I have done very little welding. I need to do add some patch panels. I have a Lincoln Electric 120-Volt MIG Flux-Cored Wire Feed Welder from Lowes. The first time I tried to use it was to fill in some very small rust holes in my bedside. I thought I could just add a couple beads to the hole and grind it down smooth. Instead, it blew a hole through the bedside increasing the size of the hole. I was using self shielded, flux-cored wire. No shielding gas. What did I do wrong. I am concerned when I start trying to tack weld my patch panels I will burn through.
I probably have the same welder as you do. One issue is flux core uses straight polarity and MIG uses reverse polarity (or vice-versa), but the polarity of the wire using flux core makes it penetrate deeper, thus it's easier to blow a hole in the work than with solid wire and shielding gas (MIG). That and the microscopically thin metal at the edge of the rusted hole. As was already mentioned, cut back till there's some meat there and weld in a patch instead of trying to fill a hole that keeps growing.
