Volume 49, Nº 6 (2019)

Abstract—For the example of quenched carbon steel 45 and U8 steel, the influence of surface hardening (electromechanical treatment, surface plastic deformation, nonabrasive ultrasonic finishing, and various combinations) on the surface structure and microhardness, the cyclic durability of the hardened samples, and the mechanisms of fatigue failure is analyzed. Research by means of optical and scanning electron microscopy, microhardness measurement, and fatigue tests shows that, for the quenched carbon steels, high-speed pulsed thermal deformation in the course of electromechanical treatment increases the surface microhardness (by more than 50%) and decreases the fatigue limit (by 20–30%). That is associated with the formation of hard nonequilibrium ultradisperse phases of nonuniform chemical composition in the surface layer. The quenched structure close to the surface is tempered, with the formation of softening zones and the appearance of residual tensile stress. Accordingly, the microhardness in these zones declines and the fatigue limit falls. Such decrease in performance of the steel on surface hardening merits further study, along with potential technologies for improving its performance. Surface hardening of carbon steels by some combination of electromechanical treatment, surface plastic deformation, and nonabrasive ultrasonic finishing permits adjustment of the structure and phase composition and the stress–strain state of surface and subsurface layers of the steel by varying the temperature and deformation. By that means, balanced strength and fatigue characteristics of the samples may potentially be obtained by appropriate preliminary heat treatment. Intense surface plastic deformation and nonabrasive ultrasonic finishing after electromechanical hardening may be used to smooth the surface, mend subsurface defects, and correct the stress–strain state of the steel. That increases the microhardness in the tempering zone by 20–25% and the fatigue limit of the samples by 25–30%.

Abstract—Attention focuses on models that may be used to synthesize situational (multivariate) procedures for assessing the standard production time of steel-wire batches in a system with independently functioning subdivisions characterized by continuous, semicontinuous, and discrete industrial processes (etching, drawing, annealing, and copper plating). Those subdivisions form part of unified material fluxes. In the system, numerous pathways permit the production of a wide range of steel wire. Those pathways are characterized by different standards; grades of steel; product diameter, shape, and mass; multivariate specialization of the drawing mills; flexible relations between the subdivisions; parallel, series, and hybrid operation of the primary and auxiliary equipment; and the use of specialized transport systems (cranes, conveyers, rail cars, and electric cars). Systems analysis of the wire-production system permits determination and description of the production pathways within individual departments; assessment of their characteristics; development of graphical models of the production processes reflecting serial and parallel operations; resolution of the models into components and microcomponents for each department; identification of key factors characterizing the organization of the production processes for all the departments; and development of normative models of the operations by combining different research methods. An incremental approach is used here. Factorial models are formulated for the piecewise situational increment in the operation of a drawing mill of type s—in particular, for the subsystem consisting of the etching bath and crane, the furnace, and the copper-plating line. In addition, the concept of an equivalent piecewise operating increment is introduced, so as to permit comparison with the increment for the rough-drawing mills. To ensure that the rough-drawing department is coordinated with the other departments, the necessary quantity of etching, heating, fine-drawing, and copper-plating equipment is determined. Models of the interrelated batch-by-batch operating increments for the departments before and after the rough-drawing department are developed. The synchronization of their operation is determined by comparing the operating increments per batch for the equipment and transport systems at the input and input of each department. That entails preliminary formulation of normative models of the transport systems’ operating increments. On that basis, an algorithm may be outlined for assessing the production time of batches of steel wire. That algorithm will be presented in part 2 of this study.

Abstract—Attention focuses on how frictional forces and the shape of the contact surface affect the stress distribution over the strip thickness in hot rolling. A differential equation for the contact stress is obtained, taking account of the nonuniform deformation. This equation is solved analytically for the slip zones, using the Amontons–Coulomb law, and also for the drag zones with constant frictional forces. The error when plane cross sections are assumed in determining the rolling force is assessed.