Vol 2016, No 6 (2016)

The changes in the parameters of a DSP-100 electric arc furnace that are induced by a decrease in the current frequency are considered. It is shown that the related decrease in the current lead resistances causes an increase in the arc power and voltage, a decrease in the reactive power, and an increase in the electrical efficiency and the power coefficient. The heat indices are expected to be significantly improved.

The design of the mold in an electroslag furnace for melting hollow billets for metal-cutting knives, which has a water-cooling mandrel, is considered. A scheme for cooling of the copper mandrel is proposed. A mathematical model is developed, and an algorithm is proposed to calculate the thermal state of the mandrel at the chosen geometric parameters, a given number of water-cooling channels, and certain cooling water parameters. It is found for an internal copper mold 200 mm in diameter that a stationary thermal regime is reached in at most 5 min. An increase in the number of channels at the same total cross-sectional area is shown to cause a decrease in the temperature gradients and the maximum temperature in the internal mold. The ANSYS software package is used to simulate the thermal state of the copper mandrel of the proposed design at given water cooling parameters. The calculations support the adequacy of the proposed mathematical model.

A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115–120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.

The kinetics of the solid-phase reduction of Cr₂O₃ with carbon under chemical catalytic action on the reacting system is studied. A significant intensification of the process in the presence of small amounts of potassium and sodium salts is established. The concepts of the catalyst action mechanism are considered and experimentally substantiated. Manufacture of iron–chromium master alloys with a restricted content of carbon can be organized at low temperatures, and they can be used in steelmaking.

The experimental data reflecting the thermodynamic features of deoxidation of liquid iron with metallic calcium are analyzed. A correction technique is proposed for a metallic melt–deoxidizer deoxidation curve according to the standard state by Henry’s law.

The structure and properties of the butt-welded joints of a 1565ch M aluminum alloy with AMg5, AMg6, AV (60661), and 7021 alloys that were performed by friction welding with mixing are studied. The mechanical properties of these joints and their fracture zones are determined as functions of a combination of the alloys to be joined. These alloys are found to have good weldability under friction welding with mixing.

Metal drop samples are taken during plasma–arc remelting of 12Kh25N16G7AR steel billets. An analysis of the drops shows that the fraction of steel nitriding in the drops accounts for 20–40% of the total steel nitriding at a nitrogen content of 0.06% in a billet. An equation is derived to estimate the nitriding of a liquid Cr–Ni–Mn steel from the nitrogen concentration in the billet to be remelted.

The fracture mechanism of the thermal barrier coating of gas turbine blades is studied. The causes of the fracture of the ceramic layer are discussed and the possible ways to increase the fatigue life of the thermal barrier coating are considered.

Based on our experimental results, we propose the following low-cost technologies in the field of steelmaking for implementation: the use of briquettes, which are alternative to solid cast iron and scrap metal and contain scale and carbon-containing wastes, in the charges of electric furnaces and converters; microalloying of metal by nitride phases; modification of steel in a ladle by SiCa + Ba master alloys; and the application of daisy-chain blowing of the metal in a ladle (small-bubble conditions). The efficiency of these technologies for melting in electric furnaces and secondary metallurgy is supported. It is shown that electromagnetic mixing of metal in combination with the optimum conditions of soft reduction of a slab should be used in continuous casting to form an internal structure in a slab at the level of the first class on the Mannesmann scale.

The laws of formation of price clusters are revealed upon statistical processing of the data on changing the quotation prices of nonferrous and precious metals, oil, black oil, gasoline, and natural gas in the postcrisis period from January 1, 2009 to November 1, 2013. It is found that the metal prices entering in the price cluster of nonferrous metals most strongly affect the formation of the nonferrous metal price and that the prices of precious metals and energy carriers correct the exchange price of the metal to some extent but do not determine its formation. Equations are derived to calculate the prices. The results of calculation by these equations agree well with the real nonferrous metal prices in the near future.