JPH0857767A - Method for manufacturing vitrified bond grindstone with excellent grinding ratio - Google Patents

Abstract

PURPOSE: To improve a grinding ratio by applying treatment of holding a vitrified bond grinding wheel in a specific nitrogen atmosphere for the specified time. CONSTITUTION: A normal vibrified bond grinding wheel manufactured by sintering a compact obtained by mixing hard abrasive grains and vitrified bond and molding this mixture is held in a nitrogen gas atmosphere of temperature: 500-1000 deg.C and pressure: 1000-2000kg/cm<2> for l-5 hours. With the vitrified bond grinding wheel placed in such a high-temperature high-pressure nitrogen atmosphere, the surface of oxide glass forming a bond bridge becomes oxynite glass containing nitrogen, and fine pores existing in the bond bridge disappear. The grinding ratio of the grinding wheel therefore becomes high.

Description

Detailed Description of the Invention

[0001]

This invention relates to a vitrified bond grindstone obtained by combining hard abrasive grains such as cubic boron nitride (hereinafter referred to as cBN) abrasive grains and diamond abrasive grains with a vitrified bond. It is about how to improve.

[0002]

2. Description of the Related Art Generally, vitrified bond wheels are
It is well known that the strength of the bond bridge has a great influence on the strength of the grindstone because the abrasive grains such as cBN are connected by a glass bond bridge. In order to improve the strength of this bond bridge and obtain an excellent vitrified bond grindstone, (a)
A method in which cBN abrasive grains and vitrified bonds containing zircon crystal grains are mixed and fired at a temperature of 950 ° C. or lower in a nitrogen atmosphere (see JP-A-54-39292).
(B) cBN abrasive grains and a vitrified bond containing lithium fluoride are mixed and the temperature is 1200 to 1 in a nitrogen atmosphere.
A manufacturing method such as a method of firing at 300 ° C. (see JP-A-57-54077) has been proposed.

[0003]

However, in recent years, in the field of grinding as well, there is a demand for higher efficiency, so that it has become necessary to grind under severer conditions, and conventional vitrified bond grindstones are used. It has not been possible to obtain a high-strength vitrified bond grindstone which cannot sufficiently deal with the above problem and has an excellent grinding ratio capable of withstanding heavy grinding.

[0004]

Therefore, the present inventors have
As a result of research to develop a vitrified bond grindstone having an excellent grinding ratio capable of withstanding heavy cutting under such severe conditions, the vitrified bond grindstone manufactured by the conventional method has a temperature of 500 to 1000 ° C. and a pressure of 1000 to 1000 ° C. 20
When a treatment (hereinafter referred to as HIP treatment) of holding for 1 to 5 hours in a nitrogen atmosphere of 00 kg / cm ² is applied, the strength is improved,
Furthermore, they have found that the grinding ratio is significantly improved.

The present invention has been made on the basis of the above findings, and is characterized by a method for producing a vitrified bond grindstone having an excellent grinding ratio by subjecting a normal vitrified bond grindstone to the above HIP treatment.

The reason for limiting the conditions of the HIP processing of the present invention as described above will be described.

(A) Atmosphere, temperature and pressure Abrasive grains and vitrified bonds are mixed and mixed, then shaped, and the resulting molded body is sintered to produce a normal vitrified bond grindstone at a temperature of 500 to 1000 ° C. pressure:
Holding in a nitrogen gas atmosphere of 1000 to 2000 kg / cm ² improves the bending strength of the abrasive grains and the bond bridge glass connecting the abrasive grains, and improves the bending strength and the grinding ratio of the grindstone itself. The reason is that when a vitrified bond grindstone is placed in the nitrogen atmosphere of high temperature and high pressure, the surface of the oxide glass forming the bond bridge becomes an oxynite glass containing nitrogen and the fine pores existing in the bond bridge disappear. Therefore, it is considered that the bending strength and the grinding ratio of the grindstone are improved.

However, the pressure in the nitrogen gas atmosphere is 100
If the pressure is less than 0 kg / cm ² and the temperature is less than 500 ° C, the desired strength cannot be obtained. On the other hand, if the pressure exceeds 2000 kg / cm ² , a large device is required, which is costly. If the temperature is maintained at a certain temperature, the bond will be re-melted and the strength will not be improved, which is not preferable.

Therefore, the HIP processing conditions of the present invention are as follows: temperature: 500 to 1000 ° C., pressure: 1000 to 20
It is preferable to keep it in a nitrogen atmosphere of 00 kg / cm ² . More preferable conditions of the HIP treatment of the present invention are temperature: 700 to 900 ° C., pressure: 1200 to 1500 kg /
It is to keep in a nitrogen atmosphere of cm ² .

(B) Holding Time The HIP processing time of the present invention varies depending on the shape, thickness, size, etc. of the grindstone to be HIP processed, but if it is less than 1 hour, the desired strength improving effect cannot be obtained, and 5 Even if it is held for a long time exceeding the time, no further improvement in strength is observed, and it is costly, which is not preferable. Therefore, it is suitable to hold for 1 to 5 hours.

[0011]

Example Vitrified binders a to d having the composition shown in Table 1 were prepared.

[0012]

[Table 1]

Further, in each case, cBN abrasive grains having an average particle diameter of 100 μm, abrasive grains such as diamond abrasive grains, and polyvinyl alcohol (hereinafter referred to as PVA) as a forming binder were prepared.

The vitrified binders a to d shown in Table 1 and the above abrasive grains were mixed in the proportions shown in Table 2, and 1% by weight of PVA was mixed as a molding binder, and then the length was 45.
mm, width: 13 mm, thickness: 5 mm, and a fan-shaped molded body having a curvature of 100 R was molded, and each molded body was degreased under the conditions shown in Table 2 and subsequently the conditions shown in Table 2. By firing, to obtain segmented sintered bodies A to D shown in Table 2 by the conventional methods 1 to 4.

[0015]

[Table 2]

After measuring the bending strength of the segment sintered bodies A to D shown in Table 2 obtained by the conventional methods 1 to 4,
The segment sintered bodies A to D were subjected to the HIP treatment under the conditions shown in Table 3 under a nitrogen atmosphere, and then the bending strength was measured again. The results are shown in Table 3.

Next, a cylindrical base metal (outer diameter: 190 mm, inner diameter: 50.8 mm, thickness: 13 mm) made of SKD-11 was prepared, and this base metal was subjected to the above HIP treatment.
The segment sintered bodies A to D according to No. 12 and the segment sintered bodies A to D according to the conventional methods 1 to 4 not subjected to the HIP treatment were adhered with an adhesive to manufacture a vitrified bond wheel. This vitrified bond wheel is attached to a surface grinder, and the material to be ground: SKD-11 (hardness: HRC50) square material, grinding wheel peripheral speed: 1500 m / min., Table feed speed: 5 m / min., Depth of cut: 5 μm, grinding Liquid: Equivalent to JISW 2 types, wet surface plunge grinding is performed, and the grinding resistance immediately after grinding is evaluated by measuring the spindle current value of the grinder. Generally, as the grinding wheel approaches its life, the roughness of the surface to be ground becomes larger. The surface roughness R of the surface to be ground
The amount to be ground until a (specified by JIS standard) reaches 0.6 μm was measured, and the grinding ratio was calculated based on the result, and these results are also shown in Table 3.

[0018]

[Table 3]

[0019]

From the results shown in Table 3, the present invention methods 1 to
Comparison of the segment sintered body A subjected to the HIP treatment of No. 3 and the segment sintered body A according to the conventional method 1 not subjected to the HIP treatment, and the segment sintered bodies B and HIP subjected to the HIP treatment of the present invention methods 4 to 6 Comparison with segment sintered body B according to conventional method 2 without treatment, segment sintered body C subjected to HIP treatment according to methods 7 to 9 of the present invention and segment sintered body C according to conventional method 3 not subjected to HIP treatment. Comparison of the present invention method 10
12 HIP-treated segment sintered bodies D and HIP
When compared with the segment sintered body D according to the conventional method 4 which is not treated, the bending strength of the segment sintered body is improved and the grinding resistance immediately after grinding is reduced by the HIP treatment of the method of the present invention. It can be seen that the grinding ratio is greatly improved.

Therefore, according to the method of the present invention in which the HIP treatment is performed, it is possible to provide a vitrified bond grindstone which is more excellent than the conventional one, and to exert an industrially excellent effect.

[Procedure amendment]

[Submission date] January 23, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

Claims (1)

[Claims] 1. A normal vitrified bond grindstone obtained by mixing vitrified bond and hard abrasive grains, shaping and sintering, and temperature: 500 to 100 ° C., pressure: 1000 to 2000 kg.
A method for producing a vitrified bond grindstone having an excellent grinding ratio, which is characterized by performing a treatment of holding in a nitrogen atmosphere of / cm ² for 1 to 5 hours.