用光学金相显微镜和扫描电镜对热轧板焊缝超声波探伤不合格区域进行了相关观察和分析，结果表明：引起探伤不合格的主要原因是焊缝中存在夹渣，这些夹渣是由于焊接时清根不干净或清根时操作不当造成根部坡口角度过小，致使熔渣来不及浮起而形成的。

The optical microscope and scanning electron microscope were used to analyze the causes of nonconformity in ultrasonic flaw detection for welding seam of hot rolled steel plates. The result of the metallographic analysis and energy spectrum analysis showed that the main reason of the unqualified was the slag inclusions in the welding seam, which were the welding slag caused by the wrong back gouging.