The Influence of Process Parameters on the Temperature Profile of Friction Stir Welded Aluminium Alloy 6063-T6 Pipe Butt Joint

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1 From the SelectedWorks of Azman Ismail Summer June 7, 2015 The Influence of Process Parameters on the Temperature Profile of Friction Stir Welded Aluminium Alloy 6063-T6 Pipe Butt Joint Azman Ismail Mokhtar Awang Shaiful Hisham Samsudin Available at:

2 The Influence of Process Parameters on the Temperature Profile of Friction Stir Welded Aluminium Alloy 6063-T6 Pipe Butt Joint Azman Ismail, Mokhtar Awang and Shaiful Hisham Samsudin Abstract The temperature profile of friction stir welded aluminum alloy 6063-T6 pipe joints will be investigated in this paper. A pipe with an outside diameter of 89 mm and a wall thickness of 5 mm will be used as test pipe piece for this experiment on closed butt joint configuration by utilizing a Bridgeport 2216 CNC milling machine and orbital clamping unit which is specially-designed to cater for this task and function. Several samples will be prepared with varying process parameters such as rotational speed and travel speed. A very simple tool was used with a flat shoulder and a cylindrical pin. An infra-red thermometer will be employed to assess the temperature profile of the friction stir welded pipe butt joints during the experiment. The correct selection of process parameters will lead to a better joining condition of the welded joint. Several good samples were produced by this experiment setting. Keywords Temperature profile AA6063-T6 pipe Butt joint Friction stir welding Bridgeport 2216 CNC milling machine A. Ismail (&) Universiti Kuala Lumpur Malaysian Institute of Marine Engineering Technology, Jalan Pantai Remis, Lumut, Perak, Malaysia M. Awang S.H. Samsudin Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak, Malaysia S.H. Samsudin Springer International Publishing Switzerland 2015 A. Öchsner and H. Altenbach (eds.), Mechanical and Materials Engineering of Modern Structure and Component Design, Advanced Structured Materials 70, DOI / _19 243

3 244 A. Ismail et al. 1 Introduction This solid state joining process was invented by Wayne Thomas from The Welding Institute, United Kingdom in This process is called as friction stir welding (FSW). FSW utilizes heat from friction to soften the adjoining section and then these sections are stirred together soundly as shown in Fig. 1 [1]. This welding process requires no filler metal and shielding gas, producing no arc and fumes. This FSW was initially developed to cater to the problem found in arc welding for aluminium such as distortion, shrinkage, and porosity. The implementation of FSW prevents such problems from occurring. This welding technique has been used for many applications due to lightweight construction, cost saving and environmental protection [2]. Pipe joining for FSW introduced complex challenges due to its tubular shape. Not many studies have been done for pipes instead of flat panels. Therefore, in order to run the experiment successfully, a proper fixture is vital. Several successful methods were introduced by previous studies [1, 3 6]. This will become the basic reference of the new built fixture called the orbital clamping unit (OCU). Hence, it is necessary to enable the available Bridgeport 2216 unit, a CNC milling machine, to run as a FSW unit for pipe joining. It is important to understand the temperature profile in the pipe piece as it determines the success of the joint to be made, residual stress imposed, grain size and the strength of the welds [7]. The welding parameters for a successful FSW process will be discussed and the temperature profile at the tool will be measured in this present study. Fig. 1 FSW process

4 The Influence of Process Parameters on the Temperature Experimental Setup An experimental setup is shown in Fig. 2. The pipe with an outside diameter of 89 and 5 mm wall thickness was used in this present study. The tool was made of surface-hardened high carbon steel H13 with 20 mm diameter of shoulder length, a Fig. 2 a FSW setup front view. b FSW side view

5 246 A. Ismail et al. Table 1 FSW welding parameters FSW sample Welding parameters Rotation speed (rpm) FSW# FSW# FSW# FSW# FSW# Travel speed (mm/s) Table 2 Chemical composition of AA6063-T6 pipe Element Percent present Manganese (Mn) Iron (Fe) Magnesium (Mg) Silicon (Si) Zinc (Zn) Titanium (Ti) Chromium (Cr) Copper (Cu) Aluminium (AI) Balance Table 3 Mechanical properties of AA6063-T6 pipe Property Value Proof stress 170 Min MPa Tensile strength 215 Min MPa Elongation A50 mm 6 Min % Hardness Brinell 75 HB Elongation A 8 Min % pin diameter of 5 and 3.8 mm of pin length. The tool was positioned with a 6 mm forward offset from the centerline [1, 8, 9]. The welding parameters used were shown in Table 1. The plunge depth and dwell time used were 4 mm and 30 s respectively. Chemical composition and mechanical properties are shown in Tables 2 and 3 respectively [10]. The infrared (IR) thermometer was used to measure the temperature profile at the rotating tool for further analysis. All samples were inspected based on the AWS D17.3 acceptance level [11]. 3 Results and Discussion An IR thermometer was used to measure the temperature profile of the full weld cycle. The IR thermometer was shot on the rotating tool shank. The outer surface of the aluminium pipe was too reflective therefore the tool shank was used as point of

6 The Influence of Process Parameters on the Temperature 247 Fig. 3 Temperature profile for FSW#1 3 (variation in rotation speed at constant travel speed) Temperature, o C Distance, mm FSW #1 FSW #2 FSW #3 measurement of temperature [1]. Figures 3 and 4 show the temperature profile measured for certain welding parameters, with the increment of rotation speed at constant travel speed and with the increment of travel speed at constant rotation speed, respectively. Based on the Fig. 3, the increment of rotation speed increases as the temperature generated from this friction process along the weld joint increases. Higher rotation speed generally generates higher temperatures. However, the recorded temperature profile varies due to pipe eccentricity, therefore causing a variation in contacts between the tool s shoulder and the outer pipe surface thus giving different temperature readings during the experiment. It was also dependent on the tool s offset setting from the axis of rotation. The measured temperature varies between and C. A constant temperature was not detected during the experiment. As noted, the temperature increases in variation throughout the weld cycle. This quite similar temperature pattern was observed by a previous study [1, 5, 7]. Based on the Fig. 4, the temperature is decreasing with the increment of travel speed and off course these readings differ due to the same reason as before; i.e. the pipe eccentricity which affects the friction contact between tool s shoulder and the outer pipe surface. The measured temperature is between and C. The increment of travel speed causes less time spent at a certain temperature level hence causing the reduction in generated temperatures. For both experiment settings, the variation in temperature did affect the weld surface roughness quality as shown in Fig. 5. The issues of secondary heating can be seen on both settings as shown in Figs. 2 and 3 respectively as the tool starts and stops at the same point in order to complete the weld cycle, which previously underwent heat treatment.

7 248 A. Ismail et al. Fig. 4 Temperature profile for FSW#3 5 (variation in travel speed at constant rotation speed) Temperature, o C Distance, mm FSW #3 FSW #4 FSW #5 Fig. 5 Surface roughness of FSW samples Surface roughness, µm FSW Sample Number# 4 Conclusion Based on the present study, the following conclusions can be made; 1. With the increment of rotation speed at constant travel speed, the temperature will increase, which was measured to be between and C. 2. With the increment of travel speed at constant rotation speed, the temperature will decrease, which was measured to be between and C. 3. The plowing effect can be achieved by offsetting the tool from its axis of rotation. 4. The variation in temperature did affect the weld surface quality (roughness). 5. The variation in temperature measurements for both welding parameters are due to pipe eccentricity which caused contact fluctuation in heat generation. 6. Secondary heating occurred in friction stir welded pipe joining. 7. Tool-surface contact fluctuated within an acceptable range during the weld cycle.

8 The Influence of Process Parameters on the Temperature 249 Acknowledgments The authors thank the Universiti Kuala Lumpur for providing the conference grant, (004) and the Department of Mechanical Engineering, Universiti Teknologi PETRONAS for providing the required facilities and assistances. References 1. Lammlein DH, Gibson BT, DeLapp DR et al (2010) Friction stir welding of small diameter pipe: an experimental and numerical proof of concept for automation and manufacturing. Proc Inst Mech Eng Part B: Kumar A, Fairchild DP, Macia ML et al (2011) Evaluation of economic incentives and weld properties for welding steel pipelines using friction stir welding. In: Proceedings of the international offshore polar engineering conference, pp Packer SM, Matsunaga M (2004) Friction stir welding equipment and method for joining X65 pipe. In: Proceedings of the international offshore polar engineering conference, pp Defalco J, Steel R (2009) Friction stir process now welds steel pipe. Weld J Am Weld Soc 88 (5): Gercekcioglu E, Eren T, Yildizh K et al (2005) The friction behavior on the external surface of the friction stir welding of AA6063-T6 tubes. The 5th international conference on tribology, pp Doos Qasim M, Wahab Bashar Abdul (2012) Experimental study of fricton stir welding of 6061-T6 aluminium pipe. IJMERR 1(3): Hwang Y-M, Kang Z-W, Chiou Y-C, Hsu H-H (2008) Eperimental study on temperature distributions within the workpiece during friction stir welding of aluminum alloys. Int J Mach Tool Manu 48(7 8): Ismail A, Awang M, Fawad H, Ahmad K (2013) Friction stir welding on aluminum alloy 6063 Pipe. In: Proceedings of the 7th Asia Pacific IIW international congress, pp Ismail A, Awang M (2014) Surface hardness of friction stir welded AA6063 pipe. MATEC web of conferences, vol. 13, 04025, pp Aalco Metals Ltd, Aluminium alloy 6063-T6, AWS D17.3 (2010) Specification for friction stir welding of aluminium alloys for aerospace application. American National Standard Institute