The electrothermal alloy materials used for radiant heating pipes should have high resistivity and high electrothermal conversion rate. Because the radiant tube is placed in the shell, its heat transfer process is different from that of ordinary outdoor electric heating elements, and its heat shield is large, so the temperature of the element must be controlled during heating to prevent the element from overheating. When the radiant tube is turned off for heating, the surface temperature of the electric heating element is about 100℃- 150℃ higher than the furnace temperature. Therefore, when selecting materials, it is necessary to analyze the furnace temperature and atmosphere in the furnace and choose the correct heating materials.
At present, the series of radiant tube heating tubes are squirrel cage type, vertical belt type and spiral type. The heating element is made of imported or domestic resistance wire, nickel-chromium wire (or tape) and iron-chromium-aluminum (wire or tape), and the protection tube is made of imported high-temperature alloy plate and heat-resistant steel plate by roll welding or centrifugal casting, which has the characteristics of high temperature oxidation resistance, good carburization resistance and long service life.