| With the vigorous development of modern industry, the application of steel wire rope is more and more extensive, and its service environment and performance requirements are increasingly stringent. In order to meet the market requirements, wire rope enterprises are also improve and optimize the production process in the steel wire drawing, heat treatment, laying.To improve the mechanical properties of the steel wire rope ulteriorly. At present, the heat treatment of steel wire is still mainly for traditional lead bath treatment, due to the high energy consumption and high pollution attract great importance to more and more industry attaches, so it has become a subject to be solved that look for green heat treatment process instead of patenting.In this paper, combined with the production practice of KSC72 A steel wire rope, the relationship between the structure and properties of steel wire during drawing and its hardening mechanism ware discussed. Using alkaline polyacrylic acid(AQ110) explored water bath treatment instead of patenting in diameter of 0.8mm steel wire. Study on the effects of microstructure and mechanical properties of steel wire in different austenitic temperature and austenitizing time and water bath processing time. Simulated actual conditions of automotive electric window lifter steel wire rope, conducted bending fatigue test on the fatigue properties and fracture mechanism of water bath treatment steel wire rope. Research results show that:(1) In the process of drawing, with the increase of the strain, the pearlite group is twisted,the spacing decreased, and tends to be in parallel, the tensile strength and hardness of the steel wire increase linearly. TEM further analysis shows that with the drawing deformation, high density dislocation, fine grain, and sub structure, the tensile, deformation and even fragmentation of the carburizing body is the main mechanism of the steel wire hardening.(2) With the increase of the heating temperature of the steel wire, the austenite grain growth.When the heating temperature of the austenite is increased from 1005 centigrade to 1025 centigrade, the tensile strength of the steel wire is increased slightly from 1220 MPa to 1244 MPa.But when the austenitizing temperature is higher than 1025 centigrade,strength decreased significantly,the shrinkage on cross section appeared decreased significantly in the heatingtemperature higher than 1015 centigrade. With austenitizing time prolonged, the tensile strength of steel wire has overall showed a rising trend, when the take-up speed from 68m/min reduced to60m/min, the tensile strength of steel wire improve 26 Mpa, shrinkage on cross section increased slightly from 57% to 58.2%. When the speed is less than 60m/min, tensile strength change very small only 10 MPa, and shrinkage decreased significantly from 58.2% to 52.7%. When the length of the bath is 25 cm, precipited iron ferrite along the austenitic grain boundary, ferrite disappeared when the length of the water bath tank is 35 cm, cementite appeared broken,distortions. With the prolongation of water bath treatment time, sorbite group size and lamellar spacing decreased, when the length of the water bath tank more than 50 cm tends to be stable,tensile strength and shrinkage are basically stable, respectively 1260 MPa and 54%.Comprehensive consideration, he choice of austenitizing temperature is 1015 centigrade, take-up speed is 60m/min and water bath length is 50 cm.(3) The first fatigue place of the steel wire rope is in the center,where contact stress is large,the statistics analysis of fracture shows that the core strand of the steel wire is all fatigue fracture,and the cup cone shaped tensile fracture of side strand wire accounted for 70%. The fatigue fracture surface of the steel wire with one side of the pulley is significantly reduced by the central strand wire, and can be judged as a late fatigue fracture. The lateral bending of the steel wire is overload tensile fracture accounted for 95%. |
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