scholarly journals Numerical Simulation of Macrosegregation Formation in a 2.45 ton Steel Ingot Using a Three-Phase Equiaxed Solidification Model

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 262
Author(s):  
Tao Wang ◽  
Engang Wang ◽  
Yves Delannoy ◽  
Yves Fautrelle ◽  
Olga Budenkova
Keyword(s):  
Early Stage ◽  
Steel Ingot ◽  
Columnar Structure ◽  
Bulk Liquid ◽  
Solidification Model ◽  
Negative Segregation ◽  
Benchmark Experiment ◽  
Three Phase ◽  
Irregular Form ◽  
Equiaxed Grains

In the present work macrosegregation during solidification of a 2.45 ton steel ingot is simulated with a pure equiaxed model, which was tested previously via modeling of a benchmark experiment. While the columnar structure is not taken into account, a packed layer formed over inner walls of the mold at an early stage of solidification reproduces to some extent phenomena generally related to zones of columnar dendrites. Furthermore, it is demonstrated that interaction of free-floating equiaxed grains with ascending convective flow in the bulk liquid results in flow instabilities. This defines the irregular form of the negative segregation zone, the formation of which at the ingot bottom corresponds to experimental observation. Vertical channels reported in experimental measurements are reproduced in simulations. It is confirmed that intensification of ingot cooling may decrease segregation in the ingot.

Numerical and Experimental Investigation of NH4Cl Solidification

2010 ◽  
Vol 649 ◽  
pp. 367-372 ◽  
Author(s):  
Laszlo Könözsy ◽  
Mihaela Stefan Kharicha ◽  
Sven Eck ◽  
Meng Huai Wu ◽  
Andreas Ludwig
Keyword(s):  
Optical Measurement ◽  
Model Alloy ◽  
Columnar Dendrite ◽  
Solidification Model ◽  
Benchmark Experiment ◽  
Diffusion Controlled ◽  
Image Velocimetry ◽  
Model Equations ◽  
Volume Method ◽  
Equiaxed Grains

This paper deals with the validation of a volume averaged multiphase solidification model based on a benchmark experiment using NH4Cl-H2O as model alloy and Particle Image Velocimetry (PIV) as optical measurement method. For the numerical modelling of the solidification, different phases (e.g. liquid, equiaxed grains and columnar dendrite trunks) have been considered. The mass, momentum, energy conservation and species transport equations for each phase have been solved. The Eulerian-Eulerian model equations have been implemented in the commercial Finite Volume Method based software FLUENT-ANSYS v6.3 using User-Defined Functions (UDF). The mass transfer has been modelled by diffusion controlled crystal growth. The simulation of the NH4Cl-H2O solidification has been numerically investigated as a two-dimensional unsteady process in the cross-section of a 100 x 80 x 10 (mm3) experimental benchmark. Since during the experiment both columnar and equiaxed growth of NH4Cl have been observed, both phenomena have been considered in the simulation. The predicted distribution of the solidification front and the measured thickness of the mushy zone have been compared with the measurements.

scholarly journals Numerical Model for Solidification Zones Selection in the Large Ingots

2015 ◽  
Vol 15 (4) ◽  
pp. 87-90 ◽  
Author(s):  
W. Wołczyński ◽  
P. Kwapisiński ◽  
B. Kania ◽  
W. Wajda ◽  
W. Skuza ◽  
...  
Keyword(s):  
Temperature Field ◽  
Structure Formation ◽  
Thermal Gradient ◽  
Steel Ingot ◽  
Columnar Structure ◽  
Equiaxed Structure ◽  
Columnar Grains ◽  
Branched Structure ◽  
Equiaxed Grains ◽  
Structural Zones

Abstract A vertical cut at the mid-depth of the 15-ton forging steel ingot has been performed by curtesy of the CELSA - Huta Ostrowiec plant. Some metallographic studies were able to reveal not only the chilled undersized grains under the ingot surface but columnar grains and large equiaxed grains as well. Additionally, the structural zone within which the competition between columnar and equiaxed structure formation was confirmed by metallography study, was also revealed. Therefore, it seemed justified to reproduce some of the observed structural zones by means of numerical calculation of the temperature field. The formation of the chilled grains zone is the result of unconstrained rapid solidification and was not subject of simulation. Contrary to the equiaxed structure formation, the columnar structure or columnar branched structure formation occurs under steep thermal gradient. Thus, the performed simulation is able to separate both discussed structural zones and indicate their localization along the ingot radius as well as their appearance in term of solidification time.

Influence of Dendritic Morphology on the Calculation of Macrosegregation in Steel Ingot

2014 ◽  
Vol 790-791 ◽  
pp. 121-126 ◽  
Author(s):  
Jun Li ◽  
Meng Huai Wu ◽  
Andreas Ludwig ◽  
Abdellah Kharicha ◽  
Peter Schumacher
Keyword(s):  
Drag Force ◽  
Steel Ingot ◽  
Dendritic Morphology ◽  
Simple Approach ◽  
Equiaxed Crystal ◽  
Modified Model ◽  
Negative Segregation ◽  
Equiaxed Zone ◽  
Three Phase ◽  
Columnar To Equiaxed Transition

The simulation of macrosegregation in a 2.45-ton steel ingot with the three-phase mixed columnar-equiaxed model was presented previously. The results showed an overestimation of the intensity of bottom negative segregation. The reason is due to the assumed globular morphology for the equiaxed crystal. Therefore, in this paper a simple approach is suggested to treat the dendritic morphology of equiaxed crystals. Three aspects are improved: the drag force between the moving equiaxed crystals and the surrounding melt, the mechanism of the columnar-to-equiaxed transition, the packing limit of the equiaxed crystals. The modified model is used to calculate the macrosegregation of the same ingot. It is found that the modified model predicts less severe negative segregation in the bottom equiaxed zone than the previous globular equiaxed model does, i.e. it agrees better to the experiment. The model considering simplified-dendritic morphology improves the calculation accuracy.

Experimental and Numerical Study of Macrosegregation in a 160 Steel Ingot

2016 ◽  
Vol 850 ◽  
pp. 299-306
Author(s):  
Zhen Hu Duan ◽  
Xuan Du ◽  
Hou Fa Shen ◽  
Bai Cheng Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Manufacturing Industry ◽  
Numerical Study ◽  
Steel Ingot ◽  
Two Phase ◽  
Negative Segregation ◽  
Equiaxed Grains ◽  
The Heat Transfer Coefficient

Large steel ingots are the important material for the equipment manufacturing industry. It is still difficult to predict and control the macrosegregation in ingot. In this paper, the cooling curves at the surface of ingot and temperature variation of the mold were measured. The carbon distribution was measured through the local region dissection of ingot. Then, based on the definite the heat transfer coefficient at the interface of mold/ingot, a two-phase model with consideration of the motion of equiaxed grains is applied for the prediction of macrosegregation in 160-t steel ingot formed during the solidification. The results indicate that the heat transfer coefficient at the interface of mold/ingot decreases sharply after starting solidification and then varies slowly. Negative segregation at the bottom of ingot forms due to the interaction of solidification interface and equiaxed grains deposition during solidification. The positive segregation appears in the riser with thanks to the solidification shrinkage and the floating enriched solute. Finally, the results of the predicted and the measured are in good agreement.

scholarly journals Structural Zones in Large Static Ingot. Forecasts for Continuously Cast Brass Ingot

2016 ◽  
Vol 16 (3) ◽  
pp. 141-146 ◽  
Author(s):  
W. Wołczyński ◽  
Z. Lipnicki ◽  
A.W. Bydałek ◽  
A.A. Ivanova
Keyword(s):  
Temperature Field ◽  
Steel Ingot ◽  
Columnar Structure ◽  
Operating Point ◽  
Gradient Field ◽  
Crystal Formation ◽  
Ingot Axis ◽  
Columnar Grains ◽  
Continuously Cast ◽  
Equiaxed Grains

Abstract Some metallographic studies performed on the basis of the massive forging steel static ingot, on its cross-section, allowed to reveal the following morphological zones: a/ columnar grains (treated as the austenite single crystals), b/ columnar into equiaxed grains transformation, c/ equiaxed grains at the ingot axis. These zones are reproduced theoretically by the numerical simulation. The simulation was based on the calculation of both temperature field in the solidifying large steel ingot and thermal gradient field obtained for the same boundary conditions. The detailed analysis of the velocity of the liquidus isotherm movement shows that the zone of columnar grains begins to disappear at the first point of inflection and the equiaxed grains are formed exclusively at the second point of inflection of the analyzed curve. In the case of the continuously cast brass ingots three different morphologies are revealed: a/ columnar structure, b/ columnar and equiaxed structure with the CET, and c/ columnar structure with the single crystal formation at the ingot axis. Some forecasts of the temperature field are proposed for these three revealed morphologies. An analysis / forecast of the behavior of the operating point in the mold is delivered for the continuously cast ingot. A characteristic delay between some points of breakage of the temperature profile recorded at the operating point and analogous phenomena in the solidifying alloy is postulated.

scholarly journals Role of hydrostatic pressure and wall effect in solidification of TC8 alloy

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Xinghong Luo ◽  
Yaya Wang ◽  
Yang Li
Keyword(s):  
Hydrostatic Pressure ◽  
Normal Gravity ◽  
Early Stage ◽  
Solidification Process ◽  
Wall Effect ◽  
Solidification Microstructure ◽  
Drop Tube ◽  
Aspect Ratios ◽  
Equiaxed Grains

Abstract The solidification experiments of TC8 alloy under both microgravity and normal gravity were conducted using a drop tube. The solidification microstructure were found composed of fine equiaxed grains formed at early stage and bigger elongated grains formed at later stage. Between the two kinds of grains a curved transition interface was observed in 1g sample, while that in μg sample was almost flat. Generally, the amounts and aspect ratios of the grains are larger, and the grain sizes are smaller in 1g sample. Besides, no visible element macrosegregation occurred in both samples. The results suggest that the solidification velocities of the samples were rapid, and consequently the convection effect and solute transport effect caused by gravity had little influence on the solidification microstructure. Therefore, the solidification process was mainly controlled by thermal diffusion, and hydrostatic pressure and wall effect played a great role in it.

Effect of Working Pressure on Microstructure and Mechanical Properties of Magnetron Sputtered ZrN Coatings

2010 ◽  
Vol 154-155 ◽  
pp. 1659-1663
Author(s):  
Zheng Bing Qi ◽  
Peng Sun ◽  
Fang Ping Zhu ◽  
Ruo Xuan Huang ◽  
Zhou Cheng Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Elastic Modulus ◽  
Failure Modes ◽  
Columnar Structure ◽  
Scratch Testing ◽  
Working Pressure ◽  
Cross Sectional ◽  
Microstructure And Mechanical Properties ◽  
Equiaxed Grains

The influence of working pressure on microstructure and mechanical properties of magnetron sputtered ZrN coatings were systemically investigated. The results reveal that a decreased working pressure results in preferred orientation evolution from (111) to (200) and cross-sectional morphologies transition from columnar structure to equiaxed grains. These microstructural changes are considered responsible for an increase in hardness and modulus with decreasing working pressure. Chip spallation and plastic deformation failure modes are observed during scratch testing, and the increased critical loads are attributed to higher hardness and elastic modulus, as well as moderate compressive stress at lower working pressure.

scholarly journals Genesis of the Koka Gold Deposit in Northwest Eritrea, NE Africa: Constraints from Fluid Inclusions and C-H-O-S Isotopes

2019 ◽  
Author(s):  
Kai Zhao ◽  
Huazhou Yao ◽  
Jianxiong Wang ◽  
Ghebsha Fitwi Ghebretnsae ◽  
Wenshuai Xiang ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Meteoric Water ◽  
Gold Mineralization ◽  
Early Stage ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Quartz Veins ◽  
Three Phase ◽  
Igneous Origin ◽  
Ne Africa

The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on the paragenetic study two main stages of gold mineralization were identified in the Koka gold deposit: 1) an early stage of pyrite-chalcopyrite-sphalerite-galena-gold-quartz vein; and 2) a second stage of pyrite-quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2-H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268℃, from NaCl-CO2-H2O(-CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water, meteoric water and magmatic water, whereas sulfur isotope suggest an igneous origin. Features of geology and ore-forming fluid at Koka deposit are similar to those of orogenic gold deposits, suggesting the Koka deposit might be an orogenic gold deposit related to granite.

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