Overview
ISO 2605-3:1985 provides an alternative statistical procedure for deriving minimum elevated‑temperature yield (or proof) stress properties for steel products used in pressure purposes when full data sets are limited. It is intended for situations where the procedures in ISO 2605‑1 and ISO 2605‑2 are difficult to meet (for example for nationally standardized steels or new alloys). The part does not define a verification test method - where verification is required it must be carried out by hot testing.
Key topics and requirements
- Purpose: Derive conservative minimum elevated‑temperature yield or proof stress values from reduced experimental data.
- Data basis: Use normalized ratios of elevated‑temperature yield to the corresponding ambient‑temperature yield from a defined set of test heats.
- Minimum data quantity: Test points should come from at least eight heats/casts, ideally contributed by multiple producers to reduce bias.
- Temperature coverage: Data should span the specified temperature range with intervals of about 50 °C, covering the whole range over which properties are required.
- Specimen representativeness: Test specimens must be representative of the thickness, section dimensions and heat‑treatment conditions for which the properties are specified.
- Statistical method: Construct a regression (“mean trend”) curve of the ratio of elevated to ambient yield values versus temperature (least‑squares fit). This mean trend is used to scale the minimum specified ambient yield.
- Derivation rule: Minimum elevated‑temperature values are obtained by factoring the mean trend by the specified minimum ambient yield and then applying a fixed reduction equal to 10% of the minimum specified ambient yield to define conservative minimums.
- Verification: This part explicitly does not prescribe a verification procedure; if verification is mandated, it must be by hot tensile testing conforming to the relevant ISO tensile test methods.
Applications and users
- Standards committees and national bodies specifying mechanical property limits for pressure-vessel steels and other steel products for pressure purposes.
- Material engineers, QA/QC personnel and manufacturers who need to establish conservative elevated temperature yield or proof stress values when full high‑temperature datasets are unavailable.
- Designers of boilers, pressure vessels and high‑temperature equipment who rely on standardized minimum properties for safety and code compliance.
- Useful for new steels, limited production runs or early stages of material qualification where hot testing data are sparse.
Related standards
- ISO 2605‑1 and ISO 2605‑2 (primary methods for deriving/verification)
- ISO/R 783 (high‑temperature tensile testing)
- ISO 6892 (room‑temperature tensile testing)
- ISO/R 831 (construction of stationary boilers)
Keywords: ISO 2605-3, elevated temperature properties, yield strength, proof stress, pressure vessels, steel products, derivation method, limited data, hot testing.