Data pertaining to induction brazing of contact materials in a 3 layered sandwich structure consisting of a silver-tin oxide (Ag-SnO(II)) layer, a silver (Ag) inter-layer and a thin layer of phosphorous free braze-A4-TUD

Contact materials for electrical switch gears are widely used for connecting and disconnecting electric circuits. These contacts are two component systems, where the contact tips are brazed to the carriers prior to installation. The contacts used in the present work is a 3 layered sandwich structure consisting of a silver-tin oxide layer, a silver inter-layer and a thin layer of the braze. The carrier itself is copper-plated steel. The brazing process is accomplished by a high frequency inductive heating process. By varying the brazing parameters, namely, temperature and time, their influence on joint formation is investigated. The brazing joint of the contact tips were characterized by microscopy and physical analytical techniques. The mechanical characteristics were determined with Vickers micro-hardness.

To investigate the dependence of temperature and/or time on joint formation, during induction brazing using high frequency inductive heating, experiments were carried out by setting up a proprietary brazing setup. Temperature monitoring was carried out using a pyrometer and thermocouple, placed deductively around the brazing sample to ascertain temperature variations in the brazing sample. Temperature disparities due to measurements with the pyrometer and thermocouple were also ascertained. To enable correct temperature determination using the pyrometer, the emissivity was investigated and compared with the thermocouple. Proper brazing data collection was ensured by investigating all relevant brazing parameters, namely, brazing temperature, sample heat up time, sample holding time under the specified brazing temperature and the time spent by the braze in the molten state. Scanning electron microscopy was carried out to investigate microstructural changes in the brazed joint at different brazing parameters. Optical light microscopy was used to acquire information about the layer thickness, microstructure evolution and porosity. Hardness of the individual brazed layers was assessed using Vickers Micro-hardness for different brazing parameters. EDX-SEM elemental mapping was carried out to ascertain the chemical compositional variations at the contact-carrier interface resulting from different brazing parameters.

This data can be re-used for brazing experiments to ascertain the correct brazing parameters for effective brazing without the inclusion of porosity, determine the brazing parameters to monitor the increase in pore size and volume, ensure the formation of the Cu-Ag-P eutectic phase to encourage a decrease in the Phosphorus content in the joint zone, determine the temperature range for dissolution of the brittle Cu(III)P phase, and automate the brazing process by using a pyrometer to determine the brazing joint temperature.