Optimizing Green Sand Properties of Fluidized Sand from Aeration and Developing New Green ...

306 Pages·2016·10.96 MB·English

by  Ananda Mani Paudel

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Dissertations Graduate College
5-2010
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Ananda Mani Paudel
Western Michigan University
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Paudel, Ananda Mani, "Optimizing Green Sand Properties of Fluidized Sand from Aeration and Developing
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OPTIMIZING GREEN SAND PROPERTIES OF FLUIDIZED SAND FROM
AERATION AND DEVELOPING NEW GREEN SAND
TESTING TECHNIQUE
by
Ananda Mani Paudel
A Dissertation
Submitted to the
Faculty of The Graduate College
in partial fulfillment of the
requirements for the
Degree of Doctor of Philosophy
Department of Industrial and Manufacturing Engineering
Advisor: Sam Ramrattan, Ph.D.
Western Michigan University
Kalamazoo, Michigan
May 2010
UMI Number: 3410416
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OPTIMIZING GREEN SAND PROPERTIES OF FLUIDIZED SAND FROM
AERATION AND DEVELOPING NEW GREEN SAND
TESTING TECHNIQUE
Ananda Mani Paudel, Ph.D.
Western Michigan University, 2010
Aeration sand filling is a new molding technique in foundry. Using this
technique, sand with smooth flow can be filled in any orientation and shape using
low-pressure air. This is not possible by conventional gravity and high-pressure blow
filling techniques. Aeration was introduced as an energy-efficient and
environmentally- friendly sand molding technique. In addition, aeration has its niche
on quality of molds it could produce. Friability, one of the crucial green properties for
the quality mold was significantly low in aeration in comparison to the gravity and
high-pressure blow filling. The fluidization action in aeration acted upon the sand clay
interfaces and created the interactions with them, and induced better surface abrasive
property. In other words, aeration lowered the friability in the green sand allowing a
lower compactibility levels in green sand molding, which was not possible with the
conventional molding techniques. The range of 30-35% was suggested as the optimal
working range of compactibility for aeration molding technique for selected sand and
clay composition.
Advance cone jolt and thermal erosion tester were developed and used to
examine the green sand properties of the foundry sand. Advance cone jolt was
sensitive to the clay composition and contamination in green sand, whereas thermal
erosion tester demonstrated its relevance in evaluating mold surface behavior at an
elevated temperature. Thermal erosion test displayed less sand erosion in the molds
built in the aeration.
Green sand in aeration was benefited by the favorable clay orientation.
Homogeneous and isotropic distribution of clay platelets occurred during fluidization,
which produced a better clay coating on the sand grains and increased the grain to
grain bonding. Scanning electron microscope displayed a uniform clay coating and
universal micro-tribometer showed greater bonding strength in the surface of the
molds produced in aeration. Casting trial along with the relevant standard AFS tests
for green sand properties were carried out, and analyzed using design of experiments
and statistical tools.
Copyright by
Ananda Mani Paudel
2010
ACKNOWLEDGEMENTS
I would like to express my gratitude to my dissertation advisor, Professor Sam
Ramrattan for his patience, guidance and counsel throughout this research. This research
also benefited from the numerous communiques and advice from Professor Pnina Ari-
Gur. I am thankful to Professor Steven Butt, Professor Leonardo Lamberson and
Professor Tarun Gupta for reviewing my work and providing valuable suggestions.
My special thanks to Dr. Hiroyasu Makino from Sintokogio, Japan for his support and
technical assistance. I would like to thank Dr. Mitchel Keil, Mr. Deepak Ravindra and
Ms. Debbie Aliya for their help during the course of experiments and sharing technical
expertise. I am equally thankful to Mr. Glen Hall, Mr. Peter Thannhauser and Mr.
Abraham Poot, for their technical support, and Mr. Kamaleshwaran Nagarajan, and Mr.
Rajiv Bharadwaj for their help in conducting the experiments.
Finally, I am grateful to my mom for her inspiration, and my wife, Puspa,
daughter, Bhawana, and son, Aaron, for their sacrifices and continual support during
these years of my study.
Ananda Mani Paudel
u
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
LIST OF TABLES ix
LIST OF FIGURES xi
CHAPTER
I. INTRODUCTION 1
H. LITERATURE REVIEW 6
Sand Molding Techniques 6
Gravity Filling 7
High-pressure Blow 8
Aeration Filling 9
Fluidizing Bed 12
Fluidizing Mechanism 12
Viscosity of Fluidized Sand 14
Molding Materials 15
Sand 15
Silica Sand 16
Olivine 18
Chromite 18
Ceramic Media 19
in
Table of Contents-Continued
CHAPTER
Clay 19
Electrostatic Force 21
Surface Tension 22
Frictional Force 22
Water 23
Relationship between Clay and Moisture 24
Critical Bentonite Content 24
Water/ Effective Clay Ratio 25
Green Sand Properties and AFS Sand Test 26
Compactibility 26
Moisture Content 28
Bulk Density 28
Permeability 28
Green Compressive Strength 30
Splitting Strength 31
Mold Hardness 31
Percent Friability 31
Sand Toughness 33
Flowability 34
Volatility 34
iv
Table of Contents-Continued
CHAPTER
Sand Control Program 35
Sand/Metal Ratio 37
Chemical Properties 37
Alternative Sand System 38
Friability in Green Sand 39
Casting Defects Due to Moisture 42
Water Explosion 43
Scabbing 43
Friability Related Casting Defects 46
Comments on AFS Standard Tests 46
Cone Jolt Toughness Test 47
Erosion Test 48
AFS Standard Testing Procedure 49
Preparation of Green Sand 49
Design of Experiments 51
Sand-Clay Interactions 51
X-ray Diffraction 51
Scanning Electron Microscope (SEM) 53
Universal Micro-tribometer 54
m. OBJECTIVE 56
IV. METHODOLOGY 60
v