1. Base metal preparation:
aluminum plate welding, the welder must carefully clean the base metal and remove any oxide and hydrocarbon contamination from the aluminum surface with oil or solvent.
The melting temperature of oxide on the surface of aluminum is 3700 degrees Fahrenheit. Therefore, the residual oxide on the surface of aluminum base metal will restrict the penetration of filler metal to the workpiece.
The oxide on the surface of aluminum can be corroded by stainless steel wire or solvent. When using stainless steel brush,
it can only be removed in a fixed direction. Be careful not to use too much force or not to be careful: the action of renting will cause oxide to embed into aluminum base metal.
At the same time, only use stainless steel on aluminum surface, do not use brush used on stainless steel or carbon steel.
2. Chemical cleaning of aluminum plate welding
Chemical cleaning efficiency is high, quality is stable, suitable for cleaning welding wire and small size, mass production of workpieces.
Two methods can be used: immersion and scrubbing. Organic solvents such as progesterone, gasoline, kerosene and other organic solvents can be used to remove oil on the surface,
wash with flowing water, air dry or low-temperature drying. Mechanical cleaning is often used when the size of the workpiece is large, the production cycle is long,
and the contamination occurs after multi-layer welding or chemical cleaning. First, wipe the surface bacteria with organic solvents such as acrylic acid and gasoline to remove oil,
and then directly use steel wire or stainless steel wire brush with diameter of 0.15mm and 0.2mm until the metal luster is exposed.
Generally, it is not suitable to use grinding wheel or ordinary sandpaper for grinding, so as to avoid the defects such as slag inclusion
when leaving the metal surface and entering the molten pool during welding. In addition, scraper and Keng knife can be used to clean the surface channeling to be welded.
After cleaning and cleaning, the workpiece and welding wire will produce oxide film again during storage,
especially in humid environment, and the oxide film grows faster in the environment polluted by acid and alkali vapor.
Therefore, the storage time of workpiece and welding wire from cleaning and cleaning to welding should be shortened as far as possible.
In humid climate, welding should be carried out within 4 hours after cleaning. After cleaning, if the storage time is too long, if it is more than 24, it should be treated again.
aluminum plate welding Preheating:
preheating aluminum parts can help to avoid welding cracks. The preheating temperature should not exceed 230 degrees Fahrenheit,
and the grip should be monitored with a grip gauge to prevent overheating. In addition, the intercalation fracture welding at the beginning
and end of the welding area can help to enhance the preheating effect. The welder should also preheat a thick piece of aluminum when welding thin materials.
3. Processing speed
The process of aluminum welding needs the treatment of “high temperature and high welding”.
Unlike steel, the higher thermal conductivity of aluminum requires higher current and voltage settings and higher welding speed.
If the welding speed is too slow, there will be too much welding penetration, especially when welding thin materials.
Shielding gas: oxygen is the most commonly used shielding gas for aluminum welding due to its excellent cleaning performance.
When welding 5xxx series aluminum alloy, the shielding gas is a mixture of oxygen and nitrogen.
The ratio of nitrogen up to 75% can reduce the effect of oxides. GMAW and GMAW are widely used.
4. Welding materials
In addition to good welding process performance, the selection of welding wire for aluminum and aluminum alloy shall meet the requirements of tensile strength.
and plasticity {through bending test} of butt joint according to vessel requirements, impact toughness requirements shall be met for aluminum clusters with continuity more than 3%,
and corrosion resistance of welded joints shall reach or approach the level of base metal for vessels with sound corrosion requirements.
Therefore, the selection of welding wire is mainly in accordance with the following principles:
1) The purity of pure aluminum welding wire is generally not lower than that of base metal;
2) The chemical composition of aluminum alloy welding wire is generally corresponding to or similar to that of base metal
3) The content of IFB corrosion element {mirror, mirror and silicon cutting in aluminum alloy welding wire is generally not lower than that of base metal}
4) When welding dissimilar aluminum materials, welding wires should be selected according to the base metal with high corrosion and high strength;
5. Post weld treatment
The residual flux and slag left in and near the weld after welding will damage the passivation film on the aluminum surface, and sometimes corrode the aluminum parts,
so it should be cleaned up. Workpieces with simple shape and general requirements can be cleaned by hot water washing or steam blowing.
Aluminum parts with high requirements and complex shapes can be washed and washed in hot water with a bristle brush in hot water, dried in an oven, or dried with hot air, or dried naturally.
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