在对火箭炮用闭锁体进行磁粉检测时, 批量出现疑似裂纹的黑色线磁痕。经低倍检验、光学显微镜及扫描电镜分析后发现, 黑色线磁痕的形成是由于负偏析引起, 不是裂纹, 属于非相关显示。结果表明: 只要连铸时选择合适的电磁搅拌强度和搅拌时间, 就可以减轻负偏析。

There appears the magnetic mark line during magnetic particle inspection of the batch atresias used by rockets. It was suspected that there might be cracks in the products. It is whereas concluded that the magnetic mark lines are caused by segregation and there are no cracks in the material following a careful analysis by macroscopic examination, scanning electronic microscope and metallographic microscope. The magnetic mark lines can be avoided by choosing the appropriate electromagnetic stirring intensity and stirring time during continuous casting.