Cold drawing machine is an industrial process in which a steel bar or rod is pulled through dies that are contoured to the desired shape. The steel is drawn at temperatures lower than the metal’s tensile strength, so it must be annealed after each pass through the die to ensure that it doesn’t break or rip under the pressure.
The first step in the cold drawing process involves submerging the raw stock, or the hot rolled steel bar or rod coils, in a lubricant. This helps the steel bars pass through the dies more easily. The lubricant also removes the abrasive scale and oxidation on the surface of the raw steel, which can cause resistance. The lubricant may also include an additive that increases the ductility of the steel.
Once the lubricant has been applied, the steel is ready to begin the actual drawing. The lead ends of the steel are sharpened to obtain a pointed shape, which helps it enter the drawing cones more easily. These cones guide the steel bar through a series of dies that reduce the steel’s cross section and shape it into a profile. The process is repeated as needed, with each pass through smaller and smaller dies, to get the desired shape.
When the ductility of the steel is high enough, it is possible to draw the steel through the dies without breaking. The cold-forming method can produce shapes that are more precise than those produced by hot extrusion, and it allows thinner materials to be used than would be practical in a hot-formed part because of work hardening.
However, the forming process can damage the structural integrity of the material and increase its brittleness, so it is important to know when the process needs to be interrupted. It is also important to understand that drawing can only be performed within a certain range of reductions, since further reductions could exceed the tensile strength of the steel or its ductility.
The physics of the forming process is complex and difficult to model accurately, so computer simulations are often used. The results of these models are then compared to experimental data. It is important to use accurate data because a difference in friction coefficient can greatly affect the drawing force, which in turn can influence the energy and power required to operate the system. The accuracy of the calculations depends on the size of the drawing die, the geometry of the forming tool, and the die half-angle. A good model should be able to predict the relationship between these variables, so that it can be used to determine the optimal conditions for a particular job. A model should be able to identify the optimum parameters for the process, as well as indicate how these parameters can be improved.