WO2005072912A1

WO2005072912A1 - Method for producing vitrified diamond whetstone

Info

Publication number: WO2005072912A1
Application number: PCT/JP2005/001124
Authority: WO
Inventors: Shoso Yamaguchi
Original assignee: Kure-Norton Co., Ltd.
Priority date: 2004-01-28
Filing date: 2005-01-27
Publication date: 2005-08-11
Also published as: CN1905992B; KR20060126742A; CN1905992A; JP4768444B2; JPWO2005072912A1; KR101143437B1

Abstract

Disclosed is a method for producing a durable vitrified diamond whetstone with good sharpening performance through firing at 650˚C or higher in the air atmosphere. Specifically, a method for producing a vitrified diamond whetstone comprising a step for firing a mixture of a vitrified binder and diamond abrasive grains in the air atmosphere is characterized in that the mixture contains a vitrified binder having a softening point higher than 650˚C and the mixture is fired at 700-900˚C in the air atmosphere.

Description

Specification

Method for manufacturing vitrified diamond wheel

Technical field

The present invention relates to a method for producing a diamond grindstone bonded with a vitrified binder.

Background art

[0002] Conventionally, a vitrified diamond grindstone has been fired in a nitrogen atmosphere. The reason is that if the diamond abrasive is heated in air, the weight of the abrasive sharply decreases from a temperature of 650 ° C or more, and the diamond abrasive is burned off at around 800 ° C. It is said that this is due to the reaction with oxygen in the air, the generation of carbon dioxide gas and, in short, the burning (Machine and Tools P156, January 1985; this data is from RCDeVries "Technical information series and UDIC Boron Nitnde; handbook of Properties GE, which has been diverted since June 1972.) Therefore, in general, sintering of vitrified diamond wheels is carried out in a non-oxygen atmosphere at a high temperature of 650 ° C or higher. For example, it was performed under a nitrogen atmosphere.

[0003] On the other hand, as an example of firing a vitrified diamond grindstone at 650 ° C or lower in an air atmosphere or a non-oxygen atmosphere, Japanese Patent Application Laid-Open No. 60-67078 discloses an aluminum phosphate-based binder with a firing temperature of 100 ° C. ° C, firing temperature 150-300 with the inorganic adhesive described in JP-A-2001-71268. C, Japanese Patent Application Laid-Open No. 2002-18726 discloses a calcination temperature of 590 ° C. or the like with a Li〇_ZnO-based binder.

[0004] Further, as a technique relating to firing of a vitrified diamond grindstone in an air atmosphere, Japanese Patent Publication No. 8-18254 discloses a method in which a powder of a vitreous binder having a softening point of 650 ° C or less is mixed. It is disclosed that the diamond abrasive grains are coated with a vitreous binder before the temperature reaches 650 ° C. or higher during firing, and thereafter firing at 650 ° C. or higher is disclosed. Non-Patent Document 1: Machines and Tools, January 1985, p.156

Patent Document 1: JP-A-60-67078

Patent Document 2: JP 2001-71268 A

Patent Document 3: Japanese Patent Application Laid-Open No. 2002-18726 Patent Document 4: Japanese Patent Publication No. 8-18254

Disclosure of the invention

Problems to be solved by the invention

[0005] However, the vitrified diamond grindstone fired in a nitrogen atmosphere has a problem in that the holding power of diamond abrasive grains is weak. That is, in general, a vitrified binder fired in a nitrogen atmosphere has lower strength than a vitrified binder fired in an air atmosphere. It is also known that diamond is generally inert and does not have very strong adhesion between diamond and other substances.It is particularly important that diamond does not have strong adhesion to glass, which mainly constitutes the vitrisulfide binder. This is the general perception of the trader. For this reason, the conventional vitrified diamond grinding wheel required the use of a large amount of binder to maintain the holding power of the diamond abrasive grains.As a result, the porosity of the grinding wheel was reduced, resulting in a poorly sharpened grinding wheel. There was a problem. For this reason, vitrified diamond whetstones are rarely used.

[0006] Further, in the above three examples of the prior art (Patent Documents 13 to 13), the diamond abrasive grains are fired at a firing temperature of 650 ° C or less, because the weight of the abrasive grains does not decrease. As a result, no durable grinding stone can be obtained due to the low holding power of the abrasive grains, and the characteristics of diamond abrasive grains are not fully utilized. As described in JP-B-8-18254, it has been proposed to use a lead component, which is an effective component for lowering the softening point of glass, as a vitreous component. Due to its extremely harmful effects on the human body, environmental problems have been raised. Recently, vitrified whetstones containing lead have not been used.

[0007] On the other hand, when a vitrified binder as described in the above three prior arts as a low softening point glass is fired at 650 ° C or more, the fluidity of the binder increases and excess It is considered impossible to manufacture a grinding wheel because the reaction causes a phenomenon that the grinding wheel swells.

[0008] In order to increase the holding power of the abrasive grains, the coefficient of thermal expansion of the binder is important in addition to the fluidity of the binder. In this regard, it is conceivable to use CBN abrasive grains (diamond and CBN are collectively called superabrasive grains), which are treated the same as diamond and have the second highest abrasive grain hardness after diamond. Generally, CBN abrasive grains lose less weight due to heating than diamond, so Typically, it is fired in an air atmosphere (in some cases, a nitrogen atmosphere) at 650-950 ° C. In general, borosilicate glass is well used as a binder for CBN abrasive grains. CBN abrasives are active on vitreous binders when compared to diamond abrasives. In addition, since the thermal expansion coefficient matches moderately with that of CBN abrasive grains, it can be a good grinding stone. Diamond abrasive grains also have the same coefficient of thermal expansion as CBN abrasive grains. Generally, a glass component having a low softening point tends to have a high thermal expansion coefficient. It uses a monovalent alkali metal (Na, K, Li) as a typical component for softening glass, but it is not preferable to use a large amount because it increases the coefficient of thermal expansion of the vitrified binder. .

[0009] In Japanese Patent Publication No. 8-18254, the force of substituting a monovalent alkali metal with a Pb component is expressed as a relationship between the amount of the monovalent alkali metal and the softening point and thermal expansion coefficient of the vitreous binder. There is no suggestion for producing a sharper and more durable vitrified diamond wheel.

[0010] Further, the softening point of borosilicate glass generally does not apply to the softening point of 650 ° C or lower required in Japanese Patent Publication No. 8-18254, and a typical example of borosilicate glass, Pyrex (registered trademark) trademark) glass, etc. have a problem with adhesion between the thermal expansion coefficient of 3. 2 X 10- ⁶ diamond abrasive grains and CBN abrasive grains matched forces softening point is higher temperatures the abrasive grains. In general, borosilicate glass undergoes phase separation depending on the heat treatment temperature, and phase separation occurs immediately after heat treatment, especially at low temperatures, and the separated SiO component becomes cristobalite crystals. this

2

Causes a rapid volume change at 200-300 ° C, causing cracks in the vitrisulfide binder. For this reason, borosilicate glass cannot be used at a firing temperature of 650 ° C or lower.

[0011] In view of the above, in order to obtain a durable and sharp vitrified diamond grindstone, it is necessary to match good adhesion to diamond abrasive grains and coefficient of thermal expansion. The borosilicate glass used together with the CBN abrasive is desired to be used as the vitrified binder to be filled. If the holding power of the diamond abrasive is insufficient in the nitrogen atmosphere firing, there is a problem.

[0012] Further, the above-mentioned prior art vitrisulfide binders cannot be used due to environmental problems. It can be fired at a low temperature of 650 ° C. or lower, but lacks the holding power of abrasive grains.

[0013] In short, in order to improve the holding power of the abrasive grains, it is considered that matching of the thermal expansion coefficient between the abrasive grains and the vitrified binder and good fluidity are necessary. It is inactive and has poor adhesion to other substances, that is, a bonding mechanism by a chemical reaction cannot be obtained. In an air atmosphere, heating at 650 ° C or more causes a rapid weight loss, so firing in an air atmosphere poses a problem.

[0014] In addition, when a vitrified binder having a low softening point of 650 ° C or less is used, the thermal expansion coefficient does not match in firing at 650 ° C or less. Further, if the binder is fired at a temperature of 650 ° C. or higher, there is a problem that the grinding stones swell.

[0015] In view of the above problems, the present invention provides good sharpness and high durability by firing at 650 ° C or more in an air atmosphere, which was conventionally considered impossible by those skilled in the art. An object of the present invention is to provide a method capable of manufacturing a certain vitrified diamond wheel.

[Summary of the Invention]

[0016] The production method of the present invention for solving the above-mentioned problem is a method for producing a vitriide diamond grinding wheel, which comprises a step of firing a mixture of a vitrisulfide binder and diamond abrasive grains in an air atmosphere, It is characterized in that a mixture containing a vitrisulfide binder having a softening point higher than 650 ° C is fired in an air atmosphere at 700 ° C to 900 ° C.

[0017] Further, the production method of the present invention is characterized in that 50 to 65 wt% of Si〇, 5 to 15 wt% of A1〇, 15 to 25 wt% of B〇, and 1 to 6 wt% of RO (RO is Ca〇, MgO and It is preferable to use a vitrisulfide binder having a chemical composition of at least one selected from BaO force and 410% by weight of R0 (R〇 is at least one selected from K0, NaO and Li〇 force). Masure,

Further, in the production method of the present invention, it is preferable to use the above-mentioned vitrifide binder by adding 110% by weight of ceramic fine powder.

[0019] Further, in the production method of the present invention, the vitrifide binder used may be a liquid which is obtained by exposing a cylindrical pellet having a height Z diameter ratio of 0.79 formed from the vitrifide binder to a firing temperature. In the test, it is preferable that the pellets have fluidity such that the ratio of the height Z diameter of the pellets becomes 0.1-0.6 by firing.

[0020] Further, the production method of the present invention provides a method for producing a diamond abrasive coated with a metal or an inorganic material. It is preferred to use granules.

[0021] In the production method of the present invention, the mixture includes cubic boron nitride abrasive grains, alumina-based abrasive grains, silicon carbide-based abrasive grains, silica, cerium oxide, and mullite in addition to the diamond abrasive grains. It may further include one or more abrasive grains selected from the group.

[0022] In the production method of the present invention, the mixture may further include an organic powder or an inorganic hollow body as a pore-forming agent.

The invention's effect

[0023] In the method for producing a vitrified diamond grinding wheel of the present invention, a vitrified binder having a softening point higher than 650 ° C is used, and firing is performed in an air atmosphere at 700 ° C to 900 ° C. Compared with conventional firing in a nitrogen atmosphere or using a low-temperature softening vitrified binder, the durability of the vitrified diamond wheel is greatly improved, and the efficiency of various grinding operations is greatly improved. Brief description of the drawings to improve the quality of the workpiece

FIG. 1 is a graph showing the results of thermogravimetric and differential thermal analysis by heating test 2.

FIG. 2 is a perspective view showing a diamond plate and a binder pad used for a fluidity and wettability test.

FIG. 3 is a photograph showing each binder pad after firing as a result of a fluidity and wettability test.

[FIG. 4] FIG. 4 is SEM photographs showing each surface of the untreated and heat-treated abrasive grains as a result of the heat treatment test of the abrasive grains.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] First, the inventor is not bound by the conventional common sense of the art.

It was confirmed whether or not the burning out of the diamond shown in (Non-Patent Document 1) can be reproduced. Surprisingly, as shown in Example 1 below, no sudden weight loss occurs at 650 ° C. or higher. The residual rate was more than / o (it would completely disappear in non-patent literature). This is contrary to common knowledge that diamonds are rapidly burned out at 650 ° C or higher. Therefore, it was considered that firing could be performed in an air atmosphere at a firing temperature of 650 ° C or higher using diamond abrasives.

[0026] For example, according to Japanese Patent Publication No. Hei 8-18254 (Patent Document 4), it is 900 if coated with a vitreous binder having a softening point of 650 ° C or less and baked with the diamond abrasive force shut off from air. There is a description that firing is possible even at around ° C. However, as a result of experiments conducted by the present inventor, calcination at 650 ° C or higher is possible even in an air atmosphere as described above, and with this discovery, a vitrified binder having a softening point of 650 ° C or higher was used. However, it was found that firing at 650 ° C or more, specifically 700-900 ° C, under an air atmosphere was possible. And, as already mentioned, there is a possibility that the borosilicate glassy vitrified binder used in CBN abrasives etc. can be used favorably, and further studies have been made with a focus on this point.

First, the details of the vitrisulfide binder suitably used in the present invention will be described.

[0028] The vitrisulfide binder used in the present invention includes a borosilicate glass-based binder, and its chemical composition is 50 to 65 wt% in consideration of the fluidity and thermal expansion coefficient of the binder. Si O, 5-15 wt% A1〇, 15-25 wt% B〇, 1-6 wt% RO (RO is Ca〇, Mg

O and Ba〇 forces are also selected), and 4 一 10wt% R〇 (R O is K 0, Na

(At least one selected from 〇 and Li 2 O) is good.

[0029] When SiO is lower than 50 wt%, the coefficient of thermal expansion increases and the softening point decreases too much. 65wt

If it is more than 10%, the softening point is too high, and the holding power of the diamond abrasive grains is insufficient, and the stability of the borosilicate glass is lost and the phase separation phenomenon occurs.

[0030] If the A1 strength is less than wt%, the softening point is too low and the stability of the borosilicate glassy material is lost, causing a phase separation phenomenon, and if it is more than 15wt%, the softening point is too high and the diamond grains are retained. Lack of power.

[0031] When R〇 (at least one selected from the group consisting of R〇 CaO, Mg〇 and Ba% forces) is less than 2 wt%, the softening point is too high and the fluidity of the binder is insufficient. The dagger point is too low.

When R 0 (R〇 is at least one selected from K 0, Na O and Li〇 force) is less than 4 wt%, the softening point is too high, the fluidity of the binder is insufficient, and the If too large, the coefficient of thermal expansion will increase too much. It should be noted that even if an inorganic element other than the above-described components or a fine ceramic material as an adjusting material is added to the vitrified binder, the vitrified binder may be powerful. For example, a fine ceramic material may be added in an amount of 11 Owt%. From the viewpoint of the effect of addition, lwt% or more is preferable to be 10wt% or less from the viewpoint of securing the preferable fluidity. Representative examples of such additives include mullite, dinolecon, anoremina, cordierite, spodumene, lithium aluminum silicate-based crystals, and the like.

[0034] The softening point of the vitrifide binder is the temperature at which the elongation reaches lmm / min when a 0.55-0.75mm diameter, 235mm long fiber is heated at 4-6 ° CZ for a minute. The viscosity is defined as about 10 ⁷ · ⁶ Boys (Glass Dictionary Asakura Shoten, page 376, line 63 from the bottom).

[0035] The vitrisulfide binder to be used in the present invention has a softening point of 650 ° C or more, preferably 675 ° C or more, more preferably 700 ° C or more, and particularly preferably 750 ° C or more. The setting of such a high soft point has the following advantages. That is, in order to reduce the softening point of the borosilicate glass-based vitrified binder to 650 ° C. or less, it is necessary to add a large amount of the softening promoting component R20 (R2), in which case the thermal expansion coefficient increases. In the firing conditions of the present invention, the properties of the borosilicate glass-based vitrified binder are energized.

[0036] On the other hand, the upper limit temperature of the softening point is up to a predetermined firing temperature, that is, 700 ° C or less, 725 ° C or less, 750 ° C or less, 800 ° C or less, 850 ° C or less, or 900 ° C. A lower temperature is better. If the predetermined upper limit is exceeded, the holding power of the diamond abrasive tends to be insufficient.

[0037] The fluidity of the vitrifide binder is important in determining the holding power between the diamond abrasive grains and the vitrifide binder. From this viewpoint, it is desirable that the vitrisulfide binder to be used in the present invention has a predetermined fluidity which can be confirmed by the following fluidity test.

[0038] A mold having a diameter of 25.4 mm is filled with 15 g of a vitrisulfide binder, and molded to a height of 20 mm. The formed cylindrical pellet is placed on a ceramic, ceramics composite material or refractory which has a surface as smooth as possible without any irregularities and which does not deteriorate at a predetermined firing temperature. The columnar pellets are fired at the same firing temperature as the grinding stone firing. Measure the diameter (largest part) and height of the cylindrical pellets taken out after firing, determine the height / diameter ratio of the pellets, and use this as the fluidity.

In the present invention, in the above-mentioned fluidity test, the height / diameter ratio of the fired pellets is It is preferable to use a vitrisulfide binder having a flowability in the range of 0.1 to 0.6. If the fluidity is less than 0.1, it is not suitable for producing a normal grinding wheel, and if it is more than 0.6, the abrasive holding power tends to decrease. The fluidity is preferably 0.15-0.55 force S, more preferably 0.2-0.50.

[0040] The vitrified diamond grindstone of the present invention preferably has an abrasive grain volume ratio of 10 to 55% and a pore volume ratio of 1070%. The binder ratio is a value obtained by subtracting the abrasive grain volume ratio and the pore volume ratio from 100. When producing a grindstone having a high porosity, an organic powder or an inorganic hollow body can be used as a pore-forming agent. The organic pore-forming agent is adjusted to a predetermined particle size, is mixed with the grindstone raw material, and forms pores as cavities appearing as it disappears during firing. Further, the inorganic hollow body is a hollow glass or ceramic material, and desirably has a softening point higher than a predetermined firing temperature. The used inorganic hollow body remains in the fired grindstone, and the hollow portion becomes a pore. The type and amount of the pore-forming agent can be appropriately determined in consideration of the grinding conditions in which the grindstone is used.

In the production of the grindstone of the present invention, a force capable of using diamond abrasive grains alone can be used in combination with another abrasive material. Other abrasives that can be used together with diamond abrasives are mainly one selected from the group consisting of cubic boron nitride abrasives, alumina-based abrasives, silicon carbide-based abrasives, silica, cerium oxide, mullite, and the like. The above abrasive grains are included. These are exemplifications, and unless otherwise deviated from the object of the present invention, they may be enumerated or other abrasive grains may be used.

[0042] The particle size range of the diamond abrasive used in the present invention is a force that can be used in a range of coarse particle size # 10000 (average diameter smaller than 1 µm) expressed by a particle size of 16/18. A range S of # 5000 is preferred, a range force of 100/120 # 3000 is more preferred, and a range of 120/140 # 1000 is particularly preferred.

[0043] The diamond abrasive used in the present invention can use an abrasive whose surface is not coated. It is more preferable to use an abrasive whose surface is coated with a metal or an inorganic material. It is.

[0044] In a preferred embodiment of the production method of the present invention, diamond abrasive grains are used as abrasives, and A grindstone is formed using a vitrified binder having a borosilicate glassy material and a softening point of 650 ° C or more, and fired in an air atmosphere at 700 to 900 ° C. According to the present method, surprisingly, the diamond abrasive grains are not burned out, and a good vitrified diamond wheel can be manufactured. For details of other manufacturing conditions and the like that are not disclosed in this specification, known methods and conditions that are common technical knowledge in the art may be applied. One skilled in the art would be able to implement any aspect of the invention by adding or changing timely conditions based on the disclosure of the invention.

[0045] The grindstone manufactured according to the present invention can be applied not only to cylindrical grinding but also to surface grinding and internal grinding. Examples of the work material include carbide, silicon, alumina, carbide, nitride, sapphire, quartz, It can be used for grinding and polishing hard and brittle materials such as glass and ceramic materials.

Hereinafter, examples of the present invention will be described together with comparative examples, but these exemplify the feasibility and usefulness of the present invention, and do not intend to limit the configuration of the present invention in any way. Example

[Heating test of diamond abrasive grains]

The diamond abrasive grains were heated to a high temperature, and a decrease in weight due to heating was confirmed.

(Heating test 1)

The following heating test was performed on the diamond abrasive grains of MBG660 mesh 120Z140 manufactured by GE.

Heating test conditions

2 g of the above-mentioned abrasive grains are put in a platinum knorebo, and the maximum holding temperature is 580 ° C and 630 in an air atmosphere. C, 700 ° C, 800 ° C, 850. After holding at 950 ° C for 7 hours at C, the residual heating ratio was calculated from the weight change before and after the caloric heat. Table 1 shows the test results.

[Table 1] Test temperature Residual heating rate (%)

5 8 0 "C 9 8 .0

6 3 0 V 9 1.3

7 0 0 ° C 7 7.8

800 ° C 7 2.5

8.5 0 ° C 6 1.5

9 5 0. C 0.0

[0049] As shown in Table 1, the force completely burned off at 950 ° C 72.5% at 800 ° C and 61.50 at 850 ° C.

The residual rate was considerably high at 5%, and did not completely disappear at 800 ° C at least as described in the prior art (Non-Patent Document 1). Regarding the heating time, the data in the non-patent literature, such as force S, which has a hold time of 3 hours, and this test, which is 7 hours, are more severe conditions. Nevertheless, the high value of the residual heat rate in the air atmosphere resulted in a sharp decrease in the residual heat rate in the air atmosphere, and diamond abrasive grains did not always completely disappear at 800 ° C. I understood. By this test, contrary to the technical common sense for a long time, contrary to the fact that it is possible to fire at high temperature in an air atmosphere using the above-mentioned diamond abrasive, it is possible to produce a strong vitrified diamond wheel It was considered possible.

(Heating test 2)

Using a thermogravimetric / differential thermal analyzer (TG / DTA6300, manufactured by Seiko Instruments Inc. (SII)), thermal analysis was performed on diamond abrasive grains of MBG600T mesh 230/270 manufactured by GE. 0.05 g of the above-mentioned abrasive grains was placed in a cup-shaped platinum dish having a diameter of 5.2 mm and a height of 2.5 mm, the temperature was raised at 10 ° C./min, and the weight change was measured.

FIG. 1 shows the temperature dependence of TG (thermogravity) and DTA (differential heat) for the abrasive grains. As shown in the figure, the weight of the abrasive grains started to decrease at around 650 ° C, and at 900 ° C more than 80% disappeared.

[Test of whetstone bending strength]

In response to the above test results, a test grindstone was manufactured using a predetermined vitrified binder and the above diamond abrasive grains, and the bending strength was measured. In this test, baking in an air atmosphere was taken as Example 1, and baking in a nitrogen atmosphere was taken as Comparative Example 1 (see Table 3). Manufacture of test wheels

As Bitorifuaido binder, the chemical composition of the following Table 2 (wt%),軟I匕点is 800 ° C, Netsu膨Zhang coefficients were from 5. 5 X 10- ^6.

[Table 2]

[0052] The mixing ratio of the abrasive was 1000 parts by weight of RVG230 / 270 (manufactured by GE), 250 parts by weight of vitrified binder, 80 parts by weight of primary binder, abrasive grain volume ratio (Vg) = 50, binder The volume ratio (Vb) was set to 20 and the pore volume ratio (Vp) was set to 30. After uniformly mixing the above-mentioned raw materials, they were filled in a mold to form a 43 × 5 × 12 (mm) rectangular parallelepiped. After drying at 40 ° C. for 12 hours, it was fired under predetermined conditions, and the bending strength of each of the obtained test whetstones was measured by the following procedure.

Test procedure for bending strength

According to the JIS standard (Bending strength test method for fine ceramics R1601, 1995), each test whetstone was subjected to three-point bending strength at a distance between spans of 30 mm and a descent rate of 0.5 mm / min. Three averages were taken for each test piece.

Table 3 shows the firing conditions and results of this test.

[Table 3] Firing temperature Firing atmosphere Maximum temperature holding time Bending strength (MPa) Example 1 85 0 V Air atmosphere 7 hours 85.0 Comparative example 1 95 0 Nitrogen atmosphere time 33.6 [0055] As shown in Table 3, the high-temperature sintering in the air atmosphere of Example 1 increased the flexural strength twice or more as compared with that in Comparative Example 1 under the nitrogen atmosphere.

[Grinding test]

The mixing ratio of the raw materials of the grinding stone used in the grinding test was 506 parts by weight of RVG230 / 270 (manufactured by GE), 494 parts by weight of silicon carbide abrasive (SiC) # 220, and had the chemical composition shown in Table 2 above. 250 parts by weight of vitrisulfide binder and 80 parts by weight of primary binder, volume ratio of diamond grain (Vg) = 25, volume ratio of silicon carbide abrasive grains (Vg) = 25, volume ratio of binder (Vb) = 20 , And the pore volume ratio were adjusted to Vp = 30. An arc-shaped segment whetstone was fabricated for the grinding test. Specifically, after mixing the above-mentioned raw materials uniformly, it is filled in a mold and molded into 32 segment whetstones with dimensions of 39.41 mm in length, 11 mm in thickness, 6 mm in width and R = 95 mm in curvature. did.

After drying the molded segment whetstone at 40 ° C. for 12 hours or more, 16 of them were fired in an air atmosphere of 850 ° C. (Example 2), and the remaining 16 were baked at 950 ° C. It was fired in a nitrogen atmosphere (Comparative Example 2).

[0057] Each of the baked segment whetstones was bonded onto a metal base having an outer circumference of 190 mm, a thickness of 10 mm, and a shaft hole of 50.8 mm, and was subjected to a finishing process. A 1A1 type grinding wheel with dimensions was manufactured.

[0058] A grinding test was performed under the conditions shown in Table 4.

[Table 4]

Whetstone dimensions: Φ 200 ΧΤ 1 0 X115 0.8 mm

Polishing layer thickness including diamond 3.0 mm

Work material: Material S I C

Dimensions 2 1 0 X 10 mm

Grinding machine: Okamoto Machine Tool horizontal axis surface grinder C N C— 5 2 B

Grinding fluid: Clecut NS201 (Soluble type) 50-fold dilution

Tooling and dressing conditions

Dresser: G C 120 G V

Dresser dimensions: Φ 1 25 XT 3 0 XH 50.8 mm

Wheel peripheral speed: 4.75 m / s (4 54 m " ¹ )

Dresser peripheral speed: 6.74m / s (1030m—outermost speed Dressing lead: 0.98mZ reV

Dress cut: 0.0 5 mm / p a s s

Dress times: 2 times

Grinding conditions

Grinding method: wet traverse grinding

Wheel peripheral speed: 25 s (2 3 8 8 m " ¹ )

Table speed: 0.16 7 m / s

Table cross feed: 2 mmZp a s s

Grinding depth of cut: 40 iim / p a s s

Total depth of cut: 0.48 X 2 times The evaluation items for the grinding test are the grinding resistance, finished surface roughness, and grinding ratio defined below.

[Grinding ratio]

The grinding ratio is obtained from the work material removal volume Z grinding wheel consumption volume.

[Grinding power]

The power consumption of the grinding wheel motor is W, and it is obtained as 612XWZ peripheral speed (60Z100). In addition, the said peripheral speed of a grindstone was used as peripheral speed.

[Finish surface roughness Rz]

In accordance with JIS B0660 (1998), the surface roughness of the finished surface of the grindstone to be tested is measured as the ten-point average roughness Rz. The ten-point average roughness Rz is extracted from the roughness curve by the reference length in the direction of the average line, and the average linear force of the extracted portion is measured in the longitudinal magnification direction. It is calculated as the sum of the average of the absolute values of the altitudes Yp of the 5th peak from the highest peak and the average of the absolute values of the altitudes of the valleys of the 5th bottom from the lowest. In the present example, when the Rz was greater than 0.5 μ μη and less than or equal to 10. μ μη, the classification was based on the standard length of 0.8 mm and the evaluation length of 4 mm.

[0061] Table 5 shows the results of the grinding test.

[Table 5]

[0063] As shown in Table 5, the grinding ratio of Example 2 was significantly higher than that of Comparative Example 2. The surface roughness of the second embodiment is also better.

[0064] The grinding wheel of Example 1 above has excellent bending strength and grinding performance because a predetermined vitrified binder has high fluidity and wettability on the surface of diamond abrasive grains during high-temperature firing in an air atmosphere. It is considered that strong adhesion was obtained between them. To verify this estimation, we tested the flowability and wettability of the vitrified binder, and performed a heat treatment test on diamond abrasive grains.

Combination ¾ † cow and wet cow test

As shown in Fig. 2, on a diamond plate (MWSL5012 manufactured by Element Six) with a length of 5. Omm, an inner diameter of 4. Omm, and a thickness of 1.2 mm, a vitrifide binder with the chemical composition shown in Table 2 above The 3 mm square pad was placed, and baked under the same conditions as in the above bending strength test, that is, under an air atmosphere at 850 ° C. or a nitrogen atmosphere at 950 ° C.

FIG. 3 shows each binder pad after firing. When fired in an air atmosphere at 850 ° C, it is clear that the binder is well fluidized and well wet to the diamond plate. Firing in a nitrogen atmosphere at 950 ° C. is less fluidized and less wet than in an air atmosphere. When examining their adhesive strength, the fired material in a nitrogen atmosphere could be easily peeled off from the diamond plate with a toe, but the fired material in an air atmosphere could not be peeled. From the results of this test, it was baked at high temperature in air atmosphere. It has been confirmed that the vitrisulfide binder has higher wettability to the diamond material and better adhesion than the nitrogen atmosphere.

Heat treatment test of diamond abrasive

A test was performed to observe the surface of the heat treated diamond abrasive. The diamond abrasive grains of MBG600T mesh 230Z270 manufactured by GE were spread on a magnetic pad, and heated in an air atmosphere at 700 ° C. for 100 minutes. The reduction in abrasive weight was 4.94 wt%. The surface of the heated diamond abrasive grains was observed by SEM.

FIG. 4 shows SEM photographs of the surfaces of the heat-treated abrasive grains, the abrasive grains, and the heat-treated abrasive grains. It was found that the diamond abrasive grains after the heat treatment had fine irregularities formed on the surface thereof, which increased the surface area of the abrasive grains.

[0067] It is considered that the abrasive grain surface exposed to the high-temperature air atmosphere partially heated by reacting with oxygen and burned to form submicron-sized irregularities. Although not wishing to be bound by theory, it is believed that the formed irregularities provide an adhesive force with an anchoring effect to the binder, thereby improving the abrasive grain holding power.

In general, a small amount of metal is added as a catalyst to diamond abrasive grains during the production of abrasives. In the present invention, such a metal catalyst improves wettability and adhesion with a vitrified binder. It has been found to help improve. The TG-DTA heating curve obtained in Heating Test 2 above suggests that a weight loss of 5-10 wt% occurs from around 650 ° C to 850 ° C, the firing temperature of this heat treatment test. In fact, in this heat treatment test, the diamond plate was burned off at around 650 ° C, and the metal catalyst was exposed. Since the metal exposed on the diamond plate is oxidized by oxygen in an air atmosphere, it is considered that the molten vitrisulfide binder wets well on the diamond via the metal oxide catalyst and causes an adhesive reaction. In this way, it is considered that the molten vitrisulfide binder can flow the diamond plate through the exposed and oxidized metal catalyst, so that the flowability is promoted and the adhesiveness is improved. .

[0069] Further, as demonstrated in the above-mentioned fluidity test, vitrification of the vitrisulfide binder is promoted in an air atmosphere, and the vitrified binder is more likely to adhere to the diamond surface than in a nitrogen atmosphere. The wettability to be improved. Therefore, in high-temperature firing in an air atmosphere, a very high adhesive strength is obtained due to the synergistic effect of the high wettability of the binder on the abrasive grain surface and the formation of irregularities on the abrasive grain surface, and the holding power of the abrasive grains is reduced. It is considered that an improved high-performance grinding wheel could be manufactured.

Comparison test of prior art whetstone

[Bending strength]

The method of manufacturing the whetstone followed the same procedure as described in the bending strength test above.

[0070] For the grindstone of Example 3, a vitrisulfide binder having a chemical composition shown in Table 2 was used.

The binder was prepared by first fritting the chemical components other than mullite and then adding the required mullite fines.

[0071] As Comparative Example 3, as described in JP-B-8-18254, a raw material containing a binder having a softening point of less than 650 ° C was fired in an air atmosphere at 700 ° C to produce a grindstone. .

[0072] As Comparative Example 4, as described in JP-A-2002-18726, a B O -ZnO-based

twenty three

The raw material containing the mixture was fired in an air atmosphere at 590 ° C. to produce a grindstone.

In each of the above comparative examples, a vitrified binder prepared by subjecting a predetermined chemical component to melt fritting was used.

[0074] Table 6 summarizes the composition and other conditions of the binder in Comparative Examples 3 and 4.

[Table 6] Comparative Example 3 Comparative Example 4

Binder composition (w t ¾

S I_〇 _{2 3 6 wt% 1 5 wt} %

A 1 ₂ 0 ₃ 7 4

B, 0 ₃ 3 3 5

Z n O 8 4 4

P b〇 4 6 0

N a _{200 2} Softening point of binder 6 <35

Firing temperature 7 0 or 5 9 O: The bending strength of each grindstone was measured in the same manner as in Example 1 above. Table 7 shows the test results.

[0077] [Table 7]

[Measurement of Reduction Rate of Wheel Weight]

The reduction rate of the weight of the grindstone during baking was measured in Examples 3 and Comparative Examples 3 and 4, and the relationship between the above results and the strength of the grindstone was examined. The reduction rate of the weight of the grindstone is calculated by calculating the weight of each grindstone before and after firing in the above manufacturing process and calculating by: (1-(weight of the grindstone after firing) / (weight of the grindstone before firing)) x 100. did. Table 8 shows the measurement results.

[0079] [Table 8]

[0080] Since the binder used is fritted (and ceramic fine powder is added), it does not contain components that decrease during firing. The same material is used for the primary binder of each grinding wheel. Therefore, the rate of decrease in the weight of the grindstone corresponds to the amount of diamond burned from the surface of each abrasive grain.

[0081] The grindstone of Example 3 had a reduction rate after firing of about 1% higher than Comparative Examples 3 and 4. That is, in the manufacturing process of Example 3, the diamond abrasive grains are easily burned off. This burning of the diamond occurs during the heating process to the firing temperature, and surprisingly, controlling the behavior of the binder and the change in the surface of the abrasive grains at the time of heating raises the wettability between them. It is considered to contribute to the improvement of the adhesiveness and adhesiveness, and can be specifically described as follows.

[0082] The amount of diamond burned off depends on the height of the softening point of the binder. For example, the vitrified binder used in Example 3 has a softening point of 800 ° C, and in the process of raising the firing temperature to a final temperature of 850 ° C, the firing temperature becomes 800 ° C. Until C, most of the diamond abrasive surface can be exposed under an air atmosphere. As shown in the above heat treatment test, the surface of the diamond abrasive grains is gradually burned off in an air atmosphere, and irregularities are formed on the surface, and the metal component is exposed in the abrasive grains containing the metal catalyst. Thereafter, when the firing temperature exceeds 800 ° C, which is the softening point of the binder, the vitrified bond 1J starts flowing and spreads on the surface of the abrasive grains. Increased wetting of the grain surface results in high adhesion between the vitrified binder and the diamond abrasive.

[0083] In Comparative Examples 3 and 4, since the softening point of the binder is lower than 650 ° C at which the diamond abrasive grains start to burn off, at 650 ° C, the diamond abrasive grains are covered with the molten vitrisulfide binder. obtain. As a result, the surface of the abrasive grains is not given an opportunity to be exposed to a high-temperature air atmosphere, and the above-mentioned advantages as seen in Example 3 cannot be obtained. It is considered that the difference in bending strength shown in FIG.

[0084] From the results of this test, it was found that when firing in an air atmosphere was performed, the use of a binder having a high softening point as in Example 3 was sufficient to produce a desired grindstone. It was shown that firing at a high temperature was important.

[0085] In short, the present invention differs from the prior art in that the use of a binder that softens at a relatively low temperature at which the diamond is not burned off protects the diamond abrasive from its burning. Begins to burn down by using a binder having a softening point higher than 650 ° C, causing moderate burnout of the abrasive grains in an air atmosphere, thereby causing the vitrified binder to bind to the diamond abrasive grains. It can improve wettability and adhesion. As a result, it is possible to manufacture a grindstone having good grinding performance with improved abrasive grain holding power.

Claims

The scope of the claims

[1] A method for producing a vitrified diamond grindstone, comprising a step of firing a mixture of a vitrified binder and diamond abrasive grains in an air atmosphere, 650. A process comprising baking a mixture containing a vitrisulfide binder having a softening point higher than C in an air atmosphere at 700 ° C to 900 ° C.

[2] 50-65wt% SiO

2,5 15wt% A1〇

2 3, 15 25wt% B〇

2 3, 1 1 6wt%

RO (RO is at least one selected from Ca〇, Mg〇 and BaO), and 4-10 wt% of R 0 (RO is at least one selected from K0, Na〇 and Li〇)

2 2 2 2 2

2. The method according to claim 1, wherein a vitrisulfide binder is used.

[3] The production method according to claim 1 or 2, characterized in that ceramic powder is added to the vitrisulfide binder in an amount of 110 wt%.

[4] The vitrified binder used in the fluidity test of exposing a cylindrical pellet having a height / diameter ratio of 0.79 to a firing temperature, which is molded from the vitrisulfide binder, is subjected to calcination to obtain a pellet having a high height. The production method according to any one of claims 13 to 13, wherein the composition has fluidity such that the ratio of diameter / diameter is 0.1 to 0.6.

[5] The production method according to any one of claims 14 to 14, wherein diamond abrasive grains coated with a metal or an inorganic material are used.

[6] The mixture is at least one selected from the group consisting of cubic boron nitride abrasive grains, alumina-based abrasive grains, silicon carbide-based abrasive grains, silica, cerium oxide, and mullite in addition to the diamond abrasive grains. 6. The method according to claim 1, further comprising abrasive grains.

7. The production method according to claim 16, wherein the mixture further comprises an organic powder or an inorganic hollow body as a pore-forming agent.