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Laser welding technology of body
Publisher: suzhou kailinneng automation equipment co., LTD Release time：2023-03-23 08:44:42 Click on the number of times：116 Shut down

As an advanced optoelectromechanical welding technology, laser welding technology has advantages such as high energy density, fast welding speed, small welding stress and deformation, and good flexibility compared with traditional automobile body welding technology. Therefore, laser welding technology is an important technical means to achieve high quality development of automobile industry. This paper introduces the application of laser welding in automobile body welding in detail. At present, the main laser welding processes used in the field of automotive body welding include laser deep penetration welding, laser wire filling welding, laser brazing and laser arc composite welding.
Laser deep penetration welding technology for automobile body


Laser deep penetration welding refers to that when the laser power density reaches a certain level, the material surface vaporizes and forms the keyhole. The metal vapor pressure in the hole and the static pressure and surface tension of the liquid around reach a dynamic balance. The laser can be irradiated to the bottom of the hole through the keyhole, and a continuous weld is formed with the movement of the laser beam. There is no need to add auxiliary flux or filler in the process of laser deep penetration welding, and the workpiece is completely welded with its own materials.


The weld obtained by laser deep penetration welding is smooth and straight, and the deformation is small, which is conducive to improving the manufacturing accuracy of automobile body. The high tensile strength of the weld ensures the welding quality of the automobile body. Fast welding speed is beneficial to improve welding production efficiency.


In automobile body welding, laser deep penetration welding technology can meet the welding requirements of body assembly welding and patchwork welding. In the body assembly welding, it is mainly used for the welding of the body top cover, side wall, door and other areas. In the body welding, it is mainly used for the welding of steel plates with different strengths, different thicknesses and different coatings.


Laser wire filling welding technology for automobile body


Laser wire filling welding is the process of pre-filling a specific welding wire in the weld or synchronizing the welding wire in the process of laser welding to form a welding joint. It is equivalent to input approximately homogeneous welding wire material into the weld pool at the same time of laser deep penetration welding.

Compared with laser deep penetration welding, laser wire filling welding used in automobile body welding has two advantages. First, it can greatly improve the tolerance of assembly gap between automobile body parts to be welded, and solve the problem that laser deep penetration welding requires too much groove gap. Second, the microstructure distribution of the weld area can be improved by using welding wire with different composition content, so as to regulate the weld performance.


In the process of automobile body manufacturing, laser wire filling welding is mainly used in the welding of aluminum alloy and steel parts. Especially in the welding process of aluminum alloy parts of automobile body, the surface tension of the molten pool is small, which is easy to lead to the collapse of the molten pool. In the laser wire filling welding process, the collapse of the molten pool can be solved to a greater extent by melting the welding wire.


Laser brazing technology for automobile body
Laser brazing uses laser as a heat source, laser beam after focusing irradiates to the surface of the welding wire to melt the welding wire, the melted wire drops and fills between the parts to be welded, metallurgical effects such as dissolution and diffusion occur between the filler metal and the workpiece, so as to achieve the effect of connecting the workpiece.
Unlike the laser wire filling welding process, the laser brazing process only melts the wire and does not melt the parts to be welded. Laser brazing has good welding stability, but the weld tensile strength is low.

在汽车车身焊接过程中，激光钎焊工艺主要对接头强度要求不高的车身部位进行焊接，如车身的顶盖和侧围之间的焊接、行李箱盖上下部之间的焊接等。
汽车车身激光-电弧复合焊工艺
激光-电弧复合焊接是采用激光和电弧两种热源同时作用到待焊工件表面，使工件经过熔化、凝固后形成焊缝的一种复合焊接工艺。
激光-电弧复合焊接兼具了激光焊接和电弧焊的优点：
一、在双热源的作用下，焊接速度得以提高，使热输入变小，焊缝变形量小，保持了激光焊接的特点；
二、具有更好的桥接能力，装配间隙容忍度更大；
三、熔池的凝固速度变慢，有利于消除气孔、裂纹等焊接缺陷，有利于改善热影响区组织和性能；
四、由于电弧的作用，使其能够焊接高反射率、高导热系数的材料，应用材料的范围更广。
在汽车车身制造过程中，激光-电弧复合焊接工艺主要应用于车身铝合金构件和铝合金-钢异种金属结合处的焊接，主要是针对装配间隙较大的部件进行焊接，如汽车车门部分位置的焊接，这是因为装配间隙能发挥激光-电弧复合焊接的桥接性能。

其他汽车车身激光焊接工艺


Laser deep penetration welding, laser wire filling welding, laser brazing and laser - arc composite welding have been more mature theoretical research and extensive practical application in the welding of automobile body.
In addition, with the improvement of the automobile manufacturing industry's requirements on the efficiency of body welding and the increase of the dissimilar material welding demand faced by the automobile lightweight manufacturing, the application of laser spot welding, laser swing welding, multi-beam laser welding and laser flight welding in the automobile body welding has been paid attention to.
01 Laser spot welding process
Laser spot welding is an advanced laser welding technology with high welding speed and high welding precision. The basic principle of laser spot welding is to focus the laser beam to a certain point on the part to be welded, so that the metal at the point instantly melts, by adjusting the laser density to achieve thermal conduction welding or deep fusion welding effect, when the laser beam stops acting, liquid metal reflow, solidified to form a joint.
There are two main forms of laser spot welding: pulsed laser spot welding and continuous laser spot welding. Pulse laser spot welding has high laser beam peak energy, but short acting time, which is generally used for magnesium alloy, aluminum alloy and other light metals welding. Continuous laser spot welding the average power of the laser beam is high, the laser action time is long, and it is widely used in steel welding. Compared with resistance spot welding in auto body welding, laser spot welding has the advantages of non-contact, spot welding trajectory can be designed independently, which can meet the requirements of high quality welding under different lap gaps of auto body materials.
02 Laser swing welding technology
Laser swing welding is a new laser welding technology which has been proposed in recent years. The main principle of this technology is to realize the rapid, orderly and small range of the laser beam oscillation by integrating the vibrating mirror group on the laser welding head, so as to achieve the effect of the laser beam moving forward while stirring.
The main swing tracks of laser swing welding include transverse swing, longitudinal swing, circular swing and infinite swing. Laser swing welding technology has obvious advantages in the process of automobile body welding. Because the flow state of molten pool can be changed significantly under the action of laser beam swing, it can eliminate unfused defects, achieve grain refinement and inhibit porosity in the same kind of automobile body material welding. It can also improve the problem that different materials are not mixed enough and the mechanical properties of welding seam are poor.


03 Multi-laser beam welding process
At present, the single laser beam can be divided into multiple laser beams by the splitter module installed in the welded joint.
Multi-beam laser welding is equivalent to the application of multiple heat sources in the welding process, can be adjusted by the energy distribution of the beam, so that different beams to achieve different functions, such as: higher energy density of the beam as the main beam, responsible for deep fusion welding, low energy density of the beam can clean and preheat the surface of the material, increase the absorption rate of the material of the laser beam energy.
04 Laser flight welding technology
Laser flight welding technology is a new and efficient laser welding technology, high welding efficiency, welding trajectory can be independently designed.
The basic principle of laser flight welding is that when the laser beam is incident on the X and Y mirrors of the scanning mirror, the Angle of the mirror is controlled by independent programming, so as to realize the deflection of the laser beam at any Angle.
In the traditional laser welding process of automobile body, the welding robot mainly drives the laser welding joint to move synchronously to achieve the welding effect. However, the welding efficiency of automobile body is severely restricted by the repetitive reciprocating motion of welding robot due to the large number and long weld length of automobile body. In contrast, laser flight welding only needs to adjust the Angle of the mirror to realize the welding of the beam in a certain range. Therefore, the application of laser flight welding technology in automobile body welding can significantly improve the welding efficiency and has broad application prospects.

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