Overview
EN ISO 439:2020 (ISO 439:2020) specifies a gravimetric method for the determination of silicon content in steel and cast iron. The procedure is applicable to silicon contents from 0.10% to 5.0% (mass fraction) and replaces the 2010 edition. The standard describes sample preparation, reagents, apparatus, stepwise analytical procedure and calculation, with safety notes (notably for perchloric acid) and precision information based on an international re-evaluation.
Keywords: EN ISO 439:2020, ISO 439:2020, silicon determination, gravimetric method, steel and cast iron, metallurgical analysis.
Key topics and technical requirements
- Scope and applicability
- Applicable range: 0.10%–5.0% silicon in steel and cast irons.
- Accuracy is reduced for samples containing molybdenum, niobium, tantalum, titanium, tungsten, zirconium or high levels of chromium.
- Principle
- Dissolve the test portion with hydrochloric and nitric acids.
- Convert acid-soluble silicon compounds to hydrated silicon dioxide using perchloric acid fumes.
- Filter, ignite residue to form impure SiO2, treat with hydrofluoric and sulfuric acids, re-ignite and weigh the SiO2 gravimetrically.
- Test portion and sampling
- Use millings or drillings (max 0.2 mm thickness).
- Recommended test portion sizes depend on expected silicon level (e.g., ~5 g for low Si, ~1 g for high Si).
- Sampling and sample preparation should follow ISO 14284.
- Reagents and apparatus
- Analytical-grade acids (HCl, HNO3, HF, HClO4, H2SO4), grade 2 water per ISO 3696.
- Equipment includes platinum crucibles, a muffle furnace (800–1 100 °C) and low-ash filter paper.
- Quality controls
- Conduct a blank test in parallel with the sample.
- The standard includes precision data and instructions for reporting results.
Applications and who uses this standard
- Quality control and chemical analysis laboratories in steel mills, foundries and metallurgy labs.
- Third-party testing laboratories performing certification, compliance and materials characterization.
- R&D teams assessing alloy composition or developing heat-treatment and processing specifications.
- Regulatory and standards organizations referencing a validated gravimetric procedure for silicon determination.
Practical benefits: reliable gravimetric measurement, clear procedural steps for reproducible results, applicable in routine QC and interlaboratory comparisons.
Related standards
- ISO 14284 - Sampling and preparation of samples for chemical composition (referenced for sampling).
- ISO 3696 - Water for analytical laboratory use (specifies grade 2 water).
- Note: EN ISO 439:2020 supersedes EN ISO 439:2010.
Safety note: Perchloric and hydrofluoric acids present significant hazards - follow laboratory safety and local regulations.
