抄録
The course of transformation of 0.68% carbon steel after rapid heating to austenizing temperatures has been investigated using hardness measurement and microscopic and dilatation techniques. The steel specimens used for the investigation have the structures with lamellar, and spheroidized pearlites and the structure consisting of spheroidized pearlite with graphite nodule. The rate of austenite formation for the lamellar pearlites is greater than the spheroidized pearlites and a finer pearlite gives a more rapid transformation than a coarse one, and when the spheroidized specimen contained graphite, a very long time is necessary for arriving at an austenite state of equilibrium. The austenizing curves obtained from hardness measurement of spheroidized specimens show a sigmoid shape, on the other hand, the austenizing for the lamellar specimens is completed more quickly after a certain incubation period. The explanation of time required to complete the transformation for the structural variables as a function of ferrite-cementite interfacial area is not sufficiently conclusive.
