Study On Substituting Forging Technology For Casting Technology Of Railway Lorry Supporting Pedestal

Supporting pedestal, whose product quality and property have a significant influence on speedup and heavy load of railroad lorry, is the key part of railroad lorry bogie. At present, the products of supporting pedestal are widely formed by the casting technology in the world. In recent years, with the advanced requirements for speedup and heavy load from rail transport, the advanced requirements for the property of supporting pedestal have been proposed. The inherent defectivenesses which include the low mechanical property, low fatigue ductility and low shock resistance of cast-steel product, and the avoidless gas cavity, shrinkage porosity, inclusion, crack, etc in cast-steel product, existed in the product of Cast-steel supporting pedestal, have threatened the high speed and safe running of railroad. Thus, improving the comprehensive mechanical property of supporting pedestal is a grave thesis need to be solved by the Ministry of Railways of China for solving the grave reform and structural adjustment confronted by the rail transport, implementing the advanced technology of heavy load, speedup, and safety, and increasing the transport benefit and efficiency. In order to insure the safety and reliability of running after railroad lorry speedup, a technology that the supporting pedestal is formed by forging instead of casting has been proposed in this thesis to improve the comprehensive mechanical property of supporting pedestal. As the cast-steel product has complex shape and the precise formed cast-steel product has a structure with high rid and thin wall, it is quite difficult to implement the technology of forming supporting pedestal by forging instead of casting. For the sake of reducing the development cycle and cost of the new product, the thesis adopt numerical simulation to improve the product structure and optimize the forming process. The main researches and results are as follows: On the basis of deep research of the key technical matters of structural finite element simulation, the structural mechanics analysis is performed for the railroad lorry turn 8AG supporting pedestal for the first time, using the universal finite element analysis software ANSYS. From the analysis, the stress distribution, strain distribution and safety factor of cast-steel (material is ZG25MnNi) product and forging-steel (material is Q235D) product under workload are obtained respectively. Through the analytical calculation of finite element software ANSYS, the structure and shape dimension of forging-steel supporting pedestal is optimized, the structure of turn 8AG forging-steel product is improved, and the safety factor of product is increased effectively, which provide the technical basis for technology design, and give the guidance for the structure improvement of the other similar forging-steel product. On the basis of deep research of the key technical matters of three-dimensional rigid visco-plastic finite element simulation of the turn 8AG supporting pedestal's forging process, the simulation is performed for the forging process of turn 8AG supporting pedestal for the first time, with the plastic forming simulation software DEFORM-3D. From the simulation, the flow law of metal and the distribution of mechanical field in the blank's forming are analyzed, and some key technical matters in the numerical simulation are handled. Through the numerical simulation for the different technology of supporting pedestal's forging process, the forging technology of forging-steel supporting pedestal is optimized, and a new forging technology and method that two forging-steel products formed in one die and left and right supporting pedestal united as one is adopted and realized for the first time. The turn 8AG supporting pedestal is taken as the study object, and the pilot production of forging-steel supporting pedestal is performed with the modified structure and the optimized forging technology. The results of the pilot production suggest that adopting the forging technology that two products formed in one die is feasible, the forging technology and die design are reasonable, the property of product is stable and credible, and the technology is also spread and applied for the development manufacture of other forging-steel supporting pedestal with the similar type such as turn K2, turn 8G, etc. Failure theory, forging theory, numerical simulation, etc are applied comprehensively in this thesis, the research results of which is a successful example for high and new technology upgrading the traditional forging industry. The researched forging-steel supporting pedestal, whose technology is advanced, scheme is novel, has been ranked as the technological innovation item of Chongqing Science and Technology Committee in 2003. With the research of this thesis, the conclusions are as follows: ①The structural finite element stress analysis is performed for the forging-steel supporting pedestal product with ANSYS for the first time. From the analysis, the structure and shape of the supporting pedestal is optimized, and the structure improvement of product is realized. ②The simulation analysis is performed for the forming process of the forging-steel supporting pedestal with the three-dimensional simulation softwareDEFORM for the first time. From the simulation, the forging technological parameters of the forging-steel supporting pedestal are optimized, and the new forging technology and method that two forging-steel products formed in one die and left and right supporting pedestal united as one is adopted and realized for the first time. ③The pilot production of the product whose structure and technology have been optimized is performed. The results of the pilot production suggest that adopting the forging technology that two products formed in one die is feasible, scheme and die design are reasonable, and the property of product is stable and credible. ④With the numerical simulation technology, the technology that the supporting pedestal is formed by forging instead of casting is realized, and the mechanical property and safety of the product are improved. ⑤The research results of the thesis have been applied for the mass production of the supporting pedestal product successfully, which provides a successful example for the information technology updating and advancing the traditional forging, and bring the remarkable economic benefit and social benefit to the enterprises. Regarded by identify-committee organized by Ministry of Education, the research method of the thesis is advanced, the analysis is reasonable, and the design development of the forging-steel product of the railroad lorry bogie supporting pedestal is solved with digital design and simulation. The research results are placed with the leading position in domestic field.