Mastering of the Technology of Assembling of Composite Mill Rolls Under the Conditions of Rail and Structural Steel Shop at the JSC “EVRAZ ZSMK”

Metallurgist - We develop a technology of assembling of composite mill rolls for the universal stands of the rail and structural steel shop at the JSC “EVRAZ ZSMK.” The proposed...     

Modification of steel with barium and strontium

The modification of steel by natural materials containing barium and strontium is considered. Thermodynamic modeling of the reduction of barium and strontium by silicon and aluminum is undertaken. The influence of modification by barium and strontium on the structure and mechanical properties of the steel is studied. The results are employed in the production of 25Γ2C and Γ13 steel in arc furnaces at the casting shop of OAO EVRAZ ZSMK and also in the production of 35XΓCЛ, 30XΓCЛ, and 12HЛ2ΦX steel at OAO Yurginskii Mashinostroitel’nyi Zavod by two-slag technology. The results of industrial tests indicate that modification with barium and strontium affects the microstructure and nonmetallic inclusions; and increases the margin of structural strength of the steel, estimated in terms of the yield point, strength, and impact strength at positive and negative temperatures. To identify the presence of barium and strontium in the steel, its structure is analyzed by means of extraction replicas on a transmission electron-diffraction microscope. The presence of barium and strontium within the grains indicates their reaction with the metallic melt, which affects the structure of the metallic matrix.     

Differential heat treatment of rails by means of rolling heat

Differential heat treatment of rails by air on the basis of the rolling heat is considered. The research is conducted at AO EVRAZ ZSMK during the reconstruction of rail production. The influence of the chemical composition of the steel and the conditions of plastic deformation and heat treatment on the onset of polymorphic transition is studied. Thermokinetic diagrams are plotted for steels of experimental chemical composition. The cooling rate over the cross section of the rail head is investigated as a function of the heat-treatment parameters. The optimal chemical composition and heat-treatment conditions are determined. The heat treatment of rail samples directly after rolling is experimentally studied. Recommendations for the industrial introduction of differential quenching are developed on the basis of the theoretical and laboratory results. Industrial tests show that the rails produced are of high quality and comply with standard requirements.     

Seventy-five years of steel production in Magnitogorsk

The history of steel production in Magnitogorsk is outlined, from the first melt to the reconstruction of the last open-hearth shop as an electrosmelting shop and the further enlargement of the oxygen-converter shop at OAO Magnitogorskii Metallurgicheskii Kombinat.     

Nonparametric modeling of oxygen-converter processes

Preliminary data analysis in the identification of multidimensional discrete–continuous processes is considered. A method is proposed for generating a working sample from an initial training sample consisting of normal operating data. The method somewhat resembles the bootstrap process. In the present case, the process begins with a training sample that reflects the properties of the object to be identified. By means of the proposed method, the unknown stochastic dependence at the limit of definition of the corresponding input–output variables for the object may be automatically derived. The identification of the oxygen-converter process in converter shop 2 at OAO EVRAZ ZSMK is considered in the case with insufficient available information and gaps in the observation sample. The model is based on a new working sample containing both the measurements and data generated by the proposed method. By using the working sample as a training sample, the precision of identification is doubled.     

Development of continuous casting at OAO MMK

The introduction of continuous casting at OAO MMK was a historic event, marking the end of uneconomical chill casting. Thanks to the introduction of continuous casting in the oxygen-converter shop, improvement in casting-machine design, and expansion of the range of steel that can be cast, unique casting characteristics have been attained: high productivity (more than 10 million t/yr), long casting runs (up to 208 melts), infrequent accidents, low rejection rates of the steel, and high quality of the continuous-cast slabs. The introduction of continuous casting in the converter shop provided a stimulus to the reconstruction of the open-hearth shop as an electrosmelting shop and the installation there of two bar-casting machines and one slab-casting machine.     

Geometric conditions in bar rolling

Analysis of the scope for more efficient bar rolling is considered; a method of rapid analysis is outlined. By this means, the geometric parameters of the rolling pathways may be represented by alternative groups of repeatedly transformed dimensionless factors, and the results of repeated transformation may be statistically analyzed, to obtain an assessment of competitiveness. The multivariant representation of the geometric conditions yields significantly more information, including unexpected technological reserves of the process. Such analysis provides a set of recommendations regarding the local correction of the deformation region in one or more passes of the steel through the mill. As an example, this approach is employed in assessing the potential for increasing the product yield in rolling structural-steel bar for cold extrusion and upsetting on small-bar and wire mills at OAO EVRAZ ZSMK. The proposed method may be used to improve the production of a wide range of steel bar.     

Extending the lining life in circulatory vacuum units at OAO EVRAZ NTMK

Practical methods for extending the life of submersible tubes in vacuum chambers are considered. The structure of periclase-chromite components is studied. Refractories corresponding to optimal vacuum-chamber operation in the converter shop at OAO EVRAZ NTMK are selected.     

Dynamic monitoring of slag oxidation and thickness in the ladle-furnace unit

Methods are proposed for ongoing monitoring of the slag oxidation and the depth of the electrical arcs in slag at the converter shop of OAO EVRAZ NTMK. Such monitoring is expected to increase the rate of metal heating, reduce the ferroalloy and power consumption, and increase the lining life in casting ladles.     

Injection of iron-bearing concentrates derived from steel-smelting slag into the converter bath

Steel-smelting slags form a large proportion of metallurgical wastes. They are generated at a rate of 150–200 kg/t of steel, on average. At current rates of steel production in Russia, the annual output of smelting slag is 9 million t, of which 8–11% consists of metallic iron and 15–40% of iron oxides. The total iron content in the slag is 20–30 wt %. Steel-smelting slag represents a valuable source of iron, which should be processed and returned to production. The slag-processing system at AO EVRAZ ZSMK permits stepwise removal of iron-bearing inclusions from the slag by magnetic separation. The iron-bearing concentrate obtained consists of three fractions: 0–10 mm (for use in sinter production); 10–80 mm (for blast-furnace use); and 80–250 mm (for use in steel smelting). The use of the 0–10 and 10–80 mm fractions in steel production in 160-t converters is considered in the present work. A mathematical model permits multivariant calculations to investigate the smelting dynamics and the distribution of added iron-bearing concentrates in the metallic melt, for different trajectories and dosing protocols. Analysis of the results yields new information regarding the hydrodynamic processes when iron-bearing concentrates from the slag-processing system at AO EVRAZ ZSMK are injected in the converter bath.     

Improved internal cooling of rollers in curvilinear continuous-casting machine

In the electrosmelting shop at OAO MMK, the internal cooling of the rollers in a curvilinear continuous slab-casting machine with a vertical section has been improved. To ensure stable heat extraction from the slab and stable difference in water temperature between the roller input and output, the rational flow rate of the cooling water within the rollers is calculated. On that basis, the water required for internal roller cooling is reduced, for slabs of different width.     

Controlling the blast-furnace hearth

At OAO EVRAZ ZSMK, the operation of the blast-furnace hearth is regulated by means of special briquets with good granulometric composition, high iron content, and low impurity content. The briquet charge depends on the total iron-ore consumption, primarily in the intermediate region of the furnace. With steady briquet content (around 2.1% of the charge), the variation in the hearth obstruction is smooth and confined to a narrow range. When the briquets account for 1.0–2.5% of the total charge, the actual mean furnace productivity increases by 6.7%; the adjusted value increases by 3.5%. The actual coke consumption is reduced by 0.5%, and the adjusted value by 0.7%.     

Nickel-free steel of increased strength and corrosion resistance for freight-car production

Nickel-free 10ΓAΦДΠ1 steel of elevated strength, low-temperature strength, and low-temperature resistance has been developed. On the basis of the new steel, a production technology for rolled sheet and cold-bent profiles (thickness 3.6–5.0 mm) for freight-car production is proposed. In the electrosmelting shop at OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), a batch of the new steel (160 t) has been produced and rolled to 4.5 × 1500 mm sheet in the 2500 mill. Coils of this steel are used to produce bent profiles for freight-car production. The new 10ΓAΦДΠ steel surpasses mass-produced 10XHДΠ 1 steel in terms of its suitability for freight-car components.     

Reconstruction of the gas-purification system for the shaft furnace and ladle-furnace unit at OAO severstal

The unsatisfactory operation of the bag filter and gas-exhaust channel from shaft furnace 2 in the electrosmelting shop at OAO Severstal is investigated. Recommendations for the elimination of these problems are formulated. The corresponding reconstruction increases the operational reliability of the gas-purification system. The residual dust concentration beyond the filter is reduced from 250–300 to 35–40 mg/m³.     

Growth of the production of rails from continuous-cast semifinished products of electrical steel

Since 2001, the Novokuznetsk Metallurgical Combine has produced 3.0 million tons of R65 railroad rails of continuous-cast steel made in electric furnaces. The combine has significantly improved all the most important quality indices of the steel during this period, and the service life of the rails has increased from 0.5·10⁹ to (0.8–1)·10⁹ tons gross. The combine has mastered the production of rails with superior cold resistance and rails suited of use in high-speed rail systems. It is beginning production of rails with a bainitic structure and rails made of hypereutectoid steels. All these results have been obtained through the construction of new production facilities and modernization of the combine’s existing equipment. Plans for future rail production include extensive reconstruction of the heat-treatment section of the rail-beam shop and reconstruction of the machine-tool bay, the latter involving replacement of part of the equipment. Arc steelmaking furnace No. 1 and two continuous casters will be rebuilt in the electric steelmaking shop. The ultimate goal is to increase the durability and reliability of the rails so as to put them on par with the best rails in the world.     

Improving the Performance of Hot-Blast Stoves at EVRAZ ZSMK

Metallurgist - A gas mixing station for admixing natural gas to the blast-furnace gas for heating the hot-blast stove was developed and put into commercial operation at BF No. 2 of EVRAZ ZSMK.     

Slag oxidation in arc furnaces

In the electrosmelting shop at OAO MMK, the smelting of steel in powerful DSP-180 arc furnaces introduced in 2006 continues to be refined. Industrial research is conducted to establish how the content of the iron oxides FeO and Fe₂O₃ in the slag depends on its total oxidation. As a result, the dependence of FeO/Fe₂O₃ on the total slag oxidation may be described. It is established that the total slag oxidation does not depend on the consumption of injected carbon in frothing the slag. Analysis of the waste gases in the same smelting period shows sharp increase in the content of carbon oxides (especially CO) and the temperature. On account of the poor assimilation of the injected carbon by the melt, much of it is oxidized in the gas phase.     

Influence of the pressure in the vacuum unit’s working chamber on the content of hydrogen and nonmetallic inclusions in steel

In electrosmelting shop 2 at Belarussian Metallurgical Plant, the removal of hydrogen from steel is studied as a function of the residual pressure in the working chamber of the RH vacuum unit. The influence of the pressure on the quantity and composition of the nonmetallic inclusions in cord steel is also investigated.     

高强度高韧性贝氏体钢轨研究

采用合金化方法生产的高强度高韧性贝氏体钢轨及道岔,其热轧态抗拉强度大于1 250 MPa,比U75V提高25%;轨腰冲击韧性大于30 J/cm2,比U75V提高3倍以上.介绍了热轧贝氏体钢轨的强化机理、生产工艺及各项检验结果.用贝氏体钢制作的铁路道岔在线路运行已一年半以上,货运量达2亿t,目前仍在使用.在北京铁路局铺设的全贝氏体组合道岔,其使用寿命进一步提高,高强度高韧性贝氏体钢在铁路使用将得到较大的社会和经济效益.     

Electrosmelting of steel with 100% solid metal batch

Operating conditions are developed for the electrosmelting of rail steel and regular steel with 100% solid metal batch. Overall, the furnace performance is comparable to that with 50% hot metal. The new approach permits savings of around 170 rub/t of steel.