Brief description of graphite electrode usage technology

Varieties of graphite electrodes
Electric arc steelmaking furnaces are generally divided into three categories, namely ordinary power electric furnaces, high power electric furnaces and ultra-high power electric furnaces. Corresponding to the power level of electric furnace steelmaking, graphite electrodes are also divided into three varieties, namely ordinary power graphite electrodes (code RP grade), high power graphite electrodes (code HP grade) and ultra-high power graphite electrodes (code UHP grade). The nominal diameter of the electrode ranges from 75mm to 700mm. The physical and chemical properties of high power and ultra-high power graphite electrodes are better than those of ordinary power graphite electrodes, such as lower resistivity, higher volume density and higher mechanical strength, small linear expansion coefficient, excellent anti-oxidation performance, etc.
Selection of graphite electrodes for AC arc steelmaking furnaces
The electrode diameter of AC arc steelmaking furnaces is shown in Table 2. Electric furnaces of different powers should use graphite electrodes of corresponding varieties, such as high power electric furnaces should use high power electrodes. Different power electric furnaces have different choices for graphite electrode diameters. It is generally believed that ordinary power electric furnaces choose RP electrodes with a diameter of 75 to 500 mm; high power electric furnaces choose HP electrodes with a diameter greater than 300 mm; and ultra-high power electric furnaces choose UHP electrodes with a diameter greater than 400 mm.
Table 2 Diameters of graphite electrodes for AC arc steelmaking furnaces

Problems to be noted when using conical joints to connect electrodes
The advantages of conical joints are that the longitudinal section of the hole wall at the electrode connection hole is conical, the outer wall is thin, the inner wall is thick, the overall strength is high, it is not easy to expand and crack, and the middle diameter of the joint is large and not easy to be broken.

The following matters should be noted when using graphite electrodes: (1) When selecting electrode types and diameters, the capacity of the electric furnace and the capacity of the transformer should be referred to. (2) During loading, unloading and transportation, graphite electrodes should be handled with care, the threads should be protected, and damage should be prevented. (3) During transportation and storage, graphite electrodes should be prevented from moisture, otherwise they must be dried before use. (4) Before connection, the dust in the thread of the electrode joint hole must be blown away with compressed air, and then the joint and electrode are tightened. The tightening torque must meet the requirements. In order to ensure that the required tightening torque can be achieved when connecting electrodes of different specifications, some electric furnace steel mills have specially manufactured a tightening wrench with a mark showing the tightening torque size to ensure correct operation. The clamp should be clamped below or above the bottom of the electrode joint hole. (5) The electrode lifting device of the electric furnace should be flexible and should not shake during operation to prevent the electrode from breaking or the joint from loosening and disengaging. (6) When loading the furnace, large pieces of material should be placed at the bottom to prevent the material from collapsing and breaking the electrode during melting. (7) During the refining period, the electrode cannot be immersed in the molten steel to increase carbon to prevent the electrode from becoming thinner, causing the electrode to break or the joint to fall off. (8) In order to prevent the electrode joint from loosening and disengaging, it is recommended to use a joint pin.