MIG Welding Stainless Steel With Pure Argon. Is It Possible?

By Bill Byers / March 26, 2019
MIG Welding Stainless Steel With Pure Argon Title Image

You have a stainless steel project to weld and you have a tank of pure Argon or

You can get a tank of pure Argon

You have some stainless steel wire and now you want to know: Is MIG welding stainless steel with pure Argon possible or even recommended?

Can you Use Pure Argon For MIG Welding Stainless Steel?

No.

100% Argon cannot be used to MIG weld stainless steel.

Using pure Argon as a shielding gas results in an unproductive electrical arc and an atmosphere that doesn't support the arc to melt the stainless steel base metal well or produce a good molten puddle of metal and a strong weld.

You will have a weld that has:

Minimal weld penetration of the stainless steel base metal.

Your filler wire will sit proud in a mound on top of the base metal.

You will have excess spatter as you weld, spatter that will need to be cleaned off your stainless steel.

Essentially a weld that isn't any good at all. Don't waste your time.

But Why I hear you ask?

Let us understand some basics of MIG welding Stainless Steel.

Why is shielding gas used at all?

MIG Welding Use Of Shielding Gas

MIG Welding Use Of Shielding Gas

The stainless steel MIG welding wire requires certain electrical features and an environment created immediately around the weld to do its job - the job of producing a good, robust weld.

The electrical arc produced by your MIG welder melts the base stainless steel and your welding wire so that they flow and fuse together to form your weld.

While the metals are hot and molten they are particularly vulnerable. Vulnerable to the Oxygen, Nitrogen and Hydrogen in the air we breathe. If the atmosphere is allowed to come in contact with the molten stainless steel it would affect the metal badly. And in contact with your hot melted stainless steel a weld with porosity would result.

MIG Welding Porosity Example

MIG Welding can produce Poor Results with Porosity

Porosity are holes both at the surface and under the surface of your weld that will cause your weld to failed under stress. The last thing you want.

Using pure Argon as a shielding gas delivered to the point of the weld, where the arc melts the metal, provides a barrier from the surrounding air that is true.

The shielding gas's job is to also help with the type of arc that is produced. Pure Argon just doesn't allow the arc to have the right characteristics and this is mainly due to insufficient Oxygen in the shielding gas. Pure Argon is just that - pure Argon.

When you choose your shielding gas the aim is to use a shielding gas that assists in producing an effective weld that has excellent strength to last a long time.

What else can I use if I can't use pure Argon gas?

I'll get to that but know this first.

As Well as Shielding Gas your MIG welder Needs to Produce Enough Amps

Amps or voltage is the fuel for your electrical arc.

Too low an amperage and your MIG welder's arc will struggle to melt the filler metal and or your stainless steel base metal. And the result? A bad weld.

At the other end of the spectrum is too high an amperage with you blowing holes through your base stainless steel. The extreme being molten metal on the floor around your feet. Damaging your stainless steel base metal - you know the stuff you wanted to fix - is the last thing you need.

To Prevent This Some questions to Ask Yourself

  • What is my MIG welder capable of? How many Amps can it produce?
  • What wire size can my MIG welder feed?
  • What type of stainless steel do I have to weld?

And just as critical

  • ​What am I trying to achieve with the weld?

​Why is this important?

Because if the weld is not critical, doesn't need to look good, you can be freer with the choice of tools you use.

  • Does the weld need to look good? Are you happy if you have weld spatter or discoloration of your stainless steel weld?
  • How does your weld need to perform over time?
  • Are you welding thin sheet metal? Thin gauges of stainless steel are more susceptible to weld decay - Intergranular Corrosion. So you need to maintain enough heat, yet weld at the lowest heat possible to produce a strong weld and good penetration of the base metal.

To clarify further

  • Is it weight bearing? If the weld fails how would it affect someone?
  • Does the stainless steel need to stay rust protected?

For example does the part live outside exposed to rain, humid conditions or the sea?

  • Is it in the food industry? Minute holes or rust areas in your stainless steel weld, where microbes could live and multiply, would cause people eating the food to get ill or worse.

Then welding the right way with compatible shielding gas along with the right stainless steel welding wire to maintain the corrosion resistant properties should be your aim.

How much Power Does My MIG Welder need to Weld Stainless Steel Well?

Most home use, home workshop MIG welders used on 120 volt circuits use a short circuit transfer method.

Short Circuit Wire Transfer

Short Circuit Wire Transfer

​What is that? I hear you say.

It is literally the method used when the MIG welder's electrical arc melts your stainless steel welding wire and transfers it over to the molten weld pool.

The beauty of the short circuit method is that it uses lower amps.

And why Tri Mix (90% Helium, 7.5% Argon, 2.5% Carbon Dioxide) shielding gas is recommended by the welder manufacturers.

Tri Mix shielding gas supports the arc in the short circuit transfer method and protects the weld pool at this lower amperage.

Close Up of MIG Welding With Tri Mix

Close Up of MIG Welding With Tri Mix

​You will still need your MIG welder to be able to produce 130 Amp which is why manufacturers that support stainless steel MIG welding with their 115 - 120 volt MIG welder recommend Tri Mix is used.

If you can get a suitable tank size, can afford Tri Mix and have the space, then go ahead and use. You'll get great results.

Tri Mix Stainless Steel Weld Profile

Tri Mix Stainless Steel Weld Profile

​The Issues With Tri Mix

  • Tri Mix may not be available to buy in your area.
  • It's common to find that you can't buy Tri Mix in small convenient cylinder sizes from local welder suppliers.
  • Or your welder suppliers can sell you Tri Mix but the smallest tank size they have is 300 cubic feet.  And that is way too much for your small project.
  • Or perhaps you just don't have the space for another tank of gas in your work shop.
  • Maybe you're just shocked at the cost of Tri Mix - it is not a cheap gas mix to buy.

And if that is why you're considering using pure Argon.

Don't go there. You will be wasting your time and gas.

Can you MIG Weld Stainless Steel with Argon Gas?

Yes.

Although pure Argon gas cannot be used to weld stainless steel less than 100% Argon gas mixes can be used.

MIG welding stainless steel with an Argon gas mix needs a shielding gas with a minimum of 5% to 2% of Oxygen gas in the shielding gas mix.

It is possible to find stainless steel MIG welding wire that supports C25 (75% Argon and 25% Carbon Dioxide), which is great. Because if you are MIG welding already the odds are that you already have this gas mix in your workshop.

Try to look for a manufacturer whose brand of stainless steel MIG wire supports and is compatible with C25 shielding gas.

I put together a guide on stainless steel MIG welding wires that can be ordered on-line. Do take a look as I have listed the supported shielding gas be it C25, Tri Mix or other Argon Oxygen Mixes.

Traditionally using C25 to weld stainless steel didn't produce a good looking weld, although the weld produced was functionally strong. With a stainless steel welding wire that supports C25 those issues are mitigated so it is well worth seeking out the right kind of welding wire for your stainless steel project.

Stainless Steel MIG Welding With High Argon Gas Mixes

And by this I mean a shielding gas mix of 98% Argon and 2% Oxygen or 99% Argon plus 1% Oxygen.

A high Argon gas mix pushes your MIG welder into spray transfer mode.

This is where your MIG welder transfers your stainless steel from the welding wire into the weld pool in a fine spray.

Spray Wire Transfer

Spray Wire Transfer

​Spray transfer needs a MIG welder that can deliver enough amperage to put your welder into spray transfer mode. Some MIG welders running on 120 volt are able to get into spray transfer mode but most often this is the domain of larger 230 volt MIG welding machines.

Check the welding parameters sheet of the stainless steel welding wire you plan on buying to find out how many Amps your welder needs to produce to use that wire and the shielding gas mix it needs to be matched with.

Match your Stainless Steel to Your Stainless Steel Filler Metal

Stainless steel comes in different blends with a variety of properties.

The addition of other alloys into the steel produces the stainless steel types. For example Chromium and Nickel are added at different levels. Highly corrosion resistant steels have Molybdenum in them.

Match your stainless steel wire to the stainless steel you are planning on welding. The multiple types of stainless steel is yet another reason to check the welding parameters of the stainless steel wire you plan to use.

Have a 230 V Welder and 100% Carbon Dioxide Gas?

Then welding stainless steel with dual shielded stainless steel flux welding wire is a choice. Take a look here to read all about it. ​

Last Words

I hope I have clarified for you why MIG welding stainless steel is not recommended with pure Argon gas and given you options for shielding gas alternatives. Some alternatives you may already have in your home workshop.

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