TRANSFORMATION SUPERPLASTICITY IN THE COMMERCIAL LOW CARBON STEELS UNDER RAPID HEATING.

Transformation superplasticity occurs depending not on the factor of micro-fine structure required in the micro-grained superplasticity but on transformation proceeding under the applied stress. In this report the effects of heating rates upon the transformation superplasticity generated during the isothermal process were investigated in low carbon steels. The main results obtained are as follows. Transformation superplasticity in low carbon steels occurred in the range of 750 to 1050 degree C under rapid heating (the heating rate: 35 similar 100 degree C/sec). The linear law between the applied stress tau and the total strain gamma per cycle was recognized within tau equals 0. 6 kg/mm. Flow curves induced by the transformation superplasticity were determined at each heating rate. The value of the strain rate sensibility m was about 1. Transformation superplasticity was not observed in the A//1 similar A//3 point ( alpha plus gamma ) region during the isothermal process.