1 Introduction
2 Experimental procedure
Machine | 3 T friction stir welding unit (WS005) |
Stir welding operation | Linear welding |
Spindle speed | 3000 rpm max |
Spindle torque rated | 86.4 Nm @1650 rpm |
Tool force (axial load on spindle) | 30 KN |
Spindle tilting | ± 10° |
Feed rate | |
X-axis | 1000 mm/min max |
Axis thrust | |
X-axis | 10 KN |
Z-axis | 30 KN max |
Thrust feed back | Through load cell |
Axis movement | |
X-axis | Servo motor-3000 rpm, 5 Nm |
Y-axis | Manual positioning and clamping |
Z-axis drive | Servo hydraulic cylinder |
Element | Carbon | Silicon | Manganese | Phosphorus | Sulphur | Iron |
---|---|---|---|---|---|---|
Content (%) | 0.400 | 0.280 | 0.670 | 0.037 | 0.029 | Balance |
3 Results and discussion
3.1 Variation of spindle torque and forces on the FSW tool
3.2 Microstructural characterization of welded joints
3.3 Tensile strength and flexural strength
Welding type | Rotational speed (rpm) | Traverse speed (mm/s) | Flexural strength (MPa) | Relative flexural strength (%) |
---|---|---|---|---|
Base | – | – | 41 | 100 |
Single side | 700 | 0.3 | 16.18 | 39.46 |
Single side | 750 | 0.3 | 25.65 | 62.56 |
Single side | 800 | 0.3 | 29.07 | 70.90 |
Double side | 700 | 0.3 | 31.79 | 77.54 |
Double side | 750 | 0.3 | 31.32 | 76.39 |
Double side | 800 | 0.3 | 32.18 | 78.49 |
3.4 Microhardness
4 Conclusions
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During the double-side friction stir welding of 6-mm polypropylene plates, the FSW tool encounters lower torque and forces than the single-side welding due to reduced amount of material interaction and uniform heating owing to short pin.
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Use of double-side FSW is able to produce defect-free welding with the laminar material flow in the stir zone.
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FTIR analysis reveals that double-side weld seam exhibits chemical similarity with the base material, whereas the absorption band at 1718 cm−1 and 1050 cm−1 reveals that oxidation occurs during single-side welding.
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The tensile properties of double-side welded joints are higher compared to the single-side welded joints as it is comparably defect free along with improved material mixed transition zone. However, under tensile loading, all the welded specimens get fractured in ductile mode.
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With an increase in tool rotation speed, the tensile properties of single-side weld improve owing to higher heat input. However, in the case of double-side welding, tool rotation speed of 750 rpm yields the highest tensile strength of 15.4 MPa.
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Flexural strength for both welding conditions improves with the increase in tool rotational speed. Moreover, single-side weld exhibits lower flexural strength than double-side welding due to the presence of a defect in the weld seam.
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Although lower average microhardness is achieved for double-side weld compared to single-side weld, due to uniform mixing by improved material flow, the microhardness variation in stir zone of the double-side weld is also less.