中文摘要：

对弹簧扁钢的全厚度范围进行C扫描成像检测时,需以一定间隔调整焦点位置以确保检测精度。本研究测量了聚焦声束焦柱高度并分析其对C扫描图像的影响,提出了应用于弹簧扁钢全厚度C扫描成像检测的焦距调整法则。此外,通过分析C扫描图像的特征区域确定缺陷边界,并通过金相试验对其进行了验证。研究结果显示：根据焦柱高度确定焦距调整间隔可在提高检测效率的同时保证较高的检测精度,所提出的缺陷图像特征边界可用于精确测量缺陷尺寸;水浸聚焦超声C扫描成像方法可用于评价弹簧扁钢内部缺陷的尺寸及其分布。

英文摘要：

When the ultrasonic C-scan image is adopted for full thickness range testing of spring flat steel, focus position must be adjusted with regular interval to keep better testing accuracy. In the research, the height of focusing column is measured and its influences to the C scan imaging are analyzed. And then, the adjusting law of focusing position for C scan imaging is proposed. Besides, the characteristic area of scanning imagery is analysis to decide the defects boundary and which is verified by metallographic test. The results indicate both higher testing accuracy and testing efficiency can be obtained by setting a proper focusing interval according to the height of focusing column, and the boundary of defect imagery proposed in the paper can he used to measure the defect＇ s dimension. Therefore, utrasonic water immersion focusing method can be used to evaluate the dimension and distribution of inner defects in spring fiat steel.