The problem of using electrodes in the steel melting process

.


Introduction
Electrodes are the main element in the operation of steel melting furnaces.Not only electrodes directly affect the timely and high-quality melting of the slag but also, reducing the consumption of electricity in metal melting is one of the most important tasks.Because of the process of metal melting is 40-70% of the whole process and the consumption of electricity is 60-80%.Acceleration of the metal melting as much as possible, the electric arc between the electrodes and the metal plays a very important role for the quality continuation of the technological process.After all, when melting steel, electrodes are damaged, broken, and as a result, the arc goes out and the melting process is disturbed.So that depending on the mechanical and thermal tolerance of electrodes and their use in melting processes, the selection of their production process, materials, selection of electrode types in accordance with the process is one of the urgent problems.As well as, high quality melting of metal in a specified period time directly depends on the electrodes.Today, the use of furnaces is increasing, and the demand for electrodes is increasing directly after the increase in power.One of the biggest problems in the process of metal melting today is damage (breakage) of electrodes.In this article, these problems are analyzed and solutions are given with a scientific and practical approach [1][2][3][4].
These are scientists who have worked on scientific research: In Central Asia [5,12], in Foreign countries [14,16].

Experimental research
Electrodes used in the steel industry are divided into several types based on their application and the types of manufactured products.They are selected for durability and thermal stability of the electrodes [13,[17][18][19][20][21][22][23][24][25].Their names are indicated in the following diagram, Fig. 1.

Fig.1. Types of electrodes
The electrodes of an arc steelmaking furnace work in extremely difficult conditions.Therefore, a number of specific requirements are imposed on the material for the manufacture of electrodes.They must have sufficient mechanical strength at low and high temperatures; have high electrical conductivity; be resistant to oxidation in the working space of the furnace and outside it, provide reliable contact in the heads of the electrode holders and the junction points of the electrode sections, have a low cost.Currently, only electrodes made of carbonaceous material meet such requirements.
Graphite electrodes are used in electric arc furnaces for several reasons.Because the temperature of the furnace is very high (1600-1800°C), electrodes that can withstand this temperature are graphite electrodes.The 1 table has types of graphite electrodes [26][27][28][29][30].

Table 1. Types of graphite electrodes RP
A conventional power graphite electrode is also called a graphite molded column to allow a current density through a graphite electrode of less than 17 A/cm 2, Mainly used in steelmaking, yellow phosphorus, silicon and other ordinary power electric furnaces.

HP
The high-current HP electrode is appropriate for casting operations or occasionally in arc furnaces.High power graphite electrode wire material for steelmaking of an electric arc furnace, which is made of petroleum coke, needle coke, coal asphalt, and hightemperature wire material produced by a series of strict process processes.In order to allow the current density through the graphite electrode to 18 ~ 25A / km 2, mainly used in a high-power steelmaking arc furnace.

UHP
Ultrahigh graphite electrodes are used to recycle steel in the arc furnace industry.The main ingredient is high-quality needle coke made from oil or coal tar.In order to allow the current density through the graphite electrode to be larger than 25A/cm 2. Mainly used for ultra-high power steelmaking electric arc furnace.
Above are the types and classification of electrodes, of which the most widely used in the steel melting process are UHP graphite electrodes.Take as an example of graphite electrodes, due to improper use of graphite electrodes in technological processes and operation, electrodes can be broken and damaged.As a result, the metal melting time increases and the cost of the product increases.If broken graphite electrodes fall into the furnace, carbon content will be added to the slag and stop the melting process in the furnace.This leads to the deterioration of the properties of steel and the decrease in the price of the product by the purchasing companies, and in some cases cases of non-purchase occur.
In addition, broken or damaged electrodes cause an increase in the consumption of electrodes and an increase in the price of the product.As a result, the amount of profit metallurgical plants receive from the sale of these products will decrease significantly.Therefore, it is necessary to reduce the consumption of electrodes in order to increase technical and economic indicators in steel production.In many countries (in particular, in Uzbekistan) steel melting furnaces of large and medium capacity are used.
Take a graphite electrodes as an example, the production technology of high-quality graphite electrodes for heavy-duty arc furnaces is quite complex.The high cost of charge materials and high power consumption determine the very high cost of special graphite electrodes for heavy-duty furnaces ($1500-2000 per 1 ton).Because of the high cost of graphite electrodes, the cost of electrodes during the operation of furnaces of ordinary power for smelting carbon steels is 8% of the cost of steel; when operating heavy-duty furnaces, such costs can exceed 15% of the cost of steel, in some cases reaching 30%.The consumption of graphite electrodes fluctuates within a significant range, which during normal operation of furnaces is 4-8 kg/t (in a well-functioning heavy-duty steel-smelting furnace, the total consumption of electrodes was 4 kg/t of steel) [31][32][33][34]40].
According to the above points, we can say that the consumption of graphite electrodes in EAF steelmaking depends not only on the quality of the electrodes, but also on the level of operation and management of steelmaking.
So what factors influence electrode breakage or failure?When these factors were analyzed, it was studied that there was too much factor dependence.The below in fig. 2 follows the main 3 factors, which are: Fig. 2. Factors causing breakage and damage of graphite electrodes [35] To minimize electrode consumption and prevent breakage and failure in steel melting furnaces, it is crucial to employ proper electrode usage techniques.Fig. 3

Fig.3. Strategies for preventing electrode breakage in steel production
Preserving the integrity of graphite electrodes during the steel melting process positively impacts both economic efficiency and metal quality [36][37][38][39].
Another problem is that during steel production in electric arc furnaces, there are high-energy losses.Generally, the operational practice of electric arc steelmaking furnaces demonstrated that the total electrode consumption correlates well with the overall electricity consumption.Therefore, any organizational and technical measures aimed at reducing the overall electricity consumption during the melting process will also reduce electrode consumption.Energy conservation is a key component of reducing the cost of steel production.Let is explore the primary energy-saving measures while taking into account changes in other cost components.
We will examine the energy balance of the Electric arc furnace (EAF), which is be expressed as follows: where - is the electricity consumed by the electric furnace installation from the energy system;  is the enthalpy of the charge and gases entering the EAF workspace;  is the chemical energy of exo-and endothermic oxidation, reduction and slag formation reactions;  is the amount of thermal energy introduced into the EAF workspace using fuel and oxygen burners;  enthalpy of the drained liquid metal and slag (useful energy consumption);  , electrical losses in the power source and secondary current supply (up to the working space of the furnace);  , thermal losses from the working space of the furnace;  represents the change in enthalpy of the lining (positive for heating and negative for cooling) [11].
The portion of electricity consumption in the balance can be expressed as follows: ,  ,    (2) From the analysis in equation ( 2) that a reduction in electricity consumption can be obtained both by reducing electrical and thermal losses, and by using other types of energy, that is, using integrated heating [9].

Fig. 4. Factors causing energy waste in steel smelting technology
On the other hand, they are associated with the unsatisfactory quality of carbon-graphite electrodes and their improper operation.If we identify issues that can occur through electrodes without increasing electrical efficiency, and when we find solutions to these problems, we improve energy efficiency and optimize electrode usage.That is, other reasons that reduce the efficiency of the furnace installation given below: Based on the above-mentioned issues, there are concerns regarding energy inefficiency, increased electrode consumption, and the adequacy of electrode strength and durability in the steel production process when using electrodes.Addressing these challenges through the provision of solutions enhances the technological process quality [22,36].

Conclusion
Electrodes ensure high-quality melting of scrap in the technological process.For this, it is important to have accurate information about the types and classification of electrodes and to choose special electrodes.This is mainly because of complexity of the production technology of graphite electrodes and their production according to the requirements of steel melting furnaces, their price increases.So, that is why in this article, the consumption of graphite electrodes in the process of steel smelting is given, and if the electrodes are damaged or broken, the condition of the consumption of the electrodes and what problems they cause are considered.Also, the technical characteristics of graphite electrodes, which are the main element of the steel smelting process, The electrode gripper should avoid clamping at the electrode joint and the hole of the electrode joint.Keep the tilting system in good condition and keep the tilting stable.
The electrode pillar is aligned with the furnace top hole, and the electrode pillar is parallel.
Avoid the existence of non-conductive materials in scrap steel.
The scrap is evenly distributed in the furnace, and the large scrap is placed at the bottom of the furnace as far as possible.
Correct electrode phase sequence, counterclockwise direction.are given, the problems that may arise in their use in the technological process are analyzed (fig.2), and several solutions are given (fig.3).
As well as, in this article, suggestions for reducing the consumption of electrodes are given.
1. Low-quality steel scrap or incorrect proportioning can lead to inadequate slag formation, which in turn prolongs the smelting process.Prolonged smelting directly contributes to higher power consumption and increased electrode usage and losses.
2. Mismatched electric furnace power supply equipment and electrode specifications can lead to problems.Electric arc furnace power transmission involves high-current and low-voltage operations.Overloading and prolonged operation can result in the most significant loss and consumption of graphite electrodes.
3. During the oxidation phase, chemical energy is deliberately elevated to enhance smelting intensity.Throughout the smelting process, there is a deliberate increase in the amount of oxygen blown to achieve rapid melting and elevate furnace temperatures within the high-temperature flame.In this furnace environment, electrodes often experience significant issues such as layering and surface oxidation.
The technical aspects of electric furnace configuration and operation are critical.This includes choosing the power transmission curve and gear during operation, controlling arc starting and arc stabilization voltage and current, and effectively coordinating the use of long, medium, and short arcs.Additionally, the configuration and utilization of water cooling systems are crucial factors that significantly impact the service life and consumption of electrodes.
. illustrates key solution factors that mitigate electrode damage.