There are many methods for the quality inspection of Straight Seam Welded Pipe, of which the physical method is also the most commonly used method of inspection. Physical testing is the method of measuring or testing using some physical phenomena. Inspection of internal flaws in straight seam welded pipe is generally based on non-destructive testing. The current non-destructive flaw detection includes magnetic flaw detection, ultrasonic flaw detection, ray detection, and penetrant flaw detection.
Magnetic flaw detection can only detect defects on the surface and near surface of the magnetic straight seam welded pipe, and only quantitative analysis can be performed on the defect. The nature and depth of the flaw can only be estimated based on experience. Magnetic testing is the use of magnetic field magnetization of the magnetic flux leakage generated by the straight seam welded pipe to find defects. According to the measurement of magnetic flux leakage method, it can be divided into magnetic powder method, magnetic induction method and magnetic recording method, of which the magnetic powder method is the most widely used.
Penetration testing is the use of certain liquid permeability and other physical characteristics to find and display defects, including two kinds of color testing and fluorescent inspection, can be used to check the surface of ferromagnetic and non-ferrous materials defects.
Radiographic inspection is a flaw detection method that uses ray-penetrating substances and attenuating properties in the material to detect defects. According to the different types of radiation used for flaw detection, it can be divided into three types: X-ray inspection, γ-ray inspection, and high-energy ray inspection. Due to the different methods of displaying defects, each type of radiographic inspection is divided into ionization, screen observation, photography, and industrial television. The ray inspection is mainly used to inspect the cracks, incomplete penetration, porosity, slag inclusions and other defects in the weld seam of the longitudinal welded pipe.
Ultrasonic waves can be used for the inspection of internal defects due to reflections at the interfaces of different media in the propagation of metals and other homogeneous media. Ultrasonic waves can inspect any weldment material, defects in any part, and can find the defect location sensitively, but it is difficult to determine the nature, shape and size of the defect.
Ultrasonic flaw detection of straight seam welded pipe is often used in conjunction with ray inspection.