E N H A N C E M E N T OF S U R F A C E QUALITY OF BRASS CASTINGS COST 
EFFECTIVELY USING NATURALLY A V A I L A B L E S A N D A N D CLAY 
AVAILABLE IN SRI LANKA 
By 
G.I.P. De Silva 
Supervised By 
Dr. N. Munasinghe 
A thesis submitted to the Department of Materials 
Engineering in the University of Moratuwa, Sri Lanka, in 
partial fulf i lment of the requirements for the degree of Master 
of Philosophy 
n(> 
Univers i ty of M o r a t u w 
86803 
University of Moratuwa 
July -2006 
86803 
D E C L A R A T I O N 
1 certify that the Thesis with the title "Enhancement of Surface Quality of Brass 
Castings Cost Effectively using Naturally available Sand and Clay available in Sri 
Lanka" is entirely my own work. It has not been accepted for any degree and it is not 
being submitted for any other degree. 
Candidate 
G.I.P De Silva Signature 
Date . ...\9-°3:.-Zf>o(> 
Supervisor 
Dr. N. Munasinghe Signature \^...^..f..^ ~/ 
Date ~ 7 . : . 2 0 0 6 
Declaration I 
ABSTRACT 
Through a survey done for the Sri Lankan foundry industry using a structured 
questionnaire it was revealed that one of the most significant quality parameter of the 
brass casting is the high surface roughness. Properties of the sand clay- mixture, the 
gating system of the mould, composition of the material to be melted and pouring 
temperature are the factors, which affect the surface roughness. Out of these factors the 
attention was focused in this work to the properties of the sand-c lay mixture like fineness 
no., clay content, moisture content and permeability etc. to reduce the surface roughness. 
A synthetically unmodified sand-clay mixtures consisting of natural sand and clay from 
different locations in Sri Lanka were analyzed with respect to the reference sand sample 
(naturally bonded sand-clay mixture) imported from Japan, which gives a considerably 
low surface roughness. 
In this research work the attention was also directed to develop a non-contact method to 
measure the surface roughness of castings using ultrasonic echo amplitude technique. 
With this method it is possible to measure the surface roughness of castings with 
improved accuracy and minimized cost. 
The results of the experimental work done in this work show that it is possible to produce 
several number of mixtures made by mixing different sand and clay available in Sri 
Lanka and those mixtures give a relatively good surface roughness for the brass castings 
with compared to the casting made with Japanese reference sample. 
Abstract II 
ACKNOWLEDGMENT 
Initially, I would like to offer my deepest gratitude to my Supervisor Dr. Nanda 
Munasinghe for his guidance, support and encouragement. Then, to Mr.Y.C.P Costha, 
Foundry Manager, Ceylon Heavy Industries and Company Ltd. (CHICO) for his kind and 
supportive advices. 
In addition to that, I like to express my thanks to Dr. S. U. Adikary, the Head of the 
Department of Materials Engineering and all the academic and non-academic staff 
members of the Department of Materials Engineering, University of Moratuwa for their 
assistance and contribution to my research work. 
Also I like to place on record my appreciation to Mr. Melvin Samarasinghe, Managing 
Director, Agrotechnica Pvt.Ltd. who always encouraged me by providing his fullest 
corporation. Again it is pleasure to thank Industrial Development Board (IDB) 
Katubedda, Paliyagoda, and Pilimathalawa and Foundry Development & Services 
Institute (FDSI) for their support and guidance during every phase of my research. 
I must be indebted to National Science Foundation (NSF) for the awarding of a research 
grant to carry out my research successfully. Thanks are extended to Ceylon Glass 
Company Limited (CGC), Naththandiya for supplying silica sand free of charge. 
At the same time I appreciate and thank to the staff of the Department of Mechanical 
Engineering and Department of Earth Resources Engineering at University of Moratuwa 
for their support and assistance. 
At last but not least, it is indeed to thank my mother and father for their encouragement, 
support and sacrifice. 
G.I.P De Silva 
Department of Materials Engineering, University of Moratuawa. 
Acknowledgment III 
CONTENT 
Declaration I 
Abstract II 
Acknowledgement III 
Content IV 
List of Figures and Tables IX 
List of Terms, Abbreviations and Symbols XIV 
1 Introduction 1 
2 Literature Review 3 
2.1 Introduction to Foundry Technology 3 
2.2 Classification of Casting Processes 6 
2.2.1 Sand Casting Processes 6 
2.2.2 Die Casting Process 10 
2.2.3 Graphite Mold Casting Process 11 
2.2.4 Centrifugal Casting Process 12 
2.2.5 Investment Casting Process 12 
2.2.6 Continues Casting Process 13 
2.3 Factors Influencing the Choice of Casting Process 14 
2.4 Sand-Clay Mixtures use for Sand Casting Process 15 
2.5 Sand Types use for Sand-Clay Mixtures 17 
2.5.1 Availability of Silica Sand in Sri Lanka 19 
2.5.2 Properties of Sand use for Sand-Clay Mixtures 19 
2.6 Clay Mineralogy 22 
2.6.1 Kaolinite 24 
Content IV 
2.6.2 Montmoril lonite 25 
2.6.3 Mite 26 
2.6.4 Identification of Clay Minerals 27 
2.6.4.1 Full Chemical Analysis 27 
2.6.4.2 Differential Thermal Analysis 28 
2.6.4.3 X-ray Diffraction Analysis (XRD) 31 
2.7 Properties and Characteristics of Sand-Clay Mixture 31 
2.7.1 Clay Content 31 
2.7.2 Moisture Content 31 
2.7.3 Permeability 32 
2.7.4 Compression Strength 32 
2.7.5 Shatter Index 30 
2.7.6 Fineness Number 33 
2.7.7 Refractoriness 33 
2.7.8 Mould Hardness 34 
2.8 Defects in Sand Casting 34 
2.9 Surface Roughness Measurement in Engineering 36 
2.9.1 Types of S urfaces 3 6 
2.9.2 Surface Finish Imperfections 37 
2.9.3 Modern Techniques of Measuring the Surface Roughness 38 
2.9.3.1 Stylus Profilometry (Contact Method) 38 
2.9.3.2 Atomic Force Microscope Method (AFM) 39 
- Contact Method 
2.9.3.3 Optical Methods (Non Contact Methods) 40 
2.9.3.4 Electron/iron Beam Method (Non Contact Method) 42 
2.10 Identification of the Problem and Project Plan 43 
3 Surface Roughness Measurement of Castings using Ultrasonic 47 
Echo Amplitude Technique 
3.1 Characteristics of Ultrasonic Beam 47 
Content V 
3.2 Basic Theories in Ultrasonic Echo Amplitude Technique 48 
3.2.1 The Attenuation due to the Transmission Medium 48 
3.2.2 The Attenuation due to the Beam Spread 50 
3.2.3 The Attenuation due to the Surface Roughness 52 
3.3 Procedure 53 
3.3.1 Detecting the Energy loss Made by the Attenuation of the 53 
Medium (Styling gel) 
3.3.2 Detecting the Energy loss made by the Surface of the Casting 55 
' 3.4 Detecting the Relationship between Ultrasonic Measurement and Stylus 56 
Measurement 
3.4.1 Detecting the Attenuation corresponding to Emery papers with 55 
Different Grit Numbers 
3.4.2 Measuring the Surface Roughness of Emery papers by using 56 
Stylus Equipment 
3.5 Discussion 59 
3.5 Conclusions 62 
v
 4 Analysis the Properties of Natural Sand and Clay samples 63 
4.1 Material Testing Equipments and Test Procedures 63 
4.2 Analysing the Shape and Particle Size Distribution of various Sand 75 
Samples 
4.2.1 Analysing the Particle Size Distribution of various Sand 74 
samples 
4.2.2 Analysing the Shape of the Particles of various Sand 78 
Samples 
* 4.3 Assuring the Clay type of Various Clay Samples 78 
4.3.1 Full chemical Analysis of various Clay Samples 79 
4.3.2 Differential Thermal Analysis of various Clay Samples 79 
4.3.3 X-ray Diffraction Analysis of Allaipathuwa and Bangadeniya 79 
Clay 
Content VI 
5 The Surface Roughness and Reusability of Sand- Clay Mixtures 82 
5.1 Analysis the Properties of Mixtures of Natural Sand and Clay 83 
5.2 Assuring The Surface finish of Castings produced using Different 87 
Sand- Clay Mixtures 
5.3 Assuring the Reusability of Different types of Sand-Clay Mixtures 92 
6 Computer Program for select a Suitable Sand- Clay Mixture 95 
6.1 Computer Program (Cast-X) 95 
6.1.1 Flow Chart of the Computer Program 97 
6.1.2 Input and Output Data of Computer Program 98 
7 Discussion 100 
7.1 Quality of the Castings Produced in Local Foundries 101 
7.2 Surface Roughness and Reusability of Developed Sand-Clay Mixtures 103 
7.3 Importance of the Computer Program for Foundry Industry 105 
7.4 Utility of Results taken from Experiments and Tests 105 
8 Conclusions 107 
9 Further Work 109 
10 References 110 
11 Annexes 113 
Annex -A : Computer Programe for Detect the Surface Roughness 
Annex -B : Locations of Natural Sand and Clay Sources 
Content VII 
11 Annexes 113 
Annex -A : Computer Programe for Detect the Surface Roughness 
Annex -B : Locations of Natural Sand and Clay Sources 
Annex -C : DTA Curve of Kiribathgoda Clay 
Annex -D : DTA Curve of Aruwakkalu Clay 
Annex -E : DTA Curve of Allaipaththuwa Clay 
Annex -F : DTA Curve of Bangadeniya Clay 
Annex -G : X R D Curve of Bangadeniya Clay 
Annex -H : X R D Curve of Allaipaththuwa Clay 
Annex - I : X-ray Diffraction Curves of Montmoril lonite Type Clays 
Annex - J : Computer Program for Select the Most Suitable Sand-Clay Mixture. 
Annex - K : The Relationship Between the Surface Roughness and Reusability of 
Different Sand-Clay Mixtures 
Content VIII 
LIST OF FIGURES AND TABLES 
List of Figures 
Figure 1: Main features of a Green Sand Mould 7 
Figure 2: Die Casting Process 11 
Figure 3: Investment Casting Process 13 
Figure 4: Schematic representation of the Continuous Casting Process 14 
Figure 5: Expansion Characteristics of Silica Sand 20 
Figure 6: SEM photographs of the Round Grain Silica Sand Particles 21 
Figure 7: Structure of Silica Tegrahedra showing (a) a Single Tetrahedron, 23 
and (b) a sheet of Tetrahedra 
Figure 8: Structure of Alumina or Magnesia Octahedra showing (a) a Single 23 
Octahedron, and (b) a sheet of Octahedrons 
Figure 9: Schematic representation of Sheets 23 
Figure 10: Schematic representation of Kaolin Structure 24 
Figure 11: Schematic representation of Montmorillonite Structure 26 
Figure 12: Schematic representation of Illite Structure 26 
Figure 13: D.T.A. Curves for Group 1(1) and Group 1(H) Clays 29 
Figure 14: D.T.A. Curves for Group l(III) Clays 29 
Figure 15: D.T.A. Curves for Group II Clays 30 
Figure 16: D.T.A. Curves for Group III Clays 30 
Figure 17: Surface Characteristics 37 
Figure 18: Schematic Diagram of Surtronic 2 38 
Figure 19: A Hypothetical Profile of a Surface 38 
Figure 20: Various Roughness Parameters 39 
Figure 2 1 : The Mechanism of the A F M Method 40 
Figure 22: Ampli tude and Width of the Surface Features 41 
Figure 23: Analysis of Casting Defects 43 
Figure 24: Factors affect to the Surface Roughness of the Sand Castings 44 
Figure 25: Attenuation Losses during Transmission 49 
Figure 26: Shape of a Typical Sound Beam from a Circular Transducer 50 
List of figures and tables IX 
Figure 27: Distribution of Intensity along the Axial Distance 51 
Figure 28: CRT Screen Appearance Corresponding to Point, P 51 
Figure 29: The Effect of Scattering for the Attenuation made by the 53 
Rough and Wavy Surfaces 
Figure 30: Detecting the Energy loss due to the Attenuation of the Couplant Medium 54 
Figure 31 : Detecting the Energy loss due to the Attenuation of the 55 
Surface of the Casting. 
Figure 32: Schematic diagram of Surtronic 2 57 
Figure 33: The Relationship between the Ultrasonic Measurement and the 58 
Stylus Measurement 
Figure 34: The Linear Relationship between the Ultrasonic Measurement and 59 
the Logarithmic value of Stylus Measurement 
Figure 35: Analyzing the Surface Roughness of Castings with various Sizes 61 
Figure 36: C R T Screen appearance corresponding to the Large No . 62 
of 1 s t Back Wall Echoes 
Figure 37: Clay content Testing Machine 63 
Figure 38: Methylene blue Clay Tester 64 
Figure 39: Ultrasonic clay Tester Accessory 65 
Figure 40: Sieve Shaker 66 
Figure 4 1 : Moisture Teller 67 
Figure 42: AFS Standard Rammer 68 
Figure 43: AFS Standard Sample 68 
Figure 44: Electric Permmeter 69 
Figure 45: Universal Sand Strength Machine 69 
Figure 46: Shatter Index Tester 71 
Figure 47: Atomic Absorption Spectrometer 71 
Figure 48: Thermal Analyzer 72 
Figure 49: X-Ray Diffractometer 72 
Figure 50: Oil fired Brass melting Furnace 73 
Figure 51 : Sieving Machine 74 
Figure 52: Particle size distribution of various sand and soil 76 
List of figures and tables X 
Samples (Sieved by 355pm mesh) 
Figure 53: Shape of the particles of Eththale Sand 78 
Figure 54: Shape of the particles of Japanese Sand 78 
Figure 55: Shape of the particles of Naththandiya Sand 78 
Figure 56 : Steps of Sand Casting Process 88 
Figure 57: Flow chart of the mathematical model 97 
Figure 58: Analysis of Responses of the Districts 98 
Figure 59: Analysis of types of Foundries 99 
Figure 60: Analysis of Foundry Items 101 
List of Tables 
Table 1: Properties of Foundry Sand 17 
Table 2: Chemical Composit ion of Foundry Sand 18 
Table 3: Chemical Analysis of Selected Samples of Clay from the Various Groups 27 
Table 4: Casting Defects and Remedies for Defects 34 
Table 5: Readings for detect the Attenuation due to The Couplant 54 
medium (Styling Gel) 
Table 6: Readings for detect the Attenuation due to the Surface of the Casting 55 
Table 7: Readings for detect the Attenuation due to the Roughness of the Sand 57 
Papers 
Table 8: Stylus Measurement and Ultrasonic Measurement for Sand Papers 58 
Table 9: Modern Techniques of measuring the Surface Roughness 60 
Table 10: Sieve Analysis of Japanese Soil 75 
Table 11: Sieve Analysis of Naththandiya Sand 76 
Table 12: Sieve Analysis of Eththale Sand 76 
Table 13: Sieve Analysis of Nawakkadu Sand 76 
Table 14: Full Chemical Analysis of various Clay Samples 78 
Table 15: Details taken from the X R D Curve of Allaipaththuwa Clay 79 
Table 16: Details taken from the X R D Curve of Bangadeniya Clay 80 
List of figures and tables XI 
Table 17: Selected Details from the X R D Curve of Nontronite (Annex-I) 80 
Table 18: Gel Indexes of Allaipathuwa and Bangadeniya Clays 81 
Table 19: Active Clay Content of Different Clays 82 
Table 20: Suitable Percentages of Different Clays to prepare 83 
Sand - Clay Mixtures 
Table 2 1 : Properties of Mixtures of Eththale sand (E) and Bangadeniya 84 
Clay (B ) under Various Proportions 
Table 22: Properties of Mixtures of Eththale sand (E) and Allaipaththuwa clay (AL) 84 
under Various Proportions 
Table 23: Properties of Mixtures of Naththandiya sand (N) and Bangadeniya 84 
clay (B ) under Various Proportions 
Table 24: Properties of Mixtures of Naththandiya sand (N) and Allaipaththuwa 84 
clay (AL) under Various Proportions 
Table 25: Properties of Mixtures of Ettale sand (E) and Kiribathgoda clay (K) 85 
under Various Proportions 
Table 26: Properties of Mixtures of Nattandiya sand (N) and Kiribathgoda 85 
clay (K) under Various Proportions 
Table 27: Properties of Mixtures of Ettale sand (E) and Aruwalckalu 86 
clay (AR) under Various Proportions 
Table 28 : Properties of Mixtures of Nattandiya sand (N )and Aruwakkalu 87 
clay ( A R ) under various Proportions 
Table 29: Properties of Japanese Soil 87 
Table 30: Surface Roughness of Castings produced using Eththale sand (E) 89 
and Bangadeniya Clay (B) 
Table 3 1 : Surface Roughness of Castings produced using Eththale sand (E) 89 
and Allaipaththuwa clay (AL) 
Table 32: Surface Roughness of Castings produced using Naththandiya sand (N) 89 
and Bangadeniya clay (B ) 
Table 33: Surface Roughness of Castings produced using Naththandiya 89 
sand (N) and Allaipaththuwa clay (AL) 
Table 34: Surface Roughness of Castings produced using Ettale sand (E) 90 
List of figures and tables XII 
and Kiribathgoda clay (K) 
Table 35: Surface Roughness of Castings produced using Nattandiya sand (N) 90 
and Kiribathgoda clay (K ) 
Table 36: Surface Roughness of Castings produced using Ettale sand (E) 90 
and Aruwakkalu clay (AR) 
Table 37: Surface Roughness of Castings produced using Nattandiya sand (N ) 90 
and Aruwakkalu clay ( A R ) 
Table 38: Surface Roughness of Casting which was produced using Japanese Sand 91 
Table 39: Reusability of different Sand-Clay Mixtures 93 
Table 40: Details of the Sand and Clay Sources 99 
Table 4 1 : Comparison of Properties of "NK" Mixtures with Japanese Sand 102 
Table 42: Comparison of Active clay (%) and Reusability of " N K " Mixtures 102 
with Japanese Sand 
Table 43: Comparison of Active clay (%) and Reusability of " N A L " and 104 
" E A L " Mixtures with Japanese Sand 
Table 44: Comparison of Properties of " N A L " Mixtures with Japanese Sand 104 
List of figures and tables XIII 
LIST OF TERMS, ABBREVIATIONS AND SYMBOLS 
AA Arithmetical Average 
RMS Root mean square 
CLA Center Line Averages 
h Ordinates 
Ra Arithmetical Average Roughness 
n Number of ordinates 
Rq R M S Roughness 
Rv Valley Roughness 
Rp Peak Roughness 
Rt Total Roughness 
L Assessment length 
1 Sampling length 
Rz Maximum peak to valley height of the profile in the assessment length 
AFM Atomic Force Microscope 
'ITS Total Integrated Scatter 
BRDF Bi-directional Reflectance Distribution Function 
a m Attenuation due to the transmission medium 
otb Attenuation due to the beam spread 
a c Attenuation due to the surface roughness 
a Total attenuation 
a c Attenuation due to the emery paper 
ctt Attenuation due to the medium ,beam spread and glass sheet 
a ' t Attenuation due to the medium ,beam spread, glass sheet and surface 
AFS American foundrymen's society 
GCS Green Compression Srength 
DTA Differential Thermal Analysis 
XRD X-Ray Diffraction 
X Wavelength 
0 Angle of incidence 
List of terms, abbreviations and symbols XIV