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This article is devoted to the following issues: calculating the values of temperatures obtained by simulating welding heating and the subsequent implementation of the welding process at the given mode parameters made it possible to obtain a welded joint of the rotor with an improved initial structure and increased mechanical properties, hydrogen resistance and durability by up to 10–15%; simulating welding heating in the areas of fusion, the overheating and normalization of the HAZ and the formation of austenite grains; specified welding heating creates the conditions for the formation of new products of austenite decomposition in the form of sorbitol in the area of the incomplete recrystallization of the HAZ. In air and gaseous hydrogen, the destruction of the combined joints took place on the weld metal, as well as on the fusion areas, the overheating and the incomplete recrystallization of the HAZ of 20H3NMFA steel as the base metal. Structural materials have a relatively low strength and high fracture toughness in air. This is manifested in a significant reduction in the elongation (δ), the area (ψ) and critical stress intensity factor (K_Ic) of welded joints and the endurance limit of cylindrical smooth rotor steel specimens, which were cut from transverse templates. Welded joints in the whole range of load amplitudes are sensitive to the action of hydrogen.

The effect of the metallurgical slags composition on their physical properties was studied employing the Directed Chemical Bonds Concept (DCBC). It provides an effective concentration and convolution of the ab-initio information on the type of bonds in multicomponent systems. The predictive models for viscosity (lnη) and electrical conductivity (lnχ) of CaF₂-Al₂O₃-CaO slag system have been built. Slag is a crucial part of various metallurgical processes. The electroslag remelting (ESR) is the best example because its efficiency and resulting ingot soundness strongly depend on slag properties. For the two slags (with 1.5 and 3% SiO₂), the condition of stable homogeneous structure (activation energies ratio Eη/Eχ ≤1) has been satisfied in the widest temperature range (1513–1773 K) with a suitable viscosity (0.02–0.09 Pa∙s) and electrical conductivity (100–270 1/Ohm∙m). The DCBC makes it possible to move from the empirical selection to the target-oriented design of a proper slag with specific physical properties.

In the present study, a new electroslag cladding method by using of the advanced current supplying mold technology was used for manufacturing the high speed steel (HSS)/ductile cast iron (DCI) composite roll. The graphite morphology, matrix microstructure, elements distribution, carbides morphology, and carbides composition have been investigated by means of optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). With increasing distance from the HSS side, a transition of graphite morphology from naught to existence and from small and dispersed to large and nonuniform was obtained at the interface. It was closely related to the fact that graphite in DCI participated in the phase change and the roll core surface and its nearby positions was heated to a high temperature by the liquid slag during the whole electroslag cladding process. Due to the combined effects of melting and elements diffusion, a significant migration of the alloying elements have occurred through the line scan analysis. Based on this, different types of carbides with the morphology and composition were found at the bonding interface. In addition, no obvious slag inclusions, porosity, shrinkage and other defects at the bonding interface were found. Results of the tensile test also illustrated that the bonding interface had a good quality and it could fully meet the requirements of the roll.

The ironmaking and steelmaking industry is one of the heavy polluters responsible for nearly 7% of global carbon dioxide and greenhouse gas (GHG) emissions. Creating new technologies and equipment and renewing the assortment of metallurgy products is compulsory to achieve the goal of climate change prevention. Lightweight and advanced higher-strength steels (AHSS) to replace old mild grades and simultaneously decrease the mass of ready products is one of the efficient ways. Three generations of AHSS of different chemical compositions and properties have already been developed, including lightweight grades alloyed with a high aluminium content. A review of the Life Cycle Assessment (LCA) results proves the energy and environmental efficiency of Advanced High Strength Steels (AHSS) compared with aluminium and HSS for the same purpose structures in vehicles. Using aluminothermic ferroaluminium from secondary materials helps to reduce the cost of lightweight steels with high aluminium content due to the 2-3 times higher assimilation of aluminium by liquid steel at both deoxidation and alloying, which was experimentally proved for HSS grades. Due to less energy consumption at ferroaluminium than secondary aluminium ingots manufacturing, alloying of AHSS (10% wt of Al) by FeAl30 reduces GHG emission for more than 0.384 t CO2-eq per ton of steel.

The paper is devoted to comparison of electroslag remelting (ESR) with consumable electrode and electroslag refining with liquid metal (ESR LM) processes. The possibility of rearrangement of the heat contributions coming from the consumable electrode and current supplying mould (non-consumable electrode, CSM) makes the core of the ESR process organisation in the CSM. The usage of liquid metal instead of consumable electrodes allows to reduce liquid bath temperature and volume in order to provide low segregation ingot. The formal assessment of physico-chemical conditions and experimental measurements of desulphurisation have shown the same level of refining ability of both processes. Replacing the classic ESR by the ESR LM is a prospective way to produce high-quality ingots from sophisticated and hard-to-deform materials, whereas manufacturing of the consumable electrodes is technically problematic and costly.