root pass

[DLN]

Anyone know if its ok to use ESAB mig 6 for a root pass....grind it..then go over it with.duelshield 7100....DL.Thanks:confused:

[OlPilot]

Need more details. What is the base metal, for one? How thick it is it? How many passes? What gas?

[DLN]

These are 28inch hydro cyclindlers with 3inch thick tops.....metals are in range ..pre heated to 350. One pass with .045 wire with 25% 75%...............Many passes with 71 dulesheild .045 with same gas......root was cleaned out with grinder....then wire wheeled................the mig six was ran first (because it leaves no slag) to get to the bottom of a very deep box bottemed vee grouve.....Thanks

[OlPilot]

DLN, I don't think I've found the exact wires you mentioned, at least not on the ESAB site. They list a "Coreshield 6, which is FC wire, E70T-6, per AWS 5.20. It's low carbon, .11 to .14%, about 1.3% manganese. If that's what you are using, the metallurgy should be fine for the root pass with sufficient preheat for that thick section, assuming low to medium carbon steel base metal, but why bother with gas (except possibly for backing if you can even do that)?

Couldn't find anything on Dualshield 7100 on the ESAB site, so I can't comment there.

Anyway, with a 3" thick section, postheat will be equally important.

[DLN]

Thanks very much......will send photos later.........DLN

[Mike Sherman]

DLN, are you asking about compatibility between the two wires or the feasibility of putting in a root pass with short arc mig and then filling out with fluxcore? There has been much research into putting in root passes with short arc mig, both in carbon steel and stainless. It is possible, and I believe a good idea. However, you must not attempt to put in anymore than is necessary to do the job. Short arc is not intended for heavy weldments and will fail if you put in to thick of a root with it. It is advisable to do the testing required to develope a procedure and make certain your welders adhere to it.

[DLN]

Thanks Mike..One of the parts was tested today.......it busted the welds on the testing frame...so I guess I did everything OK....Thanks again..........DLN