Please forget welding.  The heating of the metal around the weld is
prone to make it break once under stress.  The top piano rebuilders,
when a plate needs mending, use Lock-N-Stitch ( http://www.locknstitch.com ).
Sometimes they even ship the plate to the company, if it seems the
wisest option.  Reports are good for this system.

Gordon Stelter

 [ Reports are plentiful but first-hand experience is hard to find.
 [ Many years ago I saw a newly welded casting leaning against a wall,
 [ awaiting re-installation in a small Bechstein grand (known for its
 [ weak plate) at the shop of MMDer Janos Macsai in Budapest.  He's the
 [ only rebuilder I've met who actually attempted welding a cast iron
 [ frame.  I don't know if the repair was successful.  -- Robbie