oleb97,
As the two gentlemen have indicated, arc welding cast iron requires that certain procedures be followed. Cast iron is very high in carbon, and this is where the problems arise.
When you weld cast iron, and melt the parent metal, it goes through various states as it cools. The formation of Martensite is what causes it to crack. If you can preheat, weld, and post heat, you can help eliminate these brittle deposits.
Peening the weld bead between passes will keep it from shrinking as much, and cracking away from the casting.
Many people braze cast iron. This procedure doesn't melt the base material.
Cast iron is welded every day successfully, you just have to know the "procedure" and follow it to get the proper results.
This is turning into a novel. I am not familiar with arc welding carbon steel to cast iron. Curt's welder sounds like he has this dialed in.
To get net, you have to have the proper rod and follow the proper procedures to make it work satisfactorily. I wouldn't make my first attempt a split manifold unless I had a tutor to guide me.
Stuart
