Graphite materials are used in many different aspects of aluminum smelting. Graphite is the material of choice for electrodes for the melting of steel in electric arc furnaces (EAF). The same material is also used to produce lining blocks for blast furnaces and EAFs for aluminum smelting.
The process of making graphite blocks is more complex than making basic carbon blocks for the same purpose. This is due to the additional steps required to create the chemical and structural changes that turn carbon into graphite.
The basics of carbon blocks is the use of a carbonaceous filler that has a binder of petroleum pitch or coal tar. The carbonaceous filler may be made up of calcined anthracite coal, carbon black or petroleum coke, most often a mixture of several materials. This is then extruded or molded into large blocks and baked at temperatures of up to 1400 degrees Celsius.
The Making of Graphite
To make graphite blocks, these basic large carbon blocks are further heated to temperatures that will range between 2400 and 3000 degrees Celsius. This further heating will change the carbonaceous filler as well as the binder when it comes to the structure.
The choice of specific graphite blocks for different uses will be based on the need for a particular grain size, density, and purity of the blocks. The amount of time the blocks are heated as well as the maximum sustained temperatures in the ovens will create specific changes in the finished product.
To increase the density of the blocks, additional fillers can be impregnated into the blocks of graphite under a vacuum. After further heating and structural changes of this filler, density can be precisely controlled.
The large graphite slabs are then cut into blocks based on the sizes required by the customer. This allows for precision with the blocks, making them an ideal construction material where precision placement and fit is required.