Mixing and Extrusion
The milled coke (for graphite electrode primary needle coke is used) is mixed with coal tar pitch and some additives to form a uniform paste. This is brought into the extrusion cylinder. In a first step the air has to be removed by prepressing. Than the actual extrusion step follows where the mixture is extruded to form an electrode of the desired diameter and length. To enable the mixing and especially the extrusion process (see picture on the right) the mixture has to be viscous. This is achieved by keeping it at elevated temperature of approx. 120°C (depending on the pitch) during the whole green production process.