Thermal contraction while cooling was prevented as a representation of a special thermal stress in the surface layer of steel induced by quenching. The effects of such thermal stress on retained austenite (γR) were as follows. (A) Experiments on high carbon alloy steels. (1) The tensile stress induced by preventing the thermal contraction increased linearly with decreasing temperature and indicated the maximum value at Ms temperature, that was about 10 kg/mm2. (2) The amount of γR was markedly increased by preventing the thermal contraction. This is contrary to the expectation from the mechanism of martensite transformation which has been interpreted from the criterion of shearing stress. (3) The effective temperature range of stress on γR existed between 100∼150°C above Ms point and room temperature. (4) The rise of cooling speed at the range of above Ms temperature increased the amount of γR as the result of increment of induced tensile stress. (5) Below the Ms temperature, the rise of cooling speed decreased the amount of γR, similarly to free contraction cooling. Therefore it appears that there is no effect of stress on the thermal stabilization of austenite. (B) Stabilization of austenite by preventing thermal contraction was not observed in medium and low carbon alloy steels, and in low carbon alloy steel the amount of γR was decreased, contrary to the case with high carbon alloy steels.
(Received September 5, 1960)
* This paper was published in originally in Japanese in the Journul of the Japan Institute of Metals, 23 (1959), 299.
** Faculty of Technology, Hokkaido University.
© 2002 The Japan Institute of Metals
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