Modeling of Casting Technology of Large-Sized Ingots from Deformable Aluminum Alloys

Industrial technology has been developed for the semi-continuous casting of large-sized ingots from deformable aluminum alloys through the use of complex modeling, including computer modeling and physical modeling. The ProCAST and ANSYS software packages equipped with the FLUENT module were used for computer modeling. The physical modeling was carried out on a laboratory semi-continuous casting unit (SCCU), which represents a tenfold reduced physical model of an industrial casting unit for the vertical semi-continuous casting of ingots from aluminum alloys. An aluminum-magnesium alloy with the addition of 0.05% (wt.) of scandium was used as the object of modeling. The results of computer modeling were tested at the SCCU, and then computer modeling was carried out for casting a large ingot. According to the modes obtained in the simulation, an ingot with a section of 1310×560 mm was cast under industrial conditions, which had a good surface quality with the absence of casting defects. In the microstructure of an industrial ingot and an ingot cast on the SCCU, there were no primary intermetallic compounds Al3(Sc, Zr), which makes it possible to strengthen the alloy upon annealing. To check the manufacturability during rolling, billets with a size of 40×120×170 mm were cut from these ingots, which were hot-rolled to a thickness of 5 mm, and then cold rolled to a thickness of 1 mm. The rolling results revealed good workability of the alloy, which was reflected in the high quality of the surface and the absence of cracks at the edges of the rolled stock. The mechanical properties of sheets obtained from both ingots were at the same level, which proves the reliability of casting modes for ingots obtained by complex modeling and the validity of their use for industrial conditions of the semi-continuous casting of large ingots from aluminum alloys.

Development and mastering of technologies of production at PJSC MMK a new generation steel rolled stock for m a in pipelines

One of the key strategic directions of the long-term program for the development of the oil and gas industry is the development of the resource base, including through the acquisition of new licenses at auctions and tenders held by Russian government agencies. To make a prompt decision to purchase a license area, it is necessary to carry out an objective technical and economic assessment. Official resources contain a minimum of initial data for making a decision, which led to the need to create a unified information system for assessing subsoil plots, accumulating information on new unallocated plots. The article gives valuable information about the main capabilities of the unique information resource, which was developed by specialists of Tyumen Petroleum Scientific Center LLC. This information resource is intended to provide the Company's specialists with a tool for rapid assessment of subsurface areas based on complex parameters of geology, development, infrastructure and economics in order to make a decision on the feasibility of acquiring an asset.

STUDY OF THE INFLUENCE OF FRICTION CONDITIONS ON THE INDICATORS OF THE ROLLING PROCESS IN A WIRE BLOCK

Physical modeling of the laws of friction during pressure treatment is a complex problem and is solved with many restrictions and assumptions. Computational experiments open up alternative possibilities for investigating the influence of friction conditions on the rolling process. A deeper analysis of the friction mechanism in the wire block is required, since there is a significant scatter in the data on the coefficient of friction during high-speed rolling of wire rod. The aim of this work is to study the influence of friction conditions in the deformation zone of each of the stands of the wire block on the change in specific tensions, on the longitudinal stability of the rolling process, on the change in the angle of the neutral section and on the broadening of the metal. The study of the influence of these factors is based on the joint solution of the differential equilibrium equation of the elementary volume, isolated in the deformation zone, the plasticity equation. In this work, the range of variation of the coefficient of friction was chosen such as to reveal the patterns of rolling in conditions close to the limiting. The work investigated the influence of the coefficient of friction on the parameters of rolling wire rod with a diameter of 5.5 mm in a wire block. The study was carried out with a change in the coefficient of friction from 0.22 to 0.18 during the rolling of one roll. The friction conditions in the deformation zones of the wire block, affect the tension of the roll, affect both the transverse flow of the metal, and the reduction. The study of the process of rolling wire rod in a wire block showed that a toughening of the friction mode in contact between the metal and the rolls increases the longitudinal stability of the rolled wire in the deformation zone. The minimum value of the friction coefficient at which the process remains stable without loss of equilibrium is close to 0.2. With a decrease in the coefficient of friction, the tension of the metal in the inter-stand spaces sharply increases, which can lead to partial or complete slipping of the strip. The friction conditions in the contact between the rolls and the rolled stock affect the coefficient of transverse deformation and reduction of the metal in the stands of the wire block, as well as the power parameters.

Stressstrain state of metal at the initial stage of railway rails rolling

Based on the studies of stress­strain metal formation during railway rails rolling in roughing stands of a universal rail­and­beam mill, carried out using the DEFORM­3D software package, the authors have determined the features of distribution of the Cockcroft­Latham criterion over the cross­section of the rolled stock of various shapes. An extremely uneven distribution of the Cockcroft­Latham criterion over the roll section has been established. According to the data obtained, values of the specifed criterion are minimal in the axial zone, and in the near­surface layers the greatest value of the Cockcroft­Latham criterion and, accordingly, the highest probability of defects formation occur near the gauge vertical axis. In gauges of complex shape (“trapezium”, “recumbent trapezium”, rail gauges), the authors have revealed the presence of local zones with maximum Cockcroft­Latham criterion, located in the places where the foot of the rail profle is formed. And rolling in gauge of the “trapezium” type is marked by the presence of such a zone in the near­surface area near the gauge vertical axis. Within the framework of determining formation regularities of the diagram of metal stress­strain state at the initial stage of rail rolling, direct relationship was established between the uneven temperature distribution over the section of rolling and the values (maximum and average over the section) of the Cockcroft­Latham criterion. At the same time, it was shown that uneven temperature distribution over the cross­section of the roll tends to decrease with an increase in the coefcients of extracts along the passes and increase in tilting frequency, regardless of the shape of the used gauges. For gauges of complex shape, in addition to the listed parameters, an increase in similarity of shape of the roll and gauge used also has a signifcant effect on reducing temperature inhomogeneity. Based on the results of theoretical studies, a new mode of railway rails rolling has been developed. Its pilot testing in the conditions of a universal rail­and­beam mill of JSC “EVRAZ ZSMK” has shown a decrease in rail rejection by 0.78 % compared to the previously used rolling mode.

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.

Horizontal CCMs in small-capacity metallurgy

Production of light-section rolled products and wire rods of alloyed steel grades differs by small volume of yearly output and wide range of smelted grades. To organize production of light-section rolled products of alloyed steel grades in small volumes, OJSC “Spetsmash” elaborated concept of small-capacity production, which was implemented at several plants. It was shown that horizontal CCM can be effectively applied in the small-capacity production within complexes of light-section rolled stock of alloyed steels production. At the plant “Ferrotrade” (Beloretsk) when creating a complex for production wire rods of 6.5 mm diameter of austenite class steels and nickel-based alloys, a horizontal CCM was constructed. Production of 60 mm diameter billets by the machine was mastered, which enabled to apply a rolling mini-mill, characterizing by small dimensions and power. The horizontal CCM, constructed in 2016 at the steelmaking shop of CJSC “Izhevsk pilot-mechanical plant”, was equipped by electromagnetic stirrer (EMS). It was noted that EMS was applied for the first time in domestic metallurgy at the industrial CCM of horizontal type. In the process of this CCM mastering, more than 60 heats were casted into billets of 80, 200 and 120 mm diameter. EMS application resulted in improving average point on the central porosity to 1.2—1.8 depending on the stirring modes. In 2018 the OJSC “Spetsmash” for the Research Center “Thermodeform” (Magnitogorsk) constructed an experimental horizontal CCM, designed for casting of billets of 40—60 mm diameter by direct casting of melt from the crucible of 60 kg induction furnace into the metal reservoir 776 of the machine. Development of a project of horizontal CCM for PJSC “PlasmaTek” (Ukraine, Vinnitsy) finished, designed for production of billets of 50 and 60 mm diameter within a complex of equipment for manufacturing welding electrodes not only of alloyed but also of carbon steel grades. The designed productivity of the complex is 12,000 t/year. Basic technical characteristics of the CCM presented. Small-capacity production with horizontal CCMs can be organized as independent objects and within existing steel-works for expanding product range.

Study of factors contributing to decrease of carbide heterogeneity in bearing grades of steel

At present to meet requirement to the quality of bearing steels it is necessary of accomplish estimation of carbide heterogeneity by SEP 1520 and provide the level of carbide network, carbide liquation and streaking, not exceeding adjusted limits, required by customer. To estimate possibility to decrease carbide heterogeneity (segregation), factors influencing its value in the rolling production considered. Description of the process of long products of bearing steels production at the rolling mill 370/150 of the OJSC “BMZ - managing company of the holding “BMK” presented. Possibilities of the existing mill equipment considered for 804 accomplishing of technological operations aimed at decrease of carbide heterogeneity in the finished product. The factors studied, contributing to decrease of carbide heterogeneity under conditions of mill 370/150 operation. To determine the temperature modes effect on the level of carbide heterogeneity in bearing steels, in the process of three campaigns phased decrease of the temperature of end of rolling was accomplished. Results of data analysis obtained at the production of long products profiles of 34-50 diameter of bearing steel grades presented. Conclusion on rolled stock production of bearing steel grades with high requirements to carbide heterogeneity value was formed. It was shown that to obtain high-quality long products it is appropriate to accomplish the heating in the furnace before the rolling no less than 600 min at the temperature in the soaking zone 1150-1220°С followed by application of tech­nology of normalizing rolling and control of temperature of the end of rolling 750°С. For profiles with drawing less 25% it is rec­ommended to accomplish additional heat treatment of the finished profile - normalization. Long time heating of workpieces before the rolling at the temperature 1150-1220°С enables to decrease the carbide heterogeneity down to acceptable level (carbide liquation no more than 3 points and carbide streaking no more than 4 points). The value of carbide network is decreasing at decreasing of tem­perature of the end of the rolling and increasing deformation value in the last stands. A stable satisfactory result (CN no more than 5.4) was reached at the temperature of the end of rolling 750°С and drawing more than 25%. It was established that the higher the total drawing, the lower the point of carbide network and liquation in the finished profile, which is caused by crushing of nondissolved carbides to separate fragments.

Development and mastering of technologies of production at PJSC MMK a new generation steel rolled stock for m a in pipelines

In view of arising needs of Russian oil and gas sectors, elaboration and implementation into series production competi­tive pipe products became an actual task for domestic enterprises of metallurgical industry. Generalized results of elaboration of chemical compositions and automated technologies of sheet rolled stock of new generation production from low-alloyed pipe steels of various strength classes at PJSC MMK presented. It was shown that the selected chemical compositions ensure forming finedispersed ferrite-bainite structure with bainite of granular morphology in a wide range of cooling rates. The elaborated technological modes of sheet rolled stock production from pipe steels stipulate for elimination considerable growth of austenite grain at heating before the rolling, refinement of austenite grains due to recrystallization processes, forming of extensive subgrain structure of austenite at plastic deformation, forming disperse structures during phase transformation in the process of controlled accelerated cooling; forming of extensive fragmented structure in а-phase. The level of strength, tough-plastic properties and resistance against brittle destruction (based on results of tests with a falling weight with determination of tough component share in the break of full-thickness samples) of sheet rolled stock of pipe steels with various chemical composition of PJSC MMK production was demonstrated. Results of study of tests the sheet rolled stock of high-strength steels for pipes of large diameter presented. Objects of the elaborated pipe steels implementation indicated.

Numerical simulation of slab deformation process with different reduction values in vertical rolls of mill 2000 roughing stands

Perfection of rolled stock production processes at continuous wide-strip hot rolling mill (CWHRM) aimed at minimization of metal consumption, is an effective mean to decrease its cost. In the process of slabs rolling at CWHRM, the metal consumption is stipulated first of all by complicated workpiece forming in roughing stands during consecutive reduction by vertical and horizontal rolls. Results of the numerical study of slab deformation with different values of reduction in vertical rolls of roughing stands of mill 2000 are presented. The implementation of rolling process model based on application of DEFORM-3D program of finiteelement analysis described for evaluation of metal shifting from the edges of slab in the direction of the middle of the width. The convergence of the simulation results with the measurements data of workpiece forming during roughing rolling at Severstal mill 2000 was experimentally confirmed. It was found that an increase of reduction in vertical rolls has no significant effect on the metal shifting from a narrow edge to a wide one. Increase the total reduction in vertical rolls leads to an unfavorable stress-strain state of the edge region and the Cockcroft–Latham criterion rises by 20–30%. It was proposed to reduce the total reduction in the vertical rolls of the roughing stands of mill 2000 down to 40–50 mm. It was shown that increase of time of slab moving from the heating furnace to the scale breaker causes growth the Cockcroft-Latham criterion and does not affect the amount of metal shifting from a narrow face to a wide one. The proposed method of simulation the process of slab deformation in the roughing group of the mill 2000 proved by results of industrial rolling can to be used for further study of the effect of rolls profiling and forming of surface defects with the provision of minimal metal shifting onto a wide face.

QUANTITATIVE ASSESSMENT OF THE YIELD STRESS OF FERRITE-PEARLITIC STEELS BY STRUCTURE PARAMETERS

In various sectors of the economy, requirements are imposed on the quality of metallurgical products. The event that improves the quality of metallurgical products - thermomechanical treatment (TMT). TMT allows reducing the specific consumption of steel, increasing the service life, reliability and durability of products, which is tantamount to an increase in the volume of finished metal products. The problem of applied materials science is the establishment of a quantitative relationship between the structure and properties of steels and alloys, it underlies the development and creation of new effective ways to improve the operational characteristics of metal products. In the production of long products, (TMT) is increasingly used, which is a combination of two methods of strengthening steels: deformational by plastic deformation and thermal by phase transformations. Revealing the features of the properties of heat-treated steels makes it possible to approach the solution of this problem. The main mechanisms of hardening are solid solution hardening by alloying with relatively cheap alloying elements (Mn, Si) and dislocation and precipitation hardening using hardening heat treatment and microalloying of steel with carbide and nitride-forming elements V (C, N). The article quantifies the approximate contribution of various strengthening mechanisms to the yield stress of carbon and low-alloy steels. For St5ps steel (hot-rolled state), the yield stress is given by solid-solution and grain-boundary hardening (37.4.0% and 28.6%), in low-alloy steel 16G2AF (36.7% and 27.1%), the role of dispersion hardening (28.0%).Thermomechanical treatment of steel grade St.5ps leads to an increase in the value of dislocation hardening up to 27.6% due to an increase in the density of dislocations and the retention of most of the dislocations in the rolled stock during accelerated cooling of hot-deformed austenite.