JPH03170386A - High-speed plastic molding of ceramic - Google Patents

Abstract

PURPOSE:To carry out plastic processing at lower temperature than a conventional method and at high speed by sintering zirconia-based ceramic containing a transition metal at relatively low temperature and subjecting the zirconia- based ceramic to plastic molding. CONSTITUTION:Ceramic consisting essentially of zirconia of tetragonal system containing 0.1-5.0mol oxide of Mn, Fe, Co, Ni, Cu or Zn is subjected to plastic deformation at 1,000-1,450 deg.C in 1X10 deg./second to 5X10<-4>/second strain rate. The zirconia ceramic is obtained by adding a very small amount of a transition metal oxide to a zirconia solid solution containing Y2O3, etc., usually known as stress inducing strengthened type ceramic and sintering the solid solution at low temperature. The ratio of the zirconia component of tetragonal system is preferably >=60% in the ceramic in order to give sufficiently high-speed molding rate. Consequently, a composite ceramic material having >=60% content of zirconia component containing a transition metal can be subjected to high- speed processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for high-speed plastic forming of zirconia ceramics.

[Prior art and problems to be solved by the invention] High-strength ceramics, especially partially stabilized zirconia, have high toughness that other ceramics do not have, so they are beginning to be used as structural ceramics in mechanical parts, etc. However, for purposes of use, dimensional accuracy equivalent to or higher than that of metallic members is required. However, dimensional changes during the sintering process are large, and post-processing after sintering is often required.

Therefore, after sintering, post-processing using diamond tools and abrasive stakes is performed, but since Ceragox is usually a difficult-to-grind material, this processing cost further increases the overall cost of the product. ing.

As one means to solve these problems, a method has been discovered in which a specific ceramic containing tetragonal zirconia is plastically deformed by applying stress under heating. This method has the advantage of being able to obtain a shaped body with high dimensional accuracy with a relatively simple operation, but high-temperature heating is required for high-speed processing, and the relationship between the workpiece and the workpiece is There is a point where reactions and grain growth of the ceramic to be processed are likely to occur.

[Means to solve the problem]

The present inventors investigated a method to increase the processing speed while maintaining the advantages of the plastic processing method for zirconia-based ceramic materials, and as a result, the inventors used zirconia that was sintered with a relatively low wettability by adding transition metals. As a result, we have discovered that plastic working can be performed at lower temperatures and at higher speeds than conventional methods. The present invention is based on such knowledge.

That is, the present invention provides a polycrystalline material whose main component is tetragonal zirconia and which contains a trace amount (0.1 to 5.0 mol%) of an oxide of a transition metal (Mn, Cu, Fe, Co, Ni, or Zn). Stress is applied to the ceramic shorts under heating at 1000 to 1450°C, and the strain rate is 1 x 10°/see to 5 x 10
The present invention relates to a plastic shaping method for ceramics, which is characterized by green deformation at -'/see).

The ceramics to which this method can be applied contain tetragonal zirconia at room temperature and transition metals (Mn, Cu,
This is a zirconia ceramic made of polycrystalline material containing a small amount of oxides (Fe, Co, Ni, or Zn) at grain boundaries.

Such zirconia ceramics are usually obtained by adding a small amount of a transition metal oxide to a zirconia solid solution to which Y203 or the like, which is known as a stress-induced strengthened ceramic, is added and sintering the mixture at a low temperature. In order to obtain a sufficiently high molding speed, it is desirable that the content of the present tetragonal zirconia be 60% by volume or more in the ceramics. Therefore, even a composite ceramic material containing 60% or more of zirconia containing a transition metal can be processed at high speed.

In the method of the present invention, first, tetragonal zirconia polycrystalline ceramics containing the above-mentioned transition metal oxide
Plastic working is carried out at a temperature of 50°C, preferably 1100 to 400°C. If the processing temperature is less than 1000°C, sufficient plastic deformation cannot be achieved at high speed, while if it exceeds 1450°C, the length of the zirconia grains will become noticeable and the properties of the shaped body produced by plastic working will be significantly reduced, which is not preferable. .

In the present invention, the term "plastic deformation" includes both hypertransforming deformation in which the processed portion deforms uniformly and mold deformation in which the processed portion deforms non-uniformly.

The processing speed in plastic processing can be faster than that of ordinary zirconia ceramics, and it is uniform depending on processing temperature, ceramic grain size, zirconia content, amount of transition metal oxide added, processing method, etc. However, it is possible to process at a speed 5 to 30 times faster than normal zirconia ceramics. In this case, the applied stress can cause grain boundary sliding at the grain boundaries and does not cause fracture. A stress of MPa or more is required. For example, the addition of MnO2 with an average crystal grain size of 0.2 μm (
0.3 mol%) When tensile processing of piezogonal zirconia at 1300°C, 5XIO-'~5x10''/s
Plastic working is possible at a strain rate of about ec.

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 of ceramic, processing conditions, shape, etc., but by tensile processing, it is possible to elongate the sample to more than twice that of the sample before deformation.

The reason why the tetragonal zirconia ceramics containing the above-mentioned transition metal oxides can have a pear shape is that the crystal grain size is fine and has good symmetry, and the transition metal atoms are polarized at the grain boundaries. Because its grain boundary structure is hostile to plastic flow due to grain boundary slip, it is suitable for plastic flow due to grain boundary slip at the above processing temperature, so plastic flow is likely to occur at grain boundaries at the above processing temperature. It is also thought that this is because the residual stress generated by processing can be retained by the stress-induced transformation strengthening mechanism of tetragonal zirconia, making the molded body less likely to break.

[Effects of the Invention] According to the method of the present invention, zirconia-based ceramics can be plastically formed at high speed, and the processing efficiency of various methods such as pressing, forging, extrusion, and drawing can be greatly improved, and the process is economically efficient. Processing becomes possible.

In addition, since processing is mainly done at low temperatures, not only can heating costs (energy such as heating furnaces and electric power) be lower, but also cheaper materials can be used for certain shapes required for processing.
Plastic working of zirconia-based ceramics becomes much easier.

As described above, the method of the present invention is an extremely useful method for processing ceramics, and can greatly expand the scope of use of ceramic straw for various mechanical parts.

〔Example〕

Hereinafter, the present invention will be explained in detail by showing Examples and Comparative Examples.

Example-1. A sintered body obtained by adding 0.3 mol % of manganese acetate to YzOs-containing zirconia powder (specific surface area: 15 nf/g) synthesized by a coprecipitation method and sintering at 1200° C. was used as a test material.

The YzO'a content of the sintered body was 2.6 mol%, the grain size was 0.2 μm, and the sintered density was 6.05 g/cnl.

A 51III+ cube (surface roughness 2μ) was made from this sintered body.
m) was cut out using a SjC mold with a polished surface at 1400°C (in air) at a certain speed of 0.5 am/mi.
n (strain rate 2.7 X I O -3/sec
) was performed (processing pressure: 5 MPa), and after 8 minutes, a thin plate with a thickness of I mm was obtained. The surface roughness after molding is 0.
It was 1 μm.

Comparative example-1. Ordinary zirconia powder synthesized by coprecipitation method (specific surface area: 1
5+n/g) was sintered at 1400°C. The Y203 content was 2.6 mol%, the grain size was 0.3 μm, and the sintered density was 6.03 g/cnl.

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

Example-2. Using the same material as in Example 1, a round bar with a diameter of 3M and a length of 30 meters was made to serve as a Tetos piece. This test piece was
Machining speed 3nwn/min (2.7X
As a result of tensile processing at 1 O-''/sec), a round bar with a diameter of 1.2 mm and a length of 66 cm was obtained in 11 minutes.

Comparative example-2. The same test beads as in Example 2 were made using the material of Comparative Example 1, and the same processing was attempted, but it was difficult to form them under the one-time conditions, so processing was performed under the following conditions. Ta. Processing temperature: 1450°C, processing speed: 0. 2mm/min
(2.7 x 10-4/sec), and the processing time was 165 minutes.

Example 3 Using the materials of Example 1, boards of size 1, 5XI, and 5XIO were made. This is a SiC type with a polished surface.
Pressing was performed at 1400° C. and a processing speed of 1+n+n/min (strain rate 1.6×10−4/sec) to obtain a thickness of 9 layers in 1 minute. At this time, the surface roughness before processing was 0.8 μm, and the surface roughness after processing was 0.8 μm.
It was 01 μm.

Comparative example-3. The same test plate as in Example 3 was created 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 0.05+nm/mi
n (strain rate 8.3 x 10 -s/see
), processing time 20 minutes.

9 ? Example-4.

The same raw material zirconia powder (containing only YzC) + as in Example 1) was mixed with 0 An■, 20 wt% powder, and 0.2% manganese carbonate.
5 using a material added with 3 mol% and sintered at 400°C.
I made a cube of m+++. This test piece was applied to a pressure of 5 MPa.
As a result of pressing at a processing temperature of 1400°C, the deformation rate was 0. 5 mm/min (strain rate 1.7 x 1
0 −3/see) and deformed by 60%.

Comparative example-4. AA2 0.20 w to the same zirconia powder as Comparative Example 1
A test piece of the same size as in Example 4 was prepared using a sintered body obtained by HIP-processing the sintered body mixed with t%, and the same processing was attempted. As a result, the following conditions were required to be changed.

Processing temperature 1550℃, processing speed 0.05mm/min
(Strain rate 1.7 x 10-4/sec).

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

10 Example-5. The same test piece as in Example 1 was prepared using a material obtained by adding 0.3 mol % of copper acetate to the same zirconia raw powder (containing only y.03) as in Example 1 and sintering it at 1200°C.

When this test piece was processed using the rotating press pressure as in Example 1, the processing speed was 0. The same processing as in Example 1 was possible at 6 mm/min.

Example-6. Adding l manganese acetate to the same zirconia raw material powder as in Example 1
As a result of performing the same processing as in Example I using a material sintered at 1200°C with the addition of mole, the processing speed was 0.8 mm/m.
In processing speed was obtained.

Example-7. 0.3 of zinc acetate was added to the same zirconia raw material powder as in Example 1.
As a result of processing in Example 1 using the material sintered with addition of mol %, the same molding results as in Example 1 were obtained.

Example-8. Same as Example 1, 0 cobalt acetate was added to the zirconia raw material powder.
．． When the material of Example 1 was processed using the material sintered with 3 mol % added, certain results similar to those of Example 1 were obtained.

Claims (1)

[Claims] 0 Mn, Fe, Co, Ni, Cu or Zn oxides
．． Ceramics whose main component is tetragonal zirconia containing 1 to 5.0 mol% are strained at a strain rate of 1 x 10°/sec to 5 x 10^-^4/sec at a temperature of 1000 to 1450°C.
A high-speed plastic forming method for zirconia ceramics characterized by plastically deforming within a range of c.