Do high-frequency erw steel pipes need to be inspected after production? This answer is yes, so as to better ensure the quality of the welded pipe, so that customers can use it with confidence. Next, talk about the way of detecting the welded pipe. The method of ultrasonic testing is called ultrasonic flaw detector.

Its principle is: when the ultrasonic wave propagates in the material to be tested, the acoustic characteristics of the material and the change of the internal structure have a certain influence on the propagation of the ultrasonic wave. The technology for understanding the material properties and structural changes by detecting the degree and condition of the ultrasonic wave. It is called ultrasonic testing.

Ultrasonic testing methods usually include penetration method, pulse reflection method, tandem method, etc. Ultrasonic flaw detection is to use ultrasonic energy to penetrate deep into the metal material, and to reflect from the edge of the interface when a section enters another section.

A method of defect of a part, when the ultrasonic beam passes from the probe to the inside of the metal from the surface of the part, and a reflected wave occurs respectively when the defect and the bottom surface of the part are encountered, and a pulse waveform is formed on the fluorescent screen, and the defect position is determined according to the pulse waveform and size.

A non-destructive test method for the inspection of internal defects of materials using the effects of acoustic properties of materials and their defects on ultrasonic propagation. Ultrasonic pulse reflection methods for observing the reflection of acoustic pulses in materials are widely used, as well as penetration methods for observing changes in the amplitude of incident acoustic waves after passing through the material. Commonly used frequencies are between 0.5 and 5 MHz.

The commonly used inspection instrument is a type A display pulse reflection type ultrasonic flaw detector. According to the presence or absence of the reflected signal on the instrument oscilloscope, the time interval of the reflected signal and the incident signal, and the height of the reflected signal, the presence or absence of the reflective surface, its position and relative size can be determined. The basic structure and principle of the instrument are shown in Figure 1.

Ultrasonic waves have a variety of modes when propagating in the medium. The most commonly used tests are longitudinal waves, transverse waves, surface waves and plate waves. Longitudinal waves can be used to detect defects such as inclusions, cracks, shrinkage, white spots, delamination, etc. in metal ingots, billets, plate, large forgings and relatively simple shapes; Circumferential and axial cracks, scratches, pores in the weld, slag inclusions, cracks, incomplete penetration, etc.; surface waves can be used to detect surface defects on simple shapes; defect.

The B-type and C-type flaw detectors developed on the basis of the A-type flaw detector can obtain the signals of the reflective surfaces in different directions, and can also combine the B-type and C-type displays to obtain the three-dimensional display of the internal reflective surface of the material.

Each of the above types of flaw detectors uses a pulsed electrical signal to excite the piezoelectric transducer to emit ultrasonic waves, but an eddy current transducer can also be used to inspect the conductive material. The transducer’s transducing process is carried out on the surface of the flawed part without the need for contact with the material and without the need for a coupling agent to inspect metal materials with surface roughness and temperatures up to 500 ° C. Spiral steel tubes are used in the metallurgical industry.