Chapter

The Hardness Variation Due to Secondary Heating in Friction Stir Welding of Small Diameter Aluminium Alloy 6063 Pipe

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Abstract

Friction stir welding (FSW) is a solid state joining process which utilizes the frictional heat of a high speed rotating tool to soften the adjoining sections and stirred/joined them together as one part without filler. In the FSW of pipe joining, a tool rotating at high speeds will start and stop at the same point in order to complete full weld cycle. The FSW of a small diameter pipe can cause secondary heating to occur at the start and stop point. Several pipe samples of 89 mm outside the diameter were prepared based on several specified welding parameters at a stationary position and completed the weld cycle. The Bridgeport 2216 CNC Milling Machine and a customised orbital clamping unit (OCU) were fully utilized for the sample’s preparation. This present study analysed the variation in hardness due to secondary heating for a small pipe diameter. The hardness varies between 18.7 HRB minimum to 33.6 HRB maximum, yielding to lower value due to this condition.

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... They have also used retractable pin tool to eliminate the exit hole at the end. Ismail et al. (2016) studied the influence of secondary heating in hardness during friction stir welding of pipes. They reported that it further softens the region near the exit hole. ...
Chapter
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Chapter
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Chapter
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Conference Paper
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The weld properties remain an area of uncertainty with respect to the effect of different speeds of friction stir welding (FSW). For this purpose, hardened steel tool of FSW was used, which consists of the shoulder and pin. The shoulder of the tool not only provides additional heat generated by friction but also prevents plasticized material to escape. In the present investigation, aluminum welds were made at various welding speed using the FSW technique. The welds were characterized for mechanical properties and microstructural investigation. It is observed that good correlation exists between the mechanical properties and welding speeds. The best mechanical properties were obtained at lower welding speed.
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Tool condition is one of the main concerns in friction stir welding (FSW), because the geometrical condition of the tool pin including size and shape is strongly connected to the microstructure and mechanical performance of the weld. Tool wear occurs during FSW, especially for welding metal matrix composites with large amounts of abrasive particles, and high melting point materials, which significantly expedite tool wear and deteriorate the mechanical performance of welds. Tools with different pin-wear levels are used to weld 6061 Al alloy, while acoustic emission (AE) sensing, metallographic sectioning, and tensile testing are employed to evaluate the weld quality in various tool wear conditions. Structural characterization shows that the tool wear interferes with the weld quality and accounts for the formation of voids in the nugget zone. Tensile test analysis of samples verifies that both the ultimate tensile strength and the yield strength are adversely affected by the formation of voids in the nugget due to the tool wear. The failure location during tensile test clearly depends on the state of the tool wear, which led to the analysis of the relationships between the structure of the nugget and tool wear. AE signatures recorded during welding reveal that the AE hits concentrate on the higher amplitudes with increasing tool wear. The results show that the AE sensing provides a potentially effective method for the on-line monitoring of tool wear.
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Friction stir welding (FSW), like other friction welding techniques, has the advantage that many of the welding parameters, e.g. tool design, rotation speed and translation speed, can be controlled in a precise manner, thus controlling the energy input into the system. However, the effect of different welding speeds on the weld properties remains an area of uncertainty. In this paper, we report the results of microstructural, mechanical property and residual stress investigations of four aluminium AA5083 friction stir welds produced under varying conditions. It was found that the weld properties were dominated by the thermal input rather than the mechanical deformation by the tool.
The friction behavior on the external surface of the friction stir welding of AA6063-T6 tubes
  • E Gercekcioglu
  • T Eren
  • K Yildizh