Technology | Graphite electrode broken solution

Core tips

Internal quality of the electrode

(1) In terms of electrode nipple quality itself, there are mainly the following reasons for breaking: the strength is generally low when the bulk density of the electrode nipple is low, which is easy to break when in use; The resistivity is high, and the temperature at the electrode nipple increases rapidly when powered on, which will cause large thermal stress at the electrode connection of electrode nipple and increase the probability of fracture; The flexural strength of the electrode nipple is not enough; The internal crack electrode nipple is mixed into the finished electrode nipple to form a major hidden danger; There is no reasonable matching between the machining accuracy index of the electrode nipple and the electrode, and it is easy to break.

(2) Causes of electrode fracture. Generally, the probability of electrode breaking is low. The main reasons for electrode breaking are as follows: The electrode screw hole has quality defect; The volume density and strength of the electrode are not enough; The electrode does not match with the electrode nipple index and machining 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 transverse crack inside was mixed into the finished product and was not detected, so there was a great risk of fracture.

Preventive measures and operation suggestions

1  Preventive measures for breaking in smelting operation

(1) Reasonable distribution structure: the distribution of all kinds of scrap steel in the basket and the condition of adding into the furnace should be reasonably arranged to avoid the light and thin steel material forming a mass on the top of the furnace, and avoid the collapse of large scrap steel to break the electrode.

(2) During smelting, especially when it is close to melting down, carefully observe the distribution of unmelted furnace materials. If the bridge structure has been generated, the method of blowing oxygen or physical swing or shaking should be used first to make the burden collapse in the case of power cut and electrode has been raised high, so as to avoid the electrode being broken by material collapse.

(3) The electrode shall adopt the strength suitable for the process requirements. The connecting electrode shall adopt nuts with appropriate strength, clean them, and use special holding tools. Before replacing the electrode and lifting, the lifting ring must be fastened to ensure close contact between the lifting ring and the electrode. In order to ensure the cleanness of the interface, it is required to keep the protective end cap of the new electrode until the lifting ring is installed.

(4) The electrode holder shall avoid being clamped in the white line between the electrode connections. The electrode connection shall not be above the electrode holder. The electrode holder shall not be clamped on the open socket or the socket with lifting ring.

2 Preventive measures in the control process

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

(2) Before the electrode automatically descends, make sure there are no non-conductive objects in the scrap layer directly below the electrode.

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

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

(5) Regularly detect whether the braking force and system delay coefficient of the electrode hydraulic driving mechanism change.

The influence of key technical indexes of electrode (electrode nipple) in the process of smelting on electrode fracture has been studied in detail by many scholars. It is worth noting that the China Carbon Industry Association has conducted product quality spot checks on member enterprises, and compared the test indicators of product spot checks with national standards and enterprise standards of foreign well-known enterprises. From the test indicators, most of the tested products conform to YB - 2000 standards, and some indicators have reached or close to the standards of foreign companies. However, the actual smelting effect of domestic ultra-high power graphite electrode is obviously different from that of foreign products of the same specification. Therefore, it is one-sided to judge the quality of electrode (electrode nipple) only by relying on the physical and chemical indexes of electrode (electrode nipple). It is necessary to establish a scientific and reasonable electrode production and technical application scheme by fully considering the compatibility between the products of our factory and the smelting process, furnace structure and smelting steel types of different customers.

Conclusion

(1) Material collapse, resonance effect, non-standard clamping operation, abnormal condition of electrode regulator, hydraulic drive mechanism of electrode regulator, electrode internal quality and other factors can cause electrode broken.

(2) The phenomenon of electrode breakage can be significantly improved by taking corresponding technical and management measures for such factors as distribution structure, electrode clamping, no-load voltage of secondary short network, non-conductive object, secondary current, braking force of electrode hydraulic driving mechanism and system delay coefficient.

(3) It is one-sided to judge the quality of electrode (electrode nipple) based on the physical and chemical indexes of electrode (electrode nipple). The matching of our products with the smelting process, furnace structure and smelting steel grade of different customers should be fully considered, to establish a set of scientific and reasonable electrode production and technical application scheme, more profession graphite instructions communicate with us.