| In this paper, microstructure, phase transformation kinetics, and the micro-alloying elements vanadium of non-quenched and tempered steel F40MnV in the course of cooling after three roll cross-wedge rolling (CRW) have been studied by means of Formast-F dilatometer, Gleeble 3500 thermal simulator, optical microscope, TEM. and other test methods. At the same time, a series of hollow shaft forming experiments have been carried out on DS2000 three-roller CWR. Based on those researches carried out in the laboratory, the model which used to predict the evolution of microstructure of F40MnV was established and programmed.There are some results of the microstructure evolution of F40MnV in the course of cooling after hot rolling: TTT curve of recrystallized austenite; CCT curve of recrystallized austenite. In the course of continuous cooling transformation, the beginning temperature ofγ→αtransformation depends primarily on the austenite grain size, the smaller the grain size is, the higher the beginning temperature. V(C, N) in the existence of austenite promotesγ→αtransformation, the effect of the promotion ofγ→αtransformation increases, while the cooling rate decreases. In the conditions of completed austenitic recrystallization, the greater Z or cooling rate is, the smaller the austenite grain size, the higher the beginning temperature of ferrite and pearlite transformation, the more the volume fraction of ferrite, the higher the hardness of the product. V(C,N) precipitates at dislocation in ferrite. In the conditions of uncompleted austenitic recrystallization, dislocation obviously promotes the V (C, N) to precipitate.The microstructure of CRW sample and hot compressed sample basically have no difference in the same condition of rolling parameters and cooling rate.The input date of the program are rolling parameters an cooling rate and the output data are the volume fraction of ferrite, pearlite, bainite.
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