{"id":11,"date":"2022-04-27T04:45:00","date_gmt":"2022-04-27T04:45:00","guid":{"rendered":"https:\/\/mewelding.com\/?p=11"},"modified":"2024-03-18T12:01:18","modified_gmt":"2024-03-18T12:01:18","slug":"tig-welding-aluminum","status":"publish","type":"post","link":"https:\/\/mewelding.com\/tig-welding-aluminum\/","title":{"rendered":"Tig Welding Aluminum"},"content":{"rendered":"\n

Gas tungsten arc welding, or TIG (Tungsten Inert Gas) arc welding process <\/a>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. <\/p>\n\n\n\n

Welding With Alternating Current<\/strong><\/h2>\n\n\n\n

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

Characteristics Of The Welding Process When Using AC<\/h3>\n\n\n\n

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.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

Welding Technique<\/h3>\n\n\n\n

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.<\/p>\n\n\n\n

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\u2019s 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.<\/p>\n\n\n\n

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 \u2013 which is undesirable. Tungsten inclusions are hard particles that show up in the RT film and cause the joint to be repairable.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

Before commencement of the welding, tack welds<\/a> should be made to keep the assembly in place, and minimize warpage.<\/p>\n\n\n\n

Welding Parameters For Welding With AC<\/h3>\n\n\n\n

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.<\/p>\n\n\n\n

The shielding gas<\/a> 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.<\/p>\n\n\n\n

The tungsten electrodes can be of pure tungsten type, or zirconated tungsten.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

Material thickness Inch (mm)<\/td>Diameter of tungsten electrode Inch (mm)<\/td>Diameter of filler rod Inch (mm)<\/td>Inner diameter of gas nozzle Inch (mm)<\/td>Flow rate of shielding gas  (cfh)         <\/td>Welding current AC (amps)<\/td>No. of passes<\/td>Travel Speed (ipm)<\/td><\/tr>
0.046 (1.2)<\/td>1\/16 (1.6)<\/td>1\/16 (1.6)<\/td>\u00bc – 3\/8<\/td>20<\/td>40-60<\/td>1<\/td>14-18<\/td><\/tr>
0.063 (1.6)<\/td>3\/32 (2.4)<\/td>3\/32 (2.4)<\/td>5\/16 \u2013 3\/8<\/td>20<\/td>70-90<\/td>1<\/td>8-12<\/td><\/tr>
0.094 (2.4)<\/td>3\/32 (2.4)<\/td>3\/32 (2.4)<\/td>5\/16 \u2013 3\/8<\/td>20<\/td>95-115<\/td>1<\/td>10-12<\/td><\/tr>
0.125 (3.2 mm)<\/td>1\/8 (3.2)<\/td>1\/8 (3.2)<\/td>3\/8<\/td>20<\/td>120-140<\/td>1<\/td>9-12<\/td><\/tr>
0.187 (4.7)<\/td>5\/32 (3.9)<\/td>5\/32 (3.9)<\/td>7\/16 \u2013 \u00bd<\/td>25<\/td>160-200<\/td>1<\/td>9-12<\/td><\/tr>
0.187 (4.7)<\/td>5\/32 (3.9)<\/td>5\/32 (3.9)<\/td>7\/16 \u2013 \u00bd<\/td>25<\/td>160-180<\/td>2<\/td>10-12<\/td><\/tr>
0.250 (6.4)<\/td>3\/16 (4.8)<\/td>3\/16 (4.8)<\/td>7\/16 \u2013 \u00bd<\/td>30<\/td>230-250<\/td>1<\/td>8-11<\/td><\/tr>
0.250 (6.4)<\/td>3\/16 (4.8)<\/td>3\/16 (4.8)<\/td>7\/16 \u2013 \u00bd<\/td>30<\/td>200-220<\/td>2<\/td>8-11<\/td><\/tr>
0.375 (9.5)<\/td>3\/16 (4.8)<\/td>3\/16 (4.8)<\/td>\u00bd<\/td>35<\/td>250-310<\/td>2-3<\/td>9-11<\/td><\/tr>
0.500 (12.7)<\/td>\u00bc (6.4)<\/td>\u00bc (6.4)<\/td>5\/8<\/td>35<\/td>400-470<\/td>3-4<\/td>6<\/td><\/tr><\/tbody><\/table>
Table: recommended welding parameters for TIG welding of aluminum, with alternating current.<\/figcaption><\/figure>\n\n\n\n

Welding With Direct Current Straight Polarity<\/strong><\/h2>\n\n\n\n

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.<\/p>\n\n\n\n

Characteristics Of The Welding Process When Using DCEN<\/h3>\n\n\n\n

With DCEN polarity, the depth of penetration is high, and higher travel speeds can be used.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

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.<\/p>\n\n\n\n

What Types Of Aluminum Alloys Can Be Welded With Direct Current Straight Polarity?<\/h3>\n\n\n\n

There are no shortcuts or forgiveness when it comes to welding Aluminum, especially thin material.<\/p>\n\n\n\n

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. <\/p>\n\n\n\n

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.<\/p>\n\n\n\n

TIG Welding Aluminum DC(-) Procedures For 1\/4\u2033 To 1\u2033 6061-T6 Aluminum Plate<\/h3>\n\n\n\n