Document Type and Number:
Japanese Patent JP4311740
Kind Code:
B2
Abstract:
To provide a high strength thick steel plate in a class of 590 to 780 MPa which has excellent welded joint toughness (HAZ toughness) even when subjected to high heat input welding.
Specified components of a thick steel plate, in particular, the total content of C, Mn, Cu and Ni are controlled by a specified parameter, the average number of fine Ti-containing oxides with a mean particle diameter of 0.05 to 1 μm is controlled to ≥10,000 pieces/cm2, and also the average number of coarse Ti-containing oxides with a mean particle diameter of ≥2 μm is controlled to ≤2,000 pieces/cm2. Thus, even in a high strength thick steel plate in a class of 590 to 780 MPa, the toughness of the whole region of the HAZ in high heat input welding including, in particular, the weld heat affected zone in the vicinity of 3 to 5 mm from a melting line whose toughness is apt to decrease is remarkably improved.
COPYRIGHT: (C)2006,JPO&NCIPI
Inventors:
Yoshiomi Okazaki
Hatano etc.
Hiroyuki Takaoka
Application Number:
JP2004312916A
Publication Date:
August 12, 2009
Filing Date:
October 27, 2004
Assignee:
KABUSHIKI KAISHA KOBE SEIKO SHO
International Classes:
C22C38/00; C22C38/16; C22C38/58; B23K9/18; B23K103/04; C21C7/04; C21C7/06; C21D8/02; C22C33/04
Attorney, Agent or Firm:
Yoshiyuki Kaji
Makoto Suhara
