Hitachi Metals, Ltd.

Ryosaku Nawata

Toshiyuki Hattori

Kenji Date

Kiyoshi Furushima

Akira Noda

Wear- and seizing-resistant roll for hot rolling and method of making

The compound roll having a shell portion made of a hard, high-alloy cast steel or iron having excellent wear resistance and resistance to surface roughening and a core portion made of a tough cast iron or cast steel, the cast iron of the shell portion having a composition consisting essentially, by weight ratio, of 1.0-3.0% of C, 2.0% or less of Si, 2.0% or less of Mn, 2.0-15.0% of Cr, 10.0% or less of Mo, 2.0-8.0% of V, the balance being substantially Fe and inevitable impurities, an average diameter of crystal grains constituting a matrix of the metal structure of the shell portion being 100 .mu.m or less in a range from a surface to a depth of 50 mm when determined by an image analysis method on the crystal grains having diameters exceeding 30 .mu.m, and the crystal grains satisfying the formula: m.sub.2 .ltoreq.1.2 m.sub.1, wherein m.sub.1 is an average diameter of the crystal grains at the surface of the shell portion, and m.sub.2 is an average diameter of the crystal grains at the depth of 50 mm, is produced by a centrifugal casting method which comprises supplying a melt for the shell portion at a temperature T satisfying the formula: Tc.ltoreq.T.ltoreq.Tc+90.degree. C., wherein Tc is a primary crystal-forming temperature of the melt for the shell portion, to a hollow cylindrical mold rotatable around its longitudinal axis, at such a speed that an average shell portion-forming speed in the mold is 2-40 mm/min.

Compound roll and method of producing same

Method of producing a compound roll

The 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, the cast iron of the shell portion 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, an average diameter of primary precipitated particles constituting a matrix of the metal structure of the shell portion being 80 .mu.m or less in a range from a surface to a depth of 50 mm when determined by an image analysis method on the primary precipitated particles having diameters exceeding 30 .mu.m, and the primary precipitated particles satisfying the formula: m.sub.2 .ltoreq.1.2 m.sub.1, wherein m.sub.1 is an average diameter of the primary precipitated particles at the surface of the shell portion, and m.sub.2 is an average diameter of the primary precipitated particles at the depth of 50 mm, is produced by supplying a melt for the 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 the shell portion, to a hollow cylindrical mold rotatable around its longitudinal axis, at such a speed that an average shell portion-forming speed in the mold is 2-40 mm/min.

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Kitakyusyu, Japan

Ryosaku Nawata