The type of bricks that can withstand high temperatures as a building material is refractory bricks and flame bricks. Typically the colour of fire bricks is white and yellowish-white, weighing around 3 kg each. We have to have a high point of fusion.
Fire clay is used to make bricks of this kind. This clay can withstand high temperatures without significant changes in structural properties such as melting or softening.
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Composition of Fire Clay
A higher percentage of ‘ non-detrimental ‘ silica and alumina should be contained in flame clay. These were expected to have a very small amount of harmful acid, magnesia, iron oxide, and alkalis.
- Silica: Silica (SiO2) is brittle at about 2800°F and eventually fuses at about 3200°F. It’s about 3300°F cooling. It has been developed as the key material for refractory brick production by this fast softening and melting point.
- Alumina: Alumina (Al2O3) has a higher temperature for softening and fusion than silica. This freezes at about 3800°F. It is used in combination with silica, therefore.
- Lime, Magnesia, Iron Oxide and Alkalis: These detrimental components act as fluxes to reduce the temperature of softening and fusion.
Manufacturing Process of Fire Brick
The manufacturing process of fire brick is similar to ordinary bricks. The usual steps are
- Digging
- Weathering
- Tempering
- Moulding
- Burning
Fire bricks were produced from clay in the fire. The burnings are conducted under carefully graded temperature control in a superior style of kiln. Burning and cooling processes were kept relatively sluggish.
Types of Fire Bricks
There are mainly three varieties of refractory bricks.
Acid Refractories
- Ordinary Fire Bricks
- Silica Bricks
- Ganister Bricks
Basic Refractories
- Magnesite Bricks
- Dolomite Bricks
- Bauxite Bricks
Neutral Refractories
- Chromite Bricks
- Carborundum
- Chrome Magnesite Bricks
- Spinal Bricks
- Forsterite Bricks
Acid Refractories
Ordinary Fire Bricks:
- Made of natural flame clay with a combination of compressed clay and sand
- Includes 50-75% silica and 20-40 % alumina with a flowing matter under 10%
- Used as a good quality refractory furnace lining
- withstands up to 1600°C.
Silica Bricks:
- Contains 95 % silica
- Manufactured from sandstones and quartzite with an introduction of 2-3 % lime to serve as a binding medium or flux
- Suitable for furnace acid coating to manufacture glass for walls and arches of central open-hearth steel furnaces copper melting furnaces
- Resists up to 2000°C
Ganister Bricks:
- Ganister Bricks are crafted from ganister rock’s siliceous range.
- It stone comprises 85% silica and 10% clay and 2% lime-very solid, lightweight and stable at a high temperature of 2100°C
Basic Refractories
Magnesite Bricks:
- Manufactured from fire clay containing 85 per cent magnesium oxide, 3-5 % iron oxide, and balance lime and alumina
- Used as the furnaces ‘ basic lining
- withstands up to 1800 ° C-2100 ° C
Dolomite Bricks:
- Manufactured from the fire clay containing a high percentage of dolomite
- Cheap substitutes for magnesia bricks in furnace lining. Serpentine is used to improve their strength
- Resists temperature up to 1400℃-1600℃
Bauxite Bricks:
- Constructed of flame clay consisting of 86% Bauxite
- Resisting up to 1600°C
Neutral Refractories
These are used to isolate a furnace’s acid and base linings to stop them from reacting with each other. They are not very important because they are not being used for purposes of fire resistance.
Chromite Bricks:
Made of fire clay containing 50% chromium iron ore, 30% iron oxide (ferrous oxide) and 20% silica bauxite-temperature resistance up to 2000 ° C.
Carborundum:
- A special type of natural refractory bricks
- constructed of fire clay with a higher percentage of silicon carbide
- used in electric furnaces
- withstands temperatures up to 1900 ° C
Chrome Magnesite Bricks: They are made from a mixture of chrome and magnesite.
Spinal Bricks: Such bricks were made in equal proportions from a combination of alumina and magnesia.
Forsterite Bricks: These bricks are manufactured from magnesium silicone oxide mineral ( 2 MgO SiO2)
Laying of fire bricks: When spreading fire bricks, hot clay mortar is used, not lime or concrete mortar. Generally, in order to lay 100 nos of regular ordinary fire bricks, 1.5 to 2 ft of fire clay mortar is needed.