Although both graphitized and petroleum coke recarburizers are used as recarburizers, they differ significantly in production processes, microstructure, performance, and cost.
Below, I will provide a detailed comparison of the two from multiple perspectives.
Core Summary
• Petroleum coke recarburizer: This is a recarburizer that has not undergone graphitization heat treatment. Its carbon atoms are arranged randomly, belonging to "amorphous" or "random-layered" carbon.
• Graphitized recarburizer: This is the product of graphitizing recarburizer at high temperatures (usually >2500℃). Its carbon atoms are arranged regularly, forming a distinct graphite crystal structure.
You can understand it this way: petroleum coke recarburizer is the "raw material," while graphitized recarburizer is the "cooked material" that has been "forged" at high temperatures.
We compare them from the following dimensions:
1. Production Process:
• Graphitized recarburizer: Petroleum coke or pitch coke is heat-treated for a long time in a high-temperature graphitization furnace at 2500-3000℃, causing carbon atoms to rearrange and form graphite crystals.
• Petroleum coke recarburizer: Petroleum coke is calcined at approximately 1300℃ to remove moisture and volatile matter, but its disordered carbon structure remains unchanged.
2. Microstructure:
• Graphitized recarburizer: Ordered graphite crystal structure, arranged in layers.
• Petroleum coke recarburizer: Disordered amorphous structure or random layered structure.
3. Fixed Carbon Content:
• Graphitized recarburizer: Extremely high, usually ≥98.5%, even reaching over 99.5%.
Few impurities.
• Petroleum coke recarburizer: Relatively low, generally between 95%-98.5%.
Contains more impurities such as sulfur, nitrogen, and ash.
4. Sulfur Content:
• Graphitized recarburizing agent: Extremely low, typically ≤0.05%, even below 0.02%.
High-temperature treatment causes most of the sulfur to volatilize.
• Petroleum coke recarburizing agent: Higher, generally between 0.3% and 0.7%, one of the main sources of sulfur in molten steel.
5. Absorption Rate:
• Graphitized recarburizing agent: High and stable, typically above 90%-95%.
Due to its graphite lamellar structure, it dissolves and diffuses rapidly in molten iron.
• Petroleum coke recarburizing agent: Lower and more volatile, typically between 75% and 90%, greatly affected by process, molten iron temperature, and other factors.
6. Impact on Product Quality:
• Graphitized recarburizing agent:
° Excellent recarburizing effect and high yield.
° Significantly reduces sulfur content, beneficial for producing high-quality ductile iron and premium steel.
° Promotes graphite nucleation, improves the graphite morphology in cast iron, making the graphite finer and more uniform, thus improving mechanical properties.
• Reduces impurities and slag.
• Petroleum coke recarburizer:
• Unstable recarburizing effect, requiring excessive addition.
• Introduces harmful elements such as sulfur, increasing desulfurization costs and potentially causing defects such as brittleness and shrinkage porosity in castings.
• Weak promoting effect on graphitization.
7. Cost:
• Graphitization recarburizer: High.
Its production process requires a large amount of electricity, resulting in high equipment investment.
• Petroleum coke recarburizer: Low.
Relatively simple production process with low energy consumption.
8. Main Application Areas:
• Graphitized Carburizing Agent: High-end Applications:
° Ductile iron (especially high-end castings such as wind power and automotive parts)
° High-grade gray cast iron
° Special steels and alloy steels
° Applications requiring low sulfur and high carbon absorption rates
• Petroleum coke Carburizing Agent: General Applications:
° Ordinary gray cast iron
° Some cast steel parts that do not require low sulfur
° As a raw material for the production of graphite electrodes and graphitized carburizing agents
In actual production, with the continuous improvement of product quality requirements and increasing environmental pressure, the application scope of graphitized carburizing agents is constantly expanding, especially in high-end manufacturing industries, where it has almost become a standard configuration.
