Soldering: a non fusion method of joining metals with a filler material with a melting point lower than the metals being joined.
Welding: fusing the parent metals together by melting the parent metals, sometimes a filler material similar to the parent metals is utilized.

Key words: non fusion vs fusion.

Had the floor plate been soldered the filler material could be melted, parting the two components and allowing them to be cleaned up and left relatively intact.
With the weld however the parent metals are fused, as mentioned the joint will have to be cut and the damage repaired by welding and reshaping.
If the weld was done by torch or TIG it will likely be similar in hardness to the parent metal and usually workable with a good file. If it was done by Arc or MIG it will be harder than woodpecker lips and grinding is typically the only method of reshaping.