(1) Pre-weld preparation
Use chemical or mechanical methods to strictly align the outer oxide film on both sides of the weld bevel.
Chemical cleaning is to clean the surface of the workpiece with alkali or acid. The method can remove the oxide film and remove the oil. The specific technical process is as follows: sodium hydroxide solution with a volume fraction of 6% to 10%, soaking at 70 ° C for 0.5 min. → Washing → Nitric acid with a volume fraction of 15% is immersed for 1 min at room temperature for neutralization treatment → water washing → warm water washing → boring. The washed aluminum alloy has a matt silver white appearance.
Mechanical finishing can be done with pneumatic or electric milling cutters, but also with scrapers, trowels, etc. For thinner oxide films, a 0.25mm copper wire brush can also be used to remove the oxide film.
Immediately after finishing the welding, if the placement time exceeds 4h, it should be sorted from the beginning.
(2) Determine the installation clearance and the positioning welding distance
During the welding process, the aluminum plate is heated and expanded, causing the gap of the weld bevel to be reduced. If the installation gap before welding is too small, the groove of the two plates will be stacked during the welding process, and the unevenness and deformation of the plate surface after welding will be added. On the contrary, if the installation clearance is too large, the welding is difficult and there is a burn-through. The proper positioning welding distance can ensure the required positioning welding gap. Therefore, selecting a suitable installation clearance and positioning welding distance is a useful method to reduce the deformation.
(3) Select welding equipment
At present, there are many varieties of welding products on the market. Generally, it is preferred to use TIG welding (ie TIG welding). It is a welding method for melting the base metal and filling the wire with the arc electrode and the workpiece under the maintenance of argon. When the welder is working, because the polarity of the communication current is periodically changed, the half wave is DC positive connection and the half wave is DC reverse connection in each cycle. The positive half-wave time tungsten can emit the satisfied electrons without overheating, which is conducive to the stability of the arc. The reverse half-wave time oxide film produced by the surface of the workpiece is simply sorted out to obtain a beautiful weld with excellent appearance and excellent shape.
(4) Select aluminum welding wire
Usually 1070 pure aluminum welding wire and 4043 aluminum silicon welding wire are used.
(5) Select welding methods and parameters
Usually done by left welding, the torch and the workpiece are at an angle of 60°. When the welding thickness is 15 mm or more, it is performed by the right welding method, and the torch and the workpiece are at an angle of 90°.
When the welding wall thickness is more than 3mm, the V-shaped groove is opened, the angle is 60°~70°, the gap is not more than 1mm, and the multi-layer welding is completed. When the wall thickness is less than 1.5 mm, the groove is not opened, no gap is left, and no filler wire is added. When welding the pipe butt joint, when the pipe diameter is 200mm and the wall thickness is 6mm, the tungsten electrode with a diameter of 3~4mm should be used, with the welding current of 220~240A, the filler wire with the diameter of 4mm, with 1~2 layers. Soldered.