The characteristics of the formation of austenite in eutectoid steel

This paper is a report of the investigations carried out to determine the effect of microstructure on the rate and nature of the formation of austenite in some commercial steels. Previous work is reviewed and compared with the results of current experiments. Experimental procedure is briefly discussed. Steels used for these experiments were similar to the following S.A.E. specifications; 1020, 1045, 1080, 4140, and 52100. Studies of the 1080 type form the greater part of the work. Results are presented in graphs of hardness against time-at-austenitizatlon-temperature and in a series of photographs showing various stages of transformation for different prior structures. Conclusions drawn from results are discussed. The processes of nucleation and growth of austenite in pearlite, spheroidite, bainite, martensite, and sorbite are examined. The effects of lamellar spacing, size and distribution of spheroids, and proeutectoid constituents are noted, together with general considerations such as stability of micro-structures. The effect of chromium is briefly discussed. Possibilities for future work on austenitizatlon are presented, with emphasis on induction heating and flame hardening.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat