I also suggested using a high nickle content rod. I never even attempt to weld cast iron or forged steel without using it. These rods are expensive and don't store well for long periods without going bad, but most welding supply stores will sell these by the rod because they know this. For that job two or three rods would be enough (about $4). Grind a bevel on both pieces, not just one and then fill to just above level. Let air cool or better yet, wrap in a welding blanket or bury in sand to slow the cooling, then grind/machine to suit. The nickle content offers the flexibility needed in the joint to keep the cast or forged material from cracking during the cooling and afterward. There is a significant difference in the thermal properties between the weld material and the cast material with different rates of expansion and contraction during the welding process that causes the fracturing as the welded parts cool. Slowing the rate of cooling and providing the high nickle content in the weld produces a very strong weld when done correctly. There is a lot more to welding than just learning how to stick two pieces of metal back together.

Charley