Abstract: A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T1) equal to or higher than a tempering temperature (T0) of the second steel component and higher than a temperature of the first steel component by a temperature difference (?T) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.

Abstract: A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T1) equal to or higher than a tempering temperature (T0) of the second steel component and higher than a temperature of the first steel component by a temperature difference (?T) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.

Abstract: A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T1) equal to or higher than a tempering temperature (T0) of the second steel component and higher than a temperature of the first steel component by a temperature difference (?T) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.

Abstract: A gas quenching method of the present invention includes a first stage (t1 to t2) at which a workpiece is subjected to a rapid cooling by forcibly circulating a cooling gas, a second stage (t2 to t3) at which the circulation of the cooling gas is stopped and pressure is reduced inside the furnace to conduct heat insulation, and a third stage (as from t3) at which the workpiece is cooled again by the cooling gas. At the second stage, the workpiece is maintained at an intermediate temperature that is higher than martensite transformation start temperature, and, during this, temperature throughout the workpiece is made uniform. Therefore, it is possible to achieve a uniform quenching and suppress distortion caused by difference of the cooling speed.