Study On Pickling Process Of 65Mn Spring Steel Based On Electrochemistry

Surface quality is one of the important indexes to measure the quality of cold rolled 65Mn spring steel,and pickling process is one of the most important methods to remove iron oxide on the surface of hot rolled products.Whether the iron oxide scale is completely removed or not affects the cold rolling effect in the later stage of the material processing.Therefore,on the basis of summarizing the relevant domestic and foreign literature and information,this paper tried to study new methods,new components of pickling fluid and equipment,solve the problems of unclean pickling of 65Mn spring steel,and provide a new method and equipment for determining the end point of the entire pickling process in Nanjing Steel.First,the scale on the upper and lower surfaces of 65Mn spring steel was thoroughly studied by means of XRD and SEM methods.It was found that the structure and composition of the scales on the upper and lower surfaces of 65Mn spring steel differed obviously.The main composition of the scales on the upper surface was Fe₂O₃,and the structure of scales on the lower surface was denser Fe₃O₄.Next,the influences of the pickling solution concentration,temperature and iron ion concentration on the acid-washing end point of 65Mn spring steel were studied by electrochemical method,and the acid-washing end point of 65Mn spring steel was determined by the first zero method of potential derivative.The effects of accelerant and stabilizer on the pickling speed and effect of 65Mn spring steel were discussed.The results showed that the pickling efficiency increased obviously and the effect of hydrogen peroxide achieved optimal with an addition of accelerant.The addition of stabilizer can obviously inhibit the decomposition of hydrogen peroxide,and the effect of using malic acid as stabilizer is relatively good.Finally,a developed device for real-time monitoring the end point of pickling can monitor the whole pickling process in real time and react quickly,and thus reduce the occurrence of over-pickling and under-pickling phenomena.