Refractories are nonmetallic materials that maintain their structure at high temperatures. They are used in industries like iron and steel production, cement, lime, ceramics, and glass manufacturing where they are exposed to heat, thermal cycling, erosion, corrosion, and mechanical stress. The iron and steel industry consumes 70% of refractories globally. Refractories have been used since the Stone Age to contain fire. Common refractory materials include oxides found in nature like dolomite and magnesia from seawater. Producing refractories can involve special processes and coating methods due to their high cost and need to withstand extreme conditions.

1. Refractories
Refractories are materials (usually nonmetallic)
that maintain enough physical and chemical
identity to be used for structural purposes in the
high temperature environment encountered in
process industries

2. • Exposed to high temperatures
• Effects of other conditions
– Mechanical stress
– Thermal cycling & associated stress
– Erosion
– Corrosion by hot gas and molten materials e.g.
metals, slags or glasses

3. First Use of Refractories
• Stone age
• Value of stone substances in crude places of
fire for containing and reflecting heat
• Sandstone does not spall ( granite spall)
• Does not disintegrate ( Limestone
decomposes)

4. Uses of Refractories
• Although refractories are used in most, if not
all, of U.S. industries, the iron and steel
industry consumes 70% of the refractories
produced globally, while the cement and lime
industry consumes 7%, the ceramics industry
6%, the glass industry 3–4%, and the oil
industry about 4%.

9. Small scale Uses
• Specific applications
– Propulsion systems and friction heating at high
velocities in atmosphere (Aerospace industries)
– Nuclear energy

11. Sources of refractories
• Natural deposits of oxides on earth crust
• Seawater
– Dolomite and MgO

12. Cost issue
• Compounds of Hf, Cb, Ta, Th, U
• Plasma arc spraying to apply refractory coating
• Special processes to produce refractories of
different shapes