A fire brick is a special type of brick made using fire clay and has a good resistance against high temperatures which are used in kilns, lining furnaces, fireplaces, and fireboxes. These bricks are manufactured in a way similar to that of normal bricks, except during the burning process- Fire bricks are exposed to very high temperatures.
Fire bricks or fire clay bricks or refractory bricks are made from the fire clay. The process of manufacturing of these bricks is same as the ordinary bricks but are burnt at very high temperatures in a special type of kilns generally Hofmann’s kill. The raw materials of these bricks consists of flint clay and grog that has burned fire clay as non plastic materials and soft fire clay as plastic material.
Color of these bricks is whitish-yellow or light brown.
Comp strength of fire clay bricks varies from 3.5 N/mm2 to 48.26 N/mm2.
The water absorption % of fire bricks varies from 4 – 10%.
These bricks are generally used in lining furnaces kilns, fire boxes and fireplaces.
Acid Refractory bricks
Silica bricks: 95 – 97% silica, 1 – 2% lime
Ganister bricks: 98% ganister a hard colored stone with 10% clay, 2% lime.
These are generally used in lining furnaces having siliceous & acidic slag steel industry and coke oven.
Basic Refractory bricks.
basic refractory bricks are manufactured from magnesia, dolomite, bauxite, etc.
Magnesia bricks: magnesium above 85%, calcium oxide up to 25% & silica up to 5.5%.
Bauxite bricks: aluminium oxide above 85% & clay up to 20 %.
these type of bricks are highly resistant to corrosion and are used for lining furnaces having basic slag.
Neutral Refractory Bricks
Chromite bricks: 50% chrome, 30% Iron oxide, 20% Bauxite.
Chrome magnesite bricks: A mixture of chrome ore and magnesite ore with a min % of Chromium (III) Oxide is >18% & Magnesium Oxide is >30%.
Spinel bricks: Made from the refractory slag produced in an electric furnace consisting of magnesia & alumina.
Forsterite bricks: Made from mineral forsterite
The neutral refractory bricks are used in places where acidic and basic linings are to be separated.
A fire brick, firebrick, or refractory is a block of ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. A refractory brick is built primarily to withstand high temperature, but will also usually have a low thermal conductivity for greater energy efficiency.
There are mainly three varieties of refractory bricks;
a) Acid Refractories i. Ordinary Fire Bricks ii. Silica Bricks iii. Ganister Bricks
b) Basic Refractories i. Magnesite Bricks ii. Dolomite Bricks iii. Bauxite Bricks
c) Neutral Refractories i. Chromite Bricks ii. Carborundum iii. Chrome Magnesite Bricks iv. Spinal Bricks v. Forsterite Bricks