Broken Electrodes in Electric Arc Furnaces (Submerged Arc Furnaces) and Specific Control Measures and Solutions

Broken Electrodes in Electric Arc Furnaces (Submerged Arc Furnaces) and Specific Control Measures and Solutions 

I. Furnace charge

(1) Strengthen the acceptance and control of raw materials. During the feeding period, a special person must be arranged to conduct on-site supervision and inspection. Large pieces of steel with a large amount of refractory material attached to the steel body or entrained with refractory material are strictly prohibited from entering the electric arc furnace. Slag steel with a large amount of slag must be cleaned.

(2) Conduct secondary inspection and screening during the batching process. It is strictly prohibited to enter the furnace with non-conductive materials such as rubber and wood.

(3) In rainy weather, scrap steel and alloys with large amounts of sand and mud will be directly returned.

(4) The quality of arc-starting materials should be paid special attention to. It is strictly forbidden to mix large pieces of heavy scrap steel or baled blocks.

II. Ingredients

(1) Strictly follow the items and levels of the electric furnace batching list to batch materials. Alloy materials with poor conductivity must be added to the middle and lower part of the basket.

(2) When adding heavy scrap, slag steel, and edge wire rolls that are prone to collapse, the hydraulic grab should be placed at the bottom of the basket (the middle position of the lower part of the basket) as much as possible to reduce the impact strength of heavy scrap on the bottom of the basket while avoiding the overturning of large materials during charging, thereby reducing the risk of collapse and electrode breakage.

(3) It is strictly forbidden to add explosive materials such as sealed containers that have not been treated with holes.

(4) The ground of the material yard is hardened to completely solve the problem of large amounts of sand on the surface of steel materials in rainy weather.

III. Equipment

(1) Electrical control system problems

① After equipment maintenance, the phase sequence of the electrodes must be checked with a phase sequence meter. If the phase sequence is incorrect, any two phases in the incoming or outgoing cables of the high-voltage switch cabinet can be swapped to prevent the electrodes from loosening or breaking due to reverse phase sequence.

② After furnace replacement or maintenance, equipment personnel must test the electrode grounding signal feedback phase by phase when the electrodes are energized to ensure that the signal feedback system is sensitive and effective, and that each phase corresponds.

③ During shutdown and production intervals, check and confirm the connection status of the center line of the furnace bottom. If any problems such as false connection, fracture, or broken strands are found, restore them in time.

(2) Mechanical actuator reasons

① Pay special attention to the pressure status of the electrode hydraulic cylinder of each phase on the HMI operation screen during manual and automatic electrode lifting and lowering. If the pressure in a fixed area during the stroke is always obviously abnormal, the deformation of the hydraulic cylinder and column can be considered.

② The gap between the electrode columns is preferably such that the electrode does not shake much at the moment of starting, and there is no obvious obstruction during the lifting and lowering process, which is usually around 0.2mm (feeler gauge measurement data).

③ The gap between the electrode and the electrode hole of the small furnace cover should be at least 50mm, and the gaps between each phase should be kept as consistent as possible.

IV. Smelting operation

(1) After each furnace is charged, the furnace master must check and confirm the condition of the furnace charge after entering the furnace. If there are large materials or non-conductive materials such as heavy scrap, slag steel and edge wire rolls that are turned up around the electrode, they should be handled in time (they can be pulled or hung to the surrounding area away from the electrode with the help of tools such as spear chains and clamps).

(2) If the problem of cold materials adhering to the furnace wall suddenly collapsing and breaking the electrode frequently occurs in the middle and late stages of smelting, further optimization and adjustment of the power supply curve can be considered, with the focus on the optimization and adjustment of the power supply gear and power supply curve number during the melting period.

(3) Pay great attention to the inspection and confirmation of the furnace charge condition under the electrode of the accident phase after the electrode break accident is handled, and re-add the arc-starting material to prevent secondary breakage accidents caused by furnace charge problems.

(4) During the electrode connection operation, strictly follow the relevant purging and cleaning regulations in the operation procedures for connecting electrodes in the electric furnace, and finally tighten with a torque wrench.

(5) After a long period of shutdown (especially in winter when the temperature is low), before re-operating the electrode system, in order to prevent the electrode from breaking due to excessive shaking at the moment of starting, operate according to the following regulations:

① If the three phases are not equipped with electrodes, you can repeatedly lift and lower the electrode cross arm several times after the hydraulic system is started, and then install the electrode after the system is stable.

② If all three phases are equipped with electrodes, it is forbidden to lift or lower the three phases at the same time. First, lift or lower the single phase inching, and then lift or lower the electrodes at the same time after the system is stable.

③ If the length of the offline electrode is too long due to special reasons, the length of the upper part of the chuck and the inner part of the furnace cover must be confirmed after the online connection to avoid breaking the electrode during steel tapping or rotating the furnace cover.

V. Electrode quality

The key to solving the problem of electrode quality is to strictly control the procurement and factory acceptance of electrodes. For those whose joints and body indicators do not meet the requirements of ultra-high power graphite electrodes, they are prohibited from being put on line. At the same time, each factory can combine its own equipment, furnace conditions and electrode suppliers to jointly explore the electrode performance indicators suitable for the smelting conditions of the factory, so as to gradually clarify the requirements for the physical and chemical indicators of subsequent electrode supply. In addition, we must attach great importance to the cause analysis and responsibility division after the electrode is broken, so as to avoid the problem that the electrode break accident cannot be effectively solved for a long time due to unclear responsibilities.

Summary

The various factors and links that lead to electrode breakage are analyzed and summarized, and a series of control measures and on-site solutions are formulated in a targeted manner to effectively solve the problem of electrode breakage caused by furnace materials, equipment, on-site operations and electrode quality problems, and provide a reference for the division of responsibilities after the electrode is broken.