# US 2014/0150930 A1 · Hot press forming steel plate, formed member using same, and method for manufacturing the plate and member

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- Number: US 2014/0150930 A1
- Document ID: US20140150930A1
- Status: Published application
- Kind: A1
- Application number: 14/232,784
- Filed: 2011-07-15
- Published: 2014-06-05
- Earliest claimed: 2011-07-15
- Inventors: Kyoo-Young Lee; Jin-Keun Oh; Jong-Sang Kim; Tae-Kyo Han
- Web page: https://patentgrep.com/patent/US20140150930A1

## CPC

- C22C 38/38: with more than 1.5% by weight of manganese
- B21B 1/026: {Rolling}
- B21C 47/26: Special arrangements with regard to simultaneous or subsequent treatment of the material
- C21D 8/0263: {following hot rolling}
- C21D 9/46: for sheet metals
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/18: containing chromium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/34: with more than 1.5% by weight of silicon
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/0224: {Two or more thermal pretreatments}
- C23C 2/024: {by cleaning or etching}
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/12: Aluminium or alloys based thereon
- C21D 8/0226: {Hot rolling}
- C21D 8/0236: {Cold rolling}
- C21D 8/0273: {Final recrystallisation annealing}
- C21D 2211/001: Austenite
- C21D 2211/002: Bainite
- Y10T 428/12757: Fe
- Y10T 428/12799: Next to Fe-base component [e.g., galvanized]
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04)
- B21C: MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- 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 (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- 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 (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention relates to a hot press forming steel plate made of a composition comprising: 0.3-1.0 wt % of C; 0.0-4.0 wt % of Mn; 1.0-2.0 wt % of Si; 0.01-2.0 wt % of Al; 0.015 wt % or less of S; 0.01 wt % or less of N; and the remainder being Fe and unavoidable impurities. Further, the present. invention relates to a method for manufacturing the hot press forming steel plate, characterized by comprising the steps of: heating, to between 1100 and 1300° C., a steel slab having the composition; performing hot rolling finishing between. an Ar3 transformation point and 950° C.; and performing winding between MS and 720° C. Further, the present invention. relates to a hot press formed member characterized by having the composition, and having a dual phase microstructure made of bainite and residual austenite. In addition, the present invention relates to a method for manufacturing the hot press formed member, characterized by comprising the steps of: heating the steel plate having the composition to a temperature of an Ac3 point or higher; hot press molding the heated steel plate; performing cooling at a cooling speed of 20° C./sec or higher to a temperature between MS and 350° C.; and performing a heat treatment in a heating furnace between MS and 550° C.

## Claims

### Claim 1

A steel sheet for hot press forming, comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities.

### Claim 2 (depends on 1)

The steel sheet for hot press forming of claim 1, further comprising at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 3 (depends on 1)

The steel sheet for hot press forming of claim 1, further comprising B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 4 (depends on 1)

The steel sheet for hot press forming of claim 1, wherein the steel sheet is one of a hot-rolled steel sheet, a cold-rolled steel sheet, and a plated cold-rolled steel sheet coated with a plating layer.

### Claim 5

A method for manufacturing a steel sheet for hot press forming, the method comprising:
heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;
performing a finish hot-rolling process at a temperature within a range of Ar3 transformation point to 950° C. to form a steel sheet; and
coiling the steel sheet at a temperature within a range of Ms to 720° C.

### Claim 6 (depends on 5)

The method of claim 5, wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 7 (depends on 5)

The method of claim 5, wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 8

A method for manufacturing a steel sheet for hot press forming, the method comprising:
heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;
performing a finish hot-rolling process at a temperature within a range of Ar3 transformation point to 950° C. to form a steel sheet;
coiling the steel sheet at a temperature within a range of Ms to 720° C.;
pickling the steel sheet;
cold-rolling the steel sheet;
continuously annealing the steel sheet at a temperature within a range of 750° C. to 900° C.; and
overaging the steel sheet at a temperature within a range of Ms to 550° C.

### Claim 9 (depends on 8)

The method of claim 8, wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 10 (depends on 8)

The method of claim 8, wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 11

A method for manufacturing a steel sheet for hot press forming, the method comprising:
heating a steel slab to a temperature range of 1100° C. to 1300° C., the steel slab comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;
performing a finish hot-rolling process at a temperature within a range of Ar3 transformation point to 950° C. to form a steel sheet;
coiling the steel sheet at a temperature within a range of Ms to 720° C.;
pickling the steel sheet;
cold-rolling the steel sheet;
continuously annealing the steel sheet at a temperature within a range of 750° C. to 900° C.;
overaging the steel sheet at a temperature within a range of Ms to 550° C.; and
plating the overaged steel sheet by any one of hot-dip galvanizing, galvannealing, electro galvanizing, and hot-dip aluminizing.

### Claim 12 (depends on 11)

The method of claim 11, wherein the steel slab further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 13 (depends on 11)

The method of claim 11, wherein the steel slab further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 14

A hot-press formed member comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities, wherein the hot-press formed member has a dual phase microstructure formed by bainite and retained austenite.

### Claim 15 (depends on 14)

The hot-press formed member of claim 14, further comprising at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 16 (depends on 14)

The hot-press formed member of claim 14, further comprising B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 17 (depends on 14)

The hot-press formed member of claim 14, wherein the hot-press formed member has a TS(MPa)*EI(%) value of 25,000 MPa % or greater.

### Claim 18 (depends on 16)

The hot-press formed member of claim 16, wherein the hot-press formed member has a TS(MPa)*EI(%) value of 25,000 MPa % or greater.

### Claim 19

A method for manufacturing a hot-press formed member, the method comprising:
heating a steel sheet to a temperature equal to or higher than Ac3, the steel sheet comprising, by wt %, C: 0.3% to 1.0%, Mn: 0.01% to 4.0%, Si: 1.0% to 2.0%, Al: 0.01% to 2.0%, S: 0.015% or less, N: 0.01% or less, and the balance of Fe and inevitable impurities;
hot-press forming the heated steel sheet;
cooling the hot-press formed steel sheet to a temperature range of Ms to 550° C. at a rate of 20° C./sec or higher; and
heat-treating the cooled steel sheet at a temperature within a range of Ms to 550° C. in a heating furnace.

### Claim 20 (depends on 19)

The method of claim 19, wherein the steel sheet further comprises at least one selected from the group consisting of Mo: 0.5% or less (excluding 0%), Cr: 1.5% or less (excluding 0%), Ni: 0.5% or less (excluding 0%), Nb: 0.005% to 0.1%, and V: 0.005% to 0.1%.

### Claim 21 (depends on 19)

The method of claim 19, wherein the steel sheet further comprises B: 0.005% or less (excluding 0%) and Ti: 0.06% or less (excluding 0%).

### Claim 22 (depends on 19)

The method of claim 19, wherein the steel sheet is one of a hot-rolled steel sheet, a cold-rolled steel sheet, and a plated cold-rolled steel sheet coated with a plating layer.