High resolution measurements in liquid metal by focused ultrasonic wave

Abstract

High spatial resolution measurements in molten zinc at temperatures more than 600 °C are performed using a focused ultrasonic pulse-echo technique with clad metallic buffer rods. The focused ultrasonic waves are generated by a spherical acoustic lens which is fabricated at the end of the buffer rod. In order to evaluate its focussing ability, several experiments are carried out in molten zinc at 10 MHz. First, high resolution ultrasonic imaging is performed by raster scanning the sample in the focusing plane. The signal-to-noise ratio of the reflected signals from the sample surface at the focus is better than 35 dB which leads to very good ultrasonic images obtained from the amplitude or phase variation of the reflected signal. Second, the detection of a thin stainless wire with a diameter of 380 μm is carried out at 650 °C in molten zinc. It is found that not only the wire but also small inclusions existing in molten zinc may be detected. Third, in order to perform quantitative evaluation, V(z) curve me...