Title:
METHOD FOR PRODUCING HIGH STRENGTH/HIGH TOUGHNESS STEEL
Document Type and Number:
Japanese Patent JP2007217772
Kind Code:
A
Abstract:
To provide a method for producing a high strength/high toughness steel excellent in strength-toughness balance, suitable to a welded steel structure having ≥590 MPa tensile strength.
A steel blank having composition composed of, by mass, 0.01-0.20% C, 0.01-0.80% Si, 0.5-2.50% Mn, ≤0.020% P, ≤0.0070% S, 0.004-0.100 Al and the balance Fe with inevitable impurities, is hot-rolled, in which the rolling-completing temperature is set to the temperature zone of Ar3transformation point or higher. Successively, after quenching from the temperature zone of the Ar3transformation point or higher to ≤300°C and introducing strain at 0.05-0.5 accumulated bending strain, when the steel is reheated to the temperature of Ac1to Ac1+150°C, the heat treatment in which the heating rate to the reheating temperature is ≥1°C/s and the stagnation time in the temperature zone from Ac1to Ac1+150°C is within 90 second, is desirably continuously applied within 180 s from the quenching to the reheating treatment.
COPYRIGHT: (C)2007,JPO&INPIT
Inventors:
OI KENJI
HAYASHI KENJI
NAGAO AKIHIDE
Application Number:
JP2006041776A
Publication Date:
August 30, 2007
Filing Date:
February 20, 2006
International Classes:
C21D8/02; C22C38/00; C22C38/06; C22C38/58
Attorney, Agent or Firm:
Kenichiro Ochiai
Kazuhiro Mori
