| 摘要 |
PURPOSE:To improve remarkably the fatigue strength of mechanical parts, etc. made of a low carbon low alloy steel by subjecting said parts to a carburizing treatment to increase the carbon concn. in the surface then subjecting the parts to a heat treatment under specific conditions and further to shot peening. CONSTITUTION:Mechanical parts and structural parts having intricate shapes are produced of a low carbon low alloy steel and are subjected to a carburization hardening treatment by ordinary means then to tempering at a low temp. of 150-200 deg.C to increase the carbon concn. of the surface to 0.7-0.9%. After such parts are reheated to an austenite region of 800-850 deg.C, the parts are quickly cooled in a hot bath kept at 300-350 deg.C and is maintained for prescribed time at said temp. Shot peening of 5-40min with shots having 0.6-0.8mm. diameter at a projecting rate of 35-50mm./sec is begun from said temp. range to generate residual compressive stress in the surface of the mechanical parts and to harden the surface layer, by which the fatigue strength thereof is remarkably improved. |
