Consumption Mechanism of Graphite Electrode in Electric Furnace Steelmaking Process
Graphite electrode is used as a conductive material in electric arc furnace smelting, and its consumption is generated by the consumption of electric power.
Modern electric arc furnace steelmaking uses electric energy and chemical energy as thermal energy to realize the four-way process in steel making(P, C, O, S), two (gas, miscellaneous), two-tone (temperature, composition) purposes, the use of graphite electrodes in the user is mainly reflected in the application and consumption, and the electrode consumption .It has a direct relationship with its own quality. The consumption of graphite electrode in electric arc furnace smelting is mainly composed of the following parts
Consumption of Graphite Electrode End and Outer Circular Surface in Electric Furnace
The arc generated by the graphite electrode in the electric arc furnace is divided into long, medium and short arcs, and the melting charge and the temperature rise depend on the arc power. The arc length is proportional to the secondary voltage and inversely proportional to the secondary current and the rate of temperature rise. In order to improve the smelting speed and greatly shorten the smelting time, the high chemical energy operation of forced oxygen blowing is adopted, which puts higher requirements on the oxidation resistance and thermal shock resistance of the graphite electrode.
End consumption of the ink electrode includes - sublimation generated in the high temperature of the arc, and contact with molten steel and steel slag,The chemical reaction of birth. The oxidation loss of the graphite electrode accounts for about 2/3 of the total consumption. The oxidation loss is the product of the unit oxidation rate and the area and is proportional to the time. The longer the heating time in the smelting, the greater the consumption, so the electrode is mounted on the electrode of the arc furnace. A water-cooled spray system is essential. In normal smelting, the carbon content of the graphite electrode entering the molten steel is generally about 0.01%, and the end consumption switch is a non-cone tip shape.
Residue Consumption of Graphite Electrode Produced in Smelting
Residual consumption refers to the non-productive consumption part of the smelting process in which the lowermost electrode falls into the furnace and becomes the final waste. The generation of the residue is not only related to the intrinsic quality of the joint and the electrode, but also has a direct relationship with the magnetic card in the distribution of the cloth in the furnace, the atmosphere in the furnace and the operation of the power transmission. The main appearance phenomena are: there are "human" cracks at the bottom end of the residue and there are large longitudinal cracks or splits; the joints are not tight enough to cause the joints to oxidize and fall off or break; the joints are not in place or the joints are not good. Or the electrode is broken by the external force; the electrode is broken by the external force; the joint is broken by the external force; the unreasonable cloth in the furnace causes the area of the collapsed material after the well to be worn or the operation of the power transmission curve is unreasonable. Severely broken,the quality of the electrode itself is poor. This part of the loss, under the premise of ensuring the quality of the electrode, is not large in normal production, but direct users pay much attention to it.
4. Oxidation spalling of the electrode surface accompanied by consumption of open and falling blocks.
In normal smelting production, if the surface of the graphite electrode is uneven or accompanied by flaking and falling off.
Then there is a problem of carbon increase in molten steel. On the one hand, this phenomenon reflects the poor oxidation resistance and thermal shock resistance of the electrode; on the other hand, it is caused by excessively long oxygen blowing time or excessive oxygen blowing in the smelting, resulting in severe oxygen enrichment in the furnace and on the furnace. As a result, the electrode peroxide loss is increased; the second is that if there is a serious shedding phenomenon, the electrode problem must also be considered. This abnormal consumption is a test of the intrinsic quality and technical service level of the product.
Direct Loss Caused by Fracture of Graphite Electrode in Smelting
It is a common phenomenon that graphite electrodes are broken in all electric furnace smelting, and it is also the most important factor affecting consumption. It is normal for continuous consumption in a complex environment to use occasional breaks, but continuous breaks are not normal. The reason is related to many factors. The overall view can be divided into: artificial break and mechanical break. The artificial break mainly includes: bumping and scratching during lifting, improper connection or improper method, improper sliding in the flat holder, poor hardness of hard collision or transmission control. In addition to mechanical failures in mechanical fractures, electrode quality problems and operational problems are often present and difficult to distinguish. The main phenomena are as follows.
Electrode Body Fracture Phenomenon
First, the electrode may have structural defects and may have low strength; second, it is a short-arc operation after smelting, and there is a lateral impact force of a large collapse; third, the three-phase electrode on the furnace is not vertical and has a slag Or scraping the lid phenomenon. The sound is very brittle when broken.
Breaking of the Bottom of the Electrode Body
First, the Electrode end structure is loose or has dark lines, the joint and the hole are improperly matched or the material difference linear expansion coefficient is not matched; the second is that the phase-precision electrode is different, the electrode stroke is too long or the lifting is not sensitive; the third is that the furnace fabric is unreasonable. There is no conductive material under the electrode. When breaking, the sound is not big but the tilt is heavier.
The Joint is Broken and Irregular
First, there is a difference in the taper of the joint processing or the ellipticity of the joint hole is too large; the second is that the dust in the hole is too much, and the contact resistance is too large, so that the joint thread is locally oxidized too fast; the third is that the electrode is not in contact and the torque is not reached. The fourth is that the handle is tilted, and the electrode is not the same as the hole of the furnace cover. The sound is crisp and small when broken
Joint Fracture is a Regular Phenomenon
First, the quality of the joint itself is large, the strength of the joint can not meet the requirements of the smelting furnace; the second is the improper matching of the electrode hole and the joint tolerance or the connection torque can not reach the required kickback; the third is the excessive range of the secondary current fluctuation in the power supply or there is a sudden increase, the maximum instantaneous current far exceeds the rated value of 1.2 times or more; Fourth, the thermal shock generated when the power and power are too large is too large, and the electrode joint is reddish and the resistance is too large. The sound is boring, when broken.
