Mill, Mix & Forming
Premium quality calcined coke is crushed,screened, and hot-blended with pitch in controlled proportions. The resulting plastic mass is extruded through a forming press and cut into specified lengths before being water-cooled in a temperature-controlled bath.
Green electrodes are placed in large canscalled saggers and baked to over 800° C (1400° F) in specially designed,computer-controlled furnaces. It takes 1-to-2 weeks to carbonize the pitch depending upon the size of the electrodes being made. After cooling, the carbon electrodes are cleaned, inspected, and sample-tested.
Next, the baked electrodes are impregnated with a special pitch to give them the higher density, mechanical strength, and electrical conductivity they will need to withstand the severe operating conditions inside our customers' electric arc furnaces.
A second baking cycle, or "rebake", is required to carbonize the pitch impregnation and to drive off any remaining volatiles. Rebake temperatures reach almost 750°C (1300° F).
The rebaked carbon electrodes are further processed in long electric resistance furnaces. Laid end-to-end, or“longitudinally,” the electrodes are heated to over 3000° C (5000° F). This ultra-high temperature restructures the carbon to its crystalline form—graphite. Then the electrodes are once again cooled, cleaned, inspected, and sample-tested.
In Machining, the electrodes outer dimension are turned to its finished dimension. The two end faces are also machined to tolerance and given threaded sockets. The sockets acceptdouble-tapered, machine-threaded graphite connecting pins which allow our customers to join electrodes together into columns.