Manufacturing method for molded components
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- 株式会社豊岛技研
- Filing Date
- 2021-12-29
- Publication Date
- 2026-08-05
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a forming member.
Background Art
[0002] When casting a metal product using a casting mold (hereinafter also simply referred to as a mold) such as die-casting, bolt holes and the like may be directly punched and formed using a forming member such as a punching pin. Further, the forming member is also used for the purpose of weight reduction of the product.
[0003] Conventionally, such a forming member is manufactured using a steel material such as hot work tool steel. Further, since the forming member directly contacts the high-temperature molten metal, generally, heat treatment such as quenching and tempering is performed to improve hardness, toughness, and heat resistance.
[0004] In the forming member and the mold, a cooling path is formed to make the mold surface temperature uniform, and there is one that adopts a cooling structure for supplying a refrigerant (liquid or gas) to this cooling path. In such a cooling structure, the thickness near the tip (bottom) of the cooling path is made thin to improve the cooling efficiency.
[0005] Since the forming member constitutes a part of the mold, it can be said to be a mold part, but its life (the number of times it can be used) was not sufficient compared to the main mold. The reason is that since the forming member and the mold are made of steel as described above, corrosion and metal fatigue due to the heat history occur in the internal cooling path, and cracks are likely to enter from the tip of the cooling path. If cracks enter the forming member, there is a risk that the refrigerant will enter the cavity through the cracks, causing product defects. As a method for suppressing the occurrence of cracks, for example, the following methods are disclosed.
[0006] Patent Document 1 describes a structure in which a molten metal cooling pin (molding member) inserted into the molten metal cooling area of a mold is formed into a double-layered structure using a no-end outer cylinder and an inner cylinder, thereby preventing external leakage of refrigerant even if metal fatigue occurs in the molten metal cooling pin and cracks develop.
[0007] Furthermore, Patent Document 2 describes that by forming a nitrided layer in the cooling holes of a mold by vacuum pulse nitriding treatment, and then forming a metal layer on the nitrided layer consisting of a metal with a higher ionization tendency than Fe, a mold cooling hole with excellent stress corrosion cracking resistance can be obtained. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-29416 [Patent Document 2] Japanese Patent Publication No. 2013-159831 [Overview of the project] [Problems that the invention aims to solve]
[0009] In the method described in Patent Document 1 (insertion of an inner cylinder), it is necessary to ensure thermal conductivity by making the inner cylinder tightly attached to the outer cylinder in order to obtain the cooling effect of the refrigerant. However, this requires manufacturing an inner cylinder that conforms to the internal shape of the outer cylinder and then pressing and joining them tightly, which places a heavy burden on the manufacturing process.
[0010] Furthermore, in the method described in Patent Document 2, since the formation of the nitride layer is a surface treatment by a dry process, it is considered that gas components are less likely to penetrate the tip (deeper part) of the cooling hole when the cooling hole is elongated. Therefore, it may be difficult to ensure uniform film thickness across the entire inner surface of the cooling hole from the tip to the opening.
[0011] Molding components are particularly prone to cracking with prolonged use, and compared to molds, they have fewer reusable cycles and a shorter lifespan. As mentioned above, the methods described in Patent Documents 1 and 2 can suppress the occurrence of cracks that penetrate both the inside and outside of the molding component, but the process is more complex than conventional methods for manufacturing molding components, and depending on the shape of the cooling path, it can be difficult to manufacture molding components of consistent quality, which tends to lead to increased manufacturing costs.
[0012] This invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a molded component that has a simple manufacturing process, a long lifespan, and excellent cooling effect. [Means for solving the problem]
[0013] The present invention relates to a method for manufacturing a moldable member made of steel having cooling holes inside, and is characterized by comprising: a filling step of filling the cooling holes with a metal material having a lower melting point than the moldable member; a heat treatment step of heat treating the moldable member filled with the metal material at a temperature between the melting point of the moldable member and the melting point of the metal material to join the molten metal material with the inner surface of the moldable member; and an excavation step of excavating the solidified portion formed by the cooling and solidification of the molten metal material to form a protective portion that covers the inner surface of the moldable member.
[0014] The heat treatment process described above is characterized in that the melting of the metal material and the quenching or tempering of the molding member proceed simultaneously.
[0015] In the heat treatment process described above, the opening of the molding member is closed by the lid member. [Effects of the Invention]
[0016] The manufacturing method of the molding member of the present invention includes a filling step of filling a cooling hole with a metal material having a melting point lower than that of the molding member, and heat-treating the molding member filled with the metal material at a temperature between the melting point of the molding member and the melting point of the metal material to join the molten metal material and the inner surface of the molding member. And a drilling step of forming a protective portion that covers the inner surface of the molding member by drilling a solidified portion where the molten metal material has cooled and solidified. Therefore, the manufacturing process is simpler than the manufacturing process of the conventional molding member with crack countermeasures. In addition, cracks penetrating the molding member are less likely to occur and the life is long. Furthermore, since the protective portion and the molding member are joined, the cooling effect is excellent.
[0017] In the heat treatment step, since the melting of the metal material and the quenching or tempering of the molding member proceed simultaneously, the number of steps is reduced and the manufacturing process is simpler.
[0018] In the heat treatment step, since the opening of the molding member is closed by the lid member, it is possible to prevent the metal material or the like from spilling or vaporizing, and to prevent the adhesion of the molten metal material to the outer surface of the molding member. As a result, a plurality of molding members filled with the metal material can be heat-treated simultaneously, and the manufacturing process is further simplified.
Brief Description of Drawings
[0019] [Figure 1] It is a schematic diagram of a pin body. [Figure 2] It is a schematic diagram of a punching pin. [Figure 3] It is a flowchart showing the manufacturing process of a punching pin. [Figure 4] It is a schematic diagram of a mold structure provided with a punching pin.
Embodiments for Carrying Out the Invention
[0020] The molding member targeted by the present invention may be a steel molding member having cooling holes inside. Examples of the molding member include a mold having cooling holes inside, a punching pin, a sleeve, and the like. A punching pin, which is an embodiment of the molding member of the present invention, will be described. In FIG. 1, an example of the pin body included in the punching pin will be described. FIG. 1 is a schematic view of the pin body. In FIG. 1 and FIG. 2 described later, the ratio of the outer diameter of the punching pin body portion in the length direction of the pin major axis is, for example, 0.01 to 0.10. However, for convenience of explanation, the ratio of the outer diameter is shown larger than the actual one.
[0021] As shown in FIG. 1, before forming the protection portion described later, the punching pin 1 is composed of a pin body 2. The pin body 2 is a substantially cylindrical member with one end closed, and includes an elongated hollow cooling hole 3 inside. The pin body 2 is a steel pin subjected to heat treatment of quenching and tempering, and is, for example, alloy tool steel of JIS SKD61. A surface treatment may be applied to its surface, or a tufftride treatment (soft nitriding treatment) or the like may be applied. Note that the shape of the pin body 2 is not limited to a substantially cylindrical shape, and may be a tapered shape such as a substantially conical shape, a substantially quadrangular pyramid shape, or a substantially hexagonal pyramid shape that becomes thinner toward the tip as long as it has the cooling hole 3 inside. Also, the pin body 2 may not be subjected to heat treatment such as quenching or tempering. From the viewpoint of simplifying the manufacturing process, it is preferable that no surface treatment is applied to the surface of the pin body.
[0022] The pin body 2 has a cylindrical body portion 4, a base portion 6 connected to one end of the body portion 4 and having an opening 5 with an outer diameter larger than that of the body portion 4, and a hemispherical shell-shaped tip portion 7 connected to the other end of the body portion 4. The length of the pin body 2 is, for example, 10 cm to 50 cm. Also, the inner diameter of the cooling hole 3 is, for example, 5 mm to 50 mm. The thickness of the cylindrical portion 4 and the hemispherical shell-shaped tip portion 5 of the pin body is, for example, 1 mm to 10 mm.
[0023] Furthermore, the body portion 4 may be formed by connecting multiple cylindrical portions with different outer diameters so that it becomes narrower towards the tip. In this case, a stepped portion will be formed at the connection point of the multiple cylindrical portions. The body portion 4 may also have a tapered shape. The body portion 4 may be composed of a combination of a tapered portion and a cylindrical portion.
[0024] Next, an example of a cast pin will be described using Figure 2. Figure 2 is a simplified diagram of a cast pin. As shown in Figure 2, the cast pin 1 has a protective portion 8 that covers the inner surface of the pin body 2 with a predetermined thickness. The protective portion 8 is joined to the inner surface of the pin body 2. It is preferable that the protective portion 8 covers at least the inner surfaces of the body 4 and tip 7 of the pin body 2, from the viewpoint of suppressing cracks in thin-walled portions such as the body 4 and tip 7, where cracks are relatively likely to occur. It is even more preferable that the protective portion 8 also covers the inner surface of the base 6.
[0025] From the viewpoint of refrigerant flow (cooling performance), the thickness of the protective part 8 is preferably approximately constant in the body portion 4 and the tip portion 7. The thickness of the protective part 8 can be, for example, 0.1 mm to 10 mm. From the viewpoint of crack suppression, the thickness of the protective part 8 is preferably, for example, 0.5 mm to 10 mm, more preferably 1 mm to 10 mm, even more preferably 2 mm to 10 mm, and even more preferably 5 mm to 10 mm. Furthermore, from the viewpoint of cooling, it is preferable that the cooling path inside the protective part 8 is wide and refrigerant flows easily, so for example, the thickness of the protective part 8 is preferably 0.1 mm to 5 mm, more preferably 0.1 mm to 2 mm, even more preferably 0.1 mm to 1 mm, and even more preferably 0.1 mm to 0.5 mm. Note that the thickness of the protective part 8 may be approximately constant or not constant across the entire inner surface of the pin body 2.
[0026] It is preferable that there is no gap between the protective part 8 and the pin body 2, and that the dissimilar metals are joined in close contact. Furthermore, it is preferable that the joining of the protective part 8 and the pin body 2 is an interfacial joining, in which the base material, the pin body 2, does not melt during the manufacturing of the cast pin, and only the metal material melts to form an interface with the pin body 2 and join them. This allows for efficient heat conduction from the pin body 2 to the protective part 8, resulting in excellent cooling performance.
[0027] The protective section is formed by melting and excavating a metal material, as will be described later. The metal material can be freely selected as long as it has a lower melting point than the steel material of the pin body. Examples of metal materials that can be used include alloys such as bronze and brass, copper, zinc, and aluminum. The lower the melting point of the metal material, the easier it is to melt and the easier it is to join it with the inner surface of the pin body. From the viewpoint of joining the two components, metal materials with relatively low melting points such as zinc, aluminum, and brass are preferred. Also, from the viewpoint of thermal conductivity (cooling ability), metal materials with relatively high thermal conductivity such as copper and aluminum are preferred.
[0028] One embodiment of the manufacturing method for cast pins will be explained with reference to Figure 3. Figure 3 is a flowchart showing the manufacturing process for cast pins. As shown in Figure 3, cast pins are manufactured through the processes of filling process S1 to drilling process S3. Each process will be explained below.
[0029] In the filling process S1, a pin body with cooling holes formed inside is prepared, and a metal material with a lower melting point than the pin body is filled into the cooling holes. The metal material to be filled only needs to have a lower melting point than the molding member. Here, the melting point of the molding member refers to the melting point of the main component (for example, the pin body in a cast pin) if the molding member is composed of multiple components.
[0030] The shape of the metal material can be freely selected, such as a rod or powder, as long as it can be filled inside the cooling hole. From the viewpoint of reducing voids inside the protective part and joining it with the pin body, a shape that conforms to the internal shape of the cooling hole and can be densely filled is preferred. Specifically, a rod-shaped metal material with an outer diameter slightly smaller than the inner diameter of the cooling hole, or a powdered metal material with a small particle size (for example, powder of 100 μm or less) is preferred.
[0031] In the heat treatment step S2, for example, the pin body filled with metal material is placed in a vacuum furnace and heat-treated. The internal temperature of the vacuum furnace is set to a temperature between the melting point of the pin body and the melting point of the metal material, and the pin body filled with metal material is heat-treated for a predetermined time. If the metal material is a copper rod, the heat treatment is performed, for example, under vacuum at 1100°C for 1 hour. As a result of the heat treatment, the molten metal material and the inner surface of the pin body are welded and joined together. In the heat treatment step, any furnace other than a vacuum furnace may be used, but from the viewpoint of suppressing oxidation of the metal material, it is preferable to use a vacuum furnace or a furnace with an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere. Furthermore, from the viewpoint of suppressing the generation of voids in the molten metal material, it is preferable to use a vacuum furnace.
[0032] After heat treatment, the metal material inside the pin body cools and solidifies, forming a solidified portion. The solidified portion only needs to densely fill the inside of at least the tip and body of the pin body without any gaps. It may also densely fill the opening of the pin body, but the inside of the base does not need to be densely filled.
[0033] In the drilling process S3, the solidified portion is drilled out with a drill or the like to form a protective portion that covers the inner surface of the pin body.
[0034] The method described above for manufacturing cast pins is simpler than the manufacturing process for cast pins that have been crack-resistant by dry processes such as vacuum pulse nitriding, CVD, or PVD, or by inserting an inner cylinder, and it allows for the formation of a protective layer with uniform thickness.
[0035] Furthermore, the protective section suppresses the progression of cracks even if they occur in the pin body, which is susceptible to temperature changes and accumulates thermal history. In addition, corrosion and cracking are less likely to occur in the protective section, so cracks that penetrate the punched-out pin are less likely to occur, resulting in a longer lifespan for the punched-out pin. Specifically, while the lifespan of the main mold is about 100,000 cycles, the lifespan of conventional punched-out pins is about 1 / 10 of that, but the lifespan of the punched-out pin according to the present invention is equivalent to that of the main mold.
[0036] Furthermore, since the protective part and the pin body are joined together, heat conduction from the pin body to the refrigerant is efficient, resulting in superior cooling performance.
[0037] In the heat treatment step S2, the melting of the metal material and the quenching or tempering of the pin body may be carried out simultaneously. This eliminates the need to perform the quenching or tempering of the pin body before the metal material melting step, reducing the number of steps and thus simplifying the manufacturing process.
[0038] In the heat treatment step S2, the opening of the pin body may or may not be closed by the lid member. From the viewpoint of suppressing contamination of the furnace during heat treatment, it is preferable to close the opening of the pin body with the lid member. During heat treatment, metal material and trace components in the metal material may vaporize. By closing the opening of the pin body with the lid member, it is possible to prevent the metal material from spilling or vaporizing, and to prevent the molten metal material from adhering to the outer surface of the pin body. As a result, multiple pin bodies filled with metal material can be heat-treated simultaneously, further simplifying the manufacturing process.
[0039] In the heat treatment step S2, when the opening of the pin body is closed with a cover member, it is preferable to pressurize the metal material inward towards the pin body at a predetermined pressure through the cover member. This makes it easier for the molten metal material and the inner surface of the pin body to bond, resulting in superior thermal conductivity and a better cooling effect.
[0040] In the heat treatment process S2, it is preferable to heat-treat the pin body by placing it upright in the furnace with the base, which has a relatively large outer diameter and is easy to stabilize, facing downwards. In this case, it is preferable to heat-treat the opening with a lid member closed to prevent the molten metal material from flowing out. This allows more pin bodies to be heat-treated in the furnace without the use of special jigs, resulting in improved production efficiency and a simpler manufacturing process.
[0041] An example of a mold structure equipped with a casting pin will be explained using Figure 4. Figure 4 is a simplified diagram of a mold structure equipped with a casting pin. The main mold 9 shown in Figure 4 is, for example, a die-casting mold used in aluminum die-casting. The mold structure 10 comprises the main mold 9, a casting pin 1 inserted through a through hole 11 of the main mold 9, and an insert 12 connected to the casting pin 1. The insert 12, by being connected to the casting pin 1, forms a cooling path 13 that introduces a coolant from outside the mold structure 10 to the tip of the casting pin 1. As a coolant, for example, water, alcohol, oil, air, or other fluids can flow through the cooling path 13. Alternatively, a tube may be inserted into the cooling path 13 to allow the coolant to flow.
[0042] The casting pin 1 is positioned to penetrate the cavity 14, and the cooling path 13 is a hole extending from the back of the main mold 9 to the movable mold 9a, cavity 14, and fixed mold 9b. The bottom of the cooling path 13 is hemispherical. The casting pin 1 may also be integrated with the movable mold 9a and become part of the mold structure.
[0043] Although the present invention has been described above with reference to the figures, the method for manufacturing the molding member of the present invention is not limited thereto. For example, in the manufacturing process of the molding member, the filling process, heat treatment process, and drilling process described above may be repeated to create a multi-layered protective structure. In that case, the metal material to be filled may be selected such that its melting point gradually decreases towards the inner circumference. [Industrial applicability]
[0044] The present invention allows for the production of moldable components with a simple manufacturing process, long lifespan, and excellent cooling effect, making it suitable for use in metal casting fields such as die casting. [Explanation of Symbols]
[0045] 1. Casting pin (molding component) 2-pin body 3 cooling holes 4 Torso 5 Openings 6 base 7 Tip 8 Protective part 9 Main type 9a Movable type 9b Fixed type 10 Mold structure 11 Through hole 12 nesting 13 Cooling path 14 Cavity
Claims
[Claim 1] A method for manufacturing a steel forming member having cooling holes inside, The molding member is a cast pin having a steel pin body, the pin body having a cylindrical body and a base connected to one end of the body and having an opening with a larger outer diameter than the body, The aforementioned manufacturing method is A filling step of filling the cooling hole with a metal material with a lower melting point than the pin body, A heat treatment step in which the pin body filled with the metal material is heat-treated at a temperature between the melting point of the pin body and the melting point of the metal material to join the molten metal material with the inner surface of the pin body, The process includes an excavation step of excavating the solidified portion formed by the cooling and solidification of the molten metal material to form a protective portion that covers the inner surface of the pin body, A method for manufacturing a molding member, characterized in that, in the heat treatment step, the melting of the metal material and the quenching or tempering of the pin body proceed simultaneously, and the pin body is heat-treated with its base facing downwards and the opening closed by a lid member.