Abstract
The cooling curves of quenching oils are obtained using the JIS K 2242 method. The cooling performance of a quenching oil is able to be controlled by varied vacuum conditions, eg. hardness increase of steel is varied according to the vacuum pressure. When insufficient hardness of steel is produced, right selection of vacuum pressure in the vacuum heat treatment may help to result in required hardness of steel. In acutual field operation we can obtain satisfactory hardness and distortion of steel if we select an appropriate quenching oil in combination with right vacuum condition.
