How to weld the aluminum to steel
Aluminum and aluminum alloy materials have low density, high strength, high thermal conductivity, strong corrosion resistance, good physical and mechanical properties, so they are widely used in the welding structure of industrial products.
1. Aluminum alloy material features: aluminum is a silver white light metal with good plasticity, high conductivity and thermal conductivity, as well as oxidation resistance and corrosion resistance. Aluminum is easy to be oxidized to produce aluminum oxide film, and inclusions are easy to be produced in the weld, which will damage the continuity and uniformity of the metal and reduce its mechanical properties and corrosion resistance.
2. Welding difficulties of aluminum alloy
(1) It is easy to oxidize.
(2) It is easy to produce pores
(3) The tendency of weld deformation and crack formation is large
(4) Aluminum has high thermal conductivity
(5) The evaporation of alloy elements causes burning loss. Aluminum alloy contains elements with low boiling point (such as magnesium, zinc, manganese, etc.), which are easy to evaporate and burn under the action of high temperature arc, thus changing the chemical composition of weld metal and reducing the performance of weld metal
(6) High temperature strength and low plasticity. At high temperature, the strength and plasticity of aluminum is very low, which destroys the formation of weld metal, and sometimes causes the collapse and penetration of weld metal
(7) No color change. When aluminum and aluminum alloy change from solid to liquid, there is no obvious color change, which makes it difficult for the operator to master the heating temperature.
3 welding process of aluminum alloy
(1) Before welding, chemical or mechanical methods shall be used to strictly clean the surface oxide film on both sides of weld groove.
(2) Determine the assembly clearance and positioning welding spacing
(3) The selection of welding equipment should be AC TIG welding.
(4) The selection of welding wire is generally Al Si welding wire.
(5) Select the welding method and parameters. When welding the fixed pipe butt joint, when the pipe diameter is 200 mm and the wall thickness is 6 mm, the tungsten electrode with a diameter of 3-4 mm shall be used, the welding current of 220-240 A and the filler wire with a diameter of 4 mm shall be used, and the welding shall be completed in 1-2 layers.
