ABSTRACT
A ladle is a foundry tool or equipment specially designed to pour molten metal into a prepared mould. The pouring rate or consistency is one of the factors that may lead to a defect in a cast. To avoid casting defects (cold shut and misrun) associated with pouring, there is need for the design of a suitable pouring ladle that will reduce the time to be spent in crucible lifting, to pouring the molten metal from the crucible to fill the mould at consistent rate. In this research, a pouring ladlemachine of 50 kg molten Aluminium alloy was successfully designed, constructed and tested. The result of this research showed that the total time spent in lifting the crucible containing molten Aluminium alloy from the furnace to filling the mouldusing the pouring ladle was 53.48 sec while when using the hand-shank ladle was 81.80 sec. The speed of pouring when using the pouring ladle machine and hand-shank ladle were 0.42cm/s, 0.43cm/s respectively.The micrograph of both samples show visible well defined coarse grains. This could be due to the even distribution of the constituents as cooling takes place since no too much time was taken to pour the liquid metal into the mould. The result of the XRF tests shows the presence of the various elements detected in the alloy with their percentages at different energy level with the high percentage of Silicon detected. Thedesigned ladle machinewas able to give casts with no cold shut and misruns cast defects with less time spent and fatigue during pouring.There was time difference of 28.32 sec (34.62 % time saving) and speed difference of 0.01 cm/s (2.33 % speed increase).
TABLE OF CONTENTS
Title Page – – – – – – – – – ii Declaration – – – – – – – – – iii Certification – – – – – – – – – iv Dedication – – – – – – – – – v Acknowledgements – – – – – – – – vi Abstract – – – – – – – – – vii Table of Contents – – – – – – – – viii List of Figures – – – – – – – – – xii List of Plates – – – – – – – – – xiii List of Tables – – – – – – – – – xv List of Appendices – – – – – – – – xvi CHAPTER ONE: INTRODUCTION 1.1 Background of the Study – – – – – – – 1 1.2 Statement of the Problem – – – – – – – 1 1.3 The Present Work – – – – – – – – 2 1.4 Aim and Objectives – – – – – – – 2 1.5 Significance of the Research – – – – – – 3 1.6 Justification of the Research – – – – – – 3 1.7 Scope and Limitations of the Research – – – – – 4 CHAPTER TWO: LITERATURE REVIEW 2.1 Founding or Casting – – – – – – – 5 2.2 Advantages of Casting Process – – – – – – 5 2.3 Description of Ladle – – – – – – – 6
2.4Ladle and their Types – – – – – – – 7
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2.4.1 Hand casting ladle – – – – – – – 7 2.4.2 Hand-shank Casting Ladle – – – – – – 7 2.4.3 Transfer Ladle – – – – – – – – 7 2.4.4 Treatment Ladle – – – – – – – – 8 2.5 Ladle Pour Design- – – – – – – – 9 2.5.1 Lip Pour design – – – – – – – – 9 2.5.2 Teapot Spout design – – – – – – – 9 2.5.3 Lip-axis Design – – – – – – – – 9 2.5.4 Bottom Pour Design – – – – – – – 9 2.6 Review of Related Past Works – – – – – – 10 2.7Knowledge Gap – – – – – – – – 11 CHAPTER THREE: MATERIALS AND METHODS 3.1 Description of the Pouring Ladle Machine – – – – 12 3.2 Design Consideration – – – – – – – 14 3.3Design Theory and Procedure of the Pouring Ladle and its Components 15 3.3.1 Design of the tong gripping system – – – – – 15 3.3.2 Design of the lifting/lowering mechanism – – – – 16 3.3.3 Design of the tilting mechanism – – – – – 18 3.3.4 Design of the railing mechanism – – – – – 19 3.3.5 Design of the machine frame – – – – – – 20 3.3.6 Factor of safety – – – – – – – – 21 3.4 Results of Design Calculation – – – – – – 22 3.4.1 Tong gripping System – – – – – – – 22 3.4.2 Lifting/lowering Mechanism – – – – – – 22 3.4.3 Tilting Mechanism – – – – – – – 24
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3.4.4 Railing Mechanism – – – – – – – 25 3.4.5 Machine Frame – – – – – – – – 26 3.4.6 Factor of Safety – – – – – – – 26 3.5 Selection of Materials for the Fabrication and Assembly of the Pouring Ladle 26 3.5.1 Tong Gripping System – – – – – – – 27 3.5.2 Lifting/lowering Mechanism – – – – – – 27 3.5.3 Tilting Mechanism – – – – – – – 28 3.5.4 Railing Mechanism – – – – – – – 28 3.5.5 Machine Frame – – – – – – – – 28 3.6 Fabrication and Assembly of the Pouring Ladle – – – – 28 3.6.1 Fabrication Process Plan of the Ladle Components – – – 28 3.6.2 Assembly of the Ladle Component Parts – – – – 33 3.6.3 Principle of Operation of the Ladle – – – – – 33 3.6.4 Cost Analysis of the Pouring Ladle – – – – – 34 3.7 Performance Evaluation/Testing of the Pouring Ladle Machine – – 36 3.7.1 Performance Evaluation using Water and Aluminium Alloy Molten Metal 36 3.7.2 Determination of the Speed of Pouring – – – – – 38 3.7.3 Non-destructive Test – – – – – – – 38 CHAPTER FOUR: RESULTS AND DISCUSSION 4.1 Results – – – – – – – – – 40 4.1.1 Result of the Pouring Ladle Machine – – – – – 40 4.1.2 Determination of the Speed of Pouring – – – – – 41 4.1.3 Non-destructive Test – – – – – – – 42 4.2 Discussion of Results – – – – – – – 47 4.2.1 Result of Performance Evaluation of the Pouring Ladle – – 47
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CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Metal casting is one of the most widely used techniques for the production of metal parts. It is the process of forming metallic objects by melting metal, pouring it into a shaped cavity called a mould and allowing it to solidify. Heat is absorbed by and transferred through the mould wall during pouring of molten metal in mould cavity (Choudhari et al., 2014). Pouring of molten metal into a prepared mould is one of the processes involved in the casting process in a foundry. The ladle is the foundry tool or equipment specially designed to pour the molten metal into a prepared mould. This makes the ladle to play a very significant role in the casting process. The pouring process can affect the quality of the casting or cause defect to the cast or fatigue or even injury to the foundry men due the Manual Material Handling (MMH). Some of the factors that can lead to casting defects (such as misruns and cold shut) include; the ladle design or the type of ladle used, the pouring rate or consistency, the shaking or vibration by the foundry men when tilting the casting ladle for pouring process due to tiredness and fatigue and the delay in lifting the crucible from the furnace to pouring of the molten metal into the prepared mould (Konz, 1995).
1.2 Statement of the Problem
It is usually desired that a cast product should not have any defect. But defects occur which may be as a result of the many activities that are involved during casting process. The pouring rate or consistency is one of these factors that may lead to a defect in a cast. In order to avoid a defect which may be as a result of pouring of the molten metal from the crucible (casting defect such as cold shut and misrun), there is need for the design of a suitable ladle that will reduce the time to be spent in crucible lifting, to pouring the molten metal from the crucible into the mould at consistent rate.
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Manual Material Handling (MMH) is one of the major causes of severe industrial injury (Ciriello, 2005; Dempsey and Hashemi, 1999). It has been estimated that more than a quarter of all injuries related to industrial work are directly associated with MMH activities (Konz, 1995). Also, fatigue resulting from lifting of the ladle by two or more operators and bending to tilt it to pour the molten metal from the crucible into the mould affect the pouring rate or consistency. To solve these problems, the ladle was designed to assist the operators to lift and lower the crucible and tilt the fork lift for pouring Aluminium alloy molten metal from the crucible into the prepared mould using crank lever mechanism.
1.3 The Present Work
The research work was focused on the design, construction and testing of an improved casting pouringladlewhich would be used to lift a crucible containing 50kg molten Aluminium alloy metalfrom acrucible furnace and poured it into a prepared mould at a relatively consistent pouring rate with less fatigue on the operators while pouring the molten metal. The time taken for the pouring and speed of pouring from both the ladle machine and manual hand-shank ladle were computed and compared.
1.4 Aim and Objectives
The aim of this research is to design, construct and test an improvedcasting pouring ladle that could be used in a foundry workshop to cast 50 kg liquidAluminium alloy. The specific objectives are:
i. To carry out the design analysis of the improved casting pouring ladle.
ii. To construct the various component parts of the pouring ladle and assemble them.
iii. To carry out performance evaluation in determining the pouring time and speed of the ladle.
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iv. To carry out non-destructive test on the Aluminium alloy casts.
1.5 Significance of the Research
To solve the problems associated with pouring process such as misrun and cold shut, the ladle was designed to assist the operators to lift and lower the crucible and tilt the fork lift for pouring the molten metal from the crucible into the prepared mould using crank lever mechanism. The cost to be incurred in designing a mechanically automated ladle would be reduced to minimum because in this research work, there would be no need for electricity or electric motor, pneumatic or hydraulic system. The operators involved in the pouring process are reduced to one (1) when using this machine because only one operator would be required to operate the machine instead of two or more operators as in the case of using the manual hand-shank ladle for the pouring process.
1.6 Justification of the Research
This research was carried out to design, construct and test an improved casting pouring ladle for Aluminium alloy that would reduce the time delay in lifting and pouring process of casting from a crucible into a mould with less stress and fatigue as in the case of manual hand-shank ladle. There is need for the pouring to be relatively consistent, because inconsistent pouring may cause turbulence or sudden solidification of the molten metal in the gate. Also, when too much time is spent in between lifting of crucible from the furnace to pouring, the molten metal may start to solidify inside the crucible or when it is poured into the mould. These can cause cold shut or misrun.
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Krzystof et al. (2013), stated that one of the most important faults occurring during casting is a misrun, which may be caused both by pouring temperature being too low and insufficient castability of the liquid metal. The posture and heat from the crucible and molten metal induces stress to the operators when using the hand shank ladle for pouting process. This stress makes the operators’ hands to be shaking while pouring. This makes the pouring not to be consistent, thereby causing a casting defect such as cold shut or misrun.
1.7 Scopeand Limitations of the Research
The scope and limitations of this research are:
1. To design and construct a casting ladle of 50 kg charge capacity of molten Aluminium alloy metal for use in sand casting only where the metal is melted in crucible pit furnace.
2. There would be no use of electric motor or hydraulic cranes in design and construction of the improved casting pouring ladle.
3. Only one direction of pouring and so the moulds should be arranged linearly with their sprue basin placed close to the ladle machine.
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