JPH0825798B2 - Abrasion resistant zirconia sintered body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zirconia-based sintered body having excellent wear resistance. The zirconia-based sintered body according to the present invention has not only the general properties of the zirconia-based sintered body such as an appropriate hardness and a beautiful polished surface, but also wear resistance and impact crush resistance. It ’s so remarkable
It is used in a wide range of fields such as crusher members and industrial wear resistant structural materials.

[0002]

[Prior Art and its Problems] Currently, various crushers such as rolling ball mills, sand mills, attritors, vibration mills, hammer mills, jet mills, rod mills, roller mills, mortar and pestle combinations are widely used. in use. These pulverizers are devices that pulverize mainly by friction and impact crushing force using a pulverizing medium (media) such as balls and rolls, and devices that perform high-speed movement of particles and crush by the impact and crushing force. It is roughly divided into.

Conventionally, in the lining materials and media of these crushers, which are easily worn, natural stone, porcelain, alumina, glass, rubber, plastics, steel and agate are used depending on the kind of the object to be crushed. Are used.
However, these materials are generally prone to wear, or because their hardness is too high, they cause wear of mating members (for example, media for lining materials, media and media, etc.) that come into contact with each other, and Wear particles are often mixed in the pulverized product. However, since it is difficult to separate this mixed wear powder, it is a major obstacle in terms of process simplification and product purity. Therefore, for example, when a steel member is used, a deferring step is added, or when crushing alumina, an alumina member of the same quality is used, or a small amount of abrasion powder is allowed to be mixed. It has been devised such as using members made of different materials (rubber, plastics, etc.). However,
In the latest technical fields, such as ceramics, electronic materials, coating materials, powder materials, etc., the trace components and their microstructure in the material to be ground mixed in the fine grinding process are It has become clear that management and reliability will be greatly affected.

[0004]

DISCLOSURE OF THE INVENTION The object of the present invention is to obtain a zirconia-based sintered body having a low wear rate as a member for a crusher because it has excellent wear resistance and an appropriate hardness. And Another object of the present invention is to obtain a zirconia-based sintered body that is also excellent in wear resistance, impact crush resistance, and the like and is useful as a general industrial wear resistant structure material.

[0005]

The present inventor has conducted earnest research in view of the current state of the art as a result, and as a result, in a zirconia-based sintered body containing Y ₂ O ₃ , a specific amount of Al ₂ O _{3 was used.}
And appropriately controlling the Y ₂ O ₃ content, the composition of the crystal system, and the average crystal grain size, and lowering the porosity as compared with the conventional zirconia-based sintered body (in other words, conventional It has been found that a zirconia-based sintered body having an extremely low wear rate and excellent in wear resistance can be obtained when the bulk density is imparted to the zirconia-based sintered body of 1.).

That is, the present invention provides the following wear-resistant zirconia-based sintered bodies: (a) Y ₂ O ₃ of 2.0 mol% or more and 4.0 mol% or less and Al ₂ O. ₃ contains 0.05 wt% to 1.0 wt% or less, not including monoclinic zirconia substantially in (b) sintered body surface crystal structure of the sintered body was mirror finished, and sintered (C) average crystal grain size of the sintered body, which contains 30% or more of tetragonal zirconia that changes into monoclinic system by crushing after heat treatment and slow cooling of the body, and the balance is equiaxed zirconia. Is 2 μm or less, and (d) bulk density is 5.98 g / c.
and the m ³ or more, (e) wear resistant zirconia sintered body, wherein the wear rate by a ball mill of the sintered body in the form of a grinding medium is not more than 0.15%.

The zirconia-based sintered body of the present invention has the respective requirements described below. (1) Y ₂ O ₃ is contained in an amount of 2.0 mol% or more and 4.0 mol% or less. When the content of Y ₂ O ₃ is less than 2.0 mol%, monoclinic ZrO ₂ is likely to be already generated during the production of the sintered body. When this monoclinic ZrO ₂ is produced, a large volume change is caused by the transition, so that a crack occurs in the sintered body. Therefore, when such a sintered body is used as, for example, a member for a crusher, the resistance to friction, impact, crushing, etc. becomes insufficient, so that the wear resistance is low and the amount of wear is large, Not preferable. Further, such a sintered body lacks usefulness as an industrial wear resistant structural material. On the other hand, when the content of Y ₂ O ₃ exceeds 4.0 mol%, the equiaxed ZrO ₂ becomes excessive, the wear amount of the sintered member itself increases with the decrease in toughness, and the amount of ground powder is reduced. Since the powder diameter is also coarse, it is not suitable as a member for a crusher. Further, such a material having low toughness is also unsuitable as an industrial wear resistant structural material.

Further, the sintered body of the present invention, as a sintering aid,
It contains Al ₂ O _{3 in an amount} of 0.05% by weight or more and 1.0% by weight or less. The addition of Al ₂ O ₃ promotes sintering
It (2) The mirror-finished surface does not substantially contain monoclinic ZrO ₂ , and after the sintered body is heat-treated and gradually cooled, 30% of tetragonal ZrO ₂ which changes into monoclinic by grinding treatment is used. It includes the following. The content of the tetragonal ZrO ₂ is preferably 40% or more, more preferably in the range of 50 to 70%, but even if it exceeds this range, there is no practical problem. If the content of the tetragonal ZrO ₂ is less than 30%, the equiaxed ZrO ₂ will be excessive or the monoclinic ZrO ₂ will be produced to such an extent that the physical properties of the sintered body will be impaired.
The above-mentioned problems (1) occur. Since it is generally difficult to accurately separate the tetragonal crystal and the equiaxed crystal, the content of the tetragonal ZrO ₂ in the present invention was measured by the following method. (A) After the surface of the sintered body was ground with a 600-mesh diamond grindstone, it was mirror-finished with a 1-5 μm diamond grindstone, and the monoclinic system ZrO was obtained from the intensity ratio (area ratio) of the surface by the X-ray diffraction method. The content of ₂ is measured. The content of monoclinic ZrO ₂ is equal to that of Garvey et al. (RC Ga
rvie et al) Journal of American Ceramics Society (J. Am. Cera
m. Soc. ), 55 [6] 1972, Nos. 303-30.
It was determined by Xm (%) shown in the following formula reported on page 5. In the above formula, Im (111) represents the X-ray diffraction intensity of the (111) plane of monoclinic zirconia, and Im (11) represents the X-ray diffraction intensity of the (11) plane of monoclinic zirconia. Ict (111) indicates the X-ray diffraction intensities of the equiaxed and tetragonal zirconia (111) planes. (B) Next, the above sample was placed in an electric furnace at 1500 ° C. for 30 minutes.
After holding for 0 hour, the mixture is gradually cooled and crushed in a mortar to give particles of 10 μm or less, and the content of monoclinic ZrO ₂ is measured by the X-ray diffraction method similar to the above (a). (C) Next, the particles of 10 μm or less are 500
After holding at 1000 ° C. for 1000 hours, the mixture is gradually cooled, pulverized to 5 μm or less in a mortar, and the content of monoclinic ZrO ₂ is measured by the X-ray diffraction method similar to the above (a). (D) then, (b) and from larger one of the resultant monoclinic ZrO ₂ content in (c) subtracting the value of (b), a square with the obtained value tetragonal ZrO ₂ Content (Xt (%)). This is (b) and (c)
The monoclinic ZrO ₂ increased by the heat pulverization treatment of
This is based on the assumption that most of the tetragonal ZrO ₂ contained in the unsintered sintered body was generated by transformation. (E) Next, the content Xc (%) of the equiaxed ZrO ₂
Was calculated by the following formula. Xc (%) = 100- (Xm + Xt)

(3) The average grain size of the ZrO ₂ type crystals constituting the sintered body is 2 μm or less. Average crystal grain size is 2μ
If it exceeds m, the driving force for transitioning from tetragonal to monoclinic in the cooling process after sintering becomes large, and monoclinic ZrO 2
The amount of ₂ increases, the amount of tetragonal ZrO ₂ decreases accordingly, and the stability of the tetragon decreases, and even a slight impact causes the transition from tetragonal to monoclinic, friction and impact. Since the resistance against crushing and the like decreases, it becomes unsuitable for use as a crusher member or an industrial wear resistant structural member.
Considering further the general principle of ceramics that the smaller the crystal grain size, the greater the strength in materials having the same composition, the average grain size of the ZrO ₂ -based crystal is more preferably 1 μm or less.

(4) The bulk density of the sintered body is 5.98 g /
cm ³ or more. When the bulk density is less than 5.98 g / cm ³ , the fracture energy of the sintered body against external stress such as friction and impact becomes small, and the tetragonal ZrO ₂
There is a greater tendency to reduce the stability of. The bulk density of the sintered body is more preferably 6.00 g / cm ³ or more.

(5) The wear rate of the sintered body is 0.15% or less. If the wear rate exceeds 0.15%, the wear resistance is poor, and especially when the sintered body is used as a member for a crusher, wear powder of the zirconia sintered body mixed in the object to be crushed. Is increased, which is not preferable. The wear rate of the sintered body is more preferably 0.03% or less. In the specification of the present application, the "wear loss rate by ball mill" means
Sintered body 520g in the form of crusher media has a capacity of 400
ml alumina mill (for example, Nippon Kagaku Sangyo Co., Ltd., material = HD, format = A-3 type), water 160m
l, and 100 rpm with a rolling ball mill at room temperature
After performing a dry test for 48 hours, the medium is taken out after washing for 48 hours, washed and dried, and then the weight is measured. As the medium, a ball having a particle diameter of 15 mm is usually used for measurement.
Even if the shape is different, there is not much influence on the result of the wear rate.

The zirconia-based sintered body according to the present invention is usually manufactured as follows. During ZrO ₂ in proportions as contained _Y 2 _{O 3} as 2.0 or more mole% 4.0 mol% or less, and uniformly mixing the Zr compound solution and the Y compound solution,
After dehydration and drying, it is roasted at 400 to 1200 ° C. to obtain ZrO ₂ primary crystal powder having an average particle size of 0.5 μm or less. Then, the primary crystal powder was mixed with Al ₂ O ₃ of 1 μm or less.
Of 0.05% by weight or more and 1.0% by weight or less and dispersed by wet pulverization, followed by wax emulsion, PV
Forming aids such as A and CMC are added, mechanical press,
Isostatic press, cast molding, extrusion molding,
A known ceramic product molding method such as injection molding or granulation molding is used to mold the product into a predetermined shape and process it if necessary. The density of the molded body is about 2.0 g / cm ³ or more, more preferably about 2.5 g / cm ³ or more. The molding is fired at about 1350 to 1800 ° C, more preferably 140
Sintered body having a bulk density of 5.90 g / cm ³ is obtained by performing normal pressure or pressure application at about 0 to 1750 ° C.

The zirconia-based sintered body of the present invention has the above-mentioned (1)
In the case where the requirements of (5) to (5) are satisfied, HfO ₂ which is usually included in a Zr-containing ore and is handled as a part of ZrO ₂ may be contained unless otherwise specified,
Furthermore, various components (SiO ₂ , Ti) that may be added or mixed in the form of a sintering aid or other components during the manufacturing process.
O ₂ , Fe ₂ O ₃ , MgO, CaO, Na ₂ O, etc.) may be contained up to about 1% each.

[0014]

The reason why the zirconia-based sintered body according to the present invention is excellent in wear resistance, impact crush resistance, etc. is not clear, but it is presumed to be as follows. B. The mechanical strength of the sintered body itself is high. (2) Since it is a sintered body having a smaller porosity, in other words, a higher bulk density than the conventionally known zirconia-based sintered body, it has a low defect density as a starting point of wear and is excellent in wear resistance. (3) Since the crystal grain size is small, the amount of particle detachment wear is small and the wear resistance is excellent. Since the tetragonal ZrO ₂ is uniformly dispersed, the fracture toughness is high. E hardness is relatively low (about H _RA 89 to 91), the elastic modulus is low, the mating member (for example, media for the lining material, such as media and media) for contact with each other without damaging too, does not wear. F Because of its large specific gravity, when using it as a medium,
Demonstrates high crushing ability due to high kinetic energy. Since it has excellent chemical stability, it is less corrosive and fatigued even when stress is applied in the state of contact with powder and solvent.

[0015]

EXAMPLES Examples are shown below to further clarify the features of the present invention. Example 1 Al ₂ O ₃ was added to ZrO ₂ powder having an average particle size of 0.03 μm or less of primary crystals containing Y ₂ O ₃ in a ratio shown in Table 1 below in a wet condition. After dispersion and pulverization, 3% by weight of a wax emulsion was added as a molding aid, and the mixture was molded by an isostatic press method at a pressure of 1 ton / cm ² . The physical properties of the media having a diameter of 15 mm obtained by sintering the compact under the conditions shown in Table 1 are as shown in Table 2 and Table 3 below. Sample No. Sample Nos. 1 to 6 are the sintered bodies according to the present invention satisfying all the above conditions (1) to (5). 7 to 11 are comparative products that do not satisfy at least one of these conditions. Sample No. Only No. 8 used primary crystal grains having an average grain size of 0.8 μm.

[0016]

[0017]

520 g of each medium obtained above was placed in an alumina ball having a capacity of 400 ml, 160 ml of water was added, and a skid test was carried out at 100 rpm. After 48 hours of operation, the media was taken out, washed and dried, the weight was measured, and the wear rate was calculated from the wear loss. The results are shown in Table 3.

As is clear from the results shown in Table 3, a medium made of the zirconia sintered body according to the present invention (Sample N
o. The excellent wear resistance of 1 to 6) is apparent. In addition, the sample No. The particle size of the abrasion powder generated from No. 3 was only 0.1 μm or less.

Example 2 Sample No. 1 of Example 1 Using the same primary powder as in 2,
Using a rotary granulator, a sphere with a diameter of 5 mm and an outer diameter of 15.5
mm, length 45 mm, circumferential wall thickness 4 mm, tip thickness 1
A tubular liner with one end of 0 mm closed was produced by sintering. The sintering conditions were a temperature of 1450 ° C. and a time of 2 hours. The properties of the obtained media and tubular body were a crystal grain size of 0.4 μm, a bulk density of 6.04 g / cm ³ , and a tetragonal crystal content of 68%. The obtained media (5 kg) was charged into an attritor (manufactured by Mitsui Miike Seisakusho) having a capacity of 4.91, and the obtained tubular body was fitted into an agitator arm portion of the attritor and fixed with an epoxy resin.
80 mesh) 1.3 kg and water 1.3 kg,
The agitator was rotated at 200 rpm for 4 hours. The wear rate of the media in this case is 0.006% / h
r. The surface of the zirconia arm lining material was smooth and glossy even after using for a total of 200 hours under the same conditions, and no dimensional change was observed in the outer diameter measurement with a caliper.

Comparative Example 1 Bulk density of 92% Al ₂ O ₃ 3.6 g / cm ³ ,
Silica sand was pulverized in the same manner as in Example 2 using an agitator arm part having a bulk density of 3.6 g / cm ³ made of commercially available media having a diameter of 5 mm and 92% Al ₂ O ₃ . The wear rate of media after 4 hours is
0.11% / hr, and after 100 hours of use under the same conditions, 0.6 at the circumference of the liner inside the agitator arm.
A reduction in wall thickness of mm was observed.

Example 3 A central shaft having a blade-shaped swing hammer was rotated at a high speed in a cylindrical body, and an object to be crushed was supplied from above the cylindrical body,
In a hammer mill of a type in which a crushed material is discharged from a screen arranged below a cylindrical body, a zirconia-based sintered upholstery material having a thickness of 8 mm, a width of 45 mm, and a length of 26 mm is provided on the outer surface of each of 12 hammer tips with an epoxy resin. And the glass powder is crushed at 8000 rpm. The sintered body is
No. 1 of the first embodiment. The same zirconia primary crystal powder as that of No. 1 was used, and 1 ton / cm ² was obtained by the mechanical pressing method.
At 1450 ° C after molding into the prescribed shape under pressure
Sample No. 1 in Table 1 was fired for an hour. It has various physical properties similar to 1. It is estimated that even after a total of 500 hours of use, the lining material according to the present invention has very little wear and can be used for a long period of time.

Comparative Example 2 A lining material was produced in the same manner as in Example 3 except that Al ₂ O ₃ having a purity of 92% was used, and was joined to a hammer of a hammer mill. After a total of 300 hours of use, the wear was remarkable, and there was a great risk of damage and vibration due to displacement of the center of gravity, so further use was judged to be impossible.

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Claims (1)

[Claims] (A) Y ₂ O ₃ is 2.0 mol% or more and 4.0.
Mol% or less and 0.05 wt% or more of Al ₂ O ₃ 1.
0% by weight or less, (b) the crystal structure of the sintered body does not substantially contain monoclinic zirconia on the surface of the mirror-finished sintered body, and after the sintered body is heat-treated and gradually cooled, Includes 30% or more of tetragonal zirconia that changes into monoclinic system by pulverization, the balance is composed of equiaxed zirconia, and (c) the average crystal grain size of the sintered body is 2 μm or less, (d) The bulk density is 5.98 g / cm ³ or more, and (e) the wear rate of the sintered body in the form of a grinding medium by a ball mill is 0.
A wear resistant zirconia-based sintered body characterized by being 15% or less.