Graphite Mining Processing Plant
Machining graphite
Graphite can be machined wet or dry with ordinary machine tools but is normally machined dry. The different steps are dust extraction, cutting, turning, grinding, bondingand polishing. Click herefor safety recommendations when machining graphite.
Copy milling and form grinding
Preferred machining methods for the manufacture of Electric Discharge Machining (EDM) electrodes are milling and high-speed milling, form-grinding and EDM-cutting. Since EDM fine-grained graphite grades still have a volume of open pores of 10 to 15%, they can be impregnated with copper. Thus the advantages of the metal are combined with those of the graphite without impairing its excellentmachinability. In spite of the large block dimensions available nowadays, a complicated graphite electrode sometimes cannot be manufactured in one piece. However, it is possible to bond several parts by means of commercially available one and two-component adhesives.
Application of pyrolytic graphite
High temperature containers
Boats and crucibles for liquid-phase epitaxy
Crucibles for molecular-beam epitaxy
Reaction vessels for the gas-phase epitaxy of III-V semiconductor materials such as gallium arsenide
Trays for silicon-wafer handling
Free-standing products
Propellant rocket nozzles
Resistance heating elements
Nuclear applications
Biomedical applications
Coatings for molded graphites
Coatings for fibres
Carbon-carbon infiltration
Finishing and Surface Treatment
Due to its manufacture, a carbonartifactcontains open pores, which may make up one quarter of its volume. By filling these pores, the density, strength and conductivity of theartifactscan be increased to predetermined levels. Closing the surface pores will also reduce oxidation. Impregnating agents are usually pitch, resins and metals, which are brought into the formed bodies by a vacuum/pressure impregnatingcycle. Pitch-impregnatedartifactshave to berebakedin order to carbonize the pitch, whereas resin-impregnated parts are either thermally cured and/or carbonized. Therebakingstep also causes new pores to form, so that at least one more impregnatingoperation is necessary if a high degree of gas or liquid-tightness is requested. Usually, completely gas or liquid-tight grades are manufactured by an impregnation with furan orphenolformaldehyderesins, which are subsequently thermally cured. This resin impregnation, however, reduces the temperature stability of such grades to a maximum ofonly 200°C or slightly above.