ISO 9556:2025

Overview

ISO 9556:2025 specifies an infrared absorption method after combustion in a high‑frequency induction furnace for the determination of the total carbon content in steel and iron. The method covers carbon contents from 0.003 % to 4.5 % (mass fraction). It replaces the 1989 edition and updates normative references, adds a mandatory terms clause and recalculates precision data. The standard is produced by ISO/TC 17 in cooperation with CEN.

Key topics and technical requirements

• Principle: Combustion of a weighed test portion in pure oxygen in an induction furnace; carbon converted to CO and/or CO2 and quantified by infrared (IR) absorption.
• Scope of measurement: 0.003 % to 4.5 % total carbon.
• Calibration: Establishment of calibration curves for defined carbon ranges (clauses 8.5.1–8.5.4) to ensure accuracy across low to high carbon contents.
• Sampling & sample preparation: Follow ISO 14284 or applicable national standards; degreasing and drying of test portions.
• Test portion mass: Approximately 1 g for carbon < 1.0 % and ≈0.5 g for carbon > 1.0 % (instrument-dependent).
• Blank tests: Performed in duplicate; blank mean and difference shall not exceed 0.01 mg of carbon (clause 8.3).
• Reagents & gases: Use analytical‑grade reagents and oxygen ≥ 99.5 % (vol.); specified standard solutions (sucrose or sodium carbonate) for calibration.
• Apparatus: High‑frequency induction furnace combined with an IR carbon analyser; volumetric glassware per ISO 648/ISO 1042. See Annex C for commercial instrument features.
• Safety: Warnings about burn hazards, oxygen handling, and apparatus stabilization/cleaning procedures.

Applications and users

ISO 9556:2025 is intended for:

• Metallurgical and materials testing laboratories performing carbon analysis of steels and irons.
• Quality control and production laboratories in steel mills, foundries and heat‑treating facilities.
• R&D and failure‑analysis groups needing reliable total carbon measurement by combustion/IR.
• Instrument manufacturers and calibration laboratories that supply or validate induction furnace–IR carbon analysers. Practical uses include process control, material certification, compliance testing and verification of alloy composition.

Related standards

• ISO 14284 - Sampling and preparation of samples for chemical composition analysis.
• ISO 648 / ISO 1042 - Laboratory glassware requirements.
• Annexes in ISO 9556:2025 provide precision data (A, B) and equipment features (C).

Keywords: ISO 9556:2025, total carbon content, infrared absorption method, induction furnace, steel and iron, carbon analysis, combustion analysis, calibration curve, precision data.