Overview
EN ISO 9556:2025 (identical to ISO 9556:2025) specifies an infrared absorption method after combustion in an induction furnace for the determination of the total carbon content in steel and iron. The method covers carbon mass fractions from 0.003 % to 4.5 % and is intended for routine carbon analysis in metallurgical and testing laboratories. The technique converts sample carbon to CO2 and/or CO by high‑temperature combustion in oxygen and quantifies the gaseous products by infrared absorption.
Key Topics
- Scope and applicability: Determination of total carbon in steels and irons within 0.003–4.5 % (mass fraction).
- Principle: Combustion of a test portion in a high‑frequency induction furnace in a stream of purified oxygen; measurement of CO2/CO by infrared analyser.
- Reagents and gases: Requirements include CO2‑free water, oxygen (≥99.5 % volume), low‑carbon accelerators (e.g., copper, tungsten‑tin), and standard carbon solutions (sucrose/sodium carbonate) for calibration. Desiccants and absorbents (Mg(ClO4)2, barium carbonate, Na2CO3) and NaOH‑impregnated ceramic are specified for gas conditioning.
- Apparatus: High‑frequency induction furnace, commercial IR carbon analysers, and ordinary class A volumetric glassware (ISO 648/1042). Annex C gives features of commercial equipment.
- Procedure elements: Sampling and sample preparation, test portion handling, blank tests, calibration curve construction across different carbon ranges (separate guidance for 0.003–0.01 %, 0.01–0.1 %, 0.1–1.0 %, and 1.0–4.5 %), determination steps and data expression.
- Quality metrics: Method precision data (recalculated for this edition) and reporting requirements.
- Normative references: ISO 648, ISO 1042, ISO 14284 (sampling and prep).
Applications
- Quality control and production monitoring in steel mills, foundries and ferroalloy producers.
- Chemical analysis in independent testing laboratories and inspection bodies for material certification, purchase specifications and regulatory compliance.
- Research and development where accurate bulk carbon determination is required (metallurgy, failure analysis, process optimization).
- Trade and conformity testing where standardized carbon analysis methods are mandated.
Who should use this standard
- Metallurgical and materials laboratories, QA/QC engineers, analytical chemists, conformity assessment bodies, and equipment manufacturers (IR analysers and induction furnaces).
Related Standards
- ISO 14284 - Sampling and preparation of samples for chemical composition of steel and iron.
- ISO 648, ISO 1042 - Volumetric laboratory glassware requirements.
- EN ISO 9556:2001 - superseded by EN ISO 9556:2025.
For implementation and purchase, obtain the full text from ISO or your national CEN member body; note the document cautions about possible patent issues and specifies national adoption timelines.
