STEEL SHEET FOR SPRING, SPRING MATERIAL USING THE SAME, AND METHOD FOR MANUFACTURING THEM

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet for a spring, which has sufficient workability to be required to a fastening component such as a metallic retaining ring, a disc spring and a wavy washer, and shows superior spring characteristics after having been aged.;SOLUTION: The steel sheet has a composition comprising, by mass%, 0.03% or less C, 0.03% or less N, 0.5 to 2.0% Si, 0.5 to 2.5% Mn, 1.0 to 3.5% Cu, 15 to 18% Cr, 6 to 10% Ni, 3.5% or less Mo and the balance Fe with unavoidable impurities so that a value Md can be -20 to 30, which is defined by the expression of Md=551-462(C+N)-9.2Si-8.1Mn-29(Ni+Cu)-13.7Cr-18.5Mo; has a diplophase structure in which a matrix comprises "an austenitic phase and a martensitic phase occupying +20 to 50 vol%"; has a hardness of 400 HV or lower; and has an elongation of 5% or more.;COPYRIGHT: (C)2008,JPO&INPIT