Continuous cooling curves of an extra-low carbon steel under three cooling rates are measured. The flow stress of the steel is established in compression tests during which the temperature is continuously decreasing. The phase transformation temperatures are determined from the cooling rate curve. The latent heat during phase transformation is calculated. A new variable, related to the volume fraction of transformation, is defined. Experimental results show that the relationship between the softening ratio of the flow stress due to phase transformation and this new variable may be described by a quadratic relationship. Based on this relationship and the continuous cooling curves, the flow stresses in the two-phase region are successfully predicted.

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