Abstract: There is provided a heat treatment method in which high-quality tempering treatment can be performed in a short period of time. In this method, when an object to be treated is tempered after being quenched, the object to be treated is rapidly cooled to a 90% martensite transformation finishing temperature without being cooled to the ordinary temperature after quench heating, and then is subjected to 100% martensite transformation by using a 100° C. liquid, and thereafter, tempering treatment is performed after the whole of the object to be treated is soaked by using the 100° C. liquid.

Abstract: To provide an arrangement structure of guide chips for high frequency induction heating coil, which structure is capable of correctly positioning the center of a journal portion or a pin portion of a crankshaft, and thereby capable of uniformly applying high frequency induction heating to the journal portion or the pin portion so as to make a hardened case uniform, and which structure is capable of performing the high frequency induction heating and hardening comparatively simply and inexpensively. An upper side guide chip 21a for high frequency induction heating coil is attached to a side plate 7 in a fixed state, and at least one of left and right side guide chips 21b and 21c for high frequency induction heating coil is arranged in the side plate 7 so as to be movable along the radial direction of a journal portion 2 or a pin portion 4.

Abstract: To provide a structure of guide chips for high frequency induction heating coil which makes it possible to correctly position the guide chips for high frequency induction heating coil in the width direction of a journal portion or a pin portion of a crankshaft and which thus makes it possible to correctly position a semi-open saddle type high frequency induction heating coil in the width direction of the journal portion or the pin portion. Each of guide chips 21a to 21c includes: respective pairs of flexible bodies 24a to 24c, which pair are respectively provided in side plates 7 and 7, and have a spring function; a pair of chips 29a and 29a which are arranged and fixed in the inside of the pair of flexible bodies facing each other; and a pair of chip fixing plates 30a and 30a which are respectively arranged and fixed in the inside the pair of chips.

Abstract: There is provided a heat treatment method in which high-quality tempering treatment can be performed in a short period of time. In this method, when an object to be treated is tempered after being quenched, the object to be treated is rapidly cooled to a 90% martensite transformation finishing temperature without being cooled to the ordinary temperature after quench heating, and then is subjected to 100% martensite transformation by using a 100° C. liquid, and thereafter, tempering treatment is performed after the whole of the object to be treated is soaked by using the 100 ° C. liquid.