Large diameter lead-free solder billets are vacuum cast in production and then shipped around the world. Such billets are drawn down to solder wire diameters. Porosity at the centerline of the billet may occur and this can result in failed wire drawing. Certain alloys seem to have problematic processing history. The goal here was to find porosity in billets, then feed back information into process control in order to eliminate the problem.
Ultrasonic sound waves were sent into the material to monitor internal condition.
Ultrasonic inspection can find reflections from internal voids. Calibration billets of various alloys were prepared and the company was taught to validate UT measurements on these billets, then transfer that inspection to live material. The result was the ability to find flaws and screen material prior to shipment.