The article describes the repair of mandrels used on a continuous type PQF mill by using adapters made from billets. The starting materials are the tailstocks that have been taken out of service.

The process of repairing the mandrels allows the mandrel to be used in further work until the final regrinding to the last size range of the mandrel diameter.

The technological process of repair begins with turning the surface of the mandrel to the required size, grinding the surface, the process of cutting off the rear part of the mandrel, including the threaded connection. After the tailstock part has been cut off, the tailstock section is replaced with a transition piece manufactured in‑house. The adapter is a part with a fine tapered thread on one side, which is intended for connection to the mandrel, and with an internal thread on the other side, which serves to connect the rear part of the mandrel to the tailstock.

The provided technology will reduce the cost of purchasing new replacement tools by increasing the life cycle of the mandrel, and will reduce the number of mandrels that have become unusable by restoring the tailstock part.

The crystallizer is the most critical and most important functional unit of a continuous casting machine (hereinafter referred to as CCM). It is the main technological unit of the CCM, an assembly for removing heat during the solidification of the solidifying metal and the formation of the ingot. The main requirement for the crystallizer is to provide maximum heat removal from the solidifying steel to the cooling water, and to obtain a strong ingot shell with a good surface at the outlet of the crystallizer, which would not be destroyed by the heat of the liquid phase and the ferrostatic pressure. During the reconstruction of the CCM by the contractor company, drawings of crystallizers and crystallizer sleeves with a double‑cone internal geometry for casting 200 mm continuous cast billets were developed. The 200 mm continuous cast billet is a billet for the production of hot‑rolled seamless steel pipes. During the operation of the crystallizer sleeves with a double‑cone internal geometry, an accelerated wear of the protective coating in the lower part of the sleeve was noted, as well as an increased rejection of hot‑rolled pipes due to defects on the outer surface of the pipes. In order to identify the cause of the defect formation, complex metallographic studies of the outer surface of the pipes were carried out. As a result of the metallographic study, surface defects classified as steel mill scale on the outer surface of the pipes were identified. To minimize the “steel mill scale” defect and reduce the wear of the protective coating of the crystallizer sleeves, work was carried out to select the optimal conditions for the crystallization of the continuous cast billet: the use of crystallizer sleeves with a three‑cone internal geometry compared to a double‑cone was investigated; maintaining the temperature difference of the water at the inlet and outlet of the crystallizer within specified limits (ΔT) was tested. It was found that the use of a crystallizer sleeve with a three‑cone internal geometry for casting 200 mm billets and the stable behavior of the ΔT parameter made it possible to ensure the required quality of the surface of seamless pipes, reduce the wear of the protective coating of the crystallizer sleeves and increase the productivity of the CCM.

One of the main factors determining the final properties of metal products is the quantity, morphology and distribution of non‑metallic inclusions in steel. The article deals with the issues related to the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, in order to improve the quality of the products. During the experimental work on the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, second grade calcium carbide according to GOST 1460–81 was used. To determine the contamination of steel with non‑metallic inclusions, sampling was carried out from hot‑rolled products obtained from continuously cast billets. According to the results, it was found that the improvement of melt deoxidation in melts using calcium carbide can be achieved by increasing its consumption. In turn, the use of calcium carbide for deoxidation of the melt upon its release from the electric arc furnace into the ladle, instead of secondary aluminum ingots of grade AB87 according to GOST 295–98, helps to reduce the contamination of steel with non‑metallic inclusions.

During uniform and concentrated stretching of thin‑plate pearlite steel, a comparison of the structural dependence of strength and plastic properties, indicators of hardening intensity in the form of the degree of relative strength increase and the rate of deformation hardening, was carried out. Increased structural sensitivity is characteristic of the fracture stress, uniform relative contraction, and the degree of relative strength increase. It is recommended to evaluate the contribution of the deformation hardening intensity to the formation of the ductility of pearlitic steel by the parameters of the relative strength increase.

The results of using SLA‑technology in the manufacture of molds for obtaining wax models in lost wax casting are presented. 3D printing modes of molds have been developed to ensure the required roughness of the working surfaces and durability of the resulting molds. The optimal parameters for pressing the wax composition into molds made using SLA technology have been established. It is shown that the use of SLA technology for the manufacture of molds makes it possible to obtain wax models and castings of the required quality. An experimental technology has been developed for the production of castings from bronze by casting according to smelted models.

It has been shown that the effect of structural inheritance in casting eutectic cast irons can be explained from the standpoint of nanostructured crystallization of foundry alloys. Proposed is a mechanism of structural heredity when casting eutectic cast irons. This mechanism is determined by the stability of the crystallization centers of microcrystals of austenite, graphite, cementite. This stability has been shown to depend on the concentration of adsorbed oxygen atoms. The higher this concentration, the less stable the centers of crystallization of microcrystals of austenite, graphite, cementite in melts of eutectic cast irons, and vice versa. With an increase in overheating and (or) the holding time of melts, the concentration of adsorbed oxygen atoms in them increases. As a result, structural stability during remelting of eutectic cast irons is reduced and the effect of structural heredity is disturbed.

The article gives compositions of tin alloys and tin of the highest and first quality categories. The main impurities in tin, tin babbit and tin‑lead solders are presented. The technique of removing copper from POSM 61M solder for producing POSM 61solder by filtration is described.

The article considers the strength issues of foundry cores manufactured by the Cold‑box‑amine process. It is shown that the properties of the core mix can be controlled by adjusting the formulation. Examples of the influence of binders’ consumption on the properties of the mixes are given: a decrease in resin and polyisocyanate leads to a decrease in strength and a decrease in life. In addition, the minimum consumption of binders varies from manufacturer to manufacturer. Recipes of mixes with special additives are given, which allow, by reducing the strength of the mix, to ensure the completeness of the polymerization reaction.

A nanostructural mechanism of secondary transformations in the structure of gray cast iron is proposed. First, structureforming nanocrystals of austenite, ferrite, cementite and graphite are formed from elementary nanocrystals of iron and graphite, free atoms of iron and carbon. The crystallization centers of microcrystals of phases are formed from them. From these centers, structure‑forming nanocrystals of phases, free iron and carbon atoms, microcrystals of austenite, ferrite, cementite and graphite of binary gray cast irons are formed.

The article notes the experience of Yantai Huaheng Energy Conservation Technology Co., Ltd in applying protective anti‑corrosion polymer coatings and discusses the most promising modern recovery and strengthening technologies of thermal spraying (PAPS, AS, HVAF, HVOF) and laser cladding (LASC). Examples of installations that the company has and typical restored machine parts with protective wearand corrosion‑resistant coatings and the microstructure of coatings are given. The main stages of a typical technological process for applying coatings are noted. Using the example of the company, the feasibility and effectiveness of the development of this area in China is noted.

The paper presents temperature profiles at the depth of a steel billet with a coating of an iron-based amorphous alloy under the pulsed effect of laser radiation. With the action of a constant power heat source, the heat propagation process tends towards a limiting quasi-stationary state. The choice of technological modes of laser radiation exposure with a combination of laser beam scanning speed and radiation power is determined. The depth of the molten layer of the billet material during scanning under the condition of obtaining a high-quality product has been established.

The relevance of the work is justified by the need to refine the methodology for calculating cold rolling routes, associated with the expansion of factors that need to be taken into account in conducting such calculations. The aim of the work is to develop an algorithm for optimizing the routes of cold rolling of pipes using CRP and CRPR type mills, convenient for implementation in a software product. The paper analyzes the main parameters for optimizing the routes of cold rolling of pipes, factors limiting the field of optimal values of the geometric parameters of the billet‑pipe in each pass. Among the latter, the maximum possible reduction in the cross‑sectional area, the required reduction in the cross‑sectional area in the last pass, the requirement for the nature of the distribution of the reduction value in the cross‑sectional area, in the wall thickness and in the pipe diameter from pass to pass and other parameters are highlighted. The importance of minimizing the number of passes is noted. The main dependencies included in the method for calculating the deformation parameters of the cold rolling route using CRP and CRPR mills are analyzed and highlighted. An algorithm for calculating the route of cold rolling of pipes, with several iteration operations, has been developed. The proposed algorithm allows optimizing the rolling route of pipes made of any grades of steels and alloys, and allows optimizing most parameters, including those affecting the economic parameters of production. Depending on the grade of steel or alloy, some iteration operations can be excluded. The algorithm has been tested in the practice of calculating rolling routes for pipes made of carbon and stainless steels and alloys.

Radio‑absorbing composite materials, coatings and shields based on aluminum and iron oxides have been developed for protection of microwave devices from electromagnetic radiation (EMR). The patterns of changes in the characteristics of EMR reflection and transmission of electromagnetic shields based on the said powder‑like oxides have been established. It has been shown that the use of these composite materials for EMR shields can reduce the EMR reflection coefficient by 2–10 dB in the frequency range of 0.7–17.0 GHz and in the microwave range, and improve the operational properties of existing electromagnetic shields for the protection of electronic devices used for processing of limited distribution information, as well as in architectural electromagnetic shielding systems.

Keywords. Composite materials, electromagnetic radiation, elecomagnetic radiation shields, aluminum and iron oxides.

Many industrial enterprises use electroplating processes that lead to the formation of water containing heavy metal ions such as chromium, copper, zinc, nickel, and others. Such water is a dangerous source of environmental pollution. Most heavy metal ions belong to hazard classes I–II, they have carcinogenic and mutagenic properties, and have a cumulative effect.

The literature analysis showed that there is positive experience in the use of steelmaking slags in the processes of cleaning contaminated water of various origins from heavy metals.

The study examines the effect of acid activation on the adsorption‑structural characteristics of filtering materials created based on steelmaking slag. It is shown that during the interaction of some acids with slag, new crystallographic phases are formed

on its surface, and contact with other acids leads to the leaching of ions and their transition to the aqueous phase. It has been established that during acid activation, the specific surface area increases by 57–132 times compared to the original material.

Water is mainly composed of ice nanocrystals. The peculiarities of water crystallization can be explained on the basis of its nanostructural structure and nanostructural crystallization. Atmospheric air molecules dissolve well in water and are adsorbed by its nanocrystals. It is shown that the amount of expansion of ice, when water solidifies, is proportional to the concentration of air dissolved in it. The concentration of air dissolved in water decreases significantly with an increase in its temperature. Hot water solidifies faster than cold water because there is less air concentration in hot water. Its bubbles, released on ice crystals, reduce the rate of crystallization of water. A large supercooling of water occurs as a result of the blocking action of adsorbed air, which prevents the unification of ice nanocrystals into crystallization centers. Shaking a bottle of supercooled water leads to desorption of air and accelerated crystallization of water. Air bubbles released on dendritic ice crystals reduce the degree of branching of these crystals. It has been shown that music increases the intensity of removal of gas bubbles and is able to influence the shape of dendritic ice crystals during water crystallization. It has been shown that an increase in the volume of sound and (or) a decrease in its frequency increase the intensity of removal of air bubbles from dendritic ice crystals and increase the branching of these crystals.

It is shown that during 10–¹⁰–10^–11s, only clusters consisting of 4 or 3 water molecules can statistically form in water. It is shown that Brownian motion in water occurs as a result of collision of ice nanocrystals with Brownian particles. Brownian motion is an experimental confirmation of the nanocrystalline structure of water. It is shown that water consists of 13 % molecules and 87 % ice nanocrystals. Such a two‑phase structure provides water with structural properties, high fluidity and elasticity of steam.