Title:
PRODUCTION OF STEEL MATERIAL WITH LOW YIELD RATIO, EXCELLENT IN TOUGHNESS IN HEAT-AFFECTED ZONE
Document Type and Number:
Japanese Patent JP3820639
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To obtain a steel material with low yield ratio, excellent in toughness in a heat-affected zone at the time of large heat input welding, by providing a steel with a specific composition, dispersing oxide grains having composition phase satisfying specific equations, and applying cooling under specific cooling conditions.
SOLUTION: As to a steel composition, 0.005-0.05% Nb is mixed to perform crystal grain refining. The average density of the grains to be dispersed, having a composition satisfying equations Mn=5 to 50 atomic % and (Al+Ti)=50 to 95 atomic % and also having a size of 1-10μm, is regulated to ≥4 pieces/mm2, by which ferrite precipitation sites are formed. After heating to a temp. in the region between 1000 and 1200°C, the steel is cooled from a temp. in the region between (Ar3-40°C) and (Ar3-100°C) down to ≤400°C at ≥3°C/sec cooling rate, and then cooling is stopped. By this method, the 600N/mm2 class steel material with low yield ratio, excellent in toughness in a heat-affected zone, can be obtained.
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Inventors:
Hiroshi Iki
Kazushi Onishi
Shuichi Suzuki
Masahiko Hamada
Takeshi Ichinose
Kazushi Onishi
Shuichi Suzuki
Masahiko Hamada
Takeshi Ichinose
Application Number:
JP22391796A
Publication Date:
September 13, 2006
Filing Date:
August 26, 1996
Export Citation:
Assignee:
SUMITOMO METAL INDUSTRIES,LTD.
International Classes:
C21D8/02; C22C38/00; C22C38/14; C22C38/58; (IPC1-7): C21D8/02; C22C38/00; C22C38/14; C22C38/58
Domestic Patent References:
| JP6025742A | ||||
| JP7278736A |
Attorney, Agent or Firm:
Shoichi Hirose