TIG Welding Settings Calculator — Complete GTAW Parameters Guide
TIG welding — formally known as Gas Tungsten Arc Welding (GTAW) — is the most precise arc welding process available and the go-to method for root passes on pressure vessels and pipelines, critical aerospace structures, exotic alloys such as titanium and Inconel, and any application where weld quality cannot be compromised. Unlike MIG/GMAW, where the machine self-regulates wire feed and voltage, TIG is entirely operator-controlled — the welder simultaneously manages torch angle, arc length, travel speed, and filler rod addition by hand. Getting the machine settings right is the non-negotiable foundation: no amount of skill compensates for a machine set incorrectly.
This guide covers every TIG/GTAW parameter — amperage, tungsten selection, polarity, shielding gas, cup size, and filler rod classification — with the engineering formulas behind them, a fully working calculator, and complete reference tables for mild steel, stainless steel, aluminium, titanium, and nickel alloys. The calculator immediately below generates a complete parameter set from your inputs; the technical sections that follow explain why those numbers are correct so you can adapt them intelligently for any situation.
TIG / GTAW Settings Calculator
Amperage · Tungsten · Filler Rod · Gas Flow · Cup Size · Heat Input
Starting values only. TIG parameters are highly sensitive to operator technique, torch angle, arc length, and travel speed. Always trial-weld on matching scrap in the same position. For pressure vessel, pipeline, or aerospace applications, parameters must be validated by a qualified WPS/PQR.
How TIG Welding Works — Process Overview
TIG welding generates heat from an arc between a non-consumable tungsten electrode and the workpiece. The electrode does not melt — it only carries current and sustains the arc. Filler metal is introduced separately by the welder as a bare rod, or the weld may be made autogenously (no filler) for thin sections or sheet material.
Because the arc is produced by a constant-current (CC) power source with a drooping volt-amp curve, the welder can change arc length slightly without causing large swings in heat input — unlike GMAW/MIG, which uses a flat constant-voltage characteristic designed to self-regulate wire burn-off. This CC characteristic makes TIG the default process wherever precision heat control is required, including root passes qualifying under ASME Section IX.
TIG Welding Parameters — What You Set and Why
| Parameter | Controls | Set By | Primary Rule |
|---|---|---|---|
| Amperage | Arc heat, penetration, fusion | Machine dial + foot pedal | ~40 A per mm (DC−, mild steel) |
| Polarity | Penetration pattern, oxide cleaning | Machine switch | DC− for steel/SS/Ti/Ni; AC for aluminium |
| Tungsten Diameter | Current-carrying capacity, arc stability | Welder selects | Larger diameter = higher current capacity |
| Tungsten Type | Arc stability, contamination resistance | Welder selects | Ceriated/Thoriated for DC; Pure/Zirconiated for AC |
| Shielding Gas | Weld protection, heat input | Machine/regulator | 100% Ar for most materials; Ar/He for thick sections |
| Gas Flow Rate | Coverage area, turbulence risk | Flowmeter regulator | Cup # × 5 = CFH (× 0.472 for LPM) |
| Cup/Nozzle Size | Gas coverage width | Welder selects | #4–#6 thin; #7–#10 thick/critical |
| Arc Length | Effective voltage, penetration | Welder controls manually | Approximately equal to electrode diameter |
| Filler Rod Diameter | Bead profile, deposition rate | Welder selects | Plate thickness / 2, minimum 1.6 mm |
The Formulas Behind TIG Parameter Selection
Formula 1 — Amperage from Thickness
The fundamental TIG amperage rule is the “1-amp-per-thou” rule from imperial practice: 1 ampere per 0.001 inch (0.025 mm) of base metal thickness. In metric terms:
Formula 2 — Position and Material Correction
Formula 3 — Gas Flow Rate from Cup Size
Formula 4 — Heat Input Calculation
Heat input is critical for controlling HAZ properties, distortion, and interpass temperature. For stainless steel, excess heat input risks sensitisation; for P91 chrome-moly, it must stay within WPS limits.
DC−, DC+, and AC Polarity — Selection and Effects
Polarity is arguably the most critical setting in TIG welding. Using the wrong polarity will either destroy the tungsten electrode, fail to achieve fusion, or — in the case of aluminium — produce a weld with black, contaminated oxide inclusions. Polarity must be set before striking the arc.
Tungsten Electrode Selection — Types, Colours, and Current Ranges
Selecting the correct tungsten type, diameter, and tip geometry is as important as setting the amperage. The tungsten electrode conducts all of the welding current, sustains the arc, and must remain uncontaminated for the life of the weld. AWS A5.12 / ISO 6848 classify tungsten electrodes by their alloying addition:
| Type (AWS) | Colour Band | DC− Range (3.2 mm) | AC Range (3.2 mm) | Best Application |
|---|---|---|---|---|
| EWP — Pure Tungsten | Green | Not recommended | 20–100 A | AC aluminium (older transformer machines only) |
| EWTh-2 — 2% Thoriated | Red | Up to 400+ A | Limited | DC− steel, SS, Ni alloys — industry workhorse |
| EWCe-2 — 2% Ceriated | Grey | Up to 350+ A | Good | DC− and AC; excellent arc starts on inverters |
| EWZr-1 — Zirconiated | White | Not ideal | Up to 180 A | AC aluminium (preferred over pure for AC) |
| EWLa-1.5 — 1.5% Lanthanated | Gold | Up to 400+ A | Excellent | DC & AC — non-radioactive alternative to thoriated |
Tungsten Tip Preparation
Tip geometry dramatically affects arc stability and weld quality. For DC− applications, a tapered point concentrates the arc and gives precise control. For AC, tungsten naturally forms a hemispherical ball during the welding process — this should be allowed to form on a copper block before beginning the actual weld.
| Current Type | Tip Shape | Preparation Method | Cone Angle |
|---|---|---|---|
| DC− (steel, SS, Ti, Ni) | Ground taper point | Grind longitudinally on dedicated aluminium oxide wheel | 30°–60° |
| AC (aluminium, Mg) | Hemispherical ball | Strike arc on copper block — ball forms naturally | N/A |
| DC− automated/orbital | Truncated cone (blunt) | Grind to taper, then flat 0.5–1 mm at tip | 30°–45° + flat |
TIG Welding Settings by Material
Mild Steel (DC−, DCEN)
Use ER70S-2 or ER70S-6 filler rod (AWS A5.18) for mild steel TIG welding. ER70S-2 contains deoxidisers that make it tolerant of minor surface contamination, making it a common choice for root passes on pipe.
| Thickness (mm) | Amperage | Tungsten Ø | Filler Ø | Gas Flow (LPM) | Cup # |
|---|---|---|---|---|---|
| 0.8 | 25–40 | 1.0 mm | 1.0 mm | 6–8 | #4 |
| 1.5 | 50–70 | 1.6 mm | 1.6 mm | 7–9 | #5 |
| 2.0 | 70–90 | 1.6 mm | 1.6 mm | 8–10 | #5 |
| 3.0 | 100–130 | 2.4 mm | 2.4 mm | 9–12 | #6 |
| 5.0 | 150–180 | 3.2 mm | 2.4 mm | 10–14 | #7 |
| 8.0 | 190–240 | 3.2 mm | 3.2 mm | 12–16 | #8 |
| 10 | 220–280 | 4.0 mm | 3.2 mm | 14–18 | #8–#10 |
Stainless Steel 304/316 (DC−, DCEN)
Stainless steel retains heat far more efficiently than mild steel due to its lower thermal conductivity (~15 W/m·K vs 50 W/m·K for mild steel). This means you need 10–15% less amperage, and travel speed must be maintained to avoid sensitisation — carbide precipitation — in the heat-affected zone. Keep interpass temperature below 150 °C. Back-purge with 100% Argon for all root passes to prevent oxidation on the bore side. See our detailed guide on stainless steel weld decay for the metallurgical basis.
| Thickness (mm) | Amperage | Tungsten Ø | Filler (AWS A5.9) | Gas (LPM) | Interpass Max |
|---|---|---|---|---|---|
| 1.0 | 30–50 | 1.6 mm | ER308L / ER316L 1.6 mm | 8–10 | 150 °C |
| 2.0 | 60–80 | 1.6 mm | ER308L / ER316L 1.6 mm | 9–11 | 150 °C |
| 3.0 | 85–110 | 2.4 mm | ER308L / ER316L 2.4 mm | 10–13 | 150 °C |
| 5.0 | 130–160 | 3.2 mm | ER308L / ER316L 2.4 mm | 12–15 | 150 °C |
| 8.0 | 170–210 | 3.2 mm | ER308L / ER316L 3.2 mm | 14–17 | 150 °C |
Aluminium (AC)
Aluminium requires AC current for the cathodic cleaning action that removes the refractory Al2O3 oxide layer (melting point 2,072 °C vs 660 °C for the base metal — meaning the oxide melts at more than three times the temperature of the aluminium beneath it). Without this cleaning, fusion is impossible. Use only pure Argon — never Ar/CO2 or Ar/O2 mixes used for MIG. Aluminium’s high thermal conductivity means you need a higher amperage per mm than steel. For thin aluminium, a copper chill backing block is strongly recommended to prevent burn-through. Use ER4043 for general-purpose welding; ER5356 for structural applications requiring higher strength and better anodising response.
| Thickness (mm) | Amps (AC) | Tungsten Ø (Pure/Zr) | Filler | Gas (LPM) | Cup # |
|---|---|---|---|---|---|
| 1.5 | 50–70 | 1.6 mm | ER4043 / ER5356 2.4 mm | 10–12 | #6 |
| 2.0 | 70–90 | 2.4 mm | ER4043 / ER5356 2.4 mm | 11–13 | #6–#7 |
| 3.0 | 100–130 | 2.4 mm | ER4043 / ER5356 3.2 mm | 13–16 | #7 |
| 5.0 | 160–200 | 3.2 mm | ER5356 3.2 mm | 15–18 | #8 |
| 8.0 | 200–260 | 4.0 mm | ER5356 4.0 mm | 17–20 | #8–#10 |
| 10 | 250–320 | 4.8 mm | ER5356 4.0 mm | 18–22 | #10 |
Titanium (DC−)
Duplex Stainless Steel 2205 (DC−)
Duplex stainless steel requires careful heat input control to maintain the austenite/ferrite balance in the weld metal and HAZ. Target heat input: 0.5–2.5 kJ/mm. Interpass temperature: maximum 150 °C (some specifications specify 100 °C maximum). Use ER2209 filler rod. For a detailed guide, see Complete Guide to Welding Duplex Stainless Steels.
Step-by-Step TIG Welder Setup
- Prepare the tungsten electrode — correct type, diameter, and tip geometry for your material and polarity. Install in collet with 5–8 mm stick-out. Tighten the collet body firmly.
- Set polarity — DC− for all ferrous metals, titanium, nickel alloys, and copper; AC for aluminium and magnesium. Check the machine display or selector switch before proceeding.
- Set amperage — use the calculator above. With a foot pedal, set the machine 15–20% above your target and use the pedal to control the puddle. Without a pedal, set to calculated value.
- Set gas flow rate — connect pure Argon cylinder, open valve, set flowmeter to recommended LPM. Pre-flow for 5–10 seconds before striking the arc to purge the torch and hose.
- Set pre-flow and post-flow times — pre-flow: 0.5–1 second. Post-flow: approximately current/10 seconds (150 A → 15 seconds). Titanium: hold until below 400 °C (may need 45–90 seconds).
- Prepare filler rod — correct classification for the base metal. Clean with acetone. Do not touch the tip with bare hands — skin oils contaminate the arc.
- Prepare the base metal — clean with acetone or IPA. For stainless steel, use a dedicated stainless-steel wire brush (never a brush that has touched mild steel). For aluminium, brush with dedicated stainless brush and weld within 2–4 hours of cleaning.
- Strike the arc — use HF (high-frequency) start or lift-arc. Never scratch-start directly on the base metal — this contaminates the tungsten with base metal particles and introduces inclusions into the weld.
- Establish the puddle, then feed filler — build a molten pool first, then introduce filler rod at the leading edge of the pool at 15–20 degrees to the work surface. Keep filler rod tip inside the gas shield at all times.
- Maintain consistent arc length — arc length should equal approximately the electrode diameter. Too long: arc wanders and penetration decreases. Too short: risk of dipping tungsten into the pool, causing contamination.
- Terminate the weld correctly — use down-slope (foot pedal or machine down-slope timer) to progressively reduce current and fill the crater. Abrupt arc stops create crater cracks — a common TIG defect.
- Allow post-flow to complete — hold the torch stationary over the weld until the gas post-flow has finished. For titanium, use a trailing shield or maintain the torch and trailing shield until the weld has cooled below 400 °C.
Fully Worked Example — 316L Stainless Steel Root Pass
Problem: TIG butt weld, 316L stainless steel, 4 mm thick, flat position (1G), open root, no backing bar. Calculate all settings.
TIG Welding Troubleshooting — Defects and Parameter Fixes
| Symptom | Likely Cause(s) | Parameter Fix |
|---|---|---|
| Tungsten contamination (black or grey tip) | Tungsten dipped into weld pool; wrong polarity; arc too short | Re-prepare tungsten; verify polarity is DC−; increase arc length slightly |
| Porosity | Gas contamination or flow too low; base metal not clean; moisture; gas leaks | Increase gas flow; check all fittings for leaks; clean base metal with acetone; extend pre-flow |
| Arc wander (unstable arc) | Magnetic arc blow; tungsten not pointed correctly; arc too long | Reposition earth clamp; re-grind tungsten to correct taper; shorten arc length |
| Burn-through (thin material) | Amperage too high; travel speed too slow; gap too wide | Reduce amperage; increase travel speed; use foot pedal; add copper chill backing |
| Lack of fusion | Amperage too low; travel speed too fast; arc length too long; insufficient preheat | Increase amperage; slow travel; shorten arc; check preheat requirements |
| Grey/black stainless weld colour | Gas contamination; oxidation from insufficient shielding or post-flow; overheating | Check gas purity and connections; extend post-flow; reduce interpass temperature |
| Titanium weld discolouration (blue/purple/grey) | Inadequate shielding or back-purge; gas contamination; post-flow too short | Silver = accept; straw = marginal; blue/purple/grey = reject. Grind and re-weld. Extend post-flow; add trailing shield |
| Crater crack at weld end | Abrupt arc stop without down-slope; crater not filled | Use down-slope function; feather pedal at end; fill crater with additional filler rod before stopping arc |
| Aluminium weld turns grey/black (AC) | Incorrect gas (not pure Ar); contaminated base metal; insufficient oxide cleaning | Use 100% pure Argon only; re-clean with dedicated stainless brush; check AC frequency on inverter |
Recommended References for TIG Welding
AWS Welding Handbook Vol. 2 — Welding Processes
The authoritative AWS reference covering GTAW in full detail — process physics, equipment, parameters, and qualification. Essential for every welding engineer’s library.
View on AmazonMetals and How to Weld Them — Lincoln Electric
A practical metallurgy and welding reference covering all common engineering materials, their weldability, and recommended procedures including TIG parameters.
View on AmazonTIG Welding: The Complete Guide — Gerald Doeve
A hands-on practical guide covering TIG setup, technique, tungsten selection, and troubleshooting for beginners through to intermediate-level welders.
View on AmazonWelding Metallurgy — Sindo Kou
The definitive graduate-level text on welding metallurgy — HAZ microstructure, solidification, hot cracking, and phase transformations relevant to all GTAW applications.
View on AmazonDisclosure: WeldFabWorld participates in the Amazon Associates programme (StoreID: neha0fe8-21). If you purchase through these links, we may earn a small commission at no extra cost to you. This helps support free technical content on this site.
Frequently Asked Questions
Why does TIG welding use a constant current (CC) power source instead of constant voltage (CV)?
TIG welding requires a Constant Current (CC) power source because the arc length is controlled manually by the welder. With a Constant Voltage source, small changes in arc length cause large swings in amperage, making thermal control impossible. A CC source maintains a relatively stable amperage despite arc length variation, characterised by the steep (drooping) volt-amp curve of all TIG machines. This gives the welder precise, predictable heat input regardless of minor hand movement. By contrast, GMAW/MIG uses a flat CV characteristic specifically designed to self-regulate wire burn-off — this is why you cannot use a MIG power source for manual TIG.
When should I use AC versus DC− for TIG welding?
Use AC current for aluminium and magnesium. The positive half-cycle of AC provides cathodic cleaning action that removes the refractory aluminium oxide layer (Al2O3, melting point 2,072 °C), which otherwise prevents fusion. The negative half-cycle provides penetration heat. For all other metals — mild steel, stainless steel, titanium, nickel alloys, copper, and duplex stainless — use DC− (DCEN), which concentrates approximately 70% of arc heat into the workpiece for efficient fusion and deep penetration while keeping the tungsten electrode cool and stable.
What does a TIG foot pedal actually do and is it necessary?
A TIG foot pedal is a remote amperage control that varies current from near-zero up to the machine’s maximum set amperage. This lets you increase heat to establish the puddle, then reduce heat as the joint heats up — preventing burn-through and distortion — and precisely fill the crater at the weld end. For manual TIG welding, a foot pedal is strongly recommended. Fixed amperage without a pedal is only practical for automated or mechanised TIG (orbital welding machines, etc.) where travel speed and arc length are machine-controlled. Without a pedal on manual TIG, you lose the most important heat-control tool available to you.
What colour should my TIG weld on stainless steel be?
A correctly shielded stainless steel TIG weld should be silver to bright metallic, or at worst light straw-gold. Darker straw-gold is borderline acceptable in non-critical applications. Brown, blue, purple, or grey-black colouration indicates oxidation from insufficient gas shielding or inadequate back-purge, which degrades corrosion resistance by depleting chromium in the near-surface layer. For hygienic or corrosion-critical service, only a silver weld is acceptable. See our article on stainless steel weld decay for the metallurgical details. Discoloured welds must be re-welded or passivated by electrolytic polishing.
How long should post-flow shielding gas run after the arc stops?
As a general guide, post-flow time in seconds is approximately equal to the welding amperage divided by 10 — so at 150 A, run post-flow for approximately 15 seconds. For titanium, the requirement is much stricter: maintain shielding until the weld metal and HAZ are below 400 °C, which may take 40 to 90 seconds or more depending on section thickness. Most inverter TIG machines have an adjustable post-flow timer — set it correctly before welding, not after the arc stops. For titanium, trailing gas shields or argon-purged enclosures provide additional protection beyond the torch post-flow alone.
Which tungsten type is best for TIG welding stainless steel?
For TIG welding stainless steel on DC−, 2% Ceriated (EWCe-2, grey band) is widely considered the best choice for modern inverter TIG machines. It provides excellent arc starts at low amperage, strong arc stability across a wide current range, and good current-carrying capacity. 2% Thoriated (EWTh-2, red band) is also highly effective and remains very common in fabrication shops, though it is mildly radioactive. Lanthanated (EWLa-1.5, gold band) is an excellent non-radioactive alternative to thoriated electrodes with very similar performance. Pure tungsten (EWP, green) should not be used for DC− applications.
What is the amperage formula for TIG welding?
The fundamental TIG amperage formula is approximately 1 ampere per 0.025 mm of base metal thickness (the “1-amp-per-thou” rule). In metric: I = Thickness (mm) × Base_Factor, where the factor is approximately 40 for mild steel on DC−, 36 for stainless steel, 50 for aluminium on AC, 34 for titanium, and 56 for copper. This base value is then multiplied by a position factor: 1.00 for flat, 0.95 for horizontal, 0.85 for vertical up, and 0.80 for overhead. If using a foot pedal, set the machine 15–20% above the calculated working amperage and feather down to suit the puddle response. You can use the calculator at the top of this page to get a complete parameter set automatically.
What filler rod should I use for TIG welding 316L stainless steel?
Use ER316L filler rod (AWS A5.9) for TIG welding 316L stainless steel. The L designation indicates low carbon content (0.03% maximum), which minimises carbide precipitation in the heat-affected zone and preserves corrosion resistance. ER316L contains 2–3% molybdenum, matching the base metal chemistry and providing equivalent pitting resistance. For 304 or 304L base metal, use ER308L. Filler rod diameter is typically half the plate thickness, with 1.6 mm as the practical minimum for manual TIG. For critical applications, ensure the filler lot certificate meets the required chemical composition limits per your WPS. For more context on stainless welding metallurgy, see our guide on stainless weld decay and sensitisation.
Applicable Standards and References
- AWS A5.12 / ISO 6848 — Tungsten and tungsten-alloy electrodes for arc welding and cutting
- AWS A5.18 — Carbon steel electrodes and rods for gas shielded arc welding (ER70S series)
- AWS A5.9 — Stainless steel electrodes and rods (ER308L, ER316L, ER2209)
- AWS A5.10 — Aluminium and aluminium alloy electrodes and rods (ER4043, ER5356)
- AWS A5.16 — Titanium and titanium alloy filler metals (ERTi-2, ERTi-5)
- EN ISO 1011-1 — Welding. Recommendations for welding of metallic materials. General guidance for arc welding (thermal efficiency factors)
- ASME Section IX — Welding, Brazing, and Fusing Qualifications (WPS/PQR requirements)