Back

Advantages of Friction Stir Welding (FSW)

Friction stir welding was invented in 1992 by The Welding Institute, and the patent fell into the public domain in 2015. Therefore, this process represents both a recent progress for manufacturers in the aluminium industry, but also and above all an advantageous technique for the assembly of parts from a few centimeters to several meters long.


SBB’s machine shop has the necessary equipment to perform FSW, as well as final machining in one single machine. We work with our clients not only to assess the feasibility of their projects, but also to allow them benefit from the advantages of this new mode of production.

 

Principle

To summarize the principle of operation, this welding consists in making a junction between two components in the solid state, by jointly applying an intense pressure and friction at the point of contact between two adjacent surfaces. The rotary movement of the specific tool used to do this, creates a heating which “plasticizes” the material in the welding axis, to finally mix the interfaces. The heat is however particularly controlled and relatively well defined in the weld area. Indeed, during welding, the melting temperature of the welded metal is not reached, but remains 60-80% compared to the melting point.

 

Friction Stir Welding / FSW : an innovative aluminium technology but for which advantages ?

Without fusion or adding material, the technique significantly reduces the loss of strength, as well as the phenomena of withdrawal and distortion: little deformation of the material, even for long lengths. Since the welds are made in the solid state and at a low temperature, there is no solidification phase so no cracking possible. Unlike fusion welds which may eventually require a heat treatment after welding to increase the strength of the parts, this treatment is optional in FSW for the 2000, 6000 and 7000 series.

If SBB has chosen to invest in this innovative aluminium welding system and this new equipment, it is because not only this represents an excellent potential for automation and productivity gains, but it also holds many advantages for its customers:

 

  • Improved reliability and repeatability, once welding parameters have been defined
  • Fast process in one pass
  • High resistance and sealing of the weld, absence of porosities, inclusions, cavities or blisters
  • Aesthetic outcome due to the regularity of movement and the flatness of the weld which does not require machining or cleaning. Finally, the finishing of the back of the joint is quite acceptable and its reprocessing is optional.
  • Ultimately, the mechanical properties of the assemblies are improved: traction, fatigue, tension, bending.
  • With such a high quality and clean finish, the visual inspection phase is also accelerated.

 

FSW friction stir welding therefore makes it possible to maintain properties close to the initial material.

As a result, the dimensions of the parts before assembly are almost identical to the post-assembly dimensions: they simply add up. This improves the ability to predict the measurements of the final part : a significant asset when it needs to line up perfectly with other parts, slide or fit into an assembly to form the final product.

 

Soudure-FSW.JPG    brochure1.png

 

Increased safety for employees and a greener process

The method provides employees with a safer work environment as it is free from radiation, molten spatter, dust and toxic fumes that usually accompany arc or fusion welding (including GMAW, GTAW, SMAW). No chemicals are needed to accompany welding. We can accordingly describe the production as "clean". Shielding gas is also no longer necessary, which eliminates all the problems associated with its use and storage.

Technicians simply need safety glasses to approach and monitor their machine. Even the heat - limited - does not cause discomfort and an aluminium part can be grasped with the hands soon after its manufacture.

Not to forget the silent aspect of this process which constitutes another benefit for the factory teams!

 

New and multiple possibilities, especially in the transport sector

This process allows to efficiently weld high strength extrusion aluminium, such as 2000, 6000 and 7000 series aluminium alloys. These are difficult to weld by conventional fusion because of their sensitivity to solidification cracking, and the degradation of their mechanical properties due to heat.

FSW is also very suitable for sheet metal (3000, 5000) and casting (A356) aluminium. Finally, it is used in the context of assemblies of dissimilar materials, such as aluminium & copper or aluminium & steel.

SBB can thus meet a wide set of high-quality welding needs, for various uses:

  • Welding of extrusions
  • Welding of molded parts
  • Welding of parts made of materials non weldable by fusion, up to 12mm thick

 

Since the final products gain in lightness compared to conventional welding (especially alloys 2000, 6000 and 7000), some sectors, where weight is a challenge, pay particular attention to all these manufacturing qualities, including the transport sector: rail, automobile, shipbuilding , aeronautics or aerospace… but also energy or defense.

Indeed, FSW Friction Stir Welding is an excellent alternative to riveting and bolting. Typically, in aeronautics, the high strength aluminium alloys used for the fuselage are not weldable by conventional welding. That’s why thousands, even millions of rivets are used on planes. However, FSW can efficiently weld these alloys and eliminate a large part of the rivets (up to 60%), which results in significant weight savings.

The use of rivets also reduces the integrity of the parts: the holes create places prone to degradation and corrosion. FSW eliminates this problem, and thus increases the life of the parts concerned, which can be proved valuable on a bridge or in shipbuilding for instance.

P1290981-V2.jpg     P1300026-V3.jpg

SpaceX quickly understood all the value of this technology and is already using it in the manufacture of aluminium tanks for its Falcon 9 rocket. These elements are suffering from considerable pressure, so thanks to stronger FSW welds, it not only allows to thin the walls, but also ensures their perfect seal while reducing the overall weight of the rocket. Tesla and Honda are using FSW for the battery boxes of their electric cars. BRP, Bombardier's Recreational Products Division, applies FSW to Skidoo radiators.

We also find the use of this process to weld panels used for the superstructure of ships, hollow sections and extrusions for the manufacture of high speed trains, automobile frames, etc ...

Last example: Copper bars that carry electricity need to be glued to an aluminium part to properly expel heat. This junction is usually done by gluing one piece to the other. The FSW allows to merge the 2 materials to obtain an optimal thermal transfer.

 

To sum up, the top 10 advantages of FSW, friction stir welding, are:

  1. A high welding speed
  2. No filler material
  3. Superior mechanical properties: weld with improved strength, resistance, sealing and durability
  4. Less distortions, and therefore better controlled final dimensions
  5. Final weight assembly reduced
  6. An aesthetic weld
  7. An increased lifespan of the products concerned
  8. A process suitable for aluminium alloys, sheet metal and foundry aluminium and for dissimilar materials
  9. Greener production
  10. A safer workplace

 

SBB was one of the pioneers to use FSW Friction Stir Welding technology since 2015 in Quebec

For the record, it was at this time that the company entered into a partnership with the Quebec University in Chicoutimi (UQAC). It was not a question of carrying out tests to design prototypes, but of starting a concrete production of large, complex parts with several stages of manufacture. Intended to compose the roofs of light rail wagons made by Alstom, these oversized structures have forged SBB's FSW experience.

Consult our Customer Cases to find out more

This order galvanized the avant-garde spirit of our engineering and machining teams, who were deeply involved in mastering this latest generation of welding.

To this were added fruitful participations in forums organized by the main market players, who supported SBB's interest and commitment to this innovation: AluQuébecCQRDA (Quebec Center for Aluminium Research and Development), Alcoa InnovationCMQ (Quebec Metallurgy Center) and RTMQ (Quebec Metal Transformation Network).

Now since 2019, this tool has been installed on one of our CNC machining centers in our Blainville factory. Many steps have forged our experience, and we are happy to have successfully completed them to internalize these tool and skill which open up new manufacturing perspectives.

 

For all your projects requiring innovative welding and high performance results, both in prototyping and manufacturing, our Production and Engineering departments are available for discussion.

Contact us