Faculty phisics-metallurgical (FMF)
Faculty phisics-metallurgical (FMF) |
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Nechepurenko ZoyaSpeciality: Applied material sains sience e-mail: zoya72008@rambler.ru Theme of master's work: "Research of structural changes during plastic deformation of brass for development of the optimum mode of deformation» Leader of work: accoiate Professor Pashunsky Vladimir Victorovich |
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ESTIMATION OF RESISTANCE OF DEFORMATION OF BRASS WITH HIGH MAINTENANCE OF LEAD
The purpose of this work is development of method and obtaining of dependences of deformation resistance of brass with high content of lead.
Researches were conducted on the samples of different grades of brass, melted and rolled in industrial condition on the different level of strength in accordance with GOST 2060-90 requirements. For brass, made on the European standard of EN 12449: 1999 «Copper and copper alloys», the proper state is indicated. Tensil tests was conducted on standard round tenfold samples with the initial diameter of do=10 mm and lо=100 mm. Speed of deformation was 1 мм/min. A test machine was equipped by the electronic sensors of loading and moving, discreteness of times records - 0,1 second, basic data processed with the help of programmatic-technical complex for the test of metals of «Tochpribor». On every grade no less than two samples were tested with subsequent average readings. The chosen grade of brass and mechanical properties of melting in a state of delivery are resulted in table 1. Most chosen alloys (except for L63) are dual phase α+β brass, lead practically does not dissolve in a copper and zinc, and forms an independent phase.
The value of shif tdeformation Λ and deformation resistance in every point of diagram of tension was calculated on formulas (1):
Strengthening curve was obtained and shouing on a fig. 1.
Picture 1 - Strengthening curve of CuZn39Pb3 meltung 1 and LС 59-1 Apparently, brass of CuZn39Pb3, having a lower level of srength both large plasticity and brass of LС 59-1 with other level of properties, strenthening to approximately one level of σs, but the greater elongation on the whole leads to greater work-hardening of samples due to the increase of degree of deformation. It is necessary to mark that single opinion by appearance of dependence of σs(Λ) is not present. For example, in work [1] for approximation of resistance of deformation dependence is recommended (2):
where σ0 is value, proper the yreld limit; m and n – coefficients. In this equation, elastic deformation is not taken into account (for Λ→0 σs→σ0), that reduces precision of calculation of coefficients, and supposes the delete of part of points of primary curve of tension. Dependence (3) which describes the strengthening on the whole is proposed:
In dependences of type (2) and (3) it is possible to pay a regard to coefficient index of power n, which characterizes the degree of the deformation strengthening on the second stage of deformation - multiple sliding. On this index propensity of different metals or phases of alloy to strengthening is compared. In this work eguation (3) was chosen as approximating dependence of σs(Λ). The coefficients of equation were found by the program Statistica, module of User specific regression. Thus, dependencies were obtained dependences which allow to expect resistance of deformation of brass with high content of lead. Coefficients of equation, including the index of the deformation strengthening depends on the level of mechanical properties of alloy and his phase composition, from correlation α and β phases in that number, that not always is taken into account at experimental researches of deformation resistance. Comparing of the obtained equaltions to similar equations for other grades of brass showed accordance of coefficients. Literature 1. Богатов А.А., Мижирицкий О.И., Смирнов С.В. Ресурс пластичности металлов при обработке давлением. - М.: Металлургия, 1984. - 144 с. 2. Теория прокатки: Справочник/ А.И. Целиков, А.Д. Томленов и др. - М.: Металлургия, 1982. - 335 с. 3. Фастыковский А.Р., Перетятько В.Н. Аналитические зависимости для определения сопротивления деформации металлов и сплавов// Известия вузов. Черная металлургия, 2003, № 2, С. 68 - 69. 4. Бернштейн М.Л. Структура деформированных металлов. - М.: Металлургия, 1977. - 431 с. 5. Смирнов С.В., Пугачева Н.Б., Тропотов А.В., Солощенко А.Н. Сопротивление деформации структурных составляющих сложнолегированной латуни// Физика металлов и металловедение, 2001, Т. 91, № 2. - С. 106 - 111. |
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