SMAW vs. FCAW weld filler metal deposition... 3

[Zylinderkopf]

Greetings, engineering colleagues:

I have made a woeful attempt at uncovering the answer to my question via “keyword search” in this forum and by looking through my very few personal references that describe welding metallurgy; as such, please extend me your pardon if this question has already been answered (and especially, God forbid, answered more than once…).

A welder assigned to one of my employer’s fabrication areas mentioned to me that he has noticed that when welding ASTM A36 plate using a SMAW root pass with a 7018 electrode, and then building the weld joint up using an FCAW process that he obtains acceptable results; however, when attempting to cover FCAW passes with the SMAW process (same parent metals, etc.), he reports that the weld filler metal does not sufficiently deposit in way of the joint…that it does not seem to penetrate the FCAW –deposited metal. His question to me was “why is this so?” I, obviously, did not have any answer for him…

Even if I should investigate his FCAW process, I do not even know where to begin in this area (*embarrassing*). Any guidance that you good folks can provide me will be genuinely appreciated.

 

[gtaw]

The difficulty is due to the various components used in the flux of the FCAW and SMAW electrodes.

You should consult with your filler metal representative to see which FCAW/SMAW combinations are compatable.

If you look at the manufacture's product sheet, you will note that each manufacturer makes several different E7018 low hydrogen electrodes. Each of the electrodes meet the requirements of an E7018, but each has a slightly different flux formulation. Your job and that of the manufacturer's rep. is to find the combination of FCAW and SMAW electrodes that works together.

Best regards - Al

 

[Goahead]

The problem seems to be based on the feeling of the welder, not on objective evidence. Probably the welder is using with FCAW a much higher current than when he uses SMAW. Actually in the second case he is performing a "bead on plate" welding. He has to melt the substrate, which he does, but he cannot expect to dig any deep. On the contrary the root pass is quite thin, and FCAW with sufficient current can melt, and penetrate, most of it.

http://www.welding-advisers.com/

 

[gtaw]

I should clarify my comments.

When welding over FCAW with SMAW or welding over SMAW with FCAW, the resulting weld and slag do not always look like they would when welding on base metal. Sometimes the slag is very difficult to remove. The slag adheres to the surface of the weld bead. This is what I understood the question to be, I should have read the question more carefully.


Best regards - Al

 

[Zylinderkopf]

Thank you, "gtaw" and "Goahead" for your welcomed responses and kind consideration.

 

[HgTX]

Is it self-shielded or gas-shielded FCAW?

Hg

Eng-Tips policies: faq731-376

 

[Zylinderkopf]

Greetings, "HgTX":

Thank you for your welcomed message.

You have written:
"Is it self-shielded or gas-shielded FCAW?"

The subject process would be self-shielded FCAW; I apologize for my earlier lack of clarity in this regard.

 

[tab1999]

I've been scratching my head and still can't remember where I read that its unacceptable to weld over FCAW with SMAW.. but not vice versa.
It may have been on a Filler metal website when I was looking for a Dual Shield II Ultra 70 wire.

 

[Zylinderkopf]

Greetings, "tab1999":

Thank you for your welcomed message.

I understand EXACTLY what you mean...boy, talk about having an itch that you can't scratch!

Thank you again for sharing your thoughts.

 

[HgTX]

There's a little bit in C5.11.1 of D1.5 about FCAW-S tack welds affecting the chemistry of subsequent weld passes, with no mention of the other way around.

D1.1 & D1.8 seem to have equal heartburn either way.

Hg

Eng-Tips policies: faq731-376

 

[Zylinderkopf]

Greetings, "HgTX":

Thank you for your second welcomed message to this post.

Were it not for you I would not have thought to look in D1.5; thank you for your continued kind consderation and comments.