Introduction
It is doable, but it can be extremely difficult and irritating. Because aluminum is a softer metal than steel and stainless, feeding it through a torch lead becomes considerably more difficult. There are a few things you can do with your MIG torch to combat this.
Aluminum is one of the most often used welding materials, with a few qualities that set it apart from steel and stainless. It’s soft, making it easy to work with and mill, non-magnetic, rust, and corrosion resistant, and doesn’t spark. As a result, its primary application is in aircraft and watercraft. Obviously, building a plane may be a bit of a stretch if you’re just learning to weld at home, but you could absolutely build your own boat in your backyard after you’ve gotten the hang of it.
The key to aluminum welding
Aluminum is a relatively soft metal that has various applications but requires the addition of alloy(s) to boost its strength. Because aluminum’s characteristics differ substantially from those of steel, working with metal can bring some unique issues, such as deformation and heat sensitivity. Despite these challenges, MIG welding aluminum is not difficult provided the proper equipment and methods are used.
When MIG welding aluminum for your application, keep these crucial aspects in mind.
Tips for getting started
Consider material thickness:
Aluminum material thicknesses that can be MIG welded are 14 gauge and heavier; the thickness you can weld is determined by the output capacity of your welder. To MIG weld aluminum thinner than 14 gauge (.074 inch), specialist pulsed MIG or AC TIG welding equipment may be required.
Keep it clean:
Prior to welding, aluminum should be carefully cleaned, including the removal of any lubricants. After de-greasing, remove the oxide with a stainless wire brush, either a hand wire brush or a cup wire brush. When using a power wire brush, keep the rpm and pressures low to avoid smearing the material’s surface, which could trap oxides and contaminants beneath the surface. To avoid contaminating the base material, always clean with an aluminum-only wire brush.
Choose the right gas:
Because aluminum is a non-ferrous metal, it requires a shielding gas that is 100 percent argon. It is recommended that flow rates range between 20 and 30 cubic feet per hour.
What process should you use?
Spray transfer is the desirable mode when MIG welding metal. This is a highly smooth transport of molten metal droplets from the electrode end to the molten pool. Droplets that cross the arc have a smaller diameter than the electrode.
Spray transfer has no short-circuiting, and the deposition rate and efficiency are both comparatively good.
However, keep in mind that spray transfer generates a lot of heat, resulting in a huge weld pool with considerable penetration that might be difficult to regulate. It should not be applied to materials that are thinner than 14 gauge.
Gun and wire feeding options:
Before MIG welding aluminum, it is critical to select a gun and wire feeding system. Aluminum wire is typically fed using a spool gun or a push-pull mechanism. Spool guns improve soft wire feeding by placing a tiny pool of wire atop a pistol-grip-style gun.
Because the wire only feeds a few inches, using a spool gun removes the risk of birds nesting. A motor in the cannon pushes the wire through the liner in a push-pull system, while a motor on the feeder works as an assist motor. When welding distance from the power supply, this alternative is more ergonomic and user-friendly.
The right filler metal:
Understand the alloy of your base aluminum as well as the conditions that the finished product will be subjected to. The two most common aluminum filler wires are ER4043 and ER5356. For recommendations on wire alloys that are appropriate for your application, contact your local welding distributor or aluminum filler metal specialist.
Metal Grades
There are several varieties of aluminum filler wire available, but the most popular are 4043 and 5356. These are both aluminum alloy fillers, with 4043 containing 5% silicon and 5356 containing 5% magnesium.
- 4043: use on 4000 to 6000 series aluminum
- 5356: use on 3000, 5000 & 6000 series aluminum
The filler wires have varying properties due to the different alloys, the most notable being that 4043 is softer than 5356. When MIG welding, 5356 wire is often preferred because of its increased hardness, which allows it to feed more easily. If you’re welding 4000 series aluminum, though, you’ll need to use 4043 filler.
Hot Shortness
Aluminum is ‘hot short,’ which means it cracks easily when nearing its melting point. Essentially, when the weld cools, the aluminum becomes more prone to cracking. It normally begins where the weld ends and spreads along the full length of the weld. Weld cracks are terrible news, and you’ll have to redo it because they’re structurally weak.
Metal Preparation
When it comes to aluminum, preparedness is crucial. Aluminum is not forgiving; anything left on it will cause your weld to fail.
Any dirt, paint, oil, or other substance must be entirely removed, and this is only the beginning of the cleaning process. Aluminum also has an oxide coating that needs to be removed.
There are several methods for removing this oxide coating. The first method is to use a portable wire brush.
Choose a brush that is just for aluminum since using a brush that has previously been used on steel or stainless steel can contaminate the aluminum.
You want to brush it until it’s dull and no longer shines. It shouldn’t be glossy because that usually indicates that the metal still has an exterior covering on it.
Because aluminum is soft, using a wire brush wheel or anything similar is a no-no. It will not remove the oxide; instead, the rapid speed of the wheel will further embed it into the metal, heating it up.
If you’re using a wire brush, only scrub in one direction at a time, as sweeping back and forth might embed the oxide even deeper into the aluminum.
The second method for cleaning aluminum is to use isopropyl alcohol or acetone. It’s a good idea to clean out your metal before using a wire brush to ensure there’s nothing on the surface that will become embedded accidentally.
Keep in mind that you don’t need to go overboard with the cleaning because no matter how carefully you clean it, it will never be flawless.
When oxygen comes into contact with aluminum, it quickly begins to reconstruct its oxide coating, so once you’ve wiped and/or wire brushed it, let your welder handle the rest because you’ll never get ALL of it off.
If you’re TIG welding aluminum, a simple wipe-down of your filler rod won’t hurt either.
Although it may appear to be a chore, cleaning your aluminum carefully is necessary due to the metal’s melting points. Even if the metal is unclean or still has its oxide covering, the arc will still ignite. If you leave too much of the oxide layer on the aluminum, you may be unable to create a weld pool.
Aluminum melts at approximately 660°C, but the oxide layer on top melts at approximately 2000°C. That is, you could be melting the aluminum behind the surface layer, but you won’t be able to establish a weld pool until you burn through the oxide.
MIG Welding Aluminum
MIG welding aluminum can be much faster than TIG welding, and you can use ordinary DC settings, so you won’t require AC/DC equipment.
If you use a normal torch, welding aluminum on MIG is like “putting a wet noodle through a straw.”It is doable, but it can be extremely difficult and irritating.
Because aluminum is a softer metal than steel and stainless, feeding it through a torch lead becomes considerably more difficult.
There are a few things you can do with your MIG torch to combat this.
The first step is to replace your liner with a Teflon one, as they are meant for aluminum, to which you will attach a neck spring. While you’re changing the liner, replace your guide tube with one made of aluminum.
Make sure you have U-groove rollers since these will hold the aluminum better and help prevent bird nests.
Finally, you can acquire aluminum-specific contact tips, which will aid in wire feeding.
The second thing to remember is to maintain your torch as straight as possible during welding. The shorter the torch, the easier this is (and the shorter the travel distance for the aluminum), but it becomes difficult if you have a torch that is three or more meters long. Large loose curves or loops are acceptable, but any tight circles would almost certainly kink your wire.
You will also require an additional gas bottle. Aluminum requires pure argon gas, as opposed to steel and stainless MIG welding (which utilizes an ArCO2 mix). If you’re not going to be welding a lot of aluminum, a tiny bottle will suffice.
Loading an aluminum spool in the MIG welder is the same as loading a steel or stainless steel spool: line up the locating lug and hole, slot the spool into place, then screw the nut on to secure it in. Once turned on, pass the beginning of the wire through the inlet guide, over the roller, and into the beginning of the guide tube.
This will occasionally work, but you must have the proper setup. Otherwise, you’ll encounter bird nesting.
MIG Welding Aluminum Spool Gun
A spool gun is required if you intend to MIG weld metal with your wire feed welder.
Why can’t you simply insert a spool of aluminum wire into your MIG machine?
Because MIG aluminum wire is considerably softer than steel, it attracts birds and causes them to nest inside your cable liner.
Because the wire isn’t as stiff as mild steel wire, you’ll need to compensate by utilizing a spool gun.
Spool guns are useful for home welders, although they normally only hold a modest 1-pound roll.
The advantage of using a spool gun is that the aluminum wire does not have to go through the MIG hose, where it is likely to become rattled.
What Should You Avoid When Welding Aluminum?
Now that we’ve discussed the various methods for welding aluminum, let’s look at some common mistakes to avoid.
- Using a “one-size-fits-all” strategy: When it comes to welding aluminum, the welder must take a completely different approach than when welding steel. It is critical for the welder not to base their technique on previous experience with other metals or materials, as aluminum is very unique and can pose hazards if not handled properly.
- Wearing the incorrect PPE: Speaking of dangers, welding aluminum or any other material is inherently dangerous. Welders must always wear the appropriate personal protective equipment (PPE) and educate themselves on safety procedures and best practices. This is essential for a long and prosperous career in the industry.
- Failure to prepare: Planning is essential, both for the welder and the material being welded. Before beginning your weld, make certain that your aluminum has been properly cleaned and stored. Furthermore, prepare yourself by learning the art of aluminum welding and educating yourself on the craft. Never do anything unless you are thoroughly prepared.
- Ignoring minor details: The most successful welders will tell you that attention to detail is crucial. In this industry, even the smallest mistake can result in a complex error, especially with aluminum welding. Always pay attention to detail and double-check your work because it will benefit both your customers and your career in the long run.
- Not being patient: It takes time to learn to weld aluminum. Continue to practice and persevere; your hard work and perseverance will pay off in the end!
Factor Affecting During Aluminum Welding
To summarise, the following are some of the most common factors that make welding aluminum difficult:
Oxidation:
An aluminum oxide layer sits on top of aluminum, which melts at a much higher temperature than aluminum. High heat is required to melt through this layer, but the welder must be careful not to burn holes in the aluminum underneath.
Porousness:
Aluminum absorbs hydrogen more quickly in its molten state as it heats up. This hydrogen separates out as the metal returns to a solid state, leaving behind bubbles that cause the metal to become porous and weak.
Impurities:
Due to the sensitivity of aluminum, there are several ways for it to become contaminated by dirt, air, and water during the welding process. Because of poor shielding or excessively long arcs, aluminum can become contaminated by air that reaches the weld. Oxygen can reduce the strength and ductility of aluminum, as well as cause oxide formation on aluminum welds, which affects their appearance and complicates multi-pass welding.
Hydrogen can be obtained from a variety of sources, including moisture in electrode fluxes, humid air, damp weld joints, and others. For all of these reasons, it is critical to thoroughly clean and store aluminum prior to welding.
Thickness:
Welding aluminum necessitates working with various material thicknesses. Welders must be able to avoid burning through thinner material while penetrating thick material sufficiently to create a strong weld.
While welding aluminum presents some difficulties, it is not impossible to learn. Fortunately, there are tools and techniques available to assist in dealing with the unique properties of aluminum.
You’ll be well on your way to mastering the art of aluminum welding if you understand how aluminum reacts and how to use these tools and techniques effectively.
Troubleshooting common problems
If you encounter any of these typical issues while MIG welding aluminum, use these procedures to resolve the issue.
Burn-through (melt-through) is caused by overheating the base material
- Increase the travel speed and make shorter welds.
- Move around on the part, spreading out the heat.
- Use thicker material, change the joint design or switch the welding process to AC TIG.
- Eliminate/reduce gaps.
Dirty welds
- Instead of dragging, use a push angle.
- Increase the voltage to enter spray transfer mode.
- Use appropriate base metal cleaning methods, such as a stainless steel brush.
- Examine the shielding gas and wire alloy type.
Wrong machine settings
- Examine the inside cover of your Millermatic welder for the best beginning settings or to fine-tune for your specific application.
- Order the Millermatic MIG Calculator for accurate starting parameters.
Wire burns back to the contact tip during or at the end of the weld
- Maintain an appropriate tip-to-work distance.
- Check that the contact tip size, drive rollers, and gun liner all match the wire diameter.
Wire bird nests (piles up) in front of inlet guide on gun
- Check and adjust the tension on the driving roll.
- Make sure the drive rolls fit the wire diameter.
- If required, replace the contact tip.
- Adjust the pressure on the aluminum spool gun hub.
