Mechanical Properties And Microstructure Of Pearlite Steel After Electroplastic Rolling

As one of the main steels used in bridge slings and railway tracks,pearlitic steel has good strength and toughness.Under normal circumstances,the material will have lower plasticity while obtaining higher strength.Therefore,it is a hot research topic to ensure that the pearlitic steel obtain the better plasticity under the premise of higher strength.In this paper,pulse current(pulse frequency 500 Hz,600 Hz and 800 Hz,pulse width 50μs and 80μs)was introduced into ordinary cold-rolled pearlitic steel.The mechanical properties of the rolled samples were tested by universal testing machine and hardness tester.The morphology of pearlite was observed by scanning electron microscopy(SEM).The variation of ferrite diffraction peak was observed by X-ray diffraction(XRD)and the dislocation density of ferrite was calculated.The differences in mechanical properties and microstructure were analyzed between electro-plastic rolled pearlite steel and ordinary cold rolled pearlitic steel.Furthermore,the electric-assisted tensile test of the pearlitic steel after cold rolling deformation was further carried out.The influence of electro-plasticity on the properties of the experimental steel during the tensile test was studied.The mechanical properties of the experimental steel in cold-rolled annealed state were compared with the test results of electric-assisted tensile after cold rolling,at the same time,the similarities and differences for the mechanical properties of pearlitic steel under two experimental conditions were comprehensively analyzed.The results show that under the same reduction,the tensile strength and hardness of pearlitic steel under electro-plastic rolling has a slight decrease compared with that under cold rolling,however,the elongation of pearlitic steel has a significant increase.With the increase of the cold-rolled reduction and the electro-plastic rolled reduction,the direction of pearlite lamellae gradually turns to rolling direction,and the lamellar spacing reduced gradually.The diffraction peak angle of the ferrite is shifted to the small angle,and the dislocation density of ferrite exhibits a tendency to increase first and then decrease.After electric-assisted stretching of the cold-rolled pearlitic steel,it was found that the higher the current density,the lower the tensile strength of the material and the higher the elongation.In the case where the current density is relatively low,the tensile strength and elongation have little difference from those in ordinary tensile.When the current density is lower than 9.4A/mm~2,the deformed pearlitic steel does not have a temperature rise phenomenon during the electric assisted tension.The strength and hardness of the pearlite steel after cold rolling deformation and subsequently annealed at 500°C for various time showed a downward trend,and the dislocation density of ferrite decreased significantly compared with the cold rolling state and the electro-plastic rolling state.At the same reduction,the elongation of pearlitic steel after ordinary cold rolling followed by annealing at 500°C for 180 s is basically the same as that of ordinary cold rolling,and the latter has higher tensile strength.Compared with cold rolling,the strength and hardness of electro-plastic rolled pearlite steel do not significantly decrease while increasing the elongation of the material at the same reduction.The capability of plastic deformation of the material can be improved by using Electro-assisted tension,which can provide important experimental support for the material in the production of subsequent products.