Numerical Simulation And Microstructure Control Technology Of Heat Treatment Process After Forging For Heavy Supporting Roller

High comprehensive mechanics performance of large forgings is required, andthese indexes are obtained by heat treatment. Heat treatment is the key link to ensurethe internal quality of forgings and meet the performance requirements. Numericalsimulation technology is used for the calculation of large forgings quenchingtemperature field and organization field. It has important significance for theprediction of organization distribution of workpiece after heat treatment and thequality control and guarantee of workpiece.According to the basic phase capacity size relationship of steel, TTT curve ofbackup roll material45Cr4NiMoV steel is measured on Formastor-F automatictransformation tester by expansion method in this paper. The unsteady temperaturefield mathematic model of the quenching process is based on finite element method.The model concerns the influence of material coefficient of thermal conductivity,specific heat and other nonlinear thermal physical parameters. The method of theestablishment of organizational change mathematical model is based on thecombination of phase transition kinetics equation and incubation period superpositionprinciple. It breaks down the continuous cooling process into scores of discrete smallladder cooling process so that every small step can be handled as isothermaltransformation.This paper is based on the diffusion kinetics of phase transformation model whichcombine Avrami equation with the superposition principle, and the non-proliferationphase transition dynamics model K-M equation, using the heat treatment module offinite element software DEFORM. Then the process of3500mm Steckel millsupporting roller heat treatment was simulated, the temperature distribution in theprocess of heat treatment of the support rollers was analyzed, and the tissuedistribution of the supporting roller quenching process was also predicated. This paper combines the Taguchi robust design optimization technology with thefinite element numerical simulation technology, and applies them to optimize thedesign of the large supporting roller quenching process. in order to optimize the designof the supporting roller quenching process. Then the depth from the surface where theMartensite content is50%was regarded as the target feature, the control factors arequenching ways, quenching temperature, cooling time and the quenching mediumtemperature, the noise factors are quenching temperature measuring fluctuations,workpiece transfer time and workshop temperature. According to the simulationcalculation comparison of the initial program and the optimization program, then theMartensite layer depth can be seen deepened significantly. It provides an effectivetheoretical basis for the formulation of heat treatment process for the large forgings.