WO2020080337A1 - 薄鋼板およびその製造方法 - Google Patents
薄鋼板およびその製造方法 Download PDFInfo
- Publication number
- WO2020080337A1 WO2020080337A1 PCT/JP2019/040397 JP2019040397W WO2020080337A1 WO 2020080337 A1 WO2020080337 A1 WO 2020080337A1 JP 2019040397 W JP2019040397 W JP 2019040397W WO 2020080337 A1 WO2020080337 A1 WO 2020080337A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- less
- retained austenite
- steel sheet
- seconds
- aspect ratio
- Prior art date
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/185—Hardening; Quenching with or without subsequent tempering from an intercritical temperature
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/22—Martempering
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
-
- 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
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0436—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
-
- 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
- C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Definitions
- the present invention relates to a thin steel plate and a manufacturing method thereof.
- the thin steel sheet of the present invention has a tensile strength (TS) of 590 MPa or more, and has excellent stretch formability and bendability. Therefore, the thin steel sheet of the present invention is suitable as a material for a frame member for automobiles.
- TS tensile strength
- ferrite has an average crystal grain size of 3 ⁇ m or less and a volume fraction of 5% or less
- retained austenite has a volume fraction of 10 to 20%
- martensite has an average crystal grain size of 4 ⁇ m or less and a volume fraction of 20% or less.
- the ferrite fraction is 5% or less or the ferrite fraction is 5% to 50% and the retained austenite amount is 10% or more, and the composite structure of retained austenite and martensite is used. It is said that a steel sheet excellent in elongation, hole expandability, and deep drawability can be obtained by refining MA, which is the above, and increasing retained austenite having a size of 1.5 ⁇ m or more.
- the present invention has a tensile strength of 590 MPa or more and a thin steel sheet having good formability. And a method for manufacturing the same.
- the plate thickness of the thin steel plate targeted by the present invention is 0.4 mm or more and 2.6 mm or less.
- the elongation is improved by the retained austenite, but the retained austenite is transformed into martensite by the TRIP effect on the surface of the bending process where a large strain is applied, and it is difficult to obtain excellent bendability by this martensite.
- the shape is changed to retained austenite having a high aspect ratio, and then the retained austenite is surrounded by BCC iron having a small disorder of the crystal structure. It has been found that this suppresses damage due to martensitic transformation on the bent surface and improves bendability.
- the carbon is promoted to be unevenly distributed from the heating to the subsequent cooling process, and then retained in a temperature range of 400 ° C. or higher and 520 ° C. Turned out to be important.
- the present invention has been completed based on the above findings, and its gist is as follows.
- the area ratio of BCC iron having an aspect ratio of 2.5% or more and less than 85% and having an aspect ratio of 2.5 or more and having an orientation difference of 1 ° or less is 5% or more and 70% or less, and the BCC iron having an orientation difference of 1 ° or less.
- Retained austenite surrounded by A steel sheet having a steel structure in which the average aspect ratio of retained austenite having a top 10% equivalent circle diameter is 2.5 or more.
- the composition of the components is, in mass%, Ti: 0.001% or more and 0.2% or less, Nb: 0.001% or more and 0.2% or less, V: 0.001% or more and 0.1% or more.
- the composition of the components is, in mass%, Mo: 0.001% or more and 1.0% or less, Sb: 0.001% or more and 0.050% or less, REM: 0.0002% or more and 0.050. % Or less, Mg: 0.0002% or more and 0.050% or less, Ca: 0.0002% or more and 0.050% or less, and any one or more of them are contained.
- the average cooling rate from 740 ° C to 600 ° C is 8 ° C / s or higher and 25 ° C / or lower, and is cooled to a temperature range of 400 ° C or higher and 520 ° C or lower for 10 seconds or longer. It is retained for 80 seconds or less, and is cooled to a cooling stop temperature of 150 ° C. or higher and 300 ° C.
- the average cooling rate is 8 ° C./s or higher in a temperature range of 400 ° C. to 300 ° C., and ⁇ 50 ° C. from the cooling stop temperature.
- a temperature range of 400 ° C. to 300 ° C. and ⁇ 50 ° C. from the cooling stop temperature.
- an annealing step of heating to a temperature of 300 ° C. or more and 500 ° C. or more and then dwelling in the temperature range of 480 seconds or more and 1400 seconds or less .
- the thin steel sheet of the present invention has high strength of tensile strength (TS): 590 MPa or more and excellent formability. If the thin steel sheet of the present invention is applied to automobile parts, the weight of automobile parts can be further reduced.
- TS tensile strength
- FIGS. 1A to 1C are schematic diagrams for explaining the definition of BCC iron surrounding a retained austenite having an aspect ratio of 2.5 or more in the present invention.
- composition of the thin steel sheet is% by mass, C: 0.08% or more and 0.24% or less, Si: 0.70% or more and 2.20% or less, Mn: 0.8% or more and 3.4% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.005% or more and 0.70% or less, N: 0.0060% or less.
- % representing the content of the components means “mass%”.
- C 0.08% or more and 0.24% or less C contributes to the strengthening of the steel sheet and also has the effect of increasing the stability of retained austenite and increasing the ductility.
- it is necessary to contain 0.08% or more of C. It is preferably 0.09% or more.
- the range of the C content is 0.24% or less. It is preferably 0.23% or less.
- Si 0.70% or more and 2.20 or less Si is an element effective for increasing the elongation of the steel sheet, suppressing the precipitation of cementite, and obtaining retained austenite.
- it is necessary to contain at least 0.70% Si. It is preferably 0.80% or more.
- the Si content was set to 2.20% or less. It is preferably 2.10% or less.
- Mn 0.8% or more and 3.4% or less
- Mn is an austenite stabilizing element, and it is necessary to contain Mn in an amount of 0.8% or more in order to obtain a desired ferrite area ratio and residual austenite area ratio. It is preferably 1.2% or more.
- Mn content was set to 3.4% or less. It is preferably 3.2% or less.
- P 0.05% or less
- P is a harmful element that causes low-temperature brittleness and reduces weldability, so it is preferable to reduce it as much as possible.
- the P content is acceptable up to 0.05%.
- the content is preferably 0.02% or less, but more preferably 0.01% or less for use under more severe welding conditions. On the other hand, in manufacturing, 0.002% may be unavoidably mixed.
- S 0.005% or less S forms coarse sulfides in steel, which extend during hot rolling to form wedge-shaped inclusions, which adversely affects weldability. Therefore, since S is also a harmful element, it is preferable to reduce S as much as possible.
- the S content is set to 0.005% or less. The amount is preferably 0.003% or less, but more preferably 0.001% or less for use under more severe welding conditions. In manufacturing, 0.0002% may be unavoidably mixed.
- Al 0.005% or more and 0.70% or less
- the Al content is 0.005% or more.
- it is 0.010% or more.
- the preferable range of Al is also determined by the relationship with Si.
- Al like Si, has the effect of suppressing the precipitation of cementite and increasing the stability of retained austenite.
- the total content of Si and Al is preferably 0.90% or more, and the total content of Si and Al is more preferably 1.10% or more from the viewpoint of suppressing variations in mechanical properties.
- Al is an element that deteriorates castability, and is made 0.70% or less from the viewpoint of manufacturability. It is preferably 0.30% or less.
- N 0.0060% or less
- N is a harmful element that deteriorates the normal temperature aging property and causes unexpected cracks, and thus has a bad influence on the stretch formability. Therefore, it is desirable to reduce the N content as much as possible. In the present invention, it is 0.0060% or less. It is preferably 0.0050% or less. Although it is desirable to reduce the N content as much as possible, 0.0005% may inevitably be mixed in during production.
- the above are the basic components of the present invention.
- the thin steel sheet of the present invention contains the above-mentioned basic components, and the balance other than the above-mentioned basic components has a component composition containing Fe (iron) and inevitable impurities.
- the thin steel sheet of the invention contains the above-mentioned basic components, and the balance has a composition of Fe and inevitable impurities.
- Ti 0.001% or more and 0.2% or less
- Nb 0.001% or more and 0.2% or less
- V 0.001% or more and 0.5% or less
- Cu 0.001 % Or more and 0.5% or less
- Ni 0.01% or more and 0.5% or less
- Cr 0.001% or more and 1.0% or less
- B 0.0002% or more and 0.0050% or less
- You may contain 2 or more types as an arbitrary component. These elements improve the bendability by suppressing the damage on the bending surface by refining the crystal grains, or are elements which are austenite stabilizing elements and are effective for the overhang formability through the TRIP effect. . On the other hand, if it is contained excessively, the formation of inclusions deteriorates the overhang formability or the hardenability becomes too high, and the desired steel sheet structure cannot be obtained.
- Mo 0.001% or more and 1.0% or less
- Sb 0.001% or more and 0.050% or less
- REM 0.0002% or more and 0.050% or less
- Mg 0.0002 % Or more and 0.050% or less
- Ca 0.0002% or more and 0.050% or less
- any one kind or two or more kinds may be contained as an optional component.
- These elements are elements used for strength adjustment, inclusion control, etc., but the effect of the present invention is not impaired even if these elements are contained in the above range.
- the steel structure of the thin steel sheet of the present invention has a ferrite area ratio of 5% or more and 60% or less, an area ratio of as-quenched martensite of 10% or less (including 0%), and retained austenite of 5% or more and 20% or less,
- the upper bainite, the lower bainite, and the tempered martensite are more than 15% and less than 85% in total, and the area ratio of BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more and having an orientation difference of 1 ° or less is 5% or more and 70% or more.
- the average aspect ratio of the retained austenite having the top 10% of equivalent circle diameters among the retained austenite surrounded by the BCC iron having an orientation difference of 1 ° or less is 2.5 or more.
- Ferrite area ratio is 5% or more and 60% or less Since the ferrite phase is soft, the desired steel plate strength cannot be obtained if the area ratio exceeds 60%. Therefore, the area ratio of the ferrite phase is 60% or less. It is preferably 50% or less. On the other hand, when the content of ferrite is less than 5%, the localization effect of C is lost, so that it becomes impossible to obtain BCC iron or retained austenite with a small disorder of the desired crystal structure. Therefore, the area ratio of the ferrite phase is set to 5% or more. It is preferably at least 12%.
- the ferrite phase of the present invention is polygonal ferrite and is intended for a structure that does not include a corrosion mark or a second phase structure in the grain.
- As-quenched martensite area ratio 10% or less (including 0%) Since as-quenched martensite is extremely hard, the grain boundary becomes a starting point of crack formation in the vicinity of the surface during bending, and the bendability is significantly reduced. To obtain the bendability required in the present invention, the area ratio of martensite as quenched needs to be 10% or less. It is preferably 8% or less. The as-quenched martensite has a smaller area ratio, and may be 0%.
- Retained austenite is 5% or more and 20% or less Retained austenite improves stretch formability. To obtain the characteristics required by the present invention, it is necessary to generate 5% or more of retained austenite. It is preferably at least 8%. On the other hand, the retained austenite deteriorates the delayed fracture property, so the content was made 20% or less. It is preferably 17% or less.
- the C concentration in the retained austenite is 0.6% by mass or more, the stability of the retained austenite due to processing is increased and El is increased, which is preferable.
- a more preferable C concentration in retained austenite is 0.7% by mass or more.
- the upper limit of the C concentration is not particularly limited, but is often 1.2% or less.
- the upper bainite, the lower bainite, and the tempered martensite are more than 15% and less than 85% in total.
- the regions other than the above-mentioned structures are mainly composed of the upper bainite, the lower bainite, and the tempered martensite, and have desired strength and formability. In order to obtain it, the total needs to be more than 15% and less than 85%, and is preferably more than 30% and less than 80%.
- Area ratio of BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more and having a misorientation of 1 ° or less is 5% or more and 70% or less Out of the retained austenite surrounded by BCC iron having an orientation difference of 1 ° or less, the circle equivalent diameter top 10 % Of retained austenite has an average aspect ratio of 2.5 or more.
- BCC iron having little crystal disorder has a high ductility, and thus improves the stretch formability.
- one of the features of the present invention is to surround the retained austenite having an aspect ratio of 2.5 or more with BCC iron having an orientation difference of 1 ° or less.
- “surrounding” means enclosing 70% or more of the outer circumference of the retained austenite having an aspect ratio of 2.5 or more, when confirmed by the method described in the examples.
- the aspect ratio of the retained austenite is less than 2.5, the strain concentration at the interface between the BCC iron and the retained austenite during punching may cause voids and adverse effects due to the martensitic transformation of the retained austenite, resulting in bendability. Is reduced. Therefore, it is necessary to pay attention to the retained austenite having an aspect ratio of 2.5% or more.
- the BCC iron surrounding the retained austenite must have a small crystal structure disorder.
- the disorder is large, the ductility of the BCC iron itself is poor and the TRIP phenomenon progresses with a small strain during the stretch forming, so that the strain is not dispersed and the desired stretch formability cannot be obtained.
- the azimuth difference is within 1 °, the above adverse effect does not become apparent. Therefore, it is necessary to pay attention to the azimuth difference within 1 °.
- the "direction difference" can be represented by a KAM value measured by the method described in the examples.
- the area ratio of BCC iron surrounding the retained austenite with an aspect ratio of 2.5 or more and having an orientation difference of 1 ° or less must be 5% or more. It is preferably 10% or more.
- the area ratio is 70% or less. It is preferably 60% or less.
- the area ratio of BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more and having an orientation difference of 1 ° or less is within the above range, the area ratio of the following (i) to (iii) becomes 80% or less.
- the effect of the present invention occurs.
- the total of the following structures (i) to (iii) is more preferably 65% or less.
- Area ratio (iii) Area ratio of BCC iron surrounding a retained austenite having an aspect ratio of less than 2.5 and having a misorientation of more than 1 °
- the rest structure is not particularly specified, but other structures can be used if the above steel structure is achieved. Even if mixed, the effect of the invention is not impaired.
- the method for producing a thin steel sheet according to the present invention is a method for producing a thin steel sheet having the above-described composition, and includes a hot rolling step, a cold rolling step, and an annealing step.
- a heat treatment step after the cold rolling step and before the annealing step.
- the hot rolling process is a process of hot rolling a steel material having the above composition.
- the melting method for manufacturing the above steel material is not particularly limited, and a known melting method such as a converter or an electric furnace can be adopted. Further, secondary refining may be performed in a vacuum degassing furnace. After that, it is preferable to form a slab (steel material) by a continuous casting method from the viewpoint of productivity and quality. Further, a slab may be formed by a known casting method such as an ingot-slump rolling method or a thin slab continuous casting method.
- the hot rolling conditions for hot rolling the above steel material are not particularly limited and may be set appropriately.
- the coiling temperature after hot rolling is preferably 580 ° C. or lower, and more preferably 530 ° C. or lower from the viewpoint of the shape of the coil for cold rolling.
- the cold rolling process is a process of performing pickling and cold rolling after the hot rolling process.
- cold rolling it is necessary to promote recrystallization during annealing, refine austenite, promote localization of C, and increase the number of transformation nucleation sites to promote BCC iron production with less crystal strain. Therefore, the cold rolling rate needs to be 46% or more. It is preferably 50% or more. Although there is no upper limit, it is substantially 75% or less due to the cold rolling load.
- the pickling condition is not particularly limited, and a known manufacturing method may be adopted.
- a heat treatment step of heating to 480 ° C. or higher and cooling to room temperature may be performed. This heating is performed at 480 ° C. or more and 680 ° C. or less for 3 hours or more in the case of a box-type annealing furnace, and to 760 ° C. or more and 820 ° C. or less in the case of a continuous annealing furnace.
- carbon is insufficiently localized unless the temperature is 480 ° C. or higher, and the value of box-type annealing becomes small.
- the temperature exceeds 680 ° C, austenite is generated, and the effect of unevenly distributing carbon becomes small, so the temperature was set to 480 ° C or higher and 680 ° C or lower.
- the heating time is shorter than in the box type annealing furnace. Therefore, although austenite is generated by heating at 760 ° C., an effect of unevenly distributing carbon can be obtained.
- the temperature exceeds 820 ° C, the amount of austenite generated increases and the C concentration existing in the austenite becomes low, as in the box-type annealing furnace. Therefore, the preferable temperature range in the case of continuous annealing is 760 ° C or higher and 820 ° C or lower. And After heating, water cooling is more preferable in order to freeze the unevenly distributed state of C.
- the annealing step means that after the cold rolling step or the heat treatment step, after heating to 780 ° C. to 845 ° C., the average cooling rate from 740 ° C. to 600 ° C. is 8 ° C./s to 25 ° C./400° C.
- the annealing process is preferably performed on a continuous annealing line.
- Heating to 780 ° C or higher and 845 ° C or lower It is necessary to generate a ferrite phase by recrystallization at the time of heating and to austenitize to an appropriate fraction.
- the heating temperature needs to be 780 ° C. or higher. It is preferably 790 ° C or higher.
- the heating temperature is set to 845 ° C or lower. It is preferably 840 ° C or lower.
- Cooling at an average cooling rate from 740 ° C. to 600 ° C. of 8 ° C./s or more and 25 ° C./s or less It is necessary to suppress the formation of polygonal ferrite in cooling after heating. If polygonal ferrite is generated during this period, the crystal structure will be greatly disturbed, and retained austenite with a large aspect ratio cannot be obtained, resulting in a decrease in bendability.
- the average cooling rate from 740 ° C. to 600 ° C. which is a polygonal ferrite generation region, is set to 8 ° C./s or more. It is preferably 10 ° C / s or more.
- the upper limit of the cooling rate is 25 ° C./s or less. It is preferably 22 ° C./s or less.
- the generation temperature range is 400 ° C. It is necessary to cool to a temperature range of 520 ° C or lower. If the temperature is lower than 400 ° C., martensitic transformation will proceed and the disorder of the crystal structure will become large, so that the desired steel structure cannot be obtained. Therefore, the cooling stop temperature is set to 400 ° C. or higher. If it exceeds 520 ° C, the aspect ratio of retained austenite becomes small due to the influence of polygonal ferrite formation. Therefore, the cooling stop temperature is set to 520 ° C. or lower. It is preferably 420 ° C. or higher and 510 ° C. or lower.
- Retention in the temperature range of 400 ° C. or more and 520 ° C. or less for 10 seconds or more and 80 seconds or less It is necessary to retain it in the temperature range of 400 ° C. or more and 520 ° C. or less for a certain period of time following the cooling step. Due to this retention, the production of BCC iron in which the disorder of the crystal structure surrounding the retained austenite having a large aspect ratio is small progresses effectively. If the retention temperature is lower than 400 ° C. or higher than 520 ° C., the desired steel structure cannot be obtained due to martensite and ferrite formation.
- the residence time in the temperature range is less than 10 seconds, the area ratio of BCC iron in which the disorder of the crystal structure surrounding the retained austenite with a large aspect ratio is small cannot be obtained, and the desired overhang formability cannot be obtained. Therefore, the residence time is set to 10 seconds or more. It is preferably 20 seconds or more. On the other hand, if it exceeds 80 seconds, BCC iron with excessively small disorder of the crystal structure is generated, and desired steel sheet strength cannot be obtained. Therefore, the residence time is set to 80 seconds or less. It is preferably 60 seconds or less. In this retention, it is sufficient to stay in the temperature range of 400 ° C. or more and 520 ° C. or less for a predetermined time, and there is no restriction on thermal history such as heating, cooling, isothermal holding.
- the average cooling rate in the temperature range from 400 ° C to 300 ° C is 8 ° C / s or more and is cooled to a cooling stop temperature of 150 ° C to 300 ° C.
- 400 ° C to 300 ° C Up to an average cooling rate of 8 ° C / s or more. If it is lower than 8 ° C./s, the BCC iron with a small disorder of the crystal structure becomes excessive. It is preferably 10 ° C / s or more. After cooling, the cooling is stopped at 150 ° C or higher and 300 ° C or lower.
- a preferable cooling stop temperature is 180 ° C. or higher. More preferably, it is 200 ° C. or higher.
- the cooling stop temperature exceeds 300 ° C., martensite increases as it is quenched and bendability deteriorates.
- the temperature is preferably 280 ° C or lower, more preferably 240 ° C or lower.
- lower bainite transformation progresses in the temperature range of ⁇ 50 ° C from the cooling stop temperature.
- the C concentration in the retained austenite increases, so that the overhang formability further increases.
- the residence temperature exceeds 500 ° C. or the residence time exceeds 1400 seconds, cementite precipitates in the austenite, and the desired amount of retained austenite cannot be obtained. Therefore, in the reheating step after cooling from 150 ° C. to 300 ° C., resident for 480 seconds or more and 1400 seconds or less in the range of 300 ° C. or more and 500 ° C. or less.
- a steel material having a thickness of 250 mm and having the composition shown in Table 1 was hot-rolled, pickled, and cold-rolled, and then annealed in a continuous annealing furnace under the conditions shown in Table 2 to obtain an elongation of 0.
- a 2% to 0.4% temper rolling was performed to manufacture a steel sheet for evaluation. A part of them was subjected to a heat treatment step in a box-type annealing furnace or a continuous annealing furnace before cold rolling or before the final annealing step. Then, the obtained thin steel sheet was evaluated by the following method.
- the depth position (hereinafter, simply referred to as a plate thickness 1 / 4t portion) was photographed for 10 fields of view.
- Ferrite is a structure in which corrosion marks and second phase structures are not observed in the grains.
- As-quenched martensite is a structure observed as a white contrast in a SEM photograph, but retained austenite and cementite also have the same morphology.
- the area ratio was obtained by exposing cementite by etching with Picral etching. Then, the sum of the area ratio of martensite, the area ratio of cementite, and the area ratio of retained austenite obtained from the above-mentioned quenching was obtained from a SEM photograph, and the area ratio of cementite and the area ratio of retained austenite described below were subtracted therefrom to obtain as-quenched martens The site area ratio was calculated.
- the upper bainite is a structure in which corrosion marks and a second phase structure are recognized in the grains
- the tempered martensite and the lower bainite are structures in which a lath structure and a fine second phase structure are observed in the grains. The total of the structures of the upper bainite, the lower bainite, and the tempered martensite was obtained as the total of the above area ratios.
- EBSD electron beam backscattering diffraction method
- a region of 1 ⁇ 10 3 ⁇ m 2 or more of a plate thickness 1 ⁇ 4t part was analyzed using OIM Analysis 6 of TSL Solutions Co., Ltd. at a measurement step of 0.1 ⁇ m, and a crystal was obtained from this analysis result.
- Structural disorder was determined by the KAM (Kernel Average Misorientation) method, and BCC iron having a KAM value of 1 ° or less was determined.
- aspect ratio of the retained austenite the lengths of the target retained austenite that are the longest and the shortest were measured, and the (longest length) / (shortest length) was defined as the aspect ratio of each retained austenite.
- the area ratio of each tissue was defined as the area ratio of each tissue.
- the retained austenite having an aspect ratio of 2.5 or more is in contact with, without straddling a large angle grain boundary having an orientation difference of 15 ° or more, and not straddling a BCC iron having a KAM value of more than 1 °.
- BCC iron with a KAM value of 1 ° or less and BCC iron with a KAM value of 1 ° or less cover 70% or more of the entire circumference.
- Retained austenite with an aspect ratio of 2.5 or more residual austenite with an aspect ratio of 2.5 or more.
- BCC iron surrounding austenite According to the above definitions, BCC irons meeting the following (a) and (b) fall outside the above definition, and only BCC irons meeting the following (c) fall within the above definition.
- BCC iron having a boundary length with austenite of more than 30% of the entire circumferential length of retained austenite with an aspect ratio of 2.5 or more (b) BCC iron with a KAM value of 1 ° or more adjacent to retained austenite with an aspect ratio of 2.5 or more BCC iron (c) in which the crystal grains are present is retained austenite with an aspect ratio of 2.5 or more and is in contact with two BCC iron crystal grains across a large angle grain boundary with a misorientation of 15 ° or more.
- FIG. 1 shows a schematic diagram of the above (a) to (c).
- the area ratio of BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more there is at least one BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more that satisfies (c) above.
- BCC iron crystal grains surrounded by large-angle grain boundaries having an orientation difference of 15 ° or more were extracted, and this area was calculated as the area ratio of BCC iron surrounding the retained austenite having an aspect ratio of 2.5 or more.
- the top 10% of the equivalent circle diameter of austenite is obtained by measuring the equivalent circle diameter of the retained austenite existing in the region where the KAM value is 1 ° or less, and extracting the retained austenite of the top 10% of particle diameter from them. Then, the individual (long axis) / (short axis) of the extracted retained austenite was measured, and the average value was determined.
- the long axis and the short axis may measure the longest and shortest distances of retained austenite, respectively.
- the carbon concentration in the retained austenite was calculated from the lattice constants obtained from the peak angles of the (200) face, (220) face, and (311) face of austenite measured by the Cu-Ka line, and the formula (1).
- C concentration in retained austenite 3.5780 + 0.0330 [% C] +0.00095 [% Mn] +0.0056 [% Al] +0.0220 [% N] (1)
- the C concentration in the retained austenite obtained by this method was set to 0.6% or more as a suitable range.
- the BCC iron with a small crystal structure disorder is first deformed at the time of working, and then the retained austenite with a large aspect ratio inherent in the BCC iron with a large crystal structure disorder and the BCC iron with a small crystal structure disorder is deformed. Therefore, the stability of retained austenite against deformation is also excellent. Therefore, it is also suitable as an automobile member molded into a complicated shape.
- the overhang formability was determined by fixing a sample with a load of 100 tons using a die having a diameter of 150 mm, deforming the sample using a ball head punch with a radius of 75 mm, and measuring the forming height at the time of breakage. evaluated.
- the molding height required in the present invention is 70 mm or more when TS is 590 MPa or more and less than 780 MPa, 60 mm or more when TS is 780 MPa or more and less than 980 MPa, 50 mm when 980 MPa or more and less than 1180 MPa, and 43 mm or more when 1180 MPa or more, and particularly 1180 MPa.
- the preferred range of the steel plate having the above tensile strength was 45 mm.
- the tensile strength TS was 590 MPa or more, and it was found that good moldability was obtained. On the other hand, in Comparative Examples outside the scope of the present invention, the tensile strength did not reach 590 MPa, or the stretchability and bendability required in the present invention were not obtained.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
[1]質量%で、C:0.08%以上0.24%以下、Si:0.70%以上2.20%以下、Mn:0.8%以上3.4%以下、P:0.05%以下、S:0.005%以下、Al:0.005%以上0.70%以下、N:0.0060%以下を含み、残部がFeおよび不可避的不純物からなる成分組成と、フェライト面積率が5%以上60%以下、焼入ままマルテンサイトの面積率が10%以下(0%を含む)、残留オーステナイトが5%以上20%以下、上部ベイナイト、下部ベイナイト、焼戻しマルテンサイトが合計で15%超え85%未満であり、アスペクト比が2.5以上の残留オーステナイトを囲む方位差1°以内のBCC鉄の面積率が5%以上70%以下であり、方位差1°以内のBCC鉄に囲まれる残留オーステナイトのうち円相当径上位10%の残留オーステナイトの平均アスペクト比が2.5以上である鋼組織と、を有する薄鋼板。
[2]前記成分組成は、さらに、質量%で、Ti:0.001%以上、0.2%以下、Nb:0.001%以上0.2%以下、V:0.001%以上0.5%以下、Cu:0.001%以上0.5%以下、Ni:0.01%以上0.5%以下、Cr:0.001%以上1.0%以下、B:0.0002%以上0.0050%以下のいずれか1種または2種以上を含有する[1]に記載の薄鋼板。
[3]前記成分組成は、さらに、質量%で、Mo:0.001%以上1.0%以下、Sb:0.001%以上0.050%以下、REM:0.0002%以上0.050%以下、Mg:0.0002%以上0.050%以下、Ca:0.0002%以上0.050%以下のいずれか1種または2種以上を含有する[1]または[2]に記載の薄鋼板。
[4][1]~[3]のいずれかに記載の成分組成を有し、熱延鋼板に圧下率46%以上の冷間圧延を施す冷延工程と、前記冷延工程後、780℃以上845℃以下まで加熱した後、740℃から600℃までの平均冷却速度が8℃/s以上25℃/以下で400℃以上520℃以下の温度域まで冷却し、該温度域で10秒以上80秒以下滞留させ、400℃から300℃までの温度区間では平均冷却速度が8℃/s以上となるよう150℃以上300℃以下の冷却停止温度まで冷却し、該冷却停止温度から±50℃の温度域に2秒以上25秒以下滞留したのち、300℃以上500℃以上の温度まで加熱した後、該温度範囲で480秒以上1400秒以下滞留させる焼鈍工程と、を有する薄鋼板の製造方法。
Cは、鋼板の高強度化に寄与するうえ、残留オーステナイトの安定性を高め延性を上昇させる効果がある。本発明で所望とする特性を得るには、0.08%以上のCを含有させる必要がある。好ましくは0.09%以上である。一方、C含有量が0.24%を上回ると、焼入性が高くなりすぎて本発明で所望とする結晶構造の乱れの小さいBCC鉄が得られなくなる。そのため、C含有量の範囲を0.24%以下とした。望ましくは0.23%以下である。
Siは鋼板の伸びを上昇させ、セメンタイト析出を抑制し、残留オーステナイトを得るために有効な元素である。所望の張り出し成形性や残留オーステナイト量を得るには、少なくともSiは0.70%以上を含有させる必要がある。好ましくは0.80%以上である。一方、Siが2.20%を上回ると、化成処理性が悪化し、自動車用部材として適さなくなるため、Si含有量を2.20%以下とした。好ましくは2.10%以下である。
Mnはオーステナイト安定化元素であり、所望のフェライト面積率および残留オーステナイト面積率を得るのに0.8%以上含有させる必要がある。好ましくは1.2%以上である。一方、Mnを過度に含有すると、焼入性が高くなりすぎ、結晶構造の乱れの小さいBCC鉄が得られなくなる。以上から、Mn含有量は3.4%以下とした。好ましくは3.2%以下である。
Pは、低温脆性を発生させたり溶接性を低下させたりする有害元素であるため、極力低減することが好ましい。本発明では、P含有量は0.05%まで許容できる。好ましくは0.02%以下であるが、より厳しい溶接条件下で使用するには、0.01%以下まで抑制することがより好ましい。一方、製造上、0.002%は不可避的に混入する場合がある。
Sは、鋼中で粗大な硫化物を形成し、これが熱間圧延時に伸展し楔状の介在物となることで、溶接性に悪影響をもたらす。そのため、Sも有害元素であるため極力低減することが好ましい。本発明では、0.005%まで許容できるため、S含有量を0.005%以下とした。好ましくは、0.003%以下であるが、より厳しい溶接条件下で使用するには、0.001%以下まで抑制することがより好ましい。製造上、0.0002%は不可避的に混入する場合がある。
Alを製鋼の段階で脱酸剤として添加する場合、Al含有量を0.005%以上とする。好ましくは、0.010%以上である。また、Alの好ましい範囲はSiとの関係でも決まる。AlはSiと同様セメンタイト析出を抑制し、残留オーステナイトの安定性を高める効果がある。SiとAlは合計で0.90%以上含有させることが好ましく、機械的性質ばらつき抑制の観点からSiとAlの合計で1.10%以上含有させることがより好ましい。一方、Alは鋳造性を低下させる元素であり、製造性の観点から0.70%以下とした。好ましくは、0.30%以下である。
Nは、常温時効性を悪化させ、予期せぬ割れを発生させるため、張り出し成形性に対して悪影響をもたらす有害元素である。そのため、N含有量は出来る限り低減することが望ましい。本発明では0.0060%以下とする。好ましくは0.0050%以下である。N含有量は極力低減する方が望ましいが、製造上、0.0005%は不可避的に混入する場合がある。
フェライト相は軟質であるため、面積率が60%を上回ると所望の鋼板強度が得られない。そこで、フェライト相の面積率は60%以下である。好ましくは50%以下である。一方、フェライトが5%を下回るとCの局在化効果が失われるため、所望の結晶構造の乱れが小さいBCC鉄や残留オーステナイトが得られなくなる。そこで、フェライト相の面積率は5%以上とする。好ましくは12%以上である。本発明のフェライト相はポリゴナルフェライトであり、粒内に腐食痕や第二相組織が含まれない組織を対象とする。
焼入ままマルテンサイトは非常に硬質であるため、曲げ加工時に表面近傍で粒界が亀裂の発生起点となり曲げ性を著しく低下させる。本発明で求める曲げ性を得るには焼入ままマルテンサイトの面積率は10%以下とする必要がある。好ましくは8%以下である。焼入ままマルテンサイトの面積率は少ないほど好ましく0%であっても良い。
残留オーステナイトは張り出し成形性を改善する。本発明で求める特性を得るには、5%以上の残留オーステナイトを生成させる必要がある。好ましくは8%以上である。一方、残留オーステナイトは遅れ破壊特性を悪化させるため、20%以下とした。好ましくは17%以下である。
上記した組織以外の領域は、主に上部ベイナイト、下部ベイナイト、焼戻しマルテンサイトから構成されており、所望の強度と成形性を得るには、その合計が15%超え85%未満である必要があり、30%超え80%未満とすることが望ましい。
方位差1°以内のBCC鉄に囲まれる残留オーステナイトのうち円相当径上位10%の残留オーステナイトの平均アスペクト比が2.5以上
結晶の乱れの少ないBCC鉄は延性に富むため、張り出し成形性を向上させる。そのうえで、アスペクト比が2.5以上の残留オーステナイトを方位差1°以内のBCC鉄で囲むことが本発明の特徴のひとつである。ここで、「囲む」とは、実施例に記載の方法で確認したときに、アスペクト比が2.5以上の残留オーステナイトの外周の70%以上を囲うことを指す。
(i)アスペクト比が2.5未満の残留オーステナイトを囲む方位差1°以内のBCC鉄の面積率
(ii)アスペクト比が2.5以上の残留オーステナイトを囲む方位差1°超のBCC鉄の面積率
(iii)アスペクト比が2.5未満の残留オーステナイトを囲む方位差1°超のBCC鉄の面積率
残部組織は特に規定しないが上記した鋼組織が達成されていれば、その他の組織が混在しても発明の効果は損なわれない。
加熱時に再結晶によりフェライト相を生成させるとともに、適切な分率にオーステナイト化する必要がある。所望のフェライト面積率とするため、加熱温度は780℃以上である必要がある。好ましくは790℃以上である。一方、加熱温度が845℃を上回るとC局在化効果が失われ、特にアスペクト比の大きい残留オーステナイトが得られなくなる。そこで、加熱温度は845℃以下とした。好ましくは840℃以下である。
加熱後の冷却ではポリゴナルフェライトの生成を抑制する必要がある。この間にポリゴナルフェライトが生成すると結晶構造の乱れが大きなものになるとともに、アスペクト比の大きい残留オーステナイトが得られなくなり、曲げ性が低下する。この観点から、ポリゴナルフェライト生成域である740℃から600℃までの平均冷却速度を8℃/s以上とした。好ましくは10℃/s以上である。一方、冷却速度が大きい場合には、Cの局在化が効果的に行われなくなる。このため、冷却速度の上限は25℃/s以下とする。好ましくは22℃/s以下である。
ポリゴナルフェライト生成を抑制し、アスペクト比の大きい残留オーステナイトを取り囲む結晶構造の乱れが小さいBCC鉄を生成させるためには、その生成温度域である400℃以上520℃以下の温度域まで冷却する必要がある。400℃を下回るとマルテンサイト変態が進行してしまい、結晶構造の乱れが大きくなり所望の鋼組織が得られない。そこで冷却停止温度は400℃以上とする。520℃超の場合はポリゴナルフェライト生成の影響で残留オーステナイトのアスペクト比が小さくなる。そこで、冷却停止温度は520℃以下とする。好ましくは、420℃以上510℃以下である。
上記冷却工程に引き続いて400℃以上520℃以下の温度域に一定時間滞留させる必要がある。この滞留により、アスペクト比の大きい残留オーステナイトを取り囲む結晶構造の乱れが小さいBCC鉄の生成が効果的に進行する。滞留温度が400℃を下回る、あるいは520℃を上回ると、マルテンサイトやフェライト生成により所望の鋼組織が得られなくなる。また、該温度範囲での滞留時間が10秒を下回ると、アスペクト比の大きい残留オーステナイトを取り囲む結晶構造の乱れが小さいBCC鉄の面積率が得られず、所望の張り出し成形性が得られなくなる。そこで、上記滞留時間は10秒以上とする。好ましくは20秒以上である。一方、80秒を上回ると、過剰に結晶構造の乱れが小さいBCC鉄が生成し、所望の鋼板強度が得られなくなる。そこで、上記滞留時間は80秒以下とする。好ましくは60秒以下である。この滞留においては400℃以上520℃以下の温度域に所定の時間で留まれば良く、加熱、冷却、等温保持など熱履歴に制約されることはない。
400℃以上で変化する鋼組織を凍結するため、400℃から300℃まで平均冷却速度8℃/s以上で冷却する必要がある。8℃/sを下回ると結晶構造の乱れが小さいBCC鉄が過剰となる。好ましくは10℃/s以上である。冷却後は150℃以上300℃以下で冷却を停止する。冷却停止温度が150℃を下回ると鋼板中に存在するオーステナイトがマルテンサイト変態することで、所望の残留オーステナイト量が得られなくなる。好ましい冷却停止温度は180℃以上である。より好ましくは200℃以上である。一方、冷却停止温度が300℃を上回ると焼入れままマルテンサイトが増加し、曲げ性が悪化する。好ましくは280℃以下、より好ましくは240℃以下である。
また、冷却停止温度から±50℃の温度域においては下部ベイナイト変態が進行する。この下部ベイナイト変態進行によって残留オーステナイト中のC濃度が上昇するため、張り出し成形性がさらに上昇する。この効果を得るには、150℃以上300℃以下の冷却停止温度まで冷却した時点から再加熱までの区間、すなわち、冷却停止温度から±50℃の温度域で2秒以上25秒以下滞留させる必要がある。2秒未満では下部ベイナイト変態進行が不十分で所望の効果が得られない。一方、25秒を超えると、その効果は飽和するばかりか、次工程の300℃以上500℃以上での再加熱効果にばらつきが生じ、材質、特に強度変動が大きくなる。好ましくは3秒以上20秒以下である。
残留オーステナイト中にCを濃化させ、室温まで冷却した際に残留オーステナイトとして残存させるとともに、低温で生成した組織の結晶構造の乱れを軽減することが目的である。滞留温度が300℃を下回る、あるいは滞留時間が480秒を下回ると、残留オーステナイト中が濃化されず、熱的に不安定なオーステナイトは室温まで冷却した際にマルテンサイト変態する。このため、所望の残留オーステナイト量が得られないばかりか、結晶構造の乱れの少ないBCC鉄が減少する。一方、滞留温度が500℃を上回る、あるいは滞留時間が1400秒を上回ると、オーステナイト中にセメンタイトが析出するため、所望の残留オーステナイト量が得られない。そこで、150℃から300℃まで冷却した後の再加熱工程は、300℃以上500℃以下の範囲で480秒以上1400秒以下滞留させる。
鋼板から、圧延方向に平行な断面が観察面となるよう切り出し、板厚中心部を1%ナイタールで腐食現出し、走査電子顕微鏡で2000倍に拡大して鋼板表面から板厚の1/4の深さ位置(以下、単に板厚1/4t部という。)を10視野分撮影した。フェライトは粒内に腐食痕や第二相組織が観察されない組織である。焼入れままマルテンサイトはSEM写真で白いコントラストとして観察される組織であるが、残留オーステナイトやセメンタイトも同様の形態を呈する。そこで、ピクラールエッチングでエッチングすることでセメンタイトを現出させ、その面積率を求めた。そして、上記焼入れままマルテンサイトの面積率、セメンタイトの面積率および残留オーステナイトの面積率の合計をSEM写真から求め、そこからセメンタイトの面積率と後述する残留オーステナイトの面積率を差し引くことで焼入れままマルテンサイトの面積率を求めた。上部ベイナイトは粒内に腐食痕や第二相組織が認められる組織であり、焼き戻しマルテンサイトおよび下部ベイナイトは粒内にラス構造や微細第二相組織が観察される組織である。上部ベイナイト、下部ベイナイトおよび焼き戻しマルテンサイトの組織の合計は上記全ての面積率合計として求めた。
(a)アスペクト比2.5以上の残留オーステナイトが方位差15°以上の大角粒界を跨いで2つのBCC鉄の結晶粒に接し、2つの領域のBCC鉄とアスペクト比2.5以上の残留オーステナイトとの境界の長さがともにアスペクト比2.5以上の残留オーステナイト周全長の30%を超えるBCC鉄
(b)アスペクト比2.5以上の残留オーステナイトと隣接するKAM値1°以上のBCC鉄の結晶粒が内存するBCC鉄
(c)アスペクト比2.5以上の残留オーステナイトが方位差15°以上の大角粒界を跨いで2つのBCC鉄の結晶粒に接しているが、2つの領域のBCC鉄とアスペクト比2.5以上の残留オーステナイトとの境界の長さのどちらかがアスペクト比2.5以上の残留オーステナイト周全長の30%を超えないBCC鉄
図1に、上記(a)~(c)の模式図を示す。なお、アスペクト比が2.5以上の残留オーステナイトを取り囲むBCC鉄の面積率の算出に当たっては、上記(c)を満たすアスペクト比が2.5以上の残留オーステナイトを取り囲むBCC鉄が一つでも存在し、かつ方位差15°以上の大角粒界に囲まれたBCC鉄の結晶粒を抽出し、この領域をアスペクト比が2.5以上の残留オーステナイトを取り囲むBCC鉄の面積率として算出した。
鋼板を板厚1/4位置まで研磨後、化学研磨により更に0.1mm研磨した面について、X線回折装置でMoのKα線を用い、FCC鉄(オーステナイト)の(200)面、(220)面、(311)面と、BCC鉄(フェライト)の(200)面、(211)面、(220)面の積分反射強度を測定し、BCC鉄(フェライト)各面からの積分反射強度に対するFCC鉄(オーステナイト)各面からの積分反射強度の強度比から求めたオーステナイトの割合を残留オーステナイト分率(面積率)とみなした。
残留オーステナイト中のC濃度=3.5780+0.0330[%C]+0.00095[%Mn]+0.0056[%Al]+0.0220[%N] (1)
ここで[%M](M=C,Mn,Al,N)は各合金元素の含有濃度である。
本手法により求めた残留オーステナイト中のC濃度が0.6%以上を好適範囲とした。
得られた鋼板から圧延方向に対して垂直方向にJIS5号引張試験片を作製し、JIS Z 2241(2011)の規定に準拠した引張試験を5回行い、平均の、引張強さ(TS)、全伸び(El)を求めた。引張試験のクロスヘッドスピードは10mm/minとした。表3において、引張強さ:590MPa以上、かつTSとElとの積が17500MPa・%以上を、本発明鋼で求める鋼板の機械的性質とした。
張り出し成形性は、直径150mmのダイスで100tonの荷重でサンプルを固定し、半径75mmの球頭ポンチを用いてサンプルを変形させ、破断が生じたときの成形高さを評価した。本発明で求める成形高さはTSが590MPa以上780MPa未満であれば70mm以上、780MPa以上980MPa未満であれば60mm以上、980MPa以上1180MPa未満であれば50mm、1180MPa以上であれば43mm以上とし、特に1180MPa以上の引張強さを持つ鋼板の好適範囲を45mmとした。
曲げ性を調査するため、幅100mm、長さ35mmの短冊状サンプルを切り出し、JIS Z 2248に準拠した頂角90°のVブロック法にて曲げ試験を実施し、割れが発生しない最小のダイス径(R)を求め、板厚(t)で除することで限界曲げ半径(R/t)を求め、この好適範囲を2.0以下とした。
Claims (4)
- 質量%で、
C:0.08%以上0.24%以下、
Si:0.70%以上2.20%以下、
Mn:0.8%以上3.4%以下、
P:0.05%以下、
S:0.005%以下、
Al:0.005%以上0.70%以下、
N:0.0060%以下を含み、残部がFeおよび不可避的不純物からなる成分組成と、
フェライト面積率が5%以上60%以下、焼入ままマルテンサイトの面積率が10%以下(0%を含む)、残留オーステナイトが5%以上20%以下、上部ベイナイト、下部ベイナイト、焼戻しマルテンサイトが合計で15%超え85%未満であり、アスペクト比が2.5以上の残留オーステナイトを囲む方位差1°以内のBCC鉄の面積率が5%以上70%以下であり、方位差1°以内のBCC鉄に囲まれる残留オーステナイトのうち円相当径上位10%の残留オーステナイトの平均アスペクト比が2.5以上である鋼組織と、を有する薄鋼板。 - 前記成分組成は、さらに、質量%で、
Ti:0.001%以上、0.2%以下、
Nb:0.001%以上0.2%以下、
V:0.001%以上0.5%以下、
Cu:0.001%以上0.5%以下、
Ni:0.01%以上0.5%以下、
Cr:0.001%以上1.0%以下、
B:0.0002%以上0.0050%以下のいずれか1種または2種以上を含有する請求項1に記載の薄鋼板。 - 前記成分組成は、さらに、質量%で、
Mo:0.001%以上1.0%以下、
Sb:0.001%以上0.050%以下、
REM:0.0002%以上0.050%以下、
Mg:0.0002%以上0.050%以下、
Ca:0.0002%以上0.050%以下のいずれか1種または2種以上を含有する請求項1または2に記載の薄鋼板。 - 請求項1~3のいずれかに記載の成分組成を有し、熱延鋼板に圧下率46%以上の冷間圧延を施す冷延工程と、
前記冷延工程後、780℃以上845℃以下まで加熱した後、740℃から600℃までの平均冷却速度が8℃/s以上25℃/以下で400℃以上520℃以下の温度域まで冷却し、該温度域で10秒以上80秒以下滞留させ、400℃から300℃までの温度区間では平均冷却速度が8℃/s以上となるよう150℃以上300℃以下の冷却停止温度まで冷却し、該冷却停止温度から±50℃の温度域で2秒以上25秒以下滞留したのち、300℃以上500℃以下の温度まで加熱した後、該温度範囲で480秒以上1400秒以下滞留させる焼鈍工程と、を有する薄鋼板の製造方法。
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US17/284,534 US20210381076A1 (en) | 2018-10-17 | 2019-10-15 | Thin steel sheet and method for manufacturing same |
EP19874610.9A EP3868910A4 (en) | 2018-10-17 | 2019-10-15 | THIN STEEL SHEET AND METHOD OF MANUFACTURING ITEM |
JP2020505289A JP6822604B2 (ja) | 2018-10-17 | 2019-10-15 | 薄鋼板およびその製造方法 |
MX2021004445A MX2021004445A (es) | 2018-10-17 | 2019-10-15 | Chapa de acero delgada y metodo para fabricar la misma. |
CN201980067611.9A CN112840056B (zh) | 2018-10-17 | 2019-10-15 | 薄钢板及其制造方法 |
KR1020217011093A KR102517183B1 (ko) | 2018-10-17 | 2019-10-15 | 박강판 및 그의 제조 방법 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2018-195601 | 2018-10-17 | ||
JP2018195601 | 2018-10-17 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2020080337A1 true WO2020080337A1 (ja) | 2020-04-23 |
Family
ID=70283489
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2019/040397 WO2020080337A1 (ja) | 2018-10-17 | 2019-10-15 | 薄鋼板およびその製造方法 |
Country Status (7)
Country | Link |
---|---|
US (1) | US20210381076A1 (ja) |
EP (1) | EP3868910A4 (ja) |
JP (1) | JP6822604B2 (ja) |
KR (1) | KR102517183B1 (ja) |
CN (1) | CN112840056B (ja) |
MX (1) | MX2021004445A (ja) |
WO (1) | WO2020080337A1 (ja) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP4012055A4 (en) * | 2019-08-06 | 2022-08-31 | JFE Steel Corporation | THIN HIGH STRENGTH STEEL SHEET AND METHOD OF MAKING IT |
WO2023053909A1 (ja) * | 2021-09-30 | 2023-04-06 | Jfeスチール株式会社 | 鋼板、部材およびそれらの製造方法 |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2013181184A (ja) * | 2012-02-29 | 2013-09-12 | Kobe Steel Ltd | 温間成形性に優れた高強度鋼板およびその製造方法 |
WO2015115059A1 (ja) | 2014-01-29 | 2015-08-06 | Jfeスチール株式会社 | 高強度冷延鋼板およびその製造方法 |
WO2015151427A1 (ja) * | 2014-03-31 | 2015-10-08 | Jfeスチール株式会社 | 高降伏比高強度冷延鋼板およびその製造方法 |
WO2015151419A1 (ja) * | 2014-03-31 | 2015-10-08 | Jfeスチール株式会社 | 高降伏比高強度冷延鋼板及びその製造方法 |
JP2017186647A (ja) * | 2016-03-31 | 2017-10-12 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
JP2017214648A (ja) | 2016-05-30 | 2017-12-07 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
JP2017214647A (ja) | 2016-05-30 | 2017-12-07 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
WO2018055425A1 (en) * | 2016-09-22 | 2018-03-29 | Arcelormittal | High strength and high formability steel sheet and manufacturing method |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4998756B2 (ja) * | 2009-02-25 | 2012-08-15 | Jfeスチール株式会社 | 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 |
JP5412182B2 (ja) * | 2009-05-29 | 2014-02-12 | 株式会社神戸製鋼所 | 耐水素脆化特性に優れた高強度鋼板 |
JP6136547B2 (ja) * | 2013-05-07 | 2017-05-31 | 新日鐵住金株式会社 | 高降伏比高強度熱延鋼板およびその製造方法 |
JP6295893B2 (ja) * | 2014-08-29 | 2018-03-20 | 新日鐵住金株式会社 | 耐水素脆化特性に優れた超高強度冷延鋼板およびその製造方法 |
JP6749818B2 (ja) * | 2016-02-29 | 2020-09-02 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
WO2018189950A1 (ja) * | 2017-04-14 | 2018-10-18 | Jfeスチール株式会社 | 鋼板およびその製造方法 |
-
2019
- 2019-10-15 CN CN201980067611.9A patent/CN112840056B/zh active Active
- 2019-10-15 KR KR1020217011093A patent/KR102517183B1/ko active IP Right Grant
- 2019-10-15 EP EP19874610.9A patent/EP3868910A4/en active Pending
- 2019-10-15 WO PCT/JP2019/040397 patent/WO2020080337A1/ja active Application Filing
- 2019-10-15 US US17/284,534 patent/US20210381076A1/en active Pending
- 2019-10-15 MX MX2021004445A patent/MX2021004445A/es unknown
- 2019-10-15 JP JP2020505289A patent/JP6822604B2/ja active Active
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2013181184A (ja) * | 2012-02-29 | 2013-09-12 | Kobe Steel Ltd | 温間成形性に優れた高強度鋼板およびその製造方法 |
WO2015115059A1 (ja) | 2014-01-29 | 2015-08-06 | Jfeスチール株式会社 | 高強度冷延鋼板およびその製造方法 |
WO2015151427A1 (ja) * | 2014-03-31 | 2015-10-08 | Jfeスチール株式会社 | 高降伏比高強度冷延鋼板およびその製造方法 |
WO2015151419A1 (ja) * | 2014-03-31 | 2015-10-08 | Jfeスチール株式会社 | 高降伏比高強度冷延鋼板及びその製造方法 |
JP2017186647A (ja) * | 2016-03-31 | 2017-10-12 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
JP2017214648A (ja) | 2016-05-30 | 2017-12-07 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
JP2017214647A (ja) | 2016-05-30 | 2017-12-07 | 株式会社神戸製鋼所 | 高強度鋼板およびその製造方法 |
WO2018055425A1 (en) * | 2016-09-22 | 2018-03-29 | Arcelormittal | High strength and high formability steel sheet and manufacturing method |
Non-Patent Citations (1)
Title |
---|
See also references of EP3868910A4 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP4012055A4 (en) * | 2019-08-06 | 2022-08-31 | JFE Steel Corporation | THIN HIGH STRENGTH STEEL SHEET AND METHOD OF MAKING IT |
WO2023053909A1 (ja) * | 2021-09-30 | 2023-04-06 | Jfeスチール株式会社 | 鋼板、部材およびそれらの製造方法 |
JP7332062B1 (ja) | 2021-09-30 | 2023-08-23 | Jfeスチール株式会社 | 鋼板、部材およびそれらの製造方法 |
Also Published As
Publication number | Publication date |
---|---|
EP3868910A1 (en) | 2021-08-25 |
JP6822604B2 (ja) | 2021-01-27 |
CN112840056A (zh) | 2021-05-25 |
US20210381076A1 (en) | 2021-12-09 |
EP3868910A4 (en) | 2021-08-25 |
KR20210058918A (ko) | 2021-05-24 |
MX2021004445A (es) | 2021-07-07 |
CN112840056B (zh) | 2022-06-21 |
JPWO2020080337A1 (ja) | 2021-02-15 |
KR102517183B1 (ko) | 2023-04-03 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP6358407B2 (ja) | 鋼板及びめっき鋼板 | |
JP6252713B1 (ja) | 高強度鋼板およびその製造方法 | |
JP6354921B1 (ja) | 鋼板およびその製造方法 | |
US10550446B2 (en) | High-strength steel sheet, high-strength hot-dip galvanized steel sheet, high-strength hot-dip aluminum-coated steel sheet, and high-strength electrogalvanized steel sheet, and methods for manufacturing same | |
US10711333B2 (en) | High-strength steel sheet and method for manufacturing same | |
JP6354916B2 (ja) | 鋼板及びめっき鋼板 | |
US10954578B2 (en) | High-strength steel sheet and method for manufacturing same | |
JP5224010B2 (ja) | 縦壁部を有するホットスタンプ成形体の製造方法及び縦壁部を有するホットスタンプ成形体 | |
US20180127846A9 (en) | High-strength steel sheet, high-strength hot-dip galvanized steel sheet, high-strength hot-dip aluminum-coated steel sheet, and high-strength electrogalvanized steel sheet, and methods for manufacturing same | |
US20190106760A1 (en) | Steel sheet, coated steel sheet, and methods for manufacturing same | |
JP4650006B2 (ja) | 延性および伸びフランジ性に優れた高炭素熱延鋼板およびその製造方法 | |
JP5126844B2 (ja) | 熱間プレス用鋼板およびその製造方法ならびに熱間プレス鋼板部材の製造方法 | |
JP6988868B2 (ja) | 薄鋼板およびその製造方法 | |
US10260133B2 (en) | High-strength steel sheet and method for producing the same | |
KR102336669B1 (ko) | 고강도 용융 아연 도금 강판 및 그 제조 방법 | |
US20190276907A1 (en) | Steel sheet, coated steel sheet, and methods for manufacturing same | |
KR20190091304A (ko) | 고강도 냉연 강판 및 그 제조 방법 | |
WO2020080337A1 (ja) | 薄鋼板およびその製造方法 | |
JP6737419B1 (ja) | 薄鋼板およびその製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
ENP | Entry into the national phase |
Ref document number: 2020505289 Country of ref document: JP Kind code of ref document: A |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 19874610 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 20217011093 Country of ref document: KR Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2101002158 Country of ref document: TH |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
ENP | Entry into the national phase |
Ref document number: 2019874610 Country of ref document: EP Effective date: 20210517 |