JPH07251378A - Porous ferrous metal bond diamond grinding wheel and its manufacture - Google Patents

Abstract

PURPOSE:To provide a grinding wheel excellent in sharpness by way of promoting autogenous blade growing action of abrasive grains and making the most of an abrasive characteristic of a bond by forming the grinding wheel by respectively using diamond as the abrasive grains and ferrous metal powder as a binder and making a part of the binder as what contains a large number of pores. CONSTITUTION:A grinding stone of ferrous metal chemically and physically binding and holding abrasive grains is formed by respectively using diamond as the abrasive grains and ferrous metal powder as a binder and making a part of the binder as what contains a large number of pores. In this case, porosity of the whole grinding wheel is set in a range of 5-60%. Additionally, as the ferrous metal, it is selected from a group consisting of iron powder, carbon coated iron powder, nitrogen iron powder and a mixture of carbon and iron. The grinding wheel such as this is manufactured by heating and sintering at 900-1150 deg. after moulding the abrasive grains and the binder in a specified dimensional shape by way of mixing them, and a mechanical characteristic of the binder part and holding power of the abrasive grains are controlled by adjustment of the porosity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous iron-based metal bond diamond grindstone belonging to a metal bond grindstone for polishing or grinding various materials and a method for producing the same. More specifically, the present invention improves the porosity of the grindstone,
The present invention relates to a porous iron-based metal bond diamond grindstone that promotes the self-sharpening action of abrasive grains and utilizes the bond wear characteristics, and has excellent sharpness, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A grinding wheel is a wheel used for grinding various workpieces. The grinding wheel consists of abrasive grains, binder and pores. The abrasive grain is a cutting edge, the binder is its support, and the pores are a large number of continuous pores, which function as chip pockets that help discharge chips. Recently, it has become increasingly important to use difficult-to-cut materials such as ceramics, cemented carbide, and high-speed steel that are difficult to grind, and it becomes more and more important to grind them. Grinding wheels using superabrasives such as boron nitride abrasives have become increasingly used.

Grinding wheels using such super-abrasive grains are classified into vitrified bond type, resinoid bond type, metal bond type, silicate bond type, rubber bond type and the like depending on the kind of the binder as in the general case. Each of them has advantages and disadvantages, and in view of strength, holding power, life, etc., a metal bond type one using a metal and its alloy as a binder is mainly used for grinding a brittle material (such as ceramics).

Among these whetstones, the metal bond whetstone is
Abrasive grains are uniformly dispersed in metal powder, and the powder is molded together with a base metal, followed by press molding and sintering (or hot pressing) for molding. As the metal binder of the metal bond grindstone, for example, Cu-Sn system, Cu-Sn-Co system, Cu-Sn-F
e-Co type, Cu-Sn-Ni type, or Cu-Sn
A -Fe-Ni-based material or a material obtained by adding phosphorus to these is used.

These conventional metal bond grindstones have markedly higher bond strength than resinoid bond grindstones and vitrified bond grindstones, and have excellent grain retention required when performing strong grinding with superabrasive grains. Although it has the advantage of having force, the strength of the binder itself is strong, the binder does not wear out during the grinding process, and even if the abrasive grains wear out, they cannot fall off, so the dressing interval must be shortened. Therefore, high efficiency grinding is impossible.

Therefore, in the conventional metal-bonded grindstone, the chips are not easily discharged and are easily clogged.
Grinding resistance is large, so-called sharpness is bad and heat generation is large, the finished surface is likely to be defective, and it is extremely difficult to increase the depth of cut and increase the contact area between the grindstone and the workpiece to perform high efficiency grinding etc. There is a drawback of. In addition, these bonds also have a drawback that they soften during grinding to cause plastic flow and cause clogging on the surface of the grindstone.

In order to improve these drawbacks, a continuous porous metal bond grindstone has been proposed (JP-A-59-1).
No. 82064), the powder sintering method is not used. After sintering the solvent-soluble inorganic compound into a predetermined shape and molding, fill the voids of the obtained sintered body with abrasive grains to preheat it, and then in the voids of this abrasive-filled sintered body. Further, by pressing in a molten metal or alloy and solidifying it, and then producing by eluting the inorganic compound with a solvent, a method of adding a porosity-imparting agent as a filler and interposing pores in the abrasive grain layer is described. .

In addition, the abrasive grains are coated with a number of layers of metal and sintered by a hot press to have a structure like a vitrified bond to have pores (Japanese Patent Publication No. 54-54).
(Japanese Patent No. 31727) and the like have been proposed.

Further, a grindstone using cast iron for overcoming clogging (Japanese Patent Laid-Open No. 3-264263) has been proposed. The cast iron bond grindstone has various advantages such as high strength and high rigidity, high cutting heavy grinding, brittle fracture wear that does not cause plastic flow, and less clogging. Since the strength is too high, the dressing property is worse than that of the copper-based bond, and the high rigidity is difficult to put into practical use by the existing grinders and methods.

To form a large number of pores inside the abrasive grain layer, the pores may be impregnated with a grinding liquid to enhance the cooling performance of the grindstone, or the pores may reduce the grinding resistance and have good sharpness. In other words, it can be expected that a high quality finished surface will be obtained with less heat generation. But,
In the conventional copper-based metal-bonded grindstone, having pores naturally lowers the strength and eventually the holding force of the abrasive grains, so that sufficient grinding performance is not obtained.

Further, in the non-porous cast iron bond grindstone,
Due to the poor sinterability of cast iron powder, iron powder was added to cast iron powder, and 8,000 kgf / cm ² to 10,000 kgf /
Molded with a load of cm ² . The addition of iron powder causes the original brittle fracture behavior of cast iron to disappear, causing the same plastic deformation as copper-based bonds, and the characteristics of cast iron have not yet been extracted.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a porous iron-based metal bond diamond grindstone such as a porous cast iron bond diamond grindstone and a method for producing the same. More specifically, the present invention adjusts the porosity of the entire grindstone, and improves the performance of so-called cast iron bonded diamond grindstone by making the carbon content of the abrasive grains diamond react with the iron-based metal. The purpose is to

[0013]

The present invention has been made to solve the above problems, and the structure thereof will be specifically described below.

Generally, in the grindstone, the pores control the bond strength of the binder, and the binder is appropriately worn away without resistance during the grinding process, so that clogging is suppressed and the sharpness of the grindstone is improved. In addition, it also has the effect of dissipating a large amount of grinding heat generated during grinding, and when prevention of grinding burn is a problem, a grindstone with high porosity is required. Those with the pores of are often used.

Therefore, the present invention is characterized in that the above-mentioned pores are intervened in the iron-based metal bond surrounding the abrasive grains, and the abrasive grains are chemically and physically bonded to the iron-based metal and held. To provide a porous iron-based metal bond diamond grindstone.

The feature of the metal bond is that the bond strength is remarkably high and therefore the abrasive grain holding power is remarkably high. It is a characteristic that the metal bond positively contains pores which bring about a decrease in the abrasive grain holding power. Has not been done so far. The present invention controls the bonding strength of the metal bond so that the metal bond is appropriately abraded by the pores without resistance during the grinding process. If the porosity is lowered too much, the holding force for holding the abrasive grains becomes too strong, so the abrasive grains worn in the cutting portion remain without the binder metal falling off, and as a result, the cutting ability of the grindstone decreases, and also If the porosity is too high, the holding force for holding the abrasive grains becomes too weak, so that many abrasive grains fall off from the binder metal, and as a result, the abrasion of the grindstone increases and the life of the grindstone shortens.

Further, according to the present invention, the abrasive grains are chemically and physically bonded to the iron-based metal, and the abrasive grain holding force is controlled so as not to fall off until the abrasive grains are worn out. The chemical bond is that the carbon content of diamond as the abrasive grains reacts with the iron-based metal.

The maximum porosity of those used as a grindstone is the largest in the vitrified bond grindstone, and about 50% at the maximum except for special cases. The range actually used is often about 35% to 45%, and when the porosity reaches 50%, the strength of the grindstone is considerably lowered, and the grindstone may be broken.

However, in order to sufficiently exert the performance of superabrasive grains capable of strong grinding and to effectively use expensive abrasive grains, basically, the abrasive grain ratio is set low and the binder is We believe that it is desirable to use a metal bond with strong abrasive grain retention, use it in the minimum necessary amount, and increase the porosity.

The characteristics of cast iron in the cast iron bond grindstone are:
Not only strength but also its brittle fracture. In copper-based metal bonds, the bond component covers the surface of the grindstone due to plastic deformation, causing clogging and reducing the sharpness.
Cast iron bonds can prevent clogging due to brittle fracture. In order to take advantage of the fact that such clogging is unlikely to occur, it is necessary to overcome the drawback that the strength is too large by adjusting the strength.

As described above, the present invention is to adjust the strength of the metal bond by including a large number of pores in the metal bond in the metal bond grindstone. That is, the present invention is composed of diamond as an abrasive grain and an iron-based metal powder as a binder, the binder portion contains a large number of pores formed by powder sintering, and the abrasive grain is an iron-based powder as a binder. Provided is a porous iron-based metal-bonded diamond grindstone which is held by being chemically and physically bound to a metal.

In the porous iron-based metal bond diamond grindstone of the present invention, the porosity of the whole grindstone is adjusted to 5 to 60%, preferably 5 to 45%. In the present invention, the porosity of the whole grindstone corresponds to the porosity of the binder. The porosity is adjusted by the particle size of the iron-based metal, the grinding stone forming conditions, and the grinding stone firing conditions. This is to control the mechanical strength and abrasive grain holding force of the metal bond.

In the case of an ordinary cast iron bonded diamond grindstone, the bond itself has almost no porosity, and the gap is obtained by interposing abrasive grains, or a porosity-imparting agent is added. Is characterized in that the iron-based metal bond itself contains a large number of pores.

The porosity of the whole grindstone of the present invention is 5
If it is less than 0.1%, the bond strength becomes considerably high and the wear characteristics of the iron-based metal cannot be sufficiently exhibited, so the lower limit is made 5%. On the other hand, if the porosity is too high, the strength of the grindstone may be lowered and the stone may be broken.

The abrasive grains of the present invention are held by chemical-physical bonding with a ferrous metal as a binder. That is, the carbon content on the surface of diamond, which is an abrasive grain, is solid-dissolved in the iron-based metal. The mechanical strength of the metal bond, that is, the porosity and the abrasive grain holding force are controlled by adjusting the particle size and the carbon content of the iron-based metal powder. The iron-based metal comprises one or more selected from the group consisting of iron powder, carbon-coated iron powder, iron nitride powder, carbon and a mixture of iron.

Generally, iron contains no carbon (pure iron) to carbon steel containing a small amount of carbon, or 1.
There are a wide variety of materials, including cast iron containing more than 7% carbon. In the present invention, since the bonding strength is improved by reacting with the carbon component of diamond, the iron-based metal powder is represented by cast iron, but is not limited thereto.

A wide variety of materials can be used, from carbon that does not contain any carbon (pure iron) to carbon steel that contains a small amount of carbon, or cast iron that contains 1.7% or more of carbon. Mixed powder of iron and carbon, in the grinding stone firing of the present invention, it is possible to carry out the reaction of iron and diamond or the reaction of iron and carbon together, depending on the reaction amount of carbon and iron, brittle like cast iron It can be an iron bond that exhibits fracture behavior.

Regarding the carbon concentration of the iron-based metal and the concentration gradient of diamond, iron can contain approximately 6 to 7% of carbon. That is, for example, when the carbon content is 3%,
It is also possible to react with 3-4% carbon. When diamond and iron powder are mixed and sintered, when the sintering temperature is reached, the surface of the iron powder begins to partially melt and sintering begins. At this time, when the carbon content of iron is less than the allowable range, it is possible to react (diffusion bonding) with adjacent carbon.

When the sintering temperature is not reached, the carbon concentration gradient between diamond and iron powder is infinite. During sintering, a concentration gradient occurs in diamond and iron due to the movement of substances by diffusion. A large concentration gradient allows more carbon to react with iron, especially when the carbon content of iron is low. If the reaction proceeds too much, the abrasive grains will deteriorate, so it is necessary to select sintering conditions that cause the reaction on the surface.

The grindstone of the present invention will be described below by taking a porous cast iron bond diamond grindstone as an example.

In the present invention, the amount of carbon and the particle size of the cast iron powder are adjusted so that the porous cast iron bonded diamond grindstone has strength and abrasive grain holding power equivalent to those of the copper-based metal bonded grindstone. The strength of the cast iron bond itself can be controlled by the carbon content and particle size of the cast iron powder.
Moreover, as shown in FIG. 1, the joining of the cast iron powder and the diamond is performed by reacting the diamond and the cast iron powder to bond them.
This bonding strength can also be controlled by the carbon content and particle size of the cast iron powder.

Next, a method for manufacturing the porous iron-based bonded diamond grindstone of the present invention will be described.

In producing a porous iron-based metal-bonded diamond grindstone using diamond as the abrasive grains and iron-based metal powder as the binder, it is necessary to control the mechanical properties of the binder portion and the holding force of the abrasive grains. Characterize. After mixing the abrasive grains and the binder and molding into a predetermined size and shape,
It is characterized in that it is heated and sintered at 900 to 1150 ° C.
Diamond abrasive grains are 1 in vacuum and in insoluble atmosphere.
The above heating temperature is adopted because carbonization occurs at about 100 to 1200 ° C.

The mechanical properties of the binder part are controlled by controlling the porosity. The average particle size of the iron-based metal powder is set to 0.01 to control the mechanical properties of the binder part and the holding power of the abrasive grains.
It is made by adjusting in the range of μm to 500 μm. The mechanical properties of the binder portion and the retention of the abrasive grains are controlled by adjusting the carbon content of the iron-based bond and the diamond concentration gradient.

The method for producing the grindstone of the present invention will be described below by taking the method for producing the porous cast iron bonded diamond grindstone as an example.

The porous cast iron bonded diamond grindstone is produced by mixing diamond as abrasive grains and cast iron powder as a binder, shaping the mixture into a predetermined size and shape, and then heating and sintering at 900 to 1150 ° C.

The shaped body shaped into a grindstone is sintered by the above-mentioned sintering process. This sintering is performed under normal pressure, and the sintering temperature is at least 900 ° C. or higher. Considering the fact that the sintering temperature is deteriorated by heat when diamond is used as abrasive grains, and that the sintering proceeds when the sintering temperature becomes high and the target porosity of the entire grindstone cannot be 5 to 60%. Decide. Preferred sintering temperature is 900-
It can be said to be in the range of 1150 ° C. The sintering temperature changes depending on the type of iron-based metal and the particle size of the powder. In this way, the mechanical properties of the binder portion are controlled by controlling the porosity.

The mechanical properties of the binder portion and the holding power of the abrasive grains are controlled by controlling the average grain size of the cast iron powder from 0.01 μm to 500 μm.
It is made by adjusting in the range of μm and / or by adjusting the carbon content in the range of 1% to 4.2%.

If the porosity is lowered too much, the holding force for holding the abrasive grains becomes too strong, so that the abrasive grains worn in the cutting portion remain without the binder metal falling off, resulting in a reduction in the cutting ability of the grindstone. Also, if the porosity is raised too much, the holding force for holding the abrasive grains becomes too weak, so more abrasive grains fall off from the binder metal, and as a result, the abrasion of the grindstone increases and the life of the grindstone shortens. .

By adjusting the average particle size and the amount of carbon of the cast iron powder within the above ranges, it becomes possible to solid-phase diffuse diamond and cast iron as abrasive grains and improve the retention of the abrasive grains. Since cast iron plays a role of holding the abrasive grains, it is desirable that there be one having a small grain size so as to increase the contact area with the abrasive grains.

The porous cast iron-bonded diamond grindstone of the present invention is obtained by uniformly mixing cast iron powder and diamond abrasive grains in the same manner as in the ordinary method of manufacturing a grindstone, and molding the powder together with a base metal into a press machine as is conventionally done. It is molded and manufactured. The thus baked product is adhered to a 6A2 type cup-shaped grindstone having a grindstone diameter of 100 mm, and evaluated by a constant pressure grinding test. The superiority of the porous cast iron bond grindstone of the present invention is confirmed in comparison with ordinary non-porous cast iron bond grindstones, vitrified grindstones and resinoid grindstones.

Commercially available cast iron powder was used in the production of the grindstone. The average particle size of the cast iron powder is 100 μm or more,
Moreover, since the particle size distribution is wide, it is difficult to sinter even if the temperature is raised to the melting point of cast iron. Therefore, the sinterability, mechanical strength and porosity of the cast iron powder are adjusted by controlling the carbon content and particle size of the cast iron powder.

In order to investigate the influence of the carbon content, three kinds of commercially available cast iron powders having a carbon content of 3.0%, 3.5% and 4.0% were sized by a sieve of 38 μm or less. I was there. To examine the effect of particle size, cast iron powder with a carbon content of 3.5% is sieved to 20 μm or less, 20 μm to 32 μm.
m, 32 μm to 38 μm, 38 μm to 45 μm.

Each cast iron powder and mesh size 100/120
The diamond abrasive grains of No. 1 were mixed so as to have a concentration of 125 and were fired at a temperature of 1120 ° C. in an argon atmosphere.

Further, after the grindstone produced as described above, a constant pressure grinding test was conducted at a grinding wheel peripheral speed of 1100 m / min using alumina ceramics as a work material. Table 1 (Physical Properties and Grinding Performance of Prototype Grinding Wheel) shows physical property values and grinding results of the porous cast iron bonded diamond grinding wheel after firing.

[0046]

[Table 1]

As is clear from Table 1, the bending strength and Young's modulus increase and the strength increases as the grain size of the cast iron powder decreases. When the carbon content of the cast iron powder was 3.5%, the bending strength and Young's modulus showed the highest values. As for the grinding performance, the grinding energy (energy required to remove the work material) decreased as the cast iron powder particle size decreased, and the work material could be removed with about half the energy. The grinding ratio also showed the same result as the grinding energy.

FIG. 2 shows that the carbon content is 3.5% and the cast iron grain size is 20 μm.
Although a micrograph at m is shown, it can be confirmed that the diamond and the cast iron bond are bonded by a chemical reaction. The carbon content on the diamond surface reacts with cast iron, increasing the bonding strength. This tendency increases as the grain size decreases, and the number of contact points also increases, so bending strength and Young's modulus increase, and the holding force of the diamond abrasive grains increases during grinding, causing the abrasive grains to fall off. It seems that the grinding energy was lowered and the grinding ratio was increased due to the removal of the work material. Thus, the physical properties or grinding performance of the porous cast iron diamond grindstone can be controlled by the particle size of the cast iron powder and the amount of carbon.

[0049]

The details of the present invention will be described with reference to Examples. The present invention is not limited to these examples.

Example 1 120-mesh diamond abrasive grains and carbon content 3.5%,
Using cast iron powder with an average particle size of 20 μm or less, 1120 ° C
Was fired in an argon gas atmosphere to obtain a porous cast iron bonded diamond grindstone. This porous cast iron bonded diamond wheel was compared with a commercially available vitrified wheel, a commercially available resinoid wheel, and a commercially available non-porous cast iron bonded wheel. The shape of each grindstone is 6A with a diameter of 100 mm
It is a cup-shaped grindstone of No. 2, and the concentration is unified to 125.
The grinding test was carried out using alumina as a work material and a grinding wheel peripheral speed of 110.
A constant pressure grinding test was performed at 0 m / min.

The results are shown in FIG. 3 (explanatory diagram showing the relationship between grinding pressure and removal rate).

The removal rate of each of the whetstones increased as the grinding pressure increased, but the porous cast iron bond was about twice as fast as the commercially available vitrified whetstone which is said to have excellent sharpness. It showed grinding ability. In addition, the grinding ratio showed twice the performance of other bonds.

Example 2 A grinding test of silicon nitride was carried out using the grindstone produced in Example 1 under the same conditions as in Example 1.

The results are shown in FIG. 4 (explanatory diagram showing the relationship between the grinding time and the grinding removal amount).

With the commercially available vitrified bond grindstone and the commercially available resinoid bond grindstone, the grinding removal amount increased in proportion to the time until 30 seconds after the start of grinding, but thereafter, the grinding stone clogged and the grinding removal amount increased. There wasn't. In the porous cast iron bond grindstone of the present invention, the grinding removal amount increased in proportion to the time immediately after the start of grinding to the end of the test. It is considered that the porous cast iron bond was excellent in crushability of the bond, and thus the cutting edge of the diamond was maintained and the grinding force was maintained.

[0056]

Industrial Applicability It is possible to provide a porous iron-based metal bond diamond grindstone having desired strength and porosity. It is possible to provide a porous iron-based metal-bonded diamond grindstone capable of continuous grinding for a long time without clogging. It is possible to provide a grindstone that is sharper than a vitrified bond grindstone and has less grindstone wear than a resinoid bond grindstone. Since it can be used well with a general-purpose grinder and has excellent dressing properties, it can be dressed on the grinder like Vitrified Bond and Resinoid Bond. Can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which diamond abrasive grains and cast iron powder are reacted and bonded in a porous cast iron bonded diamond grindstone of the present invention.

FIG. 2 is a micrograph showing the state of bonding of diamond abrasive grains and cast iron bond when the carbon content of cast iron powder is 3.5% and the particle size is 20 μm.

FIG. 3 is an explanatory diagram showing a relationship between a grinding pressure and a removal rate in the grindstone of the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a grinding time and a grinding removal amount in the grindstone of the embodiment of the present invention.

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Claims (12)

[Claims] 1. A diamond abrasive grain and an iron-based metal powder as a binder, wherein the binder portion contains a large number of pores, and the abrasive grain is chemically and physically bonded to the iron-based metal. A porous iron-based metal bond diamond grindstone characterized by being retained. 2. The porous iron-based metal bond diamond grindstone according to claim 1, wherein the porosity of the whole grindstone is 5 to 60%. 3. The porous iron-based metal bond diamond grindstone according to claim 1, wherein the porosity of the whole grindstone is 5 to 45%. 4. The iron-based metal comprises one or more selected from the group consisting of iron powder, carbon-coated iron powder, iron nitride powder, and a mixture of carbon and iron. 3. The porous iron-based metal bond diamond grindstone according to 3. 5. The chemical bond according to claim 1, claim 2, claim 3 or claim 4, wherein the carbon content of diamond as abrasive grains reacts with the iron-based metal on the surface. Porous iron-based metal bond diamond grindstone. 6. When manufacturing a porous iron-based metal-bonded diamond grindstone using diamond as abrasive grains and iron-based metal powder as a binder, the mechanical properties of the binder portion and the retention of the abrasive grains are controlled. A method for producing a porous iron-based metal bond diamond grindstone, which is characterized by the above. 7. The porous iron-based metal-bonded diamond grindstone according to claim 6, wherein the abrasive grains and the binder are mixed and formed into a predetermined size and shape, and then heat-sintered at 900 to 1150 ° C. Production method. 8. The method for producing a porous iron-based metal-bonded diamond grindstone according to claim 6 or 7, wherein the mechanical properties of the binder portion and the holding power of the abrasive grains are controlled by adjusting the porosity. 9. The method for producing a porous iron-based metal-bonded diamond grindstone according to claim 8, which is performed by adjusting the carbon concentration of the iron-based metal and the concentration gradient of diamond in addition to adjusting the porosity. 10. The method for producing a porous iron-based metal-bonded diamond grindstone according to claim 8 or 9, which is adjusted depending on the particle diameter of the iron-based metal, the molding conditions and the firing conditions. 11. The average particle size of the iron-based metal is 0.0
The method for producing a porous iron-based metal-bonded diamond grindstone according to claim 10, which is adjusted in the range of 1 μm to 500 μm. 12. The method according to claim 6, wherein the iron-based metal is one or more selected from the group consisting of iron powder, carbon-coated iron powder, iron nitride powder, and a mixture of carbon and iron. 8. The method for producing a porous iron-based metal bond diamond grindstone according to claim 8, claim 9, claim 10, or claim 11.