Stainless Steel pipes and stainless steel are of two types- Welded and Seamless. Of these, seamless pipes and seamless tubes are considered the most ideal for expensive industries. That is because there is no worry of leakages or tears with seamless tubing.
This lack of worry is due to the seamless tube manufacturing process. Since they are not welded together using heat, they have no weak spots. They are single, consistent tubes of stainless steel. The method of producing seamless stainless piping is costlier than welding. But when it comes to transportation of fuels, medicines, chemicals, and harmful gases, it is a worthwhile investment.
The cold-rolling process and the cold drawing process are two ways of producing seamless tubes efficiently.
Cold rolling is a work solidifying process used to change the design of metals and is regularly used to deal with treated steel. Cold rolled hardened stainless steel as a base substance has a wide assortment of clinical, aviation, and auto designing utilizations.
Cold pilgering, also known as tube reduction or cold rolling, is a process where a tube is cold-reduced by working it between a rocking set of dies on the outside and a hardened mandrel on the inside. In this process, the hollow metallic tube is reduced along three dimensions: outer diameter, internal diameter, and wall thickness; reduction in these factors elongate the length of the tube further. In this process, 50 – 60% reduction rates are achieved in just a single pass, which is a lot higher than the reductions achievable in the cold drawing process. Seamless hollow undergoes high compressive residual stress during the cold Pilger process, thus attaining the highest quality of finished seamless pipes and tubes with a better surface finish and excellent in machine-ability.
Cold drawing is a process where the metal is stretched by using tensile forces at room temperature. In this process, the desired size of the tube is achieved by drawing it through a smaller die, elongating its length, and reducing the diameter of the seamless tube.
Cold drawing process improves the quality of the tubes with a smooth surface finish, precise dimensions, and high strength. The machine used for drawing is called a drawbench. Shalco Industries has this machine in various sizes to achieve more petite sizes. There are two ways to do this-
Sink drawing or hollow drawing, is the most uncomplicated cold drawing procedure. There is no mandrel inside the tube, hence the steel tube is passed through a smaller die, and it is worked for a smoother and more polished surface. The outer diameter of the steel tube is reduced and does not affect the wall thickness to a great extent. The inner shell is not pressurized during this process, so it can be further elongated using another cold drawing process.
The Rod drawing process reduces the outer diameter and inner wall thickness simultaneously. In this process, the tube, with a mandrel inside, is drawn through the said die. When drawn through the die, the hardened mandrel inside the tube exerts pressure reducing the wall thickness and outer diameter. The size of the seamless tubes depends upon the die and the mandrel.
While cold drawing is straightforward, pilgering is a somewhat more convoluted process. Cold drawing gives just longitudinal pressure, while pilgering bestows both longitudinal and cross overpressure as it employs consistent delicate pounding.
Accordingly, the structure in pilgering is minimized and globular. Pilger is essential for Bearing Tubes and high combination seamless tubes.