| 摘要 |
PURPOSE:To produce a steel strip of high fatigue strength, and small permanent set after repetitive uses by treating the steel strip of carbon steel or low alloy steel at the constant transformation temp., cold rolling draft and low-temp. annealing temp. within the specific ranges. CONSTITUTION:A hot- or cold-rolled steel strip of carbon steel of 0.5-0.9 C and low alloy steel is solution-heat-treated, immediately after which it is subjected to constant temp. transformation preferably within about 10sec within a molten lead bath kept at relatively low temps. of 450-500 deg.C to have uniform and fine lamella pearlite structure. Thence, the steel strip is cold-rolled at 50-80% drafts to be provided with moderate strength and necessary shape characteristics. Thence, it is subjected to low temp. annealing at 200-350 deg.C before it is formed to the prescribed shape or during the course of the forming, whereby the rate of permanent set is reduced, and the steel strip of high strength against the permissible stress and fatigue during use and particularly the breakdown life under high stress amplitude suited for production of springs is obtained. |
