K-TIG vs MIG

 

Process Comparison

What are K-TIG’s Advantages Over MIG?

MIG is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece joint, the consumable wire transfers melted droplets across the arc creating a molten weld pool which joins the material.

MIG is a low penetration process which requires extensive edge preparation and consumption of filler material. It is commonly used for welding carbon steels and stainless steels, but its use on exotic materials is limited due to higher defect rates due to reduced weld pool fluidity.

MIG is considered to be highly susceptible to defects such as inter-run fusion and side-wall fusion, and considerably more susceptible to porosity than K-TIG. The Oil and Gas, Petroleum and Chemical industries will generally not accept MIG for pressure vessel welding applications due to the higher defect risk and associated increased welder skill required to minimize these types of defects.

By contrast, K-TIG is a full penetration single pass GTAW process which uses a non-consumable electrode, eliminates or minimises filler consumption, and is suitable for most industrial metals and produces high quality results when welding exotic alloys. It is ideally suited for welding pressure equipment, static and dynamically loaded structures where defect free welds are a critical requirement.

The results speak for themselves – faster welding, fewer consumables, less prep, cleaner welds, reduced re-work and higher quality.

Jeff Thomas, Vice President, Operations, TITAN Metal Fabrication

The Benefits of Switching

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

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

  • Penetration: K-TIG is capable of performing single pass welds of up to 16mm for titanium, 14mm zirconium, 13mm austenitic stainless steels, Inconels, Hastelloys, and a wide range of nickel and cobalt alloys, and 9mm in conductive materials such as ferritic steels and carbon steels. MIG can only perform single pass welds for materials 2mm and under, anything thicker than that and an V-groove root pass will need to be applied, followed by filler pass.
  • Speed: A key benefit of K-TIG is the increased speed you enjoy. K-TIG can weld at speeds of up to 1000 mm/min while MIG is significantly slower at 400 mm/min.
  • Weld Quality: MIG is a high wire deposition welding process, so the weld quality can be acceptable but not so easy to control.  It is highly dependent on the welder's skill level for manual welding applications.  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. K-TIG, on the other hand, enjoys the benefits of keyhole welding in that vaporised impurities can exit through the back of the keyhole instead of being trapped as porosity in the solidifying weld. Lack of fusion is also avoided as the simple square butt joint design prevents the possibility of "bridging" during fill passes.
  • Joint Preparation: K-TIG requires very little preparation, a low cost simple square butt design is all that is required for most applications. Preparation costs jump up considerably with MIG welding. V- or J- groove preparations are necessary and to ensure process consistency machine groove preparation is preferred.
  • Welding Cycle Times: A combination of a low energy density arc with limited penetration capability and root and filler passes being performed at low speeds makes MIG weld cycle times rather slow. The fact that K-TIG’s high energy density keyhole can penetrate thick materials incredibly quickly and the high travel speed of the system makes for an incredibly fast welding cycle.
  • Keyhole Stability: K-TIG keyholes are inherently stable because of surface tension in the weld pool and high travel speeds. The nature of the keyhole surface also creates a naturally responsive keyhole that is capable of self-correcting for fluctuations in arc forces. MIG relies on a ‘melt through’ approach to penetration and for anything thicker than 2mm a V-groove root pass and filler passes are usually applied. This approach increases the cost of consumables, the cost of labour, increases the time of the project and makes the finished product more susceptible to defects.
  • Circumferential Weld Overlap Tie-In: The nature of the K-TIG keyhole makes the overlap and slope out of a circumferential weld extremely simple. The high energy density arc and patented torch design, mean no plasma gas or complex constricted arc is required. MIG is characterised by limited penetration, which makes the overlap difficult to fuse. A key challenge is dealing with the weld metal from the start of the weld so full penetration can be achieved at the overlap point.
  • Weld Appearance: If proper gas shielding of the face and root sides of the weld is adhered to the K-TIG process will naturally create a uniform and smooth weld appearance that will require no post-weld grinding or dressing. MIG inherently produces a rough and uneven weld appearance, due to the violent addition of filler metal.  There is typically considerable spatter that requires grinding or dressing and proper gas shielding cannot prevent this rough appearance.
  • Distortion: Slow travel speeds and the low energy density of the MIG process mean substantial shrinkage and distortion is a by-product of MIG welds. K-TIG’s ability to make single pass penetration at incredibly high travel speeds as well as the high energy density of the process mean that shrinkage and distortion are not problems of K-TIG welds.
  • Process Consistency: The MIG process can be adjusted to achieve sound welds in a mechanised mode, with a root pass followed by multiple fill passes typically.  However, the weld can vary significantly depending on whether it is in short circuit, globular, or spray transfer mode, and the transfer of large amounts of filler wire to the weld pool creates a level of inconsistency. The simplicity of the K-TIG process and the size of the electrode make erosion and process drift a virtual non-factor. The consistency of the keyhole created by the high energy density arc also means there is very little variation for the duration of the weld.
  • Consumables Costs: MIG torch nozzles and contact tips require cleaning or replacement on a regular basis due to the high amount of weld spatter. K-TIG has virtually no consumables costs, owing to the long-life of the electrode, the 100% duty cycle power supply and the sheer fact that nothing else on the system is prone to erosion or wear.
  • Skill of Operator: Training times for MIG welders are usually 1-2 weeks while it only takes 3 hours to make an unskilled operator proficient in K-TIG welding. K-TIG supervisors can be trained in 1-2 days.
  • Duty Cycle: MIG welding system are usually only provided with power supplies that are rated for 60% of the duty cycle. K-TIG uses 1000 amp power supplies giving them a 100% duty cycle rating.

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I’m currently using MIG, can I switch to K-TIG?

K-TIG has 6 simple requirements, if you have some simple automation equipment or are willing to invest in it. If you weld with materials thicker than 3mm, and larger than 3inch diameter (if circumferential); you’re well on your way. Check out this 6 questions quiz to see if K-TIG would work for you.

[http://www.k-tig.com/will-k-tig-work-for-your-business]

 

How Do I Change to K-TIG?

It really couldn’t be easier.

If you’re currently using MIG, 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.

 

 

Be a hero in your organisation.

Book a live demonstration to see what K-TIG could do for your company.