There are opinions from some here who don't know what they're talking about. Looking at Servicar Rider on this one. Cast iron has very low ductility, which is why it needs to be preheated and slow cooled to be correctly welded and maintain some of the ductility. Spreading the heat thoroughly through the part spreads the growth and shrinkage over a much larger area, preventing concentrations of stress at or near the weld area. Putting a buttload of heat into the part at the weld then letting it cool and shrink rapidly back down is a shortcut to weld failure in iron.
As I and others said earlier, it CAN be welded in short bursts and kept as cool as possible and that will work with peening, but it will NOT be as strong and ductile as an iron weldment that has been properly preheated and slow cooled. The weld will be hard and fragile, but it will hold for something that's not mission critical. A sharp impact may break that weld though. Gas welding works well also - with correct preheating, in-process heat maintenance, and slow cooling. The same as nickel rod welding. Rapid cooling from too high a heat results in movement beyond the material's ability to accommodate and the result is almost universally brittle failure, cracking, etc. You can get away with it on short welds by limiting heat input because the material doesn't grow and shrink as much.
And no, "cold" welding absolutely does NOT have the same effect as peening. Exactly the opposite in fact. A quick short stitch weld heats and cools rapidly, shrinking and putting the weld bead in tension as it does so - exactly what you don't want. Peening stretches the outer surface of the weld bead, putting it into compression - exactly what you DO want to counter the shrinkage of the bead. Leaving the bead in tension will very frequently result in cracking of the weld bead.