The mathematical model of hot deformation resistance with reference to microstructural changes during rolling in plate mill.

Abstract

Single-stage and multi-stage tension tests of Si-Mn and Nb steels have been conducted in the temperature range of 800 to 1000°C at strain rate of 1 to 10sec-1 in order to evaluate the effect of metallurgical factors on hot deformation resistance. The flow stress for both steels has been found to be expressed by Misaka's type equation. But strain rate exponent, which is constant in Misaka's equation, is temperature dependent. The flow stress increases with decrease in austenite grain size and the addition of Nb. Nb in precipitation is, found to cause the larger increase of the flow stress than Nb in solution. The flow stress in multistage tension test can be expressed by above-mentioned modified Misaka's equation if the strain term is replaced by the term considering strain accumulation. The strain accumulated during rolling can be expressed as a function of the observed deformation resistance and the calculated one for strain free austenite. With this method on-line real time evaluation of static restoration process is practicable. On the basis of the experimental results, a mathematical model for prediction of roll force calculation in plate rolling has been developed. The roll force can be calculated with good accuracy by the model.