Graphite electrode is a very significant conductive material in electric arc furnace (EAF) steelmaking, with low resistivity as well as withstand high temperature of EAF, as the melting point of graphite is around 3900℃, and scrap steel is 1700℃, while the temperature in EAF is above 3000℃. Therefore, graphite electrodes are currently the most suitable electrodes in EAF. The main raw materials of graphite electrode are petrol coke and needle coke, pitch impregnation, through more than ten processes and graphitization of 2800~3000 ℃, can reach the technical data standard of using in EAF.
Graphite electrodes uses
The graphite electrode is composed of a rod and a joint. The three electrodes are connected end to end through the joint and inserted into the EAF for use.
Graphite electrodes consumption
The consumption of graphite electrodes is related to the use of EAF steelmaking and the quality of graphite electrodes. Usually, 2 kilograms of graphite electrodes are consumed to melt one ton of steel, which accounts for a small proportion of steelmaking costs. Under all the same conditions, the larger the discharge current during steel making, the more consumption of the graphite electrode.
The following formula is used to calculate the end and side consumption of the graphite electrode:
Normal consumption of graphite electrodes: CE=Cγ+Cs（end and side consumption）
- Front end consumption：Cγ=Vγ·TOntap/W,Vγ=Kγ·I2/dnγ
TOntap——EAF power supply time,h.
W——EAF tapping weight, t.
Vγ——Consumption speed of electrode end,kg/h.
Kγ——End consumption constant (Bowman gives Kγ=0.0361 and n is usually 0.58 for AC arc furnace).
I——Arc current intensity, kA.
dγ——Electrode end diameter, m.
- Side consumption：Cs=Vs·TTop-Top/W,Vs=3Ks·S
TTop-Top——Electric furnace smelting cycle, h.
W——EAF tapping weight, t.
Vs——Electrode side consumption speed, kg/h.
Ks——Oxidation consumption rate, kg/(m2·h).
S——Oxidation surface area in EAF, m2.
The influence of 60t EAF current on the consumption of graphite electrode at different smelting time：
|Current value/KA||Smelting time/min||Electrode consumption/Kg/t|
In addition to the technical consumption of electrodes consumed by high-temperature sublimation, oxidation and participating in the reaction during the smelting process, the electrode consumption is calculated, and there is also the part which is lost when the smelting is not completed. The consumption of all graphite electrodes needs to be calculated based on the weight of each batch entering the site and the total output of steel, then can know how many graphite electrodes need to be consumed per ton of steel.
Graphite electrodes applications
- Regular power graphite electrodes are used for smelting crude steel, silicon ore smelting silicon, and phosphate ore smelting yellow phosphorus. High-power and ultra-high-power graphite electrodes are used for smelting refined steel. The power level of the graphite electrode and the power level of EAF comply with the matching rules.
- Graphite electrodes are used for high-speed cutting of die-casting molds and EDM for die-casting molds. Die-casting molds are widely used: automobile and motorcycle parts, mechanical and electronic product parts, and household appliances parts all require die-casting molds to make die-casting parts.
- Metal magnesium, aluminum and sodium generally use molten salt electrolytic processing technology, and the anode conductive material of the electrolytic cell of the processing equipment uses graphite electrodes. The conductive material of the furnace head of the resistance furnace used in the production of emery (silicon carbide) also uses graphite electrodes.