Determination of Carbon and Sulfur in Cast Iron (CS744)

Importance of the Topic

Accurate measurement of carbon and sulfur in cast iron is critical for ensuring desired mechanical properties and avoiding defects. Carbon content above 2% defines the alloy composition, while sulfur impurities can inhibit graphite formation and increase brittleness. Routine analysis supports quality control in foundries, maintaining sulfur levels below 0.15% and optimizing material performance.

Objectives and Study Overview

This application note describes a validated workflow for simultaneous determination of carbon and sulfur in cast iron using the CS744 Series elemental analyzer. The goals are to establish blank correction, calibration, and sample analysis procedures that yield precise, reproducible results suitable for foundry laboratories.

Methodology and Instrumentation

The method follows ASTM E1806 guidelines for sample preparation and employs combustion analysis. Key steps include instrument blank determination, calibration with certified reference materials, and replicate sample measurements. Analytical parameters such as purge time, integration delays, and furnace power are optimized for carbon and sulfur detection.

Used Instrumentation

• CS744 Series Carbon/Sulfur Combustion Analyzer (LECO Corporation)
• Crucibles: 528-018 or 528-018HP (ceramic, pre-baked for sulfur precision)
• Reagents: LECOCEL II combustion aid
• Accelerator: Iron chips (502-231 or 501-077)
• Auxiliaries: Metal scoops, tongs, and desiccator for crucible storage

Key Results and Discussion

Typical replicate analyses (n≥10) of cast iron yielded an average carbon concentration of 3.38% (standard deviation 0.01%) and sulfur concentration of 0.042% (standard deviation 0.001%). These results demonstrate the analyzer’s high precision and stability. The linear calibration through the origin provided accurate quantification across relevant concentration ranges.

Benefits and Practical Applications

The described procedure enables rapid, simultaneous measurement of two critical elements with a user-friendly touchscreen interface. Foundry laboratories benefit from reduced analysis time, minimal sample preparation, and reliable QC data, supporting process control and compliance with industry standards.

Future Trends and Applications

Advancements may include greater automation with robotic sample handling, integration of real-time data analytics, further miniaturization of combustion cells, and development of eco-friendly reagents. Expanding applications into other ferrous and non-ferrous alloys will enhance laboratory versatility.

Conclusion

The CS744 Series combustion analyzer provides a robust, precise, and reproducible method for determining carbon and sulfur in cast iron. Adherence to the outlined blanking, calibration, and analysis protocol ensures data quality suitable for rigorous foundry QC environments.

References

• ASTM E1806 Standard Practice for Sampling Metals
• LECO Corporation. Determination of Carbon and Sulfur in Cast Iron. Application Note, Form No. 203-821-506, 2017.