Development trend of large metal mechanical welding technology

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.
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.

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.

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. .