Overview
EN ISO 18785-2:2021 (ISO 18785-2:2018) - Friction stir spot welding (FSSW) - Aluminium - Part 2: Design of weld joints - specifies design requirements and provides guidelines for designing FSSW joints in aluminium and aluminium alloys. Adopted by CEN without modification, this standard focuses on ensuring welded assemblies are documented, specified and produced to meet end-use performance, safety and quality needs.
Key topics and technical requirements
- Scope and terminology
- Applies to aluminium and its alloys; uses terms defined in ISO 18785-1.
- Documentation and drawings
- Engineering drawings must define essential FSSW information and any special requirements (fracture-, durability-, mission- or safety-critical).
- Welding symbols shall follow ISO 2553.
- Essential weld information
- Typical items to specify: parent material (specification, thickness, temper), joint geometry, pre-weld surface condition (coatings, adhesives, sealants), tool plunge side, edge distance, orientation of asymmetric welds, weld finishing and post-weld heat treatment.
- Lap joint design
- Design shall consider material properties and common lap geometries (basic lap, multi‑layer lap, L‑stiffeners, hems, stakes, etc.). Tool-to-edge distances and spacing between welds must be specified on drawings and included in the WPS.
- Spot weld variables
- Size: minimum final dimensions (diameter or major/minor axes for elongated welds) recorded on drawings and verified by measurement methods specified.
- Location & orientation: controlled and shown on engineering drawings.
- Strength & quality: strength requirements included in the WPS and validated by destructive testing per ISO 18785-5; quality acceptance criteria likewise referenced to ISO 18785-5.
- Welding procedure and inspection
- Essential process controls to be covered by the qualified Welding Procedure Specification (WPS). Inspection methods and acceptance criteria are to follow ISO 18785-5; procedure qualification may reference ISO 18785-4.
Applications and users
- Practical for design and manufacturing of FSSW joints in industries using aluminium: automotive, aerospace, rail, marine, consumer goods, food-processing and structural fabrication.
- Primary users:
- Design engineers and structural engineers specifying joint geometry and load requirements
- Welding engineers preparing WPS/pWPS and qualifying procedures
- Quality/inspection personnel defining acceptance criteria and test plans
- Manufacturers and suppliers implementing FSSW on production lines
Related standards
- ISO 18785-1 - Vocabulary (terms and definitions)
- ISO 18785-4 - Procedure qualification (referenced for pWPS qualification)
- ISO 18785-5 - Quality and inspection requirements (inspection, testing and acceptance)
- ISO 2553 - Welding symbols on drawings
Keywords: friction stir spot welding, FSSW, aluminium, weld joint design, EN ISO 18785-2:2021, WPS, lap joint design, spot weld size, inspection.