DSpace Repository :: Browsing by Author "Koinov T."

Browsing by Author "Koinov T."

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Application of between-stand cooling in the production of hot-rolled strips
(2014-02-25) Muhin U.; Koinov T.; Belskij S.; Makarov E.
Medium grain size has been uneven over the length of hot-rolled strips of austenite of low-carbon steel during rolling on continuous mill. Assess the possibilities of metal microstructure of hot-rolled strip stabilization system between-stand refrigeration line. Rolling low carbon strips developed modes with increasing temperature end rolling along the length of the strips and rolling modes using between-stand cooling with variable flow cooling water. Using this technology mode allows to get an uniform cooling microstructure of metal strips and cut to length machine time rolling on 14 - 18 %. Treatment with an increased acceleration stabilizes the metal microstructure on rolling strips on top of the thread speed and reduces the machine time rolling on 3-9 %.
Cooling control flat-rolled products
(2017-01-01) Salikhov Z.; Genkin A.; Koinov T.
Results of the comparative analysis of two ways of flat rolling products cooling control are presented: water nozzle and roller contact cooling.
Development and theoretical study of new scheme of realization of combined process ``rolling - pressing`` using equal channel step matrix
(2017-01-01) Naizabekov A.; Lezhnev S.; Panin E.; Koinov T.; Mazur I.
Using a computer simulation it was conducted a study of new modification of the combined process ``rolling-pressing``, the distinctive feature of which is the use at the exit of equal-channel step matrix vertical rolls instead of horizontal rolls. It was performed the investigation on the stress-strain state, the deformation of the workpiece and the microstructure evolution. The values obtained were compared with those of the model with two pairs of horizontal rolls. As a result, it was found that the use of vertical rolls at the exit of the equal-channel step matrix has the following advantages: the treatment of the workpiece is more uniformly throughout the section; in general, by changing the direction of compression during rolling in the vertical rolls the deformation occurs at much lower values of the extrusion, which entails a slight change in the original dimensions of the workpiece; the initial grain size is reduced more intensively both on the surface and in the central zone.
Evaluation of the effectiveness of the use of horizontal and vertical rolls in the ``rolling-pressing`` process on the basis of the stress-strain state studying
(2017-03-01) Lezhnev S.; Naizabekov A.; Panin E.; Koinov T.; Mazur I.; Arbuz A.
In this work was performed a comparative analysis of the efficiency of horizontal and vertical rolls in the ``rolling-pressing`` process. The comparison was performed based on the study of stress-strain state of both variants with the aid of computer simulation in the program DEFORM-3D based on the finite element method. For analysis of the stress state was used the Lode-Nadai coefficient, allowing you to determine which type of deformation is realized at a specific point - tension, compression or shear. For analysis of the strain state was used equivalent strain, which allows to estimate the common level of accumulated strain. In the comparative analysis of parameters of SSS was revealed that the use of vertical rolls at the exit from the matrix during ``rolling-pressing`` process, allows you to achieve a more favorable distribution of deformation along the entire length of the deformable workpiece.
Improvement and theoretical study of new technology of forging of blanks such as ``shaft``
(2017-01-01) Kulzhabayeva A.; Panin E.; Koinov T.; Toleuova A.
In this work a new technology for forging and the tool for its implementation - strikers with sloping faces and circular segments, are developed. The use of this technology allows to implement in the course of intense deformation the processing of metal over the entire cross section. The distribution of the stress has shown that when the deformation of the almost all section of the billet is dominated by compressive stresses, contributed to the closure of internal defects. The study of the strain state has shown that the development of the strain is on forging cross, after contact of the side edges with circular segments the deformation zones are expanding, covering the entire cross section of the workpiece. When modeling the process of closing the internal defect it is found that the decrease in the angle of the faces leads to a decrease in shear strain during drawing, resulting in the closure of the defect occurs only in a zone located at a distance of 50% of the feed value. The optimal value of the angle of the faces of the dies is equal to 30° with the angle of the through hole in the axial portion of the workpiece is completely closed. The use of the angle of inclination more than 30° is not recommended, since in this case high-rise deformation is insufficient for complete closure of the defects.
Influence of bending efforts of working rolls on widening of the thin steel strip during hot rolling
(2018-01-01) Koinov T.; Bel’Skii S.M.; Mukhin Y.A.; Chuprov V.B.
Based on the Jourdain variation principle, a mathematical model of the process of free widening in hot rolling of thin sheet metal is developed. The principle applies to rigid-plastic materials and for the cinematically admissible area of speeds. As a functional of the variational equation, sum of the powers of internal resistances, frictional forces, shear forces, front and back tension was used. When solving the Jourdain variational equation for the case of rolling with tension, the Ritz method was applied. The Jourdain variational equation was transformed into a system of homogeneous equations, the left side of each represented a derivative with respect to a varying parameter. Varying parameters were the exponent of the kinematic condition, general widening in the plastic deformation zone and the widening in its neutral section. The developed model allows to study the distribution of the widening on length of the deformation zone depending on the parameters of rolling process and sheet metal. To test the adequacy of the developed free-widening model, experimental studies were carried out on a two-roll cold rolling mill. Lead samples were rolled, the measured widening values of which coincided with the theoretical calculated with an accuracy of less than 10%. Cold rolling of lead samples simulates hot rolling. Theoretical analysis of the influence of tension on the process of free widening when applying tension is consistent with the practical results presented in the literature. It is shown that the unevenness of tensile stresses in the input and output sections of the deformation zone arising from the application of tension causes the appearance of additional powers in the power balance equation, leading to a decrease in magnitude of the widening. The resulting unevenness of the tensile stresses can be used to control magnitude of the widening in thin-sheet rolling. In turn, unevenness of the tensile stresses along the width of rolled strip can be increased or decreased by means of the bending forces of work rolls of the rolling stand. The article presents a scheme for controlling the value of the rolling band widening during hot rolling with the help of bending forces of work rolls.
Influence of bending efforts of working rolls on widening of the thin steel strip during hot rolling
(2018-01-01) Koinov T.; Bel’Skii S.M.; Mukhin Y.A.; Chuprov V.B.
Based on the Jourdain variation principle, a mathematical model of the process of free widening in hot rolling of thin sheet metal is developed. The principle applies to rigid-plastic materials and for the cinematically admissible area of speeds. As a functional of the variational equation, sum of the powers of internal resistances, frictional forces, shear forces, front and back tension was used. When solving the Jourdain variational equation for the case of rolling with tension, the Ritz method was applied. The Jourdain variational equation was transformed into a system of homogeneous equations, the left side of each represented a derivative with respect to a varying parameter. Varying parameters were the exponent of the kinematic condition, general widening in the plastic deformation zone and the widening in its neutral section. The developed model allows to study the distribution of the widening on length of the deformation zone depending on the parameters of rolling process and sheet metal. To test the adequacy of the developed free-widening model, experimental studies were carried out on a two-roll cold rolling mill. Lead samples were rolled, the measured widening values of which coincided with the theoretical calculated with an accuracy of less than 10%. Cold rolling of lead samples simulates hot rolling. Theoretical analysis of the influence of tension on the process of free widening when applying tension is consistent with the practical results presented in the literature. It is shown that the unevenness of tensile stresses in the input and output sections of the deformation zone arising from the application of tension causes the appearance of additional powers in the power balance equation, leading to a decrease in magnitude of the widening. The resulting unevenness of the tensile stresses can be used to control magnitude of the widening in thin-sheet rolling. In turn, unevenness of the tensile stresses along the width of rolled strip can be increased or decreased by means of the bending forces of work rolls of the rolling stand. The article presents a scheme for controlling the value of the rolling band widening during hot rolling with the help of bending forces of work rolls.
PROCESS OPTIMIZATION FOR HOT STRIP MILL.
(1986-01-01) Koinov T.; Kihara J.
The authors propose an economic-mathematical model in which production cost is a function of technological parameters such as threading speed, thickness of transfer bar and extraction temperature from a reheating furnace. The optimization of these parameters is performed for a hot strip mill in Bulgaria and Japan. With use of the code, a new rolling schedule in which the transfer bar thickness decreased with length of strip reduced production cost and improved gage accuracy.
Quality control system for a hot-rolled metal surface
(2016-06-01) Mazur I.; Koinov T.
The modern ideas about of quality of products are based on the principle of the absolute satisfaction of requirements of recommendations of the buyer. A presence of surface defects of steel-smelting and rolling origin is peculiar to the production of hot-rolling mill. The automatic surface inspection system (ASIS) includes two digital line video cameras for the filming of the upper and lower surfaces of the flat bar, block of illumination of the upper and lower surfaces of the flat bar, computer equipment. A system that secures 100 % control of the surface of rolled metal (of the upper and lower side) detects automatically and classifies the sheet defects in the real time mode was mounted in the domestic practice in the first time in 2003 on hot rolling mill 2000 JSC «Novolipetsk Iron & Steel Corporation» (NISC). The whole assortment of the mill 2000 was divided for the five groups by the outward appearance of the surface. The works on the identification of defects of hot-rolled metal and widening of data base of knowledge of ASIS were continued after the carrying out of guarantee tests. More than 10 thousand images of defects were added to the data base during the year.
Quality control system for a hot-rolled metal surface
(2014-02-25) Mazur I.; Koinov T.
The modern ideas for the quality of products are based on the principle of the absolute satisfaction of buyer,s requirements and recommendations. A presence of surface defects of steel-smelting and rolling origin is peculiar to the production of hot-rolling mill. The automatic surface inspection system (ASIS) includes two digital line video cameras for the filming of the upper and lower surfaces of the flat bar, block of illumination of the upper and lower surfaces of the flat bar, computer equipment. A system that secures 100 % control of the surface of rolled metal (of the upper and lower side) detects automatically and classifies the sheet defects in the real time mode was mounted in the domestic practice in the first time in 2003 on hot rolling mill 2000 JSC «Novolipetsk Iron & Steel Corporation» (NISC). The whole assortment of the mill 2000 was divided for the five groups by the outward appearance of the surface. The works on the identification of defects of hot-rolled metal and widening of data base of knowledge of ASIS were continued after the carrying out of guarantee tests. More than 10 thousand images of defects were added to the data base during the year.
Research and development of technology for rolling of high-quality plates of non-ferrous metals and alloys in relief rolls
(2016-01-01) Naizabekov A.; Lezhnev S.; Koinov T.; Mazur I.; Panin E.
Studies on deformation of a plate workpiece in rolls with a surface relief in the form of annular grooves forming a trapezoidal ledges and cavities alternating each other along the entire length of the barrel (the first pair with unequal ratio of the ledge to the cavity and the second pair with equal ratio of the ledge to the cavity) have been carried out. Computer simulation of the rolling process in the rolls with unequal and equal treatment of the ledge to the depression showed the advantage of the first scheme, because in this case is implemented pure shear without compression, which is beneficial to the uniformity of distribution of accumulated plastic deformation, which, in turn, affects the forming of the workpiece. Laboratory studies have confirmed the simulation results. The analysis of the intensity of shear strain proved the superiority of the first scheme and the analysis of rolling load showed the advantage of using the relief rolls instead of smooth.
Research of flatness defects forming at 20-hi steel strips rolling mill
(2017-01-01) Shatalov R.; Maksimov E.; Koinov T.; Babkin A.
Results of researches of strips flatness from corrosion steels on the 20-hi rolling mill 1700 are presented for central and edges wavinesses type ``fur-tree``. The mathematical model for defects of a strip - ``fur-tree`` is developed. Recommendations for prevention of local defects on the strip, type ``fur-tree`` by the 20-rolling mill 1700 are created for integrated iron-and-steel works.
Research of influence equal channel angular pressing on the microstructure of copper
(2014-01-01) Lezhnev S.; Volokitina I.; Koinov T.
The effect of equal-channel angular pressing (ECAP) in step die on the microstructure and properties of preheated copper is studied. It is found that the grain size after ECAP depends slightly on the preliminary thermal treatment, but the quenching applied decreases copper hardness values by 15 %, which in turn provides to decrease the pressing force during the first pass from 620 kN to 510 kN. The minimum average grain diameter reached in case of quenching alloy M1 at 700° C, ECAP in step die at room temperature and 6 cycles of deformation is 0.6 microns.
Simulation of accelerated strip cooling on the hot rolling mill run-out roller table
(2014-02-25) Muhin U.; Koinov T.; Belskij S.; Makarov E.
A mathematical model of the thermal state of the metal in the run-out roller table continuous wide hot strip mill. The mathematical model takes into account heat generation due to the polymorphic γ → α transformation of supercooled austenite phase state and the influence of the chemical composition of the steel on the physical properties of the metal. The model allows calculation of modes of accelerated cooling strips on run-out roller table continuous wide hot strip mill. Winding temperature calculation error does not exceed 20°C for 98.5 % of strips of low-carbon and low-alloy steels.
Simulation of radial-shear rolling of austenitic stainless steel AISI-321
(2019-01-01) Naizabekov A.; Lezhnev S.; Arbuz A.; Panin E.; Koinov T.
This paper presents the results of modelling of a radial-shear rolling process of austenitic stainless steel AISI- 321. The simulation is performed by Simufact Forming Program Complex. The conditions of simulation refer to those of 14-40 radial-shear mill of Rudny Industrial Institute. The various parameters of the stress-strain state (the effective plastic strain, the effective stress, the mean normal stress and the Lode-Nadai coefficient) as well as the microstructure evolution with the rolling force are considered. It is revealed that the radial-shear rolling is an effective process for obtaining high quality round billets from stainless steels of the austenitic class.
Study of axial forces with the purpose to realize a combined process «helical rolling-pressing»
(2015-01-01) Naizabekov A.; Talmazan V.; Arbuz A.; Koinov T.; Lezhnev S.
The key factor for practical realization of the combined process «helical rolling-pressing» is the axial force of the helical rolling, which should provide a continuous pressing in the matrix after the rolls. For the measurement of the maximum axial rolling force, which is actually the reserve of friction forces, a special strain gauge has been made. The work was carried out at a three-roll helical rolling mill ``10-30`` for the case of hot rolling of steel bars with diameters of 16-25 mm at a reduction of 6 % of diameter and a temperature of 1000°C. The results shown are of 24 tests.
Study of broadening in a combined process ``rolling-pressing`` using an equal-channel step die
(2015-01-01) Naizabekov A.; Lezhnev S.; Panin E.; Koinov T.
This article is devoted to studying of broadening in a combined process ``rolling - pressing``, using an equal-channel step die. In laboratory conditions an experiment for implementation of this process, using smooth rolls and three dies with different values of angle of the channels junction was done. A formula, which allows finding the value of broadening in the combined process ``rolling-pressing``, using an equal-channel step die was obtained. This formula is applicable for any value of the angle of the channel's junction.
Study on the influence of the anti bending force of working rolls on the widening in hot rolling of thin sheet
(2014-02-25) Muhin U.; Belskij S.; Koinov T.
Based on the variation principle of Jourdan a mathematical model of the process of widening freely in hot rolling of thin sheet metal is developed The principle applies to rigid-plastic materials and for the cinematically admissible area of speeds. The developed model allows to study the distribution of the widening on the length of the deformation zone depending on the parameters of the rolling process and sheet metal. Results are obtained, characterizing the size of the widening and effectiveness of the process control on tension at the entrance and exit from the stand. The widening is dependent on the strength of anti bending.
The effect of preliminary and final heat treatment in course of the combined ``rolling-pressing`` process realization on microstructure evolution of copper
(2016-01-01) Lezhnev S.; Naizabekov A.; Panin E.; Volokitina I.; Koinov T.
A number of new methods of pressure processing of metals aimed at obtaining sub-ultrafine-grained structure have been recently developed. Their basic principle refers to realization of a simple shear scheme deformation. One of the approaches is to press blanks in matrices of different designs, in equal-channel step die in particular. However, this method has a significant disadvantage - it cannot be used to deform lengthy billets. Furthermore, this method does not provide the continuity of the pressing process. To remove these shortcomings a combined ``rolling-pressing`` process using an equal channel step matrix with calibrated and smooth rolls is developed at the Department of ``Metal Forming`` at the Karaganda State Industrial University. This work investigates the impact of the process advanced. It focuses on the preliminary and final heat treatment during its implementation on the microstructure evolution and the mechanical properties of the copper alloy produced. The results indicate that the technology proposed can be recommended for implementation in production of blanks of ferrous and non-ferrous metals and alloys with ultrafine-grained structure and good mechanical properties.
Theoretical grounds of the combined ``rolling - equal - channel step pressing`` process
(2016-01-01) Panin E.; Lezhnev S.; Naizabekov A.; Koinov T.
The present paper describes the common theoretical grounds referring to the realization of the combined ``rolling - equal-channel step pressing`` process. The investigation carried out lead to the formulation of empirical equations providing the calculation of the values of the forces of rolling, pressing and back pressure from the matrix as well as those of the diameters of the rolls determining the best capture angle of the work piece. The computer simulations required focused on the stress-strain state, the temperature distribution, the effect of the work piece tilting on the process parameters. A program for the estimation of the optimal value of the channels intersection angle in the matrix and hence of a quick determination of the optimal conditions for this combined process implementation was advanced. All results obtained indicate that the combined ``rolling-pressing`` process can be implemented to produce parts of a sub-ultrafine-grained structure.

Browsing by Author "Koinov T."

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