graphelectrode.com, Author at Graphite Electrode Manufacturer

Influence of Splattering of Lengthwise Graphitization on UHP Graphite Electrodes

Inner string graphitization is a process in which the current directly passes through the furnace core composed of roasted products in series, and the roasted products are graphitized through the thermal effect of the current. In the process of graphitization and power transmission, the baked product is treated at a high temperature above 2400°C and finally transformed into a graphite product with better conductivity and oxidation resistance. Graphitization is an important production link in the production of ultra-high power graphite electrodes, and graphite electrode products are accompanied by a series of complex physical and chemical changes in the process. By analyzing the actual changes in products and the causes of abnormal conditions during graphitization and power transmission, it is helpful to better formulate and improve process parameters and improve the product quality of graphite electrodes.

The graphitization process of a graphite electrode manufacturer uses a U-shaped inner series graphitization furnace. The products are loaded on the east and west sides of the furnace, and metallurgical coke is used as the furnace bottom material and insulation material. The joints for ultra-high power graphite electrodes are loaded into the graphitization furnace in a multi-column bundling manner. During the power transmission process, the displacement data of the product is determined by the expansion and contraction of the furnace tail-pushing equipment and is recorded and monitored by the computer. Through the summary analysis of various parameters before and after spraying the furnace in the inner string graphitization process of the joints for ultra-high power graphite electrodes. The physical and chemical changes in the graphitization process, the reasons for spraying furnaces, and the impact on product quality are explained, and corresponding solutions are proposed. It is hoped that it can promote the production of domestic large-scale ultra-high-power graphite electrode nipples.

Reason Analysis of Splattering of Lengthwise Graphitization

According to the production records, the graphite electrode nipple product was sprayed at time t6. The location of spraying furnace is located at the furnace head on the east side of the U-shaped graphitization furnace, and the maximum power transmission power has been reached when the furnace is sprayed. Before spraying the furnace, the furnace resistance increased abnormally. After spraying the furnace, re-energize and the furnace resistance returns to normal.

In addition to the length of raw materials and roasted products, the pusher device at the end of the furnace is also a factor affecting the displacement of the east and west sides. The pusher at the end of the furnace usually applies pressure to make the electrode series connection closely, so as to reduce the contact resistance between the electrode end faces. According to the research of the experimenters, the pressure should be adjusted in time during the graphitization and power transmission process to maintain a stable contact resistance. In addition, during the electrode inflation stage, the change of the pushing pressure on both sides of the furnace tail will also affect the displacement of the east and west sides to a certain extent.

In the actual power transmission process, the hydraulic pressure at the end of the furnace is controlled by the same hydraulic station. However, when there is partial blockage, oil leakage, or other problems in the hydraulic pipeline on one side, the actual acting pressure on the east and west sides may be different. This may be the reason for the difference in expansion between the east and west sides of ultra-high power graphite electrode products within a certain time interval.

As the temperature continues to rise, the graphite electrode product begins to shrink in the temperature range in the next period of time, and the amount of shrinkage gradually increases. At this time, according to the process requirements, the automatic hydraulic system at the end of the furnace needs to adjust the pressure in time to adapt to the shrinkage of the electrode string. However, when the hydraulic system at the end of the furnace fails to adjust the pressure quickly due to some reasons, and because the hydraulic device is located at the end of the furnace, it is far away from the furnace head. Affected by the frictional resistance of metallurgical coke, the pressure at the furnace head is lagging or insufficient, which is particularly likely to cause an increase in the contact resistance of the electrode end surface at the furnace head. Even in severe cases, the metallurgical coke insulation material enters the gap of the electrode end face. This leads to an abnormal increase in local contact resistance, resulting in burnout. This is also the reason why the graphitization spray furnace usually occurs at the furnace head.

Influence of Splattering of Lengthwise Graphitization on UHP Graphite Electrodes

After the graphite electrode nipple products are released from the furnace, through the analysis of the processing results, the qualification rate of the graphite electrode products on the east side of the graphitization furnace is slightly lower than that on the west side. This may be related to the larger displacement on the east side during graphitization and power transmission. In this temperature range, the chemical reaction is intensified, the stress is concentrated, and the excessive displacement will easily cause cracks in the product, resulting in unqualified products.

According to the normal distribution of bulk density and resistivity of processed graphite electrode nipples, the bulk density and resistivity of the east side are slightly lower than those of the west side. This may be related to insufficient push pressure on the middle east side during graphitization and power transmission and metallurgical coke entering the gap of the electrode end face. During the power transmission process, the contact resistance between the end faces of the electrode string on the east side is relatively high. According to Joule’s law, the east side generates more heat and has a higher degree of graphitization, so the resistivity and bulk density of the product decrease.

Solutions to Splattering of Lengthwise Graphitization

1) When graphitizing power transmission, the pushing pressure of the furnace tail should be adjusted appropriately according to the product diameter and furnace loading form. In order to avoid the situation that the furnace tail pressure cannot meet the production needs due to specification changes.

2) When graphitizing the furnace, small graphite blocks can be laid under the electrode trunk to reduce the influence of metallurgical coke friction resistance on the pushing pressure. There is hysteresis or insufficient pressure to improve the position of the furnace head.

3) The furnace tail pusher is one of the key pieces of equipment to ensure the normal power transmission of the inner string graphitization furnace. The change in its pressure is closely related to product quality, and it should be maintained and corrected regularly.

4) Graphitization During the power transmission process, the change of furnace resistance can timely and effectively reflect the real-time situation of the products in the furnace. It should be paid attention to during the power transmission process. When the furnace resistance is abnormal, the process can be adjusted in time to ensure product quality;

5) The graphitization power transmission is controlled by a computer program, and the pushing pressure can be considered to be added to the program. In order to realize real-time monitoring, and set relevant thresholds or alarm conditions for changes in furnace resistance.

Rongsheng Graphite Electrodes Manufacturer

Rongsheng graphite electrode manufacturer is an experienced manufacturer of graphite electrodes. Our graphite electrode customers continue to return orders from our manufacturers. Moreover, we support the customization of graphite electrode products and can provide you with customized graphite electrode products according to your specific usage requirements. Contact us to buy high-quality ultra-high power graphite electrode products.

The Top Uses of Graphite Electrode Nipples in Industrial Applications

Graphite electrode nipples are an essential component in various industrial applications. These small, cylindrical pieces of graphite play a significant role in the production of steel, aluminum, and other metals. Graphite electrode nipples are widely used because of their exceptional thermal and electrical conductivity, high mechanical strength, and resistance to thermal shock. This essay discusses the top uses of graphite electrode nipples in industrial applications.

One of the primary uses of graphite electrode nipples is in electric arc furnaces (EAFs). EAFs are used for melting and refining steel scrap into new steel. Graphite electrode nipples are used to conduct electricity from the power source to the charge inside the furnace. As the electric current passes through the graphite electrode nipple, it heats up and melts the scrap metal. Graphite electrode nipples are also used to inject gases into the furnace to improve the quality of the steel being produced.

Graphite electrode nipples are also used in the production of aluminum. Aluminum is produced through the process of electrolysis, which involves the use of an electric current to separate aluminum from its ore. Graphite electrodes are used as anodes in the electrolytic cell. As the electric current passes through the anode, it dissolves the aluminum oxide, releasing aluminum ions that are deposited on the cathode. Graphite electrode nipples used in aluminum production are designed to withstand the harsh chemical environment inside the electrolytic cell.

Another important use of graphite electrode nipples is in the production of silicon metal. Silicon is produced through a process called carbothermic reduction, which involves the reduction of silica with carbon in an electric furnace. Graphite electrode nipples are used to supply the electric current to the furnace and to melt the charge inside. Graphite electrode nipples used in silicon production are designed to withstand high temperatures and to resist chemical attack by the molten charge.

Graphite electrode nipples are also used in the glass industry. Glass is produced by melting raw materials such as sand, soda ash, and limestone in a furnace. Graphite electrode nipples are used to supply the electric current to the furnace and to melt the charge inside. Graphite electrodes used in glass production are designed to withstand high temperatures and to resist chemical attack by the molten charge.

In conclusion, graphite electrode nipples are essential components in various industrial applications. They are widely used in electric arc furnaces for the production of steel, in aluminum production, silicon production, and the glass industry. Graphite electrode nipples are preferred because of their excellent thermal and electrical conductivity, high mechanical strength, and resistance to thermal shock. The use of graphite electrode nipples has greatly improved the efficiency and quality of industrial processes, leading to significant cost savings and increased productivity.

Also, electrode nipples are small but critical components in many industrial applications that involve the transfer of electrical energy. These devices are typically made of conductive materials such as copper, brass, or stainless steel and are used to connect electrical circuits, facilitate the flow of electrical current, and dissipate heat.

One of the most common uses of electrode nipples is in the welding industry. Welding involves fusing two or more pieces of metal together by heating them to their melting point and then joining them with a molten metal. Electrode nipples are used in welding machines to transfer electrical current to the welding electrode, which then creates the arc that melts the metal. The electrode nipple is also responsible for holding the electrode in place and allowing for the controlled movement of the electrode during the welding process.

Another application of electrode nipples is in electroplating, a process that involves coating a metal object with a thin layer of another metal to improve its surface properties. Electrode nipples are used in electroplating to connect the electrical circuit and facilitate the transfer of ions between the anode and cathode. They also help to dissipate heat, which can build up during the electroplating process and cause damage to the equipment.

Electrode nipples are also used in the production of printed circuit boards (PCBs), which are used in a wide range of electronic devices. PCBs are made up of multiple layers of conductive material, and electrode nipples are used to connect these layers and create the electrical circuit. They are also used to connect the PCB to other electronic components, such as capacitors and resistors.

Finally, electrode nipples are commonly used in the automotive industry. They are used in spark plugs, which are essential components in the combustion engine. The electrode nipple serves as the conductor that delivers the electrical spark to ignite the fuel-air mixture in the engine.

In conclusion, electrode nipples are small but critical components that play a crucial role in a wide range of industrial applications. They are used in welding, electroplating, PCB production, metallurgy, and automotive manufacturing, among other industries. Without these devices, many of the products we use every day would not exist, and the processes that produce them would be significantly less efficient. As such, electrode nipples are an essential component of modern industrial processes, and their importance cannot be overstated.

Improving Steelmaking Processes with Advanced Electric Arc Furnace Electrodes

Steel is a vital component in many industries, from construction to manufacturing. The demand for steel continues to increase as the world population grows, and industrialization expands. The steelmaking process is energy-intensive and requires a lot of resources. Therefore, improving steelmaking processes is essential for sustainability and profitability. One way to improve the steelmaking process is by using advanced electric arc furnace electrodes. These electrodes are an important component of electric arc furnaces, which are commonly used in steelmaking. They provide the electrical energy needed to melt scrap metal and other materials to produce new steel.

RS Graphite Carbon Electrodes — RS Advanced Electric Arc Furnace Electrodes

Improving Steelmaking Processes with Advanced Electric Arc Furnace Electrodes

Traditionally, electric arc furnace electrodes have been made of graphite or carbon. However, these materials have limitations in terms of performance and durability. They tend to erode quickly, requiring frequent replacement, which adds to the overall cost of steel production.

Advanced electric arc furnace electrodes are made of high-quality materials that are designed to withstand the harsh conditions of steelmaking. They are typically made of graphite, but with a higher level of purity, which results in greater performance and longer life. Some advanced electrodes are also coated with special materials, such as silicon carbide, which further improves their durability and resistance to erosion.

One of the main benefits of using advanced electric arc furnace electrodes is increased productivity. The longer lifespan of these electrodes means that they can be used for longer periods without needing to be replaced. This reduces downtime, which can have a significant impact on the overall efficiency of the steelmaking process.

Another advantage of advanced electric arc furnace electrodes is improved energy efficiency. They have a lower electrical resistance than traditional electrodes, which means that they require less energy to operate. This can result in significant cost savings over time.

In addition to these benefits, advanced electric arc furnace electrodes can also improve the quality of the steel produced. They allow for more precise control over the melting process, which can result in a more uniform product. This is particularly important for industries that require high-quality steel for their products.

Finally, advanced electric arc furnace electrodes are also more environmentally friendly than traditional electrodes. They produce less waste and emissions, which can help to reduce the environmental impact of steel production.

RS Graphite Electrode Manufacturer noted, improving steelmaking processes is crucial for sustainability and profitability. Advanced electric arc furnace electrodes offer many benefits over traditional electrodes, including increased productivity, improved energy efficiency, better quality steel, and reduced environmental impact. As such, they are an important tool for any steelmaker looking to improve its processes and remain competitive in an ever-changing market.

Maintaining Consistent Electrode Consumption Rates in Electric Arc Furnaces

Electric arc furnaces (EAFs) are an essential component of modern steel production. They rely on a steady supply of electrodes to generate the heat necessary to melt and refine steel scrap. Electrodes are consumed during the EAF process, meaning they gradually burn away as they deliver electricity to the furnace. Maintaining consistent electrode consumption rates is critical to ensuring that the EAF operates efficiently and produces high-quality steel. According to the Rongsheng Group, the importance of electrode consumption rates in EAFs and discuss strategies for maintaining consistency.

Electrode consumption rates can vary depending on several factors, including the type of electrode, the steelmaking process, and the furnace’s operating conditions. Unpredictable consumption rates can cause issues such as inconsistent melting times and decreased furnace efficiency. Therefore, it is crucial to maintain a consistent consumption rate to achieve optimal steel production.

One strategy for maintaining consistent electrode consumption rates is to use high-quality electrodes. Quality electrodes can be made from various materials, such as graphite or carbon. They should be uniform in shape and size and have minimal impurities. High-quality electrodes have a predictable consumption rate, which helps to maintain consistent furnace operation.

Another strategy is to monitor the EAF process continuously. Monitoring allows operators to detect any changes in electrode consumption rates and take corrective action promptly. There are several monitoring methods available, such as thermal imaging and acoustic emission, which can detect changes in electrode consumption rates.

It is also important to ensure that the EAF is operating under the correct conditions. For instance, the furnace’s power settings, voltage, and current levels must be set correctly to achieve a consistent electrode consumption rate. Operators must monitor these settings regularly and adjust them as needed to maintain optimal electrode consumption rates.

Proper maintenance of the EAF and its components is also essential for consistent electrode consumption rates. Regular cleaning of the furnace’s interior and replacing worn or damaged parts, such as the furnace lid, can prevent electrode consumption from fluctuating.

Finally, proper training of personnel is critical. Steel production is a complex process, and operators must be trained to understand how to maintain a consistent electrode consumption rate. They must also know how to detect and troubleshoot issues that could cause fluctuations in electrode consumption rates.

In conclusion, maintaining consistent electrode consumption rates is critical for ensuring the efficient operation of an EAF and producing high-quality steel. Strategies for achieving this include using high-quality electrodes, monitoring the EAF process, setting correct operating conditions, maintaining the EAF, and providing proper training to personnel. By implementing these strategies, steel producers can achieve consistent and efficient steel production, which can lead to greater profitability and competitiveness. Rongsheng graphite electrodes manufacturer has rich experience in the production and sales of graphite electrodes. We can provide high-quality advanced UHP, HP, and RP graphite electrodes.

Maximizing Efficiency with Graphite Electrode 600 in Steel Production

The steel production industry is a highly competitive space where even minor improvements in efficiency can make a significant difference in profitability. One critical component in the steel production process is Graphite Electrode 600, which plays a vital role in determining efficiency and quality. In this essay, RS Graphite Electrodes Manufacturer will explore how Graphite Electrode 600 can be used to maximize efficiency in steel production, with a focus on reducing energy consumption, improving process control, and increasing production output.

RS Graphite Electrode 600 in Steel Production — Graphite Electrode 600 in Steel Production

Graphite Electrode 600 in RS Graphite Electrode Manufacturer

Graphite Electrode 600 is a premium-grade graphite material designed specifically for use in electric arc furnaces (EAFs). Its properties include high thermal and electrical conductivity, low electrical resistance, and high resistance to thermal shock and oxidation. Graphite Electrode 600 in RS Graphite Electrode Supplier has several advantages over other electrode materials, including a lower rate of consumption, greater stability and consistency during use, and lower environmental impact. It is commonly used in the steel production process for melting scrap metal and alloying elements.

Factors Affecting Efficiency in Steel Production

The steel production process is complex, and there are several factors that can impact its efficiency, including the quality of raw materials, equipment and infrastructure, and human capital. In the context of electrode use, factors such as the grade of the electrode, its dimensions, and its placement in the furnace can all have a significant impact on the efficiency and effectiveness of the steel production process. Graphite Electrode 600 has been developed to address many of these concerns.

Maximizing Efficiency with Graphite Electrode 600 for Steel Plant

1. Reducing energy consumption with the right electrode grade and dimensions

The selection of the right electrode grade and optimal dimensions is crucial in minimizing energy consumption and improving the overall efficiency of the steel production process. Graphite Electrode 600, with its high thermal and electrical conductivity and low electrical resistance, is an excellent choice for reducing energy losses due to electrical resistance. It is important to select the appropriate electrode diameter and length to match the furnace dimensions and operating conditions to achieve the desired energy efficiency.

2. Improving process control by optimizing electrode placement and use

The proper placement and use of Graphite Electrode 600 can significantly improve process control in steel production. Optimizing the electrode placement and use involves ensuring that the electrode is correctly positioned within the furnace and that its lifespan is maximized. Proper use of the electrode can reduce downtime and maintenance costs while ensuring that the process operates efficiently and effectively.

3. Increasing production output by maximizing electrode lifespan and usage

The lifespan and usage of Graphite Electrode 600 can have a significant impact on the overall production output of steel. By maximizing the electrode lifespan and usage, steel producers can increase the overall capacity of the steel production process and improve profitability. Proper selection and use of Graphite Electrode 600 can improve the productivity of the steel production process, allowing for increased output and profitability.

Graphite Electrode 600 Uses Cases Studies

1. Examples of successful implementation of Graphite Electrode 600 in steel production

Several steel producers have successfully implemented Graphite Electrode 600 in their operations to improve efficiency and profitability. RS Graphite Electrodes for Sale. For example, one steel producer in Asia was able to reduce energy consumption by 15% after switching to Graphite Electrode 600. Another producer in Europe was able to increase their production output by 10% after optimizing their electrode usage and placement.

2. Quantitative data and statistics highlighting the benefits of Graphite Electrode 600

There is ample quantitative data available to support the benefits of Graphite Electrode 600 in steel production. Studies have shown that the use of Graphite Electrode 600 can reduce electrode consumption by up to 30%, resulting in significant cost savings. Additionally, the use of Graphite Electrode 600 has been found to result in higher yields of steel per ton of electrode used, improving the overall efficiency of the steel production process.

Advantages of Using Graphite Electrode 600

In conclusion, the use of Graphite Electrode 600 in steel production can have a significant impact on efficiency, productivity, and profitability. By selecting the appropriate electrode grade and dimensions, optimizing electrode placement and use, and maximizing electrode lifespan and usage, steel producers can reduce energy consumption, improve process control, and increase production output. Furthermore, the success stories and quantitative data that support the benefits of Graphite Electrode 600 suggest that it is a valuable investment for any steel production operation looking to improve its bottom line. Get a free quote for the graphite electrode 600 from RS Graphite Electrode Company.

How to Tighten the Graphite Electrode Nipples?

The connection of graphite electrodes is realized through graphite electrode nipples. How to tighten the graphite electrode nipple? Graphite electrode manufacturers suggest that the torque required to screw the joint into the electrode screw hole to achieve a tight connection is well controlled.

The contact resistance of the graphite electrode with a smooth surface varies with the applied pressure. As the pressure increases, the contact resistance decreases. In order to reduce the contact resistance of the contact parts during electrode connection as much as possible, in addition to the two important conditions of graphite electrode material and processing accuracy, which must meet the technical standards, sufficient tightening torque must be applied when connecting electrodes in steelworks. If the tightening torque is insufficient when connecting, the contact resistance of the contact surface will increase significantly. Even high-quality electrodes will have redness and accelerated oxidation at the contact surface. Or loosening occurs in a strong vibration, increasing the chance of nipple breaking. The larger the electrode specification, the greater the tightening torque required. But the tightening torque is not as big as possible, but to reach a certain torque.

There are two main factors that affect the tightening torque not reaching the specified level. (1) The electrode processing quality is not good. If the processing surface is rough or the clearance of the thread is not well matched, it is difficult to screw into the joint, or it is still loose when it is screwed to the bottom of the screw hole, so it cannot be tightened. (2) The steel mill operator did not tighten the electrode and the joint when adding the new graphite electrode nipple, that is, the required tightening torque was not reached. In order to ensure that the required tightening torque can be achieved when connecting electrodes with different specifications, you can choose to use a graphite electrode wrench.

When tightening graphite electrodes in the smelting industry in some areas, the most common use is to clamp a graphite electrode with two iron clips for fastening operations, and there is also a “soil wrench” without a torsion structure. However, this type of tightening method not only needs to rely on the experience of master craftsmen but also faces the challenge of uneven quality of graphite electrodes from different manufacturers. A slight difference in the tightening force will make the current flow unstable. It leads to a series of problems such as the electrode is not tightened, the electrode is broken, and so on. Not only does it affect production, but it also consumes electricity, and the work efficiency and graphite electrode utilization rate are relatively low, which increases production costs.

The special graphite electrode wrench can perfectly solve these problems. It is widely used in the smelting industry in other regions. The special wrench for graphite electrodes is not only a tool for tightening graphite electrodes but also a kind of torque tool. Its appearance ended the smelting industry’s production history of relying on experience and technology when installing and replacing graphite electrodes. It provides a reliable guarantee for safe production, energy saving, and high efficiency, and cost reduction in the smelting industry.

Rongsheng graphite electrode manufacturer specializes in the production and sales of various types of graphite electrodes including graphite electrode with preset nipple products and can customize graphite electrodes and electrode nipples according to the actual needs of customers. Contact us for a free trial.

What are the reasons for the loss of graphite electrodes in vacuum furnaces?

Vacuum furnaces process hard zinc and recover zinc metal. The normal working conditions of the vacuum distillation furnace are the vacuum degree of 500~2000Pa and the temperature of 950~1050℃. Under this condition, the vapor pressure of the graphite electrode is very low, and its volatilization loss is negligible, so its service life depends on its degree of oxidation and fracture caused by mechanical and electrical failures. Specifically, what are the reasons for the loss of graphite electrodes in vacuum furnaces?

Oxidation loss of graphite

The oxidation of graphite is divided into dry oxidation (air, water, carbon dioxide gas) and wet oxidation (acid, alkali). Graphite is easily oxidized by air, water and carbon dioxide gas (CO2) at high temperature to form carbon monoxide or carbon dioxide. The product of its oxidation varies with the ambient temperature.

2C + O2 = 2CO (above 1 000°C)

C + O2 = CO2 (below 1000℃)

Graphite oxidation products are easy to escape and cannot form a dense oxide film protective layer like on some metal surfaces, so the oxidation reaction is continuous. The temperature and reaction speed at which graphite starts to oxidize are different in various cases. If the temperature at which 1% of the original weight is lost within 24 hours is set as the oxidation start temperature, the oxidation starts temperature of graphite is as follows.

1. 1. In air: 420 ~ 460 ℃;
  2. In carbon dioxide gas: about 900 °C;
  3. In water vapor: about 700°C.

Generally speaking, graphite with a large porosity, especially a large open porosity, has a large surface area participating in the reaction, and of course the oxidation rate is also fast. The higher the degree of graphitization of graphite products, the better the oxidation resistance. The aggregate of graphite products also has an important influence on oxidation resistance. Graphite products made of aggregates such as petroleum coke and natural graphite with good graphitization properties have excellent oxidation resistance. The presence of trace metal impurities will obviously promote the dry oxidation of graphite.

In the production process of graphite, metals that are usually easy to exist in the form of impurities include sodium, potassium, magnesium, calcium, iron, vanadium, copper aluminum, titanium, etc. Among them, the existence of sodium, potassium, vanadium and copper can catalyze the oxidation reaction of graphite. As the oxidation reaction proceeds, these metal impurity particles move through the material and form defects or pores. This phenomenon is more obvious in the oxidation reaction at lower temperature. According to the data, when some metal impurities are artificially added, such as adding 20 ~ 40μg/g of sodium, potassium, vanadium or copper, the oxidation rate at 550 °C can be increased by 5 times.

Electrode short circuit or crushed

The vacuum furnace uses graphite electrodes as heating elements, and requires good contact between electrode components during installation. Keep the vertical direction horizontal, and reserve an expansion gap around the installation window at the end of the electrode nut. At the same time, both ends of the electrode assembly and the furnace shell maintain good insulation performance. Due to the poor sealing of the installation window, the zinc vapor in the feeding trolley enters the electrode nut or the electrode connection card through the gap of the sealing material, and condenses into a zinc block. With the continuous growth of the condensed zinc block, it will eventually contact with the iron shell of the furnace body, causing the electrode to short-circuit and damage the electrode. After the furnace shell and electrode support plate are deformed, the expansion gap at the end of the graphite electrode nut is usually insufficient. After the power is heated up, the electrode nut is squeezed by the furnace wall around the installation window to varying degrees, and the electrode is quickly broken.

Electrode processing quality, installation quality

The electrode processing quality and installation quality also have a very important influence on the service life of the electrode. The connection thread of the electrode and the electrode nipple is poorly processed or the tolerance matching does not meet the standard, which will cause the connection between the electrode and the joint to be too loose or too tight. Too loose will cause poor contact and arcing will burn the electrodes and nipples; too tight will easily damage the threads during assembly. When assembling the electrode, during the screwing process of the electrode and the electrode joint, the action is rude, which will also cause damage to the thread and cause the electrode to be scrapped.

In addition, when the water-cooled electrode is short of water, the heat of the electrode connection card cannot be taken away in time. It will also cause poor contact between the electrode and the card board, thereby burning the electrode connection card board. In severe cases, arcing will burn the electrode and the electrode connection card.

It can be seen that the graphite electrode is still easily worn out in the process of use. Therefore, it is helpful to purchase high-quality graphite electrode products and standardize the operation and installation procedures to reduce the loss of graphite electrodes.

The Relationship between “Skin-Effect” and Electrodes Connection

At present, in electric arc steelmaking, as the discharge power and electrode diameter increase, the heat generated by the working current will increase rapidly, and the requirements for joint connection will be more stringent. To realize the ideal connection of the electrode, in addition to improving the processing quality of the joint and the joint hole, and improving the joint material, there are also appropriate requirements for the tightening torque. Make the pre-tightening force appropriate to avoid too much pre-tightening force causing breakage from the joint during work. Or the pre-tightening force is too small, causing the electrode to fall off during work.

HP graphite electrode for steelmaking — Graphite Electrodes Connection for Steelmaking

The Relationship between “Skin Effect” and Electrode Connection

When direct current passes through a conductor, the current in the cross-section of the conductor is uniform. When an alternating current passes through the conductor, the current will concentrate on the surface of the conductor. This phenomenon is called the skin effect of alternating current. The higher the frequency of the current, the more obvious the skin effect. The extent to which the current leaves the center of the conductor section and concentrates on the surface can be expressed by the depth of the skin effect.

The expression of the skin effect depth is:

In the formula, f is the frequency of the alternating current, in Hz; k is a constant, which is related to the resistivity of the conductor.

It can be seen from formula (1) that the depth of the skin effect decreases as the current frequency increases.

Due to the skin effect, when the electrode is working, under normal circumstances, about 80% of the current flows through the annular belt between the electrode joint and the outer surface, and about 20% of the current flows through the central electrode joint part. This is undoubtedly beneficial to the electrode connection. If the end faces can fit well when the electrodes are connected, the skin effect will be fully utilized, so that most of the current flows through the outer loop. Reduce the resistance heat of the joint part and avoid burning and breaking due to heat. At the same time, the good fit also makes the contact resistance very small and reduces the power consumption.

From the above, in order to make full use of the skin effect, when connecting the electrodes, it is necessary to make the end faces fit as much as possible. At the same time, when the electrode is in discharge, the connection between the electrode and the connector is easily loosened due to electromagnetic vibration. Therefore, it is necessary to apply pretension.

When the electrode connection threaded hole is processed, there are strict requirements on the perpendicularity of the end face to the thread axis, and the end face should be concave by 0.05~0.1mm, which needs to be determined according to the elastic modulus of the electrode material. The ideal connection state of the electrode is to apply an appropriate pre-tightening force to make the end face elastically compressed and deform, overcome the concave, and achieve full fit. At the same time, it is necessary to control the size of the pre-tightening force. It cannot be too big or too small. If the yield strength of the joint is exceeded, failure fracture occurs. The pre-tightening force is small, and it cannot provide enough positive pressure and friction between the threads, causing looseness.

Application of Graphite Electrode in Steelmaking Electric Arc Furnace

Graphite electrodes are mainly used as conductive materials in electric smelting furnaces. Compared with other conductive materials, the biggest advantage of graphite electrode material is that it has good electrical and thermal conductivity and better toughness, can accept the impact of larger current and does not soften or melt at high temperatures. It is used as a conductive material in the steel-making electric arc furnace, and the heat energy is transferred to the charge through arc discharge to melt the steel scrap. In the submerged arc furnace for smelting yellow phosphorus and industrial silicon, the electric energy is transferred into the charge through the electrode, and the charge itself is melted by the electric resistance heating of the charge.

The Advantages of Electric Arc Furnace for Steelmaking

Compared with other steelmaking methods, electric arc furnace steelmaking has its unique advantages. Electric arc furnace steelmaking is heated by an electric arc, and its temperature can be as high as 2 000 ℃ or more. This exceeds the maximum temperature that other steelmaking furnaces can reach when burning and heating with general fuel. The thermal efficiency is higher than that of the open hearth and converter steelmaking methods. Heating with electric energy can also accurately control the temperature and can use various elements (including aluminum, iron, and other elements that are easily oxidized) to alloy steel. Various types of high-quality steel and alloy steel are smelted, such as ball-bearing steel, stainless acid-resistant steel, high-speed tool steel, electrical steel, heat-resistant steel and alloys, and magnetic materials.

At present, electric furnace smelting adopts the traditional alkaline electric arc furnace steelmaking method. The process consists of “refilling the furnace-charging-smelting (including melting period and oxidation period)-refining outside the furnace (reduction period)-tapping-continuous casting” and so on.

According to relevant data, with the continuous improvement of ultra-high power electric arc furnaces and related technologies, the electrode consumption dropped from 6.5 kg/t to 1.2 kg/t from 1965 to 2000. The power consumption is reduced from 630 kW. h/t to 290 kW. h/t and the tapping time is reduced from 180 min to 40 min.

Artificial graphite electrodes — High-Quality Graphite Electrodes for Steelmaking

Characteristics Requirements of Graphite Electrode Materials for Steelmaking Electric Arc Furnaces

When investigating the adaptability of graphite electrodes to steel-making electric arc furnaces, the physical and chemical properties of the materials, the matching accuracy of the electrode and the joint, the reliability of the connection, and the length of the adaptable equipment (the up and down stroke of the electrode) should be analyzed one by one. Among them, the pear blossom properties of graphite electrode materials include mechanical properties, electrothermal properties, electrical conductivity, and oxidation resistance. In addition, it is necessary to understand and master the power transmission mode, smelting method, and process of the equipment.

It is very important to correctly understand the basic characteristics of graphite electrode materials. The characteristics of different grades of graphite electrodes are basically determined by the raw materials and manufacturing methods used.

Graphite electrodes should have at least the following properties on the smelting furnace. (1) Must be able to withstand the arc current required by the steelmaking process. (2) Continuous arc generation must be maintained.

In addition, the electrode should be able to be used in a wide temperature range (that is, it can be used in a state of rapid cooling and rapid heating). In the comprehensive evaluation of the performance of the graphite electrode, the thermal shock resistance index is used as the basic standard to measure the resistance of the electrode tip.

Thermal shock resistance refers to the ability of a material to resist damage under rapid cold and rapid heat. It is a comprehensive reflection of the performance of graphite electrodes.

Compared with other conductive materials, graphite electrodes have some excellent or irreplaceable characteristics under high-temperature conditions. Graphite electrodes can be used at relatively high temperatures (sublimation temperature of 3650°C), and are the only high-temperature conductive materials that can withstand high temperatures. There is no other material that can replace them in actual use. The strength of graphite increases as the temperature rises at high temperatures. Compared with other metals, graphite has the lowest coefficient of thermal expansion. When studying the characteristics of graphite electrodes, especially the thermal stress and vibration of the connection part, the coefficient of thermal expansion and the electrical resistivity is regarded as one of the most important indicators. Therefore, it is very important to choose petroleum coke with a low CTE value to produce graphite electrodes.

The Influence of Steelmaking Technology Progress on the Consumption of Graphite Electrodes

With the large-scale and ultra-high power of steelmaking electric arc furnaces, many improvements have been made to domestic UHP electric arc furnaces. For example, molten steel is reserved at the bottom of the furnace, and long-arc bubble slag submerged arc operation is used for drainage (the power transmission system is low current and high voltage). The foaming slag operation mainly reduces the radiation of the electric arc to the furnace wall and creates conditions for the long arc operation. The long-arc operation can effectively utilize power, that is, increase power factor, increase thermal efficiency, shorten smelting time and reduce electrical energy consumption. The improvement of thermal efficiency shortens the time for melting scrap steel and smelting. The use of long arc operation increases the vibration caused by the arc but can basically avoid the collapse of the electrode during the good penetration. After the current is reduced, the tip consumption of the electrode can be reduced. In addition, shortening the smelting time in an oxidizing atmosphere means that the side consumption of the electrode is also reduced. Coupled with the auxiliary electrode spray cooling, the electrode consumption of the UHP arc furnace is greatly reduced. From the level of over 2kg/t at the end of the last century to the level of 1.5 kg/t. Sometimes, it even reaches the level of 1.2~1.3 kg/t, which is especially in line with the characteristics of high production and low consumption in China’s steel industry in recent years.

In addition, the application of technologies such as out-of-furnace refining, scrap preheating, and addition of molten iron has contributed to the reduction of electrode consumption. The automatic control of electrode lifting protection makes the phenomenon of electrode breakage caused by human operation less and less.

The advancement of steelmaking technology has brought about a substantial reduction in electrode consumption, making imported electrodes of uniform material competitive advantage. It is a top priority for domestic carbon companies to break through the quality of large-size ultra-high-power electrodes as soon as possible and strive to reduce steelmaking consumption. To learn more about graphite electrodes for steelmaking electric arc furnaces, please contact us.

Influence of Temperature Distribution of Graphite Electrode Nipple on Thermal Stress

The nipple connection area in the graphite electrode column is a common part of fracture, and it is also a complex area with large electrical, thermal, and mechanical loads. There is large thermal stress in this area, so it is also a part that needs to be studied.

Experiment on the Influence of Temperature Distribution of Graphite Electrode Nipples on Thermal Stress

The calculation model selected in the experiment is the connection area formed by the φ500mm high-power electrode and the nipple(φ298.45X 372.5mm). The two sides are symmetrical with the nipple meridian as the midline, and the length is 780mm. And set the calculation model to be located directly above the furnace cover, with a current intensity of 45kA.

According to the structural characteristics of the graphite electrode nipple, the calculation is handled as an axisymmetric problem, and the load is also applied in an axisymmetric manner. In the calculation, it is assumed that the electrode and the nipple are linear elastic bodies, and the difference in the properties of the electrode and the nipple material and the orthogonal anisotropy characteristics, as well as the current steering in the electrode-nipple connection area are considered. The corresponding changes in physical parameters caused by temperature are not considered.

Part of the triangular unit is inserted, the screw contact area unit is encrypted, and the other parts gradually become thinner.

In order to simulate the actual connection conditions, two temperature calculation models are selected in this experiment.

In model 1, it is considered that the electrode bears the effect of the tightening torque. The end faces of the two electrodes are pressed and contacted normally, and the current flows in from the tapered threaded surface at the upper end of the nipple, flows out from the lower end of the nipple, and flows through the contact end faces of the two electrodes at the same time. Model 1 is used to simulate normal connection conditions.

In model 2, a thin layer of the insulator is added to the connecting end of the two electrodes, so that the current can only flow in from the threaded surface of the upper end of the nipple and flow out from the lower end. Model 2 is used to simulate the working condition when the connection end face is loose. The calculated value of this model may be slightly higher than the actual temperature value, but it can fully explain the temperature distribution and the trend of temperature rise.

The surface temperature of graphite electrodes during steelmaking is actually measured. At the end of steel-making melting, when the electrode reaches a steady-state temperature distribution, a handheld fast infrared thermometer is used to record the electrode surface temperature distribution. The measured result is used as the boundary condition of the finite element method to simulate the physical characteristics of the electrode connection area.

The surface temperature of the graphite electrode is measured as a linear distribution from the electrode clamping end to the furnace cover. The surface temperature of the calculated model is about 820~740℃.

The calculation results of experimental data show that. In steelmaking, the electrode connection area above the furnace cover is subjected to heat conduction from the electrodes in the furnace (with higher temperature), current flow through the heat generation, connection factors, and the surrounding environment, which bears a greater thermal load. The temperature distribution is parabolic along the radial direction, and the highest temperature area is in the nipple and threaded connection area. Model 2 shows a steeper temperature gradient and higher nipple temperature, which is almost double that of Model 1, which shows that the nipple bears a greater thermal load.

The following conclusions are obtained through calculation and discussion. In addition to the electrical and thermal properties of the material itself, and the current load, the connection status has a certain effect on the temperature field of the connection area. A certain torque can reduce the temperature, and excessive torque will damage the thread tooth root. Loosening of the connection surface can cause very high temperatures in the nipple.

Recommendations on Graphite Electrode Nipples

The temperature distribution has a certain influence on the size and distribution of thermal stress. Improve the temperature distribution to make it more reasonable, which can improve the thermal stress and reduce the consumption of alkali. Based on the calculation results and analysis, this article puts forward several suggestions.

(1) Requirements for material performance
The resistivity should be low. In particular, the electrical resistivity of the nipple is lower than that of the electrode, so that the power (I*R) loss is small and the thermal conductivity is large. The electrodes dissipate quickly and the radial temperature gradient is reduced.
(2) Best connection status
Use a torque wrench to apply a suitable connection torque to ensure the strength of the threaded tooth root, while the contact resistance is minimized, and the temperature of the connection area is reduced.
(3) Sincerely small contact resistance
Coating a certain substance on the connection surface can increase the friction and reduce the contact resistance value, and has good electrical and thermal conductivity. In addition, the contact area can be increased and the contact resistance can be reduced by changing the shape of the nipple.
(4) Use a cooling system to lower the temperature.

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Discussion on Vibration Forming Method to Produce Graphite Electrode

There are generally three molding methods used in the carbon industry, namely compression molding, extrusion molding, and vibration molding methods. Among them, the compression molding method is low due to labor productivity. At present, except for a small number of products with special requirements that use this molding method, the molding process in the carbon industry has basically been withdrawn. From the perspective of my country and the world, the extrusion molding method is the main molding method in the carbon industry. The graphite electrode formed by this method has preferential orientation in the axial direction, which makes the various “physical-mechanical” parameters in the axial direction of the product better than other directions, which is suitable for the use conditions of graphite electrodes and has high labor productivity. However, in order to produce large-diameter graphite electrodes or other carbon products with large cross-sections, a large-tonnage hydraulic press must be used when using this molding method. At present, the production of graphite electrodes with φ400mm in our country generally uses a 2500t hydraulic extruder, and the production of graphite electrodes with a diameter of 500mm or more uses a 3500t hydraulic extruder. Some foreign manufacturers of graphite electrodes also commonly use 4000t and 6000t hydraulic extruders, and the largest hydraulic extruder may be the 12700 hydraulic extruders of National Carbon Co. of the United States. These equipment not only have high extrusion pressure but also have a very long body due to the requirements of the electrode extruder’s molding method, so the bodyweight is very large. For example, a 3550t hydraulic extruder made in the Soviet Union is 36m long and weighs 577t. A 6300t hydraulic extruder made in Austria weighs 700t. In addition, these devices are equipped with high-power main motors, generally 300~400kW. It is conceivable that such equipment requires a large amount of investment and high energy consumption, which is not affordable by ordinary small and medium-sized factories.

Since the French VAW company vigorously introduced the vibration forming method in the 1960s, it has been widely used in the aluminum carbon industry, especially in the production of prebaked anodes, and has gradually been extended to the production of cathode carbon blocks and graphite electrodes. The vibration molding machine used in this molding method has a simple structure, a compact body, a small weight, and a low cost. According to the estimation of the French company KHD, the investment of a vibration forming machine is about 40% of that of a corresponding hydraulic extruder. The total power of the motor is only 37% of that of the extruder, and the molding energy consumption of the product is only 32% of that of the extruder. For some simple vibration forming machines in our country, the investment for one is only about 200,000 yuan, which is only about 5% of the 2500t extruder. Although its labor productivity and single-unit capacity are lower, it can also be used for the molding of large graphite electrodes with diameters above φ300mm and even φ500mm or larger. This is exactly what the small and medium-sized carbon plants hope for.

Although the vibration forming machine has many advantages mentioned above, can high-quality products be obtained by using it for the forming of graphite electrodes? At least can you get products that meet the standards? For this, most people in my country’s carbon industry hold a negative attitude. It is mainly believed that the particles in the vibration molded product are preferably oriented along the transverse direction, which is a bad orientation for graphite electrodes. Secondly, it is considered that the volume density of vibration molded products is not uniform. Because the above two points will affect a series of physical and mechanical properties of the product, people’s denial or suspicion is not unreasonable.

Based on everyone’s skepticism, some people conducted relevant discussions and analyses and finally came to the following conclusions.

1) Vibration molding, as a molding method for producing graphite electrodes, can produce ordinary graphite electrodes that are suitable for my country’s current national standard GB3072-82.

2) If the vibration hydroforming method is adopted, ordinary graphite electrodes of better quality can be produced, and the bulk density can reach more than 1.60g/cm3. If it is combined with vacuuming during the molding process, its bulk density can be further increased.

3) Since the graphite electrode formed by vibration has a higher volume density and a lower porosity, oxidation consumption can be reduced during use.

4) Due to the random orientation of the particles of the vibration-shaped electrode, its physical-mechanical properties have similar values in the axial and radial directions. Therefore, when the axial resistivity is similar to that of the extruded electrode, its radial physical-mechanical parameters are better than those of the extruded electrode.

5) The vibration forming machine, especially the small simple vibration forming machine, has little investment, but it can produce large-diameter graphite electrodes and other large-section graphite products. Moreover, its technology is easy to master, and the forming yield is high, which is suitable for small and medium carbon factories.

6) Although the vibration forming method has been developed in my country since the end of the 1960s. However, it has not been mass-produced for many years, and most manufacturers are limited to using it to produce carbon blocks and regenerated graphite electrodes. Many people hold negative attitudes about whether it can be used in the production of graphite electrodes. Therefore, a lot of work needs to be done. Only when the electrodes produced by them are proved to be at least no worse than extruded electrodes in long-term and large-scale use, can this molding method be recognized by the carbon industry in my country.

The author puts forward a little work and some opinions on the vibration forming method for the reference of colleagues. I also hope to get criticism and corrections from my colleagues. This article is from the Internet. If there is something wrong, please contact the author of this website to delete or modify it. Learn more about the graphite electrode production process.