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INTRODUCTION
Matrix of graphite fireproof crucibles is natural graphite, clay and silicon carbide.
GRAPHITE
is basis of heat conduction, electrical conduction, it gives necessary thermal
stability to crucible and is for the most part stable to chemical action. The only solvent
for graphite is melted iron. That's why graphite crucibles are not intended for melting
of cast iron and steel. One more “disadvantage” of graphite is its corrosion at oxygen's access,
beginning from 600°C. Therefore crucibles are covered with glaze, which defends graphite
from corrosion for the most part.
CLAY
is high-refractory bond for graphite articles.
SILICON CARBIDE
is additional heat conductor, which also increases mechanical strength
and durability of crucibles essentially.
Depending on composition and assignment the following types of products are distinguished:
°
°
°
°
°
°
°
°
EXAMPLES OF NOTATION CONVENTIONS:
BA 750L2 TУ.....,
that is crucible form B type A, with capacity 750 kg on copper, for melting of
non-ferrous metals with melting temperature up to 1000 C (L) in resistance furnaces (2).
ZK 175T TУ.....,
that is cylinder crucible form Z, type K, with capacity 175 kg on copper, for
melting of non-ferrous metals with melting temperature up to 1000 C (T) in induction furnaces.
AX 500 TУ.....,
that is crucible form A, type K, with capacity 500 kg on copper for melting of
non-ferrous metals in resistance and flame furnaces.
MARKING
- on clay bond:
К
-
of
,
of
Е
-
Н
-
- on carbon bond:
Х
-
L
-
Т
-
“1”
- application
only
“2”
-
Marking of crucibles includes:
1. Form of products.
2. Brand of material, from which the crucible is manufactured.
3. Number or capacity of a product.
4. Type of glaze.
5. Further details.
А
- intended for melting of non-ferrous metals with the melting temperature up to 1500 C
in induction and resistance furnaces.
for melting non-ferrous metals with melting temperature up to 1600 C in induction and
gas or liquid furnaces distribution non-ferrous metals in resistance furnaces.
С
- for casting of non-ferrous metals with working temperature up to 1600 C.
Т
- for melting precious metals with melting temperature up to 1600 C in induction and
muffle furnaces.
D
- for melting of precious metals with melting temperature up to 1250 C by heating at the
expense of passing a current through a crucible.
for foundry accessories.
for testing of non-ferrous metals.
for melting of non-ferrous metals with melting temperature up to 1500 C in resistant
and gas or liquid furnaces. They don't demand preliminary drying.
The crucibles are protected from oxidation and freting by special glazes:
for operations with metals with melting temperature lower than 1000 C.
for working in conditions of temperature over 1000 C.
As further details the following signs are adopted:
of glazes on outer surface .
crucibles are intended for resistance furnaces.
Type of glaze and further details are indicated for crucibles on clay bond only.
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