Industrial steel pipe cold drawing

Various conventional methods for drawing steel pipes.

(1) Drawing steel pipes without mandrels, used to reduce only the outer diameter of steel pipes.

(2) Drawing steel pipes with fixed short mandrels, used to reduce steel pipes' outer diameter and wall thickness. This method has a fixed mandrel and uses a fixed outer die, so the friction resistance is large, the drawing force is large, and the deformation per pass is small. The advantage is that the drawing method is simple and widely used.

(3) Drawing steel pipes with floating mandrels, commonly used for reel drawing, can produce very long steel pipes (more than 100m). The drawing force is small during floating mandrel drawing, which can increase the deformation per pass. Since there is no restriction on the pull rod, steel pipes with very small diameters can be drawn with mandrels.

(4) Drawing steel pipes with long mandrels, when drawing steel pipes, the mandrel moves with the steel pipe, which eliminates the friction resistance on the mandrel, thereby reducing the drawing force and increasing the deformation per pass. The movement of the mandrel can also reduce the roughness of the inner surface of the steel pipe. The disadvantage of drawing steel pipes with long mandrels is that the mandrel is strictly required and the rod must be removed after drawing. There are two methods of stripping the rod: one is to roll the steel pipe and the mandrel together on the inclined rolling mill to expand the steel pipe diameter slightly, and then pull the mandrel out on the rod drawing machine; the other is to use a double-die drawing system to expand the diameter before pulling the mandrel. The latter die is an additional die. When passing through the additional die, the steel pipe wall has only a small amount of deformation, and the steel pipe diameter is slightly expanded, which can reduce the rod stripping force when stripping the rod; two four-roller rolling dies can also be used for rolling and stripping.

(5) When the steel pipe is expanded and drawn, the wall thickness of the steel pipe is reduced, the diameter is increased, and the length of the steel pipe is shortened slightly; when the steel pipe is expanded and drawn, the steel pipe is fixed and the pull rod drives the mandrel through the steel pipe.