Mold and method for manufacturing the same

Abstract

To provide a die in which corrosion resistance can be imparted to a water tube by an inexpensive means, and the relative density of a sintered compact is increased to improve strength and wear resistance.SOLUTION: The method for manufacturing the mold includes a bottom 111a part forming step of forming a side 111a of a bottom wall forming part by bonding a predetermined portion of a first raw powder layer, and a body part forming step of forming a mold body forming part by repeating bonding of raw powder P upward from the side wall of the bottom wall forming part. Forming an inner shell forming portion 111a constituting a flow path extending from an opening disposed in the bottom 111a forming portion 140a to an opening disposed in another place of the bottom 140a forming portion 140a, removing the raw powder P in the inner shell forming portion 140a, attaching corrosion-resistant powder to an inner peripheral surface of the inner shell forming portion inner wall, and then sintering a powder compact 180 including the inner shell forming portion inner wall and the die body forming portion.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a mold for sintering a powder compact formed by an additive manufacturing method, and a method for manufacturing the mold. [Background technology]

[0002] A known additive manufacturing method involves alternately stacking raw powders (metal powders, alloy powders, or ceramic powders) onto a powder bed and bonding each layer of the raw powder into a predetermined shape to ultimately produce a three-dimensional object. One additive manufacturing method is the selective sintering method (Powder Bed Fusion, or PBF method), which repeatedly irradiates the raw powder with a laser beam or electron beam to directly sinter it, thereby bonding the sintered portions together to produce the desired three-dimensional object. Another method is the binder jet method, which prints a binder onto the raw powder to be stacked, forming a powder compact in which the raw powder and binder are bonded, and then sintering the powder compact to produce the three-dimensional object. The binder jet method has seen particularly rapid development and practical application in recent years due to its low equipment, raw material, and process costs and its efficient implementation (see Patent Documents 1 and 2, etc.).

[0003] While conventional powder metallurgy methods have been known to produce parts weighing up to about 100g, binder jetting has made it possible to produce powder compacts of large parts weighing up to about 30kg. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-120475 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-522331 Summary of the Invention [Problem to be solved by the invention]

[0005] As sintered compacts become larger, the use of sintered compacts to make molds such as press molding dies is being considered. Molds are sometimes equipped with water pipes for circulating cooling water. If cooling water is circulated through the water pipes of molds made from alloy tool steel such as SKD61, the problem of rusting of the water pipes occurs. On the other hand, it is not realistic to make molds from expensive materials such as corrosion-resistant stainless steel.

[0006] Furthermore, when powder compacts formed using the binder jet method are sintered, the binder decomposes at around 500°C, leaving behind carbides as a decomposition residue. When the temperature subsequently reaches the sintering temperature and sintering begins, the carbides inhibit the growth of necks between the powder particles during the sintering process, causing a decrease in the relative density of the sintered compact.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a mold that can impart corrosion resistance to a water pipe by inexpensive means and that increases the relative density of the sintered body to improve strength and wear resistance. [Means for solving the problem]

[0008] The present invention is a method for manufacturing a mold in which raw material powder is discharged from a hopper onto a powder bed and supplied while falling naturally, its surface is pressed and repeatedly stacked as a single raw material powder layer of a predetermined thickness, and as each raw material powder layer is formed, portions of the raw material powder layer are bonded to produce and sinter a powder molded body.The method includes a bottom wall forming process in which predetermined portions of the first raw material powder layer are bonded to form a bottom wall forming portion, and a main body forming process in which the raw material powder is repeatedly bonded upward from the bottom wall forming portion to form a mold main body forming portion, forming an inner shell forming portion that constitutes a flow path extending from an opening located in the bottom wall forming portion into the mold main body forming portion to an opening located elsewhere in the bottom wall forming portion, removing the raw material powder from inside the inner shell forming portion, adhering corrosion-resistant powder to the inner surface of the inner shell forming portion, and carrying out a sintering process in which a powder molded body consisting of the inner shell forming portion and the mold main body forming portion is sintered.

[0009] In the present invention, a three-dimensional powder compact is formed by the inner shell molding portion and the mold body molding portion. When this powder compact is sintered, the corrosion-resistant powder attached to the inner peripheral surface of the inner shell molding portion is also sintered, forming a corrosion-resistant coating layer, which can suppress rust when the inner shell sintered portion is used as a water pipe. In this way, in the present invention, corrosion-resistant powder is used only in areas where corrosion resistance is required, so the necessary corrosion resistance can be obtained without increasing production costs. Moreover, sintering of the corrosion-resistant powder can be performed simultaneously with sintering of the powder compact, thereby reducing production costs.

[0010] Here, the raw material powder for the inner shell molding portion is bound together using a binder, and the corrosion-resistant powder is mixed with the binder to form a slurry, which can then be applied to the inner circumferential surface of the inner shell molding portion. In this case, it is preferable to perform a preliminary sintering step at a temperature lower than that used in the sintering step before applying the corrosion-resistant powder. The temperature in the preliminary sintering step is the temperature at which the binder decomposes, for example, about 500°C. This leaves voids where the binder in the inner shell molding portion decomposes and disappears, and the corrosion-resistant powder slurry fills the voids, improving adhesion to the inner circumferential surface of the inner shell molding portion.

[0011] Furthermore, it is preferable to form an outer shell molding part that covers the outer periphery of the mold body molding part by repeatedly bonding the raw material powder from the edge of the bottom wall molding part from the second layer onward, and then form a powder compact in which the raw material powder is sealed by the outer shell molding part, bottom wall molding part, and inner shell molding part. When this powder compact is sintered, neck growth occurs between the powder in the outer shell molding part, bottom wall molding part, and inner shell molding part, forming the outer shell sintered part, bottom wall sintered part, and inner shell sintered part. Meanwhile, raw material powder and voids exist in the spaces between the outer shell molding part, bottom wall molding part, and inner shell molding part. Sintering causes neck growth between the raw material powder and shrinks the voids to form pores. Since there are no factors, such as binders, that inhibit neck growth during sintering of the raw material powder, an internal sintered part with a high relative density can be obtained.

[0012] In the present invention, the binder jet method is preferably used as a molding method for the powder compact, but is not limited thereto, and any molding method can be used. For example, a three-dimensional additive manufacturing method such as selective laser sintering (SLS) can be used. When molding the outer shell molded part, only raw material powder and voids exist in the space between the outer shell molded part and the inner shell molded part, so an internal sintered part with a high relative density can be obtained.

[0013] Here, we will explain the effect of using the binder jet method as a molding method for a powder compact having an outer shell. In this case, the raw material powder is bound by the outer shell, bottom wall forming portion, and inner shell forming portion, and the raw material powder between them is sealed. When this powder compact is sintered, the binder is decomposed and disappears in the outer shell, bottom wall forming portion, and inner shell forming portion, and the raw material powder bonds to each other by neck growth between the powders, forming the outer shell sintered portion, bottom wall sintered portion, and inner shell sintered portion. Such outer shell sintered portion, bottom wall sintered portion, and inner shell sintered portion consist of a dense structure and pores containing carbides as residues from the decomposition of the binder.

[0014] On the other hand, the raw material powder present between the outer and bottom wall molding parts and the inner shell molding part does not contain a binder. Therefore, when this powder compact is sintered, neck growth between the powders proceeds unhindered, forming an inner sintered part. This inner sintered part consists of a dense structure and pores that do not contain carbides, which are residues left behind by the decomposition of the binder. Therefore, the relative density of the inner sintered part is higher than the relative densities of the outer and bottom wall sintered parts and the inner sintered part.

[0015] For example, the relative density of the outer sintered portion, bottom wall sintered portion, and inner sintered portion is 94-97%, while the relative density of the inner sintered portion exceeds 97%. Furthermore, the relative density of the inner sintered portion can exceed 98% or even 99%. As such, since the relative density of the outer sintered portion is relatively low, it can be easily machined. Furthermore, by removing the outer sintered portion, a mold (sintered body) consisting only of the inner sintered portion, which has an extremely high relative density, can be obtained.

[0016] In the present invention, the sintered body obtained as described above can be further subjected to HIP treatment. HIP treatment can be performed at a heating temperature of 950 to 1150°C and a pressure of 50 to 120 MPa. This heating temperature is lower than the temperature used for ordinary metal sintering, so recrystallization is kept to a minimum, achieving a density approaching 100%. It is more desirable for the heating temperature for HIP treatment to be 950 to 1000°C.

[0017] In the present invention, even if the mold is relatively large, for example, weighing about 30 kg, the densification by HIP treatment is almost constant. Furthermore, because the HIP treatment is performed at a relatively low temperature, the occurrence of distortion and deformation caused by different shrinkage amounts at multiple locations, as occurs in conventional high-temperature sintering, is suppressed.

[0018] In the present invention, any method can be used to bring a slurry of a corrosion-resistant powder mixed with a binder into contact with the inner surface of the inner shell molding portion, such as immersing the powder compact in the slurry and then cleaning the outer surface of the powder compact after lifting it out of the slurry, placing the powder compact upside down and pouring the slurry into the opening of the inner shell molding portion, or spraying the slurry onto the inner shell molding portion.

[0019] The raw material powder can be powder of alloy tool steel such as SKD or SKH, and the corrosion-resistant powder can be one or more of nickel-based alloy powder, copper and copper alloy powder, aluminum and aluminum alloy powder, titanium and titanium alloy powder, and ceramic powder.

[0020] The particle size of the raw material powder is not particularly limited, but powders usable in the binder jet method, for example, with an average particle size of about 3 to 50 μm, can be used.

[0021] When the corrosion-resistant powder is mixed with a binder to form a slurry, the average particle size of the corrosion-resistant powder is preferably 1 μm or more. If the average particle size of the corrosion-resistant powder is less than 1 μm, the corrosion-resistant powder will penetrate into the inner shell formed by the raw material powder, making it difficult to form a sufficient corrosion-resistant coating layer. The upper limit of the average particle size of the corrosion-resistant powder is preferably 50 μm, taking into account the balance of sinterability with the raw material powder.

[0022] The corrosion-resistant powder slurry may be, for example, a mixture of the corrosion-resistant powder and a resin solution. The solvent may be water, alcohol, ester, glycol, glycol ether, ether, ketone, aromatic solvent, naphthenic solvent, aliphatic hydrocarbon, or amine, either alone or in combination. Suitable resins for the resin solution include polyvinyl butyral (PVB), polyvinylpyrrolidone, polyvinyl alcohol, alkyl polymethacrylate, alkyl polyacrylate, polymethacrylic acid, polyacrylic acid, cellulose resin, polyether, and polyol. The solvent and resin are not limited to these and may be selected as appropriate.

[0023] The content of the corrosion-resistant powder in the slurry may be, for example, 30 to 80 wt %, and the content of the resin solution in the slurry may be, for example, 1 to 10 wt %.

[0024] Next, the present invention is a mold comprising an internal sintered portion made of a sintered body of a first powder, an external sintered portion made of a sintered body of a second powder covering the entire circumference of the internal sintered portion, and an internal sintered portion made of a sintered body of the second powder forming a flow path extending from an opening located on the bottom surface of the external sintered portion to an opening located elsewhere on the bottom surface, wherein the first powder does not contain a binder and the second powder does contain a binder, and a corrosion-resistant coating layer formed by adhering and sintering a corrosion-resistant powder is provided on the inner surface of the internal sintered portion.

[0025] According to the present invention, outer and inner shell molding portions made of powder bound with a binder, powder sealed inside the outer and inner shell molding portions, and corrosion-resistant powder can be sintered in a single process to form a mold equipped with an outer sintered portion, an inner sintered portion, and a corrosion-resistant coating layer, thereby imparting high corrosion resistance to required areas without increasing the number of processes. [Effects of the Invention]

[0026] According to the present invention, a mold is provided that can impart corrosion resistance to a water pipe by inexpensive means and that increases the relative density of the sintered body to improve strength and wear resistance. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a cross-sectional view showing a mold according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 1A to 1C are diagrams illustrating the first half of a process for manufacturing a mold by a binder jet method according to an embodiment of the present invention. [Figure 4] 1A to 1C are diagrams schematically illustrating the latter half of the process for manufacturing a mold by a binder jet method according to an embodiment of the present invention. [Figure 5] FIG. 4 is a cross-sectional view showing a mold according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 10 is a side cross-sectional view showing a powder compact in a second embodiment. [Figure 8] 1 is a photograph of the structure of a mold according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1. First embodiment A first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a cross-sectional view showing a mold 100 of the embodiment, and Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. The mold 100 has a mold body 110 that is trapezoidal in side view and has a water pipe 120 formed inside.

[0029] The mold body 110 has a bottom wall portion 111, a long side wall portion 112 rising from one side edge of the bottom wall portion 111, a short side wall portion 113 rising from the other side edge of the bottom wall portion 111, and an inclined wall portion 114 connecting the upper edges of the long side wall portion 112 and the short side wall portion 113.

[0030] The water pipe 120 has a pair of countersunk holes 121 opening in the bottom wall 111, a long pipe section 122 extending from one of the countersunk holes 121 along the long side wall 112, a short pipe section 123 extending from the other countersunk hole 121 along the short side wall 113, and an inclined pipe section 124 connecting the upper ends of the long pipe section 122 and the short pipe section 123. It also has a bent pipe section 125 connecting the inclined pipe section 124 and the long pipe section 122.

[0031] The entire periphery of the mold body 110 is covered with an outer sintered portion 130. The periphery of the water pipe 120 is covered with an inner sintered portion 140. An inner sintered portion 150 is disposed between the outer sintered portion 130 and the inner sintered portion 140.

[0032] Next, the procedure for molding the die 100 as described above will be described. FIGS. 3A to 3E are schematic diagrams showing steps in a method for producing a sintered body according to an embodiment. As shown in FIG. 3A, a printing stage (powder bed) 11 is arranged in a printing casing 10 so that it can be raised and lowered. First, raw material powder P is supplied onto the printing stage 11 from a hopper 12 by gravity, and is then spread evenly with a roller 13 as shown in FIG. 3B to form a raw material powder layer PL having a predetermined thickness. The thickness of the raw material powder layer PL is, for example, about 40 to 50 μm, but can be appropriately set within a range of approximately 100 μm or less. The raw material powder P is made of an alloy tool steel such as SKD, and its average particle size is, for example, 3 to 50 μm.

[0033] 3(C), a liquid binder B is sprayed from an inkjet dispenser 14 onto the stacked raw material powder layer PL, except for the portion that will become the counterbore hole 121. Next, a heater 15 is passed directly above the raw material powder layer PL, and the raw material powder P in the portion that has been sprayed with the binder B is bound and hardened. This forms a bottom wall molding portion 111a that will become the bottom wall portion 111.

[0034] From the second layer onwards, the printing stage 11 is lowered by an amount equal to the thickness of the raw material powder layer PL, and a binder B is supplied to the entire peripheral edge of the laid raw material powder layer PL, including the bottom wall molding portion 111a and the entire peripheral edge of the portion that will become the counterbore 121, to bind and harden the raw material powder P. In this way, the bound and hardened powder P is piled up vertically to form parts of the long side wall molding portion 112a and the short side wall molding portion 113a that will become the long side wall portion 112 and the short side wall portion 113, and the counterbore molding portion 121a that will become the counterbore 121 (see FIG. 3(D)).

[0035] Next, the raw material powder layer PL is further laid to bond and harden the raw material powder P, and the long side wall molding portion 112a and the short side wall molding portion 113a are extended upward, and the long pipe molding portion 122a and the short pipe molding portion 123a, which become the long pipe portion 122 and the short pipe portion 123, are molded from the upper end of the countersink molding portion 121a (see Figure 3(D)).

[0036] As shown in Figure 4(A), when the molding of the short pipe molding section 123a reaches the upper end, molding of the inclined pipe molding section 124a, which will become the inclined pipe section 124, begins, and then molding of the inclined wall molding section 114a, which will become the inclined wall section 114, begins. Then, when the upper ends of the long pipe molding section 122a and the inclined pipe molding section 124a approach each other, molding of the bent pipe molding section 125a, which will become the bent pipe section 125, connects the two, as shown in Figure 4(B). This results in molding of the inner shell molding section 140a, which will become the inner shell sintered section 140.

[0037] Furthermore, the long side wall molding portion 112a and the inclined wall molding portion 114a are continuously molded and connected to each other at the upper end. By the above-described main body molding process, an outer shell molding portion 130a consisting of the long side wall molding portion 112a, the short side wall molding portion 113a, and the inclined wall molding portion 114a is molded, and the outer shell molding portion 130a becomes the outer shell sintered portion 130.

[0038] In this way, the powder compact 180 is formed. The powder compact 180 is removed from the print casing 10 by raising the printing stage 111, and the raw material powder P outside the powder compact 180 is removed by, for example, sucking it in using a suction nozzle. At the same time, the raw material powder P filled in the inner shell molding portion 140a is also removed.

[0039] Next, the inner shell molding portion 140a is filled with a slurry in which a corrosion-resistant powder made of a corrosion-resistant metal such as stainless steel is mixed with a binder, and the mixture is left standing for a predetermined period of time. In this case, the powder compact 180 is immersed in the slurry and then pulled out, and the slurry adhering to the outer surface of the powder compact 180 is removed by washing. The slurry is then dried to remove the water and solvent such as volatile components. The above immersion process may be performed once, or may be repeated multiple times until the desired thickness of the corrosion-resistant powder film is obtained. The thickness of the corrosion-resistant powder film is preferably 100 to 800 μm.

[0040] Next, the powder compact 180 is sintered. Sintering is performed, for example, at 1300 to 1400°C for about three hours, thereby obtaining a mold 100 in which the inner sintered portion 150 is disposed between the outer sintered portion 130 and the inner sintered portion 140. When the powder compact 180 is heated from room temperature during sintering, the binder B contained in the outer molding portion 130a and the inner molding portion 140a decomposes at about 500°C, leaving behind carbides as decomposition residue. These carbides inhibit the growth of necks between the powder particles in the outer molding portion 130a and the inner molding portion 140a, and a relatively large number of pores are formed in the outer sintered portion 130 and the inner sintered portion 140.

[0041] In contrast, since there is no binder in the raw material powder P between the outer shell molding portion 130a and the inner shell molding portion 140a, neck growth between the powders proceeds unhindered, forming a highly densified inner sintered portion 150 with few pores. In this way, a mold (sintered body) 100 consisting of the outer shell sintered portion 130, inner shell sintered portion 140, and inner sintered portion 150 is formed.

[0042] Here, HIP treatment can also be performed after obtaining the mold 100 of the first embodiment by sintering as described above. HIP treatment is performed, for example, at approximately 1150°C x 100 MPa, and the heating temperature for HIP treatment is lower than the heating temperature of approximately 1300°C to 1400°C used for normal sintering. This reduces energy costs and makes thermal deformation less likely to occur. This minimizes recrystallization of the metal structure of the sintered body, suppresses grain enlargement, and achieves a high density with a relative density approaching 100%. Note that the HIP treatment is not limited to the above conditions; for example, it can be performed for an appropriate amount of time at a heating temperature of approximately 950 to 1150°C and a pressure of approximately 50 to 120 MPa.

[0043] Figure 8 is a micrograph showing a partial cross section of the mold 100. In Figure 8, the black dots are pores. The black dots in the outer sintered portion 130 are large and numerous, while the black dots in the inner sintered portion 150 are small and few in number. This indicates that the relative density of the inner sintered portion 150 is higher than that of the outer sintered portion 130.

[0044] The mold 100 includes a water pipe 120 formed by an inner sintered portion 140, and the inner surface of the water pipe 120 is covered with a corrosion-resistant coating layer formed by sintering a corrosion-resistant powder. Therefore, even if cooling water is circulated through the water pipe 120 during use of the mold 100, rusting of the water pipe 120 is suppressed. As described above, in the first embodiment, the corrosion-resistant powder is used only in areas where corrosion resistance is required, so the necessary corrosion resistance can be obtained without increasing production costs. Moreover, since the corrosion-resistant powder can be sintered simultaneously with the sintering of the powder compact 180, production costs can be reduced.

[0045] Such a mold 100 has an internal sintered portion 150 with a relative density close to 100%, which provides excellent wear resistance and strength. Furthermore, since it can be easily molded even with complex processed surfaces, it results in an excellent product with low manufacturing costs and a long lifespan. The outer sintered portion 130 may be removed by machining.

[0046] 2. Second embodiment A second embodiment of the present invention will be described with reference to Figures 5 to 7. Figure 5 is a side cross-sectional view showing a mold 200 of the second embodiment. The mold 200 differs in configuration from the mold 100 of the first embodiment only in that it does not have the bottom wall portion, outer sintered portion 130, inner sintered portion 140, and internal sintered portion 150 of the first embodiment. Therefore, in the second embodiment, the hundreds digit of the reference numerals for components equivalent to those of the first embodiment will be changed from 1 to 2, and their description will be omitted.

[0047] 7 is a side cross-sectional view showing a powder molded body 280 in the second embodiment. The powder molded body 280 is configured by molding a hollow water pipe molding portion 220a inside a main body molding portion 210a. The main body molding portion 210a is formed by binding raw material powder P with a binder and hardening it, except for the water pipe molding portion 220a. The water pipe molding portion 220a is filled with raw material powder P.

[0048] The raw material powder P is removed from the water tube forming portion 220a of the powder compact 280 and subjected to preliminary sintering. The preliminary sintering is performed at 600 to 1200°C. The binder is decomposed at a sintering temperature of 600°C or higher, and sintering of the raw material powder P begins at 900°C or higher. The preliminary sintering can be performed at 600 to 900°C or 900 to 1200°C. The preliminary sintering time is set to a time that allows most of the binder in the main body forming portion 210a to be decomposed.

[0049] Next, the powder compact 280 that has been pre-sintered is immersed in a slurry in which corrosion-resistant powder is mixed with a binder, and is then pulled out after a predetermined time has passed. The slurry adhering to the outer surface of the powder compact 280 is then removed by washing, the slurry adhering to the water pipe forming portion 220a is dried, and the powder compact 280 is then sintered. This completes the mold 200.

[0050] In the second embodiment, the mold 200 also includes the water pipes 220 coated with a corrosion-resistant coating layer, and even if cooling water is passed through the water pipes 220 during use of the mold 200, rusting of the water pipes 220 is suppressed. As described above, in the second embodiment, the corrosion-resistant powder is used only in areas where corrosion resistance is required, so the necessary corrosion resistance can be obtained without increasing production costs. Moreover, since the corrosion-resistant powder can be sintered simultaneously with the sintering of the powder compact 280, production costs can be reduced.

[0051] In particular, in the second embodiment, the water pipe forming portion 220a contains many voids left behind by the decomposition of the binder during preliminary sintering, so that the slurry penetrates into the voids and adheres well to the water pipe forming portion 220a.

[0052] 3. Example of changes The present invention is not limited to the above-described embodiment, and various modifications are possible as follows. i) In the first embodiment, the preliminary sintering can be performed as in the second embodiment. In the second embodiment, the preliminary sintering can be omitted. Furthermore, in the second embodiment, the HIP treatment can be performed after sintering.

[0053] ii) In addition to the binder jet method, any three-dimensional additive manufacturing method such as selective laser sintering (SLS) can be used as a molding method for the powder molded body 180. Even with such a three-dimensional additive manufacturing method, an outer shell molding portion and an inner shell molding portion can be molded and the raw material powder can be sealed between them, thereby achieving the same effect as the above embodiment.

[0054] iii) Metal powder produced by water atomization is suitable as the raw material powder P. Water-atomized powder has an irregular shape, resulting in a large angle of repose and poor fluidity. As in the above embodiment, when raw material powder P made of metal powder for sintering is supplied and spread by gravity from hopper 12 onto printing stage 11, which is open on all sides, the metal powder is less likely to spread unnecessarily in all directions and forms a single raw material powder layer PL of a predetermined thickness. On the other hand, if metal powder with a nearly spherical shape is used, when leveled with roller 13, the good fluidity of the metal powder may cause some areas to spread too much in all directions, resulting in an uneven thickness. [Industrial Applicability]

[0055] The present invention can be used in the industrial field of dies, such as press-molding dies made of relatively large sintered bodies. [Explanation of symbols]

[0056] 10...printing casing, 11...printing stage (powder bed), 12...hopper, 13...roller, 14...inkjet dispenser, 15...heater, 100...mold, 110...mold body, 111...bottom wall portion, 111a...bottom wall molding portion, 112...long side wall portion, 112a...long side wall molding portion, 113...short side wall portion, 113a...short side wall molding portion, 114...inclined wall portion, inclined wall molding portion 114a, 120...water pipe, 121...counterbore, 122...long tube portion, 122a...long tube molding portion, 123...short tube portion, 123a...short tube molding portion, 124...inclined tube portion, 124a...inclined tube molding portion, 125...bent tube portion, 125a...bent tube molding portion, 130...outer shell sintered portion, 130a...outer shell molding portion, 140...inner shell sintered portion, 140a...inner shell molding portion, 150...inner sintered portion, 180...powder compact, B...binder, P...raw material powder, PL...raw material powder layer.

Claims

1. A method for manufacturing a mold, comprising the steps of: supplying raw material powder onto a powder bed while it is discharged from a hopper and allowed to fall naturally; pressurizing the surface of the powder bed to repeatedly stack the raw material powder layers to a predetermined thickness; and each time a raw material powder layer is formed, a portion of the raw material powder layer is bonded to produce a powder compact, which is then sintered, the method comprising the steps of: a bottom wall forming step of joining predetermined portions of the first raw material powder layer to form a bottom wall forming portion; a main body forming step of repeatedly bonding the raw material powder upward from the bottom wall forming portion to form a mold main body forming portion, molding an inner shell molding portion that forms a flow path extending from an opening disposed in the bottom wall molding portion to the interior of the mold body molding portion and to an opening disposed elsewhere in the bottom wall molding portion; After removing the raw material powder from the inner shell molding portion, a corrosion-resistant powder is attached to the inner circumferential surface of the inner shell molding portion; A method of manufacturing a mold that includes a sintering step of sintering a powder compact consisting of the inner shell molding portion and the mold body molding portion.

2. 2. A method for manufacturing a mold according to claim 1, wherein the raw material powder is bound by a binder, the corrosion-resistant powder is mixed with the binder to form a slurry, and before the slurry is adhered to the inner surface of the inner shell molding portion, a pre-sintering step is performed in which the slurry is pre-sintered at a temperature lower than that in the sintering step.

3. A method for manufacturing a mold as described in claim 1 or 2, in which from the second layer onwards, the raw material powder is repeatedly bonded from the edge of the bottom wall molding portion to form an outer shell molding portion that covers the outer periphery of the mold body molding portion, and the raw material powder is sealed by the outer shell molding portion, the bottom wall molding portion and the inner shell molding portion.

4. 3. The mold manufacturing method according to claim 1, wherein a HIP treatment is performed after the sintering step.

5. 4. The method for manufacturing a mold according to claim 3, wherein at least a part of the outer sintered portion formed by sintering the outer molded portion is removed.

6. 3. The method for manufacturing a mold according to claim 1, wherein the corrosion-resistant powder is one or more of nickel-based alloy powder, copper and copper alloy powder, aluminum and aluminum alloy powder, titanium and titanium alloy powder, and ceramic powder.

7. an inner sintered portion made of a sintered body of a first powder; an outer sintered portion made of a sintered body of a second powder covering the entire periphery of the inner sintered portion; and an inner sintered portion made of the sintered body of the second powder forming a flow path extending from an opening arranged on the bottom surface of the outer sintered portion to an opening arranged elsewhere on the bottom surface, the first powder does not include a binder and the second powder includes a binder; A mold in which a corrosion-resistant coating layer is provided on the inner peripheral surface of the inner shell sintered portion by adhering and sintering a corrosion-resistant powder.

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