ã€Abstract】 The status quo of welding technology in China's hydropower construction industry and the gap with developed countries are expounded, and the development trend of China's hydropower construction welding technology in the 21st century is forecasted.
I. Overview
Hydropower station metal structure equipment has a wide variety of applications, including water diversion pressure steel pipe, steel gate, steel ball grid, steel beam and column, turbine seat ring, volute, runner, generator frame, stator frame and rotor bracket. Wait. With the continuous development of welding technology, the comprehensive performance of the welded structure is getting better and better, and the bolted connection structure and the riveted structure have been replaced, which has become the dominant structure of the metal structure equipment of the hydropower station.
Welding technology is one of the key process technologies for the manufacture and installation of metal structure equipment for hydropower stations. At present, taking the investment and construction of a large number of hydropower projects such as the Three Gorges Project as an opportunity, major domestic hydropower construction enterprises have generally completed a round of modern technological transformation in the mid-1990s. On this basis, a new round of modernization plans was launched at the beginning of this century. The investment target is obviously concentrated in high and new technology, and the investment is further increased. A large number of high-tech welding technology and automated welding production system are adopted to ensure that these hydropower construction enterprises have unique technological advantages in the market competition.
Entering the 21st century, China's hydropower construction enterprises are facing new challenges and opportunities. They should vigorously promote the application of high-efficiency welding technology, accelerate the pace of welding technology transformation, and strive to transform the relative resource advantages into technological competitive advantages, and promote enterprise progress and industrial upgrading.
Second, the status quo of China's hydropower construction welding technology
The scale of water conservancy and hydropower projects is huge, the impact is far-reaching, the situation is complex, and the technology
High requirements, how to carry out scientific and standardized construction is a process of continuous practice and exploration. For more than half a century, especially in the past 20 years, China's water conservancy and hydropower construction industry has developed rapidly, and the scale of construction and construction speed, technology accumulation and technological innovation achievements have attracted worldwide attention. China's hydropower construction enterprises have made great progress in terms of technical level, construction quality and construction efficiency, and the long-term progress of welding technology has achieved remarkable results.
1. Welding process
The welding method applied to hydropower construction has developed from the single electrode arc welding in the early 1950s to nearly 10 kinds of submerged arc automatic welding and gas shielded welding which are widely used nowadays, which basically meets the needs of hydropower construction.
(1) The main board welding uses the submerged arc automatic welding process.
(2) Fillet welds (combined welds) of T-beams, H-beams, box beams, etc. are mainly in the shape of ship-shaped or flat-angle welding, using submerged arc automatic welding or molten gas protection automatic welding process.
(3) The welding of the water-conducting pressure steel pipe adopts the combination of automatic vertical welding, automatic horizontal welding, automatic flat welding and electrode arc welding.
(4) The aluminum busbar is welded in a large number of semi-automatic MIG welding processes, and sometimes a small amount of manual TIG welding is used.
(5) Steel bar welding mainly adopts various processes such as flash butt welding, electrode arc welding and electroslag pressure welding.
(6) Welding of other steel structure products is also carried out by a combination of electrode arc welding and semi-automatic or automatic welding.
Since the mid-1990s, the mechanization and automation rate of welding has been gradually improved. The application of high-efficiency welding methods in hydropower station metal structure equipment manufacturing plants (field), submerged arc welding and gas metal arc welding has reached about 50%. The application of the construction site has also reached about 20%, and it is increasing year by year.
2. Welding equipment
Rotary DC welding machines have all been eliminated, replaced by silicon rectifier arc welding machine, inverter welding machine, gas shielded welding machine, submerged arc welding machine, automatic vertical welding machine, automatic horizontal welding machine and automatic flat angle welding machine, etc. The application of welding power supplies is also on the rise. Welding equipment coexists in various categories, and the composition is increasingly reasonable, which can basically meet the needs of hydropower construction and production.
3. New welding technology, new technology
Because the metal structure equipment of hydropower station has many characteristics, such as small variety, small batch size, frequent changes in structure and size, and many other welding operations in the open field, the operating conditions are harsh and there are many uncertain factors. However, in recent years, due to the correct guidance of the national hydropower development and investment policy, the investment of all parties in the hydropower project has increased, the investment speed has increased, and the unprecedented development and progress of welding technology has made the hydropower construction welding technology more big change. Among them, some outstanding key construction enterprises have introduced and put into production domestic advanced "H"-shaped steel, box-shaped beam automatic welding production line, submerged arc automatic welding single-sided welding double-sided forming new technology and equipment, automatic flat fillet welding Process and equipment, full-diameter automatic welding process and equipment for large-diameter thick-walled pressure steel pipe.
Large-diameter thick-walled steel pipe single-section round longitudinal vertical weld, large-section assembled circumferential transverse weld and reinforced ring fillet weld are originally welded by arc welding, which has the disadvantage of low production efficiency. High labor intensity, high technical requirements for welder operation, difficult welding quality control and unstable quality. Since October 1999, the application of solid-core welding wire argon-filled gas protection automatic vertical welding, flat angle welding and horizontal welding in the pressure pipe welding construction of the second phase of the Three Gorges Project has improved the welding production efficiency by 3~5 compared with the traditional electrode arc welding process. Double, the welding quality is excellent and stable, and the pass rate of weld nondestructive testing is above 99%. At present, it has been widely used in the welding of pressure pipes for large hydropower projects such as Shuibuya and Longtan.
4. Welding materials
In recent years, the application of flux-cored wire has sprung up. Because the flux-cored wire has the characteristics of high deposition efficiency and less welding spatter, it is easy to realize mechanization and automatic welding. At present, major domestic hydropower construction enterprises are gradually
The use of flux cored wire to weld steel gates and other large steel structures began. At the same time, it is combined with CO 2 welding technology and has achieved good results in production. Therefore, some hydropower station metal structure equipment manufacturers have used flux cored wire CO 2 gas shielded welding as the main welding process for future steel structure products. technology. At the hydropower construction site, the flux-cored wire CO 2 gas shielded welding process technology is also trying to create conditions for popularization and application. The application of E5018 and other high-efficiency iron powder electrodes in hydropower construction also showed a clear upward trend.
5. Hydropower station steel
The development of steel for hydropower stations requires a long period of time. Since the founding of the People's Republic of China, most of the steel used in hydropower stations in China have adopted mature steels at home and abroad, such as Q235 series carbon structural steel, Q345 series, Q390 series low alloy structural steel, and 16MnR pressure vessel steel. With the improvement of the water head of the power station and the increase of the unit parameters, the amount of low-carbon quenched and tempered high-strength steel such as 590MPa grade 62CF, 610U2, SM58Q and 780MPa grade HT80 quenched and tempered high-strength steel has been increasing year by year since the 1980s.
In order to improve the mechanical conditions of high-speed over-flow parts such as the bottom hole of the power station, the overflow deep hole, the reverse arc-shaped working door and the door section of the ship lock waterway, and to reduce corrosion damage, steel lining protection is adopted. Considering the basic conditions of high-speed over-flow waterway normal operation, life extension, convenient construction, operation and maintenance, and project cost, starting from the Three Gorges Project, large-scale water conservancy and hydropower projects use steel-based stainless steel composite plates as sand discharge holes and deep holes for flood discharge. The steel lining panel is protected by the overflow surface of the ship lock anti-arc door well section. According to the flow velocity and medium content of the flow surface, 00Cr22Ni5Mo3N, 00Cr18Ni5Mo3Si2 duplex stainless steel, 0Cr13Ni5Mo martensitic stainless steel and 0Cr19Ni9N austenitic stainless steel were selected as the composite materials, the thickness of which was 4mm, and the substrate was mostly Q345 low. Alloy structural steel with a thickness of 20mm.
6. Cutting technology
At present, the application of cutting technology in hydropower construction enterprises is still relatively backward. The cutting of profiles is mainly based on manual flame cutting. The linear cutting of plates and the arc cutting of large curvature radius are mainly semi-automatic flame cutting, and the cutting of curved and special-shaped parts is adopted. CNC flame cutting or CNC plasma cutting technology. The overall cutting efficiency is low, and there are problems such as high labor intensity, difficult to control cutting quality, poor cutting quality and low dimensional accuracy, which seriously affects the improvement of production efficiency and quality of subsequent assembly and welding processes.
Third, the gap with foreign hydropower equipment processing enterprises
There is still a big gap between China's hydropower construction welding technology and developed countries such as France, Germany, Japan and Canada. Moreover, the advantages of low labor wages in hydropower construction are being inefficient in production and high in cost.
The huge gap is offset.
China's hydropower construction enterprises are numerous, scattered, and the development is extremely unbalanced, the economic scale effect is poor, coupled with the disorderly competition in the bidding market, the scientific research and technological transformation investment is seriously insufficient, and no reasonable and effective technological innovation has yet been formed. Compared with foreign large-scale hydropower equipment processing companies such as ALSTOM and Siemens, the technology gap has not been significantly reduced, and some aspects have continued to expand. Foreign large-scale hydropower equipment processing enterprises widely use mechanized, automated flux-cored welding and multi-wire submerged arc welding and other high-efficiency welding methods in welding production, with high efficiency rate of over 70%, high welding productivity and excellent welding quality. The welding cost is relatively low; the numerical control flame cutting, the long-life numerical control oxygen plasma arc cutting and the numerical control plasma arc cutting technology are widely used in the blanking process, and the numerical control laser cutting technology is also applied.
China's accession to the WTO is a great challenge for hydropower construction enterprises. The essence of this is to expand opening up to the outside world, so that the hydropower construction industry can be integrated into the world economic trend and deeper into the international market. Among them, the biggest, most realistic and most serious challenge is technological innovation. The manufacture and installation of high-tech and high value-added hydropower equipment is the focus of the international market in the future, and it is also a must for all large hydropower construction companies.
4. Looking forward to the development trend of hydropower construction welding technology in the 21st century
Since the beginning of the 21st century, with the increase of hydropower development investment, the acceleration of investment speed and the diversification of investment entities, it has brought new development opportunities to China's hydropower construction enterprises, especially after China's accession to the WTO, hydropower equipment processing industry. Faced with more intense competition. We must be soberly aware that welding technology still severely restricts the production, quality, cost and cycle of hydropower equipment manufacturing and installation. This has been confirmed by the practice of hydropower construction for four years since the beginning of the 21st century.
Combined with China's national conditions, the development direction of hydropower construction welding technology should be to improve the mechanization and automation level of welding, promote high-efficiency and energy-saving welding equipment and process technology, balance the development of welding-related technologies; combine new product development and new project start-up, research and application of new welding Processes, new technologies and new materials further improve welding production efficiency and quality, and reduce costs.
1. Cutting new technology
Hydropower construction should improve the mechanization and automation level of welding. Firstly, we must solve the technical update of steel cutting and cutting materials, improve the cutting quality and efficiency in an all-round way. At present, the relatively single flame cutting is divided into flame cutting and plasma arc cutting, forming a CNC cutting. Mainly, supplemented by manual or semi-automatic cutting, and fully exploit and utilize the advantages of CNC cutting.
Since the late 1980s, CNC flame cutting has: 1 full function, high degree of automation, can be configured with multiple torches working at the same time. 2 Effective cutting time and high production efficiency. 3 The nesting program is adopted to improve the utilization rate of the steel plate and reduce the thermal deformation. 4 cutting information is easy to prepare, modify and save. 5 The processing precision is high, the cutting quality is good, the machine is stable and reliable, and the operation is convenient. It has been widely used in China's hydropower equipment processing enterprises.
CNC flame cutting machine has many advantages that can not be ignored when cutting steel plates with thickness more than 30mm, cutting various shapes of cutting and multi-cutting torch for large-scale cutting of straight steel plates. It can be foreseen that CNC flame cutting technology will continue to play an important role in hydropower equipment manufacturing enterprises for a long period of time to come.
CNC plasma arc cutting has only been applied to China's hydropower equipment manufacturing industry for about 10 years, and its application range is narrow, and the application ratio is low. Plasma arc cutting has the advantages of no dross, narrow slit, smooth cutting surface, vertical cutting edge, high cutting precision and high productivity. It can be used for cutting stainless steel, aluminum, copper and other metals besides cutting carbon steel and low alloy steel. In recent years, due to the increase in the total amount of hydropower equipment manufacturing and the shortening of the manufacturing cycle, the steel plate cutting work of various hydropower equipment manufacturers has risen sharply, and the cutting production capacity is obviously insufficient. CNC plasma arc cutting technology, especially long-life oxygen plasma arc cutting technology can greatly reduce the cost on the basis of high quality and high speed, and has broad application prospects in hydropower equipment manufacturing enterprises.
The weight of various profiles (including welding profiles and rolled profiles) in metal structures such as steel gates accounts for more than 50% of the total weight of the gates. The types of profiles are: angle steel, flat steel, T-shaped steel, H-shaped steel. And I-beams, etc. These profiles are cut into various shapes of ends and intermediate holes, holes, and markings before forming or welding. Due to the variety of profiles, specifications and sizes, and more varied cutting content and technical requirements, we can not rely on existing equipment and means to achieve automated mass production, relying only on highly skilled personnel to use manual or semi-automatic operation. In order to further accelerate the manufacturing progress of hydropower equipment and improve the quality of manufacturing, it is necessary to change the backwardness of this operation. Domestic hydropower equipment manufacturers should develop or introduce CNC plasma cutting equipment in time.
2. Efficient welding material
The promotion and application of high-efficiency welding technology in the hydropower construction industry has been carried out for nearly 10 years, especially in the past 3 to 5 years, significant economic and social benefits have been achieved. Comprehensive analysis of the characteristics and actual conditions of the hydropower construction industry, its efficiency
The application trend of welding materials is highlighted by:
(1) CO 2 gas shielded flux cored wire with low soot, low cost and high performance.
(2) All-position iron powder electrode without baking before welding, extremely high deposition efficiency and good comprehensive performance.
(3) Submerged arc automatic welding wire, auxiliary pad and flux for single-sided welding double-sided forming.
3. Efficient welding process
In order to improve the welding production efficiency, the application of high-efficiency welding technology has formed a consensus in hydropower construction enterprises. At present, the welding of some steel structure products has replaced the original electrode arc welding process by flux cored wire CO 2 gas shielded welding. In addition, the application of high-efficiency welding methods is gradually developing in diversified directions. In addition to the traditional steel plate splicing using single wire submerged arc automatic welding, submerged arc automatic fillet welding, double wire submerged arc welding, submerged arc welding single-sided welding double-sided forming Welding techniques such as technology, gas protection automatic fillet welding, vertical welding and all-position automatic welding have been expanded in many hydropower construction companies. At the same time, some enterprises are conducting application research on the submerged arc automatic horizontal welding process, and the production efficiency and welding quality will be greatly improved.
4. Welding equipment
Maximizing the user's needs is the foundation of the development of welding equipment. Its development direction is: simple structure, convenient operation and maintenance, strong adaptability, excellent and stable welding performance, wide application standard, more general product, and control. The unity of intelligence and regulation.
(1) High-combination and multi-function (such as MIG, MAG, MMA, etc.), with a standard multi-function arc welding power source as the main body, with a variety of devices for a variety of purposes.
(2) Applying microcomputer to realize adaptive control of automatic welding machine. The microcomputer controls the dynamic and static characteristics of the arc welding power source, automatically adjusts the welding specification parameters, improves the welding performance, ensures the weld consistency, and obtains high quality welds.
(3) Welding equipment and welding auxiliary equipment that improve welding productivity and improve working conditions will have broader application prospects.
V. Suggestions
To achieve the renewal and progress of hydropower construction welding technology, in hydropower construction enterprises to promote efficient welding methods, the following issues must be dealt with:
(1) Promote efficient welding work, which is a systematic project consisting of welding equipment, welding process, welding materials, equipment maintenance and repair, personnel training, etc. Any abnormal operation of any link will affect the whole promotion and application work. Although the promotion of efficient welding methods will be greatly enhanced
High labor productivity, but in the early stage of promotion, it is a new thing, and it will inevitably encounter various problems and even resistance. At this time, the attention and support of the leaders is particularly important. Therefore, the establishment of a sound organizational system and effective operation is an important guarantee for doing a good job in this work.
(2) The promotion of efficient welding methods is a complex task involving many aspects such as technology and management. Therefore, in combination with the actual conditions of the company itself, fully investigate, carefully analyze, grasp the key points, and ensure that the promotion and application work is carried out purposefully, directionally and in an orderly manner according to the company's development trends and product types. important.
(3) The promotion work must be closely integrated with the construction and production. The technical personnel should go deep into the scene to help the workers solve the problems at the construction site, and promote and improve the enthusiasm and creativity of the workers in applying the efficient welding method.
(4) Strictly select the equipment, strengthen the maintenance and repair of the welding equipment, and ensure the integrity of the equipment.
(5) Strengthen the training of welding personnel, increase the intensity of technical exchanges, comprehensively improve the quality of welding technicians and welders in hydropower construction enterprises, to meet the needs of the promotion and application of high-efficiency welding technology, and resolutely abandon the kind of "heavy examination, light The practice of training or only examination, no training, otherwise the welder can not master the operation technology of the efficient welding method, which will seriously affect the welding efficiency and welding quality, and even lead to the promotion work.
Conclusion
After more than half a century, especially in the past 20 years, China's hydropower construction welding technology has made great progress, and the level of mechanization, automation and high efficiency has been greatly improved, but compared with other industries and foreign hydropower equipment processing enterprises. There is still a big gap, and the application process of high-efficiency welding technology can not fully adapt to the needs of rapid development of hydropower construction. At present, the process of economic globalization is accelerating, science and technology are developing rapidly, and the reform of hydropower construction enterprises is further deepened. As the main body of market competition and technological innovation, how to enhance the strength and competitiveness of enterprises by improving their technological level and technological innovation capabilities, thereby gaining greater The development is still a major issue before us.
High quality, high efficiency and low cost are the goals of high-tech welding technology. Its superior performance and good economy have been verified in long-term production practice. In the first 20 years of this century, the state has vigorously developed hydropower construction and fully opened up the hydropower investment market. The amount of steel used for hydropower construction will show a rapid growth trend in the future. This will undoubtedly set the stage for the future development of high-tech welding technology in the hydropower market. High-tech welding technology will be more brilliant tomorrow in the hydropower industry.
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