| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high breaking toughness steel with which the excellent breaking toughness can be given to a steel for structural-use without adding expensive alloy elements. SOLUTION: A steel material having a structure composed of two or more kinds of phases containing ferrite and having 40-90% ferrite area ratio in this structure is heated to 1315-1350°C, and after holding to this temperature for 5-20 min, this is cooled desirably so as not to generate bainite transformation, or the steel material after cooling is further reheated to 850-950°C, and cooled desirably so as not to generate the bainite transformation. The above steel material has desirably the composition containing 0.04-0.18% C,≤0.60% Si, 0.80-1.80% Mn,≤0.030% P,≤0.015% S and one or both of 0.02-0.08% Al and 0.16-0.50% Ti, and 0.34-0.48% Ceq (=C+Si/24+Mn/6). COPYRIGHT: (C)2004,JPO&NCIPI
|
