Current status and development trend of welding technology in heavy machinery metal structure industry

【Abstract】 This paper expounds the current situation of welding technology in China's heavy machinery metal structure industry and the gap with developed countries, and forecasts the development trend of China's heavy machinery metal structure welding technology in the 21st century.

I. Overview

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.

2. Status of industry welding technology

1. Overview at home and abroad

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, CO ₂ 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 The factory, Shanghai Zhenhua Port Machinery Company, Qiqihar Second Machine Tool Plant, etc., mainly manufacture large bridge and gantry cranes, 4~35m ³ mechanical excavators, 1~6m ³ hydraulic excavators, large pressurized gasification furnaces, Hydrogenation reactor, large stage equipment, aerospace launch tower, coke oven machinery, spiral welded pipe equipment, and large reducer, hoist, stacker and reclaimer, steel forging equipment, oxygen cylinder press, cement equipment, grinding, Large equipment such as crushing machinery, water conservancy, construction machinery, hydraulic props, port machinery and environmental protection equipment.

3. Steel for heavy machinery metal structure industry

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 CO ₂ Welding Technology Promotion and Application Exchange Conference" as an opportunity, China has successively held two national CO ₂ welding technology promotion and application exchanges in 2001 and 2004 respectively. Yes, gas shielded welding technology in the heavy machinery metal structure industry promotes the application of continuous, stable and vigorous development, gas shielded welding technology development and application capabilities, application work from large machinery companies to small and medium enterprises, and large heavy machinery enterprises gas Protective welding applications are also being promoted 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.

5. Welding equipment

The use of welding equipment in heavy machinery metal structure industry generally requires the following performance: high power supply temporary load rate, high current, long working time, long distance between welding position and power supply, remote adjustment of specification parameters, wire feeding mechanism and secondary The cable is light in weight and easy to move, and the connection of the movable part must be firm and reliable.

5.1 Manual arc welding and submerged arc automatic welding equipment

In recent years, with the adjustment of product structure and technical transformation of enterprises, China's heavy machinery metal structure industry has certain progress in welding equipment, but there is still a certain gap between the same industry and foreign advanced industrial countries. In the field of manual arc welding equipment, rotary DC welding machines have been completely eliminated, replaced by silicon rectifier arc welding machine, thyristor arc welding machine, inverter welding machine, and a small number of multi-function welding machines (such as the United States Baoguo, Lincoln, Germany MESSER, Chengdu Welding Research Weida Company, Beijing Times Technology and other manufacturers), manual welding machine accounts for about 10% of the total welding equipment. The submerged arc welding machine has been developed from the traditional MZ-1000 to small volume, large rated current, multi-wire and multi-functional direction. The industrial submerged arc automatic welding machine accounts for about 10~15% of the total welding equipment.

5.2 Gas shielded welding equipment

At present, gas shielded welding process accounts for 60-80% of heavy machinery metal structure products, and gas shielded welding equipment has become a key welding equipment in the industry. The gas shielded welding equipment has been developed from the S series welding machine imported from Matsushita, Japan in the early 1980s to the current model of the Tangshan Panasonic KR series thyristor welder. The CO ₂ gas shielded welding machine with rated current of 350A and 500A basically realizes domestic assembly and manufacturing. Among them, the welding machines produced by a group of enterprises such as Tangshan Matsushita, Mudanjiang OTC, Times Group, and Jiangsu Shuangliang Welding Equipment Co., Ltd. The use of functions and reliability, and become the main choice for the heavy machinery metal structure industry, CO ₂ gas shielded welding machine, occupying a certain amount and market share, fundamentally changed the status of large-volume imported CO ₂ gas shielded welding equipment. In the early 1980s, Taiyuan Heavy Machinery Group Co., Ltd. successfully introduced nearly 100 sets of Panasonic S series gas shielded welding equipment from Japan, and 12 sets of CY-650 welders from Miller Company of the United States. In recent years, it has continuously carried out technological transformation, and successively purchased Tangshan Panasonic KRII500 welder 80. Taiwan, Ou Xixi CPX-500 welding machine 35 sets, Panasonic WP300 TIG welding machine nearly 10 sets, Jiangsu Changzhou Liangjiu Welding Equipment Co., Ltd. KR-500S series gas shielded welding machine about 10 sets, the company gas shielded welding equipment reached more than 200 sets , accounting for about 80% of the total welding equipment; Second Heavy Machinery Group has a total of 236 welding equipment, including 133 CO ₂ gas shielded welders, accounting for 56% of its total welding equipment; Dalian Heavy Industry • Lifting Group Co., Ltd. gas shielded welding machine accounts for about 80% of the total welding equipment. In short, gas shielded welding equipment has become the main force in the industry's welding production.

With the rapid development of the application of gas shielded welding technology, the development of China's gas shielded welding equipment manufacturing industry has also made great progress. Up to now, the common welding equipment has been based on domestic production and developed many new varieties adapted to the market. Among them, Tangshan Matsushita Industrial Machine Co., Ltd., Ou Dixi Electromechanical Co., Ltd., Chengdu Welding Research Weida Automatic Welding Equipment Co., Ltd., Changzhou Liangjiu Electric Equipment Co., Ltd., Shanghai Hutong Welding Machine Factory, Beijing Times Technology Co., Ltd., etc. The welding equipment manufacturer's model has become the main choice of the industry, and it has a certain amount and market share, which makes China's welding equipment coexist in various categories, which constitutes increasingly reasonable and continuously meets the needs of welding production.

5.3 Welding professional equipment

Because the products of heavy machinery metal structure industry are single-piece small batch, the shape of welded structural parts is complex and heavy, coupled with the relationship between the design and manufacturing level of welding professional equipment, although some enterprises use welding equipment and welding robot workstations. Etc., but the overall size and number of applications is relatively small. In the late 1980s, Taiyuan Heavy Machinery Group Co., Ltd. applied the HSS-2500W double-wire narrow-gap submerged arc welding machine developed by Harbin Welding Research Institute to solve the welding of thick-walled cylinder products. The device has pre-set welding parameters, closed-loop control of welding current and voltage, and automatic and horizontal tracking sensors for automatic welding of girth welds. The system is equipped with a large welding operation frame. The welding machine is IDEALARC, DC-100 of Lincoln Company of the United States and the summary ARC1000 of Miller Company of the United States. The two welding wires on the machine head are one of the wire and one wire is straight wire, and the welding efficiency is better than that of the monofilament. The narrow gap submerged arc welding is increased by 60%, the welding wire is 8~12kg per hour, the minimum diameter of the welded workpiece is 600mm, the maximum thickness is 350mm, and the pass rate of the weld is over 90%. The system is obtained in the production of Taizhong Company. Widely used; Taiyuan Heavy Machinery Group Co., Ltd. cooperates with Harbin Welding Research Institute to develop a large-scale metallurgical crane main beam gantry double-head automatic welding machine. The maximum width of the weldable workpiece is 3m, the maximum height is 2.5m, and the maximum length is 50m. The total weight of the machine is 11 tons. Both heads are equipped with a contact two-dimensional automatic tracking system, which significantly improves the quality and automation of long-weld welding. In the mid-1990s, the welding technology for the LY12 hard aluminum plate of the space launch tower was solved. The company introduced A10-500 optimized gas shielded welding equipment from EASB of Sweden. The welding system is equipped with LAR500 thyristor power supply, MEH44SYNERGIC double drive single board machine control The system randomly stores 48 sets of optimized welding process parameters, which can be optimized by users. The welding equipment system is used to weld more than 30 tons of LY12 hard aluminum. The welding quality meets the technical requirements of space launch towers. In addition, Dalian Heavy Industry Co., Ltd. ·Special equipment for roll surfacing of Crane Group Co., Ltd.; special equipment for submerged arc automatic surfacing of squeeze roller of CITIC Heavy Machinery Co., Ltd. It can be seen that welding professional equipment plays an irreplaceable role in other welding equipment in the production of heavy machinery metal structure industry.

6. Cutting technology

In recent years, the proportion of welded parts in heavy machinery metal structure industry has increased year by year, the amount of steel cutting has increased greatly, and the quality of cutting will affect the efficiency and quality assurance of subsequent assembly and welding processes. Comprehensive improvement of cutting quality, control of cutting deformation, improvement of production efficiency and material utilization have become the key to cutting technology. At present, the industry's cutting technology has been developed from the previous manual and semi-automatic oxyacetylene cutting to the large-scale NC cutting of oxypropane. The manual or semi-automatic cutting is a good occasion. The large-scale CNC cutting equipment also basically realizes the domestic assembly and manufacturing supply. Among them, Kunshan Messer Cutting & Welding Co., Ltd., Dalian Huarui Heavy Industry CNC Equipment Co., Ltd., Shanghai Warwick Welding & Cutting Machinery Co., Ltd., Wuxi Yangtong Machinery Equipment Co., Ltd., Harbin Electric Machinery Co., Ltd., Jinan No. 2 Machine Tool, etc. The main models of production have certain functions and reliability, and have gradually become the main choice of large-scale CNC cutting equipment models in the industry, thus gradually forming China's large-scale CNC cutting equipment technology industry. Now Taiyuan Heavy Machinery Group Co., Ltd. has a total of 6 large Messer CNC cutting machines and 1 Harbin motor CNC cutting machine; CITIC Heavy Machinery Co., Ltd. has 7 large-scale CNC cutting equipment.

7. Welding materials

7.1 Overview of China's welding materials production

China has become the world's largest producer of welding materials, but it is not a strong country of welding materials. At present, there are nearly 300 domestic welding electrode manufacturers with a production capacity of about 2 million tons. In 2004, the output of welding electrodes was 1.6 million tons, accounting for 71% of the total welding materials. There are more than 200 CO ₂ solid wire welding manufacturers in the country. Since 1983, more than 50 sets of various wire production equipment have been imported from abroad, with an annual production capacity of nearly 500,000 tons. In 2004, the output of CO ₂ solid wire was 350,000. Tons, accounting for 16% of the total amount of welding consumables. At present, there are 29 manufacturers of flux cored wire in China. By the end of 2002, 17 companies have introduced 24 production lines from abroad, with an annual production capacity of about 100,000 tons. In 2004, the output of flux cored wire was about 50,000 tons, accounting for welding consumables. About 2% of the total. Generally, domestic enterprises producing CO ₂ solid wire are producing submerged arc welding wire, and the market share of the welding consumables is basically stable between 10% and 13%. In 2004, the output of submerged arc welding wire was 250,000 tons, accounting for 11% of the total welding consumables. After years of efforts by welding workers in China's welding materials industry, welding materials have grown from scratch, and the number of welding consumables has grown from small to large, making great progress and development, but from the structure, variety and quality of welding consumables, and developed countries and There is still a certain gap compared to the region.

7.2 Application of welding materials in the industry

7.2.1 Electrode

Before the 1980s, the welding methods commonly used in the heavy machinery metal structure industry were manual arc welding and submerged arc automatic welding. The structure of the welding material is mainly composed of welding electrodes, supplemented by submerged arc welding wire. With the development and popularization of gas shielded welding technology, the current manual welding rods are generally used for assembly spot welding, surfacing welding and alternative gas shielded welding wire varieties. The total welding electrode consumption in the whole industry accounts for 5~10 of the total welding materials. %. Dalian Heavy Industry·Zhezhong Group Co., Ltd. accounts for about 10% of the total welding consumables, and the proportion of welding rods used by Taiyuan Heavy Machinery (Group) Co., Ltd. has dropped from 10% to less than 5%. With the development of gas shielded welding technology and the increase of welding wire varieties, the proportion of welding rods will be reduced year by year, which makes the structure of welding materials in China gradually become more reasonable, narrowing the gap with foreign industrialized countries.

7.2.2 Submerged arc welding wire

The amount of submerged arc automatic welding wire accounts for about 10~20% of the total amount of welding consumables. Among them, about 20% of lifting equipment, large-scale pressurized gasification furnaces, etc., about 10~15% of rolling, forging, and excavation equipment. Commonly used submerged arc welding wires are: H08A, H08MnA, H08Mn2SiA, H10Mn2, H08CrMoA, H08Mn2MoA, 1Cr13, 2Cr13, 3Cr13, etc. The diameter of the welding wire is generally Ñ„2.5~Ñ„5.0mm.

7.2.3 Gas protection solid wire

Gas-shielded solid wire is growing along with the development of welding technology in China's heavy machinery metal structure industry. From the early 1980s to the mid-1980s, China's H08Mn2SiA gas-protected solid-core wire, which was produced by the main structural steels such as A3 and 16Mn at the time, was partially self-sufficient, but the welding wire was realized on the basis of the introduction of technology, equipment and software. The quality is unstable and it is in a situation of short supply. In the late 1980s, China carried out technological transformation of large-scale heavy machinery enterprises, introduced advanced foreign welding technology and equipment, and actively promoted gas shielded welding, but most of the gas shielded welding wire mainly relied on the United States (ER50-6, etc.) and Japan (KC50). , MG-50, etc.), Germany (K-52, etc.), the Netherlands (PZ6000, etc.) and other developed countries. Up to now, China's gas shielded welding solid wire has formed a certain scale of production, and the output and quality have also been greatly improved.

(1) For gas shielded welding solid wire of Q235, Q345 and Q390 structural steel, it has been developed from the traditional ER49-1 to the internationally popular ER50-6 welding wire. The commonly used specifications are Ñ„1.0mm, Ñ„1.2mm, There are three kinds of Ñ„1.6mm. In addition to meeting domestic demand, some products are also exported. At present, the domestic manufacturers with certain production scale and relatively stable quality are Jintai Metal Industry Co., Ltd., Atlantic Welding Wire Products Co., Ltd., Yichang Monkey King Welding Wire Co., Ltd., Golden Lion Welding Materials Co., Ltd., Changzhou Huatong Welding Wire Co., Ltd., Texas Juli Welding Materials Co., Ltd., Ezhou Nanta Special Welding Materials Co., Ltd., Harbin Weir Welding Co., Ltd., etc.

(2) The quality of domestic 600MPa, 700MPa high-strength steel, stainless steel, aluminum and aluminum alloy solid wire is relatively stable, such as: Jintai Metal Industry Co., Ltd. JM-60, JM-100 high-strength steel welding wire, etc.; Lion Welding Materials Co., Ltd. and Monkey King Welding Materials Co., Ltd. JS-60 (C), JS-60 (A), JS-70 high-strength steel welding wire, etc.; Golden Lion Welding Materials Co., Ltd., Changzhou Huatong Welding Wire Co., Ltd. series stainless steel Welding wire, etc.; Ezhou Nanta Special Welding Materials Co., Ltd., Changzhou Huatong Welding Wire Co., Ltd. series of aluminum and aluminum alloy solid wire.

(3) There are fewer manufacturers of 800MPa high-strength steel welding wire, heat-resistant steel welding wire and weathering steel welding wire, such as: Golden Lion Welding Materials Co., Ltd., Harbin Weir Welding Co., Ltd., Dalian Great Wall Welding Wire Co., Ltd., etc.

(4) There are not many manufacturers of carbon steel welding wire for argon-rich mixed gas protection, such as: Golden Lion Welding Materials Co., Ltd., ER50-3B produced by Dalian Great Wall Welding Wire Co., Ltd., etc.

(5) For special steels such as high-strength steel and high-alloy steel of 800MPa grade or higher, the cored wire is still mainly imported.

At present, the amount of solid wire for gas shielded welding in the industry accounts for 60~80% of the total amount of welding consumables. For example, the annual consumption of solid welding wire for gas shielded welding of Second Heavy Machinery Group Co., Ltd. is 900 tons, and the annual consumption of CITIC Heavy Machinery Co., Ltd. is 300 tons. Around, Dalian Heavy Industry·Zhezhong Group Co., Ltd. gas shielded welding solid wire accounts for 60% of the welding consumables, Taiyuan Heavy Machinery (Group) Co., Ltd. accounts for about 80%, and the annual amount of welding wire reaches 500 tons. The popularization and application of gas shielded welding solid wire has significantly improved the welding process level of the industry, effectively reduced the manufacturing cost and promoted the development of welding technology in China.

7.2.4 Flux cored wire

Flux cored wire meets the trend of high efficiency, high quality and low cost in welding production. It is widely used in the heavy machinery metal structure industry in industrialized countries. For example, the CC1000-3000t crawler crane produced by Demag, Germany, uses Fluxofil41 and Fluxofil42 (Φ1.4mm) seamless flux cored wire produced by Swiss Olympus to weld STE460 and STE690 steel. The PH2300XP (16.8m ³ ) and PH2800XP (23m ³ ) excavators produced by P&H of the United States, including the main force and transmission parts of the boom arm, the underframe beam and the gears, use the E70T of the American Hubert and Lincoln Company. -5 Φ2.4mm seamed cored wire, other parts use E70T-1 Φ2.4mm flux cored wire. E309LT-3 Φ2.4mm stainless steel flux cored wire is used before and after the bucket. In China's heavy machinery metal structure industry, due to the variety, quality and economical reasons of flux-cored wire, the industry uses less flux cored wire in addition to cooperative products and a small amount of special welding wire. According to statistics, the amount of flux cored wire only accounts for about 2% of the amount of welding consumables. In the past ten years, the research, development, popularization and application of flux cored wire in China has developed rapidly. The flux-cored wire has entered a period of basically stable development. At present, there are certain production scales in China, and the manufacturers with relatively stable quality are: Sanying Welding Industry Co., Ltd. Responsible companies (such as SQJ501 Φ1.6mm, etc.), Beijing Baosteel Welding Co., Ltd. (such as PK-YJ507Ni, PK-YD212 Φ1.6mm, etc.), Beijing Ganglian Welding Materials Co., Ltd. (such as GL-YJ502, GL-YJ507, GL-YJ502Ni Φ1.2mm, Φ1.6mm, etc., Antai Technology Co., Ltd., Beijing University of Technology (such as 2Cr13, YJ507 Φ1.6mm, etc.), Metallurgical Building Research Institute, Steel Research Institute, Hardfacing Surfacing Center Flux cored wire, etc. Compared with similar foreign products, the flux-cored wire of China has a large gap in terms of variety, quality (especially in terms of welding process performance) and price, which is far from meeting the development requirements of welding production.

8. Welding tooling

Welding tooling is an effective tool to improve welding efficiency and quality and reduce labor intensity. Enterprises should vigorously promote the use of positioners, operating frames and turning tables when not entering the automatic welding stage. The positioner allows the weld on the workpiece to be welded in the most ideal position. There are about 750 welding positioners in China, and 84% are made in China. In the heavy machinery metal structure industry, due to the complex shape of the workpiece, heavy weight, and small batch size, the application of the positioner in the industry is still not widespread. In recent years, some companies in the industry have begun to pay attention to this problem, and are equipped with many large welding positioners and operating frames. Such as CITIC Heavy Machinery Company, Dalian Heavy Industry Crane Group Co., Ltd., Taiyuan Heavy Machinery Group Corporation. Taiyuan Heavy Machinery Group Co., Ltd. has one imported 160t, 50t, 5t and 3t welding positioner from Germany, which is generally used for welding workpieces such as cylinders and gears. The welding tool such as welding positioner and operating frame is used to effectively solve the problems of production efficiency, welding quality and labor intensity.

Development trend of industry welding technology

In the 21st century, with the increase in development investment in metallurgy, mining, lifting, forging, coke ovens, towers, etc., it has brought new development opportunities to China's heavy machinery metal industry. Especially after China's accession to the WTO, the heavy machinery industry is facing more intense competition. We must be soberly aware that welding technology still severely constrains the output, quality, cost and production cycle of the heavy machinery industry. Combined with China's national conditions, the development direction of the heavy machinery metal structure industry should be to strive to improve the level of welding equipment and process technology, balance the development of welding-related technologies, combine new product development and new project projects, research and apply new welding processes, new equipment, new materials and New technologies will further improve welding production efficiency and quality, reduce costs, narrow the gap with industrialized countries, and promote the continuous development of welding technology in China.

Welding process

1.1 Manual welding and submerged arc automatic welding

In order to improve the welding efficiency of the industry, the application of efficient welding technology has become the consensus of the industry. First, as the variety of gas shielded welding wire increases, the proportion of manual welding process should be gradually reduced. The industry single wire submerged arc welding technology has been basically mature. Generally, double wire submerged arc welding has an efficiency of 30% higher than single wire submerged arc welding. Double wire narrow gap welding has an efficiency of 60% higher than single wire welding, and the maximum amount of deposited metal wire can be reached. 12kg/h. Therefore, in the future, we should focus on the application of multi-wire submerged arc welding and narrow-gap submerged arc welding technology, and develop and apply manual submerged arc welding technology. On the basis of the application of submerged arc surfacing, further development and application of strip surfacing is carried out to improve production efficiency.

1.2 Gas shielded welding

With the development of gas shielded welding technology and wire variety, the application ratio of gas shielded welding method is further improved, and the application ratio of gas shielded welding method reaches 70-80%. With the development of gas-shielded flux-cored wire technology, it is important to promote the weak link of the application industry – flux-cored wire gas shielded welding technology, especially in the industry, mainly stress-bearing parts (such as electric shovel booms, sticks, etc.) The flux-cored wire gas shielded welding technology has an irreplaceable role in the transmission parts (large-sized quenched and tempered steel welding gears, etc.), surfacing (such as large-scale plunger parts surfacing), and field construction. In the past few years, we have made a rapid development in the industry of flux-cored wire welding, promoting the development of China's flux-cored wire gas shielded welding technology and narrowing the gap with foreign countries.

2. Welding equipment

With the continuous adjustment of product structure and the rapid development of welding technology, the industry welding equipment should be developed in the following aspects.

2.1 With the continuous development of gas shielded welding technology, the proportion of manual arc welding equipment will gradually decline. The industry should vigorously promote the application of high-combination, multi-function inverter welding machines; promote the application of high-speed gas shielded welding technology.

2.2 Submerged arc automatic welding equipment is developing in the direction of small size, light weight, multi-filament and multi-function.

2.3 Continue to use the thyristor gas shielded welder to promote the application of miniaturized, digital inverter gas shielded welders (such as Beijing Times Technology Co., Ltd., Shandong Shanda Aotai Electric Co., Ltd.) to improve control system interference. Control the splash to improve the welding precision, reliability and stability of the welder, optimize the welding parameters and optimize the welding to ensure the welding quality.

2.4 Focus on the development of domestically produced flux cored wire, aluminum and aluminum alloy wire special equipment (such as American Miller CY-650 dual motor drive, single board machine control wire feeding system welding machine, Sweden ESAB company A10-500 double drive single board machine Control, aluminum wire welding equipment), to promote the application and development of the flux cored wire in the industry.

2.5 It is necessary to speed up the promotion and application of complete sets of professional welding equipment technology for thick-walled cylinder double-wire narrow-space submerged arc welding, crane main beam gantry double-head automatic welding, large-roller extrusion roller submerged arc automatic surfacing, and continuously improve welding in the industry. Mechanization and automation level.

2.6 In the face of the development of energy engineering, the development and application of arc welding robot workstations for hydraulic props and other products should be increased in the field of mining machinery.

3. Welding tooling

In the aspect of welding tooling, the popularization and application of welding positioner, operating frame and turning table, etc., for the structural characteristics of the industry, the development of combined tooling, according to the different shapes of the products, so that the welds of the parts are in the best welding position. To reduce the labor intensity of workers, improve production efficiency and ensure welding quality.

4. Cutting technology

CNC cutting machine has full function, high degree of automation, configurable multiple torches at the same time, long effective cutting time, high production efficiency, automatic programming nesting program, high material utilization rate, high processing precision, good cutting quality, etc. Features, in the future to continue to promote the application in the industry. In particular, it is important to promote the popularization of oxy-propane cutting technology. At present, the large-scale CNC cutting machine produced abroad has good quality, high precision and full function, but the price is high. The domestically produced CNC cutting machine still needs to be continuously improved and improved in terms of cutting precision, torch quality, long-term continuous working stability and fast cutting function to meet the welding production requirements and narrow the gap with foreign countries. In addition, as the market continues to improve product quality requirements, cutting technology should be developed in the field of CNC fine cutting.

5. Welding materials

5.1 Welding structure proportion and variety

At present, China's welding material production accounts for about 40% of the world's total welding consumables. Although we have become the world's largest producer of welding materials, there are still some gaps in the structure, quality and variety of welding materials compared with industrial developed countries and regions such as Europe, America, Japan and even South Korea (see Table 1). It can be seen from the table that in China's large-scale heavy machinery metal structure industry, the proportion of welding material structure is basically reasonable except for the flux cored wire, but the gas shielded welding solid core and flux cored welding wire are single (see Table 2 and Table 3). To meet the welding production needs of the industry, some of the welding wire still needs to be imported, which seriously restricts the development of welding production, which should cause us to pay enough attention.

Table 1 Proportion of developed countries and regions and consumables structure (%)

Table 2 Comparison of gas shielded welding solid wire varieties (a)

Table 3 Comparison of flux cored wire varieties (a)

5.2 Submerged arc welding wire

5.2.1 Submerged arc welding wire is widely used in welding production in the industry. The proportion of welding consumables is expected to be controlled at 10~15%, which basically reaches the foreign level, but the welding wire variety is lacking. In the future, China's submerged arc welding wire and flux should be developed in the direction of high efficiency, variety and high toughness.

5.2.2 Develop and develop submerged arc welding flux cored wire such as heat-resistant steel and low-alloy high-strength steel in China, continuously improve and improve the quality level of surfacing welding cored wire, and better meet the welding production requirements.

5.3 Gas shielded welding solid wire

China's gas shielded welding solid wire should be developed in the direction of low splash, high performance, multi-variety and environmental protection. Industry gas shielded welding solid wire welding application trends should focus on:

5.3.1 In the welding of low carbon steel, ER50-6 welding wire should be preferred, and the traditional imitation of former Soviet welding wire ER49-1 should be eliminated, so that the structure of carbon steel welding wire in China tends to be reasonable.

5.3.2 Research and development of anti-rust (such as the US ER70S-6 welding wire, etc.), argon-rich gas mixture (such as Japan YGW15 welding wire, etc.), suitable for large specifications (such as Japan YGW11, Jintai JM-58 welding wire) carbon steel gas protection Welding solid wire.

5.3.3 We should vigorously develop and promote 700MPa, 800MPa high-strength welding wire, high-alloy steel welding wire, heat-resistant steel and high-toughness steel welding wire to meet the development requirements of welding production.

5.3.4 Strengthen the research and popularization of non-coppered copper wire manufacturing technology. To provide users with high-quality non-copper welding wire, and gradually replace the traditional copper-plated welding wire to develop China's "energy-saving, environmentally friendly" welding.

5.4 gas shielded flux cored wire

Domestic flux-cored wire should be developed in the direction of excellent process performance, stable quality, wide current, low dust, low spatter, fast welding and many varieties.

5.4.1 Focus on the development of Φ1.2mm, Φ1.6mm flux cored wire, continuously improve and improve the process performance of the wire, and solve the quality stability problem of mass production.

5.4.2 Develop and produce multi-variety, high-quality, different-purpose flux-cored wire as soon as possible, such as ultra-low hydrogen high-toughness welding wire, all kinds of stainless steel, heat-resistant steel and series of wear-resistant surfacing and other flux cored wire.

5.4.3 Self-protecting flux cored wire has strong windproof capability and is suitable for field and aerial work. It has broader application prospects (such as oil transportation, gas transmission, outdoor manufacturing and installation, etc.). At present, there are no mature products in China, and we should pay enough attention to research and development as soon as possible.

5.4.4 Strengthen the research on manufacturing technology of flux cored wire, continuously improve the quality and production efficiency of flux cored wire, gradually reduce the price of flux cored wire, and promote the promotion and application of flux cored wire in the industry.

Conclusion

After more than half a century, especially in the past 20 years, China's heavy machinery metal structure industry has made great progress and development. The mechanization, automation, high efficiency, energy saving and environmental protection have been greatly improved, but with other industries, Compared with industrial developed countries, there is still a big gap. With the acceleration of economic globalization and China's accession to the WTO, international competition has become increasingly fierce. In recent years, it is a good time for China to vigorously develop the equipment manufacturing industry. China's heavy machinery metal industry is facing new opportunities and challenges, which undoubtedly set the stage for the future development of welding high-tech in the heavy machinery metal structure industry.

This requires the joint efforts of the entire industry welding industry colleagues to promote the development of China's welding technology and industry in the direction of high efficiency, high quality, energy saving, low cost, automation and environmental friendliness, in order to better adapt to the continuous development of China's welding production.