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Up Topic Welding Industry / Technical Discussions / Which filler materials are acceptable to apply over others
- - By aevald (*****) Date 04-06-2007 03:42
Hello everyone, many years ago I recall my welding instructors having a conversation with me and others in my class regarding applying E7018 weld deposits over E6010 root welds. They stated that it was okay to weld the 7018 over the top of the 6010 but not to reverse the process and weld 6010 beads over the top of 7018 welds. It struck me the other day that I couldn't really remember why it was exactly that this shouldn't be done. I thought that I remembered it having to do with trapping gas bubbles in the weld due to the weld freezing too quickly and not allowing the escape of these bubbles as they were generated by the 7018 weld deposit being liquified in the arc of the much faster freezing 6010 weld deposit. I'm really feeling the need to have this clarified for me.
     Another thought came forth as well. If this is the case with the E6010 and 7018 electrodes, are there others which could be susceptible to similar issues where they are not compatible with one another due to one application over the top of another working one way but not the other, or not at all? I am mainly referring to electrodes designed for welding on steels(mainly A-36 grade and not alloys or high-carbon or high-strength), these would include stick, solid wire, metal core wire, dualshield flux-cored wire, and gasless flux-cored wires. I'm curious to hear if any of you have ever had any issues where this posed a problem. Thank you and I look forward to hearing your replies. Regards, aevald
Parent - - By hogan (****) Date 04-06-2007 15:04
i was trying to find info on a related question in a post a while back:

let me give you a little more background on my question. in the USA, on the west coast we have more stringent seismic provisions. the current code code dealing with this is FEMA 353. the precursor to this code was sac interim guideline 267/267b ( http://www.sacsteel.org/design/interimguidelines.html ). if you look at chapter 8, page 8-14, at the bottom of the page the last paragraph states that:

Except to the extent that one requires Charpy V-Notch toughness and   
minimum yield strength, the filler metal classification is typically selected by the   
Fabricator. Compatibility between different filler metals must be confirmed by   
the Fabricator, particularly when SMAW and FCAW-SS processes are mixed.   
Generally speaking, SMAW-type filler metals may not be applied to FCAW-SS   
type filler metals (e.g. when a weld has been partially removed) while FCAW-type   
filler metals may be applied to SMAW-type filler metals. This recommendation   
considers the use of aluminum as a killing agent in FCAW-SS electrodes that can   
be incorporated into the SMAW filler metal with a reduction in impact toughness
properties.
i have not seen info on this before or after this publication. I'm just looking to educate myself on this topic a little more. any elaboration on this aspect of reworking fcaw-ss with smaw would be greatly appreciated
Parent - By js55 (*****) Date 04-06-2007 15:35
Hogan,
The aluminum 'killing' of FCAW-SS is an interesting point. And I don't know why there hasn't been much discussion. Although many of the conclusions of FEMA have been greatly contested which is why there are so few jurisdictions incorportaing it.
I would ask, since Al is being used as a killing agent wouldn't this imply that the bulk of the Al is ending up in the slag covering. In other words, if its not forming an oxide its not killing anythinng I would think.
There was also some early work by Evans that demonstrated certain amounts of Al actually being beneficial to the formation of acicular ferrite. Of course this was with SMAW.
I'm just shooting from the hip here, but I suspect that contention over FEMA's conslusions is extensive.
I'm gonna have to pull out my 353 copy and review again.
Parent - - By Joseph P. Kane (****) Date 04-06-2007 15:39
Lincoln Electric has an article written about this subject in one of their booklets.  As I remember, they take issue with the FEMA conclusion.  Sorry, I cannot remember the publication information.  I  do recall that it was maroon in color and had a column being welded in the field on the cover.  Joe Kane.
Parent - - By js55 (*****) Date 04-06-2007 16:00
The other thing is, this FEMA committee doesn't even exist anymore, so there isn't any body you can consult for "Official" interpretations.
I think the work they did was of great value to direct discussion, and the dialogue should ocntinue, but I'm not sure the conclusions hit the target they were intended for. I could be wrong but I believe the failure conclusions from Northridge and Kobe were design problems and not necessarily weld toughness problems.
Parent - - By hogan (****) Date 04-06-2007 16:18
i would agree that design issues were a major part of it, but i seem to remember that poor inspection practices (mainly ut of connections with backing) were a large part. also i believe that this was the first test of a full scale mock-up of a moment frame in a seisemic event.
Parent - - By js55 (*****) Date 04-06-2007 16:31
hogan,
Your memory is better than mine. I think I vaguely remember exactly what your saying. Although I didn't remember until you said it. AWS has their Seismic doc now and AISC has one. And some of the same ideas are expressed with due variations.
I do believe there is commercial motivations hiding behind it all.
I don't believe this is related to the original question of 6010 over 7018. I remember the same thinking from long ago, and once knew why. Or at least had it explained, but I cannot remember since I never wanted to run 6010 over 7018. This prohibition has been around for a while, the FCAW-SS stuff is fairly recent.
Parent - - By hogan (****) Date 04-06-2007 17:06
if you don't mind me asking. what, in your opinion, is the commercial motivation?
Parent - - By js55 (*****) Date 04-06-2007 17:45
It is just my opinion of course, but Northridge/Kobe really caught our attention (justifiably to be sure).
I think the advertising/vendor blitz for FEMA compliance was a bit oversold. There was a lot of chatter about FEMA this and FEMA that when at the foundational level many people were saying "hold on a minute".
This industry has a long history of 'jumping the gun' on things. Pulsing, FCAW, Robotics, etc. I think this fits in with that.
Parent - - By aevald (*****) Date 04-06-2007 18:19
Hello everyone, at this point I would like to thank all who have replied to my original post. As I suspected, it has sparked interest in some offshoots of the original question, I feel these are all great topics and worth exploring and becoming educated on.
    Back to my original question somewhat, in many cases I realize that changing mid-stream or incorporating more than one welding process in the course of manufacturing a product or other type of item will typically not be the case. Some of my interest is directed more to instances where repairs might be made to equipment or changes might made on existing structures. Incorporating different welding processes for additions, repairs, or changes to existing items might bring about problems or issues from a metallurgical standpoint. I am hoping to get a better idea as to the combinations or types of situations where this could be a problem. Once again thanks everyone for your comments and keep them coming. Regards, aevald
Parent - - By js55 (*****) Date 04-06-2007 19:30
This is a very good question and I hope others will chime in. But I have to admit, the only process layering limitations I have even heard of are the very ones that you and hogan have already mentioned. And I had completely forgotten them unitl this question came up.
Its possible that a silence on the part of the forum participants might be indicative of a lack of problems associated with this issue in the industry as a whole. There is a broad diversity in here.
And it may be that with GTAW, SMAW generally, SAW, GMAW and FCAW -G,there just isn't anything unsusal in particular such as perhaps a cellulosic coating or inordinate amounts of AL that would cause difficulties.
Parent - - By aevald (*****) Date 04-06-2007 20:59 Edited 04-06-2007 21:14
Hello again js55, I guess one of my more specific questions that might apply here would have to do with self-shielded FCAW, in particular some of the wires that are specified as single pass electrodes and the possible effects of welding over these deposits with other types of electrodes and processes. As you said, it is very likely that not very many folks have run into issues with this topic or possibly when they have they didn't realize where the difficulties were coming from. If my memory serves me correctly, Lincoln's NR211 was an electrode that was designed for single pass application and if multiple passes were deposited with this electrode you would generally experience bead cracking issues. My question, having made this last statement, would involve welding over the top of this particular weld bead with other electrode types and possibly processes and wondering if any detrimental issues might evolve. Once again, this sort of thing might only generally be done in a repair type issue or a possible structural remodeling type scenario. Looking for additional comment. Thanks and regards, aevald
Parent - - By hogan (****) Date 04-06-2007 21:05
i seem to remember the issue with the nr211 was the cooling rate if it welded anything over 1/2"
Parent - By js55 (*****) Date 04-06-2007 21:21
Generally the issue with multi pass limited wires is Si/Mn build up. I think mostly Si since it can lead to crack sensitivity. Mn build up could effect mechanicals. Si/Mn is added in heavier dosses as extra deoxidizers for heavily oxidized steels. If you run em over weld metals, or clean steels, the Mn/Si has no O2 (or much less) to oxidize and therefore will build up in subsequent passes.
The problem for other processes may be lessened (may be) in that dilution may limit the problem if subsequent process chemistries do not have additional Mn/Si,
thereby maybe even reducing the Si/Mn from that which results from the overalloyed wire.
I don't know.
Up Topic Welding Industry / Technical Discussions / Which filler materials are acceptable to apply over others

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