Method for manufacturing titanium-based compacted powder and method for manufacturing titanium-based sintered body

Abstract

To provide a method for manufacturing a titanium-based green compact, capable of producing a titanium-based green compact having a predetermined complex shape in a relatively simple manner, and to provide a method for manufacturing a titanium-based sintered compact.SOLUTION: A titanium-based green compact 1 has a hollow body part 2 forming an internal space 2b including an opening 2a to the outside, and a plate part 3 standing on an internal surface 2c facing the internal space 2b of the hollow body part 2 and extending on the internal surface 2c. A method for manufacturing the titanium-based green compact 1 of this invention comprises the steps of: arranging a core material 61 forming the internal space 2b in a core material arrangement space of a resin mold 51; filling a molding space 52 of the mold 51 with a raw material powder 71; and performing cold isostatic pressurization at a pressurization of 300 MPa or more on the mold 51 filled with the raw material powder 71 in the molding space 52 while the core material 61 is placed in the core material placement space, wherein as the core material 61, a core component material having a consistency of 50 or more is used.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a method for manufacturing a titanium-based compacted powder and a method for manufacturing a titanium-based sintered body.

Background Art

[0002] For example, titanium and titanium alloys are being considered for use in various parts because of their excellent properties such as fatigue resistance, corrosion resistance, light weight, and high specific strength. However, in general, to manufacture parts made of titanium or titanium alloy, it is necessary to perform a number of processes such as melting by electron beam melting or vacuum arc melting, casting, and in some cases, further hot rolling, heat treatment, machining, welding, etc., and the manufacturing cost increases accordingly. Due to such high costs, it is difficult to say that the application range of titanium and titanium alloys has been sufficiently expanded.

[0003] Under such circumstances, in recent years, a powder metallurgy method has attracted attention in which raw material powder containing titanium is filled into a resin mold and is subjected to cold isostatic pressing to obtain a titanium-based compacted powder in a so-called near net shape. In the powder metallurgy method, after cold isostatic pressing, heating and sintering may be performed as necessary to increase the density.

[0004] By the way, among parts made of titanium or titanium alloy, there are some in which an internal space or a recess including an opening to the outside is formed. To manufacture a titanium-based compacted powder having such an internal space by the powder metallurgy method, a core material is placed at a location corresponding to the internal space of the mold, and cold isostatic pressing is performed on the mold filled with the raw material powder in the molding space.

[0005] In this regard, Patent Document 1 proposes "a method for manufacturing a hollow structure obtained by immersing a sintered body having a base material and a core made of an iron-based material in an acid solution to dissolve and remove the core, wherein the base material is made of a material nobler than the iron-based material constituting the core, and the method includes a coating formation step in which a non-conductive coating is formed on at least a part of the surface of the base material to reduce the surface area of ​​the base material that comes into contact with the acid solution." An example of a "hollow structure" is given as an "impeller (pump impeller)."

[0006] Furthermore, Patent Document 2 describes "a method for manufacturing a metal compact having a recess, comprising the step of applying cold isostatic pressure to raw material powder filled in a resin mold while a resin core material having a shape corresponding to the recess is positioned in a location corresponding to the recess of the resin mold." According to the method described in Patent Document 2, "the occurrence of bulges on the surface of the compact near the core material can be suppressed."

[0007] Although the material is not titanium or a titanium alloy, there are technologies related to compacted powder, such as those described in Patent Documents 3 and 4. Patent Document 3 describes "a method for cold isostatic pressure molding of powder, characterized in that when performing cold isostatic pressure molding by sealing powder in a mold, placing it in a pressure vessel, and applying isostatic pressure using a liquid such as water as the pressure medium, the mold is made of a viscoplastic material." Patent Document 4 describes "a method for manufacturing compacted powder by molding raw material powder, characterized in that a cavity of a desired shape is provided in a mold made of a semi-solid material with a consistency of 15 to 300, powder raw material is filled into the cavity, and then the powder raw material is pressurized using the mold as the pressure medium." [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-17218 [Patent Document 2] International Publication No. 2021 / 060363 [Patent Document 3] Japanese Patent Application Publication No. 63-219503 [Patent Document 4] Japanese Patent Publication No. 2003-154494 [Overview of the project] [Problems that the invention aims to solve]

[0009] When a highly rigid core material, such as the "core made of iron-based material" described in Patent Document 1, is used, the core material hardly undergoes elastic deformation during cold isostatic pressing. This can lead to differences in the transmission of pressure through the raw material powder via the core material, potentially resulting in areas that are not compacted sufficiently. Consequently, with highly rigid core materials, the surface near the core material may bulge, making it difficult to produce titanium-based powder compacts of a predetermined shape. In addition, the method described in Patent Document 1 requires "immersing a sintered body having a base material and a core made of iron-based material in an acid solution to dissolve and remove the core," which cannot be considered a simple method for producing titanium-based powder compacts.

[0010] On the other hand, the manufacturing method described in Patent Document 2 uses a resin core material, which makes it possible to suppress surface bulging near the core material in the titanium-based powder compact formed after cold isostatic pressing. Furthermore, the resin core material can be removed relatively easily from the titanium-based powder compact after cold isostatic pressing.

[0011] Incidentally, titanium or titanium alloy parts come in more complex shapes, such as closed impellers, where plate sections, such as blades, are mounted on the inner surface facing an internal space that includes an opening to the outside. In some cases, titanium-based compacts with plate sections mounted in such internal spaces could not be manufactured even by placing a resin core material in a mold for cold isostatic pressing.

[0012] Patent documents 3 and 4 do not provide any consideration for manufacturing titanium-based compacts with a plate portion provided in the internal space as described above.

[0013] The object of this invention is to provide a method for manufacturing titanium-based powder compacts and a method for manufacturing titanium-based sintered bodies, which enable the relatively easy production of titanium-based powder compacts having a predetermined complex shape. [Means for solving the problem]

[0014] As a result of diligent research, the inventors discovered that by using a core material with a consistency of 50 or higher as the core material to be placed in a resin mold, it is possible to successfully manufacture titanium-based compacts with plate sections erected in the internal space. It is presumed that with materials having a consistency lower than 50 and poor fluidity, the core material will spring back during the unloading process by cold isostatic pressing, making the plate sections of the titanium-based compacts, especially those with a relatively thin thickness, prone to damage. By using a core material with a consistency of 50 or higher, damage to the plate sections is suppressed, making it possible to manufacture titanium-based compacts having such plate sections. Furthermore, core material with a consistency of 50 or higher can be easily removed from the titanium-based compact after cold isostatic pressing.

[0015] (1) The present invention provides a method for manufacturing a titanium-based compact, wherein the titanium-based compact comprises a hollow body portion that forms an internal space including an opening to the outside, and a plate portion that is vertically provided on the inner surface of the hollow body portion facing the internal space and extends on the inner surface, and the manufacturing method comprises the steps of: placing a core material that forms the internal space in the core material placement space of a resin mold; filling the molding space of the mold with raw material powder; and applying cold isostatic pressure to the mold with the molding space filled with raw material powder at a pressure of 300 MPa or more while the core material is placed in the core material placement space, wherein the core material is a core material constituent material having a consistency of 50 or more.

[0016] (2) In the method for producing titanium-based compacted powder described in item (1) above, it is preferable that the consistency of the core material constituent is 60 or more and 240 or less.

[0017] (3) In the method for producing a titanium-based compressed powder according to the above item (1) or (2), the core material constituent material preferably contains a polybutene resin or clay.

[0018] (4) In the method for producing a titanium-based compressed powder according to any one of the above items (1) to (3), in the titanium-based compressed powder for an impeller, the hollow main body portion is a casing portion including a pair of disk-shaped portions arranged at intervals from each other and provided with the internal space therebetween, and the plate portion may be blade portions extending straight or including curved portions and / or bent portions radially outward from the center of the disk-shaped portions between the disk-shaped portions.

[0019] (5) In the method for producing a titanium-based compressed powder according to the above item (4), in a cross section of the titanium-based compressed powder including the plate portion of the titanium-based compressed powder and perpendicular to the central axis, there may be a portion in the titanium-based compressed powder where the ratio of the length corresponding to the thickness of the plate portion to the total length of the space portions located on both sides of the plate portion in the circumferential direction on a perpendicular line perpendicular to the extending direction of the plate portion is 0.05 or more and 0.25 or less.

[0020] (6) In the method for producing a titanium-based compressed powder according to any one of the above items (1) to (5), as the mold, it is preferable to use a mold made of a thermoplastic resin having a Shore D hardness in the range of 30 to 120.

[0021] (7) In the method for producing a titanium-based compressed powder according to any one of the above items (1) to (6), as the mold, a mold produced using a three-dimensional modeling apparatus can be used.

[0022] (8) The method for producing a titanium-based sintered body of this invention includes a sintering step of heating and sintering a titanium-based compressed powder produced by the method for producing a titanium-based compressed powder according to any one of the above items (1) to (7).

Advantages of the Invention

[0023] According to the method for manufacturing a titanium-based compressed powder of the present invention, a titanium-based compressed powder having a predetermined complex shape can be manufactured relatively easily.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a perspective view showing an example of a titanium-based compressed powder that can be manufactured by the manufacturing method according to an embodiment of the present invention. [Figure 2] FIG. 2(a) is a plan view of the titanium-based compressed powder of FIG. 1, and FIG. 2(b) is a cross-sectional view taken along line b-b of FIG. 2(a). [Figure 3] FIG. 3(a) is a side view of the titanium-based compressed powder of FIG. 1, and FIG. 3(b) is a cross-sectional view taken along line b-b of FIG. 3(a). [Figure 4] FIG. 4(a) is a cross-sectional view taken along the central axis showing a mold and a core material that can be used for manufacturing the titanium-based compressed powder of FIG. 1, and FIG. 4(b) is a cross-sectional view taken along line b-b of FIG. 4(a). [Figure 5] FIG. 5 is a cross-sectional view taken along the central axis schematically showing a state of performing cold isostatic pressure pressing using the mold and the core material of FIG. 4. [Figure 6] FIG. 6 is a perspective view showing another example of a titanium-based compressed powder that can be manufactured by the manufacturing method according to an embodiment of the present invention. [Figure 7] FIG. 7(a) is a plan view of the titanium-based compressed powder of FIG. 6, and FIG. 7(b) is a cross-sectional view taken along line b-b of FIG. 7(a). [Figure 8] FIG. 8(a) is a side view of the titanium-based compressed powder of FIG. 6, and FIG. 8(b) is a cross-sectional view taken along line b-b of FIG. 8(a). [Figure 9] FIG. 9 is a perspective view showing still another example of a titanium-based compressed powder that can be manufactured by the manufacturing method according to an embodiment of the present invention. [Figure 10] FIG. 10(a) is a plan view of the titanium-based compressed powder of FIG. 9, and FIG. 10(b) is a cross-sectional view taken along line b-b of FIG. 10(a). [Figure 11]Figure 11(a) is a side view of the titanium-based powder compact shown in Figure 9, and Figure 11(b) is a cross-sectional view along the line bb in Figure 11(a). [Figure 12] This is a perspective view showing yet another example of a titanium-based compact that can be manufactured by a manufacturing method according to one embodiment of this invention. [Figure 13] Figure 13(a) is a plan view of the titanium-based powder compact shown in Figure 12, and Figure 13(b) is a cross-sectional view along the line bb in Figure 13(a). [Figure 14] Figure 14(a) is a side view of the titanium-based powder compact shown in Figure 12, and Figure 14(b) is a cross-sectional view along the line bb in Figure 14(a). [Figure 15] This is a perspective view showing yet another example of a titanium-based compact that can be manufactured by a manufacturing method according to one embodiment of this invention. [Figure 16] Figure 16(a) is a plan view of the titanium-based powder compact shown in Figure 15, and Figure 16(b) is a cross-sectional view along line bb in Figure 16(a). [Figure 17] Figure 15 is a side view of the titanium-based powder compact. [Modes for carrying out the invention]

[0025] Embodiments of this invention will be described in detail below with reference to the drawings. In a method for manufacturing a titanium-based compact according to one embodiment of this invention, a titanium-based compact 1, etc., is manufactured, which has a plate portion 3 provided in an internal space 2b including an opening 2a, as illustrated in Figures 1 to 3. The term "titanium-based" here includes not only pure titanium but also titanium alloys.

[0026] In order to manufacture a titanium-based compacted powder 1 having a plate portion 3 in such an internal space 2b, in this embodiment, prior to cold isostatic pressing, when placing the core material that forms the internal space in the core material placement space of a resin mold, a core material constituent material with a consistency of 50 or higher is used as the core material.

[0027] The core material, composed of a core material component with a consistency of 50 or higher, has relatively low viscosity and high fluidity. Therefore, when the load is removed after cold isostatic pressing, it is presumed that less springback occurs, thereby suppressing damage to the plate portion of the titanium compact. Furthermore, because the core material of the core material component with a consistency of 50 or higher is fluid, it can be easily removed from the titanium compact after cold isostatic pressing. As a result, titanium compacts with predetermined complex shapes can be manufactured relatively easily.

[0028] (Manufacturing method) Here, as an example, a method for manufacturing the titanium-based compact 1 shown in Figures 1 to 3 will be described in detail. This titanium-based compact 1 has a hollow body portion 2 that forms an internal space 2b including an opening 2a to the outside, and a plate portion 3 that is erected on the inner surface 2c facing the internal space 2b of the hollow body portion 2 and extends on the inner surface 2c.

[0029] Here, the hollow main body 2 includes a pair of disc-shaped portions 4a and 4b arranged parallel to each other at a distance, and a cylindrical connecting portion 5 that extends parallel to the central axis between the disc-shaped portions 4a and 4b and connects them to each other (see Figures 2 and 3). The internal space 2b is partitioned between the disc-shaped portions 4a and 4b on the outer circumference side of the connecting portion 5, and is recessed from the outer surface of the hollow main body 2, located further back than the outer surface. This internal space 2b has an opening 2a to the outside between the outer circumference surfaces of the disc-shaped portions 4a and 4b on the outer surface of the hollow main body 2. The boundary between the outer end surface and the outer circumference surface of each disc-shaped portion 4a and 4b can, if necessary, be formed with a curved chamfer 4c that extends around the entire circumference.

[0030] The plate portion 3 is provided on the inner surface 2c (more specifically, the inner end surface of the disc-shaped portions 4a and 4b facing the inner space 2b) that faces the inner space 2b. The plate portion 3 can consist of one or more plates, and in the illustrated example, there are six. Each plate portion 3 is formed integrally with the inner surface 2c (the respective inner end surface of each disc-shaped portion 4a and 4b) and extends on the inner surface 2c in a position rising from the inner surface 2c.

[0031] In this example, the multiple plate sections 3 are connected to a connecting section 5 at the center of the disc-shaped sections 4a and 4b, and have a shape that extends straight outwards radially from the connecting section 5. As shown in Figure 3, the internal space 2b is divided into multiple spatial sections corresponding to the multiple plate sections 3, and there are multiple openings 2a at the outermost radial end of each spatial section.

[0032] As shown in Figures 4(a) and (b), the mold 51 for forming the titanium-based powder compact 1 is provided with a molding space 52 that corresponds to the shape of the titanium-based powder compact 1. More specifically, the mold 51 has a pair of hollow disc-shaped wall portions 53a and 53b spaced apart from each other, a hollow cylindrical wall portion 54 extending parallel to the central axis at the center between the disc-shaped wall portions 53a and 53b and connected to each of the disc-shaped wall portions 53a and 53b, and a plurality of hollow plate-shaped wall portions 55 extending radially between the disc-shaped wall portions 53a and 53b and connected to each of the disc-shaped wall portions 53a and 53b and the cylindrical wall portion 54.

[0033] In the illustrated mold 51, a molding space 52 is partitioned within the hollow disc-shaped wall sections 53a and 53b, the cylindrical wall section 54, and the plate-shaped wall section 55. The disc-shaped portions 4a and 4b of the titanium-based compact 1 are formed on the molding surfaces inside the disc-shaped wall sections 53a and 53b, the connecting portion 5 of the titanium-based compact 1 is formed on the molding surface inside the cylindrical wall section 54, and the plate portion 3 of the titanium-based compact 1 is formed on the molding surface inside the plate-shaped wall section 55. In this mold 51, a through-hole 53c is provided in the central outer portion of one of the disc-shaped wall sections 53a for supplying raw material powder 71 to the molding space 52, but the through-hole may be provided in other parts of the mold. Also, the number of through-holes 53c is not limited to one, but may be multiple.

[0034] The mold 51 is made of resin, preferably thermoplastic resin, and is particularly suitable to be made of acrylic resin, acrylic resin containing elastomer, polylactic acid (PLA) resin, etc. In order to ensure the required strength and maintain its shape when the raw material powder 71 is filled, the resin mold 51 is preferably made of a thermoplastic resin with a Shore D hardness in the range of 30 to 120, and may also be a thermoplastic resin in the range of 30 to 85. The Shore D hardness can be measured by a test method in accordance with JIS K7215 (1986). Also from a similar viewpoint, the thickness of the resin mold 51 is preferably 0.5 mm to 2.0 mm.

[0035] The resin mold 51 can be manufactured by various methods, but it is preferable that it be manufactured using a three-dimensional molding device (so-called 3D printer). This makes it easy to manufacture molds 51 of various shapes. The molding method of the three-dimensional molding device is not particularly limited and may be any of the following: stereolithography, inkjet, inkjet powder deposition, powder sintering deposition, fused deposition, or powder bonding.

[0036] As the raw material powder 71 to fill the molding space 52 of the mold 51, various powders such as titanium powder, alloying element powder, and master alloy powder can be used in combination as needed. This titanium powder includes pure titanium powder consisting substantially only of titanium, and titanium hydride powder which mainly contains titanium and hydrogen at a concentration of 5% by mass or less. Pure titanium powder may be, for example, hydrogenated dehydrogenated powder obtained by dehydrogenating titanium hydride powder. When the raw material powder 71 contains titanium hydride powder, it is desirable to perform a step of heating and sintering the titanium-based compact 1 as described later. Furthermore, the above-mentioned alloying element powder refers to powder containing a single alloying element of a titanium alloy, and master alloy powder refers to powder containing multiple elements. The raw material powder 71 may be, for example, titanium powder alone, or it may be a mixture of titanium powder with one alloying element powder selected from the group consisting of iron, aluminum, vanadium, zirconium, tin, molybdenum, copper, and nickel, and / or two or more master alloy powders thereof. Alternatively, it is possible to use only powder containing titanium and alloying elements as the raw material powder 71. Pure titanium refers to titanium with a titanium content of 99% by mass or more. The mass ratio of alloying elements to titanium in the raw material powder 71 may be in the range of 0 to 0.33, with titanium set to 1, for example, 0 to 0.11.

[0037] The average particle size of the raw material powder 71 is preferably 10 μm to 150 μm. By using such relatively fine particles, the compressive density of the titanium-based compact after cold isostatic pressing, and furthermore, the titanium-based sintered body after heating, can be improved. The average particle size refers to the particle diameter D50 (median diameter) of the particle size distribution (volume basis) obtained by laser diffraction scattering method. Known powders such as crushed powder and atomized powder can be used as the raw material powder 71.

[0038] To manufacture a titanium-based compact 1 using the mold 51 and raw material powder 71 described above, a core material 61 is placed in the core material placement space of the mold 51 to form the internal space 2b of the titanium-based compact 1. As shown in Figure 4, the core material 61 is placed in the space between the pair of disc-shaped wall portions 53a and 53b in the mold 51, and between the plate-shaped wall portions 55 adjacent to each other in the circumferential direction on the outer circumference of the cylindrical wall portion 54. This space corresponds to the core material placement space. The fluid core material component can be poured into the core material placement space from an opening to the outside around the core material placement space to fill it, thereby placing the core material 61 in the core material placement space. After placing the core material 61, the opening of the core material placement space can be sealed by closing it with a sealing member 56, such as a plate (see Figure 5).

[0039] Furthermore, before or after the process of placing the core material 61 in the core material placement space of the mold 51, the molding space 52 of the mold 51 is filled with raw material powder 71 through the through hole 53c. After filling the molding space 52 with raw material powder 71, a plate-shaped lid member 57 made of, for example, substantially the same material as the mold 51 is provided in the through hole 53c, thereby sealing the molding space 52 (see Figure 5).

[0040] Furthermore, the order in which the process of placing the core material 61 in the core material placement space and the process of filling the molding space 52 of the mold 51 with raw material powder 71 does not matter; either process may be performed first. In addition, instead of the lid member 57 provided on the through hole 53c and / or the sealing member 56 that closes the opening of the core material placement space, the entire mold may be covered with a covering member such as a bag, although this is not shown in the figures. In this case, if necessary, a depressurization treatment inside the covering member enclosing the mold may be performed before the cold isostatic pressurization described below.

[0041] Subsequently, with the core material 61 placed in the core material placement space, the mold 51, which has the raw material powder 71 filled into the molding space 52, is subjected to cold isostatic pressing (CIP) in a cold isostatic pressing device. Here, as shown in Figure 5, the mold 51 is pressed from the outside. The sealing member 56 and the lid member 57 are considered to be part of the mold 51, and the pressing force is also applied to the sealing member 56 and the lid member 57 from the outside. As the mold 51 is pressed, the raw material powder 71 in the molding space 52 of the mold 51 is compressed and compacted to become a titanium-based compact 1.

[0042] In cold isostatic pressurization, the mold 51 is pressurized by the surrounding fluid at an isostatic pressure (hydrostatic pressure, etc.), regardless of its shape. Therefore, by cold isostatic pressurization, titanium-based compacts 1 can be manufactured using molds 51 of various shapes.

[0043] The pressure applied to the mold 51 by cold isostatic pressing is 300 MPa or more, preferably 400 MPa or more. If the pressure is less than 300 MPa, the raw material powder 71 will not be sufficiently compressed, and the shape accuracy of the titanium-based compact 1 will be insufficient. The pressure may be, for example, 750 MPa or less, or 600 MPa or less, typically 500 MPa or less. The holding time at such a pressure may be, for example, 0.5 minutes to 30 minutes.

[0044] After the cold isostatic pressing process, the titanium-based compact 1 is removed from the cold isostatic pressing apparatus along with the mold 51 and core material 61. Then, the mold 51 and core material 61 are removed from the titanium-based compact 1. At this point, the core material 61 can be easily removed because it is fluid. Depending on the type of core material constituents, the core material 61 may be removed together with a portion of the mold 51. The mold 51 may be softened by heating it to approximately 100°C in the atmosphere before removal, if necessary. This allows for the production of the titanium-based compact 1.

[0045] When manufacturing a titanium-based sintered body, a process of cold isostatic pressing is followed by a heating process of the titanium-based compact 1. When the titanium-based compact 1 is heated, the particles that make up the compact 1 sinter to form a titanium-based sintered body. The manufactured titanium-based compact or titanium-based sintered body can then be subjected to further processing such as cutting or polishing.

[0046] In this process, the titanium-based compact 1 can be heated without pressure at a temperature of, for example, 1200°C to 1300°C for 1 to 3 hours. Alternatively, or in addition to this, the titanium-based compact 1 may be subjected to hot isostatic pressing (HIP), where an isostatic pressure of approximately 100 MPa to 200 MPa is applied to the titanium-based compact 1 at a temperature of, for example, 800°C to 1000°C using a pressure medium such as argon gas for 30 to 180 minutes.

[0047] Titanium-based sintered bodies can be manufactured by unpressurized heating and / or hot isostatic pressing. When both unpressurized heating and hot isostatic pressing are performed, the order is not particularly important, but for example, hot isostatic pressing can be performed after unpressurized heating.

[0048] In the manufacturing method described above, the core material 61 placed in the core material placement space of the mold 51 shall be made of a core material constituent material having a consistency of 50 or higher.

[0049] If the consistency of the core material constituent material is 50 or higher, the core material 61 exhibits relatively low viscosity and high fluidity, allowing it to deform in accordance with the raw material powder 71 and mold 51 during cold isostatic pressing. Using such a core material 61 tends to reduce the likelihood of damage to the titanium compact 1 after cold isostatic pressing. This is presumed to be because, with a consistency of 50 or higher, the core material 61, possessing appropriate viscosity and fluidity, does not recover as much when the cold isostatic pressing load is removed. If a core material 61 made of core material constituent material with a consistency of less than 50 is used, a large springback of the core material 61 may occur when the cold isostatic pressing load is removed. This makes the titanium compact 1, in particular, more susceptible to damage to the relatively thin plate portion 3 adjacent to the core material 61 via the plate-like wall portion 55.

[0050] Previously, when manufacturing a titanium-based compacted powder 1 in which a plate portion 3 exists in an internal space 2b, it was necessary to weld the plate portion 3 in place because machining the internal space 2b was difficult. However, since titanium and titanium alloys readily combine with oxygen, welding the plate portion 3 to the welded area results in the welded area easily absorbing oxygen, leading to a problem where its mechanical properties differ from those of the surrounding area. In contrast, the above-described embodiment eliminates the need for welding, thus avoiding such problems.

[0051] Furthermore, the core material 61, having a consistency of 50 or higher due to its fluidity, can be filled and placed in core material placement spaces of various shapes. Therefore, by using such a core material 61, titanium-based compacts 1 with internal spaces 2b of various shapes can be manufactured.

[0052] Generally, core material components that do not change in consistency are used. However, if the core material components may change in consistency due to, for example, heat hardening, then it is sufficient that the consistency of the core material components immediately before filling the core material placement space in the mold 51 and immediately after removing them from the titanium-based compacted powder 1 is 50 or higher. Even if the consistency of the core material components before filling the core material placement space is 50 or higher, if the consistency falls below 50 due to hardening after filling, there is a risk of springback of the core material during cold isostatic pressing unloading.

[0053] The consistency of the core material constituent is preferably 60 or higher and 240 or lower. Setting the consistency to 60 or higher can more effectively suppress the damage to the titanium compact 1 as described above. On the other hand, setting the consistency to 240 or lower suppresses contamination of the titanium compact 1 by adhesion or penetration of the core material 61 when removing the core material 61 from the titanium compact 1. If the core material constituent material adheres to or penetrates the titanium compact 1, there is a concern that the concentration of oxygen, carbon, nitrogen, etc. will increase locally during subsequent sintering, leading to a decrease in the mechanical properties of the titanium sintered body. Furthermore, if the consistency is of an appropriate size, it becomes easier to fill the core material placement space with the core material and to remove it from there.

[0054] The consistency of the core material components is measured using a standard cone in accordance with JIS K2220:2013.

[0055] Specific examples of core material components include polybutene resin and clay. Clay is an artificial or natural soil or aggregate of particles containing soil, sand, oils and fats, pulp, etc., and possesses a predetermined adhesiveness; for example, oil clay.

[0056] (Titanium-based powder) According to the manufacturing method of the embodiment described above, the titanium-based compact 1 shown in Figures 1 to 3 can be manufactured. The specific composition of this titanium-based compact 1 is as previously described, and a further explanation will be omitted.

[0057] The titanium-based compact 1 may be made of pure titanium, or of a titanium alloy consisting of Ti-5Al-1Fe, Ti-5Al-2Fe, Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2Sn-4Zr-6Mo, or Ti-10V-2Fe-3Al, etc. In the titanium alloy components listed here, the numbers preceding each alloy element symbol indicate the content (mass %). For example, "Ti-6Al-4V" represents a titanium alloy containing 6 mass% Al and 4 mass% V.

[0058] The manufacturing targets are not limited to the titanium-based compacts 1 shown in Figures 1-3. For example, it is also possible to manufacture other titanium-based compacts, such as the titanium-based compacts 11 shown in Figures 6-8, the titanium-based compacts 21 shown in Figures 9-11, or the titanium-based compacts 31 shown in Figures 12-14.

[0059] The titanium-based compact 11 shown in Figures 6-8 has a structure almost identical to the titanium-based compact 1, except that it lacks the connecting portion 5 corresponding to the titanium-based compact 1 shown in Figures 1-3, and one of the disc-shaped portions 14a is ring-shaped with a through-hole 15 at its center that connects to the gap between it and the other disc-shaped portion 14b. The through-hole 15 constitutes part of the internal space 12b, and there is also an opening 15a to the outside on the outer end surface side of the disc-shaped portion 14a (see Figures 6 and 7). The pair of disc-shaped portions 14a and 14b are connected to each other by a plate portion 13 between them.

[0060] The titanium compacts 21 shown in Figures 9-11 have substantially the same structure as the titanium compacts 1, except that they have a connecting portion 25 with a larger diameter than the connecting portion 5 of the titanium compacts 1 shown in Figures 1-3, and each plate portion 23 extends including a curved portion that protrudes to one side in the circumferential direction (counterclockwise in Figure 11(b)) as it extends radially outward from the center of the disc-shaped portions 24a and 24b. In these titanium compacts 21, the entire plate portion 23 is a curved portion. However, although not shown, the plate portion may not be the entire thing, but may include at least one curved portion in part.

[0061] The titanium compact 31 shown in Figures 12-14 has substantially the same structure as the titanium compact 1, except that it has a connecting portion 35 with a larger diameter than the connecting portion 5 of the titanium compact 1 shown in Figures 1-3, and that each plate portion 33 extends radially outward from the center of the disc-shaped portions 34a and 34b, including at least one bend. In the illustrated titanium compact 31, each plate portion 33 has multiple bends, and as shown in Figure 14(b), it forms a zigzag shape with alternating bends that protrude to one side in the circumferential direction and bends that protrude to the other side as it extends radially outward. A corner portion 33a is formed on the outer surface of the cylindrical connecting portion 35 by connection with the end of the zigzag plate portion 33.

[0062] Although not shown in the illustrations, it is also possible to have a plate portion that contains both curved sections, as shown in the plate portion 23 of the titanium-based compacted powder 21 in Figures 9-11, and bent sections, as shown in the plate portion 33 of the titanium-based compacted powder 31 in Figures 12-14.

[0063] The titanium-based compacts 1, 11, 21, and 31 shown in Figures 1 to 14 can be used as impellers, such as in closed impellers. In these titanium-based compacts 1, 11, 21, and 31, the pair of disc-shaped portions 4a, 4b, 14a, 14b, 24a, 24b, 34a, 34b and the connecting portions 5, 25, and 35 correspond to the casing portion of the impeller. In all of the titanium-based compacts 1, 11, 21, and 31, the casing portion includes the pair of disc-shaped portions 4a, 4b, 14a, 14b, 24a, 24b, 34a, and 34b. Furthermore, the plate portions 3, 13, 23, and 33 of the titanium-based compacts 1, 11, 21, and 31 correspond to the blade portion of the impeller.

[0064] In these titanium-based impeller compacts 1, 11, 21, and 31, the plate sections 3, 13, 23, and 33, which are the blades located in the internal spaces 2b, 12b, 22b, and 32b, are sometimes relatively thin.

[0065] In this regard, taking the titanium-based compact 1 shown in Figures 1-3 as an example, when viewed in a cross-section perpendicular to the central axis including the plate portion 3 of the titanium-based compact 1, as shown in Figure 3(b), the proportion or area of ​​the thickness of the plate portion 3 occupying the internal space 2b is small. More specifically, in the titanium-based compact 1, in the above cross-section, there may be locations where the ratio (Lt / Ls) of the length Lt corresponding to the thickness of the plate portion 3 to the sum of the lengths (Ls / 2) of the spatial portions located on both sides of the plate portion 3 in the circumferential direction (Ls) on a perpendicular line PL (shown as a dashed line in Figure 3(b)) perpendicular to the direction in which the plate portion 3 extends is, for example, 0.05 or more and 0.25 or less. It is not necessary that the entire plate portion of the titanium-based compact has a location where the above ratio (Lt / Ls) is met. If there is a portion of the plate section in which the above ratio (Lt / Ls) is 0.05 or greater and 0.25 or less, then the material is considered to be a titanium-based compact in which such a ratio (Lt / Ls) exists.

[0066] The length of each space on both sides of the plate portion 3 in the circumferential direction refers to the length along the perpendicular PL from the side of the plate portion 3 to the side of the other plate portion, when there is another adjacent plate portion 3 on the side separated by the space, as shown in Figure 3(b). Alternatively, although not shown in the illustration, when there is an inner surface facing the internal space on the side separated by the space of the plate portion, the length in the perpendicular direction from the side of the plate portion to that inner surface corresponds to the length of each space on both sides of the plate portion.

[0067] Titanium-based compacts 1 that have locations where the ratio (Lt / Ls) of the length Lt corresponding to the thickness of the plate portion 3 to the sum of the lengths (Ls) of the circumferential space portions on both sides is 0.05 or more and 0.25 or less tend to be prone to damage during manufacturing due to the springback of the core material 61 mentioned above. In contrast, according to this embodiment, by using a predetermined core material component, even such titanium-based compacts 1 can be manufactured successfully while suppressing damage to the plate portion 3.

[0068] Incidentally, according to this embodiment of the invention, not only titanium-based compacts 1, 11, 21, and 31 for impellers, but also titanium-based compacts 41 for other applications shown in Figures 15-17 can be manufactured.

[0069] The titanium-based compacted powder 41 shown in Figures 15-17 has a hollow main body portion 42 that forms an internal space 42b including an opening 42a to the outside, and three plate portions 43 that are vertically mounted on the inner surface 42c of the hollow main body portion 42 facing the internal space 42b and extending on the inner surface 42c.

[0070] Here, the hollow main body 42 consists of a pair of disc-shaped portions 44a and 44b, spaced apart from each other, connected by a cylindrical connecting portion 45 that extends along the central axis between them. The internal space 42b is recessed from the outer surface of the hollow main body 42 and is demarcated by the inner surfaces of the pair of disc-shaped portions 44a and 44b and the connecting portion 45 on the internal space 42b side.

[0071] Furthermore, in the illustrated example, each plate portion 43 provided around the cylindrical connecting portion 45 extends circumferentially on the inner surface 42c facing the internal space 42b of the connecting portion 45, and forms an annular plate shape with a gradually decreasing thickness towards the radially outward direction. The number of plate portions 43 can be changed as appropriate, and may be one, two, or four or more.

[0072] The titanium-based compacted powder 41 shown in Figures 15-17 is not intended for use in an impeller, but it can be manufactured using this embodiment because it is formed without damaging the plate portion 43 provided in the internal space 42b. [Examples]

[0073] Next, the method for producing titanium-based compacted powder according to this invention was experimentally implemented, and its effects were confirmed, which are described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0074] We attempted to manufacture titanium-based compacts A, as shown in Figures 1-3, and titanium-based compacts B, as shown in Figures 9-11, by cold isostatic pressing of the raw material powder. In titanium-based compact A, the minimum value of the ratio (Lt / Ls) of the length corresponding to the thickness of the plate portion to the sum of the lengths Ls of the spaces located on both sides of the plate portion in the circumferential direction, on a perpendicular line perpendicular to the direction in which the plate portion extends, is 0.05 in a cross section perpendicular to the central axis including the plate portion. The minimum value of the same ratio (Lt / Ls) in titanium-based compact B is 0.09.

[0075] In Examples 1-8 and Comparative Examples 1-3, compacted titanium was produced. Hydrogenated dehydrogenated powder (HDH powder) was used as the raw material in Examples 1-7 and Comparative Examples 1-3. In Example 8, a mixture of HDH powder and titanium hydride powder in a mass ratio of 1:1 was used. The HDH powder had a titanium content of 99% by mass or more and an average particle size of 66 μm. The titanium hydride powder had a titanium content of 95% by mass or more, a hydrogen content of 5% by mass or less, and an average particle size of 66 μm.

[0076] In Example 9, a compacted titanium alloy was manufactured, and the raw material powder used was a mixture of the above-mentioned HDH powder and 60Al40V powder in a mass ratio of 9:1. The above-mentioned 60Al40V powder was produced by crushing a casting ingot and contained 60% by mass of aluminum and 40% by mass of vanadium, with an average particle size of 35 μm.

[0077] The molds used in the manufacturing process were fabricated using a 3D printer. The resin material used to construct the molds was polylactic acid (PLA), with a Shore D hardness of 83. The thickness of the molds was 1.0 mm. The core materials placed in the core material placement space of the molds were the core material components shown in Table 1. Note that in Table 1, "Putty for air conditioner piping" is made of polybutene resin. The consistency of the core material components was measured in accordance with JIS K2220:2013, as mentioned above. However, the silicone sealant in Comparative Example 1 hardened over time, and the carbon steel in Comparative Example 2 and the thermosetting resin in Comparative Example 3 did not have fluidity at room temperature, so their consistency could not be measured. As a result, Comparative Examples 1-3 are hard materials and are clearly considered to have a consistency of less than 50.

[0078] After placing the core material in the mold described above and filling it with raw material powder, the entire mold was wrapped in a plastic bag, the inside was depressurized, and then cold isostatic pressing (CIP) was performed using hydrostatic pressure in a cold isostatic pressing apparatus. During cold isostatic pressing, a pressure of 490 MPa was applied to the mold filled with raw material powder for 1 minute. After cold isostatic pressing, the mold was removed from the plastic bag, and most of the core material was removed by hand. Next, the mold was heated to approximately 100°C in the air to soften it. Then, the mold was removed from the titanium-based compacted powder inside using tools such as pliers.

[0079] The titanium-based compacts produced in this manner were visually inspected to check for damage, adhesion of core material, and penetration into the interior. The results are shown in Table 1.

[0080] [Table 1]

[0081] In Examples 1-9, no fracture occurred in any of the titanium-based compacts A and B. On the other hand, in Comparative Examples 1 and 3, the plate portion (wing portion) fractured in both titanium-based compacts A and B after removal from the mold. In Comparative Example 2, titanium-based compact B could not be manufactured because a core material made of carbon steel was used. Furthermore, in titanium-based compacts A and B of Examples 4-6, core material components adhered to the compacts during removal from the mold and penetrated into the interior. On the other hand, in titanium-based compacts A and B of Examples 1-3 and 7-9, there was no such adhesion or penetration of core material components. In addition, in Examples 1-3 and 7-9 in particular, filling and removing the core material into the core material placement space was easy.

[0082] From the above, it has been found that, according to the manufacturing method of this invention, titanium-based compacts having complex shapes can be manufactured relatively easily. [Explanation of Symbols]

[0083] 1, 11, 21, 31, 41 Titanium-based compacted powder 2, 12, 22, 32, 42 Hollow main body 2a, 12a, 15a, 22a, 32a, 42a opening 2b, 12b, 22b, 32b, 42b interior space 2c, 12c, 22c, 32c, 42c inner surface 3, 13, 23, 33, 43 Plate section 33a Corner 4a, 4b, 14a, 14b, 24a, 24b, 34a, 34b, 44a, 44b Disk shaped part 4c, 14c, 24c, 34c, 44c chamfered section 5, 25, 35, 45 connection part 15 Through hole section 51 molds 52 Molding space 53a Disc-shaped wall portion 53b Disc-shaped wall 53c through hole 54 Cylindrical wall section 55 Plate-shaped wall section 56 Sealing member 57 Lid member 61 Core material 71 Raw material powder A perpendicular line perpendicular to the direction in which the PL plate extends. Ls: Sum of lengths in the circumferential space on both sides of the plate portion. Length corresponding to the thickness of the Lt plate section

Claims

1. A method for manufacturing titanium-based compacted powder, The titanium-based compacted body has a hollow main body portion that forms an internal space including an opening to the outside, and a plate portion that is erected on the inner surface of the hollow main body portion facing the internal space and extends on the inner surface. The manufacturing method includes the steps of: placing a core material that forms the internal space in the core material placement space of a resin mold; filling the molding space of the mold with raw material powder; and, with the core material placed in the core material placement space, applying cold isostatic pressure to the mold with the molding space filled with raw material powder at a pressure of 300 MPa or more. As the core material, a core material component material having a consistency of 50 or higher is used. As the mold, a mold made of a thermoplastic resin having a Shore D hardness in the range of 30 to 120 is used. The titanium-based powder compact is for use in impellers. The hollow main body is a casing portion that includes a pair of disc-shaped portions arranged at intervals from each other and having the internal space between them. A method for manufacturing titanium-based powder compacts, wherein the plate portion is a blade portion that extends straight or including curved and / or bent portions between the disc-shaped portions, radially outward from the center of the disc-shaped portion.

2. A method for producing a titanium-based compacted body according to claim 1, wherein the consistency of the core material constituent is 60 or more and 240 or less.

3. A method for producing a titanium-based compacted body according to claim 1, wherein the core material constituent material includes polybutene resin or clay.

4. A method for manufacturing a titanium-based powder compact according to claim 1, wherein, in a cross section of the titanium-based powder compact including the plate portion and perpendicular to the central axis, there exists a location in the titanium-based powder compact where, on a perpendicular line perpendicular to the direction in which the plate portion extends, the ratio of the length corresponding to the thickness of the plate portion to the sum of the lengths of the spaces located on both sides of the plate portion in the circumferential direction is 0.05 or more and 0.25 or less.

5. The method for producing a titanium-based powder compact according to claim 1, wherein the mold used is one manufactured using a three-dimensional molding device.

6. A method for manufacturing a titanium-based sintered body, A method for producing a titanium-based sintered body, comprising a sintering step of heating and sintering a titanium-based powder compact produced by the method for producing a titanium-based powder compact according to any one of claims 1 to 5.

Images