Die Structure And Process Parameters Optimization Of Hot Extrusion For Austenitic Stainless Steel Pipes Based On Numerical Simulation

Hot extrusion is the advanced production process for high-performance austenitic stainless steel pipes.The die structure and process parameters of hot extrusion have a great influence on the pipes quality,extrusion energy and die life.The optimization of die structure and process parameters has become the main approaches for improving product quality and reducing production cost.With the development of computer technology,numerical simulation has become an effective tool for dies and process analysis and optimum design of the metal plastic forming.The preliminary design of hot extrusion die structure and process for the typical pipe specification AISI304 were carried out,based on which the numerical simulation model for hot extrusion was established as well.The hot extrusion process with cosine curve die cavity was analyzed coupling deformation and heat transfer by the finite element software DEFORM-2D.Through the simulation,the detailed distribution such as strain field,stress field,velocity field,temperature field,as well as the load-stroke curves,temperature field and wear of dies were obtained.In order to reduce extrusion load and improve deformation uniformity of AISI304 pipes,with the same area reduction ratio,the important die structure and process parameters,including die cavity type,container height,extrusion velocity and deformation temperature,were optimized by comprehensive application of orthogonal experiment,numerical simulation and gray relational analysis.For the single-objective optimization of less extrusion load,the effect of deformation temperature was significant.When the deformation temperature of 1175℃,extrusion velocity of 200mm/s,using the die cavity with cubic curve and 50mm height,the extrusion load was minimum;For the single-objective optimization of uniformity,the effect of extrusion velocity and deformation temperature were significant.When the deformation temperature of 1150℃, extrusion velocity of 100mm/s,using the die cavity with cubic curve and 50mm height,the deformation was the most uniform;For the multi-objective optimization of less extrusion load and deformation uniformity,the optimum parameters were as follows:1150℃(deformation temperature),100mm/s (extrusion velocity),die cavity with cubic curve and 50mm height.Owing to the disadvantages of the traditional process of austenitic stainless steel neck flange with a large hole,a new upsetting-extruding process with tubular billet was presented.The upsetting-extruding process of AISI304 austenitic stainless steel flange was simulated by the DEFORM-3D software, the result of which showed that the process was feasible.Our results and conclusions will provide relative guidance or reference for the practical production.