Laser ultrasonic detection of the solidification front during casting

摘要

A real-time sensor that directly measures properties of the solidification front would be a valuable aid to the metal casting industry. Information needed includes solidification front location, shape, and growth dynamics. The use of contacting probes is often undesirable because it can cause contamination and probe deterioration. Noncontacting laser ultrasonics offers an attractive solution to these problems, particularly if access to the free liquid surface is available. This paper presents results of laser ultrasonic measurements of the solidification front in tin and a tin-lead alloy. The ultrasonic waves were generated and detected at the liquid surface. Tin was selected for its low melting point and the availability of a suitable furnace. Results are presented for reflections from stationary and moving solidification fronts.