PURPOSE: To obtain the titled sintered powder suitable as an electrical insulating filler for sheath heater, having high insulation resistance at high temperature, excellent packing properties and fluidity, by sieving mostly globular sintered magnesia powder into given particle sizes.
CONSTITUTION: Mostly globular sintered magnesia powder calcined by a rotary kiln is screened by using sieves of 420μm and 44μm. Consequently, sintered magnesia powder for electrical having a chemical composition consisting of ≥96wt.% MgO, ≤2wt.% CaO, ≤1wt.% SiO2, ≤0.2wt.% Fe2O3, ≤0.2wt. % Al2O3 and ≤0.1wt.% B2O3, ≥107Ωcm insulation resistance at 600°C, ≤200 seconds/100g flow time and ≥2.3g/cm3 tap density and comprising ≥90wt.% particles having 420W44μm particle diameter. The prepared sintered magnesia powder is preferably used as an electrical insulating material to be packed especially into between a metallic pipe and a heater.
Nibu, Kunihiko
Takeuchi, Hiroshi
