Composite rollers have a working life 1.3-1.5 times that of monolithic rollers. In practice, however, problems tend to arise. Moreover, the tensile stress in the external band rules out the use of traditional wear-resistant materials such as cast iron. Employing preliminary axial compression of the band, i.e., prestressed composite rollers (PCR), permits the use of material of lower tensile strength. Existing designs and methods of assembly of such rollers have significant deficiencies preventing their industrial application. The basic obstacle is the assembly and disassembly of PCR by means of hydraulic clamps and auxiliary equipment that are usually customized for each type of roller. Moreover, the diameter of the roller shaft is limited by the power of the hydraulic devices for its extension, which rules out this assembly method for composite rollers in which the shaft is combined with the end pins. Special mechanical and hydraulic equipment must be used to meet the accuracy requirements on the contact sections of the band and the roller shaft. At first, only purchased cast-iron rollers were used at Chelyabinsk Metallurgical Works (CMW). However, available metallurgical, forging, pressing, and mechanical equipment permitted the organization of roller production for bar mills. Work on the manufacture of composite reinforced rollers began in 1996. Specialists developed a design and manufactured 20 rollers with external bands made from materials such as SPKhN-60 cast iron and Kh12VMF, DI-22, EI347, and R6M5 steel. Tests of the composite rollers in the finishing cells of a 250-2 wire mill and a 250-1 small-bar mill showed that the design developed is effective and reliable. However, its problems - the labor required, the manufacturing precision required in the roller components, and the radial tensile stress in the external band - render it unappealing.
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