JP2003117836A - Resin bond type grinding wheel for high efficiency grinding process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin bond type diamond and cBN grinding wheel capa ble of performing high efficiency grinding. SOLUTION: Abrasive grains for the resin bond grinding wheel are structured so that fine alumina particles smaller than abrasive grains are attached fast to the surface of each abrasive grain. A binding material is filled with a filler consisting of one or two sorts of silicon carbide and alumina having at least a mean particle size of 20 μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin bond grindstone used for grinding hard materials such as cemented carbide, cermet, ceramics and high hardness steel.

[0002]

2. Description of the Related Art As a grindstone for grinding, a GC grindstone using silicon carbide as an abrasive grain, a WA grindstone using alumina as an abrasive grain, a diamond grindstone using diamond as an abrasive grain, and cubic boron nitride (cBN) as a grindstone. Granulated cBN grindstones and the like are known. Furthermore, regarding the diamond grindstone and the cBN grindstone, a resin bond grindstone, a metal bond grindstone, a vitrified grindstone, etc. are known depending on the type of the abrasive grain binder. Of these, the resin bond grindstone has a relatively low grinding resistance and can be processed with high efficiency.
Resin bond diamond wheels are mainly used for grinding hard materials such as cemented carbide, cermet and ceramics, and resin bond cBN wheels are mainly used for grinding iron-based hard materials such as high hardness steel. Came.

[0003]

Various improvements have been made to the resin bond grindstone in order to improve the grinding efficiency. For example, a straight type resin bond grindstone in which a grindstone layer is arranged on the outer peripheral portion is used. When grinding cemented carbide, the cutting depth of the grindstone is generally 10 to 10 of the average grain size of the abrasive grains.
In the case of a grindstone having an abrasive grain size of 140/170 mesh (about 105 to 90 μm), which is about 15% and is used for ordinary roughing, the grinding condition is the grindstone peripheral speed of 1200 to 1
800 m / min, table feed speed 10-18 m / m
in, table forward / backward feed speed 60 to 120 mm / min
In this case, the cut amount per 1 pass (the one-way movement of the table front-back feed) was about 15 μm. Japanese Unexamined Patent Publication No. 6-206166 discloses a grinding wheel using an aromatic hydrocarbon-modified maleimide resin as a binder, which exhibits high-precision and high-efficiency grinding performance. According to the embodiment, the cutting depth is 0. Since it is 0.025 mm, a significant improvement in the depth of cut has not been realized. This is because when you try to increase the depth of cut, the grinding resistance increases, which causes chattering vibrations in the grindstone and cracks in the material to be ground.
Further, the grindstone may be damaged. Such a restriction on the cutting amount of the conventional resin bond grindstone is a major factor in which the grinding cost is inevitably expensive as compared with the cutting cost, and therefore improvement has been demanded.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies in view of the above circumstances, the present invention has developed a resin-bonded grindstone capable of significantly higher efficiency grinding than conventional grindstones.

First, when the depth of cut is increased in order to increase the grinding efficiency under normal grinding conditions, the grinding resistance increases, and as a result of detailed investigation of the cause of the above-mentioned inconvenience, the main cause is the abrasive grains. We obtained the knowledge that it was a dropout. Therefore, various methods of improving the holding force of the abrasive grains by the resin-based binder were investigated. As a result, when finer particles of alumina particles are fixed to the surface of the abrasive grains than the abrasive particles, irregularities are formed on the surface of the abrasive grains by the alumina particles. The mechanical holding force of the grain binder is improved, and because alumina is also hard, it is possible to dramatically increase the depth of cut during grinding, in combination with the grinding effect due to this, and therefore the grinding efficiency. It has been found that can be significantly increased.

Here, the average particle size of the alumina particles fixed to the surface of the abrasive grains needs to be finer than that of the abrasive grains, and is preferably about 1/5 to 1/20 of the average grain size of the abrasive grains. . When the average particle size of the alumina particles exceeds about 1/5 of the average particle size of the abrasive grains, it becomes difficult to adhere the alumina particles to the entire surface of the abrasive grains. This is because the unevenness becomes small, and in any case, the mechanical holding force of the abrasive grains by the bonding material is lowered. Therefore, for example, in Japanese Patent Application Laid-Open No. 3-95288,
Abrasive particles (abrasive grains) obtained by coating a refractory metal oxide with an organic metal compound are disclosed. However, since such abrasive grains have a smooth coating layer surface, the resin bond according to the present invention is disclosed. Not suitable as an abrasive grain for a whetstone.

On the other hand, currently available alumina powders have various particle shapes such as a spherical shape, a flake shape and a polygonal shape. The shape of the alumina particles fixed to the abrasive grains according to the present invention. Is preferably flaky. This is because the flake shape can make the fixing area with the abrasive grains relatively large, so that the fixing strength of the alumina particles with respect to the abrasive grains becomes high.

The amount of the alumina particles fixed to the abrasive grains is preferably about 25 to 35% by mass of the total amount of the abrasive grains, and about 30%.
It is more preferable to set it as the mass%. This is because if the amount of adhered alumina particles is too small, the abrasive grain retention force by the alumina particles is reduced, and if the amount of adhered alumina particles is too large, the alumina particle adhered layer is easily broken during grinding, resulting in the removal of abrasive grains. Because it will be easier.

[0009] Further, the alumina particle-fixed abrasive grains not only can effectively prevent the abrasive grains from falling off during the grinding process because the holding force of the abrasive grains by the bonding material is remarkably improved, but the abrasive grains are gradually dropped. The result is a new cutting edge,
It was found that good surface roughness of the material to be ground can be obtained even by using abrasive grains having a coarser grain size than the commonly used abrasive grains.

Therefore, for example, the grain size of 100/120 mesh (about 150 to 125 μ), which is coarser than the grain size of a normal grinding wheel for rough grinding, that is, 140/170 mesh.
Even if m) is used, the surface roughness of the material to be ground is similar to that obtained with a conventional grindstone using 140/170 mesh abrasive, so the amount of coarse abrasive grain cuts Since the amount can be increased, this is also advantageous in terms of grinding efficiency.

In addition, a resin bond grindstone is generally made of an inorganic material for the purpose of reducing frictional resistance with a material to be ground, improving thermal conductivity, and suppressing wear of a binder due to abrasive particles and grits generated during grinding. Although various fillers such as compounds and metals are added, when using the above-mentioned alumina particle fixed abrasive grains, in addition to granular graphite or copper powder that is usually added, finer particles than the alumina particles, Particularly, one or two selected from silicon carbide and alumina having an average particle size of 20 μm or less.
It was found that a high grinding ratio (abraded material removal volume / grinding wheel wear volume) was obtained when seeds were added as a filler. The reason why these fillers are particularly suitable for the resin-bonded grindstone according to the present invention is not necessarily clear, but with respect to the particle size of the filler, when their average particle size exceeds the above value, the abrasive grain surface It is not preferable because the abrasive grains tend to fall off during the grinding process, probably because the grain size of the alumina particles adhered to the part becomes close to that of the abrasive grain holding force of the binder.
If the addition amount of these fillers is too large, the strength of the entire binder will be reduced and the grindstone will be more likely to be worn, and if it is too small, the effect of suppressing the wear of the binder by the filler will not be obtained. It is preferably 15 to 25% by volume based on the total amount of the filler.

As the binder for the resin bond grindstone according to the present invention, any thermosetting resin such as a phenol resin, a phenol aralkyl resin, a polyimide resin, etc., which have been conventionally known, can be applied. Among them, the phenol resin is used. A so-called heat-resistant phenol resin, which is a combination of a phenol aralkyl resin and a phenol aralkyl resin, is most suitable because it has a good balance between the economic efficiency of the grindstone, the moldability and the grindstone performance.

The particle size of the diamond or cBN abrasive grains in the resin bond grindstone according to the present invention can be applied in any of the commonly used grain size ranges, but in the roughing grindstone, it is 80 to 120 mesh (about 180 to 125 μm).
m), the feature that the resin-bonded grindstone according to the present invention can be processed at high efficiency is maximized.
Particularly preferred. At this time, the content of the abrasive grains is preferably a volume ratio that does not include the adhered amount of alumina particles, and is 15 to 38% (abrasive grain concentration degree of 60 to 150) with respect to the total amount of the components other than the abrasive grains. 19% to 23% especially for roughing grindstones
(Abrasive grain concentration degree of 75 to 90) is more preferable.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION To obtain the alumina particle-fixed abrasive grains used in the resin bond grindstone according to the present invention, for example,
After the abrasive grains are first coated with water glass or silica sol, a predetermined amount of alumina powder is added and mixed therewith to adhere the alumina particles to the surface of the abrasive grains. Next, the alumina particle-attached abrasive grains are heat-treated to obtain the abrasive grains having the alumina particles adhered to the surface portion.

A conventional method may be used to produce a resin bond grindstone using the abrasive grains obtained as described above. For example, in order to produce a straight type grindstone in which a grindstone layer is arranged on the outer peripheral portion of the base metal, after mixing the abrasive grains, the thermosetting resin, and the filler with a dry stirring mixer, the base metal with a hot press is used. Form and fire so that the grindstone layer is integrated. This is taken out of the mold and further baked in a high temperature dryer. After that, processing such as lathe processing and grindstone forming processing is performed to finish the final product. Here, it goes without saying that an intermediate layer made only of a binder containing no abrasive grains may be provided between the grindstone layer and the base metal.

[0016]

EXAMPLES Hereinafter, the resin bond grindstone according to the present invention will be described in more detail by way of examples. (Example 1) <Inventive grindstone 1> As a diamond abrasive grain, a grain size of 100
/ 120 mesh (about 150-125 μm) IRV diamond abrasive grains (manufactured by Tomei Diamond), 12% by volume of water glass (sodium silicate) is added and kneaded by a kneader to form a water glass film on the surface of the abrasive grains. Then, alumina powder having an average particle size of 25 μm was added thereto and stirred to adhere the alumina powder to the surface of the abrasive grains. This is the temperature 120
After fully drying in a drier at ℃, transfer to an electric furnace, 450
The water glass coating was melted and vitrified by heating to ° C to fix the alumina particles to the surface of the diamond abrasive grains. In the alumina particle-fixed diamond abrasive grains thus obtained, the amount of the alumina particles fixed was about 30% by mass including 3 to 5% by mass of the vitreous component.

Separately, 60% by volume of a mixed resin of phenol resin / phenol aralkyl resin in a mass ratio of 60/40, 20% by volume of silicon carbide powder having a grain size of −2000 mesh (about 8 μm or less), and granular graphite (grain size of 15 to 20 μm) 11 By preparing a mixed powder composed of 9% by volume of copper powder and 9% by volume of copper powder (particle size 8 to 20 μm), the above-mentioned alumina particle-fixed diamond abrasive grains are added and mixed so that the volume ratio becomes 26.6%. A mixed powder for forming a grindstone was obtained.

An aluminum alloy grinding stone base metal is placed in the center of the grinding stone molding die having an inner diameter of 200 mm, and the space formed by the inner wall of the die and the outer periphery of the base metal is filled with the grinding stone molding mixed powder. Then, it was heated at 180 ° C. for 1 hour while applying pressure. As a result, the resin component in the mixed powder was once melted and then cured, and a resin bond grindstone in which the grindstone layer was integrally bonded and molded on the outer peripheral portion of the base metal could be obtained.

The resin bond grindstone taken out from the mold is
The resin component was completely cured by further heating at 180 ° C. for several hours in a high temperature dryer. After that, the base metal portion was lathe-processed and the grindstone layer was sharpened so as to have a predetermined size, and a finished product was obtained.

Diamond grain size 1 thus obtained
00/120 mesh, abrasive grain concentration 75 (abrasive grain volume ratio 1
9%), size 200D (grinding wheel outer diameter) x 6T (grinding wheel width) x
A grinding test was performed under the following conditions using the present grinding wheel 1 of 3 × (grinding wheel layer thickness) × 50.8 Hmm (base metal hole diameter).

Grinding machine: Surface grinder SG52 made by Washino
F-II Grinding material: WC-10 mass% Co cemented carbide plate (hardness HR
A90.0), dimensions: 150 × 150 × 30 mm Grinding method: Wet reciprocating surface grinding wheel rotation speed: 2700 rpm (peripheral speed 1700 m / mi
n) Table feed rate: 18 m / min Table front-rear feed rate: 80 mm / min Depth of cut: 20,40 μm / pass Total grinding amount: 2 mm

Under these grinding conditions, the grinding wheel 1 of the present invention could be ground without redressing until the end of the test. The results obtained are shown in Table 1.

[0023]

[Table 1]

In this embodiment, among the fillers according to claim 2, the case where only silicon carbide is added is shown.
It was confirmed that even when alumina or two kinds of silicon carbide and alumina were added instead of silicon carbide, the same grinding performance as that of the present grinding wheel 1 was exhibited.

<Comparative Grinding Stone 1> Except that the diamond abrasive grains of the present invention Abrasive Stone 1 were changed to those without fixing of alumina particles.
A comparative grindstone 1 having the same specifications as the grindstone 1 of the present invention was produced, and a grinding test under the same conditions as the test performed with the grindstone 1 of the present invention was performed.

In this case, the grinding resistance remarkably increased as the grinding time increased, and the grinding test had to be interrupted when the total grinding amount was about 1 mm. The test results at the time of this interruption are
As shown in Table 2, the grinding ratio was decreased and the grinding surface roughness was deteriorated as compared with the grindstone 1 of the present invention, which was considered to be due to the falling of diamond abrasive grains.

[0027]

[Table 2]

<Comparative Grinding Stone 2> As the abrasive grains, a grain size of 140/170 mesh (about 105 to 9) without fixing alumina particles
(0 μm) IRV diamond abrasive grains (manufactured by Tomei Diamond Co., Ltd.) were used, and the same specifications as those of the present grindstone 1 were used except that silicon carbide having a particle size of about 400/500 mesh (about 40 to 30 μm) was used as the filler. A conventional comparative grindstone 2 having a concentration of 75 was prepared, and a grinding test similar to the test performed with the grindstone 1 of the present invention was tried.

However, since the grinding resistance rapidly increased after the start of grinding at any of the cutting depths and the grinding had to be interrupted, a test was conducted with the cutting depth of 10 μm / pass. When the total grinding amount exceeded 1 mm, the grinding resistance remarkably increased. This usually appears when continuously grinding with a conventional resin bond wheel.
It was probably due to clogging.

<Comparison grindstone 3> As the abrasive grains, the grindstone of the present invention 1
100/120 mesh IRV diamond abrasive grains (made by Tomei Diamond Co., Ltd.) to which alumina particles are fixed
The particle size of the filler silicon carbide is 230/270 mesh (about 65 to 50 μm), which is slightly finer than the abrasive grain size.
A comparative grindstone 3 having the same specifications as the grindstone 1 of the present invention was manufactured except for the above.

Using this grindstone, a grinding test similar to the test carried out with the grindstone 1 of the present invention was carried out. As a result, the grinding resistance was considerably higher than that of the grindstone 1 of the present invention, and the test was interrupted when the total grinding amount was close to 2 mm. Although it was unavoidable, it could be judged that this was because the particle size of silicon carbide was inappropriate, so that the retention of the alumina particle-fixed diamond abrasive grains was insufficient and the abrasive grains were likely to fall off.

(Example 2) <Inventive grindstone 2> As grinding abrasive grains, a surface portion of 100/120 mesh cBN abrasive grains (SBN manufactured by Showa Denko) was thinly coated with silica sol prepared as follows. Alumina powder having an average particle size of 25 μm was added and stirred to adhere the alumina particles to the surface of the abrasive grains. Charge this into a room temperature dryer and heat it up to 120 ° C at a heating rate of 1 ° C / min.
After drying, it was transferred to an electric furnace and heated to 1050 ° C. at a temperature rising rate of 0.5 ° C./min to melt and vitrify the silica coating, thereby fixing the alumina particles to the surface portion of the cBN abrasive grains. Alumina particle-fixed cB thus obtained
In the N abrasive grains, the amount of alumina particles fixed was about 33 mass% including the silica glass component of 3 to 5 mass%.

Here, the method for preparing the silica sol liquid for adhering the alumina particles is as follows. Tetraethoxysilane 100 g Water 10 g DMF (N, N-dimethylformamide) 2 g Ammonia 1 g

When the above mixed liquid is heated to about 40 ° C. while being stirred, the mixed liquid gradually increases in viscosity and becomes a viscous liquid. The silica sol thus prepared was used as a fixing material for cBN abrasive grains and alumina particles.

Separately, 60% by volume of phenol resin, particle size-
A grindstone binder comprising 20% by volume of 2000-mesh silicon carbide powder, 11% by volume of granular graphite (particle size 15 to 20 μm) and 9% by volume of copper powder (particle size 8 to 20 μm),
The above-mentioned alumina particle-fixed cBN abrasive grains were added and mixed so as to be 31% by volume to obtain a mixed powder for forming a grinding stone.

Similar to the grindstone 1 of the present invention, a space formed by an inner wall of the mold and an outer peripheral portion of the base metal by arranging a whetstone base metal made of an aluminum alloy in the center of the inside of the grinding stone molding die having an inner diameter of 200 mm. To the grinding stone mixed powder and pressurize
By heating at 0 ° C. for 1 hour, the resin component in the powder for forming a grindstone is once melted and then hardened to obtain a grindstone in which the resin bond grindstone layer is integrally bonded and molded on the outer peripheral portion of the base metal. did it.

After forming the grindstone layer, the resin-bonded grindstone taken out from the mold was placed in a high temperature dryer and heated at 180 ° C. for several hours to completely cure the resin component. afterwards,
Abrasive grain concentration of 75 obtained by lathe processing of the base metal and polishing of the abrasive grain layer so as to have a predetermined finishing dimension.
Using 200D × 6T × 3X × 50.8H mm of the present grindstone 2 of the present invention, a grinding test was performed under the following conditions.

Grinder: Wasino surface grinder SG52
F-II Grinding material: SKD11 hardened steel plate (hardness HRC60 to 6
1), dimensions: 150 × 150 × 20 mm Grinding method: wet reciprocating surface grinding wheel rotation speed: 2700 rpm (peripheral speed 1700 m / mi
n) Table feed rate: 18 m / min Table front-rear feed rate: 80 mm / min Depth of cut: 20,40 μm / pass Total grinding amount: 2 mm

Under these grinding conditions, the grinding wheel 2 of the present invention could be ground without redressing until the end of the test. The results obtained are shown in Table 3.

[0040]

[Table 3]

<Comparative Grinding Stone 4> A comparative grindstone 4 having the same specifications as the grinding stone 2 of the present invention was prepared, except that the abrasive grains of the grinding stone 2 of the present invention were changed to cBN of commercially available SBN100 / 120 mesh without fixing alumina particles. The same grinding test was performed.

In this case, the cutting depth is 20 μm / pas
Even in s, not only the grinding resistance was significantly increased and the grindstone was excessively consumed due to the falling of the cBN abrasive grains, but also the roughness of the grinding surface was deteriorated and a considerable burn crack phenomenon was observed on the grinding surface. The grinding test had to be interrupted when the total grinding amount was about 0.8 mm. The results at the time of this interruption are shown in Table 4.

[0043]

[Table 4]

[0044]

As described above, the resin bond grindstone according to the present invention dramatically increases the depth of cut by about 2 to 4 times as much as the conventional resin bond grindstone under normal grinding conditions. In addition, clogging is extremely unlikely to occur during the grinding process, and there is no need to interrupt the grinding process and perform redressing. Therefore, in this respect, the effect of excellent grinding process efficiency can be obtained. The utility value above is extremely high.

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Claims (4)

[Claims] 1. A resin-bonded grindstone in which abrasive grains are bonded with a thermosetting resin, and finer alumina particles than the abrasive grains are fixed to the surface of the abrasive grains. 2. The filler according to claim 1, wherein at least one kind selected from silicon carbide and alumina having an average particle size of 20 μm or less is added as a filler for the binder made of a thermosetting resin. Resin bond whetstone. 3. The abrasive grain is diamond.
Alternatively, the resin bond grindstone according to 2. 4. The resin bond grindstone according to claim 1, wherein the abrasive grains are cubic boron nitride.