mig welding stainless steel 304. gas?

[krmoto]

Hi, I have b.o.c argoshield universal that l use for mild steel, l have also been using it for mig welding ss 304 and it seems to work well, is this a big no no? because on the boc site it says not reccomended for ss because can cause brittle welds and the carbon pick up (whatever that means) but it also says some grade's of ss inc 300 series are hi carbon content and will not be affected so much.

so can l carry on or stop and get a boc stainshield light/universal
please help cos l'm confused

 

[weldingscotty803]

what stuff are you welding? i had to weld two pieces of 40mm solid 304 round bar yesterday, could have tigged it but it wasnt worth the hassle. didnt need to be 100% penetration etc. bevelled the edges on the lathe left a 2mm gap then root and capped it. then turned it flush. job done. done with cougar 5 (co2 argon) and 316 wire.

 

[krmoto]

what stuff are you welding? i had to weld two pieces of 40mm solid 304 round bar yesterday, could have tigged it but it wasnt worth the hassle. didnt need to be 100% penetration etc. bevelled the edges on the lathe left a 2mm gap then root and capped it. then turned it flush. job done. done with cougar 5 (co2 argon) and 316 wire.

I am welding 304 1.5mm box to 1.5mm box and 1.5 box to 3mm plate, with 308LSI wire.

 

[hotrodder]

With regards to the carbon pick up... carbon can nick some of the chromium (forming chromium carbides), result is less corrosion resistance, maybe worse. CO2 is broken apart by the arc providing a source of carbon, welding creates the temps necessary

There are high carbon 300 series alloys but unless you ask for 'em (say 304H) then you'll have a low carbon flavour, designed to be pretty much immune to carbide precipitation, at least unless some carbon is added

What to do... depends on the finished product, service environment etc

 

[krmoto]

With regards to the carbon pick up... carbon can nick some of the chromium (forming chromium carbides), result is less corrosion resistance, maybe worse. CO2 is broken apart by the arc providing a source of carbon, welding creates the temps necessary

There are high carbon 300 series alloys but unless you ask for 'em (say 304H) then you'll have a low carbon flavour, designed to be pretty much immune to carbide precipitation, at least unless some carbon is added

What to do... depends on the finished product, service environment etc

cheers for that, good link, learn summut every day

 

[TechnicAl]

According to BOC "Argoshield Universal is a three component mixture of 16% carbon dioxide and 2.75% oxygen in argon."

It isnt suitable for stainless. It should make the weld go black (oxidised) which will result in very poor properties

 

[backpurge]

For most stainless MAG welding your best option is going to be Argon plus 2 to 3% CO2 (a good mix for thin sheet carbon steel as well due to the low heat input) without any O2 additions as you get in Argoshield/Coogar type mixtures.

If your doing a lot of stainless and you want a really "pucker" job it may be worth looking at one of the stainles specific MAG gases that contain betwen 25 and 80% Helium but these are quite expensive so obviously the job must warrant the extra cost.

Would avoid the previously popular Argon plus 2% O2 gases like the plague, end results are pretty rough compared to Argon/2.5% CO2 mixes