JP2022122764A - Manufacturing method of titanium-based porous body - Google Patents

Abstract

To provide a manufacturing method of a titanium-based porous body capable of obtaining a titanium-based porous body having a relatively uniform porosity and relatively high surface smoothness.SOLUTION: A method for producing a titanium-based porous body of the present invention comprises: a raw material deposition step of supplying titanium-based fibers 1 onto a mesh member 21, and causing the titanium-based fibers 1 on the mesh member 21 to drop from the mesh member 21 through only vibration of the mesh member 21 so as to be deposited onto a molding surface 11; and a raw material sintering step of sintering the titanium-based fibers 1 deposited in the raw material deposition step to obtain a titanium-based sintered body, in which an aspect ratio that is a ratio of a fiber length Lf to a fiber thickness Tf of the titanium-based fiber 1 supplied to the mesh member 21 in the raw material deposition step is 10 to 70, and as the mesh member 21 in the raw material deposition step, the mesh member 21 having a ratio of a length of a maximum dimension Lm of an opening of a mesh 22 to the fiber length Lf is 0.9 to 2.4 is used.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for producing a titanium-based porous material from titanium-based fibers.

A titanium-based porous body made of pure titanium or a titanium alloy may be manufactured by the method described in Patent Document 1 or 2, for example.

In Patent Document 1, for the purpose of "uniformly crushing and dispersing metal or inorganic material fibers, especially metal fibers, and filling them in a mold", "metal fibers are crushed, dispersed, and filled into a sheet form. A method for producing a porous body, characterized in that the metal fibers are supplied onto a sieve, and the metal fibers are pulverized, dispersed, and filled by sieving while intermittently applying pressure to the metal fibers. A method for manufacturing a sheet-like porous body” has been proposed.

In Patent Document 2, "the cross section is a polygon, the long edge that is the longest side of the polygon is 200 μm or less, the ratio of the short edge that is the shortest side to the long edge is 0.5 or less, and the total length is 1 to 1. A method for producing a sintered porous titanium body characterized by compressing titanium fibers having a length of 5 mm and an aspect ratio of 20 to 200, and sintering the obtained compression-molded body.

JP 2007-246966 A JP 2012-172179 A

A titanium-based porous material can be used, for example, as a gas diffusion layer or electrode for electrolysis of water, or as a decoration used in lighting fixtures and the like. In such applications, uniform porosity and high surface smoothness of the titanium-based porous material are sometimes required in order to achieve required air permeability, liquid permeability, aesthetic appearance, and the like.

In the manufacturing method described in Patent Document 1, "metal fibers are sieved while intermittently applying pressure", so the action of the pressure causes the titanium-based fibers, which are "metal fibers", to bend and deform. Sometimes. In this case, the porosity of the titanium-based porous material obtained after sintering becomes uneven at the deformed portions of the titanium-based fibers, and unevenness occurs on the surface of the titanium-based porous material, which impairs smoothness. Therefore, there is room for improvement in the surface properties of the titanium-based porous material to be produced in the production method described in Patent Document 1.

Further, in the production method described in Patent Document 2, since the titanium-based fibers are compressed before sintering, the titanium-based fibers are partially crushed at that time, and the porosity of the titanium-based porous body varies. It is feared that it will occur. Therefore, the manufacturing method described in Patent Document 2 has room for improvement in controlling the porosity of the manufactured titanium-based porous body.

An object of the present invention is to provide a method for producing a titanium-based porous body that can obtain a titanium-based porous body having relatively uniform porosity and relatively high surface smoothness.

In order to make the porosity of the titanium-based porous material relatively uniform and improve the surface smoothness, the titanium-based fibers supplied onto the mesh-like member are vibrated without pressurization during the production thereof. That is, it is considered effective to cause the titanium-based fibers to fall from the mesh member onto the molding surface only by the vibration of the mesh member and deposit them thereon. However, titanium-based fibers are sometimes agglomerated as described in Patent Document 1, and such agglomerates are difficult to pass through the mesh member. On the other hand, as a result of extensive research, the inventors found that by adjusting the size and shape of the titanium fiber and the size of the mesh of the mesh member, it is possible to form aggregates of the titanium fiber without pressurizing the titanium fiber toward the mesh member. It was found that the powder passed through the mesh member while being crushed and deposited well on the molding surface.

In the method for producing a titanium-based porous body of the present invention, titanium-based fibers are supplied onto a net-like member, and only by vibration of the net-like member, the titanium-based fibers on the net-like member are transferred from the net-like member onto the molding surface. and a raw material sintering step for obtaining a titanium-based sintered body by sintering the titanium-based fibers deposited in the raw material depositing step. The aspect ratio, which is the ratio of the fiber length to the fiber thickness of the titanium-based fiber to be supplied, is 10 to 70, and in the raw material depositing step, the mesh member is used as the mesh member having the longest dimension of the opening of the mesh with respect to the fiber length. A net member having a length ratio of 0.9 to 2.4 is used.

The fiber length of the titanium-based fibers supplied onto the net-like member in the raw material deposition step is preferably in the range of 1.0 mm to 6.0 mm.

The porosity of the titanium-based porous body is preferably 60% to 95%.

It is preferable that the method for producing a titanium-based porous body of the present invention further includes a surface oxidation step of oxidizing the surface of the titanium-based sintered body after the raw material sintering step.

The thickness of the titanium-based porous body is preferably within the range of 0.1 mm to 5.0 mm.

In some cases, the titanium-based porous body production method of the present invention can produce a titanium-based porous body having a surface roughness Rz of 100 μm or less on at least one surface.

According to the method for producing a titanium-based porous body of the present invention, a titanium-based porous body having relatively uniform porosity and relatively high surface smoothness can be obtained.

FIG. 4 is a schematic diagram showing a method for determining whether or not titanium-based fibers are bent fibers. 1 is a cross-sectional view along the vertical direction schematically showing a raw material depositing step in a method for producing a titanium-based porous body according to an embodiment of the present invention; FIG. 3 is a partially enlarged plan view showing an example of a mesh member that can be used in the raw material depositing step of FIG. 2. FIG. FIG. 11 is a plan view showing meshes of a mesh member of another example; FIG. 2 is a plan view showing a sectioned region when evaluating the porosity distribution of the titanium-based porous material produced in Examples.

Embodiments of the present invention will be described in detail below with reference to the drawings.
In a method for producing a titanium-based porous material according to one embodiment of the present invention, titanium-based fibers are supplied onto a mesh member, and only by vibration of the mesh-like member, the titanium-based fibers on the mesh-like member are removed as described above. A raw material depositing step of dropping and depositing the material from the mesh member onto the forming surface, and a raw material sintering step of sintering the titanium-based fibers deposited in the raw material depositing step to obtain a titanium-based sintered body are included.

Here, it is assumed that the titanium-based fibers supplied onto the net-like member in the raw material deposition step have an aspect ratio of 10 to 70, which is the ratio of fiber length to fiber thickness. In the mesh member used in the raw material deposition step, the ratio of the length of the longest opening of the mesh to the fiber length is 0.9 to 2.4. In this case, even if some of the titanium-based fibers are agglomerated, the titanium-based fibers on the net-like member are not pressurized toward the net-like member but vibrated only by vibrating the net-like member. It becomes easier to pass through the mesh of As a result, even if the titanium-based fibers on the mesh-like member are not pressurized toward the mesh-like member, many titanium-based fibers are deposited on the molding surface. bending deformation is suppressed, and the titanium-based fibers are well deposited on the molding surface. As a result, it is possible to produce a titanium-based porous body having a relatively uniform porosity and high surface smoothness.

(Titanium fiber)
Titanium-based fibers contain titanium, and are made of, for example, pure titanium or a titanium alloy. The titanium content of the titanium-based porous body may be 75% by mass or more, regardless of whether it is made of pure titanium or a titanium alloy.

When the titanium-based fiber is made of pure titanium, it can have a purity corresponding to pure titanium types 1 to 4 of JIS H4600 (2012). The titanium content (purity) of the titanium-based fiber may be, for example, 98% by mass or more, typically 99.0% to 99.8% by mass.

In the case of titanium-based fibers made of titanium alloy, the titanium alloy contains at least Ti, Fe, Sn, Cr, Al, V, Mn, Zr, Mo, platinum group (Pt, Pd, Ru, etc.), Ni, etc. It is an alloy with one kind of metal. Specific examples include Ti-6-4 (Ti-6Al-4V), Ti-5Al-2.5Sn, Ti-8-1-1 (Ti-8Al-1Mo-1V), Ti-6-2-4 -2 (Ti-6Al-2Sn-4Zr-2Mo-0.1Si), Ti-6-6-2 (Ti-6Al-6V-2Sn-0.7Fe-0.7Cu), Ti-6-2-4 -6 (Ti-6Al-2Sn-4Zr-6Mo), SP700 (Ti-4.5Al-3V-2Fe-2Mo), Ti-17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr), β-CEZ ( Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe), TIMETAL555, Ti-5553 (Ti-5Al-5Mo-5V-3Cr-0.5Fe), TIMETAL21S (Ti-15Mo-2.7Nb-3Al-0. 2Si), TIMETAL LCB (Ti-4.5Fe-6.8Mo-1.5Al), 10-2-3 (Ti-10V-2Fe-3Al), Beta C (Ti-3Al-8V-6Cr-4Mo-4Cr ), Ti-8823 (Ti-8Mo-8V-2Fe-3Al), 15-3 (Ti-15V-3Cr-3Al-3Sn), Beta III (Ti-11.5Mo-6Zr-4.5Sn), Ti-13V Titanium alloys such as -11Cr-3Al may be mentioned. In the specific examples of the alloys described above, the number added before each metal element represents the content (% by mass) of the metal element. For example, "Ti-6Al-4V" means a titanium alloy containing 6 wt% Al and 4 wt% V as alloying elements. In the case of titanium-based fibers made from titanium alloys, the titanium content of the titanium-based fibers may be, for example, 75% to 97% by weight, typically 85% to 97% by weight.

Titanium-based fibers are fibrous, and more specifically, have an aspect ratio (Lf/Tf) of 10-70, which is the ratio of fiber length Lf to fiber thickness Tf. If the aspect ratio (Lf/Tf) of the titanium-based fiber is within the range of 10 to 70, and a net-like member having a mesh with a predetermined opening is used in the raw material deposition step described later, the titanium-based fiber can pass through the net-like member. and deposits well on the molding surface. From this point of view, the aspect ratio (Lf/Tf) of the titanium-based fiber is preferably 20-50. In addition, when the aspect ratio (Lf/Tf) of the titanium-based fibers is less than 10, the titanium-based fibers tend to pass through the mesh member excessively, and in some cases, the titanium-based fibers may pass through the mesh-like member before clumps (agglomeration) of the titanium fibers are loosened. As a result, the variation in porosity in the titanium-based sintered body increases. If the aspect ratio (Lf/Tf) of the titanium-based fibers exceeds 70, the titanium-based fibers are too long to pass through the mesh member with difficulty, resulting in large variations in porosity in the titanium-based sintered body.
The aspect ratio (Lf/Tf) here is calculated by measuring the fiber thickness and fiber length of each titanium-based fiber with a scanning electron microscope (SEM) and calculating the ratio of the fiber length to the fiber thickness. It means the average aspect ratio of each titanium-based fiber. With a scanning electron microscope, for each of 100 titanium-based fibers, the fiber length is the longest straight line distance between any two points on the contour line of the titanium-based fiber. The longest linear distance between two points is measured as the fiber thickness. An average value is obtained from the measured fiber length and fiber thickness of each fiber, and the average value is defined as the length of the titanium-based fiber and the thickness of the titanium-based fiber, respectively.

The fiber length Lf of the titanium-based fiber is preferably within the range of 1.0 mm to 6.0 mm, more preferably within the range of 1.5 mm to 4.0 mm. If the fiber length Lf is within such a range, in relation to the opening of the mesh of the mesh member used in the raw material deposition step described later, the fiber can be placed on the vibrating mesh member in a relatively short time. Aggregation of the titanium-based fibers is eliminated, and the titanium-based fibers easily pass through the mesh member. In addition, as a result, the porosity of the titanium-based porous body becomes excellently uniform. The fiber length Lf of the titanium-based fibers is the average value of the fiber lengths of the respective titanium-based fibers measured when obtaining the aspect ratio described above.

The titanium-based fibers as described above can be produced, for example, by applying a coil cutting method, a chatter vibration cutting method, or the like to a titanium-containing lump or plate. In this case, it is easy to obtain a fibrous powder instead of a spherical powder, which can be favorably used as the titanium-based fiber.

It is preferable that the ratio of bent fibers in the titanium-based fibers is 7% or less based on the number of fibers. When the proportion of bent fibers is thus small, the portion of fibers that can protrude from the surface of the titanium-based porous body is reduced, so that the titanium-based porous body has a higher surface smoothness. Here, whether or not the titanium-based fibers are bent fibers is determined as follows. Observing the titanium-based fiber with an optical microscope, as shown in FIG. do. Then, of the perpendicular line perpendicular to the line segment LS1 connecting the end points Pe1 and Pe2, from the line segment LS1 to a point on the outer contour line of the titanium-based fiber 1 on the outside of the perpendicular direction (the side away from the line segment LS1) Let LS2 be the perpendicular line segment with the longest distance. If the ratio (L2/L1) of the length L2 of the longest perpendicular line segment LS2 to the length L1 of the line segment LS1 between the end points Pe1 and Pe2 is 0.1 or more, the titanium-based fiber 1 is a bent fiber We judge that it is. In addition, as shown in FIG. 1(b), the titanium-based fiber 1a branches into two or more on the way and has one or more end points Pe3 in addition to the two end points Pe1 and Pe2 (that is, three or more end points). Even with the titanium-based fiber 1a) having Pe1, Pe2 and Pe3, the ratio (L2/L1) is calculated using the minimum inclusive circle Cmin in the same manner as the titanium-based fiber 1 having only two end points Pe1 and Pe2. Then, it is determined whether or not it is a bent fiber. If the titanium-based fiber has three or more end points on the minimum inclusive circle, the above determination is not made, and such titanium-based fiber is regarded as a folded fiber.

When bent fibers are included in the titanium-based fibers, the bent fibers are not considered in the measurement of the aspect ratio (Lf/Tf) and the fiber length Lf described above. The aspect ratio (Lf/Tf) and the fiber length Lf of the titanium-based fiber remaining after removing the bent fiber and the replenishment portion to be added separately are determined by the method described above. For example, 100 samples are extracted from titanium-based fibers, and if bent fibers are included in them, the bent fibers are excluded from the sample, and the number of the removed fibers is supplemented to obtain bent fibers. Aspect ratio (Lf/Tf) and fiber length Lf can be measured for a sample that does not contain .

(Raw material deposition process)
In the raw material depositing step, the titanium-based fibers 1 are deposited on the forming surface 11 in a dry manner without using a binder or the like, as shown in FIG. At this time, for example, a mesh member 21 having meshes 22 through which the titanium-based fibers 1 pass is used as shown in FIG. More specifically, the titanium-based fibers 1 are supplied onto the mesh member 21 in a gas such as air or in a vacuum, and in that state, the mesh member 21 is vibrated, for example, as indicated by the arrows in FIG. , the titanium-based fiber 1 is passed through the mesh 22 of the mesh-like member 21, and the titanium-based fiber 1 is dropped from the mesh-like member 21 onto the molding surface 11 and deposited thereon.

The planar shape of the mesh 22 of the mesh member 21 is not particularly limited, and may be a polygonal shape, a perfect circle, an ellipse, or a circular shape including an oval. Here, regarding the dimensions of the mesh 22, the length Lm of the longest line segment Smax included in the mesh 22 and passing through the centroid Cm of the mesh 22 in plan view, the fiber length Lf of the titanium-based fiber 1 described above, is A net-like member 21 is used in which the dimensions of the mesh 22 are adjusted so that the ratio (Lm/Lf) to the .DELTA. The length Lm of the longest line segment in the mesh 22 is also referred to as the longest dimension Lm of the mesh opening.

By using the mesh member 21 having the meshes 22 having dimensions satisfying the above ratio (Lm/Lf), when the mesh member 21 is vibrated, the titanium-based fibers 1 on the mesh member 21 move the meshes 22 of the mesh member 21. Since it easily passes through and falls onto the molding surface 11 , the titanium-based fibers 1 can be favorably deposited on the molding surface 11 . At this time, it is not necessary to press the titanium-based fibers 1 on the mesh member 21 .

When dropping the titanium-based fibers 1 from the mesh member 21 onto the molding surface, it is sufficient to vibrate the mesh-like member 21 supplied with the titanium-based fibers 1 . At this time, since it is not necessary to intentionally apply pressure to the titanium-based fibers 1 on the net-like member 21 in the direction in which the titanium-based fibers 1 pass through the meshes 22 of the net-like member 21, bending deformation of the titanium-based fibers 1 does not occur. is suppressed. When the mesh member 21 has a flat plate-like outline shape, the direction in which the titanium-based fibers 1 pass through the mesh 22 corresponds to a direction orthogonal to the flat plate-shaped mesh member 21 . Preferably, when the titanium-based fibers 1 are dropped from the mesh member 21 , the titanium-based fibers 1 are not pressurized in a direction other than the direction in which the titanium-based fibers 1 pass through the mesh 22 .

As a result, most of the titanium-based fibers 1 that are almost straight without bending deformation are deposited on the molding surface 11, so that the sizes of the gaps between the titanium-based fibers 1 on the molding surface 11 are uniform. tend to be In addition, the bent and deformed titanium-based fibers are less likely to protrude from the deposition surface on the molding surface 11 . As a result, a titanium-based sintered body having a uniform porosity and secured surface smoothness can be obtained in the raw material sintering process described later.

When the ratio of the longest dimension Lm of the opening of the mesh 22 to the fiber length Lf of the titanium-based fiber 1 (Lm/Lf) is less than 0.9, the size of the mesh 22 is smaller than that of the titanium-based fiber 1. If it is too thick, it becomes difficult for the titanium-based fibers 1 to pass through the mesh 22 . If the above ratio (Lm/Lf) exceeds 2.4, the size of the meshes 22 is too large relative to the titanium-based fibers 1, so that the titanium-based fibers 1 easily pass through the meshes 22 excessively. In either case, the porosity tends to vary in the titanium-based sintered body. The ratio (Lm/Lf) of the longest dimension Lm of the opening of the mesh 22 to the fiber length Lf of the titanium-based fiber 1 is preferably 0.9 to 1.2.

As shown in FIG. 3, the mesh member 21 has square meshes 22 in plan view. However, the mesh member is not limited to this, and may have meshes of other quadrangular shapes such as triangles and rectangles, polygonal shapes with more corners than those, or circular shapes such as perfect circles, ovals, and ellipses. can do.

For example, the mesh 22a shown in FIG. 4(a) has an equilateral triangular shape. In this mesh 22a, the length of a line segment that passes through one vertex Vm and the centroid Cm and is included in the triangle is the longest dimension Lm of the mesh opening. Line segments drawn from any vertex Vm through the centroid Cm have the same length, and all of them can be regarded as the longest line segment Smax.
FIG. 4(b) shows a mesh 22b having an isosceles trapezoidal shape in plan view. In this mesh 22b, the line segment passing through the vertex Vm on the base side of the isosceles trapezoid and the centroid Cm is the longest line segment Smax, and the length of the line segment Smax corresponds to the longest dimension Lm of the opening. .

In the perfectly circular mesh 22c shown in FIG. 4(c), the line segment Smax has the longest diameter. In the elliptical mesh 22d shown in FIG. 4D, the major axis is the longest line segment Smax.

The mesh member 21 may be provided with a plurality of meshes 22 as holes through which the titanium-based fibers 1 pass. The mesh member 21 may be a metal plate or the like having a large number of holes forming a mesh 22 (so-called punching metal or the like), but as shown in FIG. It is preferable that the meshes 22 as the holes are formed between the wire rods 23 by arranging them side by side. This is because adjacent holes are separated by a certain distance in the punching metal, so it may take time for the titanium-based fibers 1 to fall, and the raw material deposition process may be prolonged. Note that the mesh member 21 may be a sieve used for sieving. As in the example shown in FIG. 2 , the mesh member 21 can also be configured such that the periphery of the mesh portion is surrounded by the peripheral wall portion 24 . In this case, the peripheral wall portion 24 prevents the titanium-based fibers 1 on the mesh member 21 from falling unintentionally from the periphery of the mesh portion. The net-like member 21 may have a flat plate shape, or may have a curved surface at least partially. When curved surfaces are included, the longest dimension of the opening shall be measured after making it into a flat plate.

The vibrating direction of the mesh-like member 21 is often set substantially parallel to the forming surface 11 on which the titanium-based fibers 1 are deposited (horizontal direction, etc.). It can be in any direction. Vibration of the mesh member 21 can be performed manually or may be performed using a device. The drop height, which is the distance between the lower surface of the mesh portion of the mesh member 21 and the molding surface 11, can be, for example, 2 cm to 50 cm.

In depositing the titanium-based fibers 1 on the molding surface 11, a mesh member is formed above the molding surface 11 so that the titanium-based fibers 1 are deposited over the entire desired deposition area on the molding surface 11. 21 can be moved while being vibrated. The mode of movement of the mesh member 21 on the upper side of the molding surface 11 can be appropriately set. While reciprocating between the sides, it can be gradually moved from one end of the deposition area to the other end to meander. The mesh member 21 may be moved such that the mesh member 21 passes the same deposition location on the forming surface 11 multiple times. However, it is preferable to set the deposited thickness of the titanium-based fibers 1 on the molding surface 11 to a predetermined thickness.

The molding surface 11 on which the titanium-based fibers 1 dropped from the mesh member 21 are deposited can be provided on a substantially flat mold 12 as shown in FIG. 2, for example. Although not shown, it is also possible to use a molding die in which side walls surrounding the molding surface are detachably provided integrally with the plate-like member or as separate members. The material of the mold 12 can be, for example, quartz, carbon, boron nitride, alumina, zirconia, magnesia, or the like.

Prior to depositing the titanium-based fibers 1, at least the deposition area of the titanium-based fibers 1 on the molding surface 11 is coated with a release layer containing boron nitride (BN) and/or titanium boride (TiB ₂ ) or the like. be able to. This facilitates the separation of the titanium-based sintered body from the molding surface 11 after sintering in the raw material sintering step. For mold 12 made of carbon, it is preferable to use a release agent containing boron nitride (BN).

When the titanium-based fibers 1 are dropped from the net-like member 21 and deposited on the forming surface 11, the time required for deposition is determined by the amount of the forming surface 11, assuming that the area of the forming surface 11 is 72,900 cm ² . It is preferably 10 to 25 minutes, more preferably 15 to 20 minutes per reference area.

(raw material sintering process)
After depositing the titanium-based fibers on the molding surface, the deposited titanium-based fibers are placed in a heating furnace, and a raw material sintering step is performed in which the titanium-based fibers are heated and sintered. Thereby, a sheet-like titanium-based sintered body is obtained. In many cases, the titanium-based fiber is placed in the heating furnace together with the mold, but the mold may not be placed in the heating furnace.

In the raw material sintering step, the titanium-based fibers are preferably heated to a temperature of 900° C. to 1100° C. for 1 to 3 hours in order to sufficiently sinter the deposited titanium-based fibers as a whole. When heating the titanium-based fibers, it is preferable to use a reduced pressure atmosphere such as a vacuum of about 10 ⁻² Pa to 10 ⁻⁴ Pa or an inert gas atmosphere such as argon gas. This can prevent excessive oxynitridation of the titanium-based fibers. Here, nitrogen gas shall not correspond to an inert gas.

When the titanium-based sintered body is obtained by heating the titanium-based fibers on the molding surface, the titanium-based sintered body may be separated from the molding surface. At this time, the release agent described above enables easy separation of the titanium-based sintered body. In addition, the titanium-based sintered body separated from the molding surface may be removed by cutting the outer edge portion, if necessary. Also, the thickness may be adjusted by pressing or rolling the titanium-based sintered body. The reduction ratio of press working or roll rolling is, for example, 60% or less, preferably 10 to 50%, more preferably 20 to 50%. The reduction ratio R is obtained from the thickness T1 before reduction (before pressing or rolling, etc.) and the thickness T2 after reduction (after pressing or rolling, etc.) from the following formula: R=100×(T1−T2)/T1. After pressing or rolling, sintering by heating may be performed. Sintering after pressing or rolling can be performed under the same conditions as the initial sintering described above.

The titanium-based sintered body thus obtained can be used as a titanium-based porous body. Alternatively, the titanium-based sintered body can be further subjected to the surface oxidation step described below, and the titanium-based porous body can be obtained after the surface oxidation step.

(Surface oxidation process)
In the surface oxidation step, the titanium-based sintered body can be oxidized by a known method such as anodization using a predetermined electrolytic bath. By setting appropriate electrolysis conditions in the oxidation treatment, the thickness of the oxide film layer covering the titanium-based sintered body can be adjusted. As a result, the titanium-containing fiber is colored in a predetermined color by the oxide film layer, and a titanium-based porous body exhibiting the desired aesthetic appearance is obtained.

The oxidation treatment is not limited to this, but can be performed, for example, as described below.
First, a titanium-based sintered body is subjected to degreasing treatment and pickling treatment. The degreasing treatment is performed to improve the wettability during the formation of the oxide film layer and to suppress color unevenness. A degreasing treatment can be performed using ethanol, acetone, or an alkaline solution. The pickling treatment is performed to make the surface roughness uniform and to remove smut. The pickling treatment may be performed once or multiple times. For example, a hydrofluoric acid-nitric acid mixture or a hydrofluoric acid-hydrogen peroxide aqueous solution can be used for pickling. By chelating and stabilizing titanium ions, a more uniform surface can be obtained, so it is preferable to perform pickling treatment using a hydrofluoric acid-hydrogen peroxide-based aqueous solution.
An oxidation treatment can then be carried out. An example of the oxidation treatment procedure is as follows. An aqueous solution of copper (II) sulfate is poured into a non-conductive electrolytic bath (made of plastic, glass, vinyl chloride, etc.). A cathode made of stainless steel or titanium is inserted inside the non-conductive electrolytic cell. A titanium-based sintered body is sandwiched between clips to form an anode, which is immersed in an aqueous solution of copper (II) sulfate. Adjust the voltage to produce the desired interference color and turn on the power. It is possible to change the color development by changing the voltage. After the oxide film layer is formed, the energization is stopped, and the titanium-based sintered body is taken out from the non-conductive electrolytic bath and washed with water. After washing with water, the surface may be coated as appropriate for the purpose of preventing discoloration.

(Titanium-based porous body)
The titanium-based porous body produced as described above contains titanium, for example, is made of pure titanium or a titanium alloy, and often has substantially the same composition as the titanium-based fiber described above. . The titanium content of the titanium-based porous body made of a titanium alloy may be 75% by mass or more. In some cases, the titanium-based porous body made of pure titanium has a titanium content of 98% by mass or more.

The titanium-based porous body has a sheet-like outer shape (outer contour) as a whole. The thickness of the sheet-like titanium-based porous body is, for example, within the range of 0.1 mm to 5.0 mm, typically 0.2 mm to 2.0 mm. The thickness of the titanium-based porous body can be measured using a thickness gauge such as Mitutoyo's ABS Digimatic Thickness Gauge 547-321.

The porosity of the titanium-based porous body is preferably 60% to 95%, more preferably 70% to 90%. The porosity ε of the titanium-based porous body is calculated from the apparent density ρ′ calculated from the volume and mass obtained from the width, length, and thickness of the titanium-based porous body, and the true density of the metal that constitutes the titanium-based porous body. Using ρ (for example, 4.51 g/cm ³ for pure titanium and 4.43 g/cm ³ for Ti-6Al-4V), it is calculated by the following formula.
ε=(1−ρ′/ρ)×100

The surface roughness Rz of at least one surface of the titanium-based porous body is preferably 100 μm or less, more preferably 85 μm or less. This ensures better surface smoothness. The surface roughness Rz of at least one surface of the titanium-based porous body may be, for example, 50 μm or more, typically 60 μm or more. The surface roughness Rz means the arithmetic mean roughness defined in JIS B0601 (2001), and is measured by Mitutoyo Surftest SJ-210.

In addition, the electrical conductivity of the titanium-based porous material is 2.0×10 ³ S/cm or more and 3.0×10 ³ S/cm or less, and further 2.4×10 ³ S/cm or more and 2.7×10 ³ It is preferably S/cm or less. This conductivity is measured by a Mitsubishi Chemical Analytech low resistivity meter MCP-T610 in accordance with JIS K7194.

A titanium-based porous body was experimentally manufactured by the manufacturing method of the present invention, and the effect thereof was confirmed. However, the description herein is for illustrative purposes only and is not intended to be limiting.

First, reference examples 1 and 2 shown in Table 1 were used to compare the properties of the deposited titanium-based fibers when the titanium-based fibers were not pressurized on the net-like member during deposition of the raw material and when the titanium-based fibers were pressurized. was subjected to a raw material deposition test.

In Reference Example 1, 30 g of titanium-based fiber was dropped from a height of 10 cm to 20 cm in a dry manner without pressurizing the titanium-based fiber on a sieve as a mesh member, and the titanium-based fiber was placed on a predetermined surface (deposition surface ) was deposited on.
In Reference Example 2, the titanium-based fibers placed on the sieve are pressed against the titanium-based fibers by rotating a pressing device having a flat plate having the same area as the mesh of the sieve, and the titanium-based fibers are removed from the sieve onto the deposition surface. It was the same as Reference Example 1, except that it was dropped on top in a dry manner.
In Reference Examples 1 and 2, a sieve having a circular outer contour and a square mesh in plan view was used.

As a result, the ratio of bent fibers in the titanium-based fibers before being placed on the sieve was 5.6%, whereas in Reference Example 2, as shown in Table 1, the ratio was 42.9%. and increased significantly. On the other hand, in Reference Example 1, the proportion of bent fibers in the titanium-based fibers remained unchanged at 5.6%. The ratio of bent fibers was calculated by the method described above.

From the above results, it was found that the number of bent fibers increased when pressurization was applied when dropping the titanium-based fibers from the sieve. When titanium-based fibers containing such bent fibers are heated and sintered, the bent fibers tend to protrude from the surface of the finally produced titanium-based porous body, and the surface smoothness is impaired. Conceivable. Therefore, in both the invention examples and the comparative examples described below, the titanium-based fibers were dropped on the sieve without being pressurized in the raw material deposition step.

Next, the raw material depositing step and the raw material sintering step described above were performed to produce a sheet-like titanium-based porous body having a substantially rectangular planar shape and a thickness of 0.3 mm. Table 2 shows the conditions of the titanium-based fiber and the mesh member used in the raw material deposition step.

In any of Invention Examples 1 to 5 and Comparative Examples 1 to 4, the titanium-based fibers were made of pure titanium with a titanium content of 99% by mass. In the raw material depositing step, the molding surface of a flat carbon mold (setter) was previously coated with boron nitride (BN) powder to form a mold release layer. After that, a side wall member is arranged around the molding surface, and 30 g of titanium-based fiber is dry-dropped from a height of 10 cm to 20 cm using a sieve from the upper side thereof, and the titanium-based fiber is placed on the side wall member on the molding surface. was deposited on the inner region of the The area of the molding surface was 99,225 cm ² , and the area of the deposition region of the titanium-based fibers inside the side wall member was 72,900 cm ² . In the raw material sintering step, the titanium-based fibers on the molding surface were heated to a temperature of 1000° C. for 3 hours to sinter the titanium-based fibers. After that, roll rolling was performed at a rolling reduction of 40%, and sintering was performed again under the same conditions as the above heating. Thus, a titanium-based porous body was obtained.

In Comparative Examples 2 and 3, it took 30 minutes or more to drop the titanium-based fibers from the sieve. . Therefore, in Comparative Examples 2 and 3, titanium-based porous bodies could not be obtained.

(Evaluation of smoothness)
The surface roughness Rz of each of the titanium-based porous bodies obtained in Invention Examples 1 to 5 and Comparative Examples 1 and 4 was measured by the method described above. Table 2 shows the surface roughness Rz of one randomly selected surface among the surface roughnesses Rz of both surfaces of the sheet-like titanium-based porous material. A surface roughness Rz of 100 μm or less was accepted. Furthermore, a surface roughness Rz of 85 μm or less was considered better. In the sheet-like titanium-based porous body produced using titanium-based fibers, the surface roughness of the surface located on the molding surface side tends to be approximately the same as the surface roughness of the surface on the back side. be. Therefore, here, the surface roughness Rz of one randomly selected surface was checked.

(Evaluation of porosity uniformity)
As indicated by broken lines in FIG. 5, a virtual quadrangle surrounding the titanium-based porous body 31 in a plan view was set, and the quadrangle was vertically and horizontally divided into 5 equal parts to set 25 divided regions Ap. Then, for each portion of the titanium-based porous body 31 in each partitioned region Ap, the porosity was obtained by the method described above, and the variation was calculated as the standard deviation σ. Table 2 shows the results. Porosity variation of 2.0% or less was considered acceptable.
In all cases, the porosity of each partitioned region Ap was within the range of 60 to 95%. In addition, since the average porosity of all the examples was within the range of 60 to 95%, the porosity of the titanium-based porous bodies produced was within the range of 60 to 95%.

(Evaluation of electrical conductivity)
The electrical conductivity of each of the titanium-based porous bodies of Invention Examples 1 to 5 was measured by the method described above. Table 2 shows the results. All invention examples showed good electrical conductivity.

(Surface oxidation)
When the titanium-based sintered body obtained by the above sintering was subjected to oxidation treatment by anodic oxidation under various conditions, red, yellow, blue, green, and purple titanium-based porous bodies were obtained. rice field. In this way, titanium-based porous bodies of various colors could be produced, and each exhibited a predetermined aesthetic appearance.

(Discussion)
The titanium-based porous bodies of Invention Examples 1 to 5 had high surface smoothness and small variation in porosity.
On the other hand, the titanium-based porous body of Comparative Example 1 exhibited a large variation in porosity. Further, the titanium-based porous body of Comparative Example 4 not only had a large variation in porosity, but also had a large surface roughness Rz and was inferior in surface smoothness. This is probably because in Comparative Examples 1 and 4, the ratio (Lm/Lf) of the longest dimension Lm of the sieve mesh to the fiber length Lf was too large. As described above, in Comparative Example 2 in which the aspect ratio of the titanium-based fibers was too large, and in Comparative Example 3 in which the ratio (Lm/Lf) of the longest dimension Lm of the mesh of the sieve and the fiber length Lf was small, the sieve It was extremely difficult for the titanium-based fibers to fall out of the mold, and a titanium-based porous body could not be produced.

As described above, according to the method for producing a titanium-based porous body of the present invention, it was found that a titanium-based porous body having relatively uniform porosity and relatively high surface smoothness can be obtained. .

Reference Signs List 1, 1a titanium-based fiber 11 molding surface 12 molding die 21 mesh member 22, 22a, 22b, 22c, 22d mesh 23 wire rod 24 peripheral wall portion 31 titanium-based porous body Cmin minimum containing circle Pe1, Pe2 end point LS1 line segment between end points LS2 Perpendicular line segment L1 Length of line segment between end points L2 Length of perpendicular line segment Cm Centroid of mesh Vm Vertex of mesh Smax Longest line segment passing through centroid of mesh Lm Longest dimension of opening Ap Section region

Claims (6)

A method for producing a titanium-based porous body, comprising:
a raw material depositing step of supplying titanium-based fibers onto a net-like member and causing the titanium-based fibers on the net-like member to fall from the net-like member onto a molding surface only by vibration of the net-like member;
a raw material sintering step of sintering the titanium-based fibers deposited in the raw material deposition step to obtain a titanium-based sintered body,
The aspect ratio, which is the ratio of the fiber length to the fiber thickness of the titanium-based fibers supplied onto the net-like member in the raw material deposition step, is 10 to 70,
A method for producing a titanium-based porous body, wherein in the raw material depositing step, a mesh member having a length ratio of the longest dimension of mesh openings to the fiber length of 0.9 to 2.4 is used as the mesh member. 2. The method for producing a titanium-based porous body according to claim 1, wherein the fiber length of the titanium-based fibers supplied onto the net-like member in the raw material depositing step is in the range of 1.0 mm to 6.0 mm. 3. The method for producing a titanium-based porous body according to claim 1, wherein said titanium-based porous body has a porosity of 60% to 95%. The method for producing a titanium-based porous body according to any one of claims 1 to 3, further comprising a surface oxidation step of oxidizing the surface of the titanium-based sintered body after the raw material sintering step. The method for producing a titanium-based porous body according to any one of claims 1 to 4, wherein the titanium-based porous body has a thickness in the range of 0.1 mm to 5.0 mm. The method for producing a titanium-based porous body according to any one of claims 1 to 5, wherein a surface roughness Rz of at least one surface of the titanium-based porous body is 100 µm or less.

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