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Aluminium - Steel welding of dissimilar materials
aluminum alloy has small density, good corrosion resistance, high electrical conductivity and thermal conductivity, excellent features. Use aluminum alloy instead of steel can greatly reduce the quality of the welding structure. The steel has good mechanical properties and weldability, aluminum - Steel welded structure has been widely used in automobile, ship manufacturing and other industries. Aluminum melting point is 660 ℃, 700 - less than steel The low melting point 900 ℃, during welding, the aluminum melt, the ShiGang still not melting, vary widely due to the density of aluminum and steel, the aluminum will float above the steel in molten pool, after cooling will cause uneven weld composition; Linear expansion coefficient between aluminum and steel large difference, causes the large residual stress in welding joint, can lead to welding crack. For the realization of the aluminium - Reliable connection of steel will need to overcome the oxide film on the surface of the aluminium and aluminium alloy of the connection block, aluminum and aluminum alloy and steel interface does not generate or reduce the brittle intermetallic compound. The existing welding method is: 1, the bonding pressure welding is in the process of welding, butt welding pieces of pressure, Heating or heating) To complete the welding method. When welding aluminum and steel, common explosion welding, magnetic pulse welding, friction stir welding, diffusion welding and other methods. 2, molten aluminum brazing - Steel weld brazing dissimilar materials with the characteristics of fusion welding and brazing, welding process, aluminum alloy and solder melts, condensation together after, formation of fusion welding joint; Aluminum and steel melt, molten solder by capillary action, inside is filled with inhalation and solid-state welding gap dissolved liquid solder and steel diffusion, condensation to form strong braze welding head, can realize aluminum alloy and steel dissimilar metal connection. 3, brazing aluminium - Steel brazing of dissimilar materials is solder in welding joint clearance, melted by heating, and parent material does not melt, liquid filler metals seep into the solid-state welding gap, cooling solidification and form a strong connection. Three kinds of aluminum - Steel welding of dissimilar materials method, pressure welding and brazing process method can realize aluminum steel connection, but the size of the workpiece shape has certain limitation, low production efficiency. Molten solder can be controlled by solder brittle between aluminum and steel metal compounds, especially the laser brazing wire filling welding, has small heat input and welding speed is fast, easy to realize automation etc, high quality, highly effective weld brazing welding joint can be obtained, broad application prospect.