Stainless steel tubes are long products (round, oval, square / rectangular).
By the way of manufacturing, stainless steel pipes are divided into two classes: welded and seamless.
Seamless tubes are those produced without a welding process at any stage of production.

By their means of production, seamless stainless pipes are divided into:

  • Hot rolling
  • Cold rolling
  • Centrifugal cast

Welded tubes imply a welding process for at least one step in the manufacturing process, typically, in forming a closed tube profile.

According to the method of preparation of a tube profile in regards to its welding and the position of a welded seam, the tubes are divided into:

  • LPD large diameter pipes - LDP.
  • Longitudinal: velded with multiple (both longitudinal and transverse) welded seams (the tube profile is formed and shaped by several steel plates in a certain way) - usually, LDP; with one longitudinal welded seam, the profile for welding is formed by sheet or a mill in a continuous cold rolling strip - the BaltInox company uses the latter method in the production of welded tubes. See the description of the production process concerning the production of tubes in mills of continuous welding.

About the main advantages of tube produced by each of the above methods

Until recently, the attitude to high-alloy steel welds was wary, but over time, with the development of new methods of welding, it has gradually improved. This sceptical attitude to welded tubes since the dawn of their production has led to the prohibition of the use of welded stainless steel tubes at important, and even more so, dangerous objects.

However, time does not stand still, and with the development of new welding processes, technologies and the quality control of welded joints, the consumer properties of welded stainless steel tubes constantly improved until, at its extreme, it reached the level of the consumer properties of seamless tubes and has even surpassed them in some parameters. Over time, welded tubes took over a very large market share from seamless tubes and currently, the share of seamless tubes in the global consumption of tubular stainless steel products is vanishingly small. Welded tubes have been successfully applied in all industries, including dangerous sites classified as having a hazard class no higher than the class 2, i.e. almost everywhere, except for very specific and super-critical applications such as the manufacture of the fuel assemblies of nuclear reactors. To be fair, it should be noted that not every seamless tube, but only those manufactured and tested according to very strict standards, can be used in super-critical industries. I.e. it can be argued that in its consumer properties and performance, welded tube is at least not inferior to the ordinary assortment of seamless tubes (manufactured according to DIN 17458; ASTM A312, A213; GOST 9940 and 9941).