| 摘要 |
PURPOSE:To obtain a composite roll excellent in resistance to surface roughness by constituting the outer shell layer of a composite roll for rolling iron and steel of a high Ni-Cr-type cast iron in which graphite is crystallized out. CONSTITUTION:While rotating a cylindrical mold for metal mold whose internal surface is previously faced on its axis, a molten cast iron having a composition containing, by weight, 2.5-3.5% C, 2.0-3.5% Si, 0.3-1.5% Mn, <0.1% P, <0.05% S, 3.0-4.5% Ni, 5.0-13.0% Cr, and 0.5-1.5% Mo is poured into the above to undergo centrifugal casting, by which the outer shell layer of a composite roll for rolling iron and steel is formed. After the outer shell layer is perfectly solidified, a molten cast iron for shaft core material is poured into the above and completely welded to the outer shell layer, by which a composite roll is formed. By this method, graphite is crystallized out in the whole of the outer shell layer for use in direct rolling because proper amounts of Ni as a graphitizing agent are contained and inoculation with Si is applied prior to casting, by which the composite roll having a structure reduced in the amount of retained austenite and excellent in resistance to surface roughness can be obtained. |
