Longitudinal welded pipe (ERW pipe or LSAW pipe) refers to a welded pipe obtained by straight seam welding of steel pipes made of hot-rolled or cold-rolled steel sheets or steel strip coils on welding equipment. It got its name because the welds of the steel pipes form a straight line. Longitudinal welded pipe manufacturers follow strict production processes during production, but it is difficult to say that 100% of the products produced are qualified and excellent, so this requires quality inspection of straight seam welded pipe manufacturers. What are the quality inspection processes for straight seam welded pipes?
1. Oil marking of straight seam welded pipes. After passing the inspection, the manufacturers of straight seam welded pipes need to apply a layer of oil on the surface, which can play a role in anti-corrosion. In the process of oiling, it is best to mark according to the user's requirements.
2. Straightening and milling of straight seam welded pipe: it is necessary to use an anvil machine to make the original curled steel plate flat. After that, the two edges of the steel plate are milled on both sides by the edge milling machine, so that it can achieve the required plate width, plate edge parallelism and groove shape.
3. Visual inspection of longitudinal seam welded pipe requires professional technicians to inspect it to ensure quality problems.
4. Ultrasonic flaw detection of straight seam welded pipe, which is a comprehensive inspection that needs to check the inner and outer welds of the straight seam welded pipe manufacturer and the base metal on both sides of the weld.
5. X-ray flaw detection of straight seam welded pipes, X-ray industrial TV inspection of the inner and outer welds of straight seam welded pipe manufacturers.
Quality inspection methods for straight seam welded pipes:
There are many quality inspection methods for longitudinal welded pipes, among which the physical method is also the most commonly used inspection method. Physical inspection is a method of measuring or inspecting by using some physical phenomena. The inspection of materials or internal defects of longitudinal welded pipes generally adopts the method of non-destructive testing. The current non-destructive testing includes magnetic testing, ultrasonic testing, radiographic testing, penetrant testing, etc.
1. Magnetic test
Magnetic flaw detection can only find defects on the surface and near the surface of magnetic longitudinal welded pipes, and can only do quantitative analysis on defects, and the nature and depth of defects can only be estimated based on experience. Magnetic inspection is to use the magnetic flux leakage generated by the magnetic field magnetization of the ferromagnetic straight seam welded pipe to find the defect. According to the different methods of measuring magnetic flux leakage, it can be divided into magnetic powder method, magnetic induction method and magnetic recording method, among which the magnetic powder method is the most widely used.
2. Penetration testing
Penetrant inspection is to use the physical properties of certain liquids such as permeability to find and display defects, including coloring inspection and fluorescent flaw detection, which can be used to inspect the defects on the surface of ferromagnetic and non-ferromagnetic materials.
3. Radiographic flaw detection
Radiographic flaw detection is a flaw detection method that uses the properties of rays that can penetrate substances and have attenuation in substances 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. Due to the different methods of displaying defects, each type of ray inspection 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 inside the welds of longitudinal seam welded pipes.
4. Ultrasonic flaw detection
Ultrasonic waves can be used in the inspection of internal defects due to the reflection on the interface of different media in the propagation of metal and other homogeneous media. Ultrasound can inspect any weldment material, any defect in any part, and can detect the defect position more sensitively, but it is difficult to determine the nature, shape and size of the defect. Therefore, ultrasonic flaw detection of straight seam welded pipes is often used in conjunction with radiographic inspection.