Characteristics of mold filling and entrainment of oxide film in low pressure casting of A356 alloy

Liu, Shan-guang; Cao, Fuyang; Zhao, Xinyi; Jia, Yandong; Ning, Zhiliang; Sun, Jianfei

doi:10.1016/j.msea.2014.12.058

Cited by 44 publications

(29 citation statements)

References 19 publications

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“…Liu et al [14] found that Sr reacted with Al 2 O 3 to form a mixed oxide, but its stoichiometry was not determined. One of the authors [53] determined that Sr additions lead to the formation of SrO.Al 2 O 3 spinel, which can easily be fractured into smaller pieces through breakaway oxidation.…”

Section: Resultsmentioning

confidence: 99%

“…Although Iwahori et al [25] speculated that Sr additions in the presence of bifilms increased the hydrogen content, there is an alternate explanation for the large increase in the number of pores with Sr additions. Liu et al [14] found that Sr reacted with Al2O3 to form a mixed oxide, but its stoichiometry was not determined. One of the authors [53] determined that Sr additions lead to the formation of SrO.Al2O3 spinel, which can easily be fractured into smaller pieces through breakaway oxidation.…”

Section: Number Density Measurementsmentioning

confidence: 99%

“…Roy et al [32] found that Sr additions to melts of an Al-9%Si-3%Cu alloy increased the number density of pores and distributed them evenly in the casting. Liu et al [14] conducted research on the effect of Sr content on porosity and the type of oxide formed in RPT samples as a result of Sr addition in A356 and 319 cast aluminum alloys. They confirmed that Sr additions increased porosity, regardless of the level of H content.…”

Section: Introductionmentioning

confidence: 99%

“…Similar results were found by Haberl et al [35] who reported almost 50% reduction in number density of pores in RPT samples after degassing. Although it is well known that degassing reduces the hydrogen content, the main contribution of degassing is considered to be the floatation of bifilms to the melt surface [14,[44][45][46].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the Effect of Melt Treatments on Melt Quality in Al-7wt %Si-Mg Alloys

Uludağ

Çetin

Dışpınar

et al. 2017

Metals

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Abstract:The effects of degassing, holding time and melt additions (Sr, Sr + Ti, Ti, B and B + Sr) on the quality of A356 melts were examined. A total of 120 reduced pressure test samples were collected. Pores in these samples were analyzed via digital image processing to determine the number density of pores as well as the statistical distribution of their sizes. Results showed that in all cases, degassing with argon reduced the number of defects regardless of the additions made to the melts. Moreover, all additions were found to degrade melt quality. The lowest number density of pores in all melts was achieved in melts with no additions that were degassed. In both degassed and non-degassed melts, Sr additions degraded the melt quality significantly. The mechanisms of melt quality improvement or degradation with different melt treatments are discussed in the paper.

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Section: Resultsmentioning

confidence: 99%

Section: Number Density Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of the Effect of Melt Treatments on Melt Quality in Al-7wt %Si-Mg Alloys

Uludağ

Çetin

Dışpınar

et al. 2017

Metals

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“…Nevertheless, in the example of an automotive industrial part studied by Hogg and co-workers [9], the measured filling velocity is lower than expected according to this simple analytical model. Moreover, testing a sudden horizontal section increase in a mould has been proven to induce oscillations that increase in amplitude when increasing the pressure ramp [7]. Therefore, the existing studies on filling flow in low pressure casting do not permit to establish clearly the relationship between mould geometry and metal front rising.…”

mentioning

confidence: 99%

Filling Characterization into a Section Restriction in Low-Pressure Casting

Sanitas¹,

Bedel²,

Mansori³

2017

World Congress on Mechanical, Chemical, and Material Engineering

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Extended AbstractToday, the need of high quality cast components for automotive and aeronautics industries leads to develop the lowpressure casting process [1], [2]. Indeed, the controlled counter gravity flow during mould filling lowers the amount of entrapped gas and oxides. This process consists of a pressurized furnace linked to the mould through a vertical rising tube. The filling is led by gradually increasing the pressure of the gas above the liquid metal. This way, the metal head pressure is compensated and the metal is pushed through the rising tube towards the mould. A velocity above 0,5m/s is experimentally known to induce defects in parts [3].Hence, the gas pressure -metal filling velocity relationship needs to be known to prevent such defects. Previous low-pressure studies used incompressible steady-state Bernoulli's equations to estimate the metal front evolution by assuming that the dynamic pressure of the fluid is negligible [4]- [7]. An analytical expression is then found at every moment linking the metal front height and the gas pressure. On their work, Fan and coworkers found a good correlation between the experimentally measured and the analytically predicted metal front evolution in plate patterns [8]. Nevertheless, in the example of an automotive industrial part studied by Hogg and co-workers [9], the measured filling velocity is lower than expected according to this simple analytical model. Moreover, testing a sudden horizontal section increase in a mould has been proven to induce oscillations that increase in amplitude when increasing the pressure ramp [7]. Therefore, the existing studies on filling flow in low pressure casting do not permit to establish clearly the relationship between mould geometry and metal front rising.This work proposes a characterization of the imposed gas pressure -metal flow velocity relationship in low pressure casting. More precisely, the relative effect of local and global horizontal section changes on filling flow is studied. To do so, experimentally measured and numerically predicted metal front position evolutions are compared in the case of different mould geometries. An AlSi 13 alloy is melt and poured by low pressure casting in 3D printed sand moulds. A 25mbar/s pressure ramp is set for filling. Three different geometries are studied with an identical global horizontal section restriction of 0.24: one cylinder, six cylinders and one ring. To track the experimental metal height evolution, electrical contacts are used. Experimental metal height versus time curves are extracted and reveal an oscillating phenomenon after section changing. Due to this phenomenon, an over-height which is not predicted by the analytical equations is observed. The velocity of the flow reaches values above 0.5m/s, leading to risks of defects. The experimental cases are then simulated using ANSYS Fluent® simulation software. A k-epsilon flow model simulates the whole low pressure systemthe metal in the mould, in the tube and in the furnace and the pressuring gas-. The observed fil...

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