JPS6055459B2 - alumina porcelain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to alumina porcelain with improved mechanical strength suitable for cutting tools, mechanical seals, butterfly valves, and the like.

Conventionally, a small amount of MgO as a crystal growth control agent has been added to high-purity fine alumina, or MgO and 1220
0 or alumina porcelain with Y203 added.

These porcelains were only used for corrosion resistance or as shipping materials, and their mechanical strength was poor, so there was a limit to their use as mechanical structural parts. The main reason why the mechanical strength of conventional high-purity alumina porcelain is not strong is that the MgO used in the past is no longer able to sufficiently control the sintering of high-purity alumina, which is fine and highly reactive. That's true.

The present invention has been made to solve the above problems, and the conventional research on sintering control of high-purity alumina has been based on the assumption that the atomic diffusion mechanism is the main one, and various additives have been investigated. In contrast, the present invention bases the sintering of alumina on a mechanism mainly based on liquid phase sintering, and achieves crystal growth through the dissolution and precipitation process of alumina in the liquid phase. It is something.

Densification during sintering of ceramic tends to involve crystal growth, and it is quite difficult to obtain a high-density sintered body with small crystal size. In particular, the more reactive fine alumina is, the more rapid crystal growth occurs, and as soon as the pores are eliminated at the grain boundaries, they become trapped within the crystal grains, resulting in large, irregular, and low-density crystals. However, the strength was also low. One way to solve this problem is to slow down the crystal growth rate as much as possible.

In this way, pores can be sufficiently eliminated and the crystals are small, so great strength can be achieved. The present invention is based on the conventionally used Ca0. Si0. , In addition to MgO, La,
Os, Ta2O5, Y, 0. A predetermined amount of 5A1, 0. By adding M
Contains 0.15 to 0.64 mol% gO, and contains component (X) (C
aO and Le. 0, the molar ratio of CaO. (
5La203 mixture) - (Y) component (SlO2 and Y
SiO2 and Y2O3 with a molar ratio of 2O3 of 1.5 to 4
In the ternary composition diagram represented by the (Z) component (Ta2O5), the components within the area (including on the sides) of triangles A, B, and C formed by the line segments connecting Said M
The total amount with gO is 0.4 to 0.9 mol%, and the balance is Al.
To provide alumina porcelain characterized by being made of 2O3 and inevitable impurities.

According to the present invention, alumina is dissolved on the fine crystal surface with a large chemical potential or on the mutual pressure contact surface of two crystal grains, passes through the liquid phase, and is precipitated on the negative curvature surface with a small chemical potential or the large grain size surface. The rate of this process is determined by either the solute diffusion rate or the solution precipitation rate, but it is currently unclear which one controls the rate, but the crystal growth rate could be slowed down by incorporating the additive of the present invention. . MgO, CaO, La2O3, SlO2 and Y2O3 are determined from the range where the strength of alumina porcelain is high, and (X
)-(Y) component (SiO
SjO2 and Y in which the molar ratio of 2 and Y2O3 is 1.5 to 4
A (X=0.7, Y=0.1 in Figure 1, which shows the ternary system composition of the (Z) component (Ta2O.)
5, Z=0.15) and B (X=0.45, Y=0.
5, Z=0.05 point)C(X=0.2, Y=0.2,
The area surrounded by the line segment connecting the point Z=0.6 was determined as the area where a liquid phase capable of dissolving alumina could be formed.

This will be explained below using examples. Example 1 Alumina with an average particle size of 0.2μ (Tie 3 manufactured by Daimei Chemical Co., Ltd.)
Micron AGl purity 99.9%) M per 1000g
gOO. 25 wt%, CaOO. O23Wt%, La2
O3O. O58Wt%, SlO2BO. O25Wt%,
Y2O3O.04Wt%~Ta2O5O. 23 wt% was added and put into an alumina porcelain ball mill with a capacity of 6 e along with 1.5 e of water, mixed for a certain period of time using an alumina ball 4 k9 with a diameter of 30 φ, and then spray-dried to form a powder with dimensions 10 x 30 x under a pressure of 1500 k9/cl. A test piece of 5tTm1rL was made and fired in an electric furnace at a temperature of 1500 to 1600°C.

The obtained alumina porcelain had a density of 3.92 g/d and a transverse rupture strength of 5800 kg/Clt.

Example 2 Alumina (manufactured by Sumitomo Chemical Co., Ltd.) with an average particle size of 0.3p
Purity 99.99% to U-2) 700g and average particle size 0.2
μ alumina (Taimicron AGl manufactured by Daimei Chemical Co., Ltd.)
Purity 99.9%) 300g, MgOO. 2wt
%, CaOO. l4Wt%, La2O3O. 35Wt%
, SiO2BO. O49wt%, Y2O3O. O8Wt
%, Ta2O5O. Add 36 wt% of water and 1.5) e polyvinyl alcohol Kg (a). 5Wt%) and volume 6
After putting it into an alumina porcelain ball mill (e) and mixing with a 4k9 alumina ball with a diameter of 30φ for a while, it was spray-dried and heated to 1500
A test piece with dimensions of 10 x 30 x 5 tWS was made at a pressure of kg/C7lf, and fired in an electric furnace at a temperature of 1500 to 1650°C.

The obtained alumina porcelain had a density of 3.91 g/al and a transverse rupture strength of 5300 k9/Cli.

Example 3 Alumina (manufactured by Sumitomo Chemical Co., Ltd. A) with an average particle size of 0.3μ
KP-20, purity 99.99%) for 1000g,
MgOO. l2Wt%, CacO3O. O38Wt%,
La2O. O. O34Wt%, SlO2BO. Ol6W
t%, Y2O3O. O35Wt%, Ta2O5O. 47
After adding V/t% and stirring and mixing with water 1.5e1 polyethylene glycol 6g (0.6Wt%) in a stirring emulsifier for 1 hour, spray drying was carried out and the dimensions were 10 x 30 x 5 twr at a pressure of 1500k9/d! Make a test piece of n, 14
It was fired in a hydrogen atmosphere at a temperature of 70 to 1550°C.

The obtained alumina porcelain had a density of 3.93 g/C7l and a transverse rupture strength of 5300 kg/Clt. Example 4 Alumina (manufactured by Reynolds Co., Ltd. RC) with an average particle size of 0.3μ
-HP-DBMl purity 99.99%) MgOO. O67wt%, CacO3O. O82Wt
%, La2O3O. l4Wt%, SlO2O. O6lW
t%, Y2O3O. O6lWt%, Ta2O5O. O9
Add lW%, water 1.5e1 polyvinyl alcohol 3
g (0.3wt%) and polyethylene glycol 2g (0.
．． 2wt%) in a stirring emulsifier, spray-drying, and applying a pressure of 1500 k9/d to a powder with dimensions 10 x 30 x
Make a 5t7m test piece and heat it to 1500-1600℃
It was fired in a butane-fired gas furnace at a temperature of .

The obtained alumina porcelain had a density of 3.93 g/CTl and a transverse rupture strength of 5700 k9/d. The above Examples 1 to 4 are shown in Figure 1 of the ternary composition diagram as A, C, C, and 2, and Examples 1 to 4 are shown in Table 1 below for easy understanding.

In addition, regarding the measurement results obtained in Examples 1 to 4, the relationship between sintered density and transverse rupture strength is shown in Fig. 2 for conventional alumina porcelain (
MgOO. 25 wt%), and
Figure 3 shows the relationship between sintered density and average grain size in comparison with conventional alumina porcelain.

As is clear from FIGS. 2 and 3, in the alumina porcelain of the present invention, the relationship between transverse rupture strength and average grain size at each sintered density of 3.89 to 3.95/CTl is the same as in Example 1. 5100-5800k9/c#f and 1.1
~1.7μ, and in the mouth of Example 2 it was 4600~
5300kg/C7ll and 1.3-20μ,
In Example 3 C, 4700 to 5300k9/C
rl and 1.4 to 1.8 μ, and in Example 4-2, 5000 to 5700 kg/cl and 1.2 to 1.8 μ
1.5μ and conventional alumina porcelain MgOO. 25W
Comparative products with added t% have transverse rupture strength of 2800 to 3900k.
9/C7ll, the average particle diameter was 1.75 to 2.75μ, and it was clearly confirmed that the alumina porcelain of the present invention had improved transverse rupture strength by at least 60% over the conventional alumina porcelain.

Furthermore, it is clear that these improvements in strength are largely related to the average grain size of the sintered particles. As described above, the alumina porcelain of the present invention has excellent strength and can be used in a wide variety of applications such as cutting tool materials and mechanical structural parts.

[Brief explanation of the drawing]

Figure 1 is a composition diagram showing the composition of the present invention, Figure 2 is a diagram showing a comparison of measured values of the relationship between sintered density and transverse rupture strength between the present invention and conventional products, and Figure 3 is a diagram showing the relationship between sintered density and transverse rupture strength. 1 is a diagram showing a comparison of the relationship between sintered density and average grain size between the present invention and a conventional product.

Claims (1)

[Claims] 1 Contains 0.15 to 0.64 mol% of MgO, component (X) (a mixture of CaO and La_2O_3 in which the molar ratio of CaO and La_2O_3 is 1.5 to 4) - component (Y)
A mixture of SiO_2 and Y_2O_3 in which the molar ratio of SiO_2 and Y_2O_3 is 1.5 to 4) - (Z) component (
In the ternary composition diagram represented by Ta_2O_5),
=0.7Y=0.15Z=0.15 point AX=0.45
Y=0.5Z=0.05 point BX=0.2Y=0.2Z
Triangle A formed by line segments connecting point C with =0.6
The total amount of the components within the areas of , B, and C (including on the sides) and the MgO is 0.4 to 0.9 mol%, and the remainder is Al_2O.
Alumina porcelain characterized by consisting of _3 and inevitable impurities.