JP2019059981A - Method for producing precisely fine molded article of superhard material - Google Patents

Abstract

To provide a novel production method for producing a precisely fine molded article of a superhard material into dimensions as designed while suppressing the generation of crazes, chips and cracks.SOLUTION: The method for producing a precisely fine molded article of a superhard material, comprises the steps in which: the cavity of a die is filled with the raw material powder of a superhard material; and the raw material powder is subjected to uniaxial pressure sintering. In the step of performing uniaxial pressure sintering, a die material in which a precise optional rugged shape is formed on the surface is placed on a punch pressurizing the raw material powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of producing precision micro-molded articles of ultra-hard materials.

  Heretofore, super hard materials such as cemented carbide, cermets and ceramics have been used as cutting tools and wear resistant tools. Because of its hardness and heat resistance, it is expected to be applied as a stamp or a stamp for use in presses, and because it is excellent in abrasion resistance and resistant to scratches and abrasion, application as a decorative item is expected. In addition, as components for MEMS and micromachines, it is considered that the expectation for a ceramic-based material excellent in heat resistance and corrosion resistance to end use in an extreme environment will be increased in the future.

  Conventionally, a molded article of a cemented carbide material such as cemented carbide, cermet, or ceramics is obtained by forming a raw material powder into a desired shape with a die and then firing it. Furthermore, in order to precisely process them into complicated shapes, various methods such as cutting / grinding using a diamond tool, laser processing, and electric discharge machining are used.

  However, the above-described superhard material is a brittle material having both hardness and brittleness, and its processing requires a great deal of cost and time. Therefore, there is a method (see Patent Documents 1 and 2) in which a molded body before firing is subjected to cutting processing and then sintered, or the molded body is calcined and the obtained calcined body is subjected to main baking A method (Patent Document 3) has been proposed.

  However, although the above method is effective for relatively large products, as the product size becomes smaller and a finer and more precise finish is required, the shape collapses during molding, cracks or cracks. And the dimensional accuracy of the final shape.

  As an existing technology, metal glass is inserted in a precision-machined mold, and it is pressed by a punch in a state kept at not less than the glass transition point and not more than the crystallization temperature to obtain precision parts (Patent Document 3) A method for producing a metallic glass micropart (Non-patent Document 1) has been proposed, in which a single glass particle is used for direct molding by microviscous flow processing. Amorphous materials such as oxide glass and metallic glass can easily flow viscous to the edges of the mold above the glass transition temperature.

  However, crystalline powders are not easy to flow like that, and it is particularly difficult to impart shapes in the same manner in ceramics even at ultra-high temperatures near the melting point. In addition, as the dimensions of the product become smaller and the processing becomes finer and more precise, the flowability problem becomes serious.

Japanese Patent Application Laid-Open No. 60-131861 Japanese Patent Application Laid-Open No. 61-97164 JP-A-62-212257 JP, 2009-97084, A

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 micro-molded article of superhard material to a designed size while suppressing the occurrence of cracks and chipping. The purpose is to

  The inventor of the present invention considered the following constitution as a result of earnestly examining a novel manufacturing method for manufacturing a precision micro-molded product of an ultrahard material to a dimension as designed while suppressing the occurrence of cracks and chipping. The present invention has been achieved.

  That is, according to the present invention, there is provided a method of producing a precision micro-molded article of a superhard material, comprising the steps of: filling a raw material powder of the superhard material in a cavity of a die; And manufacturing, wherein in the uniaxially pressure-sintering step, a mold material having a surface on which any desired uneven shape is formed is disposed on a punch for pressing the raw material powder. Is provided.

  As described above, according to the present invention, there is provided a novel manufacturing method for manufacturing precision micro-molded articles of ultra-hard materials into designed dimensions while suppressing the occurrence of cracks and chipping.

Process drawing 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 tungsten carbide based cemented carbide according to the first embodiment. A photograph of a titanium carbide-based cermet medal of Example 2. A photograph of a micro gear made of zirconia ceramics of Example 3.

  Hereinafter, the present invention will be described with the embodiment 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 producing a precision micro-molded article of super hard material according to the present invention, a method for producing a seal made of super hard material will be described. The following description will be made with reference to the process diagram shown in FIG. 1 and the schematic diagrams shown in FIGS. 2 and 3 as appropriate.

  FIG. 2 (a) schematically shows step 1. In step 1, a mold 12 is produced on the surface of which the concavo-convex shape of the stamp is formed. Specifically, after preparing the base material 10 having a short cylindrical shape, the surface of the base material 10 is engraved to form a precise concavo-convex shape representing a seal (precisely, a seal that is reversed horizontally).

  In addition, it is preferable that the raw material of the base material 10 has sufficient hardness which can function as a type | mold material, and is a heat-resistant material (that is, material which is easy to cut and excellent in heat resistance). Examples of the heat-resistant material of free-cutting property include carbon-based materials such as graphite and glassy carbon and boron nitride-based materials whose strength and processability can be adjusted by the addition of a binder. The mold material 12 may be produced by hand engraving, mechanical engraving, laser engraving or the like, or may be produced by electric discharge machining when the material is a conductive material. In the present embodiment, it is possible to use, as the mold material 12, the surface of the free-cutting substrate 10 in which the concavo-convex shape in which the minimum width of the concave portion or the convex portion is several hundred micrometers or less is formed.

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

  FIG. 2C schematically shows step 3. In step 3, the cylindrical powder formed by the die hole 22 and the lower punch 32 is filled with the raw powder 40 of the superhard material, and then the upper punch 34 is inserted from above the die hole 22.

  Here, as a superhard material, a cemented carbide (tungsten carbide based cemented carbide) based on tungsten carbide, a cermet based on titanium carbide (titanium carbide based cermet), alumina, zirconia, silicon carbide, Fine ceramics based on silicon nitride and boron carbide (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, those composite materials etc. can be illustrated. The raw material powder 40 is a mixed powder of the above-described base material and a binder (auxiliary agent), and in the present embodiment, in preparing the mixed powder, the sintered body exhibits superplastic behavior in combination with the sintering conditions Prepare the powder as you like.

  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 disposed on the lower punch 32 with the mold material 12 having the concavo-convex shape of the stamp formed on one surface and the other surface down. The raw material powder 40 is sintered while uniaxially pressing it. As a result, it is possible to obtain a sintered body having a concavo-convex shape in which a seal is imprinted on the bottom surface.

  Here, in order to perform uniaxial pressure sintering, it is necessary to set sintering conditions that cause superplastic flow of crystal grains in the sintered product during sintering together with the powder conditions of the raw material powder 40 . Superplasticity is a huge ductility that a crystalline material having fine crystal grains exhibits at high temperature, and its expression involves many parameters such as particle diameter, addition amount of auxiliary agent and binder, temperature, pressure, etc. . Generally, the smaller the particle size, the higher the added amount of auxiliary agent and binder, the higher the temperature and pressure, the superplastic flow is obtained, while the addition of auxiliary agent and binder As the amount is larger and the temperature is higher, crystal grain growth is more likely to occur during firing. Therefore, it is necessary to select an optimum combination of parameters that can develop superplasticity while suppressing crystal grain growth.

For example, in the case of producing a sintered body of tungsten carbide based cemented carbide using a standard sintering apparatus, the firing conditions are optionally shaken by combining various parameters in the range shown in the following (1) to (4) be able to.
(1) Tungsten carbide particle diameter: 0.1-10 μm
(2) Cobalt addition amount: 1-30 wt%
(3) Baking temperature 900-1600 ° C
(4) Pressure 10-100MPa

  FIG. 3 (b) schematically shows step 5. In step 5, after taking out the sintered body 50 from the die 20, the mold material 12 fixed to the bottom surface of the sintered body 50 is removed. Here, in the case where the mold 12 is graphite, it is possible to finish by sand blasting after removing pieces by sand paper or wire brush. When the sintered body 50 is a ceramic, the mold material 12 can be burned off by heating at 700 ° C. or higher in the air.

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

  As mentioned above, although the manufacturing method of the seal stamp made of super hard material was explained as one embodiment of the present invention, according to the present invention, it is needless to say that it is possible to manufacture not only a seal stamp but a precision fine molded article in general.

  Examples of precision micro-molded articles of superhard materials that can be manufactured by the present invention include MEMS parts, industrial parts, stamping marks, decorative articles, and the like. In the case of manufacturing these precision micro-molded articles, in place of the above-described seal, it is sufficient to prepare a mold material having a surface on which any precise uneven shape is formed.

  As described above, according to the present invention, it is possible to manufacture a precision micro-molded article of an ultrahard material having an arbitrary shape to a designed size while suppressing the occurrence of cracks and chipping. Become. In addition, according to the present invention, it is only necessary to precisely process the base material with good processability to produce the mold material, and it is not necessary to process the extremely hard material with extremely poor processability at high cost. It becomes possible to inexpensively manufacture precision micro-molded articles of hard materials.

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

  FIG. 4 shows a photograph of the seal produced in this experiment. As shown in FIG. 4, the outer peripheral surface of the manufactured seal stamp emitted a beautiful metallic luster, and the seal surface was free from any collapse or chipping of the seal.

(Example 2)
Using the manufacturing method of the present invention, a medal made of titanium carbide based cemented carbide was produced. In this experiment, a mixed powder of TiC powder having a particle diameter of 0.7 μm and Ni powder having a particle diameter of 1 μm was mixed at a weight ratio of 8: 2 as raw material powder, and graphite was used as a mold material. Then, uniaxial pressure sintering (vacuum, 1250 ° C., 30 MPa, holding for 1 minute) was performed in 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 the second embodiment.

(Example 3)
A micro gear made of zirconia ceramic was manufactured using the manufacturing method of the present invention. In this experiment, ZrO 2 powder having a particle diameter of 0.03 μm containing 3 mol% yttria was used as a raw material powder, and graphite was used as a mold material, and uniaxial pressure sintering was performed in a discharge plasma sintering apparatus ( A vacuum was carried out at 1200 ° C. and 30 MPa for 10 minutes.

  FIG. 6 shows a photograph of a micro gear made of zirconia ceramic of Example 3.

DESCRIPTION OF SYMBOLS 10 ... Base material, 12 ... Shape material, 20 ... Die, 22 ... Die hole, 32 ... Lower punch, 34 ... Upper punch, 40 ... Raw material powder, 50 ... Sintered body

Claims (9)

A method of producing a precision micro-molded article of superhard material, comprising
Filling the raw material powder of the super hard material in the cavity of the die;
Uniaxial pressure sintering the raw material powder, and
In the uniaxial pressure sintering step,
A manufacturing method characterized in that a mold material in which a precise arbitrary uneven shape is formed on the surface is disposed on a punch for pressing the raw material powder. The material of the mold material is a heat-resistant material of machinable property,
The method according to claim 1. The free-cutting heat-resistant material is a carbon-based material or a boron nitride-based material,
The manufacturing method according to claim 2. The carbon-based material is graphite or glassy carbon,
The method according to claim 3. The super hard material is any one material selected from cemented carbide, cermet and fine ceramics,
The manufacturing method as described in any one of Claims 1-4. The super hard material includes tungsten carbide base cemented carbide, titanium carbide base cermet, alumina base oxide ceramics, zirconia base oxide ceramics, silicon carbide base non oxide ceramics, silicon nitride base non oxide ceramics, boron carbide base non oxide ceramics Oxide ceramics or their composite materials,
The manufacturing method as described in any one of Claims 1-4. The precision micro-molded article is any one molded article selected from MEMS parts, industrial parts, seals, stamping marks for a press, and decorations.
The manufacturing method as described in any one of Claims 1-6. The uniaxial pressure sintering step is carried out under conditions that allow crystal grains to develop a superplastic flow.
The manufacturing method as described in any one of Claims 1-7. A method for producing a seal made of super hard material,
Filling raw material powder of super hard material into cylindrical cavity of die;
Uniaxial pressure sintering the raw material powder, and
In the uniaxial pressure sintering step,
A manufacturing method characterized in that a mold material on the surface of which a precise concavo-convex shape representing a seal is formed is disposed on a punch for pressing the raw material powder.