Thread: How long is too long?

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.

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.

Originally Posted by Legion

. . . . 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.

Somehow I doubt it is fluid, even when the metal is still visibly red hot some of the slag might not be molten. Try poking at it with the chipping hammer.

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

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.

I am curious, can you cut the welds and check what they were like right at the restart.

No, they're part of a trolley now. But I could do it as an experiment if I remember.