How To Do Cast Iron Welding. Dont heat over 1400 degrees F since that will put the material into the critical temperature range. Brazing can be another process of joining the cast iron but it is not a welding process.
If you cant preheat the whole part try to at least warm the weld area up to 100 degrees. To get an ultimate solution you might need to hire a cast iron welding specialist. Work on one inch at a time and allow about 45 seconds for the segment to cool down before moving on to the next one.
Preheating the cast iron part before welding will slow the cooling rate of the weld and the region surround the weld.
Cast iron is naturally brittle and most repairs are usually for broken casings or cracks. To get an ultimate solution you might need to hire a cast iron welding specialist. Unlike the traditional welding technique used to repair metal items brazing uses minimal heat to fix your cast iron pieces. Heat control will allow for proper thermal expansion for cast iron without cracking.