Changes of Microstructures and Cold Drawing Properties of V-N Microalloyed Tire Cord Steel

To explore the possibility of replacing C with V and the effect of V and N on cementite during cold drawing process,traditional grade 70 tire cord steel was microalloyed with V and N.Tensile properties and torsional properties were measured for specimens at different cold drawing strains; the precipitation phases containing V and N were analyzed by a transmission electron microscope and energy dispersive spectrometer(TEM + EDS),saturation magnetization was measured by a vibrating sample magnetometer(VSM) to predict the variation rules of cementite dissolution.It is shown that with the addition of V,tensile strength of the cold drawn samples generally increases,elongation slightly declines,and the number of torsion decreases.With the addition of N,tensile strength of the cold drawn samples increases before decreases,elongation rises,and the number of torsion decreases.V partially dissolves in ferrite or cementite.N is soluble in ferrite when its content is low,the phases containing V start to precipitate in ferrite when N increases to 0.008 2%.With the increase of V and N,the cementite tends to stabilizes during the cold drawing process.The grade 80 tire cord steel can be replaced with(grade 70 + 0.086% V).