| The effect of chromium on hardenability in high carbon steel was studied by U-curve method at quenching temperature of 800℃. The relation among the cracking induced by quenching, Ms temperature and hardenability was also studied. The activation energies for growth of austenite grain were as follows. Q_c=23,000 ㎈/㏖ Q_(0.3Cr)=32,000 ㎈/㏖ Q_(0.5Cr)=36,800 ㎈/㏖ Hardenability was dominated under constant heat-treatment condition by amounts of dissolved carbide and the precipitating velocity of carbide from austenite rather than austenite grain size before quenching. At constant hardenability, the cracking induced by quenching was prevented by reducing diameter of specimen and chromium amount. As the hardenability was smaller, the chromium reduction rate for reducing diameter of specimen must be bigger to prevent cracking induced by quenching. |
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