JP2009248207A - Vitrified grinding wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vitrified grinding wheel for increasing an abrasive grain supporting force, reducing grinding resistance and suffering from little wear of the grinding wheel while not impairing characteristics of abrasive grains, causing no broaching and securing a silicic acid (SiO<SB>2</SB>) ingredient amount sufficient for resistance to chemical or the like. <P>SOLUTION: The vitrified grinding wheel is made of a low melting boric acid soda (B<SB>2</SB>O<SB>3</SB>-Na<SB>2</SB>O-SiO<SB>2</SB>)-based glass phase with a high melting silicic acid (SiO<SB>2</SB>)-based glass phase eutectically melted as a split phase together with a flux. An appropriate amount of the high melting silicic acid glass phase is eutectically melted in the low melting boric acid soda glass phase and further the flux is added, whereby dissolution progresses. Thus, the grinding wheel with a long service life is obtained, which improves fusion with the surface of the abrasive grains without broaching (bubbling), has low expansion properties, obtains a grinding wheel characteristic value with a large abrasive grain supporting force and grinding wheel strength, is excellent in chemical resistance though baked at a low temperature, has not only a low grinding resistance but also a high wear resistance, an excellent grinding ability, high efficiency and a large grinding ratio. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vitrified grinding wheel that requires high-precision and high-efficiency grinding performance, such as internal grinding for bearing processing, and a method for manufacturing the same.

  Many internal grinding operations in bearing processing using vitrified grinding wheels employ a constant pressure grinding method in which the grinding force is controlled rather than a constant speed grinding method in which general cutting is performed at a constant speed. In this method, since the cutting speed changes depending on the grinding power, a high-performance grindstone with low grinding resistance and excellent grindability is required for high-efficiency grinding.

  In so-called “grinding start” grinding wheel shape correction (truing) and reworking (dressing), truing is possible with a small grinding wheel correction amount, that is, a long-life grinding wheel with a large workability in one dressing. There is a strong demand for grindstone performance that is required and easy to dress.

  In particular, the grinding wheel use condition when high-precision and high-efficiency grinding is required in bearing processing or the like is high-speed grinding with a grinding wheel peripheral speed of 40 to 60 m / s. Is also an important technical issue.

Further, in order to securely hold the abrasive grains in the grindstone, the bonding material (bond) needs to go through a liquid phase and then become a solid phase, and is fired. The firing temperature may be high temperature firing such as 900 ° C. to 1200 ° C. or higher.
The vitrified bond is a silicate glass that is finally made from a siliceous raw material as a main raw material. For example, when high-temperature firing at 1200 ° C. or higher is performed, a molten glass is used for a high-melting siliceous bond. A small amount of fluxing agent is added to promote the conversion. Common fluxes include boric acid (B ₂ O ₃ ) and modified oxides (R ₂ O, RO), etc., which dissolve first at a low temperature to form a liquid phase, and together with other raw materials silicic acid (SiO 2 ₂ ) Vitrification is promoted (Patent Document 1).

By the way, CBN abrasive grains used for high-performance grindstones show chemical and physical changes at a high temperature of about 900 ° C. or higher in an oxidizing (in air) atmosphere.
That is, CBN abrasive grains are subjected to sintering changes due to bonding solidification or surface alteration of the abrasive grains, changes in heat balance due to endothermic and exothermic reactions to the oxidation of the abrasive grains, changes in weight due to increased oxidation, and particle size analysis after grinding with a rocking ball mill. Since a decrease in abrasive strength is recognized, the grinding wheel manufacturing process for firing at a high temperature of 900 ° C. or higher, for example, 900 to 1000 ° C., is performed in a non-oxidizing or inert atmosphere.

  In addition, as a vitrified bond that is fired at a low temperature of 1000 ° C. or lower, there is a low-melting frit bond, which is a high-melting siliceous raw material with a large amount of flux added, melted into a glass state, and then cooled. After that, it was manufactured by pulverization.

JP 2004-188567 A

  However, in order to avoid abrasive grain damage due to high-temperature baking at 1200 ° C. or higher as described above, baking in an inert atmosphere or a low-oxygen reducing atmosphere while avoiding an oxidizing atmosphere leaves organic matter in the bond, and broaching. This results in a problem that the adhesive strength, that is, the holding power of the abrasive grains is lowered.

In addition, if a large amount of flux is used in order to fire the vitrified bond in an oxidizing atmosphere at the lowest possible temperature, the silicic acid (SiO ₂ ) component will be relatively reduced, which results in bond strength and chemical resistance (acid, (Alkali) properties are reduced, and the thermal expansion coefficient is increased, the difference in expansion from the abrasive grains is increased, and the abrasive support force is weakened. As a result, the obtained vitrified grinding wheel has a low grinding resistance, but wear resistance There is a problem that it becomes many.

  Moreover, in low temperature firing, the viscosity of the melted bond increases and the surface tension increases, so that there is a problem that the reaction area with the abrasive grains becomes small and the fusion force decreases.

Therefore, the object of the present invention is to solve the above-mentioned problems, and to ensure a sufficient amount of silicic acid (SiO ₂ ) component for chemical resistance, etc. without impairing the characteristics of the abrasive grains, without broaching. On the other hand, a vitrified grinding wheel having a large abrasive grain supporting force, a small grinding resistance and a small grinding wheel wear is to be obtained. That is, it is an object to provide an excellent vitrified grinding wheel capable of satisfying ideal characteristics of low grinding energy, small grinding wheel wear, and high grinding ratio.

In order to solve the above-mentioned problems, in the present invention, in a vitrified grinding wheel formed by bonding abrasive grains with vitrified bonds, the vitrified bonds are low-melting sodium borate (B ₂ O ₃ —Na ₂ O—). The vitrified grinding wheel is composed of a SiO ₂ ) glass phase and a high-melting silicic acid (SiO ₂ ) glass phase that is eutectic as a phase separation together with a flux.

The components of the low-melting bond forming the low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) -based glass phase are 45 to 50% by weight of SiO ₂ and B ₂ O ₃ 25 to 25%. The composition is composed of 30% by weight of the formed oxide, 5 to 10% by weight of Al ₂ O ₃ and 15 to 25% by weight of the following RO and R ₂ O.

The high-melting bond forming the high-melting silicic acid (SiO ₂ ) -based glass phase is composed of 60 to 65% by weight of SiO _{2 and} 0 to 5% by weight of B ₂ O ₃ to form an oxide, Al _2. It consists of a frit bond consisting of an intermediate oxide of 15 to 20% by weight of O ₃ and a modified oxide of the following RO and R ₂ O of 10 to 20% by weight or a mixed bond of natural minerals and additives. 10 to 30% by weight.
RO is at least one oxide selected from the group consisting of CaO, MgO, BaO and ZnO, and R ₂ O is at least Na selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O is one or more oxide containing _{2 O.}

Moreover, as said flux, a metal chloride, a metal fluoride, or an alkali nitrate is mentioned as a preferable thing.
One or more kinds of abrasive grains selected from cubic boron nitride (CBN), diamond (SD), aluminum oxide (Al ₂ O ₃ ), and silicon carbide (SiC) can be adopted as preferred abrasive grains for high-precision internal grinding. .

The vitrified grinding wheel of the present invention configured as described above has a high-melting silicic acid (SiO ₂ ) in a glass phase composed of a low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) system. ₂ ) An appropriate amount of the system bond is eutectic. A flux is added to this to promote vitrification of the eutectic phase.
A low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) -based bond is combined with 10-30% by weight of a high-melting silicic acid (SiO ₂ ) -based bond as a separated (separated) phase. By fusing, it becomes possible to obtain a characteristic bond excellent in low expansibility as abrasive grain support (adhesion) strength, bond strength, and chemical resistance.

The reason for blending 10-30 parts by weight of the high-melting silicic acid (SiO ₂ ) -based bond with respect to 100 parts by weight of the low-melting bond is that the blending amount of the high-melting bond with respect to the low-melting bond is 10 parts by weight. In the case of less than less, the silicate glass phase drops into the sodium borate glass phase and melts into a glass phase rich in sodium borate, resulting in deterioration of chemical resistance (acid, alkali), This is because the thermal expansion coefficient is increased, the thermal expansion difference from the abrasive grains is increased, and the abrasive grain support strength is weakened. As a result, the grinding ratio is reduced and the grinding wheel life is shortened. In addition, when the compounding amount of the high-melting bond exceeds 30 parts by weight, the vitrification of silicic acid (SiO ₂ ) is delayed, but the chemical resistance is improved, but the fusion strength with the abrasive grains is weakened and the grindstone strength is lowered. As a result, the wear of the grinding wheel is increased and the grinding ratio becomes small, so that a high-performance grinding wheel cannot be obtained.

Then, as the method for manufacturing such a grinding _wheel, SiO 2 45 to 50 _{wt%, B} 2 O 3 25 to 30 wt% of the formed _oxide, Al ₂ O 3 5 to 10 wt% of the intermediate oxide and below Of SiO ₂ and R ₂ O 15 to 25 wt% modified oxide consisting of 15 to 25 wt% of low-melting bond, SiO ₂ 60 to 65 wt%, B ₂ O ₃ 0 to 5 wt% forming oxide, Al 10 to 30 parts by weight of a high-melting bond comprising 15 to 20% by weight of an intermediate oxide of ₂ O _{3 and 10 to} 20% by weight of a modified oxide of RO and R ₂ O is prepared, and further 100 weights of the prepared bond After mixing 1 to 8 parts by weight of the flux and abrasive grains with respect to the part, the mixture is molded and dried, and then fired at a maximum temperature of 650 to 800 ° C. in an oxidizing atmosphere.

  The vitrified grinding wheel thus manufactured realizes a high-performance CBN internal grinding wheel with high strength and low grinding resistance by adding a predetermined amount of high-melting siliceous bond to a low-melting bond. .

Further, by setting the firing temperature to a low temperature of 800 ° C. or less, the abrasive grains such as CBN abrasive grains are not damaged even by the oxidation firing, but rather, the strength of the raw grinding stone is obtained by making the oxidizing activation atmosphere. The temporary binder as an imparting agent, organic substances such as during bonding or pore material are oxidized and burned at 300 to 500 ° C. or less at which sintering starts, and a bond base without broaching (polyfoaming) becomes possible. At the same time, the effect of residual carbide on the abrasive grain surface is improved, and the bond adhesive strength is increased.
In addition, there are advantages such as energy saving by low-temperature firing, environmental improvement by increasing the number of simultaneous firing grindstones by oxidation firing, economic efficiency, and productivity.

Since this invention is a vitrified grinding wheel in which a predetermined amount of a high-melting silicate glass phase is co-melted with a flux as a phase separation into a low-melting sodium borate glass phase, the characteristics of the abrasive grains Grinding resistance is reduced without impairing, no broaching, and while maintaining the amount of silicic acid (SiO ₂ ) component with excellent chemical resistance, the abrasive grain support is increased and the grinding wheel wear is reduced. There exists an advantage used as the vitrified grinding wheel which has performance.

In addition, in the invention as a manufacturing method of a vitrified grinding wheel in which abrasive grains, a predetermined low-melting bond and a high-melting bond and a flux are mixed, formed, dried, and fired at a predetermined temperature in an oxidizing atmosphere,
There is an advantage that an excellent vitrified grinding wheel having the ideal characteristics of low grinding energy, small grinding wheel wear, and high grinding ratio can be produced.

  The vitrified grinding wheel as an embodiment of the present invention uses the following raw materials (1) to (4), that is, 10 to 30 parts by weight of a high-melting bond with respect to 100 parts by weight of a low-melting bond. After blending (same as blending), and after mixing 100 parts by weight of this blended bond with 1 to 8 parts by weight of flux and a predetermined amount of abrasives according to the application, molding and drying the mixture It can be manufactured by firing at a maximum temperature of 650 to 800 ° C. in an oxidizing atmosphere.

The resulting vitrified grinding wheel is composed of 100 parts by weight of a low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) glass phase and a high-melting silicic acid (SiO ₂ ) glass phase of 10 to 10 parts by weight. A compounded bond containing 30 parts by weight is used, and abrasive grains are bonded with a vitrified bond in which 1 to 8 parts by weight of a flux is compounded with respect to 100 parts by weight of this compounded bond. Sodium furate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) -based glass phase and a high-melting silicic acid (SiO ₂ ) -based glass phase are eutectic together with a flux as a phase separation .

(1) Low fusibility bond (A)
The low-melting bond is softened or melted at a temperature lower than the calcination temperature of 650 to 800 ° C. in the present invention. The bond composition is as follows: SiO ₂ 45-50% by weight of formed oxides shown in Table 1 below, 25-30% by weight of B ₂ O ₃ 25%, Al ₂ O ₃ 5-10% by weight of intermediate oxides, and modified oxide RO , R ₂ O is 15 to 25% by weight. These mixtures are considered to become a sodium borate glass phase (B ₂ O ₃ —Na ₂ O—SiO ₂ ) upon melting. Since the low-melting bond contains a large amount of boric acid (B ₂ O ₃ ) and modified oxides (RO, R ₂ O), it is preferable to use a frit bond with little variation in bond components.
Incidentally, RO is at least one oxide selected from the group consisting of CaO, MgO, BaO and ZnO, and R ₂ O is at least selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O. One or more oxides containing Na ₂ O.
The low-melting bond alone is preferable because the abrasive support strength is weak and the chemical resistance (acid, alkali) is poor, and the grinding resistance is low, but the grinding wheel wear is large and the grinding ratio (grinding amount ÷ grinding wheel wear amount) is small. Whetstone performance cannot be obtained.

(2) High melt bond (B)
The softening or melting temperature of the high-melting bond is higher than the grinding stone firing temperature of 650 to 800 ° C.
Bond composition, _SiO 2 60 to 65 _wt% shown in Table 1 above, _{B 2} O 3 0 to 5 wt% of the formed _oxide, an intermediate oxide of Al ₂ O 3 15 to 20 wt% and 10-20 wt % Of a modified oxide (RO, R ₂ O).
As the high-melting bond, a frit bond or a natural mineral mainly composed of silicic acid (SiO ₂ ) and an additive may be used. Such a high-melting bond is preferably blended in an amount of 10 to 30% by weight in the low-melting bond.

(3) Fusing agent Bonding softening temperature at which the grinding stone starts to be sintered is 500 to 650 ° C or less, and by selecting a fusing agent having a decomposition temperature and a melting temperature, broaching (polyfoaming state) by the progress of sintering without decomposition is performed. It becomes a dense bond substrate without being generated.

The flux in the bond melts early at a low temperature and dissolves other components. The solid reaction causes diffusion to increase the adhesion to the abrasive grains. The bond becomes low viscosity and the foamed product has a foamy state (broaching). ) Does not occur.
In other words, at a low grinding temperature of 650 to 800 ° C., the flux accelerates the bond fusion to the abrasive grain surface, lowers the bond surface tension and increases the reaction area between the bond and the abrasive grain. A high-performance grindstone with not only low grinding resistance but also small grinding wheel wear and a large grinding ratio is provided by increasing the abrasive grain support force and grindstone strength.

  The flux used in this invention is metal chloride (zinc chloride, lithium chloride, etc.), metal fluoride (lithium fluoride, potassium fluoride, sodium fluoride, etc.), alkali nitrate (sodium nitrate, potassium nitrate, etc.) or other Examples thereof include lithium compounds (lithium carbonate, lithium phosphate, etc.).

When a small amount of the flux is added to the preparation raw material, it dissolves first to form a liquid phase, and the vitrification of silicic acid (SiO ₂ ) is promoted together with other raw materials. For the same reason, excessive addition of flux causes rapid melting of the glass, leading to bond erosion and deterioration of the grindstone strength. On the other hand, when the amount is too small, the molten glass component becomes insufficient and the strength of the grindstone becomes weak.

The flux is added in an amount of 1 to 8 parts by weight per 100 parts by weight of the prepared bond. 3 to 8 parts by weight of metal chloride and 1 to 3 parts by weight of metal fluoride and alkali nitrate or lithium compound.
When the blending amount of the flux is as small as 1 part by weight or less than 3 parts by weight, the bond becomes highly viscous due to the delay in melting, and pores remain in the important binder to hold the abrasive grains, so that the final state is broached. In particular, the adhesion force to the abrasive grains is reduced, and as a result, the hardness or strength of the grinding wheel is statically reduced, and the grinding ratio is low although grinding resistance is high and grinding resistance is low.
On the other hand, when the blending amount of the flux exceeds 3 or 8 parts by weight, the softening temperature or melting temperature of the bond decreases, the grindstone becomes similar to overfire, and the bond wettability to the abrasive grain surface is good. However, the hardness of the grinding wheel remarkably fluctuates due to the disturbance of the internal structure of the grinding wheel, the strength of the grinding wheel is weakened, and the performance of the grinding wheel deteriorates rapidly.

(4) Vitrified bond (low fusibility-high fusibility)
a) Compound Bond In this invention, 10 to 30 parts by weight of the high-melting bond is blended with 100 parts by weight of the low-melting bond.
Furthermore, 1 to 8 parts by weight of a flux is prepared with respect to 100 parts by weight of the bond thus formulated. The thus prepared bond is eutectic and vitrified at a grinding stone firing temperature of 650 to 800 ° C. or lower.
When the blending amount of the high-melting bond with respect to 100 parts by weight of the low-melting bond is less than 10 parts by weight, the softening temperature or melting temperature of the prepared bond is lower-temperature melting with respect to the grinding wheel firing temperature of 650 to 800 ° C. A bond component rich in a low-melting bond with a small amount of a silicic acid (SiO ₂ ) component and a large amount of a base component serving as a melting agent such as boric acid (B ₂ O ₃ ) and a modified oxide (RO, R ₂ O) As a result, the thermal expansion coefficient is increased, the difference in expansion from the abrasive grains is increased, and the abrasive grain supporting force is weakened. And chemical resistance also deteriorates. For this reason, although grinding resistance becomes low, grinding wheel wear is large and the grinding ratio becomes small, and a high-performance grindstone cannot be obtained.
When the blending ratio of the high-melting bond exceeds 30 parts by weight with respect to 100 parts by weight of the low-melting bond, it becomes a compounded bond with a large amount of silicic acid (SiO ₂ ) component, the softening or melting temperature becomes high, and the vitrification of the raw material is insufficient. Thus, although the abrasive grain supporting force is weak and the grinding resistance is low, the grinding wheel wear is large and the grinding wheel life is short. In addition, the melt bond has a high viscosity, the adhesion force with the abrasive grains is weak, the grinding ratio is small, and the high-performance grindstone cannot be satisfied.

b) Fused glass phase In this invention, 10 to 30 parts by weight of a high-melting bond is blended with 100 parts by weight of a low-melting bond, and 1 to 8 parts by weight of a flux with respect to 100 parts by weight of both of the prepared bonds. Is a vitrified CBN grinding wheel characterized in that
That is, an appropriate amount of a high-melting silicic acid (SiO ₂ ) -based bond is eutectic in a glass phase composed of a low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) system. A fluxing agent is added to this to promote vitrification of the eutectic phase.

10 to 30 parts by weight of high-melting silicic acid (SiO ₂ ) -based bond is divided (separated) into 100 parts by weight of low-fluidity sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) -based bond By eutecticizing as a phase, it becomes possible to obtain a characteristic bond excellent in low expansion property as abrasive grain support (adhesion) strength, bond strength, and chemical resistance.
When the blending amount of the high-melting bond with respect to the low-melting bond is less than 10 parts by weight, the glass phase rich in sodium borate is obtained by mixing and melting the sodium silicate glass phase in the form of droplets. As a result, the chemical resistance (acid, alkali) resistance is deteriorated, the thermal expansion coefficient is increased, the thermal expansion difference from the abrasive grains is increased, and the abrasive support strength is weakened. As a result, the grinding ratio is lowered and the wheel life is shortened.
When the compounding amount of the high-melting bond exceeds 30 parts by weight, the vitrification of silicic acid (SiO ₂ ) is delayed, but the chemical resistance is improved, but the fusing force with the abrasive grains is weakened and the grindstone strength is reduced. The grinding wheel wear increases and the grinding ratio becomes small, so that a high performance grinding wheel cannot be obtained.

In order to increase the bond or abrasive grain support strength to obtain a long-life grindstone, vitrification of silicic acid must be promoted together with other raw materials. For this purpose, the silicic acid (SiO ₂ ) glass phase needs to be aggregated without being separated, and therefore, the grindstone firing temperature is set to a high temperature of 650 to 800 ° C. or more to promote molten vitrification. However, in the CBN vitrified grindstone, in order to avoid abrasive grain damage, a high-temperature firing exceeding 800 ° C. requires a non-oxidizing inert atmosphere.

(1) Grinding wheel production Using CBN (cubic boron nitride) 120/140 mesh abrasive grains, a sample grinding wheel was produced so that the abrasive grain volume ratio was 45% (concentration 180).
a) Bond Table 2 shows the component composition of the low-melting (A) and high-melting (B) bonds used in the examples. Moreover, (A) applied the frit bond and (B) applied the bond which consists of a natural mineral and an additive.

In the grindstones of the examples shown in Table 3, (B) 20 parts by weight of (B) bonds are blended with 100 parts by weight of (A) bonds, and zinc chloride (ZnCl ₂₎ as a flux with respect to 100 parts by weight of these blended bonds. ) Was added by 6 parts by weight.

  In the comparative example grindstone in Table 3, frit bonds were used, and the composition of these components was also shown in Table 2.

Bond Seegel cones (JISR2204) are prepared for the bonds used in the examples and comparative examples, heated at a rate of temperature increase of 125 ° C./hour, and the deformation temperature is set as the softening temperature, and 640 ° C. and 724 ° C. are measured, respectively. . The melting (melting) temperatures were 667 ° C. and 760 ° C.
Moreover, it measured also about the thermal expansion coefficient ( ^x10 < ^-6 > / degreeC), and was 5.7 and 5.3 about the bond used by the Example and the comparative example, respectively.

b) Production process Abrasive grains, bonds and fluxes, and organic materials such as temporary binders and tissue conditioners as raw grind strength imparting agents are blended. Fill mold and compression mold. The molding grindstone was taken out of the mold, dried and fired.
The grindstone of the example was fired by holding for 3 hours at a maximum temperature of 750 ° C. with the furnace interior as an oxidizing active atmosphere. The comparative example grindstone was held and fired at 900 ° C. in a non-oxidizing inert atmosphere for 1 hour.
The fired segmented fan-shaped segment grindstone was coordinated and adhered to the outer periphery of a steel core having a hole diameter of 50.8 mm, and then finished to obtain a test grindstone having a diameter of 205 mm and a width of 5 mm.

c) Grinding wheel structure In each of the examples and comparative examples shown in Table 3, 0.3, 0.4, and 0.5 parts by weight of binder (bond) parts by weight with respect to unit weight part (1.0) of the abrasive grains. As a result, three types of whetstones were produced.
Each sample whetstone is obtained by calculating in advance the bulk density of the raw whetstone so that the value obtained by dividing the volume of the abrasive grains by the volume of the whetstone (%), that is, the abrasive rate is 45% (concentration 180), Based on the bulk density, the composition of the structure adjusting material and the molding pressure conditions were determined, and a sample grindstone was molded.

d) Grinding wheel characteristic value Table 3 shows the characteristic value of each sample grinding wheel. The degree of bonding was determined by the indicated value of dial B when the test load was 150 kg using a 6.35 mm steel ball indenter by a Rockwell hardness meter.
The grindstone structure was measured for pores, abrasive grains, and a binder (JIS R6240) at a volume ratio (%). The grindstone bending strength was measured by a two-point support and a one-point load with a square sample.
As described above, when the examples and comparative examples are compared for the specifications of the grindstones having the same (binding material / abrasive grain) ratio in Table 3, the grindstones of the examples are surely harder than the grindstones of the comparative examples. The grinding wheel bending strength was also a large value. Thus, it can be seen that the example is a vitrified grinding wheel having a long life and a large abrasive grain supporting force and grinding wheel strength, and little wear on the grinding wheel.

(2) Actual cutting test
a) Grinding conditions Horizontal axis plane traverse grinding was performed using a KURODA GS62Z surface grinder.
The dresser was a vertical SF rotary dresser V125F (Ota), and an end face of a cup-type grindstone (diameter 125 mm, edge thickness 3 mm) was used. A truing grindstone with a prismatic diamond specification was used. The dressing grindstone was a WA220 mesh vitrified grindstone, and the truing and dressing conditions were all constant.
The workpiece used was bearing steel (SUJ2), hardness HRC60, and the dimensions were square 50 × 50 mm.
The test grindstone was a fan-shaped segment CBN grinding grindstone that was bonded and coordinated to the outer periphery of the base metal core.
Grinding conditions were a grindstone peripheral speed of 33 m / s, a workpiece lateral feed speed of 0.33 m / s and a longitudinal feed width of 2 mm, with a cut amount of 0.02 mm at both ends for each lateral feed stroke, and a total cut amount of 2 mm. . As the grinding fluid, water-soluble oil (Suncool GF400, diluted 50 times) was used.

b) Measurement item Grinding resistance (watt W) was measured with a dynamometer (HIOKI 3166).
The surface roughness of the sample after completion of grinding was measured (SURFCOM 480A). The amount of grinding was also measured for the amount of change from the reference surface (MITUTOYO ID-C125B). For the grinding wheel wear amount, a laser displacement meter (KEYENCE LK-G85) was used. The grinding ratio (grinding amount / whetstone wear amount) was determined from the grinding amount (mm ³ ) and the wheel wear amount (mm ³ ). Further, from the grinding resistance (Watt W), the heat generation amount (Joule Joule) per unit grinding amount (mm ³ ) was obtained and used as grinding energy (J / mm ³ ). These results are shown in Table 4.

As is clear from the results in Table 4, the maximum grinding energy (J / mm ³ ) is about 20 to 25% lower in the examples than in the comparative examples, and the surface roughness and the amount of grinding wheel wear are also small. It has become. Accordingly, the grinding ratio was about 10 to 15% larger than that of the comparative example.

  From this result, in the internal grinding work by constant pressure grinding method using the vitrified grinding wheel of the example, the grinding energy is small, the grindability is excellent, the grinding power is small, and the fast cutting speed is possible, and the predetermined grinding clearance As a result, it was found that grinding for a short time became easy and surface roughness was improved, and a high-precision, high-efficiency, long-life grinding wheel could be realized.

Chart showing the relationship between grinding energy and number of cuts in Examples and Comparative Examples

Claims (6)

In a vitrified grinding wheel formed by bonding abrasive grains with a vitrified bond, the vitrified bond includes a low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) -based glass phase and a high-melting silica. A vitrified grinding wheel composed of an acid (SiO ₂ ) -based glass phase that is co-melted with a flux as a phase separation. The components of the low-melting bond forming the low-melting sodium borate (B ₂ O ₃ —Na ₂ O—SiO ₂ ) glass phase are 45 to 50% by weight of SiO _{2 and} 25 to 30% by weight of B ₂ O _{3 2.} The vitrified grinding wheel according to claim 1, wherein the vitrified grinding wheel is composed of 5% by weight forming oxide, 5 to 10% by weight of Al ₂ O ₃ intermediate oxide and 15 to 25% by weight of the following RO and R ₂ O modified oxides.
RO is at least one oxide selected from the group consisting of CaO, MgO, BaO and ZnO, and R ₂ O is at least Na selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O is one or more oxide containing _{2 O.} A high-melting bond forming a high-melting silicic acid (SiO ₂ ) -based glass phase is SiO ₂ 60 to 65 wt%, B ₂ O ₃ 0 to 5 wt% forming oxide, Al ₂ O ₃ 15 to consisting mixing bond of 20% by weight of the intermediate oxide and the following of the RO and _R 2 _O10~20 wt% modified an oxide frit bond or a natural mineral and an additive, 10 to 30 with respect to TeiTorusei bond The vitrified grinding wheel according to claim 1, wherein the vitrified grinding wheel is blended by weight%.
RO is at least one oxide selected from the group consisting of CaO, MgO, BaO and ZnO, and R ₂ O is at least Na selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O is one or more oxide containing _{2 O.}   The vitrified grinding wheel according to claim 1, wherein the flux is a metal chloride, a metal fluoride, or an alkali nitrate. _2. The vitrified grinding wheel according to claim 1, wherein the abrasive grains are one or more abrasive grains selected from cubic boron nitride (CBN), diamond (SD), aluminum oxide (Al ₂ O ₃ ), and silicon carbide (SiC). . SiO ₂ 45 to 50 _{wt%, B} 2 O 3 _25~30% by weight of the formed _oxide, Al ₂ O 3 _5~10 wt% of the intermediate oxide and the following of the RO and _R 2 _O15~25 wt% modified oxide to low fusible bonding 100 parts by weight of the _object, SiO 2 60 to 65 _{wt%, B 2} O 3 0 to 5 wt% of the formed _oxide, an intermediate oxide of Al ₂ O 3 15 to 20 wt% and 10-30 parts by weight of a high-melting bond composed of the following RO and R ₂ O 10-20% by weight modified oxide is prepared, and further, 1-8 parts by weight of flux and abrasive for 100 parts by weight of the prepared bond. A method for producing a vitrified grinding wheel comprising mixing grains, molding and drying the mixture, and firing at a maximum temperature of 650 to 800 ° C. in an oxidizing atmosphere.
RO is at least one oxide selected from the group consisting of CaO, MgO, BaO and ZnO, and R ₂ O is at least Na selected from the group consisting of Na ₂ O, K ₂ O and Li ₂ O is one or more oxide containing _{2 O.}

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