Overview
ISO 22826:2005 - "Destructive tests on welds in metallic materials - Hardness testing of narrow joints welded by laser and electron beam (Vickers and Knoop hardness tests)" - specifies microhardness testing procedures for transverse sections of narrow laser and electron‑beam welded joints. The standard covers both Vickers and Knoop microhardness methods (referencing ISO 6507‑1 and ISO 4545) with test forces from 0.098 N up to just under 98 N (HV 0.01 to just under HV 10) for Vickers and up to 9.8 N (just under HK 1) for Knoop. It applies to welds made with or without filler wire and is intended for narrow joint profiles (may not apply to wider hybrid laser/arc welds).
Key topics and requirements
- Scope of testing: Hardness profiling across weld metal, heat‑affected zone (HAZ) and unaffected parent metal on transverse sections.
- Test methods: Microhardness tests using Vickers (HV) and Knoop (HK) procedures in accordance with the referenced ISO hardness standards.
- Test forces: Defined nominal test forces corresponding to microhardness scales (HV 0.01…HV 10 and HK up to HK 1).
- Specimen preparation: Mechanical sectioning transverse to the weld and surface preparation/etching without thermal alteration; etching guidance referenced (ISO/TR 16060).
- Test locations: Indentations placed in weld centre, upper/lower or left/right weld regions, HAZ along the fusion line, and thermally unaffected parent metal; layouts defined as type E (individual indentations) and type R (rows of indentations).
- Positioning and spacing: Minimum distances from edges and between indentations depend on material hardenability, indentation diagonal length and selected test force; distances (L, W, M) are specified.
- Test conditions: Preferable ambient testing temperature (23 ± 5 °C) and vibration‑free environment for microhardness accuracy.
- Reporting: Test type, locations, forces, measured hardness values and specimen details must be recorded.
Applications and who uses it
ISO 22826 is used for quality control, failure analysis and materials characterization of narrow, high‑energy welds produced by laser or electron beam welding. Typical users:
- Welding inspectors and NDT laboratories performing destructive weld testing
- Materials and metallurgical engineers assessing HAZ hardening or softening
- Automotive, aerospace and precision‑manufacturing R&D and production quality teams using laser/e‑beam welding
- Certification bodies and application standards that require hardness mapping of narrow joints
Practical uses include verifying weld integrity, identifying hardened or softened zones, supporting process qualification, and correlating hardness profiles with mechanical performance.
Related standards
Keywords: ISO 22826:2005, hardness testing, Vickers hardness, Knoop hardness, laser welded joints, electron beam welded joints, microhardness, weld HAZ, weld testing.