scholarly journals Devising manufacturing techniques to control the process of zonal segregation in large steel ingots

2021 ◽  
Vol 3 (1 (111)) ◽  
pp. 6-13
Author(s):  
Anatolij Narivskij ◽  
Abdi Nuradinov ◽  
Ibrahim Nuradinov
Keyword(s):  
Cross Section ◽  
Heat Removal ◽  
External Pressure ◽  
Melt Crystallization ◽  
Phase Zone ◽  
Two Phase ◽  
Large Steel ◽  
Zonal Segregation ◽  
Manufacturing Techniques ◽  
Steel Ingots

A method of physical modeling was applied to study the effect of external actions on the processes of crystallization and the formation of the structure of ingots. A brief review of existing hypotheses about the evolution of physical, structural, and chemical heterogeneities in large steel ingots is given. The parameters of the structure and the two-phase zone have been determined, as well as the nature of the distribution of segregated materials along the cross-section of ingots, depending on the conditions of their curing. The decisive importance of convective and capillary mass transfer in the interdendritic channels of hardening ingots on the formation of a zonal heterogeneity at their cross-section has been proven. Experimentally, when crystallizing a model environment (camphene), it has been visually confirmed that the flow of segregated materials in interdendritic channels occurs when a certain amount of impurities accumulates in them. A clear dependence of the speed of this flow on the rate of melt crystallization has been established. With an increase of the hardened part of the melt, the rate of segregated material movement (Vl) increases while the rate of crystallization (R) decreases due to worsening heat release conditions. At a certain distance from the ingot’s surface, these rates become equal, and impurities are carried to the curing border, which is the main cause of the formation of zonal segregation. The results reported here show that the evolution of zonal segregation in ingots can be controlled using various techniques involving external influence on the hardening melt. This study has demonstrated that the adjustable intensity of heat removal from an ingot, as well as the addition of external excess pressure on the hardening melt, could be used as such tools. In the study, to obtain ingots with a minimum level of chemical heterogeneity, it would suffice to provide the following conditions for the curing of the alloy: a value of the alloy crystallization speeds at the level of Rcr ≥ 9·10–2 mm/s, or external pressure on the free surface of ingots Рext. ≥ 135 kPa. The industrial implementation of the reported results could make it possible to improve the technology of obtaining large blacksmith ingots, provide savings in materials and energy resources, increase the yield of a suitable metal, and improve its quality

scholarly journals Chemical and physical heterogeneities and gases in large steel ingot

2020 ◽  
Vol 96 (4) ◽  
pp. 3-9
Author(s):  
A.V. Narivskyi ◽  
◽  
A. N. Smirnov ◽  
N. I. Tarasevich ◽  
S. Ye. Kondratyuk ◽  
...  
Keyword(s):  
Cross Section ◽  
Steel Ingot ◽  
Dendritic Structure ◽  
Gas Content ◽  
High Tech ◽  
Large Steel ◽  
Technological Waste ◽  
Zonal Segregation ◽  
Cooling Intensity ◽  
Steel Ingots

For creation of the high-tech equipment that is used in energy, heavy engineering, chemistry and transport, the unique large-sized steel products are required. In the manufacture of such products, large forging ingots in the mass to 600 tons are used. However, an increase in the mass of the ingots leads to the formation of chemical and physical heterogeneity, enlargement and unfavorable distribution of non-metallic inclusions, of the development of segregation defects in them, which reduce the strength and exploitation characteristics of the metal. In this connection, the quality forgings and finished parts are not always meet the producing demands and the loss of metal, in the form of technological waste and rejects are reaching significant values. It is known that eccentric zonal segregation, especially it’s the most dangerous variety - cords, significantly reduce the quality and properties of products from large steel ingots. In connection with the continuous expansion of the production of large ingots, the problem of creating optimal technologies for their formation, which reduce or exclude the possibility of the formation of chemical heterogeneity and cords in steel during crystallization, it is currently important and relevant. In this paper it are presented the results of studies of the structure, gas distribution, physical and chemical heterogeneities in the cross section and height of an ingot in the mass of 140 tons, which was casted in vacuum from steel 25KHN3MFA. It is shown that depending on the temperature and time conditions of ingot hardening, among which the crystallization interval (due to the chemical composition of steels), cooling intensity in different volumes in height and cross section of ingot, temperature gradient before the crystallization front, solubility of alloying elements and gas content in the melt, etc. Based on this, when developing technology for large ingots to ensure their quality, optimal structure and properties should take into account not only their dimensions, but also the combination of these thermokinetic parameters on the crystallization process, dendritic structure formation, manifestations of liquation in different ingot volumes. Keywords: ingot, segregation strip and inclusions, dendrites, structure, oxygen, oxides, sulfides.

scholarly journals INFLUENCE OF METAL OXIDATION AND FEATURES OF VACUUMING ON THE FORMATION AND LOCATION OF NONMETALLIC INCLUSIONS IN LARGE STEEL INGOTS 38ХН3MФA

2020 ◽  
pp. 70-75
Author(s):  
N. Ziuban ◽  
D. Rutskii ◽  
S. Gamaniuk ◽  
M. Kirilichev ◽  
A. Popovkina
Keyword(s):  
Cross Section ◽  
Nonmetallic Inclusions ◽  
Power Engineering ◽  
Metal Oxidation ◽  
Vacuum Casting ◽  
Large Steel ◽  
Metallic Inclusions ◽  
Steel Oxidation ◽  
Steel Ingots

The article deals with the influence of steel oxidation and features of vacuuming on the processes of formation and distribution of non-metallic inclusions in large ingots and forgings intended for power engineering. It is shown that the distribution of sulfides and oxysulfides across the ingot cross-section is inversely related to each other, due to changes in oxygen and sulfur concentrations during the crystallization of the melt. Under the influence of intensification of degassing process at vacuum casting of ingots at the expense of purging of a jet of metal argon, the formed nonmetallic inclusions had the minimum sizes, more favorable distribution that caused increase in plastic characteristics of the received forgings on the average for 15-20 %

scholarly journals Mathematical Modeling of Technological Modes of Operation of Liquid Stamping of Aluminum Alloy AK7

2021 ◽  
Vol 248 ◽  
pp. 02003
Author(s):  
Vagid Kadymov ◽  
Evgeny Sosenushkin
Keyword(s):  
Mathematical Modeling ◽  
Thermal Conductivity ◽  
External Pressure ◽  
Temperature Fields ◽  
Simultaneous Solution ◽  
Phase Zone ◽  
Two Phase ◽  
Modes Of Operation ◽  
Solidification Kinetics ◽  
Thin Walled

In this paper we examine a mathematical model of solidification of the melt in a two-phase zone during the formation of forgings through liquid stamping. From the simultaneous solution of the Fourier equations of thermal conductivity for the melt, the two-phase zone, and the solid crust, the solidification kinetics has been established and the effect of external pressure on the temperature fields and components of the solidification time of hollow thin-walled forgings has been thoroughly assessed.

THE EFFECT OF HEAT DRAINAGE INTENSITY ON THE DENDRITIC AND ZONE HETEROGENEITYOF STEEL BARS

2021 ◽  
pp. 26-37
Author(s):  
Н. С. Уздиева ◽  
С. С-С. Ахтаев ◽  
А. А. Эльмурзаев ◽  
А. С. Нурадинов
Keyword(s):  
Experimental Method ◽  
Physical Modeling ◽  
External Pressure ◽  
Crucial Importance ◽  
Phase Zone ◽  
Two Phase ◽  
Steel Bars

Исследовано влияние внешних физических воздействий на процессы затвердевания и формирования структуры слитков методом физического моделирования. Определен характер распределения ликватов по сечению затвердевших слитков, параметры их структур и двухфазных зон. Доказано решающее значение конвективного и капиллярного массопереносов в междендритных каналах затвердевающих слитков на формирование зональной неоднородности по их сечению. Наглядно подтверждена экспериментальным способом возможность перемещения в междендритном пространстве затвердевающего сплава ликвирующих примесей в результате развития конвективного и капиллярного массопереносов. Доказано, что можно влиять на развитие зональной неоднородности в слитках при затвердевании сплавов путем изменения соотношения скоростей кристаллизации и движения ликватов (R/W), а также приложением внешнего давления на расплав. The effect of external physical influences on the processes of hardening and formation of bullion structure by physical modeling has been investigated. The nature of the distribution of the faces by the section of hardened bullion and the parameters of the structure of the two-phase zone have been determined. The crucial importance of convective and capillary massoperenos in the interdendriit channels of hardening bars has been proved to form zonal heterogeneity on their section. It is clearly confirmed by an experimental method in the crystallization of the transparent organic environment (kamfen) the possibility of moving in the interdendrite space of the solidifying alloy of exquoting impurities as a result of the development of convective and capillary mass-perdenos. It has been proven that it is possible to influence the development of zonal heterogeneity in bullion when alloys harden by changing the ratio of crystallization and movement of liquats (R/W), as well as whenputting external pressure on the melt.

Gas-Water Flow Behaviour During Mutual Displacement in Porous Media

2017 ◽  
Vol 10 (1) ◽  
pp. 13-22
Author(s):  
Renyi Cao ◽  
Junjie Xu ◽  
Xiaoping Yang ◽  
Renkai Jiang ◽  
Changchao Chen
Keyword(s):  
Porous Media ◽  
Relative Permeability ◽  
Gas Storage ◽  
Fluid Distribution ◽  
Water Displacement ◽  
Phase Zone ◽  
Two Phase ◽  
Flow Process ◽  
Single Well ◽  
Mutual Displacement

During oilfield development, there exist multi-cycle gas–water mutual displacement processes. This means that a cycling process such as water driving gas–gas driving water–water driving gas is used for the operation of injection and production in a single well (such as foam huff and puff in single well or water-bearing gas storage). In this paper, by using core- and micro-pore scales model, we study the distribution of gas and water and the flow process of gas-water mutual displacement. We find that gas and water are easier to disperse in the porous media and do not flow in continuous gas and water phases. The Jamin effect of the gas or bubble becomes more severe and makes the flow mechanism of multi-cycle gas–water displacement different from the conventional water driving gas or gas driving water processes. Based on experiments of gas–water mutual displacement, the changing mechanism of gas–water displacement is determined. The results indicate that (1) after gas–water mutual displacement, the residual gas saturation of a gas–water coexistence zone becomes larger and the two-phase zone becomes narrower, (2) increasing the number of injection and production cycles causes the relative permeability of gas to increase and relative permeability for water to decrease, (3) it becomes easier for gas to intrude and the invaded water becomes more difficult to drive out and (4) the microcosmic fluid distribution of each stage have a great difference, which caused the two-phase region becomes narrower and effective volume of gas storage becomes narrower.

Heat Transfer in Porous Media Heated From Above With Evaporation, Condensation, and Capillary Effects

1983 ◽  
Vol 105 (3) ◽  
pp. 485-492 ◽  
Author(s):  
K. S. Udell
Keyword(s):  
Stable State ◽  
Superheated Liquid ◽  
Phase Zone ◽  
Two Phase ◽  
Water Steam ◽  
Zone Length ◽  
Compressed Liquid ◽  
Pressure Lowering ◽  
Darcy’S Equations ◽  
Convection Dominated

Heat and mass transfer characteristics of a sand-water-steam system heated at the top and cooled at the bottom were studied. It was found that at steady-state conditions the system segregated into three regions. The top region was conduction-dominated with the voids containing a stationary superheated steam. The middle region was convection-dominated, nearly isothermal, and exhibited an upward flow of the liquid by capillary forces and a downward flow of steam due to a slight pressure gradient. The bottom portion contained a stationary compressed liquid and was also conduction dominated. The length of the two-phase convection zone was evaluated through the application of Darcy’s equations for two-phase flow and correlations of relative permeabilities and capillary pressure data. The model was in excellent agreement with the observed results, predicting a decreasing two-phase zone length with increasing heat flux. The thermodynamics of the two-phase zone were also analyzed. It was found that the vapor phase was in a superheated state as described by the Kelvin equation for vapor pressure lowering. Also, it was evident that the liquid must also be superheated for thermodynamic equilibrium to result. A stability analysis demonstrated that the superheated liquid can exist in an unconditionally stable state under conditions typical of porous systems. The degree of liquid superheat within the two-phase zone of these experiments was obtained.

A Simulation of a Generalized Thermal Radiating Fin

SIMULATION ◽  
1964 ◽  
Vol 2 (6) ◽  
pp. 19-22
Author(s):  
M.T. Janicke ◽  
L.C. Just
Keyword(s):  
Power Plant ◽  
Cross Section ◽  
Construction Material ◽  
Heat Removal ◽  
Thermodynamic Cycle ◽  
Space Applications ◽  
Maximum Heat ◽  
Electrical Systems ◽  
Extra Weight ◽  
The Relationship

The purpose of this paper is to provide a method for designing radiator fins with maximum heat removal capability per pound of construction material. This problem becomes important when radiators are designed for space applications, since all of the heat from the thermodynamic cycle must be removed by means of radiation. Moreover, space transportation vehicles are seriously limited as to payload, so that weight must be saved in all parts of a power plant. An increase in the output of a space power plant does not change the reactor, turbine, and generator as much as the radiator, with the result that, for megawatt electrical systems, the radiator is the dominant weight contributing component. A radiator could be built of coolant tubes alone, but this increases certain hazards. Meteor punctures can occur, so that the amount of area devoted to coolant tubes should be reduced as much as pos sible. Fins attached between the tubes can perform this function by extending the heat radiating surface. The extra weight of the fins is partly compensated for by a reduction in tubes and coolant. Extra savings can occur if the weight of the fin is minimized; optimum thickness, length, and cross section must be found. This paper studies the relationship between fin cross- section and radiating power.

Development of 3D Finite Element Model for Predicting Process-Induced Defects in Additive Manufacturing by Selective Laser Melting (SLM)

2016 ◽  
Author(s):  
Bilal Hussain ◽  
A. Sherif El-Gizawy
Keyword(s):  
Additive Manufacturing ◽  
Laser Beam ◽  
Selective Laser Melting ◽  
Thermal Stresses ◽  
Cost Effective ◽  
Element Model ◽  
Laser Melting ◽  
Two Phase ◽  
Free Process ◽  
Manufacturing Techniques

Selective Laser Melting (SLM) is one of the important Additive Manufacturing techniques for building functional products. Nevertheless, the absence of accurate models for predicting the SLM process behavior, delays development of cost effective and defects free process. This work presents a coupled thermo-mechanical numerical model to capture the two phase (solid-liquid) solidification melting phenomena that occur in the process. The proposed model will also predict the evolvement of process-induced properties and defects particularly residual stresses caused by temperature gradient and thermal stresses. CO2 or Nd:YAG laser beam can be used as a heat source with a Gaussian distribution for the laser beam energy.

Sign in / Sign up

Export Citation Format

Share Document