Tips and Techniques for TIG Welding Aluminum

Table of Contents

Overview
Alloys
Filler Metals
Amperage
Alternative

Summary:

TIG welding aluminum requires a shielding gas (usually argon), a tungsten non-consumable electrode and a clean surface to remove any oxide buildup (the oxide has a higher melting point than the aluminum itself, which is why it needs to be removed before welding).

The welding machine needs to either have been built for TIG welding or has the necessary accessories.A foot current control is essential since heat builds up as the weld is started, requiring less heat from the electrode toward the end of the weld. For best results use AC (alternating current) at a high frequency (with
high frequency the tungsten electrode doesn’t need to come in contact
with the aluminum, reducing contamination risk). Direct current is used an a limited alternative, but results in higher heat levels on the electrode and poor oxide cleaning.

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The torch nozzle also must have been selected for use on aluminum.  When the diameter of the electrode is changed, a wider range of heat input can be used at different metal thickness.

In the hands of a skilled welder TIG looks better and seals better than MIG aluminum welding. MIG aluminum welding is preferred for thicker pieces of metal.

New aluminum alloys such as HTS-2000 offers a lower cost method for welding aluminum. It can be used with any heat source.

TIG Aluminum Weld

AC TIG Welding

• Electrode Tip Shape for AC TIG Welding Is a “Ball”
• This “Ball” = 1 to 1½ Times the Diameter of the Tungsten
• TIG welding can be amperage controlled in different ways
  including an amptrol on the torch itself, foot pedal control and simply
  using the machine setting. Remote controls allow the user to start hot
  and reduce amperage as the weld progresses.
• The air cooled unit above simply uses the gas flow to cool the
  torch, therefore, care must be taken not to overheat the internal torch
  parts, especially when using high amperages. These torches are typically
  smaller and less expensive.
• The water cooled unit operates much like a radiator on a
  car. Water is flowed through the torch and circulated through the cooler
  by a pump. These units can operate at higher amperages and for longer
  use.
• A slight leading angle allows the user to see the puddle, especially when adding filler.
• The filler can be dipped into the puddle or placed in the joint and moved forward and back.

Aluminum Alloys

Many aluminum alloys have been developed for the TIG welding aluminum process. The most popular welding aluminum is either pure aluminum 1xxx or an aluminum manganese alloy 3003. The repair or fabrication of aluminum is done with aluminum brazing (lower cost, stronger welds), using HTS-2000 brazing rods (click link for video and more information)

They are identified in a 4 digit system with the first digit indicating the metal alloyed with the aluminum:

• 1xxx - 99% pure aluminum, no alloy
• 2xxx - aluminum copper alloy
• 3xxx - aluminum manganese alloy
• 4xxx - aluminum silicon alloy
• 5xxx - aluminum magnesium alloy
• 6xxx - magnesium, silicon and aluminum alloy
• 7xxx - zinc and aluminum alloy
• 8xxx - tin or other metal and aluminum

Recommended Filler Metals

Filler metals for TIG welding aluminum need to be high quality and without contamination.

Notes:
(1) Recommendations are for plate of "0" temper.
(2) Ductility of weldments of these base metals is not appreciably affected by filler metal. Elongation of these base metals is generally lower than that of other alloys listed.
(3) For welded joints in 6061 and 6063 requiring maximum electrical conductivity use 4043 filler metal. However, if both strength and conductivity are required, use 5356 filler metal and increase the weld reinforcement to compensate for the lower conductivity of 5356.
Source: (1) Lincoln Electric

If you're new to MIG welding and you'd like a simple training so you can learn quickly, without the headaches, Download my FREE beginner’s guide to MIG welding.

Sample Amperage Chart

Base Metal Tungsten Filler Rod Amperage for TIG welding aluminum

0.010" - 0.035" 0.040" 0.024" - 0.030" 5 - 25

0.035" - 1/8" 1/16" 0.030" - 0.045" 20 - 85

3/32" - 1/4" 3/32" 1/16" - 3/32" 50 - 180

3/16" - 3/8" 1/8" 3/32" - 1/8" 171 - 250

5/16" - 1/2" 5/32" 1/8" - 3/16" 200 - 320

Notes

- Break tungsten off and allow it to ball when welding starts or us a copper plate to ball

- Aluminum turns to a mirror color when molten

- Aluminum requires higher amperages than the same thickness steel due to heat dissipation

- Be sure to determine aluminum base type before welding

- Some aluminum is not weldable by the tig welding aluminum process

- Add more filler to aluminum welds

TIG Weld

For successful TIG welding aluminum - due to the sensitivity of some aluminum alloys some welders recommend back-stepping the first inch of each weld before completing it completely

Advantages and Disadvantages of Aluminum TIG Welding

Advantages

• A Filler Rod May or May Not Be Necessary
• AC Polarity for Aluminum & Magnesium
• High Quality Welds
• All Position Welding
• Can Be Used on a Variety of Metals
• Excellent on Very Thin Materials
• Fusion Welding is Possible
• No Slag
• No Spatter
• High Efficiency

Disadvantages

• Lack of portability (Shielding Gas Cylinder & Hoses)
• Not ideal for outdoor welding - the shielding gas is susceptible to wind & drafts
• Requires Clean Base Material
• Low Deposition Rates
• High Operator Skill Necessary
• Often Slow

Metal Cleaning Methods

Source: Lincoln Electric

Brazing Rods A Better Alternative To TIG Welding Aluminum

New technology has recently been developed which enables welders to fabricate or repair aluminum stronger than a TIG welding machine using a simpler process. Now all that is needed is a heat source such as mapp gas or propane, a turbo tip and the this brazing rod.

This procedure works for aluminum or any of the aluminum alloys.

If you're new to MIG welding and you'd like a simple training so you can learn quickly, without the headaches, Download my FREE beginner’s guide to MIG welding.

References

(1) Lincoln Electric

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