Vol 47, No 6 (2017)

Russian pipelines employ large-diameter pipe of straight-seam, two-seam, and spiral-seam type (diameter up to 1420 mm, API strength class up to K65). The newest developments in the production of large-diameter (1020, 1220, and 1420 mm) straight-seam welded pipe (strength classes K38–K65 and X42–X80, wall thickness up to 52 mm, length up to 18 mm, and working pressure up to 22.15 MPa) is stepwise press shaping (the JCOE process), proposed by SMS Meer (Germany). The SMS Meer technology is widely used at Russian pipe plants (AO Vyksunskii Metallurgicheskii Zavod, AO Izhorskii Trubnyi Zavod, PAO Chelyabinskii Truboprokatnyi Zavod) and also plants in Russia, China, and India. However, the accident statistics for Russian pipelines show that stress corrosion of the pipe wall mainly occurs in pipelines of large diameter (700–1420 mm). More than 80% of pipeline failures associated with stress corrosion occur in pipelines of diameter 1020–1420 mm. Corrosion cracking of pipe walls may be attributed to three main factors: (1) poor steel quality and pipe defects in manufacturing (such as high residual stress, microcracks and micropeeling of the metal after shaping of the pipe blank, corrugation, scratches, scabs from the rolling process, and imperfections of the weld seams); (2) the presence of a corrosive medium and its access to the metal surface; (3) multicyclic fatigue and failure of the metal on account of pulsation of the working pressure within the pipe and hydraulic shocks. In Russian oil pipelines, failures due to production defects and assembly and installation problems are twice as frequent as in the United States and Europe. Therefore, careful study of pipeline failure due to production flaws is of great importance. In the present work, a mathematical approach is proposed to determining the critical pressure in the pipe at which elastoplastic failure of the pipe will occur at rolling scabs accompanied by a scratch on the pipe’s outer surface. The results may be used in failure diagnostics of large-and medium-diameter steel pipe for major delivery pipelines and transfer pipelines.

The deformation of fine-grain E2412 steel containing 3.63% Si, with different grain size is considered. Twinning predominates in its deformation. The samples are extended on an Instron-5565 machine at strain rates \(\dot \varepsilon \) ≈ 0.002–0.660 s^–1 at 183–393 K. Samples of two types are investigated: with around 80% of the grains in the ranges 1.5–9.0 mm and 0.025–0.225 mm. (The mean grain sizes are d_me1 = 3.55 mm and d_me2 = 0.12 mm, respectively.) The relation between the number of twins and the types of steps formed on the strain and strain-rate diagrams in loading is established for the grains with d_me1 = 3.55 mm. At small loading rates, on account of the high growth rate of the twins, step formation on the strain diagrams is accompanied by marked decrease in the load. With increase in the loading rate, the spread of the load is reduced; Δσ changes sign at a strain rate \(\dot \varepsilon \) ≈ 0.04 s^–1. In fine-grain steel (d_me2 = 0.12 mm), there are no visible jumps in the load with the appearance of twins. In the fine-grain steel, the growth time of twins in the grain is small. On account of their high rate of development, the number of twins is also small. The distribution of twinned grains is plotted as a function of the grain size, at different temperatures and loading rates. The peak in the size distribution of the twinned grains is shifted to larger grains in comparison with the overall grain-size distribution of the polycrystal. There is some optimal grain size that facilitates twinning. As a rule, it is higher than the mean grain size determined from the initial grain-size distribution. The number of twins in a particular grain depends on the test temperature and the strain rate. There is a deformation temperature at which the number of twins in the grain is constant at the strain rates employed.

Analysis of the flow of liquid metal in the mold during continuous casting is a challenging mathematical problem. Nevertheless, precise solutions have bene found for some cases. Such analytical solutions may be used to verify numerical solutions. In the present work, the melt flow in the mold is studied numerically on the basis of the finite-difference approximation of the initial system of equations. This method is relatively universal: it has been successfully used in continuum mechanics, in mathematical modeling of the stress–strain state of shells in casting, and in other industrial contexts. In the present work, it is applied to the hydrodynamic and thermal fluxes of liquid metal in steel casting in a rectangular mold in a continuous-casting machine. The three-dimensional mathematical model that is obtained describes the liquid-metal fluxes in the mold. The processes that accompany the filling of the mold with melt are simulated by means of Odissei software. The calculations are based on the fundamental hydrodynamic equations, a formula from mathematical physics (the heat-conduction equation with allowance for mass transfer), and a familiar numerical method. The resulting system of differential equations is solved numerically. The region investigated is divided into finite elements. For each element, the system of equations is written in finite-difference form. Solution yields the field of flow velocities of the metal and the temperature field within the mold. The algebraic equations obtained by this means are solved by means of numerical algorithms. On that basis, a program is written in Fortran-4. The mathematical model permits variation of the mold dimensions and the cross section of the metal outlet from the submersible nozzle. It may also assist in understanding the motion of the cast metal, which affects the heat transfer by the mold walls, and in finding the optimal parameters of the liquid metal as it leaves the submersible nozzle. As an example, steel casting in a rectangular mold (height 100 cm) is considered. In casting, the metal leaves the submersible nozzle symmetrically on both sides, in the horizontal plane. The results are graphically displayed. The motion of the metal flux is shown in different cross sections of the mold. Regions of circular flow are identified, as well as regions of vertical motion in the mold. The magnitude and intensity of these regions are determined. The temperature field indicates a local hot zone at the mold wall. That may be attributed to the direct flux of hot metal from the aperture in the submersible nozzle.

Nontraditional systems developed and introduced at PAO ArcelorMittal Krivoi Rog permit greater resource and energy conservation in the application of slag coatings to converter linings.

It is possible to produce hot-rolled I-beams characterized by high strength and excellent performance. The basic chemical composition of the steel required, the corresponding smelting conditions, and the rolling technology are presented. The results of tensile tests and the impact strength of the I-beams are considered. The welding properties of the metal are assessed: the strength and cold strength of the weld joints and the susceptibility to laminar and cold cracking. The requirements on the microstructure of the I-beams to prevent brittle failure are outlined. The I-beams produced from the new steel may be used in the construction of mass-produced buildings and also in one-off structures.

Attention focuses on how plastic deformation and asymmetric loading affect the properties of Fe‒Al and Mn–Cu damping alloys. When the vibrational amplitude is small, the damping properties of Fe‒Al alloys are highly sensitive to external static loads; the sensitivity is much less for Mn–Cu alloys. With decrease in the grain size of Fe–Al alloys, the sensitivity to external static loads is much reduced.