Improving the technology of rolling rail steels by a comprehensive optimization parameter

The authors have developed a technique for improving the rolling modes of rail steels based on a complex optimization parameter. The technology of rolling rail profiles in the roughing stands of rail-and-structural steel mills and the technology of rolling ball blanks and grinding balls from the rejection of continuously cast blanks of rail steels are selected as the methodology objects. The generalized optimization parameter is the generalized Harrington desirability function, which depends on the partial desirability indicators according to the criteria of energy efficiency, quality of rolled products, material conservation and mill productivity. The share of influence of the listed partial optimization criteria on the generalized desirability function is taken into account by using weighting coefficients. Justification of the coefficient values is based on the results of a comparative analysis of reserves for reducing costs or losses in value terms. An algorithm for applying the technique has been developed. The analysis and generalization of the available initial data and additional research were carried out as a part of the first block. These studies are aimed at obtaining justified analytical dependencies of particular optimization criteria and measured rolling parameters. The second block is justification of the specific direction of rolling modes, the choice of which is carried out on the basis of checking the compliance of boundary conditions. The third block includes development of the parameters of the new rolling mode and assessment of its applicability and effectiveness. The fourth block involves pilot testing of a new rolling mode in the conditions of an existing rolling mill and if it is necessary, adjusting the methodology for determining the forecast values of the measured indicators. With the use of the developed methodology, the modes of rolling of railway and sharp rails in the roughing stands of universal rail-and-structural steel mill of JSC “EVRAZ ZSMK” were improved, and the mode of rolling grinding balls from the rejection of rail blanks at the cross-screw rolling mill of JSC “GMZ” was changed. There is a significant improvement in the quality, technical and economic indicators, which indicates the effectiveness of the developed methodology.

IMPROVEMENT OF RESCUE OPERATION WHEN POSTING GRINDING BALLS INTO A DIGGER

A characteristic feature of modern industries is the steady growth of mechanization and automation of production processes. The economic and social significance of mechanization is manifested in a wide range of measures aimed at replacing manual labor with machines and mechanisms, the transition to higher levels of mechanization, and ultimately to the highest degree of mechanization of automation. The combined development of science and technology significantly affects both complex and partial (non-complex) mechanization of production processes, generating an increase in the number of parts. A significant place in the technology of manufacturing parts is the casting process. About half of the parts are made of molten metals and other materials. One of the common methods is die casting. Shells (molds) of metal or cast iron molds, for free (gravitational) filling with liquid metal, are used repeatedly. Detachable and non-removable (solid) molds are used. The opening surface of the detachable mold can be horizontal, vertical, or combined. The subject of the study is a mold, which consists of two half-shapes with a vertical opening surface and pins of mutual centering of the shells. A wide range of enterprises: mining and processing plants, cement plants, construction plants, energy generating companies, etc. use the products of casting in the mold grinding layers. All types and sizes of grinding layers are intended for grinding of raw materials. Due to various technical reasons, during casting, a metal film is formed near the grinding balls, which fills the entire surface of the opening of the detachable mold. The operation of removing the lattice from the grinding layers is necessary to reproduce the geometric shape, quality requirements and considerations of industrial aesthetics of the product. Performing such an additional operation requires the collective work of employees with the use of physical force and appropriate tools. Existing technology with the use of metalwork tools leads to a deterioration in the appearance of the layers, and sometimes to damage the products. The essence of improving the lattice operation is to use a specially designed device for this operation, which in turn creates the conditions for mechanization of the production of grinding balls.

Research of the Process of Production of Steel Square Continuous Billets for Rolling Balls of Large Diameter

The paper investigates the technology of production of steel billets continuously cast billets for rolling balls of large diameter. In Kazakhstan, in connection with the development of new copper deposits such as Aktogay and Bozshakol, the need for large diameter steel grinding balls for primary ore processing has increased. The main problem in the operation of large diameter grinding balls is the tendency of the grinding media to break during operation. The authors of the work investigated the process of production of steel billets continuously cast billets with a cross section of 150 × 150 mm for rolling balls of large diameter (d 125 mm) in the PB LLP "KSP Steel", which showed that the breaking of grinding balls is initiated mainly by the presence of internal discontinuities (gas axial looseness) in continuously cast billets. Studies have shown that the technological scheme for the production of grinding balls with a diameter of 125 mm from continuously cast billets with a section of 150 × 150 mm, including steel smelting in an arc furnace with steel finishing on a ladle-furnace unit, deoxidation with aluminum and degassing in a ladle vacuum apparatus, casting steel in a closed jet on a continuous casting and further production of rolled stock on a rough rolling mill ensures the absence of internal discontinuities (gas bubbles, axial looseness) in the workpieces and ensures the production of high quality balls.

DETERMINATION OF THE RELATIONSHIP BETWEEN THE WEAR RATE OF GRINDING BALLS IN THE SAG MILL MILL AND THE PARAMETERS THAT CONTROL THE PROCESS

Since the end of the 20th century and the beginning of the 21st century, as a result of the large-scale implementation of the industrialization policy in Azerbaijan, a large number of industrial enterprises with powerful potential have been created. Based on this, the volume of industrial production over the past 10-15 years has increased 2.7-3.0 times. The current state of the country's economy has created ample opportunities for the development of the non-oil sectors along with the oil sector. At the same time, attention is drawn to the variety and speed of work on the extraction of precious metals. Azerbaijan International Mining Company (AIMC) is one such company and is currently engaged in exploration, production and processing at the Gadabay deposit. The high technology used here and the associated equipment and tools emphasize the need to apply and update recovery technologies, as well as various improvements over time. One of the main directions of scientific and practical work carried out here is to increase the resistance of grinding balls to corrosion. The article is devoted to determining the relationship between the wear rate of grinding balls of a semi-autogenous grinding mill and the parameters that control the process. Keywords: industrialization, industrial production, non-oil sector, mining company, drum mill, grinding balls, wear, the relationship between process controllers.

Microstructural Characterization, Tribological and Corrosion Behaviour of Forged and Cast Grinding Balls a Comparative Study

Various facilities are used in mineral processing to prepare raw material. Practically, two types of balls are used, cast balls and forged balls. They are respectively made from high chromium cast iron and forged steel and are supplied in different sizes and chemical compositions. The cast and forged balls have different microstructures and consequently display dissimilar wear behavior. The target aimed in this work is to achieve a comparative study taking into account the type of microstructure, mechanical properties, and wear behavior of these two kinds of materials. Specimens have undergone chemical, metallographic and XRD characterizations. Subsequently, these samples were subjected to hardness measurements, abrasion and friction tests in order to evaluate their wear behaviour. Tribological tests, under unlubricated environment, are carried out on both types of grinding balls in order to study the wear system. Corrosion tests are also performed on forged steel and high chromium cast iron ball samples. The obtained results reveal a large difference in terms of chemical composition and microstructural components. Chromium cast iron balls are more resistant to friction, whereas forged balls are more resistant to abrasion. Additionally, the corrosion tests reveal a narrow discrepancy in corrosion behaviour between the studied materials.

Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill

To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.