ON THE NON-EQUILIBRIUM Fe-Fe//3C PHASE DIAGRAM IN SUPER-RAPID HEATING.

In the present study alpha plus P yields gamma transformation behavior in various carbon steels over the range of up to 10**7 degree C/sec super-rapid heating was investigated. The main results are as follows: (1) The increments of transformation temperatures from the equilibrium points (Ac//1, A//c//3) in various carbon steels with increasing heating rates (up to 10**7** degree C/sec) were determined. A//c//3//f transformation curves of various hypoeutectoid steels are discontinuously jumped in two steps (0. 1%C:150 degree C/sec, 0. 3%C:250 degree C/sec, 0. 5%C:1000 degree C/sec), and with increasing heating rate, the curve approximated to the A//c//3//f point of pure iron. (2) A non-equilibrium phase diagram for less than 1. 4%C is shown. In this diagram the A//c//3//f line is flat ( equals 1130 degree C) and independent of the carbon contents at the heating rate of 10**6 degree C/sec. (3) In the alpha plus P yields gamma super-rapid heating transformation of hypoeutectoid steels there takes place two processes; i. e. , one is the P yields gamma diffusion process and the other is the alpha yields gamma diffusionless process; the former is the remained phase due to super-rapid heating.