Analysis of Cast Irons

Importance of the Topic

Precise chemical analysis of cast iron alloys is critical for controlling mechanical properties such as strength, abrasion resistance and corrosion resistance. Because cast irons contain significant levels of carbon, silicon and various alloying elements, accurate quantification of their composition ensures reliable manufacturing and consistent performance in industrial applications.

Objectives and Article Overview

This performance note demonstrates the capabilities of the LECO GDS500A glow discharge atomic emission spectrometer for rapid, multi-element analysis of cast irons. It outlines method development, calibration strategy, sample preparation, analysis times and typical precision and accuracy results for a range of cast iron standards.

Methodology and Instrumentation

The procedure employs the LECO GDS500A, featuring a glow discharge source that sputters material from the sample surface and excites ground state atoms to produce emission spectra. Key points:

• Sample preparation: chilled irons abraded with 120-grit zirconium oxide belts; as-cast irons polished with 600-grit paper.
• Accessories: LECO BG belt grinder or LECO VP polisher.
• Calibration: linear curves built from certified reference materials (CRMs) and reference materials (RMs) from Brammer, CKD, CTIF, MBH and LECO.
• Drift control: periodic use of homogeneous non-certified setup standards; substitution with CRMs/RMs when necessary.
• Analysis sequence: three burns can be completed within 90 seconds without dropping the sample; single as-cast burn requires 190 seconds total.

Key Results and Discussion

Precision and accuracy were evaluated using multiple cast iron standards, including chilled ductile, chilled grey, nickel hard, chrome hard and as-cast grey irons. Typical observations:

• Certified average recoveries within 0.1% of target values for major elements (C, Si, Fe).
• Relative standard deviations (RSDs) generally below 1% for high-abundance elements; up to 6–10% for low-level constituents like Mo and V.
• Consistent linear calibration across wide dynamic ranges for each element.

Benefits and Practical Applications

The glow discharge method on the GDS500A offers:

• Minimal matrix effects due to analysis away from the surface.
• Reduced spectral interference by focusing on ground state atom emissions.
• Rapid multi-element capability for quality control labs and production environments.
• High throughput with multiple burns without repositioning.

Future Trends and Potential Uses

Advancements in glow discharge sources and detector technologies will further enhance sensitivity for trace elements in ferrous alloys. Integration with automated sample handling and AI-driven data interpretation promises fully unattended, real-time process monitoring and tighter process control in foundries and metallurgical plants.

Conclusion

The LECO GDS500A provides a robust, fast and accurate solution for multi-element analysis of cast irons. Its glow discharge approach delivers linear calibration, low interference and high throughput, making it well suited for industrial quality assurance and research applications.

Reference

LECO Corporation. Spectroscopy Performance Note: Analysis of Cast Irons (Form No. 209-076-026), January 2007.