The welding performance of Jinan galvanized steel sheet has obvious particularity compared with the same kind of steel sheet without galvanizing. Although the thickness of zinc layer is very small for the thickness of steel plate, it has a great influence on the welding performance. In laser lap welding, the zinc vapor between the lap plate gaps will flow to the molten pool, interfere with the liquid flow in the molten pool, cause spatter and porosity, and even serious undercut.
Jinan galvanized sheet
Characteristics and defects of laser welding of galvanized sheet: according to the welding mechanism, laser welding can be divided into two categories, namely heat conduction welding and deep penetration welding. The former is mainly used for surface heat treatment of materials, while the latter is widely used in welding field. The essence of laser deep penetration welding is keyhole effect. Because of the keyhole, the laser beam can penetrate into the material, and the molten liquid metal surrounds the keyhole. The heat input of the laser to the material is mainly on the liquefying interface on the wall of the keyhole. With the movement of the laser beam, the metal in the front of the keyhole is melted and vaporized, while the liquid metal in the back of the keyhole is solidified again to form welding To complete the welding process.
One of the basic characteristics of laser welding galvanized sheet is the generation of plasma, which seriously obstructs the laser beam and reduces the absorption of laser energy, which is not conducive to the formation of small holes and maintaining stability in deep penetration welding; another feature is the formation of zinc vapor in the welding process. In the butt joint, zinc vapor can freely expand on the upper and lower surfaces of the steel plate and emit into the air Moreover, the zinc burning area is very small, generally 12mm (less than the plate thickness), and the corrosion resistance of the joint is not greatly damaged. In laser lap welding, the zinc vapor between steel plates is easy to enter into the molten pool, resulting in a series of welding defects, weakening the joint performance.