Application Of WEL-TEN780A Steel To Railway Freight Wagon In Large Size

At present, various high strength steel have been applied to the wagons in large size in China and outside China so as to reduce tare weight and increase loading capacity by means of enhancing allowable stress of the material. Such material has been adopted to our domestic wagons in large size in terms of 16Mn, 15MnVN and WEL-TEN780A with yield limit of 343Mpa, 441Mpa and 685Mpa respectively, whose yield limit is 1.46 times, 1.88 times and 2.915 times respectively of yield limit of 235Mpa for Q235 material. Among those material, yield limit of WEL-TEN780A is max. one of the material so far applied to Chinese wagons in large size, therefore, it is necessary to carry out research on welding and assembly procedure of WEL-TEN780A steel. Special procedure of WEL-TEN780A creates enormous difficulty for ensuring manufacturing quality of the steel structure as follows: a. As such steel is of high strength steel with poor welding procedure performance, hence, cracks will be easily generated, welding heat effected area softened and impact ductility decreased as well. b. If the steel is cut by the flame, welding won't been performed until the hardened layer is removed by means of machining. Hence, in the process of parts assembly, flame cutting is forbidden to be applied, otherwise, parts and components will be scraped after being cut by the flame. c. Because the steel is cut by the flame, the heating temperature of the steel is no more than 600?C, method of heating won't be permitted for eliminating excessive clearance between the pressed part and other part. If the deformation is too big after the part welded, method of flaming verification is not allowed, that is to say, these parts after welding shall be requested to conform to technical requirements as set. The above three points mean that flame cutting for parts mating and verification is cancelled in the whole production process for assembly of these steel structure parts, which rail freight wagon industry never experiences such practice in manufacturing. With research on procedure of WEL-TEN780A steel, on the basis of various function, pressing and machining procedure of WEL-TEN780A steel parent metal and welding joints, welding procedure, pressing procedure and regulation of WEL-TEN780A steel are defined, which have been performed strictly in production course of 320 ton depressed center flat wagon in terms of steel plate cutting, single part machining, parts group welding and assembly of the complete part adhering to the guideline of the single component ensuring the part & the part ensuring the complete equipment. The procedure quality in all aspects is guaranteed by means of settlement of hard points in terms of deflection of the complete part, WEL-TEN780A steel welding quality and assembly quality. The latter tests such as static strength test have proved that welding and pressing procedure of WEL-TEN780A steel is set reasonably. The research and experience of WEL-TEN780A steel applied to 320 ton depressed center flat wagon have indicated that the steel can be applied to railway freight cars in large size with appropriate procedure means for control of WEL-TEN780A steel. The service and maintenance of Chinese domestic railway freight cars will be upgraded in research, design, manufacturing. The economic benefitsand social benefits will be gained after being put into service.