sheilding gas for stainless mig

[BrokenBiker]

what is best gas for mig welding stainless? I have choice of
co2,
ar/co2 80/20,
ar/co2 95/5
or straight argon from my current rent free supplier

which do I need for stainless up to around 2-3mm thick

 

[mfletch]

I would say pure argon

 

[BrokenBiker]

I thought that, but on another recent thread people said that argon was no good.

 

[penfold]

MIG on SS will be best with 5%CO2; pure argon will work, but IIRC the arc is unstable or summat like that. 20%CO2 will not produce a stainless weld.

 

[backpurge]

To be honest none of them are ideal but the best of a bad bunch will be the 95/5 mix

 

[BrokenBiker]

cheers penfold, will have to sort out a bottle of 5% then, will stick with co2 for mild steel for now and just use the 5% for stainless. should last a lot longer that way

 

[mfletch]

Is it pure argon for tig welding ss

 

[BrokenBiker]

the argon in tig is mainly to protect the tungsten though, it has to be argon with tig regardless of material.

 

[mfletch]

I see many thanks

 

[BrokenBiker]

I think the main reason it works as a shielding gas in tig and not so well in mig is because tig is constant current supply and mig is constant voltage supply, not sure if this is correct but it is my understanding of it

 

[backpurge]

the argon in tig is mainly to protect the tungsten though, it has to be argon with tig regardless of material.

Depends on the material, you can use argon for TIG welding anything but Ar/H2 is better for austenitics, Ar/He for ally and Ar/N2 for duplex for example

 

[backpurge]

I think the main reason it works as a shielding gas in tig and not so well in mig is because tig is constant current supply and mig is constant voltage supply, not sure if this is correct but it is my understanding of it

When you are MAG welding steel you need an active component such CO2 and/or O2 to "stiffen" the arc, it also increase the penetration profile etc

 

[TechnicAl]

Depends on the material, you can use argon for TIG welding anything but Ar/H2 is better for austenitics, Ar/He for ally and Ar/N2 for duplex for example

Just as an aside

We are now being asked for Austenitics with Low Hydrogen so the ArH2 wouldnt be allowed. Its mad but thats the state of the oil and gas industry.

We use pure hydrogen as the shielding gas during annealing which obviously puts hydrogen into the wire.......we then have to heat treat later to remove it

 

[backpurge]

Just as an aside

We are now being asked for Austenitics with Low Hydrogen so the ArH2 wouldnt be allowed. Its mad but thats the state of the oil and gas industry.

We use pure hydrogen as the shielding gas during annealing which obviously puts hydrogen into the wire.......we then have to heat treat later to remove it

That is interesting, what grades Al

 

[TechnicAl]

Alloy 59 is the first one but we are expecting others, 686 maybe

We are doing Super Duplex 25 9 4 already but obviously thats not fully austenitic.