Laser welding is suitable for welding a variety of materials. The laser’s high power density and high welding speed make the laser weld and heat affected zone very small. The chemical composition of the weld can be adjusted according to the different requirements of the weld structure, and the best weld performance can be obtained by controlling the welding conditions.
Carbon steel
Low carbon steel and low alloy steel have good weld ability, but when using laser welding, the carbon content of the material (carbon equivalent C) should not be higher than 0.25%.
Calculation formula of carbon equivalent:
C=C%+Mn/6%+Ni/15%+Cr/13%+Cu/13%+Mo/4%
For materials with carbon equivalent of more than 0.3%, the welding cold crack tendency will increase. Considering a certain shrinkage of the weld in the design is conducive to reducing the residual stress and crack tendency in the weld and heat-affected zone. When the material with carbon equivalent greater than 0.3% and the material with carbon equivalent less than 0.3% are welded together, the bias weld is beneficial to limit the martensite transformation and reduce the generation of cracks. When the carbon equivalent of the material is more than 0.3%, reducing the quenching speed can also reduce the crack tendency.
Galvanized steel, because the vaporization temperature of zinc (903℃) is much lower than the melting point of steel (1535℃), zinc evaporation in the welding process causes serious pores in the weld, so it is difficult to use laser welding, especially penetrating welding. Now there are experiments to set a 0.1mm gap between the upper and lower materials to release zinc vapor from the gap. But it is difficult to operate the clearance in actual production.
The content of sulfur and phosphorus has a certain effect on the welding crack. The steel with sulfur content higher than 0.04% or phosphorus content higher than 0.04% is prone to crack during laser welding.
The surface of the carbon steel because of its surface carbon content is high, easy to produce solidification cracks and crack in the carbon layer, usually not suitable for laser welding.
Post time: Sep-28-2022