Identification of Weld Defects and Internal Burrs of High-frequency Steel Pipe Welds

Common defects in high-frequency steel pipe welds include weld cracking, cracking, unfusion, cold welding, internal and external burrs, and inclusions. For weld cracking and cracking, there are strong defect reflection echoes in the actual test, which is easy to detect and judge. The echo height of the crack is generally large (large crack wave width, small crack wave width is narrow), sometimes there are many Peak (illustrated as hot crack). When the probe is translated, the reflected wave appears continuously, and the amplitude of the probe changes. When the probe rotates, the peak will be shifted up and down.

The unfused defect is generally small, and the main characteristic of the defect reflected wave is that the waveform is relatively stable when the probe is translated, and the reflected wave amplitude is substantially the same when the two sides are detected.

High-frequency steel pipe welds are formed without metal filling materials, and there are few slag inclusions. However, problems such as burrs, rust, pitting, and composition of the coils may occur. The surface of the inclusions is irregular and is divided into point inclusions and strip inclusions. The echo signals of the point-like inclusions are similar to the point-like pores; the strip-shaped inclusion echo signals are mostly saw-toothed, the reflectivity is low, and the general amplitude is not high. Its waveform is short, often dendritic, and there are small peaks on the main peak. The amplitude of the probe changes when it is translated, and it is detected from all directions, and the reflected amplitude is different.

The molten metal extruded during the welding of the high-frequency steel pipe is scraped off by the inner and outer scrapers, but it is extremely easy to produce residual internal and external metal at the weld, that is, internal and external burrs. The outer burr is easy to see on the outer surface of the steel pipe, which helps to identify it well, but the inner burr is on the inner wall of the steel pipe, and the inspection personnel cannot see it. The echo is often mistaken for the weld defect echo, which causes misjudgment of the test result.. Under normal circumstances, the internal burrs are relatively long, and the reflected echoes are continuously and stably present. The probe is moved back and forth, and the echoes move accordingly.

Internal burrs usually have a unilateral inner burr and a trapezoidal inner burr. For a single-sided internal burr, the reflected echo can only be detected on one side of the weld and no reflected echo on the other side. In the trapezoidal inner burr, the reflected echo can be detected from both sides of the weld.

The identification of internal burr echoes can use the following multiple wave method. Adjust the probe on the vertical hole of the sensitivity test block, and mark the position of the secondary echo and the tertiary echo on the display screen of the test instrument.

The primary wave of the inner burr exceeds the secondary wave of the vertical through hole, and the third wave of the burr wave lags behind the third wave of the vertical through hole, and the burr wave can be distinguished from the horizontal scale of the display screen. The unilateral inner burr echo can only be detected from the weld side, and the trapezoidal inner burr is detected from both sides. If there is a weld defect echo, the echo is generally between the second wave and the third wave, so that the weld zone defect echo and the inner burr echo can be distinguished.

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