Study On Friction Performance Optimization And Lubricating Process During Cold Extrusion Forming Of Axle Sleeve

Because of the requirement of working mechanical properties and mass production,cold extrusion is usually used for car axle sleeve.However,the huge friction between cold extrusion die and billet has an important influence on the surface quality of workpiece and die working life.Therefore,it is of great theoretical significance and engineering value to study the friction and wear in cold extrusion process and improvement of control method.Based on the optimization of key forming process parameters and the development of new surface lubrication techniques,this paper explores the influence of different forming process parameters on surface quality,forming load and mould wear.In order to facilitate cold extrusion forming and reduce the amount of mold wear,an effective lubrication process is developed to reduce friction effects.The specific research work is as follows:1.Firstly,the deformation degree of cold extrusion was analyzed and the feasibility programme was obtained.That is the combination of pre-forming process of direct extrusion and final forming process of upsetting extrusion.Then,using DEFORM-3D software as the object of friction and wear research,the finite element model of direct extrusion was established.The influence of three core forming parameters: extrusion speed,die hardness and friction coefficient on surface damage factor,forming load and die wear depth of extruder were analyzed.Furthermore,the change of damage factor and wear depth in the friction area between workpiece and mould was investigated.2.For severe friction and wear phenomenon in cold extrusion process,core forming parameters(extrusion speed,mold hardness,friction coefficient)were taken as optimized variables.The response surface model and finite element numerical simulation were used to optimize parameters of direct extrusion process of axle sleeve in order to obtain the balance of damage factor,forming load and wear depth.The results show that the model forecasting accuracy is high and the response of the objective function to the design variable can be well illustrated.The optimum process parameter combination was obtained,as extrusion speed is 165 mm/s,mould hardness is 62 HRC,and friction coefficient is 0.05.The optimized combination of process parameters can produce cold extruding parts with good surface quality,and can effectively reduce the forming load,reduce mold wear,improve production efficiency,and bring economic benefits.3.A kind of water-based polymer composite lubricant with high energy saving and environmental protection as well as excellent lubricating and reducing properties was developed.The coating was prepared on the surface of low-carbon steel sample by dipping with water-based polymer composited lubricant.The surface tribological properties of polymer composite lubricating coating,phosphorous soap film and non-lubricating treatment were investigated by ball-disk friction test and surface microscopic morphology observation.The results showed that the polymer composite lubrication coating had the same lubrication and friction reduction characteristics as the phosphorous saponification film,the friction coefficient decreased by 67.33% and 68.79% respectively compared with dry friction,and the former was slightly lower by 2.1% in initial 5 min,and friction reduction performance was relatively stable.The surface wear of the polymer composite lubrication coating is minimal,and it is mainly characterized by slight abrasive wear.Finally,through the actual cold extrusion coating test of axle sleeve and observation results of the surface morphology of the extrusion parts of each process,it was shown that the surface quality of workpiece has been significantly improved and the forming load is lighter.Therefore,the surface friction and wear property of low carbon steel can be improved significantly by using coating process to form polymer composite lubrication coating on sample surface.