MIG Welding on Aluminum
Introduction:
In Metal Inert Gas (MIG) welding, a welding gun continuously feed the consumable wire electrode and shielding gas. But unlike steel, aluminum requires some specific changes that hamper the continuity. Since aluminum is softer metal, it requires a larger wire electrode to feed. Furthermore, due to high heat conductivity, you need to be aware of control of power supply and the filler feed rate. Our guide will give you a detailed picture of how to MIG weld aluminum successfully.
How to Aluminum Welding:
Aluminum as a soft metal requires alloys to add on for getting strength. It has a greatly varied property that those of steel. So welding on aluminum has some unique challenges. You should be more cautious while welding on aluminum since it is prone to distortion and sensitive to heat. Nevertheless, if you follow our guidelines and use the right equipment, it is not very difficult to successfully MIG welding aluminum. We present some important factors that you should bear in mind when you apply MIG welding aluminum.
1. Consider Material Thickness:
The thickness of the aluminum you are going to MIG weld on should be 14 gauge or 0.74 inches and heavier. If the aluminum is thinner than the prescribed one, you should apply specialized pulsed MIG or AC TIG equipment.
2. Keep it Clean:
Before welding the aluminum, we must clean it thoroughly and remove the lubricants and greases also with a stainless wire brush. You may brush manually or using power tool. But you need to be aware while using a power wire brush. Because if the RPMs and pressure are not low, attract oxides and other contaminants on the material surface. Experts recommend always using a wire brush for aluminum metal.
3. Choose the Right Gas:
You know that aluminum is a non-ferrous metal that requires 100% argon gas for shielding. According to the experts, you should keep the argon gas flow rate at 20-30 cubic feet per hour.
4. Use the Right Process:
At the time of MIG welding aluminum, you should apply the spray transfer process. It ensures a smooth transfer of the melted material droplets to the melted weld pool from the end of the filler electrode. Spray transfer has no short-circuiting, and you will find the efficiency and deposition rate very high. But spray transfer is not suitable for material thinner than 14 gauge since it carries higher heat that creates large pool, which is difficult to control.
5. Gun and Wire Feeding Options:
You should choose the right gun and wire feeding system for the MIG welding aluminum. You can use a spool gun for feeding aluminum wire, or you can apply push-pull system. The pistol-grip style gun ensures an improved feeding of soft wires. Since the gun feeds the wire for only few inches, it removes the chance of bird-nesting. On the other hand, push-pull system is very much user-friendly and uses a motor in the gun for pulling the wire through the liner.
6. The Right Filler Metal:
You need to understand the alloy of the aluminum and what factors can affect the finished product if you do MIG weld on it. Highly available aluminum filler wires are ER4043 and ER5356. You can also consult with the welding distributors and the filler metal representative for the right filler alloys suitable to your requirement.
Techniques for MIG Welding Aluminum:
Factors that greatly affect the weld-ability of aluminum are welding power supply, joint types, fit up & positions, and skill level of the operator. You can enhance your skill level for MIG welding aluminum if you following the technique as mentioned below:
1. Use push travel with a 10-15 degree angle where tip and nozzle should be in line with the travel. If you pulling or drag angle, it will lead to dirty and porous weld due to the lack of gas coverage.
2. Keep a proper distance between tip and work and make the contact tip lower by 1/8 inch inside the nozzle.
3. At the time of MIG welding aluminum, reflective heat and weld puddle become very hot. The wire could burn back to the contact tip if you hold the tip much closer, and it would lead to other feeding defects.
4. Always avoid using large beads. Rather use multiple pass straight beads for better appearance and reducing the possibility of burn-through, cold lapping, and other weld problems.
5. If the base metal gets heated at the time of MIG welding, you should increase the speed of the torch travel.
Common Problems and their Troubleshooting:
| Problems | Solution |
| Burn-through caused by overheating | · Make the welds shorter and increase the speed of torch travel. · Move around on the part for spreading out the heat. · Use thick material and change the design of the joint. · Reduce or eliminate gaps. |
| Dirt in the weld | · Avoid using the drag technique. Rather use push angle. · Increase the voltage for activating the spray transfer. · Use a wire brush made of stainless steel to clean the base metal. · Always use proper shielding gas and wire alloy. |
| Wrong settings of the machine | · Fine-tune the application or check the inside cover of the Miltermatic welder for the optimal setting. · Arrange a Miltermatic MIG Calculator. |
| Wire burns back to contact tip | · Keep a proper distance between tip and work. · Make sure that drive rolls, gun liner, and contact tip size match with the diameter of the wire. |
| Wire Bird-nest | · Adjust and check the tension of the drive roll. · Replace the contact tip when required. · Always check the pressure adjustment on the spool gun. |
