The graphite in blast furnaces plays a vital role in the steel-making process. Its high level of thermal stability improves energy efficiency while supporting alloying processes during the molten phase. Moreover, it is also capable of conducting current allowing for the control of various alloying elements such as vanadium and chromium.
Graphite electrodes are made of natural flake graphite. They come in different sizes and grades to suit the size of your furnace. They are typically reusable, although they do erode and shorten over time. Consequently, they represent a significant portion of the total EAF steelmaking cost. Any technology that reduces the cost of electrodes made from graphite and increases their service life is welcomed by the steel industry.
When the EAF melts metal scrap in a Steel Mill, it creates and intense arc that vaporizes the material to a molten condition. The arc heats the molten metal, reducing the energy needed to produce the steel by a factor of 10, and also allows for precise addition of various alloying elements.
The resulting molten metal is then drawn off into giant buckets called ladles, and carried to the steel mill's caster where it makes new products such as cars, trucks, and buildings. Graphite electrodes are used to supply the electrical current needed for this process. Each electrode must have enough conductivity to transport the steel at a rate up to 150 tonnes per hour to the caster.
Graphite electrodes can reach a maximum diameter of 0.75 metres (2.50 feet), and the largest electrodes weigh over two metric ton. They are extremely heat, reaching temperatures of up to 3,000°C, which is about half the temperature of sun's surface. To prevent erosion and wear, electrodes are coated in a thick layer to withstand the extreme heat. This coating protects the electrode, helps maintain stable arc conditions and reduces the amount of electrode consumed.
A ceramic coating made from SiO2/TiO2 would be a good choice for this purpose. It is resistant to both high temperatures and aqueous solutions. It can be easily applied onto the electrode surfaces to increase their protective properties.
Graphite electrodes need to be able resist the high temperatures during the melting phase as well as the acidic slag which forms. For this to happen, they need to have a high level of thermal stability and conductivity. A new study shows a multilayered SiO2/TiO2 ceramic graphite material is capable of achieving both properties. The findings of the study are promising and further research into this material could lead to more efficient, sustainable electric arc kilns. This will benefit the steel industry as well as the environment. Hexagon Resources Ltd. (ASX:HXG) has recently completed key testwork directed at enhancing graphite electrodes used in electric-arc furnaces worldwide. These tests showed how the Company’s electrodes were superior to a synthetic-only control in terms of bulk density and conductivity.
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