Shielding gas for GMAW on 304 stainless

Date 01-06-2004 17:30

Can I get people's thoughts on shielding gas for short circuit transfer GMAW for welding 300 series stainless.

I have been told the recommended gas is 90% He 7.5% Ar 2.5% CO2, but , if possible, I would like to avoid having another gas mixture for a process that is used only occasionally. I have heard that 90% Ar 10% CO2 works, but that it can increase the carbon content of the weld metal, leading to carbide precipitation.

Any comments would be appreciated

By Niekie3 (***)

Date 01-06-2004 18:42

Hi H.Dibben

I do not think that either of the gasses you mentioned are ideal. There may be very high speed welding applications that would justify shuch a high He content, but I believe it is an overkill. Also, the 10%CO2 is just too high for most S/Steel applications.

The typical gasses used are:

Ar + 1-3%O2
Ar + 1-3%CO2 (Not recommended for extra low carbon requirements.)

It is suggested that an Ar+He+O2 mixture is somewhat better for short-arc welding than those given above, but it will certainly not give you the flexibility you are looking for.

Hope this helps.

Regards
Niekie Jooste
Fabristruct Solutions

By sparx

Date 01-06-2004 19:05

The mix of Ar/He/CO2 is exceptional on light gauge short arc stainless...but that is pretty much it. you can get away with some other blends.. the 1-5% O2 or 1-4% CO2 are great for heavier plate... Ideally though, the helium blends seem to work best on short arc.
hope this helps.

By dee

Date 01-07-2004 05:34

H. Dibben,
If you are unaware of Ed Craig you may find his site very helpfull. He knows gas

http://www.weldreality.com
D

Regards
d

By jon20013 (*****)

Date 01-07-2004 14:28

I agree with all of the postings above, especially the Ed Craig one. In our own application we use 98% Ar, 2% O2 but we only use GMAW in the spray and pulsed modes.

By Sean

Date 01-08-2004 16:51

Dear Harold,

Any shielding gas with less than 3% CO2 will work when welding GMAW 300 series stainless steel. The shielding gas that you have specified is designed for short circuit transfer. If you spray transfer with this shielding gas at high voltage you will get oxidation.

The large amount of CO2 in the 90/10 mixture will break down and react with your allowing agents leading to carbide formation. There are some other tri-mix gases that will also work with stainless steels; however, if use one with a lower amount of He (which is the most expensive component in the tri-mix gas) you can save some $.

I agree with Niekie that an Ar + 1-3%O2 would probably give you some more flexibility. There are a number of industrial gas suppliers that can provide a 98% Ar 2% O2 mixture.

Sean