30 Questions for K-TIG Guru's

1. Combining K-TIG with other Processes 

Can K-TIG be combined with other welding processes?

K-TIG can be combined with other welding processes in any application where this is advantageous.

In some applications, typically heavy wall pipe or plate which is much thicker than K-TIG’s maximum penetration thickness, it may be beneficial to utilize K-TIG to produce a high quality, high speed root weld, and to fill the balance of the joint using MIG/GMAW or Submerged Arc (SAW).

2. Savings

What productivity gains & savings are achieved?

Relative to conventional TIG/GTAW welding, productivity gains and savings of more than 70% are typical, and savings in excess of 90% are common.

Relative to Plasma Arc Welding (PAW), productivity gains of more than 50% are typical.

K-TIG causes very little distortion and has allowed us to hold better dimensional tolerances on our weld joints. In a normal V-prepped joint you’re going to get significant shrinkage – the bigger the pre in the joint, the more shrinkage you’re faced with. With K-TIG we have very little dimensional change.
Jeff Thomas, Vice President, Operations, TITAN Metal Fabrication

3. Productivity Gains

Can K-TIG calculate my expected productivity gains & savings?

K-TIG can calculate the expected productivity gains and savings for your specific application, including:

  • Wire consumption comparison
  • Welding times comparison
  • Gas consumption comparison
  • Productivity comparison

On request, K-TIG will generate a Weld Comparison Report at no cost for customers with applications which are within K-TIG’s normal thickness ranges:

  • Titanium 3mm to 16mm (1/8 to 5/8 inch)
  • Stainless steel 3mm to 13mm (1/8 to 1/2 inch)
  • Alloys 3mm to 9mm (1/8 to 11/32 inch)

K-TIG can provide a customised report showing what you'll see by implementing K-TIG. Learn more here.

4. Autogenous Welding

Does K-TIG weld autogenously?

K-TIG is fully capable of welding Autogenously, or with the addition of filler material during the keyhole pass. Filler wire is usually consumed at a fraction of the rate of a standard GTAW system.

What are the thickness limits for autogenous welding?

The thickness limits of autogenous welding with K-TIG vary by material and grade, however as a general guide:

  • Up to 16mm (5/8 inch in titanium)
  • Up to 13mm (1/2 inch in stainless steel)
  • Up to 9mm (11/32 inch in Alloys)

5. Materials

What materials are well suited to K-TIG?

Numerous corrosion resistant materials and Alloys are well suited to the K-TIG process, including:

  • Titanium & titanium alloys
  • Zirconium & zirconium alloys
  • Ferritic stainless steels
  • Austenitic stainless steels
  • Duplex stainless steels
  • Super-Duplex stainless steels
  • Nickel alloys – Monel, Inconel, Incoloy, Hastelloy, Nimonic
  • Cobalt alloys
  • Super alloys

What materials are less suited to K-TIG?

Some carbon steels are less suited to K-TIG welding. Low quality, high sulphur carbon steels are generally not suitable.

What materials cannot be welded with K-TIG?

Copper and Aluminium cannot be welded with K-TIG.

6. Material Thicknesses

Does K-TIG weld in a single pass?

For most applications within K-TIG’s normal thickness range, welding is done in a single, full penetration pass.

What thicknesses can be welded in a single pass?

K-TIG will weld in a single, high speed, full penetration pass on up to 16mm in titanium and other exotic materials, 13mm in stainless steel and 9mm in Alloys.

  • Titanium 3mm to 16mm (1/8 to 5/8 inch)
  • Stainless steel 3mm to 13mm (1/8 to 1/2 inch)
  • Alloys 3mm to 9mm (1/8 to 11/32 inch)

 What if my material is thicker than K-TIG’s upper limit for a single pass?

If the material to be welded is thicker than K-TIG’s upper limit, the material will be prepped with a thick landing, and a full penetration root pass will be performed followed by a filler pass.

What if my material is thinner than K-TIG’s lower limit?

1mm and 2mm materials which are thinner than K-TIG’s lower limit for keyhole welding can be welded very effectively by the K-TIG system in TIG mode. Welds in 1mm and 2mm (1/32 to 3/32 inch) will also be full penetration welds, however they are not considered to be ‘keyhole’ welds.

7. Joint Geometries

Can K-TIG weld square butt joints?

K-TIG’s standard joint geometry for full penetration welding is square butt joints.

Do root gaps need to be set?

Root gaps are not required for K-TIG welding.

Can K-TIG weld into a V-Prep, J-Prep, U-Prep, Single-Bevel, Single-J, Double-V, Double-J and Double-U preparations?

K-TIG can weld into all standard TIG/GTAW preparations, provided that the root face/landing is within the material thickness ranges recommended.

What is the typical included angle for V-preparations?

In very thick materials where a V-preparation is required, the recommended included angle of the preparation is 60-70 degrees. The reason why we prefer a wider geometry is that you get some ‘melt-in’ from the sides of the preparation, which adds to the overall thickness which must be fully penetrated. The wider the prep, the less melt in and therefore a greater thickness of material can be penetrated in the root pass.

Can K-TIG be used for corner joints?

K-TIG can be used for corner butt joints, for materials of both equal and differing thicknesses.

K-TIG_corner_joing_fillet_weld.png

K-TIG welded corner joint showing root penetration on Duplex 16mm plate to 6mm plate.

Can K-TIG be used for fillet welds?                                                        

The K-TIG process is intended for full penetration applications, which are not always possible for fillet weld applications. Notwithstanding, there are options for performing fillet welds using the keyhole process.

It is also worth noting that in addition to being able to perform full penetration keyhole welds, the K-TIG system is also a very capable 1000amp TIG welding system that can also be used for deep penetration conventional TIG welds, including fillet welds.

8. Typical Welding Speeds

What are the typical welding speeds used in the K-TIG process?

The following are typical examples of K-TIG welding speeds when performing a single, full penetration pass. These speeds are in the middle of the operating window for the K-TIG process and can be increased (in some cases significantly) if the objective is to optimise for speed, such as may be desirable in a tube mill application.

  • 3mm materials 1000 mm/min (39 inch/min)
  • 6mm materials 500 mm/min (19.5 inch/min)
  • 8mm materials 400 mm/min (15.5 inch/min)
  • 10mm materials 300 mm/min (12 inch/min)
  • 12mm materials 250 mm/min (9.5 inch/min)
  • 14mm materials 230 mm/min (9 inch/min)
  • 16mm materials 200 mm/min (8 inch/min)

9. Current

What is the current range for K-TIG welding?

Currents range from approximately 320 to 600 amps, and occasionally higher for very thick materials.

10. Voltage

What is the voltage range for K-TIG welding?

The voltage for K-TIG welding varies somewhat depending on the welding gas, welding current and the arc length.

When K-TIG welding with argon, voltage is typically between 13V and 18V. When K-TIG welding with argon-hydrogen, voltage is typically between 17V and 23V.

The lowest voltage values are for low currents and small arc lengths, while the higher voltage values are associated with high currents and longer arc lengths.

11. Heat Input

Are heat inputs within normal limits?

Although currents are higher with K-TIG welding, the very high speed of the process results in modest heat inputs which are well within normal ranges.

For example, the heat input for a K-TIG weld on 10mm (13/32 inch) thick, 304 stainless steel is approximately 1.4kJ/mm gross. In this application the Heat Affected Zone (HAZ) extends approximately 1.25mm (1/16 inch) from the edge of the reinforcement, and 4mm (5/32 inch) from the edge of the root.

12. Distortion

Is distortion within normal limits?

K-TIG is a low distortion process. Distortion in K-TIG welds is significantly less than multi-pass GTAW and GMAW, and well within normal limits. This is particularly advantageous when welding stainless steels.

13. Reinforcement & Root Bead Profiles

Can the geometry and thickness of the reinforcement and root bead be controlled?

The profile and thickness of both reinforcement and root bead can be controlled and fine tuned to meet particular requirements.

In addition, wire can be added in order to create a heavier reinforcement if this is desirable.

14. Welding Gas

What welding gases can be used with the K-TIG process?

All welding gas combinations such as Argon-Hydrogen, Argon-Nitrogen and Argon-Helium which can be used for TIG/GTAW welding can be used for K-TIG welding.

Can straight argon be used for all K-TIG welding?

Straight argon can be used for all K-TIG welding, in all materials.

Is the addition of Hydrogen to the welding gas advantageous for stainless steel applications?

The addition of hydrogen when K-TIG welding stainless steel is beneficial to the process. Its addition increases the K-TIG arc temperature, increases weld penetration, improves the molten metal fluidity, enhances cleanness of the surface and reduces the current requirement.

15. Backing Gas

Does K-TIG welding require backing gas?

Back purging is the act of removing oxygen, water vapour and any other gases or vapours from the back of the joint both while and immediately after welding, using a backing gas.

Stainless steels, duplex steels, titanium alloys, zirconium alloys nickel alloys and other metals are sensitive to the presence of air, oxygen, hydrogen, water vapour and other vapours and gases that may combine with the hot metal as it is being joined using either a TIG/GTAW welding process or K-TIG. Such gases may combine with the metal to form undesirable compounds that may reduce corrosion resistance or result in cracks or other structural defects in the material.

K-TIG’s backing gas requirements are similar to TIG/GTAW welding.

In many applications K-TIG requires no special back purging considerations, and conventional purging dams may be used.

In some applications the management of purge pressure is either beneficial or required. In such applications K-TIG can either provide or advise on the choice of purge dams.

16. Back Pressure

Can back pressure extend K-TIG’s penetration?

Back pressure can be used to extend K-TIG’s penetration range. The addition of modest back pressure on the underside of a weld helps support the weight of the molten material within the keyhole against the influence of gravity.

For example, back pressure will have little observable impact when welding 6mm titanium, however will have an obvious and advantageous impact when welding 12-16mm (15/32 to 5/8 inch) titanium in that the operating window will be extended and the procedure will be more robust.

17. Arc Voltage Control & Arc Length Control

Does the K-TIG process require an Arc Voltage Control (AVC) or Arc Length Control (ALC)?

The K-TIG system does not require an AVC or ALC.

Each K-TIG system is provided with a mechanical arc length control system which is suitable for the majority of applications. This allows the torch to move mechanically with any variations in pipe diameter or plate surface. This works well in the majority of situations and is very robust.

Can K-TIG be used with an AVC or ALC?

If desirable for a particular application, the K-TIG torch can be fitted to an AVC or ALC.

18. Welding Positions

What welding positions does K-TIG support?

K-TIG is suitable for welding in both 1G and 2G welding positions.

19. Automation

What kinds of automation equipment can be used with K-TIG?

K-TIG can be used with most welding automation equipment, including:

  • Rotators
  • Positioners
  • Turntables
  • Seamers
  • Column & boom
  • Bugs & motorized carriages
  • Robots
  • Manipulators
  • Arc Voltage Controllers (AVC) & Arc Length Controllers (ALC)
  • Seam trackers

Can the K-TIG Controller be integrated with automation equipment?

The K-TIG controller can be integrated with most welding automation equipment.

During commissioning, the K-TIG controller can be integrated with your automation equipment, so that the entire process can be reduced to a single button press (if you would like this level of automation). One button press and the K-TIG controller will process the weld routine, turn on the rotator (or other weld automation equipment), turn on the gas, strike the arc, ramp up the current, perform the full penetration keyhole weld, perform the tie-in, ramp down the current, close the keyhole, turn off the power supply, turn off the gas, turn off the rotator and then go into standby ready for the next weld.

Can I use my existing automation equipment?

In most cases, your existing welding automation equipment can be used with and integrated to K-TIG.

20. Integration

Will K-TIG integrate to my existing weld automation equipment?

K-TIG or one of our qualified distributors will integrate your existing weld automation equipment with the K-TIG controller. There are several approaches to this, and these will be discussed on site and implemented during commissioning.

Can K-TIG recommend weld automation equipment?

K-TIG can recommend weld automation equipment for most types of fabrication, and can also provide turn-key systems with automation equipment pre-integrated with K-TIG.

21. Tack Welding

What impact do tack welds have on the K-TIG process?

Autogenous tack welds have no impact on the K-TIG process, they are consumed as part of the weld. Parts are typically tacked by a TIG/GTAW process. K-TIG can be used for this in ‘TIG’ mode.

What are the options for tack welding with K-TIG?

Autogenous tack welds can be performed manually using a TIG/GTAW process. Alternatively, once the pipes or plate are in place, K-TIG can be used to perform either tack welds or a ‘sealing pass’. For materials which require very high quality purging (such as titanium), a sealing pass can be helpful to ensure an airtight seal prior to performing the full penetration weld. Sealing passes, if required, are typically automated as part of the weld routine, and add only modestly to total weld time. In most cases however, conventional TIG/GTAW tack welds are sufficient.

22. Addition of Wire

Can wire be added?

Wire can be added to any K-TIG application if required or desirable.

When is adding wire advantageous?

Adding wire to a K-TIG weld can be advantageous in the following situations:

  • When the thickness limits of the K-TIG process are exceeded (16mm 5/8 inch in titanium and 13mm 1/2 inch in stainless steel) and a preparation is required
  • If a heavy reinforcement is desirable
  • If your procedure demands the addition of wire
  • If it is desirable to change the metallurgical properties of the weld

The K-TIG system comes with an integrated wire feeder specifically for these purposes. Where wire is used for any of these reasons, wire consumption will typically be far lower than an equivalent TIG or MIG process, and will generally be reduced by more than 90%.

The thickness of the wire used can be varied depending on the requirements of the application, and for general purposes 0.9mm or 1.0mm 1/32 inch is typical. Deposition rates can be high due to the energy density of the arc.

 

Can wire be added to meet an existing code or procedure requirement?

Wire can be added to any K-TIG weld in order to meet the requirements of an existing TIG/GTAW procedure, which may not have envisaged the potential for an autogenous GTAW weld.

In these situations, the amount of wire added is nominal – typically 1-10% of what would normally be used if GTAW welding into a V, J or U-preparation.

23. Multiple Pass K-TIG Welding

When is more than one pass required?

More than one pass is required if the material is thicker than K-TIG can penetrate in a single pass.

More than one pass will be generally be required where the thickness is:

  • Greater than 16mm (5/8 inch) in titanium
  • Greater than 13mm (1/2 inch) in stainless steels
  • Greater than 9mm (11/32 inch) in Alloys

How does K-TIG handle a multiple-pass weld?

When the material to be welded is thicker than K-TIG’s upper limit, the materials will be prepared with a shallow preparation and a thick landing.

A full penetration root pass will be performed on the landing in ‘K-TIG’ mode, and a second filling pass will be performed in ‘TIG’ mode. The wire feed and sequencing can be fully automated by the K-TIG controller.

K-TIG can achieve substantially higher deposition rates than conventional TIG/GTAW due to the higher current and higher energy density of the arc.

How thick can the landing be?

The optimal thickness of the landing is dependent on the material and thickness, but as a general rule the landing should be approximately 70% of the maximum thickness that K-TIG can penetrate in that material, to allow for melt-in from the side walls of the preparation.

For example, K-TIG’s maximum penetration in Titanium is 16mm (5/8 inch). If welding 20mm (25/32 inch) titanium, we would typically recommend performing the full penetration root pass on a landing of 10mm (13/32 inch).

What is the recommended preparation and angle?

There are many different bevel angles and geometries which can be used. We generally recommend that a V-prep with an included angle of 60-70 degrees or more is beneficial. The reason why we prefer a wider geometry is that you get some ‘melt-in’ from the sides of the preparation, which adds to the overall thickness which must be fully penetrated. The wider the prep, the less melt in and therefore a greater thickness of material can be penetrated in the root pass.

Apart from the angle of the preparation, different preparation shapes can also be beneficial. For instance, a U-prep is excellent in eliminating melt-in from the sides. Another interesting variation is welding into an inverted-V-prep, in which the welding is performed from the opposite side of the preparation. This works extremely well, and allows maximum penetration as the apex of the preparation helps to support the keyhole even in very thick materials.

24. Fitup Tolerance

How tolerant is K-TIG to fitup imperfections?

K-TIG process is more tolerant to gaps, mismatches and other fitup imperfections than Plasma Arc Welding (PAW) and much more tolerant that Laser Beam Welding (LBW) due to the high inherent stability of the weld pool and self-correcting nature of the keyhole.

Exceptional results are obtained with good fit-up, and the productivity gains and cost savings of K-TIG can be fully realised if care is taken to provide good square fitup.

What mismatch is acceptable?

Mismatch height is typically acceptable up to 20% of joint thickness. More more specific information on your application, speak to your K-TIG Engineer.  

What gap distance is acceptable?

  • Gaps of 5% of joint thickness are typically acceptable. 
  • Larger gaps may be able to be accommodated with the addition of a small amount of wire or by performing a high speed ‘sealing pass’ along the joint prior to the full penetration keyhole pass.
  • In tube forming and pressure vessel applications where there is typically tight fitup at the root and a gap at the face, K-TIG will accommodate a gap of up to 20% of joint thickness gap at the face.

Fitup_tolerance_1.jpgFitup_tolerance_2.jpg

 Left: 10mm (13/32 inch) 304 stainless steel with 2mm (1/16inch) gap on the front face and zero gap at the root, prior to welding. Right: same plate after K-TIG welding, as welded.

25. Different Material Thicknesses

Can K-TIG be used to weld materials of different thicknesses?

K-TIG can readily accommodate weld materials of different thicknesses.

26. K-TIG & Code Compliance

How does K-TIG comply with ASME and other codes? 

  • K-TIG is a GTAW Variant. As defined by ASME. 
  • Keyhole GTAW (K-TIG) is defined by ASME as one of 10 variants of the GTAW (Gas Tungsten Arc Welding)
    process.
  • All variants share a set of basic GTAW/TIG characteristics, which are defined by ASME.
  • All variants including K-TIG are, by definition, GTAW processes.

 Want more information? Download our simple fact sheet.

27. Pipe & Vessel Diameters

What is the maximum pipe or vessel diameter than can be welded with K-TIG?

There is no maximum pipe or vessel diameter which can be welded by K-TIG.

What is the minimum pipe diameter that can be welded with K-TIG?

K-TIG can readily weld pipe diameters down to 3 inches.

The reason for this is that managing the tie-in on pipes with diameters smaller than this becomes challenging as the weld is completed within seconds, requiring that the tie-in of the beginning and end of the weld is over very hot material.

28. K-TIG vs Plasma Arc Welding

What are K-TG’s advantages over Plasma Arc Welding (PAW)?

Plasma Arc Welding (PAW) was developed in the 1960’s, and until recently was the only practical choice where deep penetration welds were required. While good quality welds can be achieved, the practical upper limit for full penetration PAW welding is 8-10mm (5/16 to 13/32 inch), and is more typically used for root passes of 4-6mm (5/32 to 1/4 inch) followed by filler passes using TIG.

PAW is characterised by an orifice to pinch the arc, accurate alignment with the electrode, frequent maintenance, high level of complexity, the need for both plasma and shield gases to form the jet and protect the orifice, very accurate determination and maintenance of flow rates, low inherent stability of the keyholes due to reliance on a combination of gas pressures and energy density to achieve penetration, high degree of sensitivity to the many parameters involved, highly precise fitup and high degree of operator skill to set up, operate and maintain.

PAW is widely regarded as the most complex of the arc welding processes. PAW systems incur the highest maintenance costs of any arc welding process due to their complexity.

By contrast, K-TIG can weld materials up to 16mm (5/8 inch) in thickness, and typically operates at twice the travel speed of PAW. K-TIG is very simple to operate. The arc structure and keyhole develop spontaneously and are maintained automatically by the controller throughout the weld. There is no plasma nozzle or orifice, no precise electrode alignment is required, only one welding gas is used, flow rate is not critical, and the torches are very robust.

I’m currently using Plasma Arc Welding, should I switch to K-TIG?

If you are currently using Plasma Arc Welding (PAW) you are almost certainly a model K-TIG customer. You will probably be welding stainless steel of between 3mm and 10mm (1/8 to 13/32 inch). You will have already invested in automation equipment to provide a consistent travel speed, typically a positioner, rotator, seamer or column & boom. Your application is probably pressure vessels, suction vessels, cryogenics and you are probably performing a longitudinal seam weld followed by two circumferential welds. You are probably experiencing unacceptable defect rates and are struggling with thicker materials.

What is involved in changing to K-TIG?

A fabricator who is currently using Plasma Arc Welding (PAW) will find upgrading to K-TIG to be straightforward. The existing welding automation system (typically a positioner, rotator, seamer or column & boom) can continue to be used.

Changing from PAW to K-TIG requires only the normal setup of the K-TIG system and (if desired) integration of the controller to the existing welding automation system.

29. Manual K-TIG Welding

Can K-TIG be used for manual welding?

K-TIG is a precision process, and one of the important requirements is for consistent travel speed. It’s for this reason that K-TIG is ideally suited to applications where an automation system which controls travel speed can be used.

While in theory K-TIG could be performed manually in some situations, it is not recommended or supported.

30. Existing Power Supplies

Can I use my existing power supply for K-TIG?

It is necessary to use the K-TIG power unit due to the high level of integration which is required between the controller and the power unit.

31. Training

What training is required?

Three hours of training is sufficient for operators in a typical production situation. For a supervisor who wishes to be trained in the full capabilities of the system and how to set it up for a wide variety of different materials, material thicknesses and operating conditions, approximately 1 to 2 days of training is recommended.

Does K-TIG provide initial and ongoing training?

K-TIG or a K-TIG approved distributor will typically train your team on site as part of commissioning the system. This can be done as a small group, and can include any of your staff who you wish to be trained.

Alternatively, training can be undertaken at K-TIG head office or at the workshop of an approved K-TIG distributor.

Additional refresher training for new new staff can be requested at any time.

32. Warranty

What warranty does K-TIG provide on its equipment?

K-TIG provides a 3 year warranty on the K-TIG controller, and 1 year warranty on the power supply, torch, wire feeder and water cooler. 

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