When steel mills select calcined petroleum coke (CPC) as a recarburizer, they impose strict and even “fastidious” requirements on its properties, based on metallurgical performance, molten steel purity, and cost-effectiveness. Overall, their primary focus is on the core indicators of high carbon content and low impurities, as well as the right physical form.
Specifically, their critical requirements are reflected in the following aspects:
Core Chemical Composition: Zeroing in on “High Carbon” and “Low Impurities”
- High Fixed Carbon Content: This is the fundamental value of a recarburizer. Steel mills typically require a fixed carbon content of above 96%, with premium products demanding above 98.5%. Lower carbon content means more recarburizer must be added, which not only increases costs but also introduces more unnecessary impurities.
- Extremely Low Sulfur Content: Sulfur is a harmful element in steel, significantly affecting its mechanical properties and hot workability. For recarburizers used in steelmaking, a sulfur content below 0.5% is standard, with some specifications requiring ≤ 0.45%. Many mills explicitly include price penalty clauses in their procurement contracts for sulfur exceeding the limit, demonstrating zero tolerance for this element.
- Low Ash and Volatile Matter Content: Ash is the inorganic mineral residue left after combustion, which contaminates the molten steel and forms slag. Excessive volatile matter can cause violent boiling when added to molten steel, reducing recovery rates and posing safety risks. Therefore, recarburizers typically require ash content below 1.0% and volatile matter below 1.0%, with some specifications even demanding below 0.5%.
- Hidden Requirements for Nitrogen, Phosphorus, and Other Elements: Especially when smelting high-carbon steels and special steels, steel mills are extremely sensitive to the nitrogen and phosphorus content in recarburizers, as these elements also affect the toughness and workability of the final steel products.
Physical Form: The “Goldilocks” Particle Size
- Particle Size is a Critical Parameter: If the particles are too fine, they can be blown away by the airflow or lost to oxidation when added to the molten steel, resulting in waste. If they are too coarse, they tend to float on the surface of the molten steel, reducing the contact area with the steel and leading to slow and inefficient absorption.
- Mainstream Particle Size Specifications: Steel mills generally accept a particle size range of 1-5mm. Depending on the specific furnace type (e.g., induction furnace, converter) and steel grade requirements, this can be further refined to specifications such as 1-3mm or 0.5-5mm. Procurement contracts also clearly define the passing rate (e.g., >95%) for particle size distribution.
Other Important Indicators
- Extremely Low Moisture Content: High moisture content introduces gases into the process, increasing the hydrogen content in the molten steel, which can lead to defects like “white spots” in the steel. The moisture content is typically required to be ≤ 0.5%.
From the above requirements, it is clear that steel mills’ fastidiousness over CPC essentially reflects their ultimate pursuit of product stability and purity under extreme operating conditions. Any minor fluctuation in any of these indicators can potentially affect the final steel quality and yield rate.
Post time: Aug-17-2026