# TIG joint critique



## abarthx19 (Jan 13, 2008)

Hi,

I'm getting very close to welding up my first TIG welded frame. I've been practising extensively on some 1.5mm thick, 1.5" diameter mild steel tubing that was kindly donated by a British frame builder, and I've got to a stage where I feel pretty comfortable welding this stuff. Now that I've got nearly all of the tubes for the frame mitred and parts for the jig and heat sinks machined, I have moved on to 0.035" thick tubing.

Below are some photos of my first joints on 0.035" Chromoly tubing (1.5" & 1.25" dia). I've only got a limited supply of chromoly to practice on as its quite expensive in the UK, and I therefore want to make every practice joint count.

I think these joints have come out ok (at least better than I had expected), but I'm hoping that some of the more experience TIG welders on this forum will be able take a look and comment as necessary.

I prepped the tubes by mechanically cleaning with some fine emery cloth, then washed them with some non solvent degreaser, and finally wiped them over with Isopropyl Alcohol. The filler rod also got a bit of emery cloth and alcohol.

Welder parameters:

312 stainless filler rod.
Max amps set at 54 amps.
Foot pedal control. No pulsing.
Small gas lens with No. 8 cup.
Argon flow at 7L/min (15 cuft/hr - I think?)
6-7 seconds post flow.
1-ish second down slope.

I've been using 312 stainless filler rod as that's the nearest to Weldmold 880t that I could find in the UK - though I have now bought some 880t from Walt, but am keeping that back for the frame itself.

I think I could do with increasing the down slope time as there are a couple of small craters at the end of the welds. Also there is some blackening on the inside of the tubes and some surgaring along the path of the filler rod - hopefully back purging the frame will help control this.

A couple of questions:

- The joints don't looked cooked to me, but there is quite a bit of colour variation (gold, blue, purple) compared with other welders joints that I've seen on this forum - is this OK?

- Am I putting too much heat in to this joints - is the HAZ too big?

- I know my bead spacing is a little inconsistent but do the size/shape of the welds look right for a structurally sound joint?

Any comments / advice is appreciated. Thank you for your time.

Mark


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## RCP FAB (Jun 15, 2011)

They look a *little* on the hot side to me. Not terrible though.

The beads look good, except the 4th picture, it looks like you welded over a weld there.

From what I have experienced, the coloring is might be from not enough post flow. When using stainless filler, the weld needs to be shielded a little longer than with normal er70 filler. Again, nothing that looks bad.

One thing that I would watch out for, in pictures 3 and 5, you can see where the bead has gone off track toward the mitered tube. The heat tends to eat away the edge of the mitered tube more than the tube its against. Pointing your torch toward the unmitered tube a bit will help with this.

I ramp down the voltage with my foot, while swirling the torch slightly to get rid of craters, probably over 3-4 seconds.

Here a picture of the top tube/seat tube weld on one of my frames. You can see the darker colors at the top, where the tube is welded to the nearly 3mm wall stainless seat tube insert.

https://lh5.ggpht.com/-eJL9XYuzRjk/T1VUY3tg3sI/AAAAAAAAAlM/tI1Bwkci5Qg/IMAG0083.jpg?imgmax=1600


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## 18bikes (Jan 15, 2007)

I wonder who donated that tubing? What a kind fellow he must be 

Looking good in my opinion. Personally I would have the welder set higher and be running faster. Like you've already pointed out a bit more care at the end of a pass is needed.I'd also try some practise stuff back purged before committing to a frame. I would also suggest trying some joints that replicate a frame. THe areas I struggled with (partly due to access in the jig) are the left side of the BB shell and the inside of the head/top/down tube joint - can be tricky on a short headtube with big tubes and a dirty great big jig in the way. Try welding some of that nasty tubing into something vaguely frame shaped holding it together how you will be on the real thing, this will tell you which positions you need to practise and which ones you are find with

I'm sure someone with more welding experience will be able to comment on the welds but I would happily ride a frame that looked like that. Just needs a few tweaks and attention paying to the bead spacing to get them looking really good

EDIT- Looks like someone beat me, I agree with the above comments but would still be happy to ride a frame that looked like that (provided it wasn't made out of some stupid thin tubes)

hope this helps
matt


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## jay_ntwr (Feb 15, 2008)

I'd ride that without any hesitation. The rest of how you improve will be 90% cosmetic.


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## kampgnar (Apr 13, 2007)

Looks good, better even than some advertised _"custom frame builder"_s.

There are select areas of nice consistency which will become throughout after more hood time. The beads in the acute fillet areas are tough and you have done nicely there.
When it comes to end craters, dabbing a bit more filler in right before tapering will help. I even at times leave the rod in the puddle as I taper and pull it out right before it solidifies, which seems to give a bit more control keeping the end consistent with the rest of the bead.


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## abarthx19 (Jan 13, 2008)

*another practice joint - this time back purged*

Thanks for the feed back guys.

I've had a go at another practice piece today:

I altered the settings slightly:

Max current up to 60-65ish amps.
Increased the post flow time a little.
Down slope increased to 3 seconds.
Argon flow to 8L/hr.
Back purge at about 5-7L/hr.

























I used some of the Weldmold 880t (at 0.9mm thick, the 312 rod was 1.6mm thick). I think I prefer the fatter rod (I've some 1.2mm 880t to try out to yet).

I also had ago at back purging these practice joints (sorry about the really rubbish photo).









The gas hose made it a bit harder to get the piece in a comfortable position, and I burnt through at one point as I was off balance. The hose pulled out a couple of times loosing the argon so I had to stop, fix and re-purge, but the photo below shows that where the back purge was maintained it made quite a difference to the inside of the joint compared to the original piece (on the left).









One thing I have noticed with the back purge is that the inside of the joint has 'dropped' almost forming a little trench along the path of the filler rod. I'm sure this can't be a good thing - would adding more filler / using a larger dia filler help prevent this?

Matt, I like your idea regarding using some of those nasty tubes you gave me, to practice on within the jig to get an idea of the awkward parts. It should also help get me thinking about the whole build process / sequence.

Last summer I built up a saw horse using some of those mild steel tubes as a means to push me out of my comfort zone with regard to awkward welding positions: First TIG project - logging sawhorse - MIG Welding Forum I think practising welding in the jig will help with getting comfortable with out of position welds.

Cheers,

Mark


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## RCP FAB (Jun 15, 2011)

Looking good. I can't stand using anything smaller than .045 filler myself. .035 feels like you are constantly feeding it in.


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## TrailMaker (Sep 16, 2007)

Much improved!

I'm by no means a TIG master. Far from it. The thing I think you might think about is knowing what position you will place the frame in to do your next bead so you can move there quickly and get back to welding before the heat is lost. Those welds look very nice with the "exception" of the start/stop points being very obvious. I myself struggle with getting in a position where I can really do a long pass, and then also with rolling around the miter as I go. I am very much a "static position" welder right now, and also struggle with my arms out in the air and not braced against something, and this makes it difficult to get beads without obvious transition points. Knowing before hand exactly where the frame will move to so you can strike your arc again as quickly as possible is part of the art, but perhaps not thought of so readily.


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## customfab (Jun 8, 2008)

In the first set of photos your weld gets a little heavy and rolled up in some spots. Your getting a slight amount of cold roll in those spots. Your also not tying into your other passes all that great. You can see in one of those shots where one pass just doesn't line up with the other. 

Your second set of shots look much smoother and tied in all the way around. But at the amperage you are running I think your travel speed has to be really slow. 

Your doing a respectable passable job, but there is always room for improvement. FWIW I saw frames at NAHBS last week that had welding ten times that bad! At this point you've got it all you need is more time behind the hood.


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