What are the characteristics of insulating fire bricks?

Insulating fire brick, also popularly known as soft brick, is a kind of refractory material that is able to withstand very high temperatures up to roughly 1800 Celsius degrees. Refractory materials are of great popularity in recent years due to their usage under extreme conditions. Among the refractory bricks, large insulating fire brick is a prominent type, as it has extraordinary properties which make it convenient to use. In the passage below, some information about the classification and characteristics of insulating fire bricks will be provided and illustrated.

-        Classification and characteristics of insulating fire bricks

a.     High alumina insulating fire bricks

b.     Lightweight insulating fireclay bricks

c.      Diatomite insulating fire bricks

d.     Floating bead bricks

e.     Zirconia insulating fire bricks

Classification and characteristics of insulating fire bricks

Insulating fire bricks can be further divided, according to their contents, into several types which include high alumina insulating fire bricks, lightweight insulating fireclay bricks, diatomite insulating fire bricks and floating bead bricks.

High alumina insulating fire bricks:

They usually have bauxite with more than 48% Al2O3 in their contents. These bricks are usually manufactured by foam method and they have a service temperature of 1350 - 1500 Celsius degrees. High alumina insulating fire bricks are fireproof, so they can contact fire directly. Due to their properties of thermal resistance, high strength and remarkable energy-saving ability, they are widely used in our daily lives as thermal protective coating. For example, high alumina insulating fire bricks can be used for lining the inside of kilns, furnaces, hot blast stove and so on.

Lightweight insulating fireclay bricks:

Fireclay with 30 – 48% Al2O3 is mainly used as the raw material for this kind of bricks. These bricks are also produced using foam method, or by adding combustible materials and binding agent. The products can generally withstand roughly 1200 – 1400 Celsius degrees. The manufacture of insulation fireclay bricks is massive, taking up to over 50% of the total production of refractory bricks.

Diatomite insulating fire bricks:

Diatomite insulating fire bricks are produced with natural porous raw materials, consisting of diatomite in their contents. They can also be classified as high strength lightweight insulating fire bricks whose service temperatures are usually below 1000 Celsius degrees. As they have the characteristics of good thermal insulation and low thermal conductivity, they are utilized as the thermal protective insulation layer of heating equipment for conditions under 900 Celsius degrees.

Floating bead bricks:

Floating bead brick is made of a special type of material called floating bead which is glass-like and smooth. Floating bead is semi-dried during manufacturing process and the products generally have features of low bulk density, hollow inside, smooth surface, high thermal resistance and good insulating power.

Zirconia insulating fire bricks:

They are often manufactured using foam method with Zirconia as the main ingredient. Zirconia insulating fire bricks can also be classified as high temperature insulating fire bricks whose service temperatures are higher than 1500 Celsius degrees. They have the characteristic of being fireproof and thus can contact fire directly. Moreover, they have properties of low thermal conductivity, good thermal shock resistance, high melting point and good refractoriness, which enable them to serve in some specific situations with extreme temperatures.

Also, there are some minor types of insulating fire bricks, including lightweight silica bricks, lightweight corundum insulating bricks and so on.