Method for Calculating the Shape of Rolls for Helical Rolling

The paper is devoted to solving the problem of determining the shape of the rolls of helical rolling mills, depending on the specified profile of the deformation zone. A universal calculation method has been proposed, thanks to which it is possible to determine the shape of the working surface of a roll for all types of helical rolling mills (with mushroom-shaped, cup-shaped, barrel-shaped and disc rolls), any relative arrangement of the rolling axis and rolls axes, and various locations of the deformation zone on the rolling axis. The proposed method is implemented as a standalone exe-application with a simple intuitive interface. The application allows you to output the calculation results into txt-files, which can then be imported into CAD systems to create 3D roll models.

DIAGNOSTICS OF ROLLING EQUIPMENT SLIDING BEARINGS

Peculiarities of rolling bearings operation are analyzed. Methods of diagnostics of general purpose sliding bearings and rolling equipment are considered. Direct control of the maximum allowable wear of plain bearings during operation is proposed. It is advisable to provide remote information and consulting services to technical services of metallurgical enterprises for maintenance, repair and operation of crankshaft bearings. Bearings of electric machines of drives of rolls of rolling mills work in extremely difficult conditions with considerable overloads in the environment of the increased vibration. This leads to premature wear of the liner and its fatigue failure. The technical condition of bearings of electric machines of drives of rolls of rolling mills for the purpose of an exception of an emergency stop of production is carried out by indirect control of temperature and vibration. However, these controls do not guarantee an avoidance of an emergency. All problems with working plain bearings can be grouped into three groups: insufficient bearing capacity of the lubricating layer, unregulated clearance between the shaft and the liner, unsatisfactory technical condition of the bearing surfaces. Insufficient bearing capacity of the lubricating layer is more often associated with loss of lubricant properties due to improper maintenance of the lubrication system. The discrepancy between the size of the gap between the shaft and the liner to the normalized value arises from design, technological and operational reasons. Key words: plain bearing; failure; rolling equipment; direct wear control; remote information and consulting services

Justification for using resourcesaving banding technology in renovative production

The article substantiates the expediency of applying the basics of resource saving in the development of innovative technologies for strengthening serial parts and restoring worn ones. At the same time, the main task is the rational use of available material resources in the conditions of a decline in production, when it becomes profitable to restore metal-intensive parts worn out to a critical level. In capital repair of machines, the main problems are associated with the energy intensity of the process and a significant number of rejected parts that cannot be restored. Currently, most of the worn-out metal-intensive cast iron and steel body parts that have exhausted the resource are subjected to energy-intensive melting. For the reuse of metal-consuming parts in operation, a technology has been proposed for multilayer banding of a worn surface, in which steel tape is used instead of traditional banding rings. Winding the tape occurs under an interference in several layers. In this case, a multilayer bandage with interturn stresses is formed, which is not inferior in strength to a whole banding ring. The use of a steel “bandage” for the “treatment” of parts reduces the metal consumption for its manufacture by 2.5 times in comparison with the well-known one-piece ring made of round steel. As an example, the article substantiates the possibility of carrying out the banding process in relation to the restoration and strengthening of the seat under the bearing of the housing part. A multilayer bandage can also be used in the recovery of metal-intensive rolling rolls written off in scrap used on broadband cold rolling mills.

Efficient 3D Model to Predict Time History of Structural Dynamics in Cold Rolling Mills

Introduced is a new physics-based 3D mathematical model capable of efficiently predicting time histories of the nonlinear structural dynamics in cold rolling mills used to manufacture metal strip and sheet. The described model allows for prediction of transient strip thickness profiles, contact force distributions, and roll-stack deformations due to dynamic disturbances. Formulation of the new 3D model is achieved through combination of the highly-efficient simplified-mixed finite element method with a Newmark-beta direct time integration approach to solve the system of differential equations that governs motion of the roll-stack. In contrast to prior approaches to predict structural dynamics in cold rolling, the presented method abandons several simplifying assumptions and restrictions, including 1D or 2D linear lumped parameter analyses, vertical symmetry, continuous and constant contact between the rolls and strip, as well as inability to model cluster-type mill configurations and accommodate typical profile/flatness control mechanisms used in industry. Following spatial and temporal convergence studies of the undamped step response, and validation of the damped step response, the new model is demonstrated for a 4-high mill equipped with both work-roll bending and work-roll crown, a 6-high mill with continuously-variable-crown (CVC) intermediate rolls, and finally a complex 20-high cluster mill. Solution times on a single computing processor for the damped 4-high and 20-high case studies are just 0.37 seconds and 3.38 seconds per time step, respectively.

Dynamic Characteristics of a Multimotor Electric Motor Multichannel Control System, Taking Into Account the Elasticities of Mechanical Transmitters

The study of the dynamic characteristics of two- and three-engine thyristor electric motors with constant current, in the case of a multi-motor control system, taking into account the elasticity of mechanical shafts are reviewed in this article. Such multimotor control systems are widely used in metallurgical production. For example, in sheet rolling mills, where in the mechanical part there are moments of significant dynamic curvature. The paper also reviews the functional and structural schemes of a cohesive multi-engine system. In the case of a multi-motor touring electric motor system, the structural scheme of a two-engine drive was studied in order to determine the correct load distribution. The study was conducted using a computer program - MATALAB using 150 kW and 300 kW engines. A Kalman filter-like observation device is used to quench the binding oscillations generated in the system. The quality indicators obtained from the transient mode studies are close to the optimal parameters, so the considered system is suitable for multi-motor rolling mills.

Advancement of Roll-Gap Control to Curb the Camber in Heavy-Plate Rolling Mills

The quality of steelwork products depends on the geometric precision of flat products. Heavy-plate rolling mills produce plates for large-diameter pipes and for use in shipbuilding, mechanical engineering, and construction. This is why the precision requirements are so stringent. Today’s Mills 5000 produce flat products of up to 5 m in width; the operation of these units shows ‘camber’ defects and axial shift of the roll at the stand exit point. This induces greater loss of metal due to edge trimming and involves a higher risk of accidents. These defects mainly occur due to the asymmetry in the roll gap, which is in turn caused by their misalignment in rolling. As a result, the feed varies in gauge, and the strip moves unevenly. The paper’s key contribution consists in theoretical and experimental substantiation and development of a set of control methods intended to address roll-gap asymmetry. The methods effectively compensate for the asymmetry resulting from the “inherited” wedge, which preexists before the strip enters the stand. They also compensate for the “ongoing” roll misalignment that is caused by the difference in force on the opposite side of the stand during rolling. This comprehensive approach to addressing camber and axial displacement of the feed has not been found in other sources. This paper presents a RAC controller connection diagram that ensures that the roll gap is even across the feed. The paper notes the shortcomings of the design configuration of the controller and shows how it could be improved. The authors have developed a predictive roll-gap asymmetry adjustment method that compensates for the deviations in gauge during the inter-passage pauses. They have also developed a method to control gap misalignment during rolling. The paper showcases the feasibility of a proportional-derivative RAC. The methods have been tested by mathematical modeling and experimentally. The paper further shows oscillograms sampled at Mill 5000 after implementing the developed solutions. Tests confirm far better precision of the screw-down mechanisms on the opposite sides of the stand. This reduces the variation in gauge across the feed and thus curbs the camber defect. As a result, the geometry of the flat improves, and less metal is lost in trimming. The paper further discusses how the RAC controller interacts with the automatic gauge control system. The conclusion is that these systems do not interfere with each other. The developed systems have proceeded to pilot testing.