Carbon in Mold Powder

Importance of the Topic

Precise measurement of carbon in mold powders is essential for continuous steel casting operations as it influences mold lubricity, thermal performance, casting speed and surface quality.

Goals and Overview

This study demonstrates a reliable procedure for quantifying total carbon in mold powder samples using a LECO CS/C744 combustion analyzer. The method aligns with ASTM E2050-12a and employs high-temperature combustion followed by infrared detection to ensure rapid and accurate results.

Methodology

A fine, homogeneous powder is weighed (0.1 to 0.25 g depending on expected carbon levels) into a ceramic crucible. Each sample is mixed with LECOCEL II (or HP) and iron chip accelerators to promote combustion. Key instrument settings include purge time 15 s, analysis delay 20 s, sample cool time 5 s, furnace power 100%, integration time 50 s and baseline delays of 2 s. Data acquisition uses direct integration without a comparator and applies endline correction.

Used Instrumentation

• LECO CS/C744 or equivalent elemental analyzer
• Fluorine trap kit LECO 619-592-149
• Ceramic crucibles (baked at 1000 to 1250 °C for improved precision)
• Accelerators: LECOCEL II and LECOCEL II HP, Iron Chip accelerator
• Metal scoop for sample and accelerator dosing

Results and Discussion

Typical reproducibility was demonstrated on four mold powder formulations. Mold Powder A yielded 16.7 % C with standard deviation 0.1; Powder B 3.69 % C (s=0.01); Powder C 20.2 % C (s=0.1) and Powder D 7.86 % C (s=0.02). Calibration was performed against NIST SRM 276b tungsten carbide using a linear calibration through the origin. The low variability confirms the method’s precision across a broad concentration range.

Benefits and Practical Applications

• Fast turnaround with analysis times under a minute per sample
• High accuracy and precision support tight process control
• Enables optimization of mold powder formulation for improved casting efficiency and reduced defects

Future Trends and Potential Uses

Advances may include inline monitoring with automated sampling, integration with process control systems, and extension of the method to related flux and inclusion materials. Ongoing development of accelerator chemistries and trap technologies will further enhance performance.

Conclusion

The described combustion method on the LECO CS/C744 analyzer provides a fast, reliable and standardized approach for determining total carbon in mold powders, contributing to improved quality and efficiency in continuous casting operations.

References

• ASTM E2050-12a Standard Test Method for Determination of Total Carbon in Mold Powders by Combustion
• NIST SRM 276b Tungsten Carbide