JP7078969B2 - How to manufacture precision micromolded products of ultra-hard materials - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Announced on the web page of the exhibitor presentation at the 7th Ota Research and Development Fair on August 17, 2017. Corresponding address http: // www. pio-ota. jp / ota-r-and-d-fair / 7 / presentation. html

The present invention relates to a method for producing a precision micromolded product of an ultra-hard material.

Conventionally, cemented carbide, cermet, ceramics and other cemented carbide materials have been used as cutting tools and wear-resistant tools. Due to its hardness and heat resistance, it is expected to be applied as a stamp for pressing and branding iron, and because of its excellent wear resistance, it is resistant to scratches and wear, so it is expected to be applied as a decorative item. In addition, as parts for MEMS and micromachines, expectations for ceramic-based materials with excellent heat resistance and corrosion resistance that can withstand use in extreme environments are expected to increase in the future.

Conventionally, a molded product of a cemented carbide such as a cemented carbide, a cermet, or a ceramic is obtained by molding a raw material powder into an arbitrary shape by a mold and then firing. Further, in order to precision machine them into a complicated shape, various methods such as cutting / grinding using a diamond tool, laser machining, and electric discharge machining are used.

However, the above-mentioned ultra-hard material is a brittle material having both hardness and brittleness, and its processing requires a great deal of cost and time. Therefore, a method of performing a cutting process on the molded body before firing and then sintering (Patent Documents 1 and 2), or a method of temporarily firing the molded body, processing the obtained temporary baked body, and then performing the main firing. A method (Patent Document 3) has been proposed.

However, although the above method is effective for relatively large products, as the product dimensions become smaller and more fine and precise finishing is required, the shape during molding is deformed, cracked, and cracked. Problems, problems with dimensional accuracy of the final shape, etc. occur.

As existing techniques, a method of inserting metallic glass into a precision-machined mold and pressurizing it with a punch while keeping it above the glass transition point and below the crystallization temperature to obtain precision parts (Patent Document 3) and metal. A method for producing a metallic glass micropart (Non-Patent Document 1) has been proposed in which a single glass particle is used and directly molded by microviscosity flow processing. Amorphous materials such as oxide glass and metallic glass can easily viscously flow to every corner of the mold above the glass transition point.

However, such a flow of crystalline powder is not easy, and it is particularly difficult to give a shape to ceramics by the same method even at an ultra-high temperature near the melting point. In addition, as the dimensions of the product become smaller and the processing becomes finer and more precise, the problem of fluidity becomes more serious.

Japanese Unexamined Patent Publication No. 60-131861 Japanese Unexamined Patent Publication No. 61-97164 Japanese Unexamined Patent Publication No. 62-21257 Japanese Unexamined Patent Publication No. 2009-97084

Iron and Steel Vol.100 (2014) No. 8 p1006-1013

The present invention has been made in view of the above, and provides a novel manufacturing method for manufacturing a precision micromolded product of an ultra-hard material into dimensions as designed while suppressing the occurrence of cracks and cracks. The purpose is to do.

The present inventor has devised the following configuration as a result of diligently studying a new manufacturing method for manufacturing a precision micromolded product of an ultra-hard material to the dimensions as designed while suppressing the occurrence of cracks and cracks. However, it came to the present invention.

That is, according to the present invention, it is a method for producing a precision finely molded product of a cemented carbide selected from cemented carbide, cermet and fine ceramics, and is a step of filling the cavity of the die with the raw material powder of the cemented carbide. In the step of uniaxial pressure sintering of the raw material powder, a precise arbitrary uneven shape is formed on the surface, and the surface is made of graphite or glassy carbon , and is formed of a punch. A separately formed mold is placed in the die hole of the die on the punch that pressurizes the raw material powder, and after the uniaxial pressure sintering, the mold is removed with a sandpaper, a wire brush, or Alternatively, a manufacturing method characterized by being burned off is provided.

As described above, according to the present invention, there is provided a novel manufacturing method for manufacturing a precision micromolded product of an ultra-hard material into dimensions as designed while suppressing the occurrence of cracks and cracks.

The process chart of the manufacturing method of this embodiment. The figure which shows typically the process of the manufacturing method of this embodiment. The figure which shows typically the process of the manufacturing method of this embodiment. A photograph of a seal made of a tungsten carbide-based cemented carbide of Example 1. Photograph of a medal made of titanium carbide-based cermet of the second embodiment. Photograph of a micro gear made of zirconia ceramics of the third embodiment.

Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings.

Here, as an embodiment of the method for manufacturing a precision micromolded product of an ultra-hard material of the present invention, a method for producing a stamp made of an ultra-hard material will be described. In the following, the description will be given with reference to the process diagram shown in FIG. 1 and the schematic views shown in FIGS. 2 and 3 as appropriate.

FIG. 2A schematically shows step 1. In step 1, a mold material 12 having an uneven shape of an inscription formed on the surface thereof is produced. Specifically, after preparing the short columnar base material 10, the surface of the base material 10 is engraved to form a precise uneven shape representing a stamp (more accurately, a left-right inverted stamp).

The material of the base material 10 is preferably a heat-resistant material having sufficient hardness to function as a mold material and having free-cutting properties (that is, a material having good processability and excellent heat resistance). Examples of the free-cutting heat-resistant material include carbon-based materials such as graphite and glassy carbon and boron nitride-based materials whose strength and processability can be adjusted by adding a binder. The mold material 12 can be manufactured by hand-carving, mechanical engraving, laser engraving, or the like, or if the material is a conductive material, it can also be manufactured by electric discharge machining. In the present embodiment, a material 12 having a concave-convex shape having a minimum width of a concave portion or a convex portion of several hundred micrometers or less can be used as the mold material 12 with respect to the surface of the free-cutting base material 10.

FIG. 2B schematically shows step 2. In step 2, with the prepared mold material 12 placed on the lower punch 32 of the sintering device, the lower punch 32 is below the columnar through hole 22 (hereinafter referred to as the die hole 22) formed in the die 20. Insert from. The sintering device may be a hot press sintering device or a discharge plasma sintering device.

FIG. 2C schematically shows step 3. In step 3, the columnar cavity formed by the die hole 22 and the lower punch 32 is filled with the raw material powder 40 of the ultra-hard material, and then the upper punch 34 is fitted from above the die hole 22.

Here, as the ultra-hard material, a super hard alloy based on tungsten carbide (tungsten carbide-based super hard alloy), a cermet based on titanium carbide (titanium carbide-based cermet), alumina, zirconia, silicon carbide, and the like. Fine ceramics based on silicon nitride, boron carbide, etc. (alumina-based oxide ceramics, zirconia-based oxide ceramics, silicon carbide-based non-oxide ceramics, silicon nitride-based non-oxide ceramics, boron carbide-based non-oxide ceramics) , Or their composite materials and the like can be exemplified. The raw material powder 40 is a mixed powder of the above-mentioned base material and a binder (auxiliary agent), and in the present embodiment, when preparing this mixed powder, the fired body exhibits superplastic behavior in combination with the firing conditions. Adjust the powder so that.

FIG. 3A schematically shows step 4. In step 4, uniaxial pressure sintering is performed. Specifically, the upper punch 34 and the lower punch 32 are used in a state where the mold material 12 having the uneven shape of the stamp on one surface is arranged on the lower punch 32 with the other surface facing down. The raw material powder 40 is sintered while being pressurized in the uniaxial direction. As a result, a sintered body having an uneven shape on the bottom surface in the shape of a stamp is obtained.

Here, in performing uniaxial pressure sintering, it is necessary to set the sintering conditions so that the crystal grains in the fired product generate superplastic flow during firing together with the powder conditions of the raw material powder 40. .. Superplasticity is the enormous ductility of crystalline materials with fine crystal grains at high temperatures, and its development involves many parameters such as particle size, amount of auxiliaries and binders added, temperature, and pressure. .. In general, the smaller the grain size, the larger the amount of auxiliary agent or binder added, and the higher the temperature and pressure, the more superplastic flow can be obtained, but on the other hand, the addition of auxiliary agent and binder The larger the amount and the higher the temperature, the easier it is for the growth of crystal grains to occur during firing. Therefore, it is necessary to select the optimum combination of parameters that can exhibit superplasticity while suppressing the growth of crystal grains.

For example, when a sintered body of a tungsten carbide-based cemented carbide is produced using a standard sintering device, the firing conditions are arbitrarily set by combining various parameters within the range shown in (1) to (4) below. be able to.
(1) Tungsten carbide particle diameter: 0.1-10 μm
(2) Cobalt addition amount: 1-30 wt%
(3) Firing temperature 900-1600 ° C.
(4) Pressure 10-100MPa

FIG. 3B schematically shows step 5. In step 5, after the sintered body 50 is taken out from the die 20, the mold material 12 fixed to the bottom surface of the sintered body 50 is removed. Here, when the mold material 12 is graphite, it can be finished by sandblasting after removing the lumps with sandpaper or a wire brush. When the sintered body 50 is ceramic, the mold material 12 can be burned off by heating at 700 ° C. or higher in the atmosphere.

FIG. 3C schematically shows step 6. In step 6, a finishing process is performed as necessary. Specifically, after grinding the outer peripheral surface of the sintered body 50, a mirror finish is performed by polishing.

As described above, as one embodiment of the present invention, a method for manufacturing a stamp made of an ultra-hard material has been described, but it goes without saying that according to the present invention, not only a stamp but also a whole precision finely molded product can be manufactured.

Examples of the precision micromolded product of the ultra-hard material that can be manufactured by the present invention include MEMS parts, industrial parts, stamps for pressing, decorative parts, and the like. When manufacturing these precision micromolded products, instead of the above-mentioned stamp, a mold material having an arbitrary precise uneven shape formed on the surface may be prepared.

As described above, according to the present invention, it is possible to manufacture a precision micromolded product of an ultra-hard material having an arbitrary shape with dimensions as designed while suppressing the occurrence of cracks and cracks. Become. In addition, according to the present invention, it is only necessary to precision-process a base material having good workability to produce a mold material, and it is not necessary to process an ultra-hard material having extremely poor processability at a high cost. It is possible to inexpensively manufacture precision micromolded products made of hard materials.

(Example 1)
A seal made of a tungsten carbide-based cemented carbide was produced using the production method of the present invention. In this experiment, a mixed powder in which WC powder having a particle size of 0.1 μm and Co powder having a particle size of 1 μm were mixed at a weight ratio of 9: 1 was used as the raw material powder, and graphite was used as the mold material. Then, uniaxial pressure sintering (vacuum, temperature rise: 50 ° C./min, 1000 ° C. 50 MPa, held for 3 minutes) was performed with a discharge plasma sintering apparatus.

FIG. 4 shows a photograph of a stamp produced in this experiment. As shown in FIG. 4, the outer peripheral surface of the produced stamp had a beautiful metallic luster, and there was no crushing or chipping of the stamp on the stamp surface.

(Example 2)
A medal made of titanium carbide-based cemented carbide was produced using the production method of the present invention. In this experiment, a mixed powder in which TiC powder having a particle size of 0.7 μm and Ni powder having a particle size of 1 μm were mixed at a weight ratio of 8: 2 was used as the raw material powder, and graphite was used as the mold material. Then, uniaxial pressure sintering (vacuum, 1250 ° C., 30 MPa, 1 minute holding) was performed with a discharge plasma sintering apparatus.

FIG. 5 shows a photograph of a medal (diameter 20 mm) made of titanium carbide-based cemented carbide according to Example 2.

(Example 3)
A micro gear made of zirconia ceramics was produced using the production method of the present invention. In this experiment, ZrO2 powder having a particle size of 0.03 μm containing 3 mol% of itria was used as the raw material powder, and graphite was used as the mold material, and uniaxial pressure sintering was performed with a discharge plasma sintering device. Vacuum, 1200 ° C., 30 MPa, 10 minutes holding) was performed.

FIG. 6 shows a photograph of a micro gear made of zirconia ceramics according to the third embodiment.

10 ... base material, 12 ... mold material, 20 ... die, 22 ... die hole, 32 ... lower punch, 34 ... upper punch, 40 ... raw material powder, 50 ... sintered body

Claims (4)

A method for manufacturing precision finely molded products of cemented carbide selected from cemented carbide, cermet and fine ceramics.
The process of filling the die cavity with raw material powder of ultra-hard material,
Including the step of uniaxial pressure sintering of the raw material powder.
In the step of uniaxial pressure sintering,
A precise arbitrary uneven shape is formed on the surface, made of graphite or glassy carbon , and a mold formed separately from the punch is placed on the punch that pressurizes the raw material powder in the die hole of the die. A manufacturing method , wherein the mold material is removed or burned off with a sandpaper or a wire brush after the uniaxial pressure sintering . The ultra-hard materials include tungsten carbide-based carbide alloys, titanium carbide-based cermets, alumina-based oxide ceramics, zirconia-based oxide ceramics, silicon carbide-based non-oxide ceramics, silicon nitride-based non-oxide ceramics, and boron carbide-based non-ceramics. Oxide ceramics or composite materials thereof,
The manufacturing method according to claim 1. The precision micromolded product is a molded product of any one selected from MEMS parts, industrial parts, stamps, stamps for pressing, and decorative products.
The manufacturing method according to claim 1 or 2. The uniaxial pressure sintering step is carried out under conditions under which the crystal grains can exhibit superplastic flow.
The manufacturing method according to any one of claims 1 to 3.

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