| Metal injection molding(MIM)technology combines the characteristics of plastic injection molding and powder metallurgy,especially suitable for net forming or near net forming of small and medium metal parts with complex shape.In this paper,the metal powder injection molding(MIM)technology is used to develop the forming process of a military scope-base parts on iron-nickel alloy.In this paper,the gate position and gate type were determined by moldex 3D numerical simulation software according to the formability and feedstock flow length ratio.Using the cooling module of moldex 3D,the cooling efficiency of the cooling water path is compared and analyzed,and the cooling water path design is determined.Through the simulation and comparison experiments of injection parameters(injection temperature,injection pressure and gate flow rate),the flow wavefront,suture line,suture angle,effective holding time,warpage and volume shrinkage of the portal parts under different parameters were analyzed.The results show that when the injection temperature is 195?,the injection pressure is 28Mpa and the gate flow rate is 20cc/s,the numerical simulation result is the best.According to the results of numerical simulation and the feasibility analysis before mold opening,the mold design and manufacturing were completed.The numerical simulation results are verified by injection molding experiments.Due to the error between theory and practice,the packing pressure was optimized to three-stage control after the analysis of injection molding results,which effectively solved the problem of producing vacuum bubble at the position with large wall thickness of the scope-base parts.The forming blank meeting the requirements was obtained.The quality and density of the forming blank were 23.835g and 5.085g/cm~3respectively.The effect of sintering temperature on the microstructure and mechanical properties of the scope-base parts was studied.When the sintering temperature increases from 1265?to 1295?,the mechanical properties of the samples are improved obviously with the increase of sintering temperature.When the sintering temperature is increased to 1320?,the mechanical properties of the samples are reduced due to the abnormal growth of grains and the increase of pores.When the sintering temperature is 1295?,the sintering performance of scope-base parts is the best,the relative density is 96.9%;the dimension is within the tolerance zone,which meets the accuracy requirements,and the hardness range after sintering is 21?23HRC.After heat treatment(quenching and tempering),the tempered martensite structure is obtained.The mechanical properties of the parts are obviously improved.The product process is stable and meets the performance requirements.It can be mass produced. |
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