Magnetic flaw detection can only find the surface and near surface defects of the magnetic Q235B welded pipe,and it can only do the quantitative analysis for the defects.For the nature and depth of defects,it can only be estimated based on experience.Magnetic inspection find the defects by using leakage of magnetic,which is produced by magnetic field magnetization Q235B welded pipe.According to the different methods of measuri- ng leakage of magnetic,it can be divided into magnetic powder method, magnetic induction method and magn- etic recording method, in which the most widely used magnetic powder method.
