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The dimethylformamide3water system was studied by proton spin3spin relaxation (296 K) and refractometry (298 K), and the results in combination with published densimetric data (293 K) and data on the sound velocities (293 K) were used to simulate the associative equilibria. A consistent scheme of heteroassociative equilibria in the dimethylformamide3water system was suggested. The compositions of the heteroassociates were determined, and their stability constants (in the mole fraction scale), relaxation efficiency coefficients, limiting refractive indices, limiting sound velocities, and limiting densities were calculated.Traditional physicochemical methods often give ambiguous and contradictory data on intermolecular interactions in binary aqueous-organic systems, because the observed physicochemical property of a system is determined by a set of coexisting homo-and heteroassociates differing in the composition and stability.The viscometric data [133] and data on the sound velocity [3, 4], dielectric permittivity [5], and proton spin3lattice relaxation, obtained for the dimethylformamide (DMF)3water system, suggest the formation of stable heteroassociates DMF(H 2 O) 3 [7, 8]. This assumption is confirmed by DTA [9]. Spectroscopic studies [10, 11] suggest formation of the hydrates DMF(H 2 O) 2 in water-rich DMF3water mixtures and (DMF) 2 H 2 O in DMF-rich mixtures [6, 7]. Monte Carlo simulation [12] confirms the coexistence of the heteroassociates DMF(H 2 O) 3 , DMF(H 2 O) 2 , and DMF(H 2 O) 1 in the range of DMF mole fractions 0.0 3 0.4.It should be noted that densimetry [2, 3, 13] is less informative in this respect, because the partial and excess volumes usually show monotonic concentration dependences. However, analysis of these dependences led Scharlin et al.[13] to a conclusion that the structure of liquid water is broken owing to formation of heteroassociates, e.g., DMF(H 2 O) 2! 4 .Thus, the overwhelming majority of studies of the DMF3water system consisted in determination of the compositions of the heteroassociates and of the concentration ranges of their existence; possible schemes of heteroassociative equilibria and quantitative characteristics of such equilibria were not discussed. The only exception is the paper by Devyatov et al. [14] who examined the concentration dependence of the 1 H NMR chemical shifts in the range of DMF mole fractions 0.30 3 0.59. Based on these data, they discussed possible schemes of associative equilibria in the DMF3water system and calculated in the symmetrical mole fraction scale the stability constants of the heteroassociates DMF(H 2 O) 2 , DMF(H 2 O), and (DMF) 2 . H 2 O.In this study we examined the dimethylformamide3 water system by the methods of 1 H NMR spin3spin relaxation (296 K) and refractometry (298 K); we calculated the stability constants, relaxation efficiency coefficients, limiting refractive indices, limiting sound velocities, and limiting densities of the heteroassociates. This paper continues our studies of the structure of binary aqueous-organic systems...

Rolling is the final stage of the metallurgical cycle and has a great influence on the quantity and quality of products, as well as on various technological and economic indicators of the plant.The OJSC « BSW – Management Company of Holding «BMC» is working on the development and supply of hot-rolled round products for the automotive industry in Western Europe.The increasing requirements for the quality of the surface of hot-rolled steel are a powerful incentive to improve the technology of its production, which is impossible without the use of modern methods of control and proper identification of detected defects.The article presents the results of the study of defects of hot-rolled products of rolling mill № 1 850, having the rolling nature of formation.Metallographic study was conducted on the basis of: visual inspection of defects, in some cases with the preparation of a template for the study of macrostructure and location of defects; analysis of images of the microstructure of the cross section of the sample in the area of defects. With the help of characteristic external and microstructural features of defects, special etching in reagents, the causes of their formation were established, and recommendations for their minimization or complete elimination were proposed.

Almost all metal at OJSC «Byelorussian Steel Works» – management company of holding «Belarusian Metallurgical Company» includes today a mandatory physical-mechanical tests which allow to estimate the parameters of the raw materials, to know the reasons for loss of strength and determine operational characteristics. In the Central Factory Laboratory (CFL), laboratory of physical and mechanical tests (LPMT) for the preparation of samples of reinforcement equipment is used of knives in the cutting machine SIMA GEL-30 for cutting rebar from the mill 320 rolling shop № 1 with a diameter from 6 to 24 mm. In the drop-hummer shop annually discards off for scrap waste up to 50 knives. Hydraulic shears of drop-hummer shop used knives set of production of OJSC «Kobrin tool plant «SITOMO», made of steel grade 30ХСНВФА, according to the TU14-1-4461. The staff of the Central laboratory LFMI proposed to use waste knives drop-hummer shop for the manufacture of knives for the chopping of the machine SIMA GEL-30. On the basis of the conducted researches the technological scheme was developed for production of knives for the chopping of the machine SIMA GEL-30 cold cutting of reinforcing bar mill 320 the rolling shop № 1.