JPH10296637A - Super abrasive grain grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the grinding property of a polycrystal diamond sintered body (PCD), a polycrystal cubic boron nitride sintered body (PCBN), etc. SOLUTION: This is super abrasive grain grinding wheel comprises diamond abrasive grains sintered with glass or ceramic bond and comprises abrasive grains of 25 to 40 vol%, bond of 60 to 75 vol%, which comprises glass of 66 to 99 vol%, hexagonal boron nitride (h-BN) of 1 to 17 vol% and Sic of 0 to 15 vol%. In this case, the total amount of super grains sic and h-BN is 50 vol% or less, bond in which crystallized glass of 0 to 50 vol% is contained and h-BN whose average diameter is 20 μm or less are employed. The bond is properly broken into fine pieces due to the lubricity of h-BN, as a result, due to the self production of blades of abrasive grains and chip removing work, even PCDs and PCBNs can smoothly cut.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superabrasive grinder for grinding ultra-hard materials such as polycrystalline diamond sintered compact (PCD) and polycrystalline cubic boron nitride sintered compact (PCBN). However, it can be widely applied to grinding of hard metals, ceramics, cermets, glass, and other hard materials.

[0002]

2. Description of the Related Art PCD plays an important role in all fields where natural diamond has been used in the past. Fine and uniform diamond powder is placed on a cemented carbide base and subjected to ultra-high pressure. It is a polycrystalline body sintered at a high temperature and free from the disadvantage that it is brittle in a certain direction like natural diamond, and is a homogeneous and extremely tough polycrystalline body.

[0003] Further, PCBN was invented to solve the weak point that diamond easily reacts with an iron group metal, and a powder of cubic boron nitride (CBN) was formed by PCD.
It was sintered in the same manner as described above.

[0004] These PCD and PCBN are made of cemented carbide,
Since it has excellent physical properties such as higher wear resistance, higher fracture toughness and higher Young's modulus than ceramics, it is used as a cutting tool material and abrasion resistant tool material. According to the usage mode, it is cut into an appropriate size according to the purpose of use, and is fixed to a steel shank or a cutter body to be used as a cutting tool or the like. At this time, the shape of the cutting edge is often finished by grinding with the cemented carbide of the base in accordance with the machine to be used, the material to be processed, and the processing conditions.

[0005] This cutting tool has excellent wear resistance, so its service life is several tens of times longer than that of cemented carbide cutting tools. However, the cutting edge wears out as it is used and the cutting efficiency is reduced. Polishing is required. This re-polishing is
Since the hardness of a CD or the like is high, a long time is required for grinding. This processing is performed using a specially designed high-precision, high-rigidity grinding machine.

For the grinding, a special metal bond diamond wheel or a resin bond diamond wheel to which metal powder is added as a filler is generally used.
However, since the main components of PCD and PCBN are hard materials such as diamond, the hardness of the grindstone is almost the same as that of the workpiece, and the grindstone is severely blinded and clogged, requiring frequent dressing.

Japanese Patent Publication No. 56-41391 discloses a grindstone in which a required amount of superabrasive grains are bonded and fired by vitreous material.

[0008]

The whetstone described in the above publication has improved blindness and clogging as compared with special metal bond diamond whetstones and resin bond diamond whetstones, but it requires higher work efficiency. Today, more improvements are desired.

Japanese Patent Application Laid-Open No. 1-289668 discloses the idea that h-BN is blended in a vitrified binder to smoothly discharge chips and prevent clogging. It is shown.

An object of the present invention is to make it possible to grind ultra-hard materials such as PCD and PCBN more smoothly in consideration of the amount of h-BN added to the binder.

[0011]

In order to achieve the above object, the present invention provides a superabrasive grain grindstone obtained by sintering a superabrasive grain with a vitreous or ceramic binder. 25-40 vol (volume)% of the particles, 60
７５75 vol%, and the binder is 66 vol.
1% to 99% by volume, 1 to 17% by volume of h-BN, S
The iC is comprised of 0 to 15 vol% (claim 1).

As described above, when h-BN is added, due to its lubricating property, the binder is appropriately broken (the binder near the closed superabrasive grains is minutely broken), and the superabrasive grains are spontaneously generated. The cutting action and the removal of chips are performed, and smooth grinding can be performed. At this time, if the h-BN is less than 1.0 vol%, the action such as the spontaneous blade generation is not exhibited, and conversely, 17 v
When the amount exceeds ol%, the amount of material removed increases, but the wear of the grindstone becomes severe, chipping of the work and uneven wear of the grindstone easily occur, and the grinding ratio ((volume of material shaved by the grindstone)) ÷
(Wear volume of the grindstone)) is significantly reduced (see Examples).

If the superabrasive grains are less than 20 vol%, the degree of concentration of the superabrasive grains is too low, so that smooth grinding is not performed.
If it exceeds 0 vol%, the superabrasive grains are too dense, and the spontaneous blade generation is not performed smoothly, and clogging is likely to occur.

[0014] SiC is added as an aggregate to substitute for superabrasive grains, and if it exceeds 15 vol%, the concentration of the superabrasive grains decreases, which is not preferable.

The total amount of the superabrasive grains, SiC and h-BN is preferably 50 vol% or less (claim 2). When the total amount exceeds 50 vol%, the holding power of the superabrasive grains decreases, and the grinding wheel wears. Becomes intense.

The above-mentioned glass for the binder is made of crystallized glass (for example, ulmite: 2ZnO.SiO ₂ ) in an amount of 0 to 50 vol.
% (Claim 3), the crystallized glass has high mechanical strength even at a high temperature,
Since it has a thermal expansion coefficient close to that of BN abrasive grains, high retention of superabrasive grains can be obtained.

When the h-BN has an average particle size of 20 μm or less (claim 4), smooth lubrication can be obtained, and the action of self-generated cutting and prevention of clogging becomes smoother. .

If the super-abrasive grains are diamond abrasive grains,
It is very effective for grinding a polycrystalline diamond sintered body or a polycrystalline cubic boron nitride sintered body. That is, depending on the amount of h-BN added, PCD, PB
Grinding of CN can be performed smoothly.

[0019]

【Example】

Diamond abrasive grains: After mixing Examples 1 to 5 and Comparative Examples 1 and 2 at a mixing ratio shown in Table 1 with a concentration of 150 at $ 2000, using a mixer, the mixture was filled in a mold in the same manner as in the prior art. Baking under pressure, outer diameter: 150mm, thickness: 15mm
Were manufactured respectively. At this time, h-BN had an average particle size of 5 μm, and ulmite 20v was used as a solid component.
% of crystallized glass powder was used.

Next, for Examples 1 to 5 and Comparative Examples 1 and 2, a cutting speed (forced cutting): 0.4 mm / min, a processing time: 10 min, and a grinding wheel peripheral speed: 942 m / min, rocking width: 11 mm, grinding fluid: JISW 2 types 2%
Table 1 shows the actual cutting depth / set cutting depth × 100 (%), grinding resistance (Fn), and grinding ratio when grinding a PCD (3.2 × 0.5 mm thick, 1300 series made by GE). Shown in

[0021]

[Table 1] According to the experimental results, in each example, (actual cutting amount / set cutting amount) was twice or more and grinding resistance was reduced from 1/7 to nearly 1/40 as compared with Comparative Example 1 (conventional example). However, the grinding ratio does not decrease so much. On the other hand, in Comparative Example 2, h-BN was 18 vol%
In this case, the grinding ratio was remarkably reduced, and the wear of the grindstone was large, so that large chipping due to the wobble of the grindstone surface occurred. For this reason, the addition amount of h-BN is 17 vol% or less.

As described above, each of the examples is different from the comparative example 1.
In Example 2 shown in FIG. 1, and 2000 times of the grinding surface photographs of Comparative Example 1 shown in FIG.
Is after dressing, (b) is after processing,
Example 2 shows that the diamond abrasive grains protrude even after processing, whereas Comparative Example 1 is severely clogged.

[0023]

As can be understood from the above description, the present invention can provide h-BN at a required mixing ratio of superabrasives and binder.
Is added, so that a superabrasive grindstone having good grinding characteristics, which has not been obtained conventionally, can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photograph of a grinding surface of one embodiment, (a) after dressing and (b) after working.

FIGS. 2A and 2B are photographs of a grinding surface of a conventional example, wherein FIG. 2A shows a state after dressing and FIG.

Claims (5)

[Claims] 1. A superabrasive grindstone obtained by sintering superabrasive grains with a vitreous or ceramic binder, wherein the superabrasive grains are 25 to 40% by volume and the binder is 60 to 60%.
75 vol%, and the binder is 66 vol.
% To 99 vol%, 1 to 17 vol.
% And SiC of 0 to 15 vol%. 2. The superabrasive grinding wheel according to claim 1, wherein the total amount of said superabrasive, SiC and hexagonal boron nitride is 50 vol% or less. 3. The binder glass according to claim 1, wherein the glass contains 0 to 50 vol% of crystallized glass.
The superabrasive grindstone described in 1. 4. The hexagonal boron nitride has an average particle size of 20.
4. The superabrasive grindstone according to claim 1, wherein the diameter is not more than μm. 5. The method according to claim 1, wherein the superabrasive grains are diamond abrasive grains, and are used for grinding a polycrystalline diamond sintered body or a polycrystalline cubic boron nitride sintered body. The superabrasive grinding wheel according to any one of the above.