1. Compare the Temperatures
Heat Flow into Friction Stir Welding Tools
Objectives:
Determine the heat loss into the tool whilst friction stir welding.
Investigate an improvement in the thermal design of the welding tool.
In particular for the transient phase at the start of welds.
The following reference gives more details:
Dickerson T.L., Shi Q-Y. and Shercliff H.R., “Heat flow into friction stir welding tools”, Proc. 4th Int. Symp. On Friction Stir Welding, Salt Lake City, Utah, USA, May 2003
Figure 2: Temperature measurements from under the weld tool shoulder. The tool passed directly over the thermocouples to measure at the tool/weld interface.
500
Tool Position along Weld / [mm] 50
100
150
200
250
300
350
400
450 10 20 30 40 60 70 80 90
110
120
Temperature / [°C]
Mg Alloy, retreating side
Al Alloy, advancing side
Al Alloy, retreating side
Mg Alloy, advancing side
Passage of shoulder over original
position of thermocouples
Figure 5: Finite element models gave estimates of the heat flow (q) into the welding tools. Temperature contours are show (all same scale).
Magnesium Alloy
Aluminium Alloy
Aluminium Alloy
START
Compare the Temperatures
Boundary
Conditions
Figure 1: Instrumented welding experiments were used to generate ‘real’ data: weld temperatures and tool torque. Welds were made in aluminium and magnesium alloys.
Thermocouples
Weld
Dyno
Tool
Thermocouple data
Figure 6: A grooved tool was also assessed. The grooves inhibit heat flow.
Heat Flow
into the Tools
Temper Colours
Figure 3:Tool temperatures were estimated from temper colours.
Magnesium Alloy
Aluminium Alloy
Validation using Temperatures
Figure 7: Predicted heat loss onto the welding tool as the weld progressed. Zero time is when the tool traverse starts and so negative time is the plunge and dwell period. The steady state values are also shown on the right of the graph.
200
400
600
800
1000
1200
1400
-10 10 20 30
Welding Time / [s]
Power Loss into Tool, q / [W]
Al Alloy, Solid tool
Al Alloy, Grooves in Tool
Steady
State
/ /
Rotation Speed, 
Measured Torque, M
Tool Heat loss, q
Conclusions:
For friction stir welding of light alloys using a steel tool:
With a solid tool about 10% of the heat generated is lost through the tool.
For welds that start with a cold tool the efficiency may be 0.8 or lower.
Grooves cut into the tool shank can decrease the heat loss through the tool to about 5%, even for short welds.
P = .M
Figure 4: Gross weld input power (P) calculated from rotation speed () and welding torque (M).
f = (P-q)/P
Figure 8: The welding efficiency is the fraction of the gross power that goes into heating the weld.
Gross Weld Input Power, P
END
UNIVERSITY OF
CAMBRIDGE
Terry Dickerson, Qing-yu Shi, Hugh R Shercliff
This work was supported by the European Community under the ‘Competitive and Sustainable Growth’ Programme ( ). Contract No.: G5RD-CT