| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing steel capable of omitting softening after the hot rolling of the stock in non-refining steel having >=85 kgf/mm2 tensile strength. SOLUTION: Steel having a compsn. contg., by weight, 0.1 to 0.6% C, 0.05 to 1.0% Si, 0.3 to 2.0% Mn, 0.01 to 0.1% S, 0.05 to 1.5% Cr and 0.005 to 0.05% Al, moreover contg. one or two kinds of Ti and Nb by 0.05 to 0.3% in total, and the balance Fe with inevitable impurities is used as the stock, and, at the time of hot rolling, heating temp. is controlled to 900 to 1,150 deg.C, and it is hot-worked in the region of <=1,150 deg.C. Then, cooling is executed at a cooling rate of <=2 deg.C/sec to suppress the hardness of the steel to <=55 HB and to enable its shear cutting, moreover, at the time of hot forging, heating is executed to the temp. region of 1,200 to 1,350 deg.C, and it is hot-worked in the temp. region of >=900 deg.C, and cooling is executed at a cooling rate of 0.05 to 1 deg.C/sec to impart >=85 kgf/mm2 tensile strength thereto.
|
