Proposal for New Hearth Roller Consisting of Ceramic Sleeve and Steel Shafts Used in the Heat Treat Furnace

Conventional rollers used in a heat furnace are called hearth roll. They must be changed very frequently since high temperature of the furnace induces wear on the roll surface in short period. This paper therefore discusses a new roller structure consisting of ceramic sleeve and steel shaft connected by shrink fitting. Although all ceramic sleeve has high temperature resistance and high corrosion resistance, attention should be paid for the risk of fracture due to the thermal expansion of the steel shaft that is much larger than the one of ceramic. Simple double cylinder simulation suggests that thinner structure is useful for reducing thermal stress. The finite element analysis shows that tapered shaft thickness is desirable for the ceramics hearth roller. Finally, an application of ceramic roller to steel manufacturing machinery is considered by changing geometry and material. Since only low shrink fitting ratio can be applied to the new roller, failure analysis is also considered for preventing the coming out of the shaft from the ceramic sleeve.