Most of my work lately has been aluminium but I started today practising fusion welding of some 38mm OD (inch and a half?) mild steel tube with 1.6mm wall thickness (One sixteenth? Two president's fingernail clippings? Something?)
I am using a needle sharp 2.4mm, 2% lanth tungsten. Main amps 60, pulse ratio 33, pulse frequency 1 pps, base amps 20. I'm using a big old Furick cup.
Reasonably happy for a first try but my biggest problem is seeing the weld area. Played with helmet settings but just can't nail it. Esab or Optrel low amp specialty helmet in my future I think.
My main concern...how does one avoid undercut like this when fusion welding? Just less amps?
Reasonably happy for a first try but my biggest problem is seeing the weld area. Played with helmet settings but just can't nail it. Esab or Optrel low amp specialty helmet in my future I think.
Do you get a red flare that covers the puddle ? That is a factor of the lens. It's not an uncommon problem.
If you had a non-auto, you could cure the problem cheaply with a change of lens, autos are a PITA ! Personally I like the autos that give a blue vision.
Last edited by kiwi2wheels on Sat Aug 19, 2017 7:13 am, edited 1 time in total.
When I do low amp work, I use an auxiliary light source pointed directly at the work, away from my helmet. I can adjust the sensitivity of my helmet to it so I don't get flashes.
Regarding the undercut, fusion welds require near perfect fitment lest they undercut. With stainless, it's easier because a back purge helps by preventing the weld from sinking in. I've found it terribly difficult to get a mild steel fused weld to sit dead flush unless I'm moving along pretty quickly. And the Fupa cup isn't necessarily an advantage for the mild steel, but really important for SS.
I'm using a fluorescent light source (lamp) on my welding table but the light from it isn't great and my helmet seems very sensitive to it. That might be part of the problem...
AndersK wrote:Try a 6W led spot instead. Less IR for the helmet to trig on.
Nice first try though.
Thanks Anders, good tip.
I have resolved to try all sorts of different lights as the fluoro seems to send my helmet bananas with little provocation. I am also considering drawing lines either side of the fit up seam with black market to help guide me. Maybe I can just aim for the area between the marker lines? Although it's very likelt to burn off before I get there. Engineer's chalk maybe?
Me? Thinking out loud?
Finally, I have some very fine ER70S2 Mig wire...I'm going to try using this as filler rod with the same settings just to see if I can build up the weld area a tad.
You didn't mention what shade# you have set, I would use #9 for something like that. That might help you see better.
Is there a reason you need to weld this without filler? What you did looks great, but I'm not sure you'll ever get rid of that slight undercut unless the fit up is absolutely perfect, or you use filler. You might also try pulsing at a higher rate (like above 30), which will still help reduce the heat input but will allow you to move independently of the pulse speed. I find that at 1pps I'm pretty much forced to time my torch movement to the rate of the pulse.
Lincoln Square Wave 200
Lincoln 225 AC/DC
Harris Oxy/Acetylene torch
MosquitoMoto wrote:
I am also considering drawing lines either side of the fit up seam with black market to help guide me. Maybe I can just aim for the area between the marker lines? Although it's very likelt to burn off before I get there. Engineer's chalk maybe?
I prefer to use a scratch awl. The marker can contaminate the weld and wipe off. The surface scratch, not so much. Also helps you control visually the bead size.
1pps helps me when I work with filler, just sets a 'metronome' for me, but its use is possibly limited without filler. I am actually considering using some ER70S2 Mig wire I have as filler at this pulse rate...will give it a try.
The only reason I've not yet used filler is that I want to keep the weld very flat - I don't want to spend ages grinding welds to smooth the exhaust. In fact I'd prefer not to grind at all, but just to have subtle weld marks.
(And not hide anything under damn hipster pipe wrap!)
I will certainly try a faster pulse rate. The scratch awl is a good tip, too. Oh, and Mark, I am using shade 9 at the moment.
Again, thanks for the tips - I will post up pics of next attempts asap.
Can you switch to stainless? It fuses much better, especially with a back purge. You could try using a purge with mild steel to see if that helps. But at the end of the day, fit-up is hyper important for fusing tubing.
A sidebar: I would encourage you to use stainless wire for the welds (if a filler is used). It will be far more resistant to corrosion in your exhaust. As you know, the insides of these pipes rust due to condensation before the exhaust sufficiently warms the pipe and evaporates. Even a small drilled hole (chamfered) at low spots is a good idea to allow the moisture to wick away. Just yakking a bit regarding motorcycle exhaust scenarios.
Low carbon steel joints with tig really require the deoxidisers that fillers provide which is why fusion joints can lack strength and longevity. If you want to tig your exhausts and have flat joints try using er70s-6 filler with good fitup and pulse.
As much as I'd like to use stainless tube, I can't find it in the diameter I need. I'm going for the very best fitup I can - I learned early that its worth the prep. Next step, as mentioned before, will probably be to use Mig wire (ER70S2) as filler, with pulse.
Coldman wrote:Do you have ER70S-2 mig wire?, it's not commonly used. Most common mig wire is ER70S-6 which would give you a better result in this case.
Interesting. Mine is S2, but I can get my hands on some S6 no problem if you reckon it would be better.
