JP2002316866A - Member for heat treatment consisting of alumina sintered compact having excellent durability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for heat treatment consisting of an alumina sintered compact having excellent durability. SOLUTION: This member for heat treatment consists of an alumina sintered compact having excellent durability. (a) The alumina sintered compact has an Al2 O3 content of >=95 wt.%. (b) The pores thereof have a round shape, and are composed of sealed and connected pores. (c) The average pore size of the sintered compact is 2 to 100 μm. (d) The average crystal particle size of the sintered compact is 5 to 50 μm. (e) The relative density of the sintered compact is 50 to 70%. (f) The amount of deflection at 140 deg.C under the stress of 2 MPa is <=2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat treatment member made of an alumina sintered body having excellent durability. The heat treatment member referred to in the present invention includes electronic component materials such as a piezoelectric material and a dielectric material, a lithium ion secondary battery positive electrode material, a phosphor material and a ceramic material heat treatment container, a single crystal growing crucible, and a metal melting material. These include crucibles, furnace tubes for various electric furnaces, support tubes, radiant tubes, gas injection tubes, gas sampling tubes, thermocouples for temperature measurement, protective tubes for various devices, and support jig materials.

[0002]

[Prior art and its problems] Alumina sintered body has corrosion resistance,
It has excellent heat resistance, is inexpensive and easy to handle compared to other ceramics, and has long been used in a wide range of fields such as high-temperature members, heat treatment vessels, setters, furnace tubes, and temperature measurement protection tubes. .

[0003] In recent baking of electronic ceramics, the temperature is rapidly raised and lowered in order to minimize the evaporation component of the object to be fired and to reduce the fluctuation of the composition. On the other hand, in order to reduce the firing cost, it is desired to enhance the heat insulation of the firing furnace, reduce the weight of the firing member, and reduce the loss of thermal energy. For this reason, for example, a baking setter that is thin, lightweight, excellent in thermal shock resistance and high in load resistance is required.

[0004] The heat treatment member made of a dense sintered body has excellent corrosion resistance, but has the risk of cracking due to thermal shock at rapid temperature rise / fall, and has the disadvantage of being heavy. Have.

[0005] From such a fact, Japanese Patent No. 278806.
No. 1 proposes a firing jig that is lightweight and has excellent thermal shock resistance. However, this patent invention discloses a light-weight, excellent thermal shock-resistant baking jig that defines the porosity, pore shape, and pore diameter. It is not sufficiently satisfactory in terms of life, such as easy removal, low strength, and deformation of the jig due to use.

In general, electronic parts and the like are fired in a state where they are stacked and placed on a heat treatment setter, but a fired body directly in contact with the setter has a higher atmosphere during firing than a non-fired body. However, there is a problem that desired characteristics cannot be obtained. Therefore, a heat treatment setter used for firing electronic components and the like is required to have a moderate air permeability capable of controlling a firing atmosphere.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat treatment member made of an alumina sintered body having excellent durability.

[0008]

SUMMARY OF THE INVENTION The present invention has been studied intensively in view of the above-mentioned situation, and as a result, it has been found that alumina-based sintered bodies have a specific relative density and are rounded and closed. Found a heat treatment member made of an alumina-based sintered body with excellent durability by controlling the pore size and crystal grain size, and controlling the relative density of the sintered body. Was. In the present invention, durability means not only resistance to crack generation and cracking due to rapid heat / quenching, but also excellent corrosion resistance and creep resistance.

A first aspect of the present invention is (a) an alumina-based sintered body having an Al ₂ O ₃ content of 95% by weight or more;
The pores have a rounded shape and consist of closed and connected open pores, and (c) the average pore diameter of the sintered body is 2 to 10
0 μm, and (d) the average crystal grain size of the sintered body is 5 to 50 μm.
m, (e) the relative density of the sintered body is 50 to 70%,
(F) The amount of deflection under stress of 1400 ° C. and 2 MPa is 2
mm or less, and relates to a heat-treating member made of an alumina-based sintered body having excellent durability, which is made of an alumina-based sintered body. The second aspect of the present invention is that MgO is 0.3% by weight.
The heat treatment member according to claim 1, wherein the heat treatment member is made of an alumina sintered body having excellent durability. The third aspect of the present invention relates to the heat treatment member according to claim 1 or 2, wherein the zirconia content is 5% by weight or less.

Hereinafter, the present invention will be described in detail.

(A) Regarding that the alumina content is 95% by weight or more, in the present invention, the alumina content of the sintered body needs to be 95% by weight or more. When the alumina content is less than 95% by weight, the amount of impurities contained in the sintered body increases, the second phase and the glass phase formed by impurities at the crystal grain boundaries increase, and not only the corrosion resistance decreases, but also In addition, mechanical properties, particularly strength at high temperatures, are reduced, and as a result, creep resistance and thermal shock resistance are lowered, which is not preferable. The alumina content is preferably at least 97% by weight.

(B) With regard to the point that the pores have a rounded shape and are composed of closed and connected open pores, the formation of the closed pores and the connected open pores in the present invention requires a predetermined relative It is necessary to use organic and round particles such as organic spherical particles such as acrylic resin spherical particles and polysaccharide spherical particles as a pore-forming agent so as to obtain a density and a pore diameter. When this pore-forming agent was added to the ceramic powder, mixed and molded, and then fired, the organic pore-forming agent disappeared, leaving closed pores and connected open pores as traces. The shape of the open pores is essentially a shape based on the shape of the pore-forming agent, and the closed pores become rounded and sealed by using a rounded pore-forming agent,
Also, the closed pores can be substantially independent. The connected open pores have a shape in which the rounded pores are connected. If the pore shape is not rounded,
When stress is applied to the sintered body, stress concentration is apt to occur in the pores, and strength and thermal shock resistance decrease and deformation at high temperatures are apt to occur, which is not preferable. Note that the closed pores in the present invention refer to internal pores that do not communicate with the outside.

(C) Regarding that the average pore diameter is 2 to 100 μm, in the present invention, the average pore diameter of the sintered body is 2 to 100 μm, preferably 5 to 80 μm, more preferably 5 to 50 μm or less. It is necessary to be.
When the average pore diameter is less than 2 μm, the effect of improving the durability by pore formation is small, and when the average pore diameter exceeds 100 μm, continuous pores increase and the durability decreases, which is not preferable. The average pore diameter is obtained by mirror finishing the sintered body, observing it with a scanning electron microscope, measuring 100 pore diameters at random, converting the pore diameter into an equivalent circular diameter, and obtaining an average value: P,

## EQU1 ## The average pore diameter is determined as 1.5 × P.

(D) The average grain size of the sintered body is 5 to 50 μm.
In the present invention, the average crystal grain size of the sintered body needs to be 5 to 50 μm. When the average crystal grain size is less than 5 μm, deformation or the like occurs due to repeated use, and durability is reduced, which is not preferable. On the other hand, if it exceeds 50 μm, the thermal shock resistance is undesirably reduced. Preferably 10 to 40μ
m. The average crystal grain size is obtained by mirror-finishing a sintered body, performing thermal etching, observing with a scanning electron microscope, measuring the diameter of 100 crystal grains at random, converting the diameter into an equivalent circular diameter, and calculating the average value: Find d,

## EQU2 ## The average crystal grain size is determined as D = 1.5 × d (μm).

(E) With respect to the fact that the relative density is 50 to 70%, in the present invention, the relative density of the sintered body needs to be 50 to 70%, more preferably 53 to 68%. It is necessary that 50 relative density
% Is not preferable because the amount of pores increases and the pores are connected to each other to increase the pore diameter and decrease the durability. On the other hand, when the relative density exceeds 70%, not only is the thermal shock resistance reduced, but also the number of connected open pores is reduced, which is not preferable. In the present invention, the sintering temperature is lowered to leave pores without sufficiently sintering, or the pores are formed even when sintering at a high temperature using a raw material powder having a large particle size like a conventional porous material. Not surviving,
In the portion where no pores exist, the crystal is sintered in exactly the same manner as a conventional dense sintered body. By doing so, a heat treatment member having high thermal shock resistance, high creep resistance, and high strength and excellent corrosion resistance can be obtained.

The relative density referred to in the present invention is:

## EQU3 ## The value is calculated by (sintered bulk density / theoretical density) × 100 (%).

(F) With respect to the fact that the amount of deflection under a stress of 1400 ° C. and 2 MPa is 2 mm or less, in the present invention, the amount of deflection of the sintered body is measured under the following conditions. The sintered body was processed into 5 × 2 × 150 mm, and the upper span: 31.3 mm, the lower span: 100 mm, four-point bending, stress of 2 MPa, 1400 ° C., position of lower sample 50 mm after heating and holding for 5 hours The amount of deflection is measured. In the present invention, the deflection amount measured under the above conditions is 2
mm or less. If it exceeds 2 mm, the object to be fired cannot be fired in a large amount, and the deformation due to repeated use becomes large, so that the life as a heat treatment member is shortened. It is more preferably 1.8 mm or less. When measuring the deflection amount other than the deflection measurement sample shape, the deflection ratio measured with the same ratio of the length of the upper span and the lower span and the applied load: δ, corrected by the following equation: It is necessary that δ ′ is 2 mm or less.

Δ ′ = δ × {length of lower span (mm) / 100} In short, when the sample size becomes shorter, lower span 100
If the measurement cannot be made in mm, it is corrected from the shape.

(G) Regarding the fact that MgO is contained in an amount of 0.3% by weight or less based on the alumina sintered body, the present invention contains MgO in an amount of 0.3% by weight or less based on the alumina based sintered body. This has the effect of improving the sinterability and increasing the uniformity of the crystal grain size. Furthermore, zirconia and Mg
When O is simultaneously contained, it is possible to suppress the strength deterioration under a reducing atmosphere. The content of MgO is more preferably 0.25% by weight or less. If MgO is contained in an amount of 0.3% by weight or more, the second phase tends to precipitate at the alumina crystal grain boundaries, and the durability is poor, which is not preferable.

(H) Regarding the fact that zirconia is contained in an amount of 5% by weight or less, in the present invention, the sintered body preferably contains 5% by weight or less, more preferably 3% by weight or less. preferable. The zirconia crystal grain size is preferably 0.5 μm or less. Zirconia is important not only for improving the strength and toughness of the alumina sintered body, but also for improving the sinterability and obtaining a microstructure with a small crystal grain size distribution. If the zirconia content exceeds 5% by weight or the crystal grain size exceeds 0.5 μm, cracks occur in the sintered body due to residual expansion due to the difference in thermal expansion between zirconia and alumina due to repeated heating and cooling. However, it is not preferable because of lack of durability.

The heat treatment member of the present invention having excellent thermal shock resistance can be manufactured by various methods, one example of which is shown below.

The alumina raw material powder preferably has a purity of 99% or more and an average particle size of 2 μm or less, more preferably 1.5 μm or less. If the average particle size exceeds 2 μm, there are many defects inside the sintered body,
It is not preferable because mechanical properties such as thermal shock resistance are deteriorated.

The zirconia raw material powder may be a liquid phase
It is preferable to use a powder produced by the method
Product is 5m²/ G or more, more preferably
8m ²/ G or more. Furthermore, zirconia sol and baking
Uses a zirconium compound that becomes zirconia by formation
You can also. Specific surface area of zirconia raw material powder is 5m ²
/ G, the dispersibility of the zirconia crystal particles is reduced.
As well as zirconia crystal particles present in the sintered body
Is undesirably increased since durability is reduced.
In addition, zirconia contains 1-5 mol% of yttria
Is more preferable.

The sintered body contains SiO ₂ and TiO.
₂ , the total amount of Fe ₂ O ₃ , CaO, Na ₂ O and K ₂ O is preferably at most 2% by weight, more preferably at most 1% by weight. If the amount of impurities exceeds 2% by weight, a large amount of a glass phase is formed at the crystal grain boundary, and the high-temperature characteristics are undesirably reduced.

Each ingredient is blended with each raw material powder in a predetermined amount, and crushed, dispersed, and mixed by a crusher such as a pot mill or an attrition mill using water or an organic solvent as a solvent. When MgO is added, it may be added in the form of a magnesia compound such as a hydroxide or a carbonate at the time of pulverization, dispersion, and mixing, or a powder previously added to the alumina raw material powder may be used. The average particle size of the obtained powder was 1.
It is preferably 5 μm or less, more preferably 1.
0 μm or less. If the particle size is outside these ranges, the moldability is reduced, the obtained sintered body not only contains many defects, but a sintered body having a microstructure of the present invention cannot be obtained,
Not only is thermal shock resistance reduced, but also other mechanical properties and corrosion resistance are reduced.

For the formation of pores, acrylic resin spherical particles, polysaccharide spherical particles and the like are added as pore-forming agents to the pulverized / dispersed slurry so as to have predetermined relative density and pore diameter. It is necessary that the particle shape of the pore-forming agent is spherical, and if it is not spherical, the formed pore shape is not spherical, which is not preferable.

When a molding method such as press molding or rubber press molding is employed, if necessary, a known molding aid (eg, wax emulsion, PVA, acrylic resin, etc.) is added to the pulverized / dispersed slurry and sprayed. It is dried by a known method such as a drier to produce a molding powder, and molded using this. When the casting method is adopted, a known binder (for example, wax emulsion, acrylic resin, etc.) is added to the pulverized / dispersed slurry as necessary, and the slurry is cast and filled using a plaster type or a resin type. It is formed by casting and pressure casting. Further, when the extrusion molding method is employed, the slurry that has been pulverized and dispersed is dried, sized, and mixed with water, a binder (eg, methyl cellulose), a plasticizer (eg, polyethylene glycol), a lubricant (eg, polyethylene glycol). For example, stearic acid)
Are mixed to form a kneaded material, which is extruded. The molded body obtained as described above is fired at 1500 to 1800 ° C, more preferably 1600 to 1750 ° C to obtain a sintered body.

[0027]

The present invention will be described below with reference to examples.
The present invention is not limited thereby.

Examples 1 to 8 and Comparative Examples 1 to 8 When zirconia is added to alumina powder obtained by mixing raw materials in accordance with the amounts shown in Table 1 using alumina powder having a purity of 99.8% and an average particle diameter of 2 μm. Was prepared by mixing a predetermined amount of zirconia powder and magnesium carbonate in the case of adding magnesia so as to have a predetermined amount, and pulverizing, dispersing, and mixing using a pot mill using water or ethanol as a solvent to prepare a slurry. In Comparative Example 5, alumina powder having a purity of 99.8% and an average particle diameter of 15 μm was used. As the pore-forming agent, polysaccharide spherical particles were added and mixed so as to have predetermined porosity and pore diameter.
Also, the zirconia powder does not contain Y ₂ O ₃ ,
A powder containing 3.5 mol% and having a specific surface area of 15 m ² / g was used. Comparative Examples 4 and 5 are sintered bodies in which the pore density was not added and the relative density was within the range of the present invention by the firing temperature. A binder such as PVA was added to the obtained slurry, and the slurry was dried by a spray drier to obtain a molding powder. The obtained molding powder was press-molded in a mold at a pressure of 1 tonf / cm ² ,
Fired at 50-1800 ° C, 150mm square and 5m thick
m was prepared. Table 2 shows the properties of the sintered bodies of the obtained heat treatment setters of Examples 1 to 8 and Comparative Examples 1 to 8. Examples 1 to 8 are heat treatment setters within the scope of the present invention, and Comparative Examples 1 to 8 are heat treatment setters that do not satisfy at least one of the requirements of the present invention. It is clear that the heat treatment member of the present invention has excellent thermal shock resistance and excellent durability. The deflection amount of a rod-shaped test piece processed to 5 × 2 × 150 mm was 31.3 mm for the upper span, 100 mm for the lower span, and 2MP.
A creep test was performed at 1400 ° C. for 5 hours under the stress of “a”, and the amount of deflection of the test piece after the test was measured with a dial gauge. The thermal shock resistance was obtained by placing the obtained heat treatment setter on an refractory and inserting it into an electric furnace heated and maintained at 800 ° C., and after heating and holding for 30 minutes, immediately left the furnace while being placed on the refractory. And quenched at room temperature to evaluate the presence or absence of cracks. In addition, the presence or absence of cracks due to the repetition of the same conditions as above was also evaluated. It is clear that the heat treatment member of the present invention has excellent durability.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The heat-treating member of the present invention has excellent thermal shock resistance and corrosion resistance such that no crack is generated even when the temperature is rapidly increased or decreased, so that electronic component materials such as piezoelectrics and dielectrics, lithium ion 2 Containers for heat treatment of secondary battery positive electrode materials, phosphor materials and ceramic materials, crucibles for growing single crystals, crucibles for melting metals, furnace tubes for various electric furnaces, support tubes, radiant tubes, gas injection tubes, gas sampling tubes, temperature measurement Useful for thermocouples, protective tubes for various devices, and jig materials for supports.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuya Tani 3--24, Enri-Ono-cho, Sakai-shi, Osaka Nikkato Co., Ltd. (72) Toshio Kawanami 3-Tori Ono-cho, Sakai-shi, Osaka No. 2-24 F-term in Nikkato Co., Ltd. (reference) 4G030 AA07 AA12 AA17 AA36 BA20 BA23 BA25 BA32 CA04 CA09 4K051 AA03 BE03 4K055 AA04 AA06 HA01 HA07 HA27

Claims (3)

[Claims] 1. An alumina-based sintered body having an Al ₂ O ₃ content of 95% by weight or more, and (b) its pores are rounded and have a closed and connected open pores. (C) the average pore diameter of the sintered body is 2 to 100 μm, (d) the average crystal grain size of the sintered body is 5 to 50 μm, and (e)
The relative density of the sintered body is 50 to 70%, and (f) 140
A heat-treating member made of an alumina-based sintered body having excellent durability and having a deflection amount of 2 mm or less under a stress of 0 ° C. and 2 MPa. 2. The heat treatment member according to claim 1, wherein the heat treatment member comprises 0.3% by weight or less of MgO. 3. The heat treatment member according to claim 1, wherein the zirconia content is 5% by weight or less.