Experimentally Study the Effect of Tool Pin Profile on Weld Strength of Friction Stir Welded Aluminium 6063 Pipe

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Experimentally Study the Effect of Tool Pin Profile on Weld Strength of Friction Stir Welded Aluminium 6063 Pipe

S. M. Senthil1 | T. Pradheep2

1Assistant professor, Department of Mechanical Engineering, Kongu Engineering College, Erode

2 P.G Scholar, Department of Mechanical Engineering, Kongu Engineering College, Erode.

Abstract :- Friction stir welding (FSW) is a solid state material joining process in which the material that is being welded does not melt or recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. Compared to the fusion welding processes FSW is routinely used for joining structural aluminium alloys. Because aluminium alloy has gathered wide acceptance in the fabrication of light weight structures which requiring a high strength to weight ratio. In FSW welding parameters (rotating speed, axial load, and welding speed) and tool pin profile play major roles in deciding weld quality. In this investigation, an attempt has been made to understand the effect of tool pin profile on FSP zone formation in aluminium 6063 pipe. Two different tool pin profiles (hexagon and square) have been used to fabricate the joints. The effect of tool pin geometry on mechanical properties is investigated.

Keywords: Friction stir welding; Tool pin profile; Tensile properties

  1. INTRODUCTION

    Friction stir welding is an solid state joining process that uses heat and pressure energy to join the materials. In this a cylindrical shouldered tool with a profiled pin is rotated and plunged into the joint area between two pieces of sheet or plate material. Frictional heat between the wear resistant welding tool and the work pieces causes the latter to soften without reaching melting point. It always made a fine grain microstructure due to recrystallization arising during the process. Many experimental studies on the mechanical and micro structural properties of friction stir welding of aluminium plates have been published, but there are only few papers about aluminium pipe welding.

    Qasim et al., (2012). Investigate the friction characteristics of AA6061-T6 pipes welded by friction stir welding method. In this, the effect of welding speed, rotational speeds on FSP zone are investigated.

    Kourshid et al., (2013). Investigate the effect of rotational speed on the outer surface of friction stir welding of AA6063 aluminium pipe. They resulted if stirrers speed is increased, plastic deformation of pipes also increased.

    This paper will focus on the tool pin effects on the mechanical properties of the welded joints of friction stir welded AA 6063 pipe.

  2. EXPERIMENTAL SETUP

    Table 1: Chemical Composition (wt %) of 6063 Al

    Weight

    %

    Ai

    Si

    Fe

    Cu

    Mn

    Mg

    Cr

    Zn

    Ti

    Other each

    Each total

    6063

    Bal

    0.20-

    0.6

    0.35

    0.10

    0.10

    0.45-

    0.90

    0.10

    0.10

    0.10

    0.05

    0.15

    The material used in this study (AA6063) was received from kovai metal mart. Table 1 and 2 shows the chemical composition and mechanical properties of AA6063 pipe. A conventional vertical milling machine was used for this welding process. FSW tool is fixed on the rotating spindle head in the milling machine which moves in an up & down (linear) motion. So for circular feed a rotating clamping fixture is used to clamp the two pieces of pipe together for joining.

    Figure 2: Internal mandrel

    An external mandrel is used to support the pipes from bending, due to axial load applied during the process.

    Figure 1: FSW setup

    A special type of mandrel is used in this process. It will hold the pipe in both ends and also at the centre it supports the pipe to prevent from pouring down of the material during the process.

    Figure 2: External mandrel

    Table 2: Mechanical Properties of AA6063 alloy

    Proof stress Mpa

    Tensile strength Mpa

    Shear strength Mpa

    Elongation %

    Hardness Vickers HV

    50 min

    131

    70

    27

    25

  3. TOOL CONSIDERATIONS

    In FSW, the tool consists of two main parts (shoulder and pin) to create heat and pressure on the weld. Because contact of the pin with the work piece generates frictional, deformational heating and crucial role on material flow, contact of the shoulder with the outer surface of the work piece creates additional heating,

    expand the welding area and holding the deformed material. So that tool is an important part in the friction stir welding. Therefore, tool should have the following characteristics,

    • Good wear resistance,

    • High temperature strength,

    • Coefficient of thermal expansion,

    For welding tool high carbon steel is used for friction stir welding.

    Tensile tests were performed according to ASTM E8M-04. Tensile samples were prepared for each weld and tests were conducted by using universal testing machine. Macro tests were prepared based on ASTM E340. The optical micro scope was used during the micro structural analysis.

    Figure 3: FSW tool

    Figure 4: Weld flash

  4. RESULTS AND DISCUSSION

    Visual inspection

    During the welding process welds were visually inspected. Initially at the start of the weld root gap between the pipe should be minimum, because the bond cannot taken place well. The outer surface of the weld depends on the welding parameters selected.

    Tensile tests were conducted for all three joints produced by friction stir welding. The test results were compared based on the ultimate tensile strength of the weld produced by each pin profile.

    Table 3: Welding Parameters

    Pin profile

    Square, hexagon

    Pin length

    4.7 mm

    Shoulder diameter

    15 mm

    Rotational speed

    1600 rpm

    Welding speed

    0.75 mm/sec

    Table 3: Welding Parameters

    Pin profile

    Square, hexagon

    Pin length

    4.7 mm

    Shoulder diameter

    15 mm

    Rotational speed

    1600 rpm

    Welding speed

    0.75 mm/sec

    Figure 5: tensile strength for square pin

    Figure 6: Tensile strength for hexagon pin

    The test shows that in FSW, the property of the weld joint depends on the working parameters. The important parameter is tool pin profile because it plays a crucial role on material flow and heat generation.

  5. DISCUSSIONS

    The visual inspection and tensile tests are shows that welded workpiece having blow holes. So that mechanical strength in all three welded pieces having lower value than the base material. Reasons behind is, here we using a flat shoulder tool for rounded work pieces so it doesnt contact fully with work piece srface. So stirred materials are moving away from the welded zone and also because of the less contact heat produce by the tool is less.

    Comparing the results produced by these two pins, in which square pin gives better strength. Reason behind is, square pin having lower circumferential area so area of the HAZ is less. In welding components HAZ is the weakest part in a material. so that the square pin gives better mechanical strength comparing with hexagon pin.

  6. CONCLUSIONS

From the results several conclusions are made, Rotational speed of 1600 rpm and welding speed of 0.75 mm/sec gives better weld surface.

The comparative evaluation of the results produced by the friction stir welding of 6063 aluminium alloy the square and hexagon tools reveal that the square pin gives better mechanical strength.

REFERENCES

  1. K. Kumar, Satish V. Kailas, (2008). On the role of axial load and the effect of interface position on the tensile strength of a friction stir welded aluminum alloy Materials and Design 29: 791797.

  2. K. Elangovan, V. Balasubramanian, (2008). Influences of tool pin profile and tool shoulder diameter on the formation of friction stir processing zone in AA6061 aluminum alloy Materials and Design 29: 362373.

  3. K. Elangovan, V. Balasubramanian, (2008). Influences of tool pin profile and welding speed on the formation of friction stir processing zone in AA2219 aluminum alloy journal of materials processing technology 200: 163175.

  4. K. Elangovan, V. Balasubramanian, (2007). Influences of pin profile and rotating speed on the formation of friction stir processing zone in AA2219 aluminum alloy Materials Science and Engineering A 459: 7-18.

  5. Deepak Chouhan, Surjya K Pal, Sandeep Garg, (2013). Experimental Study on the Effect of Welding Parameters and Tool Pin Profiles on Mechanical Properties of the FSW Joints Journal of Engineering Research and Applications www.ijera.com ISSN: 2248- 9622, Vol. 3, Issue 5.

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  7. H. K. Mohanty, M. M. Mahapatra, P. Kumar1, P. Biswas and N. R. Mandal, (2012) Effect of Tool Shoulder and Pin Probe Profiles on Friction Stirred Aluminum Welds a Comparative Study J. Marine Sci. Appl. (2012) 11: 200-207

  8. Qasim M Doos and Bashar Abdul Wahab, (2012) Experimental study of friction stir welding of 6061-t6 aluminum pipe International journal of Mechanical Engineering and Robotics Research ISSN 2278 0149.

  9. A M Khourshid and I Sabry, (2013) Friction stir welding study on aluminum pipe International journal of Mechanical Engineering and Robotics Research ISSN 2278 0149.

  10. Azman Ismail, Mokhtar Awang, Hasan Fawad and Kamal Ahmad, (2013) Friction Stir Welding on Aluminum Alloy 6063 Pipe Proceedings of the 7th Asia Pacific IIW International Congress.

  11. Yan-hua ZhaoT, San-bao Lin, Lin Wu, Fu-xing Qu, (2005). The influence of pin geometry on bonding and mechanical properties in friction stir weld 2014 Al alloy Materials Letters 59: 2948 2952.

  12. K. Kumar, Satish V. Kailas, (2007). The role of friction stir welding tool on material flow and weld formation Materials Science and Engineering A 485: 367374.

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