Method for manufacturing spring having high nitrided properties

摘要

A method for forming a spring which can reduce variations in the surface hardness and the thickness of the hardened layer when the spring is nitrided. Before nitriding the spring, the thickness of an oxide film formed on the surface of the spring is reduced to 1.5 mu m or less by electropolishing or any other suitable means so that the residual stress of the spring will be -5 kgf/mm2 to 5 kgf/mm2 near its surface. With this arrangement, it is possible to increase the surface hardness and the thickness of the nitrided layer of the spring obtained by nitriding.