Laying 7018 over 6011

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I’ve used 7018 over 7018 to fill groove joints with backing, the standard thing to do with it.  Same thing for a 7018 fillet weld.  Get every bit of slag off or else risk a slag inclusion, but that’s no trouble since the 7018 slag comes off so easy.  No problem.I’ve used 6011 over 6011 to fill imperfect fit up, for more penetration in fillet welds, for farm repairs, etc.  Wire wheel to get most all the slag off, and the little bit that remains won’t trouble 6011 on the second pass.  No problem.It was suggested on another post that I instead use 7018 for subsequent passes, since it’s less liable to crack, prettier, etc.  I get that 6010 is standard for an open root groove joint, then 7018 over that, so using 7018 cover over a first pass of 6011 sounds just the same idea.  Sure. But in the open root application the root is so tiny that it all just gets cleaned up with a grinder.  A first pass of 6011 on a fillet weld or corner joint is much larger, and the edge of the 6011 weld bead tends to collect a little line of slag that doesn’t all come off with a wire wheel (not enough of a crevice to be undercut, just, there’s a tiny bit of slag along the edge of the weld).In the real world, non-code situation, how are people doing 7018 over 6011?  Do you run a grinder down each side of the 6011 weld to grind out all traces of slag and prep for the 7018?  Or can 7018 actually handle that little bit of leftover slag, in a non-code situation?  Perhaps I’ve been too scared by hearing so much that 7018 has zero tolerance for slag, and will get an immediate slag inclusion…In principle I like the idea of a first pass of 6011 and then switch to 7018, but seems tricky to get the first pass cleaned up enough.  What are you all doing for this?  Thanks.
Reply:I don't obsess over it much. Remove what you can, wire brush or wire wheel, then go to 7018. Obviously,the cleaner the better but 7018 does deal with light slag fairly well
Reply:I'll put a root in, scratch it with the next rod to knock most of the slag off, then weld it up. You should be hot enough with your 7018 to float the rest of it to the top. Pipe welders usually grind the root, but it is more to level out the high spots. They call the 2nd pass (sometimes with 7018, 8010, or whatever is spec'ed) the "hot pass" & it is mainly to burn out the "wagon tracks" - the edges you are talking about.
Reply:In a filet, corner or even a lap joint I wouldn't bother laying 7018 over anything. The point of a 6010 (or 601X if you will) in an open root joint is to get a keyhole and make sure you have sufficient root build up without suck back. In a fillet, you do not necessarily need 100% penetration so long as the legs of the filet are large enough. You will be fine just using 7018 for fillets, corners and laps and just skip the 601X rod. I also believe that for any non-code situation, you would also be fine welding it all the way out with 6011 or virtually any rod (6013, 7014, 7016,7018, etc.). Mild steel has a tensile strength of about 36,000 psi. Any 6xxx or 7xxx rod is going to be much stronger than the base metal. I don't buy into the hype about 7018 being so much better because of ductility, charpy v-notch ratings, or the rest. Yes, 7018 has all those attributes, but mild steel does not. If you are working on plain old mild steel, any rod will likely hold just fine. Farmers have been proving this for many years.Miller Multimatic 255
Reply:If I am working on a job that has specs or Xray I grinder the for each pass. It just safer to do a little extra but does take more time .Dave

Originally Posted by David Spring

I’ve used 7018 over 7018 to fill groove joints with backing, the standard thing to do with it.  Same thing for a 7018 fillet weld.  Get every bit of slag off or else risk a slag inclusion, but that’s no trouble since the 7018 slag comes off so easy.  No problem.I’ve used 6011 over 6011 to fill imperfect fit up, for more penetration in fillet welds, for farm repairs, etc.  Wire wheel to get most all the slag off, and the little bit that remains won’t trouble 6011 on the second pass.  No problem.It was suggested on another post that I instead use 7018 for subsequent passes, since it’s less liable to crack, prettier, etc.  I get that 6010 is standard for an open root groove joint, then 7018 over that, so using 7018 cover over a first pass of 6011 sounds just the same idea.  Sure. But in the open root application the root is so tiny that it all just gets cleaned up with a grinder.  A first pass of 6011 on a fillet weld or corner joint is much larger, and the edge of the 6011 weld bead tends to collect a little line of slag that doesn’t all come off with a wire wheel (not enough of a crevice to be undercut, just, there’s a tiny bit of slag along the edge of the weld).In the real world, non-code situation, how are people doing 7018 over 6011?  Do you run a grinder down each side of the 6011 weld to grind out all traces of slag and prep for the 7018?  Or can 7018 actually handle that little bit of leftover slag, in a non-code situation?  Perhaps I’ve been too scared by hearing so much that 7018 has zero tolerance for slag, and will get an immediate slag inclusion…In principle I like the idea of a first pass of 6011 and then switch to 7018, but seems tricky to get the first pass cleaned up enough.  What are you all doing for this?  Thanks.
Reply:I've run 7018 over 6011 a lot over the years. Done right there is not a problem.That aside.7018 will burn off residual contaminants without a problem. Focus on your puddle and your path. 7018 is not as fragile to lay as some people think.Lincoln 330MPXLincoln Power Mig 256Lincoln LN-25X Wire FeederMagnum PRO 250LX GT Spool GunLincoln AC/DC 225¼ Ton of Torches OFC-A OFG-AAir Carbon Arc Gouging CAC-AEverlast 62i Plasma CutterIngersoll Rand T-30 14hpInstagram: #Freebird Welds
Reply:I do 7018 over 6011 a lot because it's faster than prepping the joint to be absolutely clean of zinc or rust, paint, or other contaminants.  A quick, minimal 6011 root pass, followed by wire wheel or in critical applications, grinding the toes of the 6011 pass, and the 7018 lays over it perfectly.  7018 is very intolerant of contaminants in the parent metal, burn them off with 6011 and you're good to go.
Reply:

Originally Posted by Louie1961

In a filet, corner or even a lap joint I wouldn't bother laying 7018 over anything. The point of a 6010 (or 601X if you will) in an open root joint is to get a keyhole and make sure you have sufficient root build up without suck back. In a fillet, you do not necessarily need 100% penetration so long as the legs of the filet are large enough. You will be fine just using 7018 for fillets, corners and laps and just skip the 601X rod. I also believe that for any non-code situation, you would also be fine welding it all the way out with 6011 or virtually any rod (6013, 7014, 7016,7018, etc.). Mild steel has a tensile strength of about 36,000 psi. Any 6xxx or 7xxx rod is going to be much stronger than the base metal. I don't buy into the hype about 7018 being so much better because of ductility, charpy v-notch ratings, or the rest. Yes, 7018 has all those attributes, but mild steel does not. If you are working on plain old mild steel, any rod will likely hold just fine. Farmers have been proving this for many years.
Reply:Thanks Cary..high praise!Miller Multimatic 255
Reply:Perfect, this is exactly the sort of information was hoping to understand.  To summarize my understanding from this thread and elsewhere, and these quotes aren't all verbatim:7018 is higher tensile strength than 6011, but that doesn't matter on mild steel, which is far weaker than either rod.  Same thing for the hydrogen cracking, mild steel isn't susceptible to that so no need to choose 7018 for that purpose.  (Please no debate here on this point.)However, 7018 is much more ductile than 6011, which has a greater risk of cracks, and can't stand up to vibration and fatigue cycles the same as 7018 (and this true whether or not the rods came out of an oven, it's is simply about the ductility of the filler metal, not about hydrogen embrittlement).And, although there's such a concern about pristine joint prep for 7018, in fact it will handle rustier metal than some people think it will, and doesn't even mind the little slag left over in the "wagon tracks" toes of a 6011 bead (in a non-code setting, obviously).And it looks prettier, for when that matters.That's all making 7018 sound pretty good!But while 7018 CAN run over 6011 in a root with a little slag, and CAN run over a little rust, it has to be run well in order for it to work out well.  Compared to 7018, 6011 is more forgiving, and easier to make as good a weld as the rod can make.  A good 7018 weld is superior to a good 6011 weld, but it's easier to make the good 6011 weld, and if the 7018 weld doesn't go so well (due to prep or skill), it might very well be inferior to what 6011 would have done in the same situation.But here's the question I think this discussion all boils down to:Although it is technically true that 7018 will produce a prettier, more ductile, stronger weld, and it IS an actual, measurable difference...is the weld in a situation where this is actually a meaningful difference?  As Louie 1961 says, "If you are working on plain old mild steel, any rod will likely hold just fine. Farmers have been proving this for many years." And my local farm repair welder, well-respected in our area for fixing anything and everything well, almost exclusively uses 6011.  I don't know that that's the "official" or even the "best" procedure, but his work and his father's work shows that it is "sufficiently good for this purpose" -- his welds do not break.Some may say to do the best process that results in the best weld possible, in every situation.  Fair enough.  But does anyone have a sense of when the advantages of 7018 become meaningfully better for a weld on mild steel?  It sounds like for any mild steel on a farm, certainly for work related to a Last edited by David Spring; 6 Hours Ago at 09:50 PM.
Reply:It's either 7018 or inner shield on outdoor structural steel work. You might see some 6010 or more likely 6011 on a structural job for tacking and that's about it. No reason not to use 7018 as it's about the same price as any other electrode and it typically won't trap slag like 6013 or 7014 are more prone too .