Effect Of Cold Drawing And Annealing Process On Microstructure And Properties Of High-strength Cable

High-strength hot-dip galvanized steel wire is the main material of large-span bridge cables,it is obtained from the original wire rod through multiple processes,such as largestrain drawing and hot-dip galvanizing.The strain of drawing and temperature of hot-dip galvanizing will affect the microstructure of the steel wire,and then manifest in the quality of the macro mechanical properties.This project relies on the national key research and development plan,the key basic material technology improvement and industrialization key special project "high-performance bridge steel" to carry out basic research work.In this paper,the 450 ? annealing experiment is used to simulate the hotdip galvanizing process in production,combined with various technical methods,such as metallography,SEM,TEM,XRD,DSC,tensile experiment,torsion experiment and micro-hardness experiment to study the evolution of the structure and properties of steel wire during drawing and galvanizing process.Through the study of the drawing process,the following conclusion is obtained: the wire rod is composed of lamellar pearlite,and its arrangement has no obvious preferred orientation.As the drawing strain increases,the pearlite layer gradually turns to the drawing direction,the hindrance to dislocations weakens,the pearlite layer spacing decreases rapidly,the grains gradually become slender and fibrous.And the larger the strain,the finer the microstructure diameter.During the drawing process,the dislocation density gradually increases,and the ferrite transitions from a single slip to the stage where multiple slip systems started simultaneously.The slip direction gradually shifted to the pull direction.The result of slippage leads to the increase in <110> texture strength.During drawing,the tensile strength,yield strength,and microhardness of the steel wire gradually increase,but the torsion performance decreases.The strengthening mechanism in the drawing process can be explained by dislocation strengthening model and interface strengthening model.Through the study of the annealing process,the following conclusions are obtained: with the extension of the annealing time,the cementite partially fractures and dissolves,and then gradually spheroidizes and grows into particles and short rods.The exothermic peak corresponding to the DSC curve at 450 ° C just verifies the spheroidization of the steel wire.In the initial stage of annealing,the tensile strength,yield strength,micro hardness and torsion performance of the steel wire increases slightly with the extension of the annealing time.When the annealing time is 3 min,the tensile strength of the steel wire reaches its peak.In the subsequent stage of annealing,the tensile strength of the steel wire gradually decreases with the extension of the annealing time.During the annealing process,the evolution of the yield strength and microhardness are similar to the tensile strength.