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Tig Welding Aluminum-How To Set Up a TIG Welder

16 Min Read
Suggested Amperage Levels Based on Electrode Size and Type
Suggested Amperage Levels Based on Electrode Size and Type

Gas tungsten arc welding, or TIG (Tungsten Inert Gas) arc welding process is a commonly used process for welding of low thicknesses of aluminum and aluminum alloys. This article discusses TIG welding of aluminum with three methods – with alternating current, with direct current straight polarity, and with square wave alternating current.

tig welding aluminum settings

Welding Town

Welding With Alternating Current

The aluminum oxide layer is a characteristic feature of aluminum alloys. Alternating current, which alternates between positive and negative polarity 60 times every second, provides a cleaning action on the surface of the metal, for half the duration of every cycle. Hence, alternating current is a commonly used current type for aluminum welding.

Characteristics Of The Welding Process When Using AC

A typical characteristic of welding aluminum with alternating current with GTAW is that an oxide cleaning action takes place. The process gives the best results when the equipment is capable of supplying an equal current in both polarities, that is a balanced sinusoidal wave. An imbalance in this causes a reduction in cleaning power of the arc, which can result in a porosity ridden bead.

A good machine produces a stable arc, that operates smoothly without noise, with a smooth initiation of arc. A smooth operation would eventually have lesser tungsten inclusions in the weld.

Welding Technique

The arc initiation in GTAW welding of aluminum with alternating current is similar to the ordinary GTAW with direct current. Initially, an arc is struck on a trial/practice piece so that the tungsten tip gets heated. Then, it is retracted, and the arc is struck at the joint. This helps in avoiding tungsten inclusions in the starting of the weld bead.

The arc is struck using the GTAW torch in one hand. Due to the heat of the arc a weld puddle is formed on the base metal. It takes skill on the welder’s part to maintain a uniform size of this puddle so that a uniformly sized bead can be achieved. If the filler rod is used, it is fed at the leading edge of the puddle from one side of the center line. The filler rod is fed into the molten puddle with the other hand.

Care should be taken such that the filler rod does not come into contact with the tungsten electrode. If such contact happens, it creates chances of tungsten particles inclusion in the weld metal – which is undesirable. Tungsten inclusions are hard particles that show up in the RT film and cause the joint to be repairable.

When the welding is required to be stopped, the filler rod should be withdrawn suddenly from the cover of the shielding gas. This is necessary so that the red hot tip of the filler rod does not get oxidized by the atmospheric gases. An oxidized tip will cause introduction of oxides in the next pass, which can show up as porosity.

Generally, a short arc length should be maintained so that the size of the puddle remains in manageable size, sufficient penetration is obtained, while avoiding undercuts too.

Before commencement of the welding, tack welds should be made to keep the assembly in place, and minimize warpage.

Welding Parameters For Welding With AC

The following table lists recommended parameters for GTAW welding of aluminum with alternating current. These parameters are for all positions. However, when using them in out of position welding, lower value of the given amperage should be used. When a backing strip is used, a higher current is recommended.

The shielding gas is argon in all cases. However, sometimes a mixture of argon with helium is used when extra penetration is desired in higher thicknesses. The mixture of 75% helium with 25% argon is a popular choice of shielding gas. Helium is lighter than argon, hence it rises fast in the air. Therefore, higher rate of gas flow needs to be given to the weld when helium is used.

The tungsten electrodes can be of pure tungsten type, or zirconated tungsten.

The usual recommendations for TIG welding apply. The tungsten electrode tip should be free of any contamination. Just the right length should protrude from the gas nozzle. The arc length should be short, and generally equal to the diameter of the electrode. Stringent adherence to the welding parameters such as rate of gas flow, gas type, composition of gas mixture, type of tungsten electrode, etc. should be observed.

Material thickness Inch (mm)Diameter of tungsten electrode Inch (mm)Diameter of filler rod Inch (mm)Inner diameter of gas nozzle Inch (mm)Flow rate of shielding gas  (cfh)         Welding current AC (amps)No. of passesTravel Speed (ipm)
0.046 (1.2)1/16 (1.6)1/16 (1.6)¼ – 3/82040-60114-18
0.063 (1.6)3/32 (2.4)3/32 (2.4)5/16 – 3/82070-9018-12
0.094 (2.4)3/32 (2.4)3/32 (2.4)5/16 – 3/82095-115110-12
0.125 (3.2 mm)1/8 (3.2)1/8 (3.2)3/820120-14019-12
0.187 (4.7)5/32 (3.9)5/32 (3.9)7/16 – ½25160-20019-12
0.187 (4.7)5/32 (3.9)5/32 (3.9)7/16 – ½25160-180210-12
0.250 (6.4)3/16 (4.8)3/16 (4.8)7/16 – ½30230-25018-11
0.250 (6.4)3/16 (4.8)3/16 (4.8)7/16 – ½30200-22028-11
0.375 (9.5)3/16 (4.8)3/16 (4.8)½35250-3102-39-11
0.500 (12.7)¼ (6.4)¼ (6.4)5/835400-4703-46
Table: recommended welding parameters for TIG welding of aluminum, with alternating current.

Welding With Direct Current Straight Polarity

When it is required to weld aluminum with machine welding or automatic welding, DCEN polarity is used. When direct current is used, the cleaning of the base metal surface must be done thoroughly to remove the aluminum oxide layer. If cleaning is not done thoroughly, the oxide layer can contaminate the weld and create porosity. Note that DCEN and DCSP are the same thing, and have been used interchangeably in this article.

Characteristics Of The Welding Process When Using DCEN

With DCEN polarity, the depth of penetration is high, and higher travel speeds can be used.

The shielding gas used in this setup is argon, although sometimes mixtures of helium and argon are used. Helium is used when high depth of penetration is required. However, the flow rate of shielding gas is high when helium is used.

Thoriated tungsten electrodes can be used. Since the higher amount of heat is directed at the base metal, smaller diameter tungsten electrode can be used. This helps in obtaining a narrower bead.

What Types Of Aluminum Alloys Can Be Welded With Direct Current Straight Polarity?

There are no shortcuts or forgiveness when it comes to welding Aluminum, especially thin material.

DC(-) TIG welding Aluminum does not work on all types of Aluminum, but fortunately, 6061 is one that can be welded using this process. Also, beware that DC(-) provides no cleaning action whatsoever. A good wire brushing followed by an Acetone wipe is critical to being successful.

Here are some of the Aluminum types that can be welded using DC(-): 6061; 1100; 2219; most A-356 and A-357 Casting (although you get a dirty weld). Do Not attempt any 5XXX series Aluminum or use filler materials that are 5XXX series. Acceptable filler materials are ER4043; 1100 and 2319.

TIG Welding Aluminum DC(-) Procedures For 1/4″ To 1″ 6061-T6 Aluminum Plate

  • Torch: TIG Torch rated at 300 amps – Amperage: 175 to 225
  • Tungsten: 2% Ceriated – Tungsten Diameter: 3/32″
  • Tungsten Tip: Pointed – Pre-Heat: not required
  • Filler Material: ER4043
  • Filler Material Diameter: 1/16 to 3/32″
  • Shielding Gas: 100% Helium @ 40-50 CFH
  • Back-up Gas: not required – Polarity: DC Negative

Welding Technique

Initiate arc and hold amperage at about 200 amps. Dwell at the beginning for about 7 to 10 seconds. A puddle will form under the oxide layer. The puddle will not be shiny but when you add the filler, a better definition of the puddle will form. Do a bead-on-plate first, progressing to the job weld. Wire brush to improve appearance.
Have fun.

A high-frequency current should be used to initiate the arc. Touch starting is not recommended as that can contaminate the tungsten electrode. The arc should be struck in the welding area so that unnecessary marking of material does not occur.

To minimize the welding defects at the start and end of beads, run-on/ run-off plates should be used, if necessary. Foot operated pedals are used; this offers better control in the hands of welder. The bead is progressed gradually; the filler rod is fed into the leading edge of the molten pool.

A narrower bead can be obtained with DCSP polarity. This results in lesser distortion, and a smaller heat-affected zone.

Welding Parameters For Welding Aluminum With DCEN

The following table lists the recommended parameters in GTAW welding of aluminum with DCEN polarity. These parameters are for 75% helium with 25% argon mixture shielding gas.

Material thickness Inch (mm)Diameter of tungsten electrode Inch (mm)Diameter of filler rod Inch (mm)Inner diameter of gas nozzle Inch (mm)Flow rate of shielding gas  (cfh)         Welding current AC (amps)No. of passesTravel Speed (ipm)
0.032 (0.8)3/32 (2.4)Without filler3/83065-70152
0.046 (1.2)3/64 (1.2)3/64 (1.2)3/83035-95145
0.063 (1.6)3/64 (1.2)3/64 (1.2)3/83045-120136
0.094 (2.4)1/16 (1.6)1/16 (1.6)3/83090-185132
1/8 (3.2)1/8 (3.2)1/8 (3.2)3/830120-220120
1/8 (3.2)1/8 (3.2)Without filler3/830180-200124
¼ (6.4)1/8 (3.2)1/8 (3.2)1/240230-340122
¼ (6.4)1/8 (3.2)Without filler1/240220-240122
½ (12.7)3/16 (4.8)1/8 (3.2)1/240300-450120
½ (12.7)5/32 (3.9)Without filler1/240260-300220
¾ (19.1)3/16 (4.8)1/8 (3.2)1/240300-45026
¾ (19.1)3/16 (4.8)Without filler1/240450-47026
1 (25.4)3/16 (4.8)1/8 (3.2)5/840300-45025
Table: recommended welding parameters for TIG welding of aluminum, with direct current, electrode negative polarity.

Welding With Square Wave Alternating Current

The square wave alternating current is a non-sinusoidal periodic waveform in which the amplitude of the current alternates between the positive and negative values, and generally spends same duration at the maximum and minimum values. However, this time of current flow can be adjusted up to 20 to 1.

When this current type is used for TIG welding (or GTAW welding) of aluminum, it offers the advantages of both the reverse polarity as well as straight polarity.

When 10% DCRP is used, it offers adequate surface cleaning of the metal surface to obtain a good weld. When 90% DCSP is used, a depth of penetration equal to the regular DCSP welding is obtained.

Thus, by varying this percentage, it is possible to obtain the twin advantages of surface cleaning action seen during reverse polarity, as well as deep penetration offered by straight polarity.

Tig Welding Filler Rod Selection Chart - Reviews Of Chart
Tig Welding Filler Rod Selection Chart – Reviews Of Chart

Welding Technique When Using Square Wave AC

A superimposed high frequency current or a open-circuit voltage is required to keep the arc alive, because the arc gets extinguished in every cycle when the current approaches zero, and must be reignited.

The tungsten electrodes should be sharp pointed thoriated tungsten electrodes.

The shielding gas is argon, or a mixture of argon and helium.

4043 Aluminum TIG Welding Rods

4043 Aluminum TIG Welding Rods
4043 Aluminum TIG Welding Rods

4043 Aluminum TIG welding rods – are uncoated aluminum TIG welding rods that are good for general Aluminum TIG welding. These rods come in 1 pound boxes. The rods usually come in cut rods of diameter 1/16 inch (1.6 mm) and length 40 inches (1000 mm). The grade ‘4043’ is prominently mentioned on the consumable box.

4043 Aluminum TIG welding filler rods can be used to weld the following Aluminum alloys: 1100, 5052, 6061, and 356 aluminum castings. It is most often used to weld the 6XXX series of alloys. The silicon addition improves puddle fluidity, producing an appealing bead profile. It is less crack sensitive on the 6XXX series than other welding alloys.

Common applications are automotive parts, truck trailers, bicycles. Also ideally suited for brazing thin aluminum sheet and tubing.

  • The alloy is less sensitive to weld cracking and produces brighter welds
  • Non-heat treatable
  • Principle alloying element: Silicon

Joint Design For Welding Of Aluminum

The joint designs indicated in the figure below are applicable (with minor modifications) for all types of TIG welding of aluminum, that is – with alternating current, with DCSP polarity, and with square wave alternating current.

joint design for tig welding aluminum
joint design for tig welding aluminum

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