Determination of Carbon and Sulfur in Cast Iron (CS844)

Importance of the Topic

Accurate measurement of carbon and sulfur in cast iron is critical for controlling material properties such as strength, hardness, and machinability. Carbon content above 2% defines the iron’s microstructure, while sulfur acts as a potential contaminant that can impair graphite formation and lead to brittleness. Routine and reliable elemental analysis ensures consistent quality in foundry operations and supports regulatory compliance.

Objectives and Study Overview

This application note demonstrates a standardized workflow for simultaneous determination of carbon and sulfur in cast iron using the CS844 series elemental analyzer. The primary goals are to establish method parameters, evaluate precision and accuracy with reference materials, and provide step-by-step guidance to laboratory personnel.

Methodology and Instrumentation

The method relies on high-temperature combustion of samples in a controlled oxygen environment, followed by infrared detection of CO₂ and SO₂. Key steps include:

• Preparation of ceramic crucibles with high-temperature preheating to prevent contamination.
• Blank determination using LECOCEL II and iron chip accelerator to establish baseline signals.
• Calibration and drift correction with certified cast iron reference materials covering relevant carbon and sulfur ranges.
• Analysis of unknown samples under constant furnace power and predefined timing parameters.

Used Instrumentation

The analysis was performed on the CS844 series carbon/sulfur analyzer by LECO Corporation. Major accessories include 528-018/528-018HP crucibles, LECOCEL II flux, iron chip accelerator, and a LECO TF4 muffle furnace for crucible pretreatment.

Main Results and Discussion

Replicate analyses of three reference materials (501-024, 501-994, 502-698) demonstrated high precision and accuracy:

• Carbon levels ranged from 2.15% to 3.76% with standard deviations below 0.05%.
• Sulfur results varied between 0.012% and 0.115% with standard deviations under 0.006%.

Consistency across multiple lots confirmed the method’s robustness. Calibration curves exhibited linear behavior through the origin, supporting reliable quantification across the evaluated range.

Benefits and Practical Applications of the Method

The outlined procedure enables foundry laboratories to:

• Perform rapid and simultaneous C/S analysis in a single run.
• Maintain tight quality control with low detection limits for sulfur contamination.
• Minimize downtime through automated autoloaders and intuitive touchscreen operation.

Future Trends and Potential Applications

Advancements may include further automation of sample handling, integration with laboratory information management systems (LIMS), and expansion of the method to other ferrous alloys. Emerging sensor technologies and AI-driven data processing could enhance throughput and real-time quality feedback.

Conclusion

The CS844 series analyzer provides a validated, high-precision approach for measuring carbon and sulfur in cast iron. By following the described workflow, laboratories can achieve consistent analytical performance, support process optimization, and ensure compliance with industry standards.

References

• ASTM E1806, Standard Practice for Sampling Cast Iron for Elemental Analysis.
• LECO Corporation, Form No. 203-821-537, Application Note: Determination of Carbon and Sulfur in Cast Iron, 2017.