The effect of the microstructural parameters and the nonmetallic-inclusion content in a steel on its service properties is analyzed for the rail steels of experimental batches that are produced in Russia and abroad and exhibit different service durabilities upon full-scale tests. The dendritic structures of these steels are different. Measurements of the primary austenite grain size show that it is maximal in the rail steel produced in Austria. The pearlite-colony size in Russian steels is almost half that of Japanese steel. The interlamellar spacings in pearlite of the rail steels of various manufacturers are virtually the same. The Russian steels contain up to 3 vol percent grain-boundary ferrite. As compared to the Russian steels, the fracture toughness of the foreign steels is substantially lower. The service durability of a rail is assumed to depend mainly on the nonmetallic-inclusion cleanness of the rail steel. It is shown that quantitative metallography and fractional gas analysis can be used to control the oxide-inclusion cleanness of rail steels. The oxidic cleanness of steel calculated from fractional-gas-analysis data can be used to predict the service durability of rails.
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