Numerical Simulation And Experimental Research Water-Air Iniermittent On Heat Treatment Process Of Cr5 Stellbackup Roll

Backup roll is an important part of blooming mill, which directly affects the quality of the rolled products. To obtain high-quality backup roll, heat treatment study of backup roll is another particularly important process, in addition to improve the quality of the backup roll material. In this article, the heat treatment process of Cr5 backup roll was studied through the method of the combination of numerical simulation and experiment,for obtaining a kind of air-water alternating heat treatment process, which meets the requirements of backup roll.Firstly, the continuous curve of transformation and the thermal expansion coefficient the of Cr5 steel were measured by Gleeble-3800 thermal simulator. Besides, the mathematical model of the coupled filed of temperature, microstructure and stress were perfected by the study of the martensitic transformation of Cr5 steel.Secondly, The grid model of Cr5 steel backup roll was generated by the finite element software HYPERMESH, and the final heat treatment process of backup roll was simulated by utilizing the DERORM software. Four kinds of air-water alternating heat treatment process were desigined by controlling different water cooling time and air cooling time. The simulation results of the temperature field, microstructure field and the stress strain field of the backup roll under the four processes were analyzed respectively,and got an air-water alternating heat treatment process meets the requirements of the utilization of backup roll.Finally, the physical simulation and experiments of the backup roll were carried for the process of air-water alternating quenching and continuous spray quenching through the Gleeble-3800 thermal simulator. The mechanical properties and the organization composition of Cr5 steel specimens under two kinds of heat treatment processes were measured by tensile test, impact test, hardness test and metallographic experiment. Experimental results show that the strength, plasticity and toughness of the microstructure after air-water alternating quenching were improved obviously than the microstructure after continuous spray quenching. Although the strength and hardness of the microstructure after air-water alternating quenching was slightly decreased, the hardness of both processes were still satisfying the requirement of the backup roll. The residual Austenite is obviously improved after alternating water- air quenching treatment,which is the main reason for the increase of its plasticity and toughness.