19 modelling of interfacial heat transfer … of interfa… · die casting process and presence of...

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),

ISSN 0976 – 6359(Online) Volume 1, Number 1, July - Aug (2010), © IAEME

253

MODELLING OF INTERFACIAL HEAT TRANSFER

COEFFICIENT AND EXPERIMENTAL VERIFICATION

FOR GRAVITY DIE CASTING OF ALUMINIUM ALLOYS.

Cherian Paul

Assistant Professor

Department of Mechanical Engineering

SaintGITS College of Engineering, Kottayam, Kerala

Email: [email protected]

Parvathy Venugopal

Assistant Professor

Department of Mechanical Engineering

SaintGITS College of Engineering, Kottayam, Kerala

Email: [email protected]

ABSTRACT:

Interfacial heat-transfer coefficient has been measured during the solidification of

Aluminium alloys using permanent molds and solidification simulation technique is

being proposed in this thesis. The principal resistances to heat transfer across the casting-

die interface is the resistance of a layer of gas (assumed to be air), trapped between the

die and casting surfaces by virtue of their roughness and because of the solidification

shrinkage property exhibited during casting process and the thermal resistance offered by

the surface coating applied on the die. A Finite element simulation technique for gravity

die casting process is developed. This simulates the temperature at various locations in

die casting process and presence of hot spots, (i.e., a location in a casting that solidifies

last); in turn helps in placing the riser at the exact locations, there by increasing the

efficiency of die design. Several experiments were conducted by changing the core types

and using die coats to determine the heat transfer coefficient values by measuring the

surface roughness values of die and casting. The temperature at outside die surface is

measured and compared with the simulated results. These results were found to agree

with the experimentally determined temperatures.

International Journal of Mechanical Engineering

and Technology (IJMET), ISSN 0976 – 6340(Print)

ISSN 0976 – 6359(Online) Volume 1

Number 1, July - Aug (2010), pp. 253-274

© IAEME, http://www.iaeme.com/ijmet.html

IJMET

© I A E M E



254

Index Terms: Interfacial heat transfer coefficient, dycote, sand core, plaster core,

ANSYS

1. INTRODUCTION

MODELING of solidification can be of great benefit in improving the efficiency

of the casting process by showing how solidification defects such as shrinkage can be

avoided and by showing how smaller feeding systems can be used, improving the casting

yield. Good models require an accurate calculation of the changing temperature field in

the casting and this requires good data on the thermophysical properties of the materials

involved, but also a good knowledge of the initial conditions (the initial temperature

field) and the boundary conditions (often described by a heat-transfer coefficient).The

research described here was aimed at understanding the heat-transfer mechanisms at the

interface between a casting and its die in the gravity and low-pressure die casting of Al

alloys. In these processes, a layer of a porous refractory material is usually applied to the

die cavities. This reduces heat transfer between the cast liquid alloy and the die,

promoting filling of the cavity. It also controls the solidification rate in different areas of

the die; for example, the running and feeding parts of the die can often have a much

thicker coating applied to them to locally increase insulation. The coating also improves

the life of the die by reducing the thermal shock experienced and prevents the cast alloy

from soldering to the die material. Its further roles are to vent trapped air from the die

cavity and, in some cases, lubricate the release of the casting from the die. Studies of heat

transfer in gravity die casting process are important phenomena which will influence the

solidification process. Heat transfer between the die and casting is mainly restricted by

thin layer of air presented by virtue of surface roughness and solidification shrinkage.

Better understanding of interfacial heat transfer coefficients, boundary conditions and

material properties (density, thermal conductivity, and specific heat) will help the

designers for effective implementation of the simulation method in the riser design.

Studies have been reported on the measurement of interfacial heat transfer

coefficient and in general, a wide range has been reported. A narrow range of values is

more appropriate to model the solidification behavior accurately. This work is aimed at

finding out the interfacial heat transfer coefficients, at the interface between a casting and

its die in gravity die casting of Al alloys under various situations and to propose a shorter



255

range of heat transfer coefficient values. For this, a Finite element simulation technique

for gravity die casting process has to be developed, which should simulate the

temperature at various locations in die casting process and presence of hot spots, (i.e., a

location in a casting that solidifies last); in turn helps in placing the riser at the exact

locations, there by increasing the efficiency of die design. To validate the results obtained

by simulation, experiment has to be conducted to find the heat transfer coefficient in

gravity die casting process.

2. PROBLEM DEFINITION AND OBJECTIVES

It has been reported in the literature that the interfacial heat transfer coefficients

can vary in a range of 500-16500 W/m2K [2], which is wide range for designers to select

the appropriate values for simulating die casting process. Use of such wide range of

values in casting simulation will lead to inconsistent and in accurate results. Therefore it

is difficult to design risers properly using simulation. In this work experiments has been

conducted to narrow down the range of heat transfer coefficient values.

The main objectives are:

• Estimate the interfacial heat transfer coefficient using surface roughness and coatings

of die.

• Measure temperature variation with time (cooling curves) at specific locations in the

die and casting.

• Simulate the temperature profile using the modeled values of interfacial heat transfer

coefficient as an input parameter in solving heat transfer equation.

• Compare the simulated cooling curves with the experimentally measured curves.

3. ESTIMATION OF INTERFACIAL HEAT TRANSFER

COEFFICIENT

The procedure to estimate the interfacial heat transfer coefficient is discussed below.

3.1 Model of the interfacial heat transfer coefficient:

The interface of the die and casting will be as shown in Figure 3.1



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Figure 3.1 Surface patterns between casting and mould interface

At some time, t, after pouring a pure metal into an insulating mold (sand or ceramic) at

some pouring temperature the temperature along a line perpendicular to the mold - metal

interface would be expected appear as shown in Figure 3.2

Figure 3.2 Heat Transfer Pattern in Permanent Molds

Drop in temperature at mold and casting interface is mainly because of

• Resistance to heat offered by air gap presented in between die and casting.

� The resistance offered by the coatings applied on die surface. It is a usual practice

to apply coating on the die surface.

Air gap between the die and casting interface is formed because of

a) Solidification shrinkage of casting.

b) Surface roughness of the die and casting.

Figure 3.3 below describes the various elements for air gap formation

Figure 3.3 Casting and Die interface

These thermal resistances are evaluated by measurement of the coating thermal

conductivity and determination of the thickness of the applied coatings and the thickness

of the layer of air between the coating and casting surfaces. This system can be equated



257

to the electrical resistance system with two resistances in series which is shown in Figure

3.4.

Figure 3.4 Electrical resistance equivalent system for resistances in series

These thermal resistances are in series and were summed to determine the overall

thermal resistance.

resisttotal = resistcoat + resista

The heat transfer coefficients being reciprocal of the thermal resistance

h = (resistcoat + resista)-1

3.2 Coating resistance:

It was assumed that the coating surface could be described as a simple saw-tooth

profile, as shown in Figure 3.5

Figure 3.5 Insulating Coating on a Flat Substrate

Case i

The white coating was sprayed onto the die surface assumed to be flat. In this

case, it was assumed that the coating thickness measuring device rested on the top of the

highest peaks of the coating, and therefore was measuring distance xmax in Fig 4.3. The

mean thickness of the white coating (xmean) therefore was determined as this measured

thickness, minus half of the value of Ry, the maximum peak-to-valley height. The

thermal resistance through the die coating (resistcoat) could then be calculated using the

following expression:

(3.3)



258

Caseii

When the coating was sprayed onto a grit-blasted surface, the rough nature of the

substrate had to be taken into account as shown in Figure 4.6

Figure 3.6 Surface Profile of the Coating and Die Surfaces

It was assumed that the grit blasted die surface also had a saw-tooth profile and

the mean peak-to-valley height was denoted Rz(sub), and the maximum peak-to-valley

height denoted Ry(sub). The coating thickness measuring device was first zeroed on an

uncoated grit-blasted substrate, and therefore, the reference plane was the plane of the

highest peaks of the substrate. However, the valleys of the substrate were full of coating

material, so the reference plane lay above a coating thickness equivalent to 0.5Ry(sub).

The coating thickness measuring device was then placed on the surface of the coated

substrate and the resulting measured coating thickness was therefore from the highest

peaks of the coating to the reference plane, a distance denoted xmax. However, half of this

measured value was air (from the valleys of the coating surface). Therefore, the true

mean coating thickness was estimated as

)()(max 5.05.0 coatysuby RRxthickness −+=

The thermal resistance offered by the chromia coating was therefore equal to

(3.5)

3.3 Air resistance:

The gas in the voids between the rough casting and die surfaces would be

expected to offer a thermal resistance depending upon its thermal conductivity and

thickness, which depended on how the two rough surfaces were in contact.

In this case, the two surfaces were assumed to be in random contact as shown in

Figure 3.6, as a result of lateral thermal contraction of the casting surface and lateral

thermal expansion of the surface of the die. The two rough surfaces were equated to a

single sum rough surface in contact with a plane surface, and the roughness of this sum

rough surface was estimated by



259

shrinkagecastZdieZZ RRRR ++=Σ )(2

)(2

)( (3.6)

Reference: C.P. Hallam and W.D. Griffiths., “A Model of the Interfacial Heat- Transfer

coefficient for the Aluminum Gravity Die-Casting Process”, Metallurgical and Materials

Transactions B, vol 35B, pp. 1-15.

Where Rz(die) is surface roughness value of die, Rz(cast) is surface roughness value

of casting and Rshrinkage is the gap formed by solidification shrinkage. Rz(Σ) is the mean

peak-to-valley distance of the sum rough surface. An equivalent mean gap between the

two surfaces therefore was estimated to be 0.5Rz(Σ). Heat transfer through this interfacial

layer of gas (assumed to be air) was considered to be due to conduction only; heat

transfer by radiation and convection would be negligible. The thermal resistance of this

air layer therefore was estimated by

a

Z

ak

Rresist

)(5.0 Σ= (3.7)

Where ka is the thermal conductivity of air.

4. EXPERIMENTAL DETAILS

4.1 Equipment description:

The equipment needed for conducting experiments are (i) melting furnace,

(ii) thermocouples and (iii) steel die and these items are described below.

4.1.1 Melting furnace:

For melting of the aluminium, muffle furnace is used. The max temperature limit

for this muffle furnace is 12000C and the working temperature is 1080

0C. Before melting

the aluminium the crucible is pre heated to 4500C in order to eliminate moisture content

present in the crucible and to avoid the entrapped gases. Then the aluminium scrap of

IS63400 is charged in to the crucible for melting and is superheated to 7800C.

Figure 4.1 Melting Furnace



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4.1.2 Thermocouple:

A K-type mineral insulated thermocouple is used to measure the die temperature.

The maximum temperature that can be measured by the thermocouple is 14000C and a

digital reading unit shown in Figure is used to read the temperature.

Figure 4.2 Thermocouple

4.1.3 The Die:

Cast iron blocks are bought and are machined to required dimensions for making

the die. The die assembly consists of One Base plate 350x250x25 mm3, two Side plates

200x80x25 mm3 each, two end plates 220x80x25 mm

3 each and two half inch MS bolts

for fastening them. Two more equipments used are the crucible made of graphite and the

tongs made from MS rods. These equipments are shown below in Figure 4.3

Figure 4.3 Die Arrangement Used for Experimentation

ground level have been identified for wind power development. Six handbooks on “Wind

Energy Resource Survey in India” have so far been published covering 208 sites. The

seventh volume of Handbook covering wind data for 26 stations is ready for publication.

It is also proposed to prepare a Wind Atlas for India, which will give the overall potential

in various States and identify high windy areas and specific sites for setting up wind

power projects.

Crucibl

Tong Die



261

4.2 Material Used: Short descriptions of the materials used for conducting the experiments are given below.

4.2.1 Aluminium ingot:

IS63400 grade aluminium is used to make the melt and the composition of the

alloy used is given below in table 4.1

Table 4.1 Composition of aluminium

Element Weight %

Copper 0 – 0.1

Magnesium 0.4 - 0.9

Silicon 0.3 – 0.7

Iron 0 – 0.3

Manganese 0 – 0.4

Other elements like titanium and grain refining elements will be of 0.4%

4.2.2 Dycote 140:

Castings obtained by GDC should be

i. Metallurgical sound.

ii. Having good surface finish.

iii. Easily and rapidly produced

To achieve this, the die must be coated. Usually the dycotes are of 2 types,

insulating and lubricating coatings. Insulating coating materials contain blends of

insulation minerals such as talc, mica, titanium dioxide, alumina etc. In this experimental

work, we are using a insulating coating material dycote 140. Dycote 140 is an off white

paste with mixing ratio of 3-5 volume of soft water to 1 volume of paste. It is the

standard; general purpose dressing used extensively in all sectors and gives a medium to

fine surface finish. The major components of dycote 140 are mica, talc and sodium

silicate

4.2.3 Sand core:

The molding sand is used for making sand core. Molding sand is actually silica

sand mixed with some additives like bentonite of about 5-10% (depending on the amount

of silica present) coal dust 1-1.2% and 5-7% of water. A core of size 200x80x30 mm3

was made for the experimental work. The sand core made is shown below in Figure 4.5



262

Figure 4.5 Sand core

4.2.4 Plaster of paris core:

Experiment was conducted using a plaster of paris core. The core material is

actually phosphate bonded investment material. The investment materials consist of heat

resistant silica based material as refractory, gypsum, phosphate compound or silica

compound as binder and modifiers like sodium chloride, boric acid, potassium sulphate,

copper etc. Here we are using phosphate bonded investment material. Its main ingredients

are quartz or cristobalite or both as refractory material, magnesium oxide and acid

phosphate as binder and colloidal silica suspension as modifier. The plaster core made is

shown below in Figure 4.6

4.3 Experimental procedure:

Temperatures were measured using experimental set up shown in Figure 6.3. A

200*80*25.4 mm3

aluminium block was cast. A 0.5 mm dia mineral insulated K-type

thermocouple is used to find the temperature. Temperatures were measured outside face

of die and at a point 22 mm deep from the die surface using a k type thermocouple at

regular intervals separately. The casting alloy is poured into the mold cavity with

superheat of 1200C. The thermal histories at the mold surface and at the point from 22

mm deep were taken for every 2 sec until the temperature will reaches the maximum and

it starts decreasing. The Temperature values in simulation and experiment were measured

at the same location which is shown in Figure 4.7.



263

Figure 4.7 Location used for temperature measurement

4.4 Experiments conducted:

Many trails were conducted by using sand and plaster of paris mixed with silica

cores, without cores and also by applying die coat. The list of experiments conducted are

illustrated below in table 4.2

Table 4.2 Experimental matrix

5. SIMULATION OF CASTING SOLIDIFICATION

The heat transfer equations appropriate for the casting solidification comprises of

conduction as well as convection equations. The conduction equation is applicable for die

as well as molten metal.

Case i

Experimental conditions

Experiment No: Core used Die coat used

1 Sand core No coating done

2 Plaster of paris core No coating done

3 No core used Die coated with diecoat 140

4 No core used No coating done



264

Consider the case of die individually. The total heat flow is given by the equation.

Where ρ is the density of the die material, C is the specific heat and k is the thermal

conductivity.

Case ii

Consider the case of molten metal. Since the mode of heat transfer between the

die and the metal is conduction, the above equation proves to be ideal. Thus the heat flow

is given by the equation

Where ρ is the density of the metal, C is the specific heat and k is the conductivity

of the metal used.Here we consider the case of convection between the solidifying metal

and atmosphere. Thus the convection equation is taken into consideration. The heat flux J

generated which is the total heat per unit area is given by the equation

)( αTTmhJ −=

Where J is the flux generated, h is the interfacial heat transfer coefficient, Tm is

the temperature of the metal and Tα is the ambient temperature. For solving these

nonlinear equations, the initial and boundary conditions of the corresponding materials

are to be given as input parameters. The values of density, specific heat thermal

conductivity etc of die and metal are to be given appropriately. The most important

parameter that governs the heat transfer at the metal mold interface is the h value that is

the heat transfer coefficient value. The HTC value we obtained from experiment is to be

given as an input parameter for the simulation. For the solution of heat transfer equations,

material properties of the corresponding metal and die material are to be given as input

values. The properties of materials are shown below in table.

Material Density

Kg/m3

Conductivity

W/mK

Specific

heat

J/KgK

Convection

W/m2K

Sand 1800 1.5 1117 ---

Aluminium 2700 238 917 ---

Steel 7870 78.2 456 ---

Air 1.127 .0271 1.005 500-16500



265

Simulation of casting solidification requires solving of heat transfer equations and

for that a set of initial and boundary conditions are to be given as input parameters. Here

the initial conditions are the temperatures of various materials. They are:

• Temperature of aluminium casting is 7000C

• Temperature of die is 800C

• Temperature of sand core is 300C

In addition to the initial conditions given, boundary conditions are also to be

given for solving the heat transfer equations. The boundary conditions are the convection

coefficient values of various materials. They are given by:

• Convection coefficient value between aluminium and air is 50W/m2K.

• Convection coefficient value between sand and air is 4 W/m2K.

• Convection coefficient value for die is 10W/m2K.

Convection value for air (interfacial heat transfer coefficient) is 5347W/m2K

Schematic diagram showing various boundaries

5.1 Solution methodology

Simulation of solidification can be of great benefit in improving the efficiency of

gravity die casting process. Modeling requires an accurate calculation of the changing

temperature field in casting and correct data regarding interfacial heat transfer

coefficients between die and casting. This requires good data on the thermo physical

properties of materials involved and good knowledge of initial conditions (initial

temperature field) and boundary conditions (often described by a heat-transfer

coefficient).



266

5.2 Creation of model:

Simulation procedure for the experiments conducted is as follows. All the

volumes i.e., die; casting and core were created according to the arrangement in the

experimental setup as shown

Meshed model

After specifying all the initial and boundary condition by solving the model for

specified time interval, we can analyze the temperature distribution in the die-casting

model. For developing the model and to run the simulation ANSYS Parametric Design

Langue (APDL) code is used. Comparing the experimental and simulated results is one of

the most important processes in this work. For the comparison, we are conducting a chi-

squared test (χ2

test).

6. RESULTS AND DISCUSSIONS

The results obtained by conducting experiments are explained below.

6.1 Estimated heat transfer coefficient values:

The estimated values of heat transfer coefficient are reported below.

6.1.1 Case i. Without using any core or coating.

In this case, the resistance to heat transfer is offered due to air resistance alone.

Rz(die) = 7.42 µm



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Rz(cast) = 9.5 µm

Rshrinkage = 8.73 µm

Using equation (3.6)

Rz(Σ) = 20.78 µm

ka = 0.068355 W/mK


resista = 1.52X10-4

m2K/W

h = (1.52x10-4

)-1

= 6578 W/m

2K

6.1.2 Case ii. Using sand core

By considering equations 3.6 and 3.7,

Rz(die) = 7.42 µm

Rz(cast) = 11.35 µm

Rshrinkage = 12 µm

Rz(Σ) = 25.56 µm

ka = 0.068355 W/mK

resista = 1.84X10-4

m2K/W

h = (1.84x10-4

)-1

= 5347 W/m

2K

6.1.3 Case iii,Using dycote 140

In this case, the heat transfer is restricted due to the resistance offered by the

coating applied on the die inner surface. Here the air resistance is taken as zero.

Xmax = 31.67 µm

Ry(coat) = 17.566 µm.

Kc = .68 W/mK.


resistcoat = 2.8x10-4

m2K/W


h = (1.84x10-4

)-1

= 3571 W/m

2K



268

6.7.1.4 Case iv, Using plaster core

In the case of plaster core experiment, the air resistance alone is taken into

consideration and coating resistance is considered as zero since no coating was applied.

Rz(die) = 7.42 µm

Rz(cast) = 12.5 µm

Rshrinkage = 13.53 µm


Rz(Σ) = 28.07 µm

ka = 0.068355 W/mK


resista = 2.05X10-4

m2K/W

h = (2.05x10-4

)-1

= 4870 W/m

2K

Experimental conditions

Core used Die coat used HTC values (W/m2K)

No core used No coating done 6578

Sand core No coating done 5347

No core used Die coated with diecoat 140 3571

Plaster of paris core No coating done 4870

Table 6.1 Estimated HTC values.

6.2 Cooling curves

For each of the experiments conducted, their corresponding cooling curves were

plotted by measuring temperatures at a particular location (ref Figure 4.7) at regular

intervals using a thermocouple. The curves are shown in figure 5.1.

6.2.1 Experimentally obtained cooling curves.

Figure 6.1 Cooling curves for different experimental conditions



269

6.2.2 Simulation cooling curves

Finite element analysis was done for each of the four experimental conditions.

The experimentally calculated HTC values were given as input parameter for the analysis

and corresponding cooling curves were extracted. The simulation cooling curves are

shown below in figure 5.2

Figure 5.2 Simulation cooling curves

6.3 Comparison of results

The cooling curves obtained experimentally and through simulation are compared

are reported below.

6.3.1 Case i. Without using core or coating

Figure 6.3 Comparison of results obtained when no core or coating was used



270

6.3.2 Case ii. Using sand core.

Figure 6.4 Comparison of results obtained when sand core was used

6.3.3 Case iii. Using Plaster core.

Figure 6.5 Comparison of results obtained when plaster core was used

6.3.4 Case iv. Using Dycote 140

Figure 6.6 Comparison of results obtained when dycote 140 was used



271

For the comparison of results, chi square analysis was performed between each of

the four sets of values and finally the agreement between the each sets of values were

proved to be matching at 95% confidence interval.

The small mismatch between the results may be because of the following reasons:

• The surface roughness value of the casting was selected from the design data

available, since for as cast components the surface roughness cannot be measured.

• The solidification shrinkage has to be exactly measured and has to be incorporated in

simulation results and also the thermal expansion of the die was not taken into

consideration.

• Installation error may happen while mounting the thermocouple.

• The properties of coating material and also for plaster of paris were chosen arbitrarily.

These variations in the results can be eliminated by

• Finding the exact surface roughness values of castings produced.

• By considering the solidification shrinkage gap exactly and the thermal expansion of

the die.

• By collecting temperature histories at different locations in the experiment and this

data is to be used to calculate the HTC value theoretically.

• The properties of the chosen materials are to be considered accurately.

• Heat transfer values can be found out by changing the initial temperatures of die and

castings, boundary conditions and applying various coatings on die surface.

7. CONCLUSIONS

Heat transfer analysis were conducted on the solidification of a commercial

casting of Al alloy in a gravity die casting process. The interfacial heat transfer

coefficients were estimated using a direct method, i.e. by finding the best match between

the experimental and simulated temperature profiles in the casting. A reasonably good

agreement has been observed between experiment and modeling, thus resulting in the

generation of the value of the interfacial heat transfer coefficient. The benefits of such an

approach have been discussed. The procedure utilized to determine the interfacial heat

transfer coefficient can be applied to other casting processes.

The experimental data and subsequent calculations showed that the interfacial

heat transfer coefficient value is highest for the experiment conducted without core or



272

coating and the lowest value is for experiment with dycote 140. The HTC value again

reduced when the coating thickness was increased. The influences of air gap, die coatings

and contact area of die and casting on the interfacial heat-transfer coefficient was studied.

As the air gap is increasing, interfacial heat transfer coefficient is decreasing and as the

roughness of die surface is increasing air gap is increasing there by the heat transfer

coefficient values are decreasing.

Finite element model is proposed for the analysis of permanent mold castings.

Since the experimental and simulation cooling curves are matching for the given HTC

values, these short range of (3500- 7000 W/m2K) values can be applied for simulation of

die-casting.

FUTURE WORKS

• There is scope for reducing the error between the simulated results and experimental

results by applying exact material properties, environmental conditions and finding

ways to reduce installation errors.

• Additional experimental programs for determining interfacial heat transfer coefficients

in permanent mold casting processes for a variety of geometries and alloys should be

pursued.

• Experiments can be conducted by considering solidification shrinkage and thermal

expansion of die for measuring the air gap.

• Experiments can be conducted by incorporating more number of thermocouples at

various locations.

• Heat transfer values can be found out by changing the initial temperatures of die and

castings, boundary conditions and applying various coatings on die surface.

• The time-dependent interfacial heat transfer coefficient is the result of many factors,

that greatly complicates the resolution of the problem. Using the temperature

measurement techniques described in the present program, and awaiting advances in

computer techniques for defining three-dimensional analysis techniques, the

determination of the thermal and mechanical behavior of a casting in a permanent

mold can be resolved. A further study of the time response of direct contact

thermocouples is suggested.

• Continued support of research in this area is encouraged.



273

ACKNOWLEDGEMENT

We are deeply indebted to Dr R Sellamuthu, Professor, department of mechanical

engineering, Amrita University who has been kind enough to suggest this topic, for his

motivation and guidance throughout the duration of the project, by way of valuable

suggestions and ideas. We are thankful to our staff members of the Department of

Mechanical Engineering without whose help this dissertation would not have been

completed successfully. Last but not the least, I wish to express my heartfelt thanks to

God, my beloved parents and my dear friends whom always give the way success.

REFERENCES

1. Robert D. Pehlke and John T. Berry, “Investigation of Heat Transfer at the Mold/Metal

Interface in Permanent Mold Casting of Light Alloys”, Dept. of Materials Science and

Engineering ,The University of Michigan, October, 2005.

2. M.M Pariona, A.C.Mossi., “Numarical Simulation of Heat Transfer During the

Solidification of Pure Iron in Sand and Mullite molds”, Journal of the Braz.Soc. of

Mech.Sci&Eng, Vol XXVll, No.4. pp 399-406, October 2005.

3. C.P. Hallam and W.D. Griffiths., “A Model of the Interfacial Heat- Transfer coefficient

for the Aluminum Gravity Die-Casting Process”, Metallurgical and Materials

Transactions B, vol 35B, pp. 1-15. April 2004

4. R.W. Lewis and R.S. Ransing., “A Correlation to Describe Interfacial Heat transfer

during Solidification Simulation ans its Use in the Optimal feeding Design of

Castungs”, Metallurgical and Materials Transactions B,Vol 29B, pp.437-452. April

1998

5. W.D Griffiths., “A Model of the Interfacial Heat Transfer Coefficient during

Unidirectional Solidification of an Aluminum Alloy”. Metallurgical and Materials

Transactions B, Vol 31B, pp.285-295, April 2000.

6. Dr.S.Shamasundar, V.Gopalakrishna, Manjunatha, Badrinath, “Gravity Die Casting

Process: Die Design and Process Optimization”. ProSIM- AFTC, 326, III Stage IV

Block, Basaveshwara Nagar, April 2000.

7. Calcom SA, Parc Scientifique EPFL, CH-1015 Lausanne, Swaziland.

8. Prof. Karl B. Rundman., “Metal Casting (Reference Book for MY4130),” Dept. of

Materials Science and Engineering, Michigan Tech. University



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9. John, Campbell, “Castings Practice: The 10 Rules of Casting”, Elsevier. Materials and

Design, Vol 29, pp. 635–636, 2005.

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2000, vol. 31B, pp. 75-86.

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2000, vol. 31B, pp. 87-96.

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