Based on dilatometry tests, the effect of various values of previous deformation on the kinetics of austenite transformations during the cooling of P620Q steel has been studied. Dilatometry tests have been performed with the use of the optical dilatometry module of the plastometer Gleeble 3800. The obtained results were confronted with the metallographic analyses and hardness measurements HV30. Uniaxial compression deformations were being chosen as follows: 0, 0.15, 0.35, 0.7, 1, and 2; note, these are true (logarithmic) deformations. The strain rate of 1/s was used in each case. It was verified, an increasing deformation value causes the growth of the ferrite and pearlite start-temperatures – especially in the areas of higher cooling rates. Based on this, the assumption of acceleration of by-diffusion-driven transformations through the previous deformation has been again verified. With the increasing of previous deformation, a bainite-start temperature was being proportionally growing in the entire range of cooling rates. Nevertheless, the effect of the increasing previous deformation was in the case of a martensite-start temperature entirely opposite.Keywords: Transformation, Austenite, Dilatometry tests, Microstructure, Deformation
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