| 摘要 |
PROBLEM TO BE SOLVED: To improve the pitting fatigue strength of driving transmission mechanism parts such as gears used for automobile transmission, etc., by subjecting a steel stock of specific composition to rough forming, to carburizing and quenching, then to high-frequency heating at specific temperature, and immediately to working and providing specific required physical properties. SOLUTION: A steel stock, having a composition which consists of, by weight, 0.1-0.3% C, 0.01-0.15% Si, 0.3-1.5% Mn, 0.3-1.5% Cr, 0.01-0.06% S, 0.001-0.01% Ca, <=0.003% O, and the balance Fe, etc., and in which the value of Ca/O is regulated to 0.5-3.5, is used. The steel stock is subjected to rough forming, to carburizing and quenching, to high-frequency heating to 200-600 deg.C for 1-5 min, and immediately to working of 10-60%. By this procedure, slack quenched layer, compressive residual stress at surface, and surface roughness Rmax are regulated to <15μm, >=25 kgf/mm2, and >=2.5μm, respectively. Moreover, the relationship between the valueβ' given by making the X-ray diffraction half-width made to dimensionless by the half-width after annealing of the steel stock and the surface roughness Rmax is regulated so thatβ'>=2.29-0.401 n (Rmax) is satisfied. Further, retained austenite is regulated to <=10%.
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