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Laser welding process

Laser welding process

In today's rail transit, shipbuilding and other industries, there is an increasing demand for welding of medium and large thickness steel plates. Welding technology is a key technology in ship processing and manufacturing and the development of the shipbuilding industry. Welding man-hours account for approximately 30% to 40% of the total shipbuilding man-hours.

Welding production efficiency and welding quality directly affect the production cycle, cost and hull quality of ship processing and manufacturing. Therefore, a more optimized welding method is needed.

Laser-arc hybrid welding arises in response to needs

As a new welding technology, laser-arc hybrid welding uses laser and arc as dual heat sources, which act on the same molten pool at the same time to form a laser-guided and stable arc. The arc improves the laser absorption rate of the metal and enhances the transfer and bridging of molten droplets. A capable welding method that gives full play to the advantages of laser welding and arc welding and makes up for their respective shortcomings. Especially in the welding of medium and large thickness materials, hybrid welding technology has greater advantages. Because traditional welding methods have shortcomings such as low joint strength, low efficiency, serious deformation, and large consumption of welding materials; and single laser welding also has some shortcomings, such as high joint assembly process requirements and welding capabilities restricted by laser power. Large, poor bridging ability, serious undercutting of welds, etc.

As a new welding method, laser-arc hybrid welding has the following three significant characteristics:
1) Improve energy utilization, increase weld penetration depth and welding speed;
2) Reduce workpiece assembly requirements;
3) Improve weld quality and improve weld formation;

Laser-arc hybrid welding can achieve 1+1>2

There are many forms of laser-arc hybrid welding, including Laser-MAG/MIG hybrid welding, Laser-TIG hybrid welding, laser-plasma arc hybrid welding, etc. Among them, the commonly used laser light sources at this stage are fiber lasers and semiconductor lasers. For example, Raycus continuous fiber laser 4000W, 6000W and fiber output semiconductor laser 4000W.

Laser-MAG hybrid welding has two welding heat sources, namely laser and MAG arc. When used as a separate heat source for welding, an effective molten pool can be formed, but the characteristics of the molten pool are different: the characteristics of the laser welding molten pool are "deep and narrow" ”, the opening area is small and the depth is large, which is not conducive to the formation of the weld; the MAG arc welding molten pool is characterized by being “shallow and wide”, the opening area is large and the depth is small, which is conducive to the formation of the weld and has strong bridging ability.

During the Laser-MAG composite welding process, two heat sources act on the base material at the same time. There is mutual influence between the two heat sources, and there is also mutual influence between the two molten pools, which will eventually form a new composite molten pool. This composite molten pool has both the "large depth" of the laser molten pool and the "large area" of the arc molten pool. This composite molten pool has a large depth, good weld formation, and strong bridging ability. At the same time, because of the MAG arc welding There is welding wire filling, and the type of welding wire can be selected, so according to the performance defects of the base material itself, the appropriate welding wire can be selected and added to the welding process, thereby improving the crack resistance, fatigue resistance, and corrosion resistance of the weld at the micro level. , wear resistance and other aspects to carry out purposeful improvements. In addition, during the entire welding process, there are two heat sources acting on the base material. The mutual influence between them can increase the penetration depth and achieve the effect of "1+1>2". Therefore, the single melting point of laser-arc hybrid welding is The penetration capacity will be significantly improved. Finally, laser-arc hybrid welding can achieve multi-pass stacked welding and welding of large thickness materials, and the fusion ability of the upper and lower weld beads and side walls is very strong due to the arc.

With the development of laser-arc hybrid welding technology, its application scope is becoming more and more extensive, especially in foreign countries, but rarely in domestic applications. It has broad prospects. Its main application fields are as follows:

Among all manufacturing industries, the shipbuilding industry is the biggest beneficiary of laser-arc hybrid welding technology. In order to maintain their advantages in the high value-added shipbuilding industry, some European shipyards have widely adopted laser-arc hybrid welding technology, which has greatly improved welding quality and production efficiency in thick plate welding applications. Typical and representative is that Meyer Shipyard in Germany has adopted laser-arc hybrid welding method for ship welding. industry
Germany took the lead in applying laser-arc hybrid welding technology to the connection manufacturing of automobile doors, side panels and other components. Scholar Graf T and others reported at the International Automobile Welding Forum "Application of Laser Hybrid Welding in Volkswagen and Audi Cars [C ]" It is reported that there are 66 welds on the front door of the Volkswagen Phaeton sedan, with a total length of 4.98m, including 48 laser-arc composite welds; the total composite welding length of the body frame of the Audi A8 sedan is 4.5m.

New energy vehicles are booming, and the core of their power is the power battery. In order to reduce the overall weight of the vehicle, the power battery trays are generally made of aluminum alloy. The trays are assembled and welded, and each tray has dozens of welds. , and the weld strength requirements are high, and the welding efficiency requirements are high. Traditional arc welding and conventional laser welding are difficult to meet the requirements, and laser-arc hybrid welding is a connection method that meets the needs very well.

03.Petrochemical industry
According to research on the laser-MAG arc hybrid welding process of oil transportation pipelines, it was found that compared with using laser alone as a heat source after welding, laser-arc hybrid welding can increase the penetration depth by 20%, and the welding process is more stable with a small amount of spatter. The seam is well formed, has a good melt-to-width ratio, and has no welding defects such as undercuts or lack of fusion. After welding, the pores are controlled within a certain range by X-ray inspection, which does not affect the quality of the welded joint and meets the engineering requirements.

Laser-MIG hybrid welding is used to weld oil tanks. Due to the addition of laser, the weld penetration depth is greatly improved, so that single-sided welding can be performed, avoiding the inconvenience caused by double-sided welding. Not only the quality of welds has been improved, but also huge breakthroughs have been made in improving welding efficiency and production capacity. At present, laser-arc hybrid welding has been widely used in German oil tank manufacturing industry.

04.Aerospace field
In the aerospace field, laser-MIG/MAG arc hybrid welding technology has also begun to be used in the welding of medium-thick plates and high-strength steel, achieving 7mm thick 3CrMnSiA laser-MAG arc hybrid welding without preheating, which greatly reduces workers' labor intensity and Improved welding production efficiency.

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