Overview
CEN ISO/TR 17641-3:2005 - "Destructive tests on welds in metallic materials - Hot cracking tests for weldments - Arc welding processes - Part 3: Externally loaded tests" (ISO/TR 17641-3:2005) defines methods and procedures for externally loaded laboratory tests used to assess hot cracking susceptibility in welds and weldments. The report focuses on arc welding processes and gives practical test descriptions (hot tensile, Varestraint/Transvarestraint and flat tensile/PVR tests), assessment criteria and specimen requirements. It is primarily aimed at austenitic stainless steels, nickel and nickel‑base alloys and nickel‑copper alloys, with principles extendable to aluminium alloys and high‑strength steels by agreement.
Key Topics
- Externally loaded hot cracking tests: These tests impose controlled strain/strain rates during the brittle temperature range (BTR) to reproduce aspects of welding solidification, liquation and ductility‑dip cracking.
- Tests described:
- Hot tensile test - simulates welding thermal cycles using cylindrical specimens; Procedure A for solidification cracking (130 mm × 10 mm) and Procedure B for liquation/NST determination (110 mm × 6 mm).
- Varestraint and Transvarestraint tests - apply bending/strain to a heated weld or TIG melt run to provoke solidification or liquation cracks; useful for weld metal and HAZ assessment.
- Flat tensile / Programmable Deformation Cracking (PVR) test - measures critical strain (Vcrit) for first hot crack; suited to multipass weldments and welding procedure evaluation.
- Assessment metrics: Brittle Temperature Range (BTR), Nil Strength Temperature (NST), Ductility Recovery Temperature (DRT), critical strain (Vcrit), total crack length (Ltot) and related ratios.
- Test conditions and instrumentation: use of protective Argon atmosphere (oxygen ≤ 0.1 %) to limit oxidation, thermocouple measurement (Pt‑PtRh), controlled heating/cooling rates and defined loading rigs.
- Limitations: Tests provide quantitative ranking and reproducible within a laboratory, but do not exactly reproduce all field welding conditions; inter‑laboratory reproducibility can vary.
Applications and Users
- Used for material selection and qualification, weld metal and welding consumable evaluation, development and qualification of welding procedures, failure investigation and R&D on weldability.
- Typical users: welding engineers, materials scientists, quality control and testing laboratories, fabricators in petrochemical, power generation, aerospace and shipbuilding sectors, and standards bodies.
Related Standards
- EN ISO 17641-1:2004 - Destructive tests on welds - Hot cracking tests for weldments - Part 1: General (normative reference).
- Other parts of the ISO/TR 17641 series (general guidance and complementary test methods) are relevant when designing a full hot‑cracking assessment program.
Keywords: hot cracking tests, Varestraint, Transvarestraint, hot tensile test, flat tensile test, brittle temperature range (BTR), NST, weldability, arc welding processes.