Quality inspection process and method of straight seam welded pipe

Longitudinal welded pipe (such as ERW pipe) refers to the welded pipe obtained by the straight seam welding of the steel pipe made of hot-rolled or cold-rolled steel plate or steel strip coil welding on the welding equipment. It is named because the weld of the steel pipe is in 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, manufacturers of straight seam welded pipes need to apply a layer of oil on the surface. This can play a role in anti-corrosion, and it is best to mark according to the user's requirements during the oiling process.

2. Straightening and milling of longitudinal welded pipes. It is necessary to use an anvil press to make the original curled steel plate flat, and then use an edge milling machine to perform double-sided milling on both edges of the steel plate, so that it can achieve the required plate width, plate edge parallelism and groove shape.

3. Visual inspection of longitudinal seam welded pipes. Professional technicians are needed to check it to ensure quality problems.

4. Ultrasonic flaw detection of straight seam welded pipes. This is a comprehensive inspection that requires inspection of the inner and outer welds and the base metal on both sides of the weld.

5. X-ray inspection of straight seam welded pipes. Carry out X-ray industrial television inspection of the internal and external welds of longitudinal welded pipe manufacturers.

Quality inspection methods for straight seam welded pipes:

There are many quality inspection methods for longitudinal welded pipes, among which physical methods are also the most commonly used inspection methods. 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.

Different from the straight seam welded pipe, the seamless pipe is made of a steel ingot or a solid tube blank through perforation to make a capillary tube, and then hot rolled, cold rolled or cold drawn. The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness, and are widely used in the manufacture of structural parts and mechanical parts.

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