Numerical Simulation And Experimental Research On Compression And Quenching Process Of 42CrMo Steel

As the manufacturing level is continuously promoting,the quality requirements of complex and precise mechanical equipment and parts are becoming higher and higher,and plastic processing technology and heat treatment technology are important means of material forming and improving material performance,playing a key role in the manufacturing processing industry.During material treating processes,the final performance of the material is affected by many factors,such as loading speed,geometrical shape,friction and contact conditions in plastic processing,and temperature distribution,microstructure distribution and stress distribution in heat treatment.If the process parameters are explored and designed only by experiments,it is time-consuming and labor-intensive and cannot meet the requirements of actual production.At this stage,the numerical simulation of plastic processing and heat treatment process can be carried out by computers to assist process design and process optimization,shorten the cycle of research and development,improve product quality and reduce costs.Therefore,it is of great significance to study how to improve the accuracy of numerical simulation.42CrMo steel contains various alloying elements such as Cr and Mo.It has excellent comprehensive mechanical properties with both high strength and good plasticity,widely used in forgings,especially large-scale forgings.In this paper,a combination of computer simulation and experiment is used to construct a comparative accurate constitutive model and material performance database of 42CrMo steel.Besides,the computer simulation and experiment of material deformation and heat treatment quenching process are carried out,and the simulation results agree well with the experimental results.The stress and strain data of 42CrMo steel at different temperatures and strain rates are measured by hot compression experiments.And then the improved Johnson-Cook constitutive model and the strain-compensated Arrhenius constitutive model are constructed.The stress and strain data of 42CrMo steel are obtained under the conditions of the strain within 0-0.9.The TTT curve of the standard 42CrMo steel in the manual is fitted to obtain accurate data of TTT curve.In addition,a relatively complete and accurate 42CrMo steel database which included thermal conductivity,specific heat capacity,Young's modulus,Poisson's ratio,latent heat of phase change,expansion coefficient and other parameters is constructed.Based on the constructed database,DEFORM software is used to simulate the thermal compression process of 42CrMo steel at a deformation temperature of 1123 K and a strain rate of 0.01 s'1.The size data of samples and load-stroke curve of Top Die of the simulation results and the calculated stress-strain curve are compared with the measured results obtained under the same experimental conditions.The results show that the numerical value and variation trend of load-stroke curve and stress-strain curve are consistent with experimental results,respectively,indicating that the strain-compensated Arrhenius constitutive model can accurately describe the deformation behavior of 42CrMo steel.The DEFORM software is used to simulate the end quenching process of 42CrMo steel at 1123 K.The results show that the heat exchange between the end of the sample and water is violent,the temperature drops rapidly,and a large amount of martensite structure is formed.With the distance away from the quenching end,the content of martensite gradually decreases,and the hardness also decreases.At the same time,the end quenching experiment under the same conditions is carried out.The axial hardness distribution of the sample after quenching is measured,and the composition of structures at different position is observed.The experimental results are basically consistent with the simulation results,which manifests that the numerical simulation database of 42CrMo steel constructed in this paper is comparatively accurate.Based on this,numerical simulations of different geometries,different deformation conditions and different heat treatment processes can be carried out,laying a good foundation for the simulation and optimization of the actual production process.