JPH02208253A - Method for producing cordierite ceramic composite - Google Patents

Abstract

PURPOSE:To increase strength, toughness and thermal shock resistance with homogeneous formation of columnar mullite particles of excellent thermal resistance and spinel particles by roasting a formed product from a starting cordierite powder containing a prescribed amount of alumina powder at a prescribed temperature. CONSTITUTION:The starting particles of cordierite (2MgO.Al2O3.5SiO2) is combined with 5 to 30wt.% of alumina powder of <=5mm. The mixed powder is formed and roasted at >=1300 deg.C so that the mullite particles and spinel particles are allowed to distribute homogeneously.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for producing cordierite ceramic composites used for members requiring mechanical strength, heat resistance, and thermal shock resistance. This invention relates to a method of uniformly precipitating and dispersing columnar mullite and spinel in cordierite by utilizing a chemical reaction between illite and alumina to obtain a sintered body with excellent strength, fracture toughness, and heat resistance.

Conventional technology As is well known, ceramics are materials with high strength, high hardness, and excellent wear resistance, and are used in a wide range of applications, among which cordierite (2Mg0, 2A & 203
・5SiO2) is known as a ceramic with excellent thermal shock resistance. This cordierite ceramic has been processed into a honeycomb structure and has been put to practical use as a catalyst carrier for automobile exhaust gas purification.

In addition, heat resistance is one of the characteristics required along with thermal shock resistance, and for example, in Japanese Patent Application Laid-Open No. 53-82822, by adjusting the type and particle size of the magnesia source material, mullite (3Aρ203 / 2SLO2), Spinel (MgO-JV203), Saphirin (4Mg0
It has been shown that the pore distribution of a sintered body containing ・5A&203・2SLOz> can be controlled to improve heat resistance without deteriorating thermal shock resistance.

Further, Japanese Patent Application Laid-Open No. 58-95643 discloses a technique for obtaining a sintered body having a coefficient of thermal expansion close to that of silicon by sintering mullite and ]-Dierai 1.

In addition, Iyo, Watanabe et al. (1985, December, Ceramics Association Journal) reported that by adding mullite to cordierite and firing it, a sintered body with excellent strength and heat resistance can be obtained. .

These conventional techniques are based on talc (3Mc+0・4Sj0
2・H2C), Kao')n (A&203 ・2Sj02
・When cordierite is synthesized from raw material powder such as 2H20), it is a technology that combines it with by-products such as mullite, spinel, and sapphirine, and it also involves adding mullite powder to cordierite powder and causing a chemical reaction. This technology uses sintering to make the material denser.

However, the room temperature bending strength of conventional cordierite ceramics is 3.5 to 10, and zirconia (80 to 1
It is inferior to other structural ceramics such as 20Kg), alumina (25~5!MI7J>), and mullite (15~25~'J4rrX>).

Furthermore, the fracture toughness value of conventional cordierite is 2Mpaυ1, which is known to be lower than that of zirconia (7Mpa) and alumina (3.5Mpa).

In terms of heat resistance, it is known that the strength rapidly decreases from around 1200℃, and those with low purity have a temperature of 1350℃.
At temperatures above ℃, a liquid phase is formed and deformation occurs.

On the other hand, alumina and zirconia have excellent room temperature strength and fracture toughness values, but have poor thermal shock resistance, and do not cause a decrease in strength due to thermal shock due to water quenching, and the temperature difference is 500°C compared to copierite.
In contrast to the above, alumina is 200°C1 zirconia is 30°C
It is significantly inferior to 0℃. Therefore, it is difficult to use both alumina and zirconia as they are in applications that require thermal shock resistance and mechanical strength.

Problems to be Solved by the Invention The present invention takes into account the disadvantages of conventional cordierite ceramics in that they are inferior in room temperature bending strength, fracture toughness, and heat resistance to other ceramics such as zirconia, alumina, and mullite. The purpose of this paper is to propose a method for producing a Coop-Yelai 1-ceramics composite with excellent strength, toughness, and heat resistance by utilizing the chemical reaction of alumina.

Means for Solving the Problems In manufacturing cordierite, mullite, and spinel composite ceramics, the inventors used cordierite powder with a particle size of 20 Am or less and alumina powder with a particle size of 5I1 m or less, and during firing. The following chemical reaction produces mullite grains and spinel grains with a uniform distribution, and unlike the conventional method of adding mullite, each grain can develop into a columnar shape, resulting in a particle dispersion effect. It was discovered that it was possible to obtain a composite material with high strength, fracture toughness, and heat resistance, and that by changing the blending ratio of cordierite and alumina, it was possible to manufacture materials with different characteristics.

χ(2Mg0・2Ari203・5Sj○2)+V
(Ag203)-)Z(3A12203 ・2SLO
2) +W (MgO-A#203) That is, this invention uses cordierite raw powder with a particle size of 5. After adding 5 to 30% by weight of alumina powder below am, it is molded and heated to 1300°C.
By firing at the above temperature, the purpose is to uniformly precipitate and disperse Murai grains and spinel grains in the cordierite through the chemical reaction.

FunctionAlumina powder was used as a ceramic to be added to cordierite powder because, as shown above, mullite and spinel, which have excellent strength and heat resistance, are produced through a chemical reaction.
This is to improve heat resistance, strength, and toughness, which are disadvantages of cordierite, by combining it with cordierite.

The particle size of the cordierite powder is preferably 50 μm or less. If the particle size is larger than that, the sinterability will be reduced and the strength will be reduced. At the same time, the mixing with the alumina powder becomes insufficient, the chemical reaction becomes non-uniform, and the dispersibility of Murai 1- and spinel deteriorates.

The particle size of the alumina powder was limited to 5/1 m or less.
[If the particle size exceeds...] - This is because the dispersibility of each particle after mixing with dayerite is insufficient, and the dispersibility of mullite and spinel produced by chemical reaction deteriorates.

Note that it is preferable that the impurities in the cordierite powder be 1% by weight or less in order to produce highly pure mullite and spinel through chemical reaction.

The firing conditions for the mixture of cordierite powder and alumina powder are 1300°C or higher (preferably 1300 to 1460°C).
) is because the sintering reaction rate decreases below 1300° C. and the strength of the sintered body decreases.

In addition, when the firing temperature exceeds the melting point of Coop Yerai 1~, the amount of liquid phase generated during sintering increases, and the shape of the fired crystals changes.
Since the dimensional accuracy is affected, it is preferable that the upper limit of the firing temperature be set to the melting point of Cope Yellai 1 or higher.

Further, the firing time is set to about 0.5 to 20 hours, preferably about 1 to 10 hours, in order to ensure sufficient firing and to prevent a decrease in strength due to excessive firing.

Example particle size 20. Cordierite powder with a particle size of 577m or less
The following alumina powders were blended in the proportions shown in Table 1, mixed in a ball mill, the resulting mixed powder was press-molded at a pressure of 1.5t4, and this molded product was fired under the conditions shown in Table 1,
Table 1 shows the mechanical properties of the obtained cordierite ceramics.

For comparison, Table 1 also shows products that deviate from the production conditions of the present invention, products in which mullite and spinel were added to cordierite, and products in which mullite and spinel were added to cordierite. .

Figure 1 shows the relationship between bending strength when the amounts of alumina and mullite added are changed under the conditions of firing temperature 1425°C and firing time 2 hours, and Figure 2 shows the relationship of bending strength when the addition amount of alumina and mullite is changed. The relationship between the amount and the fracture toughness value (K+c) is shown.

In addition, Figure 3 shows the microscopic structures of the cordierite ceramic sintered body with alumina added and the cordierite ceramic sintered body with mullite added, shown in Figure (A) and Figure (B), respectively. .

From Figure 1, the effect of alumina addition on bending strength is:
It is found that 5 to 30% by weight is appropriate.

From Figure 2, the fracture toughness value increases with the addition of alumina,
It can be seen that this is higher than that with mullite added.

In addition, the addition of alumina improves the high temperature strength by approximately 100℃, and the practical heat resistance temperature is 1300℃.
and rose.

Moreover, from FIG. 3, there is a difference in the structure between the addition of alumina and the addition of mullite. In other words, the mullite grains (M) in the sintered body agglomerate to form large grains in the sintered body in which mullite 1 or more is added in Figure (B), whereas the mullite grains (M) in Figure (A) in which alumina is added are columnar. It can be seen that the mullite grains (M) and spinel grains (S) that have developed are uniformly distributed.

Next, test No. 3 of the present invention example - Day Equi 1~
A sintered ceramic body (90% by weight of cordierite + 10% by weight of alumina) as shown in Fig. 4] was produced, and this caulking plate (1) and
Comparative example test No. 1 sintered body Kucoilite 10
The coking plates 1 to 1 made with 0% by weight) were respectively attached to the lid of a coke oven as shown in FIG. 5, and the actual equipment was operated to examine the condition after 6 months of use. In Figure 5, (2) is the coke oven, (3) is the coke oven lid, and (4) is the coke oven.
(5) indicates a heat insulating material, and (5) indicates a coke.

As a result, no major cracks or deformations were observed in either case, but the chipping at the plate end that was thought to have occurred when opening and closing the furnace lid was better in Test No. 3 of the invention example than in Test No. 3 of the comparative example.
o, it was less than 1.

In addition, various types of caulking plates were manufactured using the sintered body of Test No. 3 of the present invention example, and the thickness of the caulking plate was thinner than the normal thickness.
As a result of conducting the same actual furnace test as above, test N of comparative example
It was found that it was possible to reduce the thickness by 40% while maintaining the same durability as 1, and that it was sufficiently durable for practical use.

The following margin figure 5 is a schematic plan view showing the usage state of the above caulking plate.

1... Coking plate, 2... Coke oven 3
... Furnace M4 ... Insulating material 5 ... Coke Applicant Sumitomo Metal Industries, Ltd. As described in detail of the invention, according to the method of this invention, columnar mullite particles and spinel particles with excellent heat resistance are produced. Because it can be produced in a uniform distribution, it improves strength, fracture toughness, heat resistance,
It is possible to obtain a cordierite composite with excellent thermal shock resistance, which has the great effect of being widely applicable to structural members that are subject to thermal shock, such as coking plates for coke ovens.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of alumina and mullite added and the bending strength in an example of the present invention, and FIG. 2 is a diagram showing the relationship between the amount of alumina and mullite added and the fracture toughness value in the same example. Figure 3 is a schematic diagram showing the structure of the sintered body in the same example as observed under a microscope. Fig. 4 is a perspective view showing the caulking plate used in the above example, and the addition amount (wt
%) Addition amount (wt%) (A) (B) Cork plate

Claims (1)

[Claims] A method for producing a cordierite ceramic composite, comprising adding 5 to 30% by weight of alumina powder with a particle size of 5 μm or less to cordierite raw material powder, shaping the mixture, and firing the mixture at a temperature of 1300° C. or higher.