“…2 What is more, 508 III steel material contains a lot of Cr, Ni, Mo, V and other high melting point elements, which is difficult to machine. 3 During the milling process, these solid solution elements will combine with C element to form compounds with high 1 melting point, high toughness and high hardness in the material, which makes 508 III steel material have the characteristics of high hardness, high strength, high plasticity and high profile shrinkage to promote the increase in cutting resistance and power, and the cutting process produces greater cutting force and cutting heat, 4,5 which make the tool more prone to be damaged. Figure 1.Nuclear island equipment water chamber head.Figure 2.Machining field of water chamber head.…”
Water chamber head is an important component of nuclear power unit, and the main material is 508 III steel of difficult-to-machine material, which has the characteristics of high hardness, high strength, high plasticity and high profile shrinkage, etc. During the milling process, the tool is subjected to the cyclic impact load, which make cutting force and cutting heat change violent and occurrence of tool damage failure accelerate. In this paper, the damage behavior of carbide tool for milling difficult-to-machine material is studied first, and then field experiment was carried out on 508 III steel material, tool failure modes were analyzed, which include impact damage and fatigue fracture, and the failure theory and the crack propagation of carbide material were investigated in the process of tool damage. Then, the impact damage model of carbide tool is established based on the classical strength theory, and the critical condition of impact damage is determined according to simulation analysis. Finally, the theoretical model of carbide tool fatigue life is established and the tool fatigue limit is analyzed. Theoretical basis and technical support are provided for the tool failure mechanisms analysis, life prediction, parameter optimization, tool design and development aspects during the study.
“…2 What is more, 508 III steel material contains a lot of Cr, Ni, Mo, V and other high melting point elements, which is difficult to machine. 3 During the milling process, these solid solution elements will combine with C element to form compounds with high 1 melting point, high toughness and high hardness in the material, which makes 508 III steel material have the characteristics of high hardness, high strength, high plasticity and high profile shrinkage to promote the increase in cutting resistance and power, and the cutting process produces greater cutting force and cutting heat, 4,5 which make the tool more prone to be damaged. Figure 1.Nuclear island equipment water chamber head.Figure 2.Machining field of water chamber head.…”
Water chamber head is an important component of nuclear power unit, and the main material is 508 III steel of difficult-to-machine material, which has the characteristics of high hardness, high strength, high plasticity and high profile shrinkage, etc. During the milling process, the tool is subjected to the cyclic impact load, which make cutting force and cutting heat change violent and occurrence of tool damage failure accelerate. In this paper, the damage behavior of carbide tool for milling difficult-to-machine material is studied first, and then field experiment was carried out on 508 III steel material, tool failure modes were analyzed, which include impact damage and fatigue fracture, and the failure theory and the crack propagation of carbide material were investigated in the process of tool damage. Then, the impact damage model of carbide tool is established based on the classical strength theory, and the critical condition of impact damage is determined according to simulation analysis. Finally, the theoretical model of carbide tool fatigue life is established and the tool fatigue limit is analyzed. Theoretical basis and technical support are provided for the tool failure mechanisms analysis, life prediction, parameter optimization, tool design and development aspects during the study.
“…However, the forging process of water-chamber heads usually leads to forging defects such as pits, cords, and wrinkles on the billet surface, which often leads to non-uniform cutting depth, large cutting force fluctuation, and high cutting temperatures (as high as 1000 °C) in successive milling processes. 2 Moreover, to improve steel hardenability, the substrate must be intensified and weld sensitivity must be reduced without affecting stability and usability; to this end, iron alloy elements with siderophile affinity such as Mn, Ni, and Mo are typically added. These alloy elements combined with non-metallic elements including B and C and formed hardening phases with high melting points, as well as intermetallic compounds with high toughness.…”
Difficult-to-machine 508III steel is widely applied in the water-chamber heads of steam generators for nuclear power stations of AP1000 nuclear islands. The dominant machining process for these components is heavy-duty cutting. Since 508III endures significant mechanical impacts and alternating thermal loads during milling, the cutting temperature is relatively high. High temperatures reduce the surface quality of the workpieces and accelerate insert wear, which shortens the insert service life and reduces cutting efficiency. In this article, the welding set and amplifying circuit of thermocouples were designed. Coated cemented carbide inserts were adopted. The wired half-artificial thermocouple method was utilized to conduct 508III steel milling temperature tests. The influence regularity of cutting parameters on the milling temperature was analyzed, and the regression model of the milling temperature was constructed, which provided boundary conditions for insert simulation analysis. Second, finite element simulations of the milling process and milling inserts were carried out to analyze the temperature variation regularity and insert temperature distribution during milling. The simulation results were compared with the experimental results for validation. Finally, the wear behavior of the 508III milling insert was characterized by analyzing the wear condition of both the rake surface and flank surface of the milling insert, as well as the wear amount of the flank surface. The interactive influence regularity between the insert wear and milling temperature was explored. The milling temperature distribution and insert wear state obtained from the simulation agreed with the experimental results. The availability and reliability of the designed milling temperature test system were validated, which provides theoretical foundations and technical support for developing inserts and improving the cutting efficiency of difficult-to-machine materials.
“…Кушнера [12], Кабалдина [13] и др. [14][15][16][17], так и зарубежных авторов: Блэка [18], а также фирмы -производителя инструмента SECO [19] и др., указывает на два важных аспекта проблемы стружкообразования. Первый аспект заключается в не-обходимости учета термомеханических условий напря-женно-деформационного состояния зоны резания.…”
Ключевые слова: токарная обработка; процесс стружкообразования; режимы резания; деформационные пара-метры процесса резания; спектральные характеристики; амплитудно-частотные характеристики вибросигналов.Аннотация: Задача выбора оптимального режима резания является одной из обязательных при создании тех-нологии механической обработки. При оптимальных режимах механической обработки должны существовать определенные физические условия (или совокупность условий) в технологической системе резания, обеспечи-вающие эту оптимальность. Под физическими условиями в данном случае понимается: деформационные процес-сы стружкообразования и их связь с физико-механическими характеристиками материалов при высокоскоростном пластическом деформировании; уровни и динамические характеристики самой технологической системы; резуль-таты вибрационного взаимодействия элементов системы с деформационными процессами.При установлении определенных соответствий между перечисленными факторами возникает возможность создания системы контроля процесса механической обработки. Определяющим фактором в разработке системы контроля являются результаты изучения процесса стружкообразования.Данная работа посвящена исследованию деформационных процессов стружкообразования для последующего создания системы автоматизированного выбора эффективных режимов резания. В данной работе изучаются мик-рофотографии шлифов корней стружек, а также шлифы самих стружек. Результаты изучения этих фотографий позволяют построить схему формирования отдельных фрагментов локальных объемов стружки. Представлена модель стружкообразования с параллельными границами. В работе также изучались фотографии стружек и их деформационные характеристики, полученные при обработке различных материалов в достаточно широком диа-пазоне режимов резания. Представлена схема к модели деформационного цикла при стружкообразовании. Уста-новлена корреляционная связь размеров пластически деформируемой зоны и времени деформационного цикла. Проведен численный эксперимент по изучению влияния скорости резания и рабочей подачи на изменение частоты стружкообразования. Данные исследования являются основой для создания системы автоматизированного опре-деления оптимальных режимов токарной обработки.
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