INFLUENCE OF SPINDLE SPEED AND WELDING SPEED ON MECHANICAL PROPERTIES OF FRICTION STIR WELDING

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp , Article ID: IJMET_09_11_081 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed INFLUENCE OF SPINDLE SPEED AND WELDING SPEED ON MECHANICAL PROPERTIES OF FRICTION STIR WELDING J.Yasin, T.Pravinprabu and M.Saravanakumar Department of Mechanical Engineering,PSNA college of Engineering and Technology, Dindigul. ABSTRACT Aluminium alloys are widely used in the structural industries for its low weight with high strength ration. Joining of aluminium alloys In this work carried out on Friction stir welding (FSW) in the conventional vertical milling machine for aluminium alloy 6082 by changing FSW tool instead of the milling tool.. High carbon, high chromium steel has been used for welding process. During the process pressurized heat is generated between the two plates, due to pressurized heat, plates are joined together. Heat generation is mainly depending on the tool rotational speed and transverse speed. The results found that, micro hardness, tensile strength, and metallographic structure carried at different process parameters of spindle speed, transverse speed, tool penetration with hexagonal tool structure. An optimum defect free welding is obtained at 1300 rpm spindle speeds, 70 mm/min transverse speed with tool penetration 0.15mm in the medium work weld condition. A Scanning electron microscopy (SEM) and Electron dispersive spectroscopy (EDS) test were conducted and used to investigate the particle distribution of the optimum weld samples. Keywords: Friction stir welding, Process parameter, Aluminium alloy 6082, Electron dispersive spectroscopy. Cite this Article J.Yasin, T.Pravinprabu and M.Saravanakumar, Influence of Spindle Speed and Welding Speed on Mechanical Properties of Friction Stir Welding, International Journal of Mechanical Engineering and Technology, 9(11), 2018, pp INTRODUCTION Friction Stir Welding is a solid state joining process that uses friction generated by a rotating cylindrical tool to heat and plasticize metal on either side with a joint, creating a solid, functional weld. The friction generated heat is more effective against reorganizing the microstructure of metals and metal alloys than other forms of fusion welding. Welding input parameters play a very significant role in determining the quality of a weld joint. The joint quality can be defined in terms of properties such as mechanical properties and distortion. Generally, all welding processes are used with the aim of obtaining a welded joint with excellent mechanical properties and with minimum distortion editor@iaeme.com

2 Magnetic Field Analysis of an Induction Machine with Multiphase Stator Winding Through Finite Element Method Friction stir welding the breaking point is outside the weld on tensile test where as in TIG welding the breaking point is exactly on the weld so failure mostly occurs in the TIG welding process. Most of the researchers are considered the parameter of the FSW is spindle speed, welding speed and tool geometry [1]. The parameters of the FSW machine are tool rotation speed, welding speed, and axial force. Some of the process parameters of the FSW tool geometry are pin diameter, shoulder diameter to probe diameter ratio, probe length, and probe profile [1]. However, the conventional milling (CM) machine offers tool rotational speed and welding speed through its spindle speed and table feed. Axial force is very difficult to attain in CM. In a CM machine, tool shoulder penetration executes the force parameter. When the tool shoulder penetration increases, the axial force also increases. Even in a FSW machine axial force is difficult to retain throughout the welding. But the shoulder penetration is maintained constantly [10]. The effect of weld quality is mainly depends on tool rotational speed and transverse speed (welding speed). When the tool rotational speed is increases the heat input also increased the heat input also increased [11]. Spindle speed and transverse speed are the most important ones and determine overall mechanical properties of the welds.drastic changes in the micro structural and mechanical properties of the joints with the changes in the process parameters and the tool geometry. Thus it proves that good quality weld joints can be obtained by proper selection of process parameters and using appropriate tool geometry [4]. The hardness of Heat affected zone and weld nuggets are lower than that of base metal in all the joints. The difference between Heat affected Zone and Weld Nugget zone is attributable to the grain refinement caused by concentrating stirring and produced very fine harmonized grains. Good quality weld joints can be obtained by proper selection of process parameters and using appropriate tool geometry. 2. EXPERIMENTAL WORK FSW is normally carried out by vertical milling machine. In vertical milling machine FSW tool is used instead of milling tool. During the process heat is generated between the two plates, due to heat, plates are joined together. FSW avoids problems related to melting, formation of cast microstructure and solidification of weld shrink zone that is associated with conventional fusion welding.aluminium alloy 6082 is a medium strength alloy with excellent corrosion resistance. It has the highest strength of the 6000 series alloys. Alloy 6082 is known as a structural alloy two plates of aluminium alloy 6082 has been taken for friction stir welding of butt joint with dimensions 200mm x 75 mm x 6mm. Chemical composition of aluminium alloy 6082 is mentioned in table 1 Table 1 Chemical Composition of aluminium alloy 6082(% weight) Si Fe Cu Mn Mg Cr Zn Ti Al Remaining High carbon, high chromium steel (HCHCr) has been favored among high speed steel and carbides, to weld aluminium alloy 6082 due to its low melting point and low hardness Also HCHCr tools cost comparatively less with high strength and high hot hardness [11]. Effect of weld quality is mainly depends on tool rotational speed and transverse speed. When the tool rotational speed is increases the heat input also increased the heat input also increased [12]. Following figure 1 represents the tool geometry editor@iaeme.com

3 Oleh Mykhailiuk Figure 1 Tool geometry Shoulder diameter - 15 mm, Pin diameter - 6 mm, Pin length mm The pin length was carefully chosen to ensure that there is proper penetration. The pin length also increases the heat generated in the process Heats working conditions A relation between the welding parameters, and the energy input/ unit length of the weld is assumed, and the welds so produced can be classified as cold and hot welds. The welds obtained with maximum tool speed and minimum traverse speed are treated as hot welds and the results showed that the hot welds have improved mechanical properties relative to the cold welds. [12]. The following conditions are considered for experiments Weld Quality = f (spindle speed, weld speed) Quality is proportional to spindle speed and inversely proportional to weld speed 1. Cold working welds-low spindle speed, high welding speed, the frictional heat generated is less because of poor plastic flow of material. 2. Hot working welds - higher spindle speed, low welding speed, frictional heat generation is high which enhances the plastic flow of material thus loses the tool material contact 3. Medium working welds - compromised level of spindle speed and welding speed [11]. The experiments were carried out on conventional HMT FN2V vertical milling machine with a capacity of 7.5 HP and 1800rpm.. In vertical milling machine FSW tool is used instead of milling tool. During the process heat is generated between the two plates, due to heat, plates are joined together. Kirloskar HMT machine is used for friction stir welding process. The tensile test specimens are prepared according to ASTM- E8M-04 standards. The welded joints are sliced using a capacity of 7.5 HP and 1800rpm CNC milling machine. These specimens are taken in the normal direction of the weld. The tensile test on butt joint was conducted by using FSA computer controlled 100 tones capacity universal testing machine (UTM). Hardness test was conducted by Vickers micro hardness with capacity of 10kg. Welded plates were cut at mid welded portion and specimens of size mm were obtained for metallographic study. The samples were prepared as per standard metallographic procedure from the welded plates and macro etched by using Keller s solution. The metallographic study was carried along with various zones of parent metal; heat affected zone (HAZ), thermo mechanical zone (TMZ) and weld nugget zone (WN) across the cross sections of friction stir welded specimens using scanning electron microscope (SEM). 3. RESULTS AND DISCUSSIONS 3.1. Tensile strength The material was prepared according to the ASTM E8M-04standards to evaluate the tensile strength of the joints. The tensile strength of the FSW joints was evaluated by conducting tests in editor@iaeme.com

4 Magnetic Field Analysis of an Induction Machine with Multiphase Stator Winding Through Finite Element Method a universal testing machine. For each welded plate, three specimens were prepared and tested. Figure 2 shows the tensile specimen after fracture. Figure 2 Sample tensile specimens after fracture Figure 3 Macroscopic view of welded material From the figure 3 macroscopic view reveled that various zones of welded material. The fracture has occurred mostly in the heat affected zone on the retreating side of the weldment. Table 2 shows the tensile strength of welded joints that has been fabricated at different weld conditions of hot weld, cold weld and Medium work welds. The hexagonal tool pin profile was used in these experiments. Table 2 represents the testing parameters and experimental value of tensile strength. The tensile result shows that Welding quality depends on the various process parameters presented during the welding process. Spindle speed and transverse speed of the welding play a crucial role in heat energy inputs.by cold working (low spindle speed, high welding speed) the frictional heat generated is less because of poor plastic flow of material. Therefore a lower tensile strength was obtained at 700 rpm and 900 rpm with constant welding speed of 135 mm/min. Table 2 Testing Parameters and experimental value of tensile strength Trial Trial 2 Trial 3 Experimental nature Spindle speed (rpm) Welding speed (mm/min) 1 Tensile strength (MPa) Tensile strength (MPa) Tensile strength (MPa) Tensile strength (MPa) Tool penetration (mm) Cold welds Medium welds Hot welds By Hot working (higher spindle speed, low welding speed) frictional heat generation is high which enhances the plastic flow of material thus loses the tool material contact. So the poor editor@iaeme.com

5 Oleh Mykhailiuk stirring was obtained. This is due to the increased frictional heat and insufficient frictional heat respectively. Medium welds spindle speeds of 1100 rpm and 1300 rpm with constant welding speed of 70 mm/min gives a tensile result MPa and MPa.The tensile strength of hot weld was higher than the cold weld. At the highest welding speed of 135 mm/min and the lowest welding speed of 35 mm/min lower tensile strengths were observed The medium working welded has been compromised at both extreme weld conditions of the Cold weld and hot weld. An optimum defect free wedding is obtained at 1300 rpm spindle speed, 70 mm/min welding speed gives a tensile strength MPa.The fracture has occurred mostly in the heat affected zone on the retreating side of the weldment Micro hardness Micro-hardness of the welds was measured the test load of 5N for 10 seconds. The indentations were made at the midsection of the thickness of the plates across the joint. Figures 3, 4, 5 represents that the results of micro-hardness of the welded joints prepared at various heat inputs termed as hot weld, Cold weld and medium work welded. The hardness of Heat affected zone and weld nuggets are lower than that of base metal in all the joints. The difference between Heat affected Zone and Weld Nugget zone is attributable to the grain refinement caused by concentrating stirring and produced very fine harmonized grains.a micro hardness test was carried out by Vickers hardness. RS-Retreating side, WB-Weld beam, AS-Advancing side vickers hardness Cold Work Welds RS-1 RS-2 RS-3 WB-1 WB-2 WB- 3 AS- 1 AS- 2 AS- 3 CW-700rpm CW-900RPM Figure 4 Micro hardness for cold work welds The variation of the micro-hardness values in the welded area and parent material is due to the difference between the microstructures of the base alloy and weld zone [9]. In figures 4, 5,6 represents that the micro hardness variations in cold work welds, medium work welds and hot work welds. Hence the results show that the hardness decreases in thermo mechanical affected zone towards the weld nuggets (weld beam) as compared to the parent metal editor@iaeme.com

6 Magnetic Field Analysis of an Induction Machine with Multiphase Stator Winding Through Finite Element Method 150 Medium work welds Vickers hardness RS-1 RS-2 RS-3 WB-1 WB-2 WB- 3 AS- 1 AS- 2 AS- 3 MW-1100 MW-1300 Figure 5 Micro hardness for medium work welds Hot Work Welds vickers hardness RS-1 RS-2 RS-3 WB-1 WB-2 WB- 3 AS- 1 AS- 2 AS- 3 HW-1500 HW-1700 Figure 6 Micro hardness for hot work welds 3.3. Microstructure In FSW, three different micro structural zones are identified, such as weld nuggets, heat affected zone, and unaffected base material. The weld nuggets zone experiences high strain and is prone to recrystallisation. Immediately at its side is the thermo mechanical affected zone which ends at the tool shoulder. Outside of the thermo mechanical affected zone there is a zone affected only by the heat generated during the welding process [10]. Figure 7 Heat affected zone Figure 8 Weld nugget zone Figure 7, 8, 9 represents SEM results of heat affected zone, weld nugget zone and welded zone of optimum weld. Medium work1300 rpm and 70 mm/min weld has a recrystallised microstructure that consists of very fine intensively stirred harmonized grains. These grains are homogeneous at higher heat inputs/energy than the lower heat inputs/energy. It occurs because of sufficient heat input to form homogeneous grains. The grain size of the nugget is decreasing with the increase of heat input editor@iaeme.com

7 Oleh Mykhailiuk Table 3 EDS results atom percentage Element Atomic number Series Atom in percentage Al 13 K-Series Zn 30 L-Series 5.30 O 8 K-Series Mg 12 K-Series C 6 K series Electron dispersive spectroscopy used to examine the elements presented in the Optimum welded material. From the table 3 and figure 10 results revealed that the medium work zone had the very least magnesium content. Magnesium plays a vital role in properties of aluminium 6000 series. Magnesium markedly increases the strength of aluminium without unduly decreasing the ductility. The addition of magnesium and silicon to aluminum produces the compound magnesium silicates (Mg2Si) in 6082 aluminium alloy. It shows that the quality of a weld depends on process parameters and the alloys presented in the welded nuggets zone [11]. 4. CONCLUSION The result is observed that Welding quality depends on the various process parameters presented during the welding process. Among all heat working condition welds, medium work conditions welds with the process parameters of 1300 rpm and 70 mm/min gives better results. The medium work weld has been compromised in both extreme welds conditions of CW and HW and provides better tensile results of MPa. The result shows that Spindle speed and transverse speed of the welding play a crucial role in heat energy inputs. From the Micro structural observation by SEM and EDS as shown the formation of fine equiaxed grains and uniformly distributed. The area of the weld nugget zone size slightly decreased as the welding speed increased. Weld Nuggets the medium work zone had the very least magnesium content as well as silicon content. Magnesium markedly increases the strength of aluminium without decreasing the ductility. The addition of magnesium and silicon to aluminum produces the compound magnesium silicates (Mg2Si) in 6082 aluminium alloy. It shows that the quality of a weld depends on the process parameters and alloys presented in the welded nuggets zone. Further research focused on improving the quality of weld by adding alloying editor@iaeme.com

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