Welding of Cast Iron and Nodular Graphite Cast Steel. I : Properties of the Heat Affected Zone of Cast Iron

Metallographic studies have been made on the structure and properties of the weld heat-affected zone in cast iron by the single-bead tests. The thickness of the ledeburitic layer varies with the melting point of the electrodes. In the martensitic layer, "white" and "dark" martensite were observed by using different electrodes and various welding conditions. It was determined from the isothermal transformation diagrams that these two types of martensite correspond respectively to fast and slow cooling below the M_s point, the critical cooling rate being about 1℃/sec. The amount of retained austenite was about 17 to 27 per cent, showing no appreciable difference between the electrodes. It was pointed out from the calculation that the diffusion of nickel from the deposited metal to the heat-affected zone was negligibly small.