Introduction
A high temperature furnace is an insulated chamber used to heat materials to high temperatures. There are several different types of furnaces, such as ceramic, electric, and gas-fired. As furnace temperatures reach temperatures exceeding 1500°C, it is essential to use a high temperature refractory material to protect the structural integrity of the chamber. Refractory materials, also known as ceramic materials, have a combination of properties such as high temperature strength, chemical resistance, and oxidation resistance. Common high temperature furnace refractory materials include high alumina, insulating firebrick, alumina-silicate refractories, and silicon carbide.
High Alumina Refractory Materials
High alumina refractory materials are a type of ceramic consisting of alumina (Al2O3) and fluxing agents. These materials are typically composed of more than 90% alumina and have an extremely high resistance to thermal shock, chemical attack and erosion. As a result, these refractories are suitable for use in electric furnaces, petrol and oil fired furnaces and plasma environments. High alumina materials are also preferred for furnace applications requiring non-wetting characteristics and high temperature stability.
Insulating Firebricks
Insulating firebricks are one of the most common types of refractory materials used in metal processing high temperature furnaces. These bricks are typically high alumina lubricated systems and are produced with a wide range of physical and chemical properties. An insulating firebrick’s primary function is to protect the floors and walls of furnaces from excessive heating and damage. Low cost and high thermal resistance properties make these materials ideal for furnace environments where operating temperatures are constant or regularly reach temperatures of up to 1450°C.
Alumina-Silicate Refractories
Alumina-silicate refractories are produced as a blend of alumina and silica (SiO2) used to protect furnace chamber walls. This material has relatively low thermal conductivity and is primarily used to insulate gas-fired furnaces. This material also has good oxidation resistance, superior high-temperature strength, and high thermal shock resistance. Alumina-silicate refractories are preferred in non-vacuum furnace applications, such as continuous resistance furnaces, and protective coatings for molds and ladles.
Silicon Carbide Refractory Materials
Silicon carbide refractories are manufactured from finely ground powder and are preferred for their high-temperature strength, thermal conductivity, and oxidation resistance. This material is often used for immersion heating and as a protective coating. Silicon carbide is also preferred for high temperature plasma environments, as it can withstand temperatures up to 2300°C. Additionally, this material has little thermal expansion, making it ideal for applications where thermal expansion is a major concern.
Conclusion
High temperature furnace refractory materials are essential for protecting the structural integrity of a furnace and must be selected depending on the type of furnace and its operational temperature. Commonly used refractory materials include high alumina, insulating firebricks, alumina-silicate and/or silicon carbide. Each of these materials has different properties and must be selected based on the specific application requirements. Properly selecting the right refractory material for your application will ensure a safe and efficient operation for your furnace.
