WO2011090180A1 - 材質安定性と加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法 - Google Patents

材質安定性と加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法 Download PDF

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WO2011090180A1
WO2011090180A1 PCT/JP2011/051151 JP2011051151W WO2011090180A1 WO 2011090180 A1 WO2011090180 A1 WO 2011090180A1 JP 2011051151 W JP2011051151 W JP 2011051151W WO 2011090180 A1 WO2011090180 A1 WO 2011090180A1
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steel sheet
less
galvanized steel
dip galvanized
material stability
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PCT/JP2011/051151
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English (en)
French (fr)
Japanese (ja)
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由康 川崎
達也 中垣内
金子　真次郎
長滝　康伸
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Ｊｆｅスチール株式会社
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Priority to EP11734786.4A priority Critical patent/EP2527482B1/en
Publication of WO2011090180A1 publication Critical patent/WO2011090180A1/ja

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • 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
    • C21D8/0405—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 of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the present invention relates to a high-strength hot-dip galvanized steel sheet excellent in material stability and workability suitable as a member used in industrial fields such as automobiles and electricity, and a method for producing the same.
  • the shape freezing property is significantly reduced by increasing the strength and thinning of the steel sheet.
  • it is widely performed to predict the shape change after mold release in advance during press forming and to design the mold in consideration of the amount of shape change, but when the tensile strength (TS) of the steel sheet changes.
  • TS tensile strength
  • Patent Document 1 proposes a steel sheet having excellent ductility by specifying chemical components, volume ratios of retained austenite and martensite, and manufacturing methods thereof.
  • the steel plate excellent in ductility is proposed by prescribing
  • Patent Document 3 proposes a steel sheet having excellent ductility by defining chemical components and defining volume fractions of ferrite, bainitic ferrite and retained austenite.
  • Patent Document 4 proposes a method for manufacturing a high-strength cold-rolled steel sheet in which variation in elongation in the sheet width direction is improved.
  • Patent Documents 1 to 3 the main purpose is to improve the ductility of the high-strength thin steel sheet, and therefore the hole expandability is not considered.
  • Patent Document 4 describes only the variation of the total elongation EL in the plate width direction, and does not consider the variation of the material due to the component composition and manufacturing conditions. Therefore, the development of a high-strength hot-dip galvanized steel sheet having both high ductility and high hole expansibility and excellent material stability becomes an issue.
  • the inventors have made extensive studies to obtain a high-strength hot-dip galvanized steel sheet having a tensile strength TS of 540 MPa or more and excellent in material stability and workability (high ductility and high hole expansibility). However, I found the following.
  • the positive addition of Si made it possible to improve ductility by improving the work hardening ability of ferrite, ensure strength by strengthening the solid solution of ferrite, and improve hole expansibility by relaxing the hardness difference from the second phase. Also, the use of bainitic ferrite and pearlite can alleviate the difference in hardness between soft ferrite and hard martensite, and the hole expandability can be improved.
  • the present invention has been made based on the above findings, and the gist thereof is as follows.
  • Component composition is mass% C: 0.04% to 0.13%, Si: 0.7% to 2.3%, Mn: 0.8% to 2.0%, P : 0.1% or less, S: 0.01% or less, Al: 0.1% or less, N: 0.008% or less, the balance consists of Fe and inevitable impurities, the steel structure has an area ratio And having a ferrite phase of 75% or more, a bainitic ferrite phase of 1.0% or more, and a pearlite phase of 1.0% or more and 10.0% or less, and the area ratio of the martensite phase is 1 It is excellent in material stability and workability characterized by satisfying a ratio of 0.0% or more and less than 5.0% and satisfying martensite area ratio / (bainitic ferrite area ratio + pearlite area ratio) ⁇ 0.6 High strength hot dip galvanized steel sheet.
  • a component composition it contains at least one element selected from Ca: 0.001% to 0.005% and REM: 0.001% to 0.005% in mass%.
  • the high-strength hot-dip galvanized steel sheet excellent in material stability and workability according to any one of (1) to (3).
  • a component composition it contains at least one element selected from Ta: 0.001% to 0.010% and Sn: 0.002% to 0.2% by mass%.
  • the high-strength hot-dip galvanized steel sheet excellent in material stability and workability according to any one of (1) to (4).
  • a steel slab having the component composition described in any one of (1) to (6) is hot-rolled, pickled, or further cold-rolled, and then 5 ° C / ° C to a temperature range of 650 ° C or higher. heated at an average heating rate of s or more, held at a temperature range of 750 to 900 ° C. for 15 to 600 s, cooled to a temperature range of 450 to 550 ° C., and then held at a temperature range of 450 to 550 ° C. for 10 to 200 s. Then, a method for producing a high-strength hot-dip galvanized steel sheet excellent in material stability and workability, characterized by performing hot-dip galvanizing.
  • the “high-strength galvanized steel sheet” is a galvanized steel sheet having a tensile strength TS of 540 MPa or more.
  • the hot dip galvanized steel sheet in the present invention includes both a hot dip galvanized steel sheet that has not been subjected to an alloying treatment and an alloyed hot dip galvanized steel sheet that has been subjected to an alloying treatment.
  • a high-strength hot-dip galvanized steel sheet having a tensile strength TS of 540 MPa or more and having excellent ductility and high material stability due to high ductility and high hole expansibility is obtained.
  • Si was actively added for the purpose of strengthening the solid solution of ferrite and improving the work hardenability of ferrite, creating a composite structure of ferrite, bainitic ferrite, pearlite, and a small amount of martensite, and reducing the hardness difference between the different phases.
  • Si was actively added for the purpose of strengthening the solid solution of ferrite and improving the work hardenability of ferrite, creating a composite structure of ferrite, bainitic ferrite, pearlite, and a small amount of martensite, and reducing the hardness difference between the different phases.
  • the component composition is C: 0.04% to 0.13%, Si: 0.7% to 2.3%, Mn: 0.8% to 2.0% by mass%.
  • P 0.1% or less
  • S 0.01% or less
  • Al 0.1% or less
  • N 0.008% or less
  • the ratio is 1.0% or more and less than 5.0%
  • the martensite area ratio / (bainitic ferrite area ratio + pearlite area ratio) ⁇ 0.6 is satisfied.
  • C 0.04% or more and 0.13% or less
  • C is an austenite generating element and an element indispensable for strengthening steel. If the C content is less than 0.04%, it is difficult to ensure the desired strength. On the other hand, if the amount of C exceeds 0.13% and is added excessively, the welded part and the heat-affected zone are significantly hardened, and the mechanical properties of the welded part are deteriorated, so that spot weldability, arc weldability, etc. are reduced. . Therefore, C is made 0.04% or more and 0.13% or less.
  • Si 0.7% or more and 2.3% or less Si is a ferrite-forming element and also an element effective for solid solution strengthening. In order to ensure good ductility by improving the work hardening ability of the ferrite phase, it is necessary to add 0.7% or more. Further, in order to ensure the desired area ratio of the bainitic ferrite phase and ensure good hole expansibility, addition of 0.7% or more is necessary. However, excessive addition of Si causes deterioration of surface properties, plating adhesion, and adhesion due to generation of red scale and the like. Therefore, Si is made 0.7% to 2.3%. Preferably, it is 1.2% or more and 1.8% or less.
  • Mn 0.8% or more and 2.0% or less
  • Mn is an element effective for strengthening steel.
  • it is an element that stabilizes austenite, and is an element necessary for adjusting the fraction of the second phase. For this reason, it is necessary to add 0.8% or more of Mn.
  • Mn is made 0.8% or more and 2.0% or less. Preferably they are 1.0% or more and 1.8% or less.
  • P 0.1% or less
  • P is an element effective for strengthening steel.
  • P is set to 0.1% or less.
  • S 0.01% or less S is an inclusion such as MnS, which causes deterioration in impact resistance and cracks along the metal flow of the weld.
  • To S is set to 0.01% or less.
  • Al 0.1% or less When Al exceeds 0.1%, coarse Al 2 O 3 is generated and the material deteriorates. In addition, when Al is added for deoxidation of steel, if it is less than 0.01%, many coarse oxides such as Mn and Si are dispersed in the steel and the material deteriorates. Is preferably 0.01% or more. Therefore, the Al content is 0.1% or less, preferably 0.01 to 0.1%.
  • N 0.008% or less
  • N is an element that causes the most deterioration of the aging resistance of the steel, and it is preferably as small as possible. If it exceeds 0.008%, the deterioration of the aging resistance becomes significant. Therefore, N is set to 0.008% or less.
  • the balance is Fe and inevitable impurities.
  • at least one selected from the following elements can be added as necessary.
  • Cr 0.05% to 1.0%, V: 0.005% to 0.5%, Mo: 0.005% to 0.5%, Ni: 0.05% to 1.0%
  • at least one selected from Cu: 0.05% or more and 1.0% or less Cr, V, and Mo has an effect of improving the balance between strength and ductility, and can be added as necessary.
  • the effect is obtained when Cr: 0.05% or more, V: 0.005% or more, and Mo: 0.005% or more.
  • excessive addition over Cr: 1.0%, V: 0.5%, and Mo: 0.5%, respectively results in an excessive fraction of the second phase, causing a significant increase in strength.
  • the cost increases. Therefore, when these elements are added, the amounts are set to Cr: 1.0% or less, V: 0.5% or less, and Mo: 0.5% or less, respectively.
  • Ni and Cu are effective elements for strengthening steel and can be used for strengthening steel as long as they are within the range specified in the present invention. It also has the effect of promoting internal oxidation and improving plating adhesion. In order to obtain these effects, 0.05% or more is required. On the other hand, if both Ni and Cu are added in excess of 1.0%, the workability of the steel sheet is lowered. In addition, the cost increases. Therefore, when adding Ni and Cu, the addition amount is 0.05% or more and 1.0% or less, respectively.
  • B has the effect of suppressing the formation and growth of ferrite from the austenite grain boundaries, and can be added as necessary.
  • the effect is obtained at 0.0003% or more.
  • it exceeds 0.0050% the workability deteriorates.
  • the cost increases. Therefore, when adding B, it is made into 0.0003% or more and 0.0050% or less.
  • Ca 0.001% or more and 0.005% or less
  • REM at least one selected from 0.001% or more and 0.005% or less
  • Ta at least one selected from 0.001 to 0.010% and Sn: 0.002 to 0.2% Ta, like Ti and Nb, forms high alloy carbide and alloy carbonitride. Not only contributes to strengthening, but also partially dissolves in Nb carbide and Nb carbonitride to form a composite precipitate such as (Nb, Ta) (C, N), thereby coarsening the precipitate It is considered that there is an effect of stabilizing the contribution to strength by precipitation strengthening. Therefore, when Ta is added, the content is preferably 0.001% or more. However, if added excessively, not only the above-mentioned precipitate stabilization effect is saturated but also the alloy cost increases. Therefore, when Ta is added, its content is preferably 0.010% or less. .
  • Sn can be added from the viewpoint of suppressing decarburization in the region of several tens of ⁇ m of the steel sheet surface layer caused by nitriding, oxidation, or oxidation of the steel sheet surface. By suppressing such nitriding and oxidation, the amount of martensite generated on the steel sheet surface is prevented from decreasing, and fatigue characteristics and aging resistance are improved. From the viewpoint of suppressing nitriding and oxidation, when adding Sn, its content is preferably 0.002% or more, and if it exceeds 0.2%, the toughness is reduced, so its content is reduced to 0. .2% or less is desirable.
  • Sb 0.002 to 0.2%
  • Sb can also be added from the viewpoint of suppressing decarburization in the region of several tens of ⁇ m of the steel sheet surface layer caused by nitridation, oxidation, or oxidation of the steel sheet surface, similarly to Sn. By suppressing such nitriding and oxidation, the amount of martensite generated on the steel sheet surface is prevented from decreasing, and fatigue characteristics and aging resistance are improved. From the viewpoint of suppressing nitriding and oxidation, when Sb is added, its content is preferably 0.002% or more, and if it exceeds 0.2%, the toughness is reduced, so the content is reduced to 0. .2% or less is desirable.
  • Area ratio of ferrite phase 75% or more In order to ensure good ductility, the ferrite phase needs to have an area ratio of 75% or more.
  • Area ratio of bainitic ferrite phase 1.0% or more Area ratio of bainitic ferrite phase to ensure good hole expansibility, that is, to reduce the hardness difference between soft ferrite and hard martensite 1.0% or more is necessary.
  • Area ratio of pearlite phase 1.0% or more and 10.0% or less In order to ensure good hole expansibility, the area ratio of the pearlite phase is 1.0% or more. In order to secure a desired strength-ductility balance, the area ratio of the pearlite phase is set to 10.0% or less.
  • reduce the amount of martensite that causes the material variation in the phase structure of the second phase and increase the amount of bainitic ferrite and pearlite that are softer than martensite. That is, it is necessary to satisfy the martensite area ratio / (bainitic ferrite area ratio + pearlite area ratio) ⁇ 0.6.
  • carbides such as retained austenite, tempered martensite, and cementite may be generated.
  • the area of the above ferrite, bainitic ferrite, pearlite, and martensite If the rate is satisfied, the object of the present invention can be achieved.
  • the area ratio of ferrite, bainitic ferrite, pearlite, and martensite in the present invention is the area ratio of each phase in the observation area.
  • the high-strength hot-dip galvanized steel sheet of the present invention uses a steel sheet having the above component composition and the above steel structure as a base steel sheet, and a plated film obtained by hot-dip galvanizing, or a plated film that has been subjected to alloying treatment after hot-dip galvanizing. Have.
  • the high-strength hot-dip galvanized steel sheet according to the present invention is obtained by hot rolling, pickling, or further cold rolling a steel slab having a component composition suitable for the above-described component composition range, and thereafter up to a temperature range of 650 ° C. or higher.
  • Heat at an average heating rate of 5 ° C./s or more hold for 15 to 600 s in a temperature range of 750 to 900 ° C., cool to a temperature range of 450 to 550 ° C., and 10 to 10 in the temperature range of 450 to 550 ° C. It is manufactured by holding for 200 s and then applying hot dip galvanizing.
  • the steel having the above composition is melted by a known method, and then slab is formed through a block or continuous casting, and is hot-rolled into a hot-rolled sheet.
  • hot rolling it is preferable to heat the slab to 1100 to 1300 ° C., perform hot rolling at a final finishing temperature of 850 ° C. or higher, and wind it on a steel strip at 400 to 650 ° C.
  • the coiling temperature exceeds 650 ° C.
  • the carbides in the hot-rolled sheet are coarsened, and such coarsened carbides cannot be melted during soaking at the time of annealing, so that the required strength may not be obtained.
  • pickling treatment is performed by a known method. Or after pickling, it cold-rolls further.
  • cold rolling it is not necessary to specifically limit the conditions, but it is preferable to perform cold rolling at a cold reduction rate of 30% or more. If the cold rolling reduction is low, recrystallization of ferrite is not promoted, unrecrystallized ferrite remains, and ductility and hole expansibility may decrease.
  • the hot-rolled sheet pickled or cold-rolled steel sheet is subjected to the following annealing, cooled, and then hot-dip galvanized.
  • anneal to hold for 15 to 600 s in the austenite single-phase region or the two-phase region of austenite and ferrite. When the annealing temperature is less than 750 ° C. and the holding time is less than 15 s, the hard cementite in the steel sheet is not sufficiently dissolved, the hole expandability is lowered, and further, the desired martensite area ratio cannot be obtained. Ductility decreases.
  • the annealing temperature exceeds 900 ° C.
  • the growth of austenite grains is remarkable, it becomes difficult to secure bainitic ferrite due to bainite transformation that occurs during holding after cooling, hole expansibility decreases, and the martensite area Since the ratio / (bainitic ferrite area ratio + pearlite area ratio) exceeds 0.6, good material stability cannot be obtained.
  • the holding time exceeds 600 s, austenite becomes coarse, and it becomes difficult to secure a desired strength, and it may cause an increase in cost due to a large energy consumption.
  • the holding temperature exceeds 550 ° C. or the holding time is less than 10 s, the bainite transformation is not promoted, the area ratio of bainitic ferrite is less than 1.0%, and the desired hole expandability cannot be obtained.
  • the holding temperature is less than 450 ° C. or the holding time exceeds 200 s, most of the second phase becomes austenite and bainitic ferrite having a large amount of dissolved carbon produced by promoting bainite transformation.
  • a pearlite area ratio of 0% or more cannot be obtained, and an area ratio of the hard martensite phase is 5.0% or more, and good hole expansibility and material stability cannot be obtained.
  • the hot dip galvanized steel sheet in which the plated layer is not alloyed is cooled by infiltrating the steel sheet into a plating bath at a normal bath temperature and applying hot dip galvanizing. obtain.
  • alloying of the plating layer In the temperature range below 500 ° C., alloying of the plating layer is not promoted, and it is difficult to obtain an galvannealed steel sheet. In the temperature range exceeding 600 ° C., most of the second phase becomes pearlite, the desired martensite area ratio cannot be obtained, and the balance between strength and ductility is lowered.
  • the alloying of the plating layer can be performed without any problem within the range of the present invention that satisfies the above condition of exp [200 / (400-T)] ⁇ ln (t) in a temperature range of 500 to 600 ° C.
  • the holding temperature does not need to be constant as long as it is within the above-mentioned temperature range, and even if the cooling rate changes during cooling, it may be within the specified range.
  • the gist of the present invention is not impaired.
  • the steel sheet may be heat-treated by any equipment.
  • temper rolling of the steel sheet of the present invention for shape correction after heat treatment is also included in the scope of the present invention. In the present invention, it is assumed that the steel material is manufactured through normal steelmaking, casting, and hot rolling processes, but the manufacturing process is performed by omitting part or all of the hot rolling process by thin casting, for example. You may do it.
  • 1 and 2 show No. of Steel A which is an example of the present invention in Examples described later. 15, 16, and 17 (Tables 2 and 5) and No. of Steel H as a comparative example. 18, 19, 20 (Table 2, Table 5) shows a diagram to organize TS, the relationship EL and annealing temperature (T 1). 1 and 2, it can be seen that the steel A of the present invention has a small variation in TS and EL accompanying changes in the annealing temperature, whereas the steel H of the comparative example has a large variation in TS and EL.
  • 3 and 4 show the No. of steel A which is an example of the present invention in the examples described later.
  • 24, 25, 26 (Table 2, Table 5) shows a diagram to organize TS, the relationship EL and the average holding temperature of the cooling after annealing (T 2).
  • T 2 shows a diagram to organize TS, the relationship EL and the average holding temperature of the cooling after annealing
  • the hot-rolled steel sheet (after pickling) and the cold-rolled steel sheet obtained as described above are subjected to an annealing treatment under the production conditions shown in Tables 2 to 4 by a continuous hot-dip galvanizing line, and hot-dip galvanizing treatment is performed. Furthermore, the alloying process of the plating layer was performed and the hot dip galvanized steel plate was obtained. The amount of plating was 30 to 50 g / m 2 per side. A part of a hot-dip galvanized steel sheet that was not subjected to alloying treatment after hot-dip galvanizing treatment was also produced.
  • the area ratio of ferrite, bainitic ferrite, pearlite, and martensite phase with respect to the obtained hot dip galvanized steel sheet was corroded with 3% nital after polishing the plate thickness section parallel to the rolling direction of the steel sheet, and SEM Ten fields of view were observed using a (scanning electron microscope) at a magnification of 2000 times, and obtained using Image-Pro of Media Cybernetics.
  • the obtained hot-dip galvanized steel sheet was subjected to tempering treatment at 200 ° C. for 2 hours, and then the structure of the plate thickness section parallel to the rolling direction of the steel sheet was described above.
  • the area ratio of the tempered martensite phase obtained by the above method was defined as the area ratio of the martensite phase.
  • the volume ratio of the retained austenite phase was obtained by polishing the steel plate to a 1 ⁇ 4 surface in the plate thickness direction and diffracting X-ray intensity of the 1 ⁇ 4 surface thickness. CoK ⁇ rays are used as incident X-rays, and the peaks of ⁇ 111 ⁇ , ⁇ 200 ⁇ , ⁇ 220 ⁇ , ⁇ 311 ⁇ planes of retained austenite phase and ⁇ 110 ⁇ , ⁇ 200 ⁇ , ⁇ 211 ⁇ planes of ferrite phase are used. Intensity ratios were obtained for all combinations of integrated intensities, and the average value of these ratios was taken as the volume ratio of the retained austenite phase.
  • the tensile test is performed in accordance with JIS Z 2241 using a JIS No. 5 test piece obtained by taking a sample so that the tensile direction is perpendicular to the rolling direction of the steel sheet, and TS (tensile strength), EL (all Elongation) was measured.
  • TS tensile strength
  • EL all Elongation
  • Limit hole expansion ratio ⁇ (%) ⁇ (D f ⁇ D 0 ) / D 0 ⁇ ⁇ 100
  • D f hole diameter at crack initiation (mm) D 0 is the initial hole diameter (mm).
  • ⁇ ⁇ 70 (%) was determined to be good.
  • Each of the high-strength hot-dip galvanized steel sheets of the present invention has a TS of 540 MPa or more, an excellent hole expansibility when ⁇ is 70% or more, and a high balance of strength and ductility when TS ⁇ EL ⁇ 19000 MPa ⁇ %. It can be seen that this is a high-strength hot-dip galvanized steel sheet with excellent workability. Furthermore, it can be seen that the values of ⁇ TS and ⁇ EL are small, and the steel sheet is a high-strength hot-dip galvanized steel sheet excellent in material stability. On the other hand, in the comparative example, one or more of ductility and hole expansibility are inferior, or material stability is not preferable.
  • the high-strength hot-dip galvanized steel sheet of the present invention has a tensile strength TS of 540 MPa or more, has high ductility and high hole expansibility, and is excellent in material stability.

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PCT/JP2011/051151 2010-01-22 2011-01-18 材質安定性と加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法 WO2011090180A1 (ja)

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EP2402470A1 (en) * 2009-02-25 2012-01-04 JFE Steel Corporation High-strength hot-dip galvanized steel plate of excellent workability and manufacturing method therefor
JP2012177175A (ja) * 2011-02-28 2012-09-13 Jfe Steel Corp 伸びと伸びフランジ性に優れた低降伏比高強度冷延鋼板およびその製造方法
WO2012165661A1 (ja) * 2011-06-01 2012-12-06 Ｊｆｅスチール株式会社 材質安定性、加工性およびめっき外観に優れた高強度溶融亜鉛めっき鋼板の製造方法
WO2013179497A1 (ja) * 2012-06-01 2013-12-05 Ｊｆｅスチール株式会社 伸びと伸びフランジ性に優れた低降伏比高強度冷延鋼板およびその製造方法
EP2762583A4 (en) * 2011-09-30 2015-12-02 Nippon Steel & Sumitomo Metal Corp HIGHLY RESISTANT STEEL PLATE WITH EXCELLENT RESISTANCE TO DELAYED FRACTURE AND MANUFACTURING METHOD THEREFOR
EP2623629A4 (en) * 2010-09-30 2016-08-31 Jfe Steel Corp HIGH-STRENGTH HOT-GALVANIZED STEEL SHEET WHICH HAS EXCELLENT FATIGUE FEATURES AND METHOD FOR MANUFACTURING THE SAME
EP2886674A4 (en) * 2012-08-15 2016-11-30 Nippon Steel & Sumitomo Metal Corp STEEL PLATE FOR USE IN A HOT COMPRESSION, METHOD OF MANUFACTURING THEREOF AND USING THE STEEL PLATE HOT-PRESSED ELEMENT

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JP4883216B2 (ja) * 2010-01-22 2012-02-22 Ｊｆｅスチール株式会社 加工性とスポット溶接性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法
JP5267638B2 (ja) 2011-11-17 2013-08-21 Ｊｆｅスチール株式会社 高強度溶融亜鉛めっき鋼板または高強度合金化溶融亜鉛めっき鋼板用熱延鋼板およびその製造方法
TWI454582B (zh) * 2012-06-13 2014-10-01 Jfe Steel Corp 延伸及延伸凸緣性優異之低降伏比高強度冷延鋼板及其製造方法

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JP5786319B2 (ja) * 2010-01-22 2015-09-30 Ｊｆｅスチール株式会社 耐バリ性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法
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JP2009149938A (ja) * 2007-12-20 2009-07-09 Jfe Steel Corp 高強度溶融亜鉛めっき鋼板および高強度合金化溶融亜鉛めっき鋼板の製造方法
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EP2402470A1 (en) * 2009-02-25 2012-01-04 JFE Steel Corporation High-strength hot-dip galvanized steel plate of excellent workability and manufacturing method therefor
EP2402470A4 (en) * 2009-02-25 2017-04-26 JFE Steel Corporation High-strength hot-dip galvanized steel plate of excellent workability and manufacturing method therefor
EP2623629A4 (en) * 2010-09-30 2016-08-31 Jfe Steel Corp HIGH-STRENGTH HOT-GALVANIZED STEEL SHEET WHICH HAS EXCELLENT FATIGUE FEATURES AND METHOD FOR MANUFACTURING THE SAME
JP2012177175A (ja) * 2011-02-28 2012-09-13 Jfe Steel Corp 伸びと伸びフランジ性に優れた低降伏比高強度冷延鋼板およびその製造方法
WO2012165661A1 (ja) * 2011-06-01 2012-12-06 Ｊｆｅスチール株式会社 材質安定性、加工性およびめっき外観に優れた高強度溶融亜鉛めっき鋼板の製造方法
US9340859B2 (en) 2011-06-01 2016-05-17 Jfe Steel Corporation Method for manufacturing high strength galvanized steel sheet having excellent stability of mechanical properties, formability, and coating appearance
EP2762583A4 (en) * 2011-09-30 2015-12-02 Nippon Steel & Sumitomo Metal Corp HIGHLY RESISTANT STEEL PLATE WITH EXCELLENT RESISTANCE TO DELAYED FRACTURE AND MANUFACTURING METHOD THEREFOR
WO2013179497A1 (ja) * 2012-06-01 2013-12-05 Ｊｆｅスチール株式会社 伸びと伸びフランジ性に優れた低降伏比高強度冷延鋼板およびその製造方法
KR20150004430A (ko) * 2012-06-01 2015-01-12 제이에프이 스틸 가부시키가이샤 신장과 신장 플랜지성이 우수한 저항복비 고강도 냉연 강판 및 그 제조 방법
KR101674283B1 (ko) 2012-06-01 2016-11-08 제이에프이 스틸 가부시키가이샤 신장과 신장 플랜지성이 우수한 저항복비 고강도 냉연 강판 및 그 제조 방법
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US10570470B2 (en) 2012-08-15 2020-02-25 Nippon Steel Corporation Steel sheet for hot stamping, method of manufacturing the same, and hot stamped steel sheet member

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