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 elongates the length of the tube further. In this process reduction rates of up to 50 – 60% are achieved in a single pass which is higher than the reductions achievable in the cold drawing process. During the cold pilger process seamless hollow undergoes high compressive residual stress thus attaining highest quality of finished tubes with superior surface finish, tight dimensional tolerances, and excellent machine-ability.
Cold drawing is a metalworking process where the metal is stretched by using tensile forces at room temperature. In this process desired size of the tube is achieved by drawing it through a die which is smaller than the tube, elongating the length and reducing the diameter of the tube.
Cold drawing process enhances the quality of the tubes with smooth surface finish, precise dimensions and high strength. Machine used for drawing is called a draw bench. Shalco has this machine in various sizes in order to achieve smaller sizes. We carry out different cold drawing process at our plant such as:1) Sink drawing
Sink drawing also known as hollow drawing is the simplest cold drawing procedure. In this process there is no mandrel inside the tube, so the tube is passed through a die of a smaller size and it is worked for a smoother polished surface. Only the outer diameter of the tube is reduced and not affecting the wall thickness to a great extent. During this process the inner surface is not pressurized so it can be further elongated using other cold drawing process.2) Rod drawing
Rod drawing process reduces the outer diameter and inner wall thickness at the same time. In this process the tube is drawn with a mandrel inside the tube through the die. The hardened mandrel inside the tube when drawn through the die exerts pressure reducing the wall thickness and outer diameter. Size of the tubes depends upon the die and the mandrel.