用磁法检测不锈钢残余应力的探讨

Study on Measuring Residual Stress of Stainless Steel by Magnetic Method

残余应力的存在,将影响构件的静载强度、疲劳强度、抗应力腐蚀等性能及尺寸的稳定性,严重时将直接引发裂纹缺陷。以地磁场为磁源,根据残余应力使材料磁导率改变的特性,通过微磁检测技术检测304不锈钢表面的磁场强度变化,为其内部残余应力进行了定位和初步定量。通过测量退火前后304不锈钢内部磁场强度的变化来确定残余应力的变化。通过检测数据发现残余应力大小与磁场强度之间有密切关系,在退火前后其残余应力改变的幅值一定,而磁场强度所改变的幅值也相对稳定。用磁法检测304不锈钢的残余应力是可行的。

The existence of residual stress will affect the static load strength, fatigue strength stress corrosion resistance and dimensional stability of the components. Worse still, it may directly lead to crack defects. The magnetic field intensity of 304 stainless steel was measured by micro-magnetic testing technology, and the residual stress was localized and quantified, taking the geomagnetic field as the magnetic source, based on the features that residual stress changes the permeability of materials. The residual stress was determined by measuring the magnetic field intensity of 304 stainless steel before and after annealing. The results show that there is a close relationship between the value of residual stress and the intensity of the magnetic field. The amplitude of the residual stress changes is constant before and after annealing, and the amplitude of the change of the magnetic field intensity is relatively stable. It is feasible to detect the residual stress of 304 stainless steel by magnetic method.