Iso-Molded Graphite –

cover story A Graphite Primer Graphite is one of the three readily occurring solid raw materials, the graphite particle size, and forms of carbon. It exhibits very unique proper- the molding method used in the production ties which make it an attractive material for use of the material. Of these three, the molding in several industrial applications. Some of these method has the most pronounced effect. unique properties include high electrical and thermal conductivity, good compressive and There are two primary molding methods used flexural strength, machinability to complex to produce graphite:...

Raw Materials Artificial graphite is manufactured from two basic raw materials: petroleum coke particles as the filler and coal tar pitch as the binder. The predominant filler used in the manufacture of graphite is calcined petroleum coke (See Fig #2). This material is a by-product of the distillation and coking of crude oil from the petroleum industry’s manufacture of gasoline products. Coking is a thermal treatment process applied to the petroleum residuals to bring about a thermal decomposition, or removal of its volatile fractions. The resultant petroleum coke is a solid, porous carbon material...

Crushing & Milling After milling, the coke particles and coal tar pitch, along with trace additives to facilitate processing, are combined in a heated mixer (See Fig #6) which melts the pitch and intimately mixes the pitch binder and coke filler. Various mixing times and conditions are utilized, with parameters dictated by the process specification for the particular grade being manufactured. Once the mixing cycle has been completed, the mix is allowed to cool and re-solidify into “mix balls” as they are sometimes referred. These “mix balls” are then crushed and milled into “flour” using a pulverizing...

a large pressure vessel and the pressure is applied equally in all directions through a hydraulic fluid. For this reason, the resultant pressed billet exhibits nearly no grain direction and will have nearly equal properties in all directions when converted into graphite. Baking The next step in the manufacturing process is baking the “green” billet. In reality, the billets at this stage are shades of black in color and are only referred to as “green” in that they have not yet been fired. In the baking process, the molded billets are raised to temperatures approaching 1000°C at a prescribed ramp...

Testing Physical testing to verify properties and removal of the outer mold skin are all that remain to be done before the graphite billet is ready for sale. The typical physical properties tested to characterize the graphite for quality assurance include apparent density, electrical resistivity, flexural strength, hardness and residual ash. For specific applications, additional testing is often done prior to approval, including EDM wear ratio, CTE, compressive strength, and oxidation rate. After QA approval of the graphite billet, it often undergoes a cleaning operation in which the outer surfaces...

The DarkStar Particle In conjunction with the aforementioned expansion, Mersen has continued to expand its product offerings to the marketplace. 10 years ago Mersen (Carbone of America at the time) began a program to develop an ultra-fine grain graphite that not only performed in the EDM process equivalent to anything currently available, but also was readily machinable. Based on years of experience, Mersen recognized that simply milling existing grades finer was never going to get the results desired. In order to obtain the desired material characteristics, a new raw material and new process...

Our proven ultra-fine grain EDM graphite delivers an unmatched performance/value package! Featuring Our Innovative Ultra-Fine Carbon Particle Now you can confidently handle your most challenging EDM machining operations while saving money! Top-performing DS4, featuring the DarkStar ultra-fine carbon particle, is the result of years of intense R&D and field testing/usage. DS4 is the latest EDM graphite innovation from the United State’s largest producer of specialty graphite, Mersen. It’s time to give DS4 a try… we’re confident you’ll like the results. DS4 Delivers: • Easy to machine • Excellent...