JP2631924B2 - Manufacturing method of alumina pulverizer member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a member for a pulverizer, and more particularly to a method for producing a member such as a pulverizing medium and a lining material in a dry or wet pulverizer.

[0002]

2. Description of the Related Art Conventionally, ball mills, sand mills, vibration mills, attrition mills, rod mills and the like have been widely used as mills using a milling medium. In these crushers, a crushing medium called a ball, a bead, a roll, or the like is given a motion to cause impact, crush,
The crushed material is crushed and dispersed using stress such as friction. In a jet mill or the like, pulverization is performed by giving kinetic energy to the pulverized objects and colliding between the pulverized objects or between the pulverized object and the lining material. In such a pulverizer, members that are easily worn such as a lining material and a pulverizing medium include:
Generally, natural stone, alumina, zirconia, glass, rubber,
Although plastics, alloys, and the like are used, wear of these lining materials and grinding media is not prevented in the grinding process, and therefore, there is a problem that abrasion powder is mixed into the material to be crushed. In particular, in various fields such as fine ceramics, electronic materials, semiconductor industry, coating materials, powders, etc., these abrasion powders reduce the purity of crushed materials and affect electric, magnetic, chemical properties, etc. This is a major problem in quality control of the crushed material powder.

Therefore, an attempt has been made to reduce the influence of wear powder by using a sintered body made of the same material as the material to be crushed as a pulverizer member. However, there is a disadvantage that the crusher member is greatly damaged, and the powder form of the abrasion powder to be mixed is different from that of the crushed material, and the uniformity of the quality of the crushed material is reduced.

[0004] For this reason, in general, as a member for a crusher,
Materials having excellent wear resistance such as alumina, zirconia, silicon nitride, and silicon carbide are often used. However, among these materials, silicon nitride and silicon carbide are:
Excellent in abrasion resistance, suitable for crushing when the material to be crushed is the same material as these members, but because the color tone is gray black, when white powder is used as crushed material, coloring due to mixing of abrasion powder In addition, in the case of a ceramic molded body in which the material to be crushed is pulverized and then fired in the air, there is a defect that foaming occurs due to the influence of the abrasion powder mixed in and a defective portion is formed in the fired material.

[0005] Transformation-strengthened zirconia has the advantage of being efficient as a pulverizing medium and having little wear because of its high specific gravity. However, it is expensive, and when high impact force is applied or when the temperature rises. Has the disadvantage of increased wear. Further, there is a problem that U, Th, and the like are easily mixed in and are difficult to remove, and these are mixed in the material to be ground to lower the quality of the material to be ground.

[0006] On the other hand, alumina has a drawback that it has much wear compared to zirconia, silicon nitride, silicon carbide, etc., but is inexpensive. 85 to 9
A sintered body having a purity of about 7% is used. Also, if the contamination in the pulverized product of SiO ₂ and an alkali content in the alumina is a problem, the amount of alumina is also possible to use a sintered body of about 99.0 to 99.7%. However, even when such a high-purity alumina sintered body is used, there is still a problem that the amount of wear is large.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present inventor has made intensive studies to find a member for a crusher having excellent wear resistance. In the process, conventionally, since it is inexpensive despite much abrasion, attention has been paid to alumina sintered bodies widely used as members for pulverizers, and various studies have been made on improving the abrasion resistance thereof. . As a result, by using a specific alumina raw material and controlling the alumina purity, crystal grain size, and density of the alumina sintered body to have values within a specific range, a sintered body having extremely excellent wear resistance can be obtained. The present invention has been completed here.

That is, according to the present invention, the alumina content is 99.9.
Alumina content of 99.9% by weight or more, characterized in that alumina raw material having an average crystal diameter of 0.5 μm or less is pulverized / dispersed, molded and fired, and the average particle diameter of alumina crystal is 2.5 μm or less. And a method for manufacturing a member for an alumina pulverizer made of a sintered body having a relative density of 98% or more.

[0009] The requirements to be satisfied by the pulverizer member obtained by the method of the present invention are specifically described below.

(A) When the alumina content in the sintered body is 9
9.9% by weight or more.

According to the study of the present inventors, it has been found that the wear resistance of the sintered body is sharply improved by setting the alumina content in the sintered body to 99.9% or more. This relationship is apparent from FIG. 1 showing the results of Example 1 described later.

Although the reason for the rapid improvement in wear resistance due to the alumina content of 99.9% or more is not clear,
This is because the grain boundary width becomes narrower as the sintered body becomes more purified, and as a result, wear caused by preferentially breaking the grain boundaries of the alumina crystal grains, that is, so-called particle detachment wear, is less likely to occur. It is presumed. Therefore, the amount of alumina in the sintered body is 9
9.9% or more, preferably 99.95% or more.

(B) The average grain size of the alumina crystals in the sintered body is set to 2.5 μm or less.

When the grain size of the alumina crystal in the sintered body is large, the grain boundary width is increased in the sintered body having the same alumina content because the grain boundary is reduced. As a result, it is considered that the above-described particle detachment wear easily occurs, and the wear amount increases. According to the study of the present inventors, the average crystal diameter was 2.5 μm
From the following, it was found that there was a sharp improvement in wear resistance. FIG. 2 shows the results of Example 1 described below.
It is clear from Therefore, in the pulverizer member obtained according to the present invention, the average particle size of the alumina crystal is set to 2.5 μm or less, preferably 2 μm or less.

(C) The relative density of the alumina sintered body is 98
% Or more.

In the present invention, the term "relative density" means a relative value to the theoretical density of the sintered body expressed as a percentage. Here, the theoretical density is 100% in which no vacancy exists.
It refers to the density of a dense sintered body.

The wear resistance of the alumina sintered body is greatly affected by its relative density, and the lower the relative density, the greater the amount of wear. This is presumably because as the relative density decreases, the number of vacancies increases in the grain boundaries, and the vacancies serve as a starting point of abrasion, thereby promoting the detachment of crystal grains. Therefore, in the present invention, the relative density of the sintered body is set to 98% or more, preferably 98.5% or more.

A pulverizer member satisfying the above requirements is
Although it has excellent wear resistance, when pulverizing a material used for an electronic component, it is preferable that the material further satisfies the following requirements.

That is, when pulverizing a material used for an electronic component, when a radioactive element such as uranium or thorium is contained in the member as in a conventional pulverizer member, these elements are contained in the material to be pulverized. And the quality of the electronic component is degraded. Therefore, when the member obtained according to the present invention is used for pulverizing a material for electronic components, it is appropriate to reduce the amounts of uranium and thorium, and to reduce
It is preferably at most 0 ppb (by activation analysis), more preferably at most 30 ppb. In such a pulverizer member having a small amount of uranium and thorium, the amount of uranium and thorium mixed into the crushed material is extremely small, because the amount of wear of the member itself is very small, and the quality of electronic components is degraded. It is rarely done.

The method for producing a pulverizer member of the present invention is carried out as follows.

As a raw material, an alumina raw material having an alumina content of 99.9% by weight or more and an average crystal diameter of 0.5 μm or less is used. As an alumina raw material, an alkoxide method,
Those manufactured by a method other than the buyer method, such as the bright van method, are preferred. When the alumina content is less than 99.9% by weight, the wear resistance is inferior because of the above. On the other hand, if the average crystal diameter exceeds 0.5 μm, it takes a long time to reach a predetermined crystal diameter in the pulverization / dispersion step, and as a result, the amount of impurities mixed increases, which also lowers the wear resistance. Absent.

In the method of the present invention, first, a raw material powder is obtained by pulverizing and dispersing an alumina raw material in a dry or wet method using a pulverizer such as a vibrating mill and drying. Then, using this powder, the mixture is molded into a predetermined shape by a method such as casting, injection molding, extrusion molding, or press molding according to a conventional method in the production of ceramics, and then calcined at a temperature of about 1250 to 1600 ° C. It is a sintered body. Further, the member for the crusher is obtained by finishing the member for the crusher and, if necessary, performing the construction by a method such as bonding.

In the above-mentioned production method, by appropriately selecting the type and quality of a molding aid, a sintering aid, water, etc., and selecting a pulverizing step, a firing tool, etc., components which cannot be scattered and removed by firing or the like. It is necessary to prevent as much as possible and to keep the alumina content within a predetermined range. Also,
In order to keep the particle size and sintered body density within predetermined ranges, it is necessary to avoid mixing of components that promote grain growth during the sintering process, such as Ti, Ca, alkali, etc. It is desirable that the molded body be easily sintered and the relative density of the molded body before firing be 40% or more. Incidentally, the incorporation of impurities such as Ti, Ca, and alkali is not preferable because it promotes grain growth in the sintering process and forms an impurity phase other than alumina at the grain boundaries. Therefore 500
It is preferred that the content be less than ppm.

In the member for a pulverizer of the present invention, the aforementioned (a) to
In order to satisfy the requirement (c), it is necessary to use a high-purity alumina raw material. Purification of the alumina raw material is generally carried out by an acid treatment, a heat treatment, a purification treatment of an Al-derived compound, or the like in the raw material synthesis step in the alkoxide method or the Mei-bang method. The amounts of uranium and thorium may be reduced in these steps, and in these treatment steps, the amounts of uranium and thorium can be reduced relatively easily. By using such an alumina raw material in which uranium and thorium are reduced, and by preventing uranium and thorium from being mixed in the manufacturing process of the pulverizer member, a member having a small amount of uranium and thorium, such as uranium and thorium, is 50 ppb. The following pulverizer members can be manufactured.

[0025]

The pulverizer member obtained by the production method of the present invention has excellent properties as described below, and is used for a pulverizing medium (ball, ball mill, vibration mill, attrition mill, etc.). This is extremely useful as a material for a portion that is particularly easily worn, such as a lining material, a member, or the like of a portion of the crusher that comes into contact with the object to be crushed.

(1) excellent in abrasion resistance,
Less mixing of abrasion powder into crushed material. (2) Inexpensive alumina is used as a raw material.

(3) The abrasion powder of the crusher member is fine, and even when mixed into the crushed material, the uniformity of the crushed material is hardly impaired.

(4) A crusher member having a very small amount of uranium and thorium has a very excellent wear resistance. Therefore, the amount of uranium and thorium mixed into the material to be crushed is reduced. It can be reduced to a very small amount and is therefore suitable for crushing electronic component materials.

[0029]

The present invention will be described in more detail with reference to the following examples.

[0030]

Example 1 Using a raw material having an alumina content of 99.999%, components such as SiO ₂ were uniformly added in a liquid state to the alumina raw material so as to have the composition shown in Table 1, and then roasted to obtain a raw material. Prepared. For sample No. 5, a raw material having an alumina content of 99.999% was used as it was.

First, the raw material was subjected to a specific surface area of 5 m ² /
g, and then polyvinyl alcohol was added, followed by drying with a spray drier to obtain a molding powder. Subsequently, the powder was formed into a spherical shape at a CIP of ² tons / cm ² and fired at 1250 to 1600 ° C. to obtain a ball having a diameter of 10 mm. The surface of the ball was barrel-polished to obtain a ball for grinding. The chemical composition (% by weight) of the sintered body is as shown in Table 1.

Table 1 Sample No. 1 2 3 4 5 Al ₂ O ₃ 99.5 99.8 99.91 99.99 99.995 SiO ₂ 0.17 0.04 0.04 0.008 0.004 Fe ₂ O ₃ 0.03 0.03 0.01 0.0004 0.0003 CaO 0.12 0.05 0.01 0.0001 <0.0001 MgO 0.15 0.05 0.01 0.0004 0.0003 Na ₂ O 0.03 0.03 0.02 0.0004 0.0002 K ₂ O trace trace trace 0.0003 0.0001 Put these balls for crusher half into a 2 liter ball mill, add 0.8 liter of water and 200 g of silica powder, Ball mill at 100 r. p.
m. Was operated for 50 hours to determine the amount of wear of the ball. FIG. 1 shows the relationship between the amount of alumina in the crusher ball and the amount of wear per hour of the ball. The relative density of the ball is 99
± 0.3%, and the average crystal grain size was 2 ± 0.2 μm.

From FIG. 1, it can be seen that when the alumina content is less than 99.9%, the wear amount does not greatly depend on the alumina component amount, but when the alumina content is 99.9% or more, the wear resistance sharply improves, and the wear amount decreases. 1/10 when the amount is less than 99.9%
It can be seen that it decreases below.

A wear test was performed on the sintered body having an alumina component amount of 99.99% and a relative density of 99 ± 0.3% in the same manner as described above, and the average crystal grain size of alumina and the hourly rate were measured. FIG. 2 shows the result of determining the relationship with the amount of wear of the ball. FIG. 2 shows that the average crystal grain size of alumina is 2.5.
It can be seen that when the thickness is less than μm, the abrasion amount sharply decreases.

Further, for a sintered body having an alumina content of 99.995% and an average crystal grain size of 1.2 ± 0.2 μm, the relationship between the relative temperature of the sintered body and the amount of wear was determined in the same manner as described above. The results are shown in FIG. From FIG. 3, the relative density of the sintered body is 9
When it is 8% or more, improvement in wear resistance is recognized.

[0036]

Example 2 Alumina content 99.99%, relative density 9
A container for a vibration mill having an internal volume of 2 liters was manufactured from an alumina sintered body having an average particle diameter of alumina of 9 ± 0.3% and an alumina crystal of 0.8 μm, and a silica powder was prepared by using steel balls coated with nylon. After 200 g and 400 g of water were put into operation for 10 hours, the amount of alumina mixed into the silica powder was determined by chemical analysis. As a result, the amount of alumina was 80 ppm.

On the other hand, the alumina content was 99.99.
%, A relative density of 99 ± 0.3%, and an average sintered alumina particle size of 4 μm, the same test was conducted. As a result, the amount of alumina mixed into the silica powder was 600 ppm.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an alumina content and a wear amount.

FIG. 2 is a graph showing the relationship between the average grain size of alumina crystals and the amount of wear.

FIG. 3 is a graph showing a relationship between a relative density and a wear amount of a sintered body.

Claims (2)

(57) [Claims] 1. An alumina raw material having an alumina content of 99.9% by weight or more and an average crystal diameter of 0.5 μm or less is pulverized / dispersed, molded and fired, and an alumina content of 99.9% by weight. Above, the average particle size of the alumina crystal is 2.5
A method for producing an alumina pulverizer member made of a sintered body having a relative density of 98% or less, which is not more than μm. 2. An alumina crusher member having a uranium content of 50 ppb or less and a thorium content of 50 ppb or less.
The method for producing a member for an alumina pulverizer according to claim 1, which is as follows.