Aluminium is often thought to be hard to weld, however, that’s not entirely true. Welding aluminium is just different from welding steel. It may take some practice, so here are some tips for welding aluminium.
But first, a word about safety…
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 aluminium welding:
- Arc welding
- Gas metal-arc (MIG) welding
- Gas tungsten-arc (TIG) 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.
- Comparatively cheap
- Not much equipment required
- Works on AC or DC
- 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 aluminium pieces to be welded should be clean and dry and any oxidation should be removed. Heat up the aluminium pieces to soften them so that 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 aluminium 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 aluminium time to cool down, and prevent too much heat from building up in the aluminium. As the aluminium heats up, the amperage will need to be reduced.
Gas metal-arc (MIG) welding
MIG welding was developed in the 1940’s. It uses a short circuit along with an inert gas to melt the metal.
- Very quick
- Low skill level required
- 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 aluminium, 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 Aluminium, 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 similar technique as you would for steel.
Gas tungsten-arc (TIG) welding
TIG welding uses an electrode sheathed in an inert gas.
- Very clean. Low levels of sparks, smokes, and fumes.
- Very precise, high quality.
- More expensive and more time consuming than MIG
- High skill levels required.
Tips for TIG welding:
Choose your electrode. For aluminium, the best choice is a pure tungsten rod.
Prepare your metals. Use a wire brush to scrub the aluminium surfaces clean. It’s also a good idea to preheat the aluminium.
Control the gas. Having too much argon flow at the torch can lead to an irregular arc.
Heat Sink. It’s also a good idea to use a heat sink to prevent the aluminium from warping.
Welding technique. Keep the filler rod as close to the gas cloud as possible. It can be tricky, so it’s a good idea to get as much practice beforehand.
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