On Fri, 1 Jan 2016 13:24:03 -0600, "Terry Coombs"
wrote:

wrote:
On Wed, 30 Dec 2015 21:26:03 -0600, "Terry Coombs"
wrote:

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

Yeah, the MIG wire is about 13 bucks a pound. But the faster speed of
MIG over TIG will more than make up for any extra up front costs
because I will be needing to buy wire. I do have SS MIG wire but not
the correct alloy. The alloys I have don't have the extra silicon
added. Lincoln recommends the silicon because it helps the weld bead
wet out better. This morning I ordered an oxygen flow meter that has a
low enough flow so I can accurately mix in the 2% oxygen to the 98%
argon. I'm also gonna make a new gas mixing tube. Since I have oxygen
here at the shop it will be easy to see if a bi-mix gas will work for
me. Better than buying a cylinder full only to find out it won't work
for me.
Eric

Ok , I 'm going to jump out on a limb here and guess - the only way I can
see that this can work is to have flow controls that operate at the same
pressure , and flow is controlled by something like a needle valve . That
won't work with what I have , my cheapie is just a regulator with a pressure
gauge calibrated (and not well at that) in "CFM" .
The flow meter outputs will be connected to a manifold that is
pressurized much lower than either flow meter because the manifold
connects to the gas hose for the MIG torch. So I think as long as both
flow meters show flow I'm OK.
Eric