磁粉强度H垂直干缺陷走向时．磁痕显现最清楚，显现磁痕的最小磁场强度值称为起始磁场强度Ho。当磁场方向与缺陷法线成一定角度θ时．其形成磁痕的能力就下降。对与Ho成θ角度的缺陷形成磁痕能力的研究关系到磁探基本原理，对一些实际问题，如：干法、水基、油基湿法灵敏度差异 Magnetic powder strength H vertical dry defect to the time. Magnetic marks appear most clearly, showing the minimum magnetic field strength magnetic field value is called the initial magnetic field strength Ho. When the magnetic field direction and the defect normal angle at an angle θ. Its ability to form magnetic marks decreases. The study of the ability to form a magnetic mark at a defect angle of θ with respect to Ho relates to the basic principles of magnetic exploration. For some practical problems, such as dry method, water-based, oil-based wet method, sensitivity difference