A. V. Kushnarev

Production of high-quality railroad wheels

A new technology is proposed for improving the railroad wheels produced at OAO Nizhnetagil’skii Metallurgicheskii Kombinat. Mathematical simulation of the stamping of continuous-cast billet provides information on the change in shape of the metal. The factors responsible for the poor quality of the rough wheels produced by the SMS EUMUCO method are identified. Two new stamping methods are developed, on the basis of three characteristic stages of metal flow.

Introduction of wheel production on a new pressing and rolling line

A new pressing and rolling line with high levels of mechanization and automatic control has been introduced for wheel production at OAO Nizhnetagil’skii Metallurgicheskii Kombinat, because the new product range required improved production technology. This line incorporates new designs and permits the production of high-quality cast-iron wheels at high speed.

Analysis of various versions of the deoxidation of rail steel at OAO NTMK

The deoxidation of steel melted using various types of deoxidizers during out-of-furnace treatment is studied. The total oxygen and nitrogen content and the oxygen contents in the main types of oxide nonmetallic inclusions are determined by fractional gas analysis of steel samples taken from heats performed by various schedules. The main types of nonmetallic inclusions and their size distributions are found with qualitative and quantitative metallography. The oxygen content in the rail steel is minimal (5 ppm) when calcium carbide CaC2 is introduced into the metal in tapping of a converter. When the metal is deoxidized using a steel wire filled with calcium or a steel wire filled with silicocalcium, the oxygen content in rail steel is ≈8 and ≈11 ppm, respectively. A comparison of various processes of rail steel deoxidation under the OAO NTMK conditions shows that the limitation of the aluminum content (no more than 30 ppm) or the use of a wire with a calcium or calcium carbide filler is more effective than the use of a wire filled with silicocalcium.

Reducing the melt heating in the mold to enhance rail-steel quality

The macrostructure of continuous-cast high-carbon steel (in particular, rail steel) billet may be improved by introducing macrocooling additives to prevent overheating of the melt in the casting-machine mold. The liquidus temperature of the macrocooling additives is 5–20°C lower than for the cast steel. Macrocooling strip is alloyed with boron, which ensures additional modification of the rail steel.

Optimizing the ladle treatment of rail steel at OAO NTMK

Rail steel production at OAO NTMK has a number of distinguishing features. The intermediate metal is smelted in the converter in two stages: first, the production of the intermediate metal and vanadium slag; second, the correction of the intermediate metal’s chemical composition to meet grade requirements. Then the metal is sent for ladle treatment, including reduction and alloying of the melt after discharge in a ladle‐furnace unit under slag, with argon injection; and vacuum degassing of the metal in the ladle under slag (in an RH circulation unit), prior to continuous casting.

Shell formation in a continuously cast ingot in a mold under monotonic and pulsed-continuous cooling conditions

The kinetics of the solid shell formation in a continuously cast ingot in a mold is studied under monotonic and pulsed-continuous cooling conditions. The slab shell growth rate is calculated for rail and graphitized steels under various cooling conditions. The structure formation in the solidifying metal is theoretically analyzed. During the course of cyclic cooling, transitions from a columnar to an equiaxed-grain structure and vice versa are likely to occur in the forming ingot shell. As a result, a disperse structure forms in the surface layer of the slab.