Effect Of Dimensional Stabilization Annealing Process On Microstructure And Mechanical Properties Of The Window Rope

With rapid development of auto market, demand of autos increases every year and caring for auto performance of consumers has increased. Demanding of auto quality increases obviously. Window rope, as an important part of auto, has faced requirement of better properties and longer service life from both manufactures and consumers. This paper evaluates properties of KSC72 A steel produced by Japan Kobe Steel, and prepares window rope using KSC72 A. For improving service life and dimensional stability, this paper investigates effects of annealing to window rope microstructures and properties. Optic metallographic microscope(OM), tensile test, scanning electronic microscope(SEM) are used to research variety of raw material microstructures and properties during annealing. Fatigue testing machine and grating length measuring instrument are used to investigate changing rules of fatigue properties and dimensional stability. Thus this paper obtains optimum heat treatment processing providing processing parameters of production.Research result of stabilization annealing of window rope and raw material shows:Tensile strength of 72 A steel wire under drawing state first rises and then falls during stabilization annealing. Tensile strength and yield strength falls when annealing upon 250 ℃,which meets general rule.Releasing of residual stress is proportional to time and temperature of annealing. With higher temperature and longer time of annealing, residual stress releases more. Stabilization temperature of 72 A steel raw material is recomm ended at 200-300℃.The 72 A steel wire under drawing state after stabilization annealing at 150-250℃ shows a good ability of homogenous plastic deformation. The annealing at 150℃-350℃ increases work-hardening coefficient, suggesting the increase of the ability homogenous plastic deformation.Dimensional stability rises with annealing temperature increasing, while elongation decreases. Elongation stables at 350 ℃. Stabilization time is recommended to be 120 s.Microstructure of window rope changes after stabilization annealing. Cementite dissolves first and then precipitates as particles with increasing annealing temperature. Precipitation of cementite strengthens the material.Fatigue properties of window rope increases after stabilization annealing. Dynamic f atigue property reaches the maxima at 300 ℃.Fatigue fracture analysis using SEM and TEM shows opposite changes happens during stabilization annealing. Strengthen and waken effects leads to instable or abnormal of window rope properties.