Hello welderbrent, just a bit more to follow your questions. The bubbles and porosity that indicate a mechanical issue are being generated or caused by entrapment of hydrogen(moisture related). As the name implies, E7018 or Low-Hydrogen electrodes are used to prevent an excess of hydrogen in the deposited weld metal. If there is an excess of hydrogen in the weld deposit it can lead to under-bead cracking and other mechanical/metallurgical issues. Much of the information that is available covering hydrogen in welding also influences the handling of rod, humidity limitations while welding is taking place, and also welding in the rain or wet environments. Realistically, there is a lot of welding that takes place outside of the limitations in place to govern this, as with many of the limitations, they have a safety factor involved so we aren't subjected to catastrophic failures as a result of not always meeting them, but that doesn't mean that they shouldn't be heeded. I use an example, when students ask, about this importance that goes something like this: picture a weld made with improperly cared for Low-hydrogen rod as being like a sponge and the same weld bead being made with a properly stored rod as a solid, the spongy material will not have the same strength as the solid. Even though this is an exaggerated example it does give a visual that can be readily understood.
One other point that could be brought up to further explain this might go along these lines: if you had two beakers of water in a freezer and one of these beakers had a hose in it and air was being pumped into it as it was being frozen you would end up with one beaker of solid ice and one beaker of ice with frozen bubbles entrapped in it. This would be similar to a weld bead that had been run with the moist electrode. The moist-electrode weld would have an excess of hydrogen being added to the weld pool and wouldn't be able to allow the escape of this hydrogen gas before the puddle solidified. The "good" rod on the other hand, wouldn't be introducing excessive levels of hydrogen and thus the welds made wouldn't exhibit rejectable defects.
This still hasn't answered your question about whether anyone has done testing to provide viewable hard evidence to support reasoning for keeping the rod dry. In my particular case I have seen the items that I described in my first post, I have also experienced failures attributed to wet rods, and have always been taught the reasons behind paying attention to this issue. Much of this evidence goes on at a much higher level than the average person might readily accept, I am referring to metallurgical investigation, a metallurgist could likely give all of us a very scientific explanation and upon reviewing and explaining all of this information it would make sense. So maybe some of those folks who might run into this thread could chime in. You might also consider posing this question in the Metallurgy section. Just a bit more for you to consider. Best regards, Allan
Allen,
Thanks for all the info. A lot of it I already know though your examples help understand a couple things. I have only posted a couple times but I have been certified for over 30 yrs, got CWI this past June, and try to read alot about my chosen profession. I have been monitoring this site occassionally for the past two yrs.
I was just trying to put some added weight to Al's test to be able to quantitatively state that 'when you see bubbles, there is a 90% or better chance that the rod that made the weld, as well as the rest that was similarly stored, will not pass any kind of examination. Visual, mechanical, or even x-ray.
I have been having a lot of discussions with local welders and welding suppliers about the way they are storing and using their supplies, namely 7018. Go into the welding supply and find 50 lb cans of 7018 sitting behind the counter open that they sell small lots of to the welders. I think I have gotten them to buy in 10 lb sealed cans and only sell in that or 50 lb sealed containers. But so many people don't understand and I was just looking for some good facts to totally back up the claim that the open, improperly stored rod was not any good for use in almost any application even where 'code' is not an issue.
Thanks again for all your time today. Best wishes, Brent
By 803056 
Date 10-08-2008 00:53
Edited 10-08-2008 01:13
Hello Brent:
Welding electrodes are qualified by the manufacture by welding test coupons and subjecting them to a regiment of tests described in the appropriate A5.X filler metal specifications. If the required tests are passed, the electrode is "certified" as meeting the requirements A5.X for the appropriate classification.
Once the welder has elected to ignore the storage requirements of the manufacturer or applicable code, we have no way of predicting the properties of welds deposited with that electrode. It's a crap shoot. Does the E7018 that has been left out on the bench for 1 day meet the mechanical properties of A5.1 for E7018 electrodes? I don't know. Will it have the properties of an E6010? I don't know. That is the problem, we don't know because it is tested under specific conditions as defined by the appropriate filler metal specification.
I can show you an example of a welder qualification test that was welded with E7018 that wasn't stored properly. The rod was stored in an electrode holding oven, but it wasn't turned on. According to the welder, "That would be a waste of the company's money."
The hydrogen is entrapped in the vacancies and along grain boundaries called hydrogen traps. The atoms are so small they diffuse through the atomic lattice over time. At high temperatures the hydrogen can diffuse faster because the atomic spacing of the metal's crystalline structure is more widely space and offers less obstruction to the movement of the atomic hydrogen (the smallest atom of all the elements). That's one reason why it takes hours or days for the hydrogen to diffuse through the lattice structure, the atoms of atomic hydrogen have to "work" their way through the atomic lattice and to the surface of the weld.
Best regards - Al
Hello Brent, there is one other tidbit you could relay to your welders or others that question this importance. A day or two ago....... I had a few friends that were working at the Hanford Nuclear Reservation outside of Richland, WA., when they were using E7018 they were checked out X-number of electrodes and the check-out time was noted, if they returned beyond a certain period of time for more rods a red flag was raised. Similarly, if they came back minus a rod stub in the prescribed time they would have to come up with a valid reason for not having all of them. This procedure was in place to address the issues surrounding moisture pick-up in rods that were used on that nuke. Granted that may have been taking it to the extreme, yet from a safety and quality perspective it was a valid reason.
You will certainly have a hard sell trying to convince everyone of the validity of using only properly stored electrodes. Although, the reasoning behind doing so is definitely valid. It would be interesting to see if anyone, as you questioned, has some definitive testing to further support and verify the need for proper rod handling and storage. Like so many things, defining the line between too much and just enough is always a tough one to get across. I have great respect for your interest and conviction here and hope to see others add a bit more proof, information, logic, and reasoning. Best regards, Allan
I've also had test pieces "craze" crack when they were welded with E7018 that wasn't properly stored.
I never argue with a paying customer. I always tell them to bring a fresh unopened can of E7018 to the test. I warn them that electrodes that are improperly stored will not pass the test. It never fails, one out of three welders that haven't tested before ignore the warning. On the day of the test they show up with an opened can and they insist they always use electrodes without the hot box and they never have a problem. Again, I fight the urge to tell them what is really transpiring in my pea sized brain and let them complete the test. OK, so they aren't following procedure, but there is a method to my madness!
I can not think of a single time where a welder with the open can of E7018 has passed the bend tests. I'm sorry to say I don't have a photograph of the typical results. The massive porosity depicted in the photo in my previous post is an oddity. Usually the convex surface of the bent piece is a series of very fine cracks in all directions, both transverse to the bending stress and some parallel to the bending stress.
They always bring a fresh unopened can of E7018 the next time they test. I don't even have to tell them to do so the second time around.
In case you haven't figured it out, I don't provide anything other than the test plates and backing bars at the time of the test. The welder supplies everything else. That way I don't have to hear about how they aren't used to the welding machine, how they prefer brand X instead of brand Y, and the grinder used to clean the plates was turning the wrong RPM, the wire brush was missing a few bristles, the moon was over the left shoulder, and he can weld anything including the crack of Dawn (I often wonder how she feels about having her good name sullied), and so on.
In the end the story is always the same, "I've never had a problem with any of my welds." Then again, they have never had any of their welds tested before. I love it! Where can you have so much fun and get paid doing it! :)
Best regards - Al
Thank you both very much for all your time and words of wisdom.
Short of an indepth scientific evaluation of my question, that I at least can't afford, I think you have covered all the bases very well.
Allen, I hope I didn't come across like I was trying to shut you down on your response. I knew you had no idea of my background or who I was as I had no previous posts here. Just wanted you to have a little information as to who you were talking to.
The info provided by people on this site has been very beneficial. Hope that at some point I may be able to help others out as much as you have helped me.
Have a great day, Brent
Hello Brent, I didn't take it that way at all. I also understand that experience gained through years of doing and seeing is invaluable, sometimes it's hard, as you say, to come up with the evidence that is believable and verifiable when you are trying to convince people to change their equally long-standing habits and understandings of a situation, afterall, " I've welded for decades and haven't had any failures yet" or so they will say. Prior to joining the forum here I had some fairly set ways of considering fabrication and welding of Stainless Steel, Aluminum, and a lot of other materials, I have since been educated a whole lot on some of the do's and don'ts of this material that I wouldn't have otherwise considered. Have enjoyed the thread and the information presented here. Best regards, Allan
Yup, I remember that thread...
