| 摘要 |
PURPOSE:To obtain a knockout pin having superior toughness by working a steel bar having a specified composition subjected to soln. heat treatment to a prescribed shape and by carrying out gas nitriding at a specified temp. to increase the surface hardness. CONSTITUTION:A steel bar consisting of, by weight %, <=0.05% C, <=0.3% Si, <=0.3% Mn, 5-13.5% Ni, 2.5-8.0% Cr (Ni+Cr=13.5-19.0%), 1.5-5.0% Mo, 0.1-0.8% Al, 0.1-1.0% Ti, 2.1-4.0% Co and the balance Fe with impurities is subjected to soln. heat treatment including air cooling from about 820 deg.C. It is worked to the shape of a knockout pin, and gas nitriding or gas soft-nitriding is carried out at about 470 deg.C to increase the surface hardness Hv to >=about 900 and the internal hardness HRC to about 49.
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