[Mojo88]

Recently bought new AlphaTIG200x machine and just getting comfortable with it. For now, I will be using it to TIG stainless steel (SS) exhaust systems. In the old days, I mainly used O/A or MIG, but the pipes were steel (not stainless).

So anyway, I am looking for best prep and techniques for a nice clean butt-weld joint.

I'm interested mainly in:
1) Cutting the SS pipe: any danger of contaminating SS by using cutoff wheel?
2) Angle of the cuts for butt-weld: should it be perpendicular, or chamfer?
3) Cleaning the weld area: wire brush and/or use acetone?
4) Fitment: how big can gaps be before issues?
5) Holding pipes in alignment for tack welds: best method?
6) Autogenous or use filler rod: is it 'best' to strive for autogenous?
7) Brush wheel for cleanup: what works good for cleaning weld area when done?

PURGING: I will be purging, which seems straightforward enough.

Thanks for any tips. Dave F. in Rhode Island

[5th Street Fab]

Recently bought new AlphaTIG200x machine and just getting comfortable with it. For now, I will be using it to TIG stainless steel (SS) exhaust systems. In the old days, I mainly used O/A or MIG, but the pipes were steel (not stainless).

So anyway, I am looking for best prep and techniques for a nice clean butt-weld joint.

I'm interested mainly in:
1) Cutting the SS pipe: any danger of contaminating SS by using cutoff wheel?
2) Angle of the cuts for butt-weld: should it be perpendicular, or chamfer?
3) Cleaning the weld area: wire brush and/or use acetone?
4) Fitment: how big can gaps be before issues?
5) Holding pipes in alignment for tack welds: best method?
6) Autogenous or use filler rod: is it 'best' to strive for autogenous?
7) Brush wheel for cleanup: what works good for cleaning weld area when done?

PURGING: I will be purging, which seems straightforward enough.

Thanks for any tips. Dave F. in Rhode Island

1. When I started at my old shop we used a chop saw for a couple years. Then switched to a band saw and then to a laser. In any case we used a belt sander to grind them flat and take away any possible contamination. Then we deburred the inside and out.

2. It depends on thickness and preference. We used .035 and .049 wall thickness anything over that and you may want to think about bevelling or you'll be putting too much heat into it.

3. For cleaning we used red scotch bright and then wiped it with alcohol. We had a 12 or 16 inch wheel and would brush and the pipe. But when I started it was all by hand.

4. The smaller the pipe the smaller your gaps have to be and especially if your autogenious welding them. With us we couldn't have any gaps. had to be touching all the way around. If it doesn't you can cheat a little and weld the section with filler, then grind it down and repolish and brush it. Then make your seem with a dremel so you can see it while welding.

5. I used to use a hollow pipe with one end capped. Then I made a small Valley down the center Maybe 1/16" deep. Then I drilled holes every half inch. Just tape the holes you're not using. I would put this in a vice and run a purge line through the back. I could use it to weld seems on large parts that are hard to purge or to tack pie cuts. When I tacked parts I would slip them over the bar and rest them on it. Then I would line them up how they needed to be oriented. Then I would use my torch cup to push them perfectly flat butted together and put a quick fusion tack. And I tack often at least every 3/4" especially on flat sheet metal. We wiped them with alcohol before tacking and also before welding. If my tack got to big or the haz was visible I would grind down the tack and rebrush the part.

6. It's personal preference. We did tubing autogenious and brackets and things that needed more strength with filler. If your bevelling your pipe In My opinion you should use filler because your removing metal and making it weaker.

7. We didn't do anything after welding because we wanted the color left on. So it depends on what you want.

I think we purged around 5 cfh.

Anyways hopefully this helps. All this info is from my personal experience. And is my opinions.

Sent from my SM-G920V using Tapatalk

[Mojo88]

Wow, that's a great reply, thanks very much! Much appreciated.

Can I ask you to look at this autogenous weld that I just did on 2.5" pipe (.060" wall thickness)? Is coloring ok? I have some bluish coloring there, not sure what that is but I have heard that coloring should be NOT blue?

How about smoothness and consistency?

Pic 1 - freshly welded


Pic 2 - cleaned with wire brush

[Arno]

Purging, good!

I hate exhausts that are made without purging and the big globs of oxidised metal that creates on the inside of the pipes

For bigger pieces that may be hard (or expensive) to purge you can alo use Solarflux B:

https://www.amazon.com/Weldcote-Metals- ... B00IN6JXT2

Use some methanol to create a paste/slurry and coat the back of the joint with it. Let the methanol flash off and start welding.. It creates an almost glass-like cover on the back of the weld once you light up and protects it that way. (can also be used with O/A welding as a normal flux also on the front)

Not something I use all the time (I'm just a hobby welder that makes his own exhausts) as I normally purge, but it's a good extra tool to have for some areas/conditions where a real back purge is difficult.

Bye, Arno.