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Quality Inspection Method of LSAW Welded Pipe

Date:2021-05-13    keywords: LSAW steel pipe, quality inspection

There are many ways to inspect the quality of LSAW steel pipes, among which physical methods are also the most commonly used inspection methods. Physical inspection is a method of measuring or inspecting using some physical phenomena. The inspection of internal defects of materials or longitudinally welded pipes generally adopts non-destructive testing methods. The current non-destructive testing includes magnetic testing, ultrasonic testing, radiographic testing, penetrating testing and so on.

lsaw steel pipe

1. Magnetic inspection
Magnetic inspection can only find defects on the surface and near the surface of the magnetic LSAW longitudinally welded pipe, and only quantitative analysis of the defects can be done, and the nature and depth of the defects can only be estimated based on experience. Magnetic inspection is to use magnetic field magnetization of ferromagnetic longitudinally welded pipes to generate magnetic flux leakage to find defects. According to the different methods of measuring magnetic flux leakage, it can be divided into magnetic particle method, magnetic induction method and magnetic recording method. Among them, the magnetic particle method is the most widely used.

2. Penetration test
Penetration inspection uses physical properties such as the permeability of certain liquids to discover and display defects, including color inspection and fluorescent inspection, which can be used to inspect defects on the surface of ferromagnetic and non-ferromagnetic materials.

3. Radiographic inspection
Radiographic testing is a testing method that uses radiopaque material and attenuation in the material to find defects. According to the different rays used in flaw detection, it can be divided into three types: X-ray flaw detection, γ-ray flaw detection, and high-energy ray flaw detection. Because of the different methods of displaying defects, each type of radiographic flaw detection is divided into ionization method, fluorescent screen observation method, photographic method and industrial television method. Radiographic inspection is mainly used to inspect defects such as cracks, incomplete penetration, pores, and slag inclusions in the weld of LSAW longitudinal welded pipes.

4. Ultrasonic flaw detection

When ultrasonic waves are propagated in metals and other homogeneous media, they are reflected on the interface of different media, so they can be used for internal defect inspection. Ultrasonic can inspect the defects of any weldment material and any part, and can find the defect position more sensitively, but it is difficult to determine the nature, shape and size of the defect. Therefore, LSAW longitudinal welded pipe ultrasonic flaw detection is often used in conjunction with radiographic inspection.

Tips: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW tube) and submerged arc welded straight seam steel pipes (LSAW tube) according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.

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