Laser welding technology as an optoelectronic integration of advanced welding technology, compared with the traditional auto body welding technology has a high energy density, welding speed, welding stress and deformation of small, flexible and so on.
Therefore, laser welding technology is an important technical means to realize the high-quality development of the automotive industry. Chutian Zhonggu Lianchuang in this paper describes in detail the application of laser welding in automobile body welding!
Currently applied in the field of automotive body welding the main laser welding process includes laser deep fusion welding, laser filler wire welding, laser brazing and laser arc composite welding.
Auto body laser deep welding process
Laser deep melting welding refers to the laser power density reaches a certain level, so that the material surface vaporization and the formation of a keyhole, the hole metal vapor pressure and the surrounding liquid static pressure and surface tension to achieve dynamic equilibrium, the laser can be irradiated through the keyhole to the bottom of the hole, along with the movement of the laser beam to form a continuous weld. Laser deep fusion welding welding process does not need to add auxiliary flux or filler, completely using the workpiece's own material welded into one.
The weld obtained by laser deep fusion welding is generally smooth and straight, with small deformation, which is conducive to improving the manufacturing accuracy of the auto body; the weld has high tensile strength, which ensures the quality of auto body welding; the welding speed is fast, which is conducive to improving the welding production efficiency.
In automobile body welding, laser deep fusion welding process can meet the welding needs of body group welding and welding. In the body group welding is mainly used for body roof, side, door and other areas of welding, in the body welding is mainly used for different strengths, different thicknesses, different coatings of steel welding.
Auto body laser wire filling welding process
Laser wirefill welding is a process of forming a welded joint by pre-filling the weld seam with a specific wire or synchronously feeding the wire during the laser welding process. This is equivalent to feeding a nearly homogeneous wire material into the weld pool at the same time as the laser deep melting process.
Compared with laser deep melting welding, laser filler wire welding applied to automotive body welding has two advantages, one is to significantly improve the tolerance of assembly gap between the auto body parts to be welded, to solve the problem of laser deep melting welding on the bevel gap is too high; the second is to improve the weld region through the use of different composition content of the wire to improve the distribution of the weld area, and then regulate the performance of the weld.
In the process of automobile body manufacturing, laser filler wire welding process is mainly used in the body of aluminum alloy and steel parts welding. Especially in the welding process of aluminum alloy parts of the car body, the surface tension of the molten pool is small, which is easy to lead to the collapse of the molten pool, and the laser filler wire welding process can solve the problem of molten pool collapse to a greater extent through the melting of the welding wire in the laser welding process.
Auto body laser filler brazing process
Laser brazing using laser as a heat source, the laser beam after focusing irradiation to the wire surface so that the wire melting, melting wire drops and filler to be welded between the workpiece, brazing material and the workpiece between the metallurgical effect of dissolution and diffusion, so that the workpiece to achieve the effect of connection.
Unlike the laser wire filling welding process, the laser brazing process only melts the wire but not the workpiece to be welded. Laser brazing has good welding stability, but the tensile strength of the weld obtained is low.
In the process of automobile body welding, laser brazing process is mainly for the joint strength requirements are not high body parts welding, such as the body of the roof and the side of the body between the welding, luggage cover between the upper and lower parts of the welding and so on.
Automobile body laser - arc composite welding process
Laser - arc composite welding is the use of laser and arc two heat sources at the same time to the surface of the workpiece to be welded, so that the workpiece through the melting, solidification after the formation of the weld a composite welding process.
Laser - arc composite welding combines the advantages of laser welding and arc welding, one is in the role of dual heat source, welding speed can be improved, so that the heat input becomes smaller, the weld deformation is small, to maintain the characteristics of the laser welding, the second has a better bridging ability, assembly gap tolerance is greater; three is the molten pool of the solidification speed slows down, is conducive to the elimination of pores, cracks and other welding defects, and is conducive to the improvement of the organization of the heat-affected zone and performance; Fourth, due to the role of the arc, making it possible to weld materials with high reflectivity and high thermal conductivity, a wider range of application materials.
In the car body manufacturing process, laser - arc composite welding process is mainly used in the body of aluminum alloy components and aluminum alloy - steel dissimilar metal combination of welding, mainly for the assembly gap is larger parts for welding, such as automotive door part of the position of the welding, this is because of the assembly gap can play the laser - arc composite welding of the bridging performance.
Other automobile body laser welding process
Laser deep melting welding, laser filler wire welding, laser brazing and laser - arc composite welding and other welding processes in the automobile body welding has a more mature theoretical research and a wide range of practical applications.
In addition, as the automobile manufacturing industry's demand for body welding efficiency improves and the demand for heterogeneous material welding increases in automobile lightweight manufacturing, the application of laser spot welding, laser oscillating welding, multibeam laser welding, and laser flight welding has been paid attention to in the welding of automobile bodies.
- Laser spot welding process
Laser spot welding is an advanced laser welding technology with outstanding advantages of fast welding speed and high welding precision. The basic principle of laser spot welding is to focus the laser beam to a point on the parts to be welded, so that the metal at the point of instantaneous melting, by adjusting the laser density to achieve the effect of heat conduction welding or deep melting welding, when the laser beam stops functioning, the liquid metal reflux, solidification after the formation of joints.
There are two main forms of laser spot welding: pulsed laser spot welding and continuous laser spot welding. Pulsed laser spot welding laser beam peak energy is high, but the role of time is short, generally used for magnesium alloy, aluminum alloy and other lightweight metal welding; continuous laser spot welding laser beam in general the average power is high, the laser role of time is long, and is used for steel welding. Laser spot welding in automobile body welding compared to resistance spot welding has the advantages of non-contact, spot welding trajectory can be designed independently, to meet the demand for high-quality welding of automobile body materials under different lap gap.
- Laser Oscillating Welding Process
Laser pendulum welding is a new laser welding technology proposed in recent years, which has received widespread attention. The main principle of this technology is to integrate the vibrating mirror group in the laser welding head to realize the rapid, orderly, small-scale oscillation of the laser beam, so as to achieve the effect of the beam moving forward and stirring while laser welding.
The main oscillation trajectory of laser oscillation welding includes: transverse oscillation, longitudinal oscillation, circular oscillation and infinite oscillation. Laser oscillation welding process for automobile body welding process has significant advantages, due to the role of the laser beam oscillation can significantly change the flow state of the molten pool, so not only in the same kind of automobile body material welding can eliminate the unfused defects, grain refinement and inhibit porosity; but also improve the automobile body of dissimilar materials welding of different materials are not sufficiently mixed, weld mechanical properties of the problem of poor.
- Multi-laser beam welding process
At present, the fiber laser can be installed in the welding head through the beam-splitting module will be a single laser beam into multiple laser beams.
Multi-beam laser welding is equivalent to applying multiple heat sources in the welding process, can be adjusted through the beam energy distribution, so that different beams to achieve different functions, such as: higher energy density of the beam is the main beam, responsible for the deep fusion welding, the lower energy density of the sub-beam can be cleaned on the material surface and preheat, increase the material on the laser beam energy absorption rate.
- Laser flight welding process
Laser flight welding technology is a new type of high-efficiency laser welding technology, high welding efficiency, welding trajectory can be designed independently.
The basic principle of laser flight welding is that when the laser beam is incident on the X, Y two mirrors of the scanning mirror, the angle of the mirror is controlled through the independent programming, so as to realize the deflection of the laser beam at any angle.
The traditional auto body laser welding process, mainly relying on welding robots to drive the laser welding head for synchronized movement, to achieve the welding effect. However, the number of automobile body welds, weld length is long, the repetitive reciprocating motion of the welding robot seriously limits the welding efficiency of the automobile body. In contrast, laser flight welding only needs to adjust the angle of the reflector to realize the welding of the beam within a certain range. Therefore, the application of laser flight welding technology in automobile body welding can significantly improve the welding efficiency, and has a broad application prospect.
