Title:
PRODUCTION OF HIGH TENSILE STRENGTH STEEL SHEET OF OVER 570N/MM2 CLASS EXCELLENT IN WELDABILITY AND LOW IN YIELD RATIO
Document Type and Number:
Japanese Patent JP3399983
Kind Code:
B2
Abstract:
PURPOSE: To maintain low yield ratio in a steel sheet and to improve its weldability by rolling steel having specified chemical components, thereafter executing hardening, furthermore heating it to a temp. in the two phase region and subsequently executing air cooling, hardening and tempering treatment.
CONSTITUTION: A slab constituted of, by weight, 0.05 to 0.20% C, 0.05 to 0.5O% Si, 0.30 to 1.80% Mn and 0.005 to 0.10% Al, and the balance Fe with inevitable impurities is subjected to hot rolling. It is hardened at the Ac3 point to 980°C and is thereafter subjected to special hardening of heating it to a temp. in the two phase region (the Ac1 point to the Ac3 point) and subjecting it to air cooling to a prescribed temp. Successively, it is subjected to tempering treatment at 400°C to less than the Ac1 point. In this way, the high tensile strength steel sheet of ≥570N/mm2 class excellent in weldability and low in yield ratio can be obtd. Moreover, this steel is incorporated with prescribed amounts of one or more kinds among Cu, Ni, Cr, Mo, V, Nb, B, Ti and Ca according to necessary.
Inventors:
Kazuhiko Yano
Kiyoshi Iwai
Shigeo Okano
Kiyoshi Iwai
Shigeo Okano
Application Number:
JP22609192A
Publication Date:
April 28, 2003
Filing Date:
August 25, 1992
Export Citation:
Assignee:
KABUSHIKI KAISHA KOBE SEIKO SHO
International Classes:
C21D8/02; C22C38/00; C22C38/06; (IPC1-7): C21D8/02; C22C38/00
Domestic Patent References:
| JP63286517A | ||||
| JP6455335A | ||||
| JP4110423A | ||||
| JP4318A |
Attorney, Agent or Firm:
Yoshiyuki Kaji
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