Hearth roll is one of the most important part of continuous annealing furnace. Its working condition is the decisive factor if annealing furnace can be normal production.
Work and structural features of a hearth roll
Structures and materials of hearth roll
Working at over 800 ℃ in the furnace and rotation under load, meantime mechanical damage by charge , the hearth roll material must have high temperature strength and oxidation resistance. The structure shown that centrifugal casting roll is a hollow cylinder, two alloy roll end welded. Furthermore two end shaft welded in the roll end. The thin-walled rollers to give axial thermal resistance. The insulation materials inserted from the roll barrel to roll end to reduce the temperature of the bearings.
Furnace hearth roll materials are ZG35Ni20Si or ZGCr25Ni35Nb, due to the high Ni alloy is expensive, domestic production of furnace hearth rollers using cheap ZG3Cr24Ni7SiNRe, this material has high temperature strength, endurance strength higher than ZGCr25Ni20Si2, after long-term use aging embrittlement tendency is small. Due to the addition of rare earth the oxidation resistance of the steel improved.
The diameter of the furnace hearth roll if possible use of smaller size at high temperature strength permitting to reduce the weight of the weight and save precious metal.
The furnace hearth roll commonlu use spiral roller bearings or spherical bearings . The bearing temperature is high so high-temperature grease lubrication is needed. The diameter of haft journal is usually smaller than the 0.1-0.25mm of bearing because of radial expansion.