The consumption of graphite electrode has a direct impact on the total cost of steelmaking.therefore,the development of new electrodes and the reduction of graphite electrode consumption have become an important issue in electric steelmaking.
There are three reasons why the graphite electrode for electric arc furnace causes loss during use
- side oxidation:
The side loss of the electrode is due to the action of oxygen and graphite in the furnace gas to generate carbon monoxide or carbon dioxide which consumes 50 to 70% of the total electrode consumption,the side oxidation rate has a nonlinear relationship with the surface temperature of the electrode.According to the oxidation rate,it is divided into low temperature oxidation and high temperature oxidation.Below 400 degree,it is low temperature oxidation and the above is high temperature oxidation.High temperature oxidation is must faster than low temperature oxidation,when the temperature exceeds 400 degrees.oxidation can penetrate into the graphite surface to oxidize,when the temperature exceeds 550-600 degrees,the oxidation is intensified,and as the electrode temperature increase ,the graphite oxidation accelerates.the oxygen concentration near the electrode and the gas flow velocity on the graphite surface have a significant effect on the oxidation rate of the electrode.
The high temperature graphite anti-oxidation coating developed by LMM GROUP can be dip coated on the surface of graphite electrode to form a layer of conductive and high temperature resistant oxidation protection layer on the surface of the electrode,reduce the oxidation consumption of graphite electrode,prolong the service life of the electrode,and reduce the steel
Consumption.the electrode is consumed.the high temperature resistance graphite anti-oxidation coating uses a high temperature solution and has a temperature resistance of 2600℃。It can be cured at room temperature,the coating contains oxides that promote sintering at high temperatures to form a glass network structure,enhance the gass tightness of the coating to protect against oxygen and other corrosive gases,and also interact with the substrate.Infiltration to enhance adhesion to the substrate and thermal shock resistance.in this test the method of comparative test was used NO.1Electrode was used for any treatment .The 2# electrode was coated with graphite high temperature anti-oxidation coating.Under the same test and actual working environment,the working state and oxidation resistance of the two groups of electrodes were also investigated variety.Place the sample stage on top of the balance under the furnace,the graphite electrode sample was placed on the sample stage,and the temperature of the sample was recorded at a temperature rising rate of 5℃/min to 1400℃ and the temperature of the sample was recorded every 50℃。From this,the loss rate of the sample during the heating process is calculated .
Through the above test .the following conclusions can be drawn:
- The unimpregnated graphite electrode begins to oxidize at 600℃，and the graphite electrode begins to show a relatively large loss above 800℃
- After the electrode is subjected to the graphite high-temperature anti-oxidation coating dip coating treatment,the graphite electrode has a loss at a temperature below 1100℃，but maintains a low loss rate.
- Compared with the untreated graphite electrode, the graphite electrode dip coated with graphite high temperature anti-oxidation coating has an improved outer surface oxidation resistance at 1400℃,the electrode loss rate is reduced by 60%,and the corresponding electrode service life is extended 2-3 times.therefore,the dip-coated graphite high temperature oxidation resistance coating can effectively reduce the loss caused by the side oxidation of the graphite electrode.
2. Tip loss
Electrode tip loss includes electrode evaporation,molten steel absorption,and thermal spalling,its consumption is second only to side oxidation ,accounting for 25-40%
Electrode evaporation is mainly caused by radiation and convection of high-intensity arc.the relationship between current and electrode evaporation loss is0.027*I^(I*g), where Q is the evaporation velocity of the electrode tip, g/s, I It is the arc current in units of KA.In addition,electrode evaporation is also related to electrode quality,surface temperature,and smelting process.
The molten steel absorbs and the graphite is easily melted in the molten steel,therefore,both the short arc operation and the electrode impregnation cause an increase in the electrode consumption.
The electrode is thermally exfoliated,and the thermal peeling of the electrode is closely related to the thermal conductivity,thermal expansion coefficient and elastic modulus of the electrode
3. Electrode break
Electrode breakage is an accident,generally due to several reasons:
- The electrode is subjected to a large electromagnetic stress,and the direction and magnitude of the stress alternately change and cause the oscillation of the electrode holder and the vibration of the electrode itself,when the sum of the mechanical stress,the electromagnetic force,and the thermal stress in the electrode is greater than the strength of the electrode itself will cause the electrode to break.
- b) Thermal shock from arc, steel slag, and molten steel can destroy the thermal stability of the electrode.
- c) Improper operation, such as poor loading, dip, excessive current, etc.
- d) The joint structure is unreasonable and the processing quality is not good.
- e) The electrode itself has poor physical properties.
- f) The joint is loose and disconnected.
Electrode fracture not only causes loss of electrode material, but also causes the furnace to stop working, which interrupts normal operation.
At present, measures to reduce electrode loss include: hollow electrode, impregnated electrode, coated electrode, graphite ring water-cooled composite electrode, and electrode surface water cooling technology.