1. Problems caused by improper selection of working cone Angle

When drawing the wire, the working cone Angle is too large (equivalent to the compression rate is too small), so that the contact point of the wire into the drawing die is too close to the sizing belt (for example, 14. Modulus yields 16% compression). In this case, the deformation zone is relatively short, which speeds up the deformation rate of the wire and generates a lot of heat, which easily leads to lubrication failure. If the cooling is poor, it will affect the wire structure and increase the die consumption. If the die Angle is large or the compression rate is small, it will make the contact point closer to the sizing belt, the wire in the process of flow to the sizing belt, due to the influence of the cone Angle, the wire is difficult to smooth transition to the sizing area, easy to cause the wire concave, leading to diameter reduction, if the material strength is too low will also lead to diameter reduction or ellipse phenomenon. Although the lubrication area is relatively long and can provide good lubrication immediately at the beginning, it will reduce the lubrication pressure on the contact surface and produce eddy current effect, which leads to the reverse flow of lubrication powder from the die hole and weakens the lubrication effect. In addition, various adverse effects caused by deformation will eventually lead to lubrication failure, surface cracks, scratches, die consumption aggravation and difficult to control the wire diameter. The working cone Angle is too small, resulting in the contact point of the line close to the upper end of the working cone, so that the deformation area is relatively lengthened, so that the residual work generated by the wire drawing machine on the wire increases, generates a lot of heat, and increases the power consumption of the wire drawing machine. In addition, the reduction of the lubrication zone will weaken the lubrication effect, and the residual surface lubrication powder of the wire will be exhausted at a certain point in the deformation zone. When the tensile stress is too large, in the sizing area is easy to cause axial elongation, shrinkage and ellipse problems, will eventually lead to poor lubrication, metal debris and broken wire, overheating, shrinkage.

2. Central fracture and herringbone crack phenomenon

Since its discovery, the central fracture and "man" cracks have been considered as problems caused by raw materials. But it was not until 1930 that Fenhi -- SOIl pointed out that the central fracture and "man" cracks were caused by unreasonable arrangement of drawing process (compression rate of pass, drawing pass). In the process of wire drawing, the internal organization of the wire extends along the axis, the flow rate of the organization on the surface of the wire is greater than the flow of the internal organization, and the axial tensile stress is generated in the heart. When the axial tensile stress exceeds the tensile strength of the drawing material, the "human" crack will be generated in the heart of the material, and the serious will produce cup-cone fracture (columnar). Therefore, in the formulation of drawing process should be based on drawing raw materials, drawing die type to reasonably arrange drawing process.

3 Residual stress and surface work hardening phenomena

Residual stress and work hardening are caused by residual work, which aggravates the hardening of the material and makes the surface of the wire crack, peel and draw difficult. If the process arrangement is improper, the residual work will increase, and the energy consumption of the equipment will increase the production cost.