Vol 63, No 5-6 (2019)

Using natural gas as an additional fuel in a blast furnace is known to reduce coke consumption during blast-furnace production. In a standard tuyere, the hot blast pushes the natural gas up against the surface of the blast duct, resulting in poor mixing between the natural gas and the hot blast, which in turn leads to incomplete combustion and pyrolysis of the natural gas. One approach for improving mixing between the natural gas and the hot blast is to modify the blast-channel geometry.

An engineering design solution was proposed, and the gas dynamics, thermal conditions, and stress/strain state of the air tuyere for this solution were analyzed via ANSYS modeling. Toroidal protrusions on an insert near the outlet of the air tuyere (swirlers) or on the gas inlet nozzle flange (rim) were considered; these protrusions also protect the insert against premature damage in areas subject to the most severe mechanical damage.

The following assumptions were made: The model scope includes both the fluid medium within the blast duct and the thermal insulation insert, i.e., this can be thought of as a conjugate heat exchange problem, and heat transfer to the cooling system water was taken into account using the generalized boundary conditions.

We show that modifying the insert geometry so that there is a protrusion on the working surface or installing a rim in the area where the insert starts to show damage, will increase mixing of the natural gas into the blast air and during combustion. This then increases the blast temperature at the tuyere outlet, which in turn increases the natural-gas flow rate and reduces coke usage. A similar result was achieved for wear on the insert.

Shipbuilding remains one of the most metal-consuming segments of the transport industry. For various types of vessels there is a trend of a successive increase in specifications for the specific volume of freight transport that predetermines an increase in the use of materials for construction, including thick steel plate. Considering the general trends in development of the thick plate market for shipbuilding, NLMK DanSteel has mastered production technologies for rolled product up to 35 mm thick produced from low-carbon microalloyed extra high-strength steels F420, F460, F500 intended for vessels of various types for Arctic application. Pilot plant, certified and industrial batches of heavy plates have shown a high level of strength, low-temperature impact strength at – 60°C, and a high level of welded joint mechanical properties employing various welding methods with heating input in the range from 15 ± 1 to 50 ± 2 kJ/cm. The results obtained provide NLMK DanSteel with favorable certification test results for production of extra high-strength grades F420, F460, F500 and their analogs in thickness up to 35 mm according to the IACS rules and confirm the quality of heavy plates in accordance with the requirements of DNV-GL and other marine certification association classification programs and standards.

The quality of railway wheels significantly affects the economy and security of railway transportation. In order to improve the properties of railway wheels steel is used currently with a controlled aluminum content. A feature of this steel is the increased risk of forming large alumina non-metallic inclusions. Nonmetallic inclusions in the defective and defect-free zones of a rejected wheel are studied. The causes of defect formation and a new comprehensive technology of smelting are determined, and ladle treatment and continuous casting of steel are developed, which provide avoidance of forming these defects.The main essence of the technology is the diffusion deoxidation of metal with slag of optimum composition, control of aluminum content during ladle treatment, and use of aluminum exclusively for steel alloying.

The effect of composition and thermal deformation processing (finishing temperature of rolling and coiling, cooling rate after rolling) parameters on the mechanical properties and structure of advanced Ti, Mo micro-alloyed structural (automobile sheet) ferritic steels is studied. It is established that the strength characteristics of steel increase regularly with increasing Ti content within appropriate limits and additional microalloying with molybdenum. The resultant structural state is primarily determined by the cooling rate after steel hot rolling. At relatively low values of 10–15 °C/sec polygonal ferrite is formed, and on increasing up to 30 °C/sec formation of a high dislocation acicular ferrite is observed. The expediency of reducing carbon content to 0.04–0.06 wt.% is demonstrated.

The high quality standards required for metal forming call for compliance tests aimed to guarantee that such standards are met. Such tests often imply a waste of time and of economic resources. In particular, when stainless steel pipe forming is considered, many factors need to be taken into account. This paper analyzes the effect of different process parameters and geometrical constrains on the cold forming of austenitic stainless steel pipes by the finite element method (FEM). The results of such analysis will allow one to map the effect of different parameters.

We present the results of industrial testing of the technology of processing of silver–zinc crust obtained in the process of refining of raw lead from silver in a copper-smelting converter. We perform the tests for two versions of charging of dried crust into the converter: either into the empty converter prior to pouring matte from the smelting of secondary copper-containing raw materials in a shaft furnace or during the period of conversion after obtaining white mat. In the case of charging over the white mat, we get the slags that are poorer in all analyzed metals, whereas the yield of silver and gold into copper blister is higher. According to data of balance smelting, the direct yields of silver and gold from all types of processed raw materials into blister copper are 96.72% and 97.76%, respectively.

We describe the characteristic features of the steel smelting process in the 160-metric-ton converters at EVRAZ Consolidated West Siberian Metallurgical Plant JSC for the case where 10–50% of the solid metal charge consists of ferrous converter-slag waste products. Information on the chemical composition of the slag materials and the metal and slag components of the slag/scrap mixture was combined with the scrap consumption rate to quantitatively estimate the change in fundamental process statistics. The parameters of the traditional oxygen-injection process for the 160-metric-ton converters were compared against those for the technology to be discussed in this paper. Both the decrease in the concentration of non-ferrous-metal impurities and the required impurity removal levels at the exit from the converter are specified. The oxidative metal refining production data for the 160-metric ton converters at EVRAZ Consolidated West Siberian Metallurgical Plant JSC and the cost reductions from slag/metal scrap usage indicate that the process is economically promising.

Measures were developed to reduce the fuel consumption by the walking-beam furnace of the EVRAZ ZSMK ball-rolling mill based on an analytical review of modern technical solutions for fuel saving in ferrous metallurgy heating equipment. The thermal analysis performed confirms the effectiveness of the measures.

We presented the results of scientific and practical investigations of the technology of rolling of asymmetric rail sections, namely, of point and wing rails, performed on a universal rail and structural steel mill. The detected disadvantages are described according to the initial calibration and the causes of formation of the surface defects in the course of rolling of these profiles are established. The results of the performed analysis made it possible to develop calibrations for the analyzed asymmetric rail sections with evaluation of the stressed state of the metal in the course of rolling.

The governing effect of macrostructure quality on impact resistance is established by experiment for grinding balls 50 and 60 mm in diameter prepared by screw rolling. It is shown that presence of flakes significantly reduces grinding ball impact resistance regardless of their quenched microstructure parameters. In this case there is no significant effect of ball microstructure parameters after heat treatment on their impact resistance.

Development of new heat-resistant ferritic-martensitic steels with 12% chromium designed for operation at 700–720 °С is a complex multifactorial task. The main characteristics of such steels that define the possibility of their application at elevated temperature are high values of strength within the temperature range of 20–720 °С, and high values of creep resistance at temperatures of 650 °C and above with a satisfactory ductility level (at least 6–12% at 20–720 °С). A significant amount of time is required in the case of large range of steels investigated to determine the abovementioned properties. An important task is finding readily and quickly obtained properties by which it is possible to estimate the level of steel heat resistance properties. Diagrams for isothermal decomposition of supercooled austenite are analyzed and equations are found in the present work for their connection with yield strength and creep strength of the materials studied.

The paper offers a review of the current technologies of induction heating utilized during heat treatment of mill rolls. It is shown that designing the equipment and heat treatment technology with induction heating of the mill rolls is important, first of all, to ensure high quality of heat treatment. In this case, it is necessary to comply with the following requirements: provide minimum deviations of hardness from the required values along the length of the roll body and through the depth of the hardened layer, and eliminate dangerous (thermal and structural) stresses leading to roll destruction during or after the heat treatment. These problems cannot be resolved without computer simulation. A universal method of digital design and control of thermal conditions of the induction heating equipment is considered, which ensures high quality of heat treatment of the rolls.

In Tadzhikistan the volume of gold-containing waste converted to gold is 18 tons. This waste is products of amalgamation and cyaniding processes., and with respect to end component content they may be classified as a very rich type of raw material since they contain 1.7–8.5 g/ton of gold, whereas the average gold content in ores extracted for processing in one of the richest deposits of the republic, i.e., Tarror, comprises 2.4 g/ton. In addition, treatment of these dumps does not require crushing and refining since they have adequate coarseness of a finished class. In view of this the research object is goldcontaining waste of Tarror ore and a number of other adjacent deposits that have been accumulated over a long time. Results are provided for the raw material substance composition of the test raw material and the possibilities of using thiourea leaching for processing them. The main process parameters are optimized and the degree of gold extraction at the level of 80% is demonstrated.

A fundamental production scheme is presented for processing dumps, including the following operations: preliminary acid treatment; sorption thiourea leaching; desorption; reactivation; electrolysis; melting.

The conducted study shows the possibility of improving the technology for producing monodisperse spherical granules. By modifying the surface of a die, it becomes possible to utilize the technology when granulating ErNi alloy. A potential for using the regime of forced capillary jet breakup with satellite droplets to expand the size-based operating range of the granulators in the finely-dispersed region has been demonstrated. To improve the granular quality, the forced capillary breakup regime with an excitation wavelength of about λ = 4.5d should be used.