What is the best shield gas for MIG welding 304 SS? 1

[EdDanzer]

We need to fillet weld small areas of .047 thick laser cut 304 stainless sheet. This is not a structural part, but does need some weld strength .025 308L wire seems too large so I would like to try .010 304 wire. What are some of the different shield gas mixes to try and the advantages to each?

 

[rnd2]

Ed,
I have been out of mainstream MIG welding for 14 years but as no-one has replied may as well have a go.
We found MIG shielding gas improved the weld strength and toughness by increasing % helium. Provided the overal arc characteristics remain smooth.
I always believed (never was certain) the small size of a helium molecule compared to argon and CO2 was useful to purge hydrogen out of the weld.
Pure helium and Pure CO2 produce a rough short-arc.
Argon produces a low voltage smooth spray arc.
Unless you want to set up and mix your own, proprietary gas mixtures are available with combinations of all the above gases including small amounts of oxygen.
One of the things you may want to try because welding very thin ss with MIG is extremely difficult, is to position the weldment on a slope and direct the shielding gas via a remote nozzle because a coventional nozzle completely shrouds the contact tip. With the right gas and nozzle arrangement to properly shroud the weld pool on the slope, it can assist enormously to reduce the distance the contact tip from the weld. This benefits the arc characteristic as well as helps direct the arc to the required spot.

 

[metengr]

Here is a web site by Praxair that has an excellent review of various shielding gases for GMAW (MIG). The web site should provide you with background on selection of the appropriate gas mixture.

http://www.fibralume.com/Praxair.ns...6519006c5ea1/f406fc8ace1333648525656100775f5a

 

[GRoberts]

You probably do not want to use helium in your mix as it leads to a hotter arc, and burn through will be more of a problem. A low energy mix suitable for stainless mig welding that is popular is 98% Argon, 2% O2

 

[sayee1]

The 2% O2 is required for wettability. If you use pure Argon with MIG-SS welding, the bead shape and weld metal characteristics make it difficult to weld. 98%Ar 2%O2 will be my preferred choice too.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[unclesyd]

I going to have to recommend an old reliable source for information on welding gas. He hates gas salesman.
He gets carried away but the info is good.

http://www.weldreality.com/default2.htm