I-3 ASSESSMENT OF REDUCED PRESSURE TEST FOR HYDORGEN MEASUREMENT OF ALUMINUM CASTING(Session: Casting/Molding)

The present study investigated the effect of the casting conditions for the reduced pressure test (RPT) on the melt quality of Al-Si alloy. The casting conditions considered in RPT were the atmospheric exposure during melting, sampling method, and mold pre-heating temperature. Density Index (DI) was measured to quantify the melt quality of the Al-Si alloy casted with the different casting conditions for the RPT. The sample with blocking atmospheric exposure during melting was 5.6% lower in DI than the one without blocking. DI showed a 1.9% gap between scooping-out and pouring sampling methods. Increasing mold pre-heating temperature from 100 °C to 250 °C increased the DI of the alloy from 8.5% to 18.7%. On the other hand, when the mold pre-heating temperature was 350 °C, the DI of the alloy dropped sharply to 0.9%. The melt quality of the alloys was analyzed by measuring the pores and microstructure and simulating the solidification of the samples. It was presumed that the oxides and inclusions in the molten alloys caused the difference in DI according to the atmospheric exposure and the sampling method. The difference in DI according to the mold pre-heating temperature could be understood by calculating the solidification starting time and hydrogen diffusion coefficient during the solidification of the alloys in RPT.

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Mechanical Properties and Melt Quality Relationship of Sr-modified Al-12Si Alloy

Archives of Foundry Engineering ◽

10.1515/afe-2015-0093 ◽

2015 ◽

Vol 15 (4) ◽

pp. 134-140 ◽

Cited By ~ 3

Author(s):

M. Uludağa ◽

M. Uyaner ◽

F. Yilmaz ◽

D. Dişpinar

Keyword(s):

Mechanical Properties ◽

Oxide Film ◽

Tensile Testing ◽

Porosity Formation ◽

Reduced Pressure ◽

Cast Part ◽

Pressure Test ◽

Relationship Of ◽

Good Agreement

Abstract The formation of oxide film on the surface of aluminium melts, i.e. bifilms, are known to be detrimental when they are incorporated into the cast part. These defects causes premature fractures under stress, or aid porosity formation. In this work, Al-12 Si alloy was used to cast a step mould under two conditions: as-received and degassed. In addition, 10 ppi filters were used in the mould in order to prevent bifilm intrusion into the cast part. Reduced pressure test samples were collected for bifilm index measurements. Samples were machined into standard bars for tensile testing. It was found that there was a good agreement with the bifilm index and mechanical properties.

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Critical assessment of reduced pressure test. Part 1: Porosity phenomena

International Journal of Cast Metals Research ◽

10.1179/136404604225020696 ◽

2004 ◽

Vol 17 (5) ◽

pp. 280-286 ◽

Cited By ~ 93

Author(s):

D. Dispinar ◽

J. Campbell

Keyword(s):

Critical Assessment ◽

Reduced Pressure ◽

Test Part ◽

Pressure Test

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Effect of Melt Quality and Quenching Temperature on the Mechanical Properties of SIMA 2024 and 7075

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.445.171 ◽

2012 ◽

Vol 445 ◽

pp. 171-176

Author(s):

Engin Tan ◽

Ali Riza Tarakcilar ◽

Derya Dispinar

Keyword(s):

Mechanical Properties ◽

Room Temperature ◽

Mechanical Tests ◽

Fatigue Tests ◽

Grain Structure ◽

Quenching Temperature ◽

Reduced Pressure ◽

Pressure Test ◽

Sima Process ◽

Spherical Grains

Spherical grains can be obtained by several semisolid processes in aluminium alloys. One of these methods is called Strain Induced Melt Activated (SIMA). In this work, commercially available 2024 and 7075 alloys were subjected SIMA process. First, optimised process parameters were investigated for the homogeneous spherical grain structure. This was followed by solution heat treatment of the parts. For the quenching medium, room temperature and 80°C boiling water was selected. The effect of different quenching temperatures over the mechanical properties was tested. Hardness, tensile and fatigue tests were applied. In addition, reduced pressure test was used to assess alloy quality and the results were compared with the mechanical tests.

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Weibull verification of reduced pressure test as a tool for assessing Al melt quality

International Journal of Cast Metals Research ◽

10.1080/13640461.2016.1244245 ◽

2016 ◽

Vol 30 (2) ◽

pp. 87-95 ◽

Cited By ~ 1

Author(s):

Hosein Bartar Esfahani ◽

Ramin Raiszadeh ◽

Hamid Doostmohammadi

Keyword(s):

Reduced Pressure ◽

Pressure Test

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Investigation on Double Oxide Film Initiated Pore Formation in Aluminum Casting Alloys

International Journal of Engineering and Management Sciences ◽

10.21791/ijems.2020.2.18. ◽

2020 ◽

Vol 5 (2) ◽

pp. 141-153

Author(s):

Gábor Gyarmati ◽

György Fegyverneki ◽

Mónika Tokár ◽

Tamás Mende

Keyword(s):

Pore Formation ◽

Oxide Films ◽

Aluminum Casting ◽

Reduced Pressure ◽

Double Oxide ◽

Casting Alloys ◽

Eutectic Si ◽

X Ray Computed ◽

The Relationship

The most common, and in fact, the most deleterious defects of aluminum casting alloys are the so-called double oxide films or bifilms, which have a central role in porosity formation, as they can easily unfurl and inflate into pores during the solidification of the alloys. Sr addition is generally used in the foundry industry for the modification of the eutectic Si phase of hypoeutectic Al-Si alloys. However, Sr microalloying usually leads to an increased pore formation tendency. As bifilms are preferred sites for pore formation, it should be expected that Sr additions have a significant effect on the number and/or the structure of double oxide films present in the melt. In this work, the relationship between Sr-concentration and the susceptibility to pore formation has been investigated through the evaluation of melt quality of melts which had different levels of Sr. The bifilm content of the melts was investigated by the analysis of K-mold specimens and X-ray computed tomography (CT) of reduced pressure test (RPT) samples. It was found that liquid alloys with a higher Sr concentration had a significantly greater tendency to pore formation, which can be explained by the presence of a larger number of bifilm defects in the liquid alloy.

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Quality Evaluation of Remelted A356 Scraps

Archives of Foundry Engineering ◽

10.1515/afe-2016-0069 ◽

2016 ◽

Vol 16 (3) ◽

pp. 151-156 ◽

Cited By ~ 7

Author(s):

C. Yuksel ◽

O. Tamer ◽

E. Erzi ◽

U. Aybarc ◽

E. Cubuklusu ◽

...

Keyword(s):

Cost Reduction ◽

Quality Evaluation ◽

Die Casting ◽

Raw Material ◽

Reduced Pressure ◽

Casting Quality ◽

Aluminium Casting Alloy ◽

Pressure Test ◽

Machined Parts

AbstractA356 is one of the widely used aluminium casting alloy that has been used in both sand and die casting processes. Large amounts of scrap metal can be generated from the runner systems and feeders. In addition, chips are generated in the machined parts. The surface area with regard to weight of chips is so high that it makes these scraps difficult to melt. Although there are several techniques evolved to remedy this problem, yet the problem lies in the quality of the recycled raw material. Since recycling of these scrap is quite important due to the advantages like energy saving and cost reduction in the final product, in this work, the recycling efficiency and casting quality were investigated. Three types of charges were prepared for casting: %100 primary ingot, %100 scrap aluminium and fifty-fifty scrap aluminium and primary ingot mixture were used. Melt quality was determined by calculating bifilm index by using reduced pressure test. Tensile test samples were produced by casting both from sand and die moulds. Relationship between bifilm index and tensile strength were determined as an indication of correlation of melt quality. It was found that untreated chips decrease the casting quality significantly. Therefore, prior to charging the chips into the furnace for melting, a series of cleaning processes has to be used in order to achieve good quality products.

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Assessment of Mechanism of Pore Formation in Directionally Solidified A356 Alloy

Archives of Foundry Engineering ◽

10.1515/afe-2017-0029 ◽

2017 ◽

Vol 17 (1) ◽

pp. 157-162 ◽

Cited By ~ 8

Author(s):

M. Uludağ ◽

D. Dişpinar

Keyword(s):

Pore Formation ◽

A356 Alloy ◽

Test Sample ◽

Directionally Solidified ◽

Liquid Aluminium ◽

Reduced Pressure ◽

Pressure Test ◽

Dissolved Hydrogen ◽

Copper Chill ◽

Cast Parts

Abstract It is well-known that the better the control of the liquid aluminium allows obtaining of better properties. One of the most important defects that is held responsible for lower properties has been the presence of porosity. Porosity has always been associated with the amount of dissolved hydrogen in the liquid. However, it was shown that hydrogen was not the major source but only a contributor the porosity. The most important defect that causes porosity is the presence of bifilms. These defects are surface entrained mainly due to turbulence and uncontrolled melt transfer. In this work, a cylindrical mould was designed (Ø30 x 300 mm) both from sand and die. Moulds were produced both from sand and die. Water cooled copper chill was placed at the bottom of the mould in order to generate a directional solidification. After the melt was prepared, prior to casting of the DC cast samples, reduced pressure test sample was taken to measure the melt quality (i.e. bifilm index). The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means of bifilm content, size and distribution in A356 alloy.

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