K-TIG Vs Submerged Arc Welding

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What are K-TIG’s Advantages Over Submerged Arc Welding (SAW)?

Submerged Arc Welding is a process which requires a continuously fed, consumable, solid or tubular (metal cored) electrode.

The molten weld is protected from atmospheric contamination by being ‘submerged’ under a blanket of granular flux consisting typically of lime, silica, manganese oxide, calcium fluoride and other compounds.

When molten, the flux becomes conductive and provides a current path between the electrode and the work piece. In suitable applications, SAW can achieve high deposition rates however root passes are generally not achievable.

By contrast, the K-TIG process has no consumables, requires no flux handling systems, creates no flux or slag residues, requires no inter-pass and post-weld slag removal and provides a high quality root bead.

 

Consumables have been slashed. In most applications, we’ve eliminated wire completely.
Attila Szabo, Principal Joining Engineer, GE

The Benefits of Switching

How does K-TIG overcome the issues of SAW Welding?

 K-TIG overcomes the most common issues associated with SAW:

  • Penetration: The practical upper limit for single pass SAW welding is generally considered to be 4 mm.  Beyond this thickness, a V-groove root pass is normally applied, followed by filler passes. K-TIG can easily perform single pass welds in 16mm thick titanium, 14mm zirconium, 13mm austenitic stainless steels, Hastelloys, Inconels and a wide range of nickel and cobalt alloys, and 9mm in conductive materials such as carbon steels and ferritic steels.
  • Speed: K-TIG offers significantly faster welds than SAW. SAW reaches 600 mm/min at its highest speeds while K-TIG reaches 1000 mm/min.
  • Weld Quality: The weld quality of SAW can be acceptable but not so easy to control as SAW is a high wire deposition welding process.  It can only be run in 1G position in semi-automatic mode.  Penetration is achieved by melting through the joint thickness, and due to the high amount of molten filler metal being added to the pool, porosity is often trapped in the solidifying weld.  Lack of fusion is also a significant concern, as bridging a V-groove occurs regularly without properly fusing the joint side walls.  Active flux scavenges the large weld pool for oxygen, other undesirable elements and floats them to surface as slag. K-TIG’s keyhole technology allows vaporised impurities to leave the weld through the back of the keyhole, preventing them from becoming trapped as porosity in the solidifying weld.
  • Joint Preparation: Groove preparation is required, which adds cost, and the removed joint metal must be replaced with filler metal.  Manually bevelled joints often lead to inconsistent welding results.  The flux produces a slag layer that must be removed by grinding or chipping to avoid lack of fusion in subsequent weld passes. K-TIG only requires a simple and low cost square butt joint design for most applications which cuts preparation time and costs significantly.
  • Keyhole Stability: The lack of keyhole with SAW means V-groove root passes are normally applied, followed by filler passes. This approach takes up a lot of time, contributes to labour and consumables costs and opens up the possibility of welding defects. K-TIG keyholes are inherently stable and self-correcting as a result of the high travel speeds and surface tension in the weld pool.
  • Circumferential Weld Overlap Tie-In: Limited penetration capabilities make fusing the overlap difficult with SAW and lack of fusion at the overlap is a common defect of SAW. K-TIG’s keyhole, produced by a patented torch design and a high energy density arc makes the overlap and slope out of a circumferential weld incredibly easy.
  • Weld Appearance: There is no gas shielding of the weld, the SAW process relies on a layer of flux to cover and protect the weld pool.  The resulting weld appearance can have moderately good contour, as the slag layer protects the weld surface.  The slag must be removed, which requires grinding or dressing. K-TIG only requires proper gas shielding of the face and root sides of the weld to create a smooth and uniform weld appearance that won’t require any post-weld grinding or dressing.
  • Distortion: Weld shrinkage and distortion are common welding defects attributed to SAW, because of the slow travel speeds and low energy density of the process. Comparatively, K-TIG’s high energy density and high travel speeds mean the K-TIG welds are remarkably low weld shrinkage and distortion.
  • Process Consistency: The SAW process can be tuned to achieve sound welds in a mechanised mode, with a root pass followed by multiple fill passes.  However, the weld can vary to some degree, the slag that forms during welding must be removed between weld passes, and the transfer of large amounts of filler wire to the weld pool creates a level of inconsistency. The smooth and consistent keyhole through the joint, produced by the high energy density of the K-TIG process, as well as the size of the electrode, mean that erosion, process drift and variation are negligible.
  • Consumables Costs: The SAW process utilises high volumes of large diameter filler wire and activated flux.  Due to high welding amperage, torch parts often need replacement. The electrode used in the K-TIG process is large and long lasting. Nothing else in the system is prone to wear and erosion and the power supply has a 100% duty cycle rating.
  • Skill of Operator: SAW requires extensive operator training, as lack of fusion can form easily in the weld and must be avoided with proper techniques.  Training times for SAW are typically 1 to 2 weeks, while an operator can be trained to proficiency with a K-TIG system in just 3 hours. A K-TIG supervisor can be trained in 1-2 days.
  • Duty Cycle: Submerged arc welding systems are typically provided with power supplies in the range of 400-1000 amps, and are typically only rated for 60% duty cycle. The 1000 amp supply utilised by K-TIG is far more than is required for any keyhole project which gives it a 100% duty cycle rating.

 

I’m currently using Submerged Arc Welding; can I switch to K-TIG?

If your shop is fitted with automated welding equipment, or you’re interested in investing in automated equipment making the switch to K-TIG is very easy. Making the switch would be of the most benefit to you if you work on large-scale projects and your frequently perform circumferential welds of 3mm or greater.

 

How Do I Change to K-TIG?

It really couldn’t be easier.

If you’re currently using SAW, the upgrade process is simple. Your existing welding automation system can still be used.

Literally all you have to do is setup the K-TIG system, and integrate the controller into your existing automation system (if you wish)

K-TIG Comparison Study TIG MIG