We do quite a bit of work for a local cemetery, from working on their trailers to mowers. This is a bronze place marker for one of the graves. While mowing the lawns they drive over these place markers and eventually break off the bolt attachment.
Typically the heat from the welding would discolor the top side. We remedy that by using several wet rags as a heat sink and put small stitch welds a little at a time on each all thread in rotation.
We used an aluminum bronze welding wire .035 diameter and straight Argon as the shielding gas.