Study On Electrochemical Cold Drawing Of Q235 Carbon Steel Bar

Traditional cold drawing technology can draw several times of metal materials with good plasticity at room temperature.However,due to t he aggravation of work hardening,it is necessary to pass multi pass annealing to finish the subsequent processing.Due to the particularity of the force way of drawing,it is easy to produce cracks in the process,increase the possibility of wire breaking,and the quality of surface processing is poor.In recent years,the electrochemical cold drawing?ECD?,which is developed on the basis of the electrochemical mechanical effects,can significantly reduce drawing force,especially for the drawing of high strength and high hardness materials,which provides a fea sible new processing technology.In order to clarify the basic theory and some technical problems of ECD,this paper takes the annealed carbon steel Q235 bar as the research object,and studies the main technological parameters of ECD,such as the influence of the type and concen tration of the electrolyte,the current and the second of the drawing channel on the drawing force,the surface hardness and the impact toughness;The effects of electrochemical corrosion on drawing force and surface hardness were studied.The results indicate that the anodic polarization curves showed that the self-corrosion potential and the self-corrosion current of different kinds of electrolyte?Solution of sulfuric acid,Sodium Chloride Solution,mixed solution of hydrochloric acid and sodium chloride,tap water?were significantly different.The corrosion potential and current in sulfuric acid solution are larger and belong to uniform corrosion.Corrosion in water is also uniform corrosion,but its corrosion potential and current were relatively small.The corrosion potential and corrosion current in pure sodium chloride solution are smaller than those in sulfuric acid solution.The corrosion mode is pitting corrosion,an d the local corrosion rate is faster.In the mixed solution of hydrochloric acid and sodium chloride,the H⁺added to a certain extent inhibits the pitting corrosion,but the local corrosion is still seriousThe drawing force in the drawing process can be reduced by electrochemical plasticizing technology.The drawing force can be reduced by about 45.36%in the electrolyte in the optimum parameter range,and the drawing force can be reduced by about 39.33%without the soaking part.After electrochemical etc hing,the surface hardness of the material decreases obviously,and the rate of decline is about 23.69%.In addition,the side effect of electrochemical corrosion is not obvious ly,the impact power of the material before and after corrosion is not obviousl y reduced,indicating that the electrochemical corrosion at this time does not have much influence on the toughness of the material itself.However,this effect improves the surface quality of materials and inhibits the occurrence of surface processing def ects.From the data analysis of EBSD,compared with the traditional cold drawing process,the electrochemical cold drawing process has smaller plastic deformation and lower deformation resistance.The material did not form effective texture s,the dispersion of statistical data and the preferred orientation of texture were not obvious.Compared with the traditional cold drawing,the drop rate of the single pass pull force of ECD can reach 49.79%,with the increase of drawing pass increasing,the reduction rate of drawing force decreases gradually.The electrochemical drawing technology can reduce the thickness of the deformation layer in the drawing process by the EBSD data analysis,but the electrochemical plasticizing effect is gradually weakened with the increase of the pass.Electrochemistry is gradually weakened.The thickness of the deformation layer after drawing is not much different from that of the traditional cold drawn bar.The electrochemical plasticizing effect can significantly alleviate the working hardening,and can obviously reduce the hardness of the surface of the material.The maximum single pass rate of the hardness can reach 23.68%,but the surface hardness of the material increases with the increase of the drawing pass.According to the analysis of Tafel polarization curve,the best concentration of S?H₂SO₄?solution is 0.35M⁰.5M,and the corrosion effect is the best at this time.The softening effect is better because of its fast corrosion rate and more uniform.In addition,the concentration of exchange electrons in the system can reach a dynamic equilibrium state in a relatively short time.The electrons in the system can form the carrier flow,which can increase the quantity of the drift electrons in the material rapidly,increase the kinetic energy of dislocation movement,promote the dislocation movement,relieve the hardening and reduce the deformation resistance.The linear voltammetric curve shows that the best current is 135²00m A.The suitable current density can make the system form electron flow in a short time and magnify the plasticizing effect of electrochemistry,which makes the mechanism dominate in the process of forming,effectively relieving the hardening of surface materials,reducing the deformation resistance and forming plastic forming.The main phase of the corrosion layer is iron oxide and some sulphate,and the corrosion layer is more compact and stronger than the surface of carbon steel itself.When corrosion to a certain extent,a relatively complete and strong corrosion layer is formed on the surface.The essence of the surface hardening is the dynamic balance between the obstruction of the corrosion layer and the softening effect of the electrochemical growth effect,and the softening effect is mainly reflecte d in the thickness of the softening layer.When softening plays a leading role,the thickness of the deformation layer can be greatly reduced,the resistance to deformation will be reduced,and the drawing force will be reduced.In the S solution of 0.35M⁰.5M,the softening effect of the surface layer is the best,the hardness of each channel decreases significantly,and the main road drop rate is 36.91%,and the thickness of the softening layer can reach 500?m.Under the current of 135²00m A,the thickness of the corrosion layer is uniform,and the friction coefficient will not change when the corrosion layer is not accumulated to a certain extent.Therefore,the deformation resistance will not increase,thus the drawing force is reduced,the drawing force of each pass is lower,the softening effect is better and the hardness of the surface material is maximum.The reduction rate is 35.69%,the softening effect is the best,and the softening layer thickness can reach 550?m.