The combined effect of chemical composition and cooling rate on transformation temperatures of hypoeutectoid steels

The transformation temperatures A(r3) and A(r1) of four unalloyed hypoeutectoid steels with a carbon content of 0.029-0,73 % were determined using dilatometric tests. Unusually high cooling rates of 2 and 8 degrees C s(-1) were used intentionally, corresponding to the conditions in the wire rod rolling mills The developed regression models are phenomenological and allow a simple prediction of transformation temperatures, depending only on the cooling rate and the chemical composition of the steel represented by the carbon equivalent (in the case of A(r1)), respectively by the A(c3) temperature (for A(r3)). When calculating the A(c3) temperature, it was worth considering its non-linear dependence on carbon content. It has been verified that the derived equations are applicable even at relatively low cooling rates when the austenite decomposes exclusively on ferrite and pearlite.