Generally, preheated welding is performed by heating the cast iron from 500 to 1200 degrees. However, there are a few things you want to remember when welding cast iron to steel. It is always preferred to heat the entire casting, if possible. This is the most effective and frequently used technique. The best way to do it ( i have done it lots of "wrong ways ! " Yes, cast iron can be welded to steel. Preheating the cast iron part before welding will slow the cooling rate of the weld, and the region surround the weld. Welding cast iron to mild steel is for the most part done with ornamental iron such as gates and fences. High nickel rods aka NI rod, work pretty well for tig welding cast iron, You can also beat the flux off of a nickel stick rod and use it for tig welding. ) is as follows As Scott said a 99Ni rod is best. At this temperature, the iron inside the metal gets stretched preventing it from cracking. the ornaments are typicaly cast iron such as spearpoints and fit over the top of what ever square tubing size ect you are working with. Through your welding helmet, you will see a small pool of molten steel form where the wire touches the steel. Typical preheat temperatures are 500-1200 degrees F. Don’t heat over 1400 degrees F since that will put the material into the critical temperature range. Cast steel is not the problem. Welding mild steel to cast iron or cast iron to itself can be a bitch if you don't do it right A 309 might work , a 312 a better choice. Problem is that for TIG filler ( cut length ) its insanely expensive. Touch the electrode to the steel, not the cast iron, and then pull the trigger.
Sometimes, Stick actually works better due to the affects of flux on impurities. While you are pulling the trigger, move the electrode slowly toward the cast iron until the pool of molten metal … First, usually you are doing a repair job or a retrofit if you are asking about welding cast iron to steel, so be sure to check the parts thoroughly to ensure there are no stress cracks or other signs of damage.