How to produce and where to use steel welded pipes

We live in the era of pipelines. At the same time, the main consumers of pipe products are oil and gas transport enterprises. And seamless pipes alone are indispensable. After all, the expensive production of such rolled products is not always covered by the ability to withstand hundreds of atmospheres of pressure. In many pipelines, the indicator does not reach even half of the critical values, and it becomes unprofitable to use expensive rolled products.

In addition, production technologies do not stand still, and welded steel has long been approaching seamless in terms of characteristics.

This is how welded pipes are firmly entrenched in the market and hold their positions. Due to the lower cost of production, they are worthy competitors of seamless ones. And today, more than half of large-diameter pipe products are welded.

Straight or spiral stitch

Welded pipes is a relatively young type of steel. The first samples appeared only in 1824. This type of metal products was originally produced by forging. Only at the beginning of the last century did welding of the heated edges of the workpiece become widespread. And after the advent of the electric method of welding, they began to be divided into straight and spiral stitch.

Squamous pipe rolling is produced in two stages. The steel strip is heated to the plastic state of the metal. Then it is passed through the rolls of rolling mills, which roll the billet into a "tube". After, using the method of electric welding, it is connected into a pipe. This is a cheap and simple technology, but it has some drawbacks:

• for products of different diameters, strips of different widths are needed;
• for the production of pipes of different diameters, it is necessary to constantly re-equip the entire production line;
• after the product has cooled down, stress develops in the weld, which can reduce its strength;
• if the pressure exceeds the critical one, the pipe breaks along the entire length of the seam, which greatly complicates the elimination of the gust.

Spiral-seam pipes are made by joining with a spiral seam. With this type of production, the joint itself is much longer.

But this technology has a number of advantages:

• rolled pipe is welded from a metal strip of any width;
• for the production of pipes of different diameters, you just need to reconfigure the rolling plants;
• welding does not require strong heating of the metal strip, as a result, the metal retains its properties better;
• the spiral seam is an additional reinforcing element;
• in the event of a rupture along the seam, the damage does not go along it, but obliquely, which facilitates the replacement of the damaged section of the pipeline.

Pros of welded pipes

The main advantage of welded tubular products is the relative cheapness of production. In addition, they can be produced in diameters up to 100 times the wall thickness. Therefore, they are lighter and easier to transport. Indispensable for the creation of main oil and gas pipelines.

Straight-seam production technology allows you to form not only round, but also square or rectangular pipes.

The main disadvantages of welded pipes

But this type of rental is not without drawbacks. A welded pipe withstands pressure, on average, 25-30% lower than a seamless one.

This type of steel is not suitable for bending work. Therefore, to change the direction of the line, it is necessary to use fittings.

Production technology involves the use of low-alloy carbon steels, which are more susceptible to corrosion. To slow down this process, galvanizing, waterproofing or thermal insulation is used.