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General Characteristics |
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STRONG
RESISTANCE TO HEAT : CAN BE USED IN HIGH-TEMPERATURE
CONDITIONS |
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Carbon and graphite
can be used at temperatures
of up to 3,000˚C in inert atmospheres, and can
also be used up to a maximum of 400˚C in air.
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| Atmosphere |
Maximum temperature
at which
these can be used |
Air
Steam
Hydrogen
Vacuum
Nitrogen
Chlorine
Argon |
400 ˚C
700 ˚C
1,000 ˚C
2,200 ˚C
2,200 ˚C
2,500 ˚C
3,000 ˚C |
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THERMAL
EXPANSION IS SMALL : DIMENSIONS THEREFORE REMAIN
STABLE |
|
The gragh
at right exhibits a comparison thermal
expansion coefficient of graphite and other
materials. The thermal expansion figures for
carbon and graphite are considerably lower than those
for metals.
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CARBON AND
GRAPHITE ARE GOOD CONDUCTORS OF HEAT |
The gragh
at right compares the thermal
conductivities of graphite and other materials.
Graphite has high thermal conductivity. |
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THERMAL SHOCK
RESISTANCE |
The following
general formula shows thermal shock
resistance. Carbon has high thermal conductivity
and low coefficient of thermal expansion, with a
small Young's modulus. Carbon therefore has superior
resistance to thermal shock. |
| Thermal Shock Resistance
(cal/cm·sec) = |
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K : Thermal Conductivity
(cal/cm·sec·˚C)
α : Confficient of Thermal Expansion(1/˚C)
S : Thesile Strength (kg/㎠)
E : Young's Modulus (kg/㎟) |
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Young's Modulus(kg/㎟) |
| Graphite |
500 ~ 1,500 |
Glass
|
600 ~ 750 |
| Iron |
9,000 |
| Copper |
11,000 |
| Tungsten |
35,000 |
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GRAPHITE'S
STRENGTH INCREASES AT HIGH TEMPERATURES |
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When metallic
materials are heated to high
temperatures , their strengths decrease, but
graphite becomes stronger at high temperatures.
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GRAPHITE IS
STRONGLY RESISTANT TO CORROSION AND IS NOT
ATTACKED BY CHEMICALS |
Graphite
is generally not corroded by acide and alkalis at room
temperatures. Mixed acids,
such as a mixture of phosphoric acid and potassium dichromate,
can oxidize graphite |
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GRAPHITE IS
LIGHT IN WEIGHT AND CAN BE PROCESSED EASILY |
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The apparent
density of graphite is around 2, less
than that of aluminum, the lightest of metals.
The specific gravity of graphite is 1/3 of copper or
iron. Graphite is easily machined, so that precise
machining of graphite can be avaiable.
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GRAPHITE HAS
INHERENT LUBRICITY |
| Graphite has inherent
lubricity, and will not damage other materials with which
it comes in contact. |
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MOLTEN
METALS AND MOLTEN GLASS DO NOT ADHERE TO GRAPHITE |
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