JPS62152677A - Manufacture of grindstone - Google Patents

Abstract

PURPOSE:To remarkably increase the bending strength of grindstone and the bonding strength of abrasive grains with a binder by pressing with a hot isostatic hydraulic press a sinter containing very fine abrasive grains. CONSTITUTION:A sinter containing very fine abrasive grains comprising cubic system boron nitride and/or diamond is pressed with a hot isostatic hydraulic press for obtaining a grindstone having large bending strength. In pressing, argon, nitrogen, or helium is used as an atmosphere gas, and pressure used is 30-2,000 bar, and temperature is 500-1,200 deg.C.

Description

[Detailed Description of the Invention] [Field of Application in Junior Industry] The present invention relates to a method for manufacturing a grindstone, and more specifically, to a method for producing a grindstone, which has a strong binding force between abrasive grains and a binder, and has excellent grinding performance. The present invention relates to a method that can be obtained and is particularly useful when applied to the structure of right-pored grindstones using glassy inorganic materials as binders.

[Prior art] Grinding wheels containing extremely high hardness abrasive grains such as diamond or cubic boron nitride 3'F (CBN), so-called superabrasive grains, are suitable for grinding difficult-to-process materials such as ceramics and steel. It is prized for processing.

By the way, in general, whetstones are roughly classified into three types depending on the type of binder used to bond the abrasive grains: resin pound whetstones, metal pound whetstones, and vitrified bond whetstones. Among these, resin pound and metal pound whetstones have high density, that is, the porosity is almost zero! Because it is manufactured in a calm state, it is suitable for machining workpieces that produce small, short chips, but it is suitable for machining workpieces that produce long chips, such as steel.
When grinding material, avoid clogging and wear due to clogging! ! ! 18 etc. occur, so it is difficult to say that it is appropriate.

On the other hand, a torrefied pound grindstone uses a glassy inorganic material as a binder, and is the only grindstone that can be manufactured by adjusting the porosity. Therefore, the pores were particularly opened on the grinding surface. Due to the existence of so-called open holes, the clearance required for long chips to escape as mentioned above can be increased.
Furthermore, it is possible to suppress the generation of frictional heat caused by clogging with chips, and it is also possible to spray the cooling liquid over a wide area in the grinding area. It has many advantages, such as improved penetration into the surface of the cutting material, excellent material removal rate, and good cutting quality.

Therefore, the scope of application of vitrified bond grindstones, which are formed by bonding superabrasive grains such as diamond and CBN with glassy inorganic materials, to grinding processes is increasing significantly.

[Problems to be Solved by the Invention] A hydrophite pound grindstone having such superabrasive grains is generally manufactured as follows. That is, first, superabrasive grains, alumina, 5iC5i02. General abrasive grains such as ZrO2, a binder, and additives are stirred and mixed, pressure molded, and then fired, or a so-called hot press method is applied, in which heating and pressure molding are performed on the same side. It is done. Of these, the hot press method is more suitable for manufacturing a grindstone with a porosity close to zero, and the former method is applied to the above-mentioned porous vitrified bond grindstone.

However, although superabrasive grains such as diamond and CBN have extremely high hardness, their crystal structures are all cubic crystals with covalent bonds, so in the first place there is no interaction with other substances on the surface of the abrasive grains. Chemical bond strength is very weak. Moreover, at high temperatures, the abrasive grain itself is oxidized (in the case of diamond) or reversely transformed from a cubic crystal to a hexagonal crystal with low hardness (in the case of CBN), which increases the bonding strength between the abrasive grain and the binder. There are inconveniences such as further decrease in Therefore, there is a problem in that the superabrasive grains fall off from the grinding surface of the grindstone during grinding, significantly accelerating wear of the grindstone.

The present invention solves the conventional problems and provides a porous hydrifite pound grinding wheel containing diamond and CBN as abrasive grains, which has a strong binding force between the abrasive grains and a binder.
Moreover, it is an object of the present invention to provide a method for manufacturing a grindstone having good sharpness.

[Means for Solving the Problems] In the course of intensive research to achieve the above object, the wood inventors obtained the knowledge described below. That is, in the molded and fired body obtained by molding and firing 1 g of abrasive grains, binder, and additive, the porosity, especially the content of open pores, can be controlled to the desired value of qH; However, there is a disadvantage that the binding force between the particles and the binder is weak. Therefore, after obtaining the fired body, a treatment may be further performed to increase the bonding force between the abrasive grains and the binder without eliminating the open bores present in the fired body. The inventors discovered that hot isostatic pressing (HIP), which uses gas as a pressure medium, was suitable for such a treatment method, and after confirming its effectiveness, they completed the present invention. Ta.

That is, the method for manufacturing a grindstone of the present invention is characterized by hot isostatic pressing of a fired body containing superabrasive grains made of cubic boron nitride and/or diamond.

[Specific Description] The method for producing a grindstone of the present invention can be applied to the production of any type of grindstone, but is particularly applicable to the production of a vitrified bonded grindstone having an open bore of a predetermined Hi-. Since this is a useful method, the vitrified bond grindstone will be explained below as an example.

In the method of the present invention, first, the abrasive grains used are diamond powder, cubic boron nitride (CBN) powder, or a mixture thereof.

Among these, the type and particle size of the diamond powder are not particularly limited, and may be either natural or artificial.

Furthermore, it is preferable to use abrasive grain powder that has been subjected to the surface treatment described below, since this improves the wettability with the binder, thereby increasing the bonding force with the binder.

In other words, specific surface treatment methods include etching,
Examples include surface coating. First, etching can be performed by atmospheric oxidation, chemical acid treatment, alkali treatment, or the like.

On the other hand, in surface coating, the following substances can be cited as substances that should form a coating layer.

(1) Carbides, nitrides, borides, oxides, or mixtures thereof or mutual solid solutions of transition metals of groups 4a, 5a, and 6a of the periodic table, especially those with the following formula: MCXN, O, (only L, 0≦X ≦095.0≦y≦0.95, O≦2≦0.
9, x+y+z<0.98, M is Ti.

Zr or Hf) and/or mixture thereof, mutual solid solution (2) AL; L203. Sio2. Ceramics (3) consisting of at least one selected from MgO1CaO and B2O3 S i02 , Na20. Cab, Al103,
SiC, B203, ZnO, 20 and Li2O
The method of forming these glassy coating layers made of three or more components selected from the following is not particularly limited, and examples include physical methods such as sputtering and ion blasting, and CVD. There are chemical methods represented by CV method, and among these, CV
Method D is preferred. Moreover, it is preferable that the layer thickness of these coating layers is usually set to about 0.5 to 5 -.

If this layer thickness is less than 0.5-2, the adhesion strength between the abrasive grains and the coating layer will not be sufficient, and the effect of the HIP treatment described below will be reduced.On the other hand, if the layer thickness exceeds 5- Although the bonding strength between the material and the binder increases, the effect of the HIP treatment is not so significant due to the difference in thermal expansion coefficient between the material and the binder. More preferably, it is 1-3-.

The vitreous inorganic material used as the binder is not particularly limited, and examples include borosilicate glass, lead glass, and sodium glass.

Next, the manufacturing process of a grindstone according to the method of the present invention will be sequentially explained.

First, abrasive grains, a binder, and in addition A203. S
Auxiliary abrasive grains such as iC, 5i02, dextrin, water glass, furfural, cryolite, carbon,
Predetermined amounts of additives such as quicklime are added and mixed.

At this time, it is preferable that the proportion of the abrasive grains in the fired body obtained in the next step is 1.5 to 75% by volume. If this ratio is less than 1.5% by volume, the effect of blending the abrasive grains will not be sufficient. On the other hand, if it exceeds 75% by volume, the volume occupied by the binder phase will be significantly reduced, and the effect of the HIP treatment described below will not be achieved. I can't do it anymore. More preferably, lO
~50% by volume.

Next, the obtained mixture is formed into a predetermined shape by a conventional method and then fired. The molding pressure in this case is 1 to 5 kgf
/am2, and the firing temperature needs to be determined depending on the softening point of the binder; for example, 800°C for borosilicate glass.

For high-lead glass, it is preferable to set the value to 500'00.It is preferable that the fired body thus obtained contains 5 to 55% by volume of open bores.5% by volume of open bores are ungrooved. In this case, the abrasive grain protrusion HIB-
In addition, since the abrasive grains are firmly held by the HIP treatment, the abrasive grains do not fall off during the grinding process, resulting in the inconvenience that the sharpness inherent to vitrified bond abrasive grains is lacking and clogging is likely to occur. - On the other hand, if open bores exceed 55% by volume, the retention force of the abrasive grains will not be sufficient even after HIP treatment, and although the sharpness will be good, the degree of wear will be poor and economical. It has the disadvantage of not being accurate. A more preferable content of open bores is 15 to 35% by volume. Note that the porosity of such a fired body is limited by the particle size, grain size, blending amount, molding conditions, firing conditions, etc. of the abrasive grains.

Thereafter, the obtained fired body is subjected to HIP treatment. In this step, gases such as argon, nitrogen helium, etc. are suitable as the gas used as the pressure medium. Moreover, it is preferable to set the gas pressure to 30 to 2000 bar. When the pressure is less than 30 bar, no particularly significant effect can be obtained compared to the usual cold press method or hot press method;
If it exceeds bar, the strain during sintering will increase, and there is a strong possibility that cracks will occur. More preferably 100-10
It is 00 bar. Furthermore, the processing temperature is 500-1200
It is preferable to set it at ℃.

If this temperature is less than 500°C, the relatively high melting point binder used in the present invention will not be sufficiently sintered.

On the other hand, if the temperature exceeds 1200°C, the quality of the abrasive grains changes, and the bonding strength decreases. Note that the HIP treatment in the present invention is not intended to eliminate pores, but rather to leave pores, especially open pores, as they are and to strengthen the bonding force between the abrasive grains and the binder. Therefore, it is desirable to place the sintered body into the sintering furnace without sealing it.

In such a HIP treatment process, the closed pores inside the sintered body almost disappear under pressure, but the open pores remain as they are, so the content of oven pores in the sintered body remains almost unchanged from before the HIP treatment. Therefore, it is possible to maintain a preferable oven pore content while also making the bonding force between the abrasive grains and the binder extremely strong.

[Example] Example I CB5 powder 11+40/170 41 , 6% by weight A-203 powder trout 150 23 , 6% by weight Binder diborosilicate glass 17058 27.6% by weight Wetting agent: Water glass 7.2% by weight or more The components were mixed to form a material for the grinding layer of the whetstone.

On the other hand, the above-mentioned material for the grinding layer holder (hub) was prepared by mixing A-X 203 powder (#150), borosilicate glass, and water glass at a weight ratio of 2:120.2.

By molding these materials at a molding pressure of 3 kgf/am2 for 4 minutes, a thickness of 3 kg is formed on the entire outer peripheral surface of the disc-shaped /\b.
A molded body was obtained in which a grinding layer of mm thick was formed. The outer diameter of this product was 1ooI+++a, and the length of lJ was 5 mm. Thereafter, this molded body was heated at a temperature increase rate of 290 in a hydrogen atmosphere.
After heating at a rate of 820°C/hour and holding at 820°C for 1 hour, firing was performed by cooling at a temperature decreasing rate of 80°C/hour.

Then, the obtained fired body was subjected to HIP treatment. That is, Ar gas is used as the atmospheric gas, and the pressure is 1000.
Heating at a heating rate of 290°C/hour at 80°C
The grindstone of the present invention was obtained by maintaining the temperature at 0° C. for 1 hour and then cooling at a cooling rate of 80° C./sow.

Separately, a fired body with a shape corresponding only to the CBN layer of the grindstone, that is, an annular shape, was manufactured under the same conditions as above, and a test piece was obtained by performing HIP treatment under the same conditions. .

After that, we first perform actual grinding using the above-mentioned grindstone, and calculate the grinding ratio (=amount of wear (volume) of the workpiece material/
The wear amount (volume) of the grinding wheel and the power consumption per unit grinding amount of the work material (W/cm3) were measured, and the results are shown in Table 1. Furthermore, the open pore porosity and bending strength of the test pieces were measured, and the results are also shown in Table 1.

The grinding test conditions at this time are as follows.

Work material: JIS 5KH-57 (0, furanyl hardness C scale 65, length 100mff1, width 10mm) Grinding oil: Water-soluble oil Grinding wheel peripheral speed: 1600m/min Table feed speed: 15m/min Depth of cut: 0. 01mm/Stroke Comparative Example 1 A grindstone and a test piece were manufactured in exactly the same manner as in Example 1 above, except that HIP treatment was not performed after firing, and the same evaluation was performed on each.
Shown in the table.

Table 1 Example 2 CBN powder +1120/140 42% by weight
(Those with a Ti(C,O) coating layer of two thicknesses by applying the CVD method) Electrofused mullite 11100/120 23% by weight Binder Vitreous binder crushed product - 200#27% by weight Wetting agent: Water glass A material for the grinding layer of a whetstone was prepared by mixing 8% by weight or more of each component.

On the other hand, the above material for the grinding layer holder (hub) was prepared by mixing fused mullite (#60/140), borosilicate glass, and water glass at a weight ratio of 4 = 〇 and 2.

By molding these materials in the same manner as in Example 1 above, a molded body was obtained in which a five-layered grinding layer was formed on the outer peripheral surface of a disk-shaped hub with an outer diameter of 94 mm and a thickness of 7 mm. .

Then, in a hydrogen atmosphere.

This molded body was heated at a temperature increase rate of 290°C/hour to 770°C.
After being held at C for 1 hour, it was fired by cooling at a temperature decreasing rate of 80° C./hour.

Then, the obtained fired body was subjected to HIP treatment. That is, N2 gas is used as the atmospheric gas, and the pressure is 50 ba.
r, heated at a heating rate of 290°C/hour to 750°C.
A grindstone was obtained by maintaining the temperature at a temperature of 80° C./hour for 1 hour and then cooling at a cooling rate of 80° C./hour. Furthermore, apart from this, Example 1
A test piece was manufactured in the same manner.

The grindstone and test piece thus obtained were subjected to the same evaluation test as in Example 1, and the results are shown in Table 2.

Comparative Example 2 A grindstone and a test piece were manufactured in exactly the same manner as in Example 2 above, except that HIP treatment was not performed after firing, and the same evaluation was performed on each.
Shown in the table.

Table 2 Example 3 Diamond powder (11170/200) 44,
7wt% SiC powder (11200/230)
13, 8 wt% AfL203 powder (1200/230
) 10, 6 fff amount% Binder diborosilicate glass 22.4% by weight Additive: water glass
A grinding layer material of a grindstone was prepared by mixing 8.5% by weight or more of each component, and a grindstone and a test piece were manufactured in the same manner as in Example 1.

A grinding test was conducted on this grindstone under the following conditions.

Cutting material: Si3 N4 AfL2
03-Y2 03 series sintered body (50X50X l Om
m) (IF cutting oil: Johnson Warakuts 50x liquid Grinding wheel circumferential speed: 1500 m/min Table feed speed: 10 m/min Depth of cut: 0.01 mm/stroke The grinding ratio and power consumption in this grinding test were determined by the characteristics of the test piece. They are also shown in Table 3.

Comparative Example 3 A grindstone and a test piece were manufactured in exactly the same manner as in Example 3 above, except that HIP treatment was not performed after firing, and the same evaluation was performed on each.
Shown in the table.

Table 3 Example 4 Diamond powder CD A 1140/+70 (CVD
(TiC coating layer having a thickness of 46.3% by weight and 2 μm by applying the method) A! ; L203 powder 11150 23, 2% by weight binder diborosilicate glass t? 05B(-1124
0) 25.5% by weight Primary binder: 50% dextrin aqueous solution 5% by weight Grinding layer material and fused mullite #θO/
140, using a hub material consisting of borosilicate glass in a weight ratio of 80:20 and 50% dextrin and 5% by weight, molding, firing, and HIP treatment were carried out in exactly the same manner as in Example 1 to produce a grindstone and a test piece. .

A grinding test was conducted on this grindstone under the following conditions.

Workpiece material A: Siz N4-MgO-Y203-based sintered body (4X8X25mm+, HRA 93.0) Workpiece material B: AfL203-Tic-based sintered body ground
Oil: Water-soluble oil Grinding wheel circumferential speed: 1600 m/min Cross feed: 2 mm/pass Table feed speed: 10 m 7 min Depth of cut: 0.02 mm/stroke Measure the grinding ratio and power consumption for each of work materials A and H, The results are shown in Table 4 together with the characteristics of the test pieces.

Comparative Example 4 Grindstones were produced in exactly the same manner as in Example 4 above, except that no HIP treatment was performed after firing, and the same evaluations were performed on each of the grindstones, and the results are shown in Table 4.

Table 4 Example 5 Diamond powder 12.5 tons H, B% (m
14o/17a, 2 by ion brating
- with a TiC coating layer) CBN powder 12.5 tons4. H%('
1140/170, 2 μm A by CVD method
AM203 powder ("150") 45 hair'
j: % binder (borosilicate glass 7740) medium pore increasing agent 25% - secondary binder = 50% dextrin aqueous solution 5% by weight The above components were mixed to prepare a material for the grinding layer of a grindstone. This material was molded at a molding pressure of 1 kgf/mm2 to obtain a cylindrical molded body with an outer diameter of 25 mm, an inner diameter of 6 mm, and a thickness of 15 mm. Thereafter, this molded body was heated in a water pouch atmosphere at a temperature increase rate of 250°C/h, held at 800°C for 1 hour, and then cooled at a temperature drop rate of 60°C/hour to be fired.

Then, the obtained fired body was subjected to HIP treatment. That is, Ar gas is used as the atmospheric gas, and the pressure is 500.
Heating at a heating rate of 200°C/hour at 78°C
The grinding wheel of the present invention was obtained by holding at 0° C. for 1 hour and then cooling at a temperature decreasing rate of 60″C/hour.

A grinding test was conducted on this grindstone under the following conditions.

Work material: Wi (SKD-11, inner diameter 50+++m,
Thickness: 1010FF1 was ground.

Grinding wheel circumferential speed: 800 m/min Feed speed: 10 mm/min Depth of cut: H: 0,005 It is shown in Table 5 along with i.

Comparative Example 5 A grindstone was manufactured in exactly the same manner as in Example 5 above, except that HIF treatment was not performed after firing, and the same evaluation was performed. The results are shown in Table 5.

Table 5 [Effects of the Invention] As is clear from the above explanation, the grindstone manufactured by applying the method of the present invention is compared to the conventional grindstone because it undergoes normal firing (after which HIP treatment is applied). It was confirmed that the bending strength at the knee was significantly increased, and the bond strength between the abrasive grains and the binder was greatly increased. Moreover, the HIP
Even after treatment, the open bore in the grindstone was maintained at approximately the same number of rotations as before treatment, so there was no clogging and the slippage was extremely good. Therefore, the method of the present invention is particularly useful.

long grinding 1r
Liphipo/1: Useful when applied to the production of grindstones,
Its industrial 4 blood value is high.

Claims (5)

[Claims] (1) A method for producing a grindstone, which comprises hot isostatically pressing a fired body containing superabrasive grains made of cubic boron nitride and/or diamond. (2) The pressure of the atmospheric gas in the hot isostatic press is 30-2000 bar, and the temperature is 500-1200°C.
The manufacturing method according to claim 1. (3) The manufacturing method according to claim 1, wherein the superabrasive grains are surface-treated. (4) The manufacturing method according to claim 1, wherein the fired body contains a glassy inorganic substance. (5) The manufacturing method according to claim 1, wherein the fired body has a porosity of 10 to 55% by volume, and 95% or more of the pores are open pores.