Manufacturing Process

 Elemental carbon exists naturally in many parts of the world in the forms of graphite and diamond. When mined, Graphite is not particularly useful as an engineering material, because of its softness , high impurity level and limited size. The manufacture of carbon and graphite has developed for over three-quarters of the century with the properties of the resulting products being considerably improved over those of the natural material. Carbon has been long established as a prime material for one of the rubbing pairs in a mechanical seal , bearings and many sliding applications of dry and wet running conditions. Continuous developments have kept pace with the increasingly severe requirements of the application. 

 By judicious selection of raw materials , and by using a variety of manufacturing processes , carbon and graphite can be Modified to give a range of properties suitable for different sliding applications. The raw materials are selected from naturally occurring graphites , from which some or all of the inorganic impurities have been removed. The original materials include coke derived from coal sources , residues taken from oil distillation (petroleum cokes) , and carbon blacks which are obtained from the burning of oils and gases in limited supplies of air. 

 The raw materials are powdered and bonded together with a pitch or tar , and then moulded under pressure to form a convenient size and shape. The resulting product is fired in a protective atmosphere , to approximately 1000 C. During this process , the tar and pitch are converted to a coke thereby cementing the particles of the other raw materials together to form a cohesive mass. Such a product is known as carbon-graphite. 

  Carbon and Graphite materials that are produced by this means are porous. The properties however are modified by impregnation with synthetic resins or metals. The impregnants confer increased strength , lower permeability and improved wear resistance and with some base materials both reduce and stabilize friction.