Welding Aluminum is a difficult process compared to traditional steel materials as the material is soft, sensitive to contamination, and has an oxidized layer on the top. The material also absorbs hydrogen quicker in a molten state, leaving bubbles in materials.
Welders also must be vigilant while welding, as burning through the material is easy. There are various methods of welding aluminum, but the best and most used practices are by Metal Inert Gas Welding Machines(MIG) or by Tungsten Inert Gas Welding Machines(TIG). The application of these machines is different & will require reading the machine manual for maximum efficiency.
How to Weld Aluminium
Follow the guidelines below to get the job done.
- Welding helmet (get ones with clear light technology)
- Safety Glasses
- Respirator masks recommended
- Flame resistant insulated outerwear
- Spark & Heat resistant shoes
- Proper Fume Ventilation
- Check manufacturing manual for grounding and electrical safety guidelines.
- Wipe the base material with acetone or alcohol-based solvents like isopropyl rubbing alcohol or lacquer thinner to remove contaminants, dirt, grease, oil or fingerprints, etc.
- Use multiple clean rags to clean the aluminum. Change rags once used. Do not repeat rags.
- Use a stainless-steel wire brush to clean the material. Make sure this is a dedicated brush only for the aluminum else contamination will occur. If you have a synthetic fleece with particle bounds like scotch Brite pads, we recommend using those.
- Always use the wire brush in the direction of the weld or towards the length of the material. Only brush in one direction, do not crisscross. Crisscrossing will grind oxide back into the aluminum.
- If you opt for the TIG welding method, clean the filler rod with toilet paper or paper towels. They collect dirt easily.
- We recommend preheating them with a blow torch as evenly as you can for thick pieces. Do not melt the material. Please opt for preheating for sheets greater than 10mm.
- For water stains, we recommend grinding wheels or pads. We recommend medium-grade Scotch Brite pads.
Methods of Welding Aluminum
There are plenty of welding methods in use, but the best practices for welding aluminum materials are either Tungsten Inert Gas Welding (TIG) or Metal Inert Gas Welding (MIG).
Metal Inert Gas Welding (MIG)/Gas Metal Arc Welding (GMAW)
You will need to feed an electrode wire to the welding gun for this machine and method. The device will also use a shielding gas cylinder to supply gas to the welding arc.
MIG weld is recommended for 14 gauge or thicker materials. There is a chance of burning through the material with thinner variations.
The above-stated stats are a general form to guide you in this process. Some of the specs may differ according to the machine you are using. Always follow the manufacturer’s manual and spec instructions.
Wire Types: 4043ER/5356 Wires (4043 is softer, harder feed ability and better with a spool gun, 5356 has better feed ability, stronger)
Welding Gas: 100% Argon with 25-35CFH
Wire Diameter to Use: 0.8mm to 1.2mm (0.30 to 0.35 inch)
Current Type to Use: Alternative Current
Basic Machine Settings:
You will find two dials in your MIG welder machine, one of them will control the wire speed, and the second dial controls the voltage of the electric current.
The wire speed should be according to the material thickness, and it will manage the heat being created for welding. The voltage is responsible for the transfer mode, which controls your wire interaction with the aluminum material.
You will get a chart with suggested settings for aluminum in the machine’s manual. Follow that strictly.
We recommend using U grooved rolls for aluminum. We recommend ¼ to 3/8 of an inch from the end of the contact tip for wire stick-out distance. The last thing to consider is using a one-step larger contact tip according to the wire diameter. As the torch gets warm, it usually nips.
You should use the spray transfer technique for aluminum. The wire will contact once on the base material, and you need to set the wire speed and voltage to work simultaneously and maintain a steady arc all the time. The spray transfer technique will create a hissing sound when in use.
- We recommend using a spool gun to weld aluminum using the MIG machine. There are options for a push-pull gun, but those alternatives are only for high-production devices. You can use the default torch too. Also, do not forget to attach the gas cylinder.
- Feed the wire through the torch. Follow manual instructions to do it.
- Always use a 10-to-15-degree push angle in the direction of the weld.
- Keep the nozzle about a minimum of ¾ inch from the base material; any close and you might burn the material.
- The voltage and wire speed settings are very important as you need a spray arc transfer for aluminum. You can fine-tune settings according to your welding needs.
- We recommend using a stitch motion, like how you would stitch clothes. A slight back and forth motion is the goal.
- If you have a remote amperage control on the gun, you can start with high amperage and slide it down as the metal increases in temperature. If you don’t, do one pass, let the metal cool down, and do another pass.
When you reach the end of a pass, release the trigger and press it quickly, kind of like adding tacks to fill the crater. The wire might form a ball; cut it off before the next weld.
Tungsten Inert Gas Welding
In this technique, you will use both hands, one with the TIG torch and the other with the filler metal. You’ll also need to control the machine’s output using the weld paddle or the machine parameters.
Please strictly follow the manual from the manufacturer for exact constraints as they can vary according to the type of joints to be welded.
Filler Metal to use: 4043,4943
Current to Use: Alternative current
Recommended Gas Type: Pure Argon at 15-20 cubic feet per hour
Rod for Torch: Tungsten 2% ceriated
Amperage: 90-125 depending on the type of joints
Balance: 65-75 percent
Basic Machine Settings
Most machines have an auto-set mode to set a tungsten size and material thickness. The machine will automatically regulate the amperage. You can also enter these values manually.
Balance: Balance controls the cleaning and etching of the oxide layer. Lower the balance number, more cleaning of oxide is done. The default generally ranges around 70-75 percent meaning 75 percent of alternating current is used for welding, and 25 percent is used for cleaning the oxide layer.
You will have to adjust this according to the amount of cleaning, joint designs, etc.
Frequency: This represents the concentration of the welding arc. A higher frequency will create a tighter arc. Lower settings will give flatter beads.
Use higher settings for the tight area, angle joints, outside edges of materials, etc. Use lower settings for the butt joints area that needs to be built up with weld materials.
- Please note you will have to grind the tungsten on an abrasive wheel. Do not use the wheel for other jobs as the rod might get contaminated. The general grind angle is 15 to 30 degrees. Follow manual guidelines.
- The general way to catch the torch machine is to hold it like a huge pen. Remember to brace the base of your hand on the table for maximum stability. We recommend the dominant hand. The other hand will hold the rod of filler material.
- The torch must be held at a 90 degree to the aluminum material with a ten-to-fifteen-degree push angle as you gently slide across the material. The height between the torch and the aluminum must generally be around ¼ to 3/8 of an inch.
- Do not lean the torch away if you cannot see the puddle, sit at an angle on the side to see the weld puddle and the tungsten filler.
- The filler metal rod needs a dabbing motion. Remember, the torch glides gently across the material, and the rod gets pressed in a dab- dab -dab interval. Your mantra should be to add filler or dab and move. Try to be as fluid as possible.
- You need to add the filler metal to the leading edge of the puddle, not directly beneath the tungsten. You do not want the filler metal to ball up. Dab and move away. If you add the filler faster, the puddle will be tighter. If you add filler slowly, the pool will be wider. We recommend tighter puddles.
- Always ease into the foot paddle increase it slowly to create a puddle once the puddle form makes the output paddle consistent. Not all Tig Machines have foot paddles; there will be a setting on the machine to maintain output amperage for those that don’t. Some machines also have scrollers in the nozzle. Follow the machine’s manual for using these options.
- Start to create arc and puddles and widen it out to the proper width; if it’s too hot or the torch doesn’t glide enough, the puddle will get wide and washes out.
- If the glide is too fast and you don’t have current control, you will lose the puddle. Try to get a nice, consistent puddle. The more you weld on the piece, the hotter it gets. We recommend doing a pass on the whole material, letting it cool for a while, and doing another pass.
- If you have a crater at the end of the weld, please dab one more filler metal on the crater and backstep the torch a bit.
- Remember to keep your torch at the end of the puddle during post-flow to shield the molten puddle while cooling. The shield gas also protects the tungsten.
Welding Methods to Avoid
Any welding type that uses a flux is not recommended as it results in porosity. Technically you can weld aluminum with stick welding, but the process is very difficult and messy.
There are chances of the weld puddles exploding, and you will have to scratch the flux off with pliers or pointed hammers. You would also have to clean the weld blobs with sanders. The process is time-consuming and non-efficient. If it’s just joining the materials, stick welding is possible, but we do not recommend it.
Why do you use Alternating current to TIG Weld Aluminum
Alternating currents have both positive and negative cycles. When you weld aluminum, we use an Alternating current welding system as the positive cycle scrubs the surface and breaks up the oxides in the materials. The weld penetration is done by the negative cycle.
Both cycles work in harmony to create high-quality welding results. So, in general terms, the positive cycle cleans the oxide layer, and the negative cycle penetrates the area to weld.
Can you use DC for TIG welding?
Yes, it’s possible but not recommended; the oxide layer on top of the material has a melting point of roughly 2000 degrees Celsius, whereas the aluminum itself has a melting point of approximately 600 degrees Celsius.
DC weld can melt aluminum, but it will form a molten pool underneath the layer of aluminum oxide that remains floating on top, which prevents the puddle from flowing well or being easy to judge or control.
When you add fillers, the oxide layer from the filler rod gets mixed in, and you will most likely get a lumpy mess. Technically, welding is possible, but the quality of the weld is going to be questionable.