Patent ID: 6093263
Filing Date: 2000-07-25
Classification: C21D,C22C,C23C

Abstract:
A gear formed by gas soft nitriding a steel consisting essentially of, by weight %, 0.18 to 0.23 of C, 0.15 to 0.35 of Si, 0.60 to 0.85 of Mn, 0.03 or less of P, 0.03 or less of S, 0.90 to 1.20 of Cr and 0.15 to 0.30 of Mo, with Fe and impurities as a residual, wherein said gear comprises a compound layer containing N and Fe having a thickness of 2 to 12 .mu.m on a tooth flank surface thereof and a diffusion layer formed under said compound layer having a thickness of 200 .mu.m or more and having a hardness equal to or higher than that of said steel plus Hv 50,wherein said gear is formed by:forming a gear stock of said steel; andsoft nitriding said gear stock in a mixture gas atmosphere containing 50 to 60 volume % of residual NH.sub.3 at a gas temperature of 550 to 560.degree. C.