JP2002307208A - Cutting tool made of silicon nitride sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool made of a silicon nitride sintered compact having excellent chipping resistance and wear resistance. SOLUTION: This cutting tool made of the silicon nitride sintered compact is formed of the silicon nitride sintered compact in which the orientation direction of crystal grain is controlled in a specific direction by the plastic flow of the crystal grain caused by compression-baking a premolding formed by compacting silicon nitride raw powder. The cutting tool made of the other silicon nitride sintered compact is formed of a silicon nitride sintered compact in which the major axis of crystal grain in the rake face of the cutting tool is controlled in a parallel direction to the rake face. In both cases, excellent chipping resistance is obtained by setting the X-ray intensity ratio of the rake face and at least one flank relief into a specific range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cutting tool made of silicon nitride, and more particularly, to a cutting tool made of silicon nitride which is excellent in chipping resistance and wear resistance.

[0002]

2. Description of the Related Art It has been known that a silicon nitride sintered body has high strength and high toughness, and is excellent in abrasion resistance, thermal shock resistance and fracture resistance. Further, it is known that a silicon nitride compact can be obtained with high strength and high toughness by superplastic working (hereinafter, also referred to as superplastic forging sintering) simultaneously with sintering of a molded body of silicon nitride (for example, No. 2,923,781; No. 2,944,953;
Publication). However, these sintered bodies are not intended for cutting tools. Furthermore, this sintered body has a surface with low strength, and it has not been known at all how the sintered body is useful as a cutting tool material.

[0003] Although there is no description that the particles are oriented by plastic flow during firing, Japanese Patent Application Laid-Open No. Hei 8-1 discloses a cutting tool for improving strength, toughness and chipping resistance.
No. 12705 and the like. This cutting tool improves the above performance by orienting the axis of the columnar and coarse β silicon nitride particles two-dimensionally in a direction parallel to the rake face of the cutting tool. However, since the particle orientation method is such that coarse columnar β silicon nitride particles are added and oriented before firing, the strength is 1100 due to the influence of residual pores and residual stress.
It stagnates at about MPa, and when the cut amount is increased, the fracture resistance is poor. Therefore, there has been a demand for a cutting tool which is excellent in chipping resistance, wear resistance and the like and has a longer life.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a cutting tool made of a silicon nitride sintered body which is excellent in both fracture resistance and wear resistance. is there.

[0005]

Means for Solving the Problems The present inventors have studied a cutting tool made of a silicon nitride sintered body which is excellent in both fracture resistance and wear resistance, and have completed the present invention. That is, by removing the residual pores of the preform by superplastic forging sintering, and / or by setting the rake face of the cutting tool in a specific direction, and by setting the degree of orientation of the crystal grains, It has been found that strength and toughness can be improved, and excellent fracture resistance and wear resistance can be obtained when a cutting tool is used.

[0006] The cutting tool made of a silicon nitride sintered body of the present invention comprises:
A silicon nitride-based raw material powder is compacted to produce a pre-formed body, and the pre-formed body is baked and, at the same time, is subjected to plastic flow of the crystal grains by compression, whereby the orientation direction of the crystal grains is controlled in a specific direction. And a silicon nitride-based sintered body.

The above-mentioned “silicon nitride raw material powder” is not particularly limited. However, since it is necessary that the crystal grains of the sintered body grow anisotropically, they are superplastically deformed in the firing temperature range. It is preferable to perform liquid phase sintering. Usually, α silicon nitride powder, α sialon powder, β silicon nitride powder, and β silicon nitride powder
At least one of sialon powder and sintering aid powder are used. The average particle diameter of the α silicon nitride powder, α sialon powder, β silicon nitride powder, and β sialon powder is preferably 0.1 to 2 μm. The specific surface area of these powders is preferably 5 to 15 g / m ² .

The sintering aid powder is not particularly limited, and may be any compound that forms a liquid phase in the sintering temperature range. Usually, oxides containing metal elements (eg, yttrium oxide, aluminum oxide, magnesium oxide, zirconium oxide, etc.), carbides (eg, zirconium carbide, titanium carbide, tungsten carbide, etc.), and nitrides (eg, aluminum nitride, nitride, etc.) Powders such as titanium and yttrium nitride) are used. The specific surface area of these sintering aid powders is preferably 5 to 35 g / m ² . These sintering aid powders may be used alone,
You may mix and use 2 or more types.

The "preformed body" is obtained by compacting a predetermined silicon nitride-based raw material powder. In the compacting, the raw material powder may be pressurized, and examples of the pressurizing method include a CIP (Cold Isostatic Press), a die press, and a rubber press. Molding conditions, such as temperature and pressure, at the time of compacting are appropriately adjusted depending on the type of raw material, desired shape, and the like. Furthermore, it is appropriately prepared as long as the raw material powder can be molded as it is, such as injection molding and casting molding.

The "silicon nitride-based sintered body" is obtained by compressing the preformed body at the same time as sintering and performing plastic flow (superplastic forging sintering). The orientation direction of the crystal grains is specified. It is controlled in the direction. For this reason, the major axis of the needle-like or columnar particles is oriented parallel to the compression surface, and the orientation of the major axis can dramatically improve the strength and toughness of the compression surface compared to a sintered body having a random structure. . In addition, a sintered body produced by adding coarse β silicon nitride particles prior to sintering and orienting has a smaller particle size, removes residual pores, obtains a material having high strength and high toughness, A cutting tool with excellent properties can be obtained.

The superplastic forging and sintering methods include hot compression, hot rolling, and hot extrusion. At this time, the preform is placed in a mold in a state where there is no constraint on the side faces, or in such a manner that deformation of one or more side faces is restrained. Molding conditions such as temperature and pressure during superplastic forging and sintering are appropriately adjusted depending on the shape of the preformed body, a desired shape, and the like. For example, in the case of hot compression processing, a sintering temperature of 1500 to 2000 ° C. and a molding pressure of 2-1.
The relative density of this silicon nitride-based sintered body capable of performing superplastic forging sintering under the conditions of 00 MPa and a nitrogen pressure of 1 to 10 atm is usually 97 to 100% (preferably 98 to 10%).
0%).

In the cutting tool of the present invention, any surface of the silicon nitride sintered body may be used as the rake surface, but it is preferable that the surface perpendicular to the compression axis direction at the time of plastic flow be the rake surface. In this case, the crack propagation direction when the cutting tool breaks is perpendicular to the axis of the crystal grain, so that the fracture resistance can be improved.

Another cutting tool made of a silicon nitride based sintered body of the present invention is a cutting tool made of a silicon nitride based sintered body, wherein a major axis of crystal grains on a rake face of the cutting tool is the rake face. Is controlled in a direction parallel to

In the above cutting tool, the major axis of the crystal grains on the rake face is controlled in a direction parallel to the rake face. For this reason, the crack propagation direction when the cutting tool breaks is perpendicular to the major axis of the crystal grain, and the fracture resistance can be improved. In the case of a cutting tool, the sintered body is not particularly limited as long as the major axis of the crystal grain on the rake face is controlled in a direction parallel to the rake face. This sintered body can use the aforementioned silicon nitride-based raw material powder and the like, and can be produced, for example, by the aforementioned superplastic forging sintering.

In the above-mentioned present invention and the above-mentioned other present invention, the above-mentioned rake face has an X shown in the following formula (1).
The intensity ratio R of the line diffraction peak is 0.90 to 1 (more preferably 0.95 to 1), and at least one of the flank surfaces has an intensity ratio R of 0.10 to 0.80 (more preferably 0 to 0). .15 to 0.75). R = I ₍₂₀₀₎ / (I ₍₂₀₀₎ + I ₍₀₀₂₎ ) (1) [where I ₍₂₀₀₎ and I ₍₀₀₂₎ are the (200) plane of β silicon nitride and / or β sialon, respectively. 002) represents the reflection intensity of the surface. When the intensity ratio R is 1, it means that the major axis of the β silicon nitride and / or β sialon crystal (hereinafter also referred to as c-axis) is parallel to the measurement plane in all the particles, and R is 0 The case of means that the c-axis of the β silicon nitride crystal is perpendicular to the measurement plane in all the particles.

If the strength ratio R of the rake face is less than 0.90, the number of particles of β silicon nitride and / or β sialon whose c-axis is perpendicular to the rake face increases, so that the strength of the rake face increases. And fracture resistance also decreases. If the intensity ratio R of at least one flank is greater than 0.80, β silicon nitride and / or β
Since the number of sialon particles increases and the strength of the rake face in the direction perpendicular to the flank face decreases, fracture resistance may decrease. If the intensity ratio R of one flank is less than 0.10, the number of particles of β silicon nitride and / or β sialon whose c-axis is parallel on the other flank increases, and the flank is parallel to the flank. The strength of the rake face in the direction may decrease, and the fracture resistance may decrease.

The cutting tool according to the invention has a cross section of height 3
In a three-point bending strength test method using a bending test piece having a width of 4 mm and a width of 4 mm, the strength of the rake face is 1
200 MPa or more (preferably 1300 MPa or more,
More preferably, it can be set to 1400 MPa or more. Furthermore, other three-point bending or four-point bending strength tests (for example, JIS
R 1601 bending strength test), the strength can be equal to or higher than the strength of the present strength test method based on the effective volume conversion. The effective volume can be obtained by using the following equation (2), and further, the following equation (3)
Is used to determine the correlation between the effective volume (V ₁ ) and strength (σ ₁ ) according to the strength test method of the present invention and the effective volume (V ₂ ) and strength (σ ₂ ) according to the other methods described above. it can.

[0018]

(Equation 1)

[However, V _E : effective volume, b: width of test piece, h: (height of test piece) / 2, L ₁ : (outer span−inner span) / 2, L ₂ : inner span, m: Weibull coefficient. ]

[0020]

(Equation 2)

[However, σ ₁ , σ ₂ : average intensity, V ₁ , V ₂ :
Effective volume, m: Weibull coefficient. ]

Further, the cutting tools of both inventions have a number of processing peaks of 10 in a cutting test for evaluating fracture resistance in the following examples.
Or more (preferably 14 or more).

In addition, the cutting tools of the present invention have a wear resistance of 0.95 or less, provided that the wear resistance of a cutting tool of the same composition produced by normal pressure sintering and gas pressure sintering is 1. (Preferably 0.90 or less, more preferably 0.70 or less). However, the abrasion resistance is determined by the evaluation method in the following example.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. Example 1 (1) Cutting tool made of silicon nitride sintered body (Experimental Examples 1, 2, and 4)
And 5) α silicon nitride powder (manufactured by Ube Industries, Ltd.,
“E-10”, specific surface area; 10 m ² / g, average particle size;
0.5 μm) and a sintering aid component powder [yttrium oxide (specific surface area; 10 m ² / g), aluminum oxide (specific surface area; 13 m ² / g), magnesium oxide (specific surface area;
30m ² / g), cerium oxide (specific surface area; 10 m ² /
g), zirconium oxide (specific surface area; 10 m ² / g)]
Were mixed so as to have a predetermined ratio as shown in Table 1, and wet-pulverized and mixed in ethanol using a ball mill for 40 hours. The obtained slurry was passed through a 500-mesh sieve to remove the solvent and collect the powder, and then a granulated powder was obtained using a 50-mesh sieve. This was uniaxially pressed and then subjected to a CIP (cold isostatic pressing) treatment at 196 MPa to obtain a preform of 40 × 20 × 30 mm. The obtained preform was placed in a carbon die having a bottom surface of 60 × 20 mm so that one set of side surfaces restrained deformation, and was subjected to compression processing simultaneously with sintering. Hot compression processing is 1650-175
0 ° C, 9atm of nitrogen, compressive load 36kN (final pressure 3
This was performed for 3 hours under the condition of 0 MPa). The obtained sintered body is about 60 × 20 × 10 mm, and the density is 95 to
It was about 99%. Thereafter, a surface perpendicular to the compression axis (hereinafter, referred to as N surface) is a rake surface, a surface perpendicular to the direction in which plastic flow has occurred (hereinafter, referred to as E surface), and a surface restraining deformation (hereinafter, referred to as T). Surface).
Predetermined tool shape (ISO SNGN432 type, size;
12.7mm in height, 12.7mm in width, 4.76mm in height)
Processed to.

(2) Cutting tool made of silicon nitride sintered body (Experimental Examples 3 and 6) Using the same raw material powder as in (1) above, a preform was prepared in the same manner as in (1) above, and 1650 After sintering under normal pressure in nitrogen gas at １1700 ° C., further 1600 ° C. to 1800
A sintered body obtained by gas pressure sintering at 75 ° C. and 75 atm of nitrogen was processed into a predetermined tool shape (ISO SNGN432 type).

[0026]

[Table 1]

(3) Evaluation of Cutting Tools (Experimental Examples 1 to 6) The chipping resistance and wear resistance of each of the cutting tools obtained in (1) and (2) above were evaluated by cutting tests under the following conditions. did. These results are also shown in Table 1. (Evaluation method of fracture resistance) The flank of each cutting tool is chamfered with a chamfer of 0.07 mm, and "FC200" with cast sand remaining on both end surfaces is used as a work material, under a dry method, at a cutting speed; 150 mm / min, depth of cut; 2.0 mm,
Cutting was performed three times under the same conditions at a feed speed of 1.3 mm / rev. The number of processing peaks was set to a maximum of 15. If the number of processing peaks before the occurrence of chipping is 10 or less,
Fourteen were evaluated as “○”, and fifteen (no defects occurred) as “◎”. (Evaluation method of wear resistance) The flank of each cutting tool is chamfered with a chamfer of 0.2 mm, and "FC200" having cast sand remaining on both end surfaces is used as a work material, under a dry method, at a cutting speed; Cut under the conditions of 300 mm / min, depth of cut; 1.5 mm, feed rate; 0.34 mm / min,
The maximum amount of flank wear was measured, and the flank wear (m
m).

(4) Evaluation Results (Experimental Examples 1 to 6) According to Table 1, Experimental Examples 3 and 6 using silicon nitride sintered bodies produced by normal pressure sintering and gas pressure sintering. Then, the number of processing peaks is 3 and 2 or less for 3 times, respectively.
The fracture resistance was "x". On the other hand, using the sintered body produced by superplastic forging sintering, the experimental example 1 and the experimental example 4 in which the front flank surface was the E surface, and the front flank surface was the T surface. In all of Experimental Examples 2 and 5, the number of processing hills was 15 at all three times, and there was no fracture, and the fracture resistance was excellent as “◎”. Further, Experimental Examples 1 to 1 having the same composition
Comparing the flank wear amounts of Example 3 and Example 2, which are 2.32 mm in Experimental Example 3 outside the range of the present invention, 1.46 mm respectively in Experimental Examples 1 and 2 within the range of the present invention.
(Abrasion resistance of Experimental example 3: Abrasion resistance of Experimental example 1 = 1: 0.
63), 2.18 mm (abrasion resistance of Experimental Example 3: Experimental Example 2)
The amount of abrasion was 1: 0.94), and the abrasion resistance was excellent.
Further, when the flank wear amounts of Experimental Examples 4 to 6 having the same composition were compared, it was found that Experimental Example 6 outside the scope of the present invention showed that
While it is 1.03 mm, in Experimental Examples 4 and 5 within the scope of the present invention, each is 0.41 mm (abrasion resistance of Experimental Example 6: Abrasion resistance of Experimental Example 4 = 1: 0.40). , 0.9m
m (abrasion resistance of Experimental Example 6: abrasion resistance of Experimental Example 5 = 1: 1)
0.88), which is excellent in abrasion resistance. From the above,
Experimental Examples 1, 2, 4, and 5 were found to be excellent in both the fracture resistance and the wear resistance.

Example 2 (1) Production of cutting tool made of silicon nitride sintered body (Experimental Examples 7 to
11) To confirm the effect of β silicon nitride orientation,
Using powders having the same composition and the same method as in Experimental Example 4, a preform having the shape shown in Table 2 was prepared, and subjected to hot pressing to differ in the degree of orientation of β silicon nitride and / or β sialon. Sintered body (shape; N direction 60 mm, T direction 20 mm,
E direction 6.5 to 15 mm). The obtained sintered body was processed so as to have a predetermined tool shape (ISO SNGN432 type).

(2) Preparation of Cutting Tool Made of Silicon Nitride Sintered Body (Experimental Examples 12 and 13) A preform having the shape shown in Table 2 was prepared by using granulated particles having the same composition as in the above (1). After sintering at 1600-1700 ° C. in nitrogen gas at normal pressure, the temperature is further increased from 1600 ° C. to 1800 ° C.
Sintered body (shape; gas-pressure sintered at 75 ° C and 75atm nitrogen)
(N direction 32mm, T direction 16mm, E direction 24mm)
And a sintered body obtained by hot press sintering the powder at 1700 ° C. (shape: N direction 60 mm, T direction 20 mm, E direction 10
mm), and the obtained sintered body is shaped into a predetermined tool shape (I
(SO SNGN432 type).

[0031]

[Table 2]

(3) Evaluation of Cutting Tools (Experimental Examples 7 to 13) The fracture resistance, three-point bending strength, and X-ray intensity ratio of each of the cutting tools obtained in the above (1) and (2) are as follows. Was measured and evaluated under the following conditions. These results are also shown in Table 2. Further, an X-ray chart showing the X-ray intensity ratio of Experimental Example 9 is shown in FIG. (Evaluation method for fracture resistance) Evaluation was performed in the same manner as (3) of Example 1 above. (Evaluation method of three-point bending strength) A sample of 3 × 4 × 20 (mm) was prepared by cutting a rake face as a tensile face and a front flank direction as a tensile axis, and the cross section was 3 mm in height, 4 mm in width, The three-point bending strength of a span of 16 mm was evaluated.

(Method of Measuring X-Ray Intensity Ratio) The degree of orientation of the crystal grains of β silicon nitride and / or β sialon can be determined by the following method.
It is shown using the intensity ratio R of the X-ray diffraction peaks of the (200) plane and the (002) plane of Sialon. An X-ray diffractometer (“RU-200T”, manufactured by Rigaku Denki Kogyo Co., Ltd.) was used, CuKα radiation was used as an X-ray source, and the X-ray output was 40 kV, 10 kV.
0 mA. The measurement method was an FT method, with a scan speed of 2 ° / min and a step of 0.02 °. As the slit, a divergence slit of 0.5 degree, a scattering slit of 0.5 degree, and a light receiving slit of 0.15 mm were used. Peak intensity, after separation K [alpha ₁ and K [alpha _2, with a strength of K [alpha _1.

(4) Evaluation Results (Experimental Examples 7 to 13) According to Table 2, the X-ray intensity ratio R was 0.84 for the N plane and 0.5 for the T plane.
59, E surface 0.59, Experimental Example 12 using a silicon nitride sintered body produced by powder hot press sintering, and X-ray intensity ratio was 0.72 on all surfaces. In Experimental Example 13 using a silicon nitride sintered body produced by sintering and gas pressure sintering, the number of processing peaks was 5 or 3 for each of the three times.
The number of pieces was not more than the number of pieces, and the fracture resistance was “×”. Further, the three-point bending strength was 1400 MPa in Experimental Example 12, but was a low value of 1160 MPa in Experimental Example 13.

On the other hand, an experimental example 10 (X-ray intensity ratio R; N plane 1, T plane 0.75, E plane 0.15) using a sintered body produced by superplastic forging sintering and an experiment Example 11 (X
(Line intensity ratio R; N surface 1, T surface 0.80, E surface 0.10), when the front flank is the E surface, the number of processing hills is 15 and the front flank is not lost at all three times. When the surface was a T surface, the number of processed peaks was 11 to 15, and the fracture resistance was excellent as “「 ”or“ ◎ ”. In addition, the three-point bending strength is shown in Experimental Example 1
At 0, 1900MPa (front flank; E side), 1310M
Pa (front flank; T-plane).
It showed excellent strength of 20 MPa (front flank; E side) and 1210 MPa (front flank; T side) and was found to be excellent in fracture resistance.

Further, an experimental example 7 (X-ray intensity ratio R; N surface 0.95, T surface) using a sintered body produced by superplastic forging sintering
Surface 0.50, E surface 0.48), Experimental example 8 (X-ray intensity ratio R; N surface 0.99, T surface 0.63, E surface 0.30) and Experimental example 9 (X-ray intensity ratio R) N face 1, T face 0.66, E face 0.23), the number of machining peaks is 1 for all three times.
Five pieces were not damaged, and the fracture resistance was "耐", which was better, without being affected by the front flank. The three-point bending strength is
In Experimental Example 7, 1600 MPa (front flank; E side), 15
80 MPa (front flank; T-plane);
0 MPa (front flank; E side), 1620 MPa (front flank; T side), and in Experimental Example 9, 1830 MPa
(Front flank; E side), 1430 MPa (Front flank; T)
Surface) and excellent strength, indicating that these are more excellent in fracture resistance.

In particular, when the X-ray intensity ratio of the rake face is 0.95 to
When the flank strength ratio R was 0.15 to 0.75, there was little difference in the three-point bending strength due to the difference in the front flank face, and extremely excellent fracture resistance was obtained. It should be noted that the present invention is not limited to the above-described embodiment, but may be variously modified according to the purpose and application. For example, it is also suitable for a heat-resistant alloy cutting tool requiring high fracture resistance.

[0038]

The cutting tool made of a silicon nitride sintered body according to the present invention is a sintered tool obtained by superplastic forging sintering of a green compacted preform and having a controlled orientation direction of crystal grains. By being composed of a body, strength and toughness in a specific direction can be improved, and excellent fracture resistance and wear resistance are obtained. Another cutting tool made of a silicon nitride based sintered body of the present invention is made of a silicon nitride based sintered body, and the major axis of crystal grains on the rake face of the cutting tool is
Since it is controlled in a direction parallel to the rake face, strength and toughness in a specific direction can be improved, and excellent fracture resistance and wear resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is an X-ray chart showing the X-ray intensity ratios of N-plane, T-plane and E-plane in Experimental Example 9.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Takagi 14-18, Takatsuji-cho, Mizuho-ku, Nagoya-shi Inside Japan Special Ceramics Co., Ltd. (72) Inventor Kazuhiro Urashima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi Japan Special Ceramics Co., Ltd. (72) Inventor Satoshi Iio 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan F-term (reference) 3C046 FF33 FF47 FF55 4G001 BA03 BA06 BA09 BA11 BA14 BA32 BA52 BB03 BB06 BB09 BB11 BB14 BB32 BB52 BC43 BD12 BD13 BD14 BD18 BE02 BE03 BE12

Claims (8)

[Claims] 1. A silicon nitride-based sintered body in which crystal grains are plastically fluidized by compressing and firing a preformed body obtained by compacting silicon nitride-based raw material powder to control the orientation direction of crystal grains in a specific direction. A cutting tool made of a silicon nitride-based sintered body. 2. The method according to claim 1, wherein the silicon nitride-based raw material powder includes at least one of α-silicon nitride powder, α-sialon powder, β-silicon nitride powder, and β-sialon powder, and a sintering aid powder. Cutting tool made of silicon nitride sintered body. 3. The silicon nitride sintered body according to claim 1, wherein a surface perpendicular to the compression axis direction is a rake surface of the cutting tool, and the other surface is a flank. Cutting tools. 4. On the rake face, the intensity ratio R of the X-ray diffraction peak represented by the following formula (1) is 0.90 to 1, and on at least one of the flank faces, the intensity ratio R is 4. The cutting tool made of a silicon nitride sintered body according to claim 3, wherein the cutting tool is 0.10 to 0.80. R = I ₍₂₀₀₎ / (I ₍₂₀₀₎ + I ₍₀₀₂₎ ) (1) [where I ₍₂₀₀₎ and I ₍₀₀₂₎ are the (200) plane of β silicon nitride and / or β sialon, respectively. 002) represents the reflection intensity of the surface. ] 5. The method according to claim 3, wherein the rake face has a strength of 1200 MPa or more in a three-point bending strength test method with a span of 16 mm using a bending test piece having a cross section of 3 mm in height and 4 mm in width. The cutting tool made of the silicon nitride based sintered body described in the above. 6. A cutting tool comprising a silicon nitride based sintered body, wherein a major axis of a crystal grain on a rake face of the cutting tool is:
A cutting tool made of a silicon nitride sintered body, wherein the cutting tool is controlled in a direction parallel to the rake face. 7. The intensity ratio R of the X-ray diffraction peak represented by the formula (1) is 0.90 to 1 on the rake face, and the intensity ratio R is at least one of the flank faces. The cutting tool made of a silicon nitride based sintered body according to claim 6, wherein the cutting tool is 0.10 to 0.80. 8. In a three-point bending strength test method with a span of 16 mm using a bending test piece having a cross section of 3 mm in height and 4 mm in width, the strength of the rake face is 1200 MPa or more, or based on an effective volume conversion. The cutting tool made of a silicon nitride-based sintered body according to claim 6 or 7, which exhibits equal or higher strength.