ISO 25239-1:2020

Overview

ISO 25239-1:2020 (Friction stir welding - Aluminium - Part 1: Vocabulary) provides a standardized set of definitions covering friction stir welding (FSW) of aluminium and its alloys. Prepared in collaboration with IIW and CEN, this second edition revises and expands the terminology used to describe tools, process phases, joint features and quality-related imperfections. The document supports consistent communication across design, manufacturing, inspection and procurement activities in industries using FSW.

Why this matters: a common vocabulary reduces ambiguity in welding procedure specifications (WPS), operator training, production testing and quality assurance for aluminium FSW applications.

Key Topics

The standard defines terms and illustrations for many core FSW concepts, including:

• Tool and probe features: tool, probe, shoulder, adjustable tool probe, fixed probe, bobbin tool, stationary shoulder tool
• Process phases and controls: plunge phase, dwell time (start/end), travel, axial force, rotation speed, position control, force control, temperature control
• Weld zone features: stirred zone, weld face, faying surface, heel, heel plunge depth, tilt angle (typical 0° to 5°), side tilt angle, lateral offset
• Defects and remnant features: root flaw, toe flash, underfill, hook, joint area deformation, exit hole, weld overlap area
• Personnel and equipment: operator, welding operator, single spindle, multiple spindles, welding procedure specification (WPS)

The document references ISO/TR 25901 (vocabulary for welding and allied processes) and lists related parts of ISO 25239 for full process and qualification guidance.

Applications

ISO 25239-1:2020 is practical for:

• Engineers and designers specifying FSW joints in aluminium structures
• Welding procedure developers and WPS authors who require consistent term usage
• Training programs for welding operators and production staff
• Quality and inspection teams preparing acceptance criteria and non-destructive testing plans
• Procurement and contractual documents to ensure unambiguous requirements

Typical commercial applications where this vocabulary is applied include railway carriages, consumer products, food processing equipment, aerospace structures and marine vessels.

Related Standards

Key references and related standards cited in ISO 25239-1:2020:

• ISO/TR 25901 (all parts) - Vocabulary for welding and allied processes
• Other parts of ISO 25239 - series covering procedure qualification, operator qualification and specific FSW requirements for aluminium
• ISO 17659 and ISO 17637 - related terminology and visual testing guidance

Adopting ISO 25239-1:2020 ensures clarity across documentation and operations, enabling consistent implementation of FSW for aluminium and supporting interoperable quality management across suppliers and manufacturers.