Causes of sand holes in spiral steel pipe welds

Spiral steel pipes are formed by bending the strip steel in the spiral direction through a coiling machine, and then welding it through capacitance double-sided submerged arc welding. In the production process of spiral steel pipe welding, many situations such as missed welding and misalignment are prone to occur. However, the most difficult thing to grasp in these situations is the appearance of sand holes at the butt welds of spiral steel pipes.

What is the sand hole？

During the welding process, there are particles or bubbles that have not been completely melted through on the surface or inside the weld seam, as well as sand shaped pits on the surface of the weld seam.

There are several reasons for the occurrence of sand hole:

• 1. During the welding process, the current supplied to the welding gun is too small, the capacitance time is too short, and the welding surface has hardened before the capacitance is fully welded, resulting in the appearance of sand particles or bubbles that have not been fully welded.

• 2. When the strip steel enters the curved blade shaped adjustment curve, it is not well docked, and the strip steel is not tightly jointed, resulting in excessive gaps between the docked strips.

• 3. When butt welding the strip steel, the rust or oxide skin on both sides of the strip steel was not cleaned in a timely manner.

• 4. The production equipment was not repaired and cleaned in a timely manner. Dust or dirt on the workbench accidentally fell into the welding gap of the butt welded strip steel.

• 5. The temperature in the operating workshop is too low or too humid, which can affect the temperature and dryness of the welding points.