Том 47, № 8 (2017)

Hatch (Canada) has developed a system for the nondestructive monitoring of the residual lining thickness in blast furnaces and eletrofurnaces. This system, which is based on an acoustic–ultrasound echo signal (AU-E), supplements the traditional thermal simulation of the furnace lining by means of built-in thermocouples or on the basis of the thermal load on the cooling units in the blast furnace. By this means, the position of cracks and anomalies may be determined, and the boundary between the coating and the refractory may be identified. The constraints and sources of error in the AU-E method are analyzed, and an improved version is outlined. The improved method takes account of the influence of the following factors on the wave propagation: high temperatures; the furnace shape and size; and the difference in acoustic resistance of different layers in a multilayer refractory lining. The AU-E method permits reliable and nondestructive monitoring of the refractory lining in smelting furnaces. The hardware and software of the AU-E system have been significantly improved, so as to obtain measurements of satisfactory accuracy. Estimates of the method’s precision are confirmed by physical measurements on inoperative blast furnaces. Examples of the utilization of this diagnostic system at various Russian and non-Russian plants are presented. Some technological measures that extend the blast-furnace run are noted. As shown in the present study, the use of several successive measurements permits the determination of the lining’s wear rate and the time remaining before major repair. The AU-E method continues to operate well at more than 70 blast furnaces around the world, including those at the Novolipetsk, Cherepovets, Nizhny Tagil, Western Siberian, and Magnitogorsk steel works, as well as at electrofurnaces producing ferroalloys, copper, and platinum.

Natural gas is employed to reduce coke consumption in cupola furnaces with an open or closed top. The usual approach here is combustion of the natural gas by means of burners in external chambers at the perimeter of the furnace housing. Depending on their design, the burners ensure partial or complete preliminary mixing of the gas and air, with an air excess of 1.2–1.5. Then the combustion products are sent directly to the batch bed. In this system, the coke consumption amounts to 8–9% of the metal charge, while the consumption of gaseous fuel is 30–40 m3/t of melt. In these conditions, the melt temperature rises slightly (by 10–20°C); the productivity is increased by 15–20%; and the harmful gas emissions (mainly CO) are reduced by 20–25%. The gas dynamics of the cupola furnace is periodically disrupted, with suspension of the batch bed, cooling of the melt produced, less complete chemical combustion, and damage to the furnace lining. When using this method, the gas–air mixture is supplied to the hot bed with an air excess no lower than 2.5–3.0. A high-temperature zone (1350–1380°C) of width 60–70 mm is formed and moves through the bed at a speed of 15–20 mm/min. This calls for uniform mixing of the gas and air, specific gas-dynamic conditions, and the creation of the required gas–air ratio, with an air excess of more than 2.5–3.0. If cold gas–air mixture is supplied to the furnace bed through a tuyere, the combustion zone divides the whole bed into two stages: the initial and final stages. The high temperature of the combustion zone ensures fast cooling of the material at ignition of the gas–air mixture. That prevents ignition in the space above the bed. The lack of direct contact between the high-temperature zone and the furnace’s working space improves the reliability and economic indices of this process (no heat losses). Bed combustion of natural gas in the heating of such cupola furnaces increases the productivity from 10 to 13.6 t/h (by 36%), with reduction in coke consumption by 80 kg/t (33.3%) and decrease in heat consumption by 25 kW (18.78%). The heat losses with the exhaust gases are reduced by 25.32 kW (16.2%). The total thermal efficiency of the system is increased from 35.58 to 42.26% (by 15.81%, rel.).

Experience shows that the successful introduction of automated information systems at metallurgical enterprises largely depends on the technology and software selected. In the present work, the basic technology and software options available are briefly outlined. The starting point is Agile development, which is based on iterative procedures, the dynamic formation of user requirements, and their implementation through constant dialog within working groups consisting of various specialists (users, analysts, programmers, and testers). Iteration corresponds to relatively brief development times (as a rule, months), after which the user is given the next tested version of the software, with new functional properties. The list of additional functional properties in each new version represents user priorities and is drawn from the overall list of requirements before each iteration begins. In each iteration, the following procedures are completed in sequence: verification of the computational algorithm (with the introduction of new variables, where necessary); functional modeling of the system; improvement of subsystem structure; conceptual modeling of the database; generation of a model of the database; loading of the test data in the database; creation of the functional diagrams in the mathematical library; implementation of the subsystem’s client software; testing and debugging of the software; and the development of reference documentation. The Atlassian JIRA system is used to control individual tasks and monitor their overall realization within the process of collective software development. The Atlassian Bitbucket platform provides remote storage for code storage and control of the software version. On the basis of up-to-date approaches to software development, systems that are functional, reliable, east to use, expandable, and integrable may be created. Such systems are characterized by minimum risk and acceptable cost.

A model is proposed for the solidification of thick ingots with supplementary cooling by means of mandrels. On that basis, the overheating of the liquid steel in the classical system may be eliminated. The effectiveness of supplementary cooling by means of mandrels is shown in a computational experiment. The solidification rate may be significantly modified by that means.

In the production of manganese ferroalloys from ore, about 50% of the manganese in the ore is lost. The manganese lost with the enrichment-slag tailings may be returned to the production of manganese ferroalloys by dithionate method of enrichment of the slurries. A technology is developed for the production of high-carbon ferromanganese from concentrate obtained by the chemical enrichment of tailings slurries. Low-phosphorus Mn slag is used in the production of ferrosilicomanganese and refined manganese ferroalloys. A method is described for alloying hot metal with manganese from slag during the production of lowand medium-carbon ferromanganese. Processes are developed for the production of medium-carbon ferromanganese by mixing ore–limestone melt with high-carbon ferromanganese and removing the phosphorus from Mn-bearing melts by bubbling with CO. The degree of phosphorus removal (70–90%) depends on the bubbling time. By means of improved production of manganese ferroalloys and extraction of manganese from slag and slurries, the manganese extraction may be significantly increased.

The microstructure formed in the surface layer of industrially produced steel 70 wire rod (diameter 5.5 mm), wire (diameter 4.2 mm), and thin brass-plated steel 70 wire (diameter 0.933–1.75 mm) is studied. Local surface sections with turbulent structure are identified by means of transmission and scanning electron microscopy and microhardness measurements. Those sections are associated with shear stress forming additional rotary deformation modes. With increase in the deformation, a gradient in the microhardness appears. The hardness is greatest at the surface in sections with anomalous structure. The dynamics of dislocational structure in metal with deformation is investigated. The formation of pearlite colonies in high-carbon steel is studied. The results may be used in determining the limiting deformability of wire rod and wire on drawing.

A serious environmental impact of Russian blast furnaces is the generation of copious dust on account of the low strength of the sinter and pellets employed. Their strength may be increased if red mud from alumina production is introduced in the initial batch. A problem here is that the red mud lowers the iron content in the blast-furnace batch. However, this effect may be compensated by reducing the content of fines in the batch, according to research on the chemical composition of Russian blast-furnace batch. The minimum iron content in the red mud at which such compensation is feasible is established.