Development of high temperature ultrasonic 2-D array sensor and its application to solidification monitoring for molten metals

研究了高温超声二维阵列传感器的研制及其在金属熔体凝固监测中的应用。取得的主要成果如下：(1)对常规二维超声阵列传感器进行了测试，验证了其在室温水环境中超声成像的能力和可行性。结果表明，采用二维超声阵列换能器(8×8，16×16)和块状缓冲介质相结合的传统方法，由于空间分辨率低，成像时间长，不能用于金属熔体监测。因此，建议使用高性能的超声缓冲棒及相关技术来制作高温超声阵列传感器。(2)利用数值模拟技术设计了一种锥形包层缓冲棒高温超声传感器，并验证了其对铝合金熔体凝固过程的监测能力。通过数值计算，计算了铝熔体中缓冲杆传感器探头端部的温度分布。结果表明，超声缓冲棒传感器是制作超声阵列传感器的有力元件。(3)设计并制作了一种长达1m的长缓冲棒传感器，并在实验室验证了该传感器用于金属熔体监测的可行性。此外，还发展了基于反射和散射现象的表面粗糙度评价方法，用于定量评价表面形貌。这种粗糙度评价方法有望用于监测和评价金属熔体凝固界面的表面形态。因此，长缓冲杆传感器被认为是构建有效阵列传感器的一个很有前途的候选者。

Development of a high temperature ultrasonic 2-D array sensor and its application to solidification monitoring of molten metals have been studied. The main results obtained are the following:(1) Conventional ultrasonic 2-D array sensors have been examined to verify the capability and feasibility of ultrasonic imaging in a water environment at room temperature. The results have showed that the use of the conventional technique using a 2-D ultrasonic array transducer (8×8, 16× 16)coupled with a bulk buffer medium cannot be used for molten metal monitoring because of its poor spatial resolution and time consuming for imaging. It is therefore suggested that a high performance ultrasonic buffer rod and relating techniques should be used for fabricating a high temperature ultrasonic array sensor.(2) A high temperature ultrasonic sensor with a tapered clad buffer rod is designed using a numerical simulation technique (FDM) and its ability for a solidification process monitoring of a molten aluminum alloy has been demonstrated. The temperature distribution around the probing end of the buffer rod sensor in the molten aluminum has also been evaluated by a numerical calculation (FEM). It is found that the ultrasonic buffer rod sensor is a powerful element that can be used for fabricating the ultrasonic array sensor.(3) A long buffer rod sensor of 1 m length has been designed and fabricated, and then the laboratory validation of the use of such long sensor for molten metal monitoring has been examined. In addition, surface roughness evaluation methods based on reflection and scattering phenomena have been developed to evaluate surface topography quantitatively. It is expected that such roughness evaluation methods could be useful for monitoring and evaluating the surface morphology of a solidification interface of molten metals. It is therefore considered that the developed long buffer rod sensor is a promising candidate for constructing an effective array sensor.