Laser Welding Of Zinc-Coated Steels With Filler Powder

Zinc-coated steels are used extensively in the automobile industry because they are durable and have high corrosion resistance and formability. Lasers are being used to weld zinc-coated steels due to high welding speed, small welding seam and narrow heat affected zone. However, to a great extent, the industry application of laser welding zinc-coated steels is limited, as the laser facula diameter is so small that make the laser welding need the sheet with high precision in processing and assembling.This paper studies the effect of zinc and shielding gas type on Laser weldability of zinc-coated steels. The experiment results show that, the size of laser-induced plasma is twice larger than that of cold plate laser welding when zinc coated steels are welded because the boiling point of zinc is low and easily to be volatilzed. But, zinc has a little effect on plasma controlling and weld formability by side blown shielding gas. The critical power density of laser-induced plasma varies with the type of shielding gases. Further, The weld penetration, tensile strength and formability of laser welding are found to be deeply dependent on the types of shielding gas.This paper designs a new kind of nozzle used for laser welding of zinc-coated steels with metal powder and studies the better modality of shielding gas and the powder beam with schlieren device. By comparative experiment, the paper studies the effects of powder and the processing parameter on CO₂ laser welding of zinc-coated steels. The experiment results show that, only when the powder beam aims at the area which is near the crystallization edge and the root of plasma, we can make sure that the powder enter the weld pool efficiently. In addition, the powder can be utilized availably when welding speeds are matched with proper laser power density and welding input energy. Laser welding with powder reduce high standard of the precision of workpieces processing and assembling. This technique will enhance the adaptive faculty of laser welding and extend its industry application.