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Up Topic Welding Industry / Technical Discussions / metal core arc welding
- - By patriot (*) Date 05-08-2011 03:57
Can anyone give me some pointers for metal core wire?  Is this a push mode process like GMAW, or pull mode like FCAW?  Also, what shielding gas blend do you recommend?
Parent - - By TimGary (****) Date 05-09-2011 13:30
MCAW can either push or pull. Pulling gives deeper penetration, so push on thin stuff.
75% Argon - 25% CO2 will work, but I prefer 90/10 or 92/8.
98% Argon - 2% O2 also works.
Whichever you choose, if you're doing code work, you'll need to qualify a procedure (which you should still do even if not code work just to make sure your parameters are good).

Tim
Parent - - By Lawrence (*****) Date 05-09-2011 13:54
Technique wise...... MCAW behaves much like solid wire in spray transfer mode.  A slight push angle with the electrode wire at the leading edge of the puddle provides best penetration and profile.  MCAW has penetration similar to FCAW due to the "current density" that comes from tubular wire as an electrical conductor.

MCAW will run globular with 75/25, it is doable but spatter can be an issue... It needs at least 80% argon for spray, just like solid wire and will run much higher deposition rates than solid wire or FCAW of the same diameter..

Tim...  Why would MCAW codework require procedure qualification?   Most MCAW is structural and most structural is AWS D1.1, which catagorizes MCAW wire in the same groupings as Solid wire (prequalified).,
Parent - - By TimGary (****) Date 05-10-2011 14:31
Lawrence,
Perhaps I used a poor choice of words, as a pre-qualified procedure could be used.
However, a WPS would still need to be written.
The original poster sounded like he was experimenting, so I threw in a note about a procedure to prompt him to ask more questions, if needed.
Also, IMHO, it's always good to do some destructive tests on samples, especially when experimenting, in order to identify potential problems, whether you "have" to or not.

Tim
Parent - By Lawrence (*****) Date 05-10-2011 15:43
Good stuff Tim.

I figured as much  :)
Parent - - By Blaster (***) Date 05-09-2011 14:13
My experience with it is quite limited, but we use .045 with C10 in a pulsed spray and it welds quite nicely.
Parent - By welder5354 (**) Date 05-10-2011 02:39
Blaster, i have to agree with you on the MCAW using the pulse.
We use in the shop on fillet welds (1/16 wire). 
We can weld 28 in a minute with a very nice bead.
We use a slight push.  We use 75/25, but the prefered gas is 90/10.
- - By 52757 (**) Date 05-10-2011 18:25
Lawrence and Tim, how does it compare to a ER70S-6 for dealing with mill scale? From what I have read up on this it sounds pretty good. I have had trouble with the silicon deposits but I think this is  just some fine tuning of the process. I just started using this a little. I am hoping to get away from some of the pre shotblasting before welding that we do. Thank you.
Parent - - By jwright650 (*****) Date 05-10-2011 18:44
We used some 1/16" Metal Shield MC-706 with a 90/10 that is similar to the ER70S-6. It dealt OK with light mill scale, but FCAW deals much better with it.
For some unknown reason we had sporatic porosity issues that we never could resolve. Had the Lincoln rep in here and everything. He thought it may have been spots in the roll that didn't have enough in the core or something....we could pull off 20-30 feet of wire and the porosity would go away until we put on a new roll and then all of a sudden it would return. Replaced everything from the tip/nozzle back to the bottle and never could eliminate the porosity...we gave up and took the wire off all of the machines and went back to Ultracore 71 and all of the porosity problems went away. I still had a few rolls left and decided one day to try and use it up....put in on just one machine and within the week we were gouging out welds due to porosity again.
I like the way it ran and welded but you could not predict when it would blow holes. I liked the puddle control and how you could get it to wet in, bead appearance, operator appeal and all....may give it another try in the future, but the plant manager gave me a fit until until I took that stuff off all of the machines.
Parent - - By 52757 (**) Date 05-10-2011 19:09
John. the porosity is the same problem we have with the ER70S-6, that is why I was looking at the MC-6 or the 706. We use a 92/8. The management seems bound and determined to remove all flux core  from this facility so that is not an option. Been using a L-56 but seem to have sporadic porosity the same as you have had with the MC. Reps  were here and we have never totally resolved that issue. I was hoping the MC wire might resolve this problem. Was the porosity pretty fine or was it big open pores? Thanks.
Parent - - By jwright650 (*****) Date 05-10-2011 19:24

>Was the porosity pretty fine or was it big open pores?


...swiss cheese. I had no choice but to cut it back out.
Parent - By Mat (***) Date 05-11-2011 00:48 Edited 05-11-2011 00:51
I used to burn more metalcore than I ever cared too.  As I recall, the stuff was really sensitive to shmutz on the metal (millscale, rust, etc.)  A common problem that I was warned about early on was excessive gas flow rates, resulting in gas becoming trapped within the weld.
Parent - By TimGary (****) Date 05-12-2011 13:34
My experience with MCAW was the welding of hot rolled carbon steel during the fab of metal building frames, and some structural stainless work. We changed to MCAW from ER70S-6 with 92/8 gas and never looked back. The difference was that the MCAW flowed like butter, wetting in very well at the toes of the weld with greatly reduced potential for roll over. We used this wire without cleaning the mill scale and had great results. The only time we had trouble is when we tried to save money by going to a Hyundai wire. This wire had gaps in the cored flux which would cause porosity and cracking issues. We went back to Lincoln's MC-6 and had much fewer problems. Once we tried FCAW and had a lot of worm-hole problems. The only way we could prevent that was to turn down the voltage considerably which reduced deposition rates. That along with the extra labor involved in cleaning flux sent us right back to MCAW.
I especialy liked the way MCAW works on structural stainless, especially when 98 Arg / 2 oxy gas is used. The end weld profile quality result is 100% better than solid wire.

Tim
- - By 52757 (**) Date 05-11-2011 12:49
Thanks everybody for the info.
Parent - By patriot (*) Date 05-11-2011 13:31
Just now able to check this forum again.  Thanks so much everyone for your comments.....extremely helpful!
Parent - - By jwright650 (*****) Date 05-11-2011 13:33
Here is a thread where we discussed the porosity problem that we were having.
Parent - - By 52757 (**) Date 05-11-2011 15:13
John, I remember that  thread. I aam still having the issues now that I had then with the ER70S-6. All my welder quals that get x-rayed that use the solid ER70S-6 are all acceptable "but" have indications of porosity. Any quals we take with the MC wire come out clean. We are using a MC-6. We are in process of trying to convert and use more and more of this. Have you had any experience with MC-6 or didiyoou mainly use the 706?  Thank you.
Parent - - By jwright650 (*****) Date 05-11-2011 15:24
All 706...lincoln rep said it would deal better with mill scale than the other, so that was what we used.
Parent - - By patriot (*) Date 05-13-2011 19:31
I assume the "706" is a Lincoln wire?  Is it a C-6 classification, or something different?
Parent - By jwright650 (*****) Date 05-16-2011 11:52
Yeah, the 706 is a Lincoln product....it was the newset of their MCAW lineup that is supposed to deal with millscale and rust a little better than the other MCAW wire with less deoxidizers in it.
Up Topic Welding Industry / Technical Discussions / metal core arc welding

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