To provide an electric furnace with excellent uniformity of temperature distribution, a large effective heating area of a heating element with a small size, and optionally controlling temperature with high accuracy.
This tubular electric furnace is composed of a core pipe 5, the heating element 1 vertically arranged to a longitudinal direction of the core pipe at the outside of the core pipe, a heating chamber 18 which is the inside of the core pipe and a heat-insulating material 6 enclosing the heating element. The heating element is provided with a ring-like heating part and a terminal part horizontally extending outward from both left and right edges of the ring. The heating element is composed of a lanthanum chromite ceramic material having porosity of less than 5% and a specific resistance of not less than 0.10 Ω at 1000°C. A ratio (L/R) of a length L of the terminal part to an outside diameter R of the ring in the heating element is specified within a range from 0.3 to 2.0, and the ratio (M/N) of a cross-sectional area M of the terminal part to the cross-sectional area N of the heating part is specified within the range from 1.3 to 4.0.
ONISHI KOJI
INUI KAZUYO
KAWANAMI TOSHIO
