The quality inspection process of ERW steel pipe includes on-line nondestructive testing, metallographic examination, flattening and flaring failure test and hydraulic test. Assessment process:


1. On-line nondestructive testing
The detection arm of the testing station rotates and is placed in the longitudinal welded pipe production line. The position of weld is observed by camera. The position of the probe is adjusted by using the operating rod to overlap the welding seam with the laser, and the parameters are saved. The coil number is input by DATASERVR and DACQ computer. Observe the waveform display of flaw detection interface. When the waveform exceeds the alarm line, the thickness measurement information is compared to determine whether it is a defect wave or an interference wave signal, and the pipeline is inspected visually to see whether the waveform exceeds the alarm line. If the alarm line exceeds the alarm line, an alarm will be issued. Close and readjust welding parameters in time.


2. Metallographic examination
(1) Metallographic structure of weld. Usually, after weld heat treatment, it is used to judge whether the coarse structure of heat affected zone is completely eliminated, whether it is basically the same as the base metal, and whether it is included in the weld fusion line. Usually, there are no inclusions, microcracks and structured structures in the weld, indicating the welding grid.
(2) Streamline morphology of metals. In high frequency welding, proximity effect and skin effect make the edge of strip melt and semi-melt. Under the pressure of the extrusion roll, the welding metal flows inward and outward, and the mother metal flow lines on both sides of the weld seam are raised to form clamps. Angle, known as streamline angle a, usually determines the weld to be 40 degrees to 70 degrees; beyond this range, welding parameters need to be adjusted in time.


3. Destructive testing
(1) Flattening test. Cut 100 mm welded pipe and place it under the hydraulic press.  The welding position is perpendicular to the direction of the hydraulic press. Start the hydraulic pressure. Slowly press down the welded pipe and press down 3/4 of the diameter to see if the weld cracks. If there are no cracks, weld the grid; if there are cracks, adjust the welding parameters in time.
(2) Expanding test. Place 100 mm welded pipe on the conical top core, place the conical top core under the hydraulic press, start hydraulic pressure, and slowly press down the welded pipe. When the flaring reaches 8%, check whether the weld is broken or not. If there are no cracks, weld the grid; if there are cracks, adjust the welding parameters in time.




4. Hydraulic test
In hydraulic tests, flanges are used to seal both ends of the welded pipe behind the welded flange. Then the pipe is filled with water, and the pressure is gradually applied to the pressure required by relevant standards. After a period of time, visual measurement of pipeline welding. There is no leakage at the joint. If there is no leakage, welding grid; if there is leakage, adjust welding parameters in time. In the hydraulic test, there is no leakage at the weld and the welding mesh is welded. This is also the last step in quality inspection of welded pipe.