Stick welder

If you are going to grind away a bunch of rust it isn't going to affect the strength of the joint anyway. Just don't over-do it. If you don't want to grind, what about doing a first pass with some 6010/11 which is good for dirty material and then finish with the 6013? The 6011 pass will do a lot of clean-up. You might try some 7014 instead of the 6013 since I think it will tolerate dirt better than the 6013.
billh

130 amps is a whole lot for 1/8" 6013. 6013 is a 'soft' runing rod, designed for new work, nice bead, not too much penetration. 1/8 will run nicely at 80 to 110 amps depending on the thickness of the stock. As long as at least one side of the joint is clean, the other can be rusty.
I suspect that you are running so hot that the second half of the rod is running red hot, changes the composition of the cellulose based flux in the rod shield. Result is gloppy looking welds with lots of porosity when you lose the shield.
I'd suggest grinding out the glop, run a nice pass at 100-110amps DC.
J> I picked up a Miller Thunderbolt XL 225/150 AC/DC stick welder. Any thoughts

In my (fairly limited) experience, 6013 *can* run a beautiful bead ... but it can also produce a really ugly, gloppy weld. In some of my less-than-beautiful welds, I believe the problem was not running too hot, but rather fitup issues (and/or an awkward position to get to, resulting in less-than-optimal angles, etc.). My thought, based on some input from a welding instructor at the nearby tech school, is that the flux tends to get trapped in a crack, and then the weld metal separates around it like ink rolling off crayon in those old pictures I used to do in grade school. (I may of course be wrong, but I'm suspecting that when you ran beautiful, textbook-quality beads, they were just on the face of a piece of metal, rather than actually at a joint.)
In any case, I have found it much better to go ahead and run a stitch pass with 6011 (I have an AC only machine; otherwise I'd use 6010), grind down the ridges, and then run a pass with 6013 (or 7014, 7018, etc.). More work, but I'm generally happier with the results. Having said all that, I am still a relative newbie, so any further input from those with more wisdom and experience will be welcome!

"Andy Wakefield" wrote > In any case, I have found it much better to go ahead and run a stitch If you are doing that with AC, I suggest you move on to DC. It is difficult to weld with AC because of various factors. Doing it with DC will give you a little more ability to fine tune the variables.
I think you are ready for that if you are already getting good 7018 welds with AC.
Steve

Steve, in my case DC is not an option right now, though eventually I plan to try building a converter (if I don't stumble across a great deal before then). Meanwhile, however, I have to say that my ancient AC welder works incredibly well, so much so that I cannot tell much difference between using it and using the DC machines at the tech school where I recently took a class. Also, I brought in some of my welds from home, and the instructor couldn't believe they were done with AC.
I admit that this is contrary to what I have read here -- I fully expected to experience a significant difference in smoothness, splatter, ease of start, etc. ... but I did not. I've wondered if it has to do with the type of AC machine I have; it's an *old* monster, built like a tank, with a relatively high OCV and weld voltage. (The OCV is 90 volts, higher than I think is now legal -- ?) BTW, when I tried the AC setting on the machines at school (Miller Shopmaster 300? or something like that), there WAS a huge difference between AC and DC; the AC was much harsher and harder to use. I wondered, though, whether the AC on that machine is more of a square wave pattern, or ???
In any case, with my current machine and level of ability, plus the fact that I am strictly welding as a hobby, I have not felt any great need to move to DC anytime soon. I wouldn't mind being able to run 6010 instead of 6011, but the results with 6011 are more than good enough for my purposes. I'm still using up a bunch of 6013 and 7014 that I bought early on, but increasingly I'm shifting over to 7018-AC rods; they run so smoothly, and give such nice results (at least with my machine) -- again, I can't tell any real difference from running regular 7018 on DC at school. I wouldn't be surprised to learn that the 7018-AC is not quite as strong, not up to code quality, etc., but then again I seriously doubt that anything I weld is up to code quality! Though I keep on getting better ...
Thanks for the input; you all have helped me tremendously as I continue to learn!

I'll stick with my comment on getting 6013 too hot. If you let the arc sit in one spot for a while, it seems to lose the shielding and you get a huge porous mess. As for the glop side, 6013 is a 'fill-freeze' rod originally designed for thin stock. There is really a sweet spot amperage that seems to vary by the specific job. I like it for newbies, you can get great welds in very short order by tweaking the settings. But you can get a mess if you don't do a quick practice weld on scrap to get your settings right.
If you have any of the slag left over from 6013 and try to go over it, the slag semi melts, seems to bubble up but does not fully melt and rise to the surface. Instant slag inclusions and other bad stuff. So a core pass of 6013 is prone to give you problems. 6011 has a glassy slag that melts nicely and gets out of the way.
Andy Wakefield wrote:

snipped-for-privacy@aol.com (JonS999) spluttered in news: snipped-for-privacy@mb-m01.aol.com:
Just my 2¢ ...
One other measure of performing a decent stick weld is chipping the slag off. Assuming a good form to the weld bead.
If the slag breaks out cleanly and rather easily, your heat is probably right. If it's hard to remove the heat is probably too high. This is for mild steel.
For a (generally speaking) stainless bead, when the heat is right, the slag will follow-off and need little chipping at all.