(A) preparation before welding
Selection of chemical or mechanical methods, stern exterior finishing oxide film on both sides of the weld groove.
Chemical cleaning is the use of alkali or acid cleaners piece looks, the law can remove the oxide film, but also in addition to oil, specific technical process is as follows: the volume fraction of 6% to 10% of the sodium hydroxide solution at 70 ℃ soaking mercy 0.5min → washing → volume fraction of 15% nitric acid at room temperature and soak 1min be disposed of in warm water washing → → → boring. After washing aluminum exterior is matte silver.
Mechanical finishing optional pneumatic or electric cutters, but also the choice scraper, rasp and other things, on a thin oxide film can also be polished 0.25mm copper wire brush to clear the oxide film.
After finishing welding immediately, if placed beyond time 4h, should scratch finishing.
(2) determine the installation and positioning welding gap distance
Welding process, the aluminum heat swell, resulting in reduction of the weld groove gap, the gap before welding installation if left too small, welding process will cause the two plates stacked groove, after adding weld plate surface roughness and deformation amount; Instead, the installation gap is too large, difficult welding, and can burn. Suitable tacking away to ensure that the necessary tack welding gap, therefore, choose the appropriate installation gap and tack welding distance, is a useful way to reduce distortion.
(3) Select welding equipment
Welding commodity varieties currently on the market are more usually advised to use communication GTAW (TIG welding that). It is maintained under argon, using a tungsten electrode and the workpiece Q arc welding methods occurs hot melt the filler wire and the base material. When the welding job, because communication is the polarity of the current cyclical change in each half wave cycle DCSP, half-wave DC reverse. Being connected to the half-wave time tungsten can emit electrons but Buzhi Yu meet overheating conducive stable arc. Oxide film reverse time piece looks half-wave generated by finishing off a very simple and made of light and beautiful appearance, forming an outstanding weld.
(4) Select the wire
Usually use 301 aluminum wire and 311 aluminum silicon wire.
(5) selection of welding methods and parameters
Usually left welding method, welding torch and the workpiece into a 60 ° angle. When welding thickness 15mm and above, with the right welding method, welding torch and the workpiece 90 ° angle.
When the wall thickness of 3mm or more of welding, open V-shaped groove, the angle of 60 ° ~ 70 °, the gap is not greater than 1mm, in order to complete the multi-layer welding. When the wall thickness of 1.5mm or less, without groove, leaving no gaps, without filling wire. When welding the tube fixed to the butt joints, when the diameter of 200mm, a wall thickness of 6mm, the diameter should be used tungsten electrode 3 ~ 4mm to 220 ~ 240A welding current, a filler wire diameter of 4mm, 1 to 2 layers welding finished.
