Gas tungsten arc welding

At an assumed 8 L/min torch flow and 6 minutes arc-on, the torch uses 48 L while welding. 12 starts with 2 seconds pre-flow and 8 seconds post-flow each add 2 minutes and 16 L, giving 64 L total. Account for purge, trailing gas, leaks and flow-volume reference conditions separately.

GTAW or TIG uses a nominally non-consumable tungsten electrode with shielding gas. Specify separate filler or a qualified autogenous route, plus current, arc length, travel and gas composition. Linde, TIG Welding, undated

Separate control of arc and filler is useful for precise joints, but does not make every alloy combination weldable or every neat bead acceptable. The procedure must establish material compatibility, joint design, thermal controls, and inspection. This page is a process reference, not a welding procedure specification (WPS).

Define the complete welding system

Record base-metal grade and condition, thickness, joint geometry, welding position, filler product and diameter, tungsten type/diameter/preparation, torch and cooling arrangement, shielding system, and power-source capabilities. Specify manual, mechanized, or automated operation and the applicable start/stop controls.

Check equipment ratings for the intended current, waveform, duty cycle, and torch cooling. A power source's maximum current does not establish the permissible continuous current of its connected torch, cable, collet, or electrode. Use the installed model's instructions rather than generic current-per-thickness rules.

Miller's Dynasty 300 Series manual OM-291634A, August 2022, provides a bounded example of inverter-specific tungsten guidance. Its selection table concerns ceriated/lanthanated electrodes, argon, specified polarity, and, for the AC column, 75% electrode-negative balance. These are the table's conditions, not a universal recommendation to run all GTAW at that balance. Miller owner’s manual, section 12

Choose polarity and waveform for the application

DC electrode negative is widely used for steels and other materials; AC is commonly used for aluminium because its electrode-positive portion provides oxide-cleaning action while its electrode-negative portion supplies useful workpiece heating. The chosen waveform also affects electrode loading and arc behavior.

Miller's AC-balance article describes the tradeoff between oxide removal and tungsten heating/erosion. Increasing cleaning is not a substitute for removing contamination before welding. Identify whether the actual control expresses electrode-negative percentage, electrode-positive percentage, or another scale before copying a setting. A percentage without its definition and equipment context is ambiguous. Miller, How to Implement AC Balance Control for TIG Aluminum Welding, undated technical article

Pulse frequency, peak/background current, duty fraction, and travel speed are separate variables. A pulse program is not fully described by its peak current, and equivalent average current does not prove equivalent penetration or thermal history. Preserve the qualified waveform and measurement basis where the WPS requires them.

Tungsten preparation and contamination

Choose electrode chemistry and size for the machine, current, polarity, and starting method. Identify the electrode from its packaging and designation rather than color alone. The cited Miller manual warns that manufacturers do not all use the same color identification, recommends sharpened ceriated or lanthanated electrodes for its inverter applications, and does not recommend pure tungsten for those inverters. Traditional balling practice for another machine family is therefore not automatically transferable. Miller OM-291634A, tungsten selection

Maintain clean electrode preparation and suitable grinding/dust controls. If the tungsten contacts the pool or filler, address contamination using the electrode and equipment instructions; continuing to weld can introduce inclusions or unstable behavior. Protect the hot electrode during post-flow as well as during the arc. Do not infer that “non-consumable” means immune to erosion or contamination.

Shielding is coverage, not just a flowmeter reading

Argon is common; helium and argon/helium mixtures can alter arc starting, heat transfer, and penetration. Select the gas required by the material and procedure rather than substituting a GMAW argon/CO₂ mixture. SSAB's TIG guidance proposes pure argon for its steel products and explicitly limits that recommendation's applicability to SSAB products. SSAB, Shielding gas for TIG welding, undated

Miller's shielding article, posted March 11, 2026, discusses cup geometry, gas lenses, leaks, and pre-/post-flow. Excess flow can create turbulence and entrain air; insufficient flow can also leave hot metal or tungsten unprotected. More flow is therefore not an automatic improvement. Gas-lens capability and electrode extension must be assessed with the actual joint and torch. Miller, Best Practices for Proper Shielding Gas in TIG Welding

Determine whether the root, adjacent hot metal, or a trailing region needs separate shielding. Miller's troubleshooting page identifies backside oxidation on stainless welds and discusses root purging. A torch gas envelope alone does not demonstrate adequate protection on the inaccessible side of a joint. The purge arrangement, gas quality, monitoring, and acceptance must be defined for the application. Miller, Common TIG Welding Problems, undated

Joint preparation and filler selection

Provide clean, dry joint surfaces and filler; remove identified contamination and oxides using the qualified method. Resolve root gap, groove access, alignment, backing, tack treatment, and restraint before welding. Changing joint access can change achievable shielding and electrode positioning even when nominal thickness remains constant.

Filler selection depends on both base metals, dilution, cracking behavior, required mechanical/corrosion performance, and subsequent treatment. Autogenous welding is a deliberate procedure choice, not simply an omitted purchase item. As a named example, Select-Arc's Select 308/308L GTAW product page identifies ER308/ER308L, DCEN and argon, and lists applications including 304/304L and other specified austenitic grades. That application list is not approval for every stainless joint or dissimilar combination. The page has no verified technical issue date. Select-Arc, Select 308/308L GTAW

Worked example: account for gas outside arc-on time

Use the example’s 8 L/min and the stated arc, pre-flow and post-flow times:

• Arc-on gas = 8 × 6 = 48 L.
• Additional flow time = 12 × (2 + 8) = 120 seconds = 2 minutes.
• Additional gas = 8 × 2 = 16 L.
• Total calculated torch gas = 64 L, one-third more than the arc-only estimate.

These assumed settings are not recommendations. The calculation excludes purge/trailing circuits, initial line clearing, leaks, and any overlap or interruption of timed flow. Use consistent flow-volume reference conditions when comparing this estimate with cylinder or bulk-supply capacity. Miller's pre-/post-flow discussion explains why gas use extends beyond arc time; the numerical example is independent of its setting suggestions. Miller shielding guidance

Inspect and hand off the finished weld

Investigate porosity, tungsten contamination, incomplete fusion, oxidation, cracking, distortion, and unacceptable starts/stops. Appearance helps identify a problem but does not demonstrate internal fusion, toughness, or corrosion performance. Inspection extent, acceptance limits, and any destructive or nondestructive tests belong to the governing drawing/specification and qualified procedure.

Use applicable equipment instructions and material/electrode SDS for electrical, radiation, fume, gas, and grinding hazards. Inert shielding gas does not make the complete operation hazard-free, and gas purging requires its own ventilation and access controls.

A useful production handoff records material identity, joint drawing, WPS and qualification basis, filler lot, tungsten and torch configuration, gas and purge arrangement, waveform/current controls, thermal requirements, and inspection results. Keep supplier starting guidance separate from demonstrated finished-joint capability.

Related reference

Welding methods