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About the author: Li Jialiang, born in 1956, is a professor-level senior engineer and an international welding engineer. Mainly engaged in the research of railway truck manufacturing process. He is currently a company expert and enjoys special government allowances. He has served as a council member of the sixth, seventh and eighth (2000-2011) of the China Welding Society.
First, the development of truck welding technology
In the early 1950s, China began to imitate trucks. First, the C1 30T gondola was imitated, and the steel frame was used for riveting steel and steel. With the needs of modern industrial production and the rapid development of science and technology, the continuous advancement of welding technology, the introduction of welding into the manufacture and repair of rolling stock, and gradually replaced the riveted structure with welded structure, the truck from the steel-wood mixed structure into the all-steel structure. It has successively built open cars, flat cars, box cars, tank cars, hopper cars and long special vehicles.
As a means of welding, welding must be completed by "micrometallurgy" in the short time of solidification of the molten pool, and once successful, it is impossible to analyze the base metal, select the welding material, and test the process parameters. In order to weld welding equipment and equipment, and to train welders, welding joints that meet the requirements can be welded.
1. Development of materials for trucks
In the 1950s and 1970s, steel for vehicles used Q235 ordinary carbon structural steel and welded with structural steel rod represented by J422. In the late 1980s, a Cu-P alloy 09CuPTiRe weathering steel with a yield strength of 295 MPa and a 09CuPCrNi weathering steel with a Cu-PCr-Ni alloy with a yield strength of 345 MPa were developed. Implementation of solid wire welding with CO 2 gas protection. After entering the 21st century, unlike the Cu-P-Cr-Ni high weathering steel component system, the yield strength grades of 400MPa, 450MPa, 500MPa, 550MPa high strength and high weathering steel series came out, and began to use flux cored wire welding. Among them, Q450NQR1 steel has been widely used in the manufacture of 70t and 80t trucks, which provides conditions for trucks to increase the load. Beginning in 2005, the use of aluminum alloy and TCS economical ferritic stainless steel with better weather resistance, the adoption of new materials put forward new requirements for welding equipment and welding technology.
2. Development of welding equipment
Welding equipment includes welding equipment, welding auxiliary equipment and cutting equipment. In the 1960s and 1970s, there were only manual AC welders and manual DC welders in the factories; there were a small number of gas shielded welders and submerged arc welders in the 1970s and 1980s; gas shielded welders and submerged arc welding began in the 1990s. The number of machines has risen sharply; after 2000, advanced equipment such as digital welding machines, welding machines, and welding robots have been adopted. For example, the side wall of the gondola and the end wall are equipped with a welding machine. The welding of the C80B type stainless steel gondola adopts digital welding machine and welding robot welding. In the 60-80s, the cutting process was carried out by cutting machine and manual oxyacetylene cutting. Since the 1990s, CNC flame cutting machine, CNC plasma cutting machine, fine plasma cutting machine, laser cutting machine and other automation equipment have been used.
3. Development of welding technology
In the 1960s and 1970s, the welding of vehicles was carried out by electrode arc welding and a small amount of submerged arc welding. By the end of the 1970s, the CO 2 gas shielded welding method with high efficiency and small welding deformation was started. The CO 2 gas shielded welding process is widely used in the factory. At the end of the 1990s, the use of argon-rich mixed gas protective welding methods with small splash and appearance was promoted, and the welding productivity and product quality were greatly improved. After 2000, due to the application of new materials and new technologies, the application of welding methods such as MIG welding, MAG welding and TIG welding in the truck industry was promoted.
With the application of new materials and the improvement of product quality requirements, higher requirements are placed on the reliability of welding quality. In order to reduce the influence of human factors in the manufacturing process, reduce the labor intensity of workers, improve the welding production efficiency, ensure the stability of welding quality, and promote the overall improvement of the welding process manufacturing level in the truck industry, the Ministry of Railways Transportation Bureau "Quality, quality and safety" guidelines, requirements to improve the level of manufacturing technology of trucks, and the application of trucks [2004] No. 285 to the truck manufacturers to propose key parts of the body steel structure must be automated welding, and therefore must improve vehicle parts Cutting accuracy and assembly accuracy. The Ministry of Railways Equipment Department uses automatic welding for the long straight welds of gondola in the document of transport truck [2006] No. 399. Truck enterprises vigorously promote advanced automatic and semi-automatic cutting technology, welding process and welding special machine, automatic line or flexible production line, welding robot and various low-cost production lines of different levels, which comprehensively improve the level of welding automation of truck manufacturing, automatic welding of trucks Take a big step forward. Then the equipment department proposed the concept of lean manufacturing. Each manufacturing plant carries out the production and production of gondola according to the technical requirements of documents such as No. 400 of transport trucks, and increases investment and improvement in process test research, process equipment, welding process and welding quality control. The manufacturing quality of gondola is steadily improved.
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