Method for manufacturing hot stamped body and hot stamped body

• US 9,598,745 B2
• Filed: 10/21/2011
• Issued: 03/21/2017
• Est. Priority Date: 10/22/2010
• Status: Active Grant

• Current Assignee: Aisin Takaoka Company Limited (Aisin Corp.), Nippon Steel Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Aisin Takaoka Company Limited (Aisin Corp.), Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Wada, Ryozo, Hayashi, Kunio, Aso, Toshimitsu, Tomokiyo, Toshimasa, Tanino, Hitoshi
• Primary Examiner(s): WALCK, BRIAN D
• Application Number:
  US13/879,061
• Publication Number:
  US 20130292009A1
• Time in Patent Office: 1,978 Days
• Field of Search: 148/516, 148/518, 148/534, 148/603
• US Class Current: 1/1
• CPC Class Codes: B21D 22/022 by heating the blank or stamping associated with heat treatment C21D takes precedence
• CPC Class Codes: C21D 8/005 of ferrous alloys C21D8/02 - C21D8/12 take precedence
• CPC Class Codes: C21D 8/0226 Hot rolling
• CPC Class Codes: C21D 8/0236 Cold rolling
• CPC Class Codes: C21D 8/0263 following hot rolling
• CPC Class Codes: C21D 8/0273 Final recrystallisation annealing
• CPC Class Codes: C21D 9/0068 for particular articles not mentioned below
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22C 38/008 containing tin
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/20 with copper
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/24 with vanadium
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/32 : with boron
• CPC Class Codes: C22C 38/38 : with more than 1.5% by weight of manganese
• CPC Class Codes: C22C 38/42 : with copper
• CPC Class Codes: C22C 38/48 : with niobium or tantalum
• CPC Class Codes: C22C 38/50 : with titanium or zirconium
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: C22C 38/58 : with more than 1.5% by weight of manganese
• CPC Class Codes: C23C 2/02 : Pretreatment of the material to be coated, e.g. for coating on selected surface areas C23C2/30 takes precedence
• CPC Class Codes: C23C 2/0224 : Two or more thermal pretreatments
• CPC Class Codes: C23C 2/024 : by cleaning or etching
• CPC Class Codes: C25D 5/36 : of iron or steel

Abstract

The present invention provides a method for manufacturing a hot stamped body, the method including: a hot-rolling step; a coiling step; a cold-rolling step; a continuous annealing step; and a hot stamping step, in which the continuous annealing step includes a heating step of heating the cold-rolled steel sheet to a temperature range of equal to or higher than Ac₁° C. and lower than Ac₃° C.; a cooling step of cooling the heated cold-rolled steel sheet from the highest heating temperature to 660° C. at a cooling rate of equal to or less than 10° C./s; and a holding step of holding the cooled cold-rolled steel sheet in a temperature range of 550° C. to 660° C. for one minute to 10 minutes.

Claims

1. A method for manufacturing a hot stamped body, the method comprising:

hot-rolling a slab containing chemical components which include, by mass %, 0.18% to 0.35% of C, 1.0% to 3.0% of Mn, 0.01% to 1.0% of Si, 0.001% to 0.02% of P, 0.0005% to 0.01% of S, 0.001% to 0.01% of N, 0.01% to 1.0% of Al, 0.005% to 0.2% of Ti, 0.0002% to 0.005% of B, and 0.002% to 2.0% of Cr, and the balance of Fe and inevitable impurities, to obtain a hot-rolled steel sheet;

coiling the hot-rolled steel sheet which is subjected to hot-rolling;

cold-rolling the coiled hot-rolled steel sheet to obtain a cold-rolled steel sheet;

continuously annealing the cold-rolled steel sheet which is subjected to cold-rolling to obtain a steel sheet for hot stamping; and

performing hot stamping by heating the steel sheet for hot stamping which is continuously annealed so that a heated portion at which a highest heating temperature is equal to or higher than Ac₃°

C., and a non-heated portion at which a highest heating temperature is equal to or lower than Ac1°

C. co-exist in the steel sheet,

wherein the continuous annealing includes;

heating the cold-rolled steel sheet to a temperature range of equal to or higher than Ac₁°

C. and lower than Ac₃°

C.;

cooling the heated cold-rolled steel sheet from the highest heating temperature to 660°

C. at a cooling rate of equal to or less than 10°

C./s; and

holding the cooled cold-rolled steel sheet in a temperature range of 550°

C. to 660°

C. for one minute to 10 minutes.

2. The method for manufacturing a hot stamped body according to claim 1,

wherein the chemical components further include one or more from 0.002% to 2.0% of Mo, 0.002% to 2.0% of Nb, 0.002% to 2.0% of V, 0.002% to 2.0% of Ni, 0.002% to 2.0% of Cu, 0.002% to 2.0% of Sn, 0.0005% to 0.0050% of Ca, 0.0005% to 0.0050% of Mg, and 0.0005% to 0.0050% of REM.

3. The method for manufacturing a hot stamped body according to claim 1, the method further comprising performing any one of a hot-dip galvanizing process, a galvannealing process, a molten aluminum plating process, an alloyed molten aluminum plating process, and an electroplating process, after the continuous annealing.

4. The method for manufacturing a hot stamped body according to claim 2, the method further comprising performing any one of a hot-dip galvanizing process, a galvannealing process, a molten aluminum plating process, an alloyed molten aluminum plating process, and an electroplating process, after the continuous annealing.

5. A method for manufacturing a hot stamped body, the method comprising:

hot-rolling a slab containing chemical components which include, by mass %, 0.18% to 0.35% of C, 1.0% to 3.0% of Mn, 0.01% to 1.0% of Si, 0.001% to 0.02% of P, 0.0005% to 0.01% of S, 0.001% to 0.01% of N, 0.01% to 1.0% of Al, 0.005% to 0.2% of Ti, 0.0002% to 0.005% of B, and 0.002% to 2.0% of Cr, and the balance of Fe and inevitable impurities, to obtain a hot-rolled steel sheet;

coiling the hot-rolled steel sheet which is subjected to hot-rolling;

cold-rolling the coiled hot-rolled steel sheet to obtain a cold-rolled steel sheet;

continuously annealing the cold-rolled steel sheet which is subjected to cold-rolling to obtain a steel sheet for hot stamping; and

performing hot stamping by heating the steel sheet for hot stamping which is continuously annealed so that a heated portion at which a highest heating temperature is equal to or higher than Ac₃°

C., and a non-heated portion at which a highest heating temperature is equal to or lower than Ac1°

C. co-exist in the steel sheet, wherein

in the hot-rolling, in finish-hot-rolling configured with a machine with 5 or more consecutive rolling stands, rolling is performed by setting a finish-hot-rolling temperature F_iT in a final rolling mill F_i in a temperature range of (Ac₃−

80)°

C. to (Ac₃+40)°

C., by setting time from start of rolling in a rolling mill F_i-3 which is a previous machine to the final rolling mill F_i to end of rolling in the final rolling mill F_i to be equal to or longer than 2.5 seconds, and by setting a hot-rolling temperature F_i-3T in the rolling mill F_i-3 to be equal to or lower than F_iT+100°

C., and after holding in a temperature range of 600°

C. to Ar₃°

C. for 3 seconds to 40 seconds, coiling is performed, and

the continuous annealing includes;

heating the cold-rolled steel sheet to a temperature range of equal to or higher than (Ac₁−

40)°

C. and lower than Ac₃°

C.;

cooling the heated cold-rolled steel sheet from the highest heating temperature to 660°

C. at a cooling rate of equal to or less than 10°

C./s; and

holding the cooled cold-rolled steel sheet in a temperature range of 450°

C. to 660°

C. for 20 seconds to 10 minutes.

6. The method for manufacturing a hot stamped body according to claim 5,

wherein the chemical components further include one or more from 0.002% to 2.0% of Mo, 0.002% to 2.0% of Nb, 0.002% to 2.0% of V, 0.002% to 2.0% of Ni, 0.002% to 2.0% of Cu, 0.002% to 2.0% of Sn, 0.0005% to 0.0050% of Ca, 0.0005% to 0.0050% of Mg, and 0.0005% to 0.0050% of REM.

7. The method for manufacturing a hot stamped body according to claim 5, the method further comprising performing any one of a hot-dip galvanizing process, a galvannealing process, a molten aluminum plating process, an alloyed molten aluminum plating process, and an electroplating process, after the continuous annealing.

8. The method for manufacturing a hot stamped body according to claim 6, the method further comprising performing any one of a hot-dip galvanizing process, a galvannealing process, a molten aluminum plating process, an alloyed molten aluminum plating process, and an electroplating process, after the continuous annealing.