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Section 6. Materials Science
Section 6. Materials Science
Bakhadirov Kudratkhon Gayratovich, Tashkent State Technical University, Senior scientific researcher, the Faculty of Mechanics and Machine building E-mail: bahadirov@gmail.com Rasulov Alisher Khakimovich, Tashkent State Technical University, Senior scientific researcher, the Faculty of Mechanics and Machine building E-mail: kudratg@mail.ru Rosulov Ro'zimurad Khasanovich, Tashkent Institute of Textile and Light Industry, Associate professor, the Faculty of Mechanics and Cotton Ginning Email: rasulov.ruzimurad@mail.ru Umarov Erkin Adilovich, Tashkent State Technical University, Associate professor,the Faculty
of Mechanics and Machine building E-mail: bahadirov@gmail.com Ziyamukhamedova Umida Alijanovna, Tashkent State Technical University,Associate professor, the Faculty
of Mechanics and Machine building E-mail: z.umida1973@yandex.ru Nazarov Javokhir Sobirjon o'g'li, Bachelor student, the Faculty of Oil and Gas E-mail: javohirbek.nazarov1994@mail.ru
Features of sheet metals' symmetric and asymmetric rolling
Abstract: In the article provided information on experimental results on the increase of the anisotropy coefficient can be achieved by means of plastic deformation, which is a result of shear forces on the sheet metal thickness. Keywords: super-hard materials, diamond, powder materials, hard alloy cutting and shaping tools.
Introduction. In industry, most of the metal is processed by different types of rolling. When sheet metal rolling main objective is to reduce the thickness of the sheet metal to the desired size, improve the mechanical and other properties.
Many large industries such as aeronautics, automotive and architecture of the aluminum parts are widely used due to some excellent properties of aluminum as a relatively low specific weight and high corrosion resistance. The high price and limited characteristics shaping by pressure treatment are considered major aluminum sheet shortcomings that limit its wider application in various industries.
Features aluminum sheet forming mostly envy of mechanical changes during plastic deformation hardening and the anisotropy coefficient, ie, ratio ofwidth and thickness reduction, when tested in tension, which depends on the crystallographic texture of the material. Greater anisotropy coefficient value means that when plastic deformation greater with small thickness variation.
Objects and methods of research. Asymmetric rolling is a new method characterized by geometric asymmetry associated with the difference in diameters between the two rollers and kinetic asymmetry associated with the difference in the linear speed of the
rollers, able to introduce shear intensive plastic deformation, in turn, formed by the strip thickness shear deformation texture.
There are several methods of asymmetric rolling, but for industrial applications in practice there are three main methods:
• Different speeds of the work rolls;
• various dimensions of the work rolls;
• one drive roller.
Until a few years ago metallurgical effect asymmetrically rolled samples received very little attention. This may be because, until now, this method is used mainly for the production of special new materials such as clad materials and composites. With the development of ultrathin grain materials using this technique, this method was developed to offer new possibilities of production of new steels with improved properties (strength, ductility, toughness and electrical resistance) by controlling the microstructure. In addition, the stimulus for the development of this technique is due to the need to adapt existing technologies for the production of materials with improved properties, extends the product range of the modified technological methods and improved rolling precision. In the asymmetric rolling process of rolling force is greatly reduced as compared with conventional rolling. Reducing rolling force has the great advantage
Features of sheet metals' symmetric and asymmetric rolling
that a very large deformation can be imparted to the material for the production of ultra-thin structure of the grain, texture modification and manufacture of high-strength materials. Asymmetric rolling results in the development of strains with strong shear components on the surface and in the center of the band [1]. One of the consequences of this shift component is to increase the surface area of the deformed grains to higher values than is possible in a pure strain simple compressive strain. In the case of austenite, this leads to a recrystallization nucleation or the phase transformation. The net result is a smaller ferrite grains compared with the case of conventional hot rolling [1; 2].
Scientific results and their analysis. Theoretical calculations and experimental results have shown that an increase in the coefficient of anisotropy can be achieved by means of plastic deformation, which is the result of shear forces on the sheet metal thickness of. In order to accomplish the plastic deformation of investing shear forces, there are different methods of severe plastic deformation (SPD) as equal channel angular pressing (ECAP), torsion deformation at high pressure (HPC), cyclic extrusion, comprehensive forging (VC), hourglass (IF), forced ribbed molding (PDP), packet hydrostatic extrusion (GHG), batch rolling (PP) [3].These methods aimed at improving/changing metal properties with SDI. For example, with the ECAP and the HPC obtained microstructure of nano-sized grains with. But these methods do not provide long-SDI processing, which limits the application in large industries.
The main purpose of this work was to study the effect of cold rolling asymmetric mechanical properties of technical pure aluminum sheet, in particular on the coefficient of anisotropy and strength of the material.
Asymmetric rolling industrial aluminum was investigated. Three different types of rolling were examined. Traditional (symmetric) rolling (CR), and asymmetric continuous rolling (ASRC) and asymmetric reverse rolling (ASRR). Influence of crystallograph-ic orientation of grains, and dislocation structure, which developed during plastic deformation, the mechanical characteristics of the material analyzed using tensile tests, X-ray diffraction and transmission electron microscopy. Viscoplastic self-consistent (VPSC) model was used to determine the effect of the crystallographic texture on the stress-strain curve (curve stress strain) obtained from tensile tests of rolled samples before and after heat treatment.
From these results the following conclusions:
1. With increase in the total thickness reduction, increasing the tensile strength (ff_max) and uniform deformation (e_u), conversely, decreases. After 6 passages (62% reduction) homogeneous plastic deformation was less than 2%. From all values studied reduction (28%, 48% and 62%), asymmetrically rolled samples showed a greater than limit value strain ff_max laminated samples traditional way.
2. Texture analysis showed that the samples are laminated asymmetrically crystals with orientation close to the ideal ingredients shift in texture. However, the intensity of these components were relatively low in both ASRC and ASRR samples.
3. The conditions during heat treatment (2800C and 1 hour) of the material not subjected to recrystallization and crystallographic texture obtained for different types of rolling are stored. After the heat treatment, the microstructure was characterized by the presence sub grain size 1-2 microns.
4. After the heat treatment, laminated specimens asymmetric magnification showed relatively normal anisotropy samples and laminated by a conventional starting material. At the ASRC samples observed reduction coefficient of planar anisotropy. These results show that the asymmetric rolling can be used to improve formation characteristics commercially pure aluminum sheets.
5. Selected rolling conditions and heat treatment resulting in a microstructure with grain refinement. This, i. e. this effect is strongly reflected in the samples by conventional rolling symmetrically.
Based on these results, it is possible to make the following suggestions for future work:
- In order to increase the amount of shear texture components via asymmetric rolling, it is necessary to study different parameters like different rolling rollers rotating rolling reduction ratio in one pass, and the other friction.
- Conduct additional microstructure analysis (which must include the study of microstructures of the plane of the sheet material thickness and determining disorientations subgrains cells), to explain the difference in yield stress obtained after different types of rolling as: CR, ASRC and ASRR.
References:
1. Salimi, M. and F. Sassani (2002). «Modified slab analysis of asymmetrical plate rolling.» International Journal ofMechanical Sciences 44 (9): 1999-2023.
2. Lopes, A. L. B. (2001). Análise microestrutural das instabilidades plásticas em materiais metálicos, Aveiro. PhD: 227.
3. Saidaxmedov R., Bakhadirov K. Mechanical properties of material after rolling and heat treatment. Journal of Technical University of Gabrovo -vol. 47, 2014. P. 17-19.
4. Salokhiddin D. Nurmurodov, Alisher K. Rasulov, Nodir D. Turahadjaev, Kudratkhon G. Bakhadirov. Procedure-Technique for New Type Plasma Chemical Reactor Thermo-physical Calculations. American Journal ofMaterials Engineering and Technology Vol. 3, No. 3, 2015, P. 58-62.
5. Salokhiddin D. Nurmurodov, Alisher K. Rasulov, Nodir D. Turahadjaev, Kudratkhon G. Bakhadirov. Development of New Structural Materials with Improved Mechanical Properties and High Quality of Structures through New Methods. Canadian Journal of Materials Science Research, Vol. 5, No. 3, 2016, P. 52 -58.
