Short answer: for 180 A DCEN on stainless steel, run a 3/32" (2.4 mm) tungsten. Use 2% lanthanated (blue band), 2% ceriated (orange), or 1.5% lanthanated (gold). Avoid 2% thoriated (red) on stainless — it's mildly radioactive and the modern non-thoriated tungstens equal or beat its arc characteristics. Grind to a sharp point, ~2.5× diameter long (so a 3/32" tungsten gets a 0.234" ground length). At 180 A DCEN, 3/32" sits comfortably in the middle of the 100–165 A…165–250 A overlap; it's the all-purpose stainless tungsten for sheet-to-1/4" work.

Tungsten current capacity (DCEN, mid-range)

Diameter      DCEN (DC Electrode Neg)    DCEP    AC (balanced)
─────────     ──────────────────────     ────    ─────────────
0.020"        Up to 15 A                  N/A    10–20 A
0.040"        Up to 80 A                  N/A    20–30 A
1/16"  (1.6mm) 60–150 A                  10–20  30–80 A
3/32"  (2.4mm) 100–250 A   ← 180 A here  15–30  60–130 A
1/8"   (3.2mm) 150–400 A                  25–40 100–180 A
5/32"  (4.0mm) 250–500 A                  40–55 160–240 A
3/16"  (4.8mm) 400–700 A                  55–80 200–320 A

At 180 A DCEN on stainless: 3/32" tungsten is the right choice. 1/16" is undersized (max 150 A) and will erode quickly; 1/8" is overkill and produces a less-focused arc on thin-to-medium stainless.

Why DCEN for stainless

Steel and stainless TIG run on DC Electrode Negative (DCEN) because the electron flow is from tungsten to workpiece, putting most of the heat into the work. About 70% of arc heat goes into the workpiece on DCEN, vs ~30% on DCEP (which heats the tungsten). DCEN gives deep, narrow penetration with a focused arc — exactly what stainless needs.

• DCEN: stainless, mild steel, copper, brass, titanium.
• AC (balanced): aluminum and magnesium — cleans the oxide layer.
• DCEP: rare. Sometimes for thin aluminum on a small machine. Most modern AC TIG machines use AC instead.

Tungsten type for stainless

• 2% Lanthanated (blue band) — top pick for stainless. Long life, easy starts, holds a sharp point. Default for ferrous DCEN work.
• 1.5% Lanthanated (gold band) — slight performance bump over 2%. Some shops swap to it as their universal tungsten. Buy whichever your supplier stocks.
• 2% Ceriated (orange band) — great low-amperage starts, a hair behind lanthanated at higher A. Works fine on stainless.
• 2% Thoriated (red band) — the legacy choice, mildly radioactive (Th-232). Modern shops phasing it out. Performance equal to lanthanated; the only reason to use it now is "we already have a tube of it."
• Pure tungsten (green band) — AC-only. Don't use on stainless DCEN.
• Zirconiated (white) — AC-aluminum specific. Don't use on stainless.

Tip preparation for 180 A DCEN

Geometry: pointed (conical) for DCEN, NOT balled.

  Tungsten diameter:    3/32" (0.094")
  Ground length:        2.5 × diameter = ~0.234"
  Included angle:       30° (for sheet) up to 60° (for thicker)
  Tip flat (truncation):  0.005" — slight flat improves longevity
                          without dulling the arc.

Why pointed:
  Pointed tip narrows arc cone, focuses heat into a small spot.
  Wider taper (more material at tip) handles higher amperage but
  spreads the arc — bad for sheet stainless, fine on 1/4"+ plate.

Grinding direction:
  Grind LONGITUDINALLY (parallel to tungsten axis), not radially.
  Grind marks transverse to axis create arc-wandering paths.
  Use a dedicated tungsten grinder (Sharpie, Tig King) for repeatable
  geometry — or a fine wheel with the tungsten axis-parallel.

Filler rod size for 180 A on stainless

• 0.045" (1.2 mm) ER308LSi — for 16 ga / 0.063" stainless sheet.
• 1/16" (1.6 mm) ER308LSi — for 14 ga / 0.075" through 1/8" (0.125") stainless. Default at 180 A.
• 3/32" (2.4 mm) ER308LSi — for 1/8" through 1/4" stainless. Drops the deposition time.
• 308LSi vs 308L: the "Si" is silicon for better wetting and a smoother bead. Always pick LSi for cosmetic welds.
• 309LSi: dissimilar metals (stainless to mild steel buttering).
• 316LSi: for chloride/marine service stainless (316L base material).

Cup size and gas flow

Cup #            Inside Ø    Min CFH   Max CFH   Use
─────────────    ────────    ───────   ───────   ─────────────────
#4 (1/4")        0.250"      8         12        Tight access only
#5 (5/16")       0.313"      10        14        Sheet metal
#6 (3/8")        0.375"      12        16        Sheet stainless ← 180 A
#7 (7/16")       0.438"      14        18        General-purpose
#8 (1/2")        0.500"      15        20        Most common all-around
#10 (5/8")       0.625"      18        22        Thick stainless / Ti
#12 (3/4")       0.750"      20        25        Heavy section / pipe

Gas: 100% argon, 18 CFH typical for #7–#8 cup at 180 A.

Worked example: 180 A DCEN on 1/8" stainless

Setup:
  Material:    304L stainless, 1/8" (0.125") plate
  Joint:       outside corner, square edge butt
  Process:     GTAW DCEN
  Tungsten:    3/32" 2% lanthanated, 30° point, 0.005" flat
  Filler:      1/16" ER308LSi
  Gas:         100% argon, 18 CFH, #7 cup

Recipe:
  Amperage:        180 A (peak, not pulse)
  Travel speed:    5 IPM
  Voltage (arc):   ~12 V
  Heat input:      60 × 12 × 180 / 5 / 1000 = 25.9 kJ/in

Verdict:
  HI is in the 20–30 kJ/in band typical for stainless single pass on
  this thickness. Inside that range:
    Below 18 kJ/in:  cold weld, lack of fusion risk
    Above 35 kJ/in:  sensitization (Cr depletion at HAZ), corrosion
                     resistance drops, distortion increases.

Color check (back side / oxide pattern):
  Silver / pale straw    → ideal
  Light straw / dark gold → slightly hot
  Blue / dark blue        → too hot, sensitization risk
  Black / scaly           → way too hot, redo

Pulse parameters at 180 A peak (intermediate)

• Background current: 30–50% of peak (54–90 A at 180 A peak).
• Pulse frequency: 1–5 PPS for visual rhythm; 50–200 PPS for arc-stiffening on thin sheet.
• Duty cycle (peak time): 50% standard, 35–40% for thin (less heat input).
• Pulse on 180 A, 50 A bg, 1 PPS, 50% duty → average current = 115 A → HI at 5 IPM = 16.6 kJ/in (cooler than steady).

Common stainless TIG mistakes

• Using 2% thoriated and balling the tip. Stainless DCEN tips don't ball — that's an AC-only behavior.
• Cup too small for amperage. Insufficient gas coverage = sugaring on the back side and contaminated bead.
• Skipping back-purge on tube/pipe. Sugar on the ID destroys corrosion resistance and is non-reworkable.
• Filler rod tip dipping out of gas envelope. Pull the rod back inside the cone, not into the air.
• Tungsten contamination from touching the puddle. ALWAYS regrind a contaminated tungsten — never just chip it off and continue.
• Excessive amperage on 304L → sensitization at 800–1500°F. Use 304L (low carbon) or 308LSi (low carbon filler) and keep HI under 30 kJ/in for thin material.

Tungsten size cheat sheet for stainless

Material thickness    Amperage    Tungsten      Filler size
──────────────────    ────────    ──────────    ────────────
20 ga (0.038")        40 A        1/16"         0.045"
16 ga (0.063")        80 A        1/16"         1/16"
14 ga (0.075")        110 A       1/16"         1/16"
1/8"  (0.125")        180 A       3/32"  ←      1/16"
3/16" (0.188")        220 A       3/32"         1/16"–3/32"
1/4"  (0.250")        260 A       3/32"–1/8"    3/32"
3/8"  (0.375")        300 A       1/8"          3/32"
1/2"  (0.500")        350 A+      1/8"–5/32"    1/8"

Pulse can drop average current ~25–35% for the same penetration
on the high end of each row.

Run it on your phone

The WelderCalc app holds the tungsten capacity table, filler rod sizing, gas flow, and heat-input calculation for TIG, MIG, stick, and flux-core — for stainless, carbon steel, aluminum, and Inconel. 100% offline. Free on the App Store and Google Play.

Related

• MIG amperage for 1/4" mild steel with .035 ER70S-6
• Heat input limit for SA-516 Gr 70 root pass
• MIG amperage cheat sheet (carbon steel)
• WelderCalc — welder's calculator on iOS + Android

Note: Tungsten capacity ranges vary slightly by manufacturer. Always defer to the project WPS for qualified-procedure welds.