68 Mustang Coupe
That's a Flux core weld. It will almost always be to hot for sheetmetal. Switch to solid wire and a 75/25 bottle.
Tou can try clamping a thick piece of metal on the underside of the pieces you are welding to help with burn through. I have welded two pieces of metal together without drilling a hole in the top piece. Did this on the crossmember under the radiator support to the strut rod bracket. The result looks somewhat like a plug or spot weld.When I try and plug weld, the puddle doesn't build up well. I'm afraid to hold too long, I don't want to blow through. I'm also afraid to turn the heat up for the same reason
This pic is me trying to fill the hole for almost 5 sec. I'm using the HF titanium easy flux 125 with .30 wire on its lowest heat setting, and medium low wire speed.
View attachment 855228
Yes. When you plug weld, instead of holding the wire in one spot in the middle, Move your puddle in a spiral starting by going around the entire perimeter and then spiraling in towards the center. Holding the puddle in the center will put a lot of heat in one spot making it more likely to burn through. It will also not produce enough heat around the perimeter to penetrate where it needs to penetrate the most. Also, with a flux core, the flux will get trapped around the perimeter weakening the weld as the puddle, left in the center, expands outwards.The pic looks like you are starting the weld in the middle of the hole. In optimum conditions with a nice welder that might be the best way to go (don’t know).
I am also limited to a flux core welder. I had good results by starting the weld pool at the perimeter of the hole and working the bead around, then filling the middle.