Vol 63, No 1-2 (2019)

We have reviewed the literature on coke preparation for blast furnace smelting, including studies on particle size distribution. We describe the basic requirements on coke quality in light of the widespread adoption of pulverized coal fuel injection technology for blast furnaces in the Russian and Ukrainian metallurgical industries.

Based on the analysis of the Russian-made 4 to 16 mm thick rolled products produced by thermomechanical rolling from high-strength (yield point: 433 to 828 MPa) low-alloyed welding steels obtained as a result of 15 melting runs, the effect of chemical composition and structure on the mechanical properties, such as yield point, impact toughness, and impact toughness anisotropy factor, was studied. It was shown that the yield point of manganese steel (1.62–1.80 wt. % Mn) is mainly caused by microalloying with titanium, and to a lesser degree – with niobium and vanadium. An increase in the yield point of steel in excess of 700 MPa increases its tendency to impact toughness anisotropy. Within the concentration range from 0.001 to 0.08 wt. % Ti, the value of anisotropy factor K_a , which varies from 1.45 to 1.80, does not depend on Ti content, but increases sharply to K_a = 3.19 once the Ti content increases (in excess of 0.08 wt. %). A considerable negative effect of Nb content in steel on impact toughness (KCV^{– 40}), measured on transverse specimens, has been established. A joint negative effect of Ti + Al on KCV^{– 40} is somewhat less pronounced. The presence of Al in the inclusions of complex composition (Ti-Al-Cr) noticeably reduces (by 4.5 times) the negative effect of Ti on KCV^{– 40} of highstrength manganese steel.

The effect of alloying on the properties of highly tempered steels used for production of a range of petroleum pipes is studied. It is shown that an increase in molybdenum content from 0.15 to 0.53% improves the mechanical characteristics of chromium-molybdenum steels tempered at 600–690°C significantly. Alloying with vanadium and niobium facilitates an additional increase in strength properties. The best hardening of steel with 0.32% molybdenum in a highly tempered condition is provided by combined microalloying with niobium and vanadium, although stress corrosion cracking resistance is reduced.

The practice of shaft smelting of copper-bearing charge using oxygen-enriched air at the Mednogorsk Copper–Sulfur Combine is considered. After increasing the rate of oxygen enrichment of the blast air from 30 to 36%, the output increased by 20.1% and the copper content was 33.0–35.3% in the matte and 0.5% Cu in the waste slag. The material and heat balances are presented. The effect of increasing the rate of oxygen enrichment on the furnace productivity, solid fuel consumption, composition and amount of smelting products is shown.

A comparative study is provided for the effect of Si and Fe impurities in relation to their concentration in the structure, phase composition, and mechanical properties of alloy Al–0.2Y–0.3Er–0.2Zr–0.05Sc. With a content of Fe and Si (in the amount of 0.15%), presence is noted of phases formed by iron and silicon impurities with an increased concentration of Zr, Er, and Y. These phases are not found in the structure of alloy with a lower concentration of Fe and Si (0.01%). Due to dilution of aluminum solid solution with Zr, Er and Y, alloy with an increased Fe and Si (0.15%) content shows a weaker hardening effect during annealing compared to alloy having a more supersaturated solid solution. Sc in both alloys is evenly distributed within the matrix of aluminum solid solution and does not form phases during crystallization. It is shown that the temperature for the start of recrystallization for these alloys is in the range 500–550 °C. The set of standard mechanical properties for sheet produced from these alloys is almost at the same level: yield strength of 155 MPa, ultimate strength of 166 MPa, elongation at 11.2% for alloy with 0.15% (Fe and Si) and 8.7% for alloy with 0.01% (Fe and Si). It is noted that after annealing (200 °C, 1 h) sheets hardness increases by 5 HV, which may point to aluminum solid solution decomposition.

We present the results of investigations of the influence of explosion welding and hot rolling at a temperature of 850 °C on the micromechanical properties, structure, and phase composition of the zones of joints of a five-layer “VT-20 titanium alloy–08Kh18N10T corrosion-resistant steel” composite material.

The pelletizing parameters for fine technogenic raw materials generated in the production of metallurgical silicon (Si_met) are optimized. The technogenic waste of Si_met production in ore-smelting furnaces (OSF) is barely used in other industries. Silica-containing waste (gas-treatment dust and sludge) containing 86.3 to 95.8% SiO₂ is proposed to use as a charge component. The other charge components (fine waste) are petcoke screenings, charcoal fines, and silicon screenings (Si_scr). Liquid glass laced with dust from aluminum-production precipitators is used as a binder. To be transported and loaded in an OSF, the pelletized charge must have sufficient mechanical strength. This is why the drop resistance coefficient (R_dr) is used as an optimization parameter in mathematical processing of experimental data on charge pelletizing. A model equation that describes the effects of the following three factors is derived: pelletizing duration, binder content of the charge, and Si_scr particle size. For the optimal pelletizing parameters, R_dr is equal to 82.5%. Based on the study results, a process flow diagram for the production of Si_met using an additional facility for pelletizing technogenic materials is proposed.

The effect is analyzed of organizational factors on blast furnace operating indices under contemporary intense smelting conditions: current banking time, fanning time, and compliance with the discharge schedule. The quantitative effect of these factors on blast furnace performance was established more the thirty years ago and needs adjustment. It is demonstrated that production losses associated with banking depend on duration and number, and production losses associated with fanning depend on duration, amount, and degree of blast pressure reduction. Dependences (equations) are determined for production loss connected with banking and fanning. The effect of banking and fanning time on the change in equivalent coke consumption is determined. Values obtained differ from those used previously. The effect of discharge schedule on furnace performance and specific coke consumption for AO EVRAZ NTMK loses its relevance.

Continuous casting of steel with a high sulfur content is difficult due to clogging of the submerged nozzle. Physicochemical calculations and studies of a submerged nozzle inner cavity showed that clogging occurs due to formation of calcium sulfide and a low slag assimilation capacity. With serial melting of steel there is entry of slag into the tundish. Development of a slag forming mixture with whose application in the steel-pouring ladle there is formation of slag of this composition, which enters the tundish without worsening slag assimilation properties. Use of this development makes it possible to reduce submerged nozzle clogging and recycling of melts considerably due to stopping casting.

Results are provided for assimilation under casting and rolling complex conditions of pipe rolled product of the V–N microalloying system that is characterized not only by high strength (up to K60) and ductility, but also quite good cold resistance and crack resistance in a hydrogen sulfide medium.

A scheme for electron-beam melting (EBM) is selected on the basis of analyzing and systematizing accumulated data for electron-beam treatment of an ingot surface. In order to minimize experimental work and to determine the main production parameters of the EBM process for titanium alloy ingots work is conducted for mathematical modeling of thermal processes within a treated ingot, and also mass transfer processes in a molten bath at an ingot surface. Dependences are plotted for the depth of ingot melted surface layer, and also the content within it of alloying elements on process production parameters (melting rate, specific power).

The paper presents the results of studying the formation of structure and properties of metals when using additive technologies, such as arc and laser surfacing of highly alloyed nickel alloys. The main problem of nickel-chromium alloys during treatment with highly concentrated energy sources (welding, surfacing, soldering, plasma and laser treatment) consists in low strength and heat resistance after heating to high temperatures and rapid cooling, which is typical for these methods. The maximum high-temperature strength of such alloys is achieved after quenching and subsequent aging resulting in the formation of finely-dispersed γ′- phase precipitates, which inhibit plastic deformation. However, the achieved level of high-temperature strength of nickel alloys is often reduced significantly as a result of thermal effects and unfavorable structural changes during subsequent treatment (welding, surfacing). The paper presents the results of studying the structure, phase composition and properties of EP648 alloy during argon-arc surfacing. A comparison with the EP648 alloy structures obtained by laser surfacing is provided. It was established that argon-arc welding of EP648 alloy in combination with ultrasonic treatment creates an additional effect of increasing phase dispersion, which leads to an increase in hightemperature strength of the alloy.

We propose a combined technology for the modification of the surfaces of titanium implants by laser radiation followed by the plasma spraying of biocompatible coatings. We performed comprehensive investigations of the coatings with the use of SEM, optical microscopy, and other methods. The coatings obtained by using the proposed procedure are characterized by the high adhesive strength, structural uniformity, and a sufficiently high degree of hydrophily.