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Keyhole GTAW (or Keyhole TIG) is a new, very high performance variant of the trusted and much-used TIG process. But while it has the look and feel of TIG, its performance is in an altogether different league to the more familiar variants. For example, it can easily punch through 12mm (~1/2 inch) stainless steel to give you full penetration, single pass welds at an exceptional 300mm (12 inches) per minute. You just need to present the material with clean, squared edges that butt together with good fit-up. So no expensive edge preparations and usually not even any filler material!
If you thought keyhole welding was solely the domain of very high energy density processes – EB, laser and plasma arc – then you will be pleasantly surprised. Keyhole TIG does not achieve the energy densities of these processes; rather it relies on a natural combination of arc pressure and surface tension to produce its keyhole. There is plenty of power, but even when punching through 14 mm titanium with 700 amps or more, the process itself is very quiet and doesn’t even raise ripples in the weld pool. (Click here to downlaod KGTAW_pool Video)
The process is dependent on two critical ingredients, a carefully engineered torch and the generation of a very stable surface geometry in the weld pool. This latter effect enabled by the high surface tension of liquid metals. If surface tension is working against you, your process will be inherently unstable (as in laser, EB, high current TIG etc). On the other hand, when it works for you the process enters an exciting new realm. This is the domain of keyhole TIG. To see how this can happen take a moment to view a simple soap-bubble analogy
(Click here for more info).
Keyhole TIG was invented in Australia by the CSIRO1 working in conjunction with the CRC-WS2 in the late 1990’s. The process was first used commercially in Australia in 1998, and has subsequently been adopted by many organisations around the globe. It has also been the subject of significant research and development since that time. More recently it has been appropriate to move the focus of this process from the scientific to the industrial sector, where its practical benefits can be realized. Ultratig is proud to be taking on this role.
Could this process be for you?
This process could be the innovation your line needs. Take a moment to weigh its merits against your present practice. Let’s group these under three categories: performance, user-friendliness, and cost.
Performance
The following figures illustrate the performance you can anticipate with this process. You are invited to make your own comparisons – this performance will speak for itself. These figures are for ‘square butt’ (or ‘I’) joint configuration and welded in a single pass.
- 3mm materials* at up to 1000mm/min
- 6 mm materials at 500 mm/min
- 8 mm C-Mn steel and ferritic stainless steels at 400 mm/min
- 12 mm austenitic steels and titanium alloys at 250 mm/min
Thicker materials can be welded using multi-pass techniques with a keyhole GTAW root pass (i.e. ‘Y’ joint preparations).
* The process is suitable for most metals and alloys other than those with very high thermal conductivity, principally copper and aluminium alloys.
User-friendliness
Keyhole TIG will take full advantage of in-house experience with the more conventional TIG processes. This makes the learning process easy and exciting as it builds on your existing knowledge and experience. You can expect to feel confident with the process within hours of first firing it up!
The bottom line with respect to user-friendliness is the outward simplicity of the process. Because of the torch design, the process naturally tends to form a keyhole, and in very many cases you will simply tweak the current and travel speed as you change from one product to another. But then, by drawing on your existing knowledge of TIG and the thorough description of the process provided in the documentation, you can work it to the maximum – this process is new, and there’s a lot of unexplored territory!
Cost benefits
Keyhole TIG works well with off-the-shelf power supplies and in many cases will not need wire feed. The process requires only a single shielding gas input of about 20 litres/minute. This is usually welding grade argon, although argon with additions of hydrogen or nitrogen can be used for specific materials. Trailing shields and back-purge can be added as required.
The major cost benefits arise from low consumable use, high welding speeds, simple edge requirements and single pass to completion. Consequently benefits vary according to material type and thickness, and of course your current practice. We know you will find this process very competitive.
1 CSIRO (Commonwealth Scientific and Industrial Research Organisation) is Australia’s largest public research organization. It has over 6000 staff working in numerous laboratories across the country.
2 CRC-WS (Cooperative Research Centre for Welded Structures) was a national body set up to coordinate welding research in Australia. The organization completed its term in mid 2006. |
