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Thread: TIG welding SS
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5th Feb 2017, 06:11 PM #16Philomath in training
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Some answers -
a) The material in that first photo is definitely SS (1.2mm thick); filler is 316L (diameter 1.6). Gas is certainly 100% argon - no mixes in the place.
b) Welding on DC, amps controlled with a thumb control but for those welds the maximum was 32A and I was at that. Argon is at 7 lpm a the gauge. I'll try to remember to get a balloon and check that.
c) No. 6 is 3/8" ID? I'll try that tomorrow if there is time
d) Currently around 4m away from the welder and the A/C is behind me and a distance away so I can't feel it. I'm between it and the welding
e) I might be back about 30 degrees but the tungsten is only out of the cup by about 3mm and I'm as close as I dare get.
The cup is an old one and the crud is from a previous bit of welding. I have a new No. 6 though that I'll put on. No one has ever talked about replacing cups or cleaning them so I remove crud occasional but keep using them. I'll try a larger tungsten too. The 1mm seems a bit fragile and I can't tell when I'm grinding it whether it is shiny or not. I don't think any of my electrodes (even straight out of the packet) would be considered shiny - I know the shiny you mean, like the ball end of an Al electrode. Without rushing out and checking, that colour is what I think as normal for electrodes.
Michael
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5th Feb 2017, 06:40 PM #17Senior Member
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I use a #8 if I welding stainless for any length of weld, ie traveling more than a few mm, and if appearance isn't an issue. Actually, I kind of believe the line of thought that its the argon coverage that makes the colours and improves the quality of the weld, rather that just the amount of heat. I bought a #12 gas lens but I've never done any heavier gauge stainless welding to try it since as I mostly like playing with tiny stuff. I also read of someone who said to bend the tungsten to the front of your gas lens so that will maximise the time the hot weld is in the gas, as you move forward. I thought the #12 was a better answer. That is a #6 on my torch now but you can see how huge the 12 looks in comparison. I believe that's how to get rainbow colours etc, if you are into all that. I wanted to try it but haven't done yet. To bend the tungsten, I think he said he just earths it and then bends when it is red hot, but I read that ages ago and can't be sure at all. If you're not using gas lenses I can definitely recommend them because they change the flow of gas to laminar so they flow out further and give better coverage because of the lack of turbulence. That's my tungsten appearance from the last time I used it a week ago.
20170205_181245.jpg
A simple experiment worth trying is get a polished bit of stainless, and do a small spot weld with just 3sec port flow. Watch the colour of the weld change as soon as the gas goes off, it is a dramatic change. Then try it at different seconds post flow and see the different colour, just keep experimenting with time. If your not getting any colour at all, maybe make the spot weld hotter. With different times you can get different colours as the steel is a different temp when the atmosphere gets to it. That's the same deal as you move your torch along a weld route, the hot weld will pick up the colour of its temperature when it exits the argon.
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5th Feb 2017, 11:13 PM #18Golden Member
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Yes, that's right - it's the result of how hot the weld is when it gets re-exposed to oxygen from the air. The colours come about from the depth of the oxide layer that forms. So yellows, blues etc. are still acceptable since the oxide layer is still thin enough not to affect the surface finish without wasting too much gas.
Never tried bending a tungsten, except to break the cruddy tip off
Cheers
- Mick
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6th Feb 2017, 06:37 AM #19Senior Member
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Thanks Mick, so that's why the colours are acceptable, because it means the oxidation is only very thin? I saw a thread where someone had posted "welding " they called it. It did look very pretty, every weld was very even and coloured. One guy said he was an inspector working on nuclear instalations and that it wouldn't pass, even though it was not a bad weld.
What I remembered about bending the tungsten does seem unlikely, doesn't it. Even if you do it while it is still white hot, I thought tungsten kept its hardness even at those high temps, so I'm not sure it would bend.
I never had any luck snapping off tungstens because they seemed to splinter for me, so I cut them off with a cutoff disk. Something that is relevant to low current welding is to use the grinding wheel along the length of the tungsten and not across it, when shaping the point. It helps to use a fine wheel too. I think most manuals say to do that, so maybe its not worth mentioning but its at low current when things like that really start to make a difference. If there are noticeable scratches in the tungsten or if they run round the tungsten instead of along it, they can cause the arc to start somewhere other than at the tip, making the arc bigger and less predictable.
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6th Feb 2017, 10:34 AM #20Golden Member
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There was a guy in WA selling it. I bought two tins about a year ago but wish I'd got more. He imported a whole bunch and once it was gone he wasn't going to get more. It comes in a dry grey powder that you mix with metho and paint on like thin toothpaste. The metho evaporates quickly and some dry powder sticks to the back of the weld. When you weld the front side, the back turns into this glassy flux that protects against oxidation. It's great. You can either leave it on afterwards or it just chips easily off, much more easily than stick welding flux. The only thing to watch is inclusion, but I paint the back side and then just wipe down the weld area with metho rag. Sometimes I get minor inclusion effects, where it pops a bit like galvanised but doesn't seem to bubble the weld like galv. The flux on the back flows like honey with the heat so perfect covering isn't necessary.
Michael, I suspect one of your issues is the same as the one you've always had - you run too cold, move too slowly and dwell too long and that's why your welds look overcooked. That and a few other things like arc length and torch angle are conspiring together.
Your cup and tungsten also tells a story - my tungstens are like needles (I use a dedicated bench grinder with diamond wheels) and my favourite cups are much cleaner even though they're old. The dirty cup suggests to me you're not cleaning jobs sufficiently before welding and they're hissing and spitting contaminant everywhere. The blunt tungsten suggests a wider arc, less focused with more heat going into the piece and less going into the actual weld.
Someone on here (Mick?) once gave me the advice that even test pieces should be cleaned to perfection.
Could it be an epoxy clearcoat or something?
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6th Feb 2017, 08:02 PM #21Senior Member
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You'd be ahead if you can find that lens!
Looks like a 17 torch, here, I use a 9 based one, typically use a 10 or 12 lens (in the large size rather than regular) for SS if no access issues present....you can actually see the difference in the cool down time behind the weld compared to a normal nozzle.
That cup would clean up in a blast cabinet pretty quick too. Attempting to weld gal - or contamination as the others mention, will cause that black crud.
Originally Posted by Michael G
Not quite sure what the task is, but if it's the usual thin SS job, if you get to the stage of adding filler, half the time it's gone to hell in a handbasket already.
Oh yeah, turps and kero I'd avoid, unless there's another clean-up, post doing it.
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16th Feb 2017, 12:13 PM #22Philomath in training
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The temperature is down considerably so I did some more trials.
First, the 'known stainless' piece, welding next to where I'd welded before on the assumption that all the crud had come to the surface and been brushed off.
First photo is with filler and the second without (thinking that filler may be the problem).
P1030837.JPG P1030838.JPG
This is with a 1mm electrode and cleaned up cup.
P1030834.JPG
Then a whole raft of samples. The material is the 0.6mm material I'm trying to use, prepared by sanding the varnish off and then wiping with acetone. The first photo is untouched, the second is after wire brushing. As you can see, they all clean up fine.
P1030840.JPG P1030841.JPG
There are numbers stamped next to the samples and these are -
- 30A, 1mm electrode, 1.6mm 316L filler, 7 lpm argon, with a no. 4 cup
- As per 1 but with a 1.6mm electrode
- As per 2 but with a no. 6 cup
- 30A, 2.4mm electrode with gas lens, 1.6mm 316L filler, 7 lpm argon and a 5 cup
- As per 4 but at 50A and no filler (and moving the torch much faster to try and minimise heat in)
- Pulsed - 50A max, 4pps, 41% on, 25% background current. 1.6mm electrode, 1.6mm 316L filler 7 lpm argon, no. 6 cup
- As per 6 but pulses at 1.4 pps
- 30A, 1.6mm electrode, 1.6mm 316L filler, 13 lpm argon, no. 6 cup
Any other suggestions as to what the problem could be? Even when I hold the torch over the end of the weld so the post flow gas keeps going I don't get a shiny weld as a result
Michael
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16th Feb 2017, 05:32 PM #23I break stuff...
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While my stainless TIGing is pretty ordinary, 2 through 5, and 8 all look either way too hot, or too slow on the travel speed, going by the sunken nature of the beads. Going by the settings you used for 6, I'd say its travel speed, as you ran more amps, and got a better bead profile.
On 0.8 mild steel, I'd probably run around 30A if running beads in the middle of the sheet, so I wouldn't be surprised from that and your tests, if your magic number was around 40A (without pulse). At that thickness metal, 5 amps can make a huge difference...
How far back are you pulling the filler rod after each dip? From my recollection, stainless is pretty fussy about keeping the hot end of the rod inside the gas envelope.... Mick also already mentioned torch angle, keeping up around that 10-15 degrees will help shield the weld just run, and also put the heat directly into the bead as opposed to heating the area ahead of it. Same thing with arc length, it becomes more and more critical as you get down to thinner metals, the closer you can get the more the heat goes directly into the bead, instead of the area around it. Maybe try a few experiments getting as close as you can, right to the point of fouling the tungsten. You may find you need to adjust amperage again when you get that close, it really does make a surprising amount of difference...
And finally, from my own experience experimenting with the TIG over time, don't be afraid to have a crack at some more 'extreme' settings if you're still struggling, you can sometimes learn a lot that way. I'd have a go of 15A and 60A personally, just to see where that got me. You'll need to be real fast on the filler at 60A, but your total heat input may well be less....
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16th Feb 2017, 05:48 PM #24I break stuff...
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One more thing that just occurred to me, I don't see it mentioned already - have you gone over your machine and made sure all the fittings for the gas hose are sealed up nice and tight? At that thickness in stainless, even the slightest bit of air introduced into the gas line could be an issue...
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16th Feb 2017, 06:01 PM #25Philomath in training
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Now that's one thing I can do!
The reason the welds look sunken is because they are - once the first weld went on, the sheet bowed and so there was nothing to hold the molten stainless up. Interestingly the rear of the sheet has some really nice looking beads on it.
I did make an effort while doing these runs to check that my torch was square (or close to) while welding. As for closeness, I would estimate that the tip of the tungsten was 1-2 mm off the weld pool as I had to bring the torch back before adding filler.
The shape of the beads does not worry me though as that is a practice thing. The thing that I am trying to understand at the moment is the colour of the welds. Everyone is telling me that they should be coming out shiny - they are not and I have yet to find out why.
Gas should be good - I have arranged my hoses to minimise strain on them so should not have cracks or anything but I'll check with the soapy water.
Next chance I'll try with very low amps - at the 40A per mm rule I should be around 24A so as you suggest perhaps 15A or 20A is the go, but then a couple of people have said that I'm running too cold - hence the reason for 50A, no filler and moving along briskly
Michael
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16th Feb 2017, 06:31 PM #26Golden Member
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16th Feb 2017, 06:45 PM #27
What grade of SS are you using for your test pieces, is it ferritic or austenitic?
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16th Feb 2017, 06:47 PM #28I break stuff...
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This, from my experience, would be an indicator that your amps are too low, and you're having to make up for that by traveling slower, putting more overall heat in. The bead really should not sink through on a flat test piece, in my opinion anyway.
My approach to this sort of thing is to get the beads looking like sound welds without excessive penetration first, then worry about the shiny finish once I've got to that baseline. Generally, the shiny finish will often appear on its own once everything else is right, and if not, it should only be a few small adjustments away. That's not to say you can't get there the other way, but I wonder whether you're getting overly hung up on the shiny finish at this stage?
With regard to your 50A no filler test, my gut feel is that your travel speed is still too low. Try going fast enough to only leave a 2mm wide strip on the surface where the base metal has melted, and see how that looks in terms of colour...
Really wish I had some stainless of that thickness lying around, I'd love to have a play and see what settings I came up with for you, but unfortunately I only have some 2mm...
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16th Feb 2017, 07:06 PM #29Philomath in training
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16th Feb 2017, 07:31 PM #30Philomath in training
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Bearing in mind I'm welding 0.6mm stainless, are you suggesting that I should be running around 40A, when you would run 30A on a 0.8mm piece of MS? I would have thought that the reduced conductivity of SS and the thinner material would mean that more amps will just blow holes.
With respect to a 2mm width, those beads are mostly 3mm wide (alright; +/- 0.1mm). In the second photo of post 22, that weld is without filler on 1mm material and the bead is 2mm wide.
As to shiny, the only reason I'm chasing that is because I've had people tell me that SS welds should not need to be wire brushed post weld - they should come out clean/ shiny from the process.
Michael
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