Objective To make the heating and cooling of the workpiece uniform and the carburized layer of each part of the workpiece uniform, so as to reduce uneven thermal stress and uneven tissue stress and reduce deformation. The clamping method can be changed. Disc parts are perpendicular to the oil surface, shaft parts are installed vertically, and compensation washers, abutting washers, superimposed washers, etc. Can be used. Spline hole parts can be carburized mandrels.