Cold drawing machine is used to resize and shape bars, rods, and tubes for a variety of industrial applications. The process involves pushing the lead ends of the steel bars through dies, which stretches them to their desired length and width. In addition, the process also helps to smooth and reshape the outer surface of the steel bars and tubes. After the steel bar or tube is drawn, annealing is often performed to further process and finalize it.
In general, a cold-drawn tube has a smoother outer and inner surfaces than a hot extruded one. It also has a greater degree of ductility, which makes it more suitable for a wide range of uses. It also has a higher level of strength than a hot-extruded tube, due to work hardening. In addition, the diameter-to-thickness ratio of a cold-drawn tube is more uniform than that of a hot-extruded one.
Before the drawing process begins, the rough, hot-rolled coils of steel bars or rods are cleaned of abrasive scale and coated with a technological lubricant. The lubrication improves the quality of the drawing, by increasing the friction coefficient at metal-metal contact. This reduces the draw stress and draws the wire or tube with lower forces.
The lubrication also prevents the drawing from becoming brittle. In fact, it has the effect of extending the service life of a wire or rod by up to 40%. In addition, the lubrication also makes it easier to remove the drawn products from the dies.
In order to build an energy-power mathematical model of a cold drawing machine, it is necessary to know the dependences of the tensile and yield strength indicators on the cold working of the alloy. To do this, a series of tests was carried out on the cold-drawing process for nickel wire with different re-crystallization temperatures.
The results of these experiments showed that a drawing schedule is critical to the quality of the final product. The optimum schedule depends on the specific requirements of each customer. The best choice is a high-Q value drawing schedule, which will produce a more refined, smooth ID surface, as opposed to a low-Q value draw that produces a coarser, rougher ID surface. Similarly, the optimum die angle depends on the wall thickness: A high-angle die is preferred for thin-wall rods; while low-angle dies are used for thick-wall rods. For this reason, it is very important to use a high-quality machine for the cold drawing of a rod or tube. This will ensure that the final product has a high-quality finish and meets the required specifications. The editors of TPJ would like to thank the Tube & Pipe Association, International’s Extrusion, Drawing & Tube Reducing Technology Council for their efforts in arranging this article.