JP5127185B2 - Method for producing metal composite - Google Patents

Description

  The present invention relates to a method for producing a metal composite in which a metal dense portion and a metal porous portion are integrated.

  Porous materials are used in various fields such as artificial bones and filters. And since a metal porous body has high mechanical strength and elastic modulus compared with the thing made from ceramics or resin, it is preferably used for the site | part which requires a big load.

However, even if it is a metal, if a porous body is used alone, corners and ridge lines are missing, damage is likely to occur, and reliability is poor.
Therefore, an object of the present invention is to provide a metal composite having both the properties of a porous body and the properties of a dense body.

In order to solve the problem, the method for producing the metal composite of the present invention comprises:
A metal powder compact a containing no or a small amount of a pore-forming agent composed of ammonium bicarbonate adjusted in particle size, a pore-forming agent consisting of a metal powder of the same or different kind from the metal powder and ammonium carbonate adjusted in particle size In combination with a molded body b of a mixture containing a large amount, the molded body a is filled in a mold, the mixture is filled in the remaining space, and pressure molding is performed at a pressure of 20 to 100 MPa. , combined molding and simultaneously molded article a molded body b, corners or ridges of the metal complex is characterized Rukoto formed by moldings a.
By this method, the portion derived from the molded body a does not contain a pore-forming agent or a relatively small amount even if it contains it, so that it becomes a relatively dense portion after firing. Since the part derived from the molded body b contains a relatively large amount of pore-forming agent, it becomes a porous part after firing. And since the molded object a and the molded object b are combined and fired together, the particles in each molded object are sintered together, and at the same time, the particles in the molded object a and the particles in the molded object b are interfaced. Sintering. Therefore, the dense portion and the porous portion are joined without any other objects except for the transition layer.

The individual molding means for the molded body a may be known appropriate means such as injection molding, pressure molding, extrusion molding, casting molding, sheet molding, and the like. Moldings b is a shaped body a is loaded into the mold, filling the powder mixture into the remainder space, by pressure molding, is combined with simultaneously molded body a and the molding. This is because even if the molded body a has a complicated shape, it can be combined with the molded body b .

  One or both of the molded body a and the molded body b may contain an organic binder, and the organic binders in the case of containing both may be the same as or different from each other. When both include a binder, the pressure molding may be performed at a temperature at which the binder softens. This is because the particles at the interface are more closely adhered to each other in the molding stage, and the sintering is likely to proceed.

  According to the method of the present invention, it is possible to flow in and out of gas and liquid like a porous body, and at the same time, a composite having high strength and high elastic modulus like a dense body can be obtained.

As an organic binder, it consists of polyacetal 0-50 vol%, polypropylene 0-50 vol%, and waxes 50-70 vol%. Pressure when the molded product a was charged into a mold, filled with a powder mixture comprising a molded body b on the remainder space, pressure molding is 20～100MPa. This is because if the pressure is less than 20 MPa, the bonding between the porous portion and the dense portion is insufficient, and if it exceeds 100 MPa, the load applied to the molded body a exceeds the strength of the molded body a, causing deformation and breakage. When an organic binder is contained and molded, it is desirable to degrease the organic binder by heating in the air before firing the combination. When pre-sintering the molded body whose metal is titanium, it is heated at a temperature of 800 to 1000 ° C. in a non-oxidizing atmosphere. And this sintering is performed at the temperature of 1200-1400 degreeC in non-oxidizing atmosphere.

[Example 1]
JIS type 2 (corresponding to US standard ASTM G1) having a maximum particle size of 45 μm. Pure titanium powder and ammonium hydrogen carbonate powder adjusted to a particle size of 500-1500 μm with a sieve are mixed so that the volume ratio is 64:36. A mixture for the dense part was obtained. The volume ratio was calculated from each true density and weight. As shown in FIG. 1 (a), the mixture for the dense portion is filled in a mold having a cylindrical core in the center, and by applying a pressure of 95 MPa, the outer diameter is 25 mm × the inner diameter is 15 mm × the height is 25 mm. A cylindrical shaped product a1 was obtained.

  Separately, the pure titanium powder and ammonium hydrogen carbonate adjusted to a particle size of 250 to 500 μm with a sieve were mixed at a volume ratio of 35 to 65 to obtain a porous part mixture. As shown in FIG. 1 (b), the mixture is filled in the inner space of the molded body a1, and a pressure of 85 MPa is applied as shown in FIG. 1 (c), whereby a cylindrical molded body is formed inside the molded body a1. A combined body in which b1 was molded was obtained.

  This combination was fired by holding at 1250 ° C. for 2 hours in an argon gas atmosphere. Fig. 2 (a) shows a CT image obtained by obliquely photographing the obtained sintered body with respect to the axis of the cylinder, Fig. 2 (b) shows a CT image of a transverse section, and Fig. 2 (c) shows a CT image of a longitudinal section. ). As seen in FIG. 2, the cylindrical portion (porous portion) and the cylindrical portion (dense portion) are sintered with each other, and the particles at the interface with each other are also sintered. An integrated composite was obtained. A plurality of CT cross-sectional images of this composite were taken, and the maximum diameter in the fixed direction (maximum length of the void portion by a line in a fixed direction) was measured on the obtained image. It was in the range of ˜350 μm. When this composite was compressed in the axial direction at a compression rate of 1 mm / min, the compressive strength was 118 MPa. Molded bodies a1 and b1 were not combined and molded separately, fired under the same conditions as described above, and the porosity of the obtained sintered body was calculated from the weight and the true density of titanium. The porosity of the sintered body was 29.9%, and the porosity of the sintered body corresponding to the porous portion was 60%.

[Example 2]
Pure titanium powder of the same quality as that of Example 1 and an organic binder composed of 20% by volume of polyacetal, 20% by volume of polypropylene and 60% by volume of waxes were mixed at a volume ratio of 65 to 35 to obtain a mixture for a dense part. . Then, by molding the mixture for the dense part at 165 ° C., the outer dimensions in which the legs of the regular square column with the same width are set up at the four corners of the square frame part made of a regular square column with a width of 1.71 mm as shown in FIG. A molded product a2 having a size of 22.8 mm × 22.8 mm × 22.8 mm was obtained.

  Separately, the pure titanium powder and ammonium hydrogen carbonate adjusted to a particle size of 250 to 500 μm with a sieve were mixed at a volume ratio of 35 to 65 to obtain a porous part mixture. As shown in FIG. 4, by loading the molded body a2 into a mold whose inner dimension is slightly larger than the outer dimension of the molded body a2, filling the remaining space with the mixture for the porous portion, and applying a pressure of 85 MPa, A combination body was obtained in which a substantially rectangular parallelepiped shaped body b2 was molded inside the molded body a2.

  This combination was fired by holding at 1250 ° C. for 2 hours in an argon gas atmosphere. FIG. 5 shows a cross section near the interface between the porous portion and the dense portion of the obtained sintered body. In the cylindrical part (porous part) and cylindrical part (dense part), each particle is sintered, and the particles at the interface with each other are also sintered, resulting in a composite in which the dense part and the porous part are integrated. It was. The outer dimension of the composite was 20 mm × 20 mm × 20 mm. The pore diameter of the porous part was in the range of 100 to 350 μm. The compressive strength was 67 MPa. The compacts a2 and b2 were molded separately without being combined, fired under the same conditions as described above, and the density or porosity of the obtained sintered body was calculated. The density of the sintered body corresponding to the dense part was 96. %, The porosity of the sintered body corresponding to the porous portion was 60%.

[ Reference example ]
10. The outer dimension in which the leg of the regular square column having the same width is erected at the four corners of the square frame portion made of the regular square column having a width of 1.71 mm by injection molding the mixture for the dense part prepared in Example 2 at 165 ° C. Two compacts a3 of 6 mm × 12.4 mm × 17.5 mm were obtained.
Separately, the pure titanium powder and ammonium hydrogen carbonate adjusted to a particle size of 500 to 1500 μm with a sieve were mixed at a volume ratio of 34 to 66 to obtain a porous part mixture. A molded body b3 having an outer dimension of 10.4 mm × 12.2 mm × 34.2 mm was obtained by filling the mixture for a porous portion into a mold and performing pressure molding.
Next, the compact a3 and the compact b3 were pre-sintered by holding at 800 ° C. for 1.5 hours in an argon gas atmosphere. Then, as shown in FIG. 6, the molded body a3 was fitted from both ends in the longitudinal direction of the molded body b3 to obtain a combined body. This combination was fired by holding at 1250 ° C. for 2 hours in an argon gas atmosphere to produce a composite of 9.3 mm × 10.9 mm × 30.4 mm. The composite had a compressive strength of 81 MPa, and the pore diameter of the porous portion was in the range of 100 to 350 μm. Without combining the compacts a3 and b3, they were individually molded, fired under the same conditions as described above, and the density or porosity of the obtained sintered compact was calculated. The density of the sintered compact corresponding to the dense part was 97%. The porosity of the sintered body corresponding to the porous portion was 59%.

6 is a diagram for explaining a manufacturing method of Example 1. FIG. The CT image of the sintered compact cross section obtained in Example 1 is shown. It is a figure explaining the initial process of the manufacturing method of Example 2. FIG. It is a figure explaining the intermediate process of the manufacturing method of Example 2. FIG. 4 is a cross-sectional photograph of the vicinity of an interface between a dense portion and a porous portion of a sintered body obtained in Example 2. It is a figure explaining 1 process of the manufacturing method of a reference example .

Claims (2)

A metal powder compact a containing no or a small amount of a pore-forming agent composed of ammonium bicarbonate adjusted in particle size, a pore-forming agent consisting of a metal powder of the same or different kind from the metal powder and ammonium carbonate adjusted in particle size In combination with a molded body b of a mixture containing a large amount, the molded body a is filled in a mold, the mixture is filled in the remaining space, and pressure molding is performed at a pressure of 20 to 100 MPa. combines moldings b simultaneously with molding body (a) and the molding method for producing a metal composite corners and ridges of the metal complex, wherein Rukoto formed by moldings a.   The manufacturing method according to claim 1, wherein both the molded body a and the molded body b include an organic binder, and the pressure molding is performed at a temperature at which the organic binder is softened.

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