Welding technology and development

Abstract : This paper describes the development of welding technology as a traditional basic process and technology for manufacturing.

Keywords : welding; development

Welding technology, as a traditional basic process and technology in manufacturing, has a long history of application in industry, but its development is very rapid. In just a few decades, welding has made important contributions to the development of the industrial economy in many industrial sectors, such as aerospace, shipbuilding, automotive, bridges, electronic information, marine drilling, high-rise building metal structures. Widely used in China, welding has become an important professional discipline in manufacturing technology and materials science, creating a new chapter in connection technology.

With the development of science and technology, welding has evolved from a simple component joining method and a blank manufacturing method to a production method for producing a dimensionally accurate product in the manufacturing industry. Therefore, ensuring the stability of welding product quality and improving labor productivity has become an urgent problem to be solved in the development of welding production. The following examples focus on the following.

In the mechanical manufacturing industry, many large blanks that have been produced by the whole casting and forging method have been changed into welded structures, which greatly simplifies the production process and reduces the cost. Many cutting-edge technologies such as aerospace, nuclear power, etc., are not practically possible without the use of welded structures. The position of welding in the whole industry can also be judged from the fact that the welded structure produced by the world's major industrial countries accounts for about 45% of the steel output every year. The reason why the welded structure has developed so rapidly is because it has a series of advantage. The following is an example. (1) Compared with riveting, it can save a lot of metal materials, which can reduce the metal material by about 15-20%, because it does not need auxiliary materials, such as angle steel, flat plate, no need for rivets, and After a long time, the piece can loosen and affect the quality, but the welding is absolutely impossible. Although there is only one weld, it belongs to atomic tuberculosis, so it can solve all problems adequately. Secondly, the welding structure does not need to be punched, and the workload of the scribing is relatively small, so it is labor-saving and time-saving, and the work efficiency is of course much higher. (2) Compared with castings, the production of welded structures does not require the production of wood molds and sand molds, nor does it require special smelting, casting, simple processes and short production cycles. This is especially true for single-piece and small-volume production. In other words, it is particularly time-saving compared to castings, which means high efficiency. Secondly, the welded structure saves material compared to castings. In general, it is lighter than cast steel. More than -30%, 50-60% lighter than cast iron parts, mainly because the cross section of the welded structure can be selected according to the design requirements, and it is not necessary to increase the size due to the limitation of the process like the casting. Because the liquid wants to flow well enough, it must have a large space, which will inevitably use more metal materials.

For example, the lower beam of the 12,000-ton hydraulic press has a welded structure with a net weight of 260 tons. If steel castings are used, the weight will reach 470 tons, and the weight will be reduced by nearly 45%. This is because the casting blank is not easy to guarantee the dimensional accuracy, and the machining allowance will be very high. Large, so the liquid metal used will of course be much more, and it takes a very long time. This is because the melting and cooling of the metal takes a long time, and the investment in the equipment and plant required by the welding workshop is generally They are lower than the foundry that produces the same weight and damage. It only needs a certain site and the necessary power supply. It can be processed without special complicated processes. A weld seam has completely solved the problem, so the welding and casting are compared. Under the circumstance, it saves labor and saves materials and is very economical and cheap. The above comparison illustrates the superiority of welding quality and work efficiency.

Some components have special strength requirements in certain parts. For example, the rim part of a large gear must use high-strength wear-resistant high-quality alloy steel, so that it can be used for a long time to ensure its quality, but this The kind of steel is very expensive, which will greatly increase the cost, so other parts can be made of general steel in order to save materials, which improves the performance of the gear, makes it very strong and wearable, and saves high quality steel and reduces the cost. This uses the methods of tailor welding, such as surfacing and friction welding, which are processed and then spliced ​​together to form a perfect whole. This is also advantageous.

Because of the advantages of these weldings introduced above, we can obtain high-quality components as long as we correctly understand and grasp it properly, and can use them reasonably, so welding is absolutely irreplaceable and worthy of development.

Since the birth of modern welding technology, it has been directly influenced and guided by the latest developments of various disciplines. It is well known that the influence of new technologies in materials and information science has not only led to the advent of dozens of new welding processes, but also the operation of welding processes. Manual welding to automatic welding, automation, and intelligent transition has become a recognized trend.

Welding today as a traditional technology faces the challenges of the 21st century. On the one hand, materials as the pillars of the 21st century have shown several trends, from ferrous to non-ferrous metals; from metallic to non-metallic, from structural to functional, from multi-dimensional to low Dimensional material changes; from a single material to a composite material, new material connections must place higher demands on welding technology. On the other hand, the vigorous development of advanced manufacturing technology is increasingly demanding the development of welding technology from the aspects of housing, integration, and so on. Highlight "high" and "new" to meet the challenges of new technologies in the 21st century.

In the middle of the 20th century, the welding method also developed rapidly. With the further development of science and technology, new high-precision heat source electron beams, plasma beams, laser beams, etc. appeared, which made the precision and temperature greatly higher than that of arc welding. . Vacuum electron beam welding can weld 200mm metal at a time. Laser welding has the advantage of being welded in the atmosphere. Since the spot after focusing is only 0.2-2mm, the deformation is much smaller due to the small weld seam, and the joint quality is high. . For example, in the important fields such as aero-engines and automobile bodies, immediate economic and social benefits have been created, and the technical development direction of high efficiency, low consumption, clean and flexible production is completely met.

The emergence of new materials has given rise to new topics in welding technology and has become an important driving force in the development of welding technology. Many new materials, such as heat-resistant alloys, titanium alloys, ceramics, etc., have raised new issues. In particular, the connection between dissimilar materials is not completed by the usual welding method. The superiority of solid-state connection is becoming more and more obvious. Diffusion welding and friction welding have become hot spots in the welding industry. For example, metal and ceramics have been able to be diffusion-bonded. It used to be unimaginable, so solid-state connectivity is a connection technology that will have significant development in the 21st century.

Through the previous introduction we have known that welding has now evolved from a simple component joining method and a gross manufacturing method to a basic process in the manufacturing industry and the production of precision-precision finished products. Therefore, ensuring the stability of welding product quality and improving labor productivity has become an urgent problem to be solved in the development of welding production. The need to achieve automatic control of the welding process and automation of the welding process manufacturing is becoming more and more urgent. In addition, the development of computer technology, control theory, artificial intelligence, electronic technology and robot technology has provided a very favorable technical foundation for the automation of welding process, and has penetrated into various fields of welding, and has achieved many results. The automation of welding process has become welding. One of the growth points of technology. From the perspective of the development of welding technology, welding automation, robotization and intelligence have become a trend.

After summarizing the intelligent experience of welders and applying them to the highly advanced high-tech, it is able to achieve automatic welding quickly, flexibly and safely. Nowadays, welding automation control in developed countries has achieved satisfactory results for macro welding quality (such as The control of penetration control, joint size, etc. has made great progress, and the control of micro-welding quality (metallographic structure and mechanical properties of welds) has also started. The welding process is developing from macro to micro, from simple control to intelligent control of the system.

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