Numerical Simulation Of Hot Isostatic Pressing Densification Of CuCr Contact Material

The invention of CuCr contact material is a major breakthrough in the development of vacuum circuit breaker.The traditional powder metallurgy preparation method has the defects of low density,which seriously affects its service life and performance.The hot isostatic pressing(HIP)technology fully fuses the technical advantages of cold isostatic pressing and sintering,so that the green body is compact and compact,and the relative density is more than 99%.However,the traditional empirical test method is used to determine the technological steps,and it is difficult to ensure the quality of products.Based on the theory of continuum mechanics and plastic deformation of porous materials,and the Shima viscoplastic constitutive model of ellipsoidal yield of porous materials was used to simulate the hot isostatic pressing process of CuCr25 contact material by nonlinear analysis software MSC.Marc.The effects of HIP single factor(temperature,pressure,time)on the density of blanks were studied.The results of multiple sets of optimization schemes were comprehensively evaluated.The orthogonal simulation experiment was carried out to introduce the range analysis and further summarize the analysis of HIP The influence of process parameters on the density of CuCr25 powder alloy,the optimal technological scheme and experimental verification were put forward.(1)HIP packing pressure from 90 MPa to 130 MPa,CuCr25 billet average relative density increased rapidly from 0.86 to 0.989,when the powder particles are discrete contactable sintering neck,compact billet densification rate,the final relative density with the guarantee Increase the pressure increase,When the packing pressure exceeds130 MPa,the relative density of CuCr25 compact is basically unchanged,and the densification rate is obviously reduced.At this time,the increase of packing pressure does not affect the relative density.(2)compared with the other three temperature curve program,HIP insulation temperature of 1050°C,CuCr25 compact flow is good,package and compact flow velocity difference is small,is conducive to ensuring the workpiece forming performance,while the compact pressure Distribution is more uniform,the corner of the package due to deformation caused by the stress concentration phenomenon than other programs have eased,reducing the occurrence of crack defects.(3)The influence of HIP process parameters on the density of CuCr25 contacts was obtained by orthogonal experiment.The order of RT temperature> RP pressure> Rh time,The optimum process parameters of the cylindrical CuCr25 contact material HIP are determined as 1050°C×130MPa×temperature rise for 2h,the insulation pressure is2 h,the temperature is reduced by 2h.(4)The experimental results show that the relative density of the center of the compact is the highest,reaching 98.9%,and the corner of the compact and the bottom of the compact are the most important and effective.The density near the end cap is low,the outer part of the package near the uniformity of the poor.CuCr25 contacts increased from the initial relative density of 70% to 98%,the average relative density error of about 1.4%,the simulation results consistent with the experimental results,verify the validity of the model system and reliability.