Steel sheet for hot pressing and hot pressed article using the same

Patent metadata

Field	Value
Publication number	US-10829840-B2
Application number	US-201515550355-A
Country	US
Kind code	B2
Filing date	Dec 10, 2015
Priority date	Dec 10, 2014
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

A steel sheet for hot pressing includes in a chemical composition, in percent by mass, C of 0.1% to 0.4%, Si of greater than 0% to 2.0%, Mn of 0.5% to 3.0%, P of greater than 0% to 0.015%, S of greater than 0% to 0.01%, B of 0.0003% to 0.01%, N of greater than 0% to 0.05%, Al in a content of 2×[N]% to 0.3% at a Si content of greater than 0.5% to 2.0%; or Al in a content of (0.20+2×[N]−0.40×[Si]N)% to 0.3% at a Si content of 0% to 0.5%, where [N] and [Si] are contents of N and Si, respectively, in mass percent, with the remainder being iron and inevitable impurities, where contents of Ti, Zr, Hf, and Ta, of the inevitable impurities, are each controlled to 0.005% or lower. The steel sheet includes nitride-based inclusions with an equivalent circle diameter of 1 μm or more in a number density of 0.10 per square millimeter.

First claim

The invention claimed is:

1. A hot pressed article formed of a steel sheet comprising, in a chemical composition:
C in a content of 0.1% to 0.4%;
Si in a content of 0% to 2.0%;
Mn in a content of 0.5% to 3.0%;
P in a content of greater than 0% to 0.015%;
S in a content of greater than 0% to 0.01%;
B in a content of 0.0003% to 0.01%;
N in a content of greater than 0% to 0.05%;
Al in a content of 2×[N]% to 0.3% at a Si content of greater than 0.5% to 2.0%; or Al in a content of (0.20+2×[N]−0.40×[Si])% to 0.3% at a Si content of 0% to 0.5%, where [N] and [Si] are contents of N and Si, respectively, in mass percent;
at least one element selected from the group consisting of:
V in a content of greater than 0% to 0.2%, and
Nb in content of greater than 0% to 0.2%;

with the remainder being iron and inevitable impurities,
the steel sheet having contents of Ti, Zr, Hf, and Ta, of the inevitable impurities, controlled to 0.003% or lower; and
the steel sheet comprising nitride-based inclusions with an equivalent circle diameter of 1 μm or more in a number density of less than 0.10 per square millimeter;
the steel sheet comprising nitride-based inclusions with an equivalent circle diameter of less than 1 μm in a number density of about 2 to about 100 per square millimeter;
the hot pressed article comprising martensite in an area percentage of 90% or higher of an entire microstructure thereof; and
the hot pressed article having a number density of nitride-based inclusions with an equivalent circle diameter of 1 μm or more of less than 0.10 per square millimeter.

Assignees

• Voestalpine Stahl Gmbh
• Kobe Steel Ltd

Inventors

• Murakami Toshio
• Naitou Junya
• Okita Keisuke
• Ikeda Shushi
• Sato Shinji
• Pichler Andreas
• Kurz Thomas

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D1/18

  Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62) · CPC title

• C21D9/00

  Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor · CPC title

• C22C38/58

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

• C21D8/0278

  involving a particular surface treatment  (C21D8/0294 takes precedence) · CPC title