Understanding the Chemistry of Calcium Carbide Desulfurization in Steelmaking and Its Impact on Steel Quality

Understanding the Chemistry Behind Calcium Carbide’s Role in Steel Desulfurization

Calcium carbide (CaC₂) has long been recognized as one of the most effective desulfurizing agents in iron and steel production—particularly during pre-treatment stages. Its ability to reduce sulfur content from molten iron makes it indispensable for producing high-quality steel, especially in regions like Xinjiang where raw material purity varies widely.

Why Calcium Carbide Excels in Sulfur Removal

The key lies in its unique chemical behavior under high temperatures. When introduced into molten iron, calcium carbide undergoes a well-defined reaction:

CaC₂ + [S] → CaS + 2CO↑

This exothermic process not only removes sulfur but also generates carbon monoxide gas—a critical factor in enhancing mixing efficiency when properly controlled. According to ISO 15475-2014, this method can achieve up to 85% sulfur removal efficiency if parameters are optimized.

Critical Factors Influencing Efficiency

Real-World Application in Xinjiang Steel Plants

A case study from a medium-sized steel plant in Xinjiang demonstrated that optimizing particle size (from 8 mm to 3 mm) and raising the pre-treatment temperature by 50°C led to an average sulfur reduction from 0.045% to 0.012%. This improvement allowed the facility to meet ASTM A572 Grade 50 standards consistently without increasing operational costs significantly.

Common Challenges & Practical Solutions

• Uneven Desulfurization: Often caused by poor stirring or inconsistent feed rate—solution: use mechanical stirrers with real-time monitoring.
• Excessive Gas Evolution: May result from too fine a particle size or sudden temperature spikes—solution: control particle gradation and introduce CaC₂ gradually.
• Residual Calcium Carbide: Indicates incomplete reaction—check for proper timing and ensure adequate residence time in the ladle.