Document Type

Thesis

Date of Degree

Spring 2016

Degree Name

MS (Master of Science)

Degree In

Mechanical Engineering

First Advisor

Christoph Beckermann

Abstract

Riser sleeve thermophysical properties for simulation are developed using an inverse modeling technique. Casting experiments using riser sleeves are performed in order to measure temperatures in the liquid steel, the riser sleeve, and the sand mold. Simulations are created and designed to replicate the casting experiments. Riser sleeve material thermophysical properties are iteratively modified until agreement is achieved between the simulation and the measured data. Analyses of sleeve material performance are carried out using the developed thermophysical properties. The modulus extension factor (MEF) is used to quantify sleeve performance and is determined for all riser sleeve materials studied here. Values are found to range from 1.07 to 1.27. A sleeve material's effects on casting yield are shown to depend only on the MEF and therefore a sleeve's exothermic or insulating properties serve only to increase the overall quality of the sleeve, expressed by the MEF, and do not independently affect the casting yield at any casting size studied here. The use of riser sleeves is shown to increase the maximum yield up to 40% for chunky castings, however increases of only 8% are observed for very rangy castings. Riser sleeve thickness is shown to be extremely influential on casting yield. Scaling the sleeve thickness by the riser diameter shows that, for a typical sleeve, an optimum riser sleeve thickness is 0.2 times the riser diameter for chunky castings. A scaled sleeve thickness of 0.1 is found to be an optimum sleeve thickness for very rangy castings. Below a scaled sleeve thickness of 0.1 sleeve performance is found to be highly sub-optimal.

Public Abstract

The usage of riser sleeves is ubiquitous within the metal casting industry. Despite the heavy usage of sleeves, there is little literature discussing their thermophysical properties. In this study, riser sleeve thermophysical properties for simulation are developed using an inverse modeling technique. Casting experiments using riser sleeves are performed in order to measure temperatures. Simulations are performed to replicate the experiments. Riser sleeve thermophysical properties are iteratively modified until agreement is achieved between the simulation and the measured data. These finalized properties can be used to effectively predict and therefore optimize the solidification behavior of a given casting. Analyses of sleeve performance are carried out using the developed properties. The modulus extension factor (MEF) is used to quantify sleeve performance and is determined for all riser sleeve materials studied here. A sleeve material’s effects on casting yield are shown to depend only on the MEF and therefore a sleeve’s exothermic or insulating properties serve only to increase the overall quality of the sleeve, expressed by the MEF, and do not independently affect the casting yield at any casting size studied here. Riser sleeves are found to substantially increase the maximum achievable yield for chunky castings but rangy castings only experience small increases in yield due to sleeve usage. Riser sleeve thickness is shown to be extremely influential on casting yield. By observing sleeve thickness effects on the casting yield, optimum sleeve thicknesses for chunky and rangy castings are discerned. An effective lower threshold sleeve thickness is also described.

Keywords

publicabstract, metal casting, modulus, riser, riser sleeve

Pages

xiii, 81

Bibliography

80-81

Copyright

Copyright 2016 Thomas John Williams

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