Steel production

• Furnace linings made from carbon and graphite are applied for the production of primary iron.

• Graphite electrodes and nipples (connecting pins) are applied for the production of steel. Their production is similar to the graphite production. After the baking process (for carbon material) and/or the graphitization process (for graphite) the material is machined within well- defined tolerances on length and diameter. The nipples and sockets are threaded to assure optimal electrode- nipple joining. Production process of Electrodes.

Steel Production: intro

• Steel is one of the most important and widely used products in the world. Currently, the steel industry is undergoing a process of change. As a result of ongoing technical and economic developments, the production and use of electric arc furnacesteel is, beneath the steel production in a blast furnace, becoming increasingly important, continuously gaining share of world-wide steel production over the past 30 years.

• For the manufacture of graphite electrodes for the use in the EAF selected coal-tar or petrol cokes are crushed, milled and sieved to sort it by the specific different particle size fractions. Depending on the end use different fractions are mixed together with a liquid coal tar pitch as a binder. This mix is extruded into a green product with the near final shape and dimension of the resulting electrode. This rods are baked to approx.. 800°C - 1000°C and according to the needs for the final quality of the electrode impregnated with an petroleum pitch and rebaked. Than the graphitisation step follows where the material is graphitized by heating it up to 3000°C. Crude Steel Production in the World available on this website. Steelmaking Process Chain.

table

EAF Process

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.

Scheme of the extrusion process