ã€China Aluminum Network】 Aluminum profile welding should pay attention to the following points:
(1) Pre-weld preparation Chemical or mechanical methods are used to strictly clean the surface oxide films on both sides of the weld bevel.
Chemical cleaning is the use of alkali or acid cleaning the surface of the workpiece, this method can remove the oxide film, but also remove oil, the specific process is as follows: volume fraction of 6% to 10% of sodium hydroxide solution, soaked at about 70 °C 0. 5min → washing → nitric acid with a volume fraction of 15% soaked for 1 min at room temperature for neutralization → washing → warm water washing → drying. The surface of the aluminum alloy after washing is matt silver white.
Mechanical cleaning can be pneumatic or electric milling cutters. Scrapers, trowels and other tools can also be used. For thinner oxide films, 0.25mm copper wire brush can be used to remove the oxide film.
Welding is performed immediately after cleaning. If it is left for more than 4 hours, it should be cleaned again.
(2) Determine the assembly clearance and the positioning welding distance During the welding process, the aluminum plate is heated to expand, so that the weld groove gap is reduced. If the assembly gap before welding is too small, the overlap of the two plates will be caused in the welding process. Increase the surface roughness and deformation after welding; on the contrary, if the assembly gap is too large, the welding will be difficult and burn-through may occur. The proper tack gap can guarantee the required tack gap. Therefore, choosing an appropriate assembly gap and tack gap is an effective measure to reduce deformation. According to experience, the reasonable assembly process parameters for different seam thicknesses are shown in Table 2.
(3) Selection of welding equipment There are many kinds of welding products on the market at present. Under normal circumstances, tungsten tungsten arc welding (TIG welding) should be adopted. It is a welding method that melts the base metal and the filler wire with the arc heat generated by the tungsten electrode and the workpiece under the protection of the argon gas. When the welding machine is working, since the polarity of the alternating current is a periodical change, the half wave is a direct current connection and the half wave is a direct current reverse connection in each cycle. The tungsten electrode can emit enough electrons without overheating during the half-wave to be connected, which is beneficial to the stability of the arc. The oxide film formed on the surface of the work piece during the half-wave phase of reverse welding can be easily removed to obtain a bright, beautiful, well-formed weld seam.
(4) Select wire is generally used 301 pure aluminum wire and 311 aluminum silicon wire.
(5) The welding method and parameters are generally selected by the left welding method. The welding torch and the workpiece are at an angle of 60°. When the welding thickness is 15mm or more, the right welding method is used, and the welding torch and the workpiece are at a 90° angle.
When the welding wall thickness is more than 3mm, open the V-shaped groove, the included angle is 60°~70°, the gap should not be greater than 1mm, and the multilayer welding is completed. When the wall thickness is less than 1.5mm, no groove, no clearance, no filler wire. When welding fixed pipe butt joints, when the pipe diameter is 200mm and the wall thickness is 6mm, a tungsten electrode with a diameter of 3 to 4mm, a welding current of 220 to 240A, a filler wire of 4mm in diameter, and 1 to 2 layers shall be used. After welding.
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