blueshift
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| posted on 27/10/05 at 08:50 PM |
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Gas bubbles in welds.. help
I am starting to fully weld my wishbones, and want to get some advice about gas bubbles in the welds. It seems my tack welds have bubbles of gas in
them which end up in the final pass.
In this photo I ran the welds from top-right of the picture, in both of them I started just before a tack weld which I knew had some bubbling in it
(because I filed most of it off)
I ran the welds with 0.6mm wire at 5/6 power on my Clarke 140E MKII (140A) MIG, at what I deemed to be the right wire speed for the power.
The tack welds were made at 6/6 (full power) with the same wire, which was reccomended to me but seems to be pushing the limit of what can be done
with 0.6mm wire.. needs a high wire speed, but too high and it skips and does odd things.
I associate the gas getting into the welds with working at full power, running some test beads I got some evidence of bubbles coming to the surface at
full power, but the 5/6 power beads were fine (and felt "right" when welding)
Any advice on how to stop this gas issue would be welcome (and how to sort out the bubbles that are there now)
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JoelP
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| posted on 27/10/05 at 08:52 PM |
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not to do with the bubbles, but upping to a 0.8mm wire allows you to slow the wire speed down nicely, makes it a lot easier.
I partly squeeze the trigger to start the gas for a second before i squeeze it all the way and start welding.
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Triton
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| posted on 27/10/05 at 08:58 PM |
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Porosity there me duck...(techy nerdy weld speak)
You have to keep the shroud clean and up the gas pressure as that looks like it is set too low or even running out.
The best advice is scrap that one a do it again......as all that "mint aero" has to be ground out.......
Mark
My Daughter has taken over production of the damn fine Triton race seats and her contact email is emmatrs@live.co.uk.
www.tritonraceseats.com
www.hairyhedgehog.com
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Mark Allanson
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| posted on 27/10/05 at 09:05 PM |
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I can tell by the rest of the weld that the settings are spot on. Stick with the 0.6mm wire, at the end of the pass, trigger off for a split second,
then back on for about 1/2 second. this prevents a concave crater forming at the end of the weld and gives a good gas cover.
I think the problem is with the tack welds, and any trapped gas in them will find its way to the surface. Try gently grinding or filing the tacks to
the absolute minimum size to hold it together.
Welds are looking good though!
Mark
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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blueshift
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| posted on 27/10/05 at 09:45 PM |
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Thanks Mark 
Do you agree with Triton that this wishbone is scrap? or could I grind out the porus area and run a weld over it or something?
The tubes to take the bushes and balljoint are odd sizes, from GTS, and I have (had) exactly the right number. Going to be a pain to get more.
However, I don't want to risk safety, I know the wishbones are one of the most highly stressed parts of the car (which is why I'm using
1" OD tube instead of 3/4"
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NS Dev
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| posted on 27/10/05 at 10:27 PM |
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agree with Mark, nice weld apart from the aero!
Grind the porous bit back into the good weld a bit and see what you find. If the good bit is good underneath then you should be ok to reweld the bad
bit.
If you were selling it then I guess it would go in the scrap bin but if you don;t mind a slight imperfection then it should be ok if ground out and
redone.
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stevebubs
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| posted on 27/10/05 at 10:51 PM |
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One thing I did find with my Clarke Welder was that I could press the handle slightly and start the gas flow without current.
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britishtrident
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| posted on 28/10/05 at 07:35 AM |
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Were the surfaces completely clean and dry defore the weld ?
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blueshift
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| posted on 28/10/05 at 04:36 PM |
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Thanks gents. I will attack them with a grinder tonight and take a file to the other tack welds in case I find anything suspicious.
Trident, the 'bones were certainly dry, and they were wire brushed pretty hard before starting. I got the steel pretty shiny before I built the
bones so very little rust on them. There may have been some wd40 left on them however...
Is it worth sluicing things off with brake cleaner before welding? or something else?
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Minicooper
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| posted on 28/10/05 at 05:09 PM |
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Your Gas pressure is low or the gas is been blown away, it's only the last quarter of an inch of the welds grind a little out and reweld.
Your welding apart from the slight porosity is far better than some I've seen on wishbones from so called proffesional companies
David
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blueshift
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| posted on 29/10/05 at 10:35 AM |
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I think the switch on my welder is single action on/off, I may have a look at it and perhaps bodge in an extra gas override switch.
I find the wire feed is very dependent on the straightness of the torch lead too, from looking at the electronics the feed motor seems to be current
controlled, so I have been pondering making a PWM controller for it...
... on the other hand I am learning to use it to my advantage, rotating the torch to put more kink in the lead lets me vary the wire feed as I weld
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