Best rod for overhead welding QT100 and mild steel.

I'm wondering what would be the best rod to use for overhead welding of mild
steel and QT100 plate; with a DC welder. The thickness will be 3/8 and 1/2
inch. I'm guessing rod size to be 3/32 or 1/8. Also what amperage setting
for the respective rods? I've done alot of sucessfull flat and verticle
welding with 7018 but the overhead just doesn't seem to be working out as
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A little digging told me that QT100 is the same as A514 and T1.
Any of the higehr tensile strength low-hydrogen rods will work.
Since the tensile strength is around 100 kpsi for A514, it would make sense to use a 10018 or 11018 rod.
8018 and 9018 would also work well. A preheat is recommended for heavy weldments, but since your plate is only 3/8" to 1/2" no preheat should be needed.
1/8" 11018 at around 120 amps should fit the bill.
Reply to
Ernie Leimkuhler
Did I misunderstand or is he welding the high-strength steel to mild steel? If that is the case, why not 7018 since the mild steel would be the limiting factor?
Reply to
Ted Edwards
True, but I would run at least 8018. The higher chrome in 8018 makes it a bit smoother and it is lesss prone to cracking when welding A514.
Reply to
Ernie Leimkuhler
Hi Ernie Per the AWS D1.1 matching electrode chart, the strength of the filler metal does not need to exceed the strength of the weaker base metal, nor should it exceed it by very much. As a higher strength electrode does not strengthen the weldment, & it can bring on a new set of problems, it's not best to use higher strength electrodes. But preheat is based of the higher strength steel. However, as you say, @ this thickness it's probably not a concern. Now I realize that this welding is probably not being done to D1.1, but it is grounded on good practices. Also could you or someone please give me the name of the sister news group that discussed machining & such? Somehow it has disappeared from my favorites. Thanks much John In rereading the OP, I have to wonder, did he mean welding mild steel to the 100kip steel, or did he mean 100kip to 100kip. If he meant the later then my comments are not relevant. Sorry if I misunderstood.
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John McGraw
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Ernie Leimkuhler

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