JP3050371B2 - Superabrasive grindstone and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to diamond and CBN used for grinding various materials such as metals and nonmetal materials.
The present invention relates to a grinding wheel having a superabrasive layer formed of superabrasive grains such as (cubic boron nitride). In particular, the present invention relates to a CBN grinding wheel for grinding iron-based metal materials such as steel materials and cast steel products.

[0002]

2. Description of the Related Art As a binder for this kind of grindstone, a so-called resinoid grindstone using a synthetic resin is well known.
Further, in order to perform a grinding operation with higher precision, a so-called vitrified grinding stone using a glassy or ceramics amorphous binder instead of a synthetic resin is also used.

[0003] In this vitrified grinding wheel, as described in, for example, Japanese Patent Publication No. 52-27394, an alumina binder is used as an amorphous binder in order to reduce shrinkage during firing of a binder phase and improve strength. It is known to add an aggregate made of abrasive grains or silicon carbide abrasive grains. In the same gazette, the advantages of these aggregates are extended and the disadvantages are discarded, and specific aggregates mainly composed of crystals with a modified Mohs hardness of 11 or less and a melting point of 900 ° C or more, such as zircon and mullite, shall be used. Has been proposed.

[0004]

Since the conventional amorphous binder phase has a low mechanical strength, the binder phase is easily broken,
The service life was short, and the surface roughness of the ground surface was easily deteriorated. Increasing the amount of binder phase to improve the life,
Conversely, the grinding resistance increases and the sharpness becomes dull.

In the case of using only the amorphous binder phase, since the softening point is low, the binder phase softens due to the high processing heat during truing, causing the binder phase to be covered on the surface of the abrasive grains and filling pores. There was a thing. As a result, there is also a drawback that the grinding resistance is high immediately after truing and in the initial stage of processing. Conversely, if the softening point is increased in order to increase the strength of the binder phase itself, there is a problem that it is not possible to fire sufficiently in the firing temperature range of the CBN grinding wheel.

[0006] Accordingly, a grinding stone obtained by adding a crystalline aggregate to the above-mentioned proposed amorphous binder and firing the same is excellent in solving many problems of the conventional grinding stone due to the above-mentioned amorphous binder phase. It is a thing. However, as described above, this crystalline aggregate is obtained by mixing and firing CBN, an amorphous binder, and an aggregate, and the aggregate is mixed with the amorphous binder at the time of firing. By using a substance which does not react or dissolve at all or only a part thereof, it functions as an aggregate.

[0007] This is extremely effective, but on the other hand, there is a fear that segregation may occur due to the fact that the aggregate is baked in a state of being directly in contact with the CBN due to mixing, and it is necessary to uniformly disperse the aggregate in the binder phase. Is difficult. Further, the wettability between the aggregate and the amorphous binder is not necessarily required, and it is hard to say that a stable improvement in strength is sufficient.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has the following features. (1) The superabrasive grains and the amorphous binder are mixed and fired to form a superabrasive layer. During this firing, the crystalline aggregate is reacted and precipitated from the amorphous binder. Therefore, the superabrasive layer is composed of superabrasive grains and an amorphous binder phase that binds the superabrasive grains, and has a structure in which crystalline aggregate is dispersed and contained in the binder phase. The content of the crystalline aggregate in this binder phase is 15 to 70% by volume.
It is.

(2) As the crystalline aggregate precipitated by the reaction, β-spodumene S. S. The second is that
The feature of. It may coexist with other aggregates such as ZrSiO ₄ . (3) The third feature is that CBN is most effectively used as the superabrasive.

(4) Another feature is that when the superabrasive grains and the amorphous binder are mixed, alumina abrasive grains and / or silicon carbide abrasive grains are also mixed together as a filler, so that the Is to contain a filler. It is also effective in reducing fluctuations in the thermal expansion coefficient of the superabrasive layer when the degree of concentration of the superabrasive grains is low.

[0011] (5) As a method for producing abrasive stone provided with the configuration of the superabrasive layer as described above is characterized by the following. One of them is as a binder mixed with superabrasives.
The use of an adjustment binder that does not include the previously prepared crystalline aggregate having the following configuration is used. That is, the adjustment binder is obtained by mixing a non-crystalline binder consisting of the following A, B, C, D, E, F, and G obtained by pulverizing glass with a temporary binder .
Then, the mixture of the conditioning binder and the superabrasive grains is charged into a mold and molded, and during the step of heating and firing the molded article, G
Is a reaction in which the crystalline aggregate is precipitated from the amorphous binder. A SiO ₂ 40 to 60 wt% B Al ₂ O ₃ 8~18 wt% C B ₂ O ₃ 1~10 wt% D P ₂ O ₅ 1~6 wt% E CaO, MgO, BaO of one or more 2 12% by weight F Li ₂ O or one obtained by adding one kind of Na ₂ O and K ₂ O 1 to 6% by weight G One or more of ZrO ₂ and TiO ₂ 1 to 6% by weight

(6) Therefore, although G seems to act as a nucleating agent, as the one-time binder, an aqueous solution of dextrin or a synthetic resin dissolved in an organic solvent is preferable. The firing is performed at 900 to 1200 ° C. for 1 to 5 hours,
The crystalline aggregate reactively precipitated during firing is mainly composed of β-spodumene SS.

(7) CBN is used as the superabrasive to be mixed. (8) When the binder and the superabrasive are mixed, for example, when the degree of concentration of the superabrasive is low, the alumina as a filler is used to reduce the fluctuation of the thermal expansion coefficient of the superabrasive layer. Abrasive grains and / or silicon carbide abrasive grains are added and mixed together.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments will be described below with reference to examples.

[0015]

DETAILED DESCRIPTION FIG. 1, the outer diameter D ₁ is about 334 mm, the thickness T is 16m
m, the outer diameter D _{2 of the} superabrasive layer 3 fixed to the outer peripheral end surface of the iron body 1 having the hole diameter H of 127 mm via the base layer ₂ is 3 mm.
50mm straight whetstone. Super abrasive layer 3 and base layer 2
Was formed by sticking 28 bit chips 4 having the following configuration on the outer peripheral end face of the body in close contact with each other.

That is, as shown in FIGS. 2A and 2B, the bit chip 4 has a length L of 40 mm, a width W of 16 mm, and a thickness X on the upper surface side.
And ₂ superabrasive layer 3 of 3 mm, a thickness X ₁ of the lower surface side has become more base layer 2 of 4 mm, and 28 sheets thereof on the outer end face of the body 1 of the iron as shown in FIG. 1 as joining affixed without gaps close to the arc R ₂ of the upper surface is 175mm, the circular arc R ₁ of the lower surface is formed in 167 mm.

The bit chip 4 is manufactured as follows. 20 parts of the crushed glass having the composition of the example in Table 1 and 10 parts of a 50% aqueous dextrin solution as a temporary binder are mixed to prepare an adjusted binder in advance. $ 80/100 CB as abrasive
Mix over N80 parts. This mixture is loaded into a mold,
It is molded to a bulk specific gravity of 2.5. This molded portion forms the superabrasive layer 3.

[0018]

[Table 1]

At the same time, 20 parts of the glass crushed product having the composition of the embodiment shown in Table 1 above, 15 parts of a 50% aqueous dextrin solution as a temporary binder, and 80 parts of # 100/140 fused mullite were mixed. This mixture is loaded onto the above-mentioned superabrasive layer 3 forming section and molded so as to have a bulk specific gravity of 2.2. This overlapped molded part is the part that forms the base layer 2.

Then, the superposed compacts were heated up to 1000 ° C. at a heating rate of 100 to 300 ° C./hr, held for 4 hours, fired, and cooled at a cooling rate of 100 to 300 ° C./hr. Finish the shape and dimensions. During firing, TiO in crushed glass
₂ or ZrO ₂ added thereto becomes a nucleating agent, causing a chemical reaction and causing β-spodumene S.P. S. A crystalline aggregate mainly composed of is precipitated. In this example, 40% β-spodumene S.p. S.
And 10 crystalline aggregates of ZrSiO ₄ were precipitated.
FIG. 7 shows the X-ray diffraction values.

As compared with the super-abrasive grindstone of the above embodiment, the conditions for forming and firing and the shape and dimensions are the same, and the portion relating to the configuration of the superabrasive grain layer 3 of the bit chip 4 is changed as follows. An example was made.

(Comparative Example 1) The same procedure as in Example 1 was carried out except that a glass crushed product having the composition of Comparative Example in Table 1 was used. In Comparative Example 1, no crystalline aggregate was precipitated when the molded body was fired.

(Comparative Example 2) As a glass pulverized product, a composition of the comparative example shown in Table 1 was used, and 10 parts of the pulverized product and β-spodumene SS and ZrSiO ₄ as crystalline aggregates were used. 10 parts of the mixed powder, 10 parts of a 50% aqueous dextrin solution as a one-time binder, and 80 parts of CBN (80/100) as superabrasive grains are mixed, and the mixture is charged into a mold and superabrasive. A molded body for forming the grain layer 3 was obtained. Others were the same as the example. In this comparative example, the mixed crystalline aggregate was present even after firing.

Table 2 shows the physical properties of the abrasive layer in the grinding stones of the above Examples and Comparative Examples. The abrasives of the Examples have a high strength at high temperatures, a high abrasive holding power, and a low coefficient of thermal expansion. Good.

[0025]

[Table 2]

Therefore, the results of the grinding test under the following conditions are all clear as shown by the grinding wheel radius wear amount shown in FIG. 4, the specific grinding resistance shown in FIG. 5, and the work surface roughness shown in FIG. Example products are excellent.

[0027]

As described above, the reason why the product of the embodiment has excellent physical properties and exhibits high performance and long life in actual grinding is not clear, but is considered as follows. FIG. 3 is a photograph of the structure of the superabrasive grain layer 3 of Example 1 at a magnification of 1000 times. The CBN abrasive grains are sharply angulated from the lower side of the screen to both sides, and the white area occupies almost the entire surface in direct contact with the CBN abrasive grains. The part is an amorphous binder phase. And, in the white binder phase, many gray small angular objects are dispersed. This angular material is β-spodumene S. precipitated during firing. S. It is a crystalline aggregate mainly composed of.

Such a structure is formed by mixing, shaping, and sintering a pre-adjusted binder and a superabrasive, and depositing crystalline aggregate from the binder during the sintering. it is conceivable that. In other words, it is considered that the method of this formation can sufficiently mix the superabrasive grains and the binder and maintain the wettability, uniformly disperse the aggregate, and generate a binder phase having sufficient strength.

Β-spodumene S. S. Is Mohs hardness 7
In addition to contributing to the improvement of the mechanical strength of the superabrasive layer, the thermal expansion coefficient is as low as 1.1 × 10 ⁻⁶ / C, so that 3.5 × 10 ⁻⁶ / C
A super-abrasive layer of 3.78 × 10 ⁻⁶ / C close to the above CBN is obtained.

In the practice of the present invention, in the case of a super-stone having a low concentration of super-abrasive grains such as CBN, in order to maintain the mechanical strength of the super-abrasive layer and to prevent an increase in the coefficient of thermal expansion, It is preferable to add alumina-based abrasive grains or silicon carbide-based abrasive grains as a filler in the binder.

Although the embodiment has shown the case where CBN is used as superabrasive grains, it goes without saying that diamond abrasive grains may be used. The range of the composition of the adjustment binder, the firing conditions, and the amount of the crystalline aggregate is specified because the intended effect of the present invention cannot be exerted outside the range.

[0033]

As described above, according to the present invention, according to the present invention, the superabrasive grains are firmly held by the amorphous binder phase in which the crystalline aggregate is uniformly dispersed, the grinding performance is high, and the life is improved. A super-abrasive grindstone with a long length is provided, and efficient high-quality grinding can be performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view of a superabrasive grindstone in an embodiment.

2A is a top view of one of the bit chips 4 in FIG. 1, and FIG. 2B is a side view thereof.

FIG. 3 shows a configuration of a superabrasive layer 3 in a bit chip 4;
This is a photograph of the organization of 1000 copies.

FIG. 4 is a table showing the whetstone radius wear amount of each whetstone of Examples and Comparative Examples.

FIG. 5 is a table showing the specific grinding resistance of each grindstone of an example and a comparative example.

FIG. 6 is a table showing the workpiece surface roughness of a work material ground by each of the grindstones of Examples and Comparative Examples.

FIG. 7 is a table showing X-ray diffraction values of an abrasive layer of an example.

[Explanation of symbols]

Length of one iron body R ₂ 3 of arc radius 2 base layer R ₁ 2 of arc radius 3 superabrasive layer 4 bits chip T 1 of the thickness D ₁ 1 of outside diameter D ₂ the outer diameter L 4 of the super-abrasive grinding wheel thickness the thickness of the X ₂ 2 width X ₁ 3 of W 4

Continuation of the front page (56) References JP-A-54-39292 (JP, A) JP-B-52-27394 (JP, B2) JP-B-43-28868 (JP, B1) JP-B-49-5717 (JP, B1) , B1) Japanese Patent Publication No. 44-28635 (JP, B1) Machines and Tools May 1985, pp. 95-104 (published by the Industrial Research Institute on May 1, 1985) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B24D 3/00 320 B24D 3/00 340 B24D 3/02 310 B24D 3/14

Claims (4)

(57) [Claims] The superabrasive grains are bound by an amorphous binder phase containing a crystalline aggregate reacted and precipitated during firing of the amorphous binder, and the crystalline aggregate comprises 15% of the binder phase. ~ 70% by volume, and the formation of the superabrasive layer, the superabrasive grains, A, B, C, D,
Mixing an amorphous binder consisting of E, F, and G with an adjusting binder obtained by adding a binder at one hour , a step of forming and charging the mixture in a mold, A step of heating and sintering, and in the step of heating and sintering, the presence of G causes a reaction to precipitate a crystalline aggregate from the amorphous binder. Abrasive whetstone. A SiO ₂ 40 to 60 wt% B Al ₂ O ₃ 8~18 wt% C B ₂ O ₃ 1~10 wt% D P ₂ O ₃ 1~6 wt% E CaO, MgO, BaO of one or more 2 12% by weight F Li ₂ O or one obtained by adding one kind of Na ₂ O and K ₂ O 1 to 6% by weight G ZrO ₂ , TiO ₂ 1 to 6% by weight 2. The superabrasive grinding wheel according to claim 1, wherein the crystalline aggregate is mainly composed of β-spodumene SS. 3. The superabrasive grinding wheel according to claim 1, wherein the superabrasive layer contains alumina abrasive grains and / or silicon carbide abrasive grains as a filler. 4. The nucleating agent is G, Zr ₂ O, TiO ₂ , the one-time binder is a dextrin aqueous solution or a synthetic resin dissolved in an organic solvent, and the crystalline aggregate is β-spodumene S. Mainly S. In the heating and firing process, the holding time at 900 to 1200 ° C is 1
The method according to claim 1, 2 or 3, wherein the time is from 5 to 5 hours.