Method for manufacturing hot stamped body and hot stamped body

Patent metadata

Field	Value
Publication number	US-9840751-B2
Application number	US-201715422520-A
Country	US
Kind code	B2
Filing date	Feb 2, 2017
Priority date	Oct 22, 2010
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Provided is 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 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 hot stamped body, which is formed by performing hot stamping by heating a steel sheet so that a heated portion at which a highest heating temperature is equal to or higher than Ac 3 ° 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, the steel sheet being a steel sheet for hot stamping which is continuously annealed, the hot stamped body 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, wherein:
when the amount of C in the hot stamped body is equal to or more than 0.18% and less than 0.25%, ΔHv is equal to or less than 25 and Hv_Ave is equal to or less than 200;
when the amount of C in the hot stamped body is equal to or more than 0.25% and less than 0.30%, ΔHv is equal to or less than 32 and Hv_Ave is equal to or less than 220; and
when the amount of C in the hot stamped body is equal to or more than 0.30% and less than 0.35%, ΔHv is equal to or less than 38 and Hv_Ave is equal to or less than 240,
wherein ΔHv represents a variation in Vickers hardness of the non-heated portion, and Hv_Ave represents an average Vickers hardness of the non-heated portion.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Hayashi Kunio
• Aso Toshimitsu
• Tomokiyo Toshimasa
• Tanino Hitoshi
• Wada Ryozo

Classifications

• C21D8/00

  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

• C22C38/54

  with boron · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title