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Brief history and varieties of graphite electrodes

Add time:2017-11-21

Graphite electrode (graphite electrode) of graphite electrode manufacturer is a kind of high temperature graphite conductive material, which is made of petroleum coke, bitumen coke as particle material, coal tar as bonding agent, and through} kneading, molding, baking, graphitization and mechanical processing. Graphite electrode is an important high temperature conductive material in the electric furnace. Through the graphite electrode, the electric energy is input to the electric furnace. The high temperature generated by the arc between the end of the electrode and the furnace material is used as the heat source, and the furnace material is melted for steelmaking. Some other electric smelting or electrolysis equipment often use graphite electrode as the conductive material. In 2000, the world consumes graphite electrodes of about 1 million T, and China consumes about 250 thousand T graphite electrode in 2000. Graphite electrode manufacturers make use of the excellent physical and chemical properties of graphite electrodes, and also have extensive use in other industrial sectors. The carbon products industry with graphite electrode as the main variety has become an important component of the modern raw materials industry.
Brief history
As early as in 1810, Humphry Davy (Humphry Davy) used charcoal as a carbon electrode to produce electric arc, which opened up a broad prospect for the use of carbon materials as a high temperature conductive electrode. In 1846, Stedt (Stair) and Edward (Edwards) were mixed with coke powder and sucrose to be pressurized and roasted at high temperature to produce Another kind of carbon electrode, which was dipped in concentrated sugar water to increase its bulk density, was patented.
In 1877, Bloch (C.F.Brush) and Laurence (w.H.Lawrence) of Cleveland (Cleveland), United States, used calcined petroleum coke to develop a low ash carbon electrode.
In 1899, Prof Chad (O.G.Pritchard) first reported the method of making natural graphite electrodes from Ceylon natural graphite. In 1896, Kastner (H.Y.Gastner) obtained the patent right to use electric power to heat the carbon electrode directly into the high temperature, and to produce the artificial graphite electrode, which is better than the natural graphite electrode.
In 1897, Acheson (Carborundum Co.) of the United States of America (Carborundum Co.) made the first batch of artificial graphite electrode with petroleum coke as raw material in the resistance furnace for the production of emery sand. The product specification was 22mm x 32mmX380mm. The artificial graphite electrode was used in the electrochemical industrial production of caustic soda at that time. On this basis, "Ai Qi" was designed.  The graphite furnace is made up of carbon electrode produced by petroleum coke and a small amount of resistance material (metallurgical coke) to form a "furnace core resistance", which produces high temperature after electrifying, so that the carbon electrode made from petroleum coke is "graphitized" at high temperature to obtain artificial graphite electrode.
At the end of nineteenth Century, the French Eru (P.L.T.Heroult) invented the direct electric arc furnace, which began for the production of calcium carbide and ferroalloy. It was first used for steelmaking in 1899. The electric arc furnace needed a certain number of high temperature resistant conductive electrodes.  Although Acheson Graphite Co. sold connectable electrodes around 1900, only small graphite electrodes could be produced.
In the early 20th century, carbon electrode with anthracite as raw material or natural graphite electrode with natural graphite as raw material were mainly used in EAF steelmaking. The process for producing carbon electrodes or natural graphite electrodes is relatively simple.
In 1910, the carbon electrode with diameter of 610mm has been supplied to the market. However, the excellent performance of graphite electrode and the continuous improvement of the manufacturing process, the mass production of large size graphite electrodes and the decreasing price of graphite electrodes, and the gradual conversion of graphite electrodes to the electric furnace steelmaking industry, and the gradual reduction in the use of carbon electrodes or natural graphite electrodes.
After 1960s, most of the electric arc furnaces used graphite electrodes.
The maximum diameter of graphite electrodes made in 1914~1918 years is only 356mm.
In 1924, the graphite electrode with a diameter of 406mm was produced. In 1930, it was expanded to 457mm, and in 1937 it was added to 508mm. The large size graphite electrodes of diameter 559mm, 610mm, 660mm, 711mm and 762mm were soon produced.
In 1980s, the graphite electrode diameter of 813mm was the largest arc furnace in the world. After the Second World War, the quality, equipment and manufacturing process of graphite electrode have been improved. With the continuous improvement of the power input power of the electric furnace, high power and ultra high power graphite electrodes were successfully developed in the 60~70 years of twentieth Century.
The graphite electrode consumption per ton of electric furnace steel has been reduced from 6 to 8kg in 70s to 4 ~ 6kg in 80s (ordinary power furnace) due to the continuous improvement of graphite electrode quality and the improvement of electric furnace steelmaking process. The consumption of electrode consumption per ton of steel with ultra high power graphite electrode has been reduced to about 2.5kg, and the ultra high power DC electric power has been reduced. The consumption of graphite electrode for each arc steel furnace (only 1 graphite electrodes) can be reduced to about 1.5kg. At the end of 80s, the tonnage of most electric furnaces in the electric furnace smelting and steelmaking industry of the developed countries in the world has been raised to 80 ~ 200t, so a large number of high power or ultra high power graphite electrodes with a diameter of 550 to 750mm are used.

      Electrode variety of graphite electrode manufacturer
According to the difference of raw materials used and the physical and chemical indexes of finished products, graphite electrodes are divided into 3 kinds of common power graphite electrode (RP grade), high power graphite electrode (HP grade) and ultra high power graphite electrode (UHP grade). This is because the main power supply arc furnace of the graphite electrode is used as the conductive material. In 1980s, the international electric furnace steelmaking industry divided the arc steelmaking furnace into 3 types: the ordinary power furnace (RP furnace), the high power electric furnace (HP furnace) and the super high power electric furnace (UHP furnace). The input power of the transformer with the capacity per ton of the ordinary power furnace above 20t is about 300kW/t, and the high power electric furnace is about 400kW/t. The input power of the electric furnaces below 40t is 500 ~ 600kW/t, 50 to 80t, and the input power of 400 to 500kW/t and 100t above 350 to 450kW/t is called the ultra high power furnace.
By the end of 1980s, a large number of small and medium power electric furnaces under 50t were eliminated in the developed countries. Most of the newly built electric furnaces were 80 ~ 150t ultra high power large electric furnaces, and the input power was raised to 800kW/t. In the early 90s, a part of the ultra high power furnace was further improved to 1000 to 1200kW/t. Graphite electrodes used in high-power and ultra-high-power electric furnaces operate under harsher conditions because the current density through the electrodes increases significantly.
The results are as follows: (1) the increase of the thermal expansion of the electrode and the joint caused by the increase of the electrode temperature caused by the resistance heat and the incandescent air flow, and the increase of the oxidation consumption of the electrode.
The temperature difference between the electrode center and the electrode circumference increases, and the thermal stress caused by the temperature difference increases accordingly. The electrode is prone to cracks and surface spalling.
(3) Increase the electromagnetic force, causing violent vibration, in the violent vibration, the electrode due to loose connection, tripping and lead to a greater probability of fracture. Therefore, the physical and mechanical properties of high power and ultra high power graphite electrodes must be better than ordinary graphite electrodes, such as low resistivity, large volume density and high mechanical strength, small thermal expansion coefficient and good thermal shock resistance. Table 1 lists the general standard series and the diameters of graphite electrodes for three different power arc steelmaking furnaces in the late 1980s. In order to meet the needs of high power and ultra high power furnace, two kinds of graphite electrodes, such as high power graphite electrodes and ultra high power graphite electrodes, were produced in the carbon factories of Europe and America and Japan in 80s. The graphite electrode DC EAF used in DC EAF is a new type of electric furnace steelmaking equipment developed in the early 1980s. The initial DC arc furnace was transformed on the basis of the original AC arc furnace, some used 3 graphite electrodes and some used 2 graphite electrodes.

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