SHEAVE MEMBER FOR BELT CONTINUOUSLY VARIABLE TRANSMISSIONS AND METHOD OF MANUFACTURING IT

摘要

A method of manufacturing a sheave member 81 for a belt-type continuously variable transmission, including: a forming step where an intermediate body having a sheave surface 815 is formed by applying a forging process to a material consisting of steel; a carburization step where the intermediate body is subject to a carburization treatment by being heated in a carburization gas; a cooling step where gradual cooling is carried out such that the cooling speed is equal to or less than 20° C/sec at least until the temperature of the intermediate body has passed the transformation point A1; a quenching step where water quenching is carried out after a desired portion has been subject to high-frequency heating; and a finishing step where a grinding process is applied to attain the final shape. In the cooling step, preferably, reduced pressure gradual cooing is carried out where gradual cooling is carried out while the pressure of the cooling gas that covers the intermediate body is reduced to be lower than atmospheric pressure.