Overview
EN ISO 7539-8:2008 - "Corrosion of metals and alloys - Stress corrosion testing - Part 8: Preparation and use of specimens to evaluate weldments" provides guidance on preparing, selecting and using specimens to assess the susceptibility of weldments to stress corrosion cracking (SCC). Adopted by CEN from ISO 7539-8:2000, this part complements other ISO 7539 series documents by addressing the special metallurgical and mechanical factors introduced by welding.
Key topics and requirements
- Purpose: Procedures and recommendations for stress corrosion testing of welded specimens and considerations unique to weldments.
- Weld-specific factors to consider:
- Heat affected zone (HAZ) microstructural changes and chemical segregation.
- Non‑metallic inclusions and differences between weld metal and parent metal.
- Residual welding stresses and any stress-concentrating weld geometry.
- Need to examine welds for pre-existing defects (microcracks, lack of fusion, porosity) that could bias test results.
- Specimen types described: flat weldments, circular bead weldments, bead-on-bar, direct-tension specimens (with possible notches or pre-cracks), U‑bend specimens, and others. (Example: bead-on-bar applicable to bars ~25 mm diameter.)
- Preparation and testing guidance: recommendations on specimen preparation, possible post-weld heat treatment (test specimens should reflect the intended application condition), and characterisation of weldments (residual stress, surface condition, defects) before testing.
- Testing, assessment and reporting: outlines test procedures to be used with welded specimens, methods for assessing failures (distinguishing SCC from pre-existing defects) and required test report information.
Practical applications and users
Who uses EN ISO 7539-8:2008:
- Corrosion and materials engineers evaluating weld integrity under corrosive service conditions.
- Welding engineers and metallurgists assessing welding procedures and post‑weld treatments.
- Test laboratories performing SCC testing on welded components and weld qualifications.
- Quality assurance and inspection teams in oil & gas, petrochemical, power generation, transportation and fabrication industries.
Practical uses:
- Selecting appropriate specimen geometries and test methods to reproduce service stresses in welds.
- Identifying susceptibility of weld metal, HAZ, or parent metal to stress corrosion cracking.
- Informing weld procedure specifications, post‑weld heat treatments, and failure investigations.
Related standards
- ISO 7539 series (Parts 1–7, 9) for general SCC test methods (bent‑beam, U‑bend, tension, C‑ring, pre‑cracked, slow strain rate).
- ISO 857‑1 (welding terminology) and other welding standards referenced for consistent definitions.
Keywords: EN ISO 7539-8:2008, stress corrosion testing, weldments, specimen preparation, stress corrosion cracking, heat affected zone, residual welding stresses.