Welders Galore

Welders Galore

How to MIG Weld Aluminum

Here is a Comprehensive Guide on How to MIG Weld Aluminum. Helpful Tips on Preparing Aluminum for MIG Welding, Safety Gear and Equipment you Require.

Knowing how to MIG weld aluminum to achieve beautiful welds can be mind blowing. The MIG welding process to join aluminum pieces together differs from mild steel and stainless steel. However, many welders choose to MIG weld aluminum rather than TIG welding because the equipment is more affordable and results are faster. The good news is that once you learn the basics, MIG welding aluminum isn’t too tricky.

Welding Aluminum has Unique Challenges Because of its Properties.

How to MIG Weld Aluminum

First, aluminum is a soft metal and distorts easily under intense heat. However, aluminum alloys have high thermal conductivity, meaning you require more heat than welding mild steel. This easily results in distortion due to excessive heat dissipation. Additionally, bubbles can form in the weld pool, and aluminum oxide can impact the weld’s strength.

Metal Inert Gas (MIG) welding aluminum is best for thinner gauges of aluminum sheet metal. However, successfully welding aluminum with a MIG welder requires following correct procedures.

Can MIG Welders Weld Aluminum?

MIG welding is suitable for joining aluminum alloys. To successfully MIG weld aluminum, you will need a good quality MIG welder that provides the required heat, typically 21 to 24 volts. Additionally, welding aluminum requires using pure argon shielding gas and an aluminum wire to create a strong weld.

How Difficult Is It to MIG Weld Aluminum?

MIG welding aluminum is tricky because it has a low melting point and tends to conduct heat away from the weld. Pure aluminum has a melting point of 1220.58°F. This means that MIG welding on aluminum is typically limited to sheets between 14 and 18 gauge. To weld thinner aluminum sheets, you’ll need a TIG welder.

What Equipment Do I Need To Be Able to MIG Weld Aluminum?

A good-quality MIG welder to join aluminum plates successfully. The welding machine should have settings for aluminum and have a proper welding gun, wire feeder, and spool gun. Other necessary equipment to MIG weld aluminum include a wire brush to remove the oxide layer from aluminum, the suitable filler metal, and 100 percent argon shielding gas.

Pure argon gas is the best shielding gas if you want to MIG weld aluminum. This is because it allows excellent arc start and stability. Some professional welders use a mix of argon and helium to achieve greater penetration. However, this results in an unstable arc and isn’t suitable for beginners.  

A spool gun is vitally important. Although you can use the standard welder wire feeder, the soft aluminum wire will tangle in the welding unit. So even though the spool gun is an extra investment, it is worth buying one for MIG welding aluminum without any problems.

To MIG weld aluminum successfully, it is crucial to select an aluminum welding filler wire suitable to the alloy you plan on welding. The most common MIG aluminum filler metal wires are ER4043 and ER5356.

The ER4043 is an all-purpose MIG welding wire to ensure high ductility, resistance to cracking, and excellent weld puddle liquidity. The ER5356 contains magnesium additives to improve tensile strength and prevent cracking.

Preparation of the Aluminum Before Welding It

Preparation of the Aluminum Before Welding

Preparation is key to successful aluminum MIG welding. Aluminum alloys contain a layer of oxide with a higher melting point than aluminum. You must remove this to prepare the metal for the MIG weld. Additionally, you should remove any contaminants and grease from the metal.

Use a stainless-steel wire brush or a cup wire brush to prepare the surface. It is always best to use a brush that you only use on aluminum. This way, you prevent cross contamination and ensure a cleaner, stronger weld.

Other ways to get aluminum ready for MIG welding include using a grinder or acid solution. However, using a grinding wheel regularly is not recommended because it will clog up with aluminum. If you use an acidic solution to prepare aluminum for MIG welding, rinse and dry the metal before welding.

Step-by-Step Guide on How to MIG Weld Aluminum

Knowing how to MIG weld aluminum requires sticking to the correct processes. Typically, welding aluminum requires more precision and attention to detail to achieve a clean, strong weld that is free from impurities and won’t crack. Therefore, if you are using a MIG welder for aluminum, it’s even more critical to know the proper steps.

1/ Prepare the Aluminum for Welding

Use a solvent like acetone or a strong soap solution to remove grease, oil, and water vapor from the surface of the aluminum.

2/ Remove the Surface Oxide on the Aluminum

Next, use a stainless-steel brush to remove the aluminum oxides from the surface. After this, rinse and dry the aluminum parts you plan to MIG weld.

3/ Preheat Aluminum Before Welding

Unless you work in a professional setting, preheat the aluminum to 200°F. This allows you to achieve a better weld and MIG weld thicker aluminum.

4/ Use the Correct Voltage when Welding Aluminum

Aluminum has a low melting point, so you must use the correct voltage. You can set the MIG welder to at least 21 volts—the same as for welding mild steel.

5/ The Push Method is Best to MIG Weld Aluminum

Set the welding torch at a 10° to 15° angle pointed in the direction of travel. Push the arch forward to create a clean weld pool, free of contaminants.

6/ Use the Correct Travel Speed when Welding Aluminum

You must use a faster speed to avoid weld issues when using a MIG welder for aluminum. Typically, use double the speed to MIG weld aluminum as you would use with mild steel. Remember—hot and fast is the best way to MIG weld aluminum.

7/ Maintain the Correct Distance Between Welding Torch Tip and Aluminum

MIG welding aluminum creates intense heat. If the torch tip is too close, the reflective heat can cause the wire to burn back and other feeding issues. A general rule is to use a 3/4” wire stick out and keep the tip recessed about 1/8” inside the nozzle.

8/ Create Smaller Welding Beads

Larger weld beads on aluminum tend to increase the risk of cold lapping, burn-through, and other welding defects. Therefore, it’s best to use multiple passes and create a narrower bead on each pass.

How to Resolve Common Problems When MIG Welding Aluminum

Learning how to MIG weld aluminum and create welds you can be proud of, will take time. However, here are some common issues beginners make when welding aluminum with a MIG welder and how to resolve them.

 Welding bead on Aluminum
  • Burn-through: Use faster travel speeds and make shorter welds.
  • Dirty welds: Use the push method to MIG weld aluminum or increase the voltage to ensure spray transfer. Also, make sure you use the correct push travel angle.
  • Cracked welds: Thoroughly clean aluminum surfaces beforehand and use the correct shielding gas.
  • Wire burn-back: Ensure you maintain the correct tip-to-work distance.
  • Wire bird nests: Check the settings of the drive roll and replace the contact tip if necessary.

What Safety Gear Do I Need When Welding Aluminum?

MIG welding aluminum requires the standard safety equipment for any type of welding. Here is a list of what you require:

  • Welding helmet: Wear a safety helmet with an appropriate lens shade to protect your eyes from harmful radiation and metal sparks.
  • Protective clothing: It is crucial when MIG welding aluminum to wear fire-resistant clothing and gloves. In addition, safety goggles for eye protection are essential when cleaning metal with a wire brush or grinder.
  • Use a welding respirator: To protect your health, use a welding respirator in work spaces with poor or inadequate ventilation.

How to MIG Weld Aluminum-In Conclusion

It is possible to MIG weld aluminum, and many hobbyists and DIY enthusiasts prefer this welding technique to TIG welding. Welding aluminum with a MIG welder is faster and requires less expensive equipment. However, it’s crucial to follow the proper steps to ensure that MIG weld creates clean and robust welds, free from impurities that could cause cracking.

As a general rule, when MIG welding aluminum, clean the surface of aluminum from oxides and use a faster travel speed, using the same voltage setting as you would for welding mild steel.

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