Grafit0 pages

Innovating tomorrow’s solutions . . . today

GRAFIT Crucibles
DESCRIPTION
Noltina‘s Grafit crucibles are rib formed CLAY-GRAPHITE crucibles characterised by high refractoriness and good thermal
conductivity as well as very good thermal shock resistance
and chemical resistance against fluxes. In order to meet the
specific requirements of induction furnaces, NOLTINA has
developed a specialised range of CLAY-GRAPHITE crucibles
with a specific modified electrical resistivity. This optimises
the coupling power of the crucibles especially in middle
frequency induction furnaces (Frequence 1 kHz - 3 kHz) and
avoids the risk of overheating.
APPLICATIONS
Noltina‘s Grafit crucibles are suitable for all furnace systems
for non-ferrous metal alloys and precious metals with melting
temperatures between 400°C and 1400°C.
TYPICAL METAL CASTING TEMPERATURE
400 - 1400°C (752 - 2552°F)
PERFORMANCE CHARACTERISTICS
•
•
•
•
•t

High mechanical strength.
Good thermal conductivity.
Good resistance to chemical corrosion.
High refractoriness.
Good oxidation resisistance.

IDENTIFICATION
Noltina‘s Grafit crucibles are coloured black and utilize the
suffix G to denote the type.
PATTERN RANGE
Noltina‘s Grafit crucibles are available in a wide range of sizes
and shapes. Consult the product selector or contact MorganMMS for a specific recommendation based on your requirements.
QUALITY
Noltina‘s Grafit crucibles are manufactured from premium
grade raw materials under an ISO 9001:2008 quality management system.

MorganMMS is a business within the MEM Division
of The Morgan Crucible Company plc.

INSTALLATION
Grafit crucibles are used free standing in lift out furnaces. In
fuel fired and electric furnaces the stand should be made
from similar material to the crucible to ensure uniform heating of the crucible base and provide sufficient mechanical
support. The diameter of the stand should be at least the
same as the base of the crucible and the height should be
such that the base of the crucible is level with the centre line
of the burner. The stand and crucible should be installed
centrally in the furnace. In induction furnaces the crucible stands on a refractory pedestal and must be installed
centrally within the coil. A thin layer of coke dust or other
carbonaceous material should be sprinkled on to the stand or
pedestal to prevent the crucible sticking to it.
PREHEATING / FIRST USE
Fuel-Fired and Electric Resistance Furnaces: A new crucible should be pre-heated empty in order to minimise the
temperature gradient across the crucible wall. If the furnace
refractories have been repaired or if there is a risk of the crucible having absorbed some moisture, then the furnace should
initially be heated slowly up to circa 200ºC and held at this
temperature until all moisture has been driven off.
A new crucible should initially be heated slowly and evenly to
600ºC on low power (avoiding local impingement of flame for
gas/oil fired furnaces). Subsequently the full heat input rate
should be utilised to achieve a uniform bright red condition
over the whole crucible (circa 900ºC / 1650ºF) at which point
the crucible should be charged immediately taking care to
avoid packing metal tightly or bridging ingots across the
crucible. The furnace controls can then be set to achieve the
desired metal operating temperature and heating should
continue at the full rate until the metal has reached the
desired temperature.