Carbon and Sulfur Determination in High Carbon Ferroalloys - CS744

Importance of the Topic

Accurate determination of carbon and sulfur in high-carbon ferroalloys is essential for steel and cast iron production. Carbon defines key mechanical properties and alloying behavior, while sulfur is a detrimental impurity that can compromise strength and toughness. Reliable analysis supports quality control and ensures consistent metallurgical performance.

Objectives and Study Overview

This application note presents a validated procedure for simultaneous measurement of carbon and sulfur in high-carbon ferroalloys using a LECO CS744 combustion analyzer. The study aims to optimize accelerator mixtures, establish calibration protocols, and demonstrate method accuracy and precision under routine laboratory conditions.

Methodology and Instrumentation

Sample Preparation

• Grind or select a representative powder or granular ferroalloy sample.
• Use ceramic crucibles preheated at 1350 °C for 20 min or 1000 °C for 40 min, then store in a desiccator.
Accelerator Mixture
• 0.4 g LECO iron powder
• 0.6 g vanadium pentoxide (V2O5)
• 1.5 g LECOCEL
Analysis Parameters
• Purge time: 10 s
• Analysis delay: 20 s
• Furnace mode: constant at 100 % power
• Integration time: 40–70 s
• Comparator level: 1.00 % for both elements
• Significant digits: 5
Procedure Steps
• Run three blank replicates to establish baseline.
• Calibrate with at least two reference materials (e.g., NIST, LECO CRM standards) in triplicate.
• Analyze samples in replicates, applying blank subtraction and drift correction as per instrument manual.



Main Results and Discussion


Calibration using NIST 64c and BCS 204/4 ferro-chromium standards yielded linear responses forced through the origin. Typical results for a ~0.25 g sample:
• Reference NIST 64c: 4.698 ± 0.040 % C, 0.0673 ± 0.0034 % S
• BCS 204/4: 5.620 ± 0.015 % C, 0.0101 ± 0.0002 % S
Precision and accuracy met industrial QC requirements. The V2O5-LECOCEL mixture improved sulfur recovery, and the consistent blank enabled reliable subtraction.



Practical Benefits and Applications


The described CS744 method offers:
• Rapid turnaround for routine quality control in ferroalloy and steel plants
• High analytical precision and accuracy for carbon and sulfur
• Robust performance with minimal sample preparation variability



Future Trends and Potential Applications


Emerging developments may include
• Automation with autoloaders for higher throughput
• Alternative, less hazardous accelerators
• Integration of real-time data analytics for process control



Conclusion


The CS744 combustion analysis protocol provides a reliable, precise, and accurate method for carbon and sulfur determination in high-carbon ferroalloys. Its robust calibration and accelerator strategy ensure consistency for industrial QC environments.



Instrument Used



• LECO CS744 Carbon/Sulfur Analyzer with induction furnace