When I worked at a boat yard in my younger years a salesman came in and presented a new welding rod none of us had heard about. It was called Certanium. The salesman was a former welder, and a good one. But, my boss was sceptical and wanted him to prove what he claimed. He said one of their rods could weld directly on any cast iron or cast steel, he could even weld cylinder sleeves. He said the electrode was fine for repairing cylinder blocks, and if a cylinder block had a mounting for a generator for example, and it broke off, he could fabricate a piece out of regular steel bar and weld it on to the block, and it would be fine. We thought he was just pulling our leg. The guy then claimed that if a cylinder block was cracked in the side, and it was leaking coolant, he would use the angle grinder to grind in a bit, like a V, and then just weld, and it would close it, and it would not continue to crack. My boss was just shaking his head.
The guy wanted to prove what he had said, and was taken to the workshop, and one of the guys gave him an old and worn out cylinder sleeve we had just replaced on a 6 cylinder Volvo Penta marine engine. The guy said, I am going to crack it in 4 quarters, and weld it back together again, and you can then put it in the vise and squeeze it until it cracks again. And I can guarantee you it will not crack near the welds. So, the guy did as he had said, and the guy who had found the sleeve put it in the vise, and tightened it. The sleeve cracked again, about mid between the welds. The guy who had picked out the sleeve was also our best welder, so he said, can you weld forged steel to cast iron the way you said ? He got a worn out cast iron pulley and a 4 inch long flat steel bar of forged steel. He welded it, and the vise was massive and they smacked the flat iron bar with a sledge so the pulley flew out of the vise. The iron bar was still on the pulley. They put it back several times and tightened it, and smacked the flat iron with the sledge from several angles, but it did not come loose. My boss and all the others including myself could not believe our eyes. We bought some rods, and some months later a fishing boat came in with a cracked block, and the best welder went onboard, prepared the crack as the other guy said, and welded it. We never heard from the guy again about the crack, and he used to come in to us for maintenance jobs from time to time but the engine was fine.
Bill