JPH03149186A - Metal bond tool - Google Patents

Abstract

PURPOSE:To facilitate operation of compaction forming by adding molybdenum disulfide or cubic nitriding boron as a solid lubrication material to metallic powder of a raw material so as to manufacture a metal bond tool. CONSTITUTION:A grinding grain layer, is formed, which contains at least one kind of diamond and cubic nitriding boron as a grinding grain, and at least one kind of molybdenum disulfide and cubic nitriding boron of 1-5 weight % as a solid lubrication material, and which comprises a sintered body in which the average diameter of the grains of the solid lubrication material is set one third of the average diameter of the grinding grains. Consequently, a metal bond tool remarkably superior to cutting performance can be obtained.

Description

[Detailed description of the invention] [Objective of the invention] (Industrial application field) The present invention uses metal powder as a matrix, disperses a solid lubricant and high-hardness abrasive grains in the matrix, and integrates them into one by sintering. Regarding metal bond tools,
In particular, the present invention relates to a metal bond tool that has excellent moldability when molding the raw material mixed powder at room temperature during production, has good grinding performance as a tool, and has a long life.

(Prior technology) Metal pound diamond tools that use diamond abrasive grains are conventionally used as grinding tools for grinding and finishing high-hardness fine ceramics such as aluminum oxide, silicon nitride, aluminum nitride, and silicon carbide. more widely used.

In addition, cubic boron nitride (hereinafter referred to as rCBN) is used as an abrasive grain in grinding and finishing of difficult-to-cut alloy materials such as high-speed steel and martensitic stainless steel containing vanadium (V).
It is abbreviated as J. ) dispersed in a matrix have been used.

Among the metal bond tools mentioned above, for example, metal bond diamond tools that use diamond powder as abrasive grains are generally made by mixing metal powder and, if necessary, metal powder containing a metal compound with diamond powder abrasive grains, and then press-forming the mixture. Formed by sintering. This sintering operation improves the bonding force and mechanical strength between the matrix and the diamond powder abrasive grains, and the resulting metal-bonded diamond tool can be used as a polishing/grinding tool while regenerating the grindstone surface by dressing as appropriate. has been done.

By the way, in the case of metal-bonded diamond tools suitable for heavy grinding with a large depth of cut, the raw material for the matrix is powder obtained by pulverizing chips of iron-based cast material with a high carbon content using a ball mill or stamping method. used. Then, diamond abrasive grains are uniformly mixed with the obtained high carbon iron-based alloy powder, and the molded body obtained by compression molding using, for example, a mold press machine at a pressure of about 1210++/car is further processed. Sintering is performed at 1100° C. for about 30 minutes to form an abrasive grain layer. Carbon particles are fixed and dispersed around the abrasive grains. The carbon particles act as a lubricant that reduces grinding resistance with the object to be ground, while the matrix acts as a holding material that supports and fixes the diamond abrasive grains.

(Problem to be solved by the invention) However, iron-based alloy cast materials with a high carbon content have poor formability due to their high hardness, and in order to form a predetermined shape during compression molding, high temperature conditions and large pressing forces are required. and a long molding time is required. As a result, the expensive molds are subject to significant wear and tear, requiring frequent regrinding and replacement of the molds, resulting in problems of increased manufacturing costs and a significant drop in manufacturing efficiency.

In particular, when press molding raw material powder using room-temperature mold presses, it is difficult to consolidate, and bores are likely to occur in the molded product.
Only a low grinding ratio can be obtained when sintered into tools.

Moreover, the ejection pressure during molding increases, making it difficult to perform efficient molding operations. Furthermore, when the punch is removed, cracks and chips are likely to occur in the molded body, resulting in a significant decrease in product yield.

In addition, in iron-based alloy powder obtained by pulverization using conventional pulverization methods, the size of carbon precipitates ranges from several tens of μm to 100 μm.
It is larger than the average particle size of abrasive grains (10 to 35 μm), and is also non-uniform in shape.

Therefore, the carbon particles held in the powder are likely to fall off during the crushing operation, resulting in uneven distribution and shape of carbon in the powder. In a tool material in which a matrix is formed by sintering this iron-based alloy powder, the carbon precipitates have a large diameter, so the carbon precipitates tend to fall off even during grinding, resulting in a decrease in the lubrication function. In addition, shavings and polishing debris accumulate in the depressions created by the falling off of carbon precipitates, causing clogging, and the clogging causes loss of lubricating function, causing matrix damage and plastic deformation due to seizure.

Furthermore, due to the formation of depressions near the abrasive grains, the retention strength of the matrix against the abrasive grains rapidly decreases, and diamond abrasive grains rapidly fall off, leading to a decrease in grinding and polishing efficiency, making it impossible to obtain even higher finishing accuracy. There was a problem.

Additionally, in the manufacturing process of conventional metal-bonded diamond tools, a method is generally adopted in which carbon particles are dispersed in the sintered body by directly adding carbon powder to the alloy powder raw material and performing a sintering operation. . However, with this method, it is difficult to uniformly disperse fine carbon grains as a lubricant throughout the abrasive grain layer, and coarse carbon grains tend to accumulate unevenly in the sintered body. As a result, many carbon precipitates and abrasive grains fall off, which reduces the efficiency of grinding and polishing processes, making it impossible to obtain high finishing accuracy, and posing the fundamental problem that the life of the grinding wheel itself is short.

The present invention has been made to solve the above-mentioned problems, and reduces the amount of abrasive grains and lubricant falling off during grinding, making it possible to perform grinding and polishing with high efficiency, and extending the service life. The aim is to provide long-lasting and economical metal bond tools.

[Structure of the invention]

(Means and effects for solving the problem) The present inventors discovered that the polishing properties of conventional abrasive grain layers are caused by the type of material constituting the abrasive grain layer and the particle size of the material. Abrasive grain layers were formed with various grain sizes, types and grain sizes of abrasive grains, and types and grain sizes of solid lubricants, and their polishing properties were investigated.

As a result, the abrasive grains contain at least one of diamond and cubic boron nitride, and the solid lubricant contains 1 to 5 weight percent of at least one of molybdenum disulfide and hexagonal boron nitride. To obtain a metal bond tool with significantly superior grinding properties compared to conventional ones when an abrasive grain layer made of a sintered body whose average grain size is set to 1/3 or less of the average grain size of the abrasive grains is formed. was completed.

In addition, when the average particle size of the metal powder that forms the matrix before sintering is adjusted to 1/3 or less of the average particle size of the abrasive grains, the falling off of the abrasive grains and solid lubricant can be effectively suppressed, resulting in a long service life. A layer of abrasive grains could be obtained.

The present invention has been made based on the above findings.

The metal powder used as the matrix of the metal bond tool according to the present invention includes Fe and Ni.

An alloy material consisting of a single metal element such as Cu, Co, Zn, Mg, Al, Mn, and Cr or two or more elements is used. The composition of the raw metal powder is determined by taking into account the required matrix strength, heat conductivity, type of workpiece, etc., but generally, in order to increase the retention strength of the abrasive grains, 2.
An alloy material that is a composite of more than one metal is used. However, metal powders that do not contain Fe are used for metal bond tools for grinding workpieces such as semiconductor materials, which are extremely sensitive to Fe contamination during processing.

Examples of means for pulverizing the alloy material include a method of pulverizing an ingot of the alloy material using a ball mill or a stamp mill, and a method of pulverizing the alloy material using a rapid cooling method such as a molten metal spraying method.

The above-mentioned molten metal spraying method is a method in which molten raw material is pulverized by gas spraying, water spraying, or centrifugal spraying, and the desired raw material powder is obtained by adjusting the cooling rate and powder particle size to an appropriate level depending on the spraying conditions. This is the way to obtain.

Further, as the abrasive grains, CBN may be mixed in addition to diamond powder. diamond and cb
The Knoop hardness of N is 5100.8500kg/
- All of the above have extremely high hardness and are useful as abrasive grains for processing difficult-to-grind materials. In particular, CBN abrasive grains have excellent heat resistance, so their use as abrasive grains for dry machining without using a coolant is rapidly expanding.

Further, as the solid lubricant, a powder solid lubricant consisting of at least one of molybdenum disulfide and hexagonal boron nitride is used, and this solid lubricant is
It is added to contain % by weight. Molybdenum disulfide (M o S 2 ) powder is widely used to reduce the frictional force between tools and materials in plastic working. Unlike CBN (cubic boron nitride), hexagonal boron nitride has a hexagonal crystal structure, has an excellent function as a solid lubricant, and can significantly reduce grinding resistance.

If the content of the solid lubricant in the sintered body is less than 1%, the lubricating effect during grinding will not be sufficiently exerted, while if it exceeds 5%, the impact resistance strength of the matrix will decrease and the holding power for the abrasive grains will decrease. decreases, the abrasive grains drop off significantly, and the grinding performance deteriorates. Therefore, the content of solid lubricant is set in the range of 1 to 5% by weight.

Furthermore, the average particle size of the solid lubricant is 1/3 of the average particle size of the abrasive grains.
It is set as below. This particle size ratio has a great effect on the strength and grinding properties of the matrix that holds the abrasive grains, and if the particle size ratio exceeds 173, a uniform dispersion state of the abrasive material and the abrasive grains cannot be obtained. In addition, the solid lubricant falls off from the matrix, leading to a decrease in lubrication performance and an increase in the frequency of clogging. In addition, the solid lubricant near the abrasive grains falls off, creating depressions on the sides of the abrasive grains, reducing the strength of the matrix. As a result, the holding force for holding and fixing the abrasive grains sharply decreases and the number of abrasive grains falling off increases, resulting in significant wear of the abrasive grain layer and a rapid increase in the number of times that dressing is required. Therefore, the average particle size of the solid lubricant is set to 1/3 or less of the average particle size of the abrasive grains.

Further, the metal bond tool according to the present invention uses a mixed powder of a metal powder serving as a matrix, a solid lubricant, and abrasive grains.
It is formed by compression molding using a room-temperature mold press or the like, and then bonding the resulting molded bodies together by sintering. In this case, it is preferable that the average particle size of the metal powder before the sintering operation is set to 1/3 or less of the average particle size of the abrasive grains. This is because when the particle size ratio exceeds 173, the distribution of the abrasive grains becomes uneven, making it impossible to uniformly arrange the metal powder near the surface of the abrasive grains, and the area where the abrasive grains come into contact with each other increases. This is because not only the formability is deteriorated, but also the abrasive grains fall off during grinding, and the grinding/polishing ability of the tool is reduced.

As described above, since the metal pound tool according to the present invention is manufactured by adding molybdenum disulfide or hexagonal boron nitride as a solid lubricant to the raw metal powder, the compression molding operation becomes extremely easy. That is, since the added molybdenum disulfide and hexagonal boron nitride act as a lubricant during compression molding, a high-density molded body having a predetermined shape can be formed within a short time with a small pressing force. Therefore, there is little damage to the molding die, significantly reducing the manufacturing cost of the tool, and the frequency of replacing the molding die is reduced, so the manufacturing efficiency of the tool can be significantly increased.

It is also formed by sintering metal powder that forms the matrix, highly hard abrasive grains made of at least one of diamond and CBN, and a lubricant made of molybdenum sulfide and hexagonal boron nitride, which have excellent lubricity. Therefore, it is possible to uniformly disperse the abrasive grains and lubricant in the sintered body,
In addition to obtaining a good ground surface finish, it is possible to always receive stable lubrication, which reduces grinding resistance during machining.

In addition, the average particle size of the solid lubricant and the average particle size of the metal powder forming the matrix are set to 17% relative to the average particle size of the abrasive grains.
Since it is adjusted to 3 or less, the metal powder that serves as a lubricant and a supporting material for the abrasive grains can be uniformly dispersed around the abrasive grains.

Therefore, the lubrication function during grinding is fully demonstrated, the strength of the matrix as a supporting material is ensured sufficiently, and abrasive grains are prevented from falling off. As a result, it is possible to maintain high grinding efficiency at all times, and the abrasive grain layer The lifespan of can be significantly extended.

(Examples) Next, the present invention will be described in more detail with reference to the following examples.

Examples 1-3 and Comparative Examples 4-6 Examples 1 to 3 include 3.0% carbon and Sil.

As shown in Table 1, diamond powder having an average particle size of 100 μm and a sharp blocky ridge shape was added to 80 to 83% of the iron-based alloy powder consisting of
% and further added 2 to 5% of molybdenum disulfide having an average particle size of 30 μm, and the mixture was uniformly mixed in a mortar. The above alloy powder was prepared by a molten metal spraying method, and its average particle size was 30 μm.

Next, the mixture of each composition above was filled into the raw material space of a mold press machine with an outer diameter of 80 W and an inner diameter of 15 m, and the pressure was 12 tom/ca.
Compression molding was performed by applying a pressure of r, and the obtained molded body was sintered under vacuum conditions at a temperature of 1100° C. for 30 minutes. Then, it was shaped to form a diamond grindstone with a width of 10 cm.

In addition, as Comparative Examples 4, 5, and 6, raw material mixtures in which the mixing ratio of molybdenum disulfide powder was set to 0.5%, 7%, and 0%, respectively, were molded at room temperature using the same manufacturing method as Examples 1 to 3. Processed after sintering, outer diameter 80cm, inner diameter 15cm
, a diamond grindstone with a width of lO■.

Using the diamond grindstones of Examples 1 to 3 and Comparative Examples 4 to 6 thus obtained, S with a Vickers hardness of 1700 was used.
S 3 N 4 grinding process was performed. The grinding conditions were set to a rotational speed of 300 rpm, a feed rate of 5 m/win, a grinding width of 1011 Im1, and a cutting depth of 0° 25 mm.

The grinding test results obtained in this way are shown in Examples 1 to 3 in Table 1.
, shown in the right column corresponding to Comparative Examples 4 to 6.

Here, the surface conditions of the grindstone shown in Table 1 are the results of observation using a stereomicroscope. The evaluation of the surface condition is that the surface is in good condition with no clogging etc.
On the other hand, there are "slops" on the entire surface and "cracks" in some parts.
Those that were visually recognized were marked as ×. Furthermore, the grinding ratio is expressed as the ratio of the amount of material to be ground removed to the amount of wear on the grinding wheel.

As can be seen from the results in Table 1, the diamond grinding wheels of Examples 1 to 3, in which the content of molybdenum disulfide powder as a solid lubricant was set within the range of 1 to 5% by weight, were set outside the above range. Compared with Comparative Examples 4 and 5 and Comparative Example 6 in which molybdenum disulfide was not added, it was found that the grinding ratio was higher, the grinding performance was excellent, and the product had a long life.

The surface conditions of the grinding wheels were also good, demonstrating that the lubrication function was sufficiently demonstrated and the holding power of the abrasive grains was high.

In addition, in order to confirm the quality of compression moldability using a mold press machine, a pull-out pressure test was conducted on the raw material mixed powders of Examples 1 to 3 and Comparative Examples 4 to 6. The evacuation pressure in Examples 1 to 3 and Comparative Example 5, which was added in excess, was 172% compared to Comparative Examples 4 and 6.
It was confirmed that it could be reduced to ~173.

Therefore, according to Examples 1 to 3, lubricity is sufficiently exhibited during molding, so moldability is improved and cracks and chips are less likely to occur in the molded product. Therefore, the yield of products can be increased, the life of the mold can be extended, and tool manufacturing costs can be significantly reduced.

Examples 7 to 8 and Comparative Example 9 Next, as Examples 7 to 8, 77% by weight of metal powder having the same composition as Examples 1 to 3 and having an average particle size of 30 μm was used as an average solid lubricant. Adding 3% by weight of hexagonal boron nitride with a grain size of 9.28 μm, the average grain size is 8 as rough abrasive grains.
CBN of 8 μm was added at a ratio of 20% by weight, and the mixture was uniformly mixed and press-molded with a mold at room temperature in the same manner as in Examples 1 to 3, and sintered under the same sintering conditions. A CBN grindstone with an inner diameter of 15 cm and a width of 10 cm was formed.

In addition, as Comparative Example 9, a mixture of hexagonal boron nitride with an average particle size of 44 μm in the same ratio (3%) as in Examples 7 and 8 was treated in the same method to form a CBN grindstone of the same shape. did.

Grinding of cemented carbide was carried out using the CBN grinding wheels of Examples 7 to 8 and Comparative Example 9 under the same processing conditions as Examples 1 to 3, and the surface condition and grinding ratio of the grinding wheels were measured. The influence of the grain size of hexagonal boron nitride, a lubricant, on grinding characteristics was investigated.

The grinding test results are shown in the corresponding right column of Table 1.

As can be understood from the results in Table 1, the average particle size of hexagonal boron nitride, which is a lubricant, was set to 0, 10, and 0.32, which are 1/3 or less of the average particle size of the abrasive grains. In the case of Example 7.8, compared to Comparative Example 9, which was set larger than 1/3,
The surface condition of the whetstones is good and the grinding ratio is also excellent. This is because fine hexagonal boron nitride is uniformly dispersed around the abrasive grains in the sintered body, resulting in excellent lubrication performance and increased matrix strength, suppressing the shedding of the abrasive grains and solid lubricant. This is due to this.

In addition, when the extraction pressure test was conducted for each raw material mixed powder of Examples 7, 8 and Comparative Example 9, the extraction pressure of each powder was
It was found that it was reduced to about 172 in Comparative Example 6,
It was confirmed that moldability was significantly improved.

Examples 10-12 and Comparative Examples 13-14 Examples 10-
12, first 3.0% carbon, 2% Ni, 1% Co,
An iron-based alloy powder consisting of balance iron and having an average particle size of 33 μm was prepared by a conventional molten metal spraying method. Next, diamond and CBN with an average particle size of 100 μm were added as abrasive grains to the obtained alloy powder as shown in Table 1, and molybdenum disulfide and hexagonal nitride with an average particle size of 30 μm were added as solid lubricants. Boron was mixed in the proportions shown in Table 1. The obtained raw material mixed powder was press-molded with a mold under the same conditions as in Examples 1 to 3, and then sintered to form diamond C.
A BN composite grindstone was formed.

Further, as Comparative Examples 13 and 14, the average particle size of the metal powder serving as the matrix was changed to 52 μm and 90 μm, and the particle size ratio to the average particle size (100 μm) of the abrasive grains was 0.52 to 0.52 μm.
90 and observed its effect on grinding performance.

Using the diamond CBN composite grindstones obtained in Examples 10 to 12 and Comparative Examples 13 to 14, a grinding test of Si3N4 was conducted under the same processing conditions as in Examples 1 to 3, and the results shown in Table 1 below were obtained. The results shown in the right column were obtained.

In addition, the symbol in the abrasive grain column in Table 1 indicates diamond.
The symbol CBN indicates cubic boron nitride, the symbol M in the lubricant column indicates molybdenum sulfide, and the symbol HBN indicates hexagonal boron nitride.

[Margin below]

As can be seen from the results in Table 1, diamond abrasive grains and CB
When using mixed abrasive grains with N abrasive grains and containing about 2% by weight of solid lubricant, it is possible to maintain a good grinding wheel surface condition and also ensure a high grinding ratio. be able to.

However, as shown in Comparative Example 13.14, when the average particle size of the metal powder serving as the matrix exceeds 1/3 of the average particle size of the abrasive grains, the shedding of the abrasive grains increases and the grinding ratio decreases. . Therefore, it is necessary to set the average particle size of the metal powder constituting the matrix to 1/3 or less of the average particle size of the abrasive grains.

〔Effect of the invention〕

As explained above, since the metal bond tool according to the present invention is manufactured by adding molybdenum disulfide or hexagonal boron nitride as a solid lubricant to the raw metal powder, the compression molding operation becomes extremely easy. That is, since the added molybdenum disulfide and hexagonal boron nitride act as a lubricant during compression molding, a high-density molded body having a predetermined shape can be formed within a short time with a small pressing force. Therefore, there is little damage to the molding die, significantly reducing the manufacturing cost of the tool, and the frequency of replacing the molding die is reduced, so the manufacturing efficiency of the tool can be significantly increased.

It is also formed by sintering metal powder that forms the matrix, highly hard abrasive grains made of at least one of diamond and CBN, and a lubricant made of molybdenum sulfide and hexagonal boron nitride, which have excellent lubricity. Therefore, it is possible to uniformly disperse the abrasive grains and lubricant in the sintered body,
In addition to obtaining a good ground surface finish, it is possible to always receive stable lubrication, which reduces grinding resistance during machining.

In addition, the average particle size of the solid lubricant and the average particle size of the metal powder forming the matrix are set to 17% relative to the average particle size of the abrasive grains.
Since it is adjusted to 3 or less, the metal powder that serves as a lubricant and a supporting material for the abrasive grains can be uniformly dispersed around the abrasive grains.

Therefore, the lubrication function during the grinding process is fully demonstrated, the strength of the matrix as a support material is ensured sufficiently, and the falling off of abrasive grains is suppressed, making it possible to maintain high grinding efficiency at all times. The life of the abrasive layer can be significantly extended.

Claims (1)

[Claims] 1. A metal bond tool formed by integrally sintering abrasive grains, a solid lubricant, and a metal powder forming a matrix, in which at least one of diamond and cubic boron nitride is used as the abrasive grains. while containing at least one of molybdenum disulfide and hexagonal boron nitride as a solid lubricant.
5% by weight of the solid lubricant, and the average particle size of the solid lubricant is set to 1/3 or less of the average particle size of the abrasive grains. 2. The metal bond tool according to claim 1, wherein the average particle size of the metal powder is set to 1/3 or less of the average particle size of the abrasive grains.