Friction stir welding

A hypothetical 1,200 mm traverse at 300 mm/min and 900 rev/min takes 4.0 minutes at 3.0 revolutions/mm. Doubling both speeds keeps that ratio and cuts ideal travel to 2.0 minutes. Include plunge, dwell, withdrawal, fixturing and inspection separately. Qualify the actual heat, force, material flow and weld properties.

A rotating tool plunges and traverses along the joint, softening and mixing material in the solid state. Qualify the resulting properties in and around the joint. TWI, process overview, undated

Tool, machine and fixture form one system

TWI identifies the probe and shoulder combination as a crucial process element. The rotating tool enters under axial force; backing reacts that force and side restraint prevents the plates separating as the tool advances. Conventional tooling therefore needs more than a spindle with adequate rotational speed. Confirm axial-load capacity, rigidity, travel access and how the joint is restrained throughout the path. TWI, tool functions and design, undated

Specify the tool design and material for the actual workpiece alloy, thickness and geometry. A tool used successfully on one aluminum condition is not evidence of suitability for a higher-temperature material or an arbitrary dissimilar combination. The shoulder/probe, penetration control, rotation, travel and force conditions must be considered together. Tool wear and replacement criteria belong in the qualified production route, not only in maintenance records. TWI, tool-design guidance

Joint variants and access

TWI's lap-joint guidance emphasizes adequate restraint and notes that optimum lap-tool designs generally differ from butt-weld tools because interface movement must be controlled. A butt-weld procedure is therefore not a complete qualification for the same nominal thickness in a lap joint. TWI, lap-joint guidance, undated

The European Aluminium Automotive Manual, version 2015, describes fixed-gap bobbin tools and an adaptive variant that adjusts the gap to accommodate thickness variation. This can change the need for a conventional backing bar, but still requires a suitable component and tool-access arrangement. Do not interpret “self-reacting” as requiring no fixturing or no process loads. European Aluminium, solid-state welding chapter

A bounded research example is Threadgill and colleagues' paper presented at Thermec, August 25–29, 2009. It describes an approximately rectangular processed cross-section with a double-sided bobbin tool and nearly zero net axial force on the workpiece, contrasting it with conventional-tool geometry. These are features of the studied tool arrangement, not universal joint-strength or dimensional guarantees. TWI, original bobbin-tool paper

Thermal zones and delivered condition

TWI distinguishes the weld nugget, thermo-mechanically affected zone (TMAZ) and heat-affected zone (HAZ). The nugget experiences dynamic recrystallization; the extent and microstructure of the regions depend on material and process conditions. A nominal parent-alloy/temper designation does not assign the same properties to every region of the welded component. Identify the delivered condition and required joint-property evidence, including any ordered post-weld treatment. TWI, microstructure discussion

Do not turn a comparison with fusion welding into an absolute claim of zero distortion or full parent-metal strength. Qualify the final geometry and application requirements after release from the fixture and after any thermal, machining or finishing operations. Distinguish a strong local test coupon from the evidence needed for the complete joint configuration.

Starts, stops and defects

NASA's Introduction to Friction Stir Welding, by Bob Carter, identifies sensitivity to mismatch and gap, the exit hole of conventional FSW and lack-of-penetration concerns. It notes that some “kissing bond” conditions are difficult to detect by nondestructive examination. The same presentation describes retractable-pin and self-reacting variants. Choose the start/stop and root strategy deliberately rather than assuming a traversed tool leaves an acceptable seam everywhere. No separately verified presentation issue date is assigned here. NASA, process limitations and variants

For the drawing and process plan, identify whether entry/exit features lie on removable tabs, outside the finished boundary or within a permitted region. State root, flash, surface and local thickness requirements separately. A visually regular crown does not demonstrate internal bonding, and a single examination method should not be assumed to detect every relevant discontinuity.

Procedure qualification and production inspection

ISO 25239-4:2020, edition 2, June 2020, specifies procedure requirements for FSW of aluminium and its alloys. It excludes friction stir spot welding, which belongs to the ISO 18785 series, and notes that service, material or manufacturing requirements can demand more comprehensive testing. Keep this scope attached to the standard; it is not a generic procedure qualification for all metals. ISO, part 4 scope

ISO 25239-5:2020, also edition 2, June 2020, addresses manufacturer capability, quality and inspection requirements for aluminium FSW. It does not allocate requirements to a particular product group. Specify the governing application requirements, procedure, examination coverage and acceptance criteria rather than treating the series number as a finished-product approval. ISO, part 5 scope

Original travel and rotation example

Use the hypothetical 1,200 mm traverse, 300 mm/min travel and 900 rev/min rotation:

ideal traverse time = 1,200 / 300 = 4.0 minutes

rotations per unit travel = 900 / 300 = 3.0 revolutions/mm

At 600 mm/min and 1,800 rev/min, the ratio stays at 3.0 revolutions/mm and traverse time falls to 2.0 minutes.

Add plunge, dwell, acceleration, withdrawal, fixturing and inspection before comparing full production cycles.

Manufacturing handoff

Provide the joint drawing/model, alloy and condition of each member, thickness/fit-up envelope, access and backing restrictions, final boundary and start/stop requirements. Agree tooling, restraint and control variables, delivered condition, dimensional checks and required joint examinations/tests. Request evidence representative of the production geometry and material range. The handoff and arithmetic are original planning guidance; the applicable drawing, contract and qualified procedure establish acceptance.