First attempt at welding Stainless

[Biscayne]

Hi,
I need to weld some stainless for a chimney cowl I am making (the ones you can buy never seem to last very long) so I got setup with Clarke 0.8 stainless wire and a disposable bottle of pure Argon for my 151TE. Before setting to work I tried a few welds on a small bit of scrap, to get a feel for the correct settings. Results below. The lumpy bits were on too low a current setting.

Does anyone know why all the brown/black sooty deposits? I tried turning up the flow way past the maximum setting (more than 1 turn on the regulator) and I could hear the gas flow out of the nozzle OK. Seemed to be coming out at a fair rate at maximum setting. Although I was welding outside, the site was sheltered and there was no wind.

I went on to weld the cowl, with the same results. The soot brushes off easily enough with a wire brush.

Is it possible that the gas isn't Argon or is soot something to be expected when welding stainless?

Any help most welcome.

 

[nfinch86]

Mig Welding - Stainless

Hello;

In Canada we use C-25 or one of several Tri- Mixes for mig Welding stainless Steel.
C-25 = 75% Argon & 25% Co2
100% Argon should be used for welding Aluminum !

........... Norm
www.NormsMobileWelding.blogspot.com

 

[backpurge]

You shouldn't be using straight argon to MIG/MAG weld stainless.

You need a small amount of active component in your gas mix, either argon + 2% O2 or argon + 2.5% CO2, as norm says you can also use three component mixes which have varying amounts of helium in them but to be honest these are not normally needed for "hobby type" work

 

[Biscayne]

Thanks for your replies.

I bought 100% Argon because I thought the 75/25 Argon/CO2 mix was a bit heavy on CO2 (I think Malcolm's notes on welding stainless suggested only 2-3% CO2). These are the only choices I have using disposables.

Last night I tried 75/25 but the results are exactly the same. I guess the 'soot' must originate from somewhere else. The base material is a good grade (316) but the wire is standard Clarke so I don't know what grade it is.

Anyway, the cowl is finished and should be installed at the weekend. Time will tell if the welds will perform OK.