| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for discriminating the propriety that the variation in the carburizing and quenching strain of a gear composed of steel for carburizing lies in a fixed value or below for obtaining a gear with high precision without performing grinding and polishing for gear teeth. SOLUTION: In parts composed of low carbon-containing low alloy steel for carburizing, by allowing the hardness of the noncarburized part after carburizing and quenching to satisfy inequality (1), the propriety of the variation in the strain amount by carburizing and quenching in the steel parts for carburizing is discriminated, and a gear 1 by carburizing and quenching in which the variation in the pitch shown by the interval 5 by the measurement of the base tangent length shown in figure 1 is extremely small can be produced with high efficiently: 7.5×(effective hardening depth)1/2+100×(the content of C in the core part)+5.2<=the hardness of the noncarburized part<=7.5×(effective hardening depth)1/2+100×(the content of C in the core part)+11.2...(1); wherein, the unit of the effective hardening depth is denoted by mm in the hardness of HV 550, the content of C in the core part is denoted by mass%, and the hardness of the noncarburized part is denoted by HRC.
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