JPH0672767A - Wear resistant zirconia-based sintered compact - Google Patents

Abstract

PURPOSE:To reduce the rate of wastage and to ensure resistance to wear and crushing due to shock by incorporating Y2O3, Al2O3 and SiO2 and carrying out firing so that a prescribed compsn. is obtd. CONSTITUTION:A Zr compd. soln. is mixed with a Y compd. soln. so that 2.0-4.0mol% Y2O3 is contained in ZrO2 and the resulting mixture is dehydrated, dried and roasted to obtain primary ZrO2 crystal powder. This powder is mixed with <=1.0wt.% Al2O3 and <=1.0wt.% SiO2, pulverized and compacted to form a compact having about >=2.0g/cm<3> density. This compact is then fired at 1,350-1,800 deg.C to produce the objective wear resistant ZrO2-based sintered compact having <=2.5mum average grain diameter, >=5.98g/cm<3> bulk density and <<=0.1% rate of wastage by a ball mill. The crystal structure of the sintered compact has a mirror finished surface and does not contain monoclinic Zr and the Zr in the structure consists of tetragonal Zr of >=30wt.% is converted into monoclinic Zr when the sintered compact is heat-treated, slowly cooled and pulverized and the balance isometric Zr.

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 can be 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 are widely used such as rolling ball mills, sand mills, attritors, vibration mills, hammer mills, jet mills, rod mills, roller mills, and combinations of mortar and pestle. It is used. 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 easily worn or have too high hardness, so that the mating members (for example, the media for the lining material, the media and the media, etc.) that come into contact with each other are damaged, and the material to be ground is crushed. Abrasion powder is often mixed in things. However, since it is difficult to separate this mixed wear powder, it is a major obstacle in terms of process simplification and product purity. So, for example,
If a steel member is used, a deferring process is added, or an alumina member of the same quality is used when pulverizing alumina, or a material (rubber , Plastics, etc.) are used. 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 present invention is excellent in wear resistance and impact crush resistance and has an appropriate hardness, so that the zirconia-based sintered body has a low wear rate as a member for a crusher. Aim to get.

It is another object of the present invention to obtain a zirconia-based sintered body which is excellent in wear resistance, impact crush resistance and the like and which is useful as a general industrial wear resistant structural material.

[0006]

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 SiO ₂ are contained, and the content of Y ₂ O ₃ , the composition of the crystal system, and the average crystal grain size are appropriately controlled, and the porosity is lowered as compared with the conventional zirconia-based sintered body (in other words, Then, it has been found that a zirconia-based sintered body having an extremely low wear rate can be obtained in the case of imparting a bulk density higher than that of a conventional zirconia-based sintered body.

That is, the present invention provides the following wear resistant zirconia-based sintered bodies: (a) Y ₂ O ₃ is 2.0 mol% or more and 4.0 mol% or less, Al ₂
O ₃ is contained in an amount of 1.0% by weight or less and SiO ₂ is included in an amount of 1.0% by weight or less, and (b) the crystal structure of the sintered body is mirror-finished. After being heat-treated and gradually cooled, the sintered body is not included, and contains 30% or more of tetragonal zirconia that changes into a monoclinic system by a pulverization process, and the balance consists of equiaxed zirconia. The average crystal grain size of the sintered body is 2.5 μm or less, and (d) the bulk density of the sintered body is 5.
98 g / cm ³ or more, and (e) the wear rate of the above sintered body in the form of a grinding medium by a ball mill is 0.1%.
A wear-resistant zirconia-based sintered body characterized by being:

It is essential that the zirconia-based sintered body of the present invention has the respective requirements described below.

(1) Y ₂ O ₃ is 2.0 mol% or more and 4.0 mol%
Contains the following. When the content of Y ₂ O ₃ is less than 2.0 mol%, the monoclinic ZrO ₂ is already produced at the time of producing the sintered body.
Easy to generate. 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 a member for a crusher, its resistance to friction, impact, crushing, etc. becomes insufficient, resulting in low wear resistance,
This is not preferable because the amount of wear increases. On the other hand, Y ₂ O ₃
If the content of Mn 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 powder size of the ground powder also becomes coarse. It is not suitable as a crusher member. Further, such a material having low toughness is also unsuitable as an industrial wear resistant structural material.

Further, Al ₂ O ₃ is 1.0 wt% or less and S
It contains 1.0% by weight or less of iO ₂ . 1.0% by weight
The following Al ₂ O ₃ and 1.0% by weight or less of SiO ₂ have a large effect as a sintering aid, and have an effect of enabling a decrease in sintering temperature and an increase in bulk density.

(2) Tetragonal ZrO ₂ which does not substantially contain monoclinic ZrO ₂ on the mirror-finished surface and which is changed to monoclinic by pulverization after heat treatment and slow cooling of the sintered body Contains more than 30%. The content of the tetragonal ZrO ₂ is preferably 40% or more, more preferably in the range of 50 to 80%, but even if it exceeds this range, there is no practical problem. When the content of the tetragonal ZrO ₂ is less than 30%, the equiaxed ZrO ₂ becomes excessive or monoclinic ZrO ₂ is produced to such an extent that the physical properties of the sintered body are impaired.
The above-mentioned problems (1) occur.

Since it is generally difficult to accurately separate the tetragonal crystal and the equiaxed crystal, the tetragonal ZrO ₂ of the present invention is used.
The content of was measured by the following method.

(A) The surface of the sintered body was ground with a 600-mesh diamond grindstone, and then mirror-finished with a 1-5 μm diamond grindstone. From the intensity ratio (area ratio) of the surface by the X-ray diffraction method, monoclinic The content of crystalline ZrO ₂ is measured. The content of monoclinic ZrO ₂ is Gurvey et al.
C. Garvie et al) Journal of American Ceramics Society (J.Am.Ceram.Soc.), 55 [6
] 1972, pp. 303-305, Xm (%) shown by the following formula.

[0014]

[Equation 1]

In the above formula, Im (111) represents the intensity of the X-ray diffraction line of the (111) plane of single crystal zirconia,

[0016]

[Equation 2]

Is a single crystal zirconia

[0018]

[Equation 3]

The intensity of the X-ray diffraction line of the surface is shown as Ict (1
11) shows the X-ray diffraction line intensities of equiaxed and tetragonal zirconia (111).

(B) Next, the above sample was placed in an electric furnace at 1500
After holding at ℃ for 300 hours, slowly cool and crush in a mortar to 10μ
The number of particles is m or less, and the content of monoclinic ZrO ₂ is measured by the same X-ray diffraction method as in (a) above.

(C) Next, the particles having a size of 10 μm or less are held in an electric furnace at 500 ° C. for 1000 hours, then gradually cooled, and then 5 μ in a mortar.
It is pulverized to m or less, and the content of monoclinic ZrO ₂ is measured by the X-ray diffraction method similar to the above (a).

(D) Next, the value of (a) is subtracted from the larger value of the monoclinic ZrO ₂ contents obtained in (b) and (c), and the tetragonal crystal is obtained with the obtained value. System Z
The content is rO ₂ . This is because the monoclinic ZrO ₂ increased by the heating and pulverization treatments of (b) and (c) was generated by the transfer of most of the tetragonal ZrO ₂ contained in the sintered body before the treatment. It is based on the presumption that it is a thing.

(3) The average grain size of the ZrO ₂ type crystals constituting the sintered body is 2.5 μm or less. The average grain size of crystals is 2.
If it exceeds 5 μm, the driving force for the transition from the tetragonal system to the monoclinic system becomes large in the cooling process after sintering, and the monoclinic system Z
The amount of rO ₂ increases, the amount of tetragonal ZrO ₂ decreases accordingly, and the stability of the tetragonal system decreases, so that even a slight impact causes the transition from tetragonal to monoclinic, friction,
Since the resistance to impact, crushing, etc. is reduced, it becomes unsuitable for use as a crusher member, an industrial wear resistant structural material, and the like. Considering further the general principle of ceramics that the smaller the crystal grain size, the greater the strength in the material of the same composition, the average grain size of the ZrO ₂ system crystal is 2 μm.
It is more preferably m or less.

(4) The bulk density of the sintered body is 5.98 g / cm.
Set to 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 stability of the tetragonal ZrO ₂ tends to decrease.

(5) The wear rate of the sintered body is 0.1% or less. If the wear rate exceeds 0.1%, the wear resistance is poor, and especially when using a sintered body as a crusher member, the amount of wear powder of the zirconia sintered body mixed in the crushed object. 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, "wear rate by ball mill" means an alumina mill with a capacity of 400 ml of a sintered body 520 g in the form of a crusher medium (for example, manufactured by Nippon Kagaku Sangyo Co., Ltd., material = HD, shape = A-3 type), add 160 ml of water, perform a dry test at 100 rpm with a rolling ball mill at room temperature, and after 48 hours of operation, remove the media, wash and dry, measure the weight, and reduce the loss of wear. The numerical value calculated from.
As the medium, a ball having a particle diameter of 15 mm is usually used for the measurement, but even if the particle diameter, the shape, etc. are different, the result of the wear rate is not significantly affected.

The wear-resistant zirconia-based sintered body of the present invention is usually manufactured as follows.

2.0 mol% or more of Y ₂ O _{3 in} ZrO ₂
The Zr compound solution and the Y compound solution were uniformly mixed in a proportion such that the content of the compound was 4.0 mol% or less, dehydrated and dried, and then roasted at 400 to 1200 ° C. to obtain Z having an average particle size of 0.5 μm or less.
An rO ₂ primary crystal powder is obtained. Then, a predetermined amount of Al ₂ O ₃ and SiO ₂ is added to the primary crystal powder and dispersed by wet pulverization, followed by wax emulsion, PVA, CM.
By adding a molding aid such as C, a known ceramic product molding method such as mechanical press, isostatic press, cast molding, extrusion molding, injection molding, granulation molding, etc. is formed into a predetermined shape and, if necessary, processed. To do. Al ₂ O ₃
As the supply source, not only aluminum oxide but also aluminum salt such as aluminum hydroxide can be used. Further, silica, ethyl silicate, or the like can be used as the SiO ₂ supply source, and in some cases, kaolin or the like can be used to add it in the form of a compound of Al ₂ O ₃ and SiO ₂ . The density of the molded product is about 2.0 g / cm ³ or more, more preferably about 2.5 g / cm ³ or more. The compact is fired at about 1350 to 1800 ° C., more preferably about 1400 to 1750 ° C. under normal pressure or under pressure to obtain a sintered body having a bulk density of 5.98 g / cm ³ .

The wear resistant zirconia-based sintered body of the present invention is
When the requirements (1) to (5) are satisfied, it is usually Z
Entrained in r-containing ores, unless otherwise specified Z
HfO ₂ which is handled as a part of rO ₂ may be contained, and various components (Ti) that may be added or mixed in the form of a sintering aid or other components during the manufacturing process (Ti
O ₂ , Fe ₂ O ₃ , MgO, CaO, Na ₂ O, etc.) may be contained up to about 1% each.

The hardness of the zirconia-based sintered body of the present invention is preferably Rockwell Scale A (H _RA ) of 89 or more and less than 92. In the case of having such hardness, particularly, the mating members that are in contact with each other are not damaged so much, the wear is small, and the pulverization can be efficiently performed.

[0030]

The reason why the wear resistant zirconia-based sintered body of the present invention is excellent in wear resistance, impact crush resistance and the like is as follows.
It is not clear, but it is presumed to be something like the following.

(A) Since a sintered body having a smaller porosity, that is, a bulk density higher than that of a conventionally known zirconia-based sintered body is used, its mechanical strength is large.

Since the tetragonal ZrO ₂ is uniformly dispersed, the fracture toughness is high.

(C) The hardness is relatively low (H _RA 89 to 91) and the elastic modulus is also low, so that the mating members (for example, media for lining material, media and media, etc.) that come into contact with each other are not scratched or worn. .

Since it has a large specific gravity, when it is used as a medium, it exhibits a high crushing ability due to high kinetic energy.

Since it is excellent in chemical stability, corrosion and fatigue are small even if stress is applied in the state of being in contact with the powder and the solvent.

[0036]

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Example 1 Y ₂ O ₃ , Al ₂ O ₃ and SiO _{2 in the} proportions shown in Table 1 below.
ZrO ₂ powder having an average particle size of 0.03 μm or less of primary crystals containing is dispersed and pulverized by a wet method, and then 3% by weight of wax emulsion is added as a molding aid, and the mixture is molded at a pressure of ² ton / cm ² by an isostatic press method. did. Molded body first
The physical properties of the media having a diameter of 15 mm obtained by sintering under the conditions shown in the table are as shown in Table 2 and Table 3 below. sample
Nos. 1 to 4 are the sintered bodies according to the present invention satisfying all the above conditions (1) to (5), and sample Nos. 5 to 7 are comparative products which do not satisfy at least one of these conditions. Is.
Only sample No. 5 used primary crystal grains having an average grain size of 0.8 μm.

Table 1 Sample No. Y ₂ O ₃ Al ₂ O ₃ SiO ₂ Firing temperature-Firing time Content Content Content (mol%) (wt%) (wt%) (° C) (hr) 1 2.5 0.2 0.04 1400 2 2 3.0 0.4 0.20 1420 3 3 4.0 0.8 0.02 1600 2 4 2.8 0.3 0.52 1380 3 5 3.0 1.5 1.5 0.15 1650 2 6 2.0 - 0.50 1500 3 7 2.5 0.5 1.20 1500 2 table 2 sample grain size bulk density tetragonal like axed crystal monoclinic H _RA No. (Μm) (g / cm ³ ) (%) (%) (%) 1 0.4 6.05 86 14 0 91.5 2 0.5 6.03 70 30 0 91.5 3 1.5 5.99 54 46 0 90.8 4 0.3 6.02 82 18 0 91 .05 5 2.0 5.96 65 30 30 5 88.0 6 0.6 5.75 65 0 35 85.0 7 0.5 0.5 90 90 79 16 5 86.5 520 g of each medium obtained above Alumina balls with a capacity of 400 ml (Nippon Kagaku Sangyo Co., Ltd., material = HD, shape =
A-3 type), 160 ml of water was added, and a blanking test was performed 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 loss on wear. The results are shown in Table 3.

[0039] Note No. No. 6 could not be measured because innumerable cracks were generated in the sintered body and destroyed.

From the results shown in Table 3, it is clear that the media made of the zirconia sintered body according to the present invention (Sample Nos. 1 to 4) have excellent wear resistance.

The particle size of the abrasion powder generated from sample No. 3 was only 0.1 μm or less.

Comparative Examples 1 to 2 Bulk density consisting of 92% Al ₂ O ₃ 3.6 g / cm ³ , diameter 15 mm
When the commercially available media of No. 2 was subjected to the same skiving test as in Example 1, the wear rate was 0.35%.

Further, using a commercially available medium having a bulk density of 3.92 g / cm ³ and a diameter of 15 mm, which is made of 99.5% Al ₂ O ₃ ,
When a shear test similar to the above was conducted, the wear rate reached 1.2%.

The particle size of abrasion powder generated from these Al ₂ O ₃ media was 0.2 to 0.7 μm.

Example 2 A medium was obtained in the same manner as in Sample No. 3 of Example 1 except that the diameter of the sintered body was 20 mm.

3 kg of the obtained medium was put into an alumina ball mill having a capacity of 2 l, and 1 kg of silica stone (20 to 80 mesh)
And 700 ml of water were added, and wet grinding was carried out at 95 rpm for 24 hours. The weight of 3 μm particles of ground silica reaches as high as 45%.

Comparative Example 3 Bulk density consisting of 92% Al ₂ O ₃ 3.6 g / cm ³ , diameter 20 mm
Silica stone was pulverized in the same manner as in Example 2 except that the commercially available media of 1.

The weight of the 8 μm particles of ground silica was only 27%.

Comparative Example 4 A medium was obtained in the same manner as in Example 2 except that the Y ₂ O ₃ content was 1.9 mol%.

A large number of cracks had already formed on the surface of the medium at the completion of firing. When this was used for wet grinding of silica, a large number of zirconia debris that had fallen off were mixed in the silica.

Example 3 A molding raw material was prepared by using the same primary crystal powder as that of No. 2 of Example 1, and 1.5 ton was prepared by the isostatic pressing method.
Molded at a pressure of / cm ² , outer diameter 120 mm, inner diameter 91 m
An m mortar and a matching pestle were manufactured. The surface of the mortar and pestle in contact with the crushed object was ground with a GC grindstone. The firing time and temperature of the molded body, and the crystal grain size, bulk density and tetragonal content after firing are shown in Sample N of Table 1.
Similar to those in o.2.

Using the mortar and pestle obtained above,
100-150 mesh fused alumina (SiO ₂ content 0.0
2%) 10 g was crushed by hand and crushed to the extent that no particles were felt on the fingertips.

When the ZrO ₂ content in the crushed material was quantified by chemical analysis, it was 0.008% or less.

Comparative Example 5 The same crushing operation as in Example 3 was carried out using a commercially available agate mortar and pestle (the dimensions are the same as those in Example 3). Ingredient S
It contained 0.05% of iO ₂ .

Example 4 A molding raw material was prepared using the same primary crystal powder as that of No. 2 of Example 1, molded into spheres having a diameter of 6 mm by a rotary granulator, and then at 1500 ° C. for 2 hours. Firing gave media. The obtained media has a crystal grain size of 0.4 μm and a bulk density of 6.04 g /
cm ³ , the tetragonal content was 60% and the H _RA was 91.3.

5 kg of the medium was charged into an attritor (manufactured by Mitsui Miike Seisakusho) having a capacity of 4.9 l, and then 1.3 l of water and 1.3 kg of silica sand were added to the agitator to rotate at 200 r.
Milled at pm for 4 hours.

The wear rate of the media in this case is 0.005% / h
The average particle size of the crushed material was 1.5 μm. In addition, no iron content from the steel tank was found in the crushed material.

Comparative Example 6 Silica stone was crushed in the same manner as in Example 4 except that a commercially available mullite medium having a diameter of 6 mm was used.

The wear rate of the medium was 0.58% / hr, and the average particle size of the crushed material was 2.3 μm.

Comparative Example 7 A commercially available alumina medium having a diameter of 6 mm (Al ₂ O ₃ purity 92
%), And the silica stone was crushed in the same manner as in Example 4.

The wear rate of the medium was 0.11% / hr, and the average particle size of the crushed material was 1.8 μm. In addition, iron content from the steel tank was visually observed in the crushed material. Example 5 Using the same primary crystal powder as No. 2 of Example 1, the outer diameter was
A tubular lining material having a length of 15.5 mm, a length of 45 mm, a circumferential wall thickness of 4 mm and a tip thickness of 10 mm was sealed. The obtained tubular body was fitted in an agitator arm portion of an attritor similar to that in Example 4, fixed with an epoxy resin, and silica sand was crushed in the same manner as in Example 4.

The surface of the zirconia arm lining material is smooth and glossy even after a total of 100 hours of use,
No dimensional change was observed in the outer diameter measurement with a caliper.

Comparative Example 8 A tubular lining material was manufactured in the same manner as in Example 5 except that Al ₂ O ₃ having a purity of 92% was used, and crushed silica sand in the same manner as in Comparative Example 7.

After using for a total of 100 hours, at the circumference
A wall thickness reduction of 0.6 mm was observed.

Example 6 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 the type that discharges crushed materials from a screen placed below the cylinder, zirconia-based sintered upholstery material with a thickness of 8 mm, a width of 45 mm, and a length of 26 mm is applied to the outer surface of each of the 12 hammer tips with epoxy s. Bonded with resin, 8000rp
Grind glass powder with m. The sintered body was formed by using a zirconia primary crystal powder similar to that of No. 1 of Example 1 at a pressure of 1 ton / cm ² by a mechanical pressing method, processed into a predetermined shape, and then subjected to 2 at 1600 ° C. The one that has been fired for a time
It has the same physical properties as sample No. 1 in the table.

It is estimated that even after a total of 400 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 9 A lining material was produced in the same manner as in Example 6 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 it was judged that further use was impossible.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B02C 17/22 9042-4D

Claims (1)

[Claims] 1. (a) 2.0 mol% to 4.0 mol% of Y ₂ O ₃
Hereinafter, Al ₂ O ₃ is 1.0 wt% or less and SiO ₂ is 1.
0% by weight or less, (b) the crystal structure of the sintered body is mirror-finished, the surface of the sintered body is substantially free of monoclinic zirconia, and the sintered body is heat-treated and gradually cooled, Includes 30% or more of tetragonal zirconia that changes to monoclinic by crushing,
The balance consists of equiaxed zirconia, (c) the average crystal grain size of the sintered body is 2.5 μm or less, (d) the bulk density of the sintered body is 5.98 g / cm ³ or more, and e) A wear-resistant zirconia-based sintered body, characterized in that the wear rate of the above-mentioned sintered body in the form of a grinding medium by a ball mill is 0.1% or less.