Method of producing a compound roll

A method of producing a compound roll comprising a shell portion made of a hard cast iron having excellent wear resistance and resistance to surface roughening and a core portion made of a tough cast iron or cast steel, which method comprises forming said shell portion by centrifugally casting an iron having a composition consisting essentially, by weight ratio, of 2.5-3.5% of C, 0.5-1.5% of Si, 0.5-1.5% of Mn, 0.1% or less of P, 0.05% or less of S, 3.0-5.0% of Ni, 1.0-2.5% of Cr, 0.1-1.5% of Mo and balance Fe and inevitable impurities, said shell portion having a surface portion extending radially inward from an outer surface of said shell portion, and wherein said cast iron in that part of said surface portion ranging from said outer surface to a depth of 50 mm has a metal structure comprising a matrix of primary precipitated particles having an average diameter of 80 .mu.m or less when determined by an image analysis method on the primary precipitated particles having diameters exceeding 30 .mu.m, and said primary precipitated particles satisfy the formula:

• m.sub.2 .ltoreq.1.2 m.sub.1, wherein m.sub.1 is an average diameter of said primary precipitated particles at the surface of said shell portion, and m.sub.2 is an average diameter of said primary precipitated particles at the depth of 50 mm, which method further comprises supplying a melt for said shell portion at a temperature T satisfying the formula:
• Tc-20.degree. C..ltoreq.T.ltoreq.Tc+70.degree. C., wherein Tc is a primary crystal-forming temperature of the melt for said shell portion, to a hollow cylindrical mold rotatable around its longitudinal axis.