What Materials Are Used in Cartridge Heaters?

Cartridge heaters are primarily composed of the following materials:

Metal Tube (Sheath):
The outer shell of a cartridge heater is typically made from a metal tube. Common stainless steel grades include 304, 321, 316L, 310S, INCOLOY 840, INCOLOY 800, and INCOLOY 600. These materials offer excellent corrosion resistance and high-temperature durability, making them suitable for various working environments.

Resistance Wire (Heating Element):
The core component of a cartridge heater is the resistance wire, which converts electrical energy into heat. Common materials include iron-chromium-aluminum (FeCrAl) alloys, nickel-chromium (NiCr) alloys, and molybdenum (Mo) wire. These alloys provide high-temperature stability, oxidation resistance, and mechanical strength, enabling prolonged operation under high temperatures.

Filling Material:
Inside the metal tube, the space around the resistance wire is filled with a material that offers both good thermal conductivity and electrical insulation, typically crystalline magnesium oxide (MgO) powder. This filler efficiently transfers the heat generated by the resistance wire to the surface of the metal tube, enhancing heating performance.

Insulation Materials:
To ensure safe operation, insulation materials are incorporated between the resistance wire and the metal tube to prevent electrical leakage and short circuits. Magnesium oxide serves as both a filler and an insulator in standard designs.

Additionally, depending on specific application requirements and environmental conditions, cartridge heaters may be constructed from other specialized materials, such as quartz or titanium. These materials possess unique properties tailored to particular use cases.

Summary
In conclusion, a cartridge heater is a tubular electric heating element composed of a metal sheath, resistance wire, filling material, and insulation materials. The selection and combination of these materials directly determine the heater’s performance, efficiency, and service life.