利用超声水浸C扫描检测方法检测球墨铸铁QT400-18铸件试样的声速，测量了铸件不同部位的硬度，并对该部位进行金相解剖，最后对金相照片进行图像处理，得到试样的石墨球化率。结果表明，该铸件的声速与球化率、硬度与球化率之间皆有较好的相关性。实际生产中可通过硬度测量法对球墨铸铁QT400-18的球化率进行抽检，也可采用超声声速测量法对其进行100%快速检验。

The spheroidization rate affects the properties of ductile cast iron. In this paper, ultrasonic C scanning was used to measure the velocity of ductile cast iron QT400-18 sample, and the rigidity of different parts of the sample was recorded and followed by metallographic testing for these specific positions. Afterwards, the metallographic photos were evaluated to get the spheroidization rate of graphite. The results show that the sound speed and spheroidization rate,rigidity and spheroidization rate of the casting have a good correlation. In actual production, the spheroidization rate of the product can be checked by rigidity measurement on spot, and 100% rapid tests can be carried out by ultrasonic sound velocity measurement method.