In today’s world a casting production without any defect is almost impossible. After the application of various optimization techniques and process we still are not able to get the defect free castings. So it is critically important to analyze the root cause of casting defect with in the process itself, so that any changes which can hamper the defect intensity can be invoked at the time of manufacturing or foundry shop production. The gravity die casting process is governed by its process parameters so it is required to study its process parameters and its effects. In this paper an effort has been incorporated to study the change in process parameters and their consequent effects on casting defects.

1. http://www.iaeme.com/IJMET/index.asp 208 editor@iaeme.com
International Journal of Mechanical Engineering and Technology (IJMET)
Volume 7, Issue 2, March-April 2016, pp. 208–211, Article ID: IJMET_07_02_023
Available online at
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=7&IType=2
Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
STUDY OF PROCESS PARAMETERS OF
GRAVITY DIE CASTING DEFECTS
Vasdev Malhotra
Associate Professor, Mechanical Engineering Department,
Mechanical Engineering, YMCAUST, Faridabad -121006, (India)
Yogesh kumar
M. Tech Student, Mechanical Engineering Department,
YMCAUST, Faridabad -121006 (India)
ABSTRACT
In today’s world a casting production without any defect is almost
impossible. After the application of various optimization techniques and
process we still are not able to get the defect free castings. So it is critically
important to analyze the root cause of casting defect with in the process itself,
so that any changes which can hamper the defect intensity can be invoked at
the time of manufacturing or foundry shop production. The gravity die casting
process is governed by its process parameters so it is required to study its
process parameters and its effects. In this paper an effort has been
incorporated to study the change in process parameters and their consequent
effects on casting defects.
Key words: Casting, Root cause, process parameters
Cite this Article Vasdev Malhotra and Yogesh kumar, Study of Process
Parameters of Gravity Die Casting Defects. International Journal of
Mechanical Engineering and Technology, 7(2), 2016, pp. 208–211.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=2
1. INTRODUCTION
In practical foundry shop it is quite tough to judge the exact cause for a particular
defect because they are quite intuitive in nature. So first of all it is required to identify
process parameters which can affect the process considerably and can change the
output with reasonable weightage. So it is required to identify the factors which can
affect the process and these factors are identified with the help of study of various
literatures and interaction with various foundry experts in different industries.
According to experience and expertise of foundry experts and after studying various
literatures there are lots more factors which are identified to be affecting the gravity
die casting process considerably are as follows[2]. A gravity die casting essentially
consists of following parameters such as

2. Study of Process Parameters of Gravity Die Casting Defects
http://www.iaeme.com/IJMET/index.asp 209 editor@iaeme.com
 Pouring mould temperature
 Pre heat temperature
 Pouring time
 Selection of gate and riser design
 Melt holding time
 Degasification time
 Die coat material
 Pouring velocity
 Die coat thickness
2. PROCESS PARAMETERS:
The process parameters which are critical and can affect the process considerably are
2.1. Pouring temperature:
Pouring temperature generally varies from 650 to 800 degree Celsius. When we pour
aluminum alloy then its fluidity is completely dependent upon pouring temperature.
Generally, a better fluidity in higher temperature is connected with the decreasing
viscosity and surface tension of molten metal with the increasing of pouring
temperature, which leads to the increasing filling speed. At the same time, the heat
capacity of molten alloy rises with increasing temperature of the pouring, what results
in the increase of filling time. On the other hand, the oxidation liability of magnesium
alloy increases with the pouring temperature rise, what increases the viscosity and
decreases the filling speed. Therefore, growth rate of fluidity above 735 °C is lower
than between 695 °C and 735 °C. The pouring temperature also affects the
microstructure formation at a greater extent and which in turn affects the final
structure and toughness of casting product.[1]
2.2. Preheat temperature
Preheating in the gravity die casting is done to remove the possibility of formation of
temperature gredients. If we increase the preheat temperature from a particular range
then it may affect the die coating and also it may create defects like rough surface
finish and also if the temperature is removed considerably then this may cause a
particular chilling effect which in turn leads to less solidification of core and due to
this difference in solidification rate defects like solidification shrinkage may occur.A
significant precondition for the production of high quality castings is keeping an
optimum temperature of the respective parts of the mould cavity surface[2].
2.3. Selection of gate &riser design
Feeder acts as a liquid metal reservoir provides liquid feed metal until the end of the
solidification. Riser also serves as a heat reservoir, creating a temperature gradient
that induces directional solidification. Two criteria determine whether or not a riser is
adequate. Common types of feeders are: top feeder and side feeder. The major
considerations in the casting design are the quality of the final product and the yield,
which heavily depend upon gating system and feeders. Even after spending significant
resources (man-hours, materials, machine overhead and energy) for casting
development, one of the following situations may arise during regular production. [3]

3. Vasdev Malhotra and Yogesh kumar
http://www.iaeme.com/IJMET/index.asp 210 editor@iaeme.com
1. Under design: resulting in high percentage of defective castings, due to the number or
size or placement or selection of feeders and gating and gating elements are
inadequate.
2. Over design: leading to acceptable quality level, but poor yield and thereby high cost.
In this case, the number and/or size of feeders and gating elements are much higher
than their respective optimal values.[4]
2.4. Degasification time & material
The gas used for degasification is mostly argon and nitrogen which are inert gases.
After melting the molten metal should go in to “degassing process”. In this method,
an inert gas like argon or nitrogen is injected into the flow of molten metal through
injection nozzles. The hydrogen diffuses into the bubbles. The gas is bubbled through
molten aluminum to remove absorbed hydrogen. The amount of hydrogen is reduced
gradually. This bubbling action of inert gas through spinning rotor helps oxide
particles to float to the surface. It also creates a large number of small bubbles of gas
that are mixed with the liquid alloy. Rotory degassing method is shown in Figure
given below. Degassing fluxes are added to remove hydrogen from the molten metal
as well as to lift oxides and particles to top of the bath so that they can be removed.[5]
2.5. Degasification & defects
Degasification mainly eliminates the unwanted gases from the mould by bubbling at
the bottom of the container as shown in the above figure and it controls the porosity to
a much larger extent. Porosity control in aluminum castings can be done in following
ways .Hydrogen content in the molten metal decreases by increasing the degassing
time. Degassing should be done at optimum temperature. The degassing should be
done at lowest temperature because as the temperature increases, the volume of the
gas that passes for degassing increases. The change of hydrogen content in the molten
metal, after the application of same degassing time, with the change of metal
temperature is considerable.[6]
2.6. Die coat thickness and material:
Die coat in the gravity die casting in order to obtain smooth surface finish and to
avoid direct exposure of mould to the molten metal in order to avoid direct chilling
affect. The material used for die coating is generally calcium carbide and silicon
mixture and graphite [7].
2.7. Thermal characteristics of die coat thickness:
In permanent mold casting or gravity die casting (GDC) of aluminum alloys, die
coating at the casting-mold interface is the most important single factor controlling
heat transfer and, hence, it has the greatest influence on the solidification rate and
development of microstructure. While the alloy is liquid, the coating material has only
a weak influence over heat flow and the thermal contact resistance seems to be
governed more by coating porosity and thickness [8].
3. CONCLUSION
The overall motive of this paper is to make an analysis so that a relation between
casting defects can be established. The study depicts that in practical circumstances it
is not necessary to apply special techniques to minimize the casting defects such as
computer simulation etc which makes the situation quite hypothetical in nature. The
defect free casting although not practically possible but still at a greater extent of

4. Study of Process Parameters of Gravity Die Casting Defects
http://www.iaeme.com/IJMET/index.asp 211 editor@iaeme.com
defects can be minimized by using optimum values of process parameters which can
affect the casting process considerably.
REFERENCES
[1] Adil Mohamed Elbasheer Ahmed, Mohamed Ibrahim Shukri, WaielFathiAbd El-
Wahed, “A Fuzzy Expert System for Rigging System Design”Journal of Science
and Technology 12 (02 ) December 2011 ISSN 1605 – 427X
[2] Tapan Roy, “analysis of casting defects using computer simulation” published in
Transactions oF 61st “Indian Foundry Congress” 2013
[3] Rajesh Rajkolhe, J. G. Khan, “casting defects and its remedies” published in
“International Journal of Research in Advent Technology”, Vol.2, No.3, March
2014 E-ISSN: 2321-9637
[4] K. Omura, Y. Otsuka, and M. Konishi, “Diagnostic expert system for mold level
control equipment in continuous caster,” in Proc. 6th Int. Iron and Steel Congr.,
Nagoya, Japan, 1990, pp. 62–68.
[5] B. Kalandyk, R. Zapała, A. Rakowska, Characteristics of defects present in
industrial steel castings due to metal-mould reactions, Archives of Metallurgy
and Materials 54, 2 (2009).
[6] R. Wrona, A. Stawowy, A. Macioł, A formalized description of foundry
production program, Archives of Foundry Engineering, Polish Academy of
Sciences. Commission of Foundry Engineering; ISSN 1897-3310. 7, 3, 179-182
(2007)
[7] S. Kluksa and nawarecka , Evolution of computer programming in production
processes control, Archives of Foundry Engineering Polish Academy of Sciences.
Commission of Foundry Engineering 2, 5, 80-86( 2003)
[8] Achamyeleh A. Kassie, Samuel B. Assfaw,” Minimisation of casting defects”
published in IOSR Journal of Engineering (IOSRJEN) e-ISSN: 2250-3021, p-
ISSN: 2278-8719Vol. 3, Issue 5 (May. 2013), ||V1 || PP 31-38
[9] Cherian Paul, Parvathy Venugopal, Modelling of Interfacial Heat Transfer
Coefficient and Experimental Verification For Gravity Die Casting of Aluminium
Alloys. International Journal of Mechanical Engineering and Technology, 1(1),
2010, pp. 253–274.