Greatly mysterious success.
It's been a year plus since working with mig in class. And I only used flux core one time for an hour or so. Hated the spattery smoking mess.
So today, I have to do some welding at work, and there is the flux core unit, a 120V POS, sitting there ready. Just a few inches of bead to weld together some pieces of 1/8" wall x 1.5" square tube.
No amperage setting, at least nothing with any pretence of current markings, so I leave it where the last guy had it, who was doing the same type welding, but wasn't in today.
So..... Huge surprise. Not only did I get a quite decent bead (no pics, they were in a hurry and painted it just as soon as it cooled off), but I saw the pool pretty clearly, and was able to see and weld up a substantial gap that had to be filled at one place.
I don't think I ever did that well nor saw what was going on that clearly using the big Miller monsters at the class. Shocked me....... maybe the little POS with a new roll of Home Despot (or whatever) flux core wire isn't that much of a POS.
Or maybe I actually learned something and was able to use the POS. Dunno.
Of course all flux core wire is not created equally, try some Lincoln NR211 you might be pleasantly surprised!
Well I was already pleasantly surprised, so a bit more can't hurt.....
The flux core wire at the class gave a nasty thick slag layer that resisted coming off.
The wire at work, whatever it was, gave a thinner layer that came off nicely with a wire brush, if hit before it got cold.... generally as soon as it was frozen and no longer glowing after finishing the bead..... the slag at a distance (an inch or so) was a tan sort of powdery stuff.
Maybe that is recognizable, maybe not.
And, maybe the nature of the weld helped.... it had somewhat of a "V" due to the rounded corner of one piece of tube, against the butt of the crosspiece. But nothing like a sharp inside corner which might confine the flux and maybe cook it to a more resistant coating, I just needed to weld the sides in the flat.
I was also pleased that it did not seem to spatter badly. I got a little bit, that I put down to excess stickout (bad habits returning).
All this relative niceness from a little POS 110V welder with no calibrated settings, and using flux-core. As I said, I was shocked.
I use a Lincoln 140sp 120 volt and mostly NR211. It is great for the small things, less than 3/16s. Slightly rusted or galvanized. Lots of 1/2 and 3/4 EMT + strut. I have welded 3/8, but you need to v groove and run stringers making sure you burn each in and tied together. Lot easier to use 1/8 stick. If the machine was bought in HD there is a good chance it has NR211 look on side of spool. The characteristics you describe sounds similar.
There are several decent, I hesitate to say "good" when it comes to flux core, wires out there but the Lincoln 211 is one of the best and at a good price. Get everything set just right and the slag will almost fall off by itself plus it will bridge a gap better than most, the stuff almost makes flux core a good way to weld.
I keep my little 120V Miller 140 loaded with flux core all the time for when I have to venture outside in the breeze or do a road trip. I would hate to be without it now after having to drag everything home and inside to use my larger 185 before I got the portable machine.