final project report submision

Patent Search and Analysis Report (PSAR) Reports

“Casting Defects in Aluminium Bronze and Enhancing the Mechanical Property By Heat

Trreatment.”

Submitted by

Tirth S. Upadhyay (Enrollment No.: 100870119007)

Vamit R. Patel (Enrollment No.: 100870119019)

Abhishek A. Tantia (Enrollment No.: 100870119058)

Nirav A. Patel (Enrollment No.: 110873119007)

In partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING

in

MECHANICAL ENGINEERING

Parul Institute of Technology

P.O: Limda, Ta.:Waghodia, Dist.: Vadodara

Gujarat Technological University,Ahmedabad,

1

MAY, 2014

Parul Institute of TechnologyP.O: Limda, Ta.:Waghodia, Dist.: Vadodara

DECLARATION

We hereby declare that the PSAR Reports, submitted along with the Project Report for the project entitled “Casting Defects in Aluminium Bronze and Enhancing the Mechanical Property By Heat Treatment.” submitted in partial fulfillment for the degree of Bachelor of Engineering in Mechanical Engineering to Gujarat Technological University, Ahmadabad, is a bonafide record of the project work carried out at Parul Institute of Technology, Limda under the supervision of Mr. Prashantsingh Tomar Sir and that no part of any of these PSAR reports has been directly copied from any students’ reports or taken from any other source, without providing due reference.

Name of The Students Sign of Students

1. Tirth S. Upadhyay

2. Vamit R. Patel

3. Abhishek A. Tantia

4. Nirav A. Patel

2

Parul Institute of Technology

P.O: Limda, Ta.:Waghodia, Dist.: Vadodara

CERTIFICATE

This is to certify that the PSAR reports, submitted along with the project entitled

“Casting Defects in Aluminium Bronze and Breaking of Material During

Machining.” has been carried out by Tirth Upadhyay, Vamit Patel, Abhishek

Tantia & Nirav Patel under my guidance in partial fulfillment for the degree of

Bachelor of Engineering in Mechanical Engineering 7th Semester of Gujarat

Technological University, Ahmadabad during the academic year 2013-14. These

students have partially completed PSAR activity under my guidance.

Internal Guide Head of the Department

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PHASE 1

Gujarat Technological UniversityTeam Id : 130008137

Project Team Member

Enrollment Number Student Name College Name Branch Name

100870119007 Tirth Upadhyay Parul Institute Of Technology, Limda

Mechanical Engineering

100870119019 Vamit Patel Parul Institute Of Technology, Limda


100870119058 Abhishek Tantia Parul Institute Of Technology, Limda


110873119007 Nirav Patel Parul Institute Of Technology, Limda


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ACKNOWLEDGMENTSOur first and sincere appreciation goes to Mr. Bhavesh. G. Mewada, for being our senior supervisor, for all we have learned from him and for his continuous help and support in all stages of this project. We would also like to thank him for being an open person to ideas, and for encouraging and helping us to shape our interest and ideas.

We would like to express our deep gratitude and respect to Miss. Alice D’souza whose advices and insight was invaluable to us. For all we learned from her.

In addition, we would like to thank Mr. Prashantsingh ToMar for accepting to be our supervisor in this project and for his vast knowledge in the field of Metallurgy, which helped us to address our research question. Also, thanking him for accepting to be the internal guide.

We would like to thank our family, especially our parents for always believing in us, for their continuous love and their supports in our decisions. Without whom we could not have made it here.

In the end, we would like to thank Mr. Raghvendra Joshi and Cyprum Casting for providing us with all necessary equipments and the support whenever we required. It also provided us the instruments that we used for this research.

We would extend my regards to all those who directly or indirectly were involved in this project and a warm regards to all my other group members without whom this project would never have been possible.

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Project: IDP

Definition: Casting defects in Aluminium Bronze and Enhancing its Mechanical Properties by Heat Treatment

Company: Cyprum Casting,Makarpura G.I.D.C.,Vadodara.

ABSTRACT

Aluminium bronze is a type of bronze in which aluminium is the main alloying metal added to copper, in contrast to standard bronze (copper and tin) or brass (copper and zinc). A variety of aluminium bronzes of differing compositions have found industrial use, with most ranging from 9% to 14% aluminium by weight, the remaining mass being copper; other alloying agents such as iron, nickel, manganese and silicon are also sometimes added to aluminium bronzes.

The company makes aluminum bronze bush used to prevent wear in shafts. The work piece of composite material of aluminum bronze having composition of 5% Nickel, 5% Iron, 10% Aluminum and 80% Copper. It is prepared by the metal casting process. The Aluminum used belongs to the grade C95500. The material undergoes breakage during machining and due to which the company faces high rejection. Our motto is to try to reduce the reduction rate and resulting in high profitability to the firm.

We tried to achieve the result by varying the composition of aluminium in aluminium bronze but by conducting various respective testing we observed that aluminium content should be increased but limited up to 14% in aluminium bronze.

Secondly we tried to change the composition of alloying elements like iron, nikel and manganese whose results are mentioned later in the report but we didn’t get satisfying output. We also tired changing the pouring temperature and came to the conclusion that it should be maintained in the range

of 1000 to 1300℃ .Then we checked for the pouring height of the metal but it didn’t play a major role in avoiding oxide formation. Then studying the microstructure which we got through SEM testing we learnt that the formation of slag in the molten metal resulted into the oxide formation in the casting. To avoid it we added composition of flux into molten metal which results in floating of slag above the molten metal and which made it easily removable before poring it into the mould. The casting produced with the use of flux resulted in reduction of oxide formation drastically and the material didn’t break during machining.

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We also tried to study the effect of heat treatment on various mechanical properties and tried to improve the properties of aluminium bronze alloy which resulted in the increase of its application.

INDEX1 Introduction 13

1.1 Introduction to Aluminium Bronze 13

1.2 Composition of Aluminium Bronze 15

1.2.1 Classifications of Different Grades of Al-Bronze 16

1.2.2 Classification of Cast and Wrought Alloys : 16

1.2.2.1 Cast Aluminum Bronze: 16

1.2.2.2 Wrought Aluminum Bronze: 17

1.3 Properties of Aluminium Bronze 18

1.4 Applications of Aluminium Bronze 18

1.4.1 Foundry Products 18

1.4.2 Wrought Products 20

1.5 Casting Techniques of Aluminium Bronze 20

1.5.1 Sand Casting Process 20

1.5.2 Gravity Die Casting 21

1.5.3 Low-Pressure Gravity Die Casting 21

1.5.4 Pressure Die Casting 21

1.5.5 Thixocasting 21

1.6 Objective 21

1.7 Plan of Work 22

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2 Litereture Review 23

2.1 Effect of Composition on Properties 23

2.2 Oxide Formation in Aluminium Bronze: 25

2.3 Methods for Reduction of Oxide Formation 27

2.3.1 Cleaning and Designing the Melt 27

2.3.2 Determination of insoluble Non Metallic Impurities 28

2.3.3 Addition of Fluxes 29

2.3.4 Melt Temperature 30

2.4 Heat Treatment 31

2.4.1 Procedure for Heat treatment 31

2.5 Summary 33

3 Charge Preparation 34

3.1.1 Charge Preparation 34

3.1.2 Calculations 35

4: Melting and Casting Practice 36

4.1 Basic Equipments 36

4.2 Preparing of Auminium Bronze Alloys (AB1) 40

4.3 Preparing of Nickel-Aluminium Bronze Alloy (AB2) 41

4.4 Slag Removal 41

5: Heat Treatment 44

6 Testing and Test Reports 45

6.1 Scanning Electron Microscope (SEM) Study: 45

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6.2 Energy Dispersive X-ray Spectroscopy (EDAX) 50

6.3 Hardness testing: 58

6.4 Tensile Testing: 59

7 Conclusion 61

7.1 Reduction in Oxide Formation: 61

7.2 Heat Treatment 63

8: References 64

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List of Table

Figure No. Name of Table

Page No

1 Composition of Aluminium Bronze Alloy 162 Products formed by Wrought Aluminium- Bronze 173 Oxide Formation in Copper Alloys 264 Dimensions of Test Bar 345 Composition for AB1+2% 526 Composition for AB1 537 Composition for AB2 548 Composition for AB2+2% 559 Hardness Of Cast Sample 5710 Hardness of Heat Treated Sample 5811 Harness Comparison of Cast Sample and Heat treated Sample 5812 Dimension of Test Specimen 5913 Tensile Strength of Cast and Heat Treated Sample 6014 Hardness Comparison of Cast and Heat Treated 6315 Tensile Strength of Cast and Heat Treated Sample 63

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List of Figure

Figure No. Name of Figure

Page No

1 Centrifugally cast nickel-aluminum bronze high-pressure flange for a sub-sea weapons ejection system.

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2 Wear rings for a large hydro turbine, centrifugally cast in nickel-aluminum bronze, alloy C95800

19

3 Continuous cast gear-wheel blanks, aluminum bronze, alloy C95400

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4 Unetched x 100 265 Degassing 286 Fluxes for efficent metal treatment 297 Logas 50 degassing agents and DEOX Tubes for degassing &

deoxidation30

8 Permanent Mould as a Cast Test Bar 349 Standard Sample With all Dimensions 3410 Crucible 3611 Graphite Crucible with Charge Particle 3612 Pit Furnace 3713 Pattern 3714 Mould 3815 Gating System 3816 Tongs 3917 Sand Muller 3918 Heating of Carge Material in Pit Furnace 4019 Removal of Slag 4220 Final Casting 4221 Machining after Casting 4322 Setup of SEM 4523 Test specimens 4624 Line Diagram of SEM 4725 AB1 As Cast 47

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26 AB1 Heat Treated 4827 AB1+2% As Cast 4828 AB1+2% Heat Treated 4829 AB2 As Cast 4830 AB2 Heat Treated 4931 AB2+2% As Cast 4932 AB2+2% Heat Treated 4933 Information system in SEM 5034 Initiation of X-Ray 5135 EDAX study for AB1+2% 5236 EDAX study for AB1 5337 EDAX study of AB2 5438 EDAX study for AB2+2% 5539 Test Specimen 5640 Brinell Hardness Tester 5741 Heat treated samples 5942 As cast samples 59

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CHAPTER-1 INTRODUCTION

1.1 INTRODUCTON TO ALUMINIUM BRONZE

The aluminium bronzes are a family of copper-base alloys containing approximately 5% to 11% aluminium, some having additions of iron, nickel, manganese or silicon. They include alloys suitable for sand casting, gravity die-casting and for the production of forgings, plate, sheet, tube, strip, wire and extruded rods and sections. Compared with other copper alloys, the higher strength of the aluminium bronzes is combined with excellent corrosion resistance under a wide range of service conditions.

Aluminium bronzes are the most tarnish-resistant copper alloys and show no serious deterioration in appearance and no significant loss of mechanical properties on exposure to most atmospheric conditions. Their resistance to atmospheric corrosion combined with high strength is exploited, for example, in their use for bearing bushes in aircraft frames. Aluminium bronzes also show low rates of oxidation at high temperatures and excellent resistance to sulphuric acid, sulphur dioxide and other combustion products and are, therefore, used for the construction of items exposed to either or both these conditions. For example, aluminium bronzes are used very successfully for inert gas fans in oil tankers. These operate under highly stressed conditions in a variable but very corrosive atmosphere containing salt-laden water vapour, sulphurous gases and carbon.

No engineering alloy is immune to corrosion. Corrosion resistance depends upon the formation of a thin protective film or layer of corrosion products which prevents or substantially slows down the rate of attack. The aluminium content of aluminium bronzes imparts the ability to form, very rapidly, an alumina-rich protective film which is highly protective and is not susceptible to localised breakdown and consequent pitting in the presence of chlorides. Aluminium bronzes are, therefore, very resistant to corrosion by sea water and probably find more use in sea water service than in any other environment.

Virtually all metals and alloys in common use are susceptible to some extent to crevice corrosion, i.e. accelerated attack within or just at the edge of areas shielded by close proximity to other components or by deposits on the surface. Crevice corrosion in service is particularly objectionable when it takes the form of pitting or severe surface roughening on shafts or valve spindles in the way of bearings or seals.

Any crevice corrosion of aluminium bronzes, however, takes the form of minor selective phase

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dealloying which results in little reduction of strength and practically no impairment of surface finish. Aluminium bronzes are, therefore, very widely used for pump shafts and for valve spindles - situations where pitting corrosion in crevices makes stainless steels, for example, unsuitable.

A form of selective phase dealloying of aluminium bronzes commonly known as 'dealuminification' which caused some concern some years ago is no longer a significant problem. This type of attack, similar to the dezincification of duplex brasses, results in selective dissolution of the principal alloying element (in this case aluminium) from one phase of the alloy leaving a residue of porous copper which retains the original shape and dimensions of the component but has little strength. By controlling the composition and, for the alloys of high aluminium content, the cooling rate from casting or working temperature, metallurgical structures are ensured that will not suffer dealuminification to anysignificant extent under any normal conditions of use.

Metal failures in service are often the result of the combined influence of corrosion and mechanical factors, the most common being stress corrosion, which occurs under the simultaneous action of high tensile stress and an appropriate corrosive environment, and corrosion fatigue which occurs under cyclic stressing in a corrosive environment. Brasses, for example, show high susceptibility to stress corrosion in the presence of even small quantities of ammonia, and austenitic stainless steels suffer stress corrosion cracking in hot chloride solutions.

High resistance to stress corrosion cracking is an important reason for the use of aluminium bronzes by the British Navy for underwater fastenings. High tensile brasses, formerly used for this service, were very liable to fail by stress corrosion but stress corrosion failures of aluminium bronze fasteners have proved extremely rare.

High resistance to corrosion fatigue is essential for marine propellers and it is principally for thatreason that most large propellers are made from nickel aluminium bronze. This material is quiteoutstanding in resistance to corrosion fatigue in sea water, being much superior to high tensile brass or to stainless steels. Manganese aluminium bronze, which is also used for large propellers, also has high corrosion fatigue strength though somewhat inferior to nickel aluminium bronze.

Turbulent water flow conditions can cause local erosion of the protective films on which alloysdepend for their corrosion resistance and result in localised deep attack by a combination of corrosive and erosive action. The corrosion/erosion resistance of the aluminium bronzes is substantially higher than that of the brasses and similar to that of 70/30 copper-nickel which is generally recognised to be one of the alloys most resistant to this type of attack.

At higher water flow rates, such as exist in pumps and on some areas of marine propellers, formation and collapse of vapour cavities in the water can produce very high local stresses

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leading to cavitation damage. The resistance of alloys to cavitation damage generally increases with their resistance to corrosion fatigue and with their ability to reform protective films rapidly on the metal freshly exposed by cavitation erosion. The advantages of aluminium bronze over most other alloys in these respects have already been mentioned and it will be no surprise, therefore, that aluminium bronzes show exceptionally high resistance to cavitation damage. This is an important feature in their use for marine propellers and the principal reason for their use for impellers in high duty pumps.

However, the soundness of the casting has a very significant bearing on resistance to cavitationerosion and impingement attack, and maximum resistance cannot be expected from a castingproduced by bad foundry practice.

One further property of aluminium bronzes should be mentioned in this general survey of theircorrosion resistance. In most practical engineering situations different metals or alloys are used in contact with each other in the presence of an electrolyte such as sea water or fresh water. In these circumstances the possibility of galvanic action, causing accelerated attack on the less noble metal, can be very important. Aluminium bronzes are slightly more noble than most other copper alloys and slightly less noble than the copper-nickel alloys but the differences are too small to cause significant galvanic effects. Monel, stainless steel and titanium are all considerably more noble than aluminium bronze but it is found in practice that, providing the exposed area of the more noble metal does not greatly exceed that of the aluminium bronze, very little acceleration of corrosion of the aluminium bronze occurs. It is for this reason that aluminium bronze tubeplates are used in condensers with titanium tubes [1].

1.2 COMPOSITION OF ALUMINIUM BRONZE

In addition to aluminium, the major alloying elements are nickel, iron, manganese and silicon. Varying proportions of these result in a comprehensive range of alloys to meet a wide range of engineering requirements.There are four major types of alloy available:

a)Single-phase alpha alloys:

The single-phase alpha alloys containing less than 8% of aluminium. These have a good ductility and are suitable for extensive cold working. CA102 is typical of this type. Alloys containing 3% iron, such as CA106, are single phase up to over 9% aluminium

b)Duplex alloys:

The duplex alloys containing from 8% - 11% aluminium and usually additions of iron and nickel to give higher strengths. Examples of these are the casting alloys:

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AB1 CuAl10Fe3 AB2 CuAl10Fe5Ni5

Wrought alloys: CA105 CuAl10Fe3 and CA104 CuAl10Fe5Ni5 DGS1043

c)Copper-aluminium- silicon alloys:

The copper-aluminium-silicon alloys have lower magnetic permeability:Cast AB3 CuAl6Si2FeWrought CA107 CuAl6Si2 DGS1044 These are mainly alpha alloys and have good strength and ductility.

d)Copper-manganese-aluminium alloys: The copper-manganese-aluminium alloys with good castability developed for the manufacture

of propellers.CMA1 CuMn13Al8Fe3Ni3

We will be focusing mainly on Duplex alloys i.e. AB1 and AB2 types basically in our project[2].

1.2.1 Classifications of different grades of al-bronze:

Grades Sr.no Approx. alloy composition (%)Al Fe Ni Mn Cu

AB11 9 3 - -

rest2 13 4 - -

AB2

3 10 4 5 14 11 4 4 -5 8 3 2 18

Table no 1: composition of aluminium bronze alloy

1.2.2 Classification of Cast and Wrought alloys :

1.2.2.1Cast Aluminum Bronze :

Aluminum bronze castings are produced by the recognized techniques of sand, shell, permanent mold (low-pressure die), ceramic, investment, centrifugal and continuous casting. The size of castings ranges from tiny investment cast components to very large propellers weighing 70 tons. One of the very attractive characteristics of aluminum bronzes is that, due to their short cooling range, they solidify compactly, as do pure metals. This means that, provided defects are avoided, the metal is inherently sound, more so than alloys such as gunmetal (tin bronze, UNS C90500) which may be porous unless cooled very rapidly.

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The alloy's short freezing range means that adequate feeding is required as the metal solidifies. It is also essential to prevent the aluminum oxide dross on top of the liquid metal from becoming entrapped in the castings during pouring. Avoiding internal defects therefore requires a certain degree of care, although foundries with the required expertise routinely produce castings of very high integrity. Because aluminum bronze is often selected for critical applications, it is important that casting be well designed so as to achieve best results. Consultation with an experienced founder is essential at a relatively early stage of design development. Publications are available that are helpful in the initial design work and give a good basis for consultation between the designer and the founder.

Many duplex alloy castings may be heat treated to improve the microstructure of the alloy, giving better corrosion resistance and higher strength for only a slight reduction in ductility. The treatment recommended is to soak at 1220°F (660°C) and cool in still air. The time at temperature depends on casting size and section thickness but is on the order of two hours. This treatment is used only for the most critical of applications.

1.2.2.2 Wrought Aluminum Bronze: A wide variety of wrought products are made in aluminum bronze alloys, including forgings, rod, bar, section (profile), flat, sheet, strip and plate, filler rod and wire. An indication of this variety is given in Table.

Table no 2: Products formed by Wrought aluminium- bronze

Material can be chosen from the compositions that are available but manufacturers or distributors will advise the most suitable alloy for selection. Billets from which wrought products are made continuously to ensure freedom from entrapped oxide defects, which would carry through to the final product. These billets are then hot worked by conventional methods such as extrusion, rolling or forging. Rolling, extrusion and rotary forging produce

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sections that are to final or near final dimensions and reduce the need for costly machining. This provides very useful design flexibility. Forgings are produced either freehand in simple shapes and to relatively wide tolerances, or in closed dies to close tolerances if the quantity required justifies the initial cost of the die. Hot pressing, stamping and other methods are used to produce flanged shafts, nuts and bolts[3].

1.3 PROPERTIES OF ALUMINIUM BRONZE:

Excellent strength, similar to that of low alloy steels Excellent corrosion resistance, especially in seawater and similar environments, where

the alloys often outperform many stainless steels Favorable high temperature properties, for short or long term usage Good resistance to fatigue, ensuring a long service life Good resistance to creep, making the alloys useful at elevated temperatures Oxidation resistance, for exposure at elevated temperatures and in oxidizing

environments Ease of casting and fabrication, when compared to many materials used for similar

purposes High hardness and wear resistance, providing excellent bearing properties in arduous

applications Ductility, which, like that for all copper alloys, is not diminished at low temperatures; Good weld ability, making fabrication economical Readily machined, when compared with other high-duty alloys Low magnetic susceptibility, useful for many special applications, and Ready availability, in cast or wrought forms[4].

1.4 APPLICATIONS OF ALUMINIUM BRONZE:

1.4.1FOUNDRY PRODUCTS

Impellers Bearings Propellers Gear selector forks Shafts Synchronizing rings Pumps & valves Non-sparking tools Water cooled compressors Glass moulds Tube sheets & other heat exchanger parts Pipe fittings Marine environments ornamental articles Channel covers Rudders & Propeller brackets

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Gears & Gear blanks Die-cast components Deep drawing dies Continuous cast bar & shapes Pickling equipment Centrifugal castings Rolling Mill equipment Bushes

Fig1. Centrifugally cast nickel-aluminum bronze high-pressure flange for a sub-sea weapons ejection system.

Fig2. Wear rings for a large hydro turbine, centrifugally cast in nickel-aluminum bronze, alloy C95800.

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Fig3 . Continuous cast gear-wheel blanks, aluminum bronze, alloy C95400.

1.4.2 WROUGHT PRODUCTS

Drop forgings Chain Tube sheets Impellers Tubes & Shells Compressor blades Pressure vessels Shafting Reaction & Distillation vessels Gears Pipe work Non-sparking tools Wear plates Non-magnetic equipment Springs Masonry fixings Bearings Rod, bar & shapes Fasteners Free hammer forgings Valve spindles In addition, aluminum bronzes are extensively used as metal-sprayed or weld-deposited

surfacing materials, generally over steel substrates, in order to provide wear, corrosion and sparking resistance[5].

1.5CASTING TECHNIQUES OF ALUMINIUM BRONZE:

1.5.1 SAND CASTING PROCESS:

The sand casting process is used predominantly in two fields of applications i.e. for prototypes and small-scale production on the one hand and for the volume production of castings with a very complex geometry on the other. For the casting of prototypes, the main arguments in favour of the sand casting process are its high degree of flexibility in the case of design changes and thecomparably low cost of the model. In volume production, the level of complexity and precision achieved in the castings are its main advantages[11].

1.5.2 GRAVITY DIE CASTING:

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When higher mechanical properties are required in the cast piece, such as higher elongation or strength, gravity die casting, and to a limited extent pressure die casting, are used. In gravity die casting, there is the possibility of using sand cores. Large differences in wall thicknesses can be favorably influenced with the help of risers. Cylinder heads for water-cooled engines represent atypical application[10].

1.5.3 LOW- PRESSURE GRAVITY DIE CASTING:In the low-pressure gravity die process with its upward and controllable cavity filling, the formation of air pockets is reduced to a minimum and, consequently, high casting quality can be achieved. In addition to uphill filling, the overpressure of approx. 0.5 bar has a positive effect on balancing out defects caused by shrinkage. The low-pressure die casting process is particularly advantageous in the casting of rotationally symmetrical parts, e.g. in the manufacture of passenger vehicle wheels[8].

1.5.4 PRESSURE DIE CASTING:

Pressure die casting is the most widely used casting process for aluminium casting alloys. Pressure die casting is of particular advantage in the volume production of parts where the requirement is on high surface quality and the least possible machining. Special applications (e.g.vacuum) during casting enable castings to be welded followed by heat treatment which fully exploits the property potential displayed by the casting alloy[8].

1.5.5 THIXOCASTING:

In addition to conventional pressure die casting, thixocasting is worthy of mention since heat-treatable parts can also be manufactured using this process. The special properties are achieved by shaping the metal during the solid liquid phase. Squeeze-casting is another casting process to be mentioned; here, solidification takes place at high pressure. In this way, an almost defect-free microstructure can be produced even where there are large transitions in the cross-section and insufficient feeding[8].

1.6 OBJECTIVE:

Melting and Casting of aluminium bronze. Studying the causes for oxide formation. Studying of the material by changing the composition and adding fuxes. To study the effect of aluminium on mechanical and environmental properties like

hardness, wear resistance, tensile strength and corrosion resistance of aluminium bronze. Characterization of as cast treated and heat treated aluminium bronze samples.

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1.7 PLAN OF WORK : CHARGE PREPARATION MELTING AND CASTING PRACTICE SAMPLE PREPARATION CHANGING THE COMPOSITION AND ADDITION OF FLUX HEAT TREATMENT

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Charge preparationMelting & Casting practiceSample preparationChanging the composition and addition of fluxHeat Treatment

CHAPTER 2 LITERATURE REVIEW:

The review of research papers conducted to aid in this dissertation work is presented here in five sections. The first section discusses the papers reviewed related to effect of composition on properties of aluminium bronze alloys . The second section reviews papers related to Oxide formation in aluminium bronze. In the third section papers which have provided useful insight for casting techniques of aluminium bronze are reviewed. The fourth section presents papers reporting methods for reduction of oxide formation in aluminium bronze alloys. The fifth section discusses the scope and objectives of the work conceived for this dissertation work.

2.1 EFFECTS OF COMPOSITION ON PROPERTIES:

From Copper Development Association [2] has worked on the change in properties and behavior of aluminium bronze by varying the composition of the aluminium bronze. He arrived to the conclusion that the mechanical properties of aluminium bronze depend primarily on aluminium content. Alloys with up to about 8% aluminium have a ductile single phase structure and are the most suitable for cold working into tube, sheet, strip and wire. As the aluminium content is increased to between 8% and 10% the alloys are progressively strengthened by a second, harder phase which makes them more suitable for hot working and casting. Above 10% an even greater strength and hardness is developed for specialised wear resistant applications.

The other major alloying elements also modify the structure to increase strength and corrosion resistance: iron improves the tensile strength and acts as a grain refiner; nickel improves proof stress and corrosion resistance and has a beneficial stabilising effect on the metallurgical structure; manganese also performs a stabilizing function.Z. Ahmad and P. Dvami[6] have worked on the change in properties and behavior of aluminium bronze by manganese to the aluminium bronze and find out that if manganese, at about 13%, is the major addition in a series of manganese aluminium bronzes with aluminium levels of 8 - 9%. Their foundry properties are better than the aluminium bronzes and they have good resistance to impingement and cavitation, as well as being heat treatable to low magnetic permeability. They have excellent welding properties.J. O. Edwards and D. A. Whittaker[7] have worked on the change in properties and behavior of aluminium bronze by adding iron, nickel and manganese to the aluminium bronze and had following conclusions: The addition of iron up to 1% improves the mechanical properties mainly due to its effect

on grain refinement. However the addition of iron is limited up to 5.5%.Above 1.2% the tensile strength and hardness are improved but its ductility gets lowered.

The addition of nickel to an alloy containing iron has a beneficial effect in modifying the stable structure.

The most important effect of manganese is in improving the corrosion resistance of an aluminium bronze, the addition of magnesium is sufficient up to 6%. The main drawback is that aluminum bronze with low manganese addition is susceptible to corrosion when the addition exceeds 11% a fully stable structure is obtained resulting corrosion properties.

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From the Aluminum Casting Alloys_english_PV_2012_11_30 [8] which have researched on the change in properties and behavior of aluminium bronze by adding silicon, iron, copper, nickel, manganese, magnesium, zinc and titanium to the aluminium bronze and the following conclusions can be drawn

Silicon Improves the casting properties Produces age-hardenability in combination with magnesium but causes a grey color

during anodisation In pure AlCu casting alloys (e.g. Al Cu4Ti), silicon is a harmful impurity and leads to hot

tearing susceptibility.

Iron At a content of approx. 0.2 % and above, has a decidedly negative influence on the

ductility (elongation at fracture); this results in a very brittle AlFe(Si) compound in the form of plates which appear in micrographs as “needles”; the seplates act like large-scale micro structural

separations and lead to fracture when the slightest strain is applied At a content of approx. 0.4 % and above, reduces the tendency to stickiness in pressure die

casting.

Copper Increases the strength, also at high temperatures (high temperature strength) Produces age-hardenability Impairs corrosion resistance In binary AlCu casting alloys, the large solidification range needs to be taken into account

from casting/technical point of view.

Manganese Partially offsets iron‘s negative effect on ductility when iron content is > 0.15 % Segregates in combination with iron and chromium Reduces the tendency to stickiness in pressure die casting.

Magnesium Produces age-hardenability in combination with silicon, copper or zinc; with zinc also self-hardening Improves corrosion resistance Increases the tendency towards oxidation and hydrogen absorption Binary AlMg casting alloys are difficult to cast owing to their large solidification range.

Zinc Increases strength Produces (self) age-hardenability in conjunction with magnesium.

Nickel

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increases high-temperature strength.

Titanium increases strength (solid-solution hardening) produces grain refinement on its own and together with boron.

2.2 Oxide Formation in Aluminium Bronze:

M Hansen and K Anderko[9] conducted their work to try to reduce the oxide formation in copper alloys by taking copper–oxygen system, the procedure and conclusion is explained below:

The copper-oxygen system is an example of a simple eutectic system. The high-conductivity copper used for the vast majority of electrical applications generally contains from 0.01 to 0.05% oxygen but may contain up to 0.1%.

Solidification commences with the formation of nuclei on cooling below the liquidus temperature (on line AC). As the temperature falls, these nuclei, which are essentially pure copper, proceed to grow in size, causing the liquid to become richer in oxygen. The compositionof the liquid follows the liquidus AC until, at the eutectic point C, the liquid remaining betweenthe primary grains solidifies at constant temperature to form the eutectic composed of α and Cu2O. It will be seen from the diagram that the oxygen content of the melt controls the amountof residual liquid solidifying with eutectic composition; the relative proportions of primary andeutectic constituents therefore gives a good indication of the alloy's composition.

Until the advent of modern continuous casting plant for high-conductivity copper, porosity wasalways visible in the microstructure, being an important feature of what was known as tough pitch copper. During fire-refining, air is injected into the molten copper to oxidize impurities. As a result, oxygen is absorbed by the copper. Hydrogen is also picked up in the furnace, particularly during the subsequent reducing or 'poling' operation, and co-exists in equilibrium with the oxygen. On solidification, this equilibrium is disturbed, the oxygen and hydrogen

reacting together to form steam which becomes entrapped in the casting. By carefully reducing the oxygen content to a controlled level, the volume of the steam cavities may be made to Counteract the natural solidification contraction of the metal and so produce wire bars or cake with a level top surface ideal for subsequent fabrication.

Fig: 4 Unetched x 100

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This microstructure consists of irregularly shaped primary grains of outlined by a network of and Cu20 eutectic. The constituent of the eutectic has become absorbed by the primary grains and is notvisible as separate particles. The large black areas associated with the eutectic are gascavities.

Point A B C D E F G H I°C 1083 1065 1065 1065 1200 1200 600 -375 -375O2% 0 0.008 0.39 11.2 1.5 10.2 0.0017 100 11.2

Table no: 3 oxide formation in copper alloys

From the Aluminum Casting Alloys_english_PV_2012_11_30 [8] which have worked on the melt management to reduce the oxide formation in aluminium bronze, we came to know that during transition from liquid to solid state, the dissolved hydrogen in the melt precipitates

26

and, on interacting with oxides, causes the well-known problem of micro porosity or gas porosity. The task of melt management and treatment is to keep oxide formation and, consequently, the dangers to cast quality within limits.

Here are a few key points to reduce oxide formation: Use good quality ingots Quality-oriented melting technology and equipment Correct charging of the ingots (dry, rapid melting) Temperature control during melting and casting Melt cleaning and melt control Safety measures during treatment, transport and casting

2.3 METHODS FOR REDUCTION OF OXIDE FORMATION:

2.3.1 CLEANING AND DEGASING THE MELT:

From the Aluminum Casting Alloys_english_PV_2012_11_30 [8] which worked on the methods to clean the melt we observed that casting alloys consist of effectively cleaned metal. Since reoxidation always takes place during smelting, and in practice revert material is always used, a thorough cleaning of the melt is necessary prior to casting.

Holding the aluminium melt at the correct temperature for a long time is an effective cleaning method. It is, however, very time-intensive and not carried out that often as a result. Foundry men are thus left with only intensive methods, i.e. using technical equipment or the usual commercially available mixture of salts.

According to A.W. Tracy which worked on effective cleaning of melt concluded that melt cleaning is a physical process: the gas bubbles rising through the liquid metal attach oxide films to their outer surfaces and allow hydrogen to diffuse into the bubbles from the melt. Both are transported to the bath surface by the bubbles. It is therefore clear that in order for cleaning of the melt to be effective, it is desirable to have as many small gas bubbles as possible distributed across the entire cross-section of the bath. Dross can be removed from the surface of the bath, possibly with the aid of oxide- binding salts [12].

According to J. L. Sullivan, who carried his research on inert gas flushing of melt to clean and degas the melt we came to following conclusion that, Inert-gas flushing by means of an impeller is a widely-used, economical and environmentally-sound cleaning process. The gas stream is dispersed in the form of very small bubbles by the rapid turning of a rotor and, in conjunction with the good intermixing of the melt, this leads to very efficient degassing. To achieve an optimum degassing effect, the various parameters such as rotor diameter and revolutions per minute, gas flow rate, treatment time, geometry and size of the crucible used as well as the alloy, have to be co-ordinate. The course of degassing and reabsorption of hydrogen is depicted for various casting alloys[13].According to G. W. Lorimer, F. Hasan, J. Iqbal and N. Ridley; have worked on the methods of using commercial salts and filters for reduction in oxide formation in casting and concluded that when using commercially available salt preparations, the manufacturer‘s

27

instructions concerning use, proportioning, storage and safety should be followed. Apart from this, attention should also be paid to the quality and care of tools and auxiliary materials used for cleaning so that the cleaning effect is not impaired.

If practically feasible, it is also possible to filter the melt using a ceramic foam filter. In the precision casting of high grade castings, especially in the sand casting process, the use of ceramic filters in the runner to the sand mould has proved to be a success. Above all, such a filter leads to an even flow and can retain coarse impurities and oxides[14].

FIG 5 DEGASSING

2.3.2 DETERMINATION OF INSOLUBLE NON METALIC IMPURITIES:

The literature survey related to this topic was performed because the non soluble impurities reacts with gases to form oxides which degrades the melt quality and result in casting defects.

From the Aluminum Casting Alloys_english_PV_2012_11_30 [8] which also carried the work in determining the insoluble non- metallic impurities in casting by Porous Disc Filtration Apparatus (PoDFA) method. We can conclude that for determining the number and type of insoluble non-metallic impurities in aluminium melts, the Porous Disc Filtration Apparatus (PoDFA) method, among others, can be used. In this particular method, a precise amount of the melt is squeezed through a fine filter and the trapped impurities are investigated metallographically with respect to their type and number. The PoDFA method is one of the determination procedures which facilitates the acquisition, both qualitatively and quantitatively, of the impurity content. It is used primarily for evaluating the filtration and other cleaning treatments employed and, in casting alloys production, is utilized at regular intervals for the purpose of quality control. This method is not suitable for making constant routine checks since it is very time-consuming and entails high costs[8].

Correlation between the hydrogen content and density index in unmodified Al Si9Mg alloy

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2.3.3 ADDITION OF FLUXES:

Accoding to United State, Environmental Protection Agency, "Report on the Corrosion of certain Alloys",Washington, DC. 20460, July 2001, which worked on reduction in metal losses and the the oxide formation in casting by the use of proper pouring temperature along with protective fluxes. We concluded that Metal losses and of alloying elements oxidation were decreased due to use of proper pouring temperature of alloys with using the protective fluxes. The best mechanical properties such as ultimate tensile strength and hardness are found in treated nickel aluminium bronze alloys (T-AB2), due to the effects of fluxes material such as ( Logas 50 and deoxidizing tubes E3 ) to minimize the casting defects. In addation, the effects of rise of (Ni and Fe) contents on the improving on the mechanical properties[15].

Auxiliary Materials: - Some additive materials are used such as;

Albral 2:- A calcium and sodium fluoride powder is used as a protective cover for the molten metal during melting process.

FIG 6: Fluxes for efficent metal treatment

Deoxidizing tubes (E3):- These tubes are made of copper and contain a powder of phosphorus and other elements and are by weight about (25) g used as a deoxidizing material.

- Logas 50:- A small block which is made from a crushing dolomite blocks (CaMg(CO3)2) and, used as a liquid of sodium silicate as a binder, each block weighs about (50) g[16].

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FIG 7: LOGAS 50 degassing agents and DEOX Tubes for degassing & deoxidation

2.3.4 MELT TEMPERATURE:

According to Aluminum Casting Alloys_english_PV_2012_11_30 which worked on the melt temperature in relation with the separate alloys came to the following conclusions :

The temperature of the melt must be set individually for each alloy. Too low melting temperatures lead to longer residence times and, as a result, to greater oxidation of the pieces jutting out of the melt. The melt becomes homogeneous too slowly, i.e. local undercooling allows segregation to take place, even as far as tenacious gravity segregation of the FeMnCrSi type phases. The mathematical interrelationship for the segregation of heavy intermetallic phases.

Furthermore, at too low temperatures, autopurification of the melt (oxides rising) cannot take place

When the temperature of the melt is too high, increased oxide formation and gassing can occur. Lighter alloying elements, e.g. magnesium, are subject to burn-off in any case; this must be offset by appropriate additions. Too high melting temperatures aggravate this loss by burning[8].

2.5 HEAT TREATMENT:

Heat treatment gives users of castings the possibility of specifically improving the mechanical properties or even chemical resistance. Depending on the casting type, the following common and applied methods for aluminium castings can be used:

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Stress relieving Stabilising Homogenising Soft annealing Age-hardening.

According to P. Brezina; who conducted his work on heat treatment in casting through age- hardening method concluded that for age-hardening to take place, there must be a decreasing solubility of a particular alloy constituent in the α-solid solution with falling temperature. As a rule, age-hardening comprises three steps:

In solution annealing, sufficient amounts of the important constituents for age-hardening are dissolved in the α-solid solution.

With rapid quenching, these constituents remain in solution. Afterwards, the parts are relatively soft.

In ageing, mostly artificial ageing, precipitation of the forcibly dissolved components takes place in the form of small sub-microscopically phases which cause an increase in hardness and strength. These tiny phases, which are technically referred to as “coherent or semi coherent phases”, represent obstacles to the movement of dislocations in the metal, thereby strengthening the previously easily-formable metal. The most important form of heat treatment for aluminium castings is artificial ageing[17].

2.5.1 PROCEDURE FOR HEATTREATMENT

1. SOLUTIONIZING: To bring the hardened constituents into solution as quickly as possible and in a sufficient amount, the solution annealing temperature should be as high as possible with, however, a safety margin of approx. 15 K to the softening point of the casting alloy in order to avoid incipient fusion. For this reason, it is often suggested that casting alloys containing Cu should

31

undergo step-by-step solution annealing (at fi rst 480 °C, then 520 °C). The annealing time depends on the wall thickness and the casting process. Compared with sand castings, gravity die castings require a shorter annealing time to dissolve the constituents sufficiently due to their finer microstructure. In principle, an annealing time of around one hour suffices. The normally longer solution annealing times of up to 12 hours, as for example in Al SiMg alloys, produce a good spheroidising or rounding of the eutectic silicon and, therefore, a marked improvement in elongation. The respective values for age-hardening temperatures and times for the individual casting alloys can be indicated on the respective data sheets. During the annealing phase, the strength of the castings is still very low. They must also be protected against bending and distortion. With large and sensitive castings, it may be necessary to place them.

2. QUENCHING: Hot castings must be cooled in water as rapidly as possible (5-20 seconds depending on wall thickness) to suppress any unwanted, premature precipitation of the dissolved constituents. After quenching, the castings display high ductility. This abrupt quenching and the ensuing increase in internal stresses can lead to distortion of the casting. Parts are often distorted by vapour bubble pressure shocks incurred during the rapid immersion of hollow castings. If this is a problem techniques such as spraying under a water shower or quenching in hot water or oil have proved their value as a first cooling phase. Nevertheless, any straightening work necessary at this stage should be carried out after quenching and before ageing

3. AGEING: The procedure of ageing brings about the decisive increase in hardness and strength of the cast structure through the precipitation of the very small hardening phases. Only after this does the part have its definitive service properties and its external shape and dimensions. Common alloys mostly undergo artificial ageing. The ageing temperatures and times can be varied as required. In this way, for example, the mechanical properties can be adjusted specifi cally to attain high hardness or strength although, in doing this, relatively lower elongation must be reckoned with. Conversely, high elongation can be also achieved while lower strength and hardness values will be the result. When selecting the ageing temperatures and times, it is best to refer to the ageing curves which have been worked out for many casting alloys[8].

2.6 SUMMARY:Literature survey is carried out for alloying material of aluminium bronze, causes of the oxide formation in aluminium bronze by various impurities in the melt , proper selection of casting process as per application of the alloy, avoiding the oxide formation in aluminium

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bronze by various different techniques and the effect of heat treatment in increasing various properties of aluminium bronze alloy.

CHAPTER 3 CHARGE PREPARATION :

3.1.1 CHARGE PREPARATION:

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FIG8:PERMANENT MOULD AS A CAST TEST BAR

TABLE NO 4: DIMENSIONS OF TEST BAR

FIG 9 : STANDARD SAMPLE WITH ALL DIMENSIONS

3.1.2 CALCULATIONS:

CALCULATION OF DIAMTER

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D = 25 + 2% shrinkage allowances = 25 + 0.5 ≈ 26 mm

HEIGHT CALCULATION

H = 58 + 2(21) + 2(25) + 2% shrinkage allowances = 150 + 3 ≈ 155 mm

VOLUME CALCULATION

Volume = ∏/4 * D2 * h = ∏/4 *(26)2 * 155 = 82252.3 mm3 DENSITY CALCULATION:

Density of Al-bronze = 7.45 gm/cm3 = 7.45 * 1/1000 = 0.00745 gm/mm3

WEIGHT CALCULATION:

weight of sample = volume* density

= 82252.3*0.00745 = 612.7gm ≈ 613gm of sample[18]

CHAPTER 4: MELTING AND CASTIING PRACTICE:

4.1.1 BASIC EQUIPMENTS:

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CRUCIBLE:

The most widely used method of melting copper in foundries is with crucible furnaces. Gas, oil-fired or induction furnaces are the most common crucible furnaces used in copper foundries.

Fig 10: CRUCIBLE

Fig 11: GRAPHITE CRUCIBLE WITH CHARGE PARTICLE

PIT FURNACE

A furnace made in pit for melting metal during casting process is called a pit furnace.

36

FIG12 : PIT FURNACE

It consists of a cylindrical steel shell, closed at the bottom with a grate and covered with a removable lid. The shell is lined with refractory bricks from inside. Sometimes the furnace is completely made in brick. The natural draft of air is used for the metal having low melting temperature and forced draft with the help of blower is used for metal having high melting temperature.

To prepare the furnace for melting, a deep bed of coke is kindled and allowed to burn until a state of good combustion is attained some of the coke is removed to make place for crucible. The crucible is then lowered into furnace. Metal is then charged in the crucible and the furnace lid is replaced to give natural draft. When the desired temperature is received the crucible is removed with special long handle tongs.

PATTERN

A pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process.

Patterns used in sand casting may be made of wood, metal, plastics or other materials. Patterns are made to exacting standards of construction, so that they can last for a reasonable length of time, according to the quality grade of the pattern being built, and so that they will repeatably provide a dimensionally acceptable casting.

Fig 13 : PATTERN

MOULD

Mould is hollowed-out block that is filled with a liquid or pliable material like plastic ,glass ,metal or ceramic raw material.Moulding is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called mould.

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Fig 14 : MOULD

GATING SYSTEM

The gating system serves as the path by which molten metal flows into the pattern cavity and feed the shrinkage which develops during casting solidification.

Fig 15 : GATING SYSTEM

TONGS

Tongs are used for gripping and lifting crucible,of which there are many forms adapted to their specific use.

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Fig 16 : TONGS

SAND MULLER:

Sand was mixed in the sand muller by adding sodium silicate as a binder.

Fig 17 : SAND MULLER

4.2 PREPARING OF ALUMINIUM BRONZE ALLOY (AB1)

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Casting process of this alloy started with the melt of pieces of copper and other elements such as iron, nickel, manganese, zinc and aluminum. During the melting process of alloy elements, the temperature of molten metal increased to about (1300) °C, but without using any type of treatment. In addition, the molten metal suffered from severe atmospheric conditions, due to the absence of protective fluxes. Before pouring the molten metal, a specimen was taken from the molten metal to check the alloy composition by spectrometer. Then, the molten alloy was poured into two moulds; sand and metal moulds. The melting process was repeated for the second charge from the same alloy with sufficient care during melting operation by using suitable protective layer (Albral 2) to keep the molten metal away from atmospheric conditions. In addition, steady melting operation was used (no stirring or turbulence). Layer of charcoal was used on the surface of melt to prevent the oxidation. When the melting process was finished, a specimen from the molten metal was taken to check the composition of alloy by spectro-analysis. Preheat the mould to about (100–150) °C before pouring the metal. The molten metal was poured into a ladle carefully, then, one piece of (Logas 50) was added to remove the gases out from the molten metal. Two pieces of deoxidizing tubes (E) were added for reduction of the oxide. Finally, a "non-turbulence casting method" was used to pour the molten metal into prepared moulds[20].

Fig 18 : HEATING OF CARGE MATERIAL IN PIT FURNACE

4.3 PREPARING OF NICKEL - ALUMINIUM BRONZE ALLOY (AB2):

40

This is the major alloy for this work. The alloy melting is applied as follows: -

After the crucible furnace was discharged from first alloy, it was continued on fire and the crucible walls show a red colour. The melting process started by charging the pieces of cathode copper. Then, pieces of iron were added and followed by nickel, manganese, zinc and aluminum. After the melting operation was finished, molten metal was stirred into the furnace without any protective layer. The temperature of molten metal increased for about (150) °C above its pouring temperature (i.e. to about 1350 °C) by increase the furnace flame. The furnace charge was poured into a prepared sand and metal moulds. In order to explain the importance of the right procedure of melting for the elements of nickel-aluminum bronze alloy,

The process was performed as follow : -

The crucible gas furnace was continued on fire. Charging the cathode copper pieces into the crucible. After melting the copper pieces, a flux of (Albral 2) was used as a protective layer over the surface of molten metal by 1 % of metal weight. Therefore, the required quantity from the fluxes during melting operation was about ¾ of all quantity and the reminder was added before the pouring stage, this quantity is used according to the world specifications[21]. A amount of charcoal was added over the surface of molten metal to prevent the chance of oxidation. Make an interest to Control on the temperature of the liquid during the melting operation to prevent the increase in temperature above the required limits. The pieces of iron were charged under a protective cover carefully. The pieces of nickel and then the pieces of manganese were added under a protective cover too, followed by zinc pieces and aluminum. The reminder quantity of (Albral 2) flux was added over the surface of liquid. The alloy temperature was raised to 1180°C. A specimen from the molten metal was taken to check the composition of alloy by using a spectro- analysis. Two pieces of (Logas 50) were added and submerged into the furnace crucible to remove gases from the molten metal.

The molten metal was tilted from the furnace into a ladle to transport it to the moulds. Two pieces of deoxidizing tubes (E) were placed in the ladle before tilt the molten metal to reduce the oxides and to increase fluidity to the molten metal[20].

4.4 SLAG REMOVAL:

During the preparation of melt there are lot of impurities present in the molten metal which reacts with gases or other impurities to form oxide layer when poured in the mould. The oxide layer doesn’t allow the gas to entrap out of the moulds through vent holes during solidification or cooling of the mould. Hence resulting into a porous layer inside the casting which causes the breakage of material during machining or hinders the basic mechanical properties of the material.

Due to the above mentioned disadvantages of the impurities present in the molten metal its henceforth makes it necessary to remove the impurities before the molten metal is poured in the mould.

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For removing the impurities from the molten metal the various fluxes are added into the molten metal as mentioned in the earlier section. This fluxes reacts with the impurities to form a slag which are lighter in weight as compared to the liquid metal and will form a upper most layer in the crucible and this slag should be removed by pouring the upper most layer out before pouring it in the mould. The removal of slag is shown in the figure.

Fig 19: REMOVAL OF SLAG

Fig 20: FINAL CASTING

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Fig 21: MACHINING AFTER CASTING

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CHAPTER 5: HEAT TREATMENT:The Al bronze with a nominal composition of Cu-10Al-3Fe was synthesized using liquid metallurgy route. The process started with the preparation of the charge containing required quantities of different elements like Cu, Al, and Fe. Cu pieces were charged in a graphite crucible and melted employing an oil-fired furnace. The melt surface was covered with flux (Albral) and other alloying elements were added to the melt (maintained at 1170oC ) gradually. Care was taken to add the lower melting elements like Al to add at latter stages of melting with a view to reduce losses through vaporization. The melt was stirred manually for some time to facilitate dissolution of the alloying elements.

The solution treatment was carried out at two temperatures (850oC and 900oC ) and duration in the range of 0.5, 1, 1.5 and 2 hrs respectively. Similarly, ageing was carried out at 300oC, 400oC and 500oC where in the duration of the ageing was maintained at 2 and 3 hrs respectively. The heat treated samples were subjected to water quenching in order to bring them to ambient temperature. The behavior of the alloy has been assessed in terms of the influence of the type, temperature and duration of the heat treatment on the micro structural and mechanical properties of the samples. Results showed that as cast alloy showed granular structure consisting of primary α, eutectoid α+ϒ2 and Fe rich phase. Solutionizing led to the micro structural homogenization by way of the elimination of the dendrite structure and dissolution of the eutectoid phase and other micro constituents to the form the single phase structure consisting of β. This was followed by the formation of the β martensite, retained β and α. Ageing brought about the transformation of the martensite and other micro constituents into the eutectoid phase. Also, solutionizing at 850oC for 2 hrs led the alloy to attain the highest hardness in the category of solutionized samples while ageing at 300oC for 2 hrs offered maximum hardness the aged sample.

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CHAPTER 6 TESTING AND TEST REPORTS

6.1 Scanning Electron Microscope (SEM) Study:

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with electrons in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens can be observed in high vacuum, low vacuum and in environmental SEM specimens can be observed in wet conditions.

Fig 22: Setup of SEM

Principles and Capacities:

The types of signals produced by a SEM include secondary electrons (SE), back-scattered electrons (BSE), characteristic X-rays, light (cathodoluminescence) (CL), specimen current and transmitted electrons. Secondary electron detectors are standard equipment in all SEMs, but it is rare that a single machine would have detectors for all possible signals. The signals result from interactions of the electron beam with atoms at or near the surface of the sample. In the most common or standard detection mode, secondary electron imaging or SEI, the SEM can produce very high-resolution images of a sample surface, revealing details less than 1 nm

45

in size. Due to the very narrow electron beam, SEM micrographs have a large depth of field yielding a characteristic three-dimensional appearance useful for understanding the surface structure of a sample. This is exemplified by the micrograph of pollen shown above. A wide range of magnifications is possible, from about 10 times (about equivalent to that of a powerful hand-lens) to more than 500,000 times, about 250 times the magnification limit of the best light microscopes.

Back-scattered electrons (BSE) are beam electrons that are reflected from the sample by elastic scattering. BSE are often used in analytical SEM along with the spectra made from the characteristic X-rays, because the intensity of the BSE signal is strongly related to the atomic number (Z) of the specimen. BSE images can provide information about the distribution of different elements in the sample. For the same reason, BSE imaging can image colloidal gold immuno-labels of 5 or 10 nm diameters, which would otherwise be difficult or impossible to detect in secondary electron images in biological specimens. Characteristic X-rays are emitted when the electron beam removes an inner shell electron from the sample, causing a higher-energy electron to fill the shell and release energy. These characteristic X-rays are used to identify the composition and measure the abundance of elements in the sample.

FIG 23: Test specimens

46

FIG 24: LINE DIAGRAM OF SEM

TESTING RESULT:

Fig 25 : AB1 As Cast

47

Fig 26 : AB1 Heat Treated

Fig 27 : AB1+2% As Cast

Fig 28: AB1+2% Heat Treated

Fig 29: AB2 As Cast

48

Fig 30: AB2 Heat Treated

FIg 31: AB2+2% As Cast

Fig 32 : AB2+2% Heat Treated

OBSERVATION:

From the above structural diagram we can conclude that the structure of cast aluminium i.e. AB1, AB1+2%, AB2 and AB+2% have dendrite structure and which makes the material brittle resulting in easy breakage of material and high rate of wear and tear.

On the other hand the heat treated structure diagram of the same composition form Grain structure improves strength and hardness property of the material and also the conductivity and magnetic property of the same.

49

6.2 Energy Dispersive X-ray Spectroscopy (EDAX): Energy-dispersive X-ray spectroscopy (EDS, EDX, or XEDS) is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on the investigation of an interaction of some source of X-ray excitation and a sample. Its characterization capabilities are due in large part to the fundamental principle that each element has a unique atomic structure allowing unique set of peaks on its X-ray spectrum. To stimulate the emission of characteristic X-rays from a specimen, a highenergy beam of charged particles such as electrons or protons, or a beam of X-rays, is focused into the sample being studied. At rest, an atom within the sample contains ground state (or unexcited) electrons in discrete energy levels or electron shells bound to the nucleus. The incident beam may excite an electron in an inner shell, ejecting it from the shell while creating an electron hole where the electron was. An electron from an outer, higher-energy shell then fills the hole, and the difference in energy between the higherenergy shell and the lower energy shell may be released in the form of an X-ray. The number and energy of the X-rays emitted from a specimen can be measured by an energy-dispersive spectrometer. As the energy of the X-rays is characteristic of the difference in energy between the two shells, and of the atomic structure of the element from which they were emitted, this allows the elemental composition of the specimen to be measured.

Fig 33: Information system in SEM

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Fig 34: Initiation of X-Ray

Equipment Four primary components of the EDS setup are 1. Excitation source (electron beam or x-ray beam) 2. X-ray detector 3. Pulse processor 4. Analyzer. Electron beam excitation is used in electron microscopes, scanning electron microscopes (SEM) and scanning transmission electron microscopes (STEM). X-ray beam excitation is used in X-ray fluorescence (XRF) spectrometers. A detector is used to convert X-ray energy into voltage signals; this information is sent to a pulse processor, which measures the signals and passes them onto an analyzer for data display and analysis. The most common detector now is Si (Li) detector cooled to cryogenic temperatures with liquid nitrogen; however newer systems are often equipped with silicon drift detectors (SDD) with Peltier cooling systems.

51

TEST RESULT:

TABLE 5: COMPOSITION for AB1+2%

Fig 35: EDAX study for AB1+2%

52

Element Wt.%

Al 13.6

Ni -

Fe 4.76

Cu 81.64

Total 100

TABLE 6: COMPOSITION for AB1

Fig 36: EDAX study for AB1

53

Element Wt.%

Al 13.6

Ni -

Fe 4.76

Cu 81.64

Total 100

TABLE 7: COMPOSITION for AB2

Fig 37: EDAX study of AB2

54

Element Wt.%

Al 9.24

Ni -

Fe 4.58

Cu 81.76

Total 100

TABLE 8: COMPOSITION for AB2+2%

Fig 38: EDAX study for AB2+2%

55

Element Wt.%

Al 9.24

Ni -

Fe 4.58

Cu 81.76

Total 100

6.3 Hardness testing :

Observations :

Indenter = A steel ball , Diameter - 2.5mm

Load = 10D2

= 10(2.5)2

= 62.5 Kg

Test Specimens :

Fig 39: TEST SPECIMEN

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Hardness testing machine :

Fig 40: Brinell Hardness Tester

Observation Table :

Sr.no Grade PositionDia. of

indentationHardness (HB) Avg.

Hardness(HB)

1 AB1Core 0.77 131

129Intermediate 0.77 131Case 0.78 126

2 AB1+2%Core 0.70 159


3 AB2Core 0.70 159


4 AB2+2%Core 0.73 146


For as cast samples :

TABLE 9: HARDNESS OF CAST SAMPLE

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Sr.no Grade PositionDia. of

indentationHardness (HB) Avg.

Hardness(HB)

1 AB1Core 0.55 260


2 AB1+2%Core 0.55 260


3 AB2Core 0.71 155


4 AB2+2%Core 0.50 318


For Heat treated samples :

TABLE 10: HARDNESS OF HEAT TREATED SAMPLE

Result & Conclusions :

Sr.no Grades Avg. Hardness for as cast samples (HB)

Avg. Hardness for Heat treated samples (HB)

1 AB1 129 2632 AB1+2% 159 2603 AB2 159 1514 AB2+2% 180 318

TABLE 11: HARDNESS COMPARISION OF CAST SAMPLE AND HEAT TREATED SAMPLE

From above table, We can conclude that hardness of Heat treated samples are greater than that of the as cast samples of same composition.

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6.4 Tensile Testing :

Dimensions of test specimens :

inch mm

G- Gage length 2.000 ± 0.005 50.8

D- Diameter 0.500 ± 0.010 12.5

R- Radius of Fillet 3/8 9.525

A-Length of reduced section 2.25 57.15

TABLE 12: DIMENSION OF TEST SPECIMEN

Test specimens :

Fig 41 : Heat treated samples

Fig 42 : As cast samples

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Observation table :

Sr.no GradesAs cast samples Heat treated samples

Tensile Strength % Elongation Tensile

Strength % Elongation

1 AB1 381 8.4 462 2.222 AB1+2% 422 3.78 452 2.63 AB2% 315 4.32 359 2.464 AB2+2% 457 3.06 211 0.84

TABLE 13: TENSILE STRENGTH OF CAST SAMPLES AND HEAT TREATED SAMPLES

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CHAPTER 7 CONCLUSSION :From the above project we draw the following conclusion

7.1 Reduction in Oxide Formation:

By varying the composition of aluminium content in the aluminium bronze alloy bush.

Pros

The corrosion resistance property of the aluminium bronze component increases which makes its use feasible for marine applications.

Corns

The enriched aluminium content in the alloy of aluminium bronze increases the thickness of the oxide layer film which makes the material more porous and brittle, resulting in the breakage of material during machining

Conclussion:

From the above observations we concluded that the aluminium content should be kept in the range of 5-14% by weight in aluminium bronze.

By varying the proportion of alloying agents in the aluminium bronze alloy.

i) By varying the content of iron:

Result: The addition of iron up to 1% improves the mechanical properties mainly due to its effect on grain refinement. However the addition of iron is limited up to 5.5%.Above 1.2% the tensile strength and hardness are improved but its ductility gets lowered.

ii) By varying the content of nickel:

Result: The addition of nickel to an alloy containing iron has a beneficial effect in modifying the stable structure.

iii) By varying the content of manganese:

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Result: The most important effect of manganese is in improving the corrosion resistance of an aluminium bronze, the addition of magnesium is sufficient up to 6%. The main drawback is that aluminium bronze with low manganese addition is susceptible to corrosion when the addition exceeds 11% a fully stable structure is obtained resulting corrosion properties.

POURING HEIGHT:

Conclusion: The pouring height doesn’t play a much important role in avoiding the formation of oxides during the pouring of metal in the mould.

POURING TEMPERATURE:

Conclusion:The temperature should be maintained in the range of 1000 ° C to 1300°C with the best maintained at 1180°C.

If the temperature is maintained above the mentioned temperature the aluminium bronze alloy bush which is having an austenite structure is converted into martensite structure which is brittle in nature and results in breaking of material.

FLUX ADDITION:

Analysis: When we melt the metal there is a formation of slag which results into the formation of oxide in the casting.

To avoid it we add the composition of flux into the molten metal which results floating of slag above molten metal hence it can be easily removed before pouring.

Conclusion: Reduction of oxide formation in aluminium bronze.

FINDING THE COMPOSITION OF FLUX.

Conclussion: Some of the flux we tried using by mixing various compositions of various components are:

I. Calcium and sodium fluoride powderII. Deoxidizing tubes: These tubes are made of copper and contain a powder of

phosphorus and are weight about 25g used as a deoxidizing agent.III. Logas 50

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7.2. HEAT TREATMENT:

Hardness Testing:


Sr.no Grades Avg. Hardness for as cast samples (HB)

Avg. Hardness for Heat treated samples (HB)

1 AB1 129 2632 AB1+2% 159 2603 AB2 159 1514 AB2+2% 180 318

TABLE 14: HARDNESS COMPARISION OF CAST SAMPLE AND HEAT TREATED SAMPLE

From above table, We can conclude that hardness of Heat treated samples are greater than that of the as cast samples of same composition.

Tensile Strength Testing


Sr.no GradesAs cast samples Heat treated samples

Tensile Strength % Elongation Tensile

Strength % Elongation

1 AB1 381 8.4 462 2.222 AB1+2% 422 3.78 452 2.63 AB2% 315 4.32 359 2.464 AB2+2% 457 3.06 211 0.84

TABLE 15: TENSILE STRENGTH OF CAST SAMPLES AND HEAT TREATED SAMPLES

From above table, We can conclude that tensile strength of Heat treated samples are greater than that of the as cast samples of same composition.

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CHAPTER 8: REFERENCES:

[1] Copper Development Association PUB 80www.cda.org.uk/enquiry-form.htm .

[2] Copper Development Association PUB 83www.cda.org.uk/enquiry-form.htm

[3] H. J Meigh, ‘Cast and Wrought Aluminum Bronzes - Properties, Processes and Structure’, Institute of Materials, London, 2000, 404pp.

[4] P J Macken and A A Smith, ‘The Aluminum Bronzes - Properties and Production Processes’ CDA Publication No 31, second edition 1966, Copper Development Association, St Albans, 263pp. http://www.cda.org.uk/Megab2/corr_rs/pub31/default.htm

[5] Anonymous - “Aluminum Bronze Alloys for Industry” - CDA (UK) Publication No 83,8pp, March 1986

[6] Z. Ahmad and P. Dvami - “The effect of alloying additions on the optimisation ofcorrosion resistance and mechanical properties of alpha and beta aluminium bronzes” -Paper from 6th International Congress on Metallic Corrosion, Books, Sydney, 1975, 28pages.

[7] J. O. Edwards and D. A. Whittaker - “Aluminum Bronzes containing Manganese, Nickel and Iron: Chemical Composition, Effect on Structure and Properties” - Trans. A.F.S., 1961, 69, 862-72.

[8] Aluminum Casting Alloys_english_PV_2012_11_30

[9]Constitution of Binary Alloys. M Hansen and K Anderko, McGraw Hill Book Co, 1957

[10] Eng. & Technology, Vol.25, No.6, 2007 Study on Improvement of Casting Conditions for Some Aluminum Bronze Alloys

[11] ASTM Standards:B 208 Practice for Preparing Tension Test Specimens for Copper Alloys for Sand, Permanent Mold, Centrifugal, and Continuous Castings

[12] A. W. Tracy - “Resistance of Copper Alloys to Atmospheric Corrosion” - A.S.T.M. Symposium on Atmospheric Exposure Tests on Non-Ferrous Alloys, February, 1946

[13] J. L. Sullivan - “Boundary lubrication and oxidational wear” - J. Physics, D 1999

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http://www.cda.org.uk/Megab2/corr_rs/pub31/default.htm

[14] G. W. Lorimer, F. Hasan, J. Iqbal and N. Ridley - “Observation of Microstructure and Corrosion Behaviour of Some Aluminium Bronzes” - Br. Corros. J. 21, (4), 244-248,1986, ISSN: 0007-0599

[15] United State, Environmental Protection Agency, "Report on the Corrosion of certain Alloys",Washington, DC. 20460, July 2001.

[16] P. L. France, "Applied Science in the casting of Metals", 1970

[17] P. Brezina - “Heat treatment of complex aluminum bronzes” - Internat. Met. Reviews,1982, Vol 27, No 2.

[18] American Foundrymen’s Society; Designation: B 208- 06Standard Practice for Preparing Tension Test Specimens for Copper Alloy Sand, Permanent Mold, Centrifugal, and Continuous Castings

[19] For Copper Alloy Casting; FOSECO; 05/2011

[20] Eng & Technology, Vol. 25, No.6, 2007

[21] Burns T. A., Foseco (F.S.) limited, “Foundry man’s Hand book” , Ninth Edi., 1986

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final project report submision

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