Research On Hydrostatic Extrusion And Die Structure Design Of Magnesium Alloy

Magnesium alloy has many advantages,such as low density,high specific strength,good heat dissipation and vibration reduction.However,its plasticity is poor,and it is not ideal in plastic forming.Hydrostatic extrusion is often used to process materials with poor plasticity.In this paper,the forming of tubes,rods and profiles is studied by means of hydrostatic extrusion.Tube forming with rear and front needle core is divided into two ways,with the dynamic type and fixed type structure of two kinds of needle punched.Post core mode,core angle of 1200°need more extrusion pressure than 105°,There is a linear relationship between the extrusion pressure and the natural logarithm of the extrusion ratio,The extrusion pressure can be reduced by increasing the temperature of extrusion cylinder,but decreases with the mold structure;material velocity where the dramatic changes in the core,the middle section view can be seen blank fast flow rate.In the two kinds of piercing pins,the extrusion pressure is small when the extrusion ratio is 1.3.The internal stress of the blank in the forming,the maximum value of follow-up 191MPa,fixed 214MPa.The forming method of single hole and porous die has been studied.The single hole mold takes into account the characteristics of the conical die and the flat die.Through orthogonal test to determine the extrusion ratio is 16,the mold cone angle of 75°,the design scheme of bearing length of 8mm platform and fixed length 2.5mm.Porous mold in the extrusion ratio is 12,two holes,four holes and three design has little effect on the stiffness and strength of extrusion and mould.Then for the four hole die,extrusion pressure is the biggest influence of the mold temperature,followed by the die entrance shape,impact on the uniformity of velocity is the largest die hole layout,followed by the die entrance shape,integrated both determine die hole concentric diameter 26mm the die entrance shape with deflector structure,sizing with 6mm the mold temperature is 290?.The key of mould design is to make the flow velocity of the same section of the product uniform.The extrusion ratio is 16,the selection of mold structure with the diversion chamber,the structure and size of using neural network and genetic algorithm was optimized in order to achieve the goal of uniform flow velocity,flow rate variance before and after optimization were 1.03 and 0.0674.The profile die is more complex,it is used to analyze the strength and wear of the die,and the stress of the die meets the requirements of the materiaLWear analysis of die hardness and contact friction factor.