| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing machine parts of a steel by which a blank of steel parts is made, and at least the surface parts of this blank are subjected to carburizing or carbo-nitriding treatment. SOLUTION: This steel has a chemical compsn. contg., by weight, 0.15 to 0.35% C, 0 to 0.6% Si, 0 to 5% Mn+Cr+Mo, 0 to 0.1% Al, 0 to 0.5% Cu, 0 to 0.15% S and <=0.03% P, furthermore contg., at need, <=0.02% tellurium, <=0.04% selenium, <=0.07% lead and <=0.005% calcium, and the balance iron with impurities caused by melting, and the chemical compsn. of the steel is regulated in such a manner that the Jominy curve of the steel satisfies 45HRC <=J3 <=50HRC, 39HRC<=J11 <=47HRC, 1HRC<=J25 <=40HRC and the average values of five Jominy tests J3m , J11m , J15m and J25m satisfy|J11m -J3m×14/22-J25m×8/22|<=2.5HRC and J3m -J15m <=9HRC.
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