TECHNICAL FIELD
[0001] The present subject matter generally relates to a process for manufacturing a piston of an engine and particularly relates to a cold chamber high pressure die casting process for
manufacturing a piston with desired geometry and intricate contours.
BACKGROUND
[0002] Internal combustion engines as power generating sources are employed in numerous
applications. Both gasoline and diesel internal combustion engines are available in 2-stroke and 4-
10 stroke versions. Pressure generated by ignition or compression of fuel in an internal combustion
engine provides reciprocating motion to a piston located inside a cylinder of the engine. The
reciprocating motion of the piston inside the cylinder results in generation of desired output.
[0003] Conventionally, Aluminium Silicon alloy pistons used in 2-stroke or 4-stroke versions of
gasoline and diesel engines are manufactured by employing the gravity die casting process (also
15 called Permanent Moulding Process). This process is by and large suitable for mass production but
requires the castings to be made with adequate wall thickness for achieving the proper filling of the
die and producing a casting of the desired quality. Further, this process needs a higher machining
allowance. Also, the gravity die casting process is not amenable for thin walled castings with
intricate shapes and contours. In addition, the gravity die cast pistons cannot offer the smooth as–
20 cast surface finish that is achievable in pressure die casting process. Further, pistons used in current
generation of 2-stroke engines call for tight tolerances, detailed geometry with intricate shapes and
contours. These are required to be achieved with less wall thicknesses to guarantee light weight and
3
to match the desired contours in the assembly in order to fulfil current and future emission
regulations with “near net shape” and very little machining of pistons.
[0004] Therefore, there is a need for a process of manufacturing a light weight piston that requires
least maintenance, has desired geometry, thin walls, as well as intricate shapes and contours,
without compromising current and future emission regulations5 .
SUMMARY
[0005] Embodiments disclosed include a high pressure die casting process using a Hypereutectic
Aluminium – Silicon (AL-Si) alloy comprising manufacturing a die according to a die gating design
10 derived from a casting drawing that factors in a casting contraction allowance, a machining
allowance, and a chemical composition of a determined alloy. According to an embodiment of the
process, manufacturing the casting comprises first pre-melting the hypereutectic Al-Si alloy. After
pre-melting the hypereutectic Al-Si alloy, a first flux treatment of the pre-melted hypereutectic Al-
Si alloy at a first pre-defined temperature prepares the alloy for a second flux treatment at a second
15 pre-defined temperature. After the flux treatment is complete, degassing of the flux treated
hypereutectic Al-Si alloy is implemented, wherein the degassing comprises removal of hydrogen
from the molten hypereutectic Al-Si alloy. Subsequently, both the Al Grains and the Primary Si
Grains in the hypereutectic Al-Si alloy undergo corresponding refining treatments. Refining of the
Al Grains in the hypereutectic Al-Si alloy comprises addition of Ti (Titanium) and B (Boron) to the
20 alloy and refining the Primary Silicon Grains comprises addition of P (phosphorous) to the alloy;
and finally, the prepared metal is tested and injected into to the Die Cavity using a vacuum assisted
injection.
4
[0006] Embodiments disclosed include a process for manufacturing a piston of an engine. The
method includes the step of applying high pressure in a die casting process for pushing molten metal
into detailed features with desired geometry and intricate contours in a mould.
[0007] According to an embodiment, the high pressure is applied in a cold chamber, and preferably
the metal used for production of the piston is Hyper Eutectic Aluminium Silicon alloy. Accordin5 g
to one embodiment, the alloy used in the process is Hyper - Eutectic Al-Si alloy, consisting of 12 to
25 % Silicon.
[0008] In one embodiment of the present subject matter, the die casting GATING design is done by
using a Casting Filling and Solidification Software.
10 [0009] In yet another embodiment of the present subject matter, the various elements of the die
GATING system are designed using fundamental calculations involved with molten metal flow and
associated with the cold chamber high pressure die casting process. Based on these calculations, the
dimensions of the various parts in the flow system are arrived at. However, based on the results of
the actual casting when run in production, any necessary corrections in particular dimension/s are
15 carried out by an iteration process of trial and error and the casting quality is validated by visual
observation of the machined surface, microscopy and by X-Ray examination.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The present invention, both as to its organization and manner of operation, together with
20 further objects and advantages, may best be understood by reference to the following description,
taken in connection with the accompanying drawings. These and other details of the present
5
invention will be described in connection with the accompanying drawings, which are furnished
only by way of illustration and not in limitation of the invention, and in which drawings:
[0011] Figure 1 illustrates a flow chart depicting a process for manufacturing a piston for an
internal combustion engine in accordance with the present subject matter.
[0012] FIG. 2 depicts a pre-and post-machined piston manufactured by the gravity die castin5 g
process using hypereutectic AL-Si alloy.
[0013] FIG. 3 depicts a pre-machined and post-machined piston manufactured by the high pressure
die casting process using hypereutectic AL-Si alloy.
[0014] FIG. 4 illustrates via a comparative certificate of inspection and parameters of the surface
10 finish of a post-machined piston manufactured by the gravity die casting process and the high
pressure die casting process using hypereutectic AL-Si alloy.
DETAILED DESCRIPTION
[0015] The following is a detailed description of embodiments of the invention depicted in the
15 accompanying drawings. The embodiments are introduced in such detail as to clearly
communicate the invention. However, the embodiment(s) presented herein are merely
illustrative and are not intended to limit the anticipated variations of such embodiments; on the
contrary, the intention is to cover all modifications, equivalents, and alternatives falling within
the spirit and scope of the appended claims. The detailed descriptions below are designed to
20 make such embodiments obvious to those of ordinary skill in the art.
[0016] The present subject matter relates to a high pressure die casting process for manufacturing a
piston of an internal combustion engine. The process according to the present subject matter
6
employs extra pressure which enables the molten metal to be pushed into detailed features with
desired geometry and intricate contours in a mould. The piston produced by the process of the
present subject matter offers excellent surface finish that is consistent dimensionally with precision
features, minimum draft, and “Near net shape” to the product with reduced “Post cast machining”.
[0017] The process according to the present subject matter is the cold chamber high pressure di5 e
casting process since the metal used for production of pistons is Hyper Eutectic Aluminium Alloy
that has the tendency to alloy with iron in the casting equipment at high temperatures.
[0018] The design of the gating system of the appropriate dies is done with precision (first by using
simulation software, thereafter making initial trial castings, improving upon the design using
10 theoretical calculations and finally by actual iteration (series of trial and error steps), and controlling
all foundry process parameters during the molten metal treatment and casting. The same are
explained in the accompanying Flow Chart and the Serial Write up below.
[0019] According to an embodiment of the method, high pressure die casting (HPDC) is used for
manufacturing 2-stroke channel type chain saw pistons and 4-stroke motorcycle and scooter pistons.
15 One preferred embodiment refers to the of use of a Hyper Eutectic Al-Si Alloy B 390. According to
an embodiment, the chemical composition of the alloy is determined based on a finished piston
casting drawing. Now conversely, based on the determined alloy a new piston casting drawing is
generated, and based on the thermal properties of the alloy, the die gating design is generated and
subsequently manufactured. Some embodiments utilize a casting solidification software for
20 generating the die gating design. Preferably, a machine setting, and molten metal injection
parameter is also determined.
[0020] Embodiments disclosed include a high pressure die casting process using hypereutectic ALSi
alloy comprising, generating the casting dimensions based on a casting contraction allowance, a
7
machine allowance, and a die design calculation. According to an embodiment, generating the
casting comprises first pre-melting the hypereutectic AL-Si alloy. After pre-melting, a first flux
treatment of the pre-melted hypereutectic AL-Si alloy at a first pre-defined temperature prepares the
alloy for a second flux treatment at a second pre-defined temperature. After the flux treatment is
complete, degassing of the flux treated hypereutectic Al-Si alloy is implemented, wherein th5 e
degassing comprises removal of hydrogen from the molten hypereutectic Al-Si alloy. Preferably,
both the Al and the Primary Silicon grains in the hypereutectic Al-Si alloy undergo refining after the
degassing process. Grain refining the Al in the hypereutectic Al-Si alloy comprises addition of Ti
(Titanium) and B (Boron) to the alloy, and grain refining the Primary Si in the hypereutectic Al-Si
10 comprises addition of Phosphorous (P) in the form of direct injection of Al-P metal in rod form to
the alloy; and a vacuum assisted metal injection of the hypereutectic Al-Si alloy into the Die Cavity.
[0021] According to an embodiment of the high pressure die casting process, the pre-melting of the
hypereutectic Al-Si alloy comprises pre-melting the hypereutectic Al-Si alloy to a temperature range
of 790 to 830 degrees centigrade in a Skelnar Furnace, (oil–fired High Speed Diesel Oil ), and Flux
15 treatment of this metal. This flux treatment comprises fluxing the pre-melted metal using sodium
free & calcium free granular flux wherein approximately 150 to 250 gms of flux per 100 kg of alloy
is used. The metal after this flux treatment is transferred to an Electrical Resistance Furnace
according to an embodiment, where it undergoes the second flux treatment comprising fluxing the
above pre-melted metal using sodium & calcium free granular flux wherein approximately 200 to
20 380 grams of flux per 100 kg of alloy is used at the second pre-defined temperature of
approximately 670 to 720 degrees centigrade.
[0022] In one embodiment of the high pressure die casting process, the removal of hydrogen from
the molten hypereutectic Al-Si alloy comprises plunging 150 to 300 gm degasser to remove the
8
dissolved Hydrogen. In an embodiment, Degasser 190 tablets comprising hexa chloro ethylene are
used. These tablets generate nascent chlorine which removes hydrogen. According to a preferred
embodiment, after addition of Degasser 190 tablets the high pressure die casting process further
comprises an additional ARGON DEGASSING step using a Mobile Degassing Unit with the
Impellor rotating at 300 to 320 RPM and with the Argon gas PRESSURE of 0.10 to 1.30 kg 5 /
Sq.cm, a gas FLOW RATE of 4 to 15 Litres / minute, AND a FLOW TIME OF 600 to 1200 sec.
[0023] According to an embodiment of the high pressure die casting process, the vacuum assisted
metal injection further comprises sucking out air from a die cavity from an air venting end provided
in the die cavity as the hypereutectic AL-Si alloy fills the die cavity, such that as the hypereutectic
10 AL-Si alloy keeps entering the die cavity from an injection end comprised in the die cavity, while
the air in the cavity is simultaneously sucked from the air venting end of the die cavity.
[0024] Additionally, in the high pressure die casting process, the first flux treated hypereutectic Al-
Si alloy is transferred from a first Fuel–Fired Skelner furnace to a second Electric Resistance
holding furnace for the second flux treatment of the hypereutectic Al-Si alloy at the second pre15
defined temperature. The second flux treatment comprises fluxing the pre-melted metal using
sodium and calcium free granular flux wherein approximately 200 to 380 grams of flux per 100 kg
of alloy is used at the second pre-defined temperature of approximately 670 to 720 degrees
centigrade.
[0025] According to an embodiment of the high pressure die casting process, the die casting is for
20 2-stroke channel type of chain saw pistons and 4-stroke motorcycle and scooter pistons. Preferably,
the piston has thin walls having thickness of approximately 0.8mm to 2.2 mm. In a pre-machined
condition, the piston diameter is 46mm and in a post-machined condition the piston diameter is 44
9
mm. The smooth outer surface of the piston allows for minimal machining. Preferably the Al-Si
hyper eutectic alloy contains Silicon in range of 12 % to 25%.
[0026] In a preferred embodiment of the high pressure die casting process, the molten metal
injection parameters are as follows: Die temperature of 160 to 180 degrees centigrade, Casting Time
of 6 to 8 seconds, Hydraulic Pressure of 100 to 150 kg/sq.cm, and an Injection Pressure of 200 t5 o
280 kg/sq.cm.
[0027] In some embodiments of the method, there is a loss of Magnesium during the pre-melting
stage and the fluxing stage in the skelner furnace, and the fluxing in the electric resistance furnace.
Additionally, significant loss of Magnesium happens during the degassing stage using Degasser –
10 190 tablets. In lieu of the above, and based on a Spectro test feedback, Magnesium is added back to
the alloy after the degassing stage. According to an embodiment, the degassing step is performed
using an inert gas like Argon. According to another embodiment, the degassing is performed using
Hexa Chloro ethylene. According to a preferred embodiment, the degassing is performed in two
stages, first using Hexa Chloro ethylene (introduced by Degasser 190) and then by using Argon Gas
15 (a Neutral Gas). According to an embodiment, the phosphorus material is at least one of Red
Phosphorus tablets, CuP in metallic form, and Al-P in metallic form.
[0028] According to an embodiment, the process of the present subject matter is a High Pressure
Die Casting (HPDC) process for manufacturing 2-stroke channel type of chain saw pistons and 4-
stroke motorcycle and scooter pistons with B 390 Alloy.
20 [0029] FIG. 1 illustrates the process according to an embodiment. The flow chart shows the
sequence wise process for manufacturing the piston under reference for an internal combustion
engine in accordance with the present subject matter. In step 1, the die is manufactured based on a
die gating design derived from a piston casting drawing and a determined alloy for manufacture of
10
the piston. According to one embodiment a casting solidification software is used to generate the
die gating design. In Step 2, based on determined machine settings and molten metal injection
parameters, the alloy is pre-melted in a furnace. According to an embodiment, the pre-melting is
done in a Skelner furnace at a temperature of 790 to 830 degrees centigrade. According to an
embodiment, 150 kg of the metal is pre-melted in the Skelenar (Highspeed Diesel Fired5 ,
Reverberatory Type) Furnace. Once the molten metal attains the required temperature (790 to 830
deg C), the metal is fluxed (step 3) using Sodium free and Calcium free granular Flux. According to
one embodiment, 150 to 250 gms of flux is used for every 100kg of metal. According to a preferred
embodiment, the granular flux used is Coveral 6512 of Foseco or DR 212 of Pyrotec. In this step,
10 the slag that accumulates is also removed and the molten metal is tapped into a Transfer ladle. The
cleanliness of the metal after the flux treatment is checked using the K- MOULD TEST, known to a
person having ordinary skill in the art. This test is done for each melt after the various treatments
and before using the metal. Step 4 includes a second flux treatment, wherein the second flux
treatment comprises once again treating the molten metal with sodium free and calcium free
15 granular flux at a temperature of 670 to 720 degrees centigrade. According to one embodiment,
molten metal is poured into an electric resistance holding furnace via a transfer ladle for the second
flux treatment. According to a preferred embodiment, 200 to 380 gms of granular flux for every
100 kg of metal alloy is used in the second flux treatment.
[0030] In step 5A the metal is pre-degassed by adding a degasser. According to an embodiment,
20 150 to 300 gm of degasser is used to remove dissolved Hydrogen from the melt. According to one
embodiment, the degasser is in the form of hexa chloro ethylene Tablets (50 gm each) and the
tablets are pushed into the metal with a plunger. A specific embodiment uses Degasser 190 tablets.
11
[0031] According to an optional embodiment and based on a chemical composition test in the
laboratory, a magnesium (Mg) correction is implemented. Essentially, it has been found that there
is some loss of Magnesium during the pre-melting stage in the Skelner furnace, and sometimes a
significant loss of Magnesium during the pre-degassing stage (with Degasser 190 tablets). Thus, in
step 5B, 100-250 gm of Magnesium per 100 kg of metal alloy is added if the laboratory tes5 t
confirms substantial depletion of Magnesium.
[0032] Step 6 follows the pre-degassing step and includes an Argon degassing, carried out
according to one embodiment, using a MOBILE DEGASSER UNIT–MDU (RPM of around 300)
[0033] Step 7 is concurrent with step 6 wherein during the above degassing, GRAIN REFINING of
10 the ALUMINIUM DENDRITES is implemented by adding Titanium (Ti) using Binary Al-Ti
Master Alloy. According to a preferred embodiment, the refinement is most superior with the usage
of Ternary Master Alloy, Al–5% Ti–1% B (i.e. the master alloy comprises Aluminium with 5%
Titanium and 1% Boron) rather than the usage of the Binary Al-5% Ti (i.e. Aluminium with 5%
Titanium) Master Alloy. Further the fading of the grain refinement effect with time is lesser in the
15 case of Ternary Master Alloy compared to the secondary Master Alloy. The percentage (%) addition
was established as 120 to 250 gm/100 kg melt according one embodiment. It may be noted that in
practice, the % addition varies firstly since the specification of various elements in the alloy have a
wide range, and secondly due to various conditions of metal charge like the ratio of Fresh Ingots to
Returns in the alloy prepared - the maximum % of returns being 50, as would be apparent to a
20 person having ordinary skill in the art.
[0034] Step 8 includes refinement of primary Silicon particles by addition of Phosphorous. One set
of trials concerning the refinement of Primary Silicon particles by addition of Phosphorous (P) was
performed.
12
[0035] In Trial 1, conventional Red P tablets were used, and it was noted that Toxic Fumes are
generated, inconsistent performance, effectiveness comes down on long storage of the tablets and
prolonged holding of the molten metal in the furnace.
[0036] In Trial 2, CuP (Copper Phosphorous) in metallic form (shots) was used and it was noted
that they were difficult to dissolve at lower temperature. Also, in the electric resistance type o5 f
holding furnaces wherein there is no stirring unlike in induction furnaces, and therefore it requires a
longer waiting period after addition, for the refinement to take place. Lastly, there is a problem of
Copper Pick Up associated, posing a risk of Cu value exceeding the specified limit.
[0037] In Trial 3, P was added by use of Al-P in metallic form (Rod Form) – wherein the Al-P rod
10 was very easy to dissolve at low temperature and within a short period (no waiting period at all),
also offering a very consistent performance due to direct injection of the P into the melt. After a
series of trials, the optimum addition was established as 80 to 140 gm. Thus, in a preferred
embodiment, refinement of primary Silicon particles by addition of Phosphorous includes using of
the Al-P rod in metallic form.
15 [0038] After the above fluxing, degassing (initially with the degasser and then with Argon),
correction for % Mg and the addition of Al – 5% Ti – 1% B & Al-P, the final quality of metal so
treated is checked.
[0039] According to an embodiment, the efficiency of fluxing is checked with the usage of “K –
Mould Test” known to a person having ordinary skill in the art. Other methods for efficiency
20 checking are possible as will be apparent to a person having ordinary skill in the art. The efficiency
checking using a “K-mould Test Piece” takes a very short time and is used for each melt before
usage.
13
[0040] According to an embodiment, the efficiency of degassing is tested with the usage of
Reduced Pressure Test apparatus. Other apparatuses may be used as would be apparent to a person
having ordinary skill in the art. This test takes a very short time and is used for each melt before
usage.
[0041] According to an embodiment, the effectiveness of Primary Silicon Refinement with Al-5 P
addition is checked by taking the micro structure image of the casting with the use of a microscope.
And the refinement of Aluminium grains with Al – 5 % Ti – 1% B addition is checked by a
macroscopic examination of the polished and etched sample of the said casting. A series of TP1
tests (standard test specified by Aluminium Association of America was also done during the initial
10 development stage, to determine the degree of refinement. A second test is conducted to establish
the Master Alloy to be used and arrive at the quantity of addition. The addition is never one fixed
value but can always vary at times as would be apparent to a person having ordinary skill in the art.
[0042] Additionally, it should be appreciated that even in the piston alloy, the various elements do
not have a fixed value and it is always a range, and as such, the quantum of the various metal
15 treatment additions may change with varying requirements.
[0043] FIG. 2 depicts a pre-and post-machined piston manufactured by the gravity die casting
process using hypereutectic Al-Si alloy.
[0044] FIG. 3 depicts a pre-machined and post-machined piston manufactured by the high pressure
die casting process using hypereutectic Al-Si alloy
20 [0045] FIG. 4 illustrates via a comparative certificate of inspection and parameters of the surface
finish of a post-machined piston manufactured by the gravity die casting process and the high
pressure die casting process using hypereutectic Al-Si alloy.
14
[0046] Embodiments disclosed include methods for precision manufacturing of pistons with desired
geometry, having extremely thin walls, intricate shapes and contours. Embodiments disclosed
include extremely cost-effective methods for manufacturing pistons that are light weight, and that
require minimal maintenance and machining, and that have superior surface finish. Embodiments
disclosed include methods for precision manufacturing of pistons of varied shapes and sizes bu5 t
particularly for manufacture of extremely small sized pistons.
[0047] Since various possible embodiments might be made of the above invention, and since various changes
might be made in the embodiments above set forth, it is to be understood that all matter herein described or shown
in the accompanying drawings is to be interpreted as illustrative and not to be considered in a limiting sense. Thus
10 it will be understood by those skilled in the art of systems and methods that facilitate manufacture of pistons and
piston systems, that although the preferred and alternate embodiments have been shown and described in
accordance with the Patent Statutes, the invention is not limited thereto or thereby.
[0048] The figures illustrate the architecture, functionality, and operation of possible implementations of systems
and methods according to various embodiments of the present invention. It should also be noted that, in some
15 alternative implementations, the functions noted/illustrated may occur out of the order noted in the figures. For
example, two blocks shown in succession may, in fact, be executed concurrently, or the blocks may sometimes be
executed in the reverse order, depending upon the functionality involved.
[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not
intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to
20 include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that
the terms "comprises" and /or "comprising," when used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
15
[0050] In general, the routines executed to implement the embodiments of the invention, may be part of an
operating system or a specific application, component, program, module, object, or sequence of instructions.
[0051] The present invention and some of its advantages have been described in detail for some embodiments. It
should be understood that although the system and process is described with reference to manufacture of 2 and 4
stroke engine pistons, the system and method is highly reconfigurable, and may be used in other contexts as well5 ,
especially for manufacture of castings from hypereutectic Al-Si alloys. It should also be understood that various
changes, substitutions and alterations can be made herein without departing from the spirit and scope of the
invention as defined by the appended claims. An embodiment of the invention may achieve multiple objectives,
but not every embodiment falling within the scope of the attached claims will achieve every objective. Moreover,
10 the scope of the present application is not intended to be limited to the particular embodiments of the process,
machine, manufacture, composition of matter, means, methods and steps described in the specification. A person
having ordinary skill in the art will readily appreciate from the disclosure of the present invention that processes,
machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be
developed are equivalent to, and fall within the scope of, what is claimed. Accordingly, the appended claims are
15 intended to include within their scope such processes, machines, manufacture, compositions of matter, means,
methods, or steps.
[0052] While the preferred embodiments of the present invention have been described hereinabove,
it should be understood that various changes, adaptations, and modifications may be made therein
without departing from the spirit of the invention and the scope of the appended claims. It will be
20 obvious to a person skilled in the art that the present invention may be embodied in other specific
forms without departing from its spirit or essential characteristics. The described embodiments are
to be considered in all respects only as illustrative and not restrictive.

We Claim:
1. A high pressure die casting process using hypereutectic AL-Si alloy comprising:
manufacturing a die according to a die gating design derived from a casting drawing
that factors in a casting contraction allowance, a machining allowance, and a chemica5 l
composition of a determined alloy;
pre-melting the hypereutectic AL-Si alloy;
a first flux treatment of the pre-melted hypereutectic AL-Si alloy at a first predefined
temperature;
10 a second flux treatment of the hypereutectic Al-Si alloy at a second pre-defined
temperature;
degassing the flux treated hypereutectic Al-Si alloy, wherein the degassing comprises
removal of hydrogen from the molten hypereutectic Al-Si alloy;
refining of Al grains in the hypereutectic Al-Si alloy, wherein the refining of the Al
15 grains comprises addition of Ti and B to the alloy;
refining of primary Si grains in the hypereutectic Al-Si alloy wherein the refining
comprises addition of Phosphorous to the alloy; and
a vacuum assisted metal injection of the hypereutectic Al-Si alloy into the Die cavity.
20 2. The high pressure die casting process of claim 1 wherein:
the pre-melting of the hypereutectic Al-Si alloy comprises pre-melting the
hypereutectic Al-Si alloy at a temperature range of 790 to 830 degrees centigrade.
17
3. The high pressure die casting process of claim 1 wherein:
the first flux treatment comprises fluxing the pre-melted metal in the Skelnar Furnace
using Sodium & Calcium free granular flux, wherein approximately 150 to 250 grams of
flux per 100 kg of alloy is used; and
a second flux treatment of the metal in the Electrical Holding Furnace, using Sodiu5 m
& Calcium free granular flux wherein approximately 200 to 380 grams of flux per 100 kg of
alloy is used.
4. The high pressure die casting process of claim 1 wherein:
10 the removal of hydrogen from the molten hypereutectic Al-Si alloy comprises
plunging 150 to 300 gm of degasser tablets to remove the dissolved Hydrogen; and
wherein the degasser tablets comprise hexa chloro ethylene to generate nascent
chlorine which removes hydrogen.
15 5. The high pressure die casting process of claim 1 wherein the removal of hydrogen from the
molten hypereutectic Al-Si alloy comprises:
an ARGON DEGASSING with a gas PRESSURE of 0.10 to 1.30 kg / Sq.cm, a gas
FLOW RATE of 4 to 15 Litres / minute, AND a FLOW TIME OF 600 to 1200 sec).
20 6. The high pressure die casting process of claim 1 wherein the vacuum assisted metal injection
further comprises sucking out air from a die cavity from an air venting end comprised in the
die cavity as the hypereutectic AL-Si alloy fills the die cavity, such that as the hypereutectic
18
AL-Si alloy keeps entering the die cavity from an injection end comprised in the die cavity,
the air is sucked out from the air venting end of the die cavity.
7. The high pressure die casting process of claim 1 wherein:
the first flux treated hypereutectic Al-Si alloy is transferred from a first Skelne5 r
furnace to a second holding furnace for the second flux treatment of the hypereutectic Al-Si
alloy at the second pre-defined temperature; and
wherein the second flux treatment comprises fluxing the pre-melted metal using
sodium free and calcium free granular flux wherein approximately 200 to 380 grams of flux
10 per 100 kg of alloy is used at the second pre-defined temperature of approximately 670 to
720 degrees centigrade.
8. The high pressure die casting process of claim 1 wherein the die casting is for a piston for at
least one of a 2 stroke and a 4-stroke engine.
15
9. The high pressure die casting process of claim 8, wherein the piston has thin walls having
thickness of 0.8mm to 2.2 mm.
10. The high pressure die casting process of claim 8, wherein the piston has a pre-machined
20 diameter of 46 mm and a post-machined diameter of 44mm.
11. The high pressure die casting process of claim 1 wherein the Al-Si hyper eutectic alloy
contains Silicon in range of 12 % to 25%.
19
12. The high pressure die casting process of claim 1, wherein the molten metal injection
parameters comprise a die temperature of 160 to 180 degrees centigrade, a casting time of 6
to 8 seconds, a hydraulic pressure of 100 to 150 kg/sq.cm, and an injection pressure of 200
to 280 kg/sq.cm5 .
13. The high pressure die casting process of claim 1, wherein the high pressure die casting
process further comprises addition of Magnesium material after the degassing.
10 14. The high pressure die casting process for manufacturing a piston as claimed in claim 1,
wherein the degassing step is performed using at least one of an inert gasses and Hexa
Chloro Ethylene tablets.
15. The high pressure die casting process for manufacturing a piston as claimed in claim 13,
15 wherein said inert gas is Argon.
16. The high pressure die casting process of claim 1 wherein the said primary Si grains are in the
form of cuboids.
20 17. The high pressure die casting process for manufacturing a piston as claimed in claim 1,
wherein:
20
the addition of Phosphorous in the grain refining of the Si comprises at least one of
addition of Al-P in metallic form to the alloy, addition of Red Phosphorus tablets, and
addition of CuP in metallic form.