The quality inspection process of ERW steel pipe includes on-line nondestructive testing, metallographic examination, flattening, combustion destructive test and hydrostatic test. Evaluation process:
1, online nondestructive testing
The detection arm of the testing station rotates and is placed on the longitudinal welded pipe production line. Observe the position of the weld through a camera. The position of the probe is adjusted by the lever so that the weld overlaps with the laser and saves the parameters. Input the coil number through DATASERVR and DACQ computer. The waveform of the observation defect detection interface is displayed. When the waveform exceeds the alarm line, the thickness measurement information is compared to determine whether it is a defective or interfering wave signal, and the naked eye is checked to see if the waveform is beyond the alarm line. If the alarm line exceeds the alarm line, the alarm will be issued. Close and adjust the welding parameters in time.
2. metallographic examination
(1) metallographic structure of the weld. In general, the weld heat treatment is used to determine whether the coarse structure of the heat affected zone is completely eliminated, whether the weld fusion line has inclusion or not, whether it is basically the same as the base material. Generally, the weld does not contain inclusions, micro cracks and microstructure, indicating the welding mesh.
(2) the flow pattern of metal. In high frequency welding, proximity effect and skin effect make the edge of the strip in molten and semi molten state. Under the pressure of the extrusion roller, the weld metal flows to the inside and outside, and the metal streamline rises on the two sides of the weld to form the clip. The angle of streamline angle is usually determined to be qualified at 40 to 70 degrees. Beyond this range, welding parameters need to be adjusted in time.
3, destructive testing
(1) flattening test. Cut the welding pipe about 100mm and place it under the hydraulic press. The welding position is perpendicular to the direction of the hydraulic machine. Start the hydraulic pressure. Slowly press the weld pipe and press it to 3/4 diameter to see if the weld is cracked. If there is no crack, then weld mesh; if there is a crack, adjust the welding parameters in time.
(2) combustion test. Place the approximately 100mm welded pipe on the cone top core, place the conical top core under the hydraulic press, start the hydraulic pressure, and slowly press down the welded pipe. When the flaring reaches 8%, check whether the weld is cracked. If there is no crack, then weld mesh; if there is a crack, adjust the welding parameters in time.
4, hydraulic test
In hydraulic tests, the flange is 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 of the related standard. After a period of time, the pipe welding is visually measured. There is no leakage at the seam. If there is no leakage, please weld the mesh; if there is any leakage, adjust the welding parameters in time. In the hydraulic test, there is no leakage at the weld, and the welding mesh is welded. This is the last step in the quality inspection of welded steel pipes.