Friction Stir Welding Essay

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Friction Stir welding is a new welding process developed in 1991. It is a solid state process which involves no metal melting. It takes place below the melting point of the material so there is no problem of hot defects like porosity, hot cracking, shrinkage, blow holes etc. It is a green process which doesn’t require any shielding gas or filler material with low energy consumption. It is the best technique we have today to join dissimilar materials like aluminium with copper, aluminium with zinc or two different alloys of the same material as fusion welding techniques fail to do so. So, having these many advantages it has wide range of applications in many areas like aerospace, automotive, railway and maritime industry. The
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For the shoulder, new features may consist of scrolls, knurls, ridges, grooves and concentric circles shown below in Fig.3:
For the pin, the same are round bottom cylindrical, flat bottom cylindrical, truncated cone, MX triflute, A-skew, trivex and threadless pin shown below in Fig.4:

Additional tool design consists of threaded counter flow tool, variable penetration tool etc. to tackle some problems like keyhole elimination.

Obtaining good quality of friction stir weld requires right selection of tool material as tool temperature approaches the solidus temperature of base metal. So, we have to take care of various properties of tool material like:
-elevated temperature stability
-ambient and elevated temperature strength
-wear resistance
-fracture toughness
-coefficient of thermal expansion
For example, joining of common metals like aluminium, magnesium and copper material for tool used is hot work tool steels such as H13 subsequently hardened as it has got high thermal fatigue resistance, wear resistance and toughness. In the same way, following table shows the commonly used tool materials for various base metals and thickness.

Welding parameters or process variables all together affect the result of welding process. For example, Scialpi et al. reported that the best FSW 6082Al joint was produced by a shoulder with fillet and cavity. However, the investigation by Fujii et al. showed
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