It’s not hard to understand why aluminum has become an essential part of modern manufacturing and fabrication industries. This lightweight, strong, and non-corrosive metal is chosen for everything from bicycles to spacecraft, and its pleasing appearance and machinability only enhance its popularity.
However, all of aluminum’s attributes can’t hide the reality that it can be challenging to weld and even incompatible with some types of welding. Here is what you should know about this superb material:
Why is aluminum welding so tricky?
Aluminum is soft and insulated by a thin aluminum oxide layer that melts at 3,700°F (2,037°C) while the aluminum melts at 1,200°F (650°C). Because the oxide melts at a much higher temperature, it must be removed from the workpiece before welding begins since it will prevent the arc and the weld pool from forming a connection. Thoroughly cleaning the aluminum before welding also eliminates impurities such as dirt and grease.
Another issue when welding aluminum is porosity. The material absorbs hydrogen more quickly as it heats up, and the hydrogen separates as the metal solidifies, leaving bubbles and causing porosity.
What do I need to weld aluminum?
Welding aluminum is a unique process, and it’s different from welding steel, meaning not just any gear will work. In addition to specific equipment, purchasing the correct safety equipment will avoid inherent welding risks. Here is a machine and gear checklist:
What type of welding machine is best for welding aluminum?
A quality aluminum weld begins with the right welder, and TIG welders are typically the top choice for aluminum welding. The TIG325X AC/DC TIG welder from PrimeWeld is an ideal choice for aluminum with an AC balance feature allowing you to break through the oxidation layer. This top-of-the-line model includes a foot pedal and a selection of water-cooled torches.
Can you weld aluminum with a MIG welder?
Yes, but it’s more challenging because it takes more heat than mild steel, and aluminum welding with a wire welder is infamous for burn-through. Many welding professionals recommend using the same voltage settings you would use with mild steel but doubling the travel speed.
Also, use a spool gun for MIG welding aluminum with a wire feed welder. MIG aluminum wire is softer than steel and tends to nest inside your cable liner. Since the wire isn’t as stiff, you compensate using a spool gun where the aluminum wire doesn’t travel through the MIG hose, where it often gets tangled.
Remember, for aluminum MIG welding, you use pure argon shielding gas up to 1/2” thickness, while 25% to 75% helium can be added for thicker aluminum. The minimum aluminum thickness you should attempt with MIG is about 14 ga. to 18 ga. Use a TIG welder for anything thinner than that.
The MIG285 285-Amp MIG Welder from PrimeWeld is a versatile welding machine capable of MIG, FCAW, Lift TIG, and Stick welding in one portable unit. The MIG285 is well-suited for applications in aluminum and stainless steel fabrication.
TIG welding electrodes: PrimeWeld’s 2% Ceriated Tungsten Electrodes (GREY, WC20) are perfect for welding aluminum alloys, magnesium alloys, nickel alloys, copper alloys, titanium alloys, low-alloyed steels, and stainless steel.
Aluminum rod fillers: Choose 4043 and 5356 alloy types for most jobs, and use the same size as your TIG welding electrodes.
Aluminum welding wire for MIG melding: ER 4043 or ER 5356 suits most jobs and should match your rod filler.
Argon shielding gas: PrimeWeld can supply 100% argon gas for TIG welding.
Wire cleaning brush: Wire brushes help prepare the metal’s surface before welding.
Personal Protective Equipment (PPE) including:
- Auto-darkening helmet to protect your eyes from UV light.
- Safety glasses for sparks and flying debris.
- Goatskin leather TIG welding gloves.
- Leather welding jacket that is tight but not restrictive.
- Durable denim jeans without a cuff are an excellent option for welding.
- Steel-toed work boots to protect your feet from falling metal.
Can you stick weld aluminum?
Yes. You can stick weld aluminum, but it should be your third choice for a welding method (behind TIG and MIG). It’s considerably more complex than stick welding steel, and the finished joint might not be attractive. You must carefully choose the electrode, find the correct settings, have welding experience, and lower your expectations. Ultimately, you might still decide it wasn’t worth the effort.
Many problems with aluminum welding stem from its high thermal conductivity, low melting point, and chemical composition. The first problem involves the stick welder’s power. Because aluminum conducts heat so well, heat moves away from the joint quickly, so you must put more heat into the weld pool even though it has a low melting point. You must be able to vary the amperage output on your stick welder to supply the required heat.
Aluminum’s low melting point also causes the puddle to set faster, meaning you should keep a short arc and move it faster than expected. The short arc can fuse your stick electrode in the pool if your motion isn’t fast enough. It takes lots of practice to get it right.
Another issue is the rough appearance of stick-welded aluminum. Most aluminum stick welding requires direct current electrode positive (“DCEP”) or reverse polarity, causing the flux to spatter excessively. Also, the short, fast-moving arc is often erratic, producing a bead that looks nothing like a stack of dimes.
Because the amount of heat applied to the metal is high, warping and burn-through, especially on thinner pieces, is not unusual. Getting the weld pool’s heat right takes much practice, and even seasoned welders burn through light aluminum occasionally.
Another concern is hot and cold cracking. Professional welders often preheat aluminum with an acetylene torch to help prevent warping. It also slows the heat “wicking” issue and allows a puddle to form and penetrate, producing a stronger weld with less porosity.
One final tip involves storing the special electrodes you use to weld aluminum. These electrodes are coated with a moisture-sensitive flux that should be kept in a dry area to keep them from being ruined. Since aluminum stick electrodes are expensive, stick welding aluminum might be costly.
Two processes can handle the difficult job of aluminum welding: GTAW (TIG) and GMAW (MIG). And most welders will tell you TIG will give you better results, especially on lighter gauge material, giving welders more control over heat, penetration, and appearance.
Remember the basics, and you can have a quality aluminum weld every time:
Clean the material: Remove the oxide layer with a stainless-steel wire brush before welding. To avoid contamination, use the same brush for each aluminum project and only clean in one direction.
Use the correct polarity: Even though you cleaned the material, the oxide layer immediately starts reforming. When TIG welding aluminum, you can overcome this by using alternating current (AC) polarity, and AC provides a cleaning action that breaks up the oxide layer.
Use a shorter arc length: It’s essential to use a shorter arc length to focus the heat on a small area.
Use filler metal: Adding filler metal to your aluminum weld has a cooling effect on the backside of the weld pool, creating a smooth appearance to the weld.
Hand and torch placement: During TIG welding aluminum, hold the torch by bracing it from your wrist to the tip of your pinky finger. Place your hand flat against the table, keep the torch steady, and move forward with a slight backward tilt to the torch.
Travel speed: If your speed is too slow, you risk excessive burn-through or melt-through, especially with a thinner gauge aluminum sheet.
Don’t weave: A weaving technique works with many base metals but not aluminum. A better option is a stringer bead with high heat and fast travel speed.
Adjust the balance control: Adjust the ratio between an EN (electrode-negative) and EP (electrode-positive) current, with the EN at about 70%.
Store base materials and filler metals properly: Store aluminum sheets inside to avoid contamination. If you must store them outside, stand the sheets vertically to prevent water entrapment.
Use the best equipment and accessories: PrimeWeld is the leader in affordable welding tools for home or work. Shop today for a comprehensive selection of TIG welders, MIG welders, plasma cutters, multi-process welders, argon welding gas tanks, accessories, and consumables. Give us a call at 856-500-2000 or send us a message via our contact page.