JPH01271177A - Super abrasive grain vitrified bond grinding stone and manufacture thereof - Google Patents

Abstract

PURPOSE:To extend a life of a grinding stone improving its sharpness enhancing the grinding ratio with no deterioration of rigidity of the grinding stone by using a fine dust of 2mum or less mean grain size as the aggregate of the grinding stone. CONSTITUTION:A grinding stone mixes 15 to 55vol% super abrasive grain, 2 to 10vol% oxide fine grain of 2mum or less mean grain size, 10 to 30vol% vitrified bond and 5 to 30vol% thermo-setting resin. This mixture is molded into a desired shape and sintered at 800 deg.C to 1,050 deg.C, and the grinding stone is obtained increasing porosity, improving sharpness and enhancing grinding ratio.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention provides a super-abrasive vitrified bond grindstone with improved sharpness that does not cause clogging or fusion of cutting chips even when aggregate is added thereto, and a method for manufacturing the same. Regarding.

[Prior art] A vitrified bond grindstone has a bonding material whose main component is Si.
O□ and B 0. It is a type of whetstone in which the abrasive grains are bonded together by dissolution. It has the widest range of uses and features that are indispensable, especially for precision grinding.

In other words, continuous fit pores can be created in a planned manner.

(11) It is easy to adjust the three elements of the grinding wheel structure (abrasive grains, bonding material, and pores), fiii) heat dissipation is superior to resinoid grinding wheels, and fiv) elasticity is smaller than resinoid grinding wheels for precision processing. You can list things that are suitable for you.

Vitrified bond grinding wheels melt the binding material during firing to fuse the gaps between the abrasive grains, and exhibit a strong bond after cooling.
Its action is ultimately to hold the abrasive grains with a force suitable for the manifestation of the grinding blade, but the form of this holding must be appropriate to the elements of the structure of the grinding wheel.

The main purpose of the binder is to bond the abrasive grains together after firing, but it is important to ensure that the structure of the grindstone during forming, raw grinding, and firing remains as planned from the beginning to the finished product. A suitable auxiliary binder is required. This item has dry strength but does not affect the whetstone after firing.
Or dextrin or meriken powder that disappears during baking.

Radon powder, glue, gum arabic, methylcellulose, casein, CMC1 water glass, and others have been used.

In addition, various oxides, carbides, nitrides,
Borides are used, but in recent years diamond, which is called a superabrasive, and cubic boron nitride (hereinafter referred to as CBN) have been used.
etc. have come to be widely used.

In particular, superabrasive grains are indispensable for precision machining due to their extremely high hardness.

Since the abrasive grains themselves are extremely expensive, it is known that alumina abrasive grains and silicon carbide abrasive grains are used in combination to increase the strength of the whetstone and improve grinding performance. (Tokuko Showa 52-
3147, Special Publication No. 56-41 In addition, in order to improve machinability, pores were increased and organic adhesive was added (Special Publication No. 56-41).
6-41391), a method in which organic particles having a particle size 2 to 4 times the abrasive grain size are blended and molded and fired (JP-A-59-
Various proposals have been made, such as 161269).

However, all of these proposals have advantages and disadvantages, and the forming process, such as superabrasive grains, vitrified bond (binding material)
Mixing aggregate and filling it into a mold and press forming it, but sometimes the molding does not go well or it becomes difficult to cut out the mold, and in some cases there may be defects such as non-uniformity of pores or strength of the grindstone. Some obstacles were inevitable.

[Problems to be solved by the invention] Among the above-mentioned technologies, whetstones that use aggregate are prone to welding of chips and clogging due to the use of aggregate (and may not be sharp enough). On the other hand, the technology aimed at producing grinding wheels with high porosity has problems, such as the reduction in the strength of the grinding wheel caused by pores and the non-uniformity of pores.

Furthermore, the use of soft aggregate has been proposed to solve the problems of welding and clogging, but this is a good solution as it only partially solves the problems of welding and clogging, and only slightly improves sharpness. It is not.

[Means for Solving the Problems] It is well known that increasing the porosity reduces strength but improves sharpness, and the present invention provides a whetstone that provides good sharpness without reducing strength. .

The present inventors tackled this problem, and in order to prevent the aggregate from interfering with the work material or chips due to its high porosity and without reducing the strength of the grinding wheel, the aggregate was made into fine powder with an average particle size of Iam or less. I found a temporary solution by doing this.

Furthermore, in the molding process, in order to obtain ease of molding, ease of mold removal, and improvement of the strength of the green grindstone, thermosetting resin is used and heated to its curing temperature to harden the thermosetting resin. Ease of handling of the raw grindstone in subsequent processes was ensured. This thermosetting resin completely disappears because the grindstone sintering process is carried out in an oxidizing atmosphere, and has no effect on the grindstone after sintering.

Hereinafter, the present invention will be explained in detail along with the manufacturing method.

In the present invention, the superabrasive grains are superhard materials such as CBN and diamond, and the grain size can be applied to all those commonly used for grinding wheels. Although the use of fine powder has been particularly developed in recent years, the present invention is not limited in particle size for its purpose.

Quantitatively, it is 15-55 vol 2%. 15vol%
When the amount is smaller, there is no big difference in performance from conventional whetstones such as WASA. In addition, since the amount of vitrified bond or aggregate added naturally increases, various problems (described later) are unavoidable and disappear2.On the contrary, 55vo! ! %
Second, the amount of vitrified bond decreases and the porosity decreases, making it difficult to produce a high-porosity grindstone with good cutting performance.

Next, as the bonding material, any vitrified bond that is normally used for superabrasive grains can be used.9 The amount to be blended is 10 to 30 vol 2%. l 0vol
If it is less than %, the fixing force of the superabrasive grains is weak and the abrasive grains often fall off, making the tool unsuitable. On the other hand, 30v
If the oI is 2% or more, there will be too much bond and the whetstone will tend to foam, and even if it is formed well, the whetstone will tend to have poor sharpness.

The aggregate is oxide-based and contains alumina, mullite, zirconia, etc., and has an average particle size of approximately 2Lj, m.
Use the following fine powder.

The grain size of the aggregate is preferably 2 μm or less; if the grain size is larger than this, it will begin to interfere with the workpiece, resulting in increased grinding power and poor cutting quality.

Regarding the blending amount, it is 2 to 1 Ovo β%, and if it is less than this, the whetstone tends to foam and expand, making it difficult to manufacture a whetstone of the size specified.7 On the other hand, 1 ovo
If more than 2% I is added, the bond will not dissolve well,
Furthermore, the abrasive grains of the manufactured whetstone tend to fall off, resulting in an inferior tool.

As a result, compared to the conventional case of using aggregate with a large average particle size, both types of reinforcement are almost the same, but
During grinding, since each particle size is sufficiently fine, it is hardly involved in grinding, so there is no welding or clogging of chips that impair sharpness, and it is estimated that the cutting edge will be regenerated appropriately. As the thermosetting resin used as the binding material, ordinary thermosetting resins such as phenolic resin, furan resin, and epoxy resin can be used.However, sufficient strength cannot be obtained with the commonly used auxiliary binding materials such as dextrin and American flour. Not only is it difficult to handle the green grindstone, but it is also difficult to maintain a high porosity.

The blending amount is 5 to 30 vof2%. If it is less than 5voβ%, it will not be strong enough to maintain the raw whetstone, and 30v
o If the blend exceeds 12%, the bulk will increase, so it will have elasticity during molding, and when the pressure is released, elastic recovery will occur, causing cracking of the grindstone.6 Because thermosetting resin was used,
Heating to the curing temperature, for example, about 150 to 160°C,
If you let it harden and then cut it out from the mold, you can easily mold it and cut it out from the mold.

This green whetstone is then fired at a temperature of approximately 800 to 1050° C., although the preferable temperature differs slightly depending on the vitrified bond component used. If the temperature is lower than this, the vitrified melts poorly, and the resulting grindstone has a low ability to hold the abrasive grains, resulting in more abrasive grains falling off. On the other hand, if the temperature is too high, foaming and expansion tend to occur.

These quantitative ratios are 15 to 55 voi of abrasive grains if expressed in volume as a grindstone after firing! , %, vitrified bond 10-30 vol%, aggregate (fine powder) 2-10 vo
(1.%, pores 20-50 vol%. Raw material composition: super abrasive grains 15-55 vol%, aggregate 2-1 vol%.
0vol%, vitrified bond 10-30voβ%
, the thermosetting resin is 5 to 30 voQ%, but it seems that there is not much difference from the grinding wheel structure, probably because the thermosetting resin burns during the firing stage and becomes pores [Example 1 Below, according to the example The present invention will be explained.

(Example 1) CB N abrasive grains (SBN-B manufactured by Showa Denko, particle size 170/2
00) 25vol% and borosilicate-based vitrified bond (SiO□75%, Aff.

0.3%, B203 10%, residual alkali and alkaline earth metal oxides) 28voj2%, aggregate (alumina, average particle size 0.45μ) 7Voff% was added, and phenol resin was added as a secondary binder to 15v02 of the grinding wheel volume. CBN abrasive grains with 25% pores as raw material (25voI2%)
The ratio of vitrified bond and aggregate is that the volume ratio of the grindstone after firing is abrasive grains 25voQ%, vitrified bond 28vo12%, aggregate 7voJ2%, and porosity 40vol.
%Became. At the same time as pressure molding, the mold temperature is 150-16
It was heated until it reached 0°C. Thereafter, sintering was carried out under the condition of holding at 950° C. for 6 hours.

(Comparative Example 1) CBN abrasive grains (SUN-B manufactured by Showa Denko, particle size 170/20
Alumina WA aggregate (particle size #220) was added to 0) and borosilicate-based vitrified bond, and 5 wt% of the raw material was added with a 4% aqueous solution of gum arabic as a secondary binder. C
The ratio of BN abrasive grains, vitrified bond, and aggregate is that the volume ratio of the grindstone after firing is 25voI2% abrasive grains and 2% binding material.
8voI2%, aggregate 17vol%, pores 30vot2%
It was created by determining the blending ratio so that After pressure molding, it was sintered at 950°C for 6 hours.

(Comparative Example 2) Segments for grinding wheels were created by repeating the same manufacturing method in six or more ways except that alumina powder with an average particle size of 3 μm was used instead of the aggregate (average particle size of 0645 μm) in Example 1. This was then attached to an aluminum base using epoxy adhesive to form a grindstone. In order to examine the grinding performance, a grinding test was conducted under the following conditions.

Whetstone + 14AI type 150° x L25'x 15"
x 5'x 3Xx 76.2' Grinding machine: horizontal axis surface grinding machine (grinding wheel shaft motor 3.7KW l Work material: S to H51
H11G62~64) Surface to be ground 200mm x 100mm 5K
III fHRc62-641 Ground surface 200mX
100mm grinding method: wet plane traverse grinding wheel peripheral speed: 1500 rM/min, table speed: 1
5n+/min depth of cut: 20LL, cross feed 2rs
rs/bath grinding fluid: soluble type, 50x fluid, 9ρ
Table 1 summarizes the test results obtained when each workpiece was cut by #60cc under the above conditions.

(Left below) Table 1 Grinding ratio = Workpiece material grinding amount / Grinding wheel wear amount Grinding Power consumption (W) during grinding of the movable crab grinding wheel shaft motor (Left below) [Effect J As can be seen from the above results, It is clear that the grinding wheel of the invention requires less grinding power even though the amount of grinding is the same, and has excellent sharpness.It is also clear that the value of the grinding ratio is large, and the life of the grinding wheel is long.

That is, by pulverizing the aggregate, the aggregate is not involved in grinding, and by using a thermosetting resin in combination, the raw grinding stone is made easier to handle, and the porosity is increased to improve grindability.

The present invention completely eliminates the conventional use of aggregate, which contributes to improving the strength of the grindstone, but contributes to the grinding process and impairs sharpness.

Claims (4)

[Claims] (1) A super-abrasive vitrified bond whetstone that uses fine powder with an average particle size of 2 μm or less as the aggregate of the whetstone. (2) A superabrasive vitrified bond grinding wheel comprising 15 to 55 vol% of superabrasive grains, 2 vol% to 10 vol% of oxide fine powder with an average particle size of 2 μm or less as aggregate, 10 to 30 vol% of vitrified bond, and remaining pores. (3) 15 to 55 vol% of super abrasive grains, 2 to 10 vol% of oxide fine powder with an average particle size of 2 μm or less, 10 to 30 vol% of vitrified bond, and 5 to 30 vol% of thermosetting resin are mixed and molded to a powder of 800 to 1050 vol. A method for producing a super-abrasive vitrified bond grindstone characterized by sintering at ℃. (4) 15 to 55 vol% of super abrasive grains, 2 to 10 vol% of oxide fine powder with an average particle size of 2 μm or less, 10 to 30 vol% of vitrified bond, and 5 to 30 vol% of thermosetting resin are mixed, and molded in a mold, A method for producing a superabrasive vitrified bond grindstone, which comprises heating to 150 to 160°C, removing it from a mold, and then sintering at 800 to 1050°C.