Everything about Refractory totally explained
The term
refractory refers to the quality of a material to retain its strength at high
temperatures. ASTM C71 defines refractories as "non metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to enviroments above 1000 °F (538 °C)"
1.
Refractory materials are used in linings for
furnaces,
kilns,
incinerators and
reactors. They are also used to make
crucibles
Refractory materials
Refractory materials must be chemically and physically stable at high temperatures. Depending of the operating environment they need to be resistant to
thermal shock, be chemically
inert, and/or have specific values of
thermal conductivity and coefficient of
thermal expansion.
The
oxides of
aluminium (
alumina),
silicon (
silica) and
magnesium (
magnesia) are the most important materials used in the manufacturing of refractories. Another oxide usually found in refractories is the oxide of
calcium (
lime).
Fireclays are also widely used in the manufacture of refractories.
Refractories must be chosen according to the conditions that'll face. Some applications required some special refractory materials.
Zirconia is used when the material must withstand extremely high temperatures.
Silicon carbide and
carbon are two other refractory materials used in some very severe temperature conditions, but they can't be used in contact with oxygen, as that'll oxidize and burn.
Types of refractories
Acidic refractories can't be used in a
basic environment and basic refractories can't be used in acidic environment because that'll be corroded. Zircon, fireclay and silica are acidic,
dolomite and magnesite are basic and
alumina,
chromite, silicon carbide, carbon and
mullite are neutral.
Refractory metals are also frequently used.
Refractory materials are used extensively in the metals industries, along with glass melting and other heat treatment operations.
There are two common forms of refractories, bricks or monolithics. Bricks are pre-sintered forms which can hold their shape. Monolithics are loose material which can be formed into complex shapes, or sprayed into place, and have to be
sintered before use.
Refractory Anchorage
Anti-abrasion refractory attached to pipes, chambers, etc, will require anchorage systems such as wire formed anchors or
hexmetal to support the refractory linings.
Refractory heat-up
Usually, refractories require special
heat-up techniques to insure that their performance will be attained as designed, and to avoid thermal shock and drying stresses until the operational status is achieved.
Further Information
Get more info on 'Refractory'.
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