General graphite electrode types are RP, HP, UHP, But IP and SHP exist between. Sort by power: RP<IP<HP<SHP<UHP.
Graphite electrode types
1) RP Graphite electrodes
RP graphite electrode is mainly used for regular power electric arc furnaces to smelt scrap steel, silicon and yellow phosphorus. RP graphite electrodes, referred to moulded columns of graphite, are used as the high temperature conductive material for electric arc furnaces.
2) IP Graphite electrodes
IP graphite electrode or HD graphite electrode belong to impregnated graphite electrode. The impregnating agent (asphalt) immersed into the electrode pores to remove the pores. increase the bulk density and mechanical strength of the electrode.
3) HP Graphite electrodes
HP graphite electrode is mainly used for high power electric arc furnaces with the current density range of 18–25 A/cm2. HP graphite electrode is the conducting element for electric arc furnaces steelmaking. It is made of petroleum coke, needle coke, coal pitch and produced by a series of strict production processes.
4) SHP Graphite electrodes
The graphite electrode with grade of Super High Power(SHP for short) is produced and specified with allowable current density less than 18～25A/cm2. SHP electrode is widely used in electric furnace with super high power for steel melting.
5) UHP graphite electrode is used for the recycling of steel in the electric arc furnace industry. Its main ingredient is high-value needle coke which is made from either petroleum or coal tar.
Graphite electrode voltage
The voltage between electrodes of the arc furnace is 100~600V. The electrode pressure drop is about 40 v, and the arc pressure drop is about 12V/cm. The longer the arc, the greater the pressure drop. The length of the arc is almost proportional to the voltage.
During the melting period, the voltage of the electric arc furnace changes , and the max voltage and the min voltage may differ by 2 to 5 times.
Graphite electrode wear
Graphite is a very easy to cut material, but because the graphite material used as an EDM electrode must have enough strength.
Otherwise it will damaged during operation and EDM processing. As a result, the graphite workpiece is easy to break and the tool is easy to wear during the processing.
For graphite special tools, ordinary TiAlN coating can be selected with relatively better toughness. The cobalt content is slightly higher. For diamond-coated graphite tools, the hardness is relatively better. The cobalt content is slightly lower.
Choosing a proper geometric angle for graphite tools helps reduce the vibration of the tool. Conversely, graphite workpieces are not easy to chip.