Fractional Gas Analysis Research Articles

Structure and metallurgical quality of rail steels produced by various manufacturers

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 % 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-gasanalysis data can be used to predict the service durability of rails.

Deoxidation with silicon and the control of oxide inclusions in electrical steels

The oxygen solubility in Fe-Si melts in equilibrium with SiO2 at 1873 K has been determined in a concentration range of 0.1–70 wt % Si. Model alloys are melted in quartz crucibles in an argon atmosphere. The oxygen content in analytical samples is determined by the inert-gas reducing-fusion method after careful sample preparation. The results obtained have been processed using a thermodynamic model that can calculate the oxygen activity and solubility in Fe-Si melts up to 100 wt % Si. The effects of the heating rate and the silicon content on the carbon concentration in carbonyl iron and Fe-Si alloys are studied using the inert-gas reducing-fusion method in the temperature range 1673–2373 K. Oriented electrical steels are investigated using fractional gas analysis. The main forms of oxygen in these steels are found to be silicates, Al2O3, and MgAl2O4.