| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing steel in which the structure required for allowing it to have excellent brittle fracture propagation stopping characteristics even if being applied with plastic deformation is made clear and capable of stably obtaining such structure without using expansive alloy elements. SOLUTION: This steel excellent in brittle fracture propagation stopping characteristics is the one in which, in a steel having a compsn. contg., by weight, 0.02 to 0.2% C, 0.05 to 0.5% Si, 0.5 to 2.0% Mn and 0.01 to 0.08% Al, in which Ceq is regulated to <=0.40%, Pcm is made to <=0.20%, and the balance Fe with inevitable impurities, the structure is the one contg. ferrite crystal grains in which the flattening ratio is regulated to >=2 and the minor axis size is regulated to <=5μm and subgrains of <=3μm size equivalent to a circle in the ferrite crystals, and the structure occupies the part of >=5% of the steel sheet thickness.
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