Carburizers are materials used in metallurgical processes, especially in steelmaking and casting, to add carbon to molten metal (such as iron or steel).
They are primarily made from substances with extremely high carbon content and extremely low levels of harmful impurities such as sulfur.
Main Raw Material Composition
Carburizers have a wide range of raw material sources, but their core is high-purity carbon.
The following are some common and different grades of carbon recarburizer raw materials:
Ⅰ Mainstream and High-Quality Carbon Recarburizers
These carbon recarburizers have excellent performance and are the first choice for casting and the production of high-quality steel.
1. Artificial Graphitized Carbon Recarburizers
• Raw Materials: Usually petroleum coke or pitch coke.
• Manufacturing Process: The raw materials are treated in a graphitization electric furnace at high temperatures (usually above 2300°C) to transform their microcrystalline structure into a regular graphite crystal structure.
• Characteristics: High carbon content: Usually > 98.5%, and can even reach over 99.5%.
High absorption rate: Up to 90% or more, due to the lamellar structure of graphite, which makes it easier to dissolve and diffuse in molten iron.
Extremely low sulfur content: S < 0.05%, even below 0.03%, with minimal impact on molten iron quality.
Low nitrogen content: Crucial for the production of low-nitrogen steel.
•Applications: High-end ductile iron, gray cast iron, and special steel smelting.
2. Calcinated Petroleum Coke Carburizing Agent
•Raw material: Petroleum coke.
•Manufacturing process: Petroleum coke is calcined at approximately 1200-1350°C to remove moisture and volatiles.
•Characteristics: High carbon content (typically > 98.5%), but without graphitization, its crystal structure is less regular than that of artificial graphite.
Absorption rate is lower than graphitized carburizing agents, but cost is also lower.
Sulfur content is usually slightly higher than graphitized carburizing agents.
•Applications: Ordinary cast iron and general steel grades.
II. Economical Carbon Rechargers
These carbon rechargers are lower in cost but have higher impurity content, and are typically used in applications where carbon quality requirements are not high.
1. Coal-based Carbon Rechargers
• Raw Materials: Anthracite or high-quality coal.
• Manufacturing Process: Finely selected and calcined at high temperatures.
• Characteristics: Relatively low carbon content (usually 90%-95%).
High content of impurities such as sulfur, nitrogen, and ash.
Unstable absorption rate and may introduce many impurities.
• Applications: Some ordinary castings where high-quality molten iron is not required.
2. Natural Graphite Carbon Rechargers
• Raw Materials: Natural flake graphite.
• Characteristics: High carbon content, but absorption rate varies depending on the purity of the natural graphite, and may contain other mineral impurities.
III. Other Materials (Less commonly used or in specific situations)
1. Coke Powder: Usually used in electric arc furnace smelting as part of the furnace charge, or as coarse conditioning carbon outside the furnace; contains many impurities.
2. Charcoal: With low fixed carbon content and high ash content, it is rarely used in industry anymore.
Simply put, recarburizers are essentially refined and processed "high-purity carbon." Their purity and performance are determined by the raw materials and processes used, ultimately affecting the quality and production cost of steel products.
In modern high-quality metallurgy, artificial graphitized recarburizers are the most widely used and highest-performing type.
