Analysis of Mass Transfer Process in the Pore Free Technique

1995 ◽  
Vol 117 (2) ◽  
pp. 215-219 ◽  
Author(s):  
Genick Bar-Meir
Keyword(s):  
Mass Transfer ◽  
Dimensionless Parameter ◽  
Die Casting ◽  
Air Entrainment ◽  
Mass Transfer Process ◽  
Critical Value ◽  
First Case ◽  
Pressure Die Casting ◽  
The Relationship ◽  
Transfer Mechanisms

Air entrainment is one of the most significant problems in pressure die casting. A possible solution is to use the Pore Free technique. In this technique an oxygen is introduced into the die to react with the liquid metal. The vacuum created by the reaction reduces the porosity. The life span of the mold is augmented by the reduction of the pressure during the process. In some cases the Pore Free technique yields acceptable results, i.e., low porosity, while in other cases the results are not satisfactory. These differing results can be explained by an analysis of the mechanisms involved. A simple model is proposed based on conservation laws that describes the relationship between mass transfer mechanisms and pressure deviation. The model indicates that there is a critical dimensionless parameter above which the pressure is decreased and below which the pressure is increased. In the first case, when the parameter exceeds the critical value, the technique is useful. In the second case, when the parameter is less than the critical value, introducing oxygen does not greatly reduce the porosity. The analysis demonstrates that the Pore Free and vacuum venting techniques account for two different extremes. The first case is when the flow is orderly throughout the chamber in which vacuum venting can produce acceptable results. The second case is when the flow is turbulent and the Pore Free technique is the better choice.

Pressure Die Casting: A Model of Vacuum Pumping

1996 ◽  
Vol 118 (2) ◽  
pp. 259-265 ◽  
Author(s):  
G. Bar-Meir ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Elastic Moduli ◽  
Die Casting ◽  
Total Porosity ◽  
Air Entrainment ◽  
Pressure Variation ◽  
Filling Time ◽  
Cavity Filling ◽  
Pressure Die Casting ◽  
The Relationship ◽  
Residual Air

Multifunctional characteristics of die casting parts are significantly compromised by the presence of voids, which can result in a substantial decrease in the elastic moduli and thermal conductivity. Gas/air porosity constitutes a large part of the total porosity. To reduce the porosity due to the gas/air entrainment, a vacuum can be applied to remove the residual air in the die. In some cases vacuum castings have low porosity, while in other cases the results are not satisfactory. These differing results can be explained in some instances by an analysis of the vent area. A simple model is proposed based on conservation laws which describes the relationship between vent area and pressure variation in the die. The analysis of vacuum venting indicates that there is a critical/optimum vent area below which the ventilation is poor and above which the resistance to the air flow is minimal. The model yields a simple equation to select the optimum area which is a function of the duct resistance, the evacuated volume, and the filling time. This result should be useful to the design engineer. The result also provides a tool to “measure” the vent size for numerical simulations of the cavity filling, taking into account the compressibility of the gas.

Effect of Temperature on the Properties of High Pressure Die Casting

2010 ◽  
Vol 649 ◽  
pp. 473-479 ◽  
Author(s):  
Jenő Dúl ◽  
Richárd Szabó ◽  
Attila Simcsák
Keyword(s):  
High Pressure ◽  
Data Acquisition ◽  
Die Casting ◽  
Data Acquisition System ◽  
Effect Of Temperature ◽  
High Pressure Die Casting ◽  
Die Castings ◽  
Pressure Die Casting ◽  
The Relationship

Quality of high pressure die castings is influenced by a lot of factors. Among them, the most important ones are the melt-, and die temperatures. This paper shows a data acquisition system, developed for measuring the melt and die temperatures and the results of the temperature measurements obtained under variable conditions. Evaluation of the relationship between the interrelated temperatures and the casting properties is based on analyzing the structure of the castings.

scholarly journals Interactions between gas–liquid mass transfer and bubble behaviours

2019 ◽  
Vol 6 (5) ◽  
pp. 190136 ◽  
Author(s):  
Xin Li ◽  
Weiwen Wang ◽  
Pan Zhang ◽  
Jianlong Li ◽  
Guanghui Chen
Keyword(s):  
Mass Transfer ◽  
Bubble Diameter ◽  
Water System ◽  
Mass Transfer Process ◽  
Liquid Mass ◽  
Fluid Field ◽  
Vof Model ◽  
Liquid Mass Transfer ◽  
The Relationship ◽  
Two Sides

Interactions between gas–liquid mass transfer and bubble behaviours were investigated to improve the understanding of the relationship between the two sides. The CO 2 /N 2 -water system was applied to study the bubble behaviours based on the volume-of-fluid (VOF) model. The mass transfer conditions were taken into consideration when the fluid field was analysed. The bubble behaviours were compared with and without mass transfer. The results show that the absolute slopes of the curves for mass fraction inside the single rising bubbles, with diameters from 3 to 6 mm, decrease from 0.09325 to 0.02818. It means that small single bubbles have higher mass transfer efficiency. The daughter bubbles of cutting behaviour and initial side-by-side bubbles of coalescence behaviour also perform better than the initial large bubbles and coalesced bubbles, respectively. The bubble behaviours affect the mass transfer process. However, the latter also reacts upon the former. The critical intervals between the side-by-side bubbles decrease from 2.0 to 0.9 mm when the bubble diameter changes from 3 to 7 mm. For the coalescence behaviour without mass transfer, the critical intervals are larger because there is no influence of concentration around the bubbles on the bubble motion. The coalescence of cut daughter bubbles is also influenced by the concentration. It was suggested that the interaction between the gas–liquid mass transfer and bubble behaviours cannot be ignored.

Characterization of Magnesium Automotive Components Produced by Super-Vacuum Die Casting Process

2009 ◽  
Vol 618-619 ◽  
pp. 381-386 ◽  
Author(s):  
K. Sadayappan ◽  
W. Kasprzak ◽  
Zach Brown ◽  
L. Quimet ◽  
Alan A. Luo
Keyword(s):  
Die Casting ◽  
Casting Process ◽  
Air Entrainment ◽  
Automotive Components ◽  
Vacuum Die Casting ◽  
Heat Treated ◽  
Conventional Heat Treatment ◽  
Die Casting Process ◽  
Rapidly Solidified ◽  
Pressure Die Casting

Magnesium automotive components are currently produced by high pressure die casting. These castings cannot be heat-treated to improve the strength and ductility mainly due to the casting imperfections such as porosity and inclusions created by the air entrainment during the turbulent mold filing. These imperfections also prevent magnesium components to be used for highly stressed body components. Efforts were made to produce high integrity magnesium castings through a Super-Vacuum Die Casting process. The AZ91D castings were found to have very low porosity and can be heat-treated without blisters. The tensile properties of the castings were satisfactory. The mechanical properties and thermal analysis indicate that the conventional heat treatment procedure needs to be optimized for such thin sectioned and rapidly solidified castings which have very fine microstructures.

Optimum Runner Design for Die Casting Using CFD Simulations and Verification With Water-Model Experiments

2014 ◽  
Author(s):  
Ken’ichi Kanazawa ◽  
Ken’ichi Yano ◽  
Jun’ichi Ogura ◽  
Yasunori Nemoto
Keyword(s):  
Molten Metal ◽  
Die Casting ◽  
Air Entrainment ◽  
Optimization Method ◽  
Water Model ◽  
Cfd Simulations ◽  
Mathematical Functions ◽  
Model Experiments ◽  
Runner Design ◽  
Pressure Die Casting

This study aimed to optimize the design of a runner for high-pressure die casting (HPDC) using computational fluid dynamics (CFD) simulations, and to verify the effectiveness of the runner with water-model experiments. A runner is a part of the flow path through which molten metal enters a product part. As a design problem, we sought to optimize the shape of the runner to minimize air entrainment in the runner and align the flow of molten metal after it passed through the runner. The problem was solved using our proposed nonparametric shape optimization method. The method is based on a genetic algorithm (GA), and directly treats a geometric shape that is comprised of several curves as an individual of a GA in the form of a set of mathematical functions. In addition, the crossover, which is one of the genetic operations, is defined as a weighted summation of two parent curves. Thus, the optimization method can generate optimized shapes with a lot of flexibility. The effectiveness of the optimized shape of the runner was demonstrated with both CFD simulations and water-model experiments using a visualization device for HPDC.

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