ERW pipe quality assessment process
ERW Pipe quality assessment process
The quality assessment process of ERW Electric Resistance Welding pipe consists of on-line nondestructive testing, metallographic inspection, flattening and flaring destructive tests, and hydraulic tests.
Evaluation process:
1, online non-destructive testing
The detection station's probe arm was placed in the ERW tube production line. The position of the weld was observed through the camera. The position of the probe was adjusted by using the operating rod, so that the weld coincided with the laser and the parameters were saved. Enter the coil number via the DATASERVR and DACQ computers. Observe the waveform display of the flaw detection interface. When the waveform exceeds the alarm line, compare the thickness measurement information to determine whether it is a defect wave or an interference wave signal, and visually inspect the pipe to see if the waveform exceeds the alarm line. If the alarm line exceeds the alarm line, an alarm will be given. Shut down in time and readjust welding parameters.
2, metallographic examination
(1) Metallographic microstructure of the weld. Generally, after the heat treatment of the weld seam, it is used to judge whether the heat-affected zone coarse structure is completely eliminated and whether it is basically the same with the base material, whether there is inclusion in the weld fusion line. In general, the welds are free of inclusions, microcracks, and organized structures, indicating a welded grid.
(2) Metal streamline morphology. In high-frequency welding, the proximity effect and the skin effect make the strip edge in a molten and semi-molten state. Under the pressure of the squeezing roller, the weld metal flows inwards and outwards, and the parent metal flow line on both sides of the weld is raised to form a clip. Angle, called the streamline angle α, generally determines the weld as qualified at 40° to 70°; beyond this range, the welding process parameters need to be adjusted in time.
3. Destructive test
(1) Flattening test. Cut about 100mm welded pipe and place it under the hydraulic machine. The weld position is perpendicular to the direction of the hydraulic press. Start the hydraulic pressure. Slowly press down the welded pipe and press it to 3/4 of the diameter to see if the weld cracks. If there is no crack, the welding seam is lattice; if there is crack, adjust the welding process parameters in time.
(2) Flaring test. Cut about 100mm welded pipe and place it on a conical top core; place the conical top core under the hydraulic press, start the oil pressure, slowly press the welded pipe, and when the flaring is 8%, check whether the weld is cracked. If there is no crack, the welding seam is lattice; if there is crack, adjust the welding process parameters in time.
4, hydraulic test
In the hydraulic test, flanges are used to seal both ends of the welded pipe behind the welding flange, and then the pipe is filled with water and pressure is gradually applied to the pressure required by the relevant standards. After a certain period of time, the pipe welding is visually measured. There is no leakage at the seam. If there is no leakage, weld the grid; if there is leakage, timely adjust the welding process parameters. In the hydraulic test, there was no leakage at the weld seam and the weld grid was welded. This is also the last step in the quality inspection of the welded pipe.
