Overview - EN ISO 18785-4:2021 (FSSW aluminium)
EN ISO 18785-4:2021 (ISO 18785-4:2018) specifies the required content and qualification procedures for welding procedure specifications (WPS/pWPS) for Friction Stir Spot Welding (FSSW) of aluminium and aluminium alloys. It is part of the ISO 18785 series and was adopted by CEN to provide harmonized guidance for developing, documenting and proving welding procedures for FSSW joints.
Key topics and technical requirements
This part focuses on the practical elements needed to create and qualify FSSW procedures. Major topics include:
- Content of a pWPS / WPS - mandatory technical items such as:
- manufacturer and production information
- composition and identification of parent material (aluminium and alloys)
- material dimensions and stack-up
- specified welding method and FSSW variant
- machine specifications and tool identification
- clamping systems and process conditions
- joint design, preparation and cleaning methods
- welding technique parameters and post‑weld processing
- Development and qualification of welding procedures - methods for producing and documenting a qualified procedure
- Qualification by welding procedure test - use of standardized test pieces, subscale components or actual components to validate the WPS
- Examination and testing - visual inspection, destructive testing, macrosectioning and re‑testing rules
- Range of qualification - how qualifications apply across manufacturers, materials, tooling and other variables
- Pre‑production qualification and welding procedure qualification records (WPQR/WQPR) - record forms and example WPS formats (informative annexes)
Practical applications
EN ISO 18785-4:2021 is used to ensure repeatable, controlled FSSW processes for aluminium assemblies in industries where spot-like solid-state joining is advantageous:
- Automotive body and structural components
- Aerospace and defence subassemblies
- Railway car structures
- Marine and shipbuilding panels
- Consumer goods and food‑processing equipment
Using this standard helps reduce welding defects, improve joint performance, and provide auditable procedure documentation for production and procurement.
Who should use this standard
- Welding engineers and procedure developers
- Quality and production managers in OEMs and suppliers
- Welding inspectors and test laboratories
- Certification bodies and technical purchasers involved in aluminium FSSW
Related standards
- Other parts of the ISO 18785 series (see ISO for the full set)
- National/adopted versions (EN ISO 18785-4:2021) published by CEN members
Keywords: EN ISO 18785-4:2021, Friction stir spot welding, FSSW aluminium, welding procedure specification, welding procedure qualification, aluminium alloys, welding standards.