Graphite crucible

Graphite crucible:
A graphite crucible typically is made of graphite and clay that is shaped and fired to very high temperatures to form a solid container.
It is used for melting non-ferrous or non-iron metals such as gold, silver, aluminum or brass.
Graphite, a form of carbon, is often used for crucibles because of its high temperature resistance and low reactivity with molten metals.

The material of graphite crucible can be divided into artificial graphite, clay bonded graphite, and carbon bonded graphite.
Graphite crucible is made of graphite electrode.
Clay bonded graphite crucible, the main ingredient is natural crystal graphite and clay.
Now only used in small amount of high-temperature melting of cast iron, cast steel melting and melting of precious metals.
Carbon bonded graphite crucible, the main ingredient is natural crystal graphite and silicon carbide.
Mainly used in the melting of the majority of non-ferrous metals such as copper alloy and aluminum alloy.

The purpose of a graphite crucible is to provide a non-reactive vessel that will survive the high temperatures needed for metal melting and processing.
Crucibles provide a stable container that does not react with the metals or materials being burned at high temperatures.
Graphite is carbon that might resemble flakes or sheets.
When mixed with clay, graphite can be shaped into vessels or containers that are heat-resistant and durable.
Like many ceramic containers, graphite crucibles can be brittle and should be handled with care.

Product Description
Specification of three materials
Product name Pure graphite crucible Isostatic pressing silicon carbide graphite crucible
(Carbon bonded graphite crucible)
Silicon carbide graphite crucible
(Clay bonded graphite crucible)
Test item   Standard value Result Standard value Result
Refractoriness 2000℃  1650℃  1700℃  1650℃ 1700℃
Chemical composition(%)          
C ≥99 30~45 35 35~45 40
SIC   10~40 45 15~25 20
AL2O3   6~20 10 10~20 15
SIO2   8~38 10 20~25 20
Apparent porosity ≤15% ≤25% ≤23% ≤30% ≤28%
Compressive strength ≥35MPa ≥8.5MPa ≥10.5MPa ≥8.5MPa ≥8.5MPa
Bulk density ≥1.7g/cm3 ≥1.7g/cm3 ≥2.15g/cm3 ≥1.75g/cm3 ≥1.75g/cm3

Notes of operating graphite crucibles: 

1. The crucible should be stocked in the dry situation

2. Carry the graphite crucible lightly

3. Warm the crucible in the drying machine or near the furnace. The warming temperature should be up to 500℃.

4. The crucible should be put under the furnace month flat.

5. When put the metal into the crucible, you should take the crucible capacity as your reference. 

If the crucible is too full, it will be damaged by expansion.

6. The clamps shape need as that of crucible. Avoid the concentrate stressed destroy of the crucible

7. Clean the crucible regularly and lightly.

8. The crucible should be put in the center of the furnace and leave some distance between the crucible and furnace.

9. Turn the crucible once in one week and this will help lengthen the service life.

10. The flame should not touch the crucible directly.

11.24 hours constant use will make crucibles have longer service life.

The smelt soup in the crucible should be cleared out when the furnace stop working, in order to avoid molten soup solidification and will be expanded when fire to reheat, and affect the service life of crucible or even burst.

12. We suggest that about 2 months for crucible melting aluminum alloy (every week for melting copper alloy), hanging out to check whether there is something wrong in the surface, and clean furnace hearth as well as turn the crucible, this operation is helpful to prolong the service life of crucible.

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