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Thread: How long is too long?
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21st October 2013, 11:12 PM #1Senior Member
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How long is too long?
Another question, while I'm thinking of it - I've always, when I come to the end of a rod, terminated the weld, waited for it to somewhat cool, clean off the slag and then start again with a new rod. Today a few times, to experiment, when the old rod finished I had a new one standing by, grabbed it, put it in and go again without cleaning off the slag. Maybe 10 seconds at most, when I was out of position one time? More likely 5 seconds the few other times I did it. It seemed to work OK and I guess the slag wasn't cooled right off and was still fluid enough to allow me to continue in the same spot. At least I hope so. Is this acceptable practice? The welds looked OK with no obvious slag inclusions.
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21st October 2013, 11:25 PM #2GOLD MEMBER
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Did you section the welds with a saw and check for slag inclusions, there is no other way to be sure. I would be very surprised if there were no inclusions but destructive testing tells no lies whether cut or broken in a press. At TAFE we always did this no matter how the weld appeared and the answer is not always what you want to see.
CHRIS
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21st October 2013, 11:28 PM #3Senior Member
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No I didn't, but your answer answered my question I guess. Part was non-critical and there is more than enough weld and strength to do what it needs to. But I'll know better next time.
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22nd October 2013, 12:21 AM #4.
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22nd October 2013, 12:34 PM #5SENIOR MEMBER
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The slag and weld pool solidify almost instantly, within a fraction of a second - so there's no way you can swap in a new rod in time to catch it whilst still molten. You can see it solidify before your eyes less than 5mm behind your weld pool - but you knew this anyway I reckon?
It's definitely a benefit to keep welding whilst everything is still hot if you're working on thick stuff where you're trying to maximise penetration, another benefit I can see is that the slag protects your nice new shiney weld from the arc splatter from your next weld but otherwise I can't see much benefit in not raking off the last bit of slag before tying in - it's generally not worth the risk. If you overheat the job you've got more distortion issues, etc. too.
And... there's no way I'd do it with your RB-26's - too much slag. I would only do it with a deep penetration rod that didn't produce much slag (think 6010/6011) where you can be sure you're remelting right through the slag and getting a good tie in.
Personally, I always rake off the last bit of slag and never ever ever weld over slag - not even on those annoying one sided beads you get on low amperage fillets - always grind those little mongrels out.
Cheers
- Mick
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22nd October 2013, 02:21 PM #6Senior Member
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My choice of words - "still fluid enough" - wasn't good. I didn't mean literally fluid, I meant still hot enough to not be in that self-cleaning stage where it cools and scorpions off and/or cracks alone. I thought it was maybe that if I struck a new rod soon enough it would mean the slag wasn't set up permanently and the new rod would remelt it and blast it away if I was quick enough.
But my lesson has been learned, thanks guys.
Sidenote - while looking online for some replacement Gemini 12s I came across one place that advertised them for $15.30 for 12kg! Great, I thought, it'll be worth the postage. But alas, it was a typo, sort of guessed that in advance.
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22nd October 2013, 03:54 PM #7GOLD MEMBER
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I am curious, can you cut the welds and check what they were like right at the restart.
CHRIS
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22nd October 2013, 05:07 PM #8Senior Member
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No, they're part of a trolley now. But I could do it as an experiment if I remember.
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