Research and Application Analysis of All-Aluminum Alloy Conductive Arm Technology

Research and Application Analysis of All-Aluminum Alloy Conductive Arm Technology

Ladle refining furnaces consume a large amount of electrical energy during operation. As a key component connecting the power supply to the electrodes, the conductive arm has a significant impact on the overall electrical consumption of the system. The conductive arm is responsible for supplying power to the electrodes, thereby heating and raising the temperature of molten steel. Therefore, its design should meet the requirements of light weight, high stiffness, low impedance, and long service life. One end of the electrode arm is supported by the lifting column, while the other end clamps the electrode. Reducing the weight of the conductive arm can lower the power required for electrode lifting, while significantly improving the response speed and control accuracy of the electrode regulation system.

1. Development Status of Conductive Arm Technology

During the operation of a ladle refining furnace, short-circuit discharges occur among the three-phase electrodes, generating high-power and high-temperature arcs within the molten steel. These arcs induce strong electromagnetic vibrations in the conductive arms. Consequently, conductive arms must possess excellent structural stability and mechanical strength. In addition, to ensure rapid melting of furnace materials, low electrical resistance and reactance are required. Given the high-temperature operating environment, conductive arms are generally equipped with internal water-cooling systems, and their structures are optimized to minimize static dust-induced arcing, thereby extending service life.

Early conductive arms based on conductive tube designs have gradually been phased out due to complicated maintenance requirements. Subsequently, copper-clad steel plate conductive arms were developed abroad. Compared with traditional all-steel conductive arms, their electrical performance was improved; however, they still exhibited notable drawbacks. These structures are relatively heavy—approximately 20% heavier than traditional all-steel arms—negatively affecting the responsiveness of electrode regulation systems. Furthermore, each phase is designed as an independent unit with structural differences, meaning that damage to an electrode holder requires the entire arm to be taken offline, resulting in extended maintenance periods and reduced production continuity.

2. Comparative Analysis of Different Types of Conductive Arms

Traditional all-steel conductive arms consist of a steel support structure and conductive pipes. Due to the high density and poor electrical conductivity of steel, these arms suffer from excessive weight, high electrical losses, short service life, and poor maintainability. Moreover, to meet conductivity and safety requirements, busbar connections are complex and time-consuming, and strong electromagnetic vibrations during heating increase maintenance demands for conductive pipes.

Copper–steel composite conductive arms represent an upgraded version of all-steel designs. By using copper plates on the outer surface of the arm for current conduction, conductive steel or copper pipes are eliminated, integrating both support and conduction functions into a single structure. This design effectively reduces arm impedance and improves electrical performance. However, the thickness of the copper layer is limited, resulting in insufficient conductive cross-sectional area and leaving room for further impedance reduction.

All-aluminum alloy conductive arms are fabricated using welded aluminum alloy plates in a box-type structure with internal water-cooling channels. This design ensures sufficient strength and stiffness while significantly r

educing overall weight. Lower arm mass effectively reduces system resonance, improves electrode regulator sensitivity, and enables electrode lifting speeds of up to 15 m/min. As a result, electrode movement becomes more responsive, three-phase current imbalance is greatly reduced, electrode consumption is lowered, and overall operational efficiency is improved.

3. Technical Advantages of All-Aluminum Alloy Conductive Arms

All-aluminum alloy conductive arms offer notable advantages, including corrosion resistance, rust prevention, and low weight. Compared with traditional all-steel arms, their weight can be reduced by approximately 40%. This significantly enhances the responsiveness of the electrode lifting system and allows the use of larger-diameter electrodes, increasing secondary current and improving overall furnace electrical efficiency.

Due to reduced impedance, both active power and input power are increased. Statistical data indicate that input power can be increased by approximately 9%, while the average power factor improves by about 4%, shortening the refining cycle by roughly 3.5%. In addition, reduced vibration during operation lowers electrode consumption by about 4% and improves system stability. These characteristics make all-aluminum alloy conductive arms one of the most advanced technologies currently available for ladle refining furnaces.

The box-type structure of all-aluminum alloy conductive arms integrates conduction and mechanical support, resulting in a simple, rigid, deformation-resistant design that is reliable and easy to maintain. Electrically, both resistance and reactance are significantly lower than those of traditional conductive arms. Furthermore, the absence of insulating plates at the electrode holder prevents arc formation caused by the accumulation of charged dust, thereby reducing damage to electrode holders.

From a cost perspective, the elimination of copper materials provides certain manufacturing cost advantages. Considering the corrosive effects of cooling water, magnesium alloy composite materials are typically applied for electrochemical corrosion protection, with a protection cycle of approximately five years. Under normal cooling and anti-corrosion conditions, the designed service life of all-aluminum alloy conductive arms can exceed ten years.

4. Feasibility Analysis of All-Aluminum Alloy Conductive Arm Retrofit

During retrofitting, the existing short network and water-cooled cables can remain unchanged. The removed copper–steel composite conductive arms and electrode holders may be reused as spare parts for other furnaces. Only minor adjustments to the lifting columns are required, and the original hydraulic system remains unaffected.

An economic benefit analysis based on Bensteel’s No. 5 LF furnace is presented. The furnace produces approximately 12,000 heats annually, with an average power-on time of 13 minutes per heat, molten steel weight of 165 tons, and an average active power of 17 MW. The average electrical energy consumption per ton of steel is approximately 22.32 kWh. Assuming a 3% energy-saving rate after adopting all-aluminum alloy conductive arms, annual electricity savings amount to approximately 1.326 million kWh. At an electricity price of 0.56 RMB/kWh, this corresponds to an annual cost saving of about 742,500 RMB.

In addition, assuming electrode consumption of 0.01 kg/kWh, annual electrode usage is approximately 44.19 tons. With an electrode unit price of 17.41 RMB/kg and a consumption reduction of 4%, the annual electrode cost saving is about 307,800 RMB. Combined electricity and electrode savings total approximately 1.05 million RMB per year, indicating that the retrofit investment can be recovered within three years, demonstrating strong economic feasibility.

5. Conclusions

Since the successful application of all-aluminum alloy conductive arm technology in Germany, it has been successively adopted in countries such as the United States, the United Kingdom, and France. In China, Baosteel Group first applied this technology to a 300-ton ladle refining furnace in 1999, achieving favorable results. With increasingly stringent energy-saving requirements in the steel industry, all-aluminum alloy conductive arms—due to their superior electrical performance, mechanical characteristics, and economic benefits—are expected to be more widely adopted and to become an important development direction for energy-efficient electric furnace technologies.