Forging Experiment And FEM Simulation Of 3Cr2MnNiMo Steel

3Cr2MnNiMo plastic mold steel has a very good hardenability and polishing,it is the priority choice to create large cross-section of high-quality steel mold,and the plastic mold steel market demand is relatively large,the domestic high-quality plastic mold steel is relatively small,So it is significant to study 3Cr2MnNiMo plastic mold steel.The research of this thesis was supported by the "13th Five-Year" National Key Research Project of China(2016YFB0300402),"High Performance Tool Steel and Its Application".In this thesis,the 3Cr2MnNiMo plastic mold steel is taken as the research object.The homogenization and organization were analyzed by forging experiments.The finite element software ABAQUS was used to establish the forging finite element model.The metal flow law,stress-strain,temperature change and forging quality of the forging were analyzed.The main research contents and conclusions are as follows.(1)The solidification structure of 3Cr2MnNiMo steel was observed,and dendritic segregation was clearly observed from the edge to the heart.Normalizing,quenching and tempering of the sample has a typical tempered sorbite structure,compared with the one upsetting process,the sample organization of the two upsetting was more small and uniform,indicating that under the same heat treatment process,two upsetting forging process can get a better organization;(2)Compared with the results of microstructure and surface sweep at 1200℃ high temperature diffusion,it can be seen that the dendrite segregation can be obviously improved with the increase of holding time at the same diffusion temperature.The dendrites arms and dendrites gradually become blurred or indistinguishable,and the elemental distribution is gradually uniform.For the 3Cr2MnNiMo steel,the diffusion speed of Mn and Ni elements is higher than that of Cr element at 1200℃;(3)The average hardness of one upsetting without heat-treated is 371.6 HV,and the variation of hardness at different locations is large,mainly because the tissue distribution is not uniform.After normalizing and quenching of the two forging methods,the average hardness after one-upsetting was 432.8HV and the hardness difference is 15.8HV.The average hardness after two upsetting is 439.7HV and the hardness difference is 10.5HV,Compared with one upsetting process,the hardness distribution is more evenly.The impact test was carried out after the heat treatment for the two forging process,the impact toughness difference of one upsetting and two upsetting is not large,mainly because of the smaller sample size,using one upsetting and two upsetting has little effect;(4)The forging quality measurement standards were studied,the homogeneity and isotropy of the die steel were discussed,and the calculation method of the forging ratio was summarized and analyzed.The upsetting ratio and the stretching ratio were calculated separately to measure the overall degree of deformation of the metal.It was proposed that calculating the cumulative deformation work through the finite element analysis,the isotropy of die steel is measured by the ratio of three-way cumulative deformation work;(5)The forging process was simplified,and the coupled finite element model of forging thermal coupling was established.The true stress and true strain curve of 3Cr2MnNiMo steel were determined by thermal simulation test.Through JMatPro software,the thermal conductivity and specific heat parameters of 3Cr2MnNiMo steel were calculated,and the boundary conditions were determined;(6)The whole process of forging finite element analysis of the test steel was carried out.From the aspects of temperature field,stress field,strain field,forging quality and drum coefficient,the influence of axial upsetting method and cross-forging method on the quality of forgings was compared.The results show that the use of repeated axial upsetting and cross-heading forging has its own advantages and disadvantages,but the axial upsetting forging method is simple and easy to operate;(7)The direction cumulative deformation work of the two forging methods was calculated.Under the same forging ratio,the deformation work ratio of axial upsetting is larger,and the overall deformation degree is more uniform.With the axial repeated upsetting method,the cumulative deformation work under different forging ratios was calculated.The results showed that the cumulative deformation work was increased with the increase of forging ratio.