The profile is thin in wall and complicated in structure, which is not suitable for welding.
Aluminum welding technology has its own characteristics: the thermal conductivity of aluminum is much stronger than that of steel, and the melting temperature can be burned, so argon shielded welding is needed at high temperature and high speed.
Attachment: Brief introduction of aluminum welding method.
1. The most suitable welding gun for welding aluminum is the wire drawing welding gun. If this kind of welding gun cannot be used, try to use the shortest welding gun and keep it straight. Only argon can be used as protective gas; When welding aluminum, only the shotgun method can be used.
2. If there is any wire feeding problem, you can try a conductive head one size larger than the welding wire.
3. The most commonly used welding wire for aluminum welding is soft standard welding wire. The other is harder (easier to feed wire) and is mainly used for welding operations with high requirements on hardness and strength.
4. Before welding, do a good job of removing the oxide layer on the aluminum surface, and use a special stainless steel brush to remove the oxide layer.
5. Fill the arc pit at the end of welding to prevent cracks. One method is to leave the welding torch in the molten pool for a few seconds after welding.
Preparation of substrate: When welding aluminum, the welder must carefully clean the substrate and remove any oxide and hydrocarbon pollution on the aluminum surface with oil or solvent. The melting temperature of the oxide on the aluminum surface is 3700 degrees Fahrenheit, while the aluminum substrate below it will melt at 1200 degrees Fahrenheit. Therefore, any oxide remaining on the surface of aluminum substrate will limit the penetration of filler metal into the workpiece.
To remove the oxide on the aluminum surface, stainless steel wire brush or solvent corrosion can be used. When using stainless steel brush, you can only brush in a fixed direction. Be careful not to push too hard and be careless: rough action will embed oxides into aluminum substrate. the same
Only use stainless steel brushes on aluminum surfaces, and do not use brushes that have been used on stainless steel or carbon steel. When using the chemical solvent method, make sure to clean the solvent before welding.
In order to minimize the adverse effects of hydrocarbons by using oil agents or solvents, degreasing agents should also be used. At the same time, ensure that the degreasing agent does not contain any hydrocarbons. Preheating: Preheating aluminum workpiece helps to avoid welding cracks. The preheating temperature should not exceed 230 degrees Fahrenheit. A thermometer should be used to monitor the temperature to prevent overheating. In addition, placing intermittent welding at the beginning and end of the welding area is helpful to strengthen the preheating effect. When welding thin materials, the welder should also preheat thick aluminum sheets.
Machining speed: aluminum welding process needs "high temperature and high speed" machining. Different from steel, aluminum has high thermal conductivity, which requires high temperature, current and voltage settings and high welding speed. If the welding speed is too slow, the welding penetration will be too large, especially when welding thin materials.
Protective gas: argon is the most commonly used protective gas for aluminum welding because of its excellent cleaning performance. When welding 5XXX series aluminum alloy, the protective gas used is a mixture of argon and helium. 75% helium at most can achieve the best effect of reducing the influence of magnesium oxide.
Welding wire: aluminum-filled welding wire with melting point close to the base metal is selected. The more the welder can limit the melting range of metal, the easier it is to weld alloy. Use filler wire with a diameter of 3/64- or116 inch. The larger the diameter of the filler wire, the easier it is to feed the wire. For welding thin materials, the welding wire with a diameter of 0.035 inches and pulse welding technology are adopted, and the wire is fed at a low speed (about 0/00 to 300 inches per minute), and the effect will be ideal.
Welding of concave materials: In aluminum welding, sparks will lead to welding failure. Cracks are the result of high-speed thermal expansion of aluminum material and shrinkage caused by large amount of cooling. When welding concave materials, the risk of welding cracks is the greatest, because the pits on the surface of the material will shrink and the material will tear when it cools. Therefore, the welder should create a pit with a convex shape, and the convex surface will compensate for the shrinkage caused by welding.
Power supply selection: When choosing the voltage of MIG welding machine for welding aluminum, the first thing to consider is the problem of droplet splashing or pulse.
You can use a constant current and constant pressure welder for spray welding. Arc spraying is to spray tiny droplets on the covered electrode onto the base metal by welding arc. In the application of welding thick aluminum, the welding current is required to be constant above 350 A to achieve the best effect. Pulse transition is usually carried out with the support of inverter power supply. The new power supply includes a built-in pulse program. In the pulse process of gas shielded metal arc welding, a drop of filler metal transits from covered electrode to the workpiece in each current pulse. In this process, droplet transfer will occur on the anode, achieving the effect of less spatter and high welding speed. When the pulsed gas shielded metal arc welding process is used to weld aluminum, the heat input is also well controlled, and dislocation welding can be easily carried out, so that the welder can weld thinner materials with lower wire feeding speed and lower current. Wire feeder: Push-pull wire feeder is the first choice for long-distance transportation of soft aluminum wire, which adopts closed wire feeder to protect welding wire from environmental influence. The constant torque variable speed motor in the wire feeding mechanism is responsible for wire feeding power, and at the same time guides the welding wire through the welding gun to realize constant output and constant speed. The high torque motor of the welding torch pulls the welding wire to ensure the coordination of wire feeding speed and welding arc.
Some welders use the same wire feeder to transport steel wire and aluminum wire. In this case, make
When welding, try to keep the welding torch cable straight to reduce wire feeding resistance. Carefully check the coaxiality of the drive roller and the guide tube to prevent the aluminum material from being scratched.
Use a drive roller designed for aluminum. Set the drive roller tighter to obtain a constant feed speed. Too tight setting will lead to welding wire deformation and unstable wire feeding; Too loose setting will lead to unstable wire feeding. Both of these conditions will directly lead to instability of welding arc and welding blowhole.
Welding torch: Use different welding torch pads to weld aluminum. In order to prevent the welding wire from being disturbed, we can try to tighten both ends of the gasket at the same time, thus eliminating the gap between the gasket and the gas diffuser.
Frequent replacement of gaskets can reduce the adverse effects of potential oxides on wire feeding on the rough surface of aluminum. When the welding current exceeds 200 A, a water-cooled welding torch should be used for cooling to reduce the difficulty of wire feeding.