MOLD CORE ASSEMBLY AND INVESTMENT CASTING METHOD
The present invention discloses a mold core assembly. The mold core assembly includes at least one core. The core comprises a main body member and a high temperature-resistant material with a melting point over 1500° C., the length-diameter ratio of the main body member is greater than 50, and the main body member includes a high melting point metal with a melting point over 1500° C. The mold core assembly also includes a shell mold, wherein the shell mold encloses the core to form a cavity between the shell mold and the core, so as to accommodate a molten casting metal. The present invention further discloses an investment casting method.
The present invention relates to a mold core assembly and an investment casting method and in particular, to a mold core assembly and an investment casting method for casting a casting provided with a long deep hole and a core.
BACKGROUNDAn investment casting method is widely used to mold a metal component with a complex geometric structure, especially, a component provided with an internal hole. In the investment casting method, a mold core assembly is first molded. The mold core assembly includes a shell mold and a core fastened in the shell mold; then molten steel is poured into the molded mold core assembly, to form a solid metal casting after cooling. After the casting is finished, the shell mold and the core are removed. The existing core is made of a ceramic material. The ceramic is high temperature-resistant but brittle and is subject to fracture. Especially, when a relatively large component provided with a relatively long hole is casted, a ceramic core is also relatively long. Consequently, the ceramic core is more likely subject to fracture due to low strength of the ceramic core.
Therefore, it is necessary to provide a solution to resolve the at least one problem mentioned above.
BRIEF DESCRIPTIONOne aspect of the present invention provides a mold core assembly. The mold core assembly includes: at least one core, where the core includes a main body member and includes a high temperature-resistant material with a melting point over 1500° C., a length-diameter ratio of the main body member is greater than 50, and the main body member includes a high melting point metal with a melting point over 1500° C.; and a shell mold, where the shell mold encloses the core to form a cavity between the shell mold and the core, so as to accommodate a molten casting metal.
Another aspect of the present invention provides an investment casting method. The investment casting method includes: forming at least one core, where the core includes a main body member and includes a high temperature-resistant material with a melting point over 1500° C., a length-diameter ratio of the main body member is greater than 50, and the main body member includes a high melting point metal with a melting point over 1500° C.; forming a shell mold, where the shell mold encloses the core to form a cavity between the shell mold and the core; flowing a molten casting metal into the cavity to form a casting; and removing the shell mold.
To understand the present invention better, implementation manners of the present invention are described with reference to the accompanying drawings. In the accompanying drawings:
Unless otherwise defined, the technical terms or scientific terms used herein shall be the ordinary meaning understood by a person having ordinary skill in the technical field of the present invention. “First”, “second”, and similar words used in the patent application specification and claims of the present invention do not denote any order, quantity, or importance, and are simply used to distinguish different components. Similarly, “one”, “a/an”, or the similar terms also do not impose any limitations on quantity, but indicate at least one. In addition, “connected to”, “connected with”, or the similar expressions are not used to differentiate whether two components are connected directly or indirectly. Certainly, components may be directly or indirectly connected, unless otherwise specified.
A mold core assembly in the present invention can be configured for investment casting. The mold core assembly can be configured to cast a turbine component by means of investment casting, for example, blades of various shapes and sizes, where a relatively deep inner bore can be provided inside a blade. The mold core assembly can be configured to cast a cooling pipe of an exhaust cylinder, or can be configured to cast another component, where a relatively long hole may be provided inside the casted component.
The core 12 includes a main body member 16 and includes a high temperature-resistant material with a melting point over 1500° C. A length-diameter ratio of the main body member 16 is greater than 50. In this embodiment, the main body member 16 is a cylindrical solid rod. The length-diameter ratio of the main body member 16 is of a longitudinal length L to a diameter D of a cross section that are of the main body member 16. For example, the longitudinal length L of the main body member is 300 mm, and the diameter of the cross section is 2 mm. This is merely an example, and is not limited thereto. In addition, the length-diameter ratio of the main body member 16 is not limited to a proportional relationship denoted in the figure. The main body member 16 includes a high melting point metal with a melting point over 1500 C. In this embodiment, the main body member 16 further includes the high temperature-resistant material. The high melting point metal and the high temperature-resistant material are mixed together. The main body member 16 includes a base 18 and an additive 20 mixed in the base 18. In an embodiment, the base 18 includes the high melting point metal, and the additive 20 includes the high temperature-resistant material. In another embodiment, the base 18 includes the high temperature-resistant material, and the additive 20 includes the high melting point metal. In the embodiment shown in the figure, the additive 20 is in a powder form, and distributed in the base 18. In another embodiment, the main body member 16 includes a cermet. The cermet includes the high melting point metal and a ceramic. The ceramic is a high temperature-resistant material.
In an embodiment, a high temperature-resistant material includes at least one of the following types: quartz, ceramic, platinum-group metal, or a cermet. The high temperature-resistant material may be a pure metal, an alloy, or a composite of the metal described above. The cermet is a structural material combing a hard phase ceramic with a metal or a binder phase alloy, and has good toughness and thermal stability. In an embodiment, the cermet includes a WC—Co composite material or a TiC—TiN—Mo—Ni composite material. In an embodiment, the high melting point metal includes at least one of the following types: molybdenum, tungsten, titanium, platinum-group metal, tantalum, chromium, or a niobium. The main body member 16 may include a pure metal, an alloy, or a composite of the high melting point metal described above. In an embodiment, the main body member 16 may include a molybdenum-based alloy, such as a Mo—Cr (MoCr) alloy, a Mo—Co—Cr (MoCoCr) alloy, a Mo—W alloy (MoW), or a Mo—Zr—Ti (TZM, MoZrTi) alloy. The main body member 16 may include a W-based alloy (W based alloy) or a Ti—Mo (TiMo) alloy.
Different materials are selected from the high temperature-resistant material and the high melting point metal to form the core 12. Therefore, the core 12 includes at least two different materials. The high temperature-resistant material can prevent the core 12 from distortion resulting from high temperature of a molten casting metal (such as a nickel-based super alloy or a cobalt-based super alloy). The metal material can improve strength and/or toughness of the core 12. In this embodiment, the melting point of the high melting point metal is higher than a melting point of the casting metal. The high melting point metal is not subject to melting in the high temperature of the molten casting metal.
The shell mold 14 encloses the core 12, to form a cavity 22 between the shell mold 14 and the core 12, so as to accommodate the molten casting metal (not shown in the figure). The shell mold 14 may be made of a ceramic material. A shape and a size of the shell mold 14 are the same as those of a desired component. A location of the core 12 in the shell mold 14 is determined according to that of a hole of the desired component. After the casting is finished, the core 12 in this embodiment can be completely removed by means of erosion.
The cores in the embodiments shown in
Step 43. Form a shell mold. The shell mold encloses the core, to form a cavity between the shell mold and the core. In an embodiment, a desired molding component is casted by using a mold molding material (such as wax). Next, a shell mold that envelopes a mold is formed outside of the mold. Then, the mold molding material is removed to left the shell mold. In this way, a shape and a size of the shell mold are the same as those of the component. In an embodiment, the core is embedded in the mold molding material. After the mold molding material is removed, the core is left in the shell mold. In another embodiment, after the shell mold is formed, the core is placed into the shell mold and fastened. The shell mold may be made of ceramic slurry. In this way, a mold core assembly is formed. The cavity between the shell mold and the core is formed, so as to accommodate a molten casting metal.
Step 45. Flow a molten casting metal into a cavity to form a casting. A high temperature molten casting metal is poured into the shell mold, and forms a solidified casting followed by rapid cooling. Step 47. Remove the shell mold. In an embodiment, a ceramic shell mold is removed by means of erosion. In an embodiment, the main body member of the core is manufactured by a metal similar to the casting metal. In addition, when an external surface of the main body member is not provided with a coating layer made of a high temperature-resistant material, the main body member of the core may be left in the casting, and is served as a desired component together with the casting. The main body member is a hollow tube. A high temperature-resistant filling material into which the hollow tube is filled is used to cool the hollow tube. After the casting is finished, the filling material is removed. An internal size of the hollow tube is equal to that of a desired hole. In another embodiment, the casting method 40 further includes: removing the core completely. The core can be completely removed by means of erosion; for example, when the main body member of the core includes a high temperature-resistant material, or the core has a coating layer made of the high temperature-resistant material, or the high melting point metal material of the core is different from or not similar to the casting metal, the core is completely removed. An external size of the core is consistent with that of the desired hole.
Operations of the method 40 are shown in a form of functional modules. A sequence of modules shown in
Although the present invention is described with reference to the specific implementation manners, a person skilled in the art can understand that modifications and variations of the present invention can be made. Therefore, it can be learned that the claims are intended to include all modifications and variations within the concept and protection scope of the present invention.
Claims
1. A mold-core assembly, comprising:
- at least one core comprising a main body with an aspect ratio of larger than 50 and comprising a high temperature resistant material with a melting point of higher than 1500 degree Celsius, the main body comprising a metal with a melting point of higher than 1500 degree Celsius; and
- a shell mold surrounding the at least one core and spaced away from the at least one core to define a cavity for receiving molten base metal.
2. The mold-core assembly of claim 1, wherein the main body comprises a matrix and a plurality of additives therein, the matrix comprises the metal and the plurality of additives comprise the high temperature resistant material.
3. The mold-core assembly of claim 1, wherein the main body comprises a matrix and a plurality of additives therein, the matrix comprises the high temperature resistant material and the plurality of additives comprise the metal.
4. The mold-core assembly of claim 1, wherein the at least one core further comprises a coating formed outside of the main body and comprising the high temperature resistant material.
5. The mold-core assembly of claim 1, wherein the high temperature resistant material comprises at least one of quartz, ceramic, platinum group metals and cermet.
6. The mold-core assembly of claim 1, wherein the main body comprises a tube comprising the metal, the at least one core further comprises a filler inside the tube, and the filler comprises the high temperature resistant material.
7. The mold-core assembly of claim 6, wherein the filler comprises a plurality of powders filling in the tube.
8. The mold-core assembly of claim 6, wherein the filler comprises a solid rod filling in and attached to the tube.
9. The mold-core assembly of claim 1, wherein the metal of the main body comprises at least one of molybdenum, tungsten, titanium, platinum group metals, tantalum, chromium and niobium.
10. The mold-core assembly of claim 1, wherein the main body of the at least one core comprises a cermet comprising the metal and a ceramic.
11. The mold-core assembly of claim 1, wherein the main body comprises a non-round cross-section.
12. The mold-core assembly of claim 1, wherein the main body comprises a non-straight shape.
13. A method, comprising:
- forming at least one core comprising a main body with an aspect ratio of larger than 50 and comprising a high temperature resistant material with a melting point of higher than 1500 degree Celsius, the main body comprising a metal with a melting point of higher than 1500 degree Celsius;
- forming a shell mold surrounding the at least one core and spaced away from the at least one core to define a cavity;
- introducing molten base metal to the cavity to form a cast body; and
- removing the shell mold.
14. The method of claim 13, wherein the main body comprises a matrix and a plurality of additives therein, the matrix comprises the metal and the plurality of additives comprise the high temperature resistant material.
15. The method of claim 13, wherein the main body comprises a matrix and a plurality of additives therein, the matrix comprises the high temperature resistant material and the plurality of additives comprise the metal.
16. The method of claim 13, wherein forming the at least one core further comprises forming a coating outside of the main body, and the coating comprises the high temperature resistant material.
17. The method of claim 13, wherein the main body comprises a tube comprising the metal, and forming the at least one core further comprising filling the tube with a filler comprising the high temperature resistant material.
18. The method of claim 13, wherein the metal of the main body comprises at least one of molybdenum, tungsten, titanium, platinum group metals, tantalum, chromium and niobium.
19. The method of claim 13, wherein the high temperature resistant material comprises at least one of quartz, ceramic, platinum group metals and cermet.
20. The method of claim 13, wherein the main body of the at least one core comprises a cermet comprising the metal and a ceramic.