The Ultimate Buyer's Guide for Purchasing Aluminum Mig Welding Wire

Welding aluminum

Aluminum in its pure form is a relatively soft metal that has many uses, but which requires the addition of an alloy or alloys to increase its strength and to add other qualities suitable for different applications. Common alloys are: copper, magnesium, silicon, manganese and zinc. They are identified by their series numbers:

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• Wrought Series Alloy groups
• 1xxx 99% minimum aluminum purity
• 2xxx copper
• 3xxx manganese
• 4xxx silicon
• 5xxx magnesium
• 6xxx magnesium-silicon
• 7xxx zinc
• 8xxx other
• 5xxx magnesium
• 6xxx magnesium-silicon
• 7xxx zinc
• 8xxx other

Aluminum, especially thin-gauge aluminum, presents some unique welding challenges. For many, GTAW is the preferred process, but GMAW offers some obvious benefits: higher deposition rates, less operator training and higher productivity. With these benefits come a few challenges, namely wire feeding and selecting the right type of filler metal and equipment. These challenges can be easily met, however, by knowing the answers to some common questions.

Frequently asked questions 

While filler metal for steel is typically chosen by matching the tensile strengths, strength is only one of the considerations when choosing an aluminum filler metal. Typically, there are several different aluminum filler metals that would be acceptable to use when welding aluminum base materials. In choosing a filler metal, consider:

-Base metal composition
-Ease of welding
-Joint design
-Dilution (when the filler wire and base metal combine in the weld puddle to create a different chemical make up in the weld)
-Strength of the weld
-Hot cracking sensitivity
-Ductility
-Corrosion in service
-Color matching, if the material is anodized
-Elevated service temperature (150-350 Fahrenheit)

Different filler metals address these considerations to varying degrees. In general, if strength is the primary consideration, the filler metal should closely match the base metal in tensile, yield and ductility.

Most consumable manufacturers, as well as the American Welding Society (AWS), offer information listing the relative values of these considerations of their filler metals for each base alloy. Always make sure to use an aluminum filler metal selection chart to address the weld properties listed above.

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Traditionally, welders have relied on AWS and wires, as they can be used with the most widely used aluminum alloy base metals. Hobart, however, offers an alternative to filler metals to increase strength and quality. The MaxalMig®  aluminum wire offers approximately 20% higher tensile strength and doesn’t rely on diluting the aluminum base material to gain strength. This feature often allows welders to make smaller, single-pass welds and still get reliable strength. It also helps minimize the risk of distortion since heat input is lower. 

Aluminum as a filler metal has the same oxidation problems as all aluminum. When left open, either on the shelf or installed on the welder, aluminum filler wire will oxidize, which can lead to an erratic arc. The oxidation adds resistance, can produce smut and can change the wire’s ability to feed smoothly. Many operators have spent a great deal of time adjusting tension settings, changing contact tips or checking the shielding gas trying to fix the problem when it was the oxidized wire that was at fault.

Because of its low columnar strength, feeding aluminum wire has been likened to pushing a wet noodle through a straw. Birdnesting, or the tangling of the wire between the drive roll and the liner, is a common, time-consuming and costly problem. Clearing it requires the operator to stop welding, cut the wire, discard the wire in the gun and re-feed new wire through the liner. It also may require cleaning or changing the contact tip because of the burnback caused when the wire stops feeding.

There are several ways to feed aluminum wire: Push only, spool gun, push-pull system and continuous feed push-only system.

Push only: Feeding aluminum wire through a push-only system can be difficult, but it can be done on a limited basis. It requires u-groove drive rolls to provide more surface contact with the wire, adequate drive-roll pressure and the ability to keep the gun cable straight. Any resistance in the line will likely cause the wire to misfeed. Thicker wire, such as 1/16 inch, may be fed consistently in a push-feed system. But for thinner gauges, such as .030 inch, push feeding is not very dependable.

Spool gun: Welding aluminum with a spool gun, such as the Spoolmate™ or Spoolmatic® series of guns, eliminates the possibility of birdnesting by putting a 4-inch (1-pound) spool on the gun, so the wire only feeds a few inches. Spool guns can accommodate aluminum wire diameters from .023 to 1/16 inch and allow the operator to use longer cables (15-50 foot).

A spool gun needs to have the roll changed after every pound of wire is used, compared with the 16- or 22-pound spool on a push-pull system. In tight spaces, the spool may limit access, requiring the operator to use a longer stickout. If the operator is using several pounds of aluminum per day, the few minutes needed to change spools can add up. Also, the chance of burnback exists when the end of a spool is reached, so many operators stop when a few turns are left on the spool.

Push-pull gun: With a push-pull gun, a motor in the gun pulls the wire through the liner, while the motor in the welder or feeder control becomes an assist motor. By maintaining consistent tension on the wire, the push-pull system helps eliminate birdnesting. It is more ergonomic than the spool gun since the weight of the spool is not in the operator’s hands.

Also, the spool needs to be changed less often than on a spool gun and allows the purchase of larger spools. A push-pull gun also allows cables up to 50 feet long. The only disadvantage to push-pull systems is their relatively higher price tag, but the increased productivity and the financial advantage of buying larger spools usually provide a quick return on investment. When you compare the cost of 16 1-pound spools of .035-inch aluminum filler wire with one 16-pound spool of the same diameter wire, plus the time to change 16 spools versus one spool, you’ll see that for high-volume use, a push-pull system makes financial sense. 

A welding distributor, picked at random, lists a price for a 1-pound spool of .035-inch aluminum wire as $11.46. A 16-pound roll lists for $170.24, which works out to a difference of $0.82 per pound. Now, add the time for 16 spool changes (and possibly burnbacks) for the spool gun as compared with one change for the larger spool. At five minutes to change a spool, that’s 80 minutes of extra time for each 16 pounds of filler wire used.

Continuous-feed push system: This is a relatively new addition to the field. This type of system uses a special drive system that maintains continuous contact with the wire and eliminates the possibility of birdnesting since there is no gap between the drive rolls and the liner. While it is limited to pushing the wire 15 feet, the gun is lighter than either the spool gun or the push-pull gun and requires no additional maintenance.

Check out this article for more MIG welding aluminum best practices.

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Is spray transfer the same as 'pulsed'?
And is 'synergic' beneficial for aluminium?

If it makes a diference it's and series alloys i'm primarily interested in welding

Cheers

Andrew

No, Spray transfer is when you have a welder with enough power it can melt the wire before it reaches the work piece but has enough power to mantain an electrical arc at the same time to melt the workpiece. The melted filler wire literally turns into a spray (like paint) and travels across the arc fusing with the melted metal of the workpiece. This gives good penetration and even deposit of the filler. It's good for getting heat (and a strong weld) into thicker sections.
On thinner sections of alloy it's probably to much heat to control manually and you will just end up blowing holes in the workpiece.

Pulsed is a setting/option on the welder that, during welding, ramps the power up and down really quickly. When the power is high you get good penetration and then during the low bit the workpiece gets time to cool down which stops you blowing holes in thinner sections. Very handy if you want to weld any thinner than 3mm or so.

Synergic is a program mode on a welder. Rather than adjust the voltage and wire feed speeds to get a good weld the machine is preprogrammed with a load of settings and you would just choose one thing to adjust (usually the thickness) so dial in 4mm and the welder sets the correct wire speed and voltage for you.
It's a handy function but by no means essential.
If you've never mig welded alloy before then you could probably take a synergic machine out of the box and be welding within half an hour. But, I think you would gain more using a traditional machine and spending an hour and a half with some test pieces messing around with the settings to learn what does what and how it affects the welds.
Although I admit that for 99% of my welding I never need to adjust the synergic settings as they just work fine as they are.

Anyway, like others have said, I think the £500 budget is optimistic and might be ruling out synergic sets for you.
A lot will depend on what/how you want to weld but, on a limited budget, I would say the priorities are power and duty cycle.
A 4-roll feeder and a set of the correct rollers are high on the list as well.
For £500, if I had the space and the power supply, I would be looking at some of the ex industrial machines, if you can pick up one of them for £350 then by the time you have bought a decent torch, liner, rollers and a bottle of argon you might just come in around the £500 touch I've always fancied building an aluminium boat, something around 6m so probably made from 6mm alloy hull and maybe some 4mm/5mm for the cabin and fittings

With my experience with single phase mig welding of alloy I've decided its a better idea to put the project on hold plus I don't have the workshop space for it at the moment anyway.

I think my plan for doing one would be to make up every single part as a complete kit.
All the sheets could be cut, drilled and 90% of the weld preps done. This should all stack up efficiently in a shipping container or something.
Make up a jig that can be bolted together
Make up the wiring looms, plumbing stuff and so on so it is all ready to be fitted quickly and save up enough money for a couple of decent engines
Then, once every part is ready get hold of an ex industrial 300a+ mig with water cooled torch, rent a unit with 3phase power for 6 months and dump the shipping container outside it.
Then it should just be a quick case of setting the jig up, running the final 10% of welding prep to clean up the material and welding it all together.

I'd like to think (providing the design & fab was ok) it could be done in a months worth of weekends leaving me another 5 months to fit all the bits.

I might even get ambitious and build the jig so that once I have finished welding the hull I can add & remove a few bits to turn it into a trailer for the boat!

Or, leave it so it can be taken apart and stuck on a pallet then I could offer self built kits etc for sale.

The main thing holding me back at the moment is drawing up a set of plans for the material cutting. Mainly because I know absolutely nothing about boat design.
The other thing is its probably cheaper to buy a used boat that's ready to go fishing than it is to build my own.
Might be a retirement project if the running costs are still affordable at that time..