6010, 6011, not really much different if you are just using them to weld with (as opposed to sever plate steel or any of the other weird tricks you can do with 6010). I believe 6011 is just 6010 reformulated so it can also run on AC, in fact 6011 is *the* rod to use with small AC buzzboxes.
They weld pretty similarly. If you can more easily buy usable quantities of one than the other, I don't personally see a reason to stock both.
I'm assuming you were typing '6011' when you meant to type '6010' in a few places there ..
I've been watching your posts for quite a while. Great advice.
One note, though, regarding E6010 for structural work. Heavier section steels would require preheat. It's not often hobbyists will see really thick pieces of steel, but the wire is not "low hydrogen" and could be the reason behind delayed cracking if the part stayed cool while it was being welded or if for some reason, the stock being welded was of a hardenable variety.
There are lots of sources for predicting proper preheat. Welders that want to protect themselves should be familiar with at least one of them.
The least expensive resource is Blodgett's book from J. F. Lincoln, Design of Welded Structures. Lincoln subsidizes the book to make sure that there's plenty of good engineering information out there so people don't make design or construction errors and then try to blame the wire manufacturer.
6010 is very rarely used for anything more than a root pass on structural steel, and only then if you are working with an open root weld. It is used extensively for repair work since it can burn through almost anything.
6010 lays a fairly hard, non-ductile weld because it freezes so fast. Very much the opposite of 6013.
AWS D1.1 lists all the preheat and interpass temps for steel. Very dull reading, but useful.
Oh, I agree. Its restrike capability is terrific. Tacking with low hydrogen rods is a nuisance in comparison. And the slag from 6013 always seems to get in the way. Nonetheless, 6010 wire should leave a ductile deposit. And at 60 ksi, it's not going to be particularly hard. AWS A5.1 calls for 22 percent elongation, the same as 7018 although I believe the manufacturers would do a hydrogen bake at 200 F for a day or so before pulling the 6010 tensile bars. If tack welds seem brittle, it may be because they're just thin or otherwise too small for the job. It might take more than one pass to get enough to hold for a structural application. I remember a problem with root passes when welding a diaphragm stiffener into the foot section of a jack-up barge leg. They needed to be bigger and more convex than what the welders were using at first. The thin root of concave fillets cracked very easily. We also manipulated the preheat with more on the cylinder and less on the stiffener to make the thermal strains compressive as the part cooled (both pieces were about 2 inches thick)..
My point was really that structural steels often need more preheat than welders are aware of. I suggested Blodgett because of its price. D1.1 is quite expensive, although each AWS section has a library and will have a copy of the code available if anybody wants to go to the trouble and look for it. Not too long ago, some US shipyards were complaining about cracking in hull steels. What really was happening was that the newer ship designs had heavier section steels than what was used before. They were still the same grade steels, just thicker and not by a whole lot. The shipyards thought the plate was at fault. The Gov't paid for a study and what came of it was that more preheat was required for the heavier sections. That's not making anybody happy. But, Mother Nature's a bitch and sometimes there just aren't any shortcuts.
I also don't see much discussion here on E7016 wire. As far as newbies are concerned, if they're looking for low hydrogen deposits, 7016 wire is very much more user friendly than 7018. The only drawback on the 7016 is that it's slightly less productive. It doesn't have the iron powder in the coating that 7018 has. But then the slag is much thinner and doesn't seem to get in the way as much as the 7018 slag does. I worked with an old-timer one summer and I watched him make a vertical joint with an entirely wrong rod angle (from the way I'd been taught) and the slag was still self peeling. I haven't heard of anybody using the wire for years. I don't know if it even comes in a moisture resistant coating. But it's a sweet running wire. The big users of low hydrogen electrodes are in the business of being very productive. And most of the time it's new construction, so the EXX18 or EXXX18 wires are preferred from the nominal productivity standpoint (although most users are going to spooled wire anyway). But as a maintenance wire or a repair wire, the EXX16's would be a better choice (IMHO).