ISO 25239-4:2020

Overview

ISO 25239-4:2020 - "Friction stir welding - Aluminium - Part 4: Specification and qualification of welding procedures" defines requirements for creating, specifying and qualifying welding procedures for friction stir welding (FSW) of aluminium and its alloys. It sets out how a fabricator develops a preliminary welding procedure specification (pWPS), verifies it by testing, and records the approved welding procedure (WPS/WPQR). This part excludes friction stir spot welding (covered by ISO 18785 series) and emphasizes that service or material-specific requirements may require additional testing.

Key technical topics and requirements

• Scope and terminology: Applies to aluminium and aluminium alloys; uses terms from ISO 25239‑1 and ISO/TR 25901.
• pWPS content (minimum): fabricator ID, parent material type/temper, thickness/geometry, equipment and tool identification, clamping/fixtures, joint design and sketches, joint preparation, weld details (tool motion, rotation, tilt, probe depth), welding speed and position, thermal management (preheat, post‑weld heat treatment, cooling), and post‑weld processing.
• Qualification routes:
  • Clause 5 - Qualification based on a standardized welding procedure test (when test pieces represent production geometry).
  • Clause 6 - Qualification based on a pre‑production welding test (for non‑standard geometries).
• Testing and inspection: Specifies visual, non‑destructive and destructive examination/testing per referenced standards (e.g., ISO 17637 visual testing, ISO 17639 macro/micro exam, ISO 4136 tensile, ISO 5173 bend tests, ISO 9017 fracture tests). Includes requirements for test piece shape/dimensions, specimen extraction and re‑testing.
• Process control: Supports force/position control and alternative control methods (e.g., temperature); essential variables of any control method must be documented in the pWPS.
• Range of qualification: Defines allowable ranges for material thickness, alloy families and other variables; WPQR must record acceptance levels (per ISO 25239‑5).

Practical applications - who uses it and why

• Primary users: welding engineers, fabricators, quality managers, NDT inspectors, and procurement/specification authors in industries using aluminium FSW (aerospace, marine, rail, automotive, consumer goods, food processing equipment).
• Benefits:
  • Ensures reproducible, auditable welding procedures for FSW of aluminium.
  • Reduces manufacturing risk by documenting equipment, tooling, thermal management and qualification limits.
  • Facilitates regulatory or customer compliance and consistent product quality.

Related standards

• ISO 25239 series (Parts 1–5)
• ISO 25239‑5:2020 (quality and inspection requirements)
• ISO 25239‑1 (vocabulary)
• ISO 25239‑3 (operator qualification)
• ISO 15607 (general WPS/WPQR rules)
• ISO 17637, ISO 17639, ISO 4136, ISO 5173, ISO 9017 (inspection and destructive test methods)
• ISO 18785 series (friction stir spot welding)

Keywords: ISO 25239‑4:2020, friction stir welding, FSW, aluminium welding procedures, pWPS, WPS, WPQR, welding qualification, thermal management, non‑destructive testing.