alumunium welding

Aluminum is an active metal and it reacts with oxygen in the air to produce a thin hard film of aluminum oxide on the surface. The melting point of aluminum oxide is approximately 1926 degress, which is almost three times the melting point of pure aluminum, 660 degrees. In addition, this aluminum oxide film, particularly as it becomes thicker, will absorb moisture from the air.

Moisture is a source of hydrogen which is the cause of porosity in aluminum welds. Hydrogen may also come from oil, paint, and dirt in the weld area. It also comes from the oxide and foreign materials on the electrode or filler wire, as well as from the base metal. Hydrogen will enter the weld pool and is soluble in molten aluminum. As the aluminum solidifies it will retain much less hydrogen and the hydrogen is rejected during solidification. With a rapid cooling rate free hydrogen is retained within the weld and will cause porosity. Porosity will decrease weld strength and ductility depending on the amount.

The aluminum oxide film must be removed prior to welding. If it is not all removed small particles of un-melted oxide will be entrapped in the weld pool and will cause a reduction in ductility, lack of fusion, and may cause weld cracking.

Even home welding enthusiasts who have experience welding steel may find a switch to aluminum challenging. Here's why: Because of the softness of aluminum wire, it is more difficult to feed. In addition, wire diameters and machine settings normally used for steel may not be appropriate for aluminum.

MIG welding aluminum requires different techniques than MIG welding mild steel.

Before You Start Welding

- Material thickness that can be welded with Mig process on aluminum are 14 Ga. and heavier. (How heavy depends on the output capacity of the welder being used.) To MIG weld aluminum thinner than 14 Ga. (.074") either specialized pulsed MIG or AC TIG welding equipment may be necessary.

- The removal of lubricants from the aluminum base material may be necessary. This is best done with solvents. Consult with your local Miller Welding Distributor for their recommendation.

- Oxide removal should be done after degreasing. This should be done with a stainless wire brush. This can be done with a hand wire brush or with a cup wire brush. If a power wire brush is used keep the RPM'S and pressures low to reduce smearing the surface of the material, which could entrap oxides and impurities under the surface. Always use a wire brush that is used on aluminum only, to keep from contaminating the base material.

The pure metal has a melting point less than 1200ºF and does not exhibit the color changes before melting so characteristic of most metals. For this reason, aluminum does not tell you when it is hot or ready to melt. The oxide or "skin" that forms so rapidly on its surface has a melting point almost three times as high (3200º+F). To add to this confusion, aluminum even boils at a lower temperature (2880ºF) than this oxide melts. The oxide is also heavier than aluminum and, when melted, tends to sink or be trapped in the molten aluminum. For these reasons, it is easy to see why as much as possible of this oxide "skin" must be removed before welding. Luckily, the reverse polarity half of the AC arc does an outstanding job of cleaning off quantities of this oxide ahead of the weld!

Aluminum is an excellent conductor of heat. It requires large heat inputs when welding is begun, since much heat is lost in heating the surrounding base metal. After welding has progressed a while, much of this heat has moved ahead of the arc and pre-heated the base metal to a temperature requiring less welding current than the original cold plate. If the weld is continued farther on to the end of the two plates where there is nowhere for this pre-heat to go, it can pile up to such a degree as to make welding difficult unless the current is decreased. This explains why a foot or hand Amptrol™ (current control) is recommended with your Precision TIG™ 185 or Precision TIG 275 - it enables you to easily change the current while simultaneously welding.

Some aluminum alloys exhibit “hot short” tendencies and are crack sensitive. This means that at the range of temperatures where the liquid alloy is slushy (part solid and part liquid) or just turned solid, it has not quite enough tensile strength to resist the shrinkage stresses that are occurring from cooling and transformation. The proper choice of filler metal and welding procedures along with smaller beads can help eliminate many problems of this kind. Some experts recommend backstepping the first inch or so of each aluminum weld before finishing in the normal direction.

Anyone who has worked with TIG Welders and automated TIG systems, knows the TIG weld quality is highly dependent on retaining the shape and quality of the tungsten tip. Weld start data is critical with automated TIG welding applications. Tip life is improved with a start ramp up to the low current start point then ramp to the operating current

Ensure Good Electrical Connections
The work clamp should be securely attached to the welding piece in an area free from paint and contaminants. To clean the piece, use a degreasing solvent to remove any oil and grease. Be sure that the surface is dry before you weld. Also, do not weld with flammable material nearby, such as a container of solvent or paint. As a second step, use a clean, stainless st

MIG and TIG Welding

What is MIG Welding?

The term MIG stands for Metal Inert Gas.  MIG welding is used to combine two pieces of metal together using consumable wire connected to an electrode current.  A wire passes through the welding gun at the same time as an inert gas.  The purpose of the inert gas is to protect the weld from airborne contaminants.  Argon, which is heavier than air, is the most common inert gas used because it shields the weld better; however, there are other gases (such as carbon dioxide and helium) that can be used.

MIG welding is known for its high speed welds and user-friendly utilization.  It is excellent for welding softer metals such as aluminum.  MIG welding is also less expensive and a great way to add automation.

What is TIG Welding?

TIG stands for Tungsten Inert Gas.  TIG welding uses non-consumable Tungsten along with an inert gas to weld two pieces of metal together.  The Tungsten electrode provides only the electricity, not the filler, to the welding process.  Inert gas is also used at the same time as the electrode to protect the weld from contaminants and oxidation.



A TIG weld does not always use a welding filler.  It can create an autogenous weld which occurs when one part is melted into the other.



TIG welding is a cleaner process with less sparks, fumes and smoke.  It is great for thinner materials, but due to its precision, it is more expensive than MIG welding.



RobotWorx buys and sells robots for both MIG and TIG welding applications.  Working hand-in-hand with customers, we help determine the best robots to satisfy your welding needs.

MIG Welding Robots:

    Motoman- EA1400, EA1800N, EA1900, HP20, K6, UP20-6, UP20M, UP6
    Fanuc- ArcMate 100i, ArcMate 100iB, ArcMate 120iL, ArcMate50i, ArcMate 50iB/3L, ArcMate 50iL
    Others- Panasonic, Nachi, ABB and OTC 

TIG Welding Robots:

    Motoman- EA1400, EA1400TN, EA1800, EA1900, K6, UP20-6, UP20M, UP6
    Fanuc- ArcMate 100iB, ArcMate 120i, ArcMate50i, ArcMate 50iB/3L, ArcMate 50iL
    Others - Panasonic, Nachi, ABB and OTC

Tips for Aluminum Welding using a MIG welder

Aluminum welding has got certain misconceptions tagged to it. People believe that they need to invest a large amount for the aluminum welding machine and should be highly skilled to operate it. Also they think an expensive spool gun is only suited for aluminum. On the other hand, some even think that it is possible to make excellent welds the first time wire feed welder is taken out of box. But all these conceptions are proved wrong. The basic fact is that it is quite easy to tackle aluminum welding jobs by using a compact MIG welder with practice, right equipment and proper set up. If provided with a MIG welder, welding of items like grills, railings, backyard furniture and even decorative elements is possible.

It has been seen that even experts in welding steel may find it quite tough to carry out the aluminum welding process. This is because the aluminum wire is so soft that it is hard to feed. Moreover the wire diameters and machine used of steel may not be appropriate for aluminum.

For any novice, the first thing that should be considered would be the type of machine needed for the job. It is possible for a 115 volt wire feeder welder to handle jobs that range from 22 to 12 gauges. And you can probably weld as thick as 1/8" with moderate pre heating. Then again if you are planning to weld a broader range of aluminum thicknesses, then a 230 volt machine which can weld 22 gauges would be the fine choice. For performing regular aluminum fabrication, a heavy duty machine would be the best.

Once you have selected the input voltage, the next concern would be if you need continuous or tapped voltage control model. In a continuous voltage control model, there would be room for more adjustability, fine tuning and precise control. The tapped control unit is best suited if you are on a limited budget and it is sufficient for most applications.

While using a MIG welder, it is best to make welds in the horizontal and flat positions. It would be quite easy to do fillet welds in lap joints than groove welds in butt joints. Make sure that you are not handling critical welds if you are an amateur as it can lead to serious injuries. Thinking about the shielding gas in MIG welding aluminum, it is better to use 100 percent argon. No special equipment is required as the existing regulators and gas hoses are good enough for pure blends and mixed gases.

GMAW (MIG) Aluminum Welding Hints

MAW (MIG) Aluminum Welding Hints

- Material thickness that can be welded with Mig process on aluminum are 14 Ga. and heavier. (How heavy depends on the output capacity of the welder being used.) To MIG weld aluminum thinner than 14 Ga. (.074") either specialized pulsed MIG or AC TIG welding equipment may be necessary.

- The removal of lubricants from the aluminum base material may be necessary. This is best done with solvents. Consult with your local Miller Welding Distributor for their recommendation.

- Oxide removal should be done after degreasing. This should be done with a stainless wire brush. This can be done with a hand wire brush or with a cup wire brush. If a power wire brush is used keep the RPM'S and pressures low to reduce smearing the surface of the material, which could entrap oxides and impurities under the surface. Always use a wire brush that is used on aluminum only, to keep from contaminating the base material.

- Contact your local welding distributor or aluminum filler metal representative for recommendations on wire alloys that fit your application. Know the alloy of your base aluminum and what conditions the finished part will be subjected to. The 2 most readily available aluminum filler wires are ER4043 and ER5356.

Welding Techniques

- Hook spoolgun to the positive stud on the power supply.

- For MIG welding aluminum you need to use a 10 to 15 degree push travel angle (tip and nozzle pointed in the direction of travel).

- Pulling or using a drag angle will produce porous, dirty welds because of lack of gas coverage.

- Spray transfer is the desired mode of metal transfer for welding aluminum. The spray transfer is a very smooth transfer of molten metal droplets from the end of the electrode to the molten pool. The droplets crossing the arc are smaller in diameter than the electrode. There is no short-circuiting in spray transfer. With spray transfer the deposition rate and efficiency is relatively high. The arc is very smooth, stable, and stiff and the weld bead has a nice appearance and a good wash into the sides. In the spray transfer a large amount of heat is involved which creates a large weld pool with good penetration that can be difficult to control and can not be used on materials thinner than 14 Ga. This transfer will produce a hissing sound, and no spatter.

- The short arc transfer on aluminum produces poor cleaning action, poor tie in at the edges of the weld, and large amounts of spatter and smoke.


- The reflective heat and weld puddle that is present when MIG welding aluminum is very hot. Holding the tip closer than this could lead to the wire burning back to the contact tip and other feeding problems.

- The most common shielding gas for MIG welding aluminum is 100 % argon. Flow rates of 20 to 30 CFH (cubic feet per hour) are acceptable. C25 or argon Co2 mixes are not acceptable.

- Avoid large weave beads on aluminum. If larger fillet welds are needed multiple pass straight beads will provide better appearance and have less chance of cold lapping, burn through, and other weld defects.

- It will be necessary to increase torch travel speed as the base material becomes heated during the weld.

- The skill level of the operator, joint types, fit up, and positions, as well as the welding power supply will all have great influence on the weldability of the aluminum and your success.

Common Problems/Troubleshooting

Burn-Through (Melt Through) Caused by Over Heating the Base Material

1. Increase travel speed. Make shorter welds.

2. Move around on part, spreading out the heat.

3. Use thicker material or change joint design or welding process to AC TIG.

4. Eliminate/Reduce gaps

Dirty Welds

1. Use push angle instead of drag technique.

2. Increase voltage to get into spray transfer.

3. Use proper base metal cleaning techniques (Stainless Steel Brush).

4. Check for proper shielding gas and wire alloy type.

Cannot Get Machine Set Correct

1. Check inside cover of Millermatic welders for good starting setting and fine tune for you needs.

2. Order Millermatic MIG Calculator Part # 086446 for good starting settings.

Wire burns back to contact tip during or at the end of the weld

1. Maintain a tip to work distance.

2. Check to make sure the contact tip size, drive rolls and gun liner match the wire diameter that you are using.

Wire 'Bird Nests' (piles up) in Front of Inlet Guide on Gun

1. Check and adjust drive roll tension.

2. Check to make sure drive rolls match wire diameter

3. Replace contact tip if fouled up

4. Check pressure adjustment on Aluminum spoolgun hub.

MIG Welding Shielding Gas Basics

MIG (GMAW) welding with shielding gas and a solid wire electrode produces a clean, slag-free weld without the need to continually stop welding to replace the electrode, as in Stick welding. Increased productivity and reduced clean up are just two of the benefits possible with this process.

To achieve these results in your specific application, however, it helps to understand the role of shielding gas, the different shielding gases available and their unique properties.

The primary purpose of shielding gas is to prevent exposure of the molten weld pool to oxygen, nitrogen and hydrogen contained in the air atmosphere. The reaction of these elements with the weld pool can create a variety of problems, including porosity (holes within the weld bead) and excessive spatter.

Different shielding gases also play an important role in determining weld penetration profiles, arc stability, mechanical properties of the finished weld, the transfer process you use and more.

Choosing MIG gun consumables that provide consistent and smooth shielding gas delivery are also important to making successful MIG welds.

Choosing The Right Gas

Many MIG welding applications lend themselves to a variety of shielding gas choices, and you need to evaluate your welding goals in order to choose the correct one for your specific application. The cost of the gas, finished weld properties, preparation and post-weld clean up, the base material, weld transfer process and your productivity goals all need to be taken into account when selecting a shielding gas.

Argon, Helium, Carbon Dioxide and Oxygen are the four most common shielding gases used in MIG welding, with each providing unique benefits and drawbacks in any given application.

Carbon Dioxide (CO2) is the most common of the reactive gases used in MIG welding and the only one that can be used in its pure form without the addition of an inert gas. CO2 is also the least expensive of the common shielding gases, making an attractive choice when material costs are the main priority. Pure CO2 provides very deep weld penetration, which is useful for welding thick material; however, it also produces a less stable arc and more spatter than when it is mixed with other gases. It is also limited to only the short circuit process.
Porosity, as can be seen on the face and interior of the weld bead, can be caused by inadequate shielding gas and can dramatically weaken the weld.

For many companies, including those that place an emphasis on weld quality, appearance and reducing post-weld clean up, a mixture of between 75 – 95 percent Argon and 5 – 25 percent CO2 will provide a more desirable combination of arc stability, puddle control and reduced spatter than pure CO2. This mixture also allows the use of a spray transfer process, which can produce higher productivity rates and more visually appealing welds. Argon also produces a narrower penetration profile, which is useful for fillet and butt welds. If you’re welding a non-ferrous metal — aluminum, magnesium or titanium — you’ll need to use 100 percent Argon.

Oxygen, also a reactive gas, is typically used in rations of nine percent or less to improve weld pool fluidity, penetration and arc stability in mild carbon, low alloy and stainless steel. It does cause oxidation of the weld metal, however, so it is not recommended for use with aluminum, magnesium, copper or other exotic metals.

Helium, like pure Argon, is generally used with non-ferrous metals, but also with stainless steels. Because it produces a wide, deep penetration profile, Helium works well with thick materials, and is usually used in ratios between 25 — 75 percent Helium to 75 — 25 percent Argon. Adjusting these ratios will change the penetration, bead profile and travel speed. Helium creates a ‘hotter’ arc, which allows for faster travel speeds and higher productivity rates. However, it is more expensive and requires a higher flow rate than Argon, so you’ll need to calculate the value of the productivity increase against the increased cost of the gas. With stainless steels, Helium is typically used in a tri-mix formula of Argon and CO2.

This graphic shows the difference that consumables can make in shielding gas coverage. The photo on the left shows good coverage, while the coverage in the photo on the right allows the air environment contaminate the shielding gas.

Getting the gas to the weld pool

All of your efforts selecting the right shielding gas will be wasted, however, if your equipment isn’t getting the gas to the weld. The MIG gun consumables, consisting of a diffuser, contact tip and nozzle, play a crucial role in ensuring that the weld pool is properly protected from the air atmosphere.

If you choose a nozzle that is too narrow for the application or if the diffuser becomes clogged with spatter, for example, there might be too little shielding gas getting to the weld pool. Likewise, a poorly designed diffuser might not channel the shielding gas properly, resulting in turbulent, unbalanced gas flow. Both scenarios can allow pockets of air into the shielding gas and lead to excessive spatter, porosity and weld contamination.

When selecting MIG gun consumables, choose ones that resist spatter build up and provide a wide enough nozzle bore to ensure adequate shielding gas coverage. Some companies offer nozzles with a built in spatter guard that also adds a second phase of shielding gas diffusion, resulting in even smoother, more consistent shielding gas flow.

This cutaway shows a consumable system in which the contact tip is seated in the diffuser and held in place by the spatter guard inside the nozzle.

Choosing the right shielding gas for your specific application will require a careful analysis of the type of welding you are doing as well as your operational priorities. Using the guidelines above should provide a good start to the learning process, but be sure to consult your local welding supply distributor prior to making a final decision.

MIG Welding

MIG Welding (GMAW or Gas Metal Arc Welding) — An arc welding process which joins metals by heating them with an arc. The arc is between a continuously fed filler metal (consumable) electrode and the workpiece. Externally supplied gas or gas mixtures provide shielding. Common MIG welding is also referred to as short circuit transfer. Metal is deposited only when the wire actually touches the work. No metal is transferred across the arc. Another method of MIG welding, spray transfer moves a stream of tiny molten droplets across the arc from the electrode to the weld puddle. Consumables: contact tips, shielding gas, welding wire.

MIG welding, also called GMAW, extrudes a metal wire electrode from a gun held by the welder. Power is applied to the gun by a power supply that attempts to regulate voltage at a preset level set by the welding operator. The gun also carries a shielding gas to the nozzle of the gun. A trigger on the gun turns on the gas via a solenoid in the power supply and engages the contactor, also in the power supply. Current flows down the gun through the arc and back to the power supply via the ground clamp. This process has become very popular in the last 40 years because of its speed and ease of use.

MIG and flux-cored welding guide (PDF)
MIG Aluminum: Typical operating procedures for filler and lap welding, aluminum welding parameters charts.

MIG Wire Charts: Wire type selection guide, recommended shielding gases, and welding wire feed speeds.

Tungsten Preparation

Proper tungsten preparation is critical to achieving consistent TIG welding performance. A balled tip is generally used on a pure tungsten electrode and is suggested for use with the AC TIG welding process on sine wave and conventional squarewave TIG welders. To properly ball the end of the tungsten, simply apply the AC amperage recommended for a given electrode diameter and the ball on the end of the tungsten will form itself. The diameter of the balled end should not exceed 1.5 times the diameter of the electrode (for example, a 1/8-in. electrode should form a 3/16-in. diameter end), as having a larger sphere at the tip of the electrode can reduce arc stability and/or fall off and contaminate the weld.

A pointed and/or truncated tip (for pure tungsten, ceriated, lanthanated and thoriated types) should be used for TIG welding with an inverter AC and DC welding processes. As the first rule of proper tungsten preparation, use a grinding wheel specially designated for tungsten grinding (to avoid contamination) and one that is made of borazon or diamond (to resist tungsten’s hardness). Note: if you are grinding thoriated tungsten, make sure you control and collect the dust, have an adequate ventilation system at the grinding station and that you follow manufacture’s warnings, instructions and MSDS.

Prepare the tungsten by grinding it straight on the wheel versus at a 90-degree angle to ensure that the grind marks run the length of the electrode. Doing so reduces the presence of ridges on the tungsten that could create arc wandering or melt into the weld puddle, causing contamination.

Generally, you will want to grind the taper on the tungsten to a distance of no more than 2.5 times the electrode diameter (for example, with a 1/8-in. electrode you would grind a surface 1/4 to 5/16-in. long). Grinding the tungsten to a taper eases the transition of arc starting and creates a more focused arc for better welding performance.

When welding with lower currents on thinner materials (those ranging from .005- to .040-in.), it is best to grind the tungsten to a point. A pointed tungsten allows the welding current to transfer in a focused arc and helps prevent thinner metals, such as aluminum, from becoming distorted. As a note, using pointed tungsten for higher current applications is not recommended, as the higher current can blow off the tip of the tungsten and cause weld puddle contamination.