某批次4130钢锻件超声检测结果不符合JB/T 5000.15—2007标准要求，锻钢件心部位置存在密集和单个超标缺陷，采用化学成分分析、低倍检验、金相检验、扫描电镜和能谱分析等方法对缺陷位置进行分析，结果表明：4130钢锻件原材料内部存在大量MnS和NbC夹杂物，这些夹杂物分割了钢材本身的基体连续性，在锻造加工过程中形成裂纹，造成超声检测结果不合格。最后分析了MnS和NbC夹杂物的来源及其危害性，找出了对应的工艺改善措施，改进后4130钢锻件的超声检测合格率为100%。

The ultrasonic testing results of a batch of 4130 steel forgings did not meet the requirements of JB/T 5000. 15-2007 standard. There were dense and single excessive defects in the center of the forging steel. The chemical composition analysis, macroscopic test, metallographic examination, scanning electron microscopy and energy spectrum analysis were used to analyze the location of the defects. The results show that there were a large number of MnS and NbC inclusions in the raw materials of 4130 steel forgings. These inclusions divided the matrix continuity of the steel itself, and cracks were formed during the forging process, resulting in unqualified ultrasonic testing results. Finally, the source and harmfulness of MnS and NbC inclusions were analyzed, and the corresponding process improvement measures were found out. The qualified rate of ultrasonic testing of 4130 steel forgings after improvement was 100%.