Approaches and possibilities for reducing residual stresses in induction brazed cemented carbide/steel joints

Abstract

AbstractInduction brazing is widespread in many industries due to its ability for local contactless heating as well as its high heating rates and the associated short cycle times. As a result of these advantages, this brazing process is particularly widespread in the tool industry for mass products made of cemented carbide/steel, for example, in saw blades or milling tools. The state of the art is the use of one or more pyrometers for measuring the surface temperature of the component. However, the measurement can be significantly falsified due to oxidation of the component surface and flux residues or due to the evaporation of the flux. Due to the resulting control deviations and the lack of information about the temperature inside the brazing gap, critical residual stresses can be induced in the joint, which can lead to premature failure of the component. An approach is presented that uses distance and force measurements to monitor the condition of the filler metal in the brazing gap. By using these sensors, the point in time at which the entire filler metal has liquefied can be determined. In this way, overheating of the component can be avoided and the holding time and thus also the residual stresses can be reduced to a minimum. Furthermore, numerical calculations are presented, which compare the resulting residual stresses with conventional brazing foils as well as with brazing foils with a pure copper intermediate layer. In addition, the influence of the thickness of the filler metal was examined. The results show that the choice of the right brazing foil architecture and the thickness of the brazing foil have a significant influence on the residual stresses.