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Work or back=up roll for continuous combined casting and steel rolling - comprises steel base body, low m.pt. alloy thin interlayer and wear resistant top layer applied by inert gas atomisation of molten stream
Work or back=up roll for continuous combined casting and steel rolling - comprises steel base body, low m.pt. alloy thin interlayer and wear resistant top layer applied by inert gas atomisation of molten stream
The roll comrpises (i) a base body of steel; (ii) a 0.1-1 mm thick intermediate layer of an alloy with a m.pt. below that of the base body; and (iii) a 5-100 mm thick wear resistant top layer which is applied by inert gas atomisation of a molten stream with a heat content sufficient for metallurgical bonding of the base body, the intermediate and the top layers. Prodn. involves applying the intermediate layer by flame spraying and applying the top layer by inert gas atomisation of a molten wear resistant alloy stream while the intermediate layer temp. is still above the base body temp. The intermediate layer pref. comprises an eutectoid alloy with a m.pt. of 1000-1300 deg.C, e.g. NiCrBSi alloy of compsn. 60-80 (70)% Ni, 15-25 (20)% Cr, 2-5% B, 2-5% Si, balance Mn, C and imputies or a NiCoCrAlY alloy of compsn. 0.02% C, 22.24% Co, 16.18% Cr, 12-13% Al, up to 0.5% Y and balance Ni. The intermediate and top layers are pref. applied during rotation of the base body and simultaneous linear motion w.r.t. the base body and the alloy sources. The base body is pref. preheated to 120-200 (150) deg.C before applying the intermediate layer and its pref. preheated together with the intermediate layer to 950-1050 (1000) deg.C before applying the top layer. USE/ADVANTAGE - The roll has a long service life underload. The process produces wear resistant layers of more than 50 Rockwell hardness at 500 deg.C, includes hard material particles, avoids the need for post-heat treatment and may be used insted of build-up welding for roll repair.
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