根据生产中遇到的薄形环状开口零件中的空气间隙会对磁化检测产生影响的问题，找出了影响磁场强度大小的因素。以某产品的挡圈零件为例进行磁粉检测试验，结果表明，空气间隙不仅增大了磁路的磁阻，还在间隙处产生了大的磁压降，从而造成零件上的磁化不足，使得某些细微缺陷不能很好地检出。

According to the problem that the air gap in the thin annular opening parts was to affect the magnetization detection, the factors affecting the magnetic field strength were found out. Taking the magnetic particle testing of the product of ring parts as an example,test results showed that the air gap increased the magnetic reluctance, produced a more magnetic pressure drop in the gap and resulted in the lack of magnetization, which made some minor defects difficult to be detected very well.