WO2022190601A1

WO2022190601A1 - Titanium green compact production method and titanium sintered body production method

Info

Publication number: WO2022190601A1
Application number: PCT/JP2022/000148
Authority: WO
Inventors: 昌志早川
Original assignee: 東邦チタニウム株式会社
Priority date: 2021-03-12
Filing date: 2022-01-05
Publication date: 2022-09-15
Also published as: JP7177302B1; JPWO2022190601A1

Abstract

This titanium green compact production method produces a titanium green compact 101 that has a recessed section 102. The recessed section 102 of the titanium green compact 101 has a shape whereby, in at least one cross section that includes at least part of the central axis CC of the recessed section 102, the width changes in at least part of the central axis direction of the recessed section 102 and/or has a shape that includes a curved section and/or a bent section of the central axis Cc of the recessed section 102. The titanium green compact production method includes: a step in which a core material-constituting material is caused to flow into and fill a core material arrangement space 5a that corresponds to the recessed section 102 in a resin mold 1 and a core material 11 that has a shape corresponding to the recessed section 102 is arranged; a step in which a raw material powder is filled in a molding space 2 of the mold 1; and a step in which cold isostatic pressurization is performed at an isostatic pressure of at least 300 MPa on the mold 1 which has the raw material powder filled into the molding space 2, in a state in which the core material 11 is arranged inside the core material arrangement space 5a.

Description

Method for producing titanium-based green compact and method for producing titanium-based sintered compact

The present invention relates to a method for manufacturing a titanium-based compact and a method for manufacturing a titanium-based sintered body.

Titanium and titanium alloys, for example, are being considered for use in various parts because of certain excellent properties such as fatigue resistance, corrosion resistance, light weight and high specific strength.
However, manufacturing parts made of titanium or titanium alloys generally involves a number of steps, such as melting by electron beam melting, vacuum arc melting, etc., casting, and in some cases hot rolling, heat treatment and machining, welding, and the like. required, which increases manufacturing costs. Due to such high costs, it is difficult to say that the application range of titanium and titanium alloys has been sufficiently widened.

Under such circumstances, in recent years, as a so-called near net shape, raw material powder containing titanium is filled in a resin mold, and cold isostatic pressing is applied to the raw material powder to form a predetermined shape. A powder metallurgy method for obtaining a titanium-based compact has attracted attention. In the powder metallurgy method, after cold isostatic pressing, sintering and/or hot isostatic pressing may be performed as necessary to increase the density.

As a technology related to this, Patent Document 1 discloses "In a method for producing a compacted body in which a rubber mold filled with a raw material powder is pressed uniaxially in a mold to form a compacted body of the raw material powder, the above-mentioned A method for producing a compacted body, characterized in that a portion of the outer surface of the compacted body that is substantially perpendicular to the pressurizing direction is formed by a highly rigid mold member disposed in the rubber mold. It is

In addition, Patent Document 2 describes, "In a method for producing a sintered titanium alloy by a raw powder mixing method, instead of titanium powder, titanium powder, (Ti—H) alloy powder, and titanium hydride powder are mixed with hydrogen: titanium. A method for producing a sintered titanium alloy, characterized in that a powder blended so that the mass ratio is 0.002 or more and less than 0.030 is used as a raw material powder.

Japanese Patent Application Laid-Open No. 2001-131605 JP-A-6-33165

By the way, in order to manufacture a titanium-based compact having recesses such as through holes or non-penetrating recesses by the above-described powder metallurgy method, a core material such as a core is placed in a resin mold corresponding to the recesses. is placed, and cold isostatic pressure is sometimes applied to the raw material powder filled in the mold. As a core material for such a core, Patent Document 1 uses a high-rigidity core that is a cylindrical member made of steel (see paragraph 0035).

Here, when manufacturing a titanium-based green compact having a complicated shape such as a shape in which the width of the concave portion changes in the middle of the depth direction, or a shape in which the concave portion has a curved portion or a bent portion, the core to be used However, if the core has high rigidity, it may be difficult to arrange the core at a predetermined position in the mold before filling the raw material powder. A highly rigid core with a separable structure can accommodate recesses of a somewhat complicated shape. It may not be possible to form with high accuracy. In addition, when cold isostatic pressing is applied to the titanium-based powder, it is necessary to apply a relatively large pressure, and the divided high-rigidity core is likely to be displaced. Therefore, the high-rigidity core as a core material for forming the concave portion of the titanium-based compact cannot be used for manufacturing various titanium-based compacts due to the restriction of the shape of the concave portion. can be said to be poor.

Patent Document 2 does not pay attention to the specific shape of the concave portion of the titanium-based compact or the core material to be placed in the mold.

An object of the present invention is to provide a method for manufacturing a titanium-based green compact and a titanium-based sintered body, which are capable of manufacturing a titanium-based green compact having recesses having a somewhat complicated shape by a relatively simple technique. It is to provide a method.

The inventor proposed using a core constituent material that can be poured into the core arrangement space when arranging the core in the core arrangement space corresponding to the concave portion of the titanium-based compact in the resin mold. I put it out. With such a fluid core constituent material, it is possible to spread it sufficiently in the core arrangement space. For example, by injecting the core constituent material from the opening of the core arrangement space so that the core constituent material is gradually filled from the deep part of the core arrangement space to the opening side, the inside of the core arrangement space The material constituting the core material spreads sufficiently to form a core material (core). If necessary, by closing the opening before the cold isostatic pressurization, even if the core constituent material has fluidity even during the cold isostatic pressurization, the core material The constituent material can function as a core material. In this case, the core material can be appropriately deformed as the raw material powder in the resin mold is compacted during cold isostatic pressing. That is, in the case of divided high-rigidity cores, only the contact portions of the respective cores are extremely likely to move, resulting in displacement of the cores. This makes it possible to form concave portions having complicated shapes in the titanium-based green compact.

A method for producing a titanium-based compact according to the present invention is a method for producing a titanium-based compact having a concave portion, wherein the concave portion of the titanium-based compact forms at least a part of the central axis of the concave portion. In one or more of the cross sections including, at least a part of the recess in the central axis direction has a shape that changes in width, and/or a shape that includes a curved portion and/or a bent portion of the central axis of the recess, A step of filling a core material arranging space corresponding to the recess in a resin mold with a core material forming material so as to arrange a core material having a shape corresponding to the recess; a step of filling the powder, and in a state in which the core material is arranged in the core material arrangement space, the mold filled with the raw material powder in the molding space is subjected to cold pressing at a hydrostatic pressure of 300 MPa or more. and a step of applying isotropic pressure.

In the method for manufacturing the titanium-based compact described above, the inner surface of the concave portion of the titanium-based compact may include a stepped portion, and the core material arrangement space may include a stepped portion.
Further, in the above-described method for manufacturing a titanium-based compact, the concave portion of the titanium-based compact has a relatively wide wide portion in at least one of the cross sections, and a relatively wide width portion. The core material placement space has a wide portion forming the wide portion of the recess and a narrow portion forming the narrow portion of the recess. Sometimes.

In the method for producing a titanium-based compact according to the present invention, it is preferable to use a cured resin or clay as the material constituting the core material.
In the case where a cured resin is used as the core material constituting material, when the core material constituting material is filled in the core material arrangement space, at least the core material constituting the core material arrangement used for the injection of the core material constituting material It is preferable to harden the surface layer portion present in the opening on one end side of the space or the opening on the other end side.

As the mold, it is preferable to use a mold made of a thermoplastic resin having a Shore D hardness within the range of 30 to 120.
Moreover, it is preferable to use a mold produced using a three-dimensional modeling apparatus as the mold.
In the cold isostatic pressing, it is preferable to apply a pressure of 400 MPa or more to the mold.

In the method for producing a titanium-based sintered body of the present invention, the titanium-based compact produced by any one of the above-described methods for producing a titanium-based compact is subjected to sintering and/or hot isostatic pressing. It includes the step of performing

According to the method for producing a titanium-based compact according to the present invention, it is possible to produce a titanium-based compact having recesses having somewhat complicated shapes by a relatively simple method.

1 is a perspective view showing an example of a resin mold that can be used in a method for producing a titanium-based green compact according to one embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view along the central axis of the mold, showing a state in which a core constituent material is poured into the core arrangement space of the mold of FIG. 1; FIG. 3 is a cross-sectional view showing the mold of FIG. 1 together with a core material formed of the material constituting the core material of FIG. 2 ; FIG. 4 is a cross-sectional view along the central axis of the recess, showing a titanium-based compact manufactured using the mold and core material of FIG. 3 ; FIG. 4 is a cross-sectional view schematically showing a state in which cold isostatic pressing is performed using the mold and core material of FIG. 3 ; FIG. 6 is a cross-sectional view showing the titanium-based green compact obtained by the cold isostatic pressing of FIG. 5 before removing a part of the core material and the mold. FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold; FIG. 10 is a cross-sectional view showing another example of a resin mold;

Embodiments of the present invention will be described in detail below with reference to the drawings.
A method for producing a titanium-based compact according to one embodiment of the present invention uses, for example, a resin mold 1 and a core material 11 as shown in FIGS. It includes a step of filling raw material powder and applying cold isostatic pressure, and manufactures, for example, a titanium-based green compact 101 as shown in FIG. The term "titanium-based" as used herein includes not only titanium made of pure titanium but also titanium alloy.

A titanium-based green compact 101 shown in FIG. 4 has a substantially cylindrical shape as a whole, and recesses 102 having

openings

102a and 102b are formed on the outer surface (upper and lower end surfaces in FIG. 4). It is

In this example, the concave portion 102 formed in the titanium-based green compact 101 is aligned with the central axis Cc of the concave portion 102 that coincides with the vertical direction in FIG. It has a shape in which the width perpendicular to the central axis Cc changes at least partly in the direction along (also referred to as the "central axis direction"). More specifically, the recess 102 has a width Wa on the side of the opening 102a of one end face, which is the lower side in FIG. The width decreases through 102c, and becomes width Wb at the opening 102b on the other end face side. That is, in this cross section, the recess 102 has a wide portion 102d having a relatively wide width Wa between the opening 102a and the stepped portion 102c on one end surface, and the opening 102b and the stepped portion 102c on the other end surface. and a narrow portion 102e having a width Wb and relatively narrower than the wide portion 102d. However, as will be described later, the shape of the concave portion is not limited to this, and can be appropriately changed according to the use of the titanium-based compact.

In order to manufacture the titanium-based green compact 101 having the concave portion 102 of such a complicated shape, the mold 1 used in the cold isostatic pressing has a shape corresponding to the shape of the titanium-based green compact 101. It has a space 2. The mold 1 has a cylindrical outer cylinder wall portion 3 having an inner peripheral surface that matches the outer peripheral surface of the titanium-based compact 101, and a molding space 2 defined outside between the outer cylinder wall portion 3 and the outer cylinder wall portion 3. provided at one end (lower end in FIG. 2) of the inner cylinder wall portion 5 and the outer cylinder wall portion 3, which divides the core material arrangement space 5a inside and the outer cylinder wall portion 3 and the inner cylinder at the one end side It is provided with an annular wall portion 4 that connects with the wall portion 5 .

Inside the inner cylindrical wall portion 5 of the mold 1, a core material arrangement space 5a corresponding to the shape of the concave portion 102 of the titanium-based compact 101 described above is defined. In this example, the core material arranging space 5a has a shape in which the width perpendicular to the central axis Cm of the core material arranging space 5a changes through a step in the illustrated cross section. A wide portion that forms the wide portion 102d of the recess 102 and is located on one end side of the portion 3, and a narrow portion of the recess 102 that is adjacent to the wide portion and is located on the other end side (upper end portion in FIG. 2). and a narrowed portion forming 102e. Note that the central axis Cm of the core material arrangement space 5a and the central axis Cc of the recess 102 described above are the same as those of the core material arrangement space 5a inside the inner cylinder wall 5 or the recess 102 inside the titanium-based compact 101. A cross section extending along the extending direction and orthogonal to the central axis Cm or Cc passes through the center or centroid of the core material arrangement space 5a or the recess 102 .

In the core material placement space 5a, the high-rigidity core may not be used appropriately due to reasons such as difficulty in placement and inability to form the recessed portion 102 of the titanium-based compact 101 with high accuracy. For example, a core made of a highly rigid material such as stainless steel which has a considerably high melting point is difficult to deform during cold isostatic pressurization, and thus may cause misalignment. If the core is misaligned, the concave portion of the titanium-based green compact cannot be formed into a desired shape.

On the other hand, in this embodiment, as shown in FIG. 2, for example, the core material is injected into the core arrangement space 5a of the mold 1 from an injection tool 111 or the like containing a fluid core material. to flow and fill. At this time, either one of the opening on the one end side and the opening on the other end side of the core material arrangement space 5a of the inner cylindrical wall portion 5 (opening on the one end side, which is the lower side in FIG. 2) is covered with a sealing member such as a plate. After sealing in advance at 6a, the material constituting the core can be poured from the other opening (opening on the other end side, which is the upper side in FIG. 2). Further, for example, regardless of whether the core constituent material is a cured resin or clay, which will be described later, the core constituent material can be filled by pushing the core constituent material into the core arrangement space 5a or the like. By flowing and filling the core constituent material in this way, as shown in FIG. .

Before or after placing the core material 11 in the core material placement space 5a of the mold 1, the molding space 2 of the mold 1 is filled with raw material powder, and the other end of the outer cylinder wall portion 3 of the mold 1 is attached to a disk-shaped member. Seal with 6b. It does not matter whether the step of arranging the core material 11 in the core material arranging space 5a or the step of filling the molding space 2 of the mold 1 with raw material powder is carried out before or after, and either step may be carried out first. Then, in a state where the core material 11 is arranged in the core material arrangement space 5a, the mold 1 is pressed from the outside of the mold 1 inside a cold isostatic pressing device (not shown) as shown in FIG. Cold isostatic pressing (CIP) is performed to compress and compact the raw powder. Here, it is assumed that the sealing member 6a and the disk-shaped member 6b form part of the mold 1. As shown in FIG.

The pressure applied to the mold 1 by cold isostatic pressing is set to 300 MPa or more, preferably 400 MPa or more. If the applied pressure is less than 300 MPa, the raw material powder is not sufficiently compressed, and the shape accuracy in the recesses of the titanium-based compact becomes insufficient. The applied pressure may be, for example, 600 MPa or less, typically 500 MPa or less. Also, the holding time at such pressure may be, for example, 0.5 to 30 minutes. The raw material powder in the molding space 2 of the mold 1 is pressurized and compacted by cold isostatic pressing to form a titanium-based compact 101 .
In the cold isostatic pressurization, the mold 1 is pressurized isostatically (hydrostatic pressure) by the surrounding fluid. Therefore, according to cold isostatic pressing, the titanium-based compact 101 can be manufactured using molds 1 of various shapes. Further, here, the material constituting the core material filling the core material arrangement space 5a and constituting the core material 11 can deform following the raw material powder and the mold 1 when the isotropic pressure of the fluid is applied. The core material arrangement space 5a can be made into various arbitrary shapes. As a result, titanium-based compacts 101 having recesses 102 of various shapes can be manufactured.

After pressing by cold isostatic pressing, the titanium-based compact 101 is taken out from the cold isostatic pressing device together with the mold 1 and the core material 11 . Thereafter, the outer cylinder wall portion 3, the annular wall portion 4, the sealing member 6a and the disk-shaped member 6b around the titanium-based compact 101 are removed, and as shown in FIG. The inner core material 11 and the inner cylinder wall portion 5 are taken out. The core material 11 may be taken out before removing the outer cylinder wall portion 3 and the like. Thereby, the titanium-based compact 101 can be manufactured.

When manufacturing a titanium-based sintered body, a step of subjecting the titanium-based compact 101 to sintering and/or hot isostatic pressing (HIP) after cold isostatic pressing is included. . In the sintering, the titanium-based compact 101 can be heated at a temperature of, for example, 1200° C. to 1300° C. for 1 to 3 hours depending on the material of the titanium-based compact 101 . In the hot isostatic pressurization, for example, at a temperature of 800° C. to 1000° C., an isostatic pressure of about 100 MPa to 200 MPa is applied to the titanium-based compact 101 with a pressure medium such as argon gas for 30 minutes to 90 minutes. It can work for minutes. Thereby, a titanium-based sintered body can be produced. In hot isostatic pressing, sintering generally progresses due to the treatment at a high temperature. Therefore, a titanium-based sintered body obtained by subjecting the titanium-based compact 101 only to hot isostatic pressing is also referred to herein as a titanium-based sintered body. When both sintering and hot isostatic pressing are performed, the order is not particularly limited. For example, hot isostatic pressing can be performed after sintering.

The material constituting the core material used in the above-described manufacturing method should be a material that has fluidity at least when the core material arrangement space 5a is filled. If the material constituting the core material is a material that has fluidity not only when it is filled into the core material arrangement space 5a but also after cold isostatic pressing, the core material 11 is a titanium-based compact. It can be easily taken out by letting it flow out from the concave portion 102 of 101 .

More specifically, the material constituting the core material can be a non-curing resin such as an oil-based caulking material. Clay is preferred. By using such a hardened resin or clay, the core material 11 exhibits fluidity when filled into the core material arrangement space 5a, and is hardened after that and when cold isostatic pressure is applied, the core material 11 exhibits It becomes easier for the desired characteristics to be exhibited. Examples of moisture-curable resins that cure by reacting with moisture in the air include silicone-based, modified silicone-based, polyurethane-based, and polysulfide-based resins. Dry-hardening resins are those that harden when solvent or water evaporates and dry. The mixed reaction curing resin is cured by a chemical reaction caused by mixing a main agent and a curing agent, and examples thereof include modified silicones, polyurethanes, polysulfides, silicones, and polyisobutylenes. The photocurable resin is cured by being irradiated with light of a specific wavelength such as ultraviolet rays, and includes radical polymerizable acrylate photocurable resins, cationic polymerizable epoxy photocurable resins, and the like. Of these, silicone-based moisture-curable resins (silicone resins, silicone sealants, etc.) are particularly preferred as core material constituent materials because the portions exposed to moisture cure easily and quickly, and are also suitable in terms of cost. Clay is an aggregate of artificial or natural soil or particles containing soil, sand, oil, pulp, etc., and having a predetermined stickiness. For example, oil clay, paper clay, etc. can be used.
The core constituent materials may be used singly or in combination. Further, when a plurality of core material arrangement spaces exist in one mold, the core material constituent materials used in the respective core material arrangement spaces may be the same or different from each other.

When the core material constituting material is a cured resin as described above, when filled in the core material arranging space 5a, at least the core material composing material fills the core material arranging space 5a used for injecting the core material composing material. It is preferable to harden the surface layer portion present in the opening on one end side or the opening on the other end side. Moisture-curing or dry-curing curable resins are suitable for such partial curing of the surface layer. A space for arranging the core until at least the surface layer portion of the material forming the core in the space for arranging the core 5a is cured, and the opening at one end or the opening at the other end is sealed with the disk-shaped member 6b or the like. Leakage of the core constituent material from within 5a can be suppressed. In some cases, the opening can be properly closed without using the disk-shaped member 6b. In addition, when only the surface layer portion of the core constituent material is cured, the surface layer portion is peeled off after cold isostatic pressing, and the core material 11 is discharged from the recess 102 using the fluidity of the core material 11 . Therefore, the core material 11 can be easily taken out. Curing of the surface layer portion of the core-constituting material filled in the core-arranging space 5a can be carried out in an appropriate manner according to the type of the cured resin constituting the core-constituting material. Some silicone-based or modified silicone-based moisture-curing resins cure at the surface layer in about 1 to 2 hours due to contact with air after being filled into the core arrangement space 5a. The surface layer portion of the core constituent material can be a portion extending from the opening on one end side or the opening on the other end side to a depth of 3 mm inside the core material arrangement space 5a along the direction of the central axis Cm. .
When the above-described clay is used as the core constituent material, the clay exhibits appropriate fluidity when filled into the core placement space 5a, and exhibits appropriate viscosity after filling, and remains in the recess 102. Therefore, in some cases, there is no need to take special measures to close the opening of the core material placement space 5a filled with clay. It can be subjected to inter-isostatic pressurization.

The resin mold 1 in which the core material 11 is arranged is preferably made of a thermoplastic resin, and is particularly preferably made of an acrylic resin, an acrylic resin containing an elastomer, a polylactic acid (PLA) resin, or the like. is. The resin mold 1 is preferably made of a thermoplastic resin having a Shore D hardness within the range of 30 to 120 in order to secure the required strength and maintain its shape even when the raw material powder is filled. It may be a thermoplastic resin within the range of ∼85. Shore D hardness can be measured by a test method conforming to JIS K7215 (1986). From the same point of view, it is preferable that the resin mold 1 has a thickness of 0.5 mm to 2.0 mm.

Although the resin mold 1 can be produced by various methods, it is preferably produced using a three-dimensional modeling apparatus (so-called 3D printer). Thereby, the mold 1 of various shapes can be easily produced. The modeling method of the three-dimensional modeling apparatus is not particularly limited, and may be, for example, a stereolithography method, an inkjet method, an inkjet powder lamination method, a powder sintering lamination method, a hot-melt lamination method, or a powder fixing method.

In addition to the mold 1 shown in FIGS. 1 to 3, for example,

molds

21, 31, 41, 51, 61, 71, and 81 illustrated in FIGS. 7 to 13 can also be used.

The concave portions of the titanium-based green powder produced by the

molds

21 and 31 of FIGS. It has a shape in which the width changes at least partially in the axial direction, and the mode of width change is different from that of the concave portion 102 of the titanium-based compact 101 formed by the mold 1 in FIGS. .

In the mold 21 shown in FIG. 7, the core material placement space 25a defined inside the inner cylindrical wall portion 25 is positioned at one end side and the other end side of the outer cylindrical wall portion 23, and has wide openings. , and a narrow portion that is narrow relative to the wide portion and is provided between the wide portions. Each wide portion and the narrow portion are communicated with each other via a step. As a result, the titanium-based powder compact molded by the mold 21 in FIG. , and includes a narrow portion extending between the wide portions.

In the mold 31 shown in FIG. 8, the inner cylindrical wall portion 35 has a wide portion provided in a substantially central region in the direction of the central axis Cm and an outer cylindrical wall portion separated from the wide portion in the direction of the central axis Cm. A core material placement space 35a having narrow width portions that are positioned on both sides of the portion 33 on one end side and on the other end side and are respectively opened is defined. The recessed portion of the titanium-based powder compact formed by the mold 31 includes a narrow width portion connected to each opening on one end surface side and the other end surface side, and a stepped portion on the inner surface around the center region between the narrow width portions in the central axis direction. and a wide portion of which the width increases through.

The titanium-based green compact molded by the mold 41 of FIG. 9 also has a shape in which the width of the concave portion changes at least partially in the direction of the central axis. It has a tapered shape in which the width gradually decreases toward the opening on the end face side. It can be said that this concave portion also includes a relatively wide width portion on the side of the opening on the one end surface side and a relatively narrow width portion on the side of the opening on the other end surface side. Correspondingly, the inner cylinder wall portion 45 of the mold 41 has a core material placement space 45a whose width gradually decreases from one end side to the other end side of the outer cylinder wall portion 43 .

In the mold 51 shown in FIG. 10, the center axis Cm of the core material arrangement space 55a having a constant width is crossed at three points in the width direction (horizontal direction in FIG. 10) between one end side and the other end side. It alternately bends and meanders in the direction of protruding outward. The recessed portion of the titanium-based green compact thus formed has a shape including the curved portion of the central axis of the recessed portion.
In the mold 61 of FIG. 11, the core material arrangement space 65a has a constant width and has a central axis Cm like a crank which is bent at right angles at two points on the way from one end to the other end. The concave portion of the titanium-based compact that can be molded by the mold 61 includes two curved portions of the central axis.
Note that the numbers, curvatures, angles, and other aspects of curved portions and bent portions in FIGS. 10 and 11 can be changed as appropriate.

In the above description, a mold for manufacturing a titanium-based green compact having a through-hole-shaped recess extending from the opening on one end surface to the opening on the other end surface has been described, but the mold 71 in FIG. is to manufacture a titanium-based green compact having non-penetrating recessed recesses. In this mold 71, the core material arrangement space 75a is recessed from the annular wall portion 74 on the one end side of the outer cylinder wall portion 73 in the cross section shown in the drawing, and the width of the one end portion of the outer cylinder wall portion 73 is It has a wide portion and narrow portions at both ends separated from the center of the deepest portion in the width direction. The concave portion of the titanium-based compact formed by the mold 71 has a width that changes at the deepest portion, and includes a wide portion communicating with the opening on one end surface side and narrow portions on both sides in the width direction of the deepest portion. . It can also be said that this titanium-based green compact includes a bent portion of the central axis before the deepest portion of the concave portion.

In the mold 81 shown in FIG. 13, a core material placement space 85a penetrates from one end side to the other end side of the outer cylinder wall portion 83 and extends in the width direction along the way to open the outer cylinder wall portion 83. It is. In the core material arrangement space 85a, the portion extending in the width direction can be regarded as a wide portion where the width in the direction orthogonal to the central axis Cm is wide, and can also be regarded as a bending portion where the central axis Cm is bent at right angles. The concave portion of the titanium-based compact molded by the mold 81 has a narrow width portion connected to the opening portion on the one end surface side and the opening portion on the other end surface side, and a width difference between the narrow width portions via a step. and a wide portion that extends in the direction and opens to the outer peripheral surface. Further, the concave portion has a shape including a bent portion of the central axis in a portion transitioning from the narrow width portion to the wide width portion.

As described above, the recesses provided in the titanium-based green compact can be in the form of through holes or in the form of non-penetrating depressions having bottoms. Further, the number of concave portions of the titanium-based compact is not limited to one, and may be plural.

For example, when the titanium-based green compact is cut along the central axis, a specific cross section can be obtained. , resulting in cross-sections different from the above specific cross-sections. As described above, the titanium-based green compact has a large number of cross sections corresponding to the cutting positions. And those cross sections may have cross-sectional shapes different from each other. In this case, at least one of the many cross sections has a shape in which the width changes in at least part of the central axis direction of the recess and/or a curved portion of the central axis of the recess, as in the above example. And/or any shape that includes a bent portion is included in the present invention. Such recesses have a complicated shape, and in order to manufacture a titanium-based green compact having such recesses, the material forming the core is made to flow into the core arrangement space of the mold as in the embodiment of the present invention. It is effective to fill

When a titanium-based green compact or a titanium-based sintered body is produced by the method described above, various powders such as pure titanium powder, alloying element powder, and mother alloy powder are used in combination as needed as raw material powders. can be used. Here, the pure titanium powder means a powder mainly containing titanium, the alloy element powder means a powder containing a single alloy element such as a titanium alloy, and the master alloy powder means a powder containing a plurality of elements. Pure titanium powder may contain not more than 5% by mass of hydrogen in addition to titanium. The raw material powder can be, for example, only pure titanium powder, or pure titanium powder and one kind of alloy element powder selected from the group consisting of iron, aluminum, vanadium, zirconium, tin, molybdenum, copper and nickel. Alternatively, a mixture of master alloy powders containing two or more of these elements may be used. Alternatively, a powder containing titanium and an alloying element can be used as the raw material powder. It should be noted that pure titanium preferably has a titanium content of 99% by mass or more as a metal element. The mass ratio of metals in the raw material powder can be titanium:alloying element=100:0 to 75:25, and can be titanium:alloying element=90:10.

The average particle size of the raw material powder is preferably 10 μm to 150 μm. By using such relatively fine particles, titanium-based green compacts after cold isostatic pressing and compression of titanium-based sintered compacts after sintering or hot isostatic pressing can be obtained. Density can be improved. The average particle diameter means the particle diameter D50 (median diameter) of the particle size distribution (volume basis) obtained by the laser diffraction scattering method.
Known powders such as pulverized powders and atomized powders can be used as raw material powders.

By using such raw material powder, for example, titanium made of pure titanium, Ti-5Al-1Fe, Ti-5Al-2Fe, Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al -2Sn-4Zr-2Mo, Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al titanium-based compacts and titanium-based sintered bodies made of titanium alloys can be produced. In addition, titanium-based compacts and titanium-based sintered bodies made of titanium alloys such as Ti-3Al-2.5V can be produced. In the above description, the number before each alloy metal indicates the content (% by mass). For example, “Ti-6Al-4V” refers to a titanium alloy containing 6% by mass of Al and 4% by mass of V as alloying metals.

Next, the titanium-based green compact of the present invention was produced on a trial basis, which will be described below. However, the description herein is for illustrative purposes only and is not intended to be limiting.

<Test Example 1>
(Production method)
Using a 3D printer, a mold having a cylindrical outer contour and the shape shown in FIG. 11 was fabricated. The resin material forming the mold was polylactic acid (PLA) with a Shore D hardness of 83. The thickness of the mold was 1 mm. As shown in FIG. 11, the space for arranging the core material provided in the mold has a crank shape that is bent at two points on the way from one end to the other end of the mold in the cross section of the figure. This core material placement space has a square opening with a side length of 15 mm, and a cross-sectional shape orthogonal to the central axis is rectangular at any position from one end to the other end. rice field. The outer diameter of the cylindrical outer cylinder wall portion of the mold was set to 62 mm.

Using this mold, the core material is arranged in the core material arrangement space, the molding space is filled with raw material powder, the molding space is sealed, and cold isostatic pressing (CIP) is performed by hydrostatic pressurization. rice field. As the raw material powder, HDH pure titanium powder TC-150 (D50=66 μm) manufactured by Toho Tech Co., Ltd. was used. Table 1 shows the conditions of Examples 1-6 and Comparative Examples 1-6.

In Examples 1 to 6 and Comparative Examples 1 to 3, a PLA sheet was attached to the end face of one end of the mold (lower end of FIG. 11), and the opening of the core material arrangement space on the one end side was closed. Then, from the opening on the side of the other end (upper end in FIG. 11) into the space for arranging the core, a predetermined core constituent material was flowed and filled to form the core. As the core material, in Examples 1 and 2 and Comparative Example 1, a moisture-curable resin silicone sealant (Cemedine 8000 silicone sealant, manufactured by Cemedine Co., Ltd.) was used, and in Examples 3 and 4 and Comparative Example 2, clay (Kanto Air putty manufactured by Kizai Kogyo Co., Ltd.) was used, and in Examples 5 and 6 and Comparative Example 3, a mixing reaction curing type silicone resin (KE-12 manufactured by Shin-Etsu Chemical Co., Ltd.) was used.
In Comparative Examples 4 to 6, a core made of SUS as a core material and a split mold were used. More specifically, the mold is split along the cross section shown in FIG. The two halves were joined together by fitting the core into the space for arranging the core material in the other half. In Comparative Examples 4 to 6, since the core was used by combining three-part SUS prismatic materials, the opening of the mold was closed by pasting a PLA sheet after the adhesion.

The pressurization time by cold isostatic pressurization was 1 minute in any of Examples 1-6 and Comparative Examples 1-6.

(evaluation)
Regarding the ease of arranging the core material in the core material arrangement space of the mold, it was easy in Examples 1 to 6 and Comparative Examples 1 to 3 using the predetermined core material constituting material, but the core made of SUS was used. In Comparative Examples 4 to 6 used, the core could not be placed without dividing the mold. Therefore, Comparative Examples 4 to 6 were significantly inferior to Examples 1 to 6 and Comparative Examples 1 to 3 in ease of placement of cores. In other words, in the evaluation of ease of placement of cores, Comparative Examples 4 to 6 failed, and Examples 1 to 6 and Comparative Examples 1 to 3 passed.

The appearance of each titanium-based compact obtained in Examples 1 to 6 and Comparative Examples 1 to 6 (state of the outer surface not including the inner surface of the concave portion) was observed. Table 1 shows the results. Here, "⊚" means that there was no crack or split. "O" means that there was chipping at the edge of the outer surface, but there was no noticeable crack in the main portion of the outer surface. "X" means that there was a crack or split. As can be seen from Table 1, except for the titanium-based compact of Comparative Example 4, the external appearance was generally good.

For each of Examples 1 to 6 and Comparative Examples 1 to 6, the removability of the core material from the titanium-based compact after CIP was evaluated. Table 1 shows the results.
In a normal process for molding a green compact without using a core material, the sample after CIP is heated at about 100° C. to soften and remove the mold to obtain a green compact. On the other hand, in Examples 1 to 6 and Comparative Examples 1 to 6, since the core material was used, it was necessary to remove the mold and take out the core material depending on the material of the core material. was different between the examples and the comparative examples.
In Table 1, "⊚" means that the core material could be taken out at the same time as the mold was removed. Such ease of taking out the core material is due to the fluidity of the core material even after molding of the titanium-based compact. "O" means that a green compact was obtained through a two-step process of taking out a certain amount of the core material and then peeling off the mold. The reason why the mold could not be removed without taking out a certain amount of the core material was that the core material, which had fluidity at the time of placement, had completely hardened. "X" means that it was impossible to take out the core material while maintaining the shape of the green compact. In Examples 5 and 6 and Comparative Example 3, since the inside of the core material was completely hardened, the removability was evaluated as "Good".

In order to evaluate the moldability of the recess, each titanium-based green compact was cut along the central axis so that the cross section shown in FIG. was formed. In Table 1, "o" means that the corner was right-angled, and "x" means that the corner was chipped or chamfered. As shown in Table 1, all of the titanium-based compacts of Examples 1 to 6 had good corner portions. On the other hand, the titanium-based compacts of Comparative Examples 1 to 6 had chipped or chamfered corners. In Comparative Examples 4 to 6, the core material could not be separated unless the titanium-based green compact was dismantled, so it can be said that these are examples in which the formation of the desired concave portions in the production of the titanium-based green compact failed.

<Test Example 2>
As a raw material powder, a mixed powder obtained by mixing the above HDH pure titanium powder and a 60Al-40V mother alloy powder (D50 = 55 µm, pulverized powder) at a mass ratio of 9:1 was used to obtain Ti-6Al-4V. A titanium-based green compact was produced. Other manufacturing conditions were the same as in Example 2. This titanium-based compact was evaluated for appearance, core removal efficiency, and recess moldability in the same manner as in Test Example 1. "A" and moldability of the concave portion were "O".

As raw material powders, the above HDH pure titanium powder, aluminum atomized powder (D50 = 30 µm), and iron spherical powder (D50 = 30 µm) were mixed at a mass ratio of 94:5:1. Using the powder, a Ti-5Al-1Fe titanium-based compact was produced. Other manufacturing conditions were the same as in Example 2. This titanium-based compact was evaluated for appearance, core removal efficiency, and recess moldability in the same manner as in Test Example 1. "A" and moldability of the concave portion were "O".

1, 21, 31, 41, 51, 61, 71, 81

mold

2, 22, 32, 42, 52, 62, 72, 82

molding space

3, 23, 33, 43, 53, 63, 73, 83 outer

cylinder Wall portions

4, 24, 34, 44, 54, 64, 74, 84

Annular wall portions

5, 25, 35, 45, 55, 65, 75, 85 Inner

cylinder wall portions

5a, 25a, 35a, 45a, 55a, 65a , 75a, 85a core material arrangement space 6a sealing member 6b disk-shaped member 11 core material 101 titanium-based powder compact 102

concave portion

102a, 102b opening 102c stepped portion 102d wide portion 102e narrow portion 111 injection device Cm of core material arrangement space Central axis Cc Central axis of recess Wa, Wb Width

Claims

A method for producing a titanium-based compact having recesses, comprising:
The concave portion of the titanium-based compact has a shape in which the width changes in at least part of the central axis direction of the concave portion in one or more cross sections including at least part of the central axis of the concave portion, and/or , having a shape including a curved portion and/or a bent portion of the central axis of the recess,
A step of filling a core material arranging space corresponding to the recess in a resin mold by flowing a material constituting the core, and arranging a core material having a shape corresponding to the recess;
filling the molding space of the mold with raw material powder;
In a state where the core material is arranged in the core material arrangement space, the mold filled with the raw material powder in the molding space is subjected to cold isostatic pressurization with a hydrostatic pressure of 300 MPa or more. A method for producing a titanium-based compact, comprising:
the inner surface of the recessed portion of the titanium-based compact includes a stepped portion,
2. The method for producing a titanium-based compact according to claim 1, wherein said core material placement space includes a step.
wherein the recessed portion of the titanium-based green powder includes a wide portion having a relatively wide width and a narrow portion having a relatively narrow width with respect to the wide portion in at least one of the cross sections;
3. The titanium-based compact according to claim 1, wherein the core material arrangement space has a wide portion forming the wide portion of the recess and a narrow portion forming the narrow portion of the recess. manufacturing method.
The method for producing a titanium-based green compact according to any one of claims 1 to 3, wherein a cured resin or clay is used as the core constituent material.
using the cured resin as the core constituent material,
When the core material constituting material is filled in the core material arranging space, at least the core material composing material fills the opening on the one end side or the opening on the other end side of the core material arranging space used for injecting the core material composing material. 5. The method for producing a titanium-based compact according to claim 4, wherein the existing surface layer portion is hardened.
The method for producing a titanium-based compact according to any one of claims 1 to 5, wherein a mold made of a thermoplastic resin having a Shore D hardness within the range of 30 to 120 is used as the mold.
The method for producing a titanium-based compact according to any one of claims 1 to 6, wherein a mold manufactured using a three-dimensional modeling apparatus is used as the mold.
The method for producing a titanium-based compact according to any one of claims 1 to 7, wherein a pressure of 400 MPa or more is applied to the mold by the cold isostatic pressing.
A method for producing a titanium-based sintered body, comprising:
A step of sintering and/or hot isostatically pressing the titanium-based compact produced by the method for producing a titanium-based compact according to any one of claims 1 to 8. , a method for producing a titanium-based sintered body.