Shielding gas question

By StephenK Date 06-25-2007 21:45

Hello,

I'm fairly new to welding and I have a question about shielding gasses.

I am using a Lincoln SP125 Plus 110v mig welder.

I do automotive work, specifically 409 stainless exhaust systems and intercooler systems. I also do fabrication of parts with a combination of stainless and mild steel.

I need to be able to weld stainless to stainless and stainless to mild. My local welding supply store has told me that to weld SS I will need to use 529 Trimix or the welds will be poor. They tell me that I can't use the Trimix to do mild steel.

So I'm in a bit of a corner here.. if this is true then I will need 2 bottles one bottle of 75-25 argon/co2 and another bottle of 529 Trimix.

Is this true?

By Lawrence (*****)

Date 06-25-2007 22:14

Your real limitation is the puney power supply.

309 stainless FCAW would be a good choice for your mild/stainless welds and could be done with 75/25 but I'm skeptical if a a roll of 309 FCAW can be fit on your little machine.

You could short circuit weld solid wire stainless and carbon steel with 98/2 Argon/Oxygen

Tells us the exact gas balence of your Trimix and somebody will tell you if it can work with plain carbon steel.

By StephenK Date 06-25-2007 22:21

I'd have to call the welding supply place and ask them.. they said it was a Helium trimix 529.

The machine does the job just fine.. I've done mild steel exhaust systems before no problem. The wire I typically use is .030 solid. I'm not talking about doing any heavy duty welding here.. just automotive exhaust.

By Stephan (***)

Date 06-26-2007 07:50

Stephen,

there was a fine thread a time ago and initiated by "Kix" in the forum's "Shop Talk" Section, see also:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=59069;hl=#pid59069

Perhaps it is helpful to use some of the information been contained in the answers (including links) some of the gentlemen have frankly given at that time, for responding - at least partly - your questions.

By the way, I am nearly sure - and thus agreeing 100% with Lawrence - to be able to use only one shielding-gas for both applications "Stainless to Stainless" and "Stainless to Mild Steel".

Ar/2-3% CO2 or Ar/2%O2 might be a reasonable choice to accomplish good results.

Regards,
Stephan

By js55

Date 06-26-2007 13:24

Welding suppliers love to sell the more expensive, and most often unnecessary gases. Stephen is right. You should have no trouble finding one gas to do both, as suggested here.
Myself, I find the statement by your supplier as, "welds will be poor', at best humurous. At worst irresponsible.
Poor how? Be more specific. You're the supplier. Is it really too much to ask that you actually help me?

By Kix

Date 06-29-2007 20:19

Go with the 98/2 argon/co2 because for the mild steel end of this spectrum your only welding exhaust pipe and automotive stuff so this will be plenty suitable. For the stainless this gas will work also, but i recomend going to a ER308L stainless mig wire. I know your suppose to use 309L for stainless to carbon, but for your application it will do just fine ya just have to trust me from experience. For some reason the 308L runs a lot better with the 98/2 argon/co2 mix then it does the 309L. The price of Helium tri mix is going through the roof and you don't get as much in a bottle as you do with just a Bi mix.