Cold Welding Cast Iron With MIG......
A couple years ago I had several cast iron repairs needing welded. Cracked intake & exhaust manifolds, wood stoves, & some decorative cast iron pieces. After 6 months of research, & getting several broken cast manifolds from my brothers' engine shop, I experimented with an old-time process called "Cold Welding Cast Iron With MIG". Depending on thickness, the amperage ranged from 80 to 120A, cracks beveled, end of cracks drilled, metal wire-wheeled to clean, bare, & sometimes a light grinding with fine grinding wheel.
I use .030/309L(.01 carbon content), C2(98AR/2CO2)shielding gas @18cfh, tacking at the center to start & immediately peaning with a slightly rounded end on my chipping hammer. The idea is to weld in very short beads not exceeding 1/2", peaning immediately, & allowing to cool back to room temp. I vary location with each bead with immediate peaning. When doing this, you can take your glove off after the bead & lay your bare hand on the weld & it will feel barely lukewarm. This process eliminates the expansion & contraction of the cast that is the main cause of continual cracking.
This process takes practice & you must learn parameters with amperage & I use the "pull" technique. I have had 100% success so far. Here's some pics of one of the several Rolls Royce exhaust manifolds I did that was broken & had been previously welded with SMAW that rusted away.
thanks for the excellent post,