某公司生产设备上的304不锈钢止回阀在使用过程中发生了断裂。采用宏观分析、化学成分分析、断口分析、非金属夹杂物检测、金相检验、显微硬度测试等方法对止回阀的断裂原因进行了分析。结果表明：止回阀的断裂位置位于焊缝处，为一次性过载断裂。由于焊接工艺不当，在焊缝处存在未焊透缺陷，使该止回阀管的强度降低，在较大的介质应力作用下，发生了一次性过载断裂。

The 304 stainless steel check valve on a company's production equipment fractured during use. The fracture causes of the check valve were analyzed by means of macro analysis, chemical composition analysis, fracture analysis, non-metallic inclusion detection, metallographic examination, microhardness test and so on. The results show that the fracture position of the check valve was located at the weld seam, which was one-time overload fracture. Due to the improper weld seam process, there was unwelded defect at the weld seam position, which made the strength of the check valve tube reduce. Under the action of large medium stress, one-time overload fracture occurred.