Many welders who are new to the aluminum industry do not know how to weld pure aluminum plates. This article will introduce to you the welding methods and processes of aluminum plates for your reference:
1. Master material preparation: When welding aluminum, the welder should carefully clean the base material and use oil or solvent to remove oxides and hydrocarbons on the aluminum surface. The oxide on the surface of the aluminum melts at 3700 degrees Fahrenheit, while the underlying aluminum-based metal melts at 1200 degrees Fahrenheit, so any residual oxide on the surface of the aluminum-based metal will limit penetration of the filler metal into the workpiece.
2. In order to remove oxides on the aluminum surface, you can use a stainless steel wire brush or solvent corrosion. When using a stainless steel brush, you can only brush in a fixed direction. Be careful not to use too much force and roughness, otherwise the oxides will be embedded in the aluminum-based metal.
3. Chemical cleaning
Chemical cleaning has high efficiency and stable quality. It is suitable for cleaning of mass-produced welding wires and small-sized workpieces. Two methods can be used: soaking and scrubbing. Petroleum can be removed from the surface of organic solvents such as acetone, gasoline and kerosene. Use 5%- Alkaline wash with 10% NaOH solution at 40~70℃ for 3~7 minutes (pure aluminum takes slightly longer, but not more than 20 minutes), rinse with flowing water, and then pickle with 30% HNO3 solution at room temperature for 30 seconds at 60℃ %HNO3 for about 2 minutes, rinse with flowing water, dry by infrared rays or dry at low temperature.
4. After the workpiece and welding wire have been cleaned and cleaned, the oxide film will regenerate during storage. Especially in humid environments, and in environments contaminated by vapors such as acids and alkalis, the oxide film will grow faster. Therefore, the storage time after cleaning and cleaning of the workpiece and welding wire before welding should be shortened as much as possible. In humid climates, welding should generally be performed within 4 hours after cleaning. If the storage time after cleaning is too long (such as more than 24 hours) should be reprocessed.
5. Preheating: Preheating pure aluminum plates is helpful to prevent welding cracks. The preheating temperature should not exceed 230 degrees Fahrenheit. Use a thermometer to monitor the temperature to prevent overheating. In addition, placing intermittent welding at the beginning and end of the welding area can help increase preheating efficiency. When welding thin materials, welders should also preheat thick aluminum sheets.
6. Processing speed: The aluminum welding process requires "high temperature and high speed" processing. Unlike steel, the high thermal conductivity of aluminum requires higher current and voltage to be set at higher temperatures and welding speeds. If the welding speed is too slow, the welding melt will The depth will be too large, especially when welding thin materials.
7. Shielding gas: Due to its excellent cleaning performance, argon is used as a commonly used shielding gas for aluminum welding. When welding 5XXX-series pure aluminum alloys, the shielding gas used is a mixture of argon and helium. A helium ratio of 75% can achieve the best effect of reducing the influence of magnesium oxide.
8. Cleaning after welding
The flux and slag remaining inside and outside the weld after welding will destroy the passivation film on the aluminum surface and sometimes corrode the aluminum parts. They should be cleaned. Simple shapes and general workpieces can be cleaned with simple methods, such as hot water rinsing or Steam purging: For pure aluminum plates with high requirements and complex shapes, use a hard brush to clean them in hot water, and then soak them in a chromic anhydride or potassium dichromate aqueous solution at 60 to 80°C with a concentration of 2% to 3% for 5 to 10 minutes, clean with a hard brush, wash with hot water, dry in the oven, or blow dry with hot air, or dry naturally.
