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Moisture in low hy rods. No problems,right??

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  • Cornerstone
    replied
    Originally posted by maharg View Post
    U.T. would not pick up diffusable hydrogen,you are correct it is at a microscopic level.
    Hydrogen cracking ( cold cracking) usually occures 24 to 48 hrs after welding if left at room temperature,or a few hrs if held at 200'c, that is why you usually wait 24-48 hrs before performing any NDT. and that is why sometimes it is referred to as cold cracking.
    Preheat slowes down the cooling rate giving more time for diffusable hydrogen to escape from the weld.
    Hydrogen cracking requires a hard microstructure (matinsite) stress/strain to initiate a crack.
    This is why an arc strike (martensite) outside the Heat Affected Zone is an undesireable defect,and just fileing alone does not remove the defect.
    Thanks for the explanation maharg. Xray was performed as soon as the weld cooled and I believe Mag Particle was carried out also. I did comment to the NDT crew about the state of the rods before I put them in my rod can for a few hours and there was no concern on their part. Bob.
    Last edited by Cornerstone; 06-30-2011, 08:11 AM.

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  • maharg
    replied
    diffusable hydrogen

    Originally posted by Cornerstone View Post
    "..diffusable hydrogen" Is that something microscopic that even UT would miss?
    U.T. would not pick up diffusable hydrogen,you are correct it is at a microscopic level.
    Hydrogen cracking ( cold cracking) usually occures 24 to 48 hrs after welding if left at room temperature,or a few hrs if held at 200'c, that is why you usually wait 24-48 hrs before performing any NDT. and that is why sometimes it is referred to as cold cracking.
    Preheat slowes down the cooling rate giving more time for diffusable hydrogen to escape from the weld.
    Hydrogen cracking requires a hard microstructure (matinsite) stress/strain to initiate a crack.
    This is why an arc strike (martensite) outside the Heat Affected Zone is an undesireable defect,and just fileing alone does not remove the defect.

    Leave a comment:


  • Cornerstone
    replied
    Originally posted by maharg View Post
    Even though you might be getting away with clean welds (no porosity) if you use damp/contaminated electrodes you are still putting diffusable hydrogen into that weld,that will eventually escape out of the weld,now if you have a highly restraint joint, one under stress/strain it can and will lead to cracking,the question is when. now is this worth the risk ? only you can answer that question. Use your Electrode oven,its cheap insurance.
    "..diffusable hydrogen" Is that something microscopic that even UT would miss?

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  • Sberry
    replied
    I am sure there is but as an operator I don't notice all that much difference, not that there isn't any but usually at that point didn't care or want paying attn if the rods were wet or not. I have seen new ones have a tendency to porosity and I got to agree that its the unseen that would be an issue.
    My Bud works for a tiling company, they fit and fab a shoe on a machine that took considerable effort, he says,, I will go to the store and get 2 cans of new lo-hi. The company owner (who knows more about this stuff than most people do) says he will go and comes back with stuff he got out of the dumpster of some mfg plant,,, well they work good he figures, you know,, all that stuff is nonsense, just turn the heat up. Well despite the protest and he signs the checks so off they go, weld a couple days. Big long multi pass hi stress joint, about 200 ft to the first big rock, thing was one giant underbead crack, come right off I guess. He knows more about assembling diesel engines than most people do too, another story though.

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  • maharg
    replied
    low hydrogen electrodes

    Even though you might be getting away with clean welds (no porosity) if you use damp/contaminated electrodes you are still putting diffusable hydrogen into that weld,that will eventually escape out of the weld,now if you have a highly restraint joint, one under stress/strain it can and will lead to cracking,the question is when. now is this worth the risk ? only you can answer that question. Use your Electrode oven,its cheap insurance.

    Leave a comment:


  • 1930case
    replied
    Have never had an issue like that before or since. Anyone have any ideas?
    I had some Radnor 7018AC that wasn't baked do that. Nice row of holes like you describe.
    Old unbaked 7018 didn't leave those. Weird.

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  • Cornerstone
    replied
    I know I wont push my luck the next time I leave low hy exposed for a period of time, no matter the time of year.
    Thanks for the great replies fellas, Bob.

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  • hurricunning
    replied
    Originally posted by Cornerstone View Post
    All my welding career I have kept the golden rule of storing any low hydrogen rods in the oven or in a sealed container after opening a box. Why? To keep the moisture off the flux and preventing porosity from entering the weld puddle. Simple rule that should be observed right? Well after last weeks job I'm starting to wonder...
    ...did the few hours at 250F in the rod oven make all the difference?
    Bob.
    Ok here come what some of you might think as bad 7018 welding practices, but...

    In the really cold of winter like -20C and below some Rig Weldors didn't used to use a rod oven if the job didn't require it. New boxes were opened, used and immediately put into sealed rod containers. Very little humidity in the dead of winter in the north.

    I have never had an issue with porosity on any shots except for a couple times when trying to run a cap on 2" in near gale force winds and that was nothing to do with the rods. However, this winter I was in a pinch for rods on a job and opened a box of 3/16" OK55 7018 that had been sitting around my shop for about 5 years. The box had a few rips in the plastic wrap and I was sure they had been exposed to humidity so I was going to use them for non-critical work. No time to heat them in the oven and I used them to roll 4 quick caps on 3". Wouldn't you know it but there was a very fine line of holes down the middle of the cap that came up on the film. These tracks were maybe 2" long in random spots on each weld, not necessarily at the start. They were only evident when really grinding fairly deep, not right at the surface like normal bad start porosity.

    Have never had an issue like that before or since. Anyone have any ideas?

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  • 1930case
    replied
    Figure out how to get hydrogen out of water and you'll make a million bucks :-)
    Separating water into hydrogen and oxygen by electrolysis is common.

    The flux problem is not separating hydrogen from water, but having a flux which doesn't absorb atmospheric moisture or is prevented from doing it by a barrier,


    Flux core MIG wire covers the flux with metal, solving the problem.

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  • Bistineau
    replied
    Too Little Too Late

    Originally posted by wronghand View Post
    Figure out how to get hydrogen out of water and you'll make a million bucks :-)
    It's already been done. The US Navy uses it on nuclear submarines to separate hydrogen and oxygen from seawater to supply the crew with oxygen to breath for extended submergence. The excess hydrogen is discharged overboard. Too late to try and make a million bucks off that idea.Unless you can come up with a cheaper/easier way to do it.

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  • Sberry
    replied
    I would say that I have had the same experience with wet rods but,,,, I would be leery of thinking they were good even if they shot well. I have seen 7018 welds pop right off the base metal especially with some shock, seen it with old rods, the welds looked great, popped right off, nice clean grain underneath, good fusion, picture perfect, bet they would have rayed very clean. Part of it could be the nature of the joint design though. Maybe trapped diffused gas showing up in a problem later?
    Poorly stored rods get used by the millions every day, most of the time without issue. Lots of them left in buckets, picked up where they left off yesterday.

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  • wronghand
    replied
    Originally posted by 1930case View Post
    We've rebaked and rebaked and rebaked practice 7018 rods many times, and they came off a pallet which had sat for years. They bend tested fine.

    That doesn't make it a great idea, it just means safety regimes are designed with some practical tolerance in mind.

    It WOULD be better if the industry came up with low hydrogen fluxes that didn't require baking.
    Figure out how to get hydrogen out of water and you'll make a million bucks :-)

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  • Cornerstone
    replied
    Originally posted by aametalmaster View Post
    i have some 7018 with a blue coating and it welds great...bob
    http://www.hobartbrothers.com/pdf/da...ts/7018xlm.pdf
    lol

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  • aametalmaster
    replied
    I have some 7018 with a blue coating and it welds great...Bob
    http://www.hobartbrothers.com/pdf/da...ts/7018XLM.pdf
    Last edited by aametalmaster; 06-23-2011, 07:29 PM.

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  • 1930case
    replied
    We've rebaked and rebaked and rebaked practice 7018 rods many times, and they came off a pallet which had sat for years. They bend tested fine.

    That doesn't make it a great idea, it just means safety regimes are designed with some practical tolerance in mind.

    It WOULD be better if the industry came up with low hydrogen fluxes that didn't require baking.

    Leave a comment:

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