JP2020099981A - Method for evaluating grindability of grinding wheel containing abrasive grain - Google Patents

Abstract

To provide a method for evaluating grindability of a grinding wheel containing abrasive grains in a form of abrasive grain or abrasive grain compact without performing production of a grindstone containing abrasive grains in which production process is complex and a production cost is high, and which requires many production days.SOLUTION: According to this method for evaluating grindability of a grinding wheel containing abrasive grains with use of a pin-on-disc type frictional wear evaluation device 1, instead of the grinding wheel containing abrasive grains, a material 4 to be ground is ground by abrasive grains, abrasion loss of the abrasive grains and stock removal of the material to be ground are measured, and grindability of the grinding wheel containing abrasive grains is evaluated from grinding ratio of abrasive grains which is defined by a ratio of stock removal of the material to be ground to abrasion loss of abrasive grains.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for evaluating the grindability of a grinding wheel containing abrasive grains.

Alumina sinter, alumina zirconia, cubic boron nitride, etc. are used in various industrial fields by taking advantage of their characteristics such as high hardness, high strength, high heat resistance, high abrasion resistance and high chemical resistance. ing. In particular, an alumina sintered body and alumina zirconia are used as abrasive grains which are a raw material of a heavy grinding (grinding performed by setting a high grinding load and a high grinding speed) grindstone in the steel industry.

Further, recently, a heavy grinding wheel having a larger “grinding ratio” than ever has been demanded in the market. Here, the "grinding ratio" is an index indicating the performance of the grindstone, and is represented by the following formula (A). It can be said that the larger the grind ratio, the better the performance of the grindstone.
Grinding ratio = amount of work material cut (grinding amount)/abrasion amount of grindstone (A)

Generally, it is judged that the performance is good if it is possible to grind a large amount of work material with a grindstone with a small amount of wear, but in order to obtain the grinding ratio, conventionally, at least the grinding wheel is actually used. It had to be made. Further, if the grindstone cannot be actually manufactured, or if the grindstone can be manufactured but there is no grinding apparatus for evaluation, the normal grinding ratio cannot be obtained.

Patent Document 1 describes a grindstone that is used in heavy grinding work and that has a mixture of a plurality of types of different friability, for example, sintered alumina abrasive grains and sintered high-purity alumina abrasive grains, as a compounding component. ing. Further, in Patent Document 2, as an evaluation method of a composite grindstone, a grindstone body equivalent to an actual grindstone is manufactured, and its polishing ratio (corresponding to the grinding ratio) is evaluated by using a pin-on-disk type friction/wear evaluation device. It is described that it is done.

JP, 11-138444, A Japanese Patent Laid-Open No. 2000-263448

However, as in Patent Document 1, since the grindstone used in the heavy grinding work is large, for example, with a diameter of 500 mm to 1000 mm, a large number of abrasive grains of grindstone raw material of several tens of kg and a synthetic material suitable for it. A binder such as a resin and a filler are required. Further, a large hot press and electric furnace and a grinding machine capable of withstanding high loads are required. As described above, in order to obtain the grinding ratio of the grindstone, there are problems such as large-scale installation of equipment, increase of raw material cost, and a large number of manufacturing days when manufacturing the grindstone.
In Patent Document 2, the grinding ratio of the grindstone is evaluated by a pin-on-disc type friction and wear evaluation apparatus, but since it is necessary to prepare a grindstone body for the evaluation, the work process is complicated and the cost is increased.

In view of the above, the present invention is complicated in the working process, high in manufacturing cost, and without performing preparation of a grinding wheel containing abrasive grains that requires a large number of manufacturing days, an abrasive grain or a formed body of abrasive grains. An object of the present invention is to provide a method for evaluating the grindability of a grinding wheel containing abrasive grains.

As a result of repeated intensive studies to solve the above problems, the present inventors have used a pin-on-disc type friction and wear evaluation device to perform grinding in the form of abrasive grains or a molded body of abrasive grains, and wear of the abrasive grains. Amount, and the grinding amount of the work material is measured, and the grindability of the grinding wheel including the abrasive grains is defined by the grinding ratio defined by the ratio of the grinding amount of the work material to the wear amount of the abrasive grains. The present invention has been completed by finding a method that can be easily evaluated without actually producing a grinding wheel containing
That is, the present invention provides the following (1) to (3).
(1) A method of evaluating the grindability of a grinding wheel containing abrasive grains, using a pin-on-disc type friction and wear evaluation apparatus, wherein a work material is replaced with the abrasive grains instead of the grinding wheel containing abrasive grains. Grinding, measuring the wear amount of the abrasive grains, and the grinding amount of the work material, from the grinding ratio of the abrasive grains defined by the ratio of the grinding amount of the work material to the wear amount of the abrasive grains, the A method for evaluating the grindability of a grinding wheel containing abrasive grains for evaluating the grindability of a grinding wheel containing abrasive grains.
(2) The grindability of a grinding wheel containing the abrasive grains according to (1), wherein the abrasive grains include alumina sintered body abrasive grains, alumina zirconia abrasive grains, alumina abrasive grains, or cubic boron nitride abrasive grains. Evaluation method.
(3) The method for evaluating the grindability of a grinding wheel containing abrasive grains according to (1) or (2), wherein the work material is carbon steel, special steel, titanium, resin plate, ceramics, or wood. ..

According to the present invention, the work process is complicated, the production cost is high, and the production of a grinding wheel containing abrasive grains that requires a large number of production days is performed, and in the form of abrasive grains or a molded body of abrasive grains. A method for evaluating the grindability of a grinding wheel containing abrasive grains can be provided.

It is a schematic diagram showing an example of a pin on disk type friction wear evaluation device used for a method of evaluating the grindability of a grinding wheel containing abrasive grains of the present invention.

An embodiment of the method for evaluating the grindability of the grinding wheel according to the present invention will be described in detail below, but the present invention is not limited to the following embodiment.

<Evaluation method of grindability of grinding wheel>
The present invention is a method for evaluating the grindability of a grinding wheel containing abrasive grains, using a pin-on-disc type friction and wear evaluation apparatus, wherein the abrasive grains are used as a work material instead of the grinding wheel containing the abrasive grains. Grinding, measuring the amount of wear of the abrasive grains, and the amount of grinding of the work material, from the grinding ratio of the abrasive grains defined by the ratio of the amount of grinding of the work material to the amount of wear of the abrasive grains, It is a method of evaluating the grindability of a grinding wheel containing abrasive grains for evaluating the grindability of a grinding wheel containing abrasive grains.
To evaluate the grindability of a grinding wheel, usually, for an actual grinding stone in which the abrasive grains are hardened with a resin such as a binder or a filler, a metal lump is ground using an actual grinding device, and the wear amount of the grinding stone is calculated. As described above, it is generally calculated by the following formula (A).
Grinding ratio = amount of work material cut (grinding amount)/abrasion amount of grindstone (A)
However, in the present invention, the grindability of the actual grinding wheel, the actual grinding wheel, without using the actual grinding device and the work material, of the abrasive grains or a molded body of abrasive grains by the pin-on-disc type friction wear evaluation device The grinding ratio is obtained by performing a friction wear test on a work material in a form to evaluate the grindability.
Specifically, the wear amount of the abrasive grains is calculated, and the wear amount is used as the wear amount of the grindstone in the formula (A). That is, the grinding ratio is calculated by the following formula (B), and the grindability is evaluated based on the grinding ratio of abrasive grains as a normal product described later.
Grinding ratio = amount of work material cut (grinding amount)/abrasive wear amount (B)
By the above-described evaluation method, the grindability of the grinding wheel can be evaluated without complicated manufacturing steps, high manufacturing cost, and without manufacturing a grindstone that requires many manufacturing days.

FIG. 1 is a schematic diagram showing an example of a pin-on-disk type friction and wear evaluation apparatus used in the method for evaluating the grindability of a grinding wheel of the present invention. The pin-on-disc type friction and wear evaluation apparatus 1 complies with (JIS R 1613-1993), and holds the disc-shaped work material 4 in rotation, and includes a rotary stage 3 provided with a rotation motor 2 and a test. A constant load is applied to a test body (not shown), which is an abrasive grain or a molded body of the abrasive grain, which is held at a predetermined position with respect to the surface of the work material 4 by the body holding jig 5, and the friction wear is being evaluated. A load control/displacement measuring unit 6 (not shown in detail) and a load applying section 7 (not shown in detail) for measuring displacement such as wear length and wear depth of the test piece and the work material 4. Prepare

The pin-on-disc type friction and wear evaluation device used in the present invention is not particularly limited as long as it conforms to (JIS R 1613-1993), and is, for example, a device having the following specifications.
・Test body load range: 1 to 500N
・Workpiece material rotation speed: 250 to 13000 rpm
・Work material rotation speed: 1-80 m/s
A test cell load measurement and a load cell for measuring a tangential load in the rotating direction of the work material are provided, and the frictional force can be calculated from the two loads.

Hereinafter, a method of calculating the grinding ratio of the abrasive grains using the pin-on-disk type friction and wear evaluation device will be described with reference to FIG.

In the friction and wear test, for example, in the pin-on-disc type friction and wear evaluation device 1, the peripheral speed, the pressing load (load is applied by the load control unit 6 and the load applying section 7), the grinding time, etc. are set to predetermined values. After that, the test piece held by the test piece holding jig 5 is pressed against the surface of the disk-shaped work material 4 which is rotated by the rotary stage 3 equipped with the rotation motor 2.
The amount of abraded material and the amount of wear of abrasive grains (corresponding to the amount of wear of a grindstone) in the formula (B) can be obtained, for example, by the following method.

<Evaluation of wear amount of work material after test>
The wear amount of the work material (disk body) after the test, which corresponds to the amount of the work material scraped, is calculated by the following formula (i) from the cross-sectional area of the wear mark, the wear portion diameter, and the work material density. To do.
Work material wear amount (g)=πρ ₁ rA (i)
In the above formula (i), ρ ₁ is the density of the work material (g/cm ³ ), r is the diameter of the worn portion of the test body (cm), and A is the cross-sectional area of the wear mark (cm ² ).
The cross-sectional area of the wear scar and the diameter of the worn portion can be measured by, for example, a digital microscope (manufactured by KEYENCE CORPORATION, model: VHX-6000). The diameter of the worn portion is measured as the diameter of a circle passing through the width center of the wear mark. The work material density can be measured as an apparent specific gravity of the work material by a liquid weighing method defined in JIS Z8807:2012.

<Evaluation of abrasion amount of abrasive grains after test>
The wear amount of the abrasive grains after the test is calculated by calculating the wear volume, converting the wear volume from the density of the abrasive grains to the weight, and calculating the wear amount of the abrasive grains.
First, the wear volume of the abrasive grains is calculated from the wear length before and after the test and the diameter of the abrasive grains by the following formula (ii).
Abrasive grain wear volume (cm ³ )=wear length×(abrasive grain diameter/2) ² π... (ii)
Next, the wear amount of the abrasive grains is calculated by the following equation (iii) using the density ρ _{2 of the} abrasive grains.
Abrasive grain wear amount (g)=abrasive grain wear volume×abrasive grain density ρ ₂ (iii)
The wear length (cm) is the difference in the length of the abrasive grains before and after the test. The length (cm) and diameter (cm) of the abrasive grains can be measured with, for example, a digital microscope (same as above).
The density of the abrasive grains can be measured as the apparent specific gravity of the abrasive grains by the weighing method in liquid defined in JIS Z8807:2012.
Since the abrasive grains have an irregular shape, it may not always be possible to calculate the worn volume from the length, as described above. In that case, if necessary, you may use a laser microscope or the like to analyze and calculate the volume difference before and after the test, directly measure the weight of the abrasive grains before and after the test with a scale etc. and wear amount (weight) May be calculated.

The abrasion amount of the work material calculated above is defined as "amount of the work material scraped", and the grinding ratio of the abrasive grains can be calculated from the wear amount of the abrasive grains by the formula (B). The measurement is similarly performed for three abrasive grains arbitrarily selected for each test body, and the measured values (N=3) obtained for each test body are simply averaged to obtain the value of each test body. Grinding ratio.

The amount of wear of the abrasive grains and the work material is not limited to the evaluation by the weight, and comparison in each volume is also possible.

(Evaluation of grindability of grinding wheel)
From the result of the grinding ratio of the abrasive grains obtained by the evaluation method of the present invention, the grindability of the grinding stone when the abrasive grains are actually used as the grinding stone can be evaluated as follows, for example.
In addition, hereinafter, a normal product means an abrasive grain as a comparison target of the grinding ratio when the work material is constant, a grinding ratio of the abrasive grain is Rs, and the abrasive grain of the evaluation target is The grinding ratio is R.
(A) When the grinding ratio R of the abrasive grains is compared with the grinding ratio Rs of the normal product, it is possible to estimate the superiority or inferiority of the grindability when the grinding wheel is used due to their relative size relationship.
(B) When the grinding ratio R of the abrasive grains is compared with the grinding ratio Rs of the normal product, the larger the grinding ratio R of the abrasive grains is, the better the grindability of the grinding wheel is. Can be guessed.
In addition, from the result of the grinding ratio of the abrasive grains, the grindability of the grinding stone when actually using the abrasive grains as a grinding stone, for example, from the viewpoint of performance and manufacturing cost, by the value of R/Rs, It can be evaluated (estimated) according to criteria.
B1: Particularly excellent (R/Rs value of 1.50 or more)
B2: Excellent (R/Rs value of 1.20 or more and less than 1.50)
B3: Good (R/Rs value is 1.0 or more and less than 1.20)
B4: Somewhat inferior (R/Rs value is 0.80 or more and less than 1.0)
B5: Inferior (R/Rs value is less than 0.80)
(The value of the grinding ratio of the abrasive grains is the value calculated from the formula (B), and the case where the unit of the grinding amount and the wear amount is g in the formula (B).)

<Abrasive grain>
The test body to be evaluated by the friction and wear test used in the present invention is ground in the form of abrasive grains or a molded body in which the abrasive grains are hardened with resin or the like (hereinafter, sometimes referred to as “abrasive grains”). There is no particular limitation as long as it is possible and the grinding ratio can be calculated. However, the molded body is different from the molded body obtained by the molding in the step (2) in the method for manufacturing the alumina sintered body abrasive grains described later.
The abrasive grains are not particularly limited, but are preferably alumina sintered body abrasive grains, alumina zirconia abrasive grains, alumina abrasive grains, or cubic boron nitride abrasive grains. The shape is not particularly limited as long as it can rub the work material. There are various methods for fixing the abrasive grains, or the abrasive grains, etc., such as adhesion to a jig such as a metal pin, fixation with screws, and fixation by electrodeposition.

(Alumina sintered body abrasive grain)
The alumina sintered body abrasive grain used in the present invention is not particularly limited and can be formed using a known alumina raw material. Specifically, as one aspect, it contains aluminum and at least one metal selected from the group consisting of yttrium, iron, zinc, cobalt, manganese, copper, niobium, antimony, tungsten, silver, and gallium. Is preferred.

The method for producing the alumina sintered body abrasive grains is not particularly limited, but preferably includes, for example, the following steps (1) to (3).
Step (1): Step of preparing a mixture containing a known alumina raw material Step (2): Step of molding the mixture obtained in step (1) Step (3): Molded body obtained by step (2) Step of firing to obtain alumina sintered body abrasive grains The above-mentioned manufacturing method may have the following step (4), if necessary, in order to obtain powdery alumina sintered body abrasive grains.
Step (4): A step of crushing the alumina sintered body abrasive grains obtained in the step (3)

Further, the method for producing the alumina sintered body abrasive grains preferably includes, for example, the following steps (1), (2), (3)', and (4)'.
Step (1): Step of preparing a mixture in which a known alumina raw material is mixed Step (2): Step of molding the mixture obtained in Step (1) Step (3)′: Alumina obtained in Step (2) Step of drying and then crushing the molded body of step (4)': step of firing the crushed material obtained in step (3)' to obtain alumina sintered body abrasive grains

In mixing the raw materials in the step (1), a known mixing means is used, for example, a container rotation type, a mechanical stirring type, a fluid stirring type, a non-stirring type, a high speed shearing/impact type and the like.
In the molding of the step (2), a known molding means is used, and it can be molded into an arbitrary shape by, for example, a die press, a cold isostatic press, a cast molding, an injection molding, an extrusion molding and the like.
In the step (3), the molded body obtained in the step (2) is sintered. Further, upon sintering, a known sintering method is used, and for example, various sintering methods such as a hot pressing method, an atmospheric pressure sintering method, a gas pressure sintering method, a microwave heating sintering method, and the like are used.
The sintering temperature is preferably 1400° C. or higher and 1800° C. or lower, more preferably 1600° C. or higher and 1800° C. or lower.
In step (4), the alumina sintered body obtained in step (3) is crushed. A known crushing means is used for crushing, and for example, a ball mill, a rod mill, a vibration mill, a high-pressure crushing roll, or the like is used to crush to an arbitrary size.

In step (3)', the alumina compact obtained in step (2) is dried and then pulverized. As the crushing method, the same crushing method as in the above step (4) can be used. In addition, the drying can be performed, for example, at atmospheric pressure and atmospheric pressure at about 100° C. for 2 hours or more.
In the step (4)', the pulverized product obtained in the step (3)' is fired to obtain alumina sintered body abrasive grains. Sintering can be performed by the same method as in the above step (3).

(Alumina zirconia abrasive grain)
The alumina zirconia abrasive grain used in the present invention is not particularly limited, but, for example, a zirconia-based raw material is added to alumina purified by the Bayer method (wet alkaline method), the mixture is melted in an electric furnace, and the solidified mass is crushed and sized. One can be used. It mainly consists of corundum crystals and an alumina-zirconia eutectic portion, and examples thereof include AZ(25) (alumina zirconia; zirconia 25 mass%) and AZ(40) (alumina zirconia; zirconia 40 mass%) having different zirconia contents. To be

(Cubic boron nitride abrasive)
Cubic Boron Nitride (CBN) has hardness second only to diamond and higher chemical stability than diamond, and can be used as a cubic boron nitride abrasive grain for grinding. The method for producing cubic boron nitride is not particularly limited, but, for example, hexagonal boron nitride (hBN) is added in the presence of a catalyst substance or the like to a cubic temperature of about 4 to 6 GPa and about 1400 to 1600° C. It can be produced by a method of holding hexagonal boron nitride in the thermodynamically stable region of cubic boron nitride and converting hexagonal boron nitride into cubic boron nitride.

(Work material)
The material of the work material is not particularly limited, but any material suitable for the purpose of evaluation may be used, and examples thereof include carbon steel, special steel, titanium, resin plate, ceramic, and wood.
Examples of carbon steel include S40C to S58C defined in JIS G 4051:2016, SAE1040 to SAE1095 defined in SAE standards, and the like.
Examples of the special steel include stainless steel, heat resistant steel, structural steel, superalloy, tool steel and the like.
For example, in heavy grinding abrasive grain evaluation, S45C defined in JIS G 4051:2016 (carbon steel material for machine structure) may be used without tempering such as quenching.
The dimensions of the work material used for evaluation are not particularly limited, but are, for example, φ160 mm and thickness 10 mm, and the arithmetic mean roughness Ra of the friction surface contacting the test body is, for example, 0.1 to 10 nm. is there.

<Grinding stone>
In the present invention, the grindstone, in addition to the abrasive grains, contains a binder, a filler, etc., and usually has a base metal and a layer containing the abrasive grains used in the present invention on the working surface of the base metal. Meaning
Examples of the method for fixing the abrasive grains on the working surface of the grindstone include resin bond, vitrified bond, metal bond, and electrodeposition.
Examples of the material of the base metal include steel, stainless alloy, aluminum alloy and the like.
The resin bond has good sharpness but low durability. The vitrified bond has good sharpness and good wear resistance, but internal stress is generated in the abrasive grains, and the abrasive grains are easily cracked or chipped. Electrodeposition has a large degree of freedom in shape and good sharpness.
In view of the above, in the grindstone, the method of fixing the abrasive grains is selected according to the application.
For example, in the case of a resin-bonded grindstone, a method of mixing powder of a binder such as phenol resin or polyimide resin and abrasive grains, or coating the binder with abrasive grains, filling the die with a die, and press-molding (i ), or a method in which a liquid binder such as an epoxy resin or an unsaturated polyester resin is mixed with abrasive grains, and the mixture is poured into a mold and cured (ii) to fix the abrasive layer to the working surface of the base metal. The grindstone referred to in the present invention can be obtained.
The shape of the grindstone is not particularly limited, and may be a straight type, a cup type, or the like depending on the application of the grindstone.

Here, for example, a case of producing a heavy grinding wheel having a diameter of 500 to 1000 mm will be described. First of all, a large amount of material is required when manufacturing such a large heavy grinding wheel. Specifically, for example, 40 kg of abrasive grains, 25 kg of fillers other than abrasive grains, 15 kg of resin, predetermined reinforcing glass fiber and the like are used. Further, a large-sized material mixing device according to the size, a mold, a press, an oven for baking (baking), and a conveying means are required. Molding requires several minutes to several hours, baking (baking) several tens of hours, and generally requires several days to complete the whetstone.
Further, in order to obtain the grinding ratio, a grinding device capable of rotating the grindstone at a high speed (for example, 280 km/hr) and a large steel material called a slab as a work material (for example, thickness 120 to 600 mm, width 700 mm-) is required.
As can be seen from the above, as described above, the manufacturing process of the grindstone is complicated, the manufacturing cost is high, and many manufacturing days are required.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and includes all aspects included in the concept of the present invention and the scope of the claims, and is various within the scope of the present invention. Can be modified to

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Example 1)
Alumina raw material powder (aluminum oxide (Al ₂ O ₃ ) content: 99.75 mass %, α crystallization rate of aluminum oxide: 99% or more, d ₅₀ : 0.62 μm) was added to 1,000 g of iron oxide (Kanto). Kagaku Co., Ltd., d ₅₀ : 0.52 μm) 2.5 g and granular polyvinyl alcohol (Kuraray Co., Ltd., model number PVA-205) 3.4 g were placed on a tabletop kneader (manufactured by Irie Shokai “PNV-5”. ]) for 10 minutes. Then, an yttrium (III) acetate tetrahydrate aqueous solution was prepared by dissolving 2.5 g of yttrium (III) acetate tetrahydrate (manufactured by Kanto Chemical Co., Inc.) in 300 g of distilled water, and the aqueous solution was added to the above mixture. In addition, the mixture was kneaded for 30 minutes to prepare a precursor of an alumina sintered body. Table 1 shows the compounding composition based on the above composition.
Here, the precursor of the alumina sintered body (hereinafter, may be simply referred to as “precursor”) refers to a raw material mixture before heat treatment. Further, the alumina sintered body (hereinafter, sometimes simply referred to as “sintered body”) refers to a sintered body obtained by heat-treating and sintering the precursor.

The composition of the alumina raw material powder was confirmed in advance by a fluorescent X-ray elemental analysis method. As a measuring instrument for the fluorescent X-ray elemental analysis, a scanning type fluorescent X-ray analyzer "ZSX Primus" manufactured by Rigaku Corporation was used. A measurement sample was prepared by a powder pressing method using press-formed pellets, and quantitatively analyzed by a fundamental parameter method (FP method).
Also, regarding the composition of the precursor of the alumina sintered body, as in the case of the alumina raw material powder, quantitative analysis was performed by the FP method using the above-mentioned scanning fluorescent X-ray analysis device, and it was confirmed that it was in agreement with the charged composition. confirmed.

The d ₅₀ of the alumina raw material powder and iron oxide was measured using a Microtrac particle size distribution analyzer (“Microtrac (registered trademark) HRA”, manufactured by Nikkiso Co., Ltd.).

The α crystallization rate of aluminum oxide in the alumina raw material powder was measured using a powder X-ray diffractometer (manufactured by Panalytical, model name “X'pert PRO”), characteristic X-ray: CuKα ray, tube voltage 40 kV, tube From the diffraction spectrum obtained under the condition of a current of 40 mA, the peak height (I _68.1 ) of 2θ=68.1° derived from the alumina α phase (300), and the δ phase, θ phase, χ phase, γ phase , Θ phase and ε phase derived 2θ=67.2° peak height (I _67.2 ) and calculated from the following formula (1).
α crystallization rate=I _68.1 /(I _68.1 +I _67.2 )×100(%) (1)

(Example 2)
In Example 2, a precursor of an alumina sintered body was obtained in the same manner as in Example 1 except that the yttrium (III) acetate tetrahydrate aqueous solution was not added.

(Example 3)
In Example 3, a precursor of an alumina sintered body was obtained in the same manner as in Example 1, except that the amount of iron oxide added was changed.

[Evaluation I]
Using the precursor of the alumina sintered body according to Examples 1 to 3, an alumina sintered body (hereinafter, also referred to as “test body”) was produced by the following method, and the alumina sintered body was prepared. The following test (evaluation) was performed.

(Preparation of alumina sintered body)
The precursor of the alumina sintered body was molded using an extrusion molding machine to prepare an alumina molded body. Then, this compact was held in an electric furnace (atmosphere atmosphere) at the firing temperature shown in Table 1 for 1 hour to sinter the alumina sintered body abrasive grains (φ1.6 mm, length 3.5 mm). Columnar) was obtained.
The alumina sintered body abrasive grains were fixed by adhering them to a jig made of a metal pin.
In addition, the alumina sintered body abrasive grains obtained by sintering the alumina sintered body precursor obtained in Example 1 were abrasive grains A, and the alumina sintered body precursor obtained in Example 2 was sintered alumina. The sintered abrasive grains were abrasive grains B, and the alumina sintered abrasive grains obtained by sintering the precursor of the alumina sintered body obtained in Example 3 were abrasive grains C. Among these, the abrasive grains B were used. Was used as a normal grindability product (comparison target), and the abrasive grains A and C were used as grindability evaluation targets.

[1] Grinding ratio A frictional wear test of alumina sintered body abrasive grains was performed using a rotary sliding type (pin-on-disc type) frictional wear tester. The frictional wear test was performed by pressing the alumina sintered body abrasive grains obtained in Examples 1 to 3 against a rotating disc-shaped work material, and using the work material peripheral speed of 10 m/sec and a pressing load of 50 N for 3 minutes. .. As the work material, S45C (φ160 mm, thickness 10 mm), which is carbon steel defined in JIS G 4051:2016 (carbon steel material for machine structure), was used without tempering or the like.
The wear amount of the work material and the wear amount of the alumina sintered body abrasive grains are measured by using a digital microscope (manufactured by KEYENCE CORPORATION, model: VHX-6000). It was calculated from the length and the density of the work material, and the wear amount of the alumina sintered body abrasive grains was calculated from the wear length before and after the test and the density of the test body. The grinding ratio was calculated by the following formula (B) from the wear amount of the obtained work material and the wear amount of the alumina sintered body abrasive grains.
Grinding ratio = amount of work material cut (grinding amount)/abrasive wear amount (B)

[2] Grindability From the results of the grinding ratio of the alumina sintered body abrasive grains obtained in the examples, the grinding performance of the grinding stone when the alumina sintered body abrasive grains were actually used as a grinding stone was evaluated. From the viewpoint of manufacturing cost, the value of R/Rs was evaluated (estimated) according to the following criteria.
B1: Particularly excellent (R/Rs value of 1.50 or more)
B2: Excellent (R/Rs value of 1.20 or more and less than 1.50)
B3: Good (R/Rs value is 1.0 or more and less than 1.20)
B4: Somewhat inferior (R/Rs value is 0.80 or more and less than 1.0)
B5: Inferior (R/Rs value is less than 0.80)
<R is an abrasive grain to be evaluated (abrasive grain A which is an alumina sintered body abrasive grain obtained by sintering the precursor of the alumina sintered body of Example 1, and the precursor of the alumina sintered body of Example 3 is burned). The grinding ratio of the bonded alumina sintered body abrasive grains C), Rs, is a normal product (comparison target) abrasive grain (alumina sintered body abrasive obtained by sintering a precursor of the alumina sintered body of Example 2). It is a grinding ratio of abrasive grains B) which are grains. 〉

[3] Relative Density The relative density was obtained by dividing the apparent density measured by the in-liquid weighing method of JIS Z 8807:2012 by the true density. At this time, it is assumed that the added compounds and the like all exist in an oxide state, and the true density is 3.95 for alumina, 5.01 for yttrium oxide, and 5.24 for iron oxide. Silicon oxide 2.20, sodium oxide 2.27, magnesium oxide 3.65, calcium oxide 3.34, zinc oxide 5.61, cobalt oxide 6.11, manganese oxide 5.03, oxidation Calculations were made assuming that copper was 6.31, niobium oxide was 4.47, antimony oxide was 5.20, tungsten oxide was 7.16, silver oxide was 7.14, and gallium oxide was 6.44.

[4] Crystal Particle Diameter The obtained alumina sintered body abrasive grains were cut, the cut surface was mirror-finished, and thermal etching was performed at a temperature 100° C. lower than the firing temperature for 5 minutes. The sample was observed using a scanning electron microscope (manufactured by JEOL Ltd., model name "JSM-6510V"), and cross-sectional photographs at 5000 times were taken at 5 arbitrary points. For each cross-section photograph, image analysis was performed using image analysis software (manufactured by Mountech Co., Ltd., software name "Mac-View ver. 4"), and about 500 crystal particles arbitrarily selected from 5 cross-section photographs. The volume sphere equivalent diameter was measured, the obtained measurement values (N=500) were averaged, and the average value was taken as the crystal particle diameter.

[5] Vickers hardness As a device, a model name "MVK-VL, Hardness Tester" manufactured by Akashi Co., Ltd. (currently Mitutoyo Co., Ltd.) was used. The measurement was performed under the conditions of a load of 0.98 N and an indenter driving time of 10 seconds, and was similarly performed for 15 alumina sintered body abrasive grains arbitrarily selected for each sample. Further, the obtained measured values (N=15) were averaged, and the average value was defined as Vickers hardness.

[6] Fracture toughness value Fracture toughness value JIS R 1607:2015 Based on the room temperature fracture toughness test method of fine ceramics, it was determined by the IF method (indentation method). As the device, a model name “DVK-1” manufactured by Matsuzawa Seiki Co., Ltd. (currently Matsuzawa Co., Ltd.) was used, and the measurement was performed under conditions of a maximum load of 49 N, an indenter driving speed of 50 μm/sec, and an indenter driving time of 15 seconds. The same procedure was performed for 10 alumina sintered body abrasive grains arbitrarily selected for each sample. Further, the obtained measured values (N=10) were averaged, and the average value was taken as the fracture toughness value. The calculation formula is as follows.
K _IC =0.026×E ^1/2 ×P ^1/2 ×a/c ^3/2
K _IC : Fracture toughness value (MPa·m ^1/2 )
E: Young's modulus (Pa)
P: Maximum load (N)
a: Indentation size (m)
c: Crack size (m)
In the present invention, the Young's modulus E used the value of alumina (3.9×10 ¹¹ Pa).

As shown in Table 1, when the abrasive grains A, B, and C having different compositions or compounding ratios of the precursors of the alumina sintered body were used, it was found that there was a significant difference in the grinding ratio among the three. Further, for example, since the grinding ratio of Example 1 using the abrasive grain A used as the evaluation target is relatively higher than the grinding ratio of Example 2 using the abrasive grain B used as a normal product, It can be seen that it is possible to evaluate (estimate) that the grindability of the grinding wheel containing A is excellent (B1). On the other hand, since the grinding ratio of Example 3 using the abrasive grain C to be evaluated is relatively lower than the grinding ratio of Example 2 using the abrasive grain B to be a normal product, It can be seen that it is possible to evaluate (estimate) that the grindability of a grinding wheel containing C is poor (B5).
That is, according to the simple evaluation method of the present invention, a grindstone having a high grinding ratio can be easily found simply by using the abrasive grains or a molded body of the abrasive grains without producing the grindstone.

According to the method for evaluating the grindability of a grinding wheel containing abrasive grains of the present invention, in the form of an abrasive grain or a molded body of the abrasive grain, an evaluation of the grindability of the grinding wheel composed of abrasive grains, a binder, a filler, As a result, it is possible to efficiently select the required grinding wheel without the need for manufacturing the wheel, which usually requires complicated work steps, high manufacturing cost, and many manufacturing days. ..

1: Pin-on-disc type friction/wear evaluation device 2: Rotating motor 3: Rotating stage 4: Work material 5: Specimen holding jig 6: Load control/displacement measuring unit 7. Load part

Claims (3)

Using a pin-on-disk type friction and wear evaluation device, a method of evaluating the grindability of a grinding wheel containing abrasive grains,
Instead of a grinding wheel containing the abrasive grains, the work piece is ground with the abrasive grains, the wear amount of the abrasive grains, and the grinding amount of the work material are measured, and the work amount relative to the wear amount of the abrasive grains is measured. A method of evaluating the grindability of a grinding wheel containing abrasive grains, wherein the grindability of a grinding wheel containing the abrasive grains is evaluated from the grinding ratio of the abrasive grains defined by the ratio of the grinding amount of the cutting material. The method for evaluating the grindability of a grinding wheel containing abrasive grains according to claim 1, wherein the abrasive grains include alumina sintered body abrasive grains, alumina zirconia abrasive grains, alumina abrasive grains, or cubic boron nitride abrasive grains. The method for evaluating the grindability of a grinding wheel containing abrasive grains according to claim 1 or 2, wherein the work material is carbon steel, special steel, titanium, a resin plate, ceramics, or wood.