The concentration of hydrogen is one of the most important parameters in liquid aluminum processing because it is responsible for gas porosity which affects casing quality, ie. pressure tightness, mechanical properties etc. In order to gain optimum quality, the amount of hydrogen dissolved in liquid aluminum must be known prior to casting. This has led to the development of several techniques to quantify hydrogen in liquid aluminum. Among these is the Reduced Pressure Test (RPT). The RPT is simple, very inexpensive and commonly used in aluminum foundries to obtain a qualitative evaluation of the melt hydrogen level. / In this thesis the development of the RPT to a truly quantitative level is discussed. This includes redesigning of the steel mold and the application of a riser. The mold was redesigned to improve the test sensitivity while a CO$ sb2$-bonded sand riser was applied in order to eliminate volumetric shrinkage and ensure a constant volume sample. As the sample has a constant volume, either the sample weight or density can be used to quantify the hydrogen content. The simplest technique is to use the sample weight. / Several parameters that affect the test sensitivity and reproducibility were studied, such as chamber pressure, amount of inclusions, pouring temperature, and mold temperature. It was found that there are two important parameters that strongly affect the test; chamber pressure and amount of inclusions. The lower the chamber pressure the better the test sensitivity but the poorer the test reproducibility. Increasing the amount of inclusions improves the test sensitivity. / The constant volume sample can be used to predict the amount of hydrogen in the melt for various types of alloys including 319, 356, 357 and 413 within a reasonable margin of error. The error as measured by this technique was found to be in the range of $ pm$0.025-0.049 ml./100 g.Al. if the sample weight is used, and in the range of $ pm$0.025-0.047 ml./100 g,Al. if the sample density is used. / A simple mathematical model based on a mass balance approach was developed to calculate pore size and sample density. The model predicts the density accurately for various types of alloys and different melt treatments.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28812 |
| Date | January 1994 |
| Creators | La-Orchan, Wittaya |
| Contributors | Gruzleski, J. G. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001448227, proquestno: NN05739, Theses scanned by UMI/ProQuest. |
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