Part of the reason for graphite electrode fracture is operation and control, but the quality of the electrode itself is also a decisive factor for electrode fracture.

Electrode intrinsic quality reasons

(1) Reasons for joint fracture The joint plays a key connection role in the electrode steelmaking process, and the quality of the joint is directly related to the use of the electrode in the electric furnace steelmaking process. The connection area formed by the graphite electrode and the joint is a place where the electrical, thermal, and mechanical loads are large and complex, and it is also a common fracture site. According to relevant data, in electric furnace steelmaking, more than 80% of electrode use accidents are caused by broken joints or loose tripping. As far as the quality of the joint itself is concerned, there are mainly the following reasons for the fracture: the joint has low bulk density and generally low strength, which is easy to cause fracture during use; the high thermal stress of the joint at the electrode connection increases the possibility of fracture; The bending strength is not enough; internal cracks are mixed into the finished seam, which becomes a major hidden danger in use; the matching of the joint and electrode processing accuracy indicators is not reasonable, and it is prone to breakage.

(2) Reasons for electrode fracture Generally, the probability of electrode fracture is low, and the main reasons for electrode fracture are: the quality of the electrode screw hole is defective; the volume density and strength of the electrode are not enough; the indicators of the electrode and the joint do not match the processing accuracy; The deep crack at the end of the electrode is caused by the poor thermal shock resistance of the electrode; in addition, the electrode with internal transverse cracks is mixed into the finished product without detection, and there is a great risk of breaking.

Precautionary Measures and Operation Suggestions

1 Damage prevention measures in smelting operations

(1) The distribution structure is reasonable: the distribution of various steel scraps in the basket and the feeding into the furnace should be reasonably arranged to prevent light and thin steel materials from agglomerating on the top of the furnace, making it difficult to descend, and avoiding the collapse of large pieces of steel scrap and breaking the utility poles.

(2) When smelting, especially when it is close to melting, carefully observe the distribution of unmelted charge. If a bridging structure has been formed, oxygen blowing or physical shaking or shaking must be used first to allow the charge to collapse when the power is cut off, and the electrodes have been raised to prevent the electrodes from falling off and being broken by a plunge.

(3) The electrode should adopt the strength suitable for the process requirements. Connect the electrodes with nuts of appropriate strength, clean them, and use special clamping devices. Before replacing the electrode and hoisting, the lifting ring must be tightened to ensure that the lifting ring is in close contact with the electrode. To keep the interface clean, it is required that the end cap of the new electrode remain until the lifting ring is installed.

(4) The electrode clamp should avoid being caught in the white wire between the electrode connections. The electrode connection cannot be above the electrode holder. Electrode clamps cannot be clamped on split sleeves or sleeves with rings.

2 Precautionary measures during the control process

(1) After high-voltage power transmission, it is necessary to observe whether the three-phase no-load voltage of the secondary short-circuit network is balanced (determined by the insulation resistance of the three-phase short-circuit network to ground, and the unbalanced voltage should be within 10%).

(2) Before the electrode is automatically lowered, confirm that there is no non-conductive object in the scrap steel layer directly below the electrode.

(3) After the first phase electrode falls and contacts the scrap steel, observe whether the secondary voltage of the phase electrode drops immediately.

(4) When an arc occurs in an electrode of a certain phase, the secondary current display of the electrode of this phase can be seen (the pointer of the ammeter swings greatly).

(5) Regularly detect whether the braking force of the electrode hydraulic drive mechanism and the system delay coefficient have changed.

As far as the internal quality of the electrode is concerned, the key technical indicators of the electrode (joint) during the smelting process will eventually affect the fracture of the electrode. Many scholars have conducted detailed research on this. It is worth noting that the China Carbon Industry Association has conducted product quality spot checks on member companies, and compared the testing indicators of product spot checks with national standards and corporate standards of well-known foreign companies. In terms of testing indicators, most of the indicators of all tested products meet the YB-2000 standard, and some indicators meet or approach the standards of foreign companies. However, the actual melting effect of domestic ultra-high power graphite electrodes is significantly different from that of foreign products of the same specification. Therefore, there is a certain one-sidedness in judging the quality of electrodes (joints) only by the physical and chemical indicators of electrodes (joints), which should be fully taken into account. According to the matching of our products with different customers' comprehensive factors such as smelting process, furnace structure, smelting steel type, etc., a set of scientific and reasonable electrode production and technical use schemes are established.

In summary

(1) Factors such as collapse, resonance, irregular clamping operation, abnormal electrode regulator, the hydraulic drive mechanism of the electrode regulator, and internal quality of the electrode can all cause the electric furnace electrode to break.

(2) By taking corresponding technical and management measures for factors such as fabric structure, electrode clamping, secondary short-circuit network no-load voltage, non-conductive objects, secondary current, the braking force of electrode hydraulic drive mechanism and system delay coefficient, the phenomenon can significantly improve the electrode breakage rate.

(3) According to the matching of the physical and chemical indicators of the welding rod (joint), smelting process, furnace structure, smelting, and other comprehensive factors, there is a certain one-sidedness in judging the quality of the welding rod (joint) Establish a set of scientific and reasonable welding rod production and technical use scheme.