CC BY
3
Секция
«МЕТРОЛОГИЯ, СТАНДАРТИЗАЦИЯ И СЕРТИФИКАЦИЯ»
УДК 621.923
ANALYSIS OF ELECTROCHEMICAL POLISHING OF SMALL CROSS-SECTION
CHANNELS OF MACHINE PARTS
E. A. Karelina, T. A. Pchelkina Scientific supervisor-I. V. Trifanov
Reshetnev Siberian State University of Science and Technology 31, Krasnoyarskii rabochii prospekt, Krasnoyarsk, 660037, Russian Federation
E-mail: karelina-1996@bk.ru
The analysis of existing methods of polishing the internal surfaces of channels of small cross-section of machine parts is carried out. Now, there are a number of technological processes for the manufacture of small-section channels with the appropriate surface quality.
Keywords: surface roughness, polishing, metal processing.
АНАЛИЗ ЭЛЕКТРОХИМИЧЕСКОГО ПОЛИРОВАНИЯ КАНАЛОВ МАЛОГО
СЕЧЕНИЯ ДЕТАЛЕЙ МАШИН
Е.А. Карелина, Т.А. Пчелкина Научный руководитель - И.В. Трифанов
Сибирский государственный университет науки и технологий имени академика М.Ф. Решетнева
Российская Федерация, 660037, г. Красноярск, просп. им. газ. «Красноярский рабочий», 31
E-mail: karelina-1996@bk.ru
Проведен анализ существующих методов полирования внутренних поверхностей каналов малого сечения деталей машин. В настоящее время существует целый ряд технологических процессов для изготовления каналов малого сечения с соответствующим качеством поверхности.
Ключевые слова: шероховатость поверхности, полировка, обработка металлов.
Reducing the microroughness of the inner surface of channels is becoming more and more important in many industries, such as mechanical engineering, aerospace, medicine, etc. There are a wide range of requirements regarding the surfaces of metal parts between the material and the environment. Therefore, methods are needed that improve the surface quality of small-section channels made of copper, brass or 32NKD alloy.
Improvement in surface quality can be obtained through a variety of processing methods, including coating and polishing. Electrochemical polishing (ECP) is a modern method of polishing the inner surfaces of small-section channels. Unlike electro-grinding, electrochemical polishing is a new method of polishing, cleaning and deburring metal workpieces [1]. The main advantages of the electrochemical polishing process are high productivity, good adhesion of electroplated coatings to
Актуальные проблемы авиации и космонавтики - 2021. Том 2
the electropolished surface, the ability to exclude the degreasing operation required for mechanical polishing [2].
In addition to mechanical finishing methods such as plastic deformation, lapping or polishing by grinding, electrolytic finishing methods (electro-abrasive processes) have proven beneficial when it comes to objects with complex geometric shapes. In addition to electropolishing, plasma polishing is becoming more and more important. A circuit diagram of the location of electrolytic polishing methods is shown in Figure 1:
Figure 1. Circuit diagram for the electrolytic polishing method (1) constant voltage source, (2) aqueous electrolyte solution, (3) workpiece (anode), (4) active medium, (5) container (cathode)
The metal surface of the workpiece (3) which must be processed and installed in an aqueous electrolyte solution (2), which is electrically conductive due to freely moving ions. The metal part is charged to the positive (anode) and connected via a constant voltage source (1) to the chemical tank (5). The electrolyte acts as a conductor so that metal ions can be removed from the metal part. Part of the ions moves to the cathode, while the other part remains in the electrolyte. The amount of removed metal is proportional to the current intensity of the current. Depending on the chemical composition of the aqueous electrolyte, various electrochemical and physical mechanisms occur, leading to a decrease in roughness [3].
Electrolytes based on orthophosphoric acid are most widely used for ECP of copper and its alloys. When studying the influence of various factors on the copper polishing process, it was noticed that there is a certain relationship between the concentration of phosphoric acid and the current density. The higher the acid concentration in the electrolyte, the lower the value of the limiting current density on the anodic polarization curves and the lower the operating current density at which polishing occurs.
Copper and brass can be polished in an electrolyte containing, in addition to phosphoric acid, chromic anhydride. This significantly changes the course of the polishing process. If in a conventional phosphoric acid electrolyte a good polishing quality is achieved only at the limiting current mode, then in an electrolyte containing chromic anhydride polishing occurs in a wide range of current densities 5 - 70 A/dm2 and is accompanied by the evolution of oxygen. The polishing time is reduced to 2-3 minutes.
The ability to conduct the process in a wide range of current densities is of particular interest when polishing parts of a complex configuration or a large area, the processing of which in phosphate electrolyte is connected with frequent cases of rejects. So, for example, in the process of polishing with orthophosphoric acid, membranes are often formed on the polished surface, which reduce the electrical conductivity, this leads to uneven removal of microroughnesses and a decrease in the quality of the polished surface. To remove oxide membranes from the working surface, it is necessary to "connect" abrasive particles.
The ability to conduct the process in a wide range of current densities is of particular interest when polishing parts of a complex configuration or a large area, the processing of which in
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Секция «Метрология, стандартизация и сертификация»
phosphate electrolyte is connected with frequent cases of rejects. So, for example, in the process of polishing with orthophosphoric acid, membranes are often formed on the polished surface, which reduce the electrical conductivity, this leads to uneven removal of microroughnesses and a decrease in the quality of the polished surface. To remove oxide membranes from the working surface, it is necessary to "connect" abrasive particles.
References
1. Electrolytic Plasma Polishing of Pipe Inner Surfaces, Matthias Cornelsen, Carolin Deutsch, Hermann Seitz /Metals 2018, 8, 12; doi:10.3390/met8010012
2. Nestler, K.; Bottger-Hiller, F.; Adamitzki, W.; Glowa, G.; Zeidler, H.; Schubert, A. Plasma Electrolytic Polishing—An Overview of Applied Technologies and Current Challenges to Extend the Polishable Material Range. Procedia CIRP 2016, 42, 503-507.
3. Wang, J.; Suo, L.; Guan, L.; Fu, Y. Optimization of Processing Parameters for Electrolysis and Plasma Polishing. Appl. Mech. Mater. 2012, 217-219, 1368-1371.
© Карелина Е.А., Пчелкина Т. А., 2021
