i've never heard of cast iron shattering when welded. it can be welded, to it "self" or to regular carbon steel. the welder just needs to be familiar with the process.
the problem is that cast iron absorbs & releases heat at a different rate than carbon steel or the weld filler metal. what happens when normal methods are used is that the weld it self cools & shinks, then pulls itself away from the cast iron. to prevent this the cast is preheated to a certain temperature with a torch ( if the job is big enough this preheating is repeated to maintain temp. ) after welding the piece is buried in sand or wrapped with heavy insulation to slow the cooling process down & prevent cracking. there is also a "cold" method ( no preheat ) but i don't have time to go into that as well.
although best left to a proffessional ( there should be a welding & machine shop in your area able to tackle this job )cast iron can be welded quite successfully by a welder familiar with the proccess. i know this because of my 20 plus years on the job welding experience.
robert
