Speeder

I recently aquired a small miller 135xp (mig / flux) and i want to buy some gas and some solid wire that i can use on SS, mild steel and alum. steel? (mix and match, or same material), would tri-mix and 309L/Lsi work?

ComputerJLT

for stainless you'll want to use stainless wire and pure argon
for mild or aluminumized/galvanized steel you'll use l56 mig wire and argon/co2 or straight argon gas

Speeder

the problem that i see is if i use aluminized steel for example, it will be somewhat protected from rusting, but mild steel welds will not. Since 309L/Lsi is recommended for SS/Mild steel welding, would it work decent on just mild steel (and aluminized steel)?

ComputerJLT

carbon steel will rust period. if you use ANY filler on the mild steel it will rust; even using stainless wire. to weld on aluminumizd piping use cheap l56 wire and paint over the joints you weld. thats the only way you'll keep oxide at bay.
and if you use carbon steel wire on stainless the joint will rust there too; you'll have to use uncontaminated stainless wire on stainless to get a rust free weld joint.

Jcushing

normally for stainless you use argon/co2/helium (tri) mix. from what i was told at the welding shop the helium was just there to aid in pennetration so i actually only use Ar/co2 on piping (like exhaust work) and it comes out fine.

and you use 309 filler for combining mild steel and 308 SS
and use 308 filler on 308 (duh)

straight up argon is for aluminum and purging.

ComputerJLT

you dont want co2 when welding stainless; the carbon will contaminate the weld and cause it to rust; engloid had a big thread on this on h-t a while back

Speeder

so -- Ar/Co2 and 308 or 309 for SS/mix and ER70S-6 (L-56) mild steel and aluminized. steel? argon w/ 10 co2, 5co2? 3co2?

(i want to keep costs to the minimum, so i don't want to buy 25-15% co2/argon mix AND straight argon or 3% co2 argon mix)

ComputerJLT

if your welding stainless to stainless you dont want ANY carbon in there; if you're in doubt or plan on doing some stainless down the road get straight argon. there is no price difference locally. The difference in penetration is probably not noticeable with the different gasses. I used straight argon when welding my aluminumized charge piping after building my stainless manifold.

Jcushing

taken from lincons website.....

"The shielding gas recommended for short-circuiting welding of stainless-steel contains 90% helium, 7.5% argon, and 2.5% carbon dioxide. The gas gives the most desirable bead contour while keeping the CO2 level low enough so that it does not influence the corrosion resistance of the metal. High inductance in the output is beneficial when using this gas mixture.

Single-pass welds may also be made by using argon-CO2 gas. The CO2 in the shielding gas will affect the corrosion resistance of multipass welds made with short-circuiting transfer"

Spray-Arc Transfer

DCEP (Direct Current Electrode Positive) is used for most stainless-steel welding. A 1or 2% argon-oxygen mixture is recommended for most stainless steel spray arc welding.

it depends on the welding process......

page 24 of this PDF file contains the sheilding gas chart for SS for most of the welding types
http://www.euro-inox.org/pdf/map/Bro...ability_EN.pdf

Speeder

interesting PDF.

i found a website yesterday, where a guy was advocating Ar/15-C02 for mild and Ar/3-C02 for Stainless... I wonder where i can get that (one of the places only carries tri-mix, c25 and straight argon (and mentioned that most places only carry that)