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2.3 超声波法超声波法以往被用于对数百大夹杂物的检测。但是,近年来有的是采用50～100MHz 的聚焦式高频探头检测出数10μm的夹杂物。对夹杂物位置和超声波焦点的偏离及衰减进行校正的反射波强度与显微镜观察-图像解析及酸性溶解萃取-SEN 观察求出的夹杂物直径在10～数10 μm的范围内存在着直线关系,当检测频率为50、100和125MHz 时,可以检测出的夹杂物直径的下限分别为25、17和12μm,是波长的1/4左右。与钢和夹杂物相比,气泡的音响阻抗非常小,由
2.3 ultrasonic method Ultrasonic method used in the past hundreds of large inclusions detection. However, in recent years, some use 10-50MHz focused high-frequency probe to detect a few 10μm inclusions. The intensity of the reflected wave that corrects the deviation and attenuation of the position of the inclusion and the focus of the ultrasonic wave has a linear relationship with the diameter of the inclusions in the range of 10 to 10 μm as determined by the microscope observation-image analysis and acid-soluble extraction-SEM observation, When the detection frequency is 50, 100 and 125MHz, the lower limits of inclusions that can be detected are 25, 17 and 12μm respectively, which is about 1/4 of the wavelength. Compared with steel and inclusions, the acoustic impedance of the bubble is very small, by