How do graphite electrodes work? - News

Let’s talk about How do graphite electrodes work? graphite electrode manufacturing process and Why do graphite electrodes need replacing?
1. How do graphite electrodes work?
The electrodes are part of the furnace lid and are assembled into columns. Electricity then passes through the electrodes, forming an arc of intense heat that melts the scrap steel.
The electrodes are moved down onto the scrap in the meltdown period. Then the arc is produced between the electrode and metal. By considering the protection aspect, low voltage is selected for this. After the arc is shielded by electrodes, the voltage is increased for speeding up the melting process.
2. graphite electrode manufacturing process
The graphite electrode is mainly made of petroleum coke and needle coke, and the coal bitumen is used as a binder. It is made by calcination, compounding, kneading, pressing, roasting, graphitization and machining. It is to discharge electric energy in the form of electric arc in the electric arc furnace. The conductor that heats and melts the charge can be divided into a common power graphite electrode, a high power graphite electrode and an ultra high power graphite electrode according to its quality index.

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3. Why do graphite electrodes need replacing?
According to the consumption principle, there are several reasons of replacing graphite electrodes.
• The end use: These include the sublimation of graphite material caused by the high temperature of arc and the loss of chemical reaction between the electrode and the molten steel and slag. High temperature sublimation rate at the end mainly depend on the current density going through the electrode; also related with the diameter of the electrode side after oxidation; End consumption is also related to whether to insert the electrode into the steel water to increase carbon.
• Lateral oxidation: The chemical composition of the electrode is carbon, Carbon will oxidize with air, water vapor and carbon dioxide under certain conditions, and the oxidation amount of electrode side is related to unit oxidation rate and exposure area.Normally, Electrode side oxidation accounts for about 50% of the total electrode consumption. In recent years, in order to improve the smelting speed of electric furnace, the frequency of oxygen blowing operation is increased, oxidation loss of the electrode is increased.
• Residual loss: When the electrode is used continuously at the junction of the upper and lower electrodes, a small section of the electrode or joint is detached because of oxidative thinning of the body or penetration of cracks.
• Surface peeling and dropping: The result of the poor thermal shock resistance of the electrode itself during the process of smelting.Include electrode body broken and nipple broken. Electrode broken is related to the quality and machining of graphite electrode and nipple, also related to the operation of steel making.

What Is A Graphite Electrode?

A graphite electrode is a type of electrode used in electric arc furnaces (EAFs) to melt and refine steel, iron, and other metals. It is made of graphite, a form of carbon that has unique properties such as high thermal conductivity, high melting point, low coefficient of thermal expansion, and good electrical conductivity. Graphite electrodes are essential components in the production of high-quality steel and are widely used in the metalworking industry.

Graphite electrodes are typically cylindrical in shape and range in size from 75 to 700 millimeters in diameter and 1 to 2 meters in length. They are installed in EAFs to conduct electric current and generate heat to melt and refine metal. When an electric current passes through the graphite electrodes, it generates an electric arc, which produces temperatures of up to 3,500°C (6,332°F). This extreme heat melts the metal in the furnace and allows impurities to be removed, resulting in a high-quality end product.

Graphite electrodes are chosen for EAFs due to their high electrical conductivity, low electrical resistance, and excellent thermal shock resistance. They are also relatively easy to shape and mold, which allows them to be manufactured in various sizes and shapes to meet the specific needs of different industries. The quality of graphite electrodes is determined by factors such as their electrical resistivity, flexural strength, thermal expansion coefficient, and oxidation resistance.

There are two main types of graphite electrodes: regular power (RP) and high-power (HP). RP electrodes are made from high-quality petroleum coke and are widely used in steel production. They are also used in non-ferrous metal production such as aluminum, silicon, and magnesium. HP electrodes, on the other hand, are made from high-grade needle coke and are used in the production of ultra-high-quality steel and other specialty alloys.

Graphite electrodes are typically manufactured through a process known as needle coke production. This involves heating petroleum coke at high temperatures to form needle-like structures that are then mixed with coal tar pitch and baked at high temperatures to produce graphite. The resulting graphite is then machined to the required size and shape for use in EAFs.

One of the main challenges in the graphite electrode industry is ensuring a stable supply of high-quality needle coke. The production of needle coke is a complex and expensive process, and there is a limited number of manufacturers worldwide. As a result, the cost of graphite electrodes can vary greatly depending on the availability and cost of needle coke.

In recent years, the graphite electrode industry has experienced significant fluctuations in price and demand due to factors such as changes in the global steel market, the closure of some needle coke plants, and the emergence of new EAF technology. Despite these challenges, the demand for graphite electrodes is expected to remain strong as the global steel industry continues to grow and evolve.

In conclusion, graphite electrodes are an essential component in the production of high-quality steel and other metals. Their unique properties make them ideal for use in EAFs, and their manufacture requires a complex and specialized process. Although there are challenges in the industry, the demand for graphite electrodes is expected to remain strong, and the industry will continue to evolve and innovate to meet the changing needs of the global metalworking industry.

Graphite Electrodes and the Metals Industry

Why are graphite electrodes crucial to the metals industry?

The industry has been growing progressively for some time. In recent years its progress has been rapid, particularly as a result of the decarbonisation of the steels and metals industry.

As a leading power in both industries, China sees the highest quantities of graphite electrodes both produced and used across the globe.

What are graphite electrodes?

Graphite electrodes are large cylindrical parts consisting of synthetic graphite. Synthetic graphite is created with petroleum coke, needle coke and coal bitumen, which can be used as a binder.

They can be produced in a massive range of sizes, and can be as long as 3 metres.

Why Graphite?

High electrical conductivity levels

Capacity to withstand high temperatures of up to degrees Celsius

Resistance to thermal shock

Because of these beneficial features of graphite, it is the ideal material for electrodes. They can be used in processes such as Electric Arc Furnaces (EAF), ladle refinement of steel and in the production of ferroalloys.

Graphite electrodes account for about 2-3% of the total steel production costs.

The graphite electrode serves a current supply material into the electric arc furnace space for heating an subsequent melting of the charge at high temperatures to ℃. In the cost of eaf steelmaking, the consumption of graphite electrodes accounts for about 10%.

It is made of petroleum coke and pitch coke, and high-power and ultra-high-power grades are made of needle coke. They have low ash content, good electrical conductivity, heat, and corrosion resistance, and will not melt or deform at high temperatures.

About graphite electrode grades and diameters.

We has different grades and diameters. You can choose from RP, HP or UHP grades, which can help you improve electric arc furnace performance, increase production efficiency, and increase economic benefits. We have various diameters, 150mm-700mm, which can be used for smelting operations of electric arc furnaces of different tonnages.

Correct choice of electrode type and size is very important. This will play a key role in ensuring the quality of the smelted metal and the normal operation of the electric arc furnace.

How does it work in eaf steelmaking？

Graphite electrode introduce electric current into the steelmaking furnace, which is the electric arc furnace steelmaking process. The strong current is transmitted from the furnace transformer through the cable to the holder at the end of the three electrode arms and flows into it.

Therefore, between the electrode end and the charge an arc discharge occurs, and the charge begins to melt using the heat generated by the arc and the charge begins to melt. According to the capacity of the electric furnace, the manufacturer will choose different diameters for use.

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To continuously use the electrodes during the smelting process, we connect the electrodes through threaded nipples. Since the cross-section of the nipple is smaller than that of the electrode, the nipple must have higher compressive strength and lower resistivity than the electrode.

In addition, there are various sizes and grades, depending on their use and the specific requirements of the eaf steelmaking process.

Features

Graphite electrode is a key good conductor raw material in the EAF steelmaking process.  As source of electric energy for an electric arc furnace, which is the most efficient way to heat and melt steel scrap. They conduct electricity from the power source to the furnace, allowing it to reach high temperatures necessary for steel production.

High bulk density

low specific resistance

Allow large current load

Small thermal expansion coefficient

High bending strength

Low ash content

Graphite machining performance is strong

Main factors affecting the Graphite Electrode Price.

Raw material cost: The price of petroleum coke and needle coke directly affects the production cost of it, and also affects the price.

Price of energy: The production processes of roasting and graphitization require large amounts of electricity, so fluctuations in energy prices may have an impact on the final price.

Development of electric arc furnace technology: The emergence of large-tonnage ultra-high-power electric arc furnaces places higher requirements on their performance. Therefore, the cost of production process and technology also increases accordingly.

Market demand and supply: When the number of electric arc furnaces increases, the demand will inevitably increase, and prices are likely to rise.

Shipping Costs: Price fluctuations in ocean or ground freight, which may play a role in the final price.

International economic situation: Changes in trade relations and policies and exchange rate fluctuations may have an impact on the import and export of raw materials, thereby affecting the price.

High Pure Graphite Products UHP HP RP Graphite Electrode

Graphite Electrodes are a high-temperature resistant graphite conductive refractory material used in the metallurgical industry. Graphite Electrodes are made of petroleum coke, bituminous coke as aggregates, coal tar pitch as binders, after raw material calcination, crushing and milling, batching, kneading, moulding, roasting, impregnation, graphitization and machining, which are also known as artificial graphite electrodes in order to distinguish from natural graphite electrodes made of natural graphite.

> Be careful when transporting and pilling electrodes with a forklift and avoid a collision. One layer of goods at a time; notice the balance and alignment and avoid falling or breakage.

> When loading and unloading with a forklift, wire rope must be used and steel wrapping tape cannot be employed directly to fetch electrodes.

> Electrode should be stored in a clean and dry place. When pilling up outdoors, it should be covered with rain-proof tarpaulin and the number of piling layers ought not to exceed four.

> When using electrodes, special tools should be employed to cut the steel wrapping tape, and crane should not be adopted to avoid bursting.

> Steel-wire ball, metallic brush or emery cloth is not allowed for cleaning the electrode thread, but compressed air free of oil and water is available.

> Use revolved resilient hanger and put soft truss pad under the electrode joint to avoid breakage of the thread.

> Lift the electrode to the furnace by using a hoister with resilient hangers, and find out the centre and move slowly downwards, screw and tighten with a hoop.

> If the two poles of the two electrodes are untouched or touched in overpressure, this may cause a bad effect.

> In order to avoid electrode breakage put the large materials in the lower part and small materials in the upper part.

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