Chemical Stabilization Features Of Ladle Furnace Slag In Ferrous Metallurgy

Nowadays due to the application expansion of secondary steel processing methods, which provide high-degree metal desulfurization, a problem of the ladle furnace slag (or high-calcium refining slag) stabilization arose in the ferrous metallurgy. This slag cannot be stabilized because of its self-disintegrating properties. Keywords: ladle furnace slag, secondary alumina production wastes, slag stabilization, belite, mayenit

Советская металлургия глазами американских металлургов: вторая половина 1950-х гг.

The article reveals one small page in the development of metallurgical science and technology in the Soviet Union, namely, the history of establishing scientific contacts between American and Soviet metallurgical scientists in the second half of the 1950s. Unto middle of 1950s the successful recovery of the USSR economy after the war ended with a scientific and technological breakthrough in the field of atomic and space technologies. This significantly strengthened the political and humanitarian authority of the USSR in the eyes of the world community, making the country attractive for scientific and technical cooperation. The rush of the Soviet atom and rocketry would have been impossible without high achievements in the basic sectors of the economy, such as metallurgy. The United States and its Western European allies came to understand the prospects of limited scientific and technical cooperation with the USSR and the unproductiveness of the policy of its isolation. The establishment of scientific and business contacts with Soviet metallurgical enterprises, research institutes and educational institutions forced the Americans to critically rethink their own achievements in the industry. © 2022. Zaparii V.V., Zaparii Vas.V., Sheshukov O.Yu. Soviet metallurgy in the eyes of American metallurgists: the second half of the 1950s

Features of Technogenic Iron Oxide Recovery

The overview of existing models for iron oxides reducing and an analysis of their applicability to technogenic formations is presented. The thermodynamic analysis data of iron oxides reducing reactions through solid and gas phases and experiment results presenting features of technogenic iron oxide reducing under conditions of solid-phase diffusion (limited diffusion) and partially liquid-phase diffusion (easier diffusion) of iron oxide ions. It is shown that under conditions of iron oxide ions solid-phase diffusion the reduction processes rate is significantly affected by the briquetting pressure, which increases the contact area of reacting substances. The briquetting pressure does not affect the reduction processes rate under conditions of partially liquid-phase diffusion of iron oxide ions. An ion-diffusion catalytic mechanism is proposed to describe the observed effects of technogenic iron oxide reducing. © Published under licence by IOP Publishing Ltd

Unit Ladle-Furnace: Slag Forming Conditions And Stabilization

Nowadays almost all smelted steel is processed in "ladle-furnace" (LF), where the steel is processed under refining conditions and brought to the desired temperature and chemical composition. Therefore, large amounts of refining slag are formed. Only in Russia there is about 1.4 million tons of slag exported to dumps annually. This slag cannot be processed by the schemes implemented in the industry, since the slag quickly turns into the tiniest dust during solidification and cooling. Such dust is easily aerated and carried by the wind for long distances; it pollutes soils, dissolves in ground, sedimentary and sewage waters. It also pollutes slag dumps that are suitable for processing for crushed stone. Keywords: ladle furnace slag, EAF slag, chemical composition, phase composition, secondary alumina production wastes, slag stabilizatio

Безотходная переработка ковшевого и электропечного шлака

The actual problem of mineral resources depletion in ferrous metallurgy can be effectively solved by complex reuse of technogenic waste. That waste is mostly presented by EAF (electric arc furnace) slag and LF (ladle furnace) slag. These two kinds of slag have no complex full utilization. The residues of slag are going to the dump and then the slag dump locations pollute the environment. However, the residues of EAF and LF slag can be transformed into the valuable industrial product by interaction of the slag components. This work presents the research for joint wasteless processing of EAF and LF slag with production of Portland clinker and cast iron. The article describes disadvantages of known methods of each slag processing; the paper also shows the significance of LF slag utilization. Design and calculations of the research are presented as well as its experiment methodology. The final results show five chemical compositions for the mixtures, which allow the complex processing of this slag without any waste left. Such processing provides the production of cast iron and Portland clinker both meeting requirements of normative documents. The paper also describes the results of viscosity measurements of slag compositions, the obtained slag phases, and presents the final temperature conditions. The work also considers the results of industrial tests for the developed processing technology and a complete technological chain involving the use of tilt rotary furnaces. © 2021 National University of Science and Technology MISIS. All rights reserved

Hydrogen Removal in Circulating Vacuum Degasser under Conditions of PJSC "NLMK"

For high-quality steel smelting, stage-by-stage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specified hydrogen content, the metal in the steel out-of-furnace treatment at Converter Shop No. 2 (CS-2) of PJSC "Novolipetsk Metallurgical Plant" ("NLMK") is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum derassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufficiently studied. To increase efficiency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS-2 of PJSC "NLMK", both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm.). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS-2 of PJSC "NLMK" is removal of hydrogen into the bubbles of carrier gas. © 2021 National University of Science and Technology MISIS. All rights reserved

Thermodynamic modeling of zinc recovery from ferrous metallurgy sludge

Ferrous metallurgy enterprises continuously fill dumps with steelmaking and blast furnace sludge with high zinc content. Sludge occupying significant territories of enterprises is not involved in production and harms the environment. Since zinc leads to the formation of deposits in the blast furnace, manufacturers cannot involve this sludge in sinter processing. In addition, working with sludge can lead to problems such as decrease in iron content in the sinter, decrease in productivity of sintering machines, and increase in fluctuations in the sinter chemical composition. At the same time, zinc-containing sludge can become a valuable secondary product. Zinc remains a scarce metal, which encourages the development of technologies for processing zinc-containing materials. Extraction of zinc from sludge is difficult because it is not in oxide, but in sulfate or sulfide forms. In this paper, the possibilities of zinc extraction from sludge using the FactSage software package are evaluated. The authors present results of thermodynamic calculations of the possibility of zinc extraction from four types of sludge from two Russian ferrous metallurgical plants - EVRAZ NTMK and MECHEL. The data of chemical and phase analyses of this sludge are considered, as well as simulated graphs of zinc extraction dependencies from them. The graphs were built on basis of the received data from FactSage package. Addition of the reducing agent to the sludge varied, as well as temperature of the process. In addition, the possibility of abandoning carbon as a reducing agent was evaluated. To save the reducing agent, an optimal mixture of the company's sludge was selected, in which coke consumption can be minimized. © 2022 National University of Science and Technology MISIS. All rights reserved

Microstructure of Complex Silicon-containing Modifier

Various research methods show that the microstructure of the complex siliconcontaining modifier ”Insteel 7” consists of six phases: TiFeSi2, Ca1

Method of Changing the Structure of Cast Fe–Al Alloys By Inputting Titanium-containing Modifiers

Iron–aluminum alloys with a high (more than 10 wt.%) aluminum content are alloys with sufficiently high heat resistance and can be considered as an alternative to expensive superalloys containing nickel and chromium. A method is proposed for obtaining an equiaxial structure in cast alloys of Fe- (12–14 wt.%) Al. Alloys were smelted in an open mid-frequency induction furnace by introducing titanium-containing modifiers, which can act as crystallization centers during melt solidification when they are introduced into a liquid metal, helping to obtain an optimal grain structure of the solid metal. Several modifications were used: FeTi30, FeTi30 with the addition of metallic zirconium and the complex microcrystalline modifier “Insteel 7”. All modifiers contained varying amounts of titanium. They were introduced into the melt of Fe–Al alloys 5 minutes before the metal was drained. The purpose of this study was to obtain an equiaxed grain structure of the alloys in the solid state. The desired grain shapes were achieved by introducing the FeTi30 modifier when the total titanium content in the ingot was more than 1.2% by weight. Another way to obtain the optimal structure was the introduction of FeTi30 with the addition of metallic zirconium (1.83 wt.% Ti and 0.3% Zr in the ingot). The use of the Insteel 7 modifier, consisting of Ca, Ba, Fe, Ti, Ce, and La in the form of complex silicides, is impractical because its use does not allow obtaining an equiaxial or close to equiaxial granular structure of cast Fe–Al alloys. Keywords: cast Fe–Al alloys, an open mid-frequency induction furnace, FeTi30 modifier, zirconium, Insteel 7 complex modifier, grain structure, rare earth metals silicid