Overview
EN ISO 14271:2017 - "Resistance welding - Vickers hardness testing (low‑force and microhardness) of resistance spot, projection, and seam welds" (ISO 14271:2017) is a CEN‑adopted international standard that defines procedures for Vickers hardness testing on etched cross‑sections of resistance welds. The standard covers low‑force and microhardness Vickers tests to determine hardness in the weld nugget, heat affected zone (HAZ), and parent material for ferrous and non‑ferrous sheets with thicknesses from 0.5 mm to 6 mm.
Key topics and requirements
- Scope and purpose: Specifies methods to obtain Vickers hardness (HV) in the low‑force and microhardness ranges for resistance spot, projection, and seam welds.
- Applied test forces:
- Low‑force Vickers: 1.961 N or 9.807 N
- Vickers microhardness: 0.9807 N
- (Note: forces align with ISO 6507 conventions when specified.)
- Test pieces & sectioning:
- Cross‑sections must pass through the weld nugget; sheet thickness and sectioning orientation depend on the electrode indentation shape (circular or elongated).
- Test piece thickness shall be at least 1.5 × the diagonal length of the hardness indentation.
- Surface preparation:
- Etched cross‑sections are required; for microhardness, the weld structure must be revealed to detect local variations.
- Hardness traverse locations:
- Recommended traverses: vertical + horizontal traverses or an oblique traverse.
- Horizontal traverse position: within t/4 to t/2 from the faying surface (t = plate thickness).
- Vertical traverse should be at or near the centre of the weld nugget to avoid shrinkage cavities.
- Equipment & calibration:
- Testing procedure and machine verification/calibration follow ISO 6507‑1, ‑2 and ‑3.
Applications and users
- Typical users: welding engineers, metallurgists, QA/QC laboratories, failure‑analysis teams, OEMs in automotive, aerospace, appliance and general manufacturing.
- Practical uses:
- Verify weld quality and consistency across production.
- Characterize hardness in the weld nugget, HAZ and parent metal for material qualification.
- Detect local hardness variations (microhardness) related to process parameters, post‑weld heat treatment, or material changes.
- Support root‑cause analysis of weld‑related failures and development of welding procedures.
Related standards
Keywords: EN ISO 14271:2017, Vickers hardness, microhardness, resistance welding, spot weld, projection weld, seam weld, heat affected zone, weld nugget, ISO 6507.