Friction stir welding - SIAD Società Italiana Acetilene e Derivati
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Friction Stir Welding
Friction Stir Welding is a process which exploits the concept of heat being created through friction to weld ferrous and non-ferrous alloys. Welding takes place as a continuous process and uses the partial immersion of a tool in rotation between the opposite faces of the joint. The relative motion between the tool and the layer below generates heat through friction and creates a plasticized area around the partial immersion of the tool. The tool moves along the joint line forcing the plasticized material to fuse so much so that welding takes place in a solid state.
Friction Stir Welding:
- Is not a process involving the melting of metal (therefore it does not bring with it all the defects and problems inherent in using high quantities of heat such as shrinkage, deformation, etc).
- Is not restricted to the chemical composition of the interface of the base materials.
- Does not require a filler metal, which is a reason for its choice and accreditation.
- There is no excess metal in the joints, meaning nil incision between the surfaces of the two strips, which is equivalent to an increased resistance to fatigue.
- Thicknesses up to 30 mm can be welded in a single pass.
- Works at greatly reduced temperatures, when compared to other types of welding; therefore there are not the chemical reactions of alloys with some gases which could compromise the structure.
A recently invented process, it is not yet widely used but already, today, is being experimented with in a number of sectors, amongst which:
- Aeronautics and aerospace
- Generic carpentry
- Domestic appliances
- Technical furniture
The importance of gases
Gases do not play a fundamental role in this process. For some metals no gases are used at all whilst, for others, which are susceptible to defects even at average temperatures, inert gas flows are used. Nitrogen or Argon prevent contamination of the area being worked on from atmospheric air which can result in micro defects.