Production method of low-carbon ferromanganese

In the steel metallurgy industry, low-carbon ferromanganese is an indispensable key alloy material. With its unique properties, it plays an important role in many fields such as stainless steel and structural steel. This article will comprehensively interpret low-carbon ferromanganese from aspects such as chemical composition, differences from other ferromanganese, industrial applications, raw materials, and production processes.

What is low-carbon ferromanganese?  

Low-carbon ferromanganese (LC FeMn) is a ferroalloy primarily composed of manganese (Mn) and iron (Fe), with a very low carbon content—typically less than 0.1%. It is an essential additive in steelmaking, especially in the production of high-grade and low-carbon steels where controlling the carbon content is critical.

Raw material composition for low-carbon ferromanganese production  

Manganese-rich slag or manganese ore  

Manganese-rich slag or manganese ore is the primary raw material for producing low-carbon ferromanganese. When selecting raw materials, priority should be given to those with high manganese content (typically above 40%) and low impurity levels to ensure the quality of the final product.

Reducing agents: aluminum powder or silicon iron powder  

Aluminum powder: commonly used as a reducing agent in the metal thermal reduction method, it has strong reducing properties and can effectively reduce manganese oxides.  

Silicon iron powder: with a silicon content of 75%–90%, it serves as a reducing agent in processes such as the silicon thermal method. It not only reduces manganese oxides but also plays a crucial role in controlling carbon content.

Scrap iron (used to adjust iron content)

The addition of scrap iron can adjust the iron content in low-carbon manganese iron according to production requirements, ensuring the alloy composition meets design specifications to suit various application scenarios.

Fluxes and additives (lime, fluorite, etc.)

Lime: primarily composed of calcium oxide, it reacts with impurities such as silicon dioxide (SiO₂) in the raw materials to form easily separable slag, thereby purifying the alloy.  

Fluorite: added in certain processes to lower the melting point and viscosity of the slag, improving its flowability and facilitating separation from the alloy.

Production methods for low-carbon manganese iron

Metal thermal (aluminum thermal) reduction method

Process overview

The metal thermal reduction method utilizes the reducing properties of metals such as aluminum to reduce manganese oxides into metallic manganese, thereby producing low-carbon manganese iron. This method has a relatively simple process and is easy to operate.

Main Chemical Reactions  

Taking aluminum powder reduction of manganese oxide as an example, the main reaction is: 3MnO + 2Al → 3Mn + Al₂O₃. Under high-temperature conditions, aluminum powder reacts vigorously with manganese oxide in an exothermic reaction, producing metallic manganese and aluminum oxide slag.  

Typical Process Flow  

Materials Preparation: Mix manganese ore, aluminum powder, flux, and other raw materials in a specific ratio to form a uniform mixture.

Charging: Load the mixed raw materials into a refractory crucible.

Ignition reaction: Initiate the reaction using an ignition device. The reaction occurs within the crucible, releasing a large amount of heat to melt the raw materials.

Slag removal and iron tapping: After the reaction concludes, once the temperature slightly decreases, first remove the upper layer of aluminum oxide slag, then discharge the lower layer of low-carbon manganese iron melt.

Casting: Pour the molten low-carbon manganese iron into a mold, and it will cool to form ingots.

Equipment used  

Mainly uses induction furnaces and refractory crucibles. Induction furnaces provide initial heat to promote the reaction; refractory crucibles are used to hold the reaction raw materials and products and withstand the high-temperature reaction environment.

High-Carbon Manganese Iron Decarburization Method

Process Concept

The high-carbon manganese iron decarburization method uses oxygen or other means to remove carbon from high-carbon manganese iron, converting it into low-carbon manganese iron. This method uses high-carbon manganese iron as raw material, achieving secondary processing and utilization of the raw material.

Process Types

Oxygen Blowing: Oxygen is blown into the molten high-carbon manganese iron through a nozzle. The oxygen reacts with carbon to produce carbon monoxide gas, which escapes, thereby reducing the carbon content.

AOD (Argon-Oxygen Decarburization): By alternately blowing argon and oxygen, the reaction atmosphere is controlled to achieve decarburization while minimizing manganese oxidation losses and improving manganese recovery rates.

Temperature and Gas Control

Temperature Control: The decarburization process requires high temperatures, typically between 1600°C and 1800°C, to ensure smooth reaction progress and melt fluidity.

Gas Control: Precisely control the flow rate and injection time of oxygen, as well as the argon-to-oxygen ratio (AOD method), to prevent excessive oxidation of manganese while ensuring carbon content is reduced to the target value.

Manganese Oxidation Risks and Countermeasures

Risk: During decarburization, oxygen not only reacts with carbon but may also react with manganese to form manganese oxide, leading to manganese loss and reduced product yield.

Countermeasures: By controlling the oxygen injection speed and method, and reasonably adjusting the temperature and gas ratio, the opportunity for manganese to come into contact with oxygen is reduced; in the later stages of decarburization, appropriate amounts of silicon iron powder or other reducing agents can be added to reduce the already formed manganese oxide.

What are the application areas of low-carbon manganese iron?

Metallurgical industry

Low-carbon manganese iron is commonly used in the metallurgical industry as an important alloy additive. Adding an appropriate amount of low-carbon manganese iron can improve the performance of steel, enhancing its oxidation resistance, corrosion resistance, and wear resistance. It effectively regulates the microstructure of steel, increasing its strength and hardness, and extending its service life.

Chemical industry

Low-carbon manganese iron also has widespread applications in the chemical industry. It can be used as a catalyst in organic synthesis reactions to promote chemical reactions. Low-carbon manganese iron exhibits excellent catalytic activity in certain organic synthesis reactions, such as oxidation and hydrogenation, thereby improving reaction efficiency and product purity.

Environmental protection field

Low-carbon manganese iron can also be applied in environmental remediation and wastewater treatment. For example, in water treatment processes, low-carbon manganese iron can be used as an adsorbent to remove heavy metal ions and harmful substances from water, thereby purifying water quality. This application effectively reduces wastewater pollution and protects the ecological environment.

Conclusion

In actual production, factors such as production scale, product quality requirements, and cost budgets must be comprehensively considered to select the most suitable production route, achieving a balance between economic benefits and product quality.