Ultrasonic sensor and technique for in-line monitoring of die casting process

An ultrasonic clad steel buffer rod sensor embedded in the die has been used to in-line monitor the die casting process using aluminium alloy billets with semi-solid (thixotropic) and dendritic microstructures as feedstocks. This clad steel buffer rod provided better performance than the previously reported clad zirconium buffer rod. A multiple recording technique was used for the fast data acquisition with a rate up to 0.003 s per acquisition. This single ultrasonic probe monitored the completion of the die fining, the release of the pressure, the opening of the die, part detachment and solidification of the part. The change of the ultrasonic travel time in the clad buffer rod and cast part relates to the variation of the average temperature in the die and part, respectively. The measured amplitude profile of the reflected echo at the probe end/cast part interface can be used to monitor the cold shot and complete filling. The variation of the ultrasonic attenuation coefficient in the cast part may also relate to the change of the composition, microstructure and porosity.