The Study on Worked Quenching of 0.7% Carbon Steel

Abstract

A 0.7% carbon steel was used to investigate the strengthening ratio and the mode of strengthening in the worked and quenched steel, as compared with the conventionally heat treated steel. The 0.7% carbon steel was worked over the temperature range 800°∼1200°C and immediately quenched into water. Then, the hardness of the workeda nd quenched steel and the variation of hardness after subsequent tempering treatment were measured by the Rockwell hardness tester. And the effect of hot working prior to quenching upon the thermal dilatation of the worked and quenched steel was investigated by means of a differential dilatometer. The results obtained are summarized as follows:
(1) Hardness of the worked specimens of austenite at 900°∼1200°C increased gradually as the working ratio increased.
(2) By tempering the worked and quenched steel for 1 hr at the temperature range 100°∼700°C, its hardness began to decrease at the tempering temperature of 110°C. However, the hardness of the worked and quenched steel after tempering was higher than that of the unworked and quenched steel.
(3) The amount of contraction in the dilatation curves at 180°C decreased gradually as the working ratio increased in the worked and quenched steel.
(4) It was observed that the contraction ratio in the dilatation curves of the worked and quenched steel was smaller than that of the unworked and quenched steel after isothermal heating at 122°, 150° and 200°C respectively.