Microstructure evolution of roll core during the preparation of composite roll by electroslag remelting cladding technology

Abstract

In the present study, the comprehensive analyses based on the numerical simulation, in situ observation, and metallographic detection were carried out for the roll core of GCr15/45 carbon steel composite roll manufactured by the new electroslag remelting cladding (ESRC) method. During the ESRC process, the temperature distributions at the different radial and longitudinal positions of the roll core have great changes due to the different degrees of heat conduction from the slag bath, as a result, various microstructure and properties were obtained at the different positions of the roll core. The results illustrated that the ESRC process tended to be stable as the composite height reached a certain value and the high-temperature austenitization process mainly occurred in the radial regions where R > 60 mm, whereas no significant changes occurred at the areas where R ≦ 60 mm. The coarse grains and few Widmanstatten structures with proeutectoid ferrite were generated in the roll core areas near the bimetallic interface, while the fine grains with more proeutectoid ferrite were obtained in the roll core area away from the interface. Therefore, a higher tensile strength and a better plasticity were obtained for the specimens away from the interface.

Interface Characteristics of GCr15/45 Carbon Steel Composite Billet Produced by Electroslag Remelting Cladding

“…Based on the previous report by authors, 23) the coarse grains and harmful ferritic Widmanstatten structure were observed in the heat-affected zone of the as-cast GCr15/45 carbon steel composite samples. In order to eliminate the above undesirable microstructure, an isothermal spheroidization annealing treatment was carried out.…”

“…21) For the GCr15/45 carbon steel composite billet, few Widmanstatten structures were always generated in the heat-affected zone of the roll core. 23) The Widmanstatten structure is always considered as an overheating defect, its existence generally results in a serious separation of the matrix and reduces the material's toughness and plasticity. Since to the large angle grain boundary has a certain blocking effect on the crack growth, and the fact of the larger grain size, the less grain boundary, so few obstacles are encountered during the crack growth, and finally, a higher brittleness performance is obtained.…”