Helium & stainless ?

If you have a stick machine, you can get some beautiful welds with it using some stainless rods. That assumes that you are welding mild-steel and stainless.

You can probably do the same welding ss to ss, too. Not sure

With 15 years of welding instruction under my belt, that has got to be the worst book I have ever heard of.

Did you mean TIG?

Argon is the main gas used with TIG.

OK I am going to let the "structural stainless welds" thing slide for now, but yes you can use pure Helium to TIG stainless steel. It does have a hotter arc than Argon, but can be difficult to get the arc started. The best balance is a mix of Argon and Helium.

You do not want to MIG with pure Helium.

To MIG stainless steel, you can use Argon/CO2 (C25), but it will give a lot of grey oxide around the weld area. This is the most common gas for MIG welding steel. For better effect on stainless use a tri-mix gas. Either Argon/CO2/Helium, or Argon/CO2/Oxygen.

For MIG aluminum, you can use pure Argon or an Argon/Helium mix gas.

Your best strategy for MIG is 2 tanks. One of C25 and the other pure Argon.

But that book isn't alone. Even the manufacturers of welding wire suggest that.

CO2 is not recommended (exception up to 2.5% and NOT 25%). It increases carbon content in the weld and thus it will rust.

Don't know why you repeat your statement from time to time but never prove it.

Read here:

Nick

NO, read the fine print. Yes you use Argon, but not PURE Argon.

I just read that entire page and all it mentions are a Argon/Helium/CO2 tri-mix (as I suggested) and a Argon/Oxygen gas mix for spray.

I can see that. Where on that page does it say anything about using PURE argon for MIG on Stainless?

The increase in carbon by using C25 is inconsistent at best. If you are using a 308L filler the lower carbon content of the wire should offset any you might pick up from the gas.

I am NOT recommending the use of C25 for stainless, but a lot of people do use it.

I just live-mix a tri-mix using Helium and C25.

I am quite aware of the process of Chromium Carbide embrittlement in Stainless welds.

Chromium Carbides don't do much to make Stainless welds rust, since they don't drop the chromium content that much. They can cause welds to crack under stress since they are harder than the surrounding metal, like marbles in cookie dough.

What makes stainless welds rust is disassociated iron particles in the surface. If you passivate the weld then you will not get rust spots.

You suggested (with limitations) Ar + 25% CO2. Right? | To MIG stainless steel, you can use Argon/CO2 (C25)

It will *rust*

If you read a bit between the lines, they say that yo can go *up* *to* 2.5% CO2. It is the CO2 that has an influence on corrosion. | 90% helium + 7.5% argon + 2.5% CO 2 has no effect on corrosion

It can be used. And it doesn't affect corrosion. | 99% argon - 1% oxygen is predominantly used.

The influence of 1% O2 is not that huge.

That is right. With low carbon alloys, it increases the carbon-content, with high carbon-alloys the carbon-content is decreased. It is good not to use it at all when you don't want to add/remove C. CO2 disintegrates to C + O2. The O2 can pick up carbon, the C can add carbon. I don't know where the line is.

| To MIG stainless steel, you can use Argon/CO2 (C25) OK, shouldn't you have said: Do not use C25? :-)

Ah! That is a different story! But then you might say how much CO2. Not that people think he's talking about Ar + 25% CO2 and they can leave out the He, because they don't need penetration. What you mix is (I guess):

90% He + 10% C25. That results in: 90% He, 8% Ar, 2% CO2

Nick

Nick, you are basing your strongly worded position on something you read in an Internet document. Ernie is basing what he wrote on YEARS of experience. I have been to Ernie's shop and seen dozens of stainless railing parts all beautifully welded together. I'm not asking you to change your position in any way, just to tone it down a little. Really, Ernie knows what he's talking about. Bear in mind that when you read what is written by people who sell things, that they may have a hidden agenda, and also the person who wrote it may have not fully understood what he was writing about, or finally, that it was written 100% correct but some editor changed things around a little and made it sound completely different. Ernie welds stainless - a LOT. His reputation is excellent. If some Harris tech writer says you can't weld stainless with C25 because it will rust, and Ernie says the free iron can be dealt with by passivation and it won't rust, then my money is on Ernie.

Grant

WOW, You have obviously never run spray steel MIG with an Argon/Oxygen mix. Argon/Oxy is about the hottest gas mix around.

1 or 2 percent oxygen creates and incredibly hot arc that practically vaporizes the filler wire. It isn't used as much nowadays because spray MIG has dropped way off in use. Dual-shield has taken spray MIG's place at top wire feed process indoors. It is cleaner and creates a better weld with less heat.

I was running welds with 98/2 Argon/Oxy about 24 years ago on full penetration 2" plate steel welds. It is a screaming hot process.

I won't say DON'T USE IT, because it does work, and for non-critical welds it gives sufficient shielding as long as you can mechanically clean the weld area afterwards.

No, more like 50/50 C25/He Which would yield 50% He, 38% Ar, and 12% CO2.

Interesting. I'd always thought that oxygen was always recommended for welding stainless. Am I to understand here that if I'm using dip on thin stainless sheet, then I might as well stick with the non-oxygen tri-mix I've already got and not bother scrounging up an oxygen mix at all.

Oxygen Tri-mix and helium tri-mix gasses both work well for production MIG welding of stainless.

Argon/Oxy mixes are best for MIG spray process on heavy plate steel.