Author: graphelectrode.com

Performance Index of Graphite Electrode Body and Nipple

The graphite electrode body needs the graphite electrode nipple to connect them one by one in series. Therefore, they also have certain connections and differences in performance indicators.

Graphite Electrode with the Nipple
Graphite Electrode with the Nipple

The Performance Index Difference of Graphite Electrode Body and Nipple

(1) Resistivity. The resistivity of ordinary power graphite electrode is not more than 8.5μΩ·m, 9.0μΩ·m, 10.0μΩ·m, and 10.5μΩ·m, and the resistivity of ordinary power graphite electrode nipple is not more than 8.5μΩ·m. The resistivity of the high-power graphite electrode is not more than 6.5μΩ·m and 7.5μΩ·m, and the resistivity of the high-power graphite electrode nipple is not more than 6.5μΩ·m. The resistivity of the ultra-high power graphite electrode is not more than 6.2μΩ·m and 6.5μΩ·m, and the resistivity of the ultra-high power graphite electrode nipple is not more than 5.5μΩ·m.

(2) Allowable current density and current load during electrode use. For graphite electrodes with a diameter of 300~500mm, the allowable current load of ordinary power graphite electrodes is 10000~20000A, and the allowable current density is 1318A/cm2. The allowable current load of the high-power graphite electrode is 13000~48000A, and the allowable current density is 1524A/cm2. The allowable current load of ultra-high power graphite electrode is 15000~55000A, and the allowable current density is 1830A/cm2.

(3) Flexural strength. The flexural strength of the ordinary power graphite electrode is not less than 6.4MPa, 7.8MPa, and 9.8MPa, and the flexural strength of the ordinary power graphite electrode nipple is not less than 13.0MPa. The flexural strength of the high-power graphite electrode is not less than 9.8MPa and 10.5MPa, and the flexural strength of the high-power graphite electrode nipple is not less than 14.0MPa. The flexural strength of the ultra-high-power graphite electrode is not less than 10.0MPa and 10.5MPa, and the flexural strength of the ultra-high-power graphite electrode nipple is not less than 16.0MPa.

(4) Bulk density. The bulk density of ordinary power graphite electrodes is not less than 1.52g/cm3 and 1.58g/cm3, and the bulk density of ordinary power graphite electrode nipples is not less than 1.68g/cm3. The bulk density of the high-power graphite electrode is not less than 1.60g/cm3, and the bulk density of the high-power graphite electrode nipple is not less than 1.70g/cm3. The bulk density of the ultra-high power graphite electrode is not less than 1.64g/cm3 and 1.65g/cm3, and the bulk density of the ultra-high power graphite electrode nipple is not less than 1.70g/cm3 and 1.72g/cm3.

(5) Linear expansion coefficient. In the temperature range of 100~600℃, the linear expansion coefficient of ordinary power graphite electrode is not more than 2.9×10-6℃-1. The coefficient of linear expansion of common power graphite electrode nipples is not more than 2.7×10-6°C-1 and 2.8×10-6°C-1, which are only used as reference indicators. For high-power and ultra-high-power graphite electrodes, the linear expansion coefficient is the main quality assessment index. The linear expansion coefficient of the high-power graphite electrode is not more than 2.4×10-6°C-1, and the linear expansion coefficient of the high-power graphite electrode nipple is not more than 2.2×10-6°C-1. The linear expansion coefficient of the ultra-high power graphite electrode is not more than 1.5×10-6℃-1, and the linear expansion coefficient of the ultra-high-power graphite electrode nipple is not more than 1.4×10-6℃-1.

(6) Consumption of steelmaking electrodes. The electrode consumption of ordinary power graphite electrodes is 46kg per ton of electric furnace steel. The electrode consumption of high-power graphite electrodes is 2.53.5kg per ton of electric furnace steel. The electrode consumption of ultra-high-power graphite electrodes is 1.12.5kg per ton of electric furnace steel.

The above is the performance index of the graphite electrode body and graphite electrode nipple. If you need to buy graphite electrodes and the matching nipple. Please contact us.

What are the Differences of the Electrodes for Submerged Arc Furnaces?

The role of the electrode is to conduct electricity and convert electrical energy into heat. Electrodes are divided into three types: carbon electrodes, graphite electrodes, and self-baking electrodes according to their use and production process. In submerged arc furnaces, self-baking electrodes are mainly used, but when producing ferroalloy products with lower carbon content, such as industrial silicon, graphite electrodes are required. So what are the differences among the self-baking electrodes, carbon electrodes, and graphite electrodes?

High-Quality Graphite Electrodes for Sale
High-Quality Graphite Electrodes for Sale

First of all, we must clearly distinguish these three electrodes.

  1. The carbon electrode is made of low-ash anthracite, metallurgical coke, pitch coke, and petroleum coke as raw materials, and is composed of a certain proportion and particle size. Add binder asphalt and tar when mixing, stir evenly at the proper temperature, and then press into shape. Finally, it is made by slow roasting in the roasting furnace.
  2. Graphite electrode uses petroleum coke and pitch coke as raw materials to make a carbon electrode. Then put it in a graphitized resistance furnace at a temperature of 2000-2500°C, and make it through graphitization.
  3. The self-baking electrode uses anthracite, coke, pitch, and tar as raw materials. The electrode paste is made at a certain temperature, and then the electrode paste is put into the electrode shell installed on the electric furnace. In the production process of the electric furnace, it relies on the Joule heat generated when the current passes through and the heat transfer in the furnace to self-sinter and coke. This kind of electrode can be used continuously, and sintered to form while connecting the long side, and can be fired into a large diameter.

The self-baking electrode has a simple manufacturing process and low cost and is widely used in ferroalloy production. It is usually used to produce ferrosilicon, silicon-chromium alloy, silicon-manganese alloy, high-carbon ferromanganese, low-carbon ferromanganese, high-carbon ferrochrome, low-carbon ferrochrome, silicon-calcium alloy, Ferro tungsten, etc. Self-baking electrodes are easy to increase the carbon of the alloy, and the iron skin of the electrode shell is also easy to bring the alloy into iron. Therefore, the production of iron alloys and pure metals with very low carbon content, such as micro-carbon ferrochrome, industrial silicon, silicon aluminum alloy, metal manganese, etc., uses carbon electrodes or graphite electrodes.

RS Graphite Electrode Supplier
RS Graphite Electrode Supplier

Graphite Electrodes Applications

Among them, graphite electrodes have excellent properties such as high temperature resistance, oxidation resistance, good electrical conductivity, high mechanical strength, low impurity content, and good thermal vibration resistance. Mainly used as electrode devices in electric arc furnaces and refining furnaces for smelting steel. Submerged electric furnace for producing ferroalloy, industrial silicon, yellow phosphorus, matte, calcium carbide, etc. Graphitization furnace for producing graphite electrodes, furnace for melting glass, electric furnace for producing silicon carbide, etc.

With economic development, the demand for refined steel has increased. Preparation of extruded large-size φ600~φ800mm high-quality GHP graphite electrodes, supporting the application of three-phase 6 and 9 or 12 power supply arrangements in a large ferroalloy submerged arc furnace smelting new technology method. Give full play to the high-quality characteristics of GHP graphite electrodes. Realize high-power, large-capacity, energy-saving and emission reduction, safe and efficient, low-cost smelting production in the ferroalloy submerged arc furnace industry, change the outdated technical level of ferroalloy submerged arc furnace smelting, and provide a new way for technological innovation, upgrading, and transformation of enterprises. Facilitate the virtuous cycle of green economy development.

Technical problems or product problems related to refractories and carbon materials for submerged arc furnaces. Please email us: info@graphelectrode.com.

Large Diameter Graphite Electrodes in DC Arc Furnace

The physical performance requirements of large-scale, UHP graphite electrodes, with the introduction and continuous expansion of DC electric arc furnaces in my country, are of great significance for the best use of electric arc furnaces and reducing electrode consumption. Therefore, in order to promote the development of the electric furnace steelmaking industry, it is also extremely necessary for the development of large-scale, ultra-high power electrodes. Next, we will learn more about the application and cost-saving of graphite electrodes in electric arc furnaces from two aspects: the best use conditions of the electrodes in the DC arc and the physical properties of large-size graphite electrodes for DC electric arc furnaces.

uhp graphite electordes for Arc Furnaces
uhp graphite electordes for Arc Furnaces

The Best Use Conditions of Electrodes in DC Electric Furnace

A certain electrode diameter corresponds to the best current load. Only in this way can the consumption of the electrode be the lowest, the utilization rate is the highest, and the role of the electrode can be fully and effectively played. H. Hagd et al. proposed two calculation criteria for a certain electrode diameter corresponding to the maximum current load. The first criterion is to calculate the current load capacity by considering only the thermal load; the second criterion is to calculate the current load capacity by calculating the mechanical stress through the thermal load.

Figure 5 shows the maximum tangential tensile stress of the φ600mm electrode at different current intensities. The calculation takes into account the conical shape of the electrode tip. The experimental results show that the maximum current load of the φ600mm electrode is about 85kA, and the maximum tangential tensile stress value generated at this time is 22MPa. When the current load is 62kA, the maximum tangential tensile stress on the outer surface of the electrode at the connection is 11.2MPa. This value is the lowest current intensity value at which the connection is broken, the electrode is peeled off, and the crack grows.

Fig. 6 is the upper limit of the current load corresponding to a certain diameter electrode obtained according to the thermal interception load (first criterion). Fig. 7 is the upper limit of the current load corresponding to a certain straight electrode obtained by calculating the mechanical stress (the second criterion) through the thermal load. Comparing the current load limit values obtained by the two criteria, the results are relatively consistent and satisfy the linear relationship. In practical applications, the second criterion is more important when the results obtained are applied to electric furnace electrodes. Because the second criterion is the result derived from thermal stress, and thermal stress is often one of the important reasons for electrode failure and connection damage.

The performance of graphite electrodes and nipples produced in my country is definitely different from that of H.Hagel calculation electrodes. Therefore, our application of this criterion can only use its linear relationship, and the general trend should be consistent.

Physical Properties of Large-Size Graphite Electrodes for DC Electric Solitary Furnace

With the increasing number of high-power and large-capacity DC electric furnaces, the electrode diameter is getting larger and larger, up to φ800mm, and the current interception is getting higher and higher, reaching 150kA. It is very important to choose a suitable electrode quality standard to meet the needs of high-power and large-capacity electric furnaces. All practical and theoretical studies have obtained the same results, and the performance of large-scale graphite electrodes needs to be improved even more. This requires attention to the selection of raw materials and the establishment of advanced production processes.

Higher requirements are put forward on the physical properties of large-size electrodes used in DC electric arc furnaces.

(1) The resistivity is further reduced. In this way, the power loss (I2R) is small, and a reasonable temperature gradient can also be obtained. This requires a higher graphitization temperature to ensure a decrease in resistivity.

(2) The coefficient of thermal expansion should be low. Since the graphite electrode and the graphite electrode nipple at the connection site have different thermal expansion properties in the axial and radial directions, the temperature at the nipple is higher and the thermal stress is greater. Under the premise of low thermal expansion coefficient, the axial and radial thermal expansion coefficient of the electrode should be slightly greater than or equal to the nipple and should satisfy αpTp-αNTN ≥ 0. Among them, αp is the thermal expansion coefficient of the electrode; Tp is the temperature of the electrode; αN is the thermal expansion coefficient of the nipple; TN is the temperature of the nipple. In this way, the thermal stress value is reduced. To achieve this, there must be advanced technology, raw materials, and formula to ensure.

(3) The thermal conductivity should be high. The high thermal conductivity allows the electrode to dissipate heat quickly, and the radial temperature gradient is small, which is also beneficial to improve the thermal stress. The thermal conductivity should be above 200W/m·K.

(4) It must have a certain strength. The electrode must have a certain strength, and the strength of the nipple is higher than that of the electrode. Large-size electrodes have a large weight. In order to ensure a reasonable current flow, there should be a higher pressure on the connection end surface. If the strength is insufficient, the connection thread will be damaged, local cracks will occur prematurely, and the failure rate will be accelerated. At the same time, we also hope that the modulus of elasticity should be low, so that the thermal stress σ = EaT is also reduced. Therefore, both strength and elastic modulus should be considered. The strength can be improved through process control, selection of reasonable formulas and raw materials, and multiple dipping processes.

(5) The porosity should be low. For electrodes, excessive surface porosity will increase oxidation and increase electrode consumption. Porosity can be improved by the surface treatment process.

Configuration of Graphite Electrodes for Steelmaking Electric Arc Furnaces

In the configuration of Graphite Electrodes for Steelmaking Electric Arc Furnaces, it is necessary to follow the basic principle of “normal power electric furnaces with ordinary power graphite electrodes, high-power electric furnaces with high-power graphite electrodes, and ultra-high-power electric furnaces with ultra-high-power graphite electrodes“.

Graphite Electrodes for Steelmaking Electric Arc Furnaces
Graphite Electrodes for Steelmaking Electric Arc Furnaces

Configuration Scheme of the Graphite Electrode for AC Steelmaking Electric Arc Furnace

For AC steelmaking electric arc furnace,

  • The 10~30t electric furnace is equipped with graphite electrodes with a diameter of 300~400mm.
  • The 30-50t electric furnace is equipped with graphite electrodes with a diameter of 450mm.
  • The 60~80t electric furnace is equipped with graphite electrodes with a diameter of 500mm.
  • The 100~170t electric furnace is equipped with graphite electrodes with a diameter of 550~600mm.
  • The 200t electric furnace is equipped with graphite electrodes with a diameter of 600~700mm.
  • The 250~300t electric furnace is equipped with a 700mm diameter graphite electrode.
RS High Quality Graphite Electrode
RS High-Quality Graphite Electrode

Configuration Scheme of the Graphite Electrodes for DC Steelmaking Electric Arc Furnace

For DC steelmaking electric arc furnace,

  • The 30t electric furnace is equipped with graphite electrodes with a diameter of 450mm.
  • The 60t electric furnace is equipped with graphite electrodes with a diameter of 500mm.
  • 70~80t electric furnace is equipped with graphite electrodes with a diameter of 600mm.
  • The 100~130t electric furnace is equipped with a 700mm diameter graphite electrode.
  • The 150t electric furnace is equipped with graphite electrodes with a diameter of 750mm.
uhp graphite electrode
UHP graphite electrode

Rongsheng Group, one of the graphite electrodes suppliers, provides you with Graphite Electrodes for Steelmaking Electric Arc Furnaces.

FAQ1   How to choose the electrode correctly in the electric arc furnace steelmaking?

According to the design characteristics of the electric arc furnace, reasonably select the electrode that meets the production of the electric arc furnace, and select the product with the best cost performance. It is very necessary to carefully select the electrode suitable for each furnace. The special performance of the steelmaking furnace, the feeding method, the maximum current intensity, the length of the electrode column under the holder, the distance between the sidewall of the furnace and the electrode circumference, etc., are all factors that must be considered when choosing the electrode for the electric arc furnace.

FAQ2   Why is the electrode required to be parallel and centered with the top hole of the furnace cover when steelmaking in an electric arc furnace?

The electrode column and the top hole of the furnace cover should be centered. The electrode column should avoid friction with the furnace cover, otherwise, friction with the furnace cover during lifting and lowering will cause the furnace cover to break the electrode. For AC furnaces, the three-phase electrode columns should be kept as parallel as possible.

FAQ3   What effect does the resistivity performance have on the use of electrodes in steelmaking?

The resistivity of the graphite electrode is a physical index that reflects the conductivity of the electrode and is related to the manufacturing process of the electrode. The country has qualitatively specified values for the resistivity of graphite electrodes of different specifications. Generally speaking, when steel mills choose electrodes of certain specifications, they must choose the resistivity range specified by the national metallurgical standards. Too high resistivity will cause the electrode to become red and hot when it is energized, and increase electrode oxidation consumption.

Prerequisite for the Production of UHP Graphite Electrodes

I wrote about Graphite Electrodes Raw Materials Select in my previous article. Today we will talk about choosing high-quality raw materials is a prerequisite for the production of UHP graphite electrodes.

Rongsheng High-Quality UHP Graphite Electrode
Rongsheng High-Quality UHP Graphite Electrode

Main Raw Material – Needle Coke

Needle coke must be used as the main raw material to produce ultra-high power graphite electrodes. There are two major types of needle coke, coal-based needle coke, and petroleum-based needle coke, which have a variety of quality specifications. The selection of needle focus depends on the electrode diameter. The larger the electrode diameter, the stricter the quality of needle focus. To study the quality of needle coke, first of all, we must understand the thermal expansion coefficient of the graphitized sample made from this needle coke. The second is the sulfur content and nitrogen content of the needle coke, as well as the actual particle size of the needle coke (the percentage of large particles), whether it can meet the needs of ingredients.

Although the price of coal-based needle coke is lower than that of petroleum-based needle coke, the graphitization performance of coal-based needle coke is also very good. However, the thermal expansion coefficient of coal-based needle coke is generally greater than that of petroleum-based needle coke, so coal-based needle coke is rarely used in large-diameter UHP graphite electrodes. As the carbon product industry in various countries in the world does not have a unified thermal expansion coefficient test method, Japan, Germany, and the United States each have their own test methods. Therefore, it is impossible to make a judgment by just looking at the sample or the data provided by the needle coke factory. It is necessary to collect needle coke samples from various companies and compare the results of the same method in the same laboratory.

Binder – Asphalt

Binder pitch mainly depends on three items: softening point, coking value, and bonding performance (β resin content). The softening point of the binder pitch used by the American Carbon Factory is about 110°C, and the test method is the air cube method. The softening point of the binder asphalt produced by Nippon Steel is 90±3°C and 96±3°C. The test method is the ring and ball method. The softening point of the binder asphalt produced by VFT AG in Germany is 109°C. The coking value of foreign binder asphalt is more than 55%, the beta resin content of Japanese asphalt is about 20%, and the American asphalt is slightly lower. Using this kind of pitch and controlling the proportion of pitch added during the batching, the HP graphite electrode body can reach the volume density requirement without dipping, and the UHP graphite electrode body only needs to be dipped once. Therefore, using high-quality asphalt with a slightly higher softening point and higher coking value as a binder for the production of HP and UHP graphite electrodes is a necessary means to achieve short-process production, that is, one less impregnation and one less roasting.

Impregnant – Pitch

As impregnant pitch, petroleum pitch is mostly used in the United States, and coal pitch is used in Japan and Germany. The common requirement is that the content of quinoline insolubles should be low, the lower the better. The general index is set below 0.5%, because quinoline insoluble matter affects the penetration of pitch into the micropores in the calcined electrode.

Additive

In the production of UHP graphite electrodes, it is also necessary to use appropriate additives to improve the performance of graphite electrodes.

(1) Iron oxide powder. The purpose is to increase the degree of graphitization and alleviate the “crystal swelling” during the graphitization process, which is more effective when using needle coke with higher sulfur content. When using internal tandem graphitization technology for large-diameter electrodes, the heating speed is extremely fast, and adding a small amount of iron oxide powder is beneficial to reduce the cracking waste during the graphitization process.

(2) Stearic acid. The purpose of adding is to reduce the softening point and viscosity of asphalt. This is useful when using asphalt with a higher softening point binder.

(3) Some foreign carbon factories add a small amount of mineral oil that acts as a plasticizer during the kneading process. The purpose of adding is to improve the plasticity of the electrode paste, reduce the friction force when the paste is extruded, and at the same time reduce the extrusion pressure, which is also conducive to improving the internal structure of the green electrode.

As explained in detail above, the selection of high-quality raw materials is a prerequisite for the production of UHP graphite electrodes. Therefore, it is also very important to choose a graphite electrode supplier with a reliable guarantee. Rongsheng Group provides customers with high-quality graphite electrodes. Get detailed information.

Rongsheng RP Graphite Electrodes for Sale in South Africa

Graphite electrode is a conductor that releases electrical energy in the form of an electric arc to heat and melt the charge. The main raw material for graphite electrode production is petroleum coke. Ordinary power graphite electrodes can be added with a small amount of pitch coke. The sulfur content of petroleum coke and pitch coke cannot exceed 0.5%. Rongsheng graphite electrode manufacturer provides RP graphite electrodes for sale in South Africa. For more detailed information about graphite electrodes, please continue reading.

RS High Quality RP Graphite Electrode
RS High-Quality RP Graphite Electrode

RP Graphite Electrodes for Sale

First of all, the raw materials selected for the production of graphite electrodes.

The production of RP graphite electrodes for sale can be used as raw materials for petroleum coke. Produce HP graphite electrodes, using high-quality petroleum coke and needle coke. To produce UHP graphite electrodes, it must use high-quality needle coke as raw materials. To produce high-purity graphite electrodes, a very low ash content petroleum coke is required. In order to improve the lubricity and plasticity of the paste, and to improve the electrical conductivity of the product, a part of graphite chips is also added to the production of graphite electrodes.

Choose a batch of raw materials required for the production of graphite electrodes, and then go through a series of production processes, which may take more than 90 days, and finally complete the production of a batch of graphite electrodes. If you want the finished RP graphite electrode for sale to reach the customer’s hands smoothly, you also need to understand the precautions for transporting the graphite electrode.

Graphite Electrode Delivery
Graphite Electrode Delivery

Secondly, the matters needing attention when transporting graphite electrodes.

From the Rongsheng graphite electrode manufacturer, Long-distance vehicles transporting graphite electrodes for sale should be covered with a rain-proof tarp to prevent the electrodes from getting wet. When lifting or transporting the graphite electrode, care should be taken to prevent the graphite electrode from being damaged by tilting or slipping. In order to protect the ends and threads of the graphite electrode, the electrode cannot be directly hung with an iron hook. Finally, when loading and unloading the joint box, handle it gently. Prevent the joints from bumping, causing thread damage, and reducing the service life of the graphite electrode.

Rongsheng RP graphite electrode for sale is transported to the customer’s production site or warehouse, and then it can wait to enter the customer’s actual production.

Graphite Electrodes Application
Graphite Electrodes Application

Application of RP Graphite Electrode for Sale

(1) Used in an electric arc steelmaking furnace. Graphite electrode used in steelmaking as an electrode material accounts for about 70-80% of the total consumption of graphite electrodes in China. Electric furnace steelmaking uses research graphite electrodes to introduce working current into the furnace. The powerful current at the lower end of the electrode can generate arc discharge through these gas environments, and use the heat generated by the arc to smelt.

(2) Used in a submerged electric furnace. The submerged electric furnace is mainly used to produce ferroalloys, pure silicon, yellow phosphorus, calcium carbide, and matte. Its production feature is that the lower part of the conductive electrode is buried in the charge. Therefore, in addition to the heat generated by the arc between the electric plate and the charge, heat is also generated by the resistance of the charge when the current passes through the charge.

(3) For resistance furnace. In the production process, the graphitization furnace for graphite material products, the melting furnace for melting glass, and the electric furnace for producing silicon carbide are all resistance furnaces. The material in the resistance furnace is both a heating resistor and an object to be heated.

In the actual graphite electrodes uses, there are some details that need attention.

Detailed Requirements for the Use of Graphite Electrodes

The graphite electrode should be kept dry before use. Check whether the internal thread of the electrode hole is complete. If there is dust falling, you need to use a compressed air gun to clean the surface of the graphite electrode and the internal thread of the hole. There must be no oil or water on the surface of the graphite electrode. Avoid cleaning the graphite electrode with steel wire or metal brush cloth.

In the use of graphite electrodes, it is important to carefully screw the graphite electrode connector into the electrode hole of the graphite electrode. When lifting the electrode, the buffer pad is placed on the bottom of one end of the electrode connector to prevent ground damage. It is also necessary to prevent collisions during fixation.

When installing graphite electrodes on the top of the electric furnace, the spare graphite electrode needs to be hoisted above the electrode to be connected, aligned with the electrode hole, and then slowly dropped. Rotate the spare electrode to make the spiral hook rotate and drop together with the electrode. When the electrode is completely put down at the end, the force of the rotating electrode should not be too strong. Otherwise, it is easy to cause a violent collision of the electrode hole and damage the joint thread.

The consumption of graphite electrodes during use is also inevitable. How to reduce unnecessary consumption is a key factor in saving production costs.

RS Graphite Electrodes Factory
RS Graphite Electrodes Factory

Rongsheng Graphite Electrode Manufacturer

Rongsheng graphite electrode manufacturer provides customers with high-quality graphite electrode products. Including normal high power graphite electrodes, high power graphite electrodes, ordinary power graphite electrodes, graphite electrode nipples, etc. Our graphite electrode products have participated in many exhibitions in Russia and received good comments from customers. In South Africa, there are also our graphite electrode customers. And for more information, please contact us. To get the price of graphite electrodes, please leave your specific needs on the message board on the page. Our service will always satisfy you.

Effect of Baking Process on the Quality of Graphite Electrodes

Baking is an important process for producing uhp graphite electrodes with excellent performance. Factors such as heating rate, binder pitch, and temperature field have an impact on the quality of graphite electrodes during the baking process. It can provide a reference for the production of high-quality graphite electrodes.

Ultra-high Power Graphite Electrode

The ultra-high power graphite electrode has the advantages of low resistivity, good oxidation resistance, and a small thermal expansion coefficient. It is widely used in electric arc steelmaking furnaces with high current density and harsh working conditions. And its bulk density and flexural strength also need to reach a higher level. At the same time, its elastic modulus should be appropriate. It needs to match the performance of the matching electrode joints to show good thermal shock resistance during the electric furnace steelmaking process, and it is not easy to break. Therefore, it is necessary to strictly control the process parameters of each process of ultra-high power graphite electrode production to ensure that the product quality of each process is qualified and the internal structure of the product is uniform and stable. Therefore, continuously optimizing each link of process control is an effective means to obtain better quality products.

UHP Graphite Electrode
UHP Graphite Electrode

Mechanism Analysis of the Whole Process of Baking and Heating

Regarding the primary baking, no matter what baking furnace is selected, the heat generated after the fuel is burned is transferred to the refractory brick or the steel drum of the container baking. Then, the refractory bricks or steel drums are passed to the filler. Finally, the filler transfers heat to the raw product. Quality of Graphite Electrodes, When the temperature felt by the raw product itself exceeds the softening point of the binder pitch, the green body will first soften from the glass state and then become the molten state. Just under the squeeze of the surrounding filler, it keeps its original geometric shape.

On the one hand, with the gradual increase in temperature, the binder asphalt first undergoes physical lateral infiltration and longitudinal gravity migration. If the selected binder is medium temperature asphalt, its physical migration will be greater than that of the modified asphalt binder with a high softening point. Therefore, choosing high-temperature modified asphalt instead of medium-temperature asphalt as a binder is an effective measure to improve product quality. As the temperature continues to rise, the binder asphalt begins to decompose and polymerize. The discharge of light volatiles gradually increased. Heavy residues are also continuously polymerizing. The total volume of the raw product expands in the radial and longitudinal directions, while also shrinking. The practice has proved that the longitudinal expansion of the raw product is slightly greater than the radial expansion, so the mechanical strength of the upper end of the baked product is lower than that of the lower end. This is directly related to the migration of asphalt, and the choice of high-temperature modified asphalt binder can improve this situation.

On the other hand, the elasticity, air permeability, and adsorption of the filler also play a very important role in the firing process. Appropriately reducing the adsorption and air permeability of the filler, or adding refractory bricks on top of the insulating material will help increase the coking value of the asphalt binder. If the type of filler is determined, it depends on the particle size composition of the filler. If the filler is too fine, the discharge of volatiles from large-scale raw products will be too hindered, which will cause cracks in the product. Therefore, the adsorption and air permeability of the filler should be controlled within an appropriate range. When the radial expansion force of the product and the mechanical strength of the surface of the raw product reach a dynamic balance, the coking value can be maximized. Of course, this dynamic balance is closely related to the heating rate. In order to effectively improve the mechanical strength and density of the calcined product, it is necessary to ensure that the particle size composition of the filler matches the product specifications and heating rate reasonably.

The selection and control of the baking process are very important because it directly determines the structure, performance and production cycle of the final product. In the baking process, along with the transfer of chemical reaction and mass, heat and momentum, the three-phase system undergoes a series of continuous unequal temperature phase transitions, which makes the research of the system very complicated. In order to further clarify the baking mechanism, it is necessary to analyze the baking stages. Because there are obviously different phenomena in each stage of baking.

Advantages of Oxidation-Resistant Coated Graphite Electrodes

What are oxidation-resistant coated graphite electrodes, graphite electrodes for smelting, and ultra-high power graphite electrodes? I believe many people do not understand the advantages of graphite electrodes, especially graphite electrodes with anti-oxidation coating. Now, let us first understand the graphite electrode, and then have an in-depth understanding of the advantages of oxidation-resistant coated graphite electrode in steelmaking production.

RS-Graphite-Electrodes
RS Graphite Electrodes

Rongsheng Graphite Electrodes

Rongsheng graphite electrode mainly uses petroleum coke and needle coke as raw materials. The coal pitch is used as a binder. It is made by calcination, batching, kneading, pressing, roasting, graphitization and machining. It is a conductor that releases electrical energy in the form of an arc to heat and melt the charge in the arc furnace. According to the quality index and the size of the power allowed to pass, it can be divided into ordinary power, high power, and ultra-high power.

The General Classification of Graphite Electrodes

    • (1) Ultra-high Power Graphite Electrode
    • The UHP graphite electrodes with a current density greater than 25A/cm2 are allowed. Mainly used in ultra-high power steel-making electric arc furnace.
    • (2) High Power Graphite Electrode
    • It is allowed to use a graphite electrode with a current density of 18～25A/cm2. High-power electric arc furnace mainly used for steel making.
    • (3) Ordinary Power Graphite Electrode
    • RP graphite electrode is allowed to use the graphite electrode with a current density lower than 17A/m2. It is mainly used for ordinary power electric furnaces for steel making, silicon making, and yellow phosphorus making.
    • (4) Oxidation-Resistant Coated Graphite Electrodes
    • In order to prevent the oxidation loss of the graphite electrode, the graphite electrode is usually coated with an anti-oxidation protective layer. Therefore, a graphite electrode with an anti-oxidation coating is derived.
HP graphite electrode Manufacturer
HP graphite electrode Manufacturer

Advantages of Oxidation-Resistant Coated Graphite Electrodes

A layer of the anti-oxidation protective layer is coated on the surface of the graphite electrode, which is generally a graphite electrode antioxidant. Such a graphite electrode is called an anti-oxidation graphite electrode. The formation of anti-oxidation coating makes the original graphite electrode both conductive and resistant to high-temperature oxidation. Therefore, the advantages of oxidation-resistant coated graphite electrodes are highlighted during the steelmaking process.

    • Reduce electrode consumption during steelmaking (19%~50%),
    • Extend the service life of the electrode (22%~60%),
    • Reduce the power consumption of the electrode.

Similarly, the use of antioxidant graphite electrodes can bring considerable economic and social benefits.

    1. The unit consumption of the graphite electrode is less, and the production cost is reduced to a certain extent. For example, a steel plant is calculated based on the consumption of 165 refining furnaces for the first-class LF refining furnace, which has no shutdown in the whole year, about 35 graphite electrodes per week. After adopting graphite electrode anti-oxidation technology, 373 (153 tons) electrodes can be saved every year. Based on the calculation of 16,900 yuan per ton of ultra-high-power electrodes per year, it can save 2.5857 million yuan.
    2. The graphite electrode consumes less power. The saved unit steel-making electricity consumption saves the production cost and saves energy!
    3. Because of less replacement of the graphite electrode, it reduces the labor and risk factor of the operator and improves production efficiency.
    4. Graphite electrode is a product with low consumption and low pollution. Today, energy conservation, emission reduction, and environmental protection are of great social significance.
RS Graphite Electrodes Factory
RS Graphite Electrodes for Sale

Rongsheng graphite electrode sales, including RP, HP, UHP graphite electrodes, and graphite products. Has been sold to Russia, Ukraine, Belarus, Chile, South Africa, and other countries and regions. Product quality is recognized by customers. For more services about graphite electrodes, please fill out the message form on our page and let us know your specific needs. We will reply to you as soon as possible.

High Temperature Oxidation Resistance for Graphite Electrode

The graphite electrodes used in metallurgical enterprises are mainly made of petroleum coke and coal tar pitch. It has good high-temperature performance, low thermal expansion coefficient, lightweight, strong corrosion-resistance, easy processing, and excellent thermal shock resistance. But its most obvious defect at high temperature is that it is easily oxidized. The side oxidation of the UHP electrode is due to the oxygen and graphite in the furnace gas generating CO and CO2, accounting for 50% to 70% of the total consumption. Therefore, research on the High-Temperature Oxidation Resistance for Graphite Electrode is particularly important. In order to reduce the consumption of graphite electrodes, many scientific workers in the world have carried out research work on anti-oxidation, adding coatings, and changing the ratio of raw materials, and have achieved many research results.

graphite electrode uses
graphite electrode uses

Anti-Oxidation Method of Graphite Electrode

The oxidation protection of graphite electrodes is mainly through the following two ways. That is, at lower temperatures, matrix modification, and surface-active point passivation can be adopted to protect graphite materials. As the temperature rises, the coating method must be used to isolate the substrate from contact with oxygen to achieve the purpose of oxidation protection.

Impregnated Electrode

Graphite electrodes are limited by production conditions during the manufacturing process, and inevitably leave micropores inside the electrodes. Compared with other ordered carbon atoms, the electrode surface and pores have higher activity and are the active sites of oxidation of graphite electrodes. In the high-temperature state, it gradually expands to the inside, forming the oxidation consumption of the entire graphite electrode.

RS Graphite Electrode Manufacturer
RS Graphite Electrode Manufacturer

Impregnated electrode technology has the characteristics of low investment, low cost, simple process, and strong adaptability. It is an effective way to reduce graphite electrode consumption and has obvious economic benefits.

Coated Electrode

Coating system requirements. Anti-oxidation coating is the most effective and main means of anti-oxidation of the graphite electrode. It can greatly increase the use temperature of the graphite electrode in an oxidizing environment. Its basic function is to isolate the matrix material from the oxidizing environment.

The comprehensive performance of the graphite electrode coating cannot be achieved by a single material, and a multi-functional gradient coating must be selected. Each of these layers has its own unique functions and uses, and the composite coating as a whole realizes anti-oxidation. Generally speaking, a complete coating system should contain at least three layers of the oxygen barrier layer, functional active layer or self-healing layer, adhesive layer. When designing, they must comprehensively consider the matching of the thermal expansion coefficients, chemical compatibility, and overall coordination between the layers.

RS Graphite Electrodes Factory
RS Graphite Electrodes Factory

The high-temperature anti-oxidation coating of graphite electrodes is not enough for a substance, and a single-layer coating cannot play an effective anti-oxidation role. From the RS graphite electrode manufacturer, The development direction of the coating system is multifunctional gradient composite coating. In the manufacturing method of coating, in addition to the traditional CVD method and solid infiltration method. Plasma spraying technology has been introduced at home and abroad and has received good results.

350-500mm Quasi-Ultra High Power Graphite Electrodes

In 2002, some customers have asked whether a new variety of graphite electrodes with properties between UHP graphite electrodes and HP graphite electrodes could be manufactured? In this way, it can not only meet the production needs of ultra-high power refining furnaces but also have a relatively large price drop compared to the UHP electrode. However, there is a carbon company that fulfills these customers’ demands. They have developed a new variety of graphite electrodes between ultra-high power graphite electrodes and high-power graphite electrodes, quasi-ultra high power graphite electrodes. This graphite electrode product requires various physical and chemical performance indexes to reach or be close to the UHP graphite electrode, but the production cost is greatly reduced so that the sales price also drops significantly.

RS High Quality Graphite Electrode
RS High-Quality Graphite Electrode

Brief Introduction of Quasi-Ultra High Power Graphite Electrode

The properties of quasi-ultra high power graphite electrodes are between the high power graphite electrodes and ultra-high power graphite electrodes, close to those of UHP graphite electrodes, which can meet the demand of UHP graphite electrodes for LF and high power graphite electrodes for electric are furnace, and reduce the cost of the production of HP graphite electrodes and ultra-high power graphite. The technologic processes for φ350 ~ φ500mm quasi-ultra high power graphite electrodes were introduced, which were made from imported high-ranking/ordinary needle cokes to a scale in some carbon manufacturer. The results show that the properties of products obtained are close to those of ultra-high power graphite electrodes, and can meet the demand of ultra-high power graphite electrodes for LF.

Characteristics of Quasi-Ultra High Power Graphite Electrode

(1) The calcined coke produced by China’s domestic petroleum coke and the imported ordinary-grade needle coke is mixed in a certain proportion. The physical and chemical indexes of the produced quasi-ultra-high-power graphite electrodes have all met the requirements of the enterprise standard Q/140200DNT001-2007 “Quasi-ultra-high-power graphite electrodes“, and the trial production effect has reached the expected target.

(2) The sample analysis report proves that the performance index of the quasi-ultra-high-power graphite electrode is close to that of ultra-high-power graphite electrode, which can meet the production needs of ultra-high-power refining furnace.

(3) Finally, because part of the raw materials used by China-made petroleum coke, the production cost of quasi-ultra-high-power graphite electrodes is significantly lower than that of ultra-high-power graphite electrodes. Therefore, the selling price of quasi-ultra high-power graphite electrodes has also been reduced. From the customer’s perspective, it can effectively reduce the production cost of ultra-high power refining furnaces.

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