THE DIMENSION CHANGE OF CASE-HARDENING STEELS RESULTING FROM CARBURIZING AND HEAT TREATMENT

Abstract

The dimension change of case-hardening steels resulting from carubrizing and heat treatment was investigated. Cylindrical specimens made of low carbon Cr-Mo and Ni-Cr steels were used. They were normalized, carburized, quenched, (sub-zero treated) and then tempered in accordance with usually adopted methods, and the dimension change was measured with a precise comparator at each heat treatment step. The results wefe as follows. There was no substantial difference between Cr-Mo and Ni-Cr steels with respect to dimension change resulting from carburizing and heat treatment, but fibre structure caused by rolling had an intimate relation on the dimension change of both steels. The mechanism of this phenomenon was explained by the heating and cooling transfgrmation curves gained through a Leitz dilatometer.
In conclusion, the author proposed some recommendable methods of carburizing and heat-treatment according to his experimental results.