The Mathematical Simulation Of The Hot Rod Rolling Of Low Alloy Steels

With the development of the rolling technology, the product quality is required higher than ever. The products need not only the qualified dimension, but also the good microstructure and properties. The microstructure and properties of the products are related with the chemical composition and the rolling technologies, which are different in a reasonable range. The changes of the rolling technologies can make the different of the properties of the products. Through predicting the evolution of the austenite size and the flow stress, the models can be useful tools to predict the products properties. Now there are many researches on model of hot strip rolling technologies. Because the rod rolling is a groove rolling, the deformation process of the hot rod rolling is more complicate than that of hot strip rolling. And the prediction of the rod rolling process is more difficult than the prediction of the hot strip rolling process.This paper proposes a model for predicting the microstructure evolution and the flow stress during the rod rolling. Due to the precipitation of Nb(C, N) can stop the growth of austenite, the prediction should discussed in different way. The deformation of the hot rod rolling is more complicate than hot strip rolling, the Max Width method is used to calculate the strain. The temperature model is used to compute the average temperature in each pass. The dynamic recrystallization will occur when the strain exceed the critical strain. When incomplete recrystallization happens, the residual strain will accumulate to the next pass. Combined with the microstructure evolution model, the flow stress can be calculated in different pass.The simulation of the hot rod rolling is proposed by a microstructure model. The prediction is compared of the mill data, and the results are good fit to the actual value. The main method refining the austenite size is the dynamic recrystallization. But when the steel is content of a little Nb, the precipitation of Nb(C, N) will prevent the recrystallization occurring and the austenite size changing. The small austenite size can be got when the dynamic recrystallization and precipitation happen together. The dynamic recrystallization occurs during the initial passes due to the high strains, low strain rates and high temperatures, or in the final passes as a consequence of strain accumulation.