# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DaLOsnVgTuQ
- **Gondola URL:** https://gondola.cc/posts/67391864-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/358b897dee.jpg
- **Posted:** 2026-06-29T15:52:13.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Most welding starts by melting metal. Friction stir welding never does — and that single fact is why it joins alloys that conventional fusion welding tears apart.

Invented at The Welding Institute in Cambridge in 1991 by Wayne Thomas, FSW uses a rotating, non-consumable tool with a profiled pin and a broader shoulder. The pin plunges into the seam between two clamped plates while the shoulder rides on the surface. Rotation generates frictional and adiabatic heating that drives the material to roughly 0.8 of its absolute melting temperature — hot enough to go plastic, never hot enough to liquefy. The tool then traverses the joint, and the softened metal flows around the pin from the leading to the trailing edge, where it is forged together under the shoulder’s pressure.

Because nothing melts, the defects that plague fusion welds simply don’t appear:

- No solidification cracking, porosity, or hydrogen embrittlement
- No filler metal, shielding gas, or fume
- Minimal distortion, since heat input stays low and localised
- Joint strengths reaching 70-90% of the parent material

This is why FSW became the enabling technology for aerospace aluminium. Alloys like 2024 and 7075 are nearly unweldable by arc methods, yet they form the spines of rockets. The SpaceX Falcon tanks, NASA’s SLS core stage, and the Orion crew module all rely on friction stir seams. Eclipse Aviation friction stir welded an entire business jet fuselage.

The signature of a good weld is the onion-ring pattern in cross-section — concentric bands marking each rotation of material deposited per advance. Read those rings and you read the thermomechanical history of the joint.

Sometimes the strongest bond is the one that never quite melts.

#stemantics #materialscience #welding #aerospace #engineering

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## Tags

welding, engineering, materialscience, stemantics, aerospace

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