The performance of graphite electrode is mainly reflected in whether it is suitable and how much it is consumed, and the consumption of the electrode is directly related to its own quality. The consumption of graphite electrode in arc furnace smelting mainly consists of the following parts.
Graphite electrode is used as conductive material in arc furnace smelting. Modern eaf steelmaking with electricity and chemistry for thermal energy, to achieve the four take off in the process of steelmaking (P, C, O, S), 2 (gas, noise), 2 (temperature, composition), the purpose of the use of graphite electrode performance mainly embodied in the user in how many, if applicable, and consumption and electrode consumption and its quality has a direct relationship. The consumption of graphite electrode in arc furnace smelting mainly consists of the following parts.
- Consumption of graphite electrode and cylindrical surface in electric furnace
The arc produced by the graphite electrode in the arc furnace can be divided into long arc, medium arc and short arc. Arc length is proportional to secondary voltage and inversely proportional to secondary current and heating rate. In order to improve the smelting speed and greatly shorten the smelting time, the high chemical energy operation of forced oxygen blowing is adopted. End consumption of graphite electrodes in smelting includes sublimation at high arc temperatures and chemical reactions with molten steel and slag. The oxidation loss of graphite electrode accounts for about 2/3 of the total consumption. Its oxidation loss is the product of unit oxidation speed and area and is proportional to time. The longer the heating time in smelting, the greater the consumption. In normal smelting, the carbon content of graphite electrode entering molten steel is about 0.01%, and it is normal for the end consumption switch to be non-conical tip.
- Consumption of graphite electrode residues generated during smelting
The residual consumption refers to the non-productive consumption of the lowest electrode in smelting process which falls into the furnace and becomes the final waste. The generation of the residual body is not only related to the internal quality of the connector and the electrode, but also has a direct relationship with the magnetic card, such as the distribution in the furnace, the atmosphere in the furnace and the operation of power transmission. The main appearance phenomena are: the bottom end of the residual body has a “person” type crack and a large longitudinal crack or splitting; The connection is not tight, which causes the joint to oxidize and fall off or break; Falling off or breaking due to improper connection or poor coordination; When the electrode is subjected to external force, the joint or the bottom of the hole is broken. The connector or the hole is broken when the electrode is subjected to external force. The electrode can be seriously broken if the material collapse area is large or the operation of power supply curve is unreasonable. The poor quality of the electrode itself. Under the premise of guaranteeing the quality of the electrode, the amount of loss in normal production is not large, but direct users pay great attention to it.
- The surface of the electrode is oxidized and peeled off with the consumption of splicing and dropping blocks
In normal smelting production, if the surface of graphite electrode appears uneven or accompanied by spalling and dropping, then there is a problem of carbon increasing 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, too long time of horizontal oxygen blowing or too much oxygen blowing in smelting leads to serious oxygen enrichment in the furnace and on the furnace, leading to increased loss of electrode peroxidation.The second is that if there is serious shedding, the problem of electrodes must be taken into account.This kind of abnormal consumption is a test of the inherent quality of products and technical service level.
- The direct loss caused by broken graphite electrode in smelting
Graphite electrode fracture is a common phenomenon in all electric furnace smelting, and it is also the most important factor affecting consumption. In a complex environment, it is normal for continuous consumption to break occasionally, but it is not normal for continuous consumption to break. The reason is related to many factors. In general, it can be divided into artificial fracture and mechanical fracture. Artificial fracture mainly includes: bump and scratch in the lifting, improper connection or method, improper sliding in the flat holder, hard collision or poor transmission control sensitivity. In addition to mechanical failure, the quality problem of electrode and operation problem often exist simultaneously and it is difficult to distinguish. There are the following phenomena.
(1) the phenomenon of broken electrode body
First, the electrode may have structural defects and low strength. The second is the short arc operation in smelting and the lateral impact force of material collapse is larger. Third, the three – phase electrode on the furnace is seriously not vertical and hanging furnace slag or scraping the furnace cover phenomenon. It’s very brittle and loud when it breaks.
(2) the hole bottom of the electrode body is broken
Firstly, the structure of the electrical extreme part is loose or has dark lines, improper fitting of joints and holes or mismatch of linear expansion coefficient of material difference; Second, the phase electrode is different center, the electrode stroke is too long or the rise and fall is not sensitive; Third, the furnace fabric is not reasonable, there is no conductive material under the electrode. When it breaks it is not loud but it leans heavily.
(3) the joint is broken irregularly
One is that the taper of the joint processing is different or the ellipse of the joint hole is too large; Secondly, the contact resistance caused by dust in the hole is too large, which causes the joint screw to oxidize too fast. Third, the electrode contact is not in place and does not reach the torque requirements to loosen; Four is the controller tilt, electrode and furnace cover hole different center. It breaks in a small, crisp sound.
(4) the joint is broken in a regular way
Firstly, the quality of the joints varies greatly, and the strength of the joints cannot meet the needs of smelting furnace. The second is improper fitting of the electrode hole and the joint tolerance or the connection torque can not meet the requirements and produce the back button. Third, the fluctuation range of secondary current in power supply is too large or there is sudden increase phenomenon, the maximum instantaneous current is far more than 1.2 times of the rated value; Fourth, when the power and power is too large thermal shock is too large, the electrode connection red and display resistance is too large. The sound is muffled when it breaks.