Graphite electrodes are primarily used as conductive materials in electric arc furnaces for steelmaking. Compared with other conductive materials, graphite electrodes have several key advantages: they exhibit excellent electrical and thermal conductivity as well as remarkable toughness, enabling them to withstand high-current surges without softening or melting even at elevated temperatures. As a result, graphite electrodes are widely employed in high-temperature electric arc furnaces for steel production. In electric arc furnaces used for steelmaking, graphite electrodes serve as the primary conductive material; through arc discharge, they transfer thermal energy to the charge, thereby melting scrap steel. In recent years, the proportion of electric arc furnace steel in total steel production has been increasing steadily, now exceeding 40%. Steel production from electric arc furnaces has grown rapidly—from 14.57 million tons in 2000 to 41.79 million tons in 2005—and the annual demand for graphite electrodes required for this production has reached approximately 1.9 million tons. Typically, electrode consumption costs account for about 15% to 30% of total production costs. Currently, China's electrode consumption remains very high; large steel mills alone consume around 1 million tons of graphite electrodes per year. With China’s macroeconomic environment continuing to strengthen and its steel industry experiencing rapid growth, the trend toward larger-scale electric arc furnaces and increased electrode consumption in China will only accelerate further.

Therefore, research aimed at reducing electrode consumption and improving the quality of graphite electrodes is an urgent and pressing issue that needs to be addressed by electric furnace metallurgy experts and enterprises.

Therefore, exploring and studying the mechanisms behind electrode consumption, identifying effective measures to reduce electrode consumption, and striving to lower production costs have become crucial aspects for reducing the cost of electric arc furnace steelmaking and conserving energy. Particularly in today’s rapidly developing steel industry, as electric arc furnace steelmaking continues to expand rapidly, the demand for electrodes is also steadily increasing. However, due to constraints in funding, energy availability, and production technology, the development of graphite carbon products currently struggles to fully meet the specialized needs of electric arc furnace steelmaking. As a result, electrode consumption indicators still lag considerably behind those of foreign countries, with relatively low quality and a notably acute supply-demand imbalance. For instance, large domestic steel mills mostly import electrodes used in their ultra-high-power electric arc furnaces from countries such as Japan. Consequently, reducing electrode consumption has become one of the key issues that electric furnace steelmaking enterprises must address. It is not only essential for saving energy and fully implementing the energy-saving and consumption-reducing requirements set forth in China’s “11th Five-Year Plan” for national development during the new era, but also a vital pathway for lowering electric furnace steelmaking costs, enhancing economic efficiency, and strengthening enterprises’ core competitiveness.
 

Study on the Mechanism of Electrode Consumption

The electrode is the final component of the short network. It generates a powerful electric arc at the ends of two connected graphitized electrodes, melting the charge and heating the molten steel. In essence, the electrode serves as the central hub for converting electrical energy into thermal energy. During operation, the electrode is subjected to high temperatures, oxidation by furnace gases, and impacts from collapsing charge materials. Particularly at the joint between the two electrodes, the resistance is higher and the electrical conductivity lower than in other areas, making this region more prone to disconnection, oxidation, detachment, and fracture—thus leading to significant electrode consumption, prolonged smelting times, and reduced productivity. During the steelmaking process, the electrode operates in a high-temperature environment, where its surface reacts with oxygen to form carbon monoxide, resulting in electrode consumption. Graphite electrodes are stable at low temperatures but tend to oxidize readily at high temperatures. In air, typical carbon products begin to oxidize around 450°C; graphite products with higher degrees of graphitization start oxidizing at approximately 600°C. Once the temperature exceeds 750°C, oxidation accelerates dramatically and intensifies further with rising temperature. Moreover, when heated in steam, graphite electrodes begin to oxidize at 900°C. Thus, the primary factors influencing oxidation on the sides of graphite electrodes are high temperatures and an oxidizing atmosphere—this is precisely what causes electrode oxidation and consumption. Especially with the successive introduction of new technologies such as oxygen lances at furnace doors, oil-oxygen-assisted melting, EBT bundled oxygen lances, and furnace-wall oxygen lances, the intensity of oxygen supply inside the furnace has increased, intensifying the oxidizing atmosphere and further accelerating electrode consumption. Since the end of the electrode is in direct contact with the electric arc, the end portion of the electrode sublimates, forming...

Consumption: The electrode portion comes into contact with the molten pool, and its carbon elements are absorbed by the molten pool, resulting in erosive consumption. During operation, the electrodes are subjected to electromagnetic forces, mechanical forces, and impact forces from solid raw materials, leading to fracture and spalling—thus causing fracture-induced consumption. Arc furnace electrode consumption can be categorized into chemical consumption and physical wear:

1.1 Physical Loss

The physical wear of electrodes primarily refers to the consumption at the electrode tip and on the sides, which is mainly caused by mechanical external forces and electromagnetic forces. Examples include loosening or breakage at the electrode connections, cracks in the electrode itself, and detachment of threads from the connection fittings. The underlying causes can be attributed to poor electrode quality—such as low strength—or equipment-related factors, including improper selection of electrode diameter, inadequate electrode holders, lifting mechanisms, and control systems. Additionally, operational factors, such as improper charging procedures, large chunks of scrap steel collapsing during the melting phase and striking the electrodes, or loose connections between two electrodes, can also contribute to electrode wear.

1.2 Chemical Loss

This primarily refers to the consumption of the electrode surface, including both the consumption at the electrode tip and the consumption along the electrode perimeter. Localized heating at the electrode tip causes graphite to sublimate, and as the electrode tip comes into contact with the molten steel, the graphite is absorbed, leading to its consumption at the electrode tip. The primary cause of this tip consumption is the sublimation of graphite at high temperatures and its melting into the steel slag. Under normal operating conditions, tip consumption can account for up to 50% of the electrode’s total consumption. Side consumption, on the other hand, is mainly due to the oxidation of the electrode, accounting for approximately 40% of the total consumption. The rate of this oxidation reaction is closely related to temperature:

1) When the temperature is in the range of 550℃ to 750℃, the oxidation reaction rate is controlled by the electrode itself. The effects of graphite quality and temperature on electrode consumption are stronger than the influence of air.

2) When the temperature exceeds 800℃, the air flow rate begins to dominate the reaction. The effects of air flow rate and air pressure on electrode consumption are stronger than those exerted by temperature and the electrode’s own mass.

The larger the contact area between the electrode and the air, the stronger the oxidation reaction involved, and consequently, the higher the consumption.

Oxidation loss is caused by the contact between the electrode perimeter and steel slag, as well as by contact with furnace gas.
 

Current Research Status of Electrode Consumption Reduction at Home and Abroad

In recent years, with the vigorous development of China's electric-furnace steel industry and the growing emphasis on energy conservation, consumption reduction, and lowering production costs—particularly the need to reduce electrode consumption in electric-arc furnace steelmaking—experts, scholars, and frontline workers both domestically and internationally have conducted extensive research, exploration, and practical trials in this field. As a result, several relatively effective processes have emerged, which are summarized below:

2.1 Research on Surface Modification of Graphite Electrode Melting Systems

By developing a surface alloying process for molten-system materials, we conducted a systematic study on the surface alloying of graphite electrodes and the oxidation kinetics of graphite electrodes. We established a kinetic model for the oxidation of graphite electrodes and, through comparative experiments, demonstrated that surface alloying treatment via the melt method can reduce the oxidative wear of graphite electrodes.

2.2 Optimize Power Supply System Parameters

Power supply parameters are critical factors affecting electrode consumption. By selecting a secondary-side voltage of 410V and a current of 23kA, we can minimize electrode tip consumption to the greatest extent. Maintaining stable and smooth arc furnace equipment and refining operational procedures can effectively reduce mechanical electrode wear. Practical results have demonstrated that through continuous optimization of power supply parameters and ongoing efforts to reduce mechanical electrode wear, the electrode consumption at Liansteel’s No. 1 Steelmaking Plant has been reduced from the original 5.0 kg/t to 3.81 kg/t. Selecting optimal power supply parameters, ensuring stable and smooth furnace operation, and improving process techniques can effectively lower electrode specific consumption.

2.3 Water-cooled Composite Electrode

The water-cooled composite electrode is a new type of electrode that has been developed overseas in recent years. Using a water-cooled composite electrode for steelmaking can typically reduce electrode consumption by 20% to 40%. The water-cooled composite electrode consists of an upper section made of water-cooled steel tubing and a lower section made of graphite. The water-cooled section accounts for approximately one-third of the electrode's total length. Since the water-cooled steel tubing section is free from high-temperature oxidation (graphite oxidation), electrode oxidation is significantly reduced. At the same time, the water-cooled steel tubing section maintains excellent contact with the holder. Moreover, the threads connecting the water-cooled section to the graphite section are designed with a water-cooling feature, ensuring stable geometry and preventing damage. These threads can also withstand substantial torque, enhancing the strength of the electrode interface and thereby substantially reducing electrode consumption.

2.4 Mechanism of Oxidation Prevention by Water-Sprayed Graphite Electrodes

Regarding the consumption of electrodes during the smelting process, the primary focus for reducing electrode consumption should be on minimizing end-face consumption, thereby significantly lowering the specific electrode consumption per ton of steel. In graphite electrode consumption, side oxidation accounts for approximately 50%, with peak rates reaching as high as 70%. Over the years, both domestically and internationally, extensive research has been conducted to prevent side oxidation of graphite electrodes, and various technical measures have been adopted with notable success, gradually reducing the consumption of graphite electrodes used in electric arc furnaces. Drawing on existing achievements, we have adopted a technical measure involving spraying an anti-oxidation solution onto graphite electrodes. Experimental studies have demonstrated that this technique effectively prevents side oxidation of graphite electrodes, increasing their resistance to oxidation by a factor of 6 to 7. Moreover, this technical measure is highly feasible and practical. The water-spray electrode protection method was pioneered in Japan as a new electrode protection technology. This technique employs a circular water-spraying device located beneath the electrode holder to spray water onto the electrode surface, causing the water to flow downward along the electrode’s surface. At the same time, a circular pipe above the electrode opening in the furnace cover blows compressed air onto the electrode surface, atomizing the water stream. After adopting this method, the specific electrode consumption per ton of steel has dropped to between 1.9 and 2.2 kg. Additionally, thanks to the effect of atomized steam, the service life of the refractory material furnace cover has doubled.

This new technology was first applied to ultra-high-power electric furnaces. The direct water-cooling electrode method features a simple device, convenient and safe operation, and the ability to achieve significant cooling effects with only a small amount of water. However, the main problems encountered in actual industrial production are:

1) Electrodes tend to break frequently. Some of these fractures are caused by improper handling, while others may result from localized thermal shock when dry electrodes come into contact with water, leading to uneven temperature distribution and internal stress that makes the electrodes prone to fracture under improper operating conditions.

2) The small holes on the spray ring are often blocked by cold slag and molten steel. The cooling effect of these holes is primarily concentrated in the region from the upper part of the furnace cover to the spray ring area. This cooling method does not increase power consumption or the hydrogen content in the steel. High-temperature oxidation on the electrode surface is a major factor contributing to electrode wear. Water-cooled electrodes represent an effective approach for reducing electrode consumption. Different water-cooling methods have varying effects on the thermal conditions and surface temperature distribution of the electrodes; each method has its own advantages as well as limitations. Currently, countries such as Canada, Germany, and the United States have conducted research on composite water-cooled electrodes, while Japan has carried out experiments with water-spraying electrodes. All these approaches aim to reduce electrode surface oxidation—either indirectly or directly through water cooling—thereby lowering electrode consumption.

2.5 Hollow Electrode

Electrodes also represent one of the major consumables in the smelting of ferroalloys. In recent years, Western Europe and Sweden have begun to adopt hollow electrodes in the production of ferroalloy submerged arc furnaces. Hollow electrodes are typically self-sealing; they feature a cylindrical shape with an inert gas introduced appropriately into the inner shell to create a sealed environment. Thanks to their hollow design, these electrodes enjoy improved baking conditions, which in turn enhance their strength. Generally, using hollow electrodes can lead to savings of 30% to 40% in electrode consumption, and in some cases, even up to 50%. The use of hollow electrodes not only improves electrode operating conditions but also brings a range of benefits to ferroalloy smelting, such as allowing direct smelting of fine ore powders and enabling the injection of reducing agents through the hollow electrode.

2.6 DC Arc Furnace

The DC arc furnace is a new type of smelting arc furnace that has emerged in recent years worldwide. According to publicly available information from abroad, the DC arc furnace represents one of the most effective technologies for reducing electrode consumption—typically lowering electrode consumption by about 40% to 60%. In a DC arc furnace, the negative terminal of the rectifier is connected to the graphite electrode, while the positive terminal is connected to the furnace bottom electrode (usually composed of a water-cooled metal plate and refractory materials). The graphite electrode, the molten metal pool, the furnace bottom electrode, and the rectifier together form a current circuit, and an arc is struck between the graphite electrode and the molten metal pool.

In April 1984, the Nalco Steel Plant in the United States completed construction of the world’s first 20-ton three-phase electrode DC arc furnace. From January to November 1986, this DC arc furnace produced a total of 60,000 tons of steel. The consumption of graphite electrodes in the electric furnace dropped from the original 4.77 kg per ton of steel to 1.9 kg per ton, representing a reduction of more than 60%. At the same time, power consumption was reduced by approximately 33.3%. In particular, a DC arc furnace using only one large-diameter graphite electrode consumes about half the electrode oxidation area compared to an AC furnace of the same power that uses three electrodes; consequently, the electrode consumption per ton of steel is roughly 40% lower than that of an AC furnace with the same capacity. Currently, DC arc furnaces have begun to be widely adopted and promoted in developed countries around the world. According to reports, the graphite electrode consumption in large-scale DC ultra-high-power furnaces has now been reduced to as low as 1.6 kg per ton of steel.

2.7 Permanent Electrode

In recent years, developed countries have been leveraging the comprehensive advantages of their technologies to develop permanent electrodes. These so-called permanent electrodes are water-cooled ceramic electrodes made from conductive metal-ceramic materials through specialized manufacturing processes. They exhibit extremely low oxidation, sublimation, and fracture losses. A permanently designed electrode developed in Sweden was tested on a 1.5-ton arc furnace; a single ceramic electrode segment (500 mm long) demonstrated a service life of over one year.

2.8 Improve electrode quality to reduce natural loss.

Electrodes must conduct high currents, operate at high temperatures, and withstand mechanical vibrations—all under extremely harsh working conditions. Therefore, stringent requirements are imposed on electrode quality. Specifically, electrodes must: ① have excellent electrical conductivity, meaning they should exhibit a low resistivity; ② be able to withstand high temperatures and possess high mechanical strength; ③ demonstrate good oxidation resistance, with a high temperature threshold before significant oxidation begins in air; and ④ have a regular geometric shape.

2.9 Electrode Surface Coating Technology

Electrode coating technology is a simple and effective method for reducing electrode consumption, typically lowering electrode wear by about 20%. Commonly used electrode coating materials include aluminum and various ceramic materials, which exhibit strong antioxidant properties at high temperatures and can effectively minimize oxidative wear on the electrode's side surface. The Ceracon coating developed in Japan has been tested by several manufacturers and not only reduces electrode consumption but also lowers steelmaking electricity consumption by 20 to 30 kWh per ton of steel. The most common method for applying electrode coatings is spray coating followed by grinding; this process is straightforward and easy to implement, making it the most widely adopted approach for electrode protection.

2.10 Impregnated Electrode

Impregnated electrodes typically involve immersing the electrode in a chemical solution, allowing the electrode surface to undergo a chemical reaction with the solution, thereby enhancing the electrode's resistance to high-temperature oxidation. Using impregnated electrodes can reduce electrode consumption by approximately 10% to 15% compared to conventional electrodes.