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Introduction and technical summary of laser composite welding

   Laser welding is an efficient and precise welding method using high energy density laser beam as heat source.Composite welding is a new welding technology based on laser welding combined with other welding technologies, which is very popular in the welding industry.Laser composite welding may be applied to the welding of sheet materials, including carbon steel, high alloy steel, and aluminum, with or without coating.Application fields include aerospace, rail transit, shipbuilding, automobile and related industries, electronic instruments, construction machinery, pressure vessels, medical, food and nuclear energy, etc.


Laser composite welding process:

1) Plasma arc composite welding:

   Laser plasma composite adopts the coaxial mode. The plasma arc is generated by the annular electrode and the laser beam passes through the middle of the plasma arc. The plasma arc has two main functions:

1. Provide additional energy for laser welding, improve the welding speed, and thus improve the efficiency of the whole welding process;

 

2. The plasma arc surrounding the laser can produce the effect of heat treatment, extend the cooling time, reduce the sensitivity of hardening and residual stress, and improve the microstructure performance of the weld.

 

2) Double laser beam welding technology:

   In the laser welding process, due to the high laser power density, the welding base material is rapidly heated to melt and vaporize, generating high-temperature metal steam.Under the continuous action of high power density laser, plasma cloud is easy to be generated, which not only reduces the laser absorption of workpiece, but also makes the welding process unstable.If after the formation of a larger deep penetration hole, the laser power density that continues to shine is reduced, but the larger deep penetration hole that has been formed absorbs more laser, as a result, the effect of the laser on the metal vapor is reduced and the plasma cloud can be reduced or disappeared.Therefore, with a high peak power of pulse laser beam and a continuous laser beam, or two beams of pulse width, repetition frequency, and differ from that of peak power of pulse laser composite welding was carried out on the workpiece, in the process of welding, two laser beam irradiation together artifacts, cycle to form a larger deep penetrating holes, timely stop after a laser beam irradiation, can make the plasma cloud is small or disappear, improve the absorption of laser energy and the use of workpiece, increase welding penetration, and improve the welding ability.

 

3)MIG composite welding:

   Recent studies show that laser-MIG composite heat source welding has obvious advantages in medium - thick plate welding.By adjusting the relative position of arc and laser, this welding method can effectively improve the welding adaptability, improve the adaptability to large gap and improve the weld forming. At the same time, the input arc energy can adjust the cooling rate and thus improve the microstructure.Under the interaction of laser and arc, the welding process becomes more stable and the welding speed is increased at the same time of increasing the depth of penetration.When welding, the heat input is relatively small, which means that the deformation and welding residual stress after welding are small, which can reduce the time of welding clamping, positioning, orthopedic treatment after welding, etc.In addition, the prominent feature of this method is that it can fill wire stably, so that it is easier to improve the metallurgical properties and microstructure of welding seams.

 

4)TIG composite welding:

Characteristics of TIG composite welding laser and TIG composite welding are:

1. Using arc to enhance the role of laser, small power laser can be used instead of high power laser to weld metal materials

2, in the welding of thin parts can be high-speed welding

3, can increase the depth of fusion, improve the weld forming, to obtain high-quality welding joints

4, can ease the base material end interface precision requirements

 

5) High-frequency induction composite welding technology:

   Electromagnetic induction is a heating method that relies on the eddy current resistance heat generated inside the workpiece. Like laser, it is non-contact and environmentally friendly heating with fast heating speed, which can realize the accurate control of heating area and depth. It is especially suitable for automatic material processing and has been widely used in industry.

 

6) Arc composite welding technology:

   Arc-composite heat source welding method was proposed by British scholar Steen as early as 1980s, but for a long time since then, scientists have not done further research and development on it.


Advantages of composite laser welding:

   Laser composite welding technology has great advantage and application space in aeroengine thin-wall parts manufacturing.Welding deformation is one of the main factors affecting the quality and production efficiency of thin-wall parts. The existence of welding deformation not only affects the manufacturing process of products, but also affects the performance of products.Parts welding deformations during the welding process is the basic factor of uneven heating and cooling caused by thermal stress and organization stress caused by organization transformation (phase change) material, and the residual stress after welding will be on the final machining precision and dimension stability, precipitation strengthening alloy and the formation of hot crack and the fatigue strength of parts produced adverse effect, thus realize the welding deformation control is the most main thin-walled machine box parts welding technical difficulties.Laser composite automatic welding is the most direct method to ensure the stability of the process, control the deformation of parts, and ensure the consistency and stability of the welding process.


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