抄録
The development of an ultrasonic on-line sensor for molten metals monitoring at temperature up to 1073 K is presented. This sensor consists of a piezoelectric transducer, a focused waveguide and a cooling system, and provides high spatial resolution measurements in molten metals in a pulse-echo mode at 5 or 10 MHz. A taper-shaped clad buffer rod is used as the waveguide. The length is up to 500 mm. Using the developed sensor, pulse echo measurements have been successfully performed in molten magnesium (Mg) at 973 K and aluminum (Al) at 1073 K. For molten Mg measurements, the sustainability for long time operation has been evaluated. The martensitic stainless steel is chosen as the sensor material, and no crucial corrosion has been observed in the sensor surface through 32 hours immersion test. An attempt has been made to detect alumina particles of 160 micron suspended in molten Al. Backscattered echoes from the particles are clearly observed at the focal region of the acoustic lens with a 4.4 mm radius. A numerical simulation has been used to examine the behavior of the ultrasonic echoes from the particles.
