Prediction of Deformation Resistance of Low Carbon Steels during Hot Rolling

Phenomenological approach to the description of deformation resistance behaviour of steel and its microstructure development under the service hot rolling condition is still the most common useful and powerful. Utilising different experimental equipment such as torsion plastometer [1-5], compression plastometer [6-9], or advanced laboratory mills [10, 11] as well as different deformation techniques such as single step deformation and repeated deformations [12], compression [6, 7] test or stress relaxation method [8, 9], forward (monotonic) or reversed deformation [13], is possible to predict microstructural changes and flow stress curve of material on the service hot rolling mill with fairly good accuracy. The main problem of above mentioned approaches and based on them models is that they operate only with narrow range of chemical composition of investigated steel or consider particular processes in material during hot rolling such as static and dynamic recovery, dynamic, static or metadynamic recrystallisation (SR, DR, DRX, SRX and MDRX respectively), i.e. softening/hardening behaviour Deformation behaviour of low carbon steels under hot rolling service conditions is predicted utilising a combination of isothermic single step deformation test, anisothermic interrupted test and hot rolling simulation performed on torsion plastometer. The stress σ0.05 at strain level ε = 0.05 and the restoring factor fr are proposed to be used for the description of the strengthening / restoring process during repeated deformation.