There are many kinds of quality inspection methods for stainless steel welded pipe, among which the physical method is also a common inspection method, and the physical inspection is the method of measuring or testing by using some physical phenomena. Nondestructive testing is generally used to inspect the internal defects of materials or stainless steel welded pipes. The current non-destructive testing includes magnetic testing, ultrasonic testing, radiographic testing, penetrant testing, etc.
Magnetic flaw detection can only find the surface and near surface defects of magnetic stainless steel welded pipe, and the defects can only be quantitatively analyzed, and the nature and depth of the defects can only be estimated according to experience. Magnetic inspection is to find defects by magnetic flux leakage produced by magnetizing ferromagnetic stainless steel welded pipe with magnetic field. According to the different methods of magnetic flux leakage measurement, it can be divided into magnetic powder method, magnetic induction method and magnetic recording method.
Penetrant testing is to find and display defects by using the physical properties of some liquids, such as permeability. It includes two kinds of dye testing and fluorescent testing. It can be used to check the surface defects of ferromagnetic and non ferromagnetic materials.
X-ray inspection is a kind of inspection method to find defects by using the characteristics of ray penetrating and attenuation in the material. According to the different rays used in flaw detection, it can be divided into X-ray flaw detection, gamma ray flaw detection and high energy ray flaw detection. Because of the different methods of showing defects, each kind of radiographic inspection is divided into ionization method, fluorescent screen observation method, photography method and industrial television method. X-ray inspection is mainly used to inspect the internal cracks, incomplete penetration, porosity, slag inclusion and other defects of stainless steel welded pipe.
When ultrasonic wave propagates in metal and other homogeneous media, it can be used to inspect internal defects because of its reflection on the interface of different media. Ultrasonic can detect the defects of any material and any part of the weldment, and can detect the defect location more sensitively, but it is difficult to determine the nature, shape and size of the defect. Therefore, ultrasonic flaw detection of stainless steel welded pipe is often used together with radiographic inspection.