Hey just for the next welding you might do, start at the edge don't finish at the edge(bolt slot). You build heat as you weld so do the edge while the metal is cooler so you will not have the burn out you have now. Also if you can find an old transformer or better yet switch gear(7000 volt and up) you can get copper plate from them to use as a backer plate. The weld will not stick to copper. Don't use a penny they are not copper. Just some tricks from an old welder. Like the tire upgrade.