How to Break an Old Weld

I agree with the others on the use of an angle grinder, but with one exception.

Put a cutter disc on the grinder first. They sell these things everywhere. You'll have that old weld cut faster than you can fire up the torch.

Try it; it really works fast! Like a knife thru butter.

Allan

As stated by Eldon, use a grinder with a thin blade and cut just above (couple thousandth's) the casting surface until you see a black line.

This black line will be the seam between the two mated piece's. When you see the black line then your piece will come off very easy.

Don't see a black line? Then your cutting too high or too low of the seam.

Most welds will be about 1/8" deep penetration on both piece's.

I agree that too much hammer on castiron will most likely break the castiron. Cut to the black line then use a very light tap, if needed.

T_Bone

Get a good full helmet with breathing filters, and face shield, leather gauntlet gloves, and cut the welds with metal cutting discs on a 9" depressed centre, electric mobile grinder, with metal cutoff blade ( 7" will do ).
You can't go round corners, so you will have to cut chunks off, watch the sparks !.