Determination of Oxygen and Nitrogen in Ferroalloys (ON836)

Importance of Determining Oxygen and Nitrogen in Ferroalloys

Maintaining precise levels of oxygen and nitrogen in ferroalloys is essential for controlling properties such as deoxidation efficiency, carbon yield, ductility and resistance to porosity in steel and cast iron.

Aim and Overview of the Study

This study demonstrates a robust analytical procedure for simultaneous wide-range quantification of oxygen and nitrogen in various ferroalloy matrices using the ON836 impulse furnace system with automated sample introduction.

Methodology and Analytical Workflow

Samples are introduced as powdered or granular material into graphite crucibles. An impulse heating cycle converts oxygen into CO and CO₂, detected by non-dispersive infrared (NDIR) cells, while nitrogen is quantified by a thermal conductivity detector after removal of CO₂ and H₂O.
Carrier gases (helium or argon) sweep analyte gases through mass flow control, optimized furnace power settings and timing sequences to ensure complete gas release and minimal crucible degradation.

• Sample mass: 0.10–0.14 g ferroalloy, 0.4 g nickel flux, 0.05 g graphite powder
• Analysis delay: 30 s; furnace outgas cycles: 2; integration times: O—30–70 s, N—65–120 s
• Detectors: dual NDIR cells for CO and CO₂; TC detector for N
• Automation: sample drop loader with electrode cleaning options

Main Results and Discussion

Calibration against certified reference materials (LCRM Ti and steel pins) yielded linear, force-through-origin responses for both elements. Typical analyses of ferrochromium and ferromanganese demonstrate oxygen results within ±0.005 % and nitrogen within ±0.001 %, with comparable precision for helium and argon carriers. The method accurately reproduced certified and informational nitrogen values in diverse matrices.

Benefits and Practical Applications

The described protocol offers rapid, accurate dual-element determination with minimal sample preparation. Its automation and wide dynamic range are well-suited for quality control in steelmaking plants and alloy production laboratories, facilitating real-time feedstock assessment.

Future Trends and Possibilities

Advances may include integration with process analytics for on-line monitoring, expansion to additional light gases (e.g. hydrogen), and enhanced data connectivity for digital laboratories. Emerging detector technologies could further improve sensitivity and throughput.

Conclusion

The ON836 method provides a validated, efficient solution for simultaneous oxygen and nitrogen analysis in ferroalloys, ensuring high accuracy, precision and operational ease required for industrial quality assurance.

Used Instrumentation

• ON836 impulse furnace system
• Graphite crucibles (LECO 782-720 series) and sample drop loader
• Non-dispersive infrared cells and thermal conductivity detector
• Nickel capsules, nickel flux and graphite powder for sample preparation