It consisted of mullite crystal the roller null for the roller hearth kiln which consists of

摘要

PROBLEM TO BE SOLVED: To provide a roller for a roller hearth kiln made of a mullite sintered compact, which has excellent thermal impact resistance and corrosion resistance, little deformation at high temperatures, and excellent durability. SOLUTION: The roller for the roller hearth kiln is made of a heat resistant mullite sintered compact mainly consisting of mullite crystals. (a) The weight ratio of Al2 O3 /SiO2 is 65/35 to 78/22. (b) The pores present in the sintered compact mainly have a round and closed shape. (c) The average closed pore size thereof is 2 to 50 μm. (d) The average crystal particle size of the sintered compact is 2 to 20 μm. (e) The average closed pore size/the average crystal particle size of the sintered compact is 0.5 to 3. (f) The relative density of the sintered compact is 70 to 95%. (g) The amount of deflection at 1,500 deg.C under the deflection of 2MPa is =10 mm.