Shielding Gases for TIG Welding Stainless Steels

 

For TIG welding almost any 300 series stainless steel job or project, Pure Argon might be the only shielding gas you ever need.

But for industrial work on paper mills, refineries, and power plants , there are numerous grades of stainless steels.

So, very specific procedures using argon mixes have been developed to achieve the desired properties.

Here's a breakdown of the most common shielding gases and when to use them, depending on the grade of stainless steel and the welding application.

✅ Most Common Shielding Gases for TIG Welding Stainless

Shielding Gas	Composition	Applications	Stainless Grades	Notes
Pure Argon (100% Ar)	100% Argon	Most common choice and most versatile for all grades of Stainless Steels.	301, 303, 304, 316, 321, 347, 410, 430	Clean arc, good penetration, smooth bead
Argon + 2–5% Hydrogen	98% Ar / 2–5% H₂	Better wetting action, faster travel speeds, brighter finish	Austenitic stainless (304, 316)	Not for use on ferritic/martensitic grades; avoid on thick or restrained joints
Argon + 1–3% Nitrogen	97–99% Ar / 1–3% N₂	Improves corrosion resistance  on certain grades (especially pitting)	Duplex and super duplex stainless	Used often for root pass shielding or purging
Argon + Helium (25–75%)	Ar/He blends	Higher heat input for thick sections	All grades, esp. 316, 309, duplex	Improves travel speed and penetration on thick parts
Pure Helium or He-rich mixes	100% He or 75% He / 25% Ar	High heat input, better for thick material	Not typical for stainless unless thick	Expensive, harder arc starts

🔍 Gas Selection by Stainless Steel Type

1. Austenitic (301, 303, 304, 316, 321, 347)

• Best Gas: Pure Argon
• Alternative: Argon + 2% Hydrogen for cleaner, brighter welds (especially 316)
• Notes: Avoid hydrogen on thick, multi-pass welds or if cracking is a concern

2. Duplex (2205, 2507)

• Best Gas: Argon + small % Nitrogen
• Purpose: Nitrogen helps retain proper phase balance and pitting resistance
• Important: Nitrogen may be added to both torch and purge gas

3. Ferritic (409, 430)

• Best Gas: Pure Argon
• Avoid: Hydrogen blends (risk of hydrogen embrittlement)

4. Martensitic (410, 420)

• Best Gas: Pure Argon
• Caution: Preheat and post-heat are often needed; avoid reactive gases like hydrogen

5. Precipitation-Hardening Stainless alloys (17-4PH, 17-7PH, 15-7PH)

• Best Gas: Pure Argon ( A gas lens setup like a Furick fupa12 can make a huge difference for these alloys)
• Notes: Clean welds are critical for mechanical properties 

🔄 Back Purge Gas (for full penetration or sanitary welds)

Gas Type	Usage	Notes
100% Argon	Most common for purging inside of stainless pipe or tubing	Ensures no oxidation or sugaring
Argon + Nitrogen (up to 5%)	Often used on duplex	Helps retain corrosion resistance
Nitrogen (100%)	Acceptable in some duplex or tank welding	Should be paired with proper procedure qualification

⚠️ Pro Tips

• A dual flowmeter is a convenient way to purge
• Always use high-purity gas (Grade 5.0 or better) to prevent weld contamination.
• Use gas lenses for better shielding coverage on stainless TIG welds.
• Avoid CO₂ in shielding gas for TIG—it's reactive and causes oxidation.
• purge flow rate depends on several variables but usually around 10–20 CFH for most stainless applications; adjust based on cup size and draft conditions.
• For sanitary welding, purging the inside is just as important as shielding the arc. make sure to  use appropriate flow rate to avoid suck back on inside