Coal boiler as a forge??

Has anyone used their coal boiler to do heat treating for tool making?

My son in law wanted to make a Roman short sword. He used my Axeman to heat the metal and then beat it into shape. It will get steel white hot for shaping but I'm not sure it would be effective for a heat treatment process because of the varying temperatures and need to control them properly. And the hammer pounding got pretty annoying after a while!