| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a quenching method which, when used for oil-quenching a steel member, can produce a quenched work having a high effective ratio (effective hardened depth/entire carburization depth) and superior toughness in the inside (core) thereof. <P>SOLUTION: The quenching method comprises a first cooling step of cooling a work from a quenching temperature to a first temperature region in which the temperature of the core of the work is higher than the Ms point of the core of the work at a first cooling rate, and a second step of subsequently cooling the work in a temperature region lower than the first temperature region at a second cooling rate lower than the first cooling rate, wherein the first cooling rate and the second cooling rate are controlled so that the surface of the work becomes a martensite structure after quenching, that the effective hardened depth of the work is larger than the depth generated when the work is cooled from the quenching temperature to room temperature at the second cooling rate or is equal to or smaller than the depth generated when the work is cooled from the quenching temperature of the work to room temperature at the first temperature, and that the hardness of the core of the work is equal to the hardness generated when the work is cooled from the quenching temperature of the work to room temperature at the second cooling rate. <P>COPYRIGHT: (C)2013,JPO&INPIT |
