High thermal conductivity and low melting point of aluminum alloys can lead to “burnthrough” of material if the welder fails to follow the process. To overcome these problems, the welder needs to follow the instructions in the article. This is the experience and practical experience of welding equipment selection, basic material preparation, application of appropriate technology, and visual inspection of the welded structure to ensure high quality welds. With MIG welding and TIG welding process when welding aluminum alloy.
Preparing the weld
For aluminum welding, the welder must clean the welded surface carefully. Remove surface aluminum oxide and grease from oil and grease. Aluminum oxide on the surface of the solder melts at a temperature of 3,700 F while the aluminum material of the solder parts has a melting point below 1,200 F. Therefore, the cleaning of the oxide on the surface of the weld will limit the penetration of the weld. The depth of the metal to the weld.
To clean the aluminum oxide layer, use a stainless steel brush to clean it off or use a solvent and other abrasive methods. When using brushes, brush in one direction, lightly comb and do not roughen the rough surface too, resulting in increased risk of oxide deposition on the surface of the weld.
Also, do not use brushes used for cleaning steel or stainless steel welds to clean the surface of the solder in aluminum. When using chemical cleaning solutions, be sure to clean the corrosive solvent on the surface before welding. To minimize the risk of hydrocarbons from grease or solvents from cutting to penetrate the weld, clean them with a detergent. Check to make sure the detergent does not contain hydrocarbon ingredients.
Heat the solder to prevent cracking. The heating temperature of the solder does not exceed 230F. Use a thermometer to actively maintain the temperature, avoid overheating. The welders also need to heat before the thick parts when soldering with thin parts.
Use the technique of propulsion welding
With aluminum, welds are operated with a push instead of pulling the weld for better cleaning, minimizing weld contamination and increasing the protection of the gases.
Speed of movement
Aluminum welding should be done “hot and fast”. Unlike steel, the high thermal conductivity of aluminum requires higher welding voltages, greater welding currents, and greater torque travel. If the speed of moving the mine is slow, it can lead to welding burns, especially when welding thin parts.
Argon gas, with good cleaning and penetration properties, is the most widely used gas for aluminum welding. Soldering 5XXX-series aluminum alloys, a combination of argon-shielded gas and helium – up to 75% helium – will minimize the formation of magnesium oxide.
Select a molten solder wire similar to the base material. The less the welders limit the melting range of the metal, the easier it is to weld. Using 0.8mm wires in conjunction with a low speed welding process – 100 to 300 inches per minute – is optimal.
Convex shape forming
When welding aluminum, cracking usually occurs. Cracking due to the high thermal expansion of aluminum and the shrinkage that occurs when the weld cools. The risk of cracking is great with concave welds because the surface of the weld shrinks and tear when cooled. Consequently, the welder should operate in order to form a convex weld. Because when the weld cools, the protrusion of the weld will balance the shrinkage.
Selection of welding source
When selecting welding equipment for aluminum arc welding applications, the first thing is to choose the arc or pulse arc transfer method. Soldering machines with constant-current welding mode (CC) and constant-voltage welding (CV) are used for spray arc welding. With thick aluminum parts, requiring over 350A welding currents, CC mode produces the best results.