12 research outputs found
Моделирование процесса образования недендритной морфологии при затвердевании бинарного сплава Al–Si с перемешиванием
The growth of primary crystals from a supercooled binary melt is modeled on the basis of the phase-field method with an approximate consideration for melt stirring. Changes in the concentration of the solute in the melt near the solidification region due to stirring are considered as the main reason for modifying the dendritic morphology of the crystals. The stirring effect results in a partial removal of the melt with an increased solute concentration from the region near the interface, which is called washout in the work. This effect is approximately modeled as a forced periodic replacement of the current high solute concentration in this region either at the initial concentration or at the averaged concentration in the melt. In this paper, we propose a new algorithm for choosing such a correction region, which can be used for a small intensity of stirring. A value is introduced to describe the washout intensity-the washout parameter. It is shown that when washed away dendritic morphology passes into a rosette morphology, depending on the intensity of stirring. A numerical analysis of the growth of perturbations on the surface of the initial embryo of a circular crystal is carried out. The main differences in the development of such perturbations are shown, which leads to a non-dendritic morphology of the crystal. The growth of additional branches is demonstrated due to a decrease in the solute concentration near the center of the crystal. Calculations have been performed for the case of crystal growth with a decrease in washout intensity with growth time. For this case, the secondary arms grow on additional branches growing from the center of the crystal. It is shown that at a constant value of the washout intensity near the surface of a growing crystal, only two types of morphology are possible from a small round embryo, dendritic and rosette. At the same time, if the crystal already has a rosette morphology, it is retained and with its further growth with a decrease in the washout intensity.Рост первичных кристаллов из переохлажденного бинарного расплава моделируется на основе метода фазового поля с приближенным учетом перемешивания расплава. Изменения концентрации второго компонента (примеси) в расплаве вблизи области затвердевания за счет перемешивания рассматриваются как главная причина модификации дендритной морфологии кристаллов. Эффект перемешивания приводит к частичному удалению расплава с повышенной концентрацией примеси из области вблизи границы кристаллизации, называемому в работе смывом. Данный эффект приближенно моделируется как вынужденная периодическая замена текущей высокой концентрации примеси в этой области либо на начальную концентрацию, либо на усредненную в расплаве. Предложен новый алгоритм выбора такой области коррекции, который может быть использован и для малой интенсивности перемешивания. Введен параметр для описания интенсивности смыва – параметр смыва. Показано, что при смыве дендритная морфология переходит в розеточную в зависимости от интенсивности перемешивания. Проведен численный анализ роста возмущений на поверхности исходного зародыша кристалла круглой формы. Показаны основные отличия развития таких возмущений, которые приводят к недендритной морфологии кристалла. Продемонстрирован рост дополнительных ветвей за счет понижения концентрации примеси вблизи центра кристалла. Проведены расчеты для случая роста кристалла с уменьшением интенсивности смыва со временем роста. Для данного случая отмечено явление роста вторичных ветвей на дополнительных ветвях, растущих из центра кристалла. Показано, что при постоянной величине интенсивности смыва вблизи поверхности растущего кристалла при росте из малого круглого зародыша возможны только два типа морфологии – дендритная и розеточная. При этом если кристалл уже имеет розеточную морфологию, она сохраняется и при дальнейшем его росте при уменьшении интенсивности смыва
Calculation of hardening of continuous cylinder casting
With the use of an approximated analytical method is researched the solidification process of cylindrical castings during continuous cast in a crystallizer made from several layers
Two-dimensional mathematical model for calculation of solidification of cylindrical continuous cast
The two-dimensional mathematical model for calculation of thermal field of the continuous cylindrical casting is formed on the basis of method of finite difference
HYDROMODELLING OF CASTING PROCESSES
The description of equipment for hydrodynamic experiments and methods of hydromodeling of foundry processes, allowing to carry out three-dimensional modeling of filling process, is given. This method can be used for identification of numerical models and development of casting technology of the new types of production
Modeling of precipitation kinetics of manganese and copper sulfides in interstitial free steels
Analysis of precipitation kinetics of manganese and copper sulfides in interstitial free steels
Model of precipitation is based on classical theory of nucleation and growth with description of numeric methods for modeling. Now authors present numerical calculations of precipitation kinetics. In the beginning they repeat basic formulas of this model
Modeling of precipitation kinetics of manganese and copper sulfides in interstitial free steels
Model of precipitation kinetics of copper and manganese sulfides in ultra low-carbon and interstitial free steels was created on the basis of classical nucleation and growth theory. The model includes homogeneous and heterogeneous schemes for independent nucleation of manganese and copper sulfides and simultaneous growth/shrinkage of inclusions
Analysis of precipitation kinetics of manganese and copper sulfides in interstitial free steels
Model of precipitation is based on classical theory of nucleation and growth with description of numeric methods for modeling. Now authors present numerical calculations of precipitation kinetics. In the beginning they repeat basic formulas of this model
Measuring of depth profile of defects of hot rolled steel sheet by imaging the grating on sheet surface
The approach to measure defect of mill products during their rolling is considered. The performance of supposed scheme is analyzed for real time conditions
CONTINUOUS HORIZONTAL CASTING OF PIPE BRONZE BILLET
An experimental and calculated thermal analysis of the continuous casting of bronze tube billets is developed. Calculated allowable thermal conditions of drawing for stable casting