Research And Optimization Design Of Cavity Wear Of Hot Extrusion Die For Large Diameter Thick Wall Tube

Large-diameter thick-walled pipes are the core structural components of thermal power,nuclear power,petrochemical and other industries,and are often used for large-scale construction load-bearing parts and high-temperature and high-pressure fluid transportation.In recent years,China has made innovative research results in the production process of large-diameter thick-walled pipes,but it is still plagued by die wear problems in the production process,which affects the output and quality of products.In this paper,through the combination of theoretical analysis and finite element simulation,the main factors affecting the wear of the die:the analysis of the extrusion force,and the calculation formula of the extrusion force in the forming process of the large-diameter thick-walled tube based on the upper limit method,combined with the finite element method The best extrusion angle is obtained from 57°to 59°.By analyzing the actual working conditions of the die,designing high temperature hardness,high temperature wear and die softening test,the wear law of hot extrusion die suitable for large diameter thick wall pipe was established.The second development of DEFORM 10.0 software was carried out,and the obtained wear law was successfully applied to the prediction of hot extrusion die wear.Then,using the orthogonal test method,the four parameters of the die cavity were studied:the extrusion angle angle;the radius of approach angle R₁;the radius of entering angle R₂;the land length.The peak value of the extrusion force,the peak value of the die wear,the mean square of the wear,the influence of the mean square error of the metal flow rate,were observed.The peak value of the extrusion force fluctuates little when the angle of the extrusion angle was constant.It was verified that the pre-determined angle of the extrusion angle was optimized for other parameters of the hot extrusion die cavity.The idea was feasible,and finally the best combination of parameters were obtained:the extrusion angle was 58°,the radius of approach angle R₁ was 120 mm,the radius of entering angle R₂ was 120 mm,and the land length h was 120 mm.The Y-coordinate value and wear value of the cavity of the hot extrusion die were taken under the optimal parameters.The BP neural network was used to establish the mapping relationship between the two.The network was used as the fitness function of the genetic algorithm,and the wear was the optimization target.The extrusion die cavity was iteratively optimized,and the result was a cubic polynomial fitting.The cavity curve formula could be expressed as:y?28?368.4856-0.3462?x?10?0.0099?x²-1.5857?10^-5?x³.The three evaluation criteria of wear peak,wear mean square error and metal flow rate variance were used to evaluate the optimization results,and the results were improved compared with the orthogonal test results.Provides technical guidance for the design of large-diameter thick-walled pipe hot extrusion die cavity.