is 1.90% or less.
- Mn contributes to improving the hardenability of steel and is an effective element for obtaining a metal structure containing retained austenite and tempered martensite. If Mn is less than 1.00%, the effect of addition cannot be sufficiently obtained, so Mn is made 1.00% or more. Preferably it is more than 1.50%, more preferably more than 2.00%, still more preferably more than 2.50%.
- Mn 5.00%
- Mn is made 5.00% or less.
- Mn is 4.00% or less, More preferably, it is 3.50% or less, More preferably, it is 3.00% or less.
- P 0.0005 to 0.100%
- the present invention is a technique for suppressing the segregation of P to the prior austenite grain boundaries and segregating C and B, and presupposes that P remains in the steel to some extent. Therefore, it is not necessary to reduce P excessively.
- P is reduced to less than 0.0005%, the manufacturing cost increases significantly, so P can be made 0.0005% or more. It may be 0.0010% or more.
- P is made 0.100% or less.
- P is less than 0.020%, More preferably, it is less than 0.015%, More preferably, it is less than 0.010%.
- S 0.010% or less Since S forms sulfide inclusions in steel and inhibits local ductility of the steel sheet, the smaller the amount, the more preferable element. If S exceeds 0.010%, the local ductility of the steel sheet is remarkably lowered, so S is made 0.010% or less. Preferably it is 0.0050% or less, More preferably, it is 0.0012% or less.
- the lower limit includes 0%, but if S is reduced to less than 0.0001%, the manufacturing cost increases significantly, so 0.0001% is a practical lower limit on practical steel sheets.
- Al like Si, is an element that acts to deoxidize molten steel, and is an element that promotes the formation of retained austenite and is effective in forming a metal structure containing retained austenite and tempered martensite.
- Al content is less than 0.001%, a sufficient deoxidation effect cannot be obtained.
- Al is made 0.001% or more. Preferably it is 0.015% or more, More preferably, it is 0.025% or more, More preferably, it is 0.045% or more. In terms of promoting retained austenite, it is preferably 0.055% or more, more preferably 0.065% or more, and further preferably 0.075% or more.
- Al content exceeds 2.500%, a large amount of alumina (Al 2 O 3 ) that causes surface flaws is generated, and the transformation point rises and annealing becomes difficult.
- Al is 2.500% or less. Preferably it is less than 0.600%, more preferably less than 0.200%, still more preferably less than 0.080%.
- N is a more preferable element because it forms nitrides that cause slab cracking during continuous casting of steel. If N exceeds 0.020%, slab cracks occur frequently, so N is made 0.020% or less. Preferably it is 0.010% or less, More preferably, it is less than 0.008%, More preferably, it is 0.005% or less.
- the lower limit includes 0%, but if N is reduced to less than 0.0005%, the production cost increases significantly, so 0.0005% is a practical lower limit on practical steel sheets.
- B is an element that segregates at the prior austenite grain boundaries and strengthens the grain boundaries. Both the uniform ductility and local ductility of the steel sheet of the present invention are good, the press formability is excellent, the yield strength and the tensile strength are high, the local ductility is good, the shock absorption is excellent, and the low temperature impact characteristics.
- hot dip galvanized steel sheets and galvannealed steel sheets can be obtained without adding B, but the addition of B further increases the effect of strengthening grain boundaries, and is necessary. It can be added depending on.
- B is an element that improves the hardenability of the steel and is effective in forming a metal structure containing retained austenite and tempered martensite. In order to obtain the effect of addition sufficiently, B is preferably 0.0002% or more. More preferably, it is 0.0005% or more, More preferably, it is 0.0010% or more.
- B is made 0.0200% or less.
- B is 0.0100% or less, More preferably, it is 0.0050% or less, More preferably, it is 0.0020% or less.
- the steel sheet of the present invention may contain one or more of Ti, Nb, V, Cr, Mo, Cu, Ni, Ca, Mg, REM, and Bi in order to improve characteristics. .
- Ti, Nb, and V are elements that refine the metal structure and contribute to improving the strength and ductility of the steel sheet.
- Ti, Nb, and V are all preferably 0.001% or more. More preferably, Ti and Nb are 0.005% or more, V is 0.010% or more, more preferably Ti and Nb are 0.010% or more, and V is 0.020% or more.
- Ti, Nb, and V are all preferably 0.30% or less. More preferably, Ti is less than 0.080%, Nb is less than 0.050%, V is 0.20% or less, more preferably, Ti is 0.035% or less, Nb is 0.030% or less, and V is It is less than 0.10%.
- Cr and Mo are elements that improve the hardenability of the steel and contribute to the formation of a metal structure including retained austenite and tempered martensite.
- both Cr and Mo are preferably 0.001% or more. More preferably, Cr is 0.100% or more, and Mo is 0.050% or more.
- both Cr and Mo are preferably 2.00% or less. More preferably, Cr is 1.00% or less, and Mo is 0.50% or less.
- Cu and Ni are elements that contribute to improvement in yield strength and tensile strength. In order to sufficiently obtain the effect of adding Cu and Ni, both Cu and Ni are preferably 0.001% or more. More preferably, any element is 0.010% or more.
- both Cu and Ni are preferably 2.00% or less. More preferably, any element is 0.80% or less.
- Ca, Mg, and REM are elements that contribute to the improvement of local ductility by controlling the shape of inclusions.
- the content of Ca, Mg, and REM is preferably 0.0001% or more. More preferably, any element is 0.0005% or more.
- Ca and Mg exceed 0.010%, the effect of addition is saturated and the economy is reduced, so Ca and Mg are preferably 0.010% or less. More preferably, any element is 0.002% or less.
- the REM is preferably 0.10% or less. More preferably, it is 0.010% or less.
- REM is a generic name for a total of 17 elements of Sc, Y, and lanthanoid. Lanthanoids are industrially added in the form of misch metal. The amount of REM is the total amount of these elements.
- Bi is an element that contributes to the improvement of local ductility by refining the solidified structure.
- Bi is preferably 0.0001% or more. More preferably, it is 0.0003% or more.
- Bi is preferably 0.050% or less. More preferably, it is 0.010% or less, More preferably, it is 0.005% or less.
- the balance of the component composition of the steel sheet of the present invention is Fe and inevitable impurities.
- Inevitable impurities are elements that are inevitably mixed from steel raw materials (ores, scraps, etc.) and / or in the production process, and are elements that are allowed within a range that does not impair the properties of the steel sheet of the present invention.
- % related to the tissue fraction means “volume%”.
- the metal structure of the steel sheet of the present invention is a metal structure containing, by volume%, retained austenite exceeding 5.0% and tempered martensite exceeding 5.0%. By forming this metal structure, uniform ductility and local ductility can be improved while maintaining yield strength and tensile strength.
- the retained austenite is 5.0% or less, the uniform ductility is not improved, so the retained austenite exceeds 5.0%.
- it is more than 6.0%, more preferably more than 8.0%, still more preferably more than 10.0%.
- the retained austenite is preferably less than 30.0%. More preferably, it is less than 20.0%.
- the tempered martensite is 5.0% or less, it is difficult to increase the local ductility while maintaining the yield strength and the tensile strength, so the tempered martensite is more than 5.0%. Preferably it is more than 8.0%, more preferably more than 10.0%, still more preferably more than 12.0%.
- tempered martensite 70.0% or less is preferable. More preferably, it is 50.0% or less, More preferably, it is 30.0% or less.
- the remainder of the metal structure is polygonal ferrite, martensite (martensite that has not been tempered, also referred to as fresh martensite), low temperature transformation formation structure of acicular ferrite or bainite, pearlite, and cementite. It is a structure
- Polygonal ferrite is an effective structure for enhancing uniform ductility, so it is preferable to contain more than 2.0%. More preferably, it is 3.0% or more.
- the volume% of polygonal ferrite is not uniquely determined in relation to the volume% of other structures, the upper limit cannot be set. However, if polygonal ferrite is 50.0% or more, the yield strength and tensile strength are in addition, since the local ductility is also lowered, the polygonal ferrite is preferably less than 50.0%. More preferably, it is less than 20.0%, More preferably, it is less than 10.0%.
- Martensite is a structure that inhibits the increase in local ductility while maintaining the yield strength, so that it is preferably less, and less than 5.0%. More preferably, it is less than 2.0%, More preferably, it is less than 1.0%.
- Precipitates such as low-temperature transformation formation structures of acicular ferrite and bainite, pearlite, and cementite inhibit yield strength and tensile strength, so the total content is preferably 40.0% or less. More preferably, it is 20.0% or less, More preferably, it is 10.0% or less.
- pearlite inhibits uniform ductility in addition to yield strength and tensile strength, it is preferably less than 10.0%. More preferably, it is less than 5.0%, More preferably, it is less than 3.0%.
- Precipitates such as martensite, acicular ferrite and bainite low-temperature transformation structures, pearlite, and cementite may be inevitably generated, so the lower limit is not particularly set, but the remainder of the metal structure Since it is not necessary to contain the tissue, the lower limit is 0%.
- the volume percentage of the metal structure of the steel sheet of the present invention is measured as follows.
- a specimen is taken from the steel plate, the longitudinal section parallel to the rolling direction is polished, and the metal structure at a depth of 1/4 of the thickness of the base steel plate is scanned from the boundary between the base steel plate and the plating layer by a scanning electron microscope. Observe and image with (SEM). The image is processed to calculate the area ratio of each tissue, and the calculated area ratio is defined as the volume ratio.
- Tempered martensite can be distinguished from bainite in this respect because the iron carbide present in the tempered martensite extends in a plurality of directions.
- Polygonal ferrite can be distinguished from acicular ferrite in that the form is massive and the dislocation density is low.
- the C content of retained austenite is set to 0.85 mass% or more. Preferably it is 0.87 mass% or more, More preferably, it is 0.89 mass% or more.
- the C amount of retained austenite means the C concentration in the austenite phase.
- the C content of retained austenite is preferably less than 1.50% by mass. More preferably, it is less than 1.20 mass%, More preferably, it is less than 1.10 mass%.
- the volume percentage of retained austenite and the amount of C of retained austenite are measured on the rolling surface from the boundary between the base steel plate and the plating layer to a depth position of 1 ⁇ 4 of the thickness of the base steel plate in the test piece taken from the steel plate. Is then polished and measured by measuring the X-ray diffraction intensity and diffraction peak position of the polished surface with an X-ray diffractometer (XRD).
- XRD X-ray diffractometer
- [C] ⁇ gb / [P] ⁇ gb is set to 4.0 or more. Preferably it is 5.0 or more, More preferably, it is 6.0 or more. Although an upper limit is not specifically limited, 30.0 or less is preferable from a viewpoint of productivity.
- [C] ⁇ gb and [P] ⁇ gb at the prior austenite grain boundaries are measured as follows to calculate [C] ⁇ gb / [P] ⁇ gb .
- the old austenite grain boundary is confirmed by observing the metal structure at a depth of 1/4 of the thickness of the base steel plate from the boundary between the base steel plate and the plating layer.
- a block including the prior austenite grain boundary is cut out by the lift-out method, and a needle sample for a three-dimensional atom probe (3DAP) is produced using a focused ion beam apparatus (FIB).
- 3DAP three-dimensional atom probe
- [B] ⁇ gb / [P] If ⁇ gb is less than 4.0, the low-temperature impact characteristics are not improved, so [B] ⁇ gb / [P] ⁇ gb is set to 4.0 or more. Preferably it is 5.0 or more, More preferably, it is 6.0 or more. Although an upper limit is not specifically limited, 30.0 or less is preferable from a viewpoint of productivity.
- [B] ⁇ gb and [P] ⁇ gb at the prior austenite grain boundaries are measured as follows to calculate [B] ⁇ gb / [P] ⁇ gb .
- the old austenite grain boundary is confirmed by observing the metal structure at a depth of 1/4 of the thickness of the base steel plate from the boundary between the base steel plate and the plating layer.
- a block including the prior austenite grain boundary is cut out by the lift-out method, and a needle sample for a three-dimensional atom probe (3DAP) is produced using a focused ion beam apparatus (FIB).
- 3DAP three-dimensional atom probe
- the hot dip galvanized layer and the alloyed hot dip galvanized layer may be formed under normal plating conditions and alloying conditions. However, if the Fe content of the alloyed hot-dip galvanized layer is less than 7% by mass, weldability and slidability cannot be ensured. Therefore, the Fe content of the alloyed hot-dip galvanized layer is preferably 7% by mass or more.
- the upper limit of the amount of Fe is preferably 20% by mass or less and more preferably 15% by mass or less from the viewpoint of suppression of powdering resistance.
- the amount of Fe in the alloyed hot-dip galvanized layer is adjusted by appropriately adjusting the alloying treatment conditions.
- the uniform elongation in the direction perpendicular to the rolling direction is defined as UEl (Uniform Elongation), and the total elongation (TEl 0 ) in the direction perpendicular to the rolling direction is defined as the thickness of the sheet based on the following formula (1).
- the value converted into the total elongation equivalent to 1.2 mm is defined as TEl (Total Elongation), and the local elongation in the direction perpendicular to the rolling direction corresponding to the plate thickness of 1.2 mm is defined as LEl based on the following formula (2).
- TEl TEl 0 ⁇ (1.2 / t 0 ) 0.2
- LEl TEl ⁇ UEl (2)
- UEl is the measured value of the uniform elongation was measured using a JIS5 No. tensile specimens
- TEL 0 is the measured value of total elongation as measured using a JIS5 No.
- Tensile test pieces t 0 were subjected to measurement This is the thickness of a JIS No. 5 tensile test piece.
- TEl and LEl are the total elongation and the local elongation converted in the case of a plate thickness of 1.2 mm, respectively.
- TS ⁇ UEl becomes a large value when both tensile strength (TS) and uniform elongation (UEl) are excellent, and is used as an index for evaluating uniform ductility.
- TS ⁇ LEl is a large value when both tensile strength (TS) and local elongation (LEl) are excellent, and is used as an index for evaluating local ductility.
- TS ⁇ UEl is preferably 10,000 MPa ⁇ % or more, and TS ⁇ LEl is preferably 5000 MPa ⁇ % or more. More preferably, TS ⁇ UEl is 11000 MPa ⁇ % or more, and TS ⁇ LEl is 6000 MPa ⁇ % or more. More preferably, TS ⁇ UEl is 12000 MPa ⁇ % or more, and TS ⁇ LE1 is 7000 MPa ⁇ % or more.
- the tensile strength (TS) is preferably 780 MPa or more, more preferably 980 MPa or more, and further preferably 1180 MPa or more.
- the yield ratio (YR) is preferably 0.59 or more, more preferably 0.66 or more, and further preferably 0.72 or more.
- TS ⁇ LEl is preferably 5500 MPa ⁇ % or more, and more preferably 6500 MPa ⁇ % or more.
- a plurality of sub-size Charpy impact test pieces in the width direction the length direction being the direction perpendicular to the rolling direction, the length is 55 mm, the thickness is 10 mm, and the width is the thickness of the steel sheet
- a Charpy impact test is performed in the stacked state.
- the notch shape of the test piece is defined as V notch defined in JIS Z 2242, and the Charpy impact values when the Charpy impact test is performed with the test temperatures set to ⁇ 60 ° C. and 40 ° C. are defined as IV LT and IV HT , respectively. .
- IV LT / IV HT can be used as an index for evaluating low-temperature impact characteristics.
- IV LT / IV HT is preferably more than 0.50, more preferably more than 0.60, More than 70 is more preferred.
- the steel plate before plating of the present invention may be a steel plate having the component composition of the steel plate of the present invention, and the method for producing the material steel plate is not limited to a specific production method.
- a hot-rolled steel sheet can be used as the material steel sheet.
- the cold-rolled steel plate which cold-rolled after pickling can also be used for a hot-rolled steel plate.
- an example of the manufacturing method of a raw steel plate will be described.
- the slab casting method is not limited to a specific casting method, but a continuous casting method is preferable.
- a steel ingot cast by another casting method may be used as a steel slab by partial rolling or the like.
- the high-temperature steel ingot after continuous casting or the high-temperature steel slab after partial rolling may be once cooled and then reheated and subjected to hot rolling.
- a high-temperature steel ingot after continuous casting or a high-temperature steel slab after partial rolling may be subjected to hot rolling as it is, or may be subjected to hot rolling after auxiliary heating.
- steel ingots and steel slabs used for hot rolling are collectively referred to as “slabs”.
- the temperature of the slab used for hot rolling is preferably less than 1250 ° C. More preferably, it is 1200 degrees C or less.
- the lower limit of the temperature of the slab subjected to hot rolling is not particularly limited, but is preferably a temperature at which hot rolling can be completed at Ar 3 points or more.
- the hot rolling conditions are not limited to specific conditions, but if the hot rolling completion temperature is too low, there is a risk that a coarse low-temperature transformation formation structure that extends in the rolling direction may occur in the metal structure of the hot-rolled steel sheet. is there.
- the completion temperature of hot rolling is preferably Ar 3 or higher and higher than 850 ° C. More preferably, it is Ar 3 point or higher and higher than 880 ° C., more preferably Ar 3 point or higher and higher than 900 ° C.
- the upper limit of the completion temperature of hot rolling is not specifically limited, 1000 degreeC or less is preferable at the point which refines
- the rough rolled material may be heated between the rough rolling and the finish rolling in order to maintain the completion temperature of the hot rolling in the above temperature range.
- the rough rolled material is heated so that the rear end of the rough rolled material is at a higher temperature than the leading end of the rough rolled material, and the temperature variation over the entire length of the rough rolled material at the start of finish rolling is 140 ° C. or less. It is preferable to suppress it. Due to this temperature suppression, the uniformity of the characteristics in the coil wound with the hot-rolled steel sheet is improved.
- the heating of the rough rolled material may be performed using known means.
- a solenoid induction heating device is provided between the rough rolling mill and the finish rolling mill, and heating by the solenoid induction heating device is performed based on the longitudinal temperature distribution of the rough rolled material on the upstream side of the induction heating device.
- the amount of temperature increase may be controlled.
- the conditions from the end of hot rolling to the start of winding may be normal conditions, but in order to improve the cold rolling property of the hot rolled steel sheet by softening the hot rolled steel sheet, the winding temperature should be 600 ° C or higher. preferable.
- the winding temperature is more preferably 640 ° C or higher, and further preferably 680 ° C or higher.
- the coiling temperature is preferably 750 ° C. or less, and more preferably less than 720 ° C.
- Cold rolling The conditions for cold rolling are not limited to specific conditions. Prior to cold rolling, the hot-rolled steel sheet may be descaled by pickling or the like. In order to make the metal structure after annealing uniform and further improve the local ductility, the rolling reduction of cold rolling is preferably 40% or more. If the rolling reduction is too high, the rolling load increases and rolling becomes difficult. Therefore, the rolling reduction is preferably less than 70%, more preferably less than 60%.
- the material steel plate is annealed by heating to a temperature exceeding Ac 1 point.
- Ac 1 point is the temperature at which austenite begins to form in the metal structure when the material steel plate is heated.
- the heating temperature is less than Ac 1 point, austenite is not generated, and in the metal structure of the steel sheet of the present invention, retained austenite is not obtained and uniform ductility is lowered. Therefore, the heating temperature is preferably more than Ac 1 point. More preferably, it is higher than (Ac 1 +30) ° C.
- the heating temperature is preferably (Ac 3 point-40) ° C. or higher. More preferably, it is more than Ac 3 points.
- Ac 3 point is a temperature at which ferrite disappears in the metal structure when the material steel plate is heated.
- the heating temperature When the heating temperature is too high, austenite becomes coarse, so local ductility is impaired, the heating temperature (Ac 3 point +100) ° C. or less are preferred, (Ac 3 point +50) ° C. or less is more preferable.
- the holding time at the heating temperature is not particularly limited, but is preferably 10 seconds or longer in order to make the metal structure of the material steel plate uniform. 240 seconds or less are preferable at the point which suppresses the coarsening of austenite.
- the raw steel sheet After annealing, the raw steel sheet is cooled to a temperature range of 500 ° C. or less without being kept isothermal on the way at an average cooling rate in the temperature range of 650 to 500 ° C. of 2 ° C./second or more and less than 100 ° C./second.
- the cooling temperature range that defines the average cooling rate is the temperature range of 650 to 500 ° C. In this temperature range, since ferrite and pearlite precipitate, it is necessary to control the cooling rate in order to adjust the precipitation amount and ensure the required mechanical properties.
- the average cooling rate in the temperature range of 650 to 500 ° C. is less than 2 ° C./second, polygonal ferrite and pearlite are excessively generated, and the yield strength and tensile strength decrease. Therefore, the average cooling rate in the above temperature range is 2 ° C./second or more is preferable. More preferably, it is 4 ° C / second or more, and further preferably 10 ° C / second or more.
- the average cooling rate in the temperature range of 650 to 500 ° C. is 100 ° C./second or more, the accuracy of the shape and dimensions of the steel sheet is lowered. Therefore, the average cooling rate in the above temperature range is preferably less than 100 ° C./second. . More preferably, it is 30 ° C./second or less.
- the material steel plate is cooled to 500 ° C. or less at an average cooling rate of 2 ° C./second or more and less than 100 ° C./second in a temperature range of 650 to 500 ° C.
- the cooling conditions after cooling to 500 ° C. or lower are not particularly limited, but in the metal structure after plating, the volume percentage of retained austenite and the amount of C in retained austenite are adjusted to improve uniform ductility and local ductility, and yield strength. In order to increase the temperature, it is preferable to hold the material steel plate in a temperature range of 500 ° C. or lower and 460 ° C. or higher for 4 to 45 seconds.
- a raw steel plate is hot dip galvanized according to a conventional method, and a hot dip galvanized layer is formed on one or both surfaces of the raw steel plate. Before subjecting the material steel plate to hot dip galvanization, the material steel plate may be appropriately cooled and / or heated.
- the bath temperature and bath composition of the hot dip galvanizing bath may be the usual bath temperature and bath composition.
- the plating adhesion amount may be a normal adhesion amount. For example, the range of 20 to 80 g / m 2 per side of the raw steel plate is preferable.
- the material steel plate having the hot dip galvanized layer may be heated to a required temperature and the hot dip galvanized layer may be alloyed.
- the alloying process may be performed under normal conditions. For example, the alloying process may be performed at 470 to 560 ° C. for 5 to 60 seconds. However, the condition that the amount of Fe in the plating layer is 7% by mass or more is preferable.
- the steel sheet after the plating treatment or alloying treatment is less than 300 ° C. with an average cooling rate in the temperature range from the plating temperature to 300 ° C. or the temperature range from the alloying treatment temperature to 300 ° C. being 2 ° C./second or more. Cooling.
- the cooling rate is preferably 2 ° C./second or more. More preferably, it is more than 10 ° C./second.
- the upper limit of the average cooling rate is not particularly limited, but is preferably 500 ° C./second or less from the viewpoint of economy.
- the cooling stop temperature is less than 300 ° C., the cooling stop temperature is preferably room temperature from the viewpoint of effectively performing subsequent temper rolling.
- temper rolling Before subjecting the steel sheet having the hot-dip galvanized layer or the alloyed plated layer to the two-stage heat treatment, temper rolling with an elongation of 0.10% or more is performed. By this temper rolling, concentration of C to austenite is promoted in the subsequent two-stage heat treatment, and uniform ductility and local ductility are improved, and yield strength is improved.
- the concentration of C to austenite is not promoted in the subsequent two-stage heat treatment, the uniform ductility and local ductility are not improved, and the yield strength is not improved.
- the elongation is preferably 0.10% or more. More preferably, it is 0.30% or more, More preferably, it is 0.50% or more.
- the upper limit of the elongation rate is not particularly specified, but if it is too high, the rolling load increases, so the elongation rate is preferably 2.00% or less. More preferably, it is less than 1.50%, More preferably, it is less than 1.00%.
- temper rolling temperature is not particularly specified, the lower the temperature, the more preferably room temperature, particularly preferably imparting work strain to austenite.
- a steel sheet having a hot dip galvanized layer or an alloyed hot dip galvanized layer is subjected to temper rolling with an elongation of 0.10% or more, and then the steel sheet is heated to 300 ° C. at an average heating rate of less than 10 ° C./second. Subsequently, heating is performed at an average heating rate of 10 ° C./second or more in a temperature range exceeding 300 ° C. and not more than 600 ° C., and maintained at a heating temperature in a temperature range exceeding 300 ° C. and not more than 600 ° C. for 1 second or more.
- the steel sheet contains B
- the amount of B segregation (number of atoms / nm 2 ): [B] ⁇ gb and the amount of P segregation (number of atoms / nm 2 ): [P] ⁇ gb : [B] ⁇ gb / [ P] ⁇ gb satisfies [B] ⁇ gb / [P] ⁇ gb ⁇ 4.0
- the uniform ductility and the local ductility are improved, the yield strength is improved, and the low temperature impact property is improved.
- the metal structure of the steel sheet after temper rolling in order to concentrate C to austenite and to temper martensite, the metal structure is heated to a temperature range of more than 300 ° C. and 600 ° C. or less. At this time, it heats to 300 degreeC with the average heating rate of less than 10 degree-C / sec. This heating promotes the segregation of C and B to the prior austenite grain boundaries.
- the average heating rate up to 300 ° C. is 10 ° C./second or more, segregation of C and B to the prior austenite grain boundaries is not promoted, so the average heating rate up to 300 ° C. is less than 10 ° C./second. Preferably it is 7 degrees C / second or less, More preferably, it is 3 degrees C / second or less.
- the segregation of P to the prior austenite grain boundaries can be suppressed by setting the average heating rate to a heating temperature in the temperature range exceeding 300 ° C. and 600 ° C. or less to 10 ° C./second or more.
- Equation (3) can be realized by changing the average heating rate of less than 10 ° C./second to 10 ° C./second or more at the boundary of 300 ° C.
- Equation (4) can be realized.
- the average heating rate in the temperature range exceeding 300 ° C. and not more than 600 ° C. is preferably more than 20 ° C./second.
- the steel plate is held at a heating temperature in the temperature range exceeding 300 ° C. and not more than 600 ° C. for 1 second or longer.
- the heating temperature is 300 ° C. or lower, the concentration of C into austenite becomes insufficient, the uniform ductility does not improve, hard martensite remains, local ductility is impaired, and yield strength decreases. Therefore, the heating temperature is over 300 ° C. Preferably it is over 350 degreeC, More preferably, it is over 400 degreeC.
- the heating temperature exceeds 600 ° C., the amount of retained austenite is insufficient, the uniform ductility is lowered, the tempered martensite is excessively softened, the yield strength and the tensile strength are lowered, and the hard The fresh martensite is generated, and the local ductility is lowered and the yield strength is lowered. Therefore, the heating temperature is 600 ° C. or less. Preferably it is 550 degrees C or less, More preferably, it is 500 degrees C or less.
- the heating and holding time is set to 1 second or longer. Preferably it is 5 seconds or more, More preferably, it is 15 seconds or more.
- the heating and holding time is preferably 96 hours or less. More preferably, it is 48 hours or less, More preferably, it is 24 hours or less.
- the heating and holding time is appropriately adjusted according to the heating temperature.
- the heating and holding time is preferably 20 minutes or less. More preferably, it is 6 minutes or less, More preferably, it is less than 3 minutes. From the viewpoint of productivity, a heating temperature of over 400 ° C. and a heating and holding time of 20 minutes or less are preferable.
- the steel sheet in order to correct the flatness of the steel sheet after the two-stage heat treatment is applied to the steel sheet, the steel sheet may be subjected to temper rolling, or the steel sheet may be coated with an oil or lubricating action. Good.
- the plate thickness of the steel plate of the present invention is not particularly limited to a specific range, but the effect of the two-stage heat treatment is remarkably exhibited in a versatile steel plate having a thickness of 0.8 to 2.3 mm.
- the conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited.
- the present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
- Example 1 Steels A to U having the composition shown in Table 1 were manufactured by casting molten steel using a vacuum melting furnace.
- the points Ac 1 and Ac 3 in Table 1 were determined from changes in thermal expansion when the cold rolled steel sheets of steels A to P were heated at 2 ° C./second.
- Steels A to U were heated to 1200 ° C. and held for 60 minutes, and then hot rolled under the hot rolling conditions shown in Tables 2-1 and 2-2.
- the steels A to U were rolled in 10 passes in a temperature range of Ar 3 or higher to obtain a hot rolled steel sheet having a thickness of 2.5 to 3.0 mm.
- the hot-rolled steel sheet is cooled to 500 to 680 ° C. with water spray, the cooling end temperature is set as the coiling temperature, and the hot-rolled steel sheet is inserted into an electric heating furnace maintained at this coiling temperature.
- the hot-rolled steel sheet was then cooled in the furnace to room temperature at a cooling rate of 20 ° C./hour to simulate slow cooling after winding.
- the hot-rolled steel sheet after slow cooling is pickled to form a base material for cold rolling, cold-rolled at a rolling reduction of 47 to 52%, and a cold-rolled steel sheet having a thickness of 1.2 to 1.6 mm (material) Steel plate).
- the material steel plate was heated to 650 ° C. at a heating rate of 10 ° C./second, and then heated to a temperature shown in Tables 2-1 and 2-2 at a heating rate of 2 ° C./second. Soaked for 30 to 90 seconds.
- the material steel plate is cooled to 460 ° C. under the cooling conditions shown in Tables 2-1 and 2-2, and the material steel plate is immersed in a hot dip galvanizing bath maintained at 460 ° C. to perform hot dip galvanizing on the material steel plate. did.
- Some raw steel sheets were subjected to alloying treatment by heating to 520 ° C. after hot dip galvanization.
- the material steel plate was secondarily cooled under the cooling conditions shown in Tables 2-1 and 2-2.
- “RT” indicates room temperature.
- hot-dip galvanized steel sheet or alloyed melt After subjecting the secondary steel sheet to temper rolling with an elongation of 0.50%, heat treatment was performed under the heat treatment conditions shown in Tables 3-1 and 3-2 to obtain a hot-dip galvanized steel sheet or alloyed melt.
- a galvanized steel sheet (hereinafter, hot dip galvanized steel sheet and alloyed galvanized steel sheet are collectively referred to as “plated steel sheet”) was obtained.
- temper rolling is performed without cooling to room temperature after the secondary cooling stop, and then cooling to room temperature is performed, as shown in Tables 3-1 and 3-2. Heat treatment was performed under the heat treatment conditions. For some of the material steel plates, temper rolling or heat treatment was omitted. In Tables 3-1 and 3-2, “-” in the “heat treatment condition” column indicates that no heat treatment was performed.
- test piece for XRD measurement was collected from the plated steel plate, and the rolled surface of the test piece was chemically polished from the boundary between the base steel plate and the plating layer to a 1/4 depth position of the thickness of the base steel plate.
- An X-ray diffraction test was performed on the rolled surface, and the volume fraction of retained austenite and the amount of C in retained austenite were measured.
- Mo-K ⁇ rays are incident on the test piece, the integrated intensity of the ⁇ phase (200), (211) diffraction peak, and the ⁇ phase (200), (220), (311) diffraction peak.
- the integrated intensity was measured to determine the volume fraction of retained austenite.
- the concentration distribution of C, B and P atoms was measured, and the amount of C segregation ([C] ⁇ gb ), B segregation amount ([B] ⁇ gb ) and P segregation amount ([P ] [ gamma ] gb ) was determined, and [C] [ gamma ] gb / [P] [ gamma ] gb and [B] [ gamma ] gb / [P] [ gamma ] gb were calculated.
- the longitudinal section is subjected to nital corrosion and repeller corrosion, and the boundary between the base steel sheet and the plating layer is obtained. From the above, the metal structure at the 1/4 depth position of the thickness of the base steel sheet was observed. The volume ratio of tempered martensite, polygonal ferrite, fresh martensite, and the remaining structure was measured by image processing.
- the volume ratio of fresh martensite was obtained by subtracting the volume ratio of residual austenite measured by the XRD measurement from the total volume ratio of residual austenite and fresh martensite measured by repeller corrosion.
- Yield stress (YS), tensile strength (TS), and uniform elongation (UEl) were obtained by taking a JIS No. 5 tensile specimen along the direction perpendicular to the rolling direction from the plated steel sheet, and conducting a tensile test on this specimen. Asked.
- the tensile speed was 1 mm / min until the yield point was reached, and 10 mm / min thereafter.
- the yield ratio (YR) was determined by dividing YS by TS.
- the total elongation (TEl) and local elongation (LEl) were determined by conducting a tensile test on a JIS No. 5 tensile specimen taken along the direction perpendicular to the rolling direction, and measuring the total elongation (TEl 0 ) and the uniform elongation. Based on the above formulas (1) and (2), a conversion value corresponding to the case of a plate thickness of 1.2 mm was obtained using (UEl).
- V-notched sub-size Charpy impact test specimens were taken from the plated steel sheet along the direction perpendicular to the rolling direction. When the plate thickness is 1.2 mm, 8 pieces are obtained, and when the plate thickness is 1.6 mm, 6 pieces are obtained. Were stacked and screwed, and a Charpy impact test was performed using this test piece.
- TS ⁇ UEl was 10000 MPa ⁇ % or more, and TS ⁇ LE1 was 5000 MPa ⁇ % or more, it was judged that the mechanical properties were good. Further, if IV LT / IV HT was more than 0.50, it was judged as good low temperature impact characteristics.
- Tables 4-1 and 4-2 show the results of observing the metal structure of the plated steel sheets
- Tables 5-1 and 5-2 show the results of evaluating the mechanical characteristics and low-temperature impact characteristics of the plated steel sheets.
- TS ⁇ UEl was 10,000 or more and TS ⁇ LEl was 5000 or more, which showed good uniform ductility and local ductility.
- YR showed a high value of 0.59 or more.
- IV LT / IV HT showed a high value of 0.51 or more.
- Test results for comparative examples in which the component composition or process conditions are not appropriate were inferior in any or all of yield ratio, uniform ductility, local ductility, and low-temperature impact characteristics.
- steels C, E, and N having a component composition within the scope of the present invention were used, but in test numbers 9, 22, and 40 where temper rolling was not performed, the amount of C in the retained austenite was Low, TSxUEl and TSxLEl are low.
- test numbers 10, 23, and 41 in which the heat treatment temperature is too low the tempered martensite volume fraction, the C amount of retained austenite, and [C] ⁇ gb / [P] ⁇ gb are low, and YR, TS ⁇ UEl, TS ⁇ LEl, And IV LT / IV HT is low.
- steel C having a component composition within the scope of the present invention was used, in test number 19 where the soaking temperature was too low in the annealing process, the residual austenite volume ratio and tempered martensite volume ratio were low, and TS ⁇ UEl was low.
- test numbers 4 and 18 the average cooling rate in the temperature range of 650 to 500 ° C. is too low in the first cooling step, so that in test number 4, the residual austenite volume fraction and tempered martens Site volume ratio is low, YR and TS ⁇ LE1 are low. In test number 18, the retained austenite volume fraction is low, and YR, TS ⁇ UEl, and TS ⁇ LEl are low.
- test number 5 using steel B since the amount of Si in the steel is small, the retained austenite volume fraction and the retained austenite C content are low, and YR, TS ⁇ UEl, and TS ⁇ LEl are low.
- test number 20 using steel D the amount of Mn in the steel is small, so the volume ratio of retained austenite is low and YR and TS ⁇ LEl are low.
- both uniform ductility and local ductility are good, press formability is excellent, yield strength and tensile strength are high, local ductility is good, and shock absorption is excellent.
- the hot-dip galvanized steel sheet and alloyed hot-dip galvanized steel sheet according to the present invention are optimal steel sheets for structural parts of automobile bodies such as members and pillars, and as raw material steel sheets for other machine structural parts. Therefore, the present invention has high applicability in the automobile industry and the machine component manufacturing industry.
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Abstract
Description
Cは、残留オーステナイトを得るのに必要な元素である。さらに、本発明の鋼板では、旧オーステナイト粒界に偏析することにより、粒界を強化する元素である。Cが0.03%未満であると、残留オーステナイトと焼戻しマルテンサイトを含む金属組織を得るのが困難となるので、Cは0.03%以上とする。好ましくは0.10%以上、より好ましくは0.13%以上、さらに好ましくは0.16%以上である。
Siは、セメンタイトの析出を抑制し、かつ、残留オーステナイトの生成を促進する作用をなす元素であり、また、焼戻しマルテンサイトが過度に軟質化するのを抑制して、強度の確保に寄与する元素である。
Mnは、鋼の焼入れ性の向上に寄与し、残留オーステナイトと焼戻しマルテンサイトを含む金属組織を得るのに有効な元素である。Mnが1.00%未満であると、添加効果が十分に得られないので、Mnは1.00%以上とする。好ましくは1.50%超、より好ましくは2.00%超、さらに好ましくは2.50%超である。
Pは、旧オーステナイト粒界に偏析して鋼板を脆化させるので、少ないほど好ましい元素である。ただし、本発明は、旧オーステナイト粒界へのPの偏析を抑制し、CやBを偏析させる技術であり、Pが鋼中にある程度残留していることを前提としている。そのため、Pを過度に低減する必要はない。特に、Pを0.0005%未満に低減すると、製造コストが大幅に上昇するので、Pは0.0005%以上とすることができる。0.0010%以上としてもよい。
Sは、鋼中で硫化物系介在物を形成し、鋼板の局部延性を阻害するので、少ないほど好ましい元素である。Sが0.010%を超えると、鋼板の局部延性が著しく低下するので、Sは0.010%以下とする。好ましくは0.0050%以下、より好ましくは0.0012%以下である。
Alは、Siと同様に、溶鋼を脱酸する作用をなす元素であり、また、残留オーステナイトの生成を促進し、残留オーステナイトと焼戻しマルテンサイトを含む金属組織の形成に有効な元素である。
Nは、鋼の連続鋳造中に、スラブの割れの原因となる窒化物を形成するので、少ないほど好ましい元素である。Nが0.020%を超えると、スラブ割れが頻発するので、Nは0.020%以下とする。好ましくは0.010%以下、より好ましくは0.008%未満、さらに好ましくは0.005%以下である。
Bは、Cと同様に、旧オーステナイト粒界に偏析して、粒界を強化する元素である。本発明の鋼板の均一延性及び局部延性がともに良好で、プレス成形性に優れ、また、降伏強度及び引張強度が高く、かつ、局部延性が良好で、衝撃吸収性に優れ、さらに、低温衝撃特性にも優れる、溶融亜鉛めっき鋼板及び合金化溶融亜鉛めっき鋼板は、Bを添加しなくても得ることができるが、Bを添加することで、粒界を強化する効果がさらに上昇するので、必要に応じて添加することができる。また、Bは、鋼の焼入性を向上させ、残留オーステナイトと焼戻しマルテンサイトを含む金属組織の形成に有効な元素である。添加の効果を十分に得るためには、Bは0.0002%以上とするのが好ましい。より好ましくは0.0005%以上、さらに好ましくは0.0010%以上である。
Ti、Nb、及び、Vは、金属組織を微細化し、鋼板の強度と延性の向上に寄与する元素である。Ti、Nb、及び、Vの添加効果を十分に得るためには、Ti、Nb、及び、Vは、いずれも、0.001%以上が好ましい。より好ましくは、Ti及びNbは0.005%以上、Vは0.010%以上、さらに好ましくは、Ti及びNbは0.010%以上、Vは0.020%以上である。
Cr及びMoは、鋼の焼入性を向上させ、残留オーステナイトと焼戻しマルテンサイトを含む金属組織の形成に寄与する元素である。Cr及びMoの添加効果を十分に得るためには、Cr及びMoは、いずれも、0.001%以上が好ましい。より好ましくは、Crは0.100%以上であり、Moは0.050%以上である。
Cu及びNiは、降伏強度及び引張強度の向上に寄与する元素である。Cu及びNiの添加効果を十分に得るためには、Cu及びNiは、いずれも、0.001%以上が好ましい。より好ましくは、いずれの元素も0.010%以上である。
Ca、Mg、及び、REMは、介在物の形状を制御して、局部延性の向上に寄与する元素である。Ca、Mg、及び、REMの添加効果を十分に得るためには、Ca、Mg、及び、REMは、いずれも、0.0001%以上が好ましい。より好ましくは、いずれの元素も0.0005%以上である。
Biは、凝固組織を微細化して、局部延性の向上に寄与する元素である。Biの添加効果を十分に得るためには、Biは0.0001%以上が好ましい。より好ましくは0.0003%以上である。
本発明の鋼板の金属組織は、体積%で、残留オーステナイトを5.0%超、及び、焼戻しマルテンサイトを5.0%超含有する金属組織である。この金属組織を形成することにより、降伏強度と引張強度を維持しながら、均一延性と局部延性を向上させることができる。
本発明の鋼板において、残留オーステナイトを安定化して、均一延性と局部延性を向上させるために、残留オーステナイトのC量を0.85質量%以上とする。好ましくは0.87質量%以上、より好ましくは0.89質量%以上である。なお、残留オーステナイトのC量とは、オーステナイト相におけるC濃度を意味する。
旧オーステナイト粒界におけるC偏析量(原子数/nm2):[C]γgbと、旧オーステナイト粒界におけるP偏析量(原子数/nm2):[P]γgbの比:[C]γgb/[P]γgbを4.0以上とすることにより、低温衝撃特性が顕著に向上する。
本発明の鋼板がBを含有する場合は、さらに、旧オーステナイト粒界におけるB偏析量(原子数/nm2):[B]γgbと、旧オーステナイト粒界におけるP偏析量(原子数/nm2):[P]γgbの比:[B]γgb/[P]γgbを4.0以上とすることにより、低温衝撃特性が顕著に向上する。
TEl=TEl0×(1.2/t0)0.2 ・・・(1)
LEl=TEl-UEl ・・・(2)
本発明のめっき前の鋼板(以下「素材鋼板」という)は、本発明の鋼板の成分組成を有する鋼板であればよく、素材鋼板の製造方法は、特定の製造方法に限定されない。素材鋼板としては、熱延鋼板を用いることができる。また、熱延鋼板に、酸洗後、冷間圧延を施した冷延鋼板を用いることもできる。以下、素材鋼板の製造方法の一例を説明する。
スラブの鋳造法は、特定の鋳造法に限定されないが、連続鋳造法が好ましい。他の鋳造法で鋳造した鋼塊を分塊圧延等で鋼片としてもよい。連続鋳造工程では、介在物に起因する表面欠陥の発生を抑制するために、鋳型内にて、電磁攪拌等で溶鋼を流動させることが好ましい。連続鋳造後の高温状態の鋼塊又は分塊圧延後の高温状態の鋼片は、一旦冷却された後、再加熱し、熱間圧延に供してもよい。
熱間圧延の条件は、特定の条件に限定されないが、熱間圧延の完了温度が低すぎると、熱延鋼板の金属組織において、圧延方向に展伸した粗大な低温変態生成組織が生じるおそれがある。
冷間圧延の条件は、特定の条件に限定されない。冷間圧延の前に、熱延鋼板に、酸洗等により脱スケール処理を施してもよい。焼鈍の後の金属組織を均一化し、局部延性をさらに向上させるために、冷間圧延の圧下率は40%以上が好ましい。圧下率が高すぎると、圧延荷重が増大し、圧延が困難となるので、圧下率は70%未満が好ましく、60%未満がより好ましい。
素材鋼板を、Ac1点を超える温度に加熱して焼鈍する。Ac1点は、素材鋼板を加熱した際に、金属組織中にオーステナイトが生成し始める温度である。
素材鋼板に、常法に従って溶融亜鉛めっきを施し、素材鋼板の片面又は両面に、溶融亜鉛めっき層を形成する。素材鋼板に溶融亜鉛めっきを施す前に、素材鋼板を、適宜、冷却及び/又は加熱してもよい。
めっき処理又は合金化処理後の鋼板を、めっき温度から300℃までの温度域、又は、合金化処理温度から300℃までの温度域における平均冷却速度を2℃/秒以上として、300℃未満まで冷却する。
溶融亜鉛めっき層又は合金化めっき層を有する鋼板に2段加熱処理を施す前に、伸び率0.10%以上の調質圧延を施す。この調質圧延により、後の2段加熱処理において、オーステナイトへのCの濃化が促進されて、均一延性及び局部延性が向上するとともに、降伏強度が向上する。
溶融亜鉛めっき層又は合金化溶融亜鉛めっき層を有する鋼板に、伸び率0.10%以上の調質圧延を施した後、上記鋼板を、300℃まで、平均加熱速度10℃/秒未満で加熱し、続いて、300℃を超え600℃以下の温度域に、平均加熱速度10℃/秒以上で加熱し、300℃を超え600℃以下の温度域での加熱温度に1秒以上保持する。
調質圧延後の鋼板の金属組織において、Cをオーステナイトへ濃化させるとともに、マルテンサイトを焼戻すため、金属組織を、300℃を超え600℃以下の温度域に加熱する。このとき、300℃までは、10℃/秒未満の平均加熱速度で加熱する。この加熱で、旧オーステナイト粒界へのCやBの偏析を促進する。
300℃を超え600℃以下の温度域の加熱温度までの平均加熱速度を10℃/秒以上とすることで、旧オーステナイト粒界へのPの偏析を抑制することができる。
[B]γgb/[P]γgb≧4.0 ・・・(4)
上記2段加熱の後、鋼板を、300℃を超え600℃以下の温度域の加熱温度に1秒間以上保持する。加熱温度が300℃以下であると、オーステナイトへのCの濃化が不十分となり、均一延性が向上せず、また、硬質のマルテンサイトが残存して、局部延性が損なわれるとともに降伏強度が低下するので、加熱温度は300℃超とする。好ましくは350℃超、より好ましくは400℃超である。
真空溶解炉を用いて溶鋼を鋳造して、表1に示す成分組成を有する鋼A~Uを製造した。表1中のAc1点及びAc3点は、鋼A~Pの冷延鋼板を2℃/秒で加熱した際の熱膨張変化から求めた。鋼A~Uを1200℃に加熱し60分間保持した後、表2-1、2-2に示す熱延条件で熱間圧延を行った。
Claims (6)
- 鋼板の表面に溶融亜鉛めっき層を有する溶融亜鉛めっき鋼板であって、
上記鋼板の成分組成が、質量%で、
C :0.03~0.70%、
Si:0.25~2.50%、
Mn:1.00~5.00%、
P :0.0005~0.100%、
S :0.010%以下、
sol.Al:0.001~2.500%、
N :0.020%以下、
B :0~0.0200%、
Ti:0~0.30%、
Nb:0~0.30%、
V :0~0.30%、
Cr:0~2.00%、
Mo:0~2.00%、
Cu:0~2.00%、
Ni:0~2.00%、
Ca:0~0.010%、
Mg:0~0.010%、
REM:0~0.10%、及び
Bi:0~0.050%
を含有し、残部がFe及び不可避的不純物であり、
上記鋼板の金属組織が、体積%で、残留オーステナイト:5.0%超、及び焼戻しマルテンサイト:5.0%超を含有し、上記残留オーステナイトが、C:0.85質量%以上を含有し、
上記鋼板の金属組織中の旧オーステナイト粒界におけるC偏析量(原子数/nm2):[C]γgbと、P偏析量(原子数/nm2):[P]γgbの比:[C]γgb/[P]γgbが4.0以上である
ことを特徴とする溶融亜鉛めっき鋼板。 - 前記鋼板の成分組成が、質量%で、
B :0.0002~0.0200%、
Ti:0.001~0.30%、
Nb:0.001~0.30%、
V :0.001~0.30%、
Cr:0.001~2.00%、
Mo:0.001~2.00%、
Cu:0.001~2.00%、
Ni:0.001~2.00%、
Ca:0.0001~0.010%、
Mg:0.0001~0.010%、
REM:0.0001~0.10%、及び
Bi:0.0001~0.050%
の1種以上を含有することを特徴とする請求項1に記載の溶融亜鉛めっき鋼板。 - 前記鋼板の成分組成において、Bの含有量が0.0002%以上であり、
前記鋼板の金属組織中の旧オーステナイト粒界におけるB偏析量(原子数/nm2):[B]γgbと、P偏析量(原子数/nm2):[P]γgbの比:[B]γgb/[P]γgbが4.0以上である
ことを特徴とする請求項1又は2に記載の溶融亜鉛めっき鋼板。 - 請求項1~3のいずれか1項に記載の溶融亜鉛めっき鋼板において、溶融亜鉛めっき層が合金化溶融亜鉛めっき層であることを特徴とする合金化溶融亜鉛めっき鋼板。
- 請求項1~3のいずれか1項に記載の溶融亜鉛めっき鋼板を製造する製造方法であって、
請求項1又は2に記載の成分組成の素材鋼板を、Ac1点を超える温度域に加熱して焼鈍する焼鈍工程、
焼鈍工程の後、素材鋼板を、650~500℃の温度域における平均冷却速度を2℃/秒以上100℃/秒未満として、500℃以下まで冷却する第1冷却工程、
第1冷却工程の後、素材鋼板に溶融亜鉛めっきを施すめっき工程、
めっき工程の後、素材鋼板を、めっき温度~300℃の温度域における平均冷却速度を2℃/秒以上として、300℃未満まで冷却する第2冷却工程、
第2冷却工程の後、素材鋼板に、伸び率0.10%以上の調質圧延を施す調質圧延工程、及び、
調質圧延工程の後、素材鋼板に、300℃までの温度域における平均加熱速度を10℃/秒未満として、300℃まで加熱し、次いで、300℃を超える温度域における平均加熱速度を10℃/秒超として、300℃超600℃以下の温度域に加熱し、その加熱温度で1秒以上保持する熱処理を施す2段加熱処理工程
を備えることを特徴とする溶融亜鉛めっき鋼板の製造方法。 - 請求項4に記載の合金化溶融亜鉛めっき鋼板を製造する製造方法であって、
請求項1又は2に記載の成分組成の素材鋼板を、Ac1点を超える温度域に加熱して焼鈍する焼鈍工程、
焼鈍工程の後、素材鋼板を、650~500℃の温度域における平均冷却速度を2℃/秒以上100℃/秒未満として、500℃以下まで冷却する第1冷却工程、
第1冷却工程の後、素材鋼板に溶融亜鉛めっきを施すめっき工程、
めっき工程の後、素材鋼板に、合金化処理を施す合金化工程、
合金化工程の後、素材鋼板を、合金化処理温度~300℃の温度域における平均冷却速度を2℃/秒以上として、300℃未満まで冷却する第2冷却工程、
第2冷却工程の後、素材鋼板に、伸び率0.10%以上の調質圧延を施す調質圧延工程、及び、
調質圧延工程の後、素材鋼板に、300℃までの温度域における平均加熱速度を10℃/秒未満として、300℃まで加熱し、次いで、300℃を超える温度域における平均加熱速度を10℃/秒超として、300℃超600℃以下の温度域に加熱し、その加熱温度で1秒以上保持する熱処理を施す2段加熱処理工程
を備えることを特徴とする合金化溶融亜鉛めっき鋼板の製造方法。
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CN201880088680.3A CN111684096B (zh) | 2018-03-30 | 2018-03-30 | 热浸镀锌钢板以及合金化热浸镀锌钢板 |
PCT/JP2018/013915 WO2019187124A1 (ja) | 2018-03-30 | 2018-03-30 | 溶融亜鉛めっき鋼板及び合金化溶融亜鉛めっき鋼板 |
KR1020207027470A KR102477508B1 (ko) | 2018-03-30 | 2018-03-30 | 용융 아연 도금 강판 및 합금화 용융 아연 도금 강판 |
US17/043,267 US11225701B2 (en) | 2018-03-30 | 2018-03-30 | Hot dip galvanized steel sheet and hot dip galvannealed steel sheet |
MX2020010255A MX2020010255A (es) | 2018-03-30 | 2018-03-30 | Lamina de acero galvanizada por inmersion en caliente y lamina de acero galvanizada-recocida por inmersion en caliente. |
JP2018537559A JP6421903B1 (ja) | 2018-03-30 | 2018-03-30 | 溶融亜鉛めっき鋼板及び合金化溶融亜鉛めっき鋼板 |
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WO2023095870A1 (ja) * | 2021-11-26 | 2023-06-01 | 日本製鉄株式会社 | 亜鉛めっき鋼板 |
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CN112538593B (zh) * | 2020-11-09 | 2022-06-10 | 鞍钢蒂森克虏伯汽车钢有限公司 | 一种控制表面波纹度的热镀锌if钢板生产方法 |
CN115181884B (zh) * | 2021-04-02 | 2023-08-11 | 宝山钢铁股份有限公司 | 1280MPa级别低碳低合金热镀锌Q&P钢及快速热处理热镀锌制造方法 |
CN117881811A (zh) | 2021-08-30 | 2024-04-12 | 杰富意钢铁株式会社 | 高强度钢板、高强度镀覆钢板及它们的制造方法及部件 |
CN114990425B (zh) * | 2022-01-11 | 2023-07-18 | 长沙中金智能装备有限公司 | 一种废钢破碎用刀具及其制备、修复方法 |
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CN111684096B (zh) | 2021-12-03 |
JPWO2019187124A1 (ja) | 2020-04-30 |
KR20200122382A (ko) | 2020-10-27 |
KR102477508B1 (ko) | 2022-12-16 |
CN111684096A (zh) | 2020-09-18 |
US11225701B2 (en) | 2022-01-18 |
US20210017622A1 (en) | 2021-01-21 |
MX2020010255A (es) | 2020-10-22 |
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