EFFECT OF UPSET CONDITION ON WELD STRENGTH, INTERFACE TEMPERATURE AND MATERIAL CONSUMPTION

Transcription

1 162 Chapter 7 EFFECT OF UPSET CONDITION ON WELD STRENGTH, INTERFACE TEMPERATURE AND MATERIAL CONSUMPTION 7.1 INTRODUCTION In friction welding, the optimum selection of weld parameters such as rpm, friction pressure, friction time, forging pressure and forging time are not sufficient to achieve sound weld but selection of proper upset condition like application of upset pressure in constant feed or rapid feed and application of upset pressure before braking or after braking are extremely important, without this sound weld cannot be achieved. These critical parameters are not investigated so far. In the present research, the upset conditions such as application of upset pressure in constant feed or rapid feed and the application of upset pressure (0.6 second) before braking or after braking are investigated. As they play a very important role in weld strength, material consumption, weld interface temperature, shape of flash formation, and power requirement for welding. This study helps in proper selection of upset condition to achieve sound weld with minimum material consumption. This also helps in special purpose friction welding machine design. In the present research dissimilar materials such as Al 5052 to SS 304 and Al 6061 to SS

2 are investigated. Weld cycle diagram for application of upset pressure after braking and before braking is given in Figure 7.1 and Figure 7.2 respectively. Figure 7.1 Friction weld cycle showing application of upset pressure after braking Figure 7.2 Friction weld cycle showing application of upset pressure before braking

3 EXPERIMENTAL PROCEDURE In the present research, different materials combinations such as Al 5052 to SS 304, Al 6061 to SS 304 are considered for investigations. The diameter of Al alloys and stainless steel 304 were considered as 25 mm. The initial length of 50 to 125 mm was considered. Each combination of materials were welded as per Table 7.1 to investigate the effect of upset conditions (application of upset pressure in constant feed or rapid feed and application of upset pressure (0.6 second) before braking or after braking on weld strength, upset and weld interface temperature. Other weld parameters such as rpm, friction pressure, friction time, upset pressure and upset time were kept constant for all the trails of given material combination. The strength was determined by tensile test. Temperature at the weld interface is measured with thermocouple. Trail No applied in constant feed or rapid feed applied before braking or after braking 1 in constant feed Before braking 2 in constant feed 3 Before braking 4 Table 7.1 Upset condition experimentation trails details

4 EFFECT OF UPSET CONDITIONS ON FRICTION WELDING OF AL 5052 SS 304 The Al 5052 SS 304 are welded with weld parameters as given in Table 7.2. For all the four trails weld parameters given in the table below were kept constant and upset conditions were changed as per Table 7.1. S.No. Weld Parameters Values Rpm 1400 Friction pressure (Mpa) 15.5 Friction time (seconds) 1 Upset pressure (Mpa) 62 Upset time (seconds) 5 Table 7.2 Weld parameters for Al 5052-SS EFFECT OF UPSET CONDITIONS ON FRICTION WELDING OF AL 6061 SS 304 The Al 5052 SS 304 are welded with weld parameters as given in Table 7.3. For all the four trails weld parameters given in Table 7.2 were kept constant and upset conditions were changed as per Table 7.1.

5 166 S.No. Weld Parameters Values 1 RPM Friction Pressure (Mpa) 70 3 Friction Time (Sec) 1 4 Forging Pressure (Mpa) Forging Time (Sec) 6 Table 7.3 Weld parameters for Al 6061-SS RESULTS AND DISCUSSIONS The yield strength, ultimate tensile strength, material consumption and temperature for different upset conditions are recorded in Table 7.4. Trail No applied in constant or rapid feed in constant feed in constant feed applied before braking or after braking Yield Strength (MPa) Before braking Before braking UTS (MPa) Material consumption (mm) Te mp ( C) Table 7.4 Effect of upset condition on yield strength, ultimate tensile strength, material consumption and temperature for Al 5052 SS 304.

6 Yield Strength (Mpa) EFFECT OF UPSET CONDITION ON YIELD STRENGTH FOR AL 5052-SS 304 The effect of upset condition on yield strength is shown in Figure 7.3. Maximum yield strength of MPa was obtained; upset pressure is applied after braking under rapid feed. The yield strength is least when upset pressure is applied after braking under constant feed. Effect of Upset condition on Yield Strength Before braking Before braking Upset condition Figure 7.3 Effect of upset conditions on yield strength for Al 5052 SS EFFECT OF UPSET CONDITION ON ULTIMATE TENSILE STRENGTH FOR AL 5052-SS 304 The maximum ultimate tensile strength of was obtained when upset pressure is applied (0.6 second) before braking under rapid feed. Figure 7.4 shows the effect of upset condition on ultimate tensile strength for AL 5052 SS 304. The Al 6061 is a good

7 Ultimate Tensile Strength (Mpa) 168 conductor of heat and rate of heat dissipation is very high and the delay in application of upset pressure results in decrease of interface temperature which leads to lower strength. Effect of Upset condition on Ultimate tensile Strength Before braking Before braking Upset condition Figure 7.4 Effect of upset conditions on ultimate tensile strength for Al 5052 SS EFFECT OF UPSET CONDITION ON MATERIAL CONSUMPTION FOR AL 5052-SS 304 The effect of upset condition on material consumption is shown in Figure 7.5. The material consumption was maximum when upset pressure is applied before (0.6 second) braking and under rapid feed. The reason for maximum material consumption is because more material is squeezed out as flash, as upset pressure is applied rapidly when material is in relatively in very hot condition. The material consumption is least when upset is applied under constant feed. The reason for least material consumption is because of relatively lower temperature as some of heat is dissipated due to higher thermal conductivity.

8 Ultimate Tensile Strength (Mpa) 169 Effect of Upset condition on material consumption (mm) Before braking Before braking Upset condition Figure 7.5 Effect of upset conditions on material consumption for Al 5052 SS EFFECT OF UPSET CONDITION ON WELD INTERFACE TEMPERATURE FOR AL 5052-SS 304 The effect of upset condition on weld interface temperature is shown in Figure 7.6. The weld interface temperature was maximum when upset pressure is applied before braking and under rapid feed. The reason for maximum weld interface temperature is due to application of upset pressure while part was rotating which as generated more heat.

9 Temperature Deg. C 170 Effect of Upset condition on Temperature Before braking 188 Before braking Upset condition 159 Figure 7.6 Effect of upset conditions on weld interface temperature for Al 5052 SS VARIATION OF FLASH FOR DIFFERENT UPSET CONDITIONS FOR AL 5052-SS 304 The variations of flash and material consumption under different upset conditions are shown in Figure 7.7 (a) (b) (c) (d) Figure 7.7 Variation of flash formation and material consumption for Al 5052-SS 304 under different upset condition

10 171 Figure 7.7 (a) shows the flash when upset pressure is applied before braking under constant feed. Figure 7.7 (b) shows the flash when upset pressure is applied after braking under constant feed. Figure 7.7 (c) shows the flash when upset pressure is applied before braking under rapid feed and Figure 7.7 (d) shows the flash when upset is applied after braking under rapid feed THE EFFECT OF UPSET CONDITIONS ON YIELD STRENGTH, ULTIMATE TENSILE STRENGTH, MATERIAL CONSUMPTION AND WELD INTERFACE TEMPERATURE FOR AL 6061-SS 304 The effect of upset conditions on yield strength, ultimate tensile strength, material consumption and weld interface temperature for Al 6061-SS 304 is shown in Table 7.5. The maximum yield strength and ultimate tensile strength was obtained when upset pressure is applied (0.6 second) before braking and under rapid feed.

11 172 Trail No applied in constant feed or rapid feed applied before braking or after braking Yield Strength (MPa) UTS (MPa) Material consumption (mm) Temp ( Deg.C) 1 in constant feed Before braking in constant feed Before braking Table 7.5 Effect of upset condition on yield strength, ultimate tensile strength, material consumption and temperature for Al 6061 SS 304 The graphical representation of effect of upset conditions on yield strength, ultimate tensile strength, material consumption and temperature is shown in Figure 7.8, Figure 7.9, Figure 7.10 and Figure 7.11 respectively. Figure 7.8 Effect of upset conditions on ultimate tensile strength for Al 6061 SS 304

12 173 Figure 7.9 Effect of upset conditions on yield strength for Al 6061 SS 304 Figure 7.10 Effect of upset conditions on material consumption for Al 6061 SS 304

13 Ultimate Tensile Strength (Mpa) 174 Effect of Upset condition on temperature Upset Pressure Before braking 119 Upset Pressure 208 Upset Pressure Before braking Upset condition 163 Upset Pressure Figure 7.11 Effect of upset conditions on weld interface temperature for Al6061 SS 304 The variation of flash and material consumption under different upset conditions for Al 6061 SS 304 is shown in Figure (a) (b) (c) (d) Figure 7.12 Variation of flash formation and material consumption for Al 6061-SS 304 under different upset condition

14 175 Figure 7.12 (a) shows the variation of flash and material consumption when upset pressure is applied before braking under constant feed. Figure 7.12 (b) shows the variation flash and material consumption when upset pressure is applied after braking under constant feed. Figure 7.12 (c) shows the variation flash and material consumption when application of upset pressure is applied before braking under rapid feed and Figure 7.12 (d) shows the variation flash and material consumption when application of upset pressure is applied after braking and under rapid feed.