Friction Welding of Aluminum and Plain Low Carbon Steel

Abstract

The thermal cycle during friction welding is an important factor that significantly affects on the mechanical properties and microstructures in welded joints. The weld heat input has been normally estimated using the torque during friction welding, however most of industrial friction welding machines are not able to measure the torque which cannot be available to use process control.
In this paper, the calculation of heat input rate is proposed for friction welding under a new concept for the dissimilar welded joints. This heat input concept, which is solved governing equations combined with high temperature strength, and thermal conduction is successfully expanded into joints by dissimilar materials with large differences of thermal behaviors. It is revealed that mechanical properties are correlated with the proposed heat input rate to dissimilar joints by pure aluminum and plain low carbon steel. Mechanical properties are evaluated by notch tensile strength. This weld heat input rate is also related with intermetallic phase formation that is confirmed in the transmission electron microscope observations.
As a conclusion, the optimum welding condition is obtained with increased the heat input rate.
1) By using the simple assumptions made in this study, it is possible to obtain the heat input rate, to a certain extent, to predict the mechanical properties of the friction welded joints to dissimilar materials. It is also clarified this proposed heat input rate predicts formation of intermetallic compounds at the weld interface.
2) The calculated heat input rate correlates with the tensile strength of the welds. High joint strength is obtained in the case of welds of higher heat input rate.
3) Intermetallic phase does not form when friction time is less than 1 second. This is also confirmed from the results of calculation. Intermetallic phase at weld interface is determined as Fe₄A₁₃ using diffraction pattern of TEM observation.