JP3409826B2 - Hardened alumina material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an alumina-based abrasive containing aluminum oxide (Al ₂ O ₃ ) as a main component,
The present invention relates to a technique of significantly increasing the hardness of an alumina-based material such as an alumina-based ceramic or single crystal aluminum oxide (sapphire) or a product using the same.

[0002]

BACKGROUND OF THE INVENTION For example, aluminum oxide (Al ₂ O
There is a WA abrasive material as a high-purity alumina abrasive material of ₃ ). As for the hardness, as shown in FIG. 1, the Vickers hardness is about 2000 (see WA # 24 in FIG. 1). FIG. 1 is a graph showing the results of examining the hardness of various abrasive grains. It should be noted that even with silicon carbide-based abrasive grains, as shown in FIG.
Medium, GC # 30 (A company), GC # 30 (B company), C
As shown by # 24 (manufactured by Company A) and C # 24 (manufactured by Company B), the hardness is around 3000.

Therefore, if the hardness of the WA abrasive material can be increased, silicon carbide type C, GC or C
It can be applied to the field of grinding that has been performed using a harder abrasive such as BN.

High-purity aluminum oxide (Al
The hardness of the alumina-based ceramic cutting tool (so-called white ceramic tool) manufactured by compressing and sintering ₂ O ₃ ) fine particles is at most about Vickers hardness of about 1800 (in the graph of Fig. 5, untreated tool). (See (A)). Also in this case, if the hardness of this type of ceramic tool can be increased, the progress of tool wear can be suppressed and the tool performance can be improved.

In addition, sintered aluminum oxide (Al ₂ O
₃ ) Various ceramic products made from materials are used not only in the industrial field but also in various fields. In the industrial field, for example, it is used as a bearing material, and the alumina-made bearing balls generally used for ball bearings have a Vickers hardness of about 1800. If the hardness of these ceramic products can be increased, performances such as abrasion resistance and durability can be improved and the field of application can be expanded.

The aluminum oxide (Al ₂ O ₃ ) single crystal produced by the Bernoulli method is called sapphire, ruby, alexandrite, topaz, aquamarine, spinel, etc. when it contains additives or impurities. Besides being used as a jewel, for example,
It is used for wear resistant materials such as laser devices, bearings for precision machines and wrist watches, and record hands. Since artificial sapphire single crystals with few impurities are colorless and transparent (a colorless aluminum oxide (Al ₂ O ₃ ) single crystal is also called sapphire), it is used as a transparent plate for covering the dial plate of a wristwatch.

As shown in the "untreated surface" in the graph showing the result of examining the hardness of the sapphire surface in FIG. 13, the Vickers hardness of the above-mentioned aluminum oxide single crystal is
With a test load of 1000 gf, cracks are formed around the dents, about 2000, and with a test load of 50 gf, cracks are not formed around the dents, and about 2,500. Therefore, if the hardness of these aluminum oxide single crystals can be increased, it becomes possible to improve the wear resistance, damage resistance, durability and the like of the product using the single crystal. Furthermore, if sapphire with increased hardness can be formed by polishing to form a cutting tool, mirror-cutting of ferrous metal is impossible with a single crystal diamond cutting tool unless special measures such as vibration cutting are used. It can be used as a cutting tool for processing.

[0008]

SUMMARY OF THE INVENTION Under the circumstances described above, the present invention has been completed as a result of various studies to remarkably enhance the hardness of the above-mentioned alumina-based material or a product using the same. A small Vickers hardness of 2 is obtained by adding an oxide or fluoride that forms a solid solution of aluminum oxide, which is the main component, in aluminum oxide.
600 (x 0.9807 N / mm ² , test load 300 x
The main concept is to harden it to 9.807 mN or more.

The above-mentioned alumina material includes all in the form of abrasives (abrasive grains), in the form of sintered ceramics, and in the form of alumina single crystals.

As a method of adding an additive to the alumina material, there are the following methods.

The raw material aluminum oxide (Al
₂ O ₃ ), an additive, a salt of the additive, or a solution of the additive or a salt of the additive is added to ₂ O ₃ ) to thermally decompose the raw material powder, and to add the additive to aluminum oxide to form a solid solution. Heat treatment process.

The additive powder is added to the already-produced high-purity aluminum oxide (Al ₂ O ₃ ) powder to obtain a raw material powder, which is then heat-treated to form a solid solution with the additive.

The above-mentioned already prepared alumina-based abrasives containing alumina as a main component, alumina-based ceramic cutting tool materials, alumina-based ceramic products made of them, alumina-based ceramic materials, alumina-based single crystals, etc. should be added. Heat treatment is carried out by embedding in or in contact with the powder of the substance, and the additive substance is diffused inside in a solid solution state.

As an additive, aluminum oxide (Al
₂O₃An oxide or fluoride that can be dissolved in
It is known that, for example, Fe₂O₃, Fe₂O
₃, SiO₂, K₂O, MnO, Na₂O, Li₂O,
Ga₂O₃, Gd₂O₃, N ₂O_Five, SO₃, Ho₂O
₃, In₂O₃, La₂O₃, Li₂O, TiO₂, L
u₂O₃, ZrO₂, Y₂O₃, Nd₂O₃, P
₂O_Five, SrO, PbO, Sc₂O₃, RF₂, Zn
O, Sm₂O₃, SnO₂, Ta₂O_Five, Tm₂O_Five，
UO₂, V₂O_Five, Yb₂O₃, NaF, RbF, Al
F₃, CaF₂, NaF, LiF, MgF₂, B
₂O₃, BaO, BeO, ThO₂, Bi₂O₃, CO
₂, CaO, Cr₂O₃, K₂O, CeO₂, Dy₂O
₃, Er₂O₃, Eu₂O₃and so on. These substances
One or more of
It

As a result of experiments, the addition ratio by which this additive can form a solid solution in aluminum oxide to increase hardness is 3% by weight.
Below, it has been found to be preferably below 2.5% by weight. In that case, the hardness of the alumina-based material is at least 2600 (× 0.9807 N / m in terms of micro Vickers hardness).
m ² , test load of 300 × 9.807 mN) or more, up to 4000, and a remarkable increase in hardness was observed.

Other aspects and advantages of the present invention will be apparent from the description of the preferred embodiments presented below.

[0017]

[Preferred embodiment] In the following, the above method "" is adopted as a method for adding an additive to an alumina material,
High-purity WA abrasive grains, high-purity aluminum oxide (Al
₂ O ₃ ) Alumina-based ceramic cutting tool (so-called white ceramic tool) obtained by pressurizing and sintering fine particles, aluminum oxide (Al ₂ O ₃ ) fine particles, after adding a firing aid,
A general alumina ceramic material obtained by molding by appropriate means and sintering, and a case where TiO ₂ or the like is added to an alumina oxide single crystal (sapphire) will be sequentially described. The heat treatment used the electric furnace shown in FIG.

Embodiment 1 <In the case of high-purity WA abrasive grains>

Table 1 shows the components and properties of various abrasive grains. In this embodiment, among these, WA abrasive grains having a purity of aluminum oxide of 99.5% or more were used.

[0020]

[Table 1]

FIG. 3 is a graph showing that the hardness increased as a result of adding TiO ₂ to the WA abrasive grains. In this figure, WA abrasive grains are anatase type powders of TiO ₂ ,
The rutile type and the amorphous type are individually mixed, and the mixture shown in FIG.
After heating at 1573K for 50 hours in the furnace of
Only the A abrasive grains are selected and embedded in the resin, the cross section of the WA abrasive grains is polished, and the Vickers hardness thereof is measured. In addition to the WA # 24 abrasive grains thus treated with TiO ₂ ,
In the case of the untreated WA # 24 abrasive grains, the WA # 24 abrasive grains that were simply heat treated at 1573K for 20 hours, the A # 24 abrasive grains that were treated with the addition of TiO ₂ , and the untreated same A # 24 abrasive grains. It is also shown in the figure so that the hardness can be compared.

These Vickers hardness measurements are based on JIS
R1610-1991 “Vickers hardness test method for fine ceramics”. Although the test load is changed and measured, when the test load is larger than 300 gf, cracks often occur from the corners of the Vickers dent. When cracks occur, the points in the figure are shown in black.

As shown in FIG. 3, "no processing WA #
The "24 abrasive grains" has a Vickers hardness of about 2000, but the "WA # 24 abrasive grains treated with TiO ₂ " is TiO 2.
The Vickers hardness increased from 3000 to 4000 regardless of the type of the _two powders. "WA # 2" in FIG.
“4. Heat treatment only” indicates a case where only the heat treatment is performed without embedding the WA abrasive grains in the TiO ₂ powder. In this case, the hardness of the abrasive grains does not increase, and “no treatment, WA # Two
It has almost the same hardness as "4". From this, it was confirmed that only the heat treatment did not increase the hardness of the abrasive grains.

Further, in FIG. 3, "A # 24, TiO ₂ addition treatment" indicates a case where A abrasive grains are embedded in TiO ₂ powder and heat treatment is performed, and the value in the case of "no treatment, A # 24" Is almost equal to. Thus, it was confirmed that the hardness does not increase even if TiO ₂ is added to the A # 24 abrasive grains.

Table 2 shows JIS R6123-1987.
Shown are the average and range impurity components of various abrasive grains based on the experimental results of each of eight companies according to "Explanation of chemical analysis method for alumina abrasives". According to this table, the amount of TiO ₂ in the WA abrasive grains is undetectable. TiO _{2 in} abrasive grain A is about 3%
Is. Since A abrasive grains "A # 24, TiO ₂ addition treatment" above should be added TiO ₂ is about 3% or more, does not increase the hardness be added about 3% or more TiO _2. Therefore, TiO ₂ which increases the hardness of the WA abrasive grains
The amount added is 3% or less.

[0026]

[Table 2]

FIG. 4 shows WA abrasive grains of TiO 2.₂Additive treatment
The results of examining the increase in hardness under different conditions are shown. Processed at high temperature
If the time increases, the effect of increasing hardness may decrease.
I understand. High temperature and long processing time means WA abrasive grains
TiO₂It means that the addition amount of is increased. According to
And TiO to which WA should be added to obtain the desired hardness ₂
It was found that there is an appropriate value for the amount of
From the above with reference, it is estimated that it is about 3% or less
Wear.

Embodiment 2 <In case of white ceramic tool>

FIG. 5 shows aluminum oxide (A
l₂O₃) Alumina system produced by pressing and sintering fine particles
T for ceramic cutting tools (so-called white ceramic tools)
iO ₂An example in which the hardness is increased by the addition treatment of
Indicates. In Figure 5, the white ceramic tool is TiO₂Powder of
Embedded in the furnace and heated at 1573K for 20 hours in the furnace shown in FIG.
After holding, take out and polish the cross section shown in Fig. 5,
The result of measuring the Vickers hardness of the surface of the
It is shown together with the case. Vickers hardness measurement before
The test load of 500 gf
It is a constant value. As you can see from the figure,
The Vickers hardness of the cross section is uniformly around 1800.
But TiO₂The cross section of the additive treatment tool is about 1 m from the surface
At a depth of m, the hardness increases to a maximum of about 3000
ing.

FIG. 6 and FIG. 7 show the hardness distribution in the depth direction in the tool cross section.
The effect of O ₂ addition treatment conditions can be seen. From FIG. 6 and FIG. 7, the maximum hardness value moves to the inside of the tool as the processing conditions increase the amount of TiO ₂ added to the tool surface. From this, it can be seen that even in the case of this white ceramic tool, the addition amount of TiO ₂ that maximizes the hardness of the aluminum oxide sintered cutting tool is appropriate, as in the case of the above-mentioned abrasive, and it is about 3%. It can be estimated that

FIG. 8 shows aluminum oxide (A
alumina ceramic cutting tool (so-called white ceramic tool) manufactured by sintering l ₂ O ₃ ) to increase the hardness by adding TiO ₂ to the structural carbon steel S
55C is cut at four cutting speeds, and the results of examining the progress of tool wear are shown in comparison with the case of an untreated tool. Although there is almost no difference in flank wear between a tool treated with TiO ₂ and a tool without treatment, rake face wear is less advanced in the treated tool. Therefore, it is necessary to add TiO ₂ to this type of ceramic tool. Therefore, it is understood that the progress of tool wear can be suppressed.

Embodiment 3 <Aluminum-based ceramics
For materials>

FIG. 9 shows aluminum oxide (Al ₂ O ₃ )
The hardness is increased by adding TiO ₂ to a general alumina-based ceramic material obtained by adding a sintering aid to the fine particles, molding it by an appropriate method, and heating and sintering this. I will show you how. The method of adding TiO ₂ is the same as that of the white ceramic tool except for the heating temperature and the heating time. As can be seen from FIG. 9, as compared with the case of no treatment, the addition treatment of TiO ₂
The Vickers hardness near the surface of this ceramic material reaches up to 2800. Also in this case, the peak of hardness moves from the surface to the inside as the total time of the heat treatment becomes longer. This is because as the treatment time increases, TiO ₂ permeates from the surface of the material to the inside, and the portion showing the concentration (about 3%) capable of achieving the maximum hardness gradually moves from the surface to the inside.

FIG. 10 shows the case where the TiO ₂ addition treatment condition is changed from the case of FIG. 9, and also shows the case where only the heat treatment is performed. TiO _{2 at} 1273K
Compared to the case where the addition treatment was performed 3 times for 5 hours each, 1273
A comparison is shown in the case where the TiO ₂ addition treatment at K is performed 3 times for 5 hours each, and then only the heating at 1273 K is performed for 5 hours. As can be seen from the figure, if only the heat treatment is performed after the TiO ₂ addition treatment, the hardness distribution becomes gentle. This, by heating, TiO ₂ penetrates into the inside, the concentration distribution of the TiO ₂ is supposed to be due to becomes smooth. By performing such a two-step treatment, the thickness of the hardened layer from the surface can be increased.

FIG. 11 shows how the hardness increases when Y ₂ O ₃ is added to the same general alumina ceramic material as described above. As can be seen from the figure, when the Y ₂ O ₃ addition treatment is performed, the Vickers hardness near the surface of this ceramic material is 280 at maximum, compared with the case of no treatment.
It reaches 0. Also in this case, the hardness peak moves from the surface to the inside as the total processing time increases. Again, the longer the processing time,
This is because Y ₂ O ₃ permeates into the inside of the material, and the portion showing the concentration (about 3%) capable of achieving the maximum hardness gradually moves from the surface to the inside.

FIG. 12 shows TiO _{2 at} 1273 K for a typical alumina-based ceramic material similar to that described above.
When the addition treatment was carried out for 5 hours, Y ₂ O at 1273K
_{3 When} adding treatment for 5 hours, Ti at 1273K
After performing the O ₂ addition treatment for 5 hours,
The hardness distribution of the material when the Y ₂ O ₃ addition treatment at 273 K is performed for 5 hours is shown. As can be seen from the figure, if the additive is a solid solution and can be hardened in the ceramic material, even if it is added in combination, the vicinity of the surface of the ceramic material can be appropriately hardened.

Embodiment 4 <Alumina oxide single crystal (surf
In case of

FIG. 13 shows aluminum oxide (Al
₂ O ₃ ) single crystal (sapphire)
₂ The surface hardness of the crystal of the additive-treated one and that of the untreated one are shown in comparison. As can be seen from the figure, TiO ₂
When added, Vickers hardness is 3000-400
It increased to 0. The aluminum oxide single crystal treated with the addition of TiO ₂ was abrasively molded into a cutting tool and subjected to a cutting test for ferrous metal. As a result, the tool wear was remarkably reduced as compared with the untreated tool.

FIG. 14 shows the results of measuring the hardness of the crystal surface when the treatment conditions of TiO ₂ addition were changed. Within this experimental range, the higher the treatment temperature and the longer the treatment time, the higher the surface hardness. Has increased.

FIG. 15 shows the results of examining the hardness distribution inside the crystal, showing the case where two crystal planes were subjected to the addition treatment under the two treatment conditions. There was almost no difference due to the crystal plane, and the hardness increased toward the surface within this experimental range.

It goes without saying that the scope of the present invention extends to all alumina-based materials containing aluminum oxide as a main component or products such as tools using the same, regardless of the form. Then, an additive such as TiO ₂ which can be solid-dissolved in alumina can be relatively easily added to the already formed alumina solid material by the above method “” as in each of the above-mentioned examples. Surface hardening of the above materials and the like can be performed. Also, it may be added by the above-mentioned method "" or "" when forming into a tool or the like. However, in any case, heat treatment at a predetermined temperature for a predetermined time is necessary in order to form an appropriate solid solution of the additive in the alumina. In the case of the former method, as is clear from the above-mentioned embodiment, the area near the surface of the white ceramic tool or sapphire is hardened, but in the case of the latter method, the inside of the material or the product is made uniform. Can be cured. In the latter case, in order to achieve an appropriate increase in hardness, it is essential that the concentration of the additive is 3% or less.

The measurement result of the minute Vickers hardness is
The hardness value measured with a smaller test load for the same sample is usually greater than the hardness value measured with a larger test load, although it varies somewhat with the test load. Therefore, for example, the test load 500
The test result of the sample having a test load of 300 × 9.807 mN showing 2600 by the measurement at × 9.807 mN is:
2600 or more, and from the tendency shown in FIG. 14, it is estimated that the number exceeds 3000.

[0043]

As described above, according to the present invention, the hardness of the alumina material which has been about 2000 Vickers hardness in the past or the hardness of the product using the same is 260.
Increased from 0 to 4000. As a result, if the alumina-based material hardened according to the present invention is applied to an abrasive, a cutting tool or a ceramic product, the life of the alumina-based product can be remarkably extended and the quality of the alumina-based ceramic product can be improved. Is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the Vickers hardness of various abrasives when the treatment of the present invention is not performed.

FIG. 2 is a configuration diagram of an electric heating furnace used for TiO ₂ addition treatment in each example of the present invention.

FIG. 3 is a schematic diagram showing a TiO according to the present invention in the first embodiment.
_The graph which showed the Vickers hardness of the WA abrasive material which carried out the addition process of ₂ compared with the Vickers hardness of various untreated abrasive materials.

FIG. 4 is a TiO _{2 of} WA abrasive material in Embodiment 1.
The graph which showed the Vickers hardness in various conditions of addition processing.

FIG. 5 is a TiO 2 according to the present invention in Embodiment 2;
_The graph which showed the hardness distribution of the cross section of the white ceramic cutting tool which carried out the addition treatment of ₂ compared with the hardness distribution of an untreated tool.

FIG. 6 is a graph showing the hardness distribution of the cross section of the white ceramic cutting tool according to the TiO ₂ addition treatment temperature in Embodiment 2.

FIG. 7 is a graph showing the hardness distribution of the cross section of the white ceramic cutting tool according to the addition treatment time of TiO _{2 in} the second embodiment.

FIG. 8 is a TiO according to the present invention in Embodiment 2;
₂ Graphs showing wear progression curves of a white ceramic cutting tool with addition treatment and a white ceramic cutting tool without treatment.

FIG. 9 is a TiO 2 according to the present invention in the third embodiment.
_{2 is} a graph showing the hardness distribution of the alumina-based ceramic material that has been subjected to the addition treatment in comparison with the hardness distribution of the untreated case.

FIG. 10 is a schematic diagram of a third embodiment according to the present invention.
The hardness distribution of the alumina-based ceramic material in which the O ₂ addition treatment, after the addition processing of TiO _2, showed in comparison to the case of adding the heat treatment chart.

FIG. 11 is a schematic diagram of Y _{2 according} to the present invention in Embodiment 3;
Graph shows a comparison with the hardness distribution of the non-treated hardness distribution of the alumina-based ceramic material in which the O ₃ additive process.

FIG. 12 is a schematic diagram of a third embodiment according to the present invention.
Graph showing the hardness distribution of the O ₂ and combined addition processing of Y ₂ O ₃ and alumina-based ceramic material.

FIG. 13 is a graph showing the surface hardness in the case where the TiO ₂ addition treatment according to the present invention is applied to the single crystal aluminum oxide in Embodiment 4, by comparing the surface hardness of the untreated surface.

FIG. 14 is a graph showing how the surface hardness increases according to the TiO ₂ addition treatment condition of single crystal aluminum oxide in Embodiment 4.

FIG. 15 is a graph showing an internal hardness distribution of a single crystal aluminum oxide obtained by adding TiO _{2 to the} fourth embodiment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identifier FI C30B 31/02 C04B 35/10 E (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 35/10

Claims (3)

(57) [Claims] 1. A aluminum oxide in the alumina material containing aluminum oxide 99.5% or more, Al
The aluminum from the outside of Mina material by adding a solid solution of TiO ₂
Part of the wood material has a fine Vickers hardness of 2600 (× 0.98
07 N / mm ² , a test load of 300 × 9.807 mN) or more, and the content of TiO _{2 in} the cured portion is 3% or less, a cured aluminous material. 2. The hardened aluminous material according to claim 1, which is a hardened white aluminous abrasive grain. 3. The hardened aluminous material according to claim 1, which is obtained by hardening a single crystal of aluminum oxide.