Research On Resistance Heating Bending Of S355J2W Steel Bogie Cover Plate

The bogie cover plate is one of the most important parts of railway vehicles.At present,most of them are manufactured by cold forming at room temperature.However,the formed parts often have the disadvantages of low accuracy,large springback,and poor quality.By warm and hot forming method,the forming ability of materials can be significantly improved,so the forming parts with higher accuracy can be obtained.Compared to the traditional heating method such as furnace heating,the resistance heating method can make the forming blank heated to a desired temperature in a short period of time,significantly improving the forming efficiency and saving the energy.In this dissertation,the S355J2 W steel was chosen as the experimental material.The resistance heating forming experiment of scale-down part of a bogie cover plate were carried out and the quality of formed parts were studied,thus investigating the application in the actual manufacturing process of bogie cover plates by resistance heating forming.Firstly,the range of current density used in the resistance heating forming was determined by the resistance heating experiment of S355J2 W steel and the temperature distribution of the S355J2 W steel plate under resistance heating and the deformation during forming were simulated by finite element method using MSC.Marc software.The resistance heating forming experiment of scale-down parts was carried out at different current densities,and the precision of the parts was compared to those obtained by cold forming at room temperature.It is found that as the current density increases,the forming accuracy of parts is significantly improved.What is more,the forming efficiency and surface quality are superior to the parts formed by furnace heating method.At the same time,the reliability and stability of resistance heating forming is verified.In order to determine the effects of resistance heating on the springback of parts and whether the quality of the parts after resistance heating forming can guarantee their using performance,the springback,the microstructure and the mechanical properties of the parts were studied.The results show that with the increase of current density,the springback displacement decreases.By resistance heating forming,the springback problem is not only significantly improved,the defects in the microstructure at the room temperature forming are also eliminated,causing the mechanical properties of the part increased.Among them,the tensile strength of parts can be increased by up to 13.6%,hardness can be increased by up to 13.9%,elongation can be increased by up to 23.7%,impact toughness can be increased by up to 34.2%,and the quality of molded parts can be improved.The result of resistance heating forming experiment of the scale-down parts shows that when the current density is 3.57 A/mm~2,the forming temperature can reach 450.9 ? in 10 minutes.At this condition,the precision,the springback and the quality of the formed parts are obviously improved.According to the finite element simulation results of the resistance heating forming process of the bogie cover plate,the position of electrode,heating method and the shape of the blank in the actual manufacture of bogie cover plate were studied.At the same time,the optimum process temperature is about 450 ?.The design of the semi-automatic resistance heating forming equipment was realized,and the process flow of resistance heating bending of the actual bogie cover plate was determined,which ensures the stability,high efficiency and energy saving of the part during production.What has discussed above embodies the advantages of resistance heating forming compared to the method of cold forming and furnace forming.