SOLUBLE CORE FOR HIGH-PRESSURE CASTING AND MANUFACTURING METHOD THEREOF

Abstract

According to the method for manufacturing a soluble core for high pressure casting, the method for manufacturing a core by dispersing a heat-resistant hard ceramic powder in a water-soluble chemical salt having a melting point 140 C. to 260 C. lower than a melting point of a cast metal and a heat capacity of 90 J/(mol.Math.K) or more is a very useful technology that can easily manufacture a core for high pressure casting of metals such as aluminum and magnesium, and a method for extracting a core from casting can also be simply performed by heating and extracting the core at a temperature equal to or lower than the melting point of the cast metal, and since the core material can be recycled, it is very advantageous in terms of productivity and economy.

Claims

1. A method for manufacturing a soluble core for high pressure casting, comprising: a step of manufacturing a water-soluble chemical salt mixture having a melting temperature of 390 C. to 520 C.; a step of uniformly dispersing and mixing a heat-resistant hard powder into the above water-soluble chemical salt mixture to manufacture a molten chemical salt having a heat capacity of 90 J/(mol.Math.K) or more; and a step of injecting the manufactured molten chemical salt into a core mold and solidifying the molten chemical salt to manufacture a core.

2. The method for manufacturing a soluble core for high pressure casting according to claim 1, wherein the water-soluble chemical salt mixture includes any one or more selected from the group consisting of a chloride-based chemical salt, a carbide-based chemical salt, and a sulfide-based chemical salt.

3. The method for manufacturing a soluble core for high pressure casting according to claim 2, wherein the chloride-based chemical salt includes any one or more selected from the group consisting of NaCl, KCl, MnCl.sub.2, CaCl, MgCl.sub.2, and LiCl, the carbide-based chemical salt includes any one or more selected from the group consisting of K.sub.2CO.sub.3, Li.sub.2CO.sub.3 and Na.sub.2CO.sub.3, and the sulfide-based chemical salt includes any one or more selected from the group consisting of K.sub.2SO.sub.4, Na.sub.2SO.sub.4, and Li.sub.2SO.sub.4.

4. The method for manufacturing a soluble core for high pressure casting according to claim 2, wherein the water-soluble chemical salt mixture is selected from the group consisting of water-soluble chemical salt mixtures of KCl:MnCl.sub.2:NaCl in a ratio of 45.5:33.5:20, CaCl.sub.2:KCl:MgCl.sub.2:NaCl in a ratio of 41.6:2.2:8.8:47.4, CrCl.sub.2:KCl in a ratio of 60:40, K.sub.2CO.sub.3:Li.sub.2CO.sub.3:Na.sub.2CO.sub.3 in a ratio of 25:43.5:31.5, K.sub.2CO.sub.3:MgCO.sub.3 in a ratio of 55:45, K.sub.2SO.sub.4:Li.sub.2SO.sub.4 in a ratio of 18:82, K.sub.2SO.sub.4:Na.sub.2SO.sub.4 in a ratio of 75:25, LiCl:Li.sub.2SO.sub.4:Li.sub.2CO.sub.3 in a ratio of 52.9:27.2:19.8, LiCl:Li.sub.2SO.sub.4:NaCl in a ratio of 54.8:29:16.1, LiCl:Li.sub.2CO.sub.3:Li.sub.2SO.sub.4 in a ratio of 52.9:19.8:27.2, and CaSO.sub.4:LiCl in a ratio of 14:86, in terms of a mixing ratio (Mol %).

5. The method for manufacturing a soluble core for high pressure casting according to claim 1, wherein the heat-resistant hard powder includes any one or more selected from the group consisting of TiO.sub.2, Al.sub.2O.sub.3, and ZrSiO.sub.4.

6. The method for manufacturing a soluble core for high pressure casting according to claim 1, wherein the water-soluble chemical salt mixture has a melting point 140 C. to 260 C. lower than a melting point of a cast metal.

7. The method for manufacturing a soluble core for high pressure casting according to claim 1, wherein a cast metal is an aluminum alloy or a magnesium alloy.

8. The method for manufacturing a soluble core for high pressure casting according to claim 1, further comprising: a step of installing the manufactured core in a high pressure casting mold, performing high pressure casting of a molten metal, and then performing heating to a temperature equal to or less than the melting point of the cast alloy to extract the molten core.

9. A soluble core for high pressure casting formed of a molten chemical salt having a heat capacity of 90 J/(mol.Math.K) or more obtained by uniformly dispersing and mixing a heat-resistant hard powder into a water-soluble chemical salt mixture having a melting point 140 C. to 260 C. lower than a melting point of a cast metal, which includes any one or more selected from the group consisting of a chloride-based chemical salt, a carbide-based chemical salt, and a sulfide-based chemical salt.

10. The soluble core for high pressure casting according to claim 9, wherein the chloride-based chemical salt includes any one or more selected from the group consisting of NaCl, KCl, MnCl.sub.2, CaCl, MgCl.sub.2, and LiCl, the carbide-based chemical salt includes any one or more selected from the group consisting of K.sub.2CO.sub.3, Li.sub.2CO.sub.3 and Na.sub.2CO.sub.3, and the sulfide-based chemical salt includes any one or more selected from the group consisting of K.sub.2SO.sub.4, Na.sub.2SO.sub.4, and Li.sub.2SO.sub.4.

11. The soluble core for high pressure casting according to claim 9, wherein the water-soluble chemical salt is selected from the group consisting of water-soluble chemical salt mixtures of KCl:MnCl.sub.2:NaCl in a ratio of 45.5:33.5:20, CaCl.sub.2:KCl:MgCl.sub.2:NaCl in a ratio of 41.6:2.2:8.8:47.4, CrCl.sub.2:KCl in a ratio of 60:40, K.sub.2CO.sub.3:Li.sub.2CO.sub.3:Na.sub.2CO.sub.3 in a ratio of 25:43.5:31.5, K.sub.2CO.sub.3:MgCO.sub.3 in a ratio of 55:45, K.sub.2SO.sub.4:Li.sub.2SO.sub.4 in a ratio of 18:82, K.sub.2SO.sub.4:Na.sub.2SO.sub.4 in a ratio of 75:25, LiCl:Li.sub.2SO.sub.4:Li.sub.2CO.sub.3 in a ratio of 52.9:27.2:19.8, LiCl:Li.sub.2SO.sub.4:NaCl in a ratio of 54.8:29:16.1, LiCl:Li.sub.2CO.sub.3:Li.sub.2SO.sub.4 in a ratio of 52.9:19.8:27.2, and CaSO.sub.4:LiCl in a ratio of 14:86, in terms of a mixing ratio (Mol %).

12. A method for extracting a soluble core for high pressure casting, wherein the soluble core for high pressure casting according to claim 9 is heated to a temperature equal to or less than the melting point of a product after high pressure casting, melted, extracted, and then washed with water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 shows a shape of a core for high pressure casting (symbol CL-460) according to an embodiment of the present invention.

[0035] FIG. 2 shows a front view and a side view of a high pressure casting mold and a core mounted on a specimen used in an embodiment of the present invention.

[0036] FIG. 3 shows a thermal analysis graph of soluble core (symbol CL-460) according to an embodiment of the present invention.

[0037] FIG. 4 shows a photograph of a high pressure cast product by applying a soluble core (symbol CL-460) according to an embodiment of the present invention.

[0038] FIG. 5 shows a photograph of a core after heating and extraction after high pressure casting by applying a soluble core (symbol CL-460) according to an embodiment of the present invention.

[0039] FIG. 6 shows a photograph of a boundary surface of a core after heating and extraction of a high pressure cast product by applying a soluble core (symbol CL-460) according to an embodiment of the present invention after heating and extracting the core.

[0040] FIG. 7 shows a thermal analysis graph of a soluble core (symbol SL-512) according to an embodiment of the present invention. A thermal analysis method used here is Differential Scanning calorimetry (DSC), which is a method of measuring the difference in energy input to a sample and a reference material as a function of temperature while changing the temperatures of the sample and the reference material.

[0041] FIG. 8 shows a photograph of the boundary surface of a core after heating and extraction of a high pressure cast product by applying a soluble core (symbol CL-512) according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0043] The present invention can have various modifications and various embodiments, and specific embodiments are illustrated in the drawings and specifically described in the detailed description. This is not intended to limit the present invention to specific embodiments, but should be interpreted to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0044] The terms used in the present application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

[0045] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those having ordinary knowledge in the technical field to which the present invention belongs. Terms defined in commonly used dictionaries may be interpreted as having a meaning consistent with the meaning that the terms have in the context of the relevant art, and may not be interpreted in an idealized or overly formal sense, unless explicitly defined in the present application.

[0046] Hereinafter, specific embodiments of the present invention will be described with reference to the attached drawings.

Embodiment 1

[0047] As shown in the symbol CL-460, when chloride-based chemical salts CaCl.sub.2, KCl, MgCl.sub.2, and NaCl are mixed and melted in a ratio of 41.6:2.2:8.8:47.4 (Mol %), the melting point becomes 460 C. and the heat capacity becomes 102 J/(mol.Math.K). A solution obtained by mixing 14 (wt %) of TiO.sub.2 hard particles of about 20 m and 30 (wt %) of Al.sub.2O.sub.3 powder of about 80 m hereto and heating to about 550 C. is injected into a core mold preheated to 200 C. and slowly solidified to manufacture a soluble core.

[0048] The thermal analysis result of the soluble core for high pressure casting manufactured in this way shows that melting starts at 460 C. (melting point 456 C.), as shown in FIG. 3. The core manufactured in this way was mounted in a high pressure casting mold with a casting thickness of about 40 mm, as shown in FIG. 2, and then the performance of the core was evaluated by a high pressure die casting method using AC4C aluminum alloy. For high pressure casting, AC4C aluminum alloy heated to 700 C. was used, the gate injection speed of the molten metal was 55 m/sec, and the final injection pressure was 980 kg/cm.sup.2. In addition, for core extraction after casting, the casting was heated at a temperature of 500 C. for about 5 minutes to melt and extract the core, and then washed with water.

[0049] FIG. 5 shows a shape of a casting obtained by heating and extracting a core after high pressure casting by the manufacturing method. It can be seen that it is possible to form a thick-walled product with a casting thickness of about 40 mm, and the shape of the core is transferred as it is without melting change. Also, as shown in FIG. 6, it can be seen that the casting surface is clean.

[0050] On the other hand, in a case of a core with a melting temperature of 390 C. or lower, a reaction layer was formed on the boundary surface of the casting, making it unsuitable for use as a core for high pressure casting of a thick-walled product of about 40 mm.

Embodiment 2

[0051] As shown in the symbol SL-512, when sulfide-based chemical salt CaSO.sub.4 and chloride-based chemical salt LiCl are mixed and melted in a ratio of 14:86 (Mol %), the melting point becomes 512 C. and the heat capacity becomes about 96 J/(mol.Math.K). A solution obtained by mixing 10 (wt %) of TiO.sub.2 hard particles of about 20 m and 35 (wt %) of ZrSiO.sub.4 powder of about 120 m hereto and heating to about 580 C. is injected into a core mold preheated to 300 C. and slowly solidified to manufacture a soluble core. The thermal analysis result of the soluble core for high pressure casting manufactured in this way shows that a peak due to crystal structure changes at 428 C. and a peak due to melting latent heat starts at 512 C. (melting point 512 C.) as shown in FIG. 7. The core manufactured in this way was mounted in a high pressure casting mold, as shown in FIG. 2, and then the performance of the core was evaluated by a high pressure die casting method using AC4C aluminum alloy. For high pressure casting, AC4C aluminum alloy heated to 700 C. was used, the gate injection speed of the molten metal was 55 m/sec, and the final injection pressure was 980 kg/cm.sup.2. In addition, for core extraction after casting, the casting was heated at a temperature of 530 C. for about 10 minutes to melt and extract the core, and then washed with water.

[0052] FIG. 8 is a cross-section of a casting manufactured by high pressure casting of a thick-walled product by the above-described manufacturing method and then heating and extracting a core. It can be seen that it is possible to form a thick-walled product with a casting thickness of about 40 mm, and the boundary surface of the core is transferred as it is without melting or thermal change.

[0053] On the other hand, when the melting temperature of the core becomes 520 C. or higher, it is difficult to melt and extract the core without causing thermal changes in the casting, making it unsuitable for use as a core for high pressure casting of a thick-walled product.

[0054] Although the present invention has been described in detail through specific embodiments, this is only for the purpose of specifically explaining the present invention, the present invention is not limited thereto, and it is obvious that the present invention can be modified or improved by those having ordinary knowledge in the relevant field within the technical spirit of the present invention.

[0055] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific protection scope of the present invention will be made clear by the appended claims.