304l stainless exhaust tig welding questions

[presure2]

Hey guys, getting settled in with my power pro 205, got a buddy coming by tommorow so I can set him up with an exhaust b-pipe, that will incorporate an electric cutout.
Here is a pic of one I made for a friend a couple years ago using my 110v mig machine, to give you an idea of what im going to be doing.





It will be fabricated out of 3" 304 stainless mandrel bends, and 3 bolt, 3/8" stainless flanges, and will incorporate the same style cutout that's in the pics above.

I ran a couple beads tonight, as practice, I have some dolor flux arriving tommorow to use on the inside of the joints.
Will have 1/16th and 3/32" lanth. Tungsten available, started off with ~ 50 amps without filler on some butt joints that seemed to go well, filler (using 308l 1/16 filler) needs help. Lol
Anyway, wondering if you guys could help with cup size and gas flow settings, and also maybe some suggestions on amp settings for welding to the flanges? (tubes are .065 wall)

Thanks in advance!
Manny

[Jason]

I ran 45-48a with about 5-6LPH gas with 1/16 1.5%lanth tungston with 308L 1/16 rod on 304 SS 16ga. I don't have any close-ups of the exhaust but I do of my catch can which is the same exact pipe.

This was done with a #4 cup but I used a 5 or 6 on the exhaust.. I forget which.


I did get good color in my weld.

[worntorn]

This is .065 wall 308. I don't watch the amp gauge much but I did happen to glance at it a couple of times while welding up this system. It was in the 38-42 range, no pulse.

Please excuse the big hickey in the weld, that is my Buddy's tack weld job, still trying to get him to tone those down so that I can go over them.
He likes to set the machine for about 150 amps then hit the pedal (no filler) for a tack. This is along the lines of a method Jodie suggests, and it works great, but I generally use about 75 amps or so to tack 065, not 150.

Glen

[jakeru]

.065" stainless tubing, TIG welded?

Read up, right here...
http://www.everlastgenerators.com/fo...-Welding-Video
Attachment 2433

The settings for buttwelding .065" stainless that gave these great results were, in a nutshell...

large diameter gas lens & cup
(that big cup, which looks like a #12, takes 30 cfh gas flow! Looks like he is using a WP-17 torch. 1/16" tungsten)
...
butt welding of .065" tubing without pulse
(he states with 45 amps and a .045" filler rod)
...
butt welding with low speed pulsing
(he states 90 amps peak, 10% background, 30% pulse duty cycle, and it looks like about ~1.5 pulse per second)

The solar flux on the inside of the joint is a really good idea, to help your stainless buttwelds get penetrated, and strong.

[presure2]

Thanks for the tips and pics guys!
I watched that series of vids, Jake, they are awesome, arnt they?!
It's where I got the basic settings that I started with, and yup, they seemed to work well.
I was posting to see if you guys were using diffrent settings with your machines, and from the looks of it you guys are in the same ballpark, so I'll go with that, and report back as progress is made.
What are you guys' thoughts on filler vs no filler on an exhaust like this? Right now my welds on the stainless are much nicer looking without the filler, but it seems like from what I've read you need the filler for the strength.
Thanks again guys, keep the sugesstioms and tips comin, lord knows I could use all the help I can get!

[worntorn]

I use filler rod if there is a visible gap in the fit. If the fit is very tight, no filler is needed. This is in reference to the slip fits as in the pipe shown in the photo I posted. These fits are done with a hydraulic tube expander, a new tool in the arsenal. We had to get a bit of practice in to make the fits just right so that they could be welded without filler.

Before we had the expander all of the fits were butt welds, so I always used filler rod, even if the fit was good. Otherwise the welds end up concave and rather shallow.

Glen

[presure2]

Thanks for the response, glen.
My buddy bought the car and parts over for the work, he bought a used exhaust cutout, which seems to be mild steel. I'll have to pick up some 309 filler tommorow.
He also got thinner wall ~.055 304 bends from jegs.com, so just keep that in mind if you ever get exhaust parts from them (why he didn't get them from mandrelbends mandrelbend.com I don't know)
Im going to do my very best to get good fitup with the tubes, I'll start with a few less amps seeing as how they are thinner than what I practiced on.
Pics tommorow!

[jakeru]

For butt welding, I would go with a small bit of added, small diameter filler rod for max strength if available. Especially if the fitup isn't totally "precision fit." Otherwise, agreed with glen you're likely to get some undercut, and below 100% penetration, which means below 100% strength through the weld joint.

Like Glen mentioned he sometimes does, I have gotten away using "no filler" on tight-fitting stainless lap joints. No filler usually allows quicker travel speeds and less heat input, IME.

Attachment 2438
Here is one example of a spec miata racing exhaust muffler weld that I made. I am sure I used a little filler to weld the slot-cuts, and I may have used some here and there sparingly on the lap weld, but I probably didn't use much on the lap weld. A joint like this also doesn't need any solar flux or backpurging, since you needn't penetrate the puddle all the way through to the inside of the tubing, like you would on a butt joint.

IMO, form should generally follow function with welding, and especially true on something like an exhaust system that's underneath a car. That is my philosophy anyway.

Get the full penetration and strength first so it won't crack later down the road (some engines vibrate a lot, and i've seen exhaust welds crack before, so it's possible.) And worry about getting the "perfect aesthetics" down later. You *can* get a pretty nice aesthetic relatively easy however, using pulsing and no filler rod. I think it takes a lot more practice to get a real even uniform bead width and deposit pattern adding small diameter filler rod. I know I am not quite there yet. Just because I haven't practiced TIG welding stainless tubing butt welds enough yet. I can make functionally sound welds though.

I'm pretty sure I used a #8 gas lens cup on the above weld. (It's the largest gas lens cup that I have.)

[jojobead]

when i welded steam coils we ran argon in side pipes .put rag in one end an argon tube in other with rag wedged around it.we had root opening 35 deg bevel 3/32 land.just don't have to much pressure that way u don't have carboration inside