Respective of plate welding, there are very strong and valid arguments
against doing so.  In my previous post I outlined a method that is
successful.  Over the years I've had seven plates, both upright and
grand fixed with welding, and no failure.

I mentioned heating the plate to around 500 degrees prior to starting
the welding, then proceed in steps, to allow the plate to cool back to
500 degrees or so, then proceeding, about an inch at a time, for long
cracks, then keep the plate at 500 degrees for at least 24 hours and
slowly returning it to room temperature, so as to stress relieve the
casting.

Sometimes castings are too thin, or cooled too quickly when new, such
that they leave the factory with great internal stress, which is only
added to with string tension on it.  Finding an oven to heat an entire
casting might be an issue; maybe your local pizza restaurant?

Tom Binnall
Tacoma, Washington