What Is a Cold Drawing Machine?
Cold drawing machine is an industrial process used to resize and shape metal tubes, rods, bars and coils that have been hot rolled. The cold drawing process reduces the diameter and wall thickness of the original product, shapes the profile and produces a bright finish with improved mechanical properties. The process can be used on a wide range of alloys, including carbon and low-alloy steel, stainless steel, nickel-based alloys and copper and aluminum.
The process begins with procuring raw material. The most common source of raw material for cold drawing is bar or rod coils, which are used as the starting point for the final drawn products. The raw material is then subjected to a number of preparation steps. The most important of these is pointing, which involves reducing the lead ends of the rod to a pointed end that can pass freely through the die opening. This step also removes abrasive scale, which is the result of the hot-rolling process. The rod is then coated with a drawing lubricant to facilitate the operation.
Once the pointing and lubrication are complete, the drawing process can begin. The lubricant allows the rod to enter the die openings and be reduced in size by the drawing dies. The dies are designed to reduce the diameter and wall thickness of the rod while retaining its length. The drawing process can be repeated several times to achieve the desired dimensions and tolerances. To increase the ductility of the rod and to reduce the impact on the material’s strength properties, it is typically annealed between each drawing operation.
During the drawing process, the steel experiences a series of stress cycles. These stress cycles are caused by the alternating application of tension and compression on the rod. The resulting tensile stresses cause the metal to deform and stretch. In addition, the tensile stresses induce shear forces in the rod that cause the material to break.
To prevent these stresses, the material must be drawn at a lower temperature, which is called cold drawing. This is accomplished by passing the rod through a die while it is below its re-crystallization temperature. The cold drawing process causes a similar reduction in the diameter and wall thickness of the metal, but it does not cause as great an effect on the ductility.
To design an accurate energy-power mathematical model of the drawing process, it is important to understand how these stress cycles affect the strength properties of the rod. To do this, the tensile and yield strengths of the rod must be measured at various points along the drawing route. The relationship between the changes in these strength indicators and technological parameters such as the drawing speed, the die angle and the draw force must be determined. These relationships will allow the a drawing process to be modelled using a computer program. The equations for the change in tensile and yield strength from cold work have been obtained experimentally for NP2 nickel.