Hi Kit
Can I make a suggestion?
Conscript your instructors into this project! See if you can't make the project into a class-room study or lesson. Chuckle: in the most optimistic scenario, get the school to provide the cast iron! Treat it as a challenge for the class.
I once broke the tang of an old English table knife inside the bone handle - it had rusted. We tried sticking an extension on it in our workshop, but no joy. So one of the smarter apprentices took it to college to get the welding instructor to help. It turned out that this was some of the most difficult steel to weld the instructor had ever come across, but he DID know about the problems with this very-high-carbon steel. Fixing my knife turned into a major class-room and lab exercise for the whole welding class! Yes, the tang was fixed. Everyone won.
Cheers