Conformal cooling insert

Abstract

A cooling insert for a die, such as a distributor for a high-pressure die casting assembly, and a method of manufacturing the conformal cooling insert, is provided. The cooling insert includes an inner portion formed of copper, a copper alloy, or a beryllium copper alloy and an outer portion formed of a steel material. The inner portion includes cooling channels having a complex shape. The inner portion is also manufactured using an investment casting process, for example, a process which uses a printed investment casting shell. The complex cooling channels improve cooling and reduce the duration of the casting process.

Description

CONFORMAL COOLING INSERTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT International Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 63 / 602,684, filed November 27, 2023, titled “Conformal Cooling Insert,” the entire disclosure of which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The invention relates generally to a conformal cooling insert for a die, such as an insert for use in a high-pressure die casting assembly, and methods of manufacturing the cooling insert.2. Related Art

[0003] High-pressure die casting (HPDC) is often used to manufacture parts formed of metal, for example, parts formed of aluminum or an aluminum alloy, for use in vehicles. The HPDC process includes closing a pair of die halves to form a sealed cavity, injecting molten metal under high-pressure into the sealed cavity, and holding the metal under pressure in the sealed cavity until the molten metal solidifies. Once the metal in the die solidifies, the cover half and ejector half open, and the solidified metal part is released. The die is then prepared for the next casting cycle.

[0004] The longest step of the HPDC process is the solidification step, or dwell time, specifically the time it takes for the molten metal to solidify in the die. Currently, many dies include metal inserts with cooling channels along the travel path of the molten metal or along thedie cavity. During the casting process, water or another cooling fluid flows through the cooling channels to cool the metal.

[0005] The inserts with complex conformal cooling channels have been formed by additive manufacturing, for example by selective laser sintering a maraging steel powder. However, the additive machining process is expensive and time consuming. These inserts framed by additive manfuacturing are currently expensive and usually have residual stress issues. Most additive manufactured sintered inserts only last a few hundred shots before they start to crack. Thus, a more efficient manufacturing process and more durable cooling insert is needed. Improved cooling insert designs are also needed to more efficiently remove heat and thus avoid hot spots and reduce the solidification time.SUMMARY

[0006] One aspect of the invention provides a cooling insert for a die and a more efficient method of manufacturing the conformal cooling insert for a die. The cooling insert includes an inner portion formed of copper or copper alloy and an outer portion formed of a steel material surrounding the inner portion. The cooling insert also includes at least one cooling channel.

[0007] Another aspect of the invention provides an apparatus for high-pressure die casting (HPDC) parts formed of aluminum or aluminum alloy. The apparatus comprises a die including a surface presenting a cavity for containing molten aluminum or aluminum alloy. The conformal cooling insert is disposed along the surface presenting the cavity.

[0008] Yet another aspect of the invention provides a method of high-pressure die casting a part comprising the steps of: disposing the cooling insert along a surface of a casting assembly, the surface and the cooling insert presenting a cavity for containing molten metal; and conveyingcooling fluid through the at least one cooling channel of the cooling insert while molten metal is disposed in the cavity.

[0009] Another aspect of the invention provides a method of manufacturing a cooling insert for use in a high-pressure die casting assembly. The method includes a printed ceramic shell investment casting process to form an inner portion of copper or copper alloy, wherein the inner portion includes at least one cooling channel. The method further includes disposing an outer portion of a steel material around the inner portion to form the cooling insert.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0011] Figure 1 shows a high-pressure ejector half of a die assembly including a cooling insert according to an example embodiment;

[0012] Figure 2A is an enlarged view of an investment cast conformal cooling distributor insert with an inner portion and outer portion according to an example embodiment;

[0013] Figure 2B is an enlarged view of a cooling insert with complex conformal cooling channels according to an example embodiment;

[0014] Figures 3 and 4 are other example cooling insert designs;

[0015] Figure 5 is a comparative cooling insert with conventional cooling channels; and

[0016] Figure 6 is a pie chart illustrating an example of the steps, in seconds of a cycle time, of a high-pressure die casting process.DETAILED DESCRIPTION OF EXAMPEL EMBODIMENTS

[0017] One aspect of the invention provides an improved cooling distributor insert 10 and method of manufacturing the cooling insert 10, preferably used in or along a die 12 of a high-pressure die casting assembly 14. The cooling insert 10 is manufactured using a three- dimensional printed ceramic shell investment casting process to form an inner portion 10a of copper, a copper alloy or a beryllium copper alloy. The cooling insert 10 also includes an outer portion 10b formed of a steel material and which is disposed around the inner portion 10a. The inner portion 10a manufactured using the printed investment casting process includes at least one cooling channel 16 and typically a plurality of complex cooling channels 16. This is an improvement over comparative cooling inserts and methods used to form cooling inserts, including inserts formed of H13 tool steel by forging and inserts formed with complex cooling channels using an additive manufacturing process. The forged Hl 3 material and current machining processes are not able to successfully create the desired complex cooling channels, and the additive manufacturing process is not able to cost effectively form a cooling insert which meets performance requirements.

[0018] As stated above, the inner portion 10a of the cooling insert 10 is formed of copper, a copper alloy, or a beryllium copper alloy. According to an example embodiment, the beryllium copper alloy used to form the inner portion 10a includes beryllium (Be) in an amount of 0.45 to 0.80 wt. %, cobalt (Co) in an amount of 2.40 to 2.70 wt. %, and a balance of copper (Cu).

[0019] The outer portion 10b of the cooler insert 10 is formed of a steel material and is disposed around the inner portion 10a. The outer portion 10b does not include cooling channels and is provided to increase the strength of the cooling insert 10 and prevent leakage of thecooling fluid which flows through the cooling channels 16 of the inner portion 10a. According to one embodiment, the outer portion is formed of a steel material, preferably H13 tool steel. The H13 tool steel includes chromium (Cr) in an amount of 4.75-5.50 weight percent (wt. %), molybdenum (Mo) in an amount of 1.10-1.75 wt. %, silicon (Si) in an amount of 0.80-1.20 wt. %, vanadium (V) in an amount of 0.80-1.20 wt. %, carbon (C) in an amount of 0.32-0.45 wt. %, manganese (Mn) in an amount of 0.20-0.50 wt. %, phosphorous in an amount up to 0.03 wt. %, sulfur in an amount up to 0.03 wt. %, possibility impurities in an amount up to 0.2 wt. %, and iron in an amount of at least 80.0 wt. %, based on the total weight of the steel material. According to a preferred embodiment, the steel material includes chromium (Cr) in an amount of 5.25 weight percent (wt. %), molybdenum (Mo) in an amount of 1.35 wt. %, silicon (Si) in an amount of 1.00 wt. %, vanadium (V) in an amount of 1.00 wt. %, carbon (C) in an amount of 0.40 wt. %, and manganese (Mn) in an amount of 0.40 wt. %, possibility impurities in an amount up to 0.2 wt. %, and a balance of iron, based on the total weight of the steel material.

[0020] According to other embodiments, the outer portion 10b of the cooling insert 10 can be formed of another type of steel material, ferrous material, or iron-based material. For example, the material which forms the outer portion 10b of the cooling insert 10 could be a heat resistant steel casting. Preferably, the heat resistant steel casting does not melt or corrode during high-end industrial operations involving high temperatures, and is capable of performing in conditions above 1200° F (650° C). Heat resistant steel castings are usually higher in alloy content than other types of castings. Typically, the heat resistant steel castings mainly consist of nickel and chromium. Nickel is usually present in an amount up to 70 wt. %. Chromium is usually present in an amount of 10 wt. % to 30 wt. %. Other elements, however, are used as well. These include iron, carbon, silicon, manganese, and molybdenum. Additions of up to 0.60wt. % of niobium might be added to the composition for applications requesting strong resistance to creep.

[0021] The copper inner portion 10a of the cooling insert 10 includes at least one complex cooling channel 16 and typically a plurality of complex cooling channels 16 designed for more efficient cooling during the HPDC process, relative to comparative cooling inserts which include conventional cooling channel(s). According to a preferred example embodiment, the cooling insert 10 is used for high-pressure die casting (HPDC), and more specifically as a cooling insert 10 for a distributor of the die 12.

[0022] An example of the high-pressure die casting assembly 14 including the die 12 with an example cooling insert design in the form of the distributor is shown in Figure 1. Figures 2A and 2B show an example design for the cooling insert 10 according to the present invention. The distinction between the inner portion 10a formed of copper or copper alloy and the outer portion 10b formed of the steel material is clearly shown in Figure 2A, and the design of the cooling channels 16 is clearly shown in Figure 2B. Other example cooling insert designs with complex cooling channels are shown in Figures 3 and 4. The inner portion 10a of the cooling insert 10 according to the present invention can include similar cooling channel designs. A comparative cooling insert, also a distributor, with conventional cooling channels is shown in Figure 5.

[0023] The cooling insert 10 presents a portion of a cavity surface along which molten metal flows. Typically, each cooling channel 20 includes at least one curve, and preferably a plurality of curves or bends, for example at least two, at least three, at least four, at least five, at least ten, at least fifteen, or more curves or bends. Each cooling channel 16 typically has a diameter ranging from 4 mm to 10 mm. The cooling insert 10 of the present invention can havea greater number of cooling channels 16 and can include cooling channels 16 which are closer to the cavity surface (the surface of the cooling insert 10 along which the molten metal flows) of the cooling insert 10, relative to comparative cooling inserts. According to example embodiments, the distance between at least one of the cooling channels 16 and the cavity surface is approximately 1.5x (for example 1.2x to 1.8x) the diameter of the cooling channel 16. For example, for a 5 mm diameter cooling channel 16, the depth of the cooling channel 16, relative to the cavity surface of the cooling insert 10, would be 6 to 7.5 mm. The diameter of each cooling channel 16 is typically constant along the entire length of the cooling channel 16.

[0024] In the examples of Figures 2-4, the cooling channel 16 has a numerous curves and includes multiple segments 22 located parallel to one another. The segments 22 which are parallel to one another are located the same distance from the cavity surface. The cooling insert 10 of the present invention is also less expensive to manufacture and more durable than the comparative cooling inserts which include the same type of complex cooling channels but which are not formed using the investment casting process.

[0025] As stated above, the method of manufacturing the inner portion 10b of the cooling insert 10 with the at least one complex cooling channel 16 includes a printed investment casting process. An example of an investment casting process according to another example embodiment includes the use of a printed investment casting shell. According to this process, the ceramic shell is formed by three dimensional printing or additive manufacturing the ceramic shell. The printed investment casting shell (P.I.C.S.) process does not require the wax mold or expendable patterns to produce the ceramic shell. The printed investment casting shell process can produce the ceramic shell with features that cannot be made or are difficult to make by the conventional investment casting process, such the complex cooling channels 16.

[0026] The conventional investment casting process (lost wax method) can also be used to form the copper inner portion 10a of the cooling insert 10, although it is less preferred. The conventional investment casting process begins with forming a wax pattern by injecting wax into a prefabricated die having the same geometry as the desired cast part to be formed in the casting assembly. The wax pattern is then attached to a wax gating system, which includes at least one channel through which molten material can flow. Multiple wax patterns can be attached to the gating system. The next stage is the shell building, wherein the wax assembly is immersed into a refractory ceramic slurry of hardening mixtures followed by drying. This operation is repeatedly carried out resulting in formation of a solid ceramic shell, preferably having a thickness of 14 inch to 3 / 8 inch (6mm to 9 mm). The ceramic shell is designed with cooling channels and has a design which is the negative of the desired design of the part to be formed. The next stage is dewaxing the ceramic shell. At this stage, the assembly is heated in an autoclave where most of the wax is melted out of the ceramic shell. The ceramic shell is then fired in a furnace so that the residual wax is burnt out.

[0027] After the ceramic shell is formed, preferably by additive manufacturing, the ceramic shell can be placed in a box of sand, preheated, for example to 1830° F (1000° C), and filled with the molten copper or copper alloy which is used to form the inner portion 10a of cooling insert 10. After the copper solidifies and cools, the ceramic is broken off.

[0028] The outer portion 10b of the cooling insert 10 formed of the steel material can be manufactured by filling the box of sand with the molten steel material after the copper inner portion 10a solidifies. Alternatively, the outer portion 10b can be cast around the inner portion 10a according to another method, or formed separately and then joined to the inner portion.

[0029] The process can include finish machining the inner portion 10a and / or the outer portion 10b of cooling insert 10. After the manufacturing process, the cooling insert 10 can be used in the die 12, such as the die 12 of the high-pressure die casting assembly 14.

[0030] The process according to the present invention is able to form a cooling insert 10 which includes the inner portion 10a formed of copper, copper alloy, or beryllium copper alloy and having the following properties: hardness HRB of 52 to 92; density of at least 8.62 g / cm3at 20°C; ultimate tensile strength (UTS) of at least 345 MPa, elongation of at least 20%; yield strength of at least 140 MPa; Young’s Modulus of at least 115 GPa from 70° C to 800° C; thermal expansion (at 20° C to 100° C) of at least 17.8 * 10'6'K; and heat conductivity (from 80 to 800° C) of at least 218 W / mK.

[0031] The outer portion 10b of the cooling insert 10 has the following properties: hardness HRC of 52 to 54; density of at least 7.8 g / cm3at 20°C; ultimate tensile strength (UTS) of at least 1990 MPa, elongation of at least 9.0 %; yield strength of at least 1650 MPa; Young’s Modulus of at least 210 GPa from 70° C to 800° C; thermal expansion (at 20° C to 100° C) of at least 11.0 *10‘6 / K; and heat conductivity (from 80 to 800° C) of at least 24.3 W / mK. The cooling insert 10 is able to achieve those properties at least in part due to the method of manufacturing the cooling insert 10, specifically the investment casting process.

[0032] As stated above, the cooling inert 10 is typically used in a high-pressure die casting process. During the HPDC process, the molten aluminum or other melted metal material is introduced under high velocity and pressure into the casting tooling assembly 14. In the example embodiment, the melted metal is pushed into a “biscuit” area that is adjacent the cooling insert 10, in this case the distributor, before entering a cavity between a cover half and an ejector half of the die 12. The molten metal in the cavity, as well as the molten metal along thedistributor, must be solidified before it is removed from the casting assembly 14. Figure 6 is a pie chart of the steps of an example HPDC process which illustrates that the solidification step is the longest step in the process. More specifically, Figure 6 illustrates that a typical solidification step take up about 33.6% of the process time. The complex cooling channels 16 in the distributor which allow cooling fluid to flow therethrough reduce the significant amount of time required for the molten steel material to solidify along the distributor.

[0033] As indicated above, the cooling channels 16 can be designed to control the temperature of select portions of the die assembly 14. The cooling channels 16 of the cooling insert 10 of the present invention can be designed uniformly close to the surface of the cooling insert 10. For example, each cooling channel 16 or segment of a cooling channel 16 can be located a distance from the surface along which the molten metal flows of not more than the diameter of the cooling channel 16 x 1.5. In addition, the complex designs of the cooling channels 16 can reduce the solidification time, which reduces the casting cycle time, and reduces energy consumption.

[0034] Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the disclosure and the following claims.

Claims

CLAIMSWhat is claimed is:

1. A cooling insert for a die, comprising: an inner portion formed of copper, a copper alloy, or beryllium copper alloy; said inner portion including at least one cooling channel; and an outer portion formed of a hardened tool steel material.

2. The cooling insert of claim 1, wherein said at least one cooling channel includes a plurality of curves.

3. The cooling insert of claim 2, wherein said at least one cooling channel includes at least five curves.

4. The cooling insert of claim 1, wherein said inner portion presents a surface, and one cooling channel of the at least one cooling channel has a diameter and is located a distance from the surface equal to 1.5 times to 1.8 times the diameter of the cooling channel.

5. The cooing insert of claim 4, wherein the diameter is constant along length of the cooling channel.

6. The cooling insert of claim 1, wherein the steel material of said outer portion includes chromium (Cr) in an amount of 4.75-5.50 weight percent (wt. %), molybdenum (Mo) in an amount of 1.10-1.75 wt. %, silicon (Si) in an amount of 0.80-1.20 wt. %, vanadium (V) inan amount of 0.80-1.20 wt. %, carbon (C) in an amount of 0.32-0.45 wt. %, manganese (Mn) in an amount of 0.20-0.50 wt. %, phosphorous in an amount up to 0.03 wt. %, sulfur in an amount up to 0.03 wt. %, possibility impurities in an amount up to 0.2 wt. %, and iron in an amount of at least 80.0 wt. %, based on the total weight of said steel material.

7. The cooling insert of claim 6, wherein said steel material includes the chromium (Cr) in an amount of 5.25 weight percent (wt. %), the molybdenum (Mo) in an amount of 1.35 wt. %, the silicon (Si) in an amount of 1.00 wt. %, the vanadium (V) in an amount of 1.00 wt. %, the carbon (C) in an amount of 0.40 wt. %, and the manganese (Mn) in an amount of 0.40 wt. %, based on the total weight of said steel material.

8. The cooling insert of claim 1, wherein said inner portion presents a surface, one cooling channel of said at least one cooling channel includes a plurality of curves and a plurality of segments, and said segments are disposed parallel to one another and are located an equal distance from said surface.

9. The cooling insert of claim 1, wherein said inner portion has a hardness HRB of 52 to 92; a density of at least 8.62 g / cm3at 20°C; an ultimate tensile strength (UTS) of at least 345 MPa, an elongation of at least 20%; a yield strength of at least 140 MPa; a Young’s Modulus of at least 115 GPa from 70° C to 800° C; a thermal expansion (at 20° C to 100° C) of at least 17.8 *10'6 / K; and a heat conductivity (from 80 to 800° C) of at least 218 W / mK.

10. The cooling insert of claim 1, wherein said outer portion has a hardness HRC of 52 to 54; a density of at least 7.8 g / cm3at 20°C; an ultimate tensile strength (UTS) of at least 1990 MPa, an elongation of at least 9.0 %; a yield strength of at least 1650 MPa; a Young’s Modulus of at least 210 GPa from 70° C to 800° C; a thermal expansion (at 20° C to 100° C) of at least 11.0 *10’6 / K; and a heat conductivity (from 80 to 800° C) of at least 24.3 W / mK.

11. An apparatus for high-pressure die casting (HPDC) parts formed of aluminum or aluminum alloy, comprising: a die including a surface presenting cavity for containing molten aluminum or aluminum alloy; and said cooling insert of claim 1 disposed along said surface.

12. The apparatus of claim 11, wherein said cooling insert is a distributor of the die.

13. A method of high-pressure die casting a part comprising the steps of: disposing the cooling insert of claim 1 along a surface of a casting assembly, the surface and the cooling insert presenting a cavity for containing molten metal; and conveying cooling fluid through the at least one cooling channel of the cooling insert while molten metal is disposed in the cavity.

14. A method of manufacturing a cooling insert for use in a high-pressure die casting assembly, comprising the steps of:investment casting copper, a copper alloy, or a beryllium copper alloy to form an inner portion of a cooling insert having at least one cooling channel; and disposing an outer portion formed of a steel material around the inner portion.

15. The method of claim 14, wherein the investment casting step includes forming a ceramic shell by additive manufacturing, placing the ceramic shell in a box of sand, filling the box with molten copper or copper alloy around the ceramic shell to form the inner portion; and breaking off the ceramic shell from the inner portion once the inner portion solidifies.

16. The method according to claim 14, including casting the steel material around the inner portion to form the outer portion of the cooling insert.

17. The method of claim 14, wherein the at least one cooling channel includes a plurality of curves, the inner portion presents a surface, and one cooling channel of the at least one cooling channel has a diameter and is located a distance from the surface equal to 1.5 times to 1.8 times the diameter of the cooling channel.

18. The method of claim 14, wherein said inner portion has a hardness HRB of 52 to 92; a density of at least 8.62 g / cm3at 20°C; an ultimate tensile strength (UTS) of at least 345 MPa, an elongation of at least 20%; a yield strength of at least 140 MPa; a Young’s Modulus of at least 115 GPa from 70° C to 800° C; a thermal expansion (at 20° C to 100° C) of at least 17.8 *10'6 / K; and a heat conductivity (from 80 to 800° C) of at least 218 W / mK.

19. The method of claim 14, wherein said outer portion has a hardness HRC of 52 to 54; a density of at least 7.8 g / cm3at 20°C; an ultimate tensile strength (UTS) of at least 1990 MPa, an elongation of at least 9.0 %; a yield strength of at least 1650 MPa; a Young’s Modulus of at least 210 GPa from 70° C to 800° C; a thermal expansion (at 20° C to 100° C) of at least 11.0 *10’6 / K; and a heat conductivity (from 80 to 800° C) of at least 24.3 W / mK.

20. The method of claim 14, wherein said at least one cooling channel includes a plurality of curves.

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