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Common Defects of Spiral Welded Pipes

2023-02-14

Common Defects of Spiral Welded Pipes

i) The main cause of the bubbles in the center of the weld bead is hydrogen is concealed within the weld metal as bubbles.  Thus, to eliminate this defect, remove the wire and weld the rust, oil, water, moisture, and other things, and then fully dry the flux to remove moisture. Furthermore, a higher current slows the solidification rate of liquid metal, limiting welding speed.

ii) Cracking of sulfur (crack caused by sulfur). The sulfide in the sulfur segregation zone enters the weld metal and causes cracks when welding plates with a strong sulfur segregation zone (particularly soft boiling steel). The explanation for this is the existence of hydrogen in steel and low-melting iron sulfide in the sulfur segregation zone. As a result, using semi-ballasted or ballasted steel with a lower sulfur-containing segregation zone is an effective way to avoid this. Cleaning and drying the weld surface and the flux is also required.

iii) Thermal cracking is a type of cracking caused by heat. Thermal cracks in the weld bead can form in submerged arc welding, particularly at the arc initiating and extinguishing arc craters. Backing plates are installed at the arc starting and arc extinguishing sites to eliminate such cracks. The spiral welded pipe can be reversed and welded into the overlap welding after the coil butt welding. When the weld stress is high, hot fractures are more prone to form.

iv) The presence of welding slag. Welding slag involvement refers to the amount of welding slag that remains in the weld metal.

v) There is a lack of penetration. The overlap between the inner and outer weld metals is insufficient, and the weld is not penetrated. Insufficient penetration is the term for this condition.

Disadvantages of Spiral Welded Pipes

Because the raw material is coiled steel, there is a crescent bend, and the welding point is in the elastic strip edge area. Aligning the welding torch is problematic, affecting welding quality. Set up complex weld tracking and quality inspection devices to accomplish this.

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