In muffle furnaces the hot zone chamber has a cube or a cuboid shape. The heating elements are placed along the walls. They are available up to maximum operating temperature of 1800 Degree C from 750 Degree C. They may have a gas purging facility with gasses being purged from the rear of the furnace.
Heating Elements Description:
In case of Metallic Heating Elements (MHE) – Kanthal APM and Kanthal A1 – the wire is would around alumina rods and placed along the two side walls and sometimes also along the back wall as per the wattage requirement for the job.
Kanthal APM: Kanthal APM is an advanced powder metallurgical, dispersion strengthened, ferritic iron-chromium-aluminum alloy (FeCrAl alloy) for use at tube temperatures up to 1250°C (2280°F). Kanthal APM tubes have good form stability at high temperature. Kanthal APM forms an excellent, non-scaling surface oxide, which gives good protection in most furnace environments, i.e. oxidizing, sulphurous and carburizing, as well as against deposits of carbon, ash, etc. The combination of excellent oxidation properties and form-stability makes the alloy unique.
Typical applications for Kanthal APM are as radiant tubes in electrically or gas fired furnaces such as continuous galvanizing furnaces, seal quench furnaces, holding furnaces and dosing furnaces in the aluminium, zinc, lead industries, thermocouple protection tubes, furnace muffles for sintering applications.
Kanthal A1: Kanthal A-1 is a ferritic iron-chromium-aluminium alloy (FeCrAl alloy) for use at temperatures up to 1400°C (2550°F). The alloy is characterized by high resistivity and very good oxidation resistance. Typical applications for Kanthal A-1 are electrical heating elements in industrial furnaces.
The heating element maybe in coiled form and be embedded in the hot face fiber insulation.
Molybdenum Disilicide heating elements: High-power electric Molybdenum Disilicide (MoSi2) heating elements are for element temperatures up to 1850°C (3360°F). Kanthal Super MoSi2 heating elements are available as straight or bent elements in a wide range of shapes and sizes, all characterized by long life and consistent performance.
temperature, are housed in an alumina sheath.