In this article, let Baowu take you to understand the mystery in depth.

Spiral welded steel pipe refers to a steel pipe with seams on the surface that is welded by bending and deforming a steel strip or steel plate into a round, square or other shape. According to the shape of the weld, it can be divided into straight seam welded pipe and spiral welded pipe. Large-diameter straight seam welded pipes are used for high-pressure oil and gas transportation, etc.; spiral welded pipes are used for oil and gas transportation, pipe piles, bridge piers, etc. Welded steel pipes have lower cost and higher production efficiency than seamless steel pipes.

The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is fast. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe. But compared to the same length of straight seam pipe, the length of the weld is increased by 30-100%, and the production speed is lower. Therefore, most of the welded pipes with smaller diameters use straight seam welding, and most of the welded pipes with large diameters use spiral welding.

So why are there horizontal lines on the surface of the spiral welded pipe?

The first may be due to the stress of the spiral seam submerged arc welded steel pipe. That is, the residual stress and welding stress after the steel pipe is formed.

Secondly due to the presence of hydrogen. If the flux is not dried enough, the preheating temperature is not sufficient or the preheating before welding is not carried out, and the interlayer temperature of multi-layer welding is not enough.

There is also the metallurgical factor of the spiral welded steel pipe. There are low melting point impurities in the welding process, such as copper and copper alloys.

Therefore, the horizontal stripes on the surface of the welded pipe can be avoided by the process in the processing. Of course it will not affect the use.

The above is the relevant content of welded steel pipes. If you want to know more, please pay attention to Baowu at any time.