Be real careful here.
Normally, alloys used for cast iron have additional carbon. These are designated by a "CI" reference.
The additional carbon is to reduce contraction and subsequent cracking.
Unfortunately, some filler metal companies use any high nickel alloy, without the extra carbon addition, thinking it is the same (or close), and call it a cast iron alloy.
These do not work always work as well.
My favorite for years has been aluminum bronze, A2
Works well, tensiles out well, and is available as either a stick, mig, or tig alloy.
If you need more info, let me know!!
Good Luck
brande