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Industry welding technology status
1. Overview of domestic and foreign
Welding technology is one of the key process technologies for the manufacture and installation of heavy machinery metal structure equipment. It is widely used in heavy machinery manufacturing industry in industrialized countries. Up to now, China's heavy machinery welding technology has developed in the United States (such as P&H, etc.), Germany (such as SMS, etc.), France (such as voestal, etc.), and Japan (such as Mitsubishi Heavy Industries, Komatsu, etc.). There is a big gap between countries. At present, the proportion of welded structural parts in these countries and regions is increasing. The welding metal materials consumed by high-efficiency welding methods such as automated and mechanized gas shielded welding and multi-filament submerged arc welding account for about 50% of the total amount of welding consumables. 70%, its welding production adopts mechanized, automatic and efficient welding process, which brings high welding production efficiency and good welding quality, and has strong international competitiveness.
In China's heavy machinery metal structure industry, gas-shielded welding, double-wire submerged arc automatic welding, gantry welding machine, electroslag welding and other high-efficiency welding methods are increasingly used in large-scale metal structure manufacturing enterprises, and metal structures completed by high-efficiency welding methods The parts have accounted for 50~80% of the total weight. In small and medium-sized enterprises, CO2 gas shielded solid wire and submerged arc automatic welding have also been applied. But overall, the advantage of low labor wages in China's heavy machinery manufacturing is being offset by the huge gap between low production efficiency and high quality costs, which should cause us to pay enough attention.
2. Product situation
The heavy machinery metal structure industry mainly provides heavy machinery and equipment for large-scale national backbone enterprises and national key projects. Industry manufacturing backbone enterprises such as First Heavy Machinery Group Co., Ltd., Second Heavy Machinery Group Co., Ltd., Taiyuan Heavy Machinery Group Co., Ltd., Dalian Heavy Industry Crane Group Co., Ltd., CITIC Heavy Machinery Co., Ltd., Zhengzhou Coal Machine Factory, Beijing Coal Machine Factory Shanghai Zhenhua Port Machinery Company, Qiqihar Second Machine Tool Plant, etc., mainly manufactures large bridge and gantry cranes, 4~35m3 mechanical excavators, 1~6m3 hydraulic excavators, large pressurized gasifiers, hydrogenation reactions , large stage equipment, aerospace launch tower, coke oven machinery, spiral welded pipe equipment, as well as large reducers, hoists, stackers and reclaimers, steel forging equipment, oxygen cylinder presses, cement equipment, grinding, crushing machinery, Large equipment such as water conservancy, construction machinery, hydraulic props, port machinery and environmental protection equipment.
3. Heavy duty machinery metal structure industry steel
For a long time, China's heavy machinery metal structure industry mostly uses mature steels at home and abroad, such as Q235 series carbon steel, Q345, Q390 series low alloy steel, 20g, 16MnR pressure vessel steel. In recent years, with the development of national key projects and the adjustment of product structure, the types of steel for welding have been greatly improved. Common steel plates include: Q235, Q345, Q390, 20, 35, 45, 15Mo3, 15CrMo, 13MnNiMoNbR, Wel-ten80C, A633D, 16MnR, 20g, 15MnVR, etc. Common stainless steel plates are: 0Cr18Ni9, 1Cr18Ni9Ti, 1Cr13, 2Cr13, 3Cr13, etc. Commonly used aluminum plates are hard aluminum and aluminum alloy plates; common forgings are 25, 35, 45, 40Cr, 42CrMo, 40CrNiMo, 40CrNi2Mo, 20MnMo, 42CrMnMo, 34CrNi3Mo and so on. The thickness of the plate is generally between 1 and 300 mm.
With the increasing number and variety of steel products, the annual output of welded parts has increased significantly. According to incomplete statistics, in 2005, the annual output of welded parts of Qiqihar No. 2 Machine Tool Plant was about 10,000 tons; Second Heavy Machinery Group Co., Ltd. was about 30,000 tons; Taiyuan Heavy Machinery Group Co., Ltd. was about 50,000 tons; CITIC Heavy Machinery The company has exceeded 50,000 tons; the annual output of welded parts of Shanghai Zhenhua Port Machinery Co., Ltd. is as high as 200,000 tons. With its unique advantages, welded structural parts have replaced the riveted structure and replaced the cast structure, becoming the dominant structure of metal structure equipment in the heavy machinery industry.
4. Welding process
The heavy machinery metal structure industry began to use the manual arc welding process. In the 1950s, the submerged arc automatic welding and electroslag welding process were used, which were mainly used for some thick plate butt joints, work beam and barrel welding. In recent years, some large enterprises have successively applied advanced welding methods such as double wire submerged arc welding, double wire narrow gap submerged arc automatic welding, gantry type welding machine and roller submerged arc surfacing through technical transformation to meet product manufacturing technical requirements. .
With the welding technology transformation of large-scale backbone enterprises in China, the gas shielded welding process has been widely used in the heavy machinery metal structure industry. It can be said that the gas shielded welding process has grown along with the development of welding technology in the heavy machinery metal structure industry. In the late 1980s, in order to meet the requirements of the national key engineering large-scale mechanical and technical equipment manufacturing, the introduction of foreign advanced welding technology and equipment, technical transformation of large-scale backbone heavy machinery enterprises, China's large-scale heavy machinery metal structure manufacturing enterprises through the United States, Multinational companies from Germany, Japan and other countries cooperate to manufacture large-scale metal structures, purchase foreign gas shielded welding equipment, welding consumables and other equipment in batches, and conduct welder training. With the help of foreign gas shielded welding mature technology and production technology, China has formed the production capacity of gas shielded welding in China's large metal structure industry, which fundamentally changed the manufacturing technology level of heavy machinery metal structure industry and promoted gas shielded welding in China. The development of technology. In the past ten years from the early 1990s to the present, with the first "National CO2 Welding Technology Promotion and Application Exchange Conference" as an opportunity, China has successively held two national CO2 welding technology promotion and application exchange meetings in 2001 and 2004 respectively. Gas shielded welding technology is popularized and applied in the heavy machinery metal structure industry. It is continuous, stable and vigorous. The development and application of gas shielded welding technology is enhanced. The application work is extended from large machinery enterprises to small and medium enterprises, while gas shielded welding of large heavy machinery enterprises. Applications also range from the production of co-manufactured products to the production of common products. Gas shielded welding equipment, welding consumables and accessories have basically achieved domestic supply, and gradually formed China's gas shielded welding industry.
Development trend of welding technology in heavy machinery metal structure industry
In recent years, with the rapid development of the national economy, China's heavy machinery metal structure manufacturing has made remarkable achievements. China is not only a world's largest steel consumer, but also a world machinery manufacturing power. According to the International Iron and Steel Institute (IISI), in 2004 the world's steel output reached 1.03 billion tons for the first time, and the amount of steel used was 935 million tons. China's steel output in 2004 was 272 million tons, accounting for 26% of global steel production. The annual steel consumption was 312 million tons, accounting for 33% of global steel production, of which 160 million tons were used in welded structures, accounting for steel. About 51% of the amount. In Europe and the United States and the former Soviet Union, steel for welded structures accounts for about 60% of its steel use, and Japan has more than 70%. This shows that we still have a certain gap compared with industrial developed countries. According to relevant investigations, in the 160 million tons of welded structural steel, the steel used in the metal structure of the machinery manufacturing industry accounts for about 45% of the steel volume. The rapid development of the steel industry gives the welding industry in China, especially the heavy machinery metal structure industry. The sustainable development of technology has created a lot of room for development. Entering the 21st century, China's heavy machinery industry is facing new challenges and opportunities. It should thoroughly improve the traditional welding industry with large energy consumption, high consumables, low efficiency, poor working environment and low automation, and promote the welding technology and industry to high quality and high efficiency. Energy-saving, low-cost, environmentally friendly and automation development, and strive to transform the relative advantages of human resources into technological competitive advantages, and promote enterprise progress and industrial upgrading.