performance study of lm6 alloy castings produced by investment casting process

117 Pages·2014·6.77 MB·English

PERFORMANCE STUDY OF LM6 ALLOY CASTINGS
PRODUCED BY
INVESTMENT CASTING PROCESS
A DISSERTATION
Submitted in partial fulfilment of the
requirements for the award of the degree
of
MASTER OF TECHNOLOGY
in
MECHANICAL ENGINEERING
(With Specialization in Production and Industrial Systems Engineering)
By
SANJEEV BIIANDARI
T AL L~
~~a J) 7_-x.0
cc. No..........
ate. o Li
in
DEPARTMENT OF MECHANICAL AND INDUSTRIAL ENGINEERING
INDIAN INSTITUTE OF TECHNOLOGY ROORKEE
ROORKEE-247 667 (INDIA)
JUNE, 2004
CANDIDATE'S DECLARATION
I here by declare that the work, which is being presented in the dissertation
entitled "PERFORMANCE STUDY OF LM6 ALLOY CASTINGS PRODUCED
BY INVESTMENT CASTING PROCESS", in the partial fulfillment of the
requirement, for the award of the degree of MASTER OF TECHNOLOGY in
MECHANICAL ENGINEERING with specialization in PRODUCTION AND
INDUSTRIAL SYSTEMS ENGINEERING submitted to the Department Of
Mechanical And Industrial Engineering, T.T.T. Roorkee, Roorkee (India) is an
authentic record of my own work carried out from July-2003 to June-2004 under the
supervision of Dr. Pradeep Kumar, Professor, Department Of Mechanical And
Industrial Engineering, I.I.T. Roorkee, Roorkee(India).
I have not submitted the matter embodied in this dissertation for the award of any
other degree or diploma.
Date ~gte616 y

Place Roo-t~e~ Sanjeev Bhandari
CERTIFICATE
This is to certify that the above statement made by a candidate is correct to the best of
my knowledge.
(Dr. Pradeep Kumar)
Professor
Mechanical & Industrial Engineering Dept.
Indian Institute of Technology, Roorkee
Roorkee-247667
1
ACKNOWLEDGEMENT
I express my deep and sincere sense of gratitude from the core of my heart to
Dr. Pradeep kumar, Professor, Mechanical and Industrial Engineering Department,
Indian Institute of Technology, Roorkee, for his inspiring and painstaking
supervision, encouragement and invaluable help during the course of this dissertation
work without which this work would not have been possible.
I would like thanks to the staff of Foundry Engineering Laboratory, Foundry
Shop, Fitting Initiation Centre, Metrology laboratory, Fabrication Section (WRL),
Welding Testing Laboratory, Welding Metallurgy Laboratory of Mechanical and
Industrial Engineering Department for their help and co-operation during the work.
Special thanks are due to Prem Vats, Bijender Sharma, Jagpal Singh and Pradeep
Kumar of WRL for their untiring help during the work
I would like to thank Mr. Sudhir, Mr. Ravinder Walia, Mr. Rahul Chhibber,
Research Scholars, Mechanical and Industrial Engineering Department for providing
valuable suggestions and full cooperation during the work.
I would like to express my gratitude to my mother for her kind blessings and
Miss Amita for providing- moral support and encouragement throughout this project
work.
Sanjeev Bhandari
11
ABSTRACT
The casting of liquid metals to produce solid objects is a manufacturing process that
has been practiced for over 5000 years, with investment casting being one of the
oldest known metals shaping methods Investment casting / precision casting or the
"lost wax" or "Cire Perdue" process. There are number of advantages that have been
claimed for investment casting process in comparison to ordinary sand casting
process. As there is no difficult to remove the pattern so complex shapes can be
produced by this process. It is an ideal process for achieving desired dimensional
accuracy as no rapping allowance has to given. Any metal can be shaped by this
process. The objective of the present work is to find the optimum wax — mix and then
to investigate the effect of various investment casting process parameters on the
quality of the castings and to obtain the optimal sets of process parameters. The
Taguchi technique has been used to investigate the effect of the investment casting
process parameters and subsequently to predict sets of optimal parameters for
optimum quality characteristics.
The investment casting process parameters considered were the type of
binder, wax composition, firing temperature of mould and pouring temperature.
Influences of these parameters were studied on mechanical properties of LM6 alloy
castings.
iii
CONTENTS
Page No.
CANDIDATE'S DECLARATION i
ACKNOWLEDGEMENT ii
ABSTRACT iii
CONTENTS iv
LIST OF FIGURES vii
LIST OF TABLES x
CHAPTER 1 INTRODUCTION AND PROBLEM FORMULATION
1.1 INTRODUCTION 1
1.2 TAGUCHI TECHNIQUE 2
1.3 STATEMENT OF THE PROBLEM 2
1.4 OBJECTIVES OF THE PRESENT INVESTIGATION 3
CHAPTER 2 REVIEW OF LITERATURE
2.1 INTRODUCTION 4
2.2 INVESTMENT CASTING PROCESS 4
2.2.1 Pattern Production 5
2.2.2 Pattern Assembly 6
2.2.3 Ceramic Shell Process 6
2.2.4 Dewaxing 10
2.2.5 Firing 10
2.2.6 Casting 11
2.2.7 Cleaning 12
2.2.8 Finishing 12...
2.3 PATTERN MATERIALS 13
2.3.1 Types of Wax 13
2.3.1.1 Physical properties of waxes 14
2.3.2 Other Investment Casting Pattern Materials 16
2.3.2.1 Plastics 16
2.3.2.2 Mercury 16
2.3.2.3 Nonconventional pattern materials 16
2.4 REFRACTORY MATERIALS 16
2.4.1 Fused silica 16
iv
2.4.2 Zircon (zirconium orthosilicate) 17
2.5 BINDERS 18
2.5.1 Sodium Silicate 18
2.5.2 Calcium Aluminate Cements 20
2.5.3 Bentonite 21
2.6 EVALUATION OF CASTING QUALITY 21
2.6.1 Soundness 21
2.6.2 Dimensional accuracy 21
2.6.3 Surface finish 22
2.6.4 Size 22
2.6.5 Physical properties 22
2.7 PROCESS VARIABLES AFFECTING CASTING QUALITY 23
IN INVESTMENT CASTING PROCESS
2.7.1 Factors Affecting Dimensional Accuracy 23
2.7.1.1 Wax pattern 23
2.7.1.2 Production of ceramic moulds 23
2.7.1.3 Pouring temperature of metal 24
2.7.1.4 Parting line 24
2.7.1.5 Wax injection 24
2.7.1.6 Temperature of stored patterns 24
2.7.1.7 Cleaning and finishing 24
2.7.2 Factors Affecting Surface Finish 25
2.7.2.1 Condition of pattern 25
2.7.2.2 Condition of precoat 25
-
2.7.2.3 Method of making mould 25
2.7.2.4 Method of casting 25
2.7.2.5 Metal being cast 25
2.7.2.6 Method of cleaning the casting 25
2.8 ADVANTAGES OF INVESTMENT CASTING PROCESS 25
2.9 LIMITATIONS OF INVESTMENT CASTING PROCESS 26
2.10 APPLICATIONS OF INVESTMENT CASTING PROCESS 26
2.11 CASTING DEFECTS 27
CHAPTER 3 EXPERIMENTAL PROCEDURE, EXPERIMENTATION AND
MEASUREMENT
v
3.1 DESIGN OF PATTERN 29
3.2 DESIGN OF DIE 30
3.3 EXPERIMENTAL DESIGN STRATEGY 32
3.4 SELECTION OF PROCESS PARAMETERS 33
AND THEIR LEVELS
3.4.1 Part 1: Wax characteristics 34
3.4.2 Part 2: Casting Quality Characteristics 35
3.5 EXPERIMENTATION 36
3.6 ANALYSIS PROCEDURE FOR L OA 45
3.6.1 Response Data Analysis 45
CHAPTER 4 ANALYSIS OF RESULTS & DISCUSSION
4.1 EFFECT OF WAX - MIX ON WAX PATTERN QUALITY 52
CHARACTERISTICS
4.1.1 Effect of Wax - Mix on % Shrinkage of the Wax Patterns 52
4.1.2 Effect of Wax - Mix on Surface Roughness of the 58
Wax Patterns
4.2 EFFECT OF PROCESS PARAMETERS ON CASTING 62
QUALITY CHARACTERISTICS
4.2.1 Effect of Process Parameters on Hardness of the Castings 62
4.2.2 Effect of Process Parameters on Tensile Strength of 68
the Castings
4.2.3 Effect of Process Parameters on Impact Strength of 73
the Castings
4.2.4 Effect of Process Parameters on Surface Roughness of 77
the Castings
4.2.5 Effect of Process Parameters on Porosity of the Castings 83
4.2.6 Effect of Process Parameters on % Elongation of the 88
Castings
CHAPTER 5 CONCLUSIONS AND SUGGESTIONS FOR FUTURE WORK
5.1 CONCLUSIONS 93
5.2 SUGGESTIONS FOR FUTURE WORK 96
REFERENCES 97
APPENDIX 99
vi
LIST OF FIGURES
Figure Description Page
2.1 Injection of wax into die 5
2.2 The removal of the solidified pattern from the die 6
2.3 Assembling the cluster 8
2.4 Pattern assembly dipped in ceramic slurry 8
2.5 The pattern assembly dipping is repeated until required wall 8
thickness of mold is produced
2.6 Effect of number of coats on thickness of a ceramic of a shell mold 9
2.7 The ceramic shell containing required casting shape 9
2.8 Dewaxing of the shell mold 10
2.9 Firing of shell mold 10
2.10 Typical time-temperature cycle for dewaxing (zone 1), firing (zone 2), 11
preheating (zone 3), and holding (zone 4) of solid investment molds
in a four-zone pusher-type furnace Pouring of metal in cavity
2.11 Pouring of metal in cavity 11
2.12 The cleaning of casting 12
2.13 Final castings 12
2.14 Flow under an applied stress 14
2.15 Thermal expansion of a typical wax with increasing temperature 15
2.16 Effect of temperature on linear expansion of graded-silica, 17
phosphate-bonded investment mold material used in a
producing steal castings
2.17 Typical time-temperature cycle for precoating zircon shell molds placed 18
2.18 Si02-Na2O-H20 system 19
2.19 Green strength vs. Mixing time 20
3.1 Shape of Casting Required 29
3.2 Isometric View of Two Piece Brass Die 31
3.3 Ishikawa Cause -- Effect diagram 33
3.4 Furnace used for heating the wax 37
3.5 wax patterns made according to Table 3.3 37
3.6 Furnace used for dewaxing and firing of moulds at different temperature 40
3.7 LM6 alloy castings produced by investment casting process 40
VII
3.8 Impact specimen and tensile specimen after testing 41
3.9 Microstructure and Hardness testing specimen 41

3.10 Experiment Design Flow Diagram 51
3.11 Analysis Flow Diagram 51
4.1 Average Value of % Shrinkage of wax pattern for each trial 53
4.2 Signal to Noise Ratio for each Trial 55
[Response: % Shrinkage of Wax Pattern]
4.3 Effects of Various waxes used on Average values and Signal to Noise 57
Ratio values [Response: % Shrinkage of wax pattern]
4.4 Average Value of Surface Roughness of wax pattern for each Trial 58
Signal to Noise Ratio for each Trial [Response: Surface Roughness
of Wax Pattern]
4.5 Effects of Various waxes used on Average values and Signal to Noise 60
Ratio values [Response: Surface Roughness of wax pattern]
4.6 Average Value of Hardness for each Experiment 61
4.7 Signal to Noise Ratio for each Experiment [Response: Hardness] 63
4.8 Effects of Various Process Parameters on Average values and 64
SIN values [Response: Hardness]
4.9 Average Value of Tensile Strength for each Experiment 66
4.10 Signal to Noise Ratio for each Experiment 68
[Response: Tensile Strength]
4.11 Effects of Various Process Parameters on average values and Signal to 69
Noise Ratio values [Response: Tensile Strength]
4.12 Average Value of Impact Strength for each Experiment 71
4.13 Signal to Noise Ratio for each Experiment 73
[Response: Impact Strength]
4.14 Effects of various process parameters on average values and signal 75
to noise ratio values [response: impact strength]
4.15 Average value of surface roughness for each experiment 76
4.16 Signal to noise ratio for each experiment 78
[response: surface roughness]
4.17 effects of various process parameters on average values and signal 80
to noise ratio values [response: surface roughness]
4.18 Average value of % porosity for each experiment 81
viii
4.19 Signal to noise ratio for each experiment
[response: porosity]
4.20 effects of various process parameters on averages values and signal 86
to noise ratio values [response: % porosity]
4.21 Average value of % elongation for each experiment 88
4.22 Signal to noise ratio for each experiment 90
[response: % elongation]
4.23 Effects of various process parameters on average values and signal 91
to noise ratio values [response: % elongation]
Cl Interactions between different parameters of investment casting 101
process based on average values [Response: % Porosity]
C2 Interactions between different parameters of investment casting 102
process based on average values [Response: Hardness]
C3 Interactions between different parameters of investment casting 103
process based on average values [Response: % Elongation]
C4 Interactions between different parameters of investment casting 104
process based on average values [Response: Impact Strength]
C5 Interactions between different parameters of investment casting 105
process based on average values [Response: Surface Roughness]