[KiwiDave]

Hobbyist welder here with *some* TIG experience making headers and exhaust plus other automotive odds and ends. I've never been able to get a good looking weld (shiny silver / light yellow ... not fussed about creating a rainbow) in my projects, so am seeking some help from those more experienced before I take on my next project which I'd really like to look good.

What is shown is fairly typical of my results, and I played around a bit with this tube mock up (first time back on the torch in a while) ... as low as 40A and up to 85A for the smoother / flatter weld shown, which is also the inside section shown.

I cleaned tungsten, filler (1.6mm or 1/16" 316L) and parts with acetone. As shown I was using a glass lens and 2.4mm (3/32") tungsten on this 316L SCH10 pipe.

Tips and ideas of what to try next ?? I've cut the pipe ready for another attempt.

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[tweake]

i don't normally do much that thick so i'm sure others will have a better idea than me.
however it looks cooked, typically that means travel speed to slow. going fast enough on small diameter tube/pipe is a challenge.
that looks like a single pass to me, i would try doing 2 passes instead.

also use a bigger cup, i use a jazzy 10 for doing tube.

[cj737]

I’d echo some of what Tweake said. A couple of other things: I can’t imagine why you’re using Sch10 pipe for exhaust tubes? That’s sporting a 0.109 wall thickness. Generally speaking I use stainless tube, not pipe, and run about 0.045-0.058 for exhausts.

Are you straight cutting the ends? I’d bevel slightly with pipe that thick. Also, the gas lens/cup looks to be a cheaper Amazon unit. Bin it. Get a quality CK/Miller/Furick lens and set of cups. It makes a huge difference. I use #10-#16 cups for exhaust tubes. I also use pulse with no filler. Never had a crack yet.

1.2pps, 50% on time, 25% background. For 0.063 tubing I run 55amps. Solid welds, full penetration and fully purged.

[tweake]

I can’t imagine why you’re using Sch10 pipe for exhaust tubes?

i think hes making manifolds. thats a pretty common method here for turbo manifolds.

[Arno]

i think hes making manifolds. thats a pretty common method here for turbo manifolds.

Yeah.. Especially turbo manifolds that are expected to also 'carry' the weight of the turbo and not use extra struts/supports.

Regular 304 stainless gets pretty malleable at exhaust temps close to the head so it needs the wall thickness to keep it al from drooping with a turbo hanging off of it. 321 stainless or inconel you can go much thinner wall as they don't weaken nearly as much under heat.

One thing to add.. Perhaps go to a ceramic cup with the gas lense too. Personally not too fond of the transparent style that just uses a push-fit with an O-ring on the threads. Always seems like a potential air/oxygen ingress point with the oxidation as a result.

Travel speed is king on these and also doing short runs and letting the piece cool and not saturate in heat before getting on it again. On a manifold like this, once tacked together, it's common to 'jump around' between the various pipes so the others can cool in the meantime.

Also, doing small tube sections each time (eg. quarter) means you can combat distortion in the manifold by doing opposing weld sections to pull it back in line. It'll still move on you but should be manageable. Also the smaller sections mean you usually can get a bit more comfortable along the travel distance which also helps with the speed and result.

Altough manifolds inevitably tend to get really tricky in some parts near collectors and the like where access gets... 'difficult'

Planning out your welds for access is critical as it's the classic situation of painting yourself in a corner if you don't.. (or cheat and have difficult pieces metal 3D printed )

Bye, Arno.

[cj737]

Well if it is for a turbo inlet manifold, I’d be using 321 or even 347 with a welded mounting plate. The tube thickness of 0.63 will hold the weight easily. But I stand by original post, never seen Sch10 used as exhaust tubes.