JPH0952756A - Alumina ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide alumina ceramic having high purity, denseness and machinability by using specific Al2 O3 powder containing Y2 O3 as a raw material and applying a specified firing condition. SOLUTION: This alumina ceramic uses the raw materials consisting of 99.05-99.85wt.% Al2 O3 , 0.01-0.10wt.% MgO, 0.05-0.50wt.% SiO2 , and 0.05-0.50wt.% Y2 O3 and also uses the raw material powder being 0.4-1.0μm average particle diameter of Al2 O3 powder and having >=5m<2> /g BET specific surface area and is produced by maintaining the max. temp. of the firing in the range of 1,550-1,650 deg.C at least for one hour or more. This sintered compact has >=3.85g/cm<3> Archimedes density, 5-20μm average particle diameter, <=1,500kgf/ mm<2> Vickers hardness and >=370MPa elastic modulus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to alumina ceramics having high purity and excellent compactness and machinability.

[0002]

_2. Description of the Related Art Fine ceramics represented by alumina (Al ₂ O ₃ ) are superior in heat resistance and abrasion resistance to metals and plastics, but are difficult to process and expensive, and have been sufficiently put into practical use. It is hard to say.

Until now, the average particle diameter was several μm (1 μm).
A ceramic raw material containing Al ₂ O ₃ (exceeding 1) as a main component (99% by weight) and a glass phase component such as SiO ₂ which is a sintering aid, MgO, CaO in a total amount of 1% by weight is 1500
The average particle size is 20 by firing at ~ 1600 ° C.
Disclosed is a method for obtaining alumina ceramics having a size of ˜40 μm.

Japanese Patent Publication No. 63-66795, Japanese Patent Publication No. 3-5
As disclosed in Japanese Patent No. 1244, the Al ₂ O ₃ content is set to 99.6 to 99.9% by weight, and the balance is SiO ₂ , M.
High-purity alumina ceramics composed of gO and CaO are characterized by high wear resistance and low impurity content. No description of adding Y ₂ O ₃ is found in these documents.

Japanese Patent Publication No. 7-12969, Japanese Patent Publication No. 7-174
No. 59 discloses that Y ₂ O ₃ , MgO, La ₂ O ₃ and ZrO ₂
The effect of improving the insulating property due to the reduction of the crystal grain size of the Al ₂ O ₃ sintered body by the addition is described.
_The effect of accelerating and increasing the crystal grain growth of the Al ₂ O ₃ sintered body due to the lowering of the liquid phase precipitation temperature during sintering with _2- Y ₂ O ₃ and SiO ₂ —Y ₂ O ₃ system has not been investigated. Further, there is a description that it is desirable to add SiO ₂ as little as possible.

[0006]

However, it is difficult to densify such alumina ceramics having a high Al ₂ O ₃ content during sintering.

Therefore, see Japanese Patent Publication No. 6-88832.
Expensive chemical synthesis method such as alkoxide method
Densification due to₂O_ThreeRaw material particle size is 0.3 μm
Research using the following raw materials is also actively carried out, but sintering
The average particle size of the body is 2 μm or less, and the Vickers hardness is 1500
kgf / mm² Since it is above, the workability is low, and raw materials and powder
The problem was that the final price was high and the manufacturing process was complicated.

[0008]

The present invention is based on Al₂O_ThreeContained
Content of 99.05 to 99.85% by weight, MgO content of 0.
01-0.10% by weight, SiO₂Content 0.05-0.
50% by weight, Y₂O_ThreeContent of 0.05 to 0.50% by weight
The maximum firing temperature of the raw material powder constituted by
Keep the temperature within the range of 1650 ℃ for at least 1 hour.
Alumina ceramics sintered body
Lukimeds density is 3.85 g / cm^Three Above, the average particle size is
Vickers hardness of 1500 kg within the range of 5 to 20 μm
f / mm²Below, and the elastic modulus is 370 MPa or more
Method for obtaining alumina ceramics characterized by
Is made clear.

In the present invention, the Al ₂ O ₃ content is 99.
The reason why it is limited to the range of 05 to 99.85% by weight will be shown.
If it is less than 99.05% by weight, the glass phase or the rare earth oxide phase segregates at the grain boundaries, and the mechanical properties inherent to Al ₂ O ₃ are deteriorated, which is not preferable, and if it exceeds 99.85% by weight, densification or It is not suitable because it is difficult to increase the crystal grain size and improvement in workability cannot be expected.

The content of MgO represented by 0.01 to 0.10% by weight is within the range intentionally added to commercially available alumina powder, and can be treated as a known range. Therefore, although not particularly mentioned, it was noted that the color tone of the sintered body changes depending on the content.

0.05 to 0.50% by weight of the SiO ₂ content is the same as Y ₂ O ₃ described later or 1: 4 to 4: 1.
Since it was effective to use within the range of preferably 1: 2 to 2: 1, it was set to this range.

Here, the reason why the mixing ratio of SiO ₂ and Y ₂ O ₃ is the same amount or within the range of 1: 4 to 4: 1 is because a liquid phase having a relatively low melting point is formed in this composition range. , Promoting the growth of crystal grains.

Y ₂ O ₃ is a characteristic element of the new compounding system according to the present invention, and has a crystal structure of rare earth oxide C type,
At the same time, both ionic radius ratios of Y ³⁺ and O ²⁻ (r _caton /
r _anion ) is 0.693.

Α-Al ₂ O ₃ is a corundum type, but is in agreement with the rare earth oxide C type in that it has a hexacoordinate oxygen ion.

In addition, since the rare earth oxide C type has a structure in which two oxygen ions with eight coordinations are eliminated, aluminum ions are easily introduced into the rare earth oxide C type, and substitution is facilitated.

For example, Al _{2 is} used as a sintering aid for Si ₃ N _4.
One of the reasons why the O ₃ -Y ₂ O ₃ system is widely used is
The function is that the melt of l ₂ O ₃ —Y ₂ O ₃ is stable in the temperature range of 1550 to 1650 ° C. and the α → β phase transition of Si ₃ N ₄ is smoothly performed.

On the other hand, the ionicity of the bond shown by Pauling is equal to P _Mg-O = P _YO = 0.73, and A
Since it is higher than P _Al-O = 0.63 of l ₂ O _3, the ionic bondability is as high as that of MgO, and the feature is that the mobility at high temperature is remarkable.

Therefore, although the diffusion of Al ₂ O ₃ is promoted, the solid solution amount is relatively small, and it has the function of promoting the growth of crystal grains of Al ₂ O ₃ alone.

The reason for setting the maximum firing temperature to 1550 to 1650 ° C. is that if the temperature is less than 1550 ° C., the densification does not proceed sufficiently, and if it is 1650 ° C. or more, decomposition of SiO ₂ or the like occurs and the composition becomes out of order. Is increased to 40 μm or more, the mechanical properties of the sintered body are deteriorated, which is not preferable.

Similarly, if the holding time is less than 1 hour at the maximum temperature, densification does not proceed sufficiently and grain growth of 5 to 20 μm does not occur, which is not preferable. Considering the industrial productivity and the appropriate crystal grain growth range of the sintered body, 1 to 8 hours is suitable.

In addition, Al₂O_ThreeThe average particle size of the powder is 0.4
If it is less than μm, it is usually not commercially available or expensive.
It was difficult to handle and was excluded. Over 1.0 μm
And densification was hindered. BET specific surface area is 5m² / G not
Similarly, when it was full, the densification at the time of sintering decreased, so it was excluded.

Boring hole grinding (axial water injection),
Metal bond diamond core drill wheel (# 120, φ8mm, wheel peripheral speed is 60m / mi)
n. , The cut is 40 mm / min. , Total cut is 1
As a basis for selecting a power resistance value of 600 N or less by the Kistler dynamometer when processing is performed under the condition of 0 mm × 10 times, when the power resistance value exceeds 600 N, the abrasion amount of the grindstone becomes significantly large and clogging easily occurs. The rate of occurrence of chipping and cracks increases with the change in the grindstone.

[0023]

Since it is possible to use a commercially available Al ₂ O ₃ powder or a firing furnace, it is possible to reduce the processing time and cost without considering the increase in manufacturing cost.

[0024]

EXAMPLE An example of the present invention will be described below.

As the Al ₂ O ₃ raw material powder, the purity is 99.85.
% By weight (the balance is unavoidable compounds such as Na ₂ O and Fe ₂ O ₃ ), average particle size is 0.6 μm, purity 99.99% by weight
MgO, purity 99.99% by weight SiO ₂ , purity 9
9.9 wt% Y ₂ O ₃ was evaluated in the compounding system shown in Table 1 below.

Mix these compounds in a ball mill for 24 hours
After that, it was granulated by a known spray drying method. this
1.4t / cm² 75 × 100 × 2 by hydrostatic pressurization
It was molded into a 0 mm plate-shaped body. This molded body in the atmosphere
After the temperature was raised to each maximum temperature in, the firing was performed for the same holding time.
This sintered body is measured for the bulk density by the Archimedes method,
The Vickers hardness with a load of 10 kgf was measured. Also baked
For the average particle size of the aggregate, magnify the SEM photograph of the polished surface and break the line.
It was measured by cutting method.

Next, for the purpose of evaluating the machinability of the sintered body after the above measurement, cutting was performed under the following machining conditions.

Grinding method: Boring boring (axial center water injection) Wheel used: Metal bond diamond core drill wheel (# 120, φ8 mm) Wheel peripheral speed: 60 m / min. Notch: 40 mm / min. Total incision: 10 mm x 10 times

Drilling was carried out by a GC (grinding center) under these conditions, and the grinding resistance value in the Z-axis direction during this processing was detected by a Kistler dynamometer to be used as an evaluation index of grinding workability. If the grinding resistance value was 600 (N) or less, it was determined that the workability was good. The results are shown in Table 1.

[0030]

[Table 1]

From the above results, the alumina ceramics of the present invention
X is 3.85 g / cm^Three Sintered body density and sintered body
Average particle size is 5 to 20 μm, power resistance of 30% or more
Confirmed to have good workability that enables reduction of values
Was done.

FIG. 1 shows a schematic view of an SEM photograph of the polished surface of the alumina ceramics of the present invention.

[0033]

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily densify the alumina ceramics while maintaining the Al ₂ O ₃ content in the alumina ceramics at 99.05 to 99.85% by weight, and to have a composition excellent in machinability. The system was established.

The alumina ceramics disclosed herein are
Al ₂ O ₃ content is 99.05 to 99.85% by weight, Mg
O content 0.01 to 0.10% by weight, SiO ₂ content 0.05 to 0.50% by weight, Y ₂ O ₃ addition amount 0.05 to
The raw material powder composed of 0.50% by weight is obtained by keeping the maximum firing temperature within the range of 1550 to 1650 ° C. for at least 1 hour or more.

According to the present invention, when the alumina ceramic member is manufactured, it is possible to reduce the raw material cost and excel in the machinability, so that the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 shows the SE of the polished surface of the alumina ceramics of the present invention.
It is a schematic diagram of the photograph at the time of M observation.

Front page continuation (72) Inventor Hidehiro Endo 1618 Ida, Nakahara-ku, Kawasaki City, Advanced Technology Research Laboratories, Nippon Steel Corporation (72) Yutaka Sato 1618 Ida, Nakahara-ku, Kawasaki City Company Advanced Technology Research Center

Claims (3)

[Claims] 1. An Al ₂ O ₃ content of 99.05 to 99.8.
5% by weight, the content of MgO is 0.01 to 0.10% by weight,
Regarding a raw material powder composed of a SiO ₂ content of 0.05 to 0.50 wt% and a Y ₂ O ₃ content of 0.05 to 0.50 wt%, the average particle diameter of the Al ₂ O ₃ powder is 0. .4 ~
Alumina ceramics having a BET specific surface area of 1.0 μm, a BET specific surface area of 5 m ² / g or more, and a maximum temperature during firing kept in the range of 1550 to 1650 ° C. for at least 1 hour or more. 2. The sintered body according to claim 1, wherein the sintered body has an Archimedes density of 3.85 g / cm ³ or more and an average particle diameter of 5 to 2.
Vickers hardness is 1500kgf / m in the range of 0μm
Alumina ceramics characterized by having m ² or less and an elastic modulus of 370 MPa or more. 3. Al ₂O_ThreeContent is 99.0-59.8
5% by weight, the content of MgO is 0.01 to 0.10% by weight,
SiO₂Content is 0.05 to 0.50% by weight, Y₂O_ThreeIncluding
Raw material whose content is comprised between 0.05 and 0.50% by weight
Al powder₂O_ThreeThe average particle size of the powder is 0.4 to
1.0 μm, BET specific surface area 5 m² / G or more, baking
The maximum temperature is less than 1550 to 1650 ℃
Alumina ceramics sintered by holding for 1 hour or more
In the body, boring and drilling grinding (axial center water injection),
Metal bond diamond core drill grinding wheel
Stone (# 120, φ8mm, grinding wheel peripheral speed is 60m / mi
n. , The cut is 40 mm / min. , Total cut is 1
Kistler when processing under the condition of 0 mm x 10 times
The power resistance value by the dynamometer is 600N or less
Alumina ceramics to collect.