Can you use e 70 flux core to weld 4130 sheet its .250 it's a 4 link bracket to be welded to 1.750 .120 wall mild steel tubing
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I would have to prove it out with lots of testing before saying a definite yes.
With the right preheat, and the right classification of flux core wire, I think it could be done. however if you are talking about using a 115 volt mig welder for the job, I would really discourage that.
The application also is a big factor too . If the weld failing would cause someone to get hurt or damage property, its probably not a good idea to try something that is not mainstream.