| Atmospheric corrosion of heavy rail steel not only brings a lot of economic losses,wastes a lot of resources,but also poses great safety hazards.Therefore,the corrosion resistance of heavy rail steel is as important as its strength and toughness,and heavy-duty and"green virtuous cycle"will be an inevitable trend.In this paper,different pearlite microstructures were obtained by alloying with different chromium content and different heat treatment processes,and were carried out in a simulated atmospheric environment in a concentration of(1.0±0.05)×10-2mol/L Na HSO3(sodium bisulfite)solution.72,120,240,360,480h long-term corrosion and 0,10,30,60min initial corrosion experiments,using weightlessness method,SEM,XRD and electrochemical methods for detection and analysis.By adding 0%,0.353%,and 0.682%Cr to U71Mn heavy rail steel,the interlamellar spacing of the pearlite structure is 0.291,0.250,0.224?m,respectively.The average corrosion weight loss rates of the three groups of experimental steels were 1.572,1.387,1.190g/(m2·h),the ratio of?/?*in the rust layer was 0.717,0.868,0.997,and the polarization resistance was3.715,8.604,13.739?·cm2,and the equivalent capacitance of the rust layer is 8.434×10-6,0.411×10-6,0.081×10-6F/cm2.With the increase of the corrosion time,the average corrosion rate is the fastest at 120h,the corrosion rate of the rust layer with certain protective effect formed at 240h is the slowest,and it tends to be flat after 360h.The smaller the pearlite sheet spacing,the smaller the corrosion weight loss rate,the greater the ratio of rust layer?/?*and the polarization resistance,the slower the corrosion rate,the smaller the rust layer pores and thickness,the finer the gap,the smaller the rust layer and the substrate The better the binding ability,the better the atmospheric corrosion resistance,and the 0.682%pearlite structure has the best corrosion resistance.For the 0.682%chromium U71Mn heavy rail steel with the best corrosion resistance,the pearlite lamella distances are 0.391,0.331,0.268,0.197?m,respectively,through temperature-controlled cooling,furnace cooling,door cooling,and air cooling heat treatment processes.Long-term corrosion in the simulated atmospheric environment,the average corrosion weight loss rates of the four groups of experimental steels were 1.0241,0.9988,0.8864,0.9857g/(m2·h),and the average values of?/?*ratios were 1.0505,1.1870,1.2966,1.2109,the experimental steel with a lamellar distance of 0.268?m has the smallest corrosion weight loss rate,the largest?/?*ratio,the slowest corrosion rate,the most stable rust layer,and the best protection and corrosion resistance to the substrate.Through SEM and Linescan analysis of the surface and cross-sectional morphology of the rust layer,it is concluded that the rust layer of0.268?m experimental steel has more?-Fe OOH and?-Fe OOH,and the outer rust layer is stable Fe2O3,which has a protective effect and corrodes the surface of the rust layer.Smooth,thin and dense,with small holes and gaps,the best corrosion resistance,and the ability of the rust layer to bond with the substrate better.The overall comparison of 0.268?m experimental steel's Ecor gradually increases after 120h,and the surface is more difficult to be corroded.After 72h,the capacitive impedance of the semicircle in the high frequency range is slightly higher,indicating that the microstructure has a higher charge transfer resistance and a lower corrosion rate.It has a strong inhibitory effect on corrosion and has relatively good corrosion resistance.Through the analysis of the initial corrosion process,from 0 min to 10 min,the experimental steel corrosion produces Fe2+in the form of lamellar compound Fe(OH)2;as the corrosion time increases to 30min,the Fe2+compound reacts to form a large amount of layered?-Fe OOH and small Measuring lath Fe3O4;when the corrosion time is extended to 60min,a large amount of layered?-Fe OOH reacts and transforms into a large amount of needle-shaped?-Fe OOH and a small amount of Fe3O4and Fe2O3.?-Fe OOH is small,stable,and has a certain protective effect,which has a better protective effect on the substrate and prevents secondary corrosion.Two methods of heat treatment and alloying elements are used to obtain pearlite structures with different degrees of fineness.The weight loss rate per micron of the alloying element pearlite structure is 3 to 5 times that of the heat-treated pearlite structure,indicating that the heat-treated pearlite structure is more resistant to atmospheric corrosion.excellent. |
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