Fatigue property is superior the steel for the spring and the steel wire and the spring null for the spring

摘要

PURPOSE: To obtain a steel for a spring having high strength and excellent in fatigue properties by specifying its compsn. constituted of C, Si, Mn, Cr, V, Nb and Fe and the properties of contained inclusions and percipitates. ;CONSTITUTION: In a steel contg., by weight, 0.5 to 0.8% C, 0.8 to 2.5% Si, 0.4 to 1.3% Mn and 0.4 to 2% Cr, furturemore contg., at need, 0.05 to 0.5% V and/or 0.05 to 0.5% Nb and moreover contg. 0.1 to 2% Ni and/or 0.1 to 0.5% Mo, and the balance Fe with inevitable impurities, the m.p. of oxide inclusions contained therein is regulated to ≤1500°C, and the size of carbide precipitates and nitride precipitates are regulated to ≤15μm. In this way, the objective steel for a high strength spring excellent in fatigue properties can be obtd. This steel is subjected to hardening and tempering treatment, by which the objective high strength steel wire for a spring having crystalline grain size, of No.11, or more 3 to 20% retained austenitic amt., ≥205kgf/mm² tensile strength and ≤0.95 proof stress ratio after low temp. annealing at ≥400°C and the objective spring having residual stress shown by the formula and inequalities can be obtd.;COPYRIGHT: (C)1993,JPO&Japio