JP2002001667A - Metal bonded grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixing form of metal powder of a binder capable of providing the best characteristics of a binding layer after sintering on a metal bonded grinding wheel. SOLUTION: The metal spongy powder higher in a melting point or higher in strength than the conventionally used metal powder is mixed with other metal powder and used as the binder for the metal bonded grinding wheel. The spongy powder (reduced iron powder) 10 is powder having a large number of voids 10a communicating with each other inside and opened to the surface, the other metal powder (tin powder) 30 melts and enters the voids 10a of the spongy powder 10, and it is possible to add characteristics which tin has to the binder while keeping characteristics iron has as it is and to provide the best characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal bond whetstone in which abrasive grains are bonded by a sintering method using a binder made of metal powder.

[0002]

2. Description of the Related Art As a grindstone using superabrasive grains such as diamond abrasive grains and CBN abrasive grains, there are a resin bond grindstone, a vitrified grindstone and a metal bond grindstone. Resin-bonded grindstones are made of synthetic resin such as phenolic resin and polyimide resin, which holds and holds abrasive grains. Vitrified whetstones are made of vitreous material that holds and holds abrasive grains. The grains are mixed and molded and held together by sintering.

[0003] Resin bond grinding wheels, vitrified grinding wheels,
Each metal bond grindstone has advantages and disadvantages, and because of its strength, holding power, and life, metal bond grindstones are mainly used for cutting and grinding fragile materials such as glass, ceramics, and refractory bricks. Metal-bonded grindstones are superior to resin-bonded grindstones in heat resistance and life, and are superior to vitrified grindstones in strength and life.

[0004] In the case of a manufacturing method in which a base metal and an abrasive material layer are simultaneously formed, a metal bond whetstone is formed by uniformly mixing abrasive grains with a metal powder, embedding it together with the base metal, press forming and sintering. Is done. In the case of a manufacturing method in which the abrasive material layer is separately manufactured and then joined to the base metal, the abrasive material layer is sintered after pressing or sintered as a powder. Examples of the metal powder as a binder include copper-tin, copper-tin-cobalt, copper-tin-iron-cobalt, copper-tin-nickel, and copper-tin-iron-nickel. I have.

[0005]

Conventionally, metal powders generally used as a binder for a metal bond grindstone are spherical, dendritic, and scale-like metal powders. As a dense solid. Further, since the bonding between powders is due to diffusion or melting of the powder surface during sintering, the uniformity and performance of the structure of the bonding layer after sintering depend on the particle size of the powder. The larger the particle size of the powder, the poorer the uniformity of the structure and the performance varies, and the smaller the particle size of the powder, the better the uniformity of the structure and the more stable the performance. For this reason, a powder having a small particle size must be used in order to obtain stable performance in grinding efficiency and life with little wear of the binder holding the abrasive grains. However, the finer the particle size, the more difficult it is to handle in stirring and other steps.

[0006] The characteristics of the metal powder have advantages and disadvantages depending on each metal. The characteristics of the bonding layer after sintering are
By mixing various kinds of metal powders, it is possible to obtain a certain level of balanced characteristics, but the best characteristics are not always obtained. For example, if tin powder which is suitable for lowering the sintering temperature but lowers the strength is added to high-strength iron powder, the strength is reduced by the influence of the tin powder. Further, when copper powder having excellent thermal conductivity but low abrasive holding power is added to cobalt powder having high abrasive holding power, the abrasive holding power is weakened by the influence of the copper powder.

[0007] The problem to be solved by the present invention is to obtain, in a metal bond grinding wheel, a mixed form of a metal powder of a binder, which can obtain the best properties of a bonding layer after sintering.

[0008]

Means for Solving the Problems The inventors of the present invention have set forth the point that the metal powder generally used as a binder for a conventional metal bond grinding wheel is a fine solid powder but is a dense solid. Fundamentally reviewed from the form of, when using a mixture of sponge-like metal powder having a void opening on the surface and other metal powder, both metal powders act to compensate for each other's disadvantages, The inventors have found that the best characteristics can be obtained, and have completed the present invention.

That is, the metal bond grindstone of the present invention uses, as a binder for abrasive grains, a metal bond obtained by mixing a sponge-like metal powder having a large number of voids opened on the surface and other metal powders with each other and communicating with each other inside. A metal bond grindstone, a metal powder having a higher melting point than the other metal powder as the sponge-like metal powder, or
It is characterized in that a metal powder having a higher strength than the other metal powder is used.

[0010] By mixing the sponge-like metal powder and the other metal powder as a binder of the metal bond grindstone, the other metal powder enters the voids of the sponge-like metal powder, and the characteristics of the sponge-like metal powder remain unchanged. The properties of other metal powders can be added to the binder. For example, when tin powder suitable for lowering the sintering temperature is mixed with high-strength sponge-like iron powder, the sintering temperature can be lowered while maintaining the strength of iron. This means that the sponge-like iron powder becomes the skeleton of the binder, and the tin powder to be mixed has the role of the filler. Further, since tin having a high thermal conductivity enters the voids of the sponge-like iron powder, heat dissipation is enhanced, and burning and deformation during processing are reduced, so that processing can be performed efficiently.

The relationship between the sponge-like metal powder and the other metal powder is determined by setting the sintering temperature higher than the melting point of the other metal powder because the melting point of the sponge-like metal powder is higher than the melting point of the other metal powder. In addition, other molten metal can enter the voids of the sponge-like metal powder. Also,
Since the strength of the other metal powder is lower than the strength of the sponge-like metal powder and the sponge-like metal powder can be elastically deformed,
By repeatedly applying pressure during molding, another metal powder can be caused to enter the voids of the sponge-like metal powder.

For example, when iron sponge powder is used as the sponge metal powder and tin powder is used as the other metal powder, the sintering temperature is made higher than the melting point of tin, so that the iron sponge powder becomes The shape of the powder is maintained and the tin becomes molten. In this state, a gap 10a opened on the surface of the iron sponge-like powder 10 shown in FIG.
The molten tin enters as shown by the arrow in FIG. Since the iron sponge powder 10 has a higher strength than the tin powder and can be elastically deformed, the molten tin enters the voids 10a opened on the surface of the iron sponge powder 10 due to the pressure during molding.

When the other metal powder enters the voids of the sponge-like metal powder, the cross section of the metal powder becomes the same as the finer one, and the holding power of the abrasive grains and the abrasion of the bonding layer are stabilized. Efficiency is stabilized. In addition, by controlling the temperature and pressure during sintering, it is possible to leave an arbitrary amount of voids in the sponge-like metal powder, thereby adjusting the hardness of the bonding layer or applying a cooling liquid to the voids during processing. Can be held.

[0014] Further, since the sponge-like iron powder forms a high-strength skeleton, abrasive grains are not buried in the binder, and the processing performance of the grindstone can be maintained. In a conventional iron-tin based metal bond grindstone 50, for example,
As shown in FIG. 3A, since the low-strength tin 30 is present between the high-strength irons 20, the abrasive grains 40 during the grinding process are indicated by broken lines in the drawing. Is low strength tin 30
, So that the sharpness of the grindstone decreases. On the other hand, in the grindstone 1 of the present invention, as shown in FIG.
Since the low-strength tin 30 is in the state of the skeleton, the abrasive grains 40 are supported by the skeleton of the high-strength iron sponge-like powder 10 and can maintain the protruding height.

The particle size range of the sponge-like metal powder is 10 to 2
It is preferably set to 00 μm. When the particle size is less than 10 μm, the communicating voids become smaller and the effect of the sponge-like metal powder becomes smaller, and because the voids are smaller, the surface tension becomes larger and other metals hardly penetrate into the voids. There is no difference in performance with metal powder. On the other hand, when the particle size is 200
If it exceeds μm, it takes time for other metals to penetrate to the center of the sponge-like metal powder, and the effect of the penetration is not sufficiently exhibited.

Here, the range of 10 to 200 μm is larger than the range of the particle size of the metal powder of the conventional binder. However, even if the sponge-like metal powder having the particle size in this range is used, other pores are formed in the internal voids. By being filled with the metal powder, the bonding layer after sintering has a fine structure, the holding power of the abrasive grains is stable, the wear rate of the bonding layer is constant, and stable characteristics can be obtained. . In addition, since the grain size is large, the number of grain boundaries is reduced, and the impact resistance and corrosion resistance are improved.

The appropriate mixing ratio of the sponge-like metal powder in the binder varies depending on the material of the sponge-like metal powder, but is preferably in the range of 20 to 80% by volume.
If this ratio is less than 20% by volume, the connection of the sponge-like metal powder is deteriorated, and it is difficult to obtain the above-described effect as the skeleton. On the other hand, if this ratio is more than 80% by volume, the ratio of voids into which other metal powder does not penetrate becomes large with respect to all voids of the sponge-like metal powder, which is not preferable.

The sponge-like metal powder usable in the present invention includes iron powder for powder metallurgy, chemically treated alloy powder, and the like, and is relatively easily available on the market and is most suitable as a binder for metal bond grinding wheels. It is a sponge-like powder of iron called reduced iron powder. Commonly available iron powders for powder metallurgy include sprayed iron powder, electrolytic iron powder, and reduced iron powder. Sprayed iron powder and electrolytic iron powder have relatively smooth particle surfaces and weak entanglement between particles. Poor moldability. On the other hand, since the reduced iron powder has an irregular particle shape, the particles are well entangled with each other and have excellent moldability. Further, the reduced iron powder has a sponge shape in which individual particles are communicated with each other and has a large number of voids opened on the surface and has high strength, so that it is particularly suitable as a sponge-like metal powder used in the present invention. ing.

[0019]

Embodiments of the present invention will be described below based on test examples. As shown in FIG. 1, the thickness is 1.2 m
m, a metal-bonded grindstone 1 in which eight segments 3 are arranged at regular intervals through slits 4 on the outer peripheral surface of a base metal 2 having an outer diameter of 95 mm, and a sponge-like metal powder is mixed as shown in Table 1. Made by changing. The binders for forming the segments of the grinding wheels of the inventions 1 to 8 are sponge-like reduced iron powder having an average particle diameter of 40 μm, copper powder and tin powder having an average particle diameter of 40 μm, and the abrasive grains are diamond having an average particle diameter of 400 μm. Abrasive grains. The conventional product is a conventional metal-bonded grindstone that does not use sponge-like reduced iron powder. Table 1 also shows the average cutting speed and the amount of segment wear when concrete was ground as a material to be ground under dry conditions using an electric grinder.

[0020]

[Table 1]

As can be seen from Table 1, the grindstones of Inventions 1 to 6 using the binder containing sponge-like reduced iron powder in the range of 20 to 80% by volume have the same sharpness as the grindstone of the conventional product. While maintaining it, the amount of wear of the segment is reduced. The grindstones of Invention 7 having a low blending ratio of reduced iron powder and Invention 8 having a high blending ratio both have the same sharpness and abrasion amount as conventional grinding wheels.
It has been confirmed that it is desirable to be within the range of 0 to 80% by volume.

[0022]

Advantages of the Invention (1) As a binder for a metal bond grindstone, a sponge-like metal powder is mixed with other metal powders which are internally connected to each other and have a large number of voids opened on the surface. The other metal powder enters the voids of the metal powder, and the characteristics of the sponge-like metal powder can be added to the binder while maintaining the characteristics of the sponge-like metal powder, so that the best characteristics can be obtained.

(2) As the sponge-like metal powder, a metal sponge-like powder having a higher melting point than a metal powder (another metal powder) conventionally used as a binder for a metal bond grindstone, or a metal having a high strength. By using the sponge-like powder, the sintering temperature is increased in the sintering step of forming the abrasive material layer, and other metal powders are introduced into the voids of the sponge-like metal powder, and the characteristics of the sponge-like metal powder remain unchanged. The properties of other metal powders can be added to the binder. In addition, while maintaining the strength of the sponge-like metal powder having high strength, the sintering temperature can be lowered and the sintering cost can be reduced.

(3) By setting the mixing ratio according to the particle size of the sponge-like metal powder and the material of the sponge-like metal powder in a specific range, the above effect can be further enhanced.

[Brief description of the drawings]

FIG. 1 is a front view showing a metal bond grindstone subjected to a test.

FIG. 2 is a diagram illustrating the entry of another metal into the voids of the sponge-like metal powder.

FIG. 3 is a diagram illustrating embedding of abrasive grains in a bond layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal bond whetstone 2 Base metal 3 Segment 4 Slit 10 Sponge-like powder 10a Void

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masanori Matsukawa 210 Noritake Diamond, Tanushimaru-cho, Ukiha-gun, Fukuoka Prefecture Noritake Diamond Corporation (72) Inventor Toshinori Takakura 210-Dainichi Takeno, Tanushimaru-cho, Ukiha-gun, Fukuoka Noritake Diamond Shares In-house F term (reference) 3C063 AA02 AB03 BA03 BA24 BB02 BC01 BC02 BC08 BC09 BG05 BG07 CC02 FF08 FF22 FF23

Claims (4)

[Claims] 1. A metal bond grindstone using a metal bond obtained by mixing a sponge-like metal powder having a large number of voids open to the surface and other metal powders with each other and a metal powder as a binder of abrasive grains, A metal bond whetstone using a metal powder having a higher melting point than the other metal powder or a metal powder having a higher strength than the other metal powder as the sponge-like metal powder. 2. The sponge-like metal powder has a particle size range of 1
The metal-bonded grindstone according to claim 1, which has a thickness of 0 to 200 µm. 3. The metal-bonded grinding wheel according to claim 1, wherein the ratio of the sponge-like metal powder in the binder is in the range of 20 to 80% by volume. 4. The metal bond grinding wheel according to claim 1, wherein the sponge-like metal powder is a reduced iron powder.