Theoretic And Experimental Research On Three-Roll Cross Wedge Rolling Of Non-Quenched And Tempered Steel Hollow Shafts

Cross wedge rolling is a efficient shaft processing technique. It has advantage on saving sources that the non-quenched and tempered steel used in cross wedge rolling. In this paper, with a investigation of three-roll cross wedge rolling, the hot-forming microstructure changes of non-quenched and tempered steel were investigated. Numerical simulation for hot-forming process of non-quenched and tempered steel hollow shaft is executed with the thermal, mechanical and microstructural evolution coupled. And then simulation results are verified in combination with actual rolling experiments.In the paper, compressed tests were carried out by using thermo-simulation machine Gleeble-3500. The mechanical behavior and microstructural changes of the typical shaft non-quenched and tempered steel 40MnV for cross wedge rolling are investigated by using single/double-hit compressed tests and metallographic analysis. Mathematic models were established, involving: grain growth model during reheating, mathematical empirical equations with the kinetics of dynamical recrystallization model during hot forming, dynamical recrystallized grain size model, the kinetics of static recrystallization model after hot working and grain size model, grain growth model after recrystallization, mathematic model of deformation resistance. Also, the restraining functions of carbonitrides have been investigated, which were acted on on reheating and recrystallization process. The establishment of all of these models lays a foundation for further developing controlled rolling, virtual simulation of part rolling process and prediction on microstructural properties.Non-linear rigid-plastic finite element method model has been build for simulating the three-roll cross wedge rolling process of steel 40MnV hollow shaft with the thermal, mechanical and microstructural evolution coupled. The model has been build on the platform of DEFORM software with the aid of redevelop based on the mathematic models obtained from physical simulation tests. The distributions of temperature strain, strain rate, stess and grain size of workpiece were analyzed respectively. The hot rolling experiments were carried out by three-roll cross wedge rolling mill. The microstructural models obtained from physical simulation tests were validated by contrasted with grain sizes of workpiece. The visual program for steel 40MnV rolling microstructure changes was developed by VB6.0 programming language based on the mathematic models in this paper. It can realize prediction on microstructure by changing technological parameters and guided the actual manufacture.