JP2000280175A - Super-finishing grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super-finishing grinding wheel of relatively low cost and excellent grinding performance. SOLUTION: In a super-finishing grinding wheel in which alumina-based abrasive grains are bound by vitrified binding agent, the alumina-based abrasive grains include fine crystal sintered alumina-based abrasive grains, and the vitrified binding agent contains P2O5 by 3-15 wt.%, preferably. The fine crystal sintered alumina-based abrasive grains are manufactured by a chemical process started from unclear species of aluminum oxide of sub-micro grain to become abrasive trains through drying, crushing and sintering processed, so thousands of millions of high purity particulartes exist in a single piece of abrasive grains. While ordinary abrasive grains are easy to be abraded by polishing, the fine crystal sintered alumina-based abrasive grains continuously has excellent cutting effect because new sub-micron grains continuously comes out. This is because the fine crystal sintered abrasive grains themselves form a relief angle when crushed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vitrified superfinishing wheel used for final finishing of a cylindrical outer surface, a flat surface, a ball bearing raceway surface and the like.

[0002]

2. Description of the Related Art Recently, a super-finished grinding wheel combining a super-hard abrasive such as cubic boron nitride and diamond with a vitrified binder has been known as a grinding wheel used for the final finishing of a cylindrical outer surface, a flat surface and a ball bearing raceway surface. (JP-A-5-253848, JP-A-62-14815).
9, JP-A-2-274465). There is also known a super-finishing grindstone whose shape is devised by bonding or the like using a super-finishing grindstone in which the above-mentioned super-hard abrasive grains and a vitrified binder are combined (Japanese Patent Laid-Open No. 5-32978).
No. 0).

[0003] However, a super-finishing grindstone combining a super-hard abrasive grain and a vitrified binder has a high price because the price of the abrasive grains used for the grindstone is high. Therefore, the use of these super-finishing wheels is widely used mainly for raceway surfaces of small-diameter ball bearings, but is rarely used for other purposes. Therefore, relatively inexpensive vitrified superfinishing wheels using general abrasives such as fused white alumina abrasives (WA) and silicon carbide abrasives (GC) are still widely used.

[0004]

However, currently, super-finishing wheels using fused white alumina-based abrasive grains (WA) and silicon carbide-based abrasive grains (GC) mainly used in the market are:
In order to satisfy the high machinability required in the market, it is necessary to select a softer grinding wheel, which results in greater consumption of the grinding wheel, while hardening the grinding wheel reduces the wear. As a result, the wear of the grindstone is reduced, but there is a problem that the high machinability required in the market is not satisfied.

Therefore, in order to solve the above-mentioned problems, with regard to the development of a super-finishing wheel, emphasis is now placed on the development of a super-finishing wheel using super-hard abrasive grains such as cubic boron nitride and diamond. I have. On the other hand, the present invention does not include super hard abrasive grains such as cubic boron nitride and diamond, and is relatively inexpensive, yet satisfies the high machinability required in the market and has excellent durability. The purpose is to provide a finishing whetstone.

[0006]

In order to achieve the above object, the present invention uses a microcrystalline sintered alumina-based abrasive in a super-finishing whetstone using alumina-based abrasive. An object of the present invention is to provide a vitrified super-finishing wheel that is relatively inexpensive and has excellent durability by including P ₂ O ₅ in a vitrified binder in order to effectively use the finishing wheel.

[0007] Preferably, the alumina-based abrasive is microcrystalline sintered.
Containing sintered alumina grains and fused white alumina grains and
When the vitrified binder is 3 to 15 wt% P_TwoO_FiveIncluding
And more preferably, the vitrified binder is SiO 2
_Two40-55wt%, Al_TwoO _Three15-25 wt%, monovalent
Alkali metal oxide (R_TwoO) and divalent alkaline earths
11 to 21 wt% in total with metal oxide (RO), B_Two
O_Three5 to 15 wt%, P _TwoO_Five3 to 15 wt%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A microcrystalline sintered alumina-based abrasive is
It is disclosed in Japanese Patent Publication No. 5-20232 and the like,
Alumina abrasive grains are obtained by sintering sol or gel of alumina precursor, but especially sintered alumina consisting of fine (submicron) alumina crystals by adding a seed (seed crystal) before firing. Can be obtained. The feature is that the crushing resistance of the abrasive grains is improved, and large crushing and falling off of the abrasive grains during grinding are reduced, making them effective as cutting blades. Abrasive grains that can be improved.

In a general method for producing general-purpose abrasive grains, a raw material is heated, melted and cooled to form a crystal, and then pulverized to a desired particle size. Therefore, the number of crystals contained in one abrasive grain is one to several. On the other hand, microcrystalline sintered alumina-based abrasive grains are manufactured by a chemical process that starts with submicron aluminum oxide nuclides and passes through the dry pulverization and sintering process to form abrasive grains. There are billions of high-purity fine particles. Therefore, normal abrasive grains are easily worn flat during grinding, but fine-crystalline sintered alumina-based abrasive grains continue to have excellent sharpness because new submicron particles come out one after another. This is because the crushing of the microcrystalline sintered abrasive grains themselves forms a relief angle.

According to the present invention, by applying microcrystalline sintered alumina-based abrasive grains having such characteristics to a super-finishing wheel, it satisfies the high machinability required in the market while being relatively inexpensive. It is intended to provide a super-finishing whetstone having excellent durability. For the superfinishing wheel of the present invention, it is preferable to use fused white alumina abrasive grains together with the above microcrystalline sintered alumina abrasive grains. Microcrystalline sintered alumina-based abrasives are more expensive than fused white alumina-based abrasives, and the improvement in grinding performance is not proportional to the amount added. 50 for usage
If it exceeds wt%, clogging occurs and normal grinding cannot be performed.
Therefore, the amount of the microcrystalline sintered alumina-based abrasive is preferably 5 to 50% by weight, more preferably 10 to 5% by weight based on the total amount of the abrasive.
0 wt%.

The vitrified binder used in the superfinishing wheel of the present invention is characterized by containing P ₂ O ₅ . Since the microcrystalline sintered alumina-based abrasive grains degrade by reacting with the vitrified binder at a high temperature, they are fired at a low temperature,
It is disclosed that firing should be performed at a temperature of 100 ° C. or lower, more preferably 1000 ° C. or lower, and even about 900 ° C. (JP-A-61-56872 and others). For this purpose, it is effective to decrease the amount of SiO ₂ or Al ₂ O ₃ and increase the amount of monovalent alkali metal oxide and B ₂ O _3. The vitrified binder disclosed in the prior art, which discloses a vitrified grindstone using the above, generally has such a chemical composition.

The inventor of the present invention initially conceived of applying microcrystalline sintered alumina-based abrasive grains to a superfinishing wheel, and prototyped a superfinishing wheel, but could not obtain expected performance. . Therefore, because the particle size of the super-finishing abrasive grains is small,
Considering that it may be due to the sensitivity to the reaction with the vitrified binder, the known low-temperature baked binder (JP-A-3-68678 and JP-A-8-90472) may be used. However, the superfinishing grinding performance did not improve as expected. Through such circumstances, during the intensive study, the addition of P ₂ O ₅ to the vitrified binder significantly improves the grinding performance of the superfinishing wheel using microcrystalline sintered alumina-based abrasive grains. I found something.

Although not intending to be bound by theory, the present inventor thinks as follows. That is, (1) P ₂ O ₅ has a role of assisting the melting of the vitrified binder, and therefore does not adversely affect the grinding performance.
It enables firing at a temperature as low as possible at 0 ° C. to 1000 ° C. (2) B ₂ O ₃ and an oxide of a monovalent alkali metal (R
₂ O), etc. However, after these ingredients which are vitrified bond the molten stability problem of the melt viscosity tends to be greatly reduced vitrified bond occurs.

In addition, the formation of a vitrified binder and abrasive grains
Of the microcrystalline sintered alumina-based abrasive grains
It may not be possible to take advantage of the characteristics. In contrast
P _TwoO_FiveIs molten after the vitrified binder has melted
Crystalline sintered alumina-based abrasive with little change in viscosity
The characteristic of can be utilized. Divalent alkaline earth metal
Oxide (RO) has the same function, but P_TwoO_Five, B_TwoO
_ThreeAnd a monovalent alkali metal oxide (R_TwoO)
Absent.

(3) P_TwoO_FiveIs aluminum phosphate compound
Al as a typical example of a material_TwoO_ThreeChemical bonding with components
Good. (4) The coefficient of thermal expansion of vitrified binder is comparable to that of abrasive grains.
It is better to match as much as possible. Generally, the thermal expansion coefficient of the abrasive and vitrified binder is ±
When 2 × 10E-6 or more is released, cracks occur in the binder
The removal of abrasive grains is promoted. Thermal expansion of alumina abrasive grains
The number is about 8.0 × 10E-6. B_TwoO_ThreeIs the thermal expansion
Super hard with low coefficient of thermal expansion
Use to help melt vitrified binders that use abrasives
Will be An oxide of a monovalent alkali metal (R_TwoO) is thermal expansion
Works to increase the tension coefficient. Therefore vitrified
B to help the binder melt_TwoO _ThreeOr monovalent alkali gold
Oxides of the genus (R_TwoO), depending on the quantity of each
Thermal expansion coefficient does not match with the abrasive grains,
Cracks may occur and the abrasive grains may fall off.
You.

On the other hand, the thermal expansion coefficient of P ₂ O _{5 has} the function of increasing the thermal expansion coefficient, but is not as large as that of a monovalent alkali metal oxide (R ₂ O). For the above reasons, by adding P ₂ O ₅ to the vitrified binder, 900 ° C. to 1 ° C.
It can be fired at as low temperature as possible at 000 ° C. In addition, it has an effective chemical bond with microcrystalline sintered alumina abrasive grains,
By mating the thermal expansion coefficient with the abrasive grains as much as possible, the abrasive grains are prevented from falling off at an early stage, and the cutting action of the microcrystalline sintered alumina-based abrasive grains is helped to produce a super-finishing wheel with better machinability and a long life. It is considered possible.

By containing ₃ to 15% by weight of P ₂ O ₅ ,
In particular, a super-finishing stone excellent in performance was obtained. P
_The effect of ₂ O ₅ starts to appear at 3 wt%, and the performance peaks at 6 to 12 wt%. If it exceeds 15% by weight, the desired performance cannot be obtained. Suitable chemical compositions of the vitrified bond of the _{invention, SiO 2 40~55wt%, Al 2} O 3 15~25
wt%, the total of the monovalent alkali metal oxide (R ₂ O) and the divalent alkaline earth metal oxide (RO) is 11 to 2
_{1wt%, B 2 O 3 5~15wt} %, P 2 O 5 3~15wt%
including.

The role of each of the above components of the vitrified binder is as follows. When the content of SiO ₂ is less than 40% by weight, the bond strength is reduced. When the content is more than 55% by weight, the melting temperature of the bond increases and the firing temperature must be increased. A
If l ₂ O ₃ is less than 15% by weight, there is a problem in the stability of the bond. If it exceeds 25% by weight, the melting temperature of the bond increases and the firing temperature must be increased. R ₂ O (R is an alkali metal) plus RO (R is an alkaline earth metal) is 11 wt.
%, The melting temperature of the bond must be increased and the firing temperature must be increased. If it exceeds 21% by weight, there is a problem in bond stability. If the content of B ₂ O ₃ is less than 5% by weight, the melting temperature of the bond increases and the firing temperature must be increased. If the content is more than 15% by weight, there is a problem in the stability of the bond.

In recent years, finishing work has been emphasized for frictional parts in connection with the high performance and long life of mechanical parts, and they have been widely adopted. Short time R _max 0.05 to 0.1 [mu] m or less of mirror finishing and precision as well as high cutting amount also joined economy is required thereto. In particular, high machinability is required. The range of the particle size of the abrasive used is 280 to 6000 according to JIS, but there are many fines of 1000 or less mainly. The degree of bonding of the grindstone is plus 100 in rockwell hardness and plus 1 in minus 60.
00 is harder and minus 60 is softer. Recently, softening with a rather low degree of coupling has been mainly used.

In general, the size and shape of the superfinishing wheel used is determined by the work material and the structure of the machine. 2 x 2 x 15 mm as minimum dimension and 25 x 5 as maximum dimension
It is about 0x120 mm, and there may be larger and smaller dimensions. The shape is almost a rectangular parallelepiped, but there is also a shape with a rounded tip. Generally, the structure (composition) of the superfinishing grindstone used has an abrasive grain ratio (Vg) of 32% to 46% and mainly 35% to 43%. The binder ratio (Vb) is 5% to 20%, and the porosity (Vp) is 44% to 55%.

From the above manufacturing range, an appropriate super-finishing wheel is selected and used from the viewpoint of finished surface roughness, grinding conditions and economy.

[0022]

The present invention is not limited to the following examples, and the present invention will be described by way of examples. Reference Example Microcrystalline sintered alumina abrasive grains (trade name: SG abrasive grains, particle size JIS No. 3000) developed by Norton, and commercially available fused white alumina abrasive grains (trade name: WA, particle diameter JIS 30)
No. 00) in an equal weight ratio (50:50), a vitrified binder disclosed in JP-A-8-90422 for low-temperature firing, and a modified one having the chemical composition shown in Table 1 Using the binders (1) to (3), superfinishing wheels (1) to (3) were produced as shown in Table 2.

As a comparison, the most commonly used (commercially available product A) super-finished grinding wheel with 100% fused white alumina grit was tested. The structure of the superfinishing wheel is a commonly used structure, the abrasive grain ratio is 37% by volume, the vitrified binder ratio is 9% by volume, the porosity is 54% by volume, and the hardness of the vitrified superfinishing wheel is Rockwell hardness H scale. (1/8 ″ scale 60 kgf load) in the range of −30 to −40.

[0024]

[Table 1]

[0025]

[Table 2]

Test Grinding Stone Mixing Procedure and Grinding Conditions 5 parts by weight of a 30% dextrin aqueous solution and each vitrified binder are agitated and mixed with 100 parts by weight of each abrasive grain of WA and WA + SG abrasive grains. The bulk specific gravity of the raw grindstone is adjusted so that the value obtained by dividing the volume of the abrasive grains, the vitrified binder and the pores by the volume of the grindstone becomes 37% by volume of the abrasive grain, 9% by volume of the vitrified binder, and 54% by volume of the porosity. A square grindstone of 60 × 12 × 25 mm was formed by previously calculating and calculating the mixing ratio of each test grindstone based on this.

The structure of the superfinishing wheel of the commercial product (A) was the above structure. After the test whetstones (1) to (3) are molded,
The obtained raw whetstone was dried, and further baked at a maximum temperature of 900 ° C. for 2 hours for a predetermined time of 30 hours. The obtained grindstone was cut into a predetermined size after the measurement of Rockwell hardness and then subjected to a grinding test.

As a comparison, a commercially available superfinishing wheel with 100% fused white alumina grit was tested. The grinding test is a super finishing machine (manufactured by Seibu Automatic Equipment Co., Ltd.). The grinding fluid uses water-insoluble mineral oil. The work material is SUJ-2 (58/62 in HRC). 20mm
The working surface of the whetstone is 10 mm in circumferential width and 5 m in axial direction
m, the wear direction was 20 mm, the work dimensions were 50 mm in diameter and 5 mm in width, and the outer surface of the cylinder was ground by a plunge method. The surface roughness of the work material before the test was 1.3 μmRz. The super finishing condition is 1785 cpm grinding wheel frequency and 197 rp work rotation.
m, the whetstone amplitude was 2 mm, the maximum inclination angle was 20 degrees, and the conditions were 1 minute / 1.

[0029]

[Table 3]

The results are shown in Table 3. As shown in Table 3, the performance of the test grindstone (1) was inferior to that of the commercial product (A), and the test binder (2) and the test binder (3) were cut. The amount was inferior and some direction of durability was observed. However, despite the use of microcrystalline sintered alumina-based abrasive grains, the improvement of performance, especially the machinability, is almost more than that of a grindstone using a commercially available (A) fused white alumina-based abrasive grains. Absent. (Example 1) Binders (11) to (4) having the chemical compositions shown in Table 4 in the same manner as the test grindstones (1) to (3) of the reference example.
Using (16), test whetstones (11) to (11) shown in Table 5
(18) was prepared, and a grinding test was performed in the same manner as in Reference Example. Table 6 shows the results.

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

The rock well hardness of all test wheels was -3.
It was in the range of 0-40. No burns were observed in any of the workpieces. With respect to the surface roughness, the grindstone having a larger cutting amount than the commercial product (A) was slightly inferior to the commercial product (A). This is because the surface roughness tends to deteriorate as the cutting amount increases. However, these values are within the allowable range and there is no problem.

According to Table 6, based on the commercial product (A), the test grindstone (11) was 100 wt% of fused white alumina abrasive grains.
Thus, the grinding wheel containing no P ₂ O ₅ in the vitrified binder had inferior performance. Performance was generally improved when microcrystalline sintered alumina abrasive grains were used. In addition, the performance of the grindstone containing P ₂ O ₅ in the vitrified binder was improved. Particular a microcrystalline sintered alumina abrasive grains, the amount of P ₂ O ₅ in a vitrified bond is 6～12Wt% inclusive test grinding wheel (14), (15), (17) the cutting amount 10% grinding ratio is improved more becomes more than double the amount of P ₂ O ₅ in the vitrified bond has a peak performance at 9~12wt%. 15 wt% of P ₂ O ₅ in the vitrified binder
The test grindstone (18) was 1.8 times better in performance than the commercial product (A), but was inferior in performance to the test grindstone (17).

In the test whetstone (15) containing microcrystalline sintered alumina-based abrasive grains and the test whetstone (16) not containing microcrystalline sintered alumina-based abrasive grains, microcrystalline sintered alumina-based abrasive grains were used. The grinding ratio of the test grindstone (15) that contained No. was more than twice that of the test grindstone (16) that did not include the microcrystalline sintered alumina-based abrasive grains. Therefore, it can be seen that the microcrystalline sintered alumina-based abrasive grains and P ₂ O ₅ in the vitrified binder had a synergistic effect, resulting in better performance. (Example 2) In the same manner as in Example 1, the relationship between the content of the microcrystalline sintered alumina-based abrasive grains and the grinding performance was examined. As shown in Table 7, the content ratio of WA and SG was changed, and the test binder (14) of Example 1 was used as the binder.

A grinding test of the prepared grindstone was performed in the same manner as in Example 1. Table 8 shows the results.

[0038]

[Table 7]

[0039]

[Table 8]

Test wheel (21) to test wheel (26)
, The Rockwell hardness ranged from -30 to -40. The test grindstone (25) and the test grindstone (26) were initially clogged and could not be properly ground. For the test grindstones (21) to (24), the work material did not burn. With respect to the surface roughness, the grindstone having a larger cutting amount than the commercial product (A) was slightly inferior to the commercial product (A).
This is because the surface roughness tends to deteriorate as the cutting amount increases. However, these values are within the allowable range and there is no problem.

As can be seen from Table 8, the effect of the addition of the microcrystalline sintered alumina-based abrasive grains began to appear when the content of the microcrystalline sintered alumina-based abrasive grains was more than 10 wt% with respect to the total amount of the abrasive grains. %
Up to this point, both the amount of cutting and the durability of the grinding wheel have increased, and the grinding ratio has increased. However, when more than 50 wt% of microcrystalline sintered alumina abrasive grains were added, clogging occurred and normal grinding could not be performed.

Accordingly, the content of the microcrystalline sintered alumina-based abrasive grains in the vitrified superfinishing wheel is desirably 10 to 50% by weight based on the total content of the abrasive grains in the wheel.

[0043]

As described above, the super-finishing wheel of the present invention can achieve grinding performance nearly 2.8 times that of conventional fused white alumina abrasive grains. Therefore, it is possible to supply a super-finished grinding wheel which is relatively inexpensive and has excellent grinding performance, especially excellent durability and sharpness, as compared with a commercially available product using 100% fused white alumina abrasive grains. The contribution can be said to be extremely large.

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[Procedure amendment]

[Submission date] April 3, 2000 (200.4.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

The vitrified binder used in the superfinishing wheel of the present invention is characterized by containing ₃ to 15% by weight of P ₂ O ₅ . Microcrystalline sintered alumina abrasive grains react with vitrified binder at high temperature and deteriorate, so firing at low temperature,
Preferably 1100 ° C or less, more preferably 1000 ° C
In the following, it is disclosed that firing should be performed at a temperature of about 900 ° C. (Japanese Patent Laid-Open No. 61-56872 and others). For this purpose, it is effective to decrease the amount of SiO ₂ or Al ₂ O ₃ and increase the amount of monovalent alkali metal oxide and B ₂ O _3. The vitrified binder disclosed in the prior art, which discloses a vitrified grindstone using the above, generally has such a chemical composition.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

The inventor of the present invention initially conceived of applying microcrystalline sintered alumina-based abrasive grains to a superfinishing wheel, and prototyped a superfinishing wheel, but could not obtain expected performance. . Therefore, because the particle size of the super-finishing abrasive grains is small,
It may sensitive to reaction with the vitrified bond may be due, most low-temperature firing of the binder in a known vitrified bond (JP-A-3-68678 and the 8-90 4 22 No.) However, the super-finishing grinding performance did not improve as expected. Through these circumstances, while the intensive overlapping study, the addition 3 to 15% of P ₂ O ₅ in a vitrified bond, superfinishing grindstone grinding performance using a microcrystalline sintered alumina abrasive grain It was found that it improved remarkably.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

On the other hand, the thermal expansion coefficient of P ₂ O _{5 has} the function of increasing the thermal expansion coefficient, but is not as large as that of a monovalent alkali metal oxide (R ₂ O). For the above reasons, by adding P ₂ O ₅ to the vitrified binder in an amount of ₃ to 15 wt%, it is possible to fire at as low a temperature as possible at 900 ° C. to 1000 ° C. And the thermal expansion coefficient is matched to the abrasive grains as much as possible to prevent the abrasive grains from falling off at an early stage and assist the cutting action of the microcrystalline sintered alumina-based abrasive grains to provide a super-finishing wheel with better machinability and long life It is thought that it can be manufactured.

 ──────────────────────────────────────────────────続 き Continued on the front page (74) One of the above agents 100077517 Patent Attorney Takashi Ishida (3 outsiders) (72) Inventor Kazushi Nakashio 2-3-20 Yoshiura Shinmachi, Kure City, Hiroshima Prefecture Cle Norton Co., Ltd. F term (for reference) 3C063 AA02 AB01 BB03 BB07 BB14 BC05 BD01 CC02 CC04 FF20 FF23 FF30

Claims (3)

[Claims] 1. A superfinishing whetstone for bonding alumina-based abrasive grains with a vitrified binder, wherein said alumina-based abrasive grains include microcrystalline sintered alumina-based abrasive grains, and wherein said vitrified binder includes P ₂ O ₅ . A super-finishing whetstone characterized by including: 2. The method according to claim 1, wherein the alumina abrasive grains comprise 5 to 50% by weight of microcrystalline sintered alumina abrasive grains and 50 to 50% by weight of fused white alumina.
95 wt%, and the vitrified binder is 3 to 1
Superfinishing grindstone according to claim 1 comprising a P ₂ O ₅ of 5 wt%. 3. The method according to claim ₂ , wherein the vitrified binder is SiO _{2.
40~55wt%, Al 2 O 3 15~25wt} %, 11~21wt% , the total of the monovalent alkali metal oxides (R ₂ O) and divalent alkaline earth metal oxides (RO), B ₂ O
₃ 5 to 15 wt%, according to claim 1 or 2 superfinishing grindstone according an amount 3 to 15% of P ₂ O _5.