Numerical Simulation And Process Optimization Of The Cr8 Steel Working Roll Quenching Process

As a consumable part of the mill, the working roll is used to make plastic deformation of the rolling material,whichhas a great influence onproduction efficiency and product quality. Since its working conditions are very complex, usually need to bear abrasion, dynamic load and severetemperature change,the requirements of service performance are extremely stringent.In order to enhance the service performance of working roll, not only need to strictly control the quality of forging, but also should constantly improve the heat treatment process.The heat treatment process has a tremendous impact on the final service performance of the working roll.First of all, the phasetransformation process for Cr8 steel in stages of heating and quenching was analysedthrough experiment. By the researchof phasetransformation of austenite in different heating rates, the relationship between heating rate and start point and end point in phasetransformation of austenite was got, and the CHT curve for Cr8 steel was protracted, and the mathematical model of graingrowth for Cr8 steel was established by using the sellarmodel, which provided the theoretical guidance for the craftwork in heating process; through the test of phase transformation for Cr8 steel in different cooling rate, the point of phasetransformation in continuous cooling rate for Cr8 steel was got, and the CCT curve for Cr8 steel was protracted.Then, the geometric model and numerical simulation modelwas established with the prototype of Cr8 steel large working roll in a certain factory.The basic parameters, such as thermal conductivity, thermal diffusivity and so on, were measured by the experimental method,and the numerical simulation mathematics library was perfectecd. The heating process and quenching process of the Cr8 steel working roll was simulated by utilizing the DEFORM software,and temperature field, microstructure field,stress field distribution and the evolution rules were analyzed.Thirdly, in view of the problems of large residual stress and shallow hardening layer in the original process, the robust design of quenching process was carried out by means of the Taguchi method. By selecting the influence factor and the noise factor, the quenching time, quenching method and quenching process parameters were optimized; Through the analysis of the signal to noise ratio and variance of a large number simulation data, a new quenching process was developed, which was based on multiple factors.Finally, the new quenching process was numerically simulated, and compared with the original process in the performance parameters. The results show that the residual stress of Cr8 steel roll is greatly reduced under the new quenching process, and the depth of hardened layer has been increased, so it is proved that the new quenching process is practical and effective,which provides an important reference for the design and optimization of the quenching process of Cr8 steel working roll.