Welding Reference Library · Gases & Cylinder Safety

Helium and Helium Mixes

Helium makes a hotter, broader arc than argon. It is used alone or mixed with argon for TIG and MIG welding of thick aluminum, copper and other metals that pull heat away fast.

Ref WG-0406AWS A5.32

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Helium is an inert shielding gas like argon, but it behaves differently in the arc:

It needs a higher arc voltage for the same arc length, so more heat goes into the work.
It gives a wider, deeper penetration profile and faster travel speeds.
It is much lighter than argon and rises away from the weld, so it needs higher flow rates.
Arc starting is harder in pure helium, especially in TIG.
It costs more than argon, and supply is often tight.

Helium is usually blended with argon to get some of the extra heat while keeping good arc starting and lower gas use.

How to identify

Cylinder labels show the gas and percentages. "75 He / 25 Ar" means 75% helium and 25% argon. Some suppliers list argon first. Read the label rather than the color or the trade name.

Common helium-bearing gases

Gas	Typical use	Notes
100% helium	TIG and MIG on thick aluminum and copper; DCEN TIG on aluminum	Hardest arc starting; highest flow
75% He / 25% Ar	Thick aluminum and copper, MIG and TIG	Hot arc with better starting than pure helium
50% He / 50% Ar	Medium to thick aluminum	Balance of heat and cost
25% He / 75% Ar	Aluminum and stainless, TIG and MIG	Small heat boost over argon
90% He / 7.5% Ar / 2.5% CO2	Short-circuit MIG on stainless	The common stainless tri-mix

How to use it

Use helium where the base metal is thick or highly conductive and argon alone gives poor fusion or slow travel.
Raise the flow rate compared with argon. Use the procedure or the gas supplier's guidance.
Use a flowmeter calibrated for helium or the blend, or apply the maker's correction factor. An argon flowmeter reads helium wrong.
Expect higher arc voltage and adjust machine settings.

Key points

On aluminum, helium blends can reduce or remove the need for preheat on thick sections. Follow the WPS.
Helium blends can increase travel speed enough to offset their higher cost on production work.
Coded work must use the gas listed on the WPS.
Helium can displace oxygen in confined spaces, mainly near ceilings and high points. Ventilate.

Common mistakes

Using argon flow settings with helium and getting porosity.
Reading helium flow on an argon flowmeter without correction.
Expecting easy TIG arc starts in pure helium.
Swapping argon for a helium blend without changing settings.

Governing standards: AWS A5.32 (welding shielding gases); ISO 14175 (shielding gas classification); the WPS and the gas supplier's data.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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