Overview
ISO 2566-1:2021 - Steel: Conversion of elongation values (Part 1: Carbon and low-alloy steels) defines a standardized method to convert room-temperature percentage elongation after fracture measured on one gauge length to an equivalent value on another gauge length. Conversions are based on the well‑known Oliver formula and use the internationally preferred proportional gauge length of 56.5√S (S = cross‑sectional area). The document includes conversion formulae, tables and figures for common proportional and fixed (non‑proportional) gauge lengths.
Keywords: ISO 2566-1:2021, elongation conversion, steel elongation, gauge length, carbon and low-alloy steels, tensile testing, conversion factors.
Key topics and technical requirements
- Scope: Applies to carbon, carbon‑manganese, molybdenum and chromium‑molybdenum steels with tensile strength 300–700 N/mm² in hot‑rolled, normalized or annealed conditions (with or without tempering).
- Formula basis: Conversions use the Oliver formula (presented as Formula (1) and converted version relative to 56.5√S as Formula (2)).
- Gauge lengths covered:
- Proportional gauge lengths (e.g., 4√S, 5.65√S, 8.16√S, 11.3√S; 56.5√S is preferred).
- Non‑proportional (fixed) gauge lengths: 50 mm, 80 mm, 100 mm, 200 mm.
- Tables and figures: Precomputed conversion factors and actual conversion tables (Tables 1–21, Figures 1–5) enable practical conversions.
- Limitations and exclusions:
- Not applicable to cold‑reduced steels, quenched & tempered steels, or austenitic steels.
- Not applicable when gauge length exceeds 25√S or when width/thickness ratio > 20.
- For strip thickness under 4 mm, the formula index may change and conversion values require agreement between customer and supplier.
- Use for acceptance: Conversions are for acceptance by agreement; in disputes, testing shall be performed on the gauge length specified in the relevant specification.
Practical applications - who uses this standard
- Quality and metallurgical engineers converting tensile test results between labs or specifications.
- Test laboratories and inspection bodies standardizing reported percent elongation values.
- Steel producers, suppliers and purchasers reconciling contract requirements specified on different gauge lengths.
- R&D teams comparing mechanical data from components or samples with differing cross sections and gauge lengths.
Practical workflows covered include converting between proportional gauge lengths (simple multipliers), converting fixed gauge lengths for equal or different cross‑sections, and two‑stage conversions via 56.5√S for complex cases.
Related standards and notes
- ISO 2566 is a multi‑part series - consult other parts for additional materials or conditions.
- Use conversion factors and figures within the stated material and geometric limits; ensure customer/supplier agreement where conversions affect acceptance decisions.
For accurate implementation, refer to the full ISO 2566-1:2021 text for tables, figures and exact formulae.
