| 摘要 |
PURPOSE:To prevent thoroughly deterioration in the toughness of an unnormalized steel contg. specified amounts of C, Si, Mn, Al, P and S and having specified tensile strength by subjecting the steel to stress relieving annealing after cold working while controlling a temper parameter P as a standard to a certain range. CONSTITUTION:An unnormalized steel consisting of, by weight, 0.12-0.22% C, <0.5% Si, 0.7-1.6% Mn, 0.008-0.04% Al, <0.025% P, <0.015% S and the balance Fe with inevitable impurities and having 50kg.f/mm.<2> tensile strength is cold worked, and it is subjected to sress relieving annealing while controlling a temper parameter P prescribed by the equation to 17X10<2>-18X10<3>. In the equation, T is heating temp. ( deg.K) and (t) is heating time (hr). |
