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.     

Improving the durability and reliability of vacuum-chamber linings

Several practical methods of improving the durability of vacuum-chamber linings in the converter shop at OAO Nizhnetagil’skii Metallurgicheskii Kombinat are considered.     

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.     

Smelting low-silica hot metal at OAO NTMK

In the blast-furnace shop at OAO Nizhnetagil’skii Metallurgicheskii Kombinat (NTMK), the smelting of low-silica vanadium hot metal is being introduced. Theoretical and experimental data reveal the influence of the pressure in the furnace’s working space and coke quality on the reduction of titanium and the formation of refractory titanium compounds. The residence time of the melt in the hearth depends on its dimensions.     

Interaction between molten steel and different kinds of MgO based tundish linings

Abstract

Interactions between the molten steel and the refractory linings are of fundamental importance for the steelmaking industry. During the casting process, the steel cleanliness can be made worse because of the reoxidation of the molten steel in contact with the atmosphere and/or other sources of oxygen (refractories, top slag, etc.). In the industrial trial periods, four tundish refractory linings (preformed boards, two kinds of gunning materials and dry vibrating material, all MgO based refractories) were used in order to evaluate the interactions between the refractories and the molten steel. Owing to the small dimension of the tundish (5 ton) used in the continuous casting at Villares Metals SA, after casting, the chilled steel was cut in order to show, in a single section, the stopper, submerged entry nozzle, MgO ramming and the working refractory lining. Cross-sections of samples from the steel/refractory interface were investigated by electron probe microanalysis (EPMA). Four major aspects were observed at the steel/refractory interface: steel infiltration into the tundish refractory lining, mainly in the gunning materials; a steel oxidised layer formed at the steel/refractory lining interface; formation of a spinel layer between steel and tundish working refractory lining; and many particles were found in the steel phase, near to the steel/refractory interface, being a potential source of non-metallic inclusions.     

Development of new heat-treatment methods for rail at OAO Nizhnetagil’skii Metallurgicheskii Kombinat

The selection of coolants for rail quenching at OAO Nizhnetagil’skii Metallurgicheskii Kombinat (NTMK) is considered. Thermohardening in aqueous polymer solution or hot water has been developed and tested. Economically alloyed steel may be used for rail manufacture after thermal hardening by compressedair cooling. The microstructure of disperse plastic pearlite is formed in three-stage quenching, with pearlite production in the surface layers of the rail during the first two stages.     

Optimizing the composition of coking batch

The optimization of coking batch at OAO Nizhnetagil’skii Metallurgicheskii Kombinat (NTMK) is considered theoretically and on the basis of practical experience. An integral characteristic of the batch is proposed: the optimality coefficient K _opt. On that basis, the optimal batch composition may be assessed and the mechanical strength of the coke may be predicted.     

轧钢加热炉用耐火材料的合理选用

根据轧钢加热炉炉衬材料的工作特点以及我国耐火原材料的具体特性,合理地进行耐火材料的选择,并对膨胀缝进行合理的设计,达到轧钢加热炉长寿、高性价比及节能的要求。     

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.     

MgO–C bricks for BOF linings

Abstract

MgO–C brick linings have become standard in basic oxygen furnaces (BOFs) all over the world. Developments in the refractory technology for BOFs over the last few years and their impact on the lifetime and performance of refractory linings are presented. These developments comprise optimised shapes for the lining of BOF and steel fibre reinforced MgO–C bricks. Optimised shapes with double wedges lead to a smooth inner surface of the refractory lining and fewer stresses and refractory consumption. Stainless steel fibre reinforced MgO–C bricks have proven to be the ultimate choice for scrap impacts or other areas with ultra high mechanical loads. They have brought down refractory wear in these particular areas significantly. Moreover, typical lining patterns of different zones in a BOF and the development of the raw material grades (MgO grades and graphite) for refractories as well as the development of lining lifetimes over the last years are discussed.     

科学管理降低钢包内衬耐料消耗

侵蚀、冲刷、熔融、剥落、水化等原因导致了钢包内衬耐火材料的损毁，在了解了钢包内衬耐火材料的蚀损机理及炼钢工艺和设备对钢包内衬的影响，并掌握了耐火材料的技术发展方向后，通过采用新材料、优化砌筑工艺和科学的管理，可以达到提高钢包运行安全系数和降低钢包内衬耐火材料成本的目的。     

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.     

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.     

Durability of Brick Lined Steel Ladles from a Mechanical Point of View

The refractory lining in steel ladles is exposed to chemical and mechanical loads during the heats. Mechanical loads develop from the thermal expansion of the refractories which is confined either by the steel construction or by regions of different temperature within the refractory material. The aim of this work was the investigation of factors influencing the mechanical durability of refractory steel ladle linings and the clarification of failure mechanisms. Especially irreversible strains at the hot face of the working lining caused by compressive stresses induce an opening of joints at the hot face. The irreversible strains reduce the compressive stresses in circumferential direction and increase the probability of tensile failure. A further effect of the irreversible strains is a reduced stability of the working lining. Of special interest in this context is a possible controlled expansion of bricks to counterbalance the irreversible compressive strains.     

钢包工作衬用耐火材料的研究现状及最新进展

综述了近年来钢包工作衬用耐火材料的研究现状及最新进展, 尤其对传统钢包工作衬用耐火材料的应用背景及存在问题进行了分析和汇总.在此基础上, 进一步提出了适用于超低氧钢(或洁净钢)冶炼用耐火材料的研发方向, 即通过耐火原料组分选择和结构匹配设计, 实现对耐火材料性能的精确控制.新型钢包工作衬用耐火材料需兼顾优异热机械性能的同时, 还应具备钢水净化的功能.      

Extending the life of the tundish and lining of the intermediate ladle in a six-strand continuous bar-casting machine

Continuous steel-bar casting on a multistrand machine in superlong series is limited by the working-layer wear of the intermediate ladle’s lining within the slag band and the region of jet incidence. The lining life may be significantly increased by using high-strength concrete tundishes of special geometric shape, taking account of the specific ladle and the casting conditions. A fundamentally new metal-intake design for the casting of superlong series at multistrand continuous bar-casting machines is investigated. In the converter shop at OAO Enakievskii Metallurgicheskii Zavod, a casting series of maximum length 64 melts proves possible. This corresponds to the casting of 9300 t of steel from a single intermediate ladle. For optimal organizational and technological conditions, increase in this characteristic by a factor of 1.5–1.6 may be expected.     

Production of cold-rolled strip from low-alloy 10ЮA steel

A new production technology for cold-rolled sheet from low-alloy steel is proposed for a sheet-rolling shop at OAO MMK; the steel is smelted in accordance with Technical Specifications TU 14-4-1333-2002.     

Improving the accelerated cooling of rolled steel

The basic stages in improving the accelerated cooling of rolled steel are considered for the 350 small- and medium-bar mill in bar-rolling shop 2 at OAO Oskol’skii Elektrometallurgicheskii 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.     

Improving the reduction and ladle treatment of Electrosteel for rail production

Research in the electrosmelting shop at OAO EVRAZ ZSMK indicates that, if inert gas is injected into molten rail steel in the ladle for 122 min, rather than 63 min, the quantity of nonmetallic oxide inclusions may be reduced, without impairing overall rail quality. Industrial experiments show that replacing MnS18 silicomanganese with FeMnSi30HP silicomanganese in the reduction of rail steel is economically effective in the electrosmelting shop at OAO EVRAZ ZSMK. The assimilation of carbon and silicon is increased by 4 and 13%, respectively. The mechanical properties and macrostructure of rails obtained by this experimental technology match those of the steel currently produced. According to the calculation results, the use of FeMnSi30HP ferroalloy provides savings of 13.99 and 32.64 rub/t for rails of category T1 and NE, respectively.