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.

Basics for TIG Welding Aluminum

As we strive to meet the demands of increasingly fast-paced industries, our focus on productivity can often overshadow some of the basic techniques necessary for our welding application. Unknowingly, we may come to rely too much on technology to solve our problems and keep products moving out the door.

Unfortunately, when we forget the basics, our equipment (no matter how advanced) can easily fall short of the job. Following is a discussion of good TIG welding practices for aluminum applications. These basics are applicable regardless of whether you use a conventional AC power source or power sources with squarewave or advanced squarewave capabilities.
WCALTIG2
Knowing the basics of TIG welding
aluminum is important no matter how
advanced the equipment you use.

Clean Aluminum is Good Aluminum
Cleaning aluminum before TIG welding is essential to avoid contaminates, which can lead to lack of fusion, inclusions or porosity. Most TIG power sources provide good cleaning action during the EP (electrode positive) portion of the weld cycle, however, you should never rely solely on this cleaning action to do the job for you.

Instead, first wipe the base metal with a cloth to remove dirt, oil or grease. This procedure, though outwardly simplistic, is absolutely necessary.

Equally important is removing the oxides that naturally form on the aluminum. This procedure can be done mechanically, by using a scraping tool or a stainless steel wire brush, or chemically, by applying an acidic solution designated for aluminum oxide removal. If you choose to remove the oxides mechanically, remember to designate the scraping tool or wire brush for that purpose only—using these tools for multiple jobs could cause contaminants to be introduced to the aluminum. Using a power brush is not recommended as it can also re-embed contaminants into the metal. Finally, if you are considering using the chemical method to remove oxides, consult your local welding distributor for the best product options.

To prevent the drawing of contaminants from the backside of a joint, remember to clean both sides of the aluminum. Also be certain that you are using clean filler rods, as they too can contain dirt and/or oxides—clean the rods using a clean or new Scotch Bright ™ pad dedicated to the purpose.

The Basics
Remembering the following basics about shielding gases and tungsten can help you avoid problems when TIG welding aluminum.

Gases: Pure argon offers the advantage of being more cost effective than helium and is a good, all-purpose gas that produces a focused, concentrated arc. Adding helium to your argon mixture can provide greater penetration when welding aluminum over 3/8-inch thick. It also increases your arc voltage from 13 to 18 volts (the range for argon) up to a range of 22 to 25 volts, thus increasing your overall power for a given amperage setting. For the infrequent welding of heavier aluminum, adding helium to gain voltage can be helpful; however, if you weld thicker aluminum on a regular basis, you should invest in a larger power supply. Finally, adding 3 to 5% percentage of helium can also stabilize your arc on low-end applications.
WCALTIG1
To avoid contamination when TIG welding
aluminum, clean both sides of the joint
with a stainless steel brush designated
solely for that purpose.

Generally, pure helium is used for TIG welding aluminum only in specialized applications or for DC aluminum
welding. Helium is much more expense and requires good welding skills and exceptional cleanliness.

Gas Flow: Bear in mind that setting your gas flow too high can lead to problems, including but not limited to porosity and/or pin holes. When using argon and/or an argon/helium mixture, set your gas flow between 5 to 20 CFH (cubic feet per hour) for flat position aluminum welding and at approximately 20 CFH for all other welding positions. When welding overhead, vertical or horizontal the addition of helium can also be beneficial because it is lighter that air and will float upward to protect the weld.

Use approximately one second of pre-flow prior to welding aluminum and use one second of post-flow for every 15 amps with which you have been welding. Both pre- and post-flow help prevent tungsten and weld puddle contamination.

Tungsten Style and Diameter: If you are using a conventional AC or squarewave power source, balled pure tungsten works well on aluminum applications that are above 100 amps. For example, 3/32 tungsten can be used up to 180 amps without problems. You can also use pointed zirconiated tungsten for 100-plus amp applications, but at even higher amperages than pure tungsten (a 3/32 zirconiated tungsten can be used up to 210 amps).

For applications below 100 amps on thinner gauge aluminum (.005 to .093 inches), it is best to use 2% tungsten, ceriated or thoriated. Sharpening these tungstens to a point helps prevent distortion by better focusing the arc and also gives you better control. If you are using an advanced squarewave power source, a pointed 2% ceriated tungsten provides an especially focused arc and allows for the use of a smaller diameter for even greater arc control.

Note: Thorium is radioactive; therefore, you must always follow manufacture’s warnings, instructions and the MSDS (Material Safety Data Sheet) for its use.

Tungsten Extension: Regardless of the type of tungsten you use to TIG weld aluminum, remember that the tungsten should extend no more than the distance that equals the inside diameter (ID) of the nozzle. For example, a number eight nozzle is ½-inch across, so your electrode extension should not exceed ½ inch. Following this basic rule increases your visibility of the weld puddle and tungsten and reduces the possibility of touching the tungsten to the weld puddle. It also provides better weld puddle control.

Other Considerations
Also consider factors such as equipment, joint preparation and arc starting during the process of TIG welding aluminum.

Equipment: Conventional AC sine wave, conventional square wave and advanced square wave power sources are all acceptable for aluminum TIG welding, but you will need basic operator controls including: pre flow, post flow and high frequency arc starting capabilities. Your power supply should also be large enough to handle the amperage requirements of your application.
ALTIGbead
Achieving quality TIG welds on aluminum,
like the one shown here, is a matter of
both skill and good welding practices.

An air-cooled TIG torch will work well for aluminum applications under 200 amps or for fieldwork, but you should consider using water-cooled torch for welding above 200 amps or where torch size matters for comfort or limited access joints.

Joints: When welding aluminum above 3/16-inches thick, it is a good practice to prepare the joint to be welded beforehand. Creating a ‘V’ groove on 3/16- to ½-inch thick aluminum helps minimize distortion by lessening the amount of heat input required to create a sound weld. For aluminum that is over ½-inch thick, preparing a ‘J’ bevel or a ‘U’ groove works best.

TIG Welding Aluminum

Although many metals are TIG welded, the metal most frequently associated with the process is aluminum, especially with metals of a smaller thickness. Many other processes, of course, can join aluminum, but in the lighter gauges the most applicable process is TIG. The popularity of aluminum in automotive applications has brought TIG welding to a new golden age. Mechanically strong and visually appealing, TIG welding is the number one process chosen by professional welders for professional racing teams, and the avid auto enthusiast or hobbyist.

That Confusing Thing About Aluminum

The process is well suited for aluminum, but there are a few characteristics of the metal that bring up points that must be considered if this material is to be welded with consistent ease and quality. 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.

That Aluminum is Hot

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 Lincoln Precision TIG® welder – 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.

Filling the Gap

The metal produced in the weld pool is a combination of filler and parent metals that must have the strength, ductility, freedom from cracking, and the corrosion resistance required by the application. See table below for recommended filler metals for various aluminum alloys.

Maximum rate of deposition is obtained with filler wire or rod of the largest practical diameter while welding at the maximum practical welding current. Wire diameter best suited for a specific application depends upon the current that can be used to make the weld. In turn, the current is governed by the available power supply, joint design, alloy type and thickness, and the welding position.
A Quality Deposit

TIG Weld SampleGood weld quality is obtained only if the filler wire is clean and of high quality. If the wire is not clean, a large amount of contaminant may be introduced into the weld pool, because of the relatively large surface area of the filler wire with respect to the amount of weld metal being deposited.

Contaminants on the filler wire are most often an oil or a hydrated oxide. The heat of the welding releases the hydrogen from these sources, causing porosity in the weld. Lincoln ER4043 and Lincoln ER5356 aluminum welding wire is manufactured under rigorous control to exacting standards and is packaged to prevent contamination during storage. Since filler wire is alloyed, or diluted, with the base metal in the weld pool, the compositions of both the filler wire and the base metal affect the quality of the weld.

The Three Cs: Clean, Clean and CLEAN

Pieces to be welded are usually formed, sheared, sawed, or machined prior to the welding operation. Complete removal of all lubricants from these operations is a prerequisite for high-quality welds. Particular care must be taken to remove all oil, other hydrocarbons, and loose particles from sawed or seared edges prior to welding. Sheared edges should be clean and smooth – not ragged. For ease of cleaning, lubricants used in fabrication should be promptly removed.

Beginner Guide to Aluminum

This page is far from a comprehensive tutorial; it's just some tips and some links to more authoritative information. It's intended for people who want to learn to weld aluminum, but have little no experience in welding aluminum, or even in welding in general. This was a description of me a couple of months ago. In my attempts to learn to weld aluminum, I gathered all the information I could find from a lot of different sources – the very simplistic and under-informative manual that came with the welder, lots of reading on the web, basic welding books with very short sections on aluminum, and very advanced books that were written for engineers which had more equations and formulas than practical welding advice. Then using what I had learned, coupled with a lot of trial and error, I eventually figured out how to get two pieces of aluminum to stick together without cracking, warping, shriveling, or breaking. Along the way I made several key discoveries that would have saved me a lot of trial and error time if someone had just told me about them. I thought I’d share the little I do know and maybe it’ll help someone out there learn to weld aluminum faster than they would have otherwise.

    What do you equipment do you need?
    A TIG (GTAW) welder. Most sources say a TIG (Tungsten Inert Gas) welder, also called a GTAW (Gas Tungsten Arc Welder), is the best method of welding aluminum. I’ve heard aluminum can also be welded with a MIG welder or a stick welder or even a with a gas torch. Since I’ve only used the TIG for aluminum, that’s what I’ll be writing about. TIG welders are fairly expensive and it’s hard to justify buying even the lowest quality units unless you are making money with your welding. The more expensive units ($6000) have a bunch of features that make doing high quality welding on aluminum possible. We have a bottom-of-the-line ($2500) Hobart welder that is described as good for the hobbyist or farmer. As tempting as it was to blame the machine while I was making charred bits of twisted metal instead of neatly welded joints, I came to realize that adequate welds can be made, even with a cheapo machine. What do you get when you spend the extra money on a welder? More amperage (meaning the ability to weld thicker metal), water cooling (I don’t know what advantage this provides, but the gas hood glows orange on our air cooled unit when it’s at maximum output, and it’s only 165A), square wave AC (this allow grinding a ceriated tungsten to a point for a more stable arc), frequency adjustment, and adjustment of the ratio of positive to negative current for better cleaning or penetration. Since my machine has none of these features, I can’t offer any advice on how to make use of them.
    Good welding gloves. I have crappy welding gloves and the painful blisters to prove it.
    A good welding helmet. I hear the gold tinted auto darkening helmets are the best. I have a $20 helmet with a tiny window that falls off my head when I flip it down.
    Argon gas. Mixes will not work for aluminum with the exception of an Argon / Helium mix. Don’t take the tank from you MIG welder to use on your TIG welder – it won’t work at all. You will just make a bunch of burnt metal and soot.
    Aluminum welding rod. I got the 4043, which seems to be the most recommended. There is a good chart at http://www.tinmantech.com on which rod to use for which alloys as well as a ton of excellent metalworking and aluminum welding information. At this point I don’t have any idea how to tell one alloy from another, and I'm not doing any mission critical welding, so don't worry about it. The 4043 has been working well for me.
    A dedicated stainless steel brush that you only use for aluminum. Write “aluminum” on it so it doesn’t get used for anything else.
    A metal bench would be nice. I don’t have one. Stopping your weld to put out a fire is a pain in the ass. This happens to me all the time.
    A squirt bottle with water. This is not for cooling the work, it’s for putting out small fires that aren’t big enough to use a fire extinguisher on. Cooling aluminum rapidly may cause it to crack in or near the weld.
    A fire extinguisher might not be a bad idea if you don’t want to get fired for burning down the shop.
    This next one is VERY important: a heavy long sleeve cotton work shirt. TIG welding produces more UV radiation than any other welding process. The first time I used the TIG I was wearing a tee shirt. I used the welder for 10 min if even that. The front of my biceps and a spot at the bottom of my neck were painfully burned with blisters and peeling skin. I just takes a few minutes to do some serious burning.
    11. Clamps or Vise Grips or whatever your going to use to hold your work in place and some blocks or bars of aluminum or copper to use as heat sinks.

Aluminum, Oxidation, Hydrogen and Porosity

Aluminum, Oxidation, Hydrogen and Porosity.
Aluminum has a high maximum solubility for hydrogen atoms in the liquid form and a low solubility at the solidification point.

Hydrogen dissolved in the liquid weld metal will try to rise out of the weld during the aluminum solidification. Some hydrogen gas pores will be trapped and porosity will occur.

Aluminum combines with oxygen to form an aluminum oxide layer. This micro surface layer will form instantaneously if the oxide is removed by machining or grinding. The oxide layer is porous and can easily trap moisture, oil, grease and other materials. The aluminum oxide layer provides excellent corrosion resistance, but must be removed before welding as it prevents fusion due to its much high melting point point than the aluminum alloy .

Arc polarity, plasma molecular action, mechanical cleaning, solvents and chemical etching are all used to attack the oxide layer. When MIG welding if the layer is not removed sufficiently a black soot will appear either side of the weld. To eliminate the soot, first try to lower the arc length (voltage) as this makes the MIG plasma more dense which provides a more concentrated plasma cleaning action.

The majority of aluminum weld porosity results from entrapped hydrogen gas in the weld pool. Hydrogen is highly soluble in molten aluminum. Hydrogen can be derived from many sources.

[a] Hydrogen from base metal contaminates, hydrocarbons, lubricant, oils dirt, grease, moisture, paints and compressed air and contaminates from pneumatic cleaning tools or cleaning brushes.

[b] Hydrogen from lubricant contaminates on the alum weld wire surface.

[c] Hydrogen from moisture, water leaks in water cooled torches. Water from the gas cylinders. Water from the porous, hydrated, alum oxide layer on the base metal surface.

[d] Hydrogen that results from high humidity, condensation on parts and weld wires.

[e] Hydrogen that results from contaminates from grinding wheels.

To minimize hydrogen and weld porosity potential consider, cleaning, degreasing, stainless wire brushes or carbide wheels to remove the oxide surface. Remember you can always find porosity in the alum weld, the real question is how much is acceptable and what inspection and weld process control method will be used to control the porosity.

To reduce aluminum weld porosity potential, slow down the weld solidification rate to allow the hydrogen to exit. Reduce alum weld porosity with the following 11 points.

[1] To remove the alum surface oxide consider a die grinder (>30,000-rpm) rotary, coarse carbide file. An effective cleaning solution is acetone, beware highly flammable..

[2] Increasing weld parameters, with MIG increase the wire feed rate.

[3] Increase weld size.

[4] Avoid weaves.

[5] Slow down weld travel speed.

[6] Use smaller diameter MIG wires.

[7] Evaluate the weld procedure so that weld heat and weld sequence is used as a tool for porosity reduction.

[8] Use lowest possible MIG weld voltage. Low weld voltage results in short arc lengths which create more energy in the arc plasma providing improved arc cleaning action of the surface alum oxides.

[9]Use a higher energy gas mix like 60 helium - 40 argon. The helium requires higher weld voltage. The 60 helium mix is superior to the common 75 helium 25 argon mix, as the the higher argon content helps stabilize the arc and provides superior weld cleaning action.

[10] Don't use MIG wire wipes clipped on the wire.

[11] Don't use anti spatter within 2 inches of the weld. If you know how to set a weld you would not use anti-spatter.

THIS ALUMINUM MIG WIRES A BARGAIN

If you get your aluminum MIG wire at a bargain price, its likely you will have weld consequences. To test an aluminum MIG wire, take two 1/4 alum plates, six inches long. Start a 3/16, horizontal fillet weld approx. one inch from the end of the plate. Make the weld is four inches long. Don't weave use fore hand. After the weld has cooled, put welded plate in vice and use hammer to fold the plates in on the weld.

In contrast to steel welds, a good, alum weld with proper side wall fusion should break in most cases in the weld metal. Examine the broken weld surface for porosity. Clean looking, small pore porosity is found in the best of aluminum welds. Blackish looking small porosity often results from lubricants from the material surface. Small gray, oxidized weld porosity often results from air trapped in the joint or oxygen from the gas cylinders or lines. Extensive shiny porosity may be an indication of moisture pickup. Ensure synthetic impermeable hoses are used for your aluminum MIG gas delivery rather than neoprene or rubber hoses.

Weld porosity can be blamed on many materials that can contaminate both the weld wires and base metals. With aluminum, hydrogen is the prime cause. The bottom line keep the plates clean and at the ambient shop temperature. If necessary for your application grind the weld edges. Provide a protective cover for the alum weld wires. When the weld wires are not in use store in clean dry area. Good manufacturers of aluminum MIG wires will use extensive manufacturing controls to ensure you have a clean consistent MIG wire. There is a price to be paid for this weld wire quality. Compare your bargain priced aluminum wire with a quality and consistent product from a company like Alcotec.

aluminum alloys

Weight. Aluminum is three times lighter than steel and yet aluminum can provide higher strength when alloyed with specific elements.

None Magnetic. Since aluminum is nonmagnetic, arc blow is not a problem during aluminum welding.

Thermal Conductivity. With a thermal conductivity rate that is five to six times higher than steel and the aluminum welds watch out for lack of weld fusion especially at the weld starts. With alum being more sluggish and less fluid, aluminum can be welded in all positions with spray and pulsed with relative ease. In contrast to steel the high conductivity of aluminum acts as a heat sink making weld fusion and weld penetration more difficult to achieve on parts > 4 mm.. However on thin parts, the rapid build up of heat in the alum parts can add to high weld fluidity and weld burn through potential.

Aluminum Porosity and Hydrogen. When MIG or TIG welding aluminum, the weld decision maker should always be aware that this is one of the metals most susceptible to porosity. Hydrogen dissolved in the liquid weld metal will try to escape as the aluminum solidifies and the trapped hydrogen will result in weld porosity which is often extensive. The main cause of porosity in aluminum welds is the absorption of hydrogen in the weld pool which forms gas pores in the solidifying weld metal. The most common sources of hydrogen are hydrocarbons and moisture from contaminants on the aluminum base metal and on the filler wire surface. Also water vapor from the MIG or TIG shielding gas will provide the same results.

Hydrogen cracking is common with carbon steels but hydrogen cracking will not occur with aluminum. Hot cracking or solidification cracking is a primary cause for alumin

ALUMINUM Liquation Cracking. In contrast to hot cracking which occurs in the weld, while MIG or TIG welding aluminum liquation cracking will occur in the heat affected zone (HAZ). With liquation cracking low melting point films are formed at the grain boundaries and these films (liquid elements)cannot withstand the contraction stresses during the weld metal solidification. Heat treatable alloys, like the 6xxx and 7xxx series are sensitive to liquation cracking. To reduce the potential for liquation cracking, consider a weld wire with a lower melt temperature than the parent metal. With alloy 6061 - 6082, liquation cracking can occur in the partially melted zone when a weld with good dilution is made with 5356 or similar filler metal is utilized. In contrast when welding the same alloys with 4043 liquation cracking should not occur.

MIG Welding Aluminum Tips.

In the nineteen nineties, Ed set the first multi-robot robot line in North America, to weld a large aluminum application as seen with ABB robots welding aluminum golf cart frames, (above photo). Ten years later, in contrast to more than 80% of the robots in the auto industry welding "carbon steel" parts, the four robots welding aluminum frames achieved much greater robot production efficiency, less down time and less weld rework. In 2008, the robots and the MIG weld equipment have far surpassed the welding needs of today's applications, with this in mind, one can only wonder how much robot MIG weld quality and productivity improvement could be made in the auto / truck industry, if management focussed on process MIG welding training expertise and materials as provided in Ed's robot weld process control training resources.


    When one robot has a weld issue that has to be rectified, the other 3 will not be working.
1990s: ABB Fort Collins. CO. I was the robot weld manager for ABB robotics. The robot application had four ABB robots in a single cell working together on a complex, thin gage, aluminum golf cart frame. No push-pull guns were utilized. The customer was concerned that with the typical aluminum wire feed and arc start issues with aluminum that four robots working together involved some risk. To attain confidence in the project the customer requested a test phase with a robot producing ten thousand arc starts with no more than ten arc ignition issues.

I set the initial test data to ensure no weld start issues and after 7000 arc starts without a single burn back or arc ignition issue, the customer was satisfied. I then established the robots welds to compensate for the aluminum gage part fit and gap issues and of course provided optimum start and stop data. Each of the ABB robots produced approx. 30 to 40 welds per-frame.

ABB provided an automatic torch alignment system. The ABB system can make 3-D and angular calculation via its BullsEye automatic TCP calibration system.

The ABB Bulls Eye system automatically adjusts the TCP program to the torch, eliminating the need for touchups and minimizing down time

The ABB system also provided automatic error-handling capability-a necessary feature when robots are in close proximity the robots complete almost 130 welds on each frame.

ABB used robot I/O between all four robots. If one robot had an error, it communicated the error the other three. The other robots would then finish the weld they are doing, but will not move to the next weld until they receive a "clear to go" signal. In the meantime, the robot with the error automatically goes to a service position where an operator checks the problem.

Programming four robots to weld simultaneously on a small frame application was a challenge easily handled by ABB. Adding to the complexity was the need to program error handling as well as welding. Each group of welds had to have its own error handler program, so developers had to keep in mind the path of each robot and make sure that it wouldn't cross the path of another robot.

The robots used regular MIG guns, push pull guns were not necessary.

For optimum wire feed, we set Alco Tech dee-reelers and hard plastic liners.

How To Successfully Weld Aluminum with a Compact MIG Welder

When it comes to welding aluminum items around the home or garage, there are a few misconceptions we hope to clear up: 1) That you need to invest in a $4,000 welding machine and be highly skilled to have success; 2) With no practice you can make excellent welds the first time the wire feed welder is taken out of the box; and 3) You need an expensive spool gun suited for aluminum.

The truth is that with practice, the right equipment and proper set-up, a compact MIG welder will be able to tackle occasional aluminum welding jobs. Using your MIG welder, you will be able to work on a variety of items around your home and yard, such as grills, railings, backyard furniture, boat docks and even decorative elements. Compact MIG welders, such as the SP, Weld-Pak or Pro models from Lincoln Electric, are available at distributors and retail outlets.

A Word About Aluminum
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. In order to be successful, ask yourself these questions:

What Machine Do I Need?
The first decision is what type of machine is right for the job. Keep in mind that a 115 volt wire feeder welder can handle jobs that range from 22 to 12 gauge and with moderate preheating, you can probably weld as thick as 1/8". Be aware that preheating should be limited to 250 degrees F maximum.

Another option is a 230 volt machine which can weld from 22 gauge all the way to 3/16". Proper preheat can take the range to 1/4". If you will need to weld a broader range of aluminum thicknesses, consider investing in the 230v machine.

Remember, if you plan on doing regular aluminum fabrication, you will need a heavy duty machine. The 115 volt and 230 volt compact MIG welder models are acceptable for occasional aluminum jobs, but not recommended for heavy duty aluminum use. For daily production welding on heavier aluminum, consider a welder that has greater than 200 amps output.

After you have chosen your input voltage, another common question you will be asked when selecting a welder is whether you want a continuous or tapped voltage control model.

A continuous voltage control model lets you set an infinite range of voltage within the rating of the machine, allowing more adjustability, fine tuning and precise control. This permits you to more easily adapt the voltage to your application and particular skill level.

If you're on a budget, opt for the tapped control unit. This machine has a rotary switch with four or five fixed voltage choices. It will not give you the control of a continuous model, but it can be slightly easier to get up to speed with and costs less to purchase and will be adequate for most applications.

What Type of Welds Can be Made?
For these types of machines, it is best to make welds in the horizontal and flat positions. In general, fillet welds in lap joints are made more easily than groove welds in butt joints. Fillet welds in tee joints are preferred over corner joints. Keep in mind that home welding by an amateur is not recommended for critical welds where failure could result in serious injury.

What Type of Shielding Gas is Required?
MIG welding aluminum is different than welding steel when it comes to shielding gas requirements. For aluminum, 100 percent argon is the gas of choice, whereas steel welding calls for a mixed gas or 100 percent CO2 gas. The good news is that no special equipment is needed - your existing regulators (with the exception of CO2 regulators) and gas hoses can be used for both pure blends and mixed gases.

What Polarity Setting is Needed?
All MIG welding, including on aluminum materials, requires electrode positive polarity, while flux-cored processes typically use electrode negative. If you are switching your wire feed welder between processes, make sure to switch your polarity. This is a common mistake that many beginning welders make.

What Aluminum Wire Electrode Alloy Type Should I Buy?
You will not obtain good results attempting to weld on aluminum with a steel wire electrode.

Instead, our recommendation is that compact MIG welders should be limited to .035" diameter 4043 aluminum alloy filler metal. A 5356 aluminum alloy electrode may commonly be recommended by retailers and distributors, since it is a stiffer wire and can be easier to feed. However, with these types of wire feed welders, there is often not enough amperage to achieve a good weld with 5356. Even though 4043 is a softer wire, following the proper steps outlined below will ensure good feedability.

Do not use other diameter wires. Specifically, you should avoid 0.030" wire (it is difficult to feed) and 3/64" wire (these compact machines do not typically produce enough current to reliably melt this diameter of wire).

How Do I Set-Up My Machine to Weld Aluminum?
Now that you know the type of machine you want and its capabilities/limitations, it is important to know how best to set it up. Follow these tips:

Purchase an Aluminum Feeding Kit
Attention to feeding issues is much more critical when it comes to aluminum welding. It is highly recommended that you purchase an aluminum feeding kit, which includes the following items:

    Non-metallic liner - designed to minimize the amount of friction on the wire
    U-shaped drive rolls - to avoid crushing or deforming the soft aluminum wire. These drive rolls do not shave the wire like V-groove drive rolls. Using V-groove drive rolls, the resulting wire shavings can clog the liner and lead to feeding problems.
    Inlet and outlet guides - designed specifically to avoid wire shaving.
    Contact tips - as compared to those used for the same diameter of steel wire electrode, contact tips for aluminum have larger diameter holes, since as aluminum heats up, it expands more than steel. Therefore, contact tips for aluminum applications are sized small enough to maintain good electrical contact, but large enough to allow for expansion.

Load Wire Into the Machine
There is a trick to properly loading aluminum wire into a wire feed welder. While the same technique should be used with steel wire electrodes, it is especially important with aluminum wire loading, to avoid feeding problems during welding.