| With the rapid development of high-speed railway in China,the quality requirements for railway wheels,which are the important traveling components,are increased.However,the traditional characterization methods for composition and microstructure have the problems of small analysis area(μm level)and slow analysis speed,in order to meet the characterization requirements of railway wheels largesection(cm level),the characterization and analysis methods for the composition,microstructure are studied and established,and the correlation between composition,microstructure and performance are discussed.The study is based on the concept of material genetic engineering.Sampling scheme for different parts of the railway wheel section was designed.A high-throughput characterization method of composition,microstructure and performance for large-scale materials was established based on the spark source original position statistic distribution analysis technology,highthroughput image acquisition technology,image recognition processing technology,and mechanical properties(hardness,tensile etc.)analysis technology.The correlation between the composition,microstructure and performance was discussed.The results will provide an experimental and theoretical support for the comprehensive quality evaluation of the railway wheels,and provide data support to improve the machining process,the heat treatment and the usage.In the paper,the spark source original position statistic distribution analysis technology was used to statistically characterize the composition distribution of the train rim.The results show that the compositional segregation differences of the three train rims exsit mainly in four elements of C,Mn,S,and Al.While Si,Cr,and V elements have reached a high statistical homogeneity within the statistical range of the95% confidence interval.There is no obvious difference in the result of statistical segregation degree of each element.Because of its low content,the volatility of Mn seems more serious than that of other elements.In the paper,the high-throughput scanning electron microscope was used for the first time to efficiently collect microstructure images in the range of cm-size on railway wheel materials,and image recognition,image segmentation and quantitative statistics of microstructure were studied,and the image batch processing template was set up,which can be used to realize the quantitative characterization of the microstructure.The results show that from the rim to the hub,the area fraction of the ferrite gradually increases.The area fraction of ferrite and the lamellar spacing of pearlite show a gradual increasing trend from the wheel tread downwards,and the area fractions of ferrite at the spokes and the hub have no obvious distribution law.Abnormal upper bainite structure was found in one wheel rimsIn this paper,the automatic micro Vickers hardness tester was used to realize the original position quantitative statistical distribution characterization of micro Vickers hardness in a large range.It is found that the hardness changes regularly with position,the hardness values decrease from the rim to the hub,and the same decreasing distribution trend can be seen on the rim from the tread surface downwards.The tensile properties of different parts on the wheel at room temperature were also studied,and it was found that the tensile strength and yield strength of the rim were higher than that of the web.Based on the characterization results,the correlation between the composition,structure and performance of different parts on the section was studied.It was found that the segregations of Mn,S,and Al are closely related to the size and distribution of inclusions,and the distribution of microstructure has a great influence on the segregation behavior of C element.Both the content differences of microalloying elements and the different quenching process conditions have great effect on microstructure distributions,which cause the hardness distribution of different parts of the railway wheel. |
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