Laser welding is to use high-energy laser pulse to locally heat the material in a small area.
The energy of laser radiation is guided to the internal diffusion of the material through heat transfer, and the material is melted to form a specific molten pool to achieve the purpose of welding.
Laser welding machine is a machine for laser material processing.
According to its working mode, it is divided into laser mold welding machine, automatic laser welding machine, laser spot welding machine and optical fiber transmission laser welding machine.
The laser welding machine can be used for welding die steel of S136, SKD-11, NAK80,8407,718,738, H13, P20, W302, 2344 and other models, and the welding effect is good.
Carbon steel is welded by laser welding machine with good effect, and its welding quality depends on the content of impurities.
In order to obtain good welding quality, preheating is required when the carbon content exceeds 0.25%.
When steels with different carbon contents are welded to each other, the welding torch can be slightly biased to the side of low-carbon materials to ensure the quality of joints.
Because the heating speed and cooling speed of laser welding machines are very fast, when welding carbon steel, with the increase of carbon content, the welding crack and notch sensitivity will also increase.
Medium and high carbon steels and ordinary alloy steels can be well welded by laser, but preheating and post-weld treatment are required to eliminate stress and avoid cracks.
In general, stainless steel welding is easier to obtain high-quality joints than conventional welding.
Due to the high welding speed and small heat-affected zone of laser welding, the overheating phenomenon and the adverse effect of large linear expansion coefficient during stainless steel welding are reduced, and the weld has no defects such as pores and inclusions.
Compared with carbon steel, stainless steel is easier to obtain deep penetration narrow weld because of its low thermal conductivity, high energy absorption and melting efficiency.
The joints with good appearance, smooth and beautiful welds can be obtained by welding thin plates with low-power laser.
Copper and copper alloys
Welding copper and copper alloy is easy to cause the problem of incomplete fusion and incomplete penetration, so energy-concentrated and high-power heat sources should be adopted and preheating measures should be taken;
When the thickness of the workpiece is thin or the structural stiffness is small and there are no deformation prevention measures, it is easy to produce large deformation after welding, and when the welded joint is subject to large rigid constraints, it is easy to produce welding stress;
It is also easy to produce thermal cracks when welding copper and copper alloys;
Porosity is a common defect in copper and copper alloy welding.
Laser welding technology can be used for almost all thermoplastics and thermoplastic elastomers. Common welding materials include PP, PS, PC, ABS, polyamide, PMMA, polyoxymethylene, PET and PBT.
Other engineering plastics, such as polyphenylene sulfide PPS and liquid crystal polymers, can not directly use laser welding technology because of their low laser transmittance.
Generally, carbon black is added to the bottom material so that the material can absorb enough energy to meet the requirements of laser transmission welding.
Laser welding of aluminum alloy
The main difficulty in laser welding of aluminum and its aluminum alloy is its high reflectivity to 10.8pon CO2 laser beam.
Aluminum is a good conductor of heat and electricity.
The high density of free electrons makes it a good reflector of light.
The reflectivity of the initial surface exceeds 90%, that is, deep penetration welding must start with less than 10% of the input energy, which requires high input power to ensure the necessary power density at the beginning of welding, and small holes are generated.
Laser welding of magnesium alloys
The density of Mg alloy is 36% lower than that of Al, which has attracted much attention as a high-specific strength material.
Therefore, pulsed YAG laser and continuous C02 laser welding tests were carried out.
For AZ31B-H244 alloy (3.27% Al, 0.79% Zn) with a plate thickness of 1.8mm, the best welding conditions with fewer defects were average power of 0.8kw, 5ms, 120Hz, 300mm/s and focus size of 0.42mm.
Good penetration weld was obtained by continuous C02 laser welding.
Low alloy high strength steel
For laser welding of low alloy high-strength steel, as long as the selected welding parameters are appropriate, the joint with the mechanical properties equivalent to the base metal can be obtained.
HY-130 steel is a typical low alloy high strength steel.
After quenching and tempering, it has high strength and high crack resistance.
With the conventional welding method, the weld and HAZ structure are the rod combination of coarse grain, partial fine grain and original structure.
The toughness and crack disturbance of the joint are much worse than that of the base metal, and the weld and HAZ metal structures are particularly sensitive to cold cracks in the as-welded state.
Laser welding can weld more than these materials and laser welding can be carried out among a variety of dissimilar metals.
Research shows that laser welding can be carried out among a variety of dissimilar metals such as copper nickel, nickel titanium, copper titanium, titanium molybdenum, brass copper and low carbon steel copper under certain conditions.