Method for manufacturing a casting having a flow passage

Abstract

To provide a method of manufacturing a casting formed with a flow passage portion which can be manufactured more economically and manufactured with an internal flow passage portion made more robust, and a casting manufactured by the method.SOLUTION: A method of manufacturing a casting formed with a flow passage portion includes a step of manufacturing a smart core in which an inside of a tubular pipe 11 is filled with a filler 12, a step of inserting the smart core into a metal mold in which a cavity corresponding to a shape of a casting to be manufactured is formed, a step of casting by injecting a molten metal into the cavity, and a step of removing the filler in the smart core. The step of casting is performed by a high-pressure casting method. According to the present invention, a casting can be manufactured more economically and manufactured with an internal flow passage portion made more robust.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a casting having a flow passage formed therein and a casting manufactured by the same, and more particularly, to a method for manufacturing a casting having a flow passage formed therein and a casting manufactured by the same. [Background technology]

[0002] Recently, as the development of electric vehicles, hybrid vehicles, and the like has become more active, existing internal combustion engines, such as engines and transmissions, are being replaced with various power conversion components, such as drive motors and inverters and converters. These power conversion components generate more heat than existing components during the process of charging and converting electricity for use. As a result, such power conversion components, as well as other components that generate a lot of heat, require essential cooling flow paths. Conventionally, in order to form a flow passage in a part manufactured by casting, two parts are separately manufactured by casting so that the flow passage is formed, and then these parts are joined by bolts 3 or the like, and a gasket 2 is inserted for airtightness of the joined surfaces, to produce a casting 1 in which a flow passage portion 4 is formed by joining, as shown in FIG.

[0003] This existing method requires a complicated process of manufacturing and mechanically joining two pieces. In addition, if there is a defect inside the casting and the gasket is damaged, causing a leak, water may penetrate the power semiconductor, which may cause not only a system failure but also a fire in the vehicle. Therefore, there is a need to develop technology to make the flow path of the power conversion parts more robust. The matters described in the above background art are intended to aid in understanding the background of the invention, and may include matters that are not prior art already known to those having ordinary skill in the art to which this technology pertains. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korea Publication No. 10-2000-0017994 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a manufacturing method for a casting having a flow path portion that can be manufactured more economically and with an internal flow path portion that is more robust, and a casting manufactured by this method. [Means for solving the problem]

[0006] The manufacturing method of the present invention for a casting having a flow path portion includes the steps of manufacturing a smart core having a filler material filled inside a tubular pipe, inserting the smart core into a mold having a cavity corresponding to the shape of the casting to be manufactured, injecting molten metal into the cavity to cast, and removing the filler material from the smart core, and is characterized in that the hardness of the tubular pipe is 70Hv or more.

[0007] The casting step is characterized in that it is performed by a high pressure casting method.

[0008] The tubular pipe has a stretch ratio of 15% or more.

[0009] The particle size of the filler is characterized by being 100 μm or less.

[0010] The filler has a thermal conductivity of 0.1 to 1 W / m·°C.

[0011] The step of manufacturing the smart core includes filling the inside of the tubular pipe with a filler, drawing and extruding the tubular pipe filled with the filler, and bending the tubular pipe to correspond to the shape of a flow passage portion to be formed in the casting.

[0012] The molten metal and the tubular pipe are made of the same material.

[0013] The tubular pipe is made of aluminum material, The thickness of the tubular pipe is characterized by being equal to or greater than 1.25 mm and less than 4 mm.

[0014] In addition, the manufacturing method of the present invention for a casting having a flow path portion includes the steps of manufacturing a smart core having a filler material filled inside a tubular pipe, inserting the smart core into a mold having a cavity corresponding to the shape of the casting to be manufactured, injecting molten metal into the cavity to cast, and removing the filler material from within the smart core, wherein the particle size of the filler material is 100 μm or less.

[0015] The filler is characterized in that it is made of silica.

[0016] The filler has a thermal conductivity of 0.1 to 1 W / m·°C.

[0017] The casting of the present invention is characterized in that a tubular pipe having a shape of a flow passage portion is inserted and cast integrally, and the hardness of the tubular pipe is 70 Hv or more.

[0018] The molten metal and the tubular pipe are made of the same material.

[0019] The tubular pipe is made of aluminum.

[0020] The thickness of the tubular pipe is characterized by being equal to or greater than 1.25 mm and less than 4 mm.

[0021] The tubular pipe has a bent flow path, and the elongation of the tubular pipe is 15% or more.

[0022] The joint interface between the tubular pipe and the casting is formed within 30 μm. Effect of the Invention

[0023] According to the manufacturing method of the present invention for a casting having a flow passage formed therein, instead of the conventional two-piece manufacturing method, a one-piece integral casting is performed using a smart core, which is more economical. In addition, the flow path of components having flow path portions formed therein, such as power conversion components, can be made more robust than conventional components, making it possible to prevent dangers such as vehicle fires. Also, by considering the materials of the tubular pipe and the filler, it is possible to minimize defects in the casting due to residues in the flow passage. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view showing a conventional method for manufacturing a casting having a flow passage portion. [Diagram 2] 5A to 5C are diagrams illustrating a manufacturing method of a casting having a flow passage portion according to the present invention. [Diagram 3] FIG. 2 is a diagram showing a cross-sectional shape of a casting produced according to the present invention and a cross-sectional shape of a comparative example. [Figure 4] FIG. 2 is a diagram showing a tubular pipe before removal of filler material according to one embodiment of the method for producing a casting. [Diagram 5] 5A shows the problem of removing the filler in the tubular pipe of FIG. 4. FIG. 5B shows the problem of removing the filler in the tubular pipe of FIG. [Figure 6]6A is a diagram showing a tubular pipe before removal of a filler material according to an embodiment of a method for producing a casting product different from that shown in FIG. 4. FIG. 6B is a diagram showing a tubular pipe after removal of a filler material in the tubular pipe of FIG. 6A. [Figure 7] 1A is a diagram showing a comparative example of a tubular pipe after removal of the filler, FIG. 1B is a diagram showing a comparative example of a tubular pipe after removal of the filler, and FIG. 1C is a diagram showing a comparative example of a tubular pipe after removal of the filler. [Figure 8] FIG. 11 is a diagram showing a casting produced by a manufacturing method for a casting according to another embodiment of the present invention. [Figure 9] FIG. 11 is a diagram showing the relationship between the thickness of a tubular pipe and heat transfer efficiency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] For a fuller understanding of the invention, its operating advantages, and the objects attained by its practice, reference should be made to the accompanying drawings in which a preferred embodiment of the invention is illustrated and the contents thereof. In describing the preferred embodiments of the present invention, the description of known techniques or repeated descriptions that may unnecessarily obscure the gist of the present invention will be shortened or omitted. FIG. 2 shows a manufacturing method of a casting having a flow path portion according to the present invention. Hereinafter, with reference to FIG. 2, a manufacturing method of a casting having a flow path portion according to one embodiment of the present invention and a casting manufactured by the method will be described. Unlike conventional methods, the present invention provides a more economical manufacturing method in which a casting having a flow passage formed therein is manufactured in one piece by integral casting using a so-called smart core, while ensuring the robustness of the flow passage. To this end, the manufacturing method of the present invention provides a tubular pipe that serves as a flow passage. Although an aluminum pipe is shown as an example in the drawings, the tubular pipe in the present invention is not limited to an aluminum pipe, as will be described later.

[0026] However, when the casting to be manufactured is made of aluminum, it is more preferable to use an aluminum pipe. Then, a feeder is used to fill the inside of the tubular pipe with the filler material to a minimum of about 80%. Such filler is removed in the final step. In the present invention, the casting with the flow passage formed is produced by integral casting in one piece. The reason for filling the tubular pipe with the filler is to enable the tubular pipe for forming the flow passage to withstand the casting pressure of high pressure casting. The tubular pipe thus filled with the filler is then drawn and extruded to reduce its cross-sectional area and stretch it longitudinally, so that the filler inside becomes compacted to a minimum of about 95%. In addition, by filling both ends of the tubular pipe with resin or the like, the filler inside can be prevented from leaking. When both ends of the tubular pipe are filled with resin, the tubular pipe portion filled with resin is cut and then the filler is removed before the filler is removed.

[0027] Thereafter, the tubular pipe 11 is bent to conform to the actual shape of the flow passage to be formed in the casting, thereby completing a smart core in which the filler material 12 is filled inside the tubular pipe 11. The present invention is more preferable for a casting in which a flow passage portion having a bend is formed, but it is of course applicable to the manufacture of a casting for a flow passage portion other than the bend. In the present invention, the smart core manufactured as described above is inserted into a mold manufactured in the shape of the product, and then die casting is performed to realize the shape of the casting 31 to be manufactured. The smart core in the present invention is formed by filling a tubular pipe for forming a flow passage with a dense filler material, so that it can be cast without deformation even when molten metal is injected at high pressure during high-pressure casting. Also, the material of the tubular pipe may be different depending on the material of the casting to be manufactured.

[0028] In particular, when the molten metal is aluminum, the tubular pipe is also made of aluminum, and is cast after being inserted. The tubular pipe is integrally joined to the casting, and the aluminum improves heat conduction, thereby improving cooling performance. The joining interface is within 30 μm, and more preferably, no interface is present. That is, the tubular pipe and the molten metal may be made of the same material, particularly aluminum, which means that the base material of the alloy is the same, but the details that make up the alloy may be slightly different. If a tubular pipe made of steel is applied to the smart core of the present invention when manufacturing a casting by high pressure casting of an aluminum part, no crimping occurs during high pressure casting, but an interface of 300 to 500 μm with the aluminum is formed, resulting in a decrease in heat transfer efficiency.

[0029] However, depending on the purpose of casting, the present invention can also be applied to tubular pipes and molten metal made of materials that are not the same, so that a robust flow passage can be formed by high pressure casting. Also, unlike the casting 31 produced according to the present invention as shown in FIG. 3, in the case of a tubular pipe 20 made of an aluminum material without a filler, it is crimped as shown during high pressure casting, and therefore a normal casting cannot be produced. After the above casting is completed, the filler material filled in the smart core is removed using air or other means to produce the shape of the casting to be manufactured, but the removal of the filler material may vary depending on the filler material used. That is, when the filler is a particle that is crystallized like salt, physical removal by a water jet of 200 bar or more into a tubular pipe is preferable. And if the filler is a non-crystallized particle such as sand, it can be removed by injecting a water jet of 200 bar or more or air of 2 bar or more into the tubular pipe.

[0030] In addition, when solid-solution sand, a mixture of sand and resin, is used in whole or in part as filler, the resin contained in the solid-solution sand can be burned off by heat treatment at 400°C or higher, and then removed by injecting a water jet of 200 bar or more or air of 2 bar or more. However, since the manufacturing method of the casting of the present invention aims not only to ensure that the smart core is not deformed during the high-pressure casting process, but also to prevent residues of the filler material from remaining in the flow path, which may result in defective casting, a tubular pipe and filler material under more specific conditions can be applied for this purpose.

[0031] That is, after the tubular pipe 11 and the filler 12 are subjected to a high temperature and high pressure environment as shown in FIG. 4, when the filler is removed, the filler may remain inside the tubular pipe 11 as shown in FIG. 5A, and the filler inside the tubular pipe 11 may not be crushed as shown in FIG. 5B. The filler remains when it is driven into the tubular pipe 11 by the high temperature and high pressure casting environment and remains there. The filler is not crushed when some of the filler has crystallized and is difficult to crush. To solve this problem, in another embodiment of the present invention, as shown in FIG. 6A, the strength of the tubular pipe 11-1 is increased, or the material of the filler 12-1 is selected to be soft and not hardened, so that no compression or residue occurs in the flow path portion P after the filler is removed, as shown in FIG. 6B.

[0032] First, the tubular pipe of the present invention is intended to be a tubular pipe that cannot withstand high casting pressure during high pressure casting, and by making such a tubular pipe that cannot withstand high casting pressure withstand high casting pressure during high pressure casting, it is possible to manufacture a robust flow path portion of the casting product. Since the casting pressure in normal high-pressure casting is 60 MPa or more, the tubular pipe of the present invention is preferably applied to tubular pipes having materials and dimensions that cause deformation of the shape when cast at a casting pressure of 60 MPa or more while inserted into a mold. An aluminum tubular pipe is an example of a tubular pipe that may be deformed when cast under a casting pressure of 60 MPa or more. In Table 1, we checked whether the aluminum tubular pipe has a hardness that can withstand a casting pressure of 60 MPa or more through additional heat treatment, the elongation rate for bending, and whether the filler remains. Here, the filler used was sand with a size of 100 μm.

[0033] [Table 1]

[0034] In Table 1, A6061 and A6063 represent aluminum materials, and T4 and T6 represent types of heat treatment. The case where the filler remained was indicated by "O", and the case where the filler did not remain was indicated by "X". Also, depending on the degree of bending, ○ is good, ◎ is very good, and △ is average. In order to prevent any filler from remaining after the filler removal step, it is preferable that the tubular pipe has high hardness. Therefore, in the case of aluminum materials, only aluminum with a hardness of 70Hv or more, such as A6061-T4 and A6063-T4, can withstand high casting pressure during high pressure casting and prevent filler residue. On the other hand, if the hardness is high, the bendability decreases, so in the case of a tubular pipe that requires bending, the elongation rate as well as the hardness must be taken into consideration. It can be seen that when the hardness is too high, such as in A6061-T6 and A6063-T6, the elongation rate is low and bending properties are poor. Therefore, if necessary, the stretching ratio is more preferably 15% or more.

[0035] Therefore, the smart core tubular pipe according to another embodiment of the present invention preferably has a hardness of 70Hv or more and an elongation rate of 15% or more, and may be A6061-T4 or A6063-T4, as can be seen from Table 1. The above conditions can be satisfied by the material and heat treatment conditions of the tubular pipe, so in addition to A6061-T4 and A6063-T4, A2024-T3 or A7075-T4 can also be applied. The above conditions of the tubular pipe can prevent the filler from remaining when the filler is removed, but the effect of preventing the filler from remaining can be maximized by taking into consideration the conditions of the filler. That is, in order to prevent the filler from being compressed and remaining in the tubular pipe, it is preferable that the size of the filler is 100 μm or less.

[0036] Moreover, it is more preferable that the material has no reactivity with tubular pipes made of aluminum alloy or the like. If the particle size of the filler is larger than this or if it is reactive with the tubular pipe, it may remain inside the tubular pipe, forming dimples due to the pressure and being compressed. Furthermore, if the filler has a high thermal conductivity, the temperature of the filler may rise due to the temperature of the molten metal, causing the filler to melt or deform. Therefore, it is more preferable that the thermal conductivity of the filler be within a certain range. That is, the thermal conductivity is more preferably 0.1 to 1 W / m·°C. The filler in the present invention may be any substance that satisfies the above requirements for particle size, reactivity and thermal conductivity and that can be removed after filling. Examples of such fillers may preferably be sand, silica-based materials, and more preferably silica-based materials with smaller particles. Comparative examples of conditions different from the above-mentioned preferable conditions for the filler are summarized in Table 2, with the results of Case 1 being shown in Figure 7A, those of Case 2 in Figure 7B, and those of Case 3 in Figure 7C. The pipes applied to the filler experiments in Table 2 correspond to A6063-T4.

[0037] [Table 2] As shown in FIG. 7A, when the conditions of chemical reactivity and thermal conductivity are satisfied, but the powder size exceeds the condition of 100 μm or less, the filler is compressed inside the tubular pipe. As shown in FIG. 7B, even if the thermal conductivity and powder size satisfy the conditions, if intermolecular bonding occurs, it becomes impossible to remove the filler from inside the tubular pipe. As shown in Figure 7C, when the conditions for chemical reactivity and powder size are met but the thermal conductivity does not meet the condition of 0.1 to 1 W / m°C, the filler melts and the tubular pipe deforms. In contrast to this, for example, in the case of a casting 32 of the present invention shown in FIG. 8 in which a tubular pipe made of A6063-T4 material is filled with a silica-based filler that has no chemical reactivity, a thermal conductivity of 0.2 W / m°C, and a powder size of 10 to 40 μm, it can be confirmed that there is absolutely no residue or compression of the filler in the flow path portion P, and that there is absolutely no deformation of the flow path portion P.

[0038] In this way, the casting produced by the present invention has a flow passage formed inside that matches the shape of the smart core, and can be produced in one piece in one casting process. This makes it possible to improve the robustness of the flow passage portion formed in the casting and reduce the cost. Furthermore, when the tubular pipe of the smart core of the present invention is made of aluminum, since it is inserted during high pressure casting, its thickness (t) must be limited to a minimum of 1.25 mm. If the thickness is less than 1.25 mm, it may melt in molten aluminum at 600°C or higher during casting. Generally, in die casting, the average part production time is 45 to 100 seconds, with 80% of this time spent cooling the product.

[0039] In other words, it takes about 35 to 80 seconds for the hot molten metal at 660 to 680°C to come into contact with the pipe and cool to 200 to 250°C. At this time, the pipe must be able to withstand the high temperature of the molten metal, but if the pipe is less than 1.25 mm thick, it may melt locally due to the molten metal and lose its function. Therefore, it is preferred that the thickness of the smart core pipe of the present invention used in high pressure casting processes be a minimum of 1.25 mm. As shown in FIG. 4, if the pipe thickness is 4 mm or more, the thermal conduction efficiency falls to less than 50 W / (m·K), which may be disadvantageous in terms of thermal conduction efficiency, so it is more preferable that the pipe thickness be less than 4 mm.

[0040] Although the present invention has been described with reference to the illustrated drawings, it is not limited to the described embodiments, and it is obvious to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, such modifications and variations should be considered to fall within the scope of the claims of the present invention, and the scope of the rights of the present invention should be interpreted based on the scope of the claims. [Explanation of symbols]

[0041] 11, 11-1: Tubular pipe 12, 12-1: Filler 31, 32: Castings

Claims

1. Manufacturing a smart core having a tubular pipe filled with a filler material; Inserting the smart core into a mold having a cavity corresponding to the shape of a casting to be produced; A step of casting by injecting molten metal into the cavity; removing the filler material within the smart core; The casting step is performed by a high pressure casting method. The step of manufacturing the smart core comprises: filling the inside of the tubular pipe with a filler material; drawing and extruding the tubular pipe filled with the filler material; and bending the tubular pipe according to a shape of a flow passage to be formed in the casting.

2. 2. The method for manufacturing a casting having a flow passage portion according to claim 1, wherein the elongation ratio of the tubular pipe is 15% or more.

3. The method for manufacturing a casting having a flow passage portion according to claim 1, wherein the particle size of the filler is 100 μm or less.

4. 4. The method for manufacturing a casting having a flow passage formed therein according to claim 3, wherein the filler has a thermal conductivity of 0.1 to 1 W / m·°C.

5. The method for manufacturing a casting having a flow passage portion according to claim 1, wherein the molten metal and the tubular pipe are made of the same material.

6. Manufacturing a smart core having a tubular pipe filled with a filler material; Inserting the smart core into a mold having a cavity corresponding to the shape of a casting to be produced; A step of casting by injecting molten metal into the cavity; removing the filler material within the smart core; The casting step is performed by a high pressure casting method. The method for manufacturing a casting having a flow passage formed therein is characterized in that the tubular pipe is made of an aluminum material.

7. The method for manufacturing a casting having a flow passage portion according to claim 1, wherein the tubular pipe has a thickness of 1.25 mm or more and less than 4 mm.

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