Hello everyone, recently they brought me a piece of cast iron and I soldered it with a 3/32 Ni99 stick with a dc + inverter and it left me a very convex cord and lack of fusion. because it does not melt well despite having the amperage recommended maximum.
I'm not a "pro" or whatever, but I did just finish welding a lot of cast about 45 minutes ago and its fresh on my mind. Like stated above, you need a good preheat. Depending on how much heat you can get into the part, I'd say it should be at least too hot to touch and after you finish welding, it should cool slowly. A welding blanket works good, you can bury the part in a bucket of sand or dry dirt, if the part isn't too hot I've wrapped a part in a welding apron. How big of a part are you welding? Grind your weld clean, bevel if you need to, preheat, and just go slow. It's different than steel. Make sure you wire brush the root between welds, the weld heat can bring a lot of crud to the surface. Try to find some scrap cast iron to learn on. Don't get too frustrated with it, there is a LOT of variety when it comes to cast iron and cast iron is porous so there are lots of variables.