Method for manufacturing hot stamped body having vertical wall and hot stamped body having vertical wall

Patent metadata

Field	Value
Publication number	US-9512499-B2
Application number	US-201113879068-A
Country	US
Kind code	B2
Filing date	Oct 21, 2011
Priority date	Oct 22, 2010
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

The present invention provides a method for manufacturing a hot stamped body having a vertical wall, 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 Ac 1 ° C. and lower than Ac 3 ° 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.

First claim

The invention claimed is:

1. A method for manufacturing a hot stamped body, in which a DI inch value which is a quenching index and is calculated based on ASTM A255-67 is equal to or more than 3, 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 heating temperature of an entire steel sheet for hot stamping is equal to or higher than Ac 3 ° C., a highest heating temperature is equal to or higher than Ac 3 ° C., and forming a vertical wall,
wherein the continuous annealing includes:
heating the cold-rolled steel sheet to a temperature range of equal to or higher than Ac 1 ° C. and lower than Ac 3 ° 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, in which a DI inch value which is a quenching index and is calculated based on ASTM A255-67 is equal to or more than 3, 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 heating temperature of an entire steel sheet for hot stamping is equal to or higher than Ac 3 ° C., a highest heating temperature is equal to or higher than Ac 3 ° C., and forming a vertical wall,
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 i T in a final rolling mill F i in a temperature range of (Ac 3 −80)° C. to (Ac 3 +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-3 T in the rolling mill F i-3 to be equal to or lower than F i T+100° C., and after holding in a temperature range of 600° C. to Ar 3 ° C. for 3 seconds to 40 seconds, coiling is performed,
the continuous annealing includes:
heating the cold-rolled steel sheet to a temperature range of equal to or higher than (Ac 1 −40)° C. and lower than Ac 3 ° 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.

Assignees

• Tomokiyo Toshimasa
• Hayashi Kunio
• Aso Toshimitsu
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Tomokiyo Toshimasa
• Hayashi Kunio
• Aso Toshimitsu

Classifications

• C21D8/00 Primary

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/42

  with copper · CPC title

• C21D8/0273

  Final recrystallisation annealing · CPC title

• C22C38/24

  with vanadium · CPC title