On-Line Monitoring of Liquid Metal Quality by Focused Ultrasound

为了对熔融金属质量进行在线监测，研制了一种在高温环境下提供高空间分辨率测量的高性能超声传感器。利用所研制的10 MHz聚焦传感器在脉冲回波模式下进行了多次实验，以研究所研制的监测系统的性能。实验中使用了熔融的锌、铝和镁。研究结果表明：(1)有限差分法数值模拟技术是设计高性能复合缓冲棒超声传感器的有效工具。通过仿真，研制出了具有良好导波能力和高信噪比的聚焦超声传感器。(2)实验验证了聚焦超声传感器在800℃铝液和650℃锌液中夹杂物检测中的应用。来自两种熔融金属中的粒子的反向散射信号在透镜的焦点区域清晰可见。因此，认为所开发的超声技术是一种有前途的在线监测熔融金属加工过程的候选者。

A high performance ultrasonic sensor that provides a high spatial resolution measurement in high temperature environments has been developed in order to make an on-line monitoring of molten metal quality. Several experiments have been carried out using the developed focused sensors at 10 MHz in a pulse echo mode to investigate the performance of the developed monitoring system. Molten zinc, aluminum, and magnesium were used in the experiments. The main results obtained are the following:(1) It has been shown that a numerical simulation technique with a finite difference method is a very useful tool for better designing high performance ultrasonic sensors with a clad buffer rod. Using such simulation, focused ultrasonic sensors having excellent wave guidance ability with high signal to noise ratio have been successfully developed.(2) Laboratory validation of the use of focused ultrasonic sensors for inclusion particle detection in molten aluminum at 800 ℃ as well as molten zinc at 650 ℃ has been demonstrated. Back-scattered signals from particles in both molten metals are clearly visible at the focal region of the lens.It is therefore considered that the developed ultrasonic technique is a promising candidate for on-line monitoring during molten metal processing.