JP2003094343A - Grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have superior frangibility, impact absorption capacity, and grinding ratio in grinding a material hard to be ground. SOLUTION: An elastic base metal 2 of a super abrasive grain wheel 1 is provided with an abrasive grain layer 3 with brittle super abrasive grains SD retained by bond. The bond whose hardness is set within a range of HRF 30-80, is so formed that different types of thermosetting resin of 10-60 vol.% or preferably 20 vol.% such as all aromatic polyimides is heat treated and mixed to the thermosetting resin such as phenolics or polyimide. Or, it is formed by mixing the heat-treated phenolics or engineering plastic of 10-60 vol.% to the thermosetting resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a work material, particularly Ti.
The present invention relates to a grindstone for grinding difficult-to-cut materials such as N-based cermets.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
When grinding difficult-to-cut materials such as TiN cermet, SiC, Si ₃ N _4, etc., for example, when TiN cermet is ground with a superabrasive wheel such as a resin bond grindstone, TiN cermet is a work material such as cemented carbide. Since the hardness is higher than the above, the wheel life is shortened to about 1/10, and there is a problem that the machinability is further deteriorated if the nitrogen content in the work material increases. The present invention, in view of such a situation,
An object of the present invention is to provide a grindstone capable of improving the grinding ratio by improving the grinding surface roughness in grinding a difficult-to-cut material and improving the grinding ratio.

[0003]

The present inventors have found that when a difficult-to-cut material such as TiN-based cermet, SiC, or Si ₃ N ₄ is ground with a super-abrasive wheel, the super-abrasive particles are super strong for metal bonding. A resin bond superabrasive grain (hereinafter referred to as SD), which is more brittle and has better friability than an abrasive grain (hereinafter referred to as MD), has a bond (binder) having a higher grinding ability and a higher toughness. The present invention has been made on the basis of the findings that the abrasive grains are less likely to fall off, the shock absorbing power is larger, and the grinding ratio is higher. That is, the present invention, in the base metal, in a grindstone provided with an abrasive grain layer, in which fragile superabrasive grains are held by bonds,
The bond consists of a mixture of multiple resin materials,
Hardness is characterized in that it is in the range of H _R F30~80.

According to the present invention, when grinding a difficult-to-cut material such as TiN-based cermet, the fragile superabrasive grains SD are ground while being finely crushed, so that the grinding ability is high and the crushed fine cutting edge is The grinding ratio is high by continuing to grind the work material. Further, since the bond of this abrasive grain layer has a high toughness, it has a high impact absorbing power, and it is possible to suppress the removal of the abrasive grains and improve the grindability, and the sharpness is stable and the self-generating action is smoothly performed.

Moreover, the bond is formed by mixing a thermosetting resin (preferably phenol resin or polyimide) with a different type of thermosetting resin (preferably wholly aromatic polyimide) which is heat-treated at a ratio of 10 to 60 vol%. It may be one. Alternatively, the bond may be a mixture of a thermosetting resin and a heat-treated phenol resin in a proportion of 10 to 60 vol%. Or, the bond is 10 to 60 vol of engineering plastic obtained by heat treatment of thermosetting resin.
It may be mixed at a ratio of%. The bond mixed as described above has high heat resistance by heat treatment of the resin to be added, so that heat damage is small and wear resistance is also high.
In particular, a mixture of wholly aromatic polyimide as a different type of thermosetting resin is thermally stable. In addition, by setting the base metal to one with a relatively low elastic modulus, it is possible to absorb impact not only with superabrasive grains or abrasive grain layers but also with the base metal when grinding difficult-to-cut materials and reduce cutting resistance. Further, it is possible to further suppress the removal of the abrasive grains and improve the grindability.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
It will be described with reference to FIG. 1 is a cross-sectional view of the grindstone according to the embodiment along the axis of rotation, FIG. 2 is a partial plan view of the grindstone shown in FIG. 1, and FIG. 3 and subsequent figures show experimental results.
Is a diagram showing a grinding ratio of a difficult-to-cut material by superabrasive grains SD and MD, FIG. 4 is a diagram showing a grinding performance of a TiN-based cermet due to a difference in material of a base metal, and peripheral speeds and grinding ratios by wheels of Examples and Comparative Examples. FIG. 6 is a diagram showing the relationship between the cumulative amount of machining using TiN cermet as a work material and the grindstone surface state, FIG. 7 is a diagram showing thermogravimetric analysis results, and FIG. 8 is for each bond. The figure which shows the relationship between SiC filler and transverse rupture strength, FIG.
Is a diagram showing the flexural modulus of each bond when 25 vol% of SiC filler was added, and FIG. 10 is a diagram showing the degree of wear of the edge of each wheel in different heat treatment atmospheres. Figure 1
2 and 2, the superabrasive wheel 1 according to the embodiment
Indicates a cup-shaped resin wheel grindstone,
It is held rotatably around the rotation axis O. The wheel 1 is provided with a substantially cylindrical base metal 2 on its outer peripheral surface along the rotation axis O, and a segment type or integral type abrasive grain layer 3 is provided on the upper surface of the base metal 2 in the rotation axis O direction. ing. Here, the base metal 2 is made of a material having a relatively high elasticity, and is formed, for example, by mixing an Al powder with a thermosetting resin.

Further, the abrasive grain layer 3 is made by using fragile resin-bonding superabrasive grains SD as superabrasive grains, and is dispersed in the abrasive grain layer 3 and fixed by a bond (bonding agent). Then, as the bond, a mixture of a plurality of types of resin materials is mainly used, and for example, a thermosetting resin,
For example, a mixture of a phenol resin or polyimide and a thermosetting resin of a different heat-treated type, for example, wholly aromatic polyimide is used. In this case, the bond is a mixture of a phenol resin or polyimide with 10 to 60 vol% of a powder of wholly aromatic polyimide, preferably a phenol resin or polyimide and a wholly aromatic polyimide of 8%.
Mix in a ratio of 0 to 60%: 20 to 40% so that the total becomes 100%. In this case, the wholly aromatic polyimide is preferably heat-treated at about 300 to 800 ° C. in a nitrogen atmosphere. In addition, heat treatment in a hydrogen atmosphere or an oxygen atmosphere can be considered, but the degree of wear during grinding of the abrasive grain layer 3 of the superabrasive grain wheel 1 is the smallest when heat treated in a nitrogen atmosphere.

As another example of the bond, a thermosetting resin is used.
You may mix the phenol resin hardened by 0-60 vol% heat processing. In this case, the phenol resin is preferably heat-treated at about 300 to 800 ° C. in a nitrogen atmosphere to be cured. As another example of the bond, a thermosetting resin may be added to 10
60 vol% heat-treated engineering plastic may be mixed. The engineering plastic is preferably heat-treated at about 300 to 800 ° C. in a nitrogen atmosphere. The mixing ratio of the other type of thermosetting resin to the thermosetting resin such as phenol resin or polyimide is 10 to 6
The content of 0 vol% is less than 10%, because the ratio of the thermosetting resin such as phenol resin or polyimide is large, the elastic modulus of the bond is large, and the impact absorbing power when grinding difficult-to-cut materials is low. This is because if it exceeds 60%, the elastic modulus of the bond is lowered, the holding power of the superabrasive grains is significantly lowered, and the grinding ratio is deteriorated. Abrasive grain layer 3 bonds thus obtained, the hardness is set to H _R F30~80. Here, when the hardness is less than H _R F30, the elastic modulus is too small and the deformation of the abrasive grain layer 3 when stress is applied is too large, and conversely, when the hardness exceeds H _R F80, the elastic modulus is If it is too large, the shock absorbing power is small, the crushing of the superabrasive grains during grinding and the self-generated effect are not sufficiently performed, and the superabrasive grains are more likely to be worn smoothly.

Since the superabrasive grain wheel 1 according to the present embodiment has the above-mentioned structure, the fragile superabrasive grains SD are ground while being finely crushed, which has a high grinding ability and is crushed. The grinding ratio is high because the minute cutting edge continues to grind the work material. Further, the bond of the abrasive grain layer 3 has a high impact absorbing power, the abrasive grains are less likely to fall off, the sharpness is stable, and the self-generating action is smoothly performed. By heat-treating the wholly aromatic polyimide or the like to be added, heat resistance is high, heat damage is small, and wear resistance is high. Moreover, by providing the abrasive grain layer 3 on the base metal 2 having a relatively low elastic coefficient, it is possible to further absorb the impact when grinding a difficult-to-cut material and reduce the grinding resistance.
It is possible to further suppress the removal of abrasive grains and improve the grindability. On the other hand, when a difficult-to-cut material is ground using an abrasive grain layer in which a tough metal bond superabrasive grain MD is fixed with a metal bond, the superabrasive grains are not sufficiently crushed during grinding and wear out. It is not suitable for grinding difficult-to-cut materials because it wears smoothly such that a flat surface such as a flank is formed on the surface of the abrasive grain in the cutting direction, it is hard to change the cutting edge, and it does not sufficiently perform self-regeneration. There is a drawback that

Next, an example of grinding performed in connection with the superabrasive wheel 1 according to the above-described embodiment will be described by taking a TiN cermet as an example of a difficult-to-cut material. <Experiment 1> First, using the fragile resin bond super-abrasive grains SD and the tough metal super-abrasive grains MD used in the present embodiment, a phenol resin is used as a bond to form an abrasive grain layer. A cup wheel having a shape as shown in FIG. The grinding conditions are as follows. Machine: Makino tool grinder, wheel shape: 6A2.50 ^D × 30 ^T × 3 ^W × 3 ^X grain size & outlet: # 170 (conc. 75) Wheel peripheral speed: 800 m / min Table speed: 4 m / min Depth of cut: 20 μm Grinding fluid: Chemical solution (× 50)

FIG. 3 shows fragile resin bond superabrasive grains SD and tough metal bond superabrasive grains MD obtained as a result of the experiment 1.
The grinding ratios are shown. In the surface observation of both wheels,
In MD, the wear of the superabrasive grains was smooth and it was difficult to change the cutting edge, but in SD, there were many crushed superabrasive grains and the minute cutting edge continued to shave the work material, so the grinding ratio was M
It is higher than D and the sharpness is stable, so it can be said that the autogenic action was performed smoothly. That is, since MD is hard to crush the abrasive grains, the tips of the superabrasive grains are worn flat and T
It can be said that the super abrasive grains are not suitable for grinding difficult-to-cut materials such as iN cermet. On the other hand, fragile SD has high friability and is easy to create a sharp cutting edge, and it can be said that it is a grinding type suitable for grinding difficult-to-cut materials such as TiN-based cermets.

<Experiment 2> Next, the difference in grindability of the difficult-to-cut material due to the elastic modulus of the base metal will be examined. Resin base metal 2 (Al powder 80 vol% + thermosetting resin 20 vol)
%) And the elastic modulus is (1 × 10 ⁴ MPa), Comparative Example 1,
2 as Fe base metal (elastic modulus: 7.8 × 10 ⁴ MPa),
Creep feed grinding is performed by using Al base metal (elasticity: 21 × 10 ⁴ MPa) and dispersively disposing fragile superabrasive grains SD on each base metal using phenol resin as a bond material to form a resin bond abrasive grain layer. Was done. The grinding conditions for each wheel are as follows. Machine: Okamoto PSG-63A Wheel diameter: 200 ^D x 6 ^T Wheel peripheral speed: 1000 m / min Depth of cut: 1 mm Workpiece: 12.7 □ x 5 t x 10 pieces Grinding fluid: W2 (Soluble type)

From the experimental results shown in FIG. 4, no difference was found in the grinding resistance among the three types at a low feed rate of 20 mm / min. However, as the feed rate increased, the grinding resistance gradually changed and the grinding resistance was elastic. The higher the coefficient, the larger it was, and the wheel according to the example was the smallest. In addition, when observing the wheel surface after grinding, the wheels according to the examples showed the least loss of abrasive grains. From this experiment, it was found that when the grinding conditions became strict, the removal of the abrasive grains was promoted, but in the example having the impact absorbing power, the abrasive grains were less dropped and the grindability could be improved.

<Experiment 3> Next, the wheel according to the embodiment,
A grinding test of a TiN-based cermet was performed with a wheel as a comparative example using a heat resistant resin bond. The experimental conditions are as follows. In each of the examples and the comparative examples, the superabrasive grains were fragile SD, and the base metal was made of 70% Al powder + thermosetting resin. The bonding is based on the mixing ratio of phenol resin 8: wholly aromatic polyimide 2 in the example, and the heat resistance resin is 100% in the comparative example. Machine: Okamoto Surface Grinder PSG6EV power 1.1KW grindstone diameter: 0.99 ^D × 7 ^T wheel peripheral speed: 900 meters / min, and 1500 m / min workpiece feed rate: 10 m / min cut: 5 [mu] m Coolant: w-2 (1:50 ) Grinding fluid: W2 (Soluble type)

Experimental results are shown in FIGS. 5 and 6.
In addition, the grinding ratio and power in FIG.
The value of min is 100%. In FIG. 5, the grinding ratios of both the example and the comparative example increase as the wheel peripheral speed increases, but the example has a larger grinding ratio. Further, in the comparative example, the power increased significantly as the wheel peripheral speed increased, but in the example, the change in the power was small.
Further, when the ground surface was observed, it was found that the example had less peeling and a good surface was obtained. In the observation of the grindstone surface state according to FIG. 6, in the comparative example, the amount of superabrasive grains dropped greatly as the cumulative processing amount increased, but in the examples in which the retention of the abrasive grains was good, the amount of superabrasive grains was not dropped and the wheel was worn. There were few.

Also, the bond of the abrasive layer 3 in the embodiment (for example, phenol resin + whole aromatic polyimide = 8:
2) as an example, the thermogravimetric analysis result with a phenol resin as a comparative example is shown in FIG. 7, and the phenol resin shows a rapid weight loss at about 300 to 400 ° C.
In the examples, no sudden weight loss is observed up to about 500 ° C. Therefore, it can be said that the example is relatively stable against heat. In addition, a bond of the abrasive grain layer 3 (for example, phenol resin + whole aromatic polyimide = 8: 2) is used as an example, and a phenol resin and a heat-resistant resin are used as Comparative Examples 1 and 2, and as shown in FIG. Instead of the SiC filler 25vo
When 1% is added, the mechanical strength (flexural strength) of Comparative Example 2 decreases as the content of the SiC filler increases, but that of Examples and Comparative Example 1 increases, and Has higher mechanical strength. From this, it can be said that the examples have excellent abrasive grain holding power. In addition, a bond of the abrasive grain layer 3 (for example, phenol resin + whole aromatic polyimide = 8:
2) as an example, using a phenol resin and a heat-resistant resin as Comparative Examples 1 and 2, and adding SiC filler instead of superabrasive grains as shown in FIG.
It can be said that the example and the comparative example 2 are smaller than the comparative example 1 and are excellent in shock absorbing power.

<Experiment 4> Next, a grinding test of a wheel having a bond under different heat treatment conditions was conducted. The experimental conditions are as follows. The sample was made by adding 20 vol% of heat-treated wholly aromatic polyimide to a polyimide as a bond to hold the superabrasive grains SD, and the base metal was made of 70% Al powder + thermosetting resin. Regarding the heat treatment conditions for the wholly aromatic polyimide, samples A, B, and C were used in a nitrogen atmosphere, a hydrogen atmosphere, and an air atmosphere, and a sample D was not heat-treated.
And Further, the heat treatment temperature was set to 400 ° C., and the treatment was performed for 1 hour. Machine: Okamoto Surface Grinder PSG6EV power 1.1KW Wheel ^{diameter: 200 D × 6 T × 3} X wheel peripheral speed: 1500 m / min Table speed: 10 m / min cut: 20 [mu] m

According to the results of the experiment shown in FIG. 10, the one that was heat-treated in the nitrogen atmosphere had the least wear on the edge of the wheel, and then the one was in the hydrogen atmosphere and the air atmosphere, and the one that was not heat-treated had the most edge wear. It was Therefore, it can be said that it is preferable to use the one heat-treated in the nitrogen atmosphere or the hydrogen atmosphere, and preferably the one heat-treated in the nitrogen atmosphere for grinding the difficult-to-cut material.

[0019]

According to the present invention as described above, the grinding wheel according to the present invention, the bond comprises a material obtained by mixing a plurality of kinds of resin material, since the hardness is what is in the range of H _R F30~80, When grinding difficult-to-cut materials such as TiN cermet, fragile super-abrasive grains are placed in the abrasive grain layer to perform grinding while finely crushing, so the grinding ability is high and the crushed minute cutting edge is cut The grinding ratio is high by continuing to grind the material.
Further, since the bond of the abrasive grain layer has a small hardness and an excellent toughness, it has a high impact absorbing power, and the abrasive grains are prevented from falling off, so that the grindability can be improved. In addition, the sharpness is stable and the self-reliance is smooth.

Moreover, the bond is formed by mixing thermosetting resins of different kinds heat-treated with heat-curable resins, heat-treated phenolic resins, or heat-treated engineering plastics in a proportion of 10 to 60 vol%. Since it has high heat resistance, it is less likely to be damaged by heat and has high wear resistance.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view taken along an axis of rotation of a grindstone according to an embodiment of the present invention.

FIG. 2 is a partial plan view of the grindstone shown in FIG.

FIG. 3 is a diagram showing a grinding ratio of a difficult-to-cut material by superabrasive particles SD and superabrasive particles MD provided on an abrasive particle layer of a cup wheel.

FIG. 4 is a diagram showing the grinding performance of a TiN-based cermet depending on the material of the base metal.

FIG. 5 is a diagram showing a relationship between a peripheral speed and a grinding ratio by wheels of an example of the present invention and a comparative example.

FIG. 6 is a diagram showing a relationship between a cumulative amount of machining using a TiN-based cermet as a work material and a grindstone surface state in Examples and Comparative Examples of the present invention.

FIG. 7 is a diagram showing a thermogravimetric analysis result of each bond.

FIG. 8 is a graph showing the relationship between the content of SiC filler and the transverse rupture strength for each bond,

FIG. 9 is a diagram showing the flexural modulus of each bond when 25 vol% of SiC filler is added.

FIG. 10 is a diagram showing the degree of wear of the edges of the wheels having different heat treatment atmospheres.

[Explanation of symbols]

1 Super Abrasive Wheel 2 units 3 Abrasive layer

Claims (4)

[Claims] 1. A grindstone in which a base metal is provided with an abrasive grain layer in which fragile superabrasive grains are held by a bond, wherein the bond includes a material in which a plurality of kinds of resin materials are mixed, and has a hardness of H _R A grindstone characterized by being in the range of F30 to 80. 2. The grindstone according to claim 1, wherein the bond is formed by mixing thermosetting resins of different types heat-treated with a thermosetting resin at a ratio of 10 to 60 vol%. 3. The grindstone according to claim 1, wherein the bond is formed by mixing a thermosetting resin with a heat-treated phenol resin at a ratio of 10 to 60 vol%. 4. The grindstone according to claim 1, wherein the bond is made by mixing a thermosetting resin with a heat-treated engineering plastic at a ratio of 10 to 60 vol%.