JP2791403B2 - High-speed plastic forming of ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-speed plastic forming method of zirconia ceramics.

[Problems to be solved by conventional technology and invention]

High-strength ceramics, especially partially stabilized zirconia, have high toughness that no other ceramics have, so they have begun to be used as structural ceramics in mechanical parts, etc.
Dimensional accuracy equal to or higher than that of metallic members is required for applications. However, the dimensional change during the sintering process is large, and often requires post-processing after sintering.

Therefore, post-processing using a diamond tool or abrasive grains is performed after sintering, but since ceramics are usually difficult to grind, there is a problem that this processing cost further increases the cost of the entire product. .

As one of means for solving such problems, a molding method has been found in which a specific ceramic containing tetragonal zirconia is plastically deformed by applying a stress while heating.
This method has the advantage that a molded body with high dimensional accuracy can be obtained by relatively simple operation, but high-speed processing requires high-temperature heating, and the processing of the workpiece and the workpiece is difficult. There is a problem that the reaction and the grain growth of the ceramic to be processed easily occur.

[Means for Solving the Problems] The present inventors have studied a method of increasing the processing speed while maintaining the advantages of such a plastic working method for a zirconia-based ceramic material. By using sintered zirconia, it has been found that plastic working can be performed at a lower temperature and at a higher speed than before. The present invention is based on such findings.

That is, the present invention comprises tetragonal zirconia as a main component and a transition metal (Mn, Cu, Fe, Co, Ni or Zn) in a trace amount (0.1%).
~ 5.0 mol%) containing polycrystalline ceramics
High speed (strain rate 1 × 10 ゜ / se) by applying stress while heating at 0 ° C
The present invention relates to a plastic forming method for ceramics, which is characterized by plastically deforming at a rate of c.about.5 × 10 ⁻⁴ / sec).

Ceramics to which this molding method can be applied contain tetragonal zirconia at room temperature and have transition metals (Mn, Cu, Fe, C
It is a zirconia ceramic composed of a polycrystal containing an oxide of o, Ni or Zn) in a minute grain boundary.

Such zirconia ceramics can be obtained by adding a small amount of a transition metal oxide to a zirconia solid solution to which Y ₂ O ₃ or the like, which is generally known as a stress-induced strengthening type ceramic, is added, followed by sintering at a low temperature. In order to obtain a sufficiently high molding speed, the tetragonal zirconia component is desirably 60% by volume or more in the ceramics. Therefore, high-speed processing is possible even with a composite ceramic material containing 60% or more of a zirconia component containing a transition metal.

In the method of the present invention, first, a tetragonal zirconia polycrystalline ceramic containing the transition metal oxide described above is 1000 to 1450.
C., preferably at a temperature of 1100 to 1400.degree. If the working temperature is lower than 1000 ° C., the plastic deformation cannot be sufficiently performed at a high speed. On the other hand, if the working temperature is higher than 1450 ° C., the grain growth of zirconia becomes remarkable, and the properties of the formed body by the plastic working are unpreferably reduced.

In the present invention, the term “plastic deformation” includes both superplastic deformation in which a processed portion is uniformly deformed and plastic deformation in which a processed portion is non-uniformly deformed.

The processing speed in plastic working can be faster than that of ordinary zirconia ceramics, and is not uniform depending on the processing temperature, the crystal grain size of the ceramic, the amount of zirconia-containing transition metal oxide added, the processing method, etc. But,
Processing at a speed 5 to 30 times the processing speed of ordinary zirconia ceramics is possible. In this case, the applied stress needs to have a stress of 100 MPa or more which can cause grain boundary slip at a crystal grain boundary and does not cause fracture. For example,
When MnO2 added (0.3 mol%) tetragonal zirconia with an average grain size of 0.2 μm is stretched at 1300 ° C., 5 × 10
Plastic working at a strain rate of about ^{−4 to} 5 × 10 ⁻³ / sec is possible. The processing speed can be further increased by increasing the amount of transition metal added or raising the processing temperature. The amount of plastic deformation given by the above-described processing method varies depending on the type, processing conditions, shape, and the like of the ceramics, but it is possible to stretch twice or more of the sample before deformation in the tensile processing.

The above-mentioned tetragonal zirconia ceramics containing a transition metal oxide can be plastically formed because the crystal grain size is fine and the symmetry is good, and the transition metal atoms are deflected to the grain boundary, and the Since the boundary structure is compatible with plastic flow due to grain boundary sliding, it is suitable for plastic flow due to grain boundary sliding at the above-mentioned processing temperature. It can be considered that the residual stress caused by the above can be held by the stress-induced transformation strengthening mechanism of tetragonal zirconia, so that the molded body is hardly broken.

〔The invention's effect〕

By the method of the present invention, zirconia-based ceramics can be plastically molded at high speed, and are pressed, forged, extruded,
The processing efficiency of various methods such as drawing can be greatly improved, and processing with good economy can be performed. In addition, plastic processing of zirconia ceramics is not only possible because heating is mainly performed at low temperatures, so that heating costs (energy such as heating furnace and electric power) can be low, and inexpensive molding materials can be used for processing. Is much easier.

As described above, the method of the present invention is a very useful method for processing ceramics, and can greatly expand the range of use of ceramics for various mechanical parts and the like.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example-1. 0.3 mol% of manganese acetate was added to Y ₂ O ₃ -containing zirconia powder (specific surface area: 15 m ² / g) synthesized by a coprecipitation method, and 1200 ° C.
Was used as a test material. The sintered body has a Y ₂ O ₃ content of 2.6 mol%, a grain size of 0.2 μm, and a sintered density of
6.05 g / cm ³ .

A 5 mm cube (surface roughness 2 μm) was cut out from this sintered body and the surface was polished at 1400 ° C using a SiC stamping die.
(In air), molding speed 0.5mm / min (strain speed 2.7 × 10 ^-3 / s
ec) to perform press working (working pressure: 5 MPa), and 8 minutes later, a thin plate having a heat of 1 mm was obtained. The surface roughness after molding was 0.1 μm.

Comparative Example-1. Ordinary zirconia powder synthesized by a coprecipitation method (specific surface area: 1
5m ² / g) was sintered at 1400 ° C. The Y ₂ O ₃ content was 2.6 mol%, the grain size was 0.3 μm, and the sintered density was 6.03 g / cm ³ .

The same test piece as in Example 1 was cut out from this sintered body,
When processing was performed to the same size at the same temperature and pressure, the forming speed was 0.05 mm / min (strain rate 2.7 × 10 ⁻⁴ / sec) and the forming process took 40 minutes.

Example-2 A round piece having a diameter of 3 mm and a length of 30 mm was prepared using the same material as in Example 1 to obtain a test piece. This test specimen was
As a result of drawing at a working rate of 3 mm / min (2.7 × 10 ⁻³ / sec) at a temperature of ° C., a round bar having a diameter of 1.2 mm and a length of 66 mm was obtained in 11 minutes.

Comparative Example-2. The same test piece as in Example 2 was prepared using the material of Comparative Example 1, and the same processing was attempted. However, molding was difficult under the same conditions. Was done.
Processing temperature 1450 ° C, processing speed 0.2mm / min (2.7 × 10 ^-4 / sec)
The processing time was 165 minutes.

Example 3 A plate having a size of 15 × 15 × 10 mm was made using the material of Example 1. This was subjected to press working at 1400 ° C. at a working speed of 1 mm / min (strain speed 1.6 × 10 ⁻³ / sec) with a SiC mold whose surface was polished, and worked to a thickness of 9 mm in a working time of 1 minute. At this time, the surface roughness before processing was 0.8 μm, and the surface roughness after processing was 0.01 μm.
μm.

Comparative Example-3 The same test plate as in Example 3 was prepared using the same material as in Comparative Example 1, and the same processing as in Example 3 was performed. The following condition changes were required for processing. Processing temperature 1450 ° C, processing speed 0.05mm / min (strain speed 8.3 × 10 ^-5 / sec), processing time 20
Minutes.

Example -4. Example 1 and the same raw material zirconia powder (Y only ₂ O ₃ content)
20 wt% of Al ₂ O ₃ powder and 0.3 mol% of manganese carbonate
A 5mm cube was made from the material sintered at 1400 ° C.
As a result of press-molding this test piece at a pressure of 5 MPa and a processing temperature of 1400 ° C., the deformation rate was 0.5 mm / min (strain rate 1.7 × 10 ⁻³ / sec).
Deformed by 60%.

Comparative Example-4 20% by weight of Al ₂ O _{3 was} mixed with the same zirconia powder as in Comparative Example 1, and a test piece having the same size as in Example 4 was prepared using a sintered body obtained by HIP treatment, and the same processing was performed. As a result, the following conditions had to be changed.

Processing temperature 1550 ° C, processing speed 0.05mm / min (strain speed 1.7 × 1
0 ^-4 / sec).

Table 1 shows comparison results of the processing conditions of Examples 1 to 4 and Comparative Examples 1 to 4.

Example -5. Example 1 and the same zirconia raw material powder (Y only ₂ O ₃ content)
The same test piece as in Example 1 was prepared using a material obtained by adding 0.3 mol% of copper acetate to the mixture and sintering at 1200 ° C.

When this test piece was processed under the same press pressure as in Example 1, the same processing as in Example 1 was possible at a processing speed of 0.6 mm / min.

Example-6. As a result of performing the same processing as in Example 1 using a material obtained by adding manganese acetate to the same zirconia raw material powder as in Example 1 by 1 mol and sintering at 1200 ° C., the processing speed was 0.8 mm / min. The processing speed was obtained.

Example-7. Zinc acetate was added to the same zirconia raw material powder as in Example 1 at 0.3.
As a result of processing of Example 1 using the material sintered by adding mol%, a molding result similar to the result of Example 1 was obtained.

Example-8 Cobalt acetate was added to the same zirconia raw material powder as in Example 1.
The processing of Example 1 was performed using the material sintered by adding 0.3 mol%, and the same molding result as the result of Example 1 was obtained.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiromichi Okamura 345 Yanagimachi, Takada, Odawara-shi, Kanagawa Japan Examiner, Odawara Research Laboratory, Soda Co., Ltd. Koji Amemiya (56) References JP-A-62-17087 (JP, A) 63-182279 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 41/80 C04B 35/48

Claims (1)

(57) [Claims] An oxide of Mn, Fe, Co, Ni, Cu or Zn is 0.1 to 5.0
At a temperature of 1000-1450 ° C, a strain rate of 1 × 10 ゜ / sec is applied to a ceramic mainly composed of tetragonal zirconia containing mol%.
A high-speed plastic forming method for zirconia ceramics, which is plastically deformed in a range of 5 × 10 ⁻⁴ / sec.