| 摘要 |
PROBLEM TO BE SOLVED: To produce soft-nitrided parts exhibiting excellent fatigue resistance and wear resistance and to provide a method for producing a steel for soft- nitriding excellent in machinability and forming into the stock thereof. SOLUTION: This producing method is the one in which steel having a chemical compsn. contg., by weight, 0.15 to 0.45% C, 0.05 to 0.5% Si, 0.2 to 2.5% Mn, 0.002 to 0.2% S, 0.5 to 1.5% Cu, 0.25 to 0.75% Ni also so as to satisfy 1.8<=Cu/Ni<=2.2, 0.5 to 2% Cr, 0.05 to 0.5% V, <=1.0% Ti, <=1.0% Zr also so as to satisfy 0.04 to 1.0% Ti+Zr, 0.01 to 0.3% Al, <=0.008% N and Ti+Zr-1.2S >0%, contg., if necessary, one or more kinds among Mo, W, Pb and Ca, and the balance Fe with impurities, in which the maximum diameter of Ti carbosulfides and Zr carbosulfides in the steel is regulated to <=10μm, and the total content thereof is regulated to >=0.05% by cleanliness is subjected to spheroidizing after hot working to regulate its hardness Hv to <=180 and is subjected to cold working to regulate its hardness Hv to >=250. The soft- nitrided parts are ones in which the hardness of the surface after soft-nitriding is regulated to >=600, the effective hardening depth is regulated to >=0.1 mm, and the hardness Hv of the core part is regulated to >=250.
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