Title:
HOT-PRESSED STEEL SHEET MEMBER AND PROCESS FOR PRODUCTION THEREOF
Document Type and Number:
WIPO Patent Application WO/2007/129676
Kind Code:
A1
Abstract:
A hot-pressed steel sheet member which exhibits excellent toughness after quenching
without any subsequent treatment and which has a tensile strength of 1.8GPa or
above has a microstructure which has a prior austenite grain size of 10μm
or below and which contains spontaneously tempered martensite. The chemical
composition of the steel sheet contains C: 0.26 to 0.45%, Mn+Cr: 0.5 to 3.0%, Nb:
0.02 to 1.0%, Ti in an amount satisfying the relationship:3.42N+0.001 ≤
Ti ≤ 3.42N+0.5, one or more of Si: 0.5% or below, Ni: 2% or below, Cu: 1% or
below, V: 1% or below and Al: 1% or below, and, if necessary, one or more of B: 0.01%
or below, Nb: 1.0% or below, Mo: 1.0% or below and Ca: 0.001 to 0.005%. The steel
sheet is kept at a temperature ranging from the Ac3 point to (the Ac3
point + 100°C) for at most 5 minutes, hot-pressed, and then quenched by cooling
at a rate of the upper critical cooling rate or above to the Ms point and at an average
cooling rate of 10 to 500°C/sec from the Ms point to 150°C.
Inventors:
NISHIBATA TOSHINOBU (JP)
Application Number:
PCT/JP2007/059415
Publication Date:
November 15, 2007
Filing Date:
April 25, 2007
Export Citation:
Assignee:
SUMITOMO METAL IND (JP)
NISHIBATA TOSHINOBU (JP)
NISHIBATA TOSHINOBU (JP)
International Classes:
C22C38/00; B21B3/00; C21D9/46; C22C38/58
Foreign References:
| JP2004353026A | 2004-12-16 | |||
| JP2003147499A | 2003-05-21 | |||
| JP2005133180A | 2005-05-26 | |||
| JP2005205477A | 2005-08-04 | |||
| JP2005097725A | 2005-04-14 | |||
| JP2006152427A | 2006-06-15 |
Attorney, Agent or Firm:
HIROSE, Shoichi (4-2 Nihonbashi Honcho 4-chom, Chuo-ku Tokyo 23, JP)
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