Tips for Welding Aluminum

Aluminum is often thought to be hard to weld; however, that’s not entirely true. Welding aluminum is similar to welding steel. Using a few tips for welding aluminum, you’ll be equipped to achieve strong, durable, and aesthetically pleasing welds, enhancing the quality of your workmanship and expanding your welding capabilities. Whether you’re a seasoned professional or a hobbyist looking to develop your skills, mastering aluminum welding can open a world of possibilities for your projects. It may take some practice, so here are some tips for welding aluminum.

Welding Aluminum Safely

Before you start welding, make sure the area is well-ventilated. You don’t want to be breathing in any hazardous fumes. Always make sure you have the proper protective equipment. This should include:

• A welding mask to protect your eyes
• Gloves and leathers to protect you from molten metal splatters
• Leather shoes or boots to protect your feet from dripping hot metal
• A respirator if welding for long periods

Types of Welding

There are three main types of aluminum welding:

• Arc welding
• Gas metal-arc (MIG) welding
• Gas tungsten-arc (TIG) welding

Arc Welding

Arc welding is one of the oldest welding methods. It uses a welding power supply to create an electric arc to melt the metal. The molten metal cools and solidifies to form a strong, durable bond between the pieces being joined.

Arc welding is used for many types of metals and alloys, making it a staple in construction, manufacturing, and repair work. It can be performed with either alternating current (AC) or direct current (DC), depending on the materials and applications. The choice of electrode and filler material also varies depending on the specific requirements of the job, including the type of metal being welded, the desired strength of the weld, and the working environment.

Pros:

• Comparatively cheap
• Not much equipment required
• Works on AC or DC

Cons:

• Takes a lot of training and practice to master
• Not intended for thin metal

Tips for Arc Welding:

• Have your equipment ready. While both AC and DC will work, it is best to use DC.
• Prepare the pieces to be welded. The aluminum pieces to be welded should be clean and dry, and any oxidation should be removed. Heat the aluminum pieces to soften them so they are easier to weld. Use a jig to position the pieces on a flat surface as close together as possible.
• Introduce the filler rod. Place the rod on the seam of the aluminum pieces and work the flame a few inches above the rod. The forward travel will be much faster than it would be with steel, and you will have to feed the rod much quicker. The rod will melt into a metal pool that should cover the seam on both sides.
• Cool down. Let the welded metal cool and remove unwanted slag by chipping it away. This will give the aluminum time to cool down between welds and prevent too much heat from building up in the aluminum. As the aluminum heats up, the amperage will need to be reduced.

Gas Metal-Arc (MIG) Welding

MIG welding was developed in the 1940s. It uses a short circuit and an inert gas to melt the metal, creating a robust and clean weld between metal pieces.

MIG welding involves feeding a continuous solid wire electrode through a welding gun into the weld pool, joining the base materials together. The welding gun emits inert shielding gas, typically argon or a mixture of argon and carbon dioxide, over the weld pool. This gas shields the weld area from atmospheric contaminants like oxygen and nitrogen, which can cause weld defects such as porosity and brittleness.

Pros:

• Very quick
• Low skill level required

Cons:

• Can only be used on thin to medium-thick metals
• Weld is not as clean as TIG welding
• High levels of sparks, fumes, and smoke

Tips for MIG Welding:

• Prepare your equipment. Use a push-pull wire feed to avoid tangles or jamming.
• Prepare your metal. Clean the aluminum, remove any oxide, and file any edges to be joined. Again, it is easier to weld thicker pieces.
• Push, don’t pull. Pulling or using a drag angle will result in dirty welds. For Aluminum, it’s better to push at a 10- to 15-degree angle.
• Practice laying a bead. Using multiple pass straight beads will give the weld a better appearance and reduce the risk of weld defects.
• Use a heat sink. Using a heat sink, such as brass, will absorb excess heat and allow you to weld slower and with a similar technique as you would for steel.

How Do You Weld Aluminum with a MIG Welder?

MIG welding aluminum requires a different approach than welding steel due to aluminum’s lower melting point and higher thermal conductivity. Here’s a step-by-step guide on how to MIG weld aluminum:

1. Set up your equipment. This will include the following:

   • A MIG welder capable of welding aluminum. This often means it should have a pulse welding feature and the ability to use 100% argon gas or a mix of argon and helium.
   • A 5356 or 4043 aluminum welding wire is commonly used. The diameter of the wire should be appropriate for the thickness of the aluminum being welded.
   • 100% argon gas as a shielding gas to protect the weld pool from atmospheric contamination.
   • A spool gun or push-pull gun to prevent a jam in the welder’s feeding mechanism.

2. Clean the aluminum thoroughly before welding to remove any oxide layer and contaminants. Use a stainless steel brush designated for aluminum and acetone or a specialized cleaning agent.

3. Preheat if necessary. Thick aluminum may require preheating to about 200°F to reduce the risk of cracking. However, be cautious not to overheat the metal.

4. Adjust your welder settings based on the thickness of the aluminum. Aluminum generally requires a higher wire feed speed and voltage than steel. If your welder has pulse settings, use them, as they can help control heat input and improve weld quality.

5. When learning to weld aluminum with MIG, maintain a consistent travel speed and gun angle. A push technique, which involves tilting the gun slightly forward in the direction of the weld, is often recommended.

6. Practice good heat management. Due to aluminum’s high thermal conductivity, managing heat input is essential to prevent warping and burn-through. This might involve pulsing the trigger on thinner materials or making multiple passes on thicker sections.

7. After welding, clean the weld area again to remove any oxide formation and check for defects.

Gas Tungsten-Arc (TIG) Welding

TIG (Tungsten Inert Gas) welding, also known as Gas Tungsten Arc Welding (GTAW), is a highly precise and clean welding process renowned for producing high-quality, spatter-free welds on various metals. Unlike other welding methods, TIG welding uses an electrode sheathed in an inert gas. This process involves using a non-consumable tungsten electrode to generate the weld arc, which melts the base metal and forms the weld pool.

TIG welding uses an inert gas shield, typically argon or a mixture of argon and helium, which protects the weld area from oxidation and other forms of contamination that can compromise the strength and appearance of the weld. Because the electrode is not consumed during welding, welders can have greater control over the weld, allowing for more precise and detailed work.

Pros:

• Very clean. Low levels of sparks, smoke, and fumes.
• Very precise, high quality.

Cons:

• More expensive and more time-consuming than MIG
• High skill levels required.

Tips for TIG Welding:

• Choose your electrode. For aluminum, the best choice is a pure tungsten rod.
• Prepare your metals. Use a wire brush to scrub the aluminum surfaces clean. It’s also a good idea to preheat the aluminum.
• Control the gas. Too much argon flow at the torch can lead to an irregular arc.
• Use a heat sink to prevent the aluminum from warping.
• Keep the filler rod as close to the gas cloud as possible. This can be tricky, so try to get as much practice beforehand as possible.