JP2008208028A5 - - Google Patents

Description

Cutting tool and manufacturing method thereof

The present invention relates to a cutting tool including a cubic boron nitride (cBN) sintered body and a method for manufacturing the cutting tool . In particular, wear resistance and chipping resistance is relates again and again by cutting Engineering improved.

  cBN is a high-hardness substance next to diamond, and cBN-based sintered bodies are used for various cutting tools, wear-resistant parts, impact-resistant parts and the like.

  With this type of sintered body, it is difficult to achieve both hardness and strength, and the following patent document is cited as a document disclosing a technique for achieving this compatibility.

Japanese Patent Publication No.62-25630 Japanese Patent Publication No.62-25631 JP 5-186272 A

  However, each of the above technologies is not always sufficient in terms of both hardness and strength. For example, when the above-mentioned sintered body is used for a cutting tool, there is a problem that the cutting edge becomes sharp due to flank wear and crater wear, and the cutting edge tends to be lost, resulting in unstable tool life.

Accordingly, a main object of the present invention is to provide a cutting tool having excellent fracture resistance and a method for producing the same by optimizing crater resistance and strength.

The cutting tool of the present invention is a cutting tool including a sintered body obtained by sintering cBN particles with a binder phase. This bonded phase has a continuous structure in two dimensions. In addition, this bonded phase is at least one of carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides, Fe, Co, and Ni of the transition metal groups 4a, 5a, and 6a. 1 or more selected from the group consisting of carbides, nitrides, carbonitrides, borides, and their mutual solid solutions. The content of cBN is 45% to 70% by volume, and the average particle size of the cBN particles is 2 to 6 μm. Furthermore, the average value of the binder phase thickness is 1.5 μm or less, and its standard deviation is 0.9 or less. And this tool is a tool for cutting at a speed of 150 m / min or more. However, in the cutting tool of the present invention, when the thickness of the bonding layer is measured at 20 points or more, the standard deviation at the number of measurement points reaching the convergence point of the standard deviation is more than 0.9, and the convergence point is reached. Excluding cutting tools with a standard deviation of 0.9 or less at no measurement points. Note that the average particle size of the cBN particles means a particle size at which the cumulative volume% is 50%.

The cBN sintered body of a conventional cutting tool (cBN particles have an average particle size of 2 to 6 μm) has a standard deviation of the binder phase thickness exceeding 0.9. That is, there is a large variation in the thickness of the binder phase, and there is a portion occupying a large volume only with the binder phase. Since this part is a weak part (defect) in the sintered body, the crack is likely to progress, and the fracture resistance of the tool is not sufficient.

  In high-speed cutting, the cutting edge becomes hot and the material strength decreases. In addition, crater wear develops and the shape of the cutting edge becomes sharp, which also reduces the strength of the cutting edge. Due to the impact applied to the blade edge in such a state, it is presumed that a crack is generated in parallel with the cutting edge in the portion where crater wear has occurred, and this crack develops due to intermittent impact and leads to a defect.

Therefore, in the cutting tool of the present invention, the variation in the binder phase thickness is made smaller than that of the conventional sintered body, so that the number of defective portions is reduced and the fracture resistance is improved. When the average thickness and standard deviation of the binder phase exceed the above 1.5 μm and 0.9 μm, the binder phase alone occupies a large volume, and the effect of improving the fracture resistance is small. Moreover, since the minimum of the average thickness of a binder phase exhibits the function as a binder phase, about 0.2 micrometer is preferable. Furthermore, if the average particle size of the cBN particles is less than 2 μm, the heat resistance of the particles is poor and crater wear tends to develop, resulting in poor fracture resistance. If it exceeds 6 μm, the fracture resistance is inferior to the impact during cutting. The particle size of cBN particles is suitably 2-6 μm.

In order to obtain the cutting tool of the present invention, the binder phase material is coated on cBN, or raw materials are mixed by a special method. The coating of the binder phase material is induced by chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating, or compressive shear force, friction force, and impact force during mechanical mixing before sintering. And a method utilizing a mechanochemical reaction. As a special mixing method, an ultrasonic mixing method or a ball mill method using a dispersing material is optimal.

In addition, a plasma sintering apparatus, a hot press apparatus, or an ultrahigh pressure sintering apparatus can be used for the sintering process for obtaining the cutting tool of the present invention.

According to the present invention, it is possible to obtain a cutting tool excellent in wear resistance and fracture resistance by reducing the variation in the thickness of the binder phase in the cBN sintered body.

  Embodiments of the present invention will be described below.

(Example 1)
76% by weight of Ti nitride, 18% by weight of Al, 3% by weight of Co, and 3% by weight of Ni were mixed, and the compound that had been heat-treated in a vacuum at 1200 ° C. for 30 minutes was pulverized to obtain a binder phase powder. Produced. In this binder phase powder, peaks such as TiN, Ti ₂ AlN, TiAl _{3 and the} like were observed by XRD (X-ray diffraction). This binder phase powder and cBN powder having an average particle size of 3 μm were mixed by the method shown in Table 1 so that the volume content of cBN was 60% by volume. The detailed conditions of each mixing method are as follows. Here, no. In step 2, cBN was coated with TiN by RF sputtering. The average thickness of the coating is 50 nm. No. No dispersing material is used in the mixing of the two.

Ultrasonic mixing method--cBN and binder powder were put into ethyl alcohol, and 20 kHz ultrasonic vibration was added and mixed.
BM method-> A ball having a diameter of 10 mm, a cBN powder, and a binder powder were put in a pot, and wet mixing was performed in ethyl alcohol at 250 rpm for 800 minutes.
Dispersant → 2% by weight of polyvinyl alcohol was added as a dispersant.

Then, the mixed powder was sintered under 5 GPa, 1300 ° C., ultrahigh pressure and high temperature. Any resulting XRD of the sintered body _{cBN, TiN, TiB 2, AlB} 2, AlN, Al 2 O 3, WC were observed.

When the structures of these sintered bodies were photographed with a metallographic microscope at a magnification of 1500, cBN particles that appeared black and a binder phase that appeared white were observed. In this photograph, an arbitrary straight line was drawn and the binder phase thickness was measured. This measurement is performed by measuring 20 or more points of the thickness of the binder phase on the arbitrary straight line, that is, the distance between the cBN particles, and obtaining the average of the measured values. And the average value and standard deviation of Table 1 were calculated | required from each measured value.

  Furthermore, when these sintered bodies were processed into cutting tools, a cutting test was carried out under the following conditions, and the tool life leading to chipping was measured, the results shown in Table 1 were obtained.

Cutting test conditions:
Work material: SCM415, HRC58-62, φ100mm × L300mm, with 6 V-shaped grooves in the longitudinal direction.
Tool shape: SNG432 NL-25 * 0.15-0.2
Holder: FN11R
Cutting conditions: V = 180 m / min, d = 0.3 mm, f = 0.15 mm / rev, dry

  As is apparent from this result, the tool life is improved by about twice when the average value of the binder phase thickness is 1.5 μm or less and the standard deviation is 0.9 or less. It can also be seen that, in order to produce a sintered body having such a binder phase thickness, an ultrasonic mixing method or a ball mill method using a dispersing material is preferable when mixing binder phase materials. In addition, a method of coating the binder phase on the cBN particles is also effective.

(Example 2)
75% by weight of Ti nitride, 22% by weight of Al, 2% by weight of Co, and 1% by weight of Ni were mixed, and the compound that had been heat-treated in vacuum at 1240 ° C. for 32 minutes was pulverized to obtain a binder phase powder. Produced. XRD showed peaks of TiN, Ti ₂ AlN, TiAl _{3 and the} like. This binder phase powder and cBN powder having an average particle size of 4.8 μm were mixed by an ultrasonic mixing method and a ball mill (BM) method without using a dispersing agent so that the volume content of cBN was 65%. The detailed conditions of each mixing method are as follows.

Ultrasonic mixing method-> cBN and binder powder were put into acetone and mixed by adding ultrasonic vibration of 25 kHz.
BM method-> A ball having a diameter of 10 mm, a cBN powder, and a binder powder were put in a pot, and wet mixing was performed in ethyl alcohol at 200 rpm for 600 minutes.

Then, this powder was sintered at 4.85 GPa, an ultrahigh pressure of 1310 ° C., and a high temperature. Any resulting XRD of the sintered body _{cBN, TiN, TiB 2, AlB} 2, AlN, Al 2 O 3, WC were observed. The structure of these sintered bodies was observed by the following method. In each of the following methods, the method for measuring the binder phase thickness is the same as in Example 1.
1) When photographed with a metallographic microscope at a magnification of 1500, cBN particles that look black and a binder phase that looks white were observed. In this photograph, an arbitrary straight line was drawn and the binder phase thickness was measured.

  2) When a photograph was taken with a scanning electron microscope (SEM) at a magnification of 3000, cBN particles and a binder phase were observed. In this photograph, an arbitrary straight line was drawn and the binder phase thickness was measured.

  3) When a photograph was taken with a TEM (Transmission Electron Microscope) at a magnification of 10,000, cBN particles and a binder phase were observed. In this photograph, an arbitrary straight line was drawn and the binder phase thickness was measured.

  4) When a photograph was taken at a magnification of 10,000 with Auger Electron Spectroscopy, cBN particles and a binder phase were observed. In this photograph, an arbitrary straight line was drawn and the binder phase thickness was measured.

  5) When photographed at 1500 times with a metallographic microscope, cBN particles that look black and a binder phase that looks white are observed. This was image-analyzed, binarized so that the area ratio of black particles corresponding to cBN particles was equal to the volume content of cBN, the portion corresponding to the binder phase was identified, and the binder phase thickness was measured.

  6) When photographed at 1000 times with a metallographic microscope, cBN particles appearing black and a binder phase appearing white were observed. Image analysis of this and measurement of luminance on an arbitrary straight line showed periodicity. When it is divided into a dark part (where it hits cBN particles) and a bright part (where it hits the binder phase) at a certain brightness, the brightness is determined so that the ratio is equal to the volume content of cBN, and the length of the bright part is combined. The phase thickness was taken.

  The average value and the standard deviation of the binder phase thickness thus measured were calculated as shown in Table 2.

  When these sintered bodies are processed into cutting tools, a cutting test is performed under the following conditions, and the tool life leading to fracture is measured, the sintered body of the ultrasonic mixing method is about 20 minutes, the sintered body of the ball mill method Was lost in about 5 minutes. Therefore, it can be seen that it is preferable to mix the binder phase material by the ultrasonic mixing method rather than the ball mill method without using the dispersing material.

Cutting test conditions:
Work material: SCM420, HRC59-61, φ100mm × L300mm, with 8 V-shaped grooves in the longitudinal direction.
Tool shape: SNG432 NL-25 * 0.15-0.2
Holder: FN11R
Cutting conditions: V = 150 m / min, d = 0.25 mm, f = 0.11 mm / rev, dry

(Example 3)
80% by weight of Ti nitride and 20% by weight of Al were mixed, and the compound which had been heat-treated at 1200 ° C. for 30 minutes in a vacuum was pulverized to produce a binder phase powder. This powder showed peaks of TiN, Ti ₂ AlN, TiAl _{3 and the} like by XRD. The binder phase powder was coated on a cBN powder having an average particle size of 3.5 μm so that the volume content of cBN was in the ratio shown in Table 3. The coating was performed using an RF sputtering PVD apparatus. When this coated powder was observed by TEM, it was found that TiBN was coated almost uniformly with an average layer thickness of 50 nm on the cBN powder. The TiN-coated cBN particles and the binder phase powder were mixed with a ball mill without using a dispersing agent. The mixing by the BM method was performed by wet mixing in acetone at 260 rpm for 650 minutes with a 10 mm diameter ball, cBN powder and binder powder placed in a pot. The mixed powder was sintered at 4.8 GPa, 1350 ° C. under high pressure and high temperature. Any resulting XRD of the sintered body _{cBN, TiN, TiB 2, AlB} 2, AlN, Al 2 O 3, WC were observed.

  When the structures of these sintered bodies were photographed with a metallographic microscope at a magnification of 1500, cBN particles that appeared black and a binder phase that appeared white were observed. Moreover, when arbitrary straight lines were drawn in this photograph and the binder phase thickness was measured, the average values and standard deviations shown in Table 3 were obtained.

  Furthermore, these sintered bodies were processed into cutting tools, a cutting test was carried out under the following conditions, and the tool life leading to chipping was measured. The results are also shown in Table 3.

Cutting test conditions:
Work material: SCM415, HRC58-62, φ100mm × L300mm, with 6 V-shaped grooves in the longitudinal direction.
Tool shape: SNG432 NL-25 * 0.15-0.2
Holder: FN11R
Cutting conditions: V = 160 m / min, d = 0.2 mm, f = 0.13 mm / rev, dry

  From these results, it is understood that the content of cBN is preferably 45 to 70% by volume. In particular, good results are obtained at 60 to 70% by volume.

Example 4
The binder phase raw material powders having various compositions were mixed, and the compound heat treated in vacuum at 1230 ° C. for 32 minutes was pulverized to prepare binder phase powders. This binder phase powder and cBN powder having an average particle size of 4.1 μm were mixed by a ball mill method using a dispersing agent so that the volume content of cBN was 62%. Mixing by the BM method was carried out by placing a ball having a diameter of 10 mm, a cBN powder, and a binder powder in a pot and performing wet mixing in acetone at 190 rpm for 700 minutes. The dispersing material is polyvinyl alcohol. Then, the mixed powder was sintered at 5.1 GPa, ultrahigh pressure of 1310 ° C., and high temperature. The peaks of the compounds shown in Table 4 were observed in XRD of the obtained sintered body.

  When the structures of these sintered bodies were observed with a metallographic microscope at a magnification of 1000, cBN particles that appeared black and a binder phase that appeared white were observed. When an arbitrary straight line was drawn in this photograph and the binder phase thickness was measured, the average values and standard deviations shown in Table 4 were obtained.

  Furthermore, when these sintered bodies were processed into cutting tools, a cutting test was performed under the following conditions, and the tool life leading to fracture was measured, the results shown in Table 4 were obtained.

Cutting test conditions:
Work material: SCM415, HRC58-62, φ100mm × L300mm, with 6 V-shaped grooves in the longitudinal direction.
Tool shape: SNG432 NL-25 * 0.15-0.2
Holder: FN11R
Cutting conditions: V = 190 m / min, d = 0.15 mm, f = 0.11 mm / lev, dry

  As can be seen, at least one of the periodic table 4a, 5a and 6a transition metal carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides, Fe, Co, and Ni as the binder phase. It can be seen that one or more kinds selected from the group consisting of one kind of carbide, nitride, carbonitride, boride, and their mutual solid solution are good.

(Example 5)
70% by weight of Ti nitride, 25% by weight of Al, 3% by weight of Co, and 2% by weight of Ni were mixed, and the compound which had been heat-treated in vacuum at 1250 ° C. for 25 minutes was pulverized to obtain a binder phase powder. Produced. This powder showed peaks of TiN, Ti ₂ AlN, TiAl _{3 and the} like by XRD. The powder obtained by ultrasonically mixing the binder phase powder and the cBN powder having the average particle size shown in Table 5 so that the volume content of cBN is 57% is sintered at 4.9 GPa, 1320 ° C. under high pressure and high temperature. did. Ultrasonic mixing was performed by adding cBN and binder powder in ethyl alcohol and applying ultrasonic vibration of 23 kHz. Any resulting XRD of the sintered body _{cBN, TiN, TiB 2, AlB} 2, AlN, Al 2 O 3, WC were observed.

  When the structures of these sintered bodies were photographed with a metallographic microscope at a magnification of 1500, cBN particles that look black and a binder phase that looks white were observed. When an arbitrary straight line was drawn in this photograph and the binder phase thickness was measured, the average values and standard deviations shown in Table 5 were obtained.

  Furthermore, when these sintered bodies were processed into cutting tools, a cutting test was performed under the following conditions, and the tool life leading to fracture was measured, the results shown in Table 5 were obtained.

Cutting test conditions:
Work material: SCM415, HRC58-62, φ100mm × L300mm, with 6 V-shaped grooves in the longitudinal direction.
Tool shape: SNG432 NL-25 * 0.15-0.2
Holder: FN11R
Cutting conditions: V = 170 m / min, d = 0.25 mm, f = 0.14 mm / rev, dry

  As is clear from this result, it can be seen that defects can be suppressed when the average particle size of cBN is 2.0 to 6.0 μm.

The cutting tool of the present invention can be suitably used as a cutting tool that requires both hardness and strength.

Claims (3)

A cutting tool comprising a sintered body obtained by sintering cBN particles in a binder phase,
The bonded phase is continuous in two dimensions,
This binder phase includes at least one of carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides, Fe, Co, and Ni of the transition metal groups 4a, 5a, and 6a. Including one or more selected from the group consisting of carbides, nitrides, carbonitrides, borides, and their mutual solid solutions,
The cBN content is 45-70% by volume,
the average particle size of the cBN particles is 2 to 6 μm,
The average value of the binder phase thickness at 1.5μm or less state, and are a standard deviation of 0.9 or less,
Cutting tool The tool characterized by a tool der Rukoto for cutting at 150 meters / min or faster.
However, when the thickness of the bonding layer is measured at 20 points or more, the standard deviation at the number of measurement points reaching the convergence point of the standard deviation is more than 0.9, and the standard deviation at the number of measurement points not reaching the convergence point Excludes cutting tools with a 0.9 or less.   2. The cutting tool according to claim 1, obtained by mixing raw material powder composed of cBN particles and binder phase powder by any of the following methods.
  (1) Ultrasonic mixing method
  (2) Ball mill method using dispersion material
  (3) A method in which the cBN particles of this raw material powder are coated with the binder phase material by a ball mill method without using a dispersing material.   cBN particles having an average particle size of 2 to 6 μm, and carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides of group 4a, 5a, and 6a transition metals in the periodic table, Providing at least one kind of binder phase powder selected from the group consisting of at least one carbide of Fe, Co, Ni, nitride, carbonitride, boride, and their mutual solid solution;
  Mixing the cBN particles and the binder phase powder by any of the following methods so that the cBN content is 45-70% by volume;
  (1) Ultrasonic mixing method
  (2) Ball mill method using dispersion material
  (3) A method in which the cBN particles of this raw material powder are coated with the binder phase material by a ball mill method without using a dispersing material.
  Sintering the mixed raw material powder, obtaining an average binder phase thickness of 1.5 μm or less, a standard deviation of 0.9 or less, and obtaining a tool for cutting at a speed of 150 m / min or more; A method for manufacturing a cutting tool, comprising:
However, when the thickness of the bonding layer is measured at 20 points or more, the standard deviation at the number of measurement points reaching the convergence point of the standard deviation is more than 0.9, and the standard deviation at the number of measurement points not reaching the convergence point Excludes cutting tools with a 0.9 or less.