Fracture Analysis And Technical Improvement On Mini Special Wire Rope During Production

With the development of modern industrial equipment, the application scope of high strength fine steel wire rope is wider and wider, performance requirements are also getting higher and higher, mini wire ropes for PU synchronization and special flexible wire ropes for cars are one of two representative products. The high wire breaking rate of mini wire ropes has a bad influence on the continuity of producing, which leads to the increasing of cost significantly. Therefore, this article is aimed to find out the reason of wire breaking through the statistics analysis of mass samples and combining technology tests, and propose improved production technology to decrease wire breaking ratio and increase properties of wire rope, in order to decrease the cost.The results show that wire breaking during the production process of mini-special ropes often occurs in twisting process. To conduct the investigation, 263 mini-special wire breaking samples were collected. Among them, 29 pieces of samples with a fraction of 11.0% were produced in wet-pulling process and 234 pieces of samples with a fraction of 89.0% were produced in twisting process.According to the macroscopic fracture morphology of the statistical drawing samples, the fractures can be divided into several types, such as pen-shaped, flushshaped, ramp-like stubble, etc. Among that, the samples with ramp-like stubble fracture have a fraction of 37.9%, where the fracture often originates from the surface of wire scope, mainly caused by poor lubrication or defects such as surface crack. On the other way, the factures of twisting samples can also be divided into profile flush gap, profile edge embossment, small dimples in the core, profile holes and profile necking, 70% of which are the samples with the characteristics of profile flush gap, profile edge embossment, and the fracture mostly derives from the surface defect of wires. In addition, the main differences between the twisting stress state and drawing stress state include: First, the large shear stress component, and the second is the maximum surface stress, which has high sensitivity to the surface defects of wire. And the diameter of twisting wire is less than that of wire produced by wet drawing. Above can result in much smaller breakage rate of wire in wet drawing process than that in twisting process. The different composite modes such as torsion, bending, drawing, etc. in twisting process lead to the different macroscopic morphologies of twisting fracture samples.In the research of raw materials, the influence of composition and the inclusion level of raw materials on the wire breaking and properties of wires were studied, and the improved methods were also put forward. The prediction technique of wire breaking was determined by the study of work hardening behavior. In the wet tensile process, the zinc layer thickness of wire, the kinds of lubricant, the choice of wire drawing die and die chain have obvious effects on the wire breaking ratio. During the twisting process, lay length is the main parameter affecting the whole rope breaking force. To optimize the extreme value of breaking force and scatter difference, the laying tension s force of every wire should be uniform.After the use of the improving technology Including drawing, twisting, the improve of the surface quality, the average monthly wire breaking rate in 2014 reduced from 247 per ton in 2013 to 113 per ton, a decline of 54%, which has significant production efficiency.