Overview
EN ISO 6306:2023 (ISO 6306:2020) – Chemical analysis of steel - Order of listing elements in steel standards – defines a standardized sequence and presentation rules for listing chemical elements in steels and most other iron‑based alloys (excluding foundry irons). Prepared by ISO/TC 17/SC 4 and adopted by CEN, this document aims to reduce confusion in specifications, improve interoperability of steel data, and support computerised handling and international standardization.
Key topics and requirements
- Scope: Applies to steels and most iron‑based alloys; foundry irons are excluded.
- Element grouping and sequence:
- Group 1 (primary order): C, Si, Mn, P, S, Cr, Ni, Mo, N - five core elements for all steels plus four important alloying elements for alloy and stainless steels.
- Group 2 (other elements): Any remaining elements determined, listed in alphabetical order by chemical symbol (typical examples: Al, As, B, Co, Cu, Nb, Pb, Sn, Ti, V, W, Zr).
- Group 3: Hydrogen (H) is reserved to the end.
- Recommended order (concise): C, Si, Mn, P, S, Cr, Ni, Mo, N; then other elements alphabetically; then H.
- Units and presentation:
- Elements (except H) reported in % mass fraction regardless of content.
- Hydrogen reported in mg/kg (mass fraction).
- Maximum values in composition tables shall be given per se (no “max.” or ≤ symbols). A table footnote must state: “Maximum values unless indicated otherwise.”
- Numeric precision: The standard fixes the number of digits to the right of the decimal for composition entries (ranges defined for values <0.010%, 0.010–0.10%, 0.10–3.00%, and >3.00%). A special rule applies to carbon in the 0.030–0.10% range.
Applications and users
Who benefits:
- Standards committees and technical authors drafting steel specifications
- Steel producers and mills preparing product data sheets
- Metallurgical and chemical analysis laboratories reporting results
- Quality managers, procurement officers and material engineers comparing grades
- Database and software developers managing steel composition records
Practical uses:
- Creating consistent chemical composition tables and datasheets
- Enabling accurate data exchange across national and international specifications
- Reducing errors when merging datasets from multiple sources and supporting automated processing
Related standards
- ISO/TR 6306:1989 (withdrawn; basis for current document)
- ASTM A751 (referenced for numerical digit conventions)
Keywords: EN ISO 6306:2023, ISO 6306, chemical analysis of steel, order of listing elements, steel chemical composition, reporting units, steel standards.
