scholarly journals Reoxidation Processes Prediction in Gating System by Numerical Simulation for Aluminium Alloys

2017 ◽  
Vol 17 (3) ◽  
pp. 23-26 ◽  
Author(s):  
M. Brůna ◽  
D. Bolibruchová ◽  
R. Pastirčák
Keyword(s):  
Free Surface ◽  
Aluminium Alloys ◽  
Oxide Films ◽  
Front Tracking ◽  
Gating System ◽  
Liquid Aluminium ◽  
Surface Time ◽  
Filling Pattern ◽  
Entrained Air ◽  
Flow Experiments

Abstract Pouring of liquid aluminium is typically accompanied by disturbance of the free surface. During these disturbances, the free surface oxide films can be entrained in the bulk of liquid, also pockets of air can be accidentally trapped in this oxide films. The resultant scattering of porosity in castings seems nearly always to originate from the pockets of entrained air in oxide films. Latest version of ProCast software allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up in casts. During a filling calculation, ProCast can calculate different indicators which allow to better quantify the filling pattern. The fluid front tracking indicator “Free surface time exposure” has the units [cm2*s]. At each point of the free surface, the free surface area is multiplied by the time. This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow. Experiments to validate this new functions were executed.

Characterization of Casting Defects in Aluminium Alloys

2012 ◽  
Vol 430-432 ◽  
pp. 984-987
Author(s):  
Guo Wu ◽  
Keyna O'Reilly ◽  
Marina Galano
Keyword(s):  
Aluminium Alloys ◽  
Oxide Films ◽  
Melting Process ◽  
Major Type ◽  
Induction Melting ◽  
Liquid Aluminium ◽  
Alumina Crucible ◽  
Oxide Defects ◽  
Scanning Electron

In this paper, typical defects in aluminium alloys cast by conventional pouring of liquid metal into a cylindrical alumina crucible and an induction melting process are characterized by using macroetching, optical microscopy and scanning electron microscopy. Oxide film defects are generated in both processing methods. Oxide films formed during casting are a major type of defect observed in the microstructures of aluminium alloys products. It has been found that pouring of molten metal into a mould and induction stirring lead to different forms of oxide defects. Under induction stirring, such low-density entrained defects are found to be carried to near the surface of the liquid aluminium alloys and submerged surface oxide films become entangled.

scholarly journals Effect of the pressed ceramic filters on the reoxidation process

2018 ◽  
Vol 157 ◽  
pp. 02004
Author(s):  
Marek Brůna ◽  
Dana Bolibruchová ◽  
Richard Pastirčák
Keyword(s):  
Aluminium Alloys ◽  
Oxide Films ◽  
Simulation Software ◽  
Gating System ◽  
Ceramic Filters

Article is focused on reoxidation processes during filtration of aluminium alloys. Many of our experiments proven, that when using filtration media in gating system, reoxidation occurs. Main goal of this article is to point out reoxidation problems occurring during filtration of aluminium alloys. Reason to conduct this work was anomalies discovered by experimental casts, which pointed out that after filtration of primary alloys, small oxide films was detected. Oxides was absent, when we poured without filtration media. Simulation software ProCAST was used during our research.

Comparison of flow behaviour in pressurized gating systems using water models and numerical simulation

2016 ◽  
Vol 14 (3) ◽  
pp. 652-674
Author(s):  
V. Jaiganesh ◽  
K. Prakasan
Keyword(s):  
Flow Visualization ◽  
Flow Behaviour ◽  
Water Model ◽  
Gating System ◽  
Commercial Software ◽  
Content Type ◽  
Filling Pattern ◽  
Flow Through ◽  
Water Models ◽  
Critical Sections

Purpose The purpose of this work is to visualize the flow behaviour in critical sections of a pressurized gating system. Design/methodology/approach The investigation was carried out using water models of gating system that were designed, invoking the principles of similitude. Water was used as the filling medium, and the manner of flow through various sections of the gating system and the cavity was recorded with a high-speed camera capable of capturing images up to 10,000 frames per second. This was followed by an analysis of the results obtained from each phase. Finally, computer simulations of flow were carried out using commercial software. The manner of filling as observed during experiments and that during simulation were compared so as to draw some useful conclusions on the utility of flow visualization using water models and the capability of software to predict the filling pattern during casting process. It was understood that water models are powerful aids for understanding the intricacies of flow through critical sections of the gating systems. Findings It was observed that water models are a reliable indicator of the mould-filling process. Further, substantial differences in the filling pattern were observed between water model experiments and filling simulation using commercial software. Research limitations/implications The findings are limited to horizontal plate-type castings. Also, the influence of surface roughness in the flow through the runner is not considered. Originality/value This work facilitates understanding of the importance of flow visualization on the quality and reliability of castings.

Analysis of dynamic characteristics of bubble rise under a free surface

2020 ◽  
Vol 98 (11) ◽  
pp. 981-992
Author(s):  
Ying Zhang ◽  
Qiang Liu ◽  
Wenbin Li ◽  
Xiaolong Lian ◽  
Jinglun Li ◽  
...  
Keyword(s):  
Free Surface ◽  
Immersed Boundary Method ◽  
Weber Number ◽  
Front Tracking ◽  
Terminal Velocity ◽  
Immersed Boundary ◽  
Tracking Method ◽  
Free Interface ◽  
Front Tracking Method ◽  
Moving Interface

The rising process of a bubble occurs in several natural and industrial apparatuses. This process is computationally studied using the front tracking method for a moving interface whose surface properties are solved in terms of an immersed-boundary method. The results show that the free interface does not influence the bubble before the centroid velocity of the bubble reaches the terminal velocity, which reaches a stable value or fluctuates at it, with the distance h (between the centroid of the bubble and the free surface) reaching a certain value. When the Reynolds number increases, the time to reach terminal velocity will decrease, and the influence of the viscous factor on the terminal velocity is also weakened. The dramatic interaction between a bubble and free surface is beneficial to accelerate film draining out. It is also shown that the shape of the bubble gradually becomes an ellipse as the Weber number (We) decreases, and it is beneficial to reduce the resistance of the bubble. The free surface could accelerate the bubble breaking at high We values.

Understanding the occurrence of the surface turbulence in a nonpressurized bottom gating system: Numerical simulation of the melt flow pattern

2015 ◽  
Vol 232 (3) ◽  
pp. 230-241 ◽  
Author(s):  
Ali Kheirabi ◽  
Amir Baghani ◽  
Ahmad Bahmani ◽  
Morteza Tamizifar ◽  
Parviz Davami ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Liquid Metal ◽  
Flow Pattern ◽  
Oxide Films ◽  
Critical Value ◽  
Surface Velocity ◽  
Complete Agreement ◽  
Gating System ◽  
Melt Flow ◽  
Surface Turbulence

Surface turbulence during the filling of the mold triggers the entrainment of oxide films, which appears to be detrimental to the soundness of the final casting. Nonpressurized and bottom-gating systems have been employed in order to avoid such casting defects by reducing the surface velocity of the liquid metal. However, recent studies have shown that the melt front velocity in the mold entrance may exceed the critical value in the nonpressurized and bottom-gating systems. Therefore, a study was conducted on numerical simulation melt flow pattern in nonpressurized and bottom-gating systems. It was noted that the liquid metal enters the gate and then mold cavity with a higher velocity by formation of dead zones and vortex flows in runner's end. Therefore, the current designs based on conventional gating system ratio seem to be not optimized and unable to avoid the surface turbulence. Numerical results were in complete agreement with experimental observations. Understanding the reasons for occurrence of the surface turbulence in nonpressurized and bottom-gating systems provides information on the required steps to improve the design of the gating systems and minimize the entrainment of oxide films during the filling of the mold.

A multiscale front tracking method for compressible free surface flows

2007 ◽  
Vol 62 (13) ◽  
pp. 3538-3548 ◽  
Author(s):  
Zhiliang Xu ◽  
James Glimm ◽  
Yongmin Zhang ◽  
Xinfeng Liu
Keyword(s):  
Free Surface ◽  
Front Tracking ◽  
Free Surface Flows ◽  
Surface Flows ◽  
Tracking Method ◽  
Front Tracking Method

scholarly journals Double oxide film defects and the properties of aluminum castings. A review

2019 ◽  
pp. 5-12
Author(s):  
Mahmoud Ahmed El-Sayed
Keyword(s):  
Liquid Metal ◽  
Oxide Film ◽  
Aluminium Alloys ◽  
Oxide Films ◽  
Light Metal ◽  
Metal Alloy ◽  
Double Oxide ◽  
Factors Influencing ◽  
Aluminum Castings ◽  
Alloy Castings

Entrapped double oxide films are known to be the most detrimental defects in cast aluminium alloys. The research reported here was aimed at surveying the results of previous researches studying how these defects develop with time, with the intention of understanding their behaviour in the liquid metal once they have formed. This would give a better understanding of factors influencing the properties of light metal alloy castings which will lead to the development of improved practices by which healthier castings with reliable and more reproducible properties are obtained.

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