纵波探伤是检测中厚钢板内部质量的主要方式。探伤钢板按不同标准、不同级别进行检测判定。对于钢板内部存在的缺陷，有些是标准允许的，有些则是纵波探伤技术性问题而无法检测出来。目前对缺陷的定性、定量技术，还不能完全满足科研人员了解产品内部缺陷详细情况的要求。为此笔者阐述了探伤合格钢板存在缺陷的原因，及缺陷定性、定量的不确定性问题。

Detection of thick steel plate by longitudinal wave is the main form of testing internal quality. We judge the quality of steel plate according to different standards and different level. For internal defects, some of them are allowed by standards, whereas some others are due to testing technique of longitudinal wave detection. The current shortcomings of qualitative and quantitative techniques can not fully meet the requirement of scientific researchers to understand details of defect in the steel plate, and an effort is therefore made to give the explanation of it.