Experimental Investigation of Optimum Process Parameters for Friction Stir Welding of Copper Plate

Abstract

Conventional welding of copper and its alloys tends to degrade the mechanical strength at the welded area due to high thermal diffusivity and melting point. Friction stir welding (FSW) is an excellent alternative for joining of these materials against fusion joining. FSW is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. In this thesis work the process parameters were optimized by using the Taguchi technique based on Taguchi’s L9 orthogonal array. The main objective of this experimental investigation is to optimize the process parameters of FSW for joining of 5 mm thick copper plate using a constant square tool pin profile and the variable process parameters of tool rotational speeds of (750, 950 and 1180) rpm, tool traverse speeds of (20, 30, 40) mm/min, and tool tilt angles of (1, 1.5 and 2) degrees. Mechanical and microstructure analysis has been performed to evaluate the characteristics of friction stir welded copper plates. The tensile properties of all the weld joints showed a relative correspondence to the variation of the hardness in the weld zone. Tensile strength and hardness of FSW joints have been predicted for the optimum FSW process parameters, and their percentage contribution to a better joint is calculated using the signal-to-noise ratio, means, and analysis of variance. Based on the study, the analysis of variance for tensile strength results shows that the tool tilt angle was the most influential FSW process parameter with a percentage of contribution of 42.37%. The analysis of variance for average hardness results shows that the tool rotational speed is the most influential parameter, with a percentage of contribution of 85.85%. The maximum tensile strength of welded joint was 129.489 MPa at the process parameters of 1180 rpm of the tool rotational speed, 20 mm/min of the welding speed, and 2 degrees of tool tilt angle. The maximum hardness of welded joint was 86.65HRB at 1180 rpm tool rotation, 20 mm/min weld speed and 2 degrees of tool tilt angle. From the experimental investigation it is found that the joints fabricated at a tool rotation speed of 1180 rpm, traverse speed of 20 mm/min, and tool tilt angle of 2 degrees resulted in better mechanical properties compared to other process parameters. From the experimental results the optimal microstructural arrangement of welded joint was obtained from the weld joints by using optimum process parameters of 1180 rpm of tool rotational speed, 20mm/min of the welding speed, and 2 degrees of tool tilt angle.Conventional Welding Of Copper And Its Alloys Tends To Degrade The Mechanical Strength At The Welded Area Due To High Thermal Diffusivity And Melting Point. Friction Stir Welding (Fsw) Is An Excellent Alternative For Joining Of These Materials Against Fusion Joining. Fsw Is An Emerging Solid State Joining Process In Which The Material That Is Being Welded Does Not Melt And Recast. This Process Uses A Non-Consumable Tool To Generate Frictional Heat In The Abutting Surfaces. In This Thesis Work The Process Parameters Were Optimized By Using The Taguchi Technique Based On Taguchi?�?S L9 Orthogonal Array. The Main Objective Of This Experimental Investigation Is To Optimize The Process Parameters Of Fsw For Joining Of 5 Mm Thick Copper Plate Using A Constant Square Tool Pin Profile And The Variable Process Parameters Of Tool Rotational Speeds Of (750, 950 And 1180) Rpm, Tool Traverse Speeds Of (20, 30, 40) Mm/Min, And Tool Tilt Angles Of (1, 1.5 And 2) Degrees. Mechanical And Microstructure Analysis Has Been Performed To Evaluate The Characteristics Of Friction Stir Welded Copper Plates. The Tensile Properties Of All The Weld Joints Showed A Relative Correspondence To The Variation Of The Hardness In The Weld Zone. Tensile Strength And Hardness Of Fsw Joints Have Been Predicted For The Optimum Fsw Process Parameters, And Their Percentage Contribution To A Better Joint Is Calculated Using The Signal-To-Noise Ratio, Means, And Analysis Of Variance. Based On The Study, The Analysis Of Variance For Tensile Strength Results Shows That The Tool Tilt Angle Was The Most Influential Fsw Process Parameter With A Percentage Of Contribution Of 42.37%. The Analysis Of Variance For Average Hardness Results Shows That The Tool Rotational Speed Is The Most Influential Parameter, With A Percentage Of Contribution Of 85.85%. The Maximum Tensile Strength Of Welded Joint Was 129.489 Mpa At The Process Parameters Of1180 Rpm Of The Tool Rotational Speed, 20 Mm/Min Of The Welding Speed, And 2 Degrees Of Tool Tilt Angle. The Maximum Hardness Of Welded Joint Was 86.65hrb At 1180 Rpm Tool Rotation, 20 Mm/Min Weld Speed And 2 Degrees Of Tool Tilt Angle. From The Experimental Investigation It Is Found That The Joints Fabricated At A Tool Rotation Speed Of 1180 Rpm, Traverse Speed Of 20 Mm/Min, And Tool Tilt Angle Of 2 Degrees Resulted In Better Mechanical Properties Compared To Other Process Parameters. From The Experimental Results The Optimal Microstructural Arrangement Of Welded Joint Was Obtained From The Weld Joints By Using Optimum Process Parameters Of 1180 Rpm Of Tool Rotational Speed, 20mm/Min Of The Welding Speed, And 2 Degrees Of Tool Tilt Angle.