COMPRESSIBLE INSERTS FOR INGATE DESIGN IN HIGH-PRESSURE DIE CASTING

[0001]The subject disclosure relates to high pressure die casting and, in particular, to a system and method for preventing freeze up of an ingate of a die during a pressure intensification phase of a die casting process.

[0002]A die casting process includes flowing a molten metal into a chamber or cavity of a die and allowing the metal to cool and solidify. Die casting includes a filling phase in which molten metal is flowed into a chamber of a die and a subsequent intensification phase during which a pressure in the chamber is increased to reduce or eliminate porosity in the resulting product. The filling phase involves injecting the molten metal into the chamber via an ingate or multiple ingates. A piston (also called a plunger) in a shot sleeve pushes the molten metal through the ingate or ingates into the chamber. During the intensification phase, the piston can be used to increase the pressure. However, due to a thin wall of the ingate, the ingate can freeze up during the intensification phase, thereby preventing intensification pressure from being transferred into the chamber. Accordingly, it is desirable to provide a system and method for preventing ingate freeze off during an intensification phase of the die casting process.

SUMMARY

[0003]In one exemplary embodiment, a die casting system is disclosed. The die casting system includes a die forming a casting chamber, an ingate in fluid communication with the casting chamber for introducing a molten metal into the casting chamber along a flow direction, the ingate having a first surface movable in a direction perpendicular to the flow direction of the molten metal, and a pressurization device configured to bias the first surface to cause the ingate to have a first cross-sectional area in a plane perpendicular to the flow direction based on a first pressure of the molten metal in the ingate and to have a second cross-sectional area in the plane perpendicular to the flow direction based on a second pressure of the molten metal in the ingate, wherein the second pressure is greater than the first pressure.

[0004]In addition to one or more of the features described herein, the second pressure is greater than the first pressure and the second cross-sectional area is greater than the first cross-sectional area.

[0005]In addition to one or more of the features described herein, the molten metal has the first pressure during a filling phase of a die casting operation and has the second pressure during an intensification phase of the die casting operation.

[0006]In addition to one or more of the features described herein, the pressurization device is one of a pressure valve, a low modulus metal, a spring, and a hydraulic device.

[0007]In addition to one or more of the features described herein, the low modulus metal is at least one of Titanium, Iron, Copper, High Entropy Alloy (HEA), Aluminum alloy, low carbon steel, stainless steel, a phase change material, and a bi-metallic material made by an additive manufacturing process.

[0008]In addition to one or more of the features described herein, the die further includes a first die segment and a second die segment that are configured to mate to each other to form the casting chamber and the ingate, wherein the pressurization device is disposed within one of the first die segment and the second die segment.

[0009]In addition to one or more of the features described herein, the die casting system further includes a piston configured to control a pressure within the ingate.

[0010]In another exemplary embodiment, a die is disclosed. The die includes a casting chamber, an ingate in fluid communication with the casting chamber for introducing a molten metal into the casting chamber along a flow direction, the ingate having a first surface movable in a direction perpendicular to the flow direction of the molten metal, a cavity, and a pressurization device disposed within the cavity, the pressurization device configured to cause the ingate to have a first cross-sectional area in a plane perpendicular to the flow direction based on a first pressure of the molten metal in the ingate and to have a second cross-sectional area in the plane perpendicular to the flow direction based on a second pressure of the molten metal in the ingate, wherein the second pressure is greater than the first pressure.

[0011]In addition to one or more of the features described herein, the second pressure is greater than the first pressure and the second cross-sectional area is greater than the first cross-sectional area.

[0012]In addition to one or more of the features described herein, the molten metal has the first pressure during a filling phase of a die casting operation and has the second pressure during an intensification phase of the die casting operation.

[0013]In addition to one or more of the features described herein, the pressurization device is one of a pressure valve, a low modulus metal, a spring, and a hydraulic device.

[0014]In addition to one or more of the features described herein, the low modulus metal is at least one of Titanium, Iron, Copper, High Entropy Alloy (HEA), Aluminum alloy, low carbon steel, stainless steel, a phase change material, and a bi-metallic material made by an additive manufacturing process.

[0015]In addition to one or more of the features described herein, the die further includes a first die segment and a second die segment that are configured to mate to each other to form the casting chamber and the ingate, wherein the pressurization device is disposed within one of the first die segment and the second die segment.

[0016]In addition to one or more of the features described herein, the die further includes a piston that controls a pressure in the ingate.

[0017]In yet another exemplary embodiment, a method of die casting is disclosed. A molten metal is poured into an ingate of a die, the die including the ingate and a casting chamber. The molten metal is injected at a first pressure from the ingate into the casting chamber along a flow direction, wherein the ingate includes a first surface movable in a direction perpendicular to the flow direction of the molten metal and the first surface defines a first height when the molten metal is at the first pressure. A pressure to the molten metal is increased to a second pressure greater than the first pressure, wherein the first surface defines a second height greater than the first height when the molten metal is at the second pressure.

[0018]In addition to one or more of the features described herein, the molten metal has the first pressure during a filling phase of a die casting operation and has the second pressure during an intensification phase of the die casting operation.

[0019]In addition to one or more of the features described herein, the method further includes controlling the pressure using a pressurization device that is selected from one of a pressure valve, a low modulus metal, a spring, and a hydraulic device.

[0020]In addition to one or more of the features described herein, the low modulus metal is at least one of Titanium, Iron, Copper, High Entropy Alloy (HEA), Aluminum alloy, low carbon steel, stainless steel, a phase change material, and a bi-metallic material made by an additive manufacturing process.

[0021]In addition to one or more of the features described herein, the pressurization device is disposed within a cavity of the die.

[0022]In addition to one or more of the features described herein, the method further includes controlling at least one of the first pressure and the second pressure of the molten metal in the ingate using a piston.

[0023]The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:

[0025]FIG. 1 shows a schematic diagram of a die casting system, in accordance with an exemplary embodiment;

[0026]FIG. 2 shows a perspective view of a section of the ingate, in an illustrative embodiment;

[0027]FIG. 3 shows a first casting die during a filling phase of a die casting process, in an illustrative embodiment;

[0028]FIG. 4 shows the first casting die during an intensification phase of the die casting process, in an illustrative embodiment;

[0029]FIG. 5 shows a second casting die during a filling phase of a die casting process, in an illustrative embodiment;

[0030]FIG. 6 shows the second casting die during the intensification phase of the die casting process, in an illustrative embodiment;

[0031]FIG. 7 shows a third casting die during the filling phase, in an illustrative embodiment;

[0032]FIG. 8 shows the third casting die during the intensification phase, in an illustrative embodiment;

[0033]FIG. 9 shows a fourth casting die during the filling phase, in an illustrative embodiment;

[0034]FIG. 10 shows the fourth casting die during the intensification phase, in an illustrative embodiment; and

[0035]FIG. 11 is flowchart of a method for performing a die casting operation using the methods disclosed herein

DETAILED DESCRIPTION

[0036]The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0037]In accordance with an exemplary embodiment, FIG. 1 shows a schematic diagram of a die casting system 100. The die casting system 100 includes a die 102 having a chamber 104 for forming a part and an ingate 106 in fluid communication with the chamber 104. The ingate 106 has an opening 108 through which a molten metal can be poured into the ingate. A piston 110 can be moved through the ingate 106 to inject the molten metal into the chamber 104 during a filling phase of the die casting process. Once, the chamber 104 is filled, the piston 110 compresses the molten metal in the ingate 106 and chamber 104 during an intensification phase of the die casting process. During the filling phase, the molten metal is at a first pressure and during the intensification phase, the molten metal is at a second pressure higher than the first pressure. A cavity 112 includes a pressurization device (not shown) that applies a pressure on the ingate 106.

[0038]FIG. 2 shows a perspective view 200 of a section of the ingate 106, in an illustrative embodiment. The ingate 106 is in the shape of a cuboid having four surfaces 202a, 202b, 202c and 202d that define a channel for the ingate, an inlet 204 and an outlet 206. The molten metal flows through the ingate 106 from the inlet 204 to the outlet 206 along a flow direction 208. A surface (e.g., first surface 202a) is movable along a direction perpendicular to the flow direction, as indicated by movement arrow 210 while the three remaining surfaces (e.g., surfaces 202b, 202c and 202d) are fixed in space. For purposes of discussion the movement arrow 210 is oriented along a vertical direction. A cross-section of the ingate 106 in a plane perpendicular to the flow direction 208 has a width w, a height h, and a cross-sectional area A, where A=w*h. The first surface 202a is configured to move vertically based on a pressure within the ingate 106. The first surface 202a rises as the pressure in the ingate 106 increases, thereby increasing the height h and the corresponding cross-sectional area A and lowers as the pressure in the ingate decreases, thereby decreasing the height h and the corresponding cross-sectional area A. A pressurization device (shown in FIGS. 3-10) applies a biasing force vertically downward on the first surface 202a. The pressure within the ingate 106 works against the pressurization device to control the height h of the first surface 202a.

[0039]FIG. 3 shows a first casting die 300 during a filling phase of a die casting process, in an illustrative embodiment. The first casting die 300 includes a first die segment 302 and a second die segment 304. The first die segment 302 and the second die segment 304 are configured to mate to each other to form a chamber 104 and an ingate 106. One of the first die segment 302 and the second die segment 304 can include the cavity 112 in which a pressurization device 306 can be disposed. For illustrative purposes, the cavity 112 is in the first die segment 302.

[0040]The pressurization device 306 is a pressurized chamber 308 having a pressure valve 310. The sides of the pressurized chamber 308 can be made of a low modulus metal. A side 312 of the pressurized chamber 308 forms the movable surface (i.e., first surface 202a) of the ingate 106. An internal pressure within the pressurized chamber 308 biases the first surface 202a downward toward its opposite surface (i.e., surface 202c) of the ingate 106. During the filling process, an ingate pressure balances the internal pressure of the pressurized chamber 308 to place the side 312 at a first position in which the first surface 202a has a first height h₁, resulting in a first cross-sectional area A₁. The first height h₁ is relatively small. For illustrative purposes, the height is h₁=3-5 millimeters (mm). The first pressure is low due to low back pressure in the die cavity and the high velocity flow of the molten metal through the ingate and into the casting chamber.

[0041]FIG. 4 shows the first casting die 300 during an intensification phase of the die casting process, in an illustrative embodiment. During the intensification process, the pressure within the ingate rises to a second pressure greater than the first pressure, thereby balancing the internal pressure of the pressurized chamber 308 when the side 312 rises to a second position (i.e., a second height h₂ greater than the first height h₁). For illustrative purposes, the second height is h₂=5-7 millimeters (mm). The second height results in a second cross-sectional area A₂. The pressure valve 310 can relieve the internal pressure of the pressurized chamber 308 during the intensification phase.

[0042]FIG. 5 shows a second casting die 500 during a filling phase of a die casting process, in an illustrative embodiment. The cavity 112 includes a metal alloy 502 surrounded by a low modulus metal 504. The metal alloy 502 can be a Titanium alloy, Iron alloy, Copper alloy, High Entropy Alloy (HEA), Aluminum alloy, low carbon steel, stainless steel, a phase change material or other suitable alloy. The metal alloy becomes soft and compressible at high pressures and/or high temperatures. The metal alloy insert surrounded by the low modulus metal can be made by an additive manufacturing process such as a bi-metallic material. A side 506 of the low modulus metal 504 forms the first surface 202a of the ingate 106. During the filling stage, the metal alloy 502 establishes the first surface 202a at the first height h₁.

[0043]FIG. 6 shows the second casting die 500 during the intensification phase of the die casting process, in an illustrative embodiment. During the intensification process, the pressure within the ingate rises to a second pressure greater than the first pressure. This increased pressure causes the metal alloy 502 to weaken and deform, allowing the side 506 to rise, thereby establishing the first surface 202a at second height h₂.

[0044]FIG. 7 shows a third casting die 700 during the filling phase, in an illustrative embodiment. The cavity 112 includes a piston 702 and a biasing member such as a spring 704 having a spring constant k. The piston 702 forms the first surface 202a. The spring 704 biases the piston 702 downward toward opposite surface 202c. During the filling process, the molten metal within the ingate 106 has a first pressure that balances the pressure of the spring to establish the first surface 202a at the first height h₁.

[0045]FIG. 8 shows the third casting die 700 during the intensification phase, in an illustrative embodiment. During the intensification process, the pressure within the ingate rises to a second pressure greater than the first pressure, thereby balancing the pressure provided by the spring to establish the first surface 202a at the second height h₂.

[0046]FIG. 9 shows a fourth casting die 900 during the filling phase, in an illustrative embodiment. The cavity 112 includes a piston 902 and a hydraulic device 904. The piston 902 forms the first surface 202a. The hydraulic device 904 places the piston 902 and thus the first surface 202a at a first height h₁ with respect to the opposite surface 202c.

[0047]FIG. 10 shows the fourth casting die 900 during the intensification phase, in an illustrative embodiment. During the intensification process, the hydraulic device 904 can raise the piston 902, thereby placing the first surface 202a at a second height h₂.

[0048]While the die casting system is discussed with respect to one movable surface of the ingate, in other embodiments, a second surface of the ingate (i.e., one of surfaces 202b, 202c, 202d) can also move in a direction perpendicular to the flow direction 208. The first surface 202a can move along one dimension or axis while the second surface (one of surfaces 202b, 202c, 202d) can move along a second axis. The second surface can have a second pressurization device that controls its operation. The second pressurization device can be any of the pressurization devices disclosed herein.

[0049]FIG. 11 is flowchart 1100 of a method for performing a die casting operation using the methods disclosed herein. In box 1102, a molten metal is injected from the ingate into the casting chamber with the molten metal at a first pressure during a filling phase. The first surface 202a defines a first height h₁ when the molten metal is at the first pressure. In box 1104, the pressure of the molten metal is raised to a second pressure greater than the first pressure during an intensification phase. The first surface 202a defines a second height h₂ when the molten metal is at the second pressure. With the first surface at the second height, the onset of freeze out at the ingate is reduced or prevented during the intensification phase.

[0050]The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “or” means “and/or” unless clearly indicated otherwise by context. Reference throughout the specification to “an aspect”, means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various aspects.

[0051]When an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0052]Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

[0053]Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs.

[0054]While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof.