DIYbanter - View Single Post - Tri-mix VS Bi-mix gas for 304SS welding

Terry Coombs[_2_]

wrote:
On Wed, 30 Dec 2015 14:56:12 -0600, "Terry Coombs"
wrote:

wrote:
To All,
So another SS welding job has come my way that would benefit,
timewise, by using MIG instead of TIG. I have a Lincoln SP125 Plus
welder and will be welding 1/16 maximum thickness 304SS for this
job. According to Lincoln my welder should have no problem doing
this weld as long as the right gas mix is used. C25 gas is about
1/3 the price of Tri-mix with 90% helium. I tried using flow
gauges to mix C25 with pur argon in order to get a Bi-mix ratio of
98% argon, 2% CO2 which Lincoln recommends, but I wasn't real happy
with the appearance of the welds. This could be because the flow
gauges weren't accurate enough, or I couldn't set then accurately
enough, or that the gasses didn't mix properly (which I doubt), or
because I can't weld worth a ****. Or it could be because the welds
would look crappy no matter who did the welding because 98% argon
2% CO makes crappy looking welds. I could try the mixing trick with
the oxygen but I don't have a flow meter that is for a low enough
flow. So I am thinking about buying a cylinder of 98% argon, 2%
oxygen. Can anyone here give me good advice about how well the 304
will weld with .030 308lSi wire and 98%A, 2%O mixed gas?
Thanks,
Eric

Why won't pure argon work ? Is MIG that much different from TIG ?
I've never used SS in my MIG machine , it interests me to know what
to expect if and when I do . I have 2 "flow" guages , but only one
is actually a flow gauge the other is a cheapie .
I did try TIG with C25 once, it wasn't pretty . I think the SS
takes up carbon from the CO2 .
Greetings Terry,
Pure argon won't work for MIG because the SS needs an "active" gas to
get hot enough. When using TIG the heat is of course controlled by the
arc between the tungsten and the work, but with MIG all the heat can
only come from the actual arc between the filler metal and the work. I
have tried pure argon with SS before I knew better and it doesn't work
very well. Tri-mix with 90% helium works well partly because the
helium doesn't carry the heat away as much as other gases. But it
costs a lot and I won't be using it much so I would rather use a
cheaper gas mix.
Cheers,
Eric

OK , thanks . With the cost of SS MIG wire I'm probably not going to go
there now that I have a TIG machine but it's good to know .
--
Snag