Common Problems And Solutions Of Graphite Electrodes in Electric Furnace Steelmaking

12. How to choose electrodes correctly in electric arc furnace steelmaking?

According to the design characteristics of the electric arc furnace, the electrodes that meet the production of the electric arc furnace are reasonably selected, and the products with the best cost performance are selected. Careful selection of electrodes suitable for each furnace is very necessary. The special characteristics of the steelmaking furnace, the charging method, the maximum amperage, the length of the electrode column under the gripper, the distance between the furnace side wall and the electrode circumference, etc. It is a factor that must be considered when choosing electrodes for electric arc furnaces.

13. What are the effects of resistivity properties on the use of electrodes in steelmaking?

The resistivity of graphite electrodes is a physical index that reflects the electrical conductivity of electrodes, which is related to the manufacturing process of electrodes. The country has qualitative values for the resistivity of graphite electrodes of different specifications and varieties. When using the electrode, it must be selected within the resistivity range specified by the national metallurgical standard. Too high resistivity will cause the electrode to become red and hot when it is energized, which will increase the oxidation consumption of the electrode.

14. What is the effect of bulk density properties on the use of electrodes in steelmaking?

The bulk density of the graphite electrode reflects the compact state of the electrode and is closely related to the manufacturing process of the electrode. The country has stipulated values for the bulk density of graphite electrodes of different specifications and varieties. Products with low bulk density indicate that the overall structure of the product has high porosity, and the oxidation rate of the product is faster when the product is high temperature, which is likely to cause an increase in electrode consumption. Generally speaking, when steel mills choose electrodes, the electrode bulk density is within the specified value. However, the higher the bulk density is, the better, because some electrodes with too high bulk density are sometimes prone to surface peeling, falling blocks and cracks during steelmaking due to poor thermal shock resistance, which will affect steelmaking.

15. Why should steel mills prevent mixing of multiple products when using graphite electrodes?

The graphite electrodes used by steel mills are often supplied by multiple manufacturing companies. Mixing multiple products in steelmaking will not only make it difficult for steel mills to count the consumption of a single product, but also due to the differences in raw materials and manufacturing processes used by different manufacturers. , The physical and chemical properties and processing tolerances of electrodes and joints of various manufacturers have certain differences. Therefore, the matching tolerances generated when mixed use are likely to cause the electrodes to fall off and break. The correct use method is to use the products of a certain manufacturer alone, and then connect the products of another manufacturer after the end. To reduce the number of electrode replacements using different manufacturers, Electrodes of the same manufacturer should use the matching joints of the same manufacturer to prevent mixed use.

16. What are the characteristics of needle coke?

Needle coke is a high-quality carbon raw material. It is divided into two types: coal series and oil series. The surface of needle coke has obvious stripe patterns. Hence it is called needle coke. Needle coke is easy to graphitize at high temperature above 2000 degrees. The graphite electrode produced by it not only has low resistivity, high bulk density, but also small thermal expansion coefficient, which is the best choice for the production of ultra-high-power electrodes and high-power electrodes. Necessary raw materials for electrodes. The price of needle coke is much more expensive than ordinary coke, currently about 5-8 times higher.

17. Will the vacuuming system on the electric arc furnace affect the consumption of electrodes?

The fan used in the dust collection system generates a certain negative pressure during operation, which increases the air flow rate around the red hot electrode during steelmaking, thereby increasing the oxidation consumption of the electrode. When steelmaking, a well-adjusted dust collection system is It maintains a good working environment and stabilizes the consumption of electrodes.

18. How to avoid the increase of electrode consumption during steelmaking?

To avoid the increase of electrode consumption during steelmaking, the following should be done: (1) Maintain a good power supply state, and transmit electricity within the allowable current intensity range of the electrode according to the design requirements of the electric furnace. (2) Prevent the arc starting point from immersing in the molten pool. (3) Prevent the electrode from being immersed in molten steel to increase carbon. (4) If conditions permit, the electrode adopts spray cooling technology. (5) Set up the correct exhaust emission system. (6) Adopt the correct oxygen blowing system.

19. How long does the production cycle of graphite electrodes take?

The production process and corresponding time of a batch of ultra-high-power or high-power graphite electrodes are as follows: electrode pressing (3 days) - roasting (25 days) - impregnation (4 days) - re-roasting (15) --Graphitization (10 days)--Machining, quality inspection (2 days)--Finished product packaging and delivery (1 day), that is, from material feeding to product delivery, the fastest cycle without production stoppage is 60 days , and the production of electrode joints requires more two-dipping and three-baking treatment than electrodes, and the fastest production cycle is 90 days.

20. What are the characteristics of electrodes produced by tandem graphitization furnaces?

The development direction of the graphitization furnace is the internal heat series graphitization furnace. Since the current density of the series-connected column is the same, the difference in the resistivity of the electrodes is very small; secondly, the resistivity of the two ends of the graphitized product in the inner string is slightly lower than that of the middle part (the resistivity of the two ends of the graphitized product of the Acheson furnace is higher than that of the middle part), It is beneficial to reduce the resistance of the joint when the user is using it, and alleviate the phenomenon of overheating and redness at the joint. Therefore, the quality uniformity of the electrodes produced by the tandem graphitization furnace is better than that of the Acheson furnace, and it is more suitable for the production of electric arc furnace steelmaking. Require.

21. Why does the quality of electrode joints play an important role in electric arc furnace steelmaking?

The joint plays a key role in the connection of the electrode in steelmaking. The quality of the joint is directly related to the use of the electrode in the electric furnace steelmaking. No matter how good the quality of the electrode is, if there is no high-quality joint with it, it will Problems can also arise. According to relevant data, more than 80% of the electrode use accidents in EAF steelmaking are caused by broken joints and loose and tripped joints. Therefore, the selection of high-quality electrode joints is a guarantee condition for the normal use of EAF steelmaking electrodes.

22. What quality indicators of graphite electrode (joint) products have an impact on electric furnace steelmaking?

(1) Quality indicators such as bulk density, resistivity, strength, elastic modulus and thermal expansion coefficient of the electrode. (2) Quality indicators such as bulk density, resistivity, strength, elastic modulus and thermal expansion coefficient of the joint. (3) The machining accuracy of electrodes and joints, no matter how good the quality of electrodes and joints is, if there is no good machining accuracy (mainly refers to the cooperation between electrodes and joints), the use effect is not good. (4) The quality of the internal structure of electrodes and joints requires that there are no internal cracks that cause hidden dangers in use.

23. What are the consequences of severe oxidation of the electrode end face at the upper end of the electrode holder?

When steel is made in a smelting furnace, scrap steel is burned in the furnace. At the same time, due to oxygen blowing in the furnace, the height of the flame column is often higher than the electrode end face at the upper end of the holder, which is easy to oxidize the electrode end face. If the oxidation is serious, the electrode end face will be deformed by The plane becomes an inclined plane. When the new electrode is connected to the upper end, the oxidation deformation of the end face of the lower electrode cannot make good contact with the new electrode, and the electrode gap is large, which is easy to cause oxidation and breakage of the internal joint. Without changing the steelmaking conditions, the best preventive measure is to add a protective cover on the electrode end face at the upper end of the holder to block flame and air, so as to protect the electrode end face.