PURPOSE: To enable the long and consecutive heat air treatment at more than 1,100C by fabricating blades and blade wheel with the ceramics which has the heat resistance of 1,200W1,400C and the tensile strengh of more than 100kg/cm2 with the temperature range.

CONSTITUTION: Blades 1 and blade wheels are fabricated with ceramics which have the heat resistance of 1,200W1,400C and the tensile strength of more than 100kg/cm2. The ceremics suitable as the material for fan blade 1 and blade wheel 2 are sintered silicon nitride or silicone carbide, and are made by non- pressurized sintering. Thus by making the blade and blade wheel of the ceramics the long and consecutive heat air treatment at about 1,100C can be done to improve the heating efficiency. Specidically this is appricable to any furnace like a holding furnace and an annealing furnace.