[Joe Jones]

I am on a road trip right now, but I want to get back to my home and workshop to start building huge wind sculptures out of stainless steel. I have done a lot of MIG welding, but never with stainless wire or the associated gasses.

Is there anything special I need to know about this process? I have a big bottle of "Tri-Gas" which I was told to use for Stainless.

The metal will be 14 gauge stainless, and the pieces will probably be shaped using an English wheel or a planishing hammer.

I tend to "GO BIG" so for an idea of what I want to build, check out the You Tube videos of the Andrew Howe wind sculptures!

Joe

[Poland308]

What grade of SS?

[Olivero]

No mixing gases, use 100% pure argon for stainless and just regular 308L wire.

Run like a breeze.

[Coldman]

You need trimix. Pure argon will give a grey/ black looking weld that won't polish out.

[Olivero]

You need trimix. Pure argon will give a grey/ black looking weld that won't polish out.

Really?

I was always told it was supposed to be pure.

[tweake]

You need trimix. Pure argon will give a grey/ black looking weld that won't polish out.

Really?

I was always told it was supposed to be pure.

mig really wants to have an active gas component for a good arc. but i think you cannot have high co2 due to the carbon. so its either a low co2 mix or an o2 mix.

[Poland308]

You can use pure if you need too. But a mix is better.

[weldin mike 27]

100 percent pure for aluminium only

[Arno]

Snippet the Lincoln website:

the recommended shielding gas to use for short circuit stainless steel MIG welding is a tri-mix shielding gas, such as 90%He/7.5%Ar/2.5%CO2. The high thermal conductivity of helium helps provide a flatter weld bead and good fusion into the base plate. While high helium blends can be more expensive than other types of shielding gases, the high percentage of helium in the mix helps counteract the cold, sluggish bead characteristics. Another acceptable shielding gas mix for short circuit stainless steel MIG welding is 98%Ar/2%O2 (or an equivalent 98%Ar/2%CO2). This latter mix produces a colder weld than the helium tri-mix and therefore the molten weld puddle does not wet out as well.

Also:

you do not want to use the same type of shielding gas that you use with carbon steel wire, such as 75%Ar/25%CO2 or 100%CO2. Both carbon and oxygen from the shielding gas react with the stainless steel in the heat of the arc, resulting in some oxidization and reduction in corrosion resistance. The maximum level of oxygen or carbon dioxide that should be used in a shielding gas mix with stainless steel is 3% or 5% respectively.

Part of the difficulty with MIG on stainless is it's lower electric and heat conductivity which makes it harder than on mild steel to get a good weld bead and penetration with short-circuit MIG.

98%Ar/2%O2 or 98%Ar/2%CO2 is probably the cheapest and most easy to get (helium ones are pretty expensive..). Good idea to do some trial runs and see what you need to change as far as machine settings go to get the weld bead you want/need on stainless.

Bye, Arno.