High-Field domain formation in thyristor structures at ultrahigh current densities

We have studied the mechanism of high-field domain formation in thyristor structures at ultrahigh current densities (J≫100 A/cm²) and the related effect of anomalous buildup of the direct residual voltage. The analysis is based on the results of numerical simulation of the process of double injection with allowance for accompanying nonlinear effects.     

Improving air-tuyere operation in blast furnaces by means of coatings and sealant

To extend the life of air tuyeres and reduce heat losses through their surfaces, boron-carbide sealant is applied to tuyeres with a sprayed aluminum coating after heat treatment. The influence of the B₄C-based sealant on the heat losses is theoretically assessed. The efficiency of the sealant is confirmed by industrial trials at OAO NLMK and by metallographic investigation of samples from used tuyeres.     

Utilization of Mineral Waste: A Method for Expanding the Mineral Resource Base of a Mining and Smelting Company

Metallurgist - As the population grows, the need for mineral resources increases, resulting in an intensification of their extraction. This increases the amount of industrial waste and, thus, the...     

Reindustrialization principles in the heat treatment of die steels

The reindustrialization of production is considered. As an example, a working model is developed for the heat-treatment equipment used in the production of dies made from special steels. In reindustrialization, productive capacity that has been lost or has grown outdated during deindustrialization must be restored or modernized. Heat treatment is of particular importance since it is part of the manufacture and restoration of most tools. Modern Russian equipment permits high-quality heat treatment of many special steels so as to ensure the required mechanical properties. All the basic groups of die steels are considered in terms of their performance: steel of increased wear resistance; secondary-hardening crumple-resistant steel; steel with elevated impact strength; steel of moderate thermostability and high ductility; steel of elevated thermostability and ductility; and steel of high thermostability. The requirements on the properties of these groups are analyzed, and possible means of attaining those properties by heat treatment are identified. By comparing the specific purpose of die steels, their required properties, and the possible means of attaining those properties by heat treatment, the appropriate equipment is chosen. Modern Russian equipment permits high-quality heat treatment of die steels so as to ensure the required mechanical properties. At present, it is important to create production systems that incorporate the vast wealth of Russian specialists’ accumulated experience and the best available technologies. This is a very complex problem, in both engineering and economic terms.     

Production of periodic bars by vibrational drawing

One aspect of improving blade production is the production of blanks with a periodic profile from nickel and titanium alloys. In certain cases of vibrational deformation (in particular, in vibrational drawing), periodic change in the diameter of rod or wire over its axis is observed. This is associated with frictional oscillation and stability loss in deformation (on reaching the yield point in the rod, with the appearance of necking, or as a result of inertial forces). Formulas are obtained for use in determining the conditions of unstable deformation and stabilizing the production of periodic bars by regulating the parameters of vibrational drawing.     

Dynamic current localization during turn-off of high-power microgate bipolar switches

The turn-off process of semiconductor switches with distributed microgates in the presence of small embedded technological inhomogeneities of their structure parameters is considered. The process dynamics is studied based on the analytical model of residual plasma displacement and the space charge region dynamics in the base, taking into account ionization in high electric fields. A spatially inhomogeneous switch structure is modeled by two groups of controlled cells with different parameters, i.e., emitter injection efficiencies or carrier lifetimes in n-type bases. Voltage coupling of all cells is complemented by the device interaction with the external circuit. The detrimental effect of current localization at the turn-off stage, which occurs even at a relatively small parameter variance, was studied within the proposed model. The results obtained allow quantitative characterization of the effect of technological inhomogeneities on safe operating area of high-power microgate bipolar switches.