JP2010253607A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet cutting tool having high chipping resistance and wear resistance. <P>SOLUTION: The cermet cutting tool 1 is configured of: a hard phase 4 composed of, as a main component, Ti as carbide, nitride and carbo-nitride of one or more elements of groups 4, 5 and 6 metal in the periodic table; and a bonding phase 5 composed mainly of at least one of Co and Ni. In a cross-sectional texture observation, the cermet cutting tool 1 has a flocculating part 2 having an average particle diameter of 50-200 μm and occupying 60-90 area%, and a matrix part 3 enclosing the circumference of the flocculating part 2 and occupying 10-40 area%. The ratio (d<SB>1</SB>/d<SB>2</SB>) of the average particle diameter d<SB>1</SB>of the hard phase 4 (4a) in the flocculating part 2 to the average particle diameter d<SB>2</SB>of the hard phase 4 (4b) in the matrix part 3 is 1.5-5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cutting tool made of cermet.

  Currently, cermets mainly composed of Ti are widely used as cutting tools. Although it is known that the hard phase of the cermet is likely to have a cored structure composed of a core part and a peripheral part, in Patent Document 1, for example, the first is made of a cored structure having a core part with a particle size of 1 μm or less. Around the agglomerated part having an average particle diameter of 10 to 150 μm consisting of the B1 type crystal (hard phase) and the third B1 type crystal (hard phase) which is not a cored structure, the core part has a core diameter larger than 1 μm. A cermet cutting tool comprising a hard phase arrangement surrounded by a second B1-type crystal (hard phase) having a structure is disclosed, and in FIG. The cermet of the structure | tissue which consists of a structure smaller than the particle size of is described. And it is described that good fracture resistance can be exhibited in wet high-speed milling.

  Moreover, in patent document 2, the cutting made from cermet which consists of a structure | tissue in which the 1st hard phase of (Zr, Ti) CN and the 2nd hard phase of (Ti, W, Mo, Zr) CN exist as a mutually independent particle | grain. A tool is disclosed, and a cermet having an average particle size of 0.05 to 0.5 μm and a hard phase can be made fine, excellent in hardness, strength and toughness, and excellent in welding resistance due to the inclusion of Zr. It is described that it becomes.

JP-A-9-174306 JP 2008-25008 A

  However, as in the cutting tool of Patent Document 1 described above, the structure in which the hard phase particle size in the agglomerated portion is smaller than the particle size in the peripheral portion can exhibit good fracture resistance in wet high-speed milling, for example, There has been a problem that wear resistance is reduced under cutting conditions such as high-speed continuous cutting of castings.

  Further, as in Patent Document 2, even in a cermet in which the first hard phase of (Zr, Ti) CN and the second hard phase of (Ti, W, Mo, Zr) CN exist as mutually independent particles, Although the particle size of the phase can be reduced and carbon steel shows high wear resistance in dry intermittent turning of carbon steel, there is a problem that wear resistance is reduced under cutting conditions such as high-speed cutting of castings. It was.

  Therefore, the cutting tool of the present invention is for solving the above-mentioned problems, and its purpose is to further improve the cutting performance, and particularly high wear resistance and fracture resistance even under cutting conditions for high-speed cutting of castings. A cutting tool is provided.

The cutting tool of the present invention includes a hard phase composed of one or more carbides, nitrides, and carbonitrides of Group 4, 5, and 6 metals in the periodic table mainly composed of Ti, and mainly at least Co and Ni. It is composed of a binder phase composed of one kind, and in the cross-sectional structure observation, it wraps around the agglomerated part having an average particle diameter of 50 to 200 μm present at a ratio of 60 to 90% by area and 10%. It has a matrix portion which is present in a proportion of 40 area%, the ratio of the average particle size d ₂ of the hard phase in the average particle diameter d ₁ and the matrix portion of the hard phase in the aggregation unit _(d 1 / _{d 2)} is 1.5 to 5.

  Here, in the above configuration, it is preferable that the content of the binder phase in the aggregation portion is smaller than the content of the binder phase in the matrix portion.

According to the cutting tool of the present invention, the agglomerated part having an average particle size of 50 to 200 μm is present in a ratio of 60 to 90% by area, and is composed of a structure surrounding the periphery with a matrix part, and the hard phase in the agglomerated part is formed. When the ratio (d ₁ / d ₂ ) between the average particle diameter d ₁ and the average particle diameter d ₂ of the hard phase in the matrix portion is 1.5 to 5, in a cutting condition such as high-speed cutting of a casting It was also found that the wear resistance and fracture resistance were improved.

  Here, in the above configuration, when the content of the binder phase in the aggregate portion is less than the content of the binder phase in the matrix portion, the balance between wear resistance and fracture resistance is improved.

An example of the cutting tool of this invention is shown, It is a scanning electron micrograph about (a) surface vicinity and (b) inside.

  An example of the cutting tool of the present invention will be described based on scanning electron micrographs of (a) 500 times and (b) 3000 times in FIG.

As shown in FIG. 1 (b), the cutting tool 1 of the present invention includes a hard phase 4 made of a nitride or carbonitride of the fourth, fifth, and sixth metals of the periodic table mainly composed of Ti, and mainly Co. And a cermet composed of a binder phase 5 composed of at least one of Ni. Further, as shown in FIG. 1A, the cutting tool 1 wraps around the agglomerated part 2 having an average particle diameter of 50 to 200 μm, which is present at a ratio of 60 to 90% by area, and 10 to 10%. The matrix portion 3 is present at a ratio of 40 area%, and the average particle diameter d ₁ of the hard phase 4 (4a) in the aggregation portion 2 and the average particle diameter d of the hard phase 4 (4b) in the matrix portion 3 the ratio of _{2 (d} 1 / d ₂₎ is composed of tissue that is 1.5 to 5.

  As a result, the wear resistance and fracture resistance of the cutting tool, particularly the fracture resistance of the cutting tool 1 is improved under the cutting conditions of high-speed cutting of the casting.

  That is, when the agglomerated part 2 does not exist in the cutting tool 1 or when the average particle size of the agglomerated part 2 is smaller than 50 μm, and when the abundance ratio of the agglomerated part 2 is less than 60 area%, the agglomerated part 2 The effect of improving toughness due to the presence of N is not obtained, and both wear resistance and fracture resistance are reduced. Conversely, if the average particle size of the agglomerated part 2 exceeds 200 μm, abnormal wear of the tool may occur, and if the abundance ratio of the agglomerated part 2 is more than 90 area%, the defect resistance decreases. There is.

Here, in the above configuration, when the content of the binder phase 5 in the agglomerated part 2 is less than the content of the binder phase 5 in the matrix part 3, the agglomerated part becomes harder, so that the wear resistance is improved. . According to the present invention, the ratio (d ₁ / d ₂ ) between the average particle diameter d ₁ of the hard phase 4 (4a) in the aggregation part 2 and the average particle diameter d ₂ of the hard phase 4 (4b) in the matrix part 3 is. it is 1.5-5 aggregation, i.e., since the average particle size d ₂ of the hard phase 4b of the matrix portion 3 is smaller than the average particle size d ₁ of the hard phase 4a aggregation unit 2, the difference in capillary effect There is a tendency that a larger amount of the binder phase 5 exists in the matrix part 3 than in the part 2.

  Here, as is apparent from the scanning electron micrograph of FIG. 1, the hard phase 4 is composed of the first hard phase 7 observed as black particles, grayish white particles, or a grayish white periphery around the white core. It is comprised from the 2nd hard phase 8 observed as particle | grains which consist of a cored structure in which a part exists. The grayish white color may appear to be a color tone close to white or may be a color tone close to gray depending on the conditions of photography. Here, the first hard phase 7 is black particles made of TiCN, but may contain Co or Ni. Moreover, the outer periphery of the 1st hard phase 7 may have a gray-white peripheral part, and may have a cored structure.

  In addition, the measurement of the particle size of the hard phase 2 in this invention is measured according to the measuring method of the average particle size of the cemented carbide prescribed | regulated to CIS-019D-2005. At this time, when the hard phase 4 has a cored structure, the particle diameter is measured as one hard phase 4 up to the outer edge of the peripheral part including the core part and the peripheral part.

Further, the total content ratio of the nitrides or carbonitrides of Periodic Tables 4, 5, and 6 metals mainly composed of Ti forming the hard phase contained in the cutting tool 1 is 70 to 96% by mass. On the other hand, when the content ratio of the binder phase 3 is 4 to 30% by mass, the cermet hardness and toughness are excellent in balance. In the agglomerated part 2, it is desirable that the hard phase content is 88 to 96% by mass and the binder phase content is 4 to 12% by mass in terms of improving wear resistance. Moreover, in the matrix part 3, it is desirable that the content rate of a hard phase is 80-90 mass% and the content rate of a binder phase is 10-20 mass% from the point of the improvement of fracture resistance. Furthermore, it is desirable for the binder phase to contain 65 mass% or more of Co with respect to the total amount of iron group metal in order to increase the thermal shock resistance of the cutting tool. In addition, in order to maintain the favorable sinterability of the cermet so that the burned skin surface of the cermet becomes a smooth surface, Ni is contained in an amount of 5 to 50% by mass, particularly 10 to 35% by mass as an iron group metal. It is desirable to make it contain.
(Production method)
Next, the manufacturing method of the cutting tool mentioned above is demonstrated.

Two kinds of mixed raw material powders are prepared as raw materials.
The first mixed raw material powder is composed of TiCN powder having an average particle diameter of 1 to 3 μm, desirably 1.5 to 2.5 μm, and the other periodic tables 4, 5 and 6 described above having an average particle diameter of 0.1 to 2 μm. Any one of group metal carbide powder, nitride powder or carbonitride powder, Co powder having an average particle size of 1.0 to 3.0 μm, and Ni powder having an average particle size of 0.3 to 0.8 μm at least one, and mixed powder of MnCO ₃ powder having an average particle size 0.5~10μm desired.

On the other hand, the second raw material powder is composed of TiCN powder having an average particle diameter of 0.6 to 1 μm, desirably 0.8 to 1.0 μm, and the above-described other periodic table 4 having an average particle diameter of 0.1 to 2 μm. Any one of group 5 and 6 metal carbide powder, nitride powder or carbonitride powder, Co powder with an average particle size of 1.0 to 3.0 μm and Ni with an average particle size of 0.3 to 0.8 μm A mixed powder obtained by mixing at least one kind of powder and MnCO ₃ powder having an average particle diameter of 0.5 to 10 μm as required is used.
TiC powder and TiN powder may be added to the first and second raw materials, but these raw material powders constitute TiCN in the cermet after firing.

  Next, a binder is added to the first raw material powder, granulated into granules having an average particle size of 50 to 300 μm, and heat-treated at 800 to 1300 ° C. for 0.2 to 1 hour in a vacuum atmosphere. At this time, if the heat treatment temperature is lower than 800 ° C., it is destroyed during the molding process, so that the agglomerated portion 2 having a predetermined size cannot be formed. Conversely, if the heat treatment temperature exceeds 1300 ° C., Voids or cracks are generated by the difference in shrinkage between the agglomerated portion 2 and the matrix portion 3 in the cermet, and the fracture resistance of the cutting tool 1 is lowered.

  Then, the heat-treated first raw material powder and the non-heat-treated second raw material powder are mixed under wet conditions such as a vibration mill and a rotary mill, and known molding such as press molding, extrusion molding, injection molding and the like. It is formed into a predetermined shape by a method.

Thereafter, according to the present invention, the cermet having the predetermined structure described above can be produced by firing the molded body under the following conditions. As firing conditions,
(A) The temperature is raised to 1050 to 1250 ° C.
(B) In an atmosphere filled with an inert gas such as nitrogen (N ₂ ) of 30 to 2000 Pa, the temperature is increased to 1300 to 1450 ° C. at a temperature increase rate of 0.1 to 2 ° C./min,
(C) While raising the temperature to 1500-1600 ° C. at a rate of temperature increase of 3-15 ° C./min in a vacuum atmosphere, maintaining the vacuum atmosphere or an atmosphere filled with an inert gas for 0.5-2 hours,
(D) Firing is performed at a cooling rate of 6 to 15 ° C./min.

  Then, if desired, a coating layer is formed on the surface of the cermet. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as the coating layer forming method.

TiCN powder having an average particle diameter (d ₅₀ value) of 2.0 μm as measured by the microtrack method, WC powder having an average particle diameter of 1.1 μm and the amount of C shown in Table 1, TiN powder having an average particle diameter of 1.5 μm, an average particle TaC powder having a diameter of 2 μm, NbC powder having an average particle diameter of 1.5 μm, ZrC powder having an average particle diameter of 1.8 μm, VC powder having an average particle diameter of 1.0 μm, Ni powder having an average particle diameter of 2.4 μm, and an average particle diameter Using a 1.9 μm Co powder, the first mixed powder prepared at the ratio shown in Table 1 was wet mixed by adding isopropyl alcohol (IPA) using a stainless steel ball mill and a carbide ball, and paraffin was added. After adding 3% by mass and mixing, granules having an average particle diameter shown in Table 1 were formed by a spray dryer, and heat treatment was performed under the conditions shown in Table 1.

  Similarly, the second mixed raw material powder shown in Table 1 is prepared using the raw material powder, mixed with the first mixed raw material powder subjected to the heat treatment in a wet condition in a vibration mill, and further mixed with a binder. Thus, a mixed powder for molding was obtained.

And using this mixed powder for molding, it was press-molded into a tool shape of CNMG120408 at 200 MPa. Then, (a) the temperature is increased to 1200 ° C. at a temperature increase rate of 10 ° C./min, and (b) the temperature is increased to 1400 ° C. at a temperature increase rate of 0.5 ° C./min in an atmosphere filled with 1000 Pa of nitrogen (N ₂ ). (C) In the process of heating up to 1575 ° C. at a rate of 7 ° C./min in a vacuum atmosphere, maintaining in that state for 1 hour, and (d) cooling at a cooling rate of 10 ° C./min Firing was performed under firing conditions.

  The obtained cermet was observed with a scanning electron microscope (SEM), and image analysis was performed in a region of 8 μm × 8 μm using a commercially available image analysis software for each of the surface and the interior at a 10000 × magnification. Then, the presence state of the hard phase and the presence of the surface region were confirmed, and the average particle diameters thereof were measured, and the ratios thereof were calculated. The results are shown in Table 2.

Next, using the obtained cermet cutting tool, cutting tests (abrasion resistance evaluation test and fracture resistance evaluation test) were performed under the following cutting conditions. The results are shown in Table 2.
(Abrasion resistance evaluation)
Work material: FC250
Cutting speed: 350 m / min Feed: 0.20 mm / rev
Cutting depth: 1.0mm
Cutting state: wet (uses water-soluble cutting fluid)
Evaluation method: Time until the wear amount reaches 0.2 mm (defect resistance evaluation)
Work material: S45C
Cutting speed: 100 m / min Feed: 0.05 to 0.5 mm / rev
Cutting depth: 1.5mm
Cutting condition: Dry evaluation method: Time (seconds) until machining and chipping under the condition of machining for 10 seconds for each feed
From Tables 1-2, the sample No. in which the average particle diameter of the aggregated part exceeds 200 μm. In No. 7, abnormal wear occurred. In addition, the sample No. In 8 and 9, the fracture resistance decreased. Furthermore, sample No. 1 in which the heat treatment temperature of the first raw material mixed powder exceeds 1300 ° C. In No. 10, cracks occurred in the matrix portion of the cermet, and both wear resistance and fracture resistance were reduced. In addition, the sample No. 11 and 12 also had low wear resistance.

  On the other hand, sample no. Nos. 1 to 6 exhibited excellent wear resistance, good fracture resistance, and long tool life.

DESCRIPTION OF SYMBOLS 1 Cutting tool 2 Aggregation part 3 Matrix part 4 Hard phase 4a Hard phase in the agglomeration part 4b Hard phase in the matrix part 5 Bonding phase 7 1st hard phase 8 2nd hard phase

Claims (2)

A hard phase composed of one or more carbides, nitrides, and carbonitrides of Group 4, 5, and 6 metals of the periodic table mainly containing Ti, and a binder phase mainly composed of at least one of Co and Ni In the cross-sectional structure observation, the aggregate part having an average particle diameter of 50 to 200 μm existing at a ratio of 60 to 90 area% and the periphery of the aggregate part are wrapped at a ratio of 10 to 40 area%. A ratio of the average particle diameter d ₁ of the hard phase in the aggregated portion to the average particle diameter d ₂ of the hard phase in the matrix portion (d ₁ / d ₂ ). Is a cutting tool of 1.5-5.   The cutting tool according to claim 1, wherein the content of the binder phase in the aggregated portion is less than the content of the binder phase in the matrix portion.