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ИРКУТСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ ПУТЕЙ СООБЩЕНИЯ
3. Разработаны модельные представления кинетики деструкции нижнего слоя покрытия, на их основе даны практические и технологические рекомендации по оптимизации и активизации процесса очистки.
4. Экспериментально подтверждена целесообразность ультразвуковой активизации этапа химической обработки очищаемой поверхности, предложены конструктивные решения и наиболее оптимальные параметры работы излучателя.
5. Рассмотрены различные комбинации приемов очистки, с учетом обеспечения условия неповреждаемости поверхности обрабатываемых изделий.
БИБЛИОГРАФИЯ
1. Смирнов Н. С., Простаков М. Е., Липкин Я. М. Очистка поверхности стали. 2-е изд. перераб. и доп. М. : Металлургия, 1978. 232 с.
Introduction.
With the development and application of new hot forging dies steel with excellent performance, the 5CrMnMo steel is falling into disuse in some developed countries, but the steel has not only good toughness, tensile strength and wear resistance, but also good hardness and high temperature mechanical properties. It is used to produce kinds of suffer and minitype forging dies. And it is a kind of cheap and economical material for hot forging dies [1]. The rigidity and the wear resistance, the good toughness and anticorrosion have a direct effect on the use and life of dies. Ordinary quenching and tempering process is so limited that it can not meet the requirements of use. The failure and damage occurs mostly from on the surface or beginning from the surface, in order to improve the life, the reasonable surface strengthening technology which can improve the material potential, improve surface performance and prolong the use life of dies was used. The layer treated on QPQ had lots of advantages such as high rigidity, high wear resistance and a little distortion. The QPQ was used on treating hot forging dies, which can improve the use life. By
Штта
2. Шастин В. И., Белунник А. И., Лоцманов Г. С. Удаление лакокрасочных покрытий излучением лазера // Лазерные технологические установки и перспективы их применения на предприятиях отрасли : материалы совещ. М., 1986. 83 с.
3. А. С. 1374523 (СССР) МКИ В 08 В 7/04. Способ очистки поверхностей от труднорастворимых слоистых покрытий / авт.-изобрет. Шастин В. И. ; Иркут. филиал по заоч. обучению КИИГА ; заявл. 10.07.86 № 4088573.
4. Горюнов Ю. В., Перцов Н. В., Сумм Б. Д. Эффект Ребиндера. М. : Наука, 1966. 128 с.
5. Лихтман В.И., Щукин Е.Д., Ребиндер П.А. Физико-химическая механика металлов. М.: - АН СССР,1962. - 156с.
6. Ребиндер П.А. Физико-химическая механика. Новая область науки. - М.: Знание, 1958. 64с.
7. Попилов Л.Я. Ультразвуковая интенсификация очистки и гальванических процессов. - М.: Машиностроение, 1969. - 187с.
.1.017
increasing the depth of layer to enhance the support capacity of dies, reduce processing temperature heat treatment to reduce deformation, which ensure the accuracy of dies and application in practice.
The rare earth (RE) with the atomic structure and the activity has widely used in many fields. Since the 1960s, researchers began to use RE in the chemical heat treatment for steel. After the 1980s, the research on the RE in the chemical heat treatment appeared upsurge in our country and a lot of fruits had been applied in production [2].
In order to improve the production efficiency and the quality of the layer, the RE was used in the QPQ process, the results showed that the speed of ni-triding was highly improved and the performance of nitriding layer and the nitriding structure was improved.
1 Experiment
1.1 The experimental material and equipment
The material was 5CrMnMo steel, the chemical component is shown in table 1, the samples were incised by WEDM, the size was 7*7*30mm, the up and
Xiong Guanggyao, Zhou Zejie, He Bolin, Zhao Longzhi УДК 669
EFFECT OF RARE EARTH ON THE QPQ TREATMENT ON THE DIES STEEL
МЕХАНИКА. ТРАНСПОРТ. МАШИНОСТРОЕНИЕ. ТЕХНОЛОГИИ
The chemical components of 5CrMnMo steel
Table 1
Element C Si Mn Cr Mo S P
Content 0.54 0.37 1.38 0.72 0.25 0.014 0.025
down plane were polished, QPQ salt-bath and mix RE metal.
The experiment was done in a crucible furnace with the size was 0150*250mm, the furnace power was 3KW, and the material was graphite, the temperature was measured by WRP-120 platinum and rhodium - platinum thermocouple, and the temperature controlled by KSW-8D-16 automatic temperature control.
1.2 The experiment craft process
The content of CNO- in nitriding furnace had direct effect on the quality of the QPQ treatment, the hardness was well when the content of CNO- was 34% to 38 %. In this experiment, the content of CNO- was 36%, then four groups of RE (the content were 0 percent, 1 percent, 3 percents, 5 percents and 7 percents ) were added at 560°C, the craftwork experiment was done at 560°C for three hours. The microstructure observation and micro-hardness measurement of these samples were done finally, according to the results, the optimum amount of Rare Earth was determined. 1.3 The microstructure observation and micro-hardness measurement
The surface performance and micro-structure were observed on the JSM—6360LA SEM, the thickness of nitriding layer was measured on SMV special test software on the JSM—6360LA SEM. The sample rigidity was measured on the 401MVA Microscopic Vickers hardness tester under the test load of 100 gf and keep on for 10 second, the surface Microscopic Vickers hardness HV01 (three average value) of nitrid-ing layer was measured. The glide wear experiment was done on the M-2000 wear experiment machine and the grinding of standard samples without lubrication sliding friction, the load was 490N, the rotate speed was 200r/min, according to the samples weight loss (average of two samples) to compare their wear resistance.
2. The results and analysis
2.1 The effects of RE on nitriding layer thickness and rigidity
Table 2 shows the relative of 5CrMnMo steel which was treated in different RE contents for 3 hours at 560°C between the nitriding layer thickness and surface hardness. It was shown from the microstructure of nitriding layer that RE had obvious favor in the infiltration. With the enhancement of the RE contents, the nitriding speed improved. When the contents came to 3% to 5%, the speed was the highest. The content of RE in RE-QPQ salt-bath exist an optimum value, That is to say, when the RE is 3 to 5%, the layer thickness (28 ~ 30 ^m) was thicker than those materials without the RE (15 ~ 20 ^m). And the hardness of the surface layer has emerged in a similar trend, at 3 percent the hardness was the highest. The results indicate that the optimum value of RE in RE-QPQ salt bath was 3% to 5%, the nitriding thickness increased obviously, and the rigidity of layer surface improved, the HV01 rigidity was 1139 to 1140 which was the two time higher than the HV01 (521) of the substrate. Thereby, it was not difficult to conclude that the reason that the thickness and the rigidity of the nitriding layer increased was the the proper amount of RE had help to infiltration in the RE-QPQ. The nitriding speed had improved 30 percents, the nitriding structure was also improved, the layer became thick, consequently, the layer rigidity was improved and the distribution of the nitriding layer rigidity was also improved.
2.2 The effect of RE on nitriding layer micro-structure
Fig.1 shows the micro-structure of nitriding layer section of 5CrMnMo hot dies steel for 3 hours at 560°C without RE. Fig2 and Fig3 show the microstructure of nitriding layer section on 5CrMnMo hot dies stee with 3% and 5% of the total quality of the RE-QPQ salt bath, respectively. From Fig. 1 to Fig. 3, we can see that the salt bath without RE, some large coarse grains appear, and infiltrated along the
Tabel 2
The effects of RE chroma on nitriding layer thickness and rigidity
RE chroma 0 1 3 5 7
Layer thickness 19.2 22.9 26.6 27.1 23.7
Micro-rigidity 1032 1090 1139 1140 1067
ИРКУТСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ ПУТЕЙ СООБЩЕНИЯ
grain boundary. But nitriding layer was thick with the RE-QPQ salt bath treatment. The reason was probably the RE inproved the activity of N atom, and changed the appearance of Fe2-3N, and then the structure was refined.
Fig. 1. The SEM of rigidificate layer 600* nitring temperature : 560oC nitriding time : 3h treatment craftwork : QPQ salt bath
Fig. 2. The SEM of rigidificate layer 500* nitring temperature : 560oC nitriding time : 3h treatment craftwork : QPQ salt bath and 3%RE
Fig. 3. The SEM of rigidificate layer 500* nitring temperature : 560°C nitriding time : 3h treatment craftwork : QPQ salt bath and 5% RE
2.3 The effect of RE on nitriding layer wear resistance
The wear-resistance test of 5CrMnMo steel was done on the three samples treated for 3 and 4 hours at 560°C, some were tested in QPQ, others in the RE-QPQ. The wear-resistance results were shown in table 3. From table 3, it is obviously that the wear-resistance of the samples which were treated in RE-QPQ was two times higher than the samples in ordinary QPQ. The reason was lots of compounds of s laves structure which was high rigidity and exiguous formed on nitriding layer with RE-QPQ. Furthermore, the rare-earth playing important role in micro-alloy can improve the surface layer structure. The solid solution strengthening, and the formation of compounds, such as refined grains can improve tensile strength and wear resistance.
2.4 The mechanism of RE on nitriding layer.
The QPQ technical principle is nitrocarburizing and oxidation processes compound, the structure of the compound mostly is infiltration compounds Fe2-3N and oxide Fe3O4. The reasons why the nitriding speed is improved and the nitriding layer structure is changed in the RE-QPQ mainly is as following:
Firstly, the active RE atom increased the nitrid-ing reaction speed, more active N atom and C atom appear which improved the nitrogen potential in salt bath and increased the flux number of N and C to diffuse from the surface.
Secondly, the infiltration of the large-size rare earth atoms in the crystal RE enrichment cause huge iron atom lattice distortion, which is favor to nitrogen and carbon atoms transition and Segregate in the layer in priority, then the C and N concentration in the layer is enhancing. As the high C, N concentration gradient appears on the surface the speed infiltration and [C] and [N] atomic proliferation is promoting.
Thirdly, the permeation of the RE atom produce the vacancy in its periphery, which caused the density of the vacancy and the dislocation increase, so the
Table 3
The wear-resistance test of 5CrMnMo steel
craftwork Original mass/g Treated mass/g Wear mass/g
No treatment 10.7696 10.7647 0.0049
QPQ, 3h 10.8078 10.8066 0.0012
3%RE and QPQ, 3h 10.9980 10.9969 0.0011
5%RE and QPQ, 3h 10.6548 10.6542 0.0009
МЕХАНИКА. ТРАНСПОРТ. МАШИНОСТРОЕНИЕ. ТЕХНОЛОГИИ
multi-channel for the nitrogen atom proliferation is provided. Above three factors all can play the role in urging to infiltrate.
Finally, the rare earth permeating in the steel is favor to refine the superficial crystal grain and the micro alloy. After the infiltration the superficial crystal grain to be thin. The main reason that after permeating the steel in the substrate, the rare earth atom gathered in the crystal boundary and formed the special compound, which strengthened crystal boundary and retarded carbide to separate out from the crystal boundary, the modified carbide shape, the distribution and the crystal boundary condition make the layer structure, the performance was improving. But the permeation of the excessive rare earth atom caused the stress field made of the distortion the crystal lattice, the crystal boundary, the vacancy, the dislocation formed mutually restricts appears, which caused the proliferation atom to break through the nail difficultly, then the proliferation nitrogen atom is retarding. Therefore, the RE-QPQ salt bath only having the right amount of rare earth, can improve the properties of the infiltration layer. 3 Conclusions
(1) RE-QPQ Salt bath with the right amount rare earth (3 ~ 5% salt bath gross weight), may enhance infiltrates speed, increase the thickness of the nitriding layer, the layer microstructure performance and enhances the hardness and the wear-resistance, but the brittleness decrease.
(2) The craft of the RE-QPQ salt bath is so simply, stable that it can be applied easily in the practice, which may enhance the dies service life.
Acknowledgment
The word was Sponsored by Opening to the
Foundation Key Laboratory of Conveyance and
Equipment, Ministry of Education .
REFERENCES
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Лукьянов Д. А., Куцый Н.Н. УДК 629.3.015
ИССЛЕДОВАНИЕ, МОДЕЛИРОВАНИЕ И ОПТИМИЗАЦИЯ ДИНАМИЧЕСКИХ ХАРАКТЕРИСТИК МОТОР-ВЕНТИЛЯТОРОВ ЭЛЕКТРОВОЗОВ
Опыт эксплуатации электровозов нового поколения ЭП-1 показал, что межремонтный ресурс вспомогательных машин (мотор-вентиляторов, мотор-компрессоров) этих электровозов в 1,5 - 2 раза меньше расчетного. Например, 50% электро-
двигателей вспомогательных машин выходят из строя при пробеге 150-300 тыс. км., а еще 23% при пробеге 300 - 450 тыс.км. вместо расчетных 600 тыс.км.[1]. Проведенные исследования показали, что уровень вибрации мотор-вентиляторов элек-
