New member! Guidelines for Exhaust work..

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Hey guys,New member here and to the world of welding.  I'm a big auto enthusiast and always had people weld me up intercooler piping, mounts, exhaust components, etc. So I just figured I would save some money and hopefully learn a new skill.  I picked up a Lincoln Easy MIG 140 Welder a couple months ago and just getting some time to work on projects.  My first project was going to be creating an x-pipe for my M3.  The oem x-pipe system is stainless so I was hoping to go that route. I believe it's 16GA.  What's the best combo to attack with my current setup?  I read on the forum that the tri-gas is the best setup, but also the most expensive.  I guess I could always use steel and get it powdercoated if it's that much easier.  Thanks in advance for any comments or suggestions!Mike
Reply:getting a good weld with anything less than trigas on that machine will be trying in the best of circumstances. i would do a fair bit of tinkering welding before i would want to do stainless exhaust. maybe get some scrap mild steel and spend a weekend playing with plain co2 before worrying about stainless.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Originally Posted by turkgetting a good weld with anything less than trigas on that machine will be trying in the best of circumstances. i would do a fair bit of tinkering welding before i would want to do stainless exhaust. maybe get some scrap mild steel and spend a weekend playing with plain co2 before worrying about stainless.
Reply:I use 98% Ar, 2% CO2 for stainless work.  The weld puddle has more fluidity than the short-arc friendly tri-mix.  This could be a problem for a new welder on thin tubing.  The gas is about 1/3 the cost of tri-mix.  Others have also had luck with 98% Ar, 2% O2, but I think that leaves too much chance for oxide formation.Note: If you go with stainless, you should solar flux or purge the back side.If you are going to use carbon steel, you *can* use 100% CO2, but the penetration profile might be an issue on thin tubing.  That, and the fittings for CO2 are not the same as for Ar, CO2, He and blends.  A common mixture for carbon steel is CO2 up to 25% with the remainder Ar.  However, there is a clear benefit to CO2, cost.  You get a lot more bang for your buck with CO2 since it is a liquid in the cylinder.I don't know of anyone who powdercoats exhaust pipe.  Most carbon steel tubes I have seen are either plain or aluminized.
Reply:Originally Posted by FegenbushI use 98% Ar, 2% CO2 for stainless work.  The weld puddle has more fluidity than the short-arc friendly tri-mix.  This could be a problem for a new welder on thin tubing.  The gas is about 1/3 the cost of tri-mix.  Others have also had luck with 98% Ar, 2% O2, but I think that leaves too much chance for oxide formation.Note: If you go with stainless, you should solar flux or purge the back side.If you are going to use carbon steel, you *can* use 100% CO2, but the penetration profile might be an issue on thin tubing.  That, and the fittings for CO2 are not the same as for Ar, CO2, He and blends.  A common mixture for carbon steel is CO2 up to 25% with the remainder Ar.  However, there is a clear benefit to CO2, cost.  You get a lot more bang for your buck with CO2 since it is a liquid in the cylinder.I don't know of anyone who powdercoats exhaust pipe.  Most carbon steel tubes I have seen are either plain or aluminized.
Reply:Originally Posted by WCM3Well, another project I'm working on is intercooler piping.  The current pipes are stainless but I would like to route them differently.  It'll be 2.5" stainless I would like to use again.  Do you think I should try the 98% Ar / 2% O2 mixture?  Like I said, I'm new at this and would need to purchase some stainless wire as well.
Reply:I would strongly recommend that you stick with a tri-mix for short-circuiting of stainless, especially considering your machine.  While a 98/2 (O2 or CO2) mix will offer better performance in some areas your little machine lacks the amperage and voltage needed to take advantage of these traits.  The He content of the tri-mix will aid in heat transfer and the CO2 will help with the wetting and puddle fluidity.98/2 mixes are more commonly seen when doing axial or pulsed spray transfer where much higher amperage/voltage is used.  Heat transfer is no longer a problem with a 300-400 amp machine, but the high Ar content adds to the stability of the arc (smoother spray) and the O2 or CO2 helps the puddle flow better.Last edited by sn0border88; 02-24-2011 at 03:57 PM.Have we all gone mad?