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K-TIG vs SAWKeyhole TIG and Submerged Arc Welding Compared
What is K-TIG?Keyhole GTAW explained
Overview
A high energy density variant of GTAW, K-TIG (Keyhole TIG) is a high speed, single pass,full penetration welding technology that welds up to 100 times faster than TIG welding inmaterials up to 5/8in (16mm) in thickness, and typically operates at twice the speed ofplasma welding.
K-TIG works across a wide range of applications, and is particularly well suited to lowerconductivity materials such as stainless steels, nickel alloys, titanium alloys and mostcorrosion resistant and exotic materials. It easily handles longitudinal and circumferentialwelds on pipe, plate, spooling, vessel, tank and other materials in a single pass:
Titanium at 3mm to 16mm (1/8 to 5/8 inch) Stainless steel at 3mm to 13mm (1/8 to 1/2 inch) Carbon steel at 3mm to 9mm (1/8 to 11/32 inch)
K-TIG’s extremely fast welding times result in dramatic reductions in labor costs, weldingcycle times, rework and repair costs, gas and power usage. K-TIG’s single pass, fullpenetration welds significantly reduce or eliminate grinding and reworking. The K-TIGprocess dramatically reduces or eliminates the need for wire, eliminates edge bevelling,and requires only a square butt joint, but can also weld into all standard GTAWpreparations. No root gap is required.
The Process
Keyhole TIG is not a Plasma welding process. It is a much simpler, high productivity GTAWvariant developed by the Australian Government’s Commonwealth Scientific & IndustrialResearch Organisation (CSIRO), in conjunction with the Cooperative Research Centre forWelded Structures before being acquired and commercialised by K-TIG.
The System
The K-TIG 1000 System has been precision engineered to deliver the Keyhole GTAWprocess in a robust, intelligent and user friendly form. The K-TIG 1000 System ismanufactured in Adelaide, South Australia, is being used by many of the world’s mostproductive fabricators and has been exported to 18 countries.
K-TIG welding is a new productivity benchmark.The speed, penetration, quality and overall savingsgenerated by the process are extraordinary.
Attila Szabo, Principal Joining Engineer, GE
PAGE 2 OF 7
PENETRATION Up to 16mm Up to 4mm
SPEED Up to 1000mm/min Up to 600mm/min
WELD QUALITY Very high due to benefits fromkeyhole mode
Reasonably good, porosity and lackof fusion are the main types ofdefects. Active flux scavenges thelarge weld pool for oxygen, otherundesirable elements and floatsthem to surface as slag
JOINT PREPARATION Very low cost, simple square buttdesign
High, due to V- or J-groovepreparation for any thickness over4mm, due to limited penetration andlarge weld pool that can drop out dueto gravity
WELDING CYCLE TIMES Very fast, high speed and deeppenetration
Very slow, medium travel speed andthe need for multiple weldpasses. Slag from the flux must beremoved by chipping or grinding,otherwise will cause lack of fusion;this is very time consuming
KEYHOLE STABILITY High inherent stability, self-correctingkeyhole
No keyhole; slow, multi-passpenetration and fill passes
CIRCUMFEREN-TIALWELD OVERLAP TIE-IN
Very simple, just slope down, novoids
Often experience lack of fusion orincomplete penetration @ overlapdue to weld metal build up from startof weld, limited pen capability
WELD APPEARANCEVery smooth and good contour; nodressing or grinding required oneither crown or root
Reasonably good contour with slag(from the flux) that must be removedby chipping away or grinding
DISTORTIONVery low overall distortion due tohigh energy density, low heat input,and high travel speeds
Very high overall distortion due tolow energy density, high heat input,and slow travel speeds
PROCESSCONSISTENCY
Very consistent keyhole, no processdrift
Good consistency, no keyhole, multi-pass welding that must be monitoredto avoid lack of fusion and otherdefects
CONSUMABLES COSTS Very low, long electrode lifeHigh, large diameter filler wire andflux that must be added to cover andprotect weld pool
SKILL OF OPERATOR Very low High
DUTY CYCLE 100% Typically 60%
K-TIG SAW
K-TIG vs SAWKeyhole TIG and Submerged Arc Welding Compared
PAGE 3 OF 7
PENETRATION
Up to 16mm
K-TIG comfortably performs single passwelds in 16mm thick titanium, 13mmaustenitic stainless steels, Hastelloys,Inconels and a wide range of nickel andcobalt alloys, and 9mm in conductivematerials such as ferritic steels & carbonsteels.
Up to 4mm
The practical upper limit for single passSAW welding is generally considered to be4mm. Beyond this thickness, a V-grooveroot pass is normally applied, followed byfiller passes.
SPEED
Up to 1000 mm/min
Typical speeds are:• 3mm material at up to 1000mm/min• 4mm material at up to 750mm/min• 6mm material at up to 600mm/min• 8mm material at up to 500mm/min• 12mm material at up to 350mm/min• 14mm material at up to 250mm/min• 16mm material at up to 200mm/min
Up to 600 mm/min
SAW welding is significantly slower than K-TIG. Typical speeds are:• 1mm material - N/A• 2mm material - N/A• 6mm material – multipass• 8mm materials – multipass• 12mm material – multipass• 14mm material – multipass• 16mm material – multipass
WELDQUALITY
Very high
One of the benefits of keyhole welding isthe exit path available for any vaporizedimpurities to leave the weld through theback of the keyhole. This prevents theevolved gases from becoming trapped asporosity in the solidifying weld. Anotherbenefit is the simple square butt jointdesign, which eliminates the possibility of"bridging" during fill passes and resultantlack of fusion.
Reasonably good
SAW is a high wire deposition weldingprocess, so the weld quality can beacceptable but not so easy to control. Itcan only be run in 1G position in semi-automatic mode. Penetration is achievedby melting through the joint thickness, anddue to the high amount of molten fillermetal being added to the pool, porosity isoften trapped in the solidifying weld. Lackof fusion is also a significant concern, asbridging a V-groove occurs regularlywithout properly fusing the joint sidewalls. Active flux scavenges the large weldpool for oxygen, other undesirableelements and floats them to surface asslag.
JOINT PREPARATION
Low cost, simple square butt design
A simple square butt joint design isrequired, no groove to fill (unless greaterthan 14-16mm thick).
Costly V- or J-groove preparation
Groove preparation is required, whichadds cost, and the removed joint metalmust be replaced with fillermetal. Manually beveled joints often leadto inconsistent welding results. The fluxproduces a slag layer that must beremoved by grinding or chipping to avoidlack of fusion in subsequent weld passes.
K-TIG SAW
K-TIG vs SAWKeyhole TIG and Submerged Arc Welding Compared
PAGE 4 OF 7
WELDING CYCLETIMES
Very fast
The high energy density keyhole permitssingle pass penetration of thick joints at avery high travel speed, resulting inminimal weld passes accomplished in veryshort time.
Rather slow
The low energy density arc has limitedpenetration capability, and the root and fillpasses are performed at moderate travelspeeds, resulting in numerous weld passesaccomplished in fairly lengthy weldingtimes. Inter-pass removal of slag isrequired (after every weld pass).
KEYHOLE STABILITY
High inherent stability, self-correctingkeyhole
K-TIG keyholes have extremely highstability, due to the high travel speeds andsurface tension in the weld pool. As aresult, there is no requirement to seek abalance between arc force (plasmacolumn) and surface tension - the natureof the keyhole surface is such that itnaturally and dynamically self-corrects forfluctuations in the arc forces.
No keyhole; pen + fill passes
There is no keyhole, simply a "meltthrough" approach. Beyond 4mmthickness, a V-groove root pass is normallyapplied, followed by filler passes. Thisapproach takes much longer, costs more interms of labor and consumables, and isprone to welding defects.
CIRCUMFEREN-TIALWELD OVERLAP TIE-IN
Very simple, just slope down, no voids
The K-TIG keyhole is produced from a highenergy density arc and patented torchdesign, without any plasma gas or complexconstricted arc required. As a result, atthe overlap and slope out of acircumferential weld, the process isextremely simple to slope down to closeout the keyhole and end the weld.
Potential for Lack of Fusion at overlap
Due to the limited penetration capabilityof the process, the overlap can be difficultto "tie in" or fuse properly, as the weldmetal from the original start of the weld(with considerable filler wire added) canbe a barrier to full penetration at theoverlap point.
WELD APPEARANCE
Very good and smooth contour
With proper gas shielding of the face androot sides of the weld, the K-TIG processinherently produces a very smooth anduniform weld appearance that requires nofurther grinding or dressing.
Good appearance, reasonable contourdue to flux protection
There is no gas shielding of the weld, theSAW process relies on a layer of flux tocover and protect the weld pool. Theresulting weld appearance can havemoderately good contour, as the slag layerprotects the weld surface. The slag mustbe removed, which requires grinding ordressing.
DISTORTION
Very low
Due to the high energy density of theprocess, the high travel speeds that can beachieved with single pass penetrationresult in remarkably low weld shrinkageand distortion.
Very high
Due to the low energy density of theprocess, the slow travel speeds that aretypical with multiple weld passes result insubstantial weld shrinkage and distortion.
K-TIG SAW
K-TIG vs SAWKeyhole TIG and Submerged Arc Welding Compared
PAGE 5 OF 7
PROCESSCONSISTENCY
Very high
The high energy density arc from K-TIGproduces a smooth and consistent keyholethrough the joint, with very little variationfor the duration of the weld. The processis simple enough, and the electrode islarge enough, that erosion (and processdrift) are negligible.
High
The SAW process can be "dialed in" toachieve sound welds in a mechanizedmode, with a root pass followed bymultiple fill passes. However, the weldcan vary to some degree, the slag thatforms during welding must be removedbetween weld passes, and the transfer oflarge amounts of filler wire to the weldpool creates a level of inconsistency.
CONSUMABLES COSTS
Very low
Long electrode life, nothing else erodes orwears, 100% duty cycle power supply.
High
The SAW process utilizes high volumes oflarge diameter filler wire and activatedflux. Due to high welding amperage, torchparts often need replacement.
SKILL OF OPERATOR
Very low
K-TIG requires minimal training due to thesimplicity of the process and thesophistication of the K-TIG controller. Anunskilled operator is sufficient.
High
SAW requires extensive operator training,as lack of fusion can form easily in theweld and must be avoided with propertechniques.
DUTY CYCLE
100 %
K-TIG utilises a 1000 amp power supply,which is considerably more than isrequired for any keyhole process, and israted for 100% duty cycle.
Typically 60%
Submerged arc welding systems aretypically provided with power supplies inthe range of 400-1000 amps, and aretypically only rated for 60% duty cycle.
K-TIG SAW
K-TIG vs SAWKeyhole TIG and Submerged Arc Welding Compared
PAGE 6 OF 7
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