The cartridge
heater is a high-quality seamless metal tube, with electrothermal
alloy wire (nichrome wire, ferrochrome wire) evenly twined around
the the central axis in the tube. The gap in it is compactly filled
with oxydic magnesia with fine insulativity and thermal
conductivity, and the nozzle is sealed with silica gel or ceramics.
This kind of metal armored electrothermal element has the function
of heating gases, molds and a variety of liquids.
