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How to MIG Weld Aluminum with a Spool Gun

Reverend Greg
7 Min Read
General MIG Welding Settings for Aluminum
General MIG Welding Settings for Aluminum

MIG welding aluminum is a pretty complicated process, especially if it’s your first time. But you need a spool gun to get the job done. Running aluminum wire through a regular MIG welder often turns into a big mess. Putting the spool of wire on a gun prevents the wire from getting tangled up in the line. But even with a spool gun, many welders still struggle to work with aluminum. Some of the biggest problems come from a lack of preparation, as well as using improper methods. By following this in-depth guide, you can start welding aluminum with a spool gun in no time.

MIG welding aluminum is a pretty complicated process, especially if it’s your first time. But you need a spool gun to get the job done.

Welding Town

MIG welding aluminum with a spool gun requires some specific techniques and equipment to ensure successful welds. Aluminum is different from steel, and it presents certain challenges due to its lower melting point and greater heat conductivity. Here’s a step-by-step guide on how to MIG weld aluminum using a spool gun:

Materials and Equipment You’ll Need:

  1. MIG Welder with Spool Gun: Ensure your MIG welder is compatible with a spool gun attachment. Spool guns are commonly used for aluminum welding because they minimize wire feeding issues.
  2. Aluminum Wire: Use aluminum welding wire, which is specifically designed for MIG welding aluminum. Common diameters are 0.030″ (0.8mm) and 0.035″ (0.9mm).
  3. Aluminum Workpiece: The pieces of aluminum you intend to weld.
  4. Shielding Gas: Use 100% argon or an argon-helium mix as a shielding gas. Argon provides excellent coverage and protection for aluminum welding.
  5. Safety Gear: Wear appropriate safety gear, including a welding helmet, welding gloves, and safety glasses.

Step-by-Step Guide:

  1. Prepare Your Workpiece:
    • Ensure your aluminum pieces are clean and free from contaminants. Use a wire brush or a stainless steel brush to remove any oxidation or impurities.
    • Securely clamp the workpieces to prevent movement during welding.
  2. Set Up Your MIG Welder:
    • Install the spool gun attachment on your MIG welder following the manufacturer’s instructions.
    • Load the appropriate size of aluminum wire onto the spool gun.
    • Adjust the tension on the wire feeder to ensure smooth wire feeding without crushing the wire.
    • Set your MIG welder to the recommended settings for aluminum welding. These settings may vary depending on your specific machine and the thickness of the aluminum, so consult your welder’s manual for guidance.
    • Connect the spool gun to the welding machine and attach the appropriate gas hose to the argon or argon-helium cylinder.
  3. Select the Right Technique:
    • Aluminum welding typically uses a “push” technique, where you push the weld pool away from you. This helps prevent contamination and ensures better penetration.
    • Maintain a consistent travel speed and gun angle. A 10-15 degree push angle is generally recommended.
  4. Welding Technique:
    • Start by creating a “tack weld” to secure the workpieces in place. This helps prevent warping due to heat.
    • Position the spool gun approximately 1/4 to 1/2 inch (6-12 mm) above the workpiece.
    • Begin welding by pulling the trigger on the spool gun, creating an arc. Move the gun steadily along the joint, ensuring proper fusion of the aluminum.
    • Pay close attention to the appearance of the weld pool. It should have a shiny, fluid appearance, indicating proper penetration.
    • Keep a consistent travel speed, and maintain a short arc length (about 1/4 inch or 6 mm).
  5. Cool Down:
    • Allow the weld to cool gradually to reduce the risk of cracking.
  6. Inspect and Clean:
    • Inspect your weld for any defects, such as cracks or incomplete fusion.
    • Clean off any spatter or residue from the weld with a wire brush.
  7. Repeat as Needed:
    • Continue welding along the joint as needed until you’ve completed the desired length or project.
  8. Post-Welding:
    • Turn off the MIG welder and disconnect the spool gun.
    • Let the workpiece cool completely before handling it.
    • If necessary, grind down the weld bead to achieve a smooth, finished appearance.

MIG welding aluminum with a spool gun can be challenging, especially for beginners, but with practice and attention to technique, you can achieve strong and clean welds on aluminum materials. Always follow safety precautions and consult your welding machine’s manual for specific settings and recommendations.

What gas do you use to weld aluminum with a spool gun?
To weld aluminum with a spool gun, you should use 100% Argon. You should always use 100% Argon when Mig or TIG welding aluminum because it does not add carbon.

What size wire do I need for aluminum MIG welding?
You should match the wire size to the tip that your spool gun came with. Generally, you should use a .030 or .035 wire, but you may want to go a little bigger or smaller depending on the metal thickness.

Do you push or drag with an aluminum spool gun?
You always want to push the spool gun with aluminum because you are keeping the flow of air in front of the puddle rather than behind it. The shielding gas needs to be concentrated over the molten part of the metal.

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