日本金属学会誌

J. Japan Inst. Metals, Vol. 39, No. 3 (1975),
pp. 255-261

On the Non-equilibrium Fe-Fe3C Phase Diagram in Super-Rapid Heating

Nobuhiro Iguchi1, Kiyoshi Yokota2 and Yoshiyuki Miwa3

1Faculty of Science and Engineering, Waseda University, Tokyo
2Faculty of Science and Engineering, Waseda University Tokyo. Now, Emeritus Professor of Waseda University
3Graduate School, Waseda University, Tokyo

Abstract:

In the present study α+P→γ transformation behavior in the various carbon steels over the range of up to 107°C/sec super-rapid heating was investigated in the same method as previously employed for eutectoid steel.
The main results obtained are as follows:
(1) The increments of transformation temperatures from the equilibrium points (Ac_1, Ac_3) in various carbon steels with increasing heating rates (up to 107°C/sec) were determined. Ac_3f transformation curves of varioud hypoeutectoid steels are disconteniously jumped in two steps (0.1%C: 150°C/sec, 0.3%C: 250°C/sec, 0.5%C: 1000°C/sec), and with increasing heating rate, the curve approximated to the Ac_3f point of pure iron.
(2) A non-equilibrium phase diagram for less than 1.4%C steel was shown. In this diagram Ac_3f line is flat (=1130°C) and independent of the carbon contents at the heating rate of 106°C/sec.
(3) In the α+P→γ super-rapid heating transformation of hypoeutectoid steels there takes place two processes; i.e. one is the P→γ diffusion process and the other is the α→γ diffusionless process, the former is the remained phase due to super-rapid heating.


(Received 1974/08/15)

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