JP3080873B2 - Abrasion resistant alumina ceramics and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant alumina ceramic, and more particularly to a wear-resistant alumina ceramic useful as a material for a wear-resistant member and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the fact that ceramics are superior to metal materials in wear resistance and corrosion resistance, and ceramics have been used as a wear-resistant material instead of conventional metals. As this type of ceramics, alumina, zirconia, silicon nitride, silicon carbide, and the like are generally known. Among them, alumina ceramics mainly composed of alumina, which is high in hardness, excellent in corrosion resistance, and inexpensive, are exemplified. Widely used. Normally, alumina ceramics are poor in productivity due to poor sinterability only with alumina alone. Therefore, firing is performed by adding a sintering aid or other additives.

[0003]

However, in the conventional alumina ceramics, the content of Al ₂ O ₃ is 90%.
Since a large amount of the additive is added to the extent of about 95% by weight, a large amount of the second phase and the glass phase other than the alumina crystal is generated at the alumina grain boundary, and the original hardness and strength of the alumina cannot be obtained. However, there is a problem that sufficient wear resistance cannot be obtained. To solve this problem, Al ₂ O ₃ 95 ~
98% by weight as a main component, and 40 to 85% by weight of SiO ₂
%, MgO of 10 to 55% by weight, and CaO of 5 to 50% by weight. Alumina ceramics obtained by adding 2 to 5% by weight of a sintering aid have been proposed in JP-A-7-206514. In Japanese Patent Application Laid-Open No. Hei 7-237961, Al ₂
90 to 95% by weight of O ₃ as a main component, and SiO ₂ 3.0
5.0 wt%, MgO 1.0 to 1.5 wt% and B ₂ O ₃
Alumina ceramics with an addition of 0.5 to 3.5% by weight have been proposed.

Japanese Unexamined Patent Publication No. 7-206514 discloses a technique in which the wear resistance is improved by reducing the amount of a sintering aid, but the sintering property increases as the alumina content increases. Therefore, there is a problem that, depending on the firing temperature, the crystal grain size distribution is apt to be widened and the wear resistance is likely to be reduced.
In addition, when this alumina ceramic is used as a grinding ball, it exhibits excellent properties in rubbing wear, that is, wear when only a grinding ball and water are put into a ball mill and rotated. It was found that the actual wear when the powder was ground was not yet satisfactory.

[0005] Further, the one described in Japanese Patent Application Laid-Open No. 7-237961 shows excellent wear resistance even when the Al ₂ O ₃ content is 90 to 95% by weight, which is almost the same as the conventional one, B added for the purpose of suppressing and lowering the firing temperature
₂ O ₃ exhibits a considerable vapor pressure even at 1000 ° C., and is liable to evaporate during firing, so that its composition tends to fluctuate, inevitably causing variations in its properties, and the inside of the ceramic due to the evaporation of B ₂ O _3. Holes may be formed in the holes, which may lead to a decrease in wear resistance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inexpensive alumina ceramic which can be sintered at a low temperature, has less variation in characteristics, and has excellent wear resistance.

[0007]

According to the present invention, Al ₂ O ₃ 88 is basically used as a means for achieving the above object.
By weight to less than 95% by weight is the main component of the alumina ceramic, and 72-85% by weight of SiO ₂ and MgO
The auxiliary component composed of 3-25 wt% and CaO 3-25 wt%, the content of each component of the sub component SiO ₂ 3.6 to 10
Wt%, MgO 0.2-2.5 wt% and CaO 0.2-
2.5% by weight, while adding them in a total amount of 5 to 12% by weight, while adding unavoidable impurities to 0.5% by weight.
In the present invention, the amount of defects in ceramics is suppressed to 5% or less so that actual wear can be prevented.

[0008] In the present specification, the amount of defects in ceramics means that the ceramics are ground using a surface grinder under the following conditions, then polished, mirror-finished, and the mirror-finished surface (hereinafter, mirror-finished surface). Is photographed with a scanning electron microscope at a predetermined magnification (usually 500 times), and the photograph is subjected to image analysis to separate a defective portion and a non-defective portion by binarization. The ratio of the area to the entire image (that is, the area ratio (%)). This defect part includes not only pores but also defects at the level that does not affect the bulk density value of the sintered body after grinding and polishing, which occur during mirror finishing and that do not affect the bulk density value of the sintered body. It is.

The mirror finishing is performed using a surface grinder and a resin bond type diamond grindstone.
With 40 diamond wheels, the peripheral speed of the wheels is 1500
m / sec, depth of cut: 8 μm, left and right feed speeds (hereinafter, “workpiece”) of non-ground ceramics
It is called work feed. ) At 17 m / sec and grinding about 80 μm, stop cutting and reciprocate the grindstone 5 times, then replace the grindstone with # 400 diamond grindstone,
After grinding about 50μm under the conditions of 0m / sec, depth of cut 5μm and work feed 13m / sec, stop the cut and remove the whetstone 1
0 reciprocation, further replace the grindstone with a # 600 diamond grindstone, after grinding about 20-30 μm under the conditions of a peripheral speed of 1500 m / sec, a cutting depth of 2 μm, and a work feed of 10 m / sec, stop the cutting and grind the grindstone. Grinding was performed by reciprocating 15 times, and then a diamond pad having 40 μm diamond abrasive grains embedded in the ground surface of the ground ceramic was pressed at 2.6 kgf / cm ² and polished for 3 minutes. After polishing to 2.6 kgf / cm ² with diamond abrasives for 5 minutes, 2.6 kg with 3 μm diamond abrasives
Polishing is performed by applying pressure to f / cm ² for 15 minutes, and finally by applying pressure to 1.3 kgf / cm ² with 1 μm diamond abrasive for 5 minutes.

That is, the abrasion-resistant alumina ceramics according to the present invention comprises at least 88% by weight and less than 95% by weight of Al ₂ O ₃ , 3.6 to 10% by weight of SiO _{2 and} 0.2 to 0.2% of MgO.
2.5% by weight, 0.2 to 2.5% by weight of CaO, and 0.5% by weight or less of unavoidable impurities, and the sum of the contents of the sub-components SiO ₂ , MgO and CaO is 5 to 1%.
2% by weight, and when the sum of the contents of SiO ₂ , MgO and CaO of the sub-components is 100, the proportion of each component is 72 to 85% by weight of SiO ₂ , 3 to 25% by weight of MgO,
CaO 3 to 25% by weight, and the unavoidable impurities also include alkali metal oxides 0.4% by weight or less, TiO ₂
0.2% by weight or less, the subcomponent exists as a glass layer at the alumina crystal grain boundary, and has an average crystal grain size of 1.0 to 5.0 μm.
m, bulk density 3.60 g / cm ³ or more, Vickers hardness 1
The flexural strength is at least 100 and the flexural strength is at least 40 kgf / mm ² .

The content of the main component Al ₂ O ₃ is 9
A range from 0 to 94.5% by weight is more preferred. The content of the sub-components is 5 to 10% by weight of SiO ₂ and MgO.
0.4 to 1.5% by weight, CaO 0.3 to 1.5% by weight, and when the sum of their contents is 100, the proportion of each component is 73 to 84% by weight of SiO _{2, and} 0.3% of MgO. More preferably, it is in the range of 5 to 15% by weight and 4 to 15% by weight of CaO.

Further, the present invention further enhances the strength and toughness of the alumina ceramics and further makes ZrO ₂ per 100 parts by weight of the basic composition comprising the above component composition in order to make the macrostructure more uniform. 0.01-1
The content is 5 parts by weight, preferably 0.05 to 10 parts by weight, and more preferably 0.1 to 8 parts by weight.

Further, the present invention provides a method of mixing raw material powders in a predetermined ratio, pulverizing the mixture into powder having an average particle size of 0.5 to 1.0 μm, and molding the obtained fine powder into a predetermined shape. An object of the present invention is to provide a method for producing abrasion-resistant alumina ceramics, which comprises obtaining a compact having a bulk density of 1.90 to 2.10 g / cm ³ and firing the compact. In this case, the specific surface area of fine powder after pulverization is preferably 8m ² / g~15m ² / g, also,
The firing temperature of the molded body is preferably from 1350 to 1600 ° C.

[0014] The content of the unavoidable impurities are set to 0.5 wt% or less, among them, Na ₂ O
The content of alkali metal oxides such as K2O and K ₂ O is 0.45% by weight or less, preferably 0.4% by weight or less.
The content of ₂ is suitably controlled to 0.2% by weight or less, preferably 0.15% or less.

[0015] Further, since the defect amount has a great effect on the wear resistance of ceramics, the defect amount on the mirror-finished surface needs to be 5% or less. This means that the defect amount is 5%
If these values are exceeded, these defects are a starting point of abrasion, which promotes abrasion, which leads to a reduction in abrasion resistance and, at the same time, a reduction in impact resistance. This defect amount is preferably 3% or less, more preferably 2% or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the abrasion-resistant alumina ceramics according to the present invention is prepared by mixing raw materials having the above-mentioned composition, pulverizing the mixture, and crushing the mixture to have an average particle size of 1.0 μm or less and a specific surface area. 8m ² / g or more, more specifically, an average particle diameter of 0.5 to 1.0 [mu] m, a specific surface area to prepare a raw material powder of 8m ² / g~15m ² / g, a predetermined raw material powder obtained Formed into a shape to obtain a molded body with a bulk density of 1.90 to 2.10 g / cm ³
It is manufactured by baking it at a temperature of 1350 to 1600 ° C. Specifically, for example, it can be manufactured by the following method.

(1) First, compounds of the respective constituent elements constituting the alumina ceramics are blended so as to have the above composition ratio, and if necessary, a ZrO ₂ raw material is added, and the ball mill is wet-processed in water or an organic solvent. And a known pulverizer such as an attrition mill, and then pulverized, mixed and dispersed to prepare a raw material powder.

As the alumina raw material as the main component, those having an alumina purity of 99.7% by weight or more, a specific surface area of 2 m ² / g or more, and an average particle diameter of 3 μm or less, preferably 0.5 to 3 μm are suitable. Further, this alumina raw material may be one produced by the alum method or the like, but it is preferable to use an alumina raw material by the Bayer method, which has an advantage that it can be produced at low cost.

As the raw materials for MgO and CaO among the subcomponents, salts such as oxides, hydroxides and carbonates can be used, but the average particle size is 3.0 μm or less, more preferably 0.5 to 0.5 μm.
It is appropriate to use one of 3.0 μm. Also, Si
As the O ₂ raw material, silica stone, quartz, silica sol, ethyl silicate and the like can be used, and clay minerals such as kaolin and Z
Tetragonal zirconia in which a rare earth element such as Y ₂ O ₃ is dissolved in rO ₂ as a stabilizer may be used. As the raw material of the ZrO _2, average particle diameter of 1.0μm or less, more preferably, at 0.5 to 1.0 [mu] m, a specific surface area of 5 m ² / g or more, more preferably, those 5~16m ² / g When tetragonal zirconia in which a stabilizer such as Y ₂ O ₃ is dissolved is used as a raw material, the toughness can be improved by the stress-induced phase transformation effect.

The raw materials of the alumina ceramics include:
Usually, unavoidable impurities such as Fe ₂ O ₃ , Na ₂ O, K ₂
O and TiO ₂ etc. are included, but among the unavoidable impurities, alkali metal oxides and TiO ₂ generate the second phase or cause abnormal grain growth. Used, in particular, Na ₂ O and K ₂ O are Si
O ₂ or the like and readily to form a glass phase, the content of alkali metal oxide to 0.45 wt% or less, also, TiO ₂
Has a content of 0.2% by weight or less, preferably 0.1% by weight, since it promotes crystal growth and causes abnormal grain growth.
Raw materials are selected and blended so as to be 5% or less.

The pulverization, mixing and dispersion are carried out in a wet manner in water or an organic solvent.
0 to 1500 cps is preferred. If the viscosity is high,
It is preferable to adjust the viscosity by appropriately adding a dispersant such as sodium acrylate or polycarboxylate. The average particle size of the powder obtained by pulverization is 1.0 μm or less, and the specific surface area is 5 m ² / g.
Or, more specifically, an average particle diameter of 0.5 to 1.0 [mu] m, is ground to be a specific surface area of 8m ² / g~15m ² / g. Pulverization to a predetermined particle size, for example, using a ball mill 20mm
It can be carried out by crushing with an alumina ball of φ for 96 hours.

(2) The slurry thus obtained is dried and granulated to obtain a granulated powder. The drying method is selected according to the molding method to be used. Generally, when a molding method or a CIP (cold isostatic pressing) molding method is adopted, drying with a spray dryer is performed, and casting molding is also performed. When tumbling granulation molding is employed or when extrusion molding and injection molding are employed, it is preferable to select drying by a dryer.

It is important that the granulated powder is crushed even at a low pressure in the molding in the next step, and the granulated powder having poor crushing property leads to an increase in the amount of defects contained in the sintered body. Granulated powder having good crushability can be obtained by appropriately selecting the type and amount of the binder to be added to the slurry and various conditions during the spray drier treatment. In addition, as a binder,
Any conventionally used one such as polyvinyl alcohol (PVA), acrylic resin, and paraffin wax emulsion may be used, and sodium acrylate, polycarboxylate, or the like may be used as a dispersant.

For example, in the case of drying using a spray drier, a binder of 1 to 5% by weight based on the solid content (raw material powder) may be added to the slurry pulverized in the above step. When the binder is added, its viscosity becomes 50
If it exceeds 0 cps, add a dispersant to increase the viscosity to 50 cps.
Adjust to less than 0 cps. The obtained slurry is spray-dried and granulated at a temperature of 150 to 250 ° C. by a spray drier. This molding powder usually has a water content of 0.2.
２2%, with a particle size of 40-100 μm. Then, using this powder, a molding pressure of 500 to 20 is applied by a mold press, CIP or the like according to a conventional method in the production of ceramics.
It is formed into a predetermined shape at 00 kgf / cm ² .

Further, when molding by a molding method such as rolling granulation, cast molding, extrusion molding, injection molding, etc., the spray dryer step is omitted, and the slurry is used as it is or simply dried to obtain a raw material for molding. But can be used. For example,
When the casting method is used as the molding method, the ground slurry is adjusted to have a viscosity of 150 cps or less using a dispersant such as sodium acrylate or polycarboxylate, and molded using a gypsum mold.

In the case of using rolling granulation as a molding method, a binder is added to the pulverized slurry, which is dried at 80 to 120 ° C. by a drier, and the dried powder is pulverized by a pulverizer such as an atomizer. Through a # 40- # 80 mesh sieve to obtain a powder under the sieve. This powder is used as it is to perform rolling granulation.

Further, when extrusion molding or injection molding is employed as a molding method, the pulverized slurry is subjected to 80-80
After drying at 120 ° C., the dried powder is pulverized with a pulverizer such as an atomizer, and a powder under the sieve is obtained through a # 40- # 80 mesh sieve.
0%, and in the case of injection molding, 15 to 30% are added and mixed by a mixer to prepare a molding clay, and extrusion molding or injection molding is performed.

Regardless of the molding method, the obtained molded body must have a bulk density of 1.90 g / cm ³ or more, and more preferably 1.95 g / cm ³ or more. . If the bulk density is less than 1.90 g / cm ³ , defects in the obtained sintered body increase, which is not preferable.

The molded body obtained in this way is 1350-
By firing at 1600 ° C., more preferably at 1400 to 1550 ° C., the desired wear-resistant alumina ceramics can be obtained.

The reason why the wear-resistant alumina ceramics according to the present invention is limited to the composition within the above range is as follows. That is, the content of Al ₂ O ₃ is 88% by weight to 95% by weight.
The reason is that when the Al ₂ O ₃ content is less than 88% by weight,
The amount of the glass phase and the second phase generated inside the sintered body increases, and the strength and hardness of the sintered body decrease, and the impact resistance and wear resistance decrease, which is not preferable. When the Al ₂ O ₃ content is 95% by weight or more, the amount of the glass phase generated inside the sintered body becomes too small, so that the sinterability is deteriorated,
This is because, as the firing temperature increases, segregation of the glass phase tends to occur at the alumina crystal grain boundaries, which causes abnormal grain growth and lowers the hardness, toughness, and strength, which is not preferable.

The sub-components SiO ₂ , MgO and CaO are added as sintering aids, but these sub-components are mainly present at the alumina crystal grain boundary as a glass phase, and the crystal growth is suppressed. Suppress, improve bulk density and suppress internal defects to improve wear resistance. The content of each subcomponent is limited to the above range for the following reason.

That is, the content of SiO ₂ , MgO and CaO is 3.6 to 10% by weight of SiO _2, 0.2 to 2.5% by weight of MgO,
In the range of 0.2 to 2.5% by weight of CaO, not only the difference in thermal expansion and wettability with Al ₂ O ₃ crystal becomes appropriate, but also the control of the crystal grain size and distribution becomes easy, and the alumina crystal grain becomes easy to control. Field strength and toughness are increased, and impact resistance and wear resistance are improved. However, if at least one of the contents of SiO ₂ , MgO and CaO is out of the above range, the alumina grain boundary strength becomes low or the second phase particles are formed, and the crystal grain size is reduced by impact or friction with the counterpart material. In addition to causing grain removal and toughness, the crystals tend to be large in the firing stage and abnormal grain growth is likely to occur, inevitably resulting in poor uniformity of the crystal grain size, resulting in reduced impact resistance and wear resistance. Therefore, the above range is not preferable.

More specifically, if the content of SiO ₂ is less than 3.6% by weight, the sinterability decreases, and if it exceeds 10% by weight, the alumina grain boundary strength decreases. And On the other hand, if the content of MgO is less than 0.2% by weight, the uniformity of the crystal grain size is poor, and the content is less than 2.
If the content exceeds 5% by weight, the second phase is precipitated, so the content of MgO is set to 0.2 to 2.5% by weight. Further, when the content of CaO is less than 0.2% by weight, the sinterability is reduced. When the content exceeds 2.5% by weight, the sinterability is reduced and abnormal grain growth is caused. The content was 0.2 to 2.5% by weight.

Further, the sum of the contents of SiO ₂ , MgO and CaO, that is, the content of the subcomponent is set to 5 to 12% by weight is that if it is less than 5% by weight, it exists at the alumina crystal grain boundary. The amount of the glass phase is reduced, and the existence of the glass phase becomes non-uniform, which causes a decrease in sinterability and abnormal grain growth of crystals, and a decrease in impact resistance and wear resistance. On the other hand, when the content of the auxiliary component exceeds 12% by weight, the glass phase becomes too large, and the hardness, toughness and strength are reduced,
Since the impact resistance and abrasion resistance are lowered, the above range is set.

Further, when the sum of the contents of SiO ₂ , MgO and CaO is defined as 100, the proportion of each component, that is, the composition of the sub-component is 72 to 85% by weight of SiO ₂ , 3 to 25% by weight of MgO, The reason for setting the content of CaO to 3 to 25% by weight is as follows. That is, when the content of SiO ₂ in the auxiliary component is less than 72% by weight, the sinterability decreases, and when it exceeds 85% by weight, the amount of the glass phase increases. If the content of MgO is less than 3% by weight, the uniformity of the crystal grain size becomes poor. If the content exceeds 25% by weight, the second phase is precipitated. The above range was set. Furthermore,
If the proportion of CaO in the auxiliary component is less than 3% by weight, the sinterability is reduced. If the content exceeds 25% by weight, not only the sinterability is reduced but also the crystal is liable to grow. The content was in the above range.

The abrasion-resistant alumina ceramic of the present invention is obtained by adding 0.01 to 15 parts by weight of ZrO ₂ to 100 parts by weight of the basic composition having the above-mentioned component composition.
The strength and toughness can be further improved, and at the same time, the alumina grain boundary glass phase can be dispersed uniformly, the crystal grain size distribution can be narrowed, and the structure of the sintered body can be made uniform. This Z
The reason for setting the amount of rO ₂ added to the above range is that if the amount added is less than 0.01 part by weight based on 100 parts by weight of the basic composition,
If the effect of addition is not sufficient, and if it exceeds 15 parts by weight, the hardness is reduced, and Zr particularly containing no stabilizer is added.
The use of O ₂ powder is not preferred because monoclinic zirconia is likely to be present in the sintered body, and microcracks occur, leading to a reduction in wear resistance and impact resistance. The additive amount of ZrO ₂ is usually the is a 0.01 to 15 parts by weight with respect to the basic composition 100 parts by weight, preferably 0.
The suitable amount is from 05 to 10 parts by weight, more preferably from 0.1 to 8 parts by weight.

In this case, the ZrO ₂ raw material to be added preferably has an average particle size of not more than 1.0 μm.
This is because when the average particle size of the ZrO ₂ raw material exceeds 1.0 μm,
It is not preferable because monoclinic zirconia is likely to be present in the sintered body, and microcracks are generated, leading to a decrease in wear resistance and impact resistance. Further, as the ZrO ₂ raw material, a solid solution of a stabilizer such as a rare earth element oxide can be used. In this case, a rare earth element oxide,
For example, in the case of a ZrO ₂ raw material containing Y ₂ O ₃ as a stabilizer, it is preferable to use a material having a Y ₂ O ₃ content of 5 mol% or less, whereby the zirconia has a toughness due to a stress-induced transformation effect. Improvement can be achieved.

According to the present invention, as described above, the main component A
specific accessory ingredients l ₂ O ₃ with the addition of a predetermined amount at a predetermined ratio, by suppressing the amount of inevitable impurities contained in the raw material, the average crystal in the range of 1.0~5.0μm It has a particle size and a bulk density of 3.60 g / cm ³ or more.
Defects such as porosity and shedding due to finishing are as small as 5% or less, and alumina ceramics excellent in wear resistance can be obtained.

If the average crystal grain size of the sintered body exceeds 5 μm, a decrease in hardness and the like will occur, resulting in a decrease in wear resistance. The average crystal grain size of the sintered body is preferably 3 μm or less, more preferably 2.5 μm or less. If chipping resistance is a problem, it may be appropriately set within a range of 5 μm or less in consideration of the balance with wear resistance. Further, when the maximum diameter (crystal grain size when the cumulative volume is 100%) exceeds 10 μm, the crystal grain size distribution is wide, and the hardness decreases, and as a result, the wear resistance decreases, which is not preferable. Therefore, the maximum diameter is preferably 10 μm or less, more preferably 8 μm or less.

The reason why the bulk density is set to 3.60 g / cm ³ or more is that if the bulk density is less than 3.60 g / cm ³ , the sintering degree is insufficient and there are many pores serving as defects. This is not only undesirable because it not only causes a decrease in strength, hardness and toughness but also promotes abrasion. The bulk density is preferably 3.65 g / cm ³ or more.

The alumina ceramics according to the present invention has a small crystal grain size, is dense and has few defects, and thus exhibits excellent properties in impact resistance and wear resistance. Therefore, compared to the conventional sintered body having the same Al ₂ O ₃ content, higher strength,
High hardness and high toughness. The Vickers hardness of the alumina ceramic of the present invention is 110 at a load of 10 kgf.
It shows a high hardness of 0 or more and has a flexural strength of S1601.
Has a high strength of 40 kgf / mm ² or more in the three-point bending method specified in (1). Furthermore, in the case of a spherical shape like a ball for grinding,
The crushing strength measured by applying a stress between one ball and the cemented carbide plate is 25 kgf / mm ² or more. This crushing strength (σ
c) is obtained by the formula: σc = 4 × P / (π × D2) (kgf / mm ² ). In the formula, P is the breaking strength (kgf), D is the ball diameter (mm)
It is.

If the Vickers hardness is less than 1100, the abrasion resistance is lowered, which is not preferable. In addition, the bending strength is less than 40 kgf / mm ² or the crushing strength is 25 kgf / mm ²
If it is less than 10%, the impact resistance and the wear resistance will be reduced, which is not preferable. Furthermore, the fracture toughness is JIS1607 (IF
Method), it is 3.0 MPa√m or more in the measurement method specified in the above method.

[0043]

Example 1 Each raw material was blended so as to obtain a sintered body having the composition shown in Tables 1 and 2, and each obtained mixture was mixed with a 92% alumina pot mill (internal volume 7.2 liter) and 20 mmφ.
4% at a concentration of 60% using crushed balls made of 92% alumina
The slurry was wet-ground for 8 hours to obtain a slurry containing fine powder having an average particle size shown in Tables 3 and 4 and a specific surface area of 8 m ² / g or more. An aqueous solution of polyvinyl alcohol is added to the obtained slurry for 3 to 5 minutes.
The viscosity was adjusted to 350 cps by adding it as a weight% binder, and this was dried and granulated with a spray drier maintained at 200 ° C. to obtain a molding powder. This molding powder was molded into a spherical shape and a plate shape by a CIP molding method at a molding pressure of 1 tonf / cm ² (molding pressure of only Sample Nos. 20 and 38: 300 kgf / cm ² ). The obtained molded body was fired at 1380 to 1600 ° C. to obtain a ball having a diameter of 10 mm and a plate having a size of 50 × 50 × 4 mm. The ball was barrel-polished to obtain a crushing ball, and the plate was cut and ground to obtain a bending strength measurement test piece specified in JIS1601.

Samples Nos. 1 to 2 were used as alumina raw materials.
For 1, 24-39, the aggregated secondary particle size was 45 μm.
m, a specific surface area of 2.5 m ² / g, a purity of 99.6%, and a raw soda alumina raw material prepared by the Bayer method.
For No. 22, a reactive alumina raw material having an average particle size of 1.0 μm, a specific surface area of 6 m ² / g, and a purity of 99.8% was further added.
No. 23 has a secondary particle size of 55 μm and a specific surface area of 1.5 m ² /
g, raw soda alumina raw material produced by the Bayer method with a purity of 99.7% was used.

As a raw material of MgO and CaO, a carbonate having a purity of 99.5% was used, and as a raw material of SiO ₂ , kaolin was used. Samples 5, 8, 10, 15 and 25 as a ZrO ₂ raw material had an average particle size of 1.0.
μm, zirconium dioxide having a specific surface area of 12 m ² / g and a purity of 99.9% was used. For Sample 13, 2.8 mol% of Y ₂ O ₃ was used.
Zirconium dioxide having an average particle size of 0.5 μm and a specific surface area of 18 m ² / g was used.

Further, an abrasion resistance test was carried out using each of the obtained crushing balls by the following method. That is, a grinding ball was put into a 2 liter capacity alumina ball (purity 92%) ball mill to half its volume, 900 g of alumina raw material powder having an average particle size of 25 μm, a specific surface area of 1.2 m ² / g, and water of 0.1 g. 7 liters were charged and ground at a ball mill rotation speed of 100 rpm for 24 hours. The difference between the ball weights before and after the test was determined as a percentage of the ball weight before the test, and this was defined as the wear rate.
The obtained result, the bulk density of the ball for grinding, crystal grain size,
Tables 3 and 4 show the defect amount, Vickers hardness and flexural strength, the bulk density of the compact, the average particle size and the specific surface area of the pulverized powder. The bending strength was measured using a test piece processed from a plate.

[0047]

[Table 1]

[Table 2]

[0048]

[Table 3]

[Table 4]

In Tables 1 and ₂ , the amount of ZrO ₂ is shown by the amount (parts by weight) relative to 100 parts by weight of the basic composition comprising alumina, sintering aid and unavoidable impurities. In Tables 1, 2 and 3 and 4, the sintered bodies of Sample Nos. 1 to 17 satisfy the conditions of the present invention, and the sintered bodies of Sample Nos.
39 is out of the scope of the present invention which does not satisfy at least one of the conditions defined in the present invention.

The average crystal grain size was determined by grinding the sintered body with a diamond grindstone in the order of # 140 → # 400 → # 600, and then using a diamond grindstone to make a 40 μm → 6 μm → 3 μm →
The surface was polished in order of 1 μm to obtain a mirror surface, which was thermally etched.
Observe and photograph at a magnification that allows observation of more than one crystal, measure the area of one crystal by image analysis from the photograph, convert it to equivalent circular diameter (D), and calculate D × 1.5 as the particle size of the crystal The crystal grain size of 100 crystals was measured in this manner, the volume of the crystal was calculated based on this value, and the crystal grain size when the cumulative volume was 50% was defined as the average crystal grain size.

The amount of defects in the sintered body was determined by mirror-finish the sample to be measured in the same manner as in the measurement of the crystal grain size, and using the mirror-finished surface as it was with a scanning electron microscope at a magnification of 500 times. Observation and photographing in the above, binarize the photograph into a defective part and a non-defect part by image analysis and separate, determine the area ratio (%) occupied by the defective part, Amount. The defects include not only pores but also defects at a level that does not affect the density of the sintered body after grain removal that occurs when the sintered body is subjected to the above-described grinding and polishing. Defect portions and non-defect portions are obtained by image analysis of scanning electron micrographs of mirror-finished surfaces of the alumina ceramics according to the present invention (sample No. 1) and the alumina ceramics outside the scope of the present invention (sample No. 22). FIGS. 1 and 2 show the binarized diagrams respectively. In the figure,
Black portions indicate defects.

As is evident from the results shown in Tables 3 and 4, the grinding balls made of alumina ceramics according to the present invention have excellent wear resistance with a wear rate of 0.1% or less. From the results shown in FIGS. 1 and 2, it can be understood that the alumina ceramics according to the present invention has an extremely small defect amount of 0.5%, whereas the sample No. 22 has an extremely large defect amount of 9.6%. Also, from the results of Sample Nos. 38 and 39, even if the component composition is within the range of the present invention, the abrasion resistance is reduced if the defect amount is large, and the defect amount is the average after pulverization in the production process. It can be seen that it depends on the particle size and the bulk density of the compact.

[0053]

As is clear from the above description, according to the present invention, a) excellent abrasion resistance under high load due to excellent strength, hardness, toughness and impact resistance; b) Excellent wear resistance when used as a crusher member, so less wear powder is mixed into the material to be crushed. Abrasion-resistant alumina-based ceramics having excellent properties such as less impairing uniformity and c) use of inexpensive alumina as a raw material can be obtained.

Therefore, the abrasion-resistant alumina ceramics according to the present invention can be used not only for pulverizing / dispersing media, pulverizer lining materials, containers and agitators, but also for various industrial wear-resistant materials. As the best.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a binarized image of a mirror-finished surface of a wear-resistant alumina ceramics according to the present invention.

FIG. 2 is an explanatory diagram showing a binarized image of a mirror-finished surface of a wear-resistant alumina ceramics outside the scope of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-206514 (JP, A) JP-A-1-286957 (JP, A) JP-A-62-252364 (JP, A) JP-A-61-252 101456 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/10-35/119

Claims (3)

(57) [Claims] 1. A Al ₂ O ₃ less than 88 wt% to 95 wt%, SiO ₂ from 3.6 to 10 wt%, MgO 0.2 to
2.5% by weight, 0.2 to 2.5% by weight of CaO, and 0.5% by weight or less of unavoidable impurities, and the sum of the contents of the sub-components SiO ₂ , MgO and CaO is 5 to 1%.
2% by weight, and when the sum of the contents of SiO ₂ , MgO and CaO of the sub-components is 100, the proportion of each component is 72 to 85% by weight of SiO ₂ , 3 to 25% by weight of MgO,
A CaO 3 to 25 wt%, 0.4 wt% alkali metal oxide of the unavoidable impurities less, TiO ₂
0.2% by weight or less, the subcomponent exists as a glass layer at the alumina crystal grain boundary, and has an average crystal grain size of 1.0 to 5.0 μm.
m, a bulk density of 3.60 g / cm ³ or more, a Vickers hardness of 1100 or more, and a flexural strength of 40 kgf / mm ² or more. 2. Al ₂ O ₃ 88 wt% or more and less than 95 wt%, SiO ₂ 3.6 to 10 wt%, MgO 0.2 to 0.2 wt%
2. The composition according to claim 1, wherein ZrO ₂ is contained in an amount of 0.01 to 15 parts by weight based on 100 parts by weight of the basic composition consisting of 2.5% by weight, 0.2 to 2.5% by weight of CaO, and the balance substantially consisting of unavoidable impurities. Abrasion resistant alumina ceramics as described. 3. When producing the wear-resistant alumina ceramics according to claim 1 or 2, a raw material powder comprising a compound of each constituent element constituting the alumina ceramics is blended in a predetermined ratio, and a mixture thereof is used. Has an average particle size of 0.
It is characterized in that it is pulverized to a powder of 5 to 1.0 μm, and the obtained fine powder is formed into a predetermined shape to obtain a formed body having a bulk density of 1.90 to 2.10 g / cm ³ , which is then fired. Claim 1
3. The method for producing an abrasion-resistant alumina-based ceramic described in 1. above.