FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
IMPROVED METHOD FOR ACHIVING HIGHER PHYSICAL PROPERTIES FOR A356 ALLOY WITH GRAVITY DIE
CASTING
ENDURANCE TECHNOLOGIES PVT. LTD.,
an Indian Company,
of B 1/3 Chakan Industrial Area, Village Noghoje, Taluka Khed,
Dist. Pune- 410501, Maharashtra, India.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF DISCLOSURE
The present disclosure generally relates to a method for improving the properties of A356 alloy.
BACKGROUND
A356 alloy has better mechanical strength, ductility, hardness, fatigue strength, pressure tightness, fluidity and machinability as compared to other alloys. Hence, A356 alloy is used in a number of applications such as airframe castings, machine parts, truck chassis parts, aircraft, missile components and structural parts requiring high strength. Further, the strength and elongation of A356 alloy can be increased by using modifier Strontium and grain refiner Titanium Boron along with the T6 heat treatment process using the Gravity Die Casting (GDC) process. T6 heat treatment is a process which includes solutionizing, water quenching followed by aging. The elongation and tensile strength plays an important part in improving the fatigue life of components. Although the A356 alloy exhibits higher elongation properties, research is being carried out to further improve the elongation properties of components made with A356 alloy and GDC process for applications, such as, cast alloy wheels. Accordingly, parameters that influence the elongation and tensile strength of the A356 alloy are identified and processes that improve elongation and tensile strength of A356 alloy are studied.
The conventional method for manufacturing cast products using the A356 alloy includes melting ingots of the aluminum A356 alloy at 730 degree Centigrade. The molten aluminum A356 ingots are degassed with nitrogen

and treated with master alloys such as Strontium (Sr) and Titanium-Boron (TiB). Granular flux is used to remove inclusions and dross from the molten A356 alloy. Thereafter, gravity die casting method is used and the molten aluminum A356 alloy is poured into metal moulds to manufacture cast products. Subsequently, the cast products are subject to T6 heat treatment process which includes solutionizing at 535 +/5° C temperature for 6 hours. Thereafter, water quenching is done at 80° +/- 5°C for 2 minutes. After the quenching operation, the sizing of the cast product is done to control distortion of the cast product. Followed by sizing operation, aging of the cast product is carried out at 185 +/- 5° C temperature for 3 hours. Shot blasting, machining and painting operations are performed on the cast product for achieving the final finished product.
However, the above conventional method for manufacturing components from aluminum A356 alloy is inefficient and fails to achieve desired elongation and tensile strength. Accordingly, there is a need to overcome the shortcomings of the conventional method for manufacturing components from aluminum A356 alloy so that the final products has desired elongation and tensile strength.
OBJECTS
Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide processes for improving properties of A356 alloy.
Another objective of the present disclosure is to provide gravity die-casting and T6 heat treatment processes for improving and achieving minimum 9% elongation and minimum tensile strength of 285 MPa for A356 alloy.
Yet another objective of the present disclosure is to provide a process for improving fatigue life of components made from A356 alloy.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
In accordance with the present disclosure there is provided a method for casting a casting product from at least one molten A356 aluminum ingot, the method comprising the following steps:
> degassing the molten A356 aluminum ingot by treating with an inert gas;
> metal treating the molten A356 aluminum ingot with a master alloy;
> filtering the degassed molten aluminum ingot and pouring the filtered molten aluminum ingot into a mould to form a cast product;
> cooling said cast product;
> heat treating the filtered molten aluminum ingot by:

• solutionizing the cast product at a predetermined first temperature for a predetermined first time period in an electric heat treatment furnace;
• quenching the solutionized cast product at a predetermined second temperature for a predetermined second time period to form a quenched cast product; and
• aging the quenched cast product at a predetermined third temperature for a predetermined third time period in an electric heat treatment furnace to form an age hardened cast product.
Typically, the inert gas is nitrogen.
Generally, the master alloy is selected from the group consisting of Strontium and Titanium Boron.
Preferably, the step of filtering includes at least one filter arrangement selected from the group consisting of foam filter and wire mesh filter.
Typically, the step of solutionizing is carried out at a predetermined first temperature in the range of 525°C to 540°C.
Typically, the step of quenching is carried out at a predetermined third temperature in the range of 75°C to 85°C.
Generally, the solidified cast product formed in the step of quenching is sized to remove distortion.

Typically, the step of aging is carried out at a predetermined temperature in the range of 155°C to 190°C.
Preferably, the step of solutionizing is carried out at a predetermined first time period in the range of 4 to 6 hours.
Typically, the step of quenching is carried out at a predetermined second time period in the range of 2 to 15 minutes.
Generally, the step of aging is carried out at a predetermined third time period in the range of 3 to 4 hours.
Specifically, the age hardened cast product is surface treated by at least one surface treating methods consisting of shot blasting, machining and painting.
BRIEF DESCRIPTION OF THE FIGURES
Other aspects of the disclosure will become apparent by consideration of the accompanying drawing and their description stated below, which is merely illustrative of a preferred embodiment of the disclosure and does not limit in anyway the nature and scope of the disclosure.
Figure 1 illustrates a flow diagram depicting the various steps followed in the method for improving mechanical properties of a cast product configured from A356 aluminum alloy before heat treatment and surface treating operations performed on the cast product in accordance with the present disclosure;

Figure 2 illustrates a flow diagram depicting the various steps followed during heat treatment and surface treating operations performed on the cast product in accordance with the present disclosure;
Figure 3 illustrates the equi-axed microstructure of A356 alloy after T6 treatment at 200 X resolution;
Figure 4 illustrates the equi-axed microstructure of A356 alloy after T6 treatment at 500 X resolution;
Figure 5 illustrates a tensile stress verses strain diagram for an A356 alloy cast product manufactured in accordance with an embodiment of the present disclosure; and
Figure 6 illustrates a tensile stress verses strain diagram for an A356 alloy cast product manufactured in accordance with another embodiment of the present disclosure.
DETAILED DESCRIPTION
Improving elongation for A356 alloy with gravity die casting and T6 heat treatment processes of the present disclosure will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the

following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Figure 1 illustrates a flow diagram depicting the various steps followed in the method for improving mechanical properties of a cast product configured from A356 aluminum alloy before heat treatment and surface treating operations performed on the cast product. In the casting process, aluminum ingots are melted in a crucible which is heated by the heat produced in a furnace. Particularly, the ingots of the aluminum A356 alloy are melted at

730 deg C. After the aluminum ingots are melted and the process of degassing and metal treatment is carried out using master alloys such as Strontium (Sr) and Titanium-Boron (TiB). More particularly, titanium is added between 0.15%-0.20% by mass to achieve creation of the nucleation sites and Strontium (Sr) is added between 0.010%-0.015% by mass for silicon modification. The A356 alloy is further treated using granular flux to remove the inclusions and dross. Before casting of the A356 alloy, the material properties of the A356 alloy are verified using the optical emission spectrometer, more particularly, the A356 alloy should possess the following material properties before it can be cast using gravity die casting. The following table depicts the material properties that the A356 alloy should possess before casting thereof:

Si Fe Mg Mn Sr Ti Al and inevitable impurities
6.5- Max 0.25-0.35 Max 0.10 0.010- 0.15-0.20 BAL
7.5 0.2 0.015
Generally, Gravity Die Casting (GDC) process is used for configuring the cast product from the A356 alloy. The die used in the Gravity Die Casting (GDC) process is prepared by applying die coat at 250° C. Further, the die is designed with a feeder, a riser, and a spot cooling system. To ensure laminar flow during the pouring operation, a foam filter is used in the funnel and a wire mesh filter is used on the gate of the die to reduce metal turbulence. The molten aluminum A356 alloy at 730 deg C is poured into metal moulds to manufacture the cast products. The die cooling is started 25 seconds after

the pouring is complete and is stopped at 160 seconds after the pouring is complete. The cooling rate during the casting operation is around 1.75 °C per second. Further, in order to avoid defects in the cast product directional cooling during the casting process is ensured. After Gravity Die Casting, the cast product is removed from the die.
After removing the cast product from the die used in the Gravity Die Casting process, each cast product is air cooled. Thereafter, heat treatment and surface treating operations are performed on the cast product. Figure 2 illustrates a flow diagram depicting the various steps followed during heat treatment and surface treating operations performed on the cast product.
Firstly, the cast product is solutionized in a gas fired heat treatment furnace by maintaining the molten aluminum A356 alloy at a temperature of 535°C +/- 5° C for about 6 hours. Subsequently, the cast product is quenched in water at 80 +/- 5° C for 2 minutes and sizing of the wheels is carried out to remove the distortion. After sizing operation, aging operation is carried out at 185 +/-50 C. Thereafter, shot blasting, machining and painting operations are performed on the solidified final product. After heat treatment of the cast product configured from the aluminum A356 alloy, the micro structure of the aluminum A356 alloy is enhanced, thereby improving the mechanical properties of the cast product of aluminum A356 alloy. Figure 3 and Figure 4 illustrate the equi-axed microstructure of A356 alloy after T6 treatment at 200 X resolution and 500 X resolution respectively.
According to another embodiment of the present disclosure, there is provided another method for manufacturing cast product using the A356

alloy. In accordance with this embodiment, the ingots of the alumium A356 alloy are procured. Thereafter, the ingots of the aluminum A356 alloy are melted at 730 deg C. After the ingots of A356 alloy are melted, the molten aluminum A356 alloy is degassed using Nitrogen, The ingots of A356 alloy are treated with master alloys such as Strontium (Sr) and Titanium-Boron (TiB). After the degassing and metal treatment operation, the molten metal is filtered out by using a foam filter in funnel and wire mesh filter in the gate area. Additional wire mesh filter was used at the gate area to reduce the metal turbulence. The temperature stability of the Die is ensured and measured with the lazer gun. The molten aluminum A356 alloy is poured into metal modlds for manufacturing cast alloy wheels. During the Die casting process, the spot cooling was done to ensure the directional cooling. The cooling is started within 25 seconds after the pouring is complete and stopped at 160 seconds after the pouring is complete. The cooling rate provided during the casting operation is around 1.75 degree C per second.
After the gravity Die casting, each alloy wheel sample is air cooled. Thereafter, the alloy wheels are solutionized in an electric heat treatment furnace with temperature control within +/- 2.5 deg C by maintaining a temperature of 530°C +/- 5°C for about 4 hours. Thereafter, the alloy wheels are quenched in water at 80 +/- 5 °C for 15 minutes and subsequently the sizing operation is done in mechanical presses to reduce the warping of the wheels. After the sizing operation, aging of the component is carried out at 160 +/- 5 °C for 4 hours in an electric furnace. Thereafter, shot blasting, machining and painting operations are performed on the solidified final product.

After the heat treatment of the cast product surface treating operations are performed on the cast product. The machining of the cast products is performed using vertical machining centers to ensure the finish and dimensionality according to JASO standard.
TEST RESULTS
Experiments and tests were conducted for determining effectiveness of the cast products manufactured using A356 alloy in accordance with the present disclosure. The tests were directed towards determining the elongation along with tensile strength of the cast product manufactured in accordance with the present disclosure and ascertaining whether the cast product manufactured in accordance with the present disclosure exhibits enhanced mechanical properties such as elongation along with tensile strength. The cast product in accordance with the present disclosure is prepared as per JASO standard and is tested using Universal Testing Machine (UTM) and extensometers with 25mm gage length. The cast product was tested and the mechanical properties of the cast product, particularly, the elongation, 0.2% yield, and the tensile strength were determined. The following table depicts the mechanical properties, particularly, the tensile strength, 0.2% yield strength and percent elongation of the A356 alloy cast product manufactured in accordance with the present disclosure.

Sample Number Tensile
Strength (MPa) 0.2% Yield
Strength
(MPa) %
Elongation
1 291.12 220.42 10.67

2 295.62 235.00 10.66
3 309.59 240.00 13.42
4 293.40 205.00 11.20
5 297.95 230.00 14.53
6 294.34 225.34 12.28
7 301.83 235.00 15.34
8 297.25 223.00 14.50
9 300.50 219.00 12.70
10 300.20 215.00 11.60
Referring to Figure 5 and Figure 6 of the accompanying drawings, the tests conducted revealed that the cast product in accordance with the present disclosure exhibit a minimum elongation of 9% and a minimum tensile strength of 285 MPa as compared to conventionally manufactured cast product which exhibits a minimum elongation of 3% and a minimum tensile strength of 250 MPa. Figure 5 illustrates a tensile stress verses strain diagram for an A356 alloy cast product manufactured in accordance an embodiment. Figure 6 illustrates a tensile stress verses strain diagram for an A356 alloy cast product manufactured in accordance with another embodiment. In both cases, the minimum elongation is greater than 9%. The primary reason for achieving the higher elongation and the tensile is attributed to equi-axed grain structure as shown in Figure 3 and globularity of the silicon particles as shown in Figure 4. These microstructure properties are leading to strengthening effects resulting improved tensile and strength and elongation properties, as per the present disclosure.

TECHNICAL ADVANTAGES
The technical advancements offered by the present disclosure include the realization of:
> cast products with improved elongation by minimum 9% as compared to the conventionally manufactured cast products;
> cast products with increased tensile strength of minimum 285MPa as compared to tensile strength of minimum 250MPa of the conventionally manufactured cast products;
> cast products manufactured in accordance with the process of the present disclosure exhibit improved fatigue life.
In view of the wide variety of embodiments to which the principles of the present disclosure can be applied, it should be understood that the illustrated embodiments are exemplary only. The numerical values given of various physical parameters and dimensions are only approximations and it is envisaged that the values higher or lower than the numerical values assigned to the parameters, dimensions and quantities fall within the scope of the disclosure.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the

embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

We claim:
1. A method for casting a casting product from at least one molten A356
aluminum ingot, said method comprising the following steps;
> degassing the molten A356 aluminum ingot by treating with an inert gas;
> metal treating the molten A356 aluminum ingot with a master alloy;
> filtering said degassed molten A356 aluminum ingot and pouring said filtered molten A356 aluminum ingot into a mould to form a cast product;
> cooling said cast product;
> heat treating said filtered molten aluminum ingot by:

• solutionizing said cast product at a predetermined first temperature for a predetermined first time period in an electric heat treatment furnace;
• quenching said solutionized cast product at a predetermined second temperature for a predetermined second time period to form a quenched cast product; and
• aging said quenched cast product at a predetermined third temperature for a predetermined third time period in an electric heat treatment furnace to form an age hardened cast product.

2. The method as claimed in claim 1, wherein said inert gas is nitrogen.
3. The method as claimed in claim 1, wherein said master alloy is selected from the group consisting of Strontium and Titanium Boron.
4. The method as claimed in claim 1, wherein the step of filtering includes at least one filter arrangement selected from the group consisting of foam filter and wire mesh filter.

5. The method as claimed in claim 1, wherein the step of solutionizing is carried out at a predetermined first temperature in the range of 525°C to 540°C.
6. The method as claimed in claim 1, wherein the step of quenching is carried out at a predetermined third temperature in the range of 75°C to 85°C.
7. The method as claimed in claim 1, wherein said solidified cast product formed in the step of quenching is sized to remove distortion.
8. The method as claimed in claim 1, wherein the step of aging is carried out at a predetermined temperature in the range of 155°C to 190°C.
9. The method as claimed in claim 1, wherein the step of solutionizing is carried out at a predetermined first time period in the range of 4 to 6 hours.
10. The method as claimed in claim 1, wherein the step of quenching is carried out at a predetermined second time period in the range of 2 to 15 minutes.
11. The method as claimed in claim 1, wherein the step of aging is carried out at a predetermined third time period in the range of 3 to 4 hours.
12. The method as claimed in claim 1, wherein said age hardened cast product is surface treated by at least one surface treating methods consisting of shot blasting, machining and painting.