Claims:WE CLAIM:

1) A low pressure die casting system (100) for producing casts, said system (100) comprising:
• a low pressure die casting unit having a mould cavity (30e) with an inlet (30ai) configured at an operative bottom of said mould cavity (30e) to selectively introduce pressurized molten material into mould cavity (30e), said inlet (30ai) connected to a molten material feeder (20); and
• a molten material cooling system configured to selectively circulate cooling fluid, having a pre-determined temperature and pressure, after said mould cavity (30e) being filled with pressurized molten material, wherein cooling fluid is circulated, for a pre-determined time, surrounding a portion of said mould cavity (30e) for additionally cooling molten material and solidifying molten material to form a cast in shape of the mould cavity (30e).

2) The system (100) as claimed in claim 1, wherein area between said feeder (20) and said molten material cooling system is insulated by insulations.

3) The system (100) as claimed in claim 1, wherein cooling fluid is water.

4) The system (100) as claimed in claim 1 and 2, wherein said molten material cooling system includes a demineralization unit (70) for dematerializing water.

5) The system (100) as claimed in claim 1, wherein said feeder (20) has a surrounding portion configured with a hollow space to maintain temperature of molten material passing through said feeder (20).

6) A method for producing casts by using a low pressure die casting system (100), said method comprising:
• providing a low pressure die casting unit having a mould cavity (30e) with an inlet (30ai) configured at an operative bottom of said mould cavity (30e), said inlet (30ai) connected to a molten metal feeder (20);
• introducing selectively pressurized molten material into mould cavity (30e) by said feeder (20) through said inlet (30ai); and
• circulating selectively, at a pre-determined temperature, cooling fluid, by a molten metal cooling system, configured to selectively circulate cooling fluid, having a pre-determined temperature, after said mould cavity (30e) being filled with pressurized molten material, wherein cooling fluid is circulated, for a pre-determined time, surrounding a portion of said mould cavity (30e) for additionally cooling molten material and solidifying molten material to form a cast in shape of the mould cavity (30e).

7) The method as claimed in claim 6, providing insulations between said feeder (20) and said molten material cooling system.

8) The method as claimed in claim 6, circulating fluid is cooling water.

9) The method as claimed in claim 6 and 7, dematerializing cooling water by a demineralization unit (70) provided in said molten material cooling system.

10) The method as claimed in claim 6, wherein said feeder (20) has a surrounding portion configured with a hollow space to maintain temperature of molten material passing through said feeder (20).
, Description: FORM – 2

THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10 and rule 13)

SYSTEM AND METHOD FOR PRODUCING CASTING UTILIZING FLUID COOLING FOR EXPEDITING SOLIDIFICATION

ALICON CASTALLOY LIMITED
An Indian Company
of D-II Block, Plot No.58/59, MIDC Chinchwad,
Pune-411019, Maharashtra, India.

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
FIELD

[001] The present subject matter relates to a casting system and method and, more particularly, to a low pressure die casting system and method for producing casting using fluid cooling for expediting solidification.

BACKGROUND

One type of casting system is a low pressure die casting systems (hereinafter referred to as LPDC) in which molten material is inserted in a mould cavity (formed of a top portion and a bottom portion) through bottom of the mould cavity and solidification of molten material proceeds from the top portion of towards the bottom portion. As solidification starts from the top portion, in the top portion secondary-dendrite arm spacing (hereinafter referred to as S-DAS) between the molecules is very tight and due to that the S-DAS value is very small as compared to S-DAS value at the bottom portion. However, for casts like engine cylinder(s), which are typically made of aluminium material, combustion chamber is casted at the bottom portion of the cast and is produced with more S-DAS value and such more S-DAS value reduces efficiency of combustion chamber when exposed to high combustion temperature during its operative working configuration. Hence, though LPDC system provides high yield and provides low cost castings, gravity die casting systems (hereinafter referred to as GDC) are preferred because in GDC molten material is poured from the top portion towards the bottom portion and hence bottom portion cools first providing very tight secondary-dendrite arm spacing (S-DAS) between the molecules and small S-DAS value as compared to S-DAS value at the top portion. Hence, even though GDC systems have big feeder and gating systems, provides low yield and is costly process, GDC systems are preferred over LPDC systems just to achieve less S-DAS value at the bottom portion.

Hence, there is a need for providing a LPDC system that produces cast with less S-DAS value at the bottom portion or any desired portion of the cast at low cost.

OBJECTS

[002] Some of the objects of the arrangement of the present disclosure are aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative and are listed herein below.

An object of the present disclosure is to provide a low pressure die casting system for producing casts that utilizes additional fluid cooling to achieve expedite solidification.
Another object of the present disclosure is to provide a low pressure die casting system for producing casts utilizing additional fluid cooling to achieve desired cast properties like low S-DAS value at desired location.

Yet another object of the present disclosure is to provide a low pressure die casting system for producing low cost casts utilizing fluid cooling and providing high yield.

Further objects of the present subject matter will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the subject matter without placing limitations thereon.

SUMMARY

[003] The present disclosure relates to a Low Pressure Die Casting (LPDC) system with a molten material cooling system, in accordance with one embodiment of the present disclosure. The low pressure die casting (LPDC) system with a molten material cooling system is utilized to produce a cast of desired shape that cools the molten material (especially disposed in the bottom portion of the mould) during solidification for achieving expedite solidification. Moreover, when pressurized molten fluid is filled in a mould, a cooling fluid is circulated inside the mould such that the desired portion (mainly, the bottom portion) is additionally cooled along with its natural cooling. The resulting cast formed with the expedite solidification by circulation of fluid results in providing low secondary-dendrite arm spacing (S-DAS) which was not possible by conventionally systems at less cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[004] With the above and other related objects in view, the subject matter consists in the details of construction and combination of parts as will be more fully understood from the following description, when read in conjunction with the accompanying drawings in which:

Figure 1 represents a schematic representation of a low pressure die casting system with a molten material cooling system, in accordance with one embodiment of the present subject matter;

Figure 2 is an enlarged view of a bottom portion of mold cavity with a cooling pipe, in accordance with another embodiment of the present subject matter;

Figure 3 is a schematic perspective view of an engine cylinder produced by the die casting system of Figure 1.

DETAILED DESCRIPTION

[005] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Hereinafter, the following detailed description will be described with reference to the accompanying drawings

[006] The present subject matter relates to a low pressure die casting system with a molten material cooling system. The low pressure die casting system has a low pressure die casting unit and a molten material cooling system. The low pressure die casting unit includes a mould cavity with an inlet provided at an operative bottom portion of the mould cavity. The inlet is connected to a molten material feeder through which pressurized molten material is selectively introduced in the mould cavity till the mould cavity is entirely filled with molten material. When the cavity is filled with molten material, the molten material cooling system selectively circulates, for a pre-determined time, cooling fluid which has a pre-determined temperature and pressure around a portion of cavity for additionally cooling molten material and solidifying molten material to form a cast in shape of cavity. In one preferable example, the cooling fluid is water because of its non-explosive property.

[007] Referring now to the exemplary drawings (FIGURE 1, FIGURE 2 and FIGURE 3), where the subject matter of the present subject matter is generally referred to with numeral (100), it can be observed that a low pressure die casting system with a molten material cooling system is provided to produce casting of an engine cylinder, as illustrated in Figure 3. The low pressure die casting system (100) includes:

o a low pressure die casting unit which comprises a molten material container (10), molten material, a pressurizing unit (not illustrated in Figures), a feeder or a stalk tub (20) and a mould (30); and
o a molten material cooling system which comprises a cooling pipe (40), an outlet temperature gauge (50), a cooling tower (60), a demineralization unit (70) and an inlet temperature gauge (80).

[008] The molten material container (10) is an enclosed container with a first conduit (10a) and a second conduit (10b). The first conduit (10a) is provided to selectively fill molten material in the molten material container (10). Molten material to be filled can be any material of which the engine cylinder or any other cast is desired to be made. Due to advantage of light weight, generally, molten material is considered as aluminum. However, the present disclosure is not to be limited to the use of aluminum material and other materials of which casting is desired can be utilized. The second conduit (10b) is provided to introduce pressure in the molten material container (10) by the pressurizing unit.

[009] Feeder or stalk tube (20), hereinafter is referred to as the feeder (20), has at least two openings, namely, a first opening (20a) and a second opening (20b). The first opening (20a) is inserted at a pre-determined depth in the molten material filled in the molten material container (10). The second opening (20b) is used to introduce molten material in the mould (30) when the molten material is pressurized. The feeder (20) has a surrounding portion with a hollow space (not illustrated in Figures) to maintain temperature (i.e. the hot temperature) of molten material passing through the feeder (20) and prevent it from cooling because of molten material cooling system.

[010] The mould (30) is formed of a bottom part (30a), at least one middle part (30b and 30c) and a top part (30d). The bottom part (30a), the middle part (30b and 30c) and the top part (30d) when assembled form a mould cavity or cavity (30e). In this example, the bottom part (30a) shapes molten material to form a combustion chamber of the engine cylinder. The middle part (30b) shapes molten material to form an inlet of the engine cylinder and the middle part (30c) shapes molten material to form an exhaust of the engine cylinder. The top part (30d) shapes molten material to form the opposite portion of the combustion chamber.

[011] The bottom part (30a) of the mould (30) is provided with an inlet (30ai) that is connected to the molten material feeder (20) {also known as feeder (20)} and receives pressurized molten material therefrom till the cavity (30e) formed is completely filled.

[012] The cooling pipe (40) is configured to pass through the mould (30) to additionally cool molten material and/or additionally cool partially cooled molten material to enhance solidification process of the engine cylinder. In one embodiment, the cooling pipe (40) is passes through the bottom potion of the mould (30), however, when desired, the cooling pipe (40) can be circulated in any portion of the mould (30). The cooling pipe (40) is build of at least one inlet pipe (40), at least one central pipe (40b), at least one exhaust pipe (40c) and a circulating pipe (40d). The inlet pipe (40) is connected to the central pipe (40b), the central pipe (40b) is connected to the exhaust pipe (40c), the exhaust pipe (40c) is connected to circulating pipe (40d) and the circulating pipe (40d) is connected to the inlet pipe (40a) thereby circulating cooling fluid from the inlet pipe (40a) to the circulating pipe (40d) and back to the circulating pipe (40d) thereby circulating cooling fluid and completing one cooling cycle. Moreover, the inlet pipe (40a) receives cooling fluid which passes to the central pipe (40b) where heat exchange is initiated between cooling fluid and hot molten material such that cooling fluid becomes hot and hot molten fluid is cooled for achieving solidification. Hot cooling-fluid is then is exhausted through the exhaust pipe (40c). The central pipe (40b) can be of any shape and can be bend in any form to achieve any form such as semi-circular form as illustrated in FIGURES 1 and 2. Also, the inlet pipe (40a), the central pipe (40b) and the exhaust pipe (40c) can be introduced, conveyed and removed from any portion of the mould (30) as is not limited to the configuration illustrated in FIGS. 1 and 2. Pipe fittings (41) can be provided wherever needed for fitting one or more of the inlet pipe (40), the central pipe (40b) and the exhaust pipe (40c).

[013] The circulating pipe (40d) is connected between the exhaust pipe (40c) and the inlet pipe (40). The circulating pipe (40d) receives hot cooling-fluid from the exhaust pipe (40c). The outlet temperature gauge (50) is provided for determining the temperature of hot cooling-fluid. Once the temperature is determined, hot cooling-fluid is introduced in the cooling tower (60). In the cooling tower (60), hot cooling-fluid is cooled at a pre-determined temperature to achieve cooling fluid of desired temperature. Cooling fluid is then directed to the demineralization unit (70) for removing scales. Once demineralized, temperature of cooling fluid is determined by the first inlet temperature gauge (80). Cooling fluid is then re-directed to the inlet pipe (40) for beginning another cycle.

[014] In accordance with one embodiment, the area between the feeder (20) and the cooling pipe (40) of the molten material cooling system is insulated by insulations so that molten material flowing through the feeder does not get cooled and solidify in the feeder (20).

[015] The present disclosure discloses a method for forming a cast using a low pressure die casting system with a molten material cooling system. The method includes filling through the first conduit (10a), a predetermined quantity, of molten material in the molten material container (10) of which cast is to be formed. After filling molten material in the molten material container (10), pressurizing unit is actuated to introduce, through the second conduit (10b), pressure on molten material contained in the molten material container (10). Pressurization of molten material causes molten material to rise in feeder/stalk tube (20) and fill the cavity (30e) of the mould (30). Once the cavity (30e) is filled, the pressure is maintained for a pre-determined time and the solidification of molten material is initiated.

[016] Simultaneously, cooling fluid, having a pre-determined temperature, is circulated, at a pre-determined pressure, in the mould (30) through the cooling pipe (40) for providing additional cooling of molten material and enhancing solidification process to achieve desired S-DAS value of cast.

[017] Cooling fluid gains heat after passing through the mould (30) and the heated cooling fluid is passed through the cooling tower (60) to again achieve cooling fluid of desired temperature. After cooling, cooling fluid is passed to the demineralization unit (70) for removing scales. Cooling fluid after flowing through the demineralization unit (70) is ready to be circulated for another shot of another cast formation in the mould (30).

[018] A test was carried out by an LPDC system (of the present disclosure) and using water for cooling to produce an engine cylinder with three in-line combustion chambers, namely, a first combustion chamber (C1), a second combustion chamber (C2) and a third combustion chamber (C3) (as shown in Figure 3), wherein the second combustion chamber (C2) is in between the first combustion chamber (C1) and the third combustion chamber (C3). The test material, test parameters/conditions and considerations were as follows:

o Name of molten material (alloy) of which cast was produced: AlSi7Cu3Mg0.35 (Fe)
o Temperature range of molten material: 700-720°C
o Temperature of Mould (30) (By using Thermocouple):
? Bottom part (30a) of the Mould Preheating Temperature as determined by a thermocouple - Min 350°C
? Bottom part (30a) Mould Temperature Range in running - 350 to 450°C
o Filling Time of the cavity (30e) of the mould (30): 220 ~ 250Seconds
o Cooling Time Without Pressure: 50 ~ 60 Seconds
o Water pressure of Cooling (Set pressure) in Running condition (Cooling fluid is distilled water):
? 2.5 Bar only for top center pin
? Rest All 2.5 Bar.(Flow Rate 200ltr/hr )
o Water pressure of Cooling: 2.5 bar Max with flow control (Flow Rate 200ltr/hr for CC1 & CC3,For CC2 240ltr/hr)
o Cooling temperature of water was selected from the range of 30 degree Celsius to 35 degree Celsius.

After filling of the cavity (30e) with the molten material AlSi7Cu3Mg0.35 (Fe), cooling process was initiated and the portion of the combustion chamber was subjected to cooling by using water. Moreover, the top portions of the combustion chamber (C1 and C3) (where the spark plug fits) were cooled for 50 Seconds and the top portion of the combustion chamber (C2) (where the spark plug fits) was cooled for 70 Seconds. The top side channel was cooled for 50 seconds. The bottom portions of the combustion chamber (C1 and C3) were cooled for 100 seconds and the bottom portion of the combustion chamber (C2) is 130 seconds. In the process, it was observed that cooling/solidification was achieved in 220 seconds to 240 second and conventionally with only air cooling was 240 to 260 seconds hence saving up approximate 20 seconds of time and provides expedite solidification. Additionally, around 60 seconds was provided in each case (i.e. conventional as well as in present invention) for achieving complete cooling. Resulting S-DAS value achieved was 22.3 microns.

[019] In one embodiment, the system (100) is completely automated by using different types of sensors, controllers and like other automating devices and the process can be remotely monitored, controlled and manipulated.

[020] Thus, the low pressure die casting system (100) with a molten material cooling system can achieve S-DAS value less than 25 microns and hence the system (100) can be used in replacement of Gravity die casting and achieve all advantages of Low pressure die casting systems over Gravity die casting system typically like low cost at high yield.

[021] In one embodiment, along with water cooling, air cooling is can also be used simultaneously for faster solidification.

[022] The foregoing description conveys the best understanding of the objectives and advantages of the present subject matter. Different embodiments may be made of the inventive concept of this subject matter. It is to be understood that all matter disclosed herein is to be interpreted merely as illustrative, and not in a limiting sense.