JPH09221354A - Wear resistant aluminous ceramics and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain aluminous ceramics capable of sintering at a low temp., free from unevenness in characteristics and excellent in wear resistance with low-cost starting materials. SOLUTION: Alumina is used by 88 to <95wt.% as the principal component of aluminous ceramics and 3.6-10wt.% SiO2 , 0.2-2.5wt.% MgO and 0.2-2.5wt.% CaO are added by 5-12wt.%, in total, as subsidiary components to the alumina. When the total amt. of the SiO2 , MgO and CaO is represented by 100wt.%, the amts. of the SiO2 , MgO and CaO are 72-85wt.%, 3-25wt.% and 3-25wt.%, respectively. The amt. of inevitable impurities is reduced to <=0.5wt.%, the amt. of defects is limited to <=5% and ZrO2 may further be added by 0.01-15wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wear resistant alumina ceramics, and more particularly to wear resistant alumina ceramics useful as a material for wear resistant members 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 in wear resistance and corrosion resistance to metal materials, and ceramics have been used as wear resistant member materials in place of conventional metals. Alumina, zirconia, silicon nitride, silicon carbide and the like are generally known as ceramics of this type. Among them, alumina-based ceramics mainly composed of alumina, which have high hardness, excellent corrosion resistance and are inexpensive, are known. Widely used. Normally, alumina-based ceramics are poor in productivity because they have poor sinterability when only alumina is used alone. Therefore, sintering is performed by adding a sintering aid and other additives.

[0003]

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

The one disclosed in Japanese Patent Laid-Open No. 7-206514 has improved wear resistance by reducing the addition amount of a sintering aid. However, as the alumina content increases, the sinterability increases. Therefore, there is a problem in that it has to be fired at a high temperature because it lowers, and the grain size distribution tends to be broadened depending on the firing temperature, and the wear resistance tends to be lowered.
In addition, when this alumina ceramics is used as a grinding ball, it shows excellent characteristics in dry wear, that is, wear when only the grinding ball and water are put into a ball mill and rotated, but actually alumina etc. It has become clear that the actual wear of the crushed powder is not yet satisfactory.

Further, the one described in Japanese Patent Laid-Open No. 237961/1990, which has an Al ₂ O ₃ content of 90 to 95% by weight, shows excellent wear resistance even at the same level as the conventional one, but it is B added for the purpose of suppressing and lowering the firing temperature
₂ O ₃ represents a significant vapor pressure even 1000 ° C., tend to cause variations in the composition liable to evaporate during firing, inevitably cause variations in properties, moreover ceramics inside due to the evaporation of B ₂ O ₃ There is a risk that voids will be formed in the surface and the wear resistance will be reduced.

Therefore, an object of the present invention is to obtain at low cost alumina ceramics which can be sintered at a low temperature, have less variation in characteristics, and are excellent in wear resistance.

[0007]

As a means for achieving the above-mentioned object, the present invention basically comprises Al ₂ O _{3 in an amount of} 88% by weight or more and less than 95% by weight as a main component of alumina ceramics. 72 to 85% by weight of SiO _{2 and} 3 to _{2 of} MgO
5% by weight and 3 to 25% by weight of CaO are added as auxiliary components, and the content of each component of the auxiliary component is SiO ₂ 3.6 to 10% by weight,
0.2 to 2.5% by weight of MgO and 0.2 to 2.5% by weight of CaO
Then, while adding them so that the total amount thereof becomes 5 to 12% by weight, inevitable impurities are suppressed to 0.5% by weight or less, and the defect amount of ceramics is suppressed to 5% or less. It is a thing.

In the present specification, the defect amount of ceramics means that the ceramics are ground by a surface grinder under the following conditions, then polished and 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 the defective portion and the non-defective portion by binarization, and the defective portion is The ratio of the area occupied in the entire image (that is, the area ratio (%)). This defect part includes not only pores, but also defects after grain removal that occurs during grinding and polishing of the sintered body and mirror finishing, and at a level that does not affect the bulk density value of the sintered body. Be done.

For the mirror finish, a surface grinder and a resin-bond type diamond grindstone are used.
Forty diamond whetstones, and the peripheral speed of the whetstone is 1500
m / sec, depth of cut 8 μm, left and right feed rate of ceramics (hereinafter referred to as work), which is a non-ground object
It is called work feeding. ) At 17 m / sec for about 80 μm, stop the incision, move the grindstone back and forth 5 times, and then replace the grindstone with a # 400 diamond grindstone with a peripheral speed of 150
After grinding about 50 μm under the conditions of 0 m / sec, depth of cut 5 μm, and work feed of 13 m / sec, stop the depth of cut and set the grindstone to 1
Reciprocate 0 times and replace the grindstone with a # 600 diamond grindstone. Grind approximately 20 to 30 μm under the conditions of peripheral speed of 1500 m / sec, depth of cut of 2 μm, and work feed of 10 m / sec. Grinding is performed by reciprocating 15 times, and then, a diamond pad in which 40 μm diamond abrasive grains are embedded is pressed at 2.6 kgf / cm ² and ground for 3 minutes on the ground surface of the ground ceramics. 2.6 kgf / cm ² of diamond abrasive grains are pressed and polished for 5 minutes, then 3 μm diamond abrasive grains of 2.6 kg
It is carried out by pressurizing to f / cm ² and polishing for 15 minutes, and finally pressurizing to 1.3 kgf / cm ² with 1 μm diamond abrasive grains and polishing for 5 minutes.

That is, the wear-resistant alumina ceramics according to the present invention comprises Al ₂ O _{3 of} 88% by weight or more and less than 95% by weight,
SiO ₂ 3.6-10% by weight, MgO 0.2-2.5% by weight,
CaO 0.2-2.5% by weight, the balance consisting essentially of inevitable impurities, the sum of the contents of SiO ₂ , MgO and CaO being 5-12% by weight, said SiO ₂ , MgO and CaO
When the sum of the contents of is 100, the ratio of each component is SiO ₂
72 to 85% by weight, MgO 3 to 25% by weight, CaO 3 to
25% by weight, the unavoidable impurities are 0.5% by weight or less,
The feature is that the amount of defects is 5% or less.

The content of Al ₂ O ₃ which is the main component is 9
The range of 0-94.5% by weight is more preferable. Further, the contents of the subcomponents are 5 to 10% by weight of SiO ₂ , and MgO 0.
4 to 1.5% by weight and CaO 0.3 to 1.5% by weight, and the proportion of each component is Si when the sum of their contents is 100.
O ₂ 73-84% by weight, MgO 3.5-1% by weight, CaO 4
More preferably, it is in the range of ˜15% by weight.

Further, in the present invention, in order to further improve the strength and toughness of the alumina-based ceramics and further homogenize the macrostructure thereof, ZrO ₂ is added to 100 parts by weight of the basic composition having the above-mentioned composition. 0.01-1
5 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight.

Further, in the present invention, the raw material powders are mixed in a predetermined ratio, the mixture is finely pulverized to a powder having an average particle size of 0.5 to 1.0 μm, and the fine powder thus obtained is molded into a predetermined shape. The present invention provides a method for producing wear-resistant alumina-based ceramics, characterized by obtaining a molded body having a bulk density of 1.90 to 2.10 g / cm ³ and firing it. 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 1350 to 1600 ° C.

The content of the unavoidable impurities is set to 0.5% by weight or less. Among them, Na ₂ O
The content of alkali metal oxides such as K ₂ O and 0.45 wt% or less, preferably 0.4 wt% or less, and TiO 2
The content of ₂ is preferably suppressed to 0.2% by weight or less, preferably 0.15% or less.

Since the amount of defects has a great influence on the wear resistance of ceramics, the amount of defects on the mirror-finished surface is preferably 5% or less. This is because if the amount of defects exceeds 5%, these defects are the starting points of wear and promote wear, leading to a decrease in wear resistance and at the same time a drop in impact strength, which is not desirable. The amount of this defect is preferably 3% or less, more preferably 2% or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the wear-resistant alumina ceramics according to the present invention is prepared by mixing the raw materials so as to have the above composition and crushing the mixture to obtain 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 Molded into a shape to obtain a molded body having a bulk density of 1.90 to 2.10 g / cm ³ ,
It is produced by firing this at a temperature of 1350 to 1600 ° C., and specifically, for example, it can be produced by the following method.

(1) First, compounds of the respective constituent elements constituting the alumina-based ceramics are blended so as to have the above composition ratio, ZrO ₂ raw material is added if necessary, and a ball mill is wet-processed in water or an organic solvent. A raw material powder is prepared by pulverizing, mixing and dispersing using a known pulverizer such as an attrition mill.

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 manufactured by the alum method or the like, but it is preferable to use the alumina raw material by the Bayer method, and there is an advantage that it can be manufactured at low cost.

Of the subcomponents, salts such as oxides, hydroxides and carbonates can be used as raw materials for MgO and CaO, but the average particle size is 3.0 μm or less, more preferably 0.5 to 0.5 μm.
It is suitable to use one having a thickness of 3.0 μm. Also, Si
As the O ₂ raw material, silica stone, quartz, silica sol, ethyl silicate, etc. 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 Is preferable, and 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.

As the raw material of the alumina ceramics,
Usually, unavoidable impurities such as Fe ₂ O ₃ , Na ₂ O, K ₂
O and TiO ₂ etc. are contained, but among the unavoidable impurities, alkali metal oxides and TiO _{2 form} the second phase or cause abnormal grain growth, so that the content of the unavoidable impurities is as small as possible. Used, especially Na ₂ O and K ₂ O are Si
In order to easily form a glass phase with O ₂ etc., the content of alkali metal oxides should be 0.45% by weight or less, and TiO ₂
Since it promotes crystal growth and causes abnormal grain growth, its content is 0.2% by weight or less, preferably 0.1% by weight or less.
The raw materials are selected and blended so as to be 5% or less.

Grinding, mixing and dispersion are carried out in water or an organic solvent by a wet method, and the viscosity of the slurry at that time is 5
0-1500 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 a polycarboxylic acid salt. The powder obtained by crushing has an average particle size of 1.0 μm or less and a specific surface area of 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. Grinding to a specified particle size is done with a ball mill, for example, 20 mm
It can be performed by pulverizing with a φ alumina ball for 96 hours.

(2) A granulated powder is obtained by drying and granulating the slurry thus obtained. The drying method is selected according to the molding method used. Usually, when a die press or CIP (cold isotropic pressure press) molding method is used as the molding method, drying with a spray dryer is used, and also casting molding is performed. And, when rolling granulation molding is adopted or when extrusion molding and injection molding are adopted, it is preferable to select drying by a dryer.

It is important for the granulated powder to be crushed even in a low pressure in the molding in the next step, and the granulated powder having poor crushability leads to an increase in the amount of defects contained in the sintered body. The 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 dryer treatment. As a binder,
Any conventionally used polyvinyl alcohol (PVA), acrylic resin, paraffin wax emulsion or the like may be used, and as the dispersant, sodium acrylate, polycarboxylic acid salt or the like may be used.

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

When molding is carried out by a molding method such as rolling granulation, cast molding, extrusion molding, injection molding, the spray dryer step is omitted, and it is used as a raw material for molding as a slurry or simply by drying. But you can use it. For example,
When cast molding is used as the molding method, the crushed slurry is adjusted to have a viscosity of 150 cps or less by using a dispersant such as sodium acrylate or polycarboxylic acid salt, and molded using a gypsum mold.

When rolling granulation is used as the molding method, a binder is added to the crushed slurry, which is dried at 80 to 120 ° C. by a dryer, and the dry powder is crushed by a crusher such as an atomizer. , # 40 to # 80 mesh sieve to obtain powder under the sieve. This powder is used as it is for rolling granulation.

Further, when extrusion molding or injection molding is adopted as the molding method, the crushed slurry is dried at 80 to 80
After drying at 120 ° C, the dry powder is crushed by a crusher such as an atomizer and passed through a # 40 to # 80 mesh sieve to obtain powder under the sieve.
0%, in the case of injection molding, 15-30% is added and mixed by a mixer to prepare a kneaded material for molding, and extrusion molding or injection molding is performed.

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

The molded product obtained in this manner is
By firing at a temperature of 1600 ° C., more preferably 1400 to 1550 ° C., the target wear-resistant alumina ceramics can be obtained.

The wear-resistant alumina ceramics according to the present invention is limited to the composition within the above range for the following reason. That is, the content of Al ₂ O ₃ is 88% by weight or more and 95% by weight or more.
When the Al ₂ O ₃ content is less than 88% by weight,
The amounts of the glass phase and the second phase generated inside the sintered body increase, the strength and hardness of the sintered body decrease, and the impact resistance and wear resistance decrease, which is not preferable. Further, when the Al ₂ O ₃ content is 95% by weight or more, not only the amount of the glass phase generated inside the sintered body becomes too small and the sinterability decreases, but
This is because the segregation of the glass phase is likely to occur in the alumina crystal grain boundaries with the increase of the firing temperature, which causes abnormal grain growth and causes a decrease in hardness, toughness, and strength, which is not preferable.

Further, the above-mentioned sub-components SiO ₂ , MgO and CaO are added as sintering aids, but these sub-components exist mainly in the alumina crystal grain boundaries as a glass phase, and the crystal grain growth is caused. Suppresses to improve bulk density and internal defects to improve wear resistance. The reason for limiting the content of each of the subcomponents to the above range is as follows.

That is, the contents of SiO ₂ , MgO and CaO are 3.6 to 10% by weight of SiO _2, 0.2 to 2.5% by weight of MgO,
When the content of CaO is 0.2 to 2.5% by weight, the difference in thermal expansion from Al ₂ O ₃ crystals and the wettability are appropriate, and not only the control of the crystal grain size and distribution becomes easy, but also the alumina crystal grains Increases field strength and toughness, and improves impact resistance and wear resistance. However, if even one of the contents of SiO ₂ , MgO and CaO deviates from the above range, the alumina grain boundary strength becomes low, or the second phase particles are generated, and the crystal grain size due to impact or friction with the counterpart material. In addition to causing grain breakage and toughness of the crystal, the crystal tends to grow during the firing stage and abnormal grain growth is likely to occur, which inevitably results in poor uniformity of the crystal grain size, resulting in reduced impact resistance and wear resistance. Since it is not preferable because it is not preferable.

Specifically, if the content of SiO ₂ is less than 3.6% by weight, the sinterability is lowered, and if it exceeds 10% by weight, the grain boundary strength of alumina is lowered, so that the above range is satisfied. And Further, if the content of MgO is less than 0.2% by weight, the uniformity of the crystal grain size becomes poor, and the content is 2.
When it exceeds 5% by weight, the second phase is precipitated, so the content of MgO was set to 0.2 to 2.5% by weight. Further, if the content of CaO is less than 0.2% by weight, the sinterability is lowered, and if the content exceeds 2.5% by weight, the sinterability is lowered 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 accessory component is set to 5 to 12% by weight means that if it is less than 5% by weight, it exists in the alumina crystal grain boundary. The amount of the glass phase becomes small, the presence of the glass phase becomes non-uniform, the sinterability is lowered, abnormal grain growth of crystals is caused, and the impact resistance and the abrasion resistance are lowered, which is not preferable. On the other hand, when the content of the subcomponent exceeds 12% by weight, the glass phase becomes too much and the hardness, toughness and strength are deteriorated.
Since the impact resistance and wear resistance are reduced, the above range is set.

Furthermore, when the sum of the contents of SiO ₂ , MgO and CaO is 100, the ratio of each component, that is, the composition of the sub-components is 72 to 85% by weight of SiO ₂ , 3 to 25% by weight of MgO, The reason why the CaO content is 3 to 25% by weight is as follows. That is, if the amount of SiO ₂ in the subcomponents is less than 72% by weight, the sinterability will decrease, and if it exceeds 85% by weight, the glass phase content will increase, so the above range was made. Further, if the content of MgO is less than 3% by weight, the uniformity of the crystal grain size becomes poor, and if the content exceeds 25% by weight, the second phase precipitates, so the proportion of MgO in the subcomponents is The above range was set. Furthermore,
When the proportion of CaO in the subcomponents is less than 3% by weight, the sinterability is lowered, and when the content exceeds 25% by weight, not only the sinterability is lowered but also crystals are easily grown. The content was within the above range.

The wear-resistant alumina ceramics of the present invention is prepared 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 composition.
It is possible to further improve strength and toughness, at the same time uniformly disperse the alumina grain boundary glass phase, narrow the crystal grain size distribution, and make the structure of the sintered body uniform. This Z
The amount of rO ₂ added is in the above range because when the amount added is less than 0.01 parts by weight per 100 parts by weight of the basic composition,
If the addition effect is not sufficient and the amount exceeds 15 parts by weight, the hardness is lowered, and Zr containing no stabilizer is added.
If O ₂ powder is used, monoclinic zirconia is likely to exist in the sintered body, and microcracks are generated, which leads to deterioration in wear resistance and impact resistance, which is not preferable. 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 appropriate amount is from 05 to 10 parts by weight, more preferably from 0.1 to 8 parts by weight.

In this case, as the ZrO ₂ raw material to be added, it is preferable to use one having an average particle diameter of 1.0 μm or less.
This is because when the average particle size of the ZrO ₂ raw material exceeds 1.0 μm,
Monoclinic zirconia is likely to exist in the sintered body, and microcracks are generated, which leads to deterioration in wear resistance and impact resistance, which is not preferable. Further, as the ZrO ₂ raw material, a solid solution of a stabilizer such as rare earth element oxide may be used. In this case, the 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 Y ₂ O ₃ content of 5 mol% or less, which makes it possible to improve the toughness due to the stress-induced transformation effect of zirconia. It is possible to improve.

According to the present invention, as described above, the main component A
The average crystal within the range of 1.0 to 5.0 μm is obtained by adding a specific subcomponent to l ₂ O ₃ in a predetermined ratio in a predetermined amount and suppressing the amount of unavoidable impurities contained in the raw material. It has a particle size and a bulk density of 3.60 g / cm ³ or more, and
Defects such as porosity and shedding due to finishing are less than 5%, and it is possible to obtain an alumina ceramic having excellent wear resistance.

If the average crystal grain size of the sintered body exceeds 5 μm, hardness is lowered and abrasion resistance is lowered, which is not preferable. The average crystal grain size of this 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 the range of 5 μm or less in consideration of the balance with abrasion resistance. Furthermore, when the maximum diameter (crystal grain size when the cumulative volume is 100%) exceeds 10 μm, the crystal grain size distribution is wide and hardness is lowered, resulting in a reduction in wear resistance, which is not preferable. Therefore, the maximum diameter is preferably 10 μm or less, more preferably 8 μm or less.

The bulk density is set to 3.60 g / cm ³ or more because the bulk density of less than 3.60 g / cm ³ results in insufficient sintering degree and many defective pores. This is not preferable because not only the strength, hardness and toughness are deteriorated, but also wear is accelerated. The bulk density is preferably 3.65 g / cm ³ or more.

The alumina-based ceramics according to the present invention exhibit excellent impact resistance and wear resistance because they have a small crystal grain size, are dense and have few defects. Therefore, it has higher strength than the conventional sintered body with the same level of Al ₂ O ₃ content,
High hardness and high toughness. The Vickers hardness of the alumina ceramics of the present invention is 110 at a load of 10 kgf.
It shows high hardness of 0 or more, and bending strength is S1601.
It has a high strength of 40 kgf / mm ² or more in the three-point bending method specified in 1. Furthermore, if it is spherical like a ball for crushing,
The crushing strength measured by applying stress by sandwiching one ball between cemented carbide plates 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 deteriorated, which is not preferable. Also, the bending strength is less than 40 kgf / mm ² or the crush strength is 25 kgf / mm ²
If it is less than 100%, impact resistance and abrasion resistance are deteriorated, which is not preferable. Furthermore, fracture toughness is JIS 1607 (IF
In the measuring method specified in (Method), it is 3.0 MPa√m or more.

[0043]

Example 1 Each raw material was blended so as to obtain a sintered body having a composition shown in Tables 1 and 2, and each mixture obtained was mixed with a 92% alumina pot mill (internal volume 7.2 liter) and 20 mmφ.
4 using a 92% alumina crushing ball of 60% concentration
It 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. To the obtained slurry, add polyvinyl alcohol aqueous solution to 3 to 5
The viscosity was adjusted to 350 cps by adding as a binder by weight%, and this was dried and granulated with a spray dryer maintained at 200 ° C to obtain a molding powder. This molding powder was molded into a spherical shape and a plate shape by the 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 x 50 x 4 mm. The ball was barrel-polished to be a crushing ball, and the plate was cut and ground to be a bending strength measuring test piece defined in JIS1601.

Sample Nos. 1 and 2 were used as the alumina raw material.
For 1 and 24 to 39, the aggregated secondary particle size is 45 μ
m, a specific surface area of 2.5 m ² / g, and a raw soda alumina raw material manufactured by the Bayer method with a purity of 99.6%.
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 prepared as a sample.
No. 23 has a secondary particle size of 55 μm and a specific surface area of 1.5 m ² /
Raw soda alumina raw materials having a purity of 99.7% and a purity of 99.7% were 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. As the ZrO ₂ raw material, Samples 5, 8, 10, 15 and 25 had an average particle size of 1.0.
μm, specific surface area 12 m ² / g, zirconium dioxide having a purity of 99.9% was used, and 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, each of the obtained balls for grinding was subjected to an abrasion resistance test by the following method. That is, the crushing balls were put into a ball mill made of alumina (purity 92%) having a capacity of 2 liters to a half of the volume, and 900 g of alumina raw material powder having an average particle diameter of 25 μm and a specific surface area of 1.2 m ² / g and water of 0. 7 liters were put and pulverized at a ball mill rotation speed of 100 rpm for 24 hours. The difference in ball weight before and after the test was calculated as a percentage of the ball weight before the test, and this was taken as the wear rate.
The obtained results are the bulk density of the grinding balls, the crystal grain size,
Tables 3 and 4 show the amount of defects, Vickers hardness and bending strength, the bulk density of the molded product, the average particle size of the pulverized powder and the specific surface area. The bending strength was measured by a test piece processed from the 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) added to 100 parts by weight of the basic composition consisting of alumina, a sintering aid and inevitable impurities. In addition, in Tables 1, 2 and 3, and Table 4, the sintered bodies of Sample Nos. 1 to 17 satisfy the conditions of the present invention.
39 is out of the scope of the present invention that does not satisfy at least one of the conditions specified in the present invention.

The average crystal grain size is obtained by grinding the sintered body with a diamond grindstone in the order of # 140 → # 400 → # 600, and then further grinding with diamond abrasive grains of 40 μm → 6 μm → 3 μm →
Polishing is performed in order of 1 μm to finish it into a mirror surface, which is heat-etched, and then a scanning electron microscope shows 100 crystals in the visual field.
Take a photograph by observing at a magnification that allows you to observe more than one piece, measure the area of one crystal by image analysis from the photograph, convert it to the equivalent circular diameter (D), and calculate D × 1.5 as the grain size of the crystal. The crystal grain size of 100 crystals was measured in this way, and the volume of the crystal was calculated based on this value. The crystal grain size when the cumulative volume was 50% was taken as the average crystal grain size.

The amount of defects in the sintered body was mirror-finished on the sample to be measured in the same manner as in the measurement of crystal grain size, and the mirror-polished surface was left as it was with a scanning electron microscope at a magnification of 500 times. The photograph is taken by observing with, and the image is binarized into defect and non-defect by image analysis, and the area ratio (%) occupied by the defect is calculated. And quantity. The defects include not only pores but also defects after grain removal that occur when the sintered body is finished by grinding and polishing, and at a level that does not affect the density of the sintered body. Defective and non-defective parts of a scanning electron micrograph of a mirror-finished surface of the alumina-based ceramics (Sample No. 1) according to the present invention and the alumina-based ceramics (Sample No. 22) outside the scope of the present invention by image analysis. The binarized figures are shown in FIGS. 1 and 2, respectively. In the figure,
Black areas indicate defects.

As is clear from the results shown in Tables 3 and 4, the alumina-based ceramic pulverizing balls according to the present invention have an excellent wear resistance with a wear rate of 0.1% or less. From the results shown in 1 and 2, it can be seen that the alumina ceramics according to the present invention has an extremely small defect amount of 0.5%, while the sample No. 22 has an extremely large defect amount of 9.6%. Further, from the results of sample numbers 38 and 39, even if the component composition is within the range of the present invention, if the amount of defects is large, the wear resistance decreases, and the amount of defects is the average after grinding in the manufacturing process. It can be seen that it depends on the particle size and the bulk density of the molded body.

[0053]

As is apparent from the above description, according to the present invention, a) the strength, hardness, toughness and impact resistance are excellent, and thus the wear resistance under high load is good, b) When used as a member for a crusher, it has excellent wear resistance, so less abrasion powder is mixed into the material to be ground. It is possible to obtain wear-resistant alumina-based ceramics having excellent properties such as less deterioration of uniformity and c) use of inexpensive alumina as a raw material.

Therefore, the wear-resistant alumina ceramics according to the present invention can be used not only for crushing / dispersing media, lining materials for crushers, containers, crusher members such as stirrers, but also for various industrial wear-resistant members. As is the best.

[Brief description of drawings]

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

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

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 8, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Since the amount of defects has a great influence on the wear resistance of ceramics, the amount of defects on the mirror-finished surface is required to be 5% or less. This has a defect amount of 5%
If it exceeds, these defects are the starting points of wear and promote wear, leading to a drop in wear resistance and, at the same time, a drop in impact strength. The amount of this defect is preferably 3% or less, more preferably 2% or less.

Claims (5)

[Claims] 1. Al ₂ O ₃ 88% by weight or more and less than 95% by weight,
SiO ₂ 3.6-10% by weight, MgO 0.2-2.5% by weight,
CaO 0.2-2.5% by weight, the balance consisting essentially of inevitable impurities, the sum of the contents of SiO ₂ , MgO and CaO being 5-12% by weight, said SiO ₂ , MgO and CaO
When the sum of the contents of is 100, the ratio of each component is SiO ₂
72 to 85% by weight, MgO 3 to 25% by weight, CaO 3 to
25% by weight, the unavoidable impurities are 0.5% by weight or less,
A wear-resistant alumina-based ceramic characterized by having a defect amount of 5% or less. 2. Al ₂ O ₃ 88% by weight or more and less than 95% by weight,
SiO ₂ 3.6-10% by weight, MgO 0.2-2.5% by weight,
0.2 to 2.5% by weight of CaO and the balance of 100 parts by weight of a basic composition consisting essentially of unavoidable impurities were added to 0.2% of ZrO ₂ .
The wear-resistant alumina ceramics according to claim 1, wherein the wear-resistant alumina ceramics is contained in an amount of 01 to 15 parts by weight. 3. The wear resistance according to claim 1, wherein the alkali metal oxides contained as the inevitable impurities are 0.4% by weight or less and the TiO ₂ is 0.2% by weight or less. Alumina ceramics. 4. The wear-resistant alumina ceramics according to claim 1, which has an average crystal grain size of 1.0 to 5.0 μm and a bulk density of 3.60 g / cm ³ or more. 5. A raw material powder is blended in a predetermined ratio, the mixture is pulverized into a powder having an average particle size of 0.5 to 1.0 μm, and the obtained fine powder is molded into a predetermined shape to have a bulk density of 1. 90-2.
The method for producing wear-resistant alumina-based ceramics according to claim 1, wherein a molded body of 10 g / cm ³ is obtained and is fired.