JP2002356734A - Hard metal alloy, and cutting tool using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard metal alloy of which the hardness and thermal conductivity in a high-temperature region of >=500 deg.C in particular are high, and also to provide a cutting tool having excellent wear resistance, plastic deformation resistance and tool fracture resistance even in machining of the hard machining materials such as stainless steel. SOLUTION: The hard metal alloy 1 has a structure which consists of a tungsten carbide phase 2, a solid-solution phase 3 composed of the carbides, nitrides and carbonitrides of at least two metals selected from the group consisting of the group IVa, Va, and VIa metals of the periodic table, and a binding phase 5 containing at least one iron family metal. Moreover, this hard metal alloy contains, as the above solid-solution phase 3, at least a Zr-Nb solid-solution phase 7 containing Zr and Nb, and further the ratio of the average grain size d2 of the Zr-Nb solid-solution phase 7 to the average grain size d1 of the tungsten carbide phase 2, d2 /d1 , is 0.5 to 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tungsten carbide-based cemented carbide having high strength and high toughness used for cutting tools and the like, and particularly suitable for cutting difficult-to-cut materials such as stainless steel. It relates to the cutting tool used.

[0002]

2. Description of the Related Art Conventionally, a cemented carbide widely used for metal cutting is a WC-hard alloy composed of a hard phase mainly composed of tungsten carbide and a binder phase of an iron group metal such as cobalt.
Co-based alloy or the above WC-Co-based alloy
There are known systems in which solid solution phases such as carbides, nitrides, and carbonitrides of metals of groups a, 5a, and 6a are dispersed. These cemented carbides are mainly used as cutting tools for cutting cast iron, carbon steel, and the like, but recently, use for cutting stainless steel has been promoted. Since stainless steel has characteristics such as excellent corrosion resistance, oxidation resistance, and heat resistance, it is used in a wide range of fields and the amount of processing is increasing year by year.

[0003]

However, stainless steel is known as a difficult-to-cut material because work hardening easily occurs, heat conductivity is low, heat is easily generated, and reactivity with a cutting tool is high. When stainless steel was cut using a conventional cutting tool, there was a problem that the wear of the cutting tool was large and the tool life was shortened.

Accordingly, an object of the present invention is to
Providing cemented carbide with enhanced thermal conductivity and strength in the high temperature range of ℃ or higher, and using this, it has excellent wear and plastic resistance even when cutting difficult-to-cut materials such as stainless steel. An object of the present invention is to provide a cutting tool having deformability and fracture resistance.

[0005]

The present inventor has solved the above-mentioned problems.
As a result of investigation, the tungsten carbide phase and iron group metal
In a cemented carbide containing a binder phase of
Zr-Nb solid solution containing at least Zr and Nb
Precipitates the body phase and the tungsten carbide phase
Average particle size d₁Of the Zr—Nb solid solution phase with respect to
Particle size d_TwoRatio (d _Two/ D₁) Is controlled within the range of 0.5 to 2.
The thermal conductivity and high temperature strength of cemented carbide
And use it as a cutting tool
This makes it possible to cut difficult-to-cut materials such as stainless steel.
Also has excellent wear resistance, plastic deformation resistance and fracture resistance
It has been found that a cutting tool can be obtained.

That is, the cemented carbide of the present invention comprises a tungsten carbide phase and a solid solution phase comprising at least two kinds of carbides, nitrides and carbonitrides selected from the group consisting of metals of Groups 4a, 5a and 6a of the Periodic Table. And a binder phase containing at least one iron group metal, wherein the solid solution phase contains a Zr-Nb solid solution phase containing at least Zr and Nb, and the solid solution phase has an average particle diameter d ₁ of the tungsten carbide phase. the ratio of the average particle size d ₂ of Zr solid solution phase (d ₂ / d ₁₎ is characterized in that from 0.5 to 2.

Here, the content of the Zr—Nb solid solution phase is 1 to 10% by volume based on the total amount, and the total content of the solid solution phases other than the Zr—Nb solid solution phase in the solid solution phase is the total amount. The content is desirably 1 to 10% by volume.

The content of Ta in the metals of Groups 4a, 5a and 6a of the periodic table is 1% in terms of TaC in the total amount.
Even if the content is less than the weight%, a cemented carbide having excellent tool properties can be obtained.

[0009] Further, the tungsten carbide phase may be
95% by volume, wherein the binder phase is 1 to 2
It is desirable to contain it at a ratio of 0% by volume.

[0010] The cutting tool of the present invention is made of the above-mentioned cemented carbide.
a, 5a, 6a metal carbide, nitride, carbonitride, T
It is desirable that at least one kind of coating layer selected from the group consisting of iAlN, TiZrN, diamond and Al ₂ O ₃ is formed as a single layer or a plurality of layers.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A cemented carbide according to the present invention will be described with reference to FIG. According to FIG. 1, a cemented carbide 1 comprises a tungsten carbide phase 2 and a periodic table No. 4a,
A hard phase 4 composed of a solid solution phase 3 composed of at least two kinds of carbides, nitrides and carbonitrides selected from the group of 5a and 6a metals, and a binder phase containing at least one type of iron group metal as a main component And 5.

According to the present invention, the Zr—Nb solid solution phase 7 containing at least Zr and Nb is used as the solid solution phase 3.
And the ratio of the average particle size d ₂ of the Zr—Nb solid solution phase 7 to the average particle size d ₁ of the tungsten carbide phase 2 (d ₂ / d
It is a great feature that ₁ ) is 0.5 to 2, whereby the hardness and thermal conductivity of the cemented carbide 1 can be increased, and by using this as a cutting tool, A cutting tool having excellent wear resistance, plastic deformation resistance and fracture resistance even when cutting difficult-to-cut materials is obtained.

That is, when the Zr—Nb solid solution phase 7 is not contained, the hardness and the thermal conductivity of the cemented carbide 1 decrease, so that the cemented carbide 1 is used as a cutting tool to cut hard-to-cut materials such as stainless steel. When the cutting is performed, since the cutting temperature rises remarkably, the hardness of the cemented carbide 1 decreases, and the wear resistance and the plastic deformation resistance of the tool decrease.

The average particle diameter d of the tungsten carbide phase 2
₁ and the average particle diameter d ₂ of the Zr—Nb solid solution phase 7 (d ₂ /
If d ₁ ) is less than 0.5, the thermal conductivity of the cemented carbide 1 decreases, the cutting temperature increases, the wear resistance of the cemented carbide 1 decreases, and conversely, the tungsten carbide phase 2 The ratio of the average particle diameter d ₁ to the average particle diameter d ₂ of the Zr—Nb solid solution phase 7 (d ₂ /
When d ₁ ) is larger than 2, the precipitation of the Zr—Nb solid solution phase 7 becomes excessive, so that the strength of the cemented carbide 1 is reduced and tool damage may be increased.

Here, the Zr-Nb solid solution phase 7 contains Zr or Nb as a main component, and particularly when the total amount of Zr and Nb is Zr.
50% by weight based on the total amount of metals in the r-Nb solid solution phase 7
As described above, in particular, it is made of carbide, nitride and carbonitride in an amount of 70% by weight or more. In order to improve cutting performance, Zr-Nb solid solution phase 7
The molar ratio represented by Zr / (Zr + Nb) is 0.1 to
It is desirably 0.95, especially 0.3 to 0.8.

In the Zr-Nb solid solution phase 7, in order to improve the compatibility with the binder phase 5 and to increase the strength and the thermal conductivity, the Zr-Nb group metal of the group 4a, 5a or 6a of the periodic table is used.
metals other than r or Nb (Ti, V, Cr, Mo, T
a, W), and in particular, W and / or Ti may be contained in a ratio of 30% by volume or less in total. In addition, the content ratio of each metal component in the solid solution phase 3 in the present invention can be determined by energy dispersive X-ray analysis (EDS).

Further, from the viewpoint of satisfying both thermal conductivity and alloy strength and hardness, the content of the Zr—Nb solid solution phase 7 is 1 to 10% by volume based on the total amount of the cemented carbide 1. It is preferable that the composition of the Zr—Nb solid solution phase 7 is 0.3 to 0.9 in a molar ratio of Zr / (Zr + Nb),
In particular, it is preferably 0.5 to 0.8.

As the solid solution phase 3, other than the Zr—Nb solid solution 7, metals other than Zr or Nb (Ti, V, Cr, M) in the metals of Groups 4a, 5a, and 6a of the periodic table.
o, Ta, and W), and the presence of at least one other solid solution phase 8 composed of carbides, nitrides, and carbonitrides mainly composed of Ti, In particular, it is desirable to maintain oxidation resistance at high temperatures.

The total content of the solid solution phase 8 other than the Zr—Nb solid solution phase 7 in the solid solution phase 3 is such that the oxidation resistance at a high temperature and the strength and hardness of the cemented carbide 1 are compatible. And 1 to 10% by volume of the total amount of cemented carbide.

Further, according to the present invention, T of the metals of Groups 4a, 5a and 6a of the periodic table in the total amount of cemented carbide 1 is used.
excellent wear resistance even when the content of a is 0.8% by weight or less, particularly 0.5% by weight or less in terms of TaC,
Plastic deformation resistance and fracture resistance can be maintained, that is, Vickers hardness (Hv) is 1400 or more and fracture toughness (K _1c ) without using a Ta material which is very expensive compared to other materials. Cemented carbide 1 having excellent thermal and mechanical properties of 12 MPa / m ^1/2 or more, three-point bending strength of 2500 MPa or more, and thermal conductivity at 800 ° C. of 70 W / m · K or more.

On the other hand, the tungsten carbide phase 2 is composed of hexagonal crystals represented by WC and has an average particle diameter of 0.5 to
It is dispersed in the cemented carbide 1 in a polygonal shape of 3 μm. In the present invention, the average grain size of the crystal refers to a value obtained by measuring a sufficient inside of a section of the cemented carbide 1 observed by a scanning micrograph (SEM) by an intercept method.

Further, according to the present invention, high hardness, high strength,
In order to maintain high toughness and high thermal conductivity, the content of tungsten carbide phase 2 in the total amount of cemented carbide 1 should be 60 to 95% by volume, especially 80 to 90% by volume in terms of WC. Is desirable.

On the other hand, in the cemented carbide 1, the binder phase 5 existing between the tungsten carbide phases 2 is an iron group metal such as Co, Ni, Fe, etc. As a main component, particularly in a proportion of 80% by weight or more.
It is desirable that the content is 20 to 20% by volume, particularly 10 to 15% by volume.

(Production Method) In order to produce the above-mentioned cemented carbide, first, for example, 80 to 90% by weight of tungsten carbide powder having an average particle size of 0.5 to 10 μm and an average particle size of 0.5 to 10 μm Of Zr and Nb carbide, nitride and carbonitride powder or solid solution powder thereof in a total amount of 0.1%
Periodic table 4a, 5a, 6a metal other than Zr and Nb having an average particle size of 0.5 to 10 μm (Ti,
V, Cr, Mo, Ta, W) carbide, nitride and carbonitride powders or solid solution powders of two or more of these metals in a total amount of 0.1 to 10% by weight, average particle size of 0.5 to 10 μm
5 to 15% by weight of iron group metal, and further, if desired, metal tungsten (W) powder or carbon black (C) is mixed.

Next, the mixed powder is molded into a predetermined shape by a known molding method such as press molding, casting, extrusion molding, cold isostatic press molding, and the like.
In a vacuum of 15 Pa, the temperature is increased at 1 to 20 ° C./min,
The above-mentioned cemented carbide can be obtained by firing at ℃ 1,500 ° C. for 0.2 to 5 hours, particularly 0.5 to 2 hours.

The above-mentioned cemented carbide of the present invention has excellent mechanical properties and thermal properties of high hardness, high strength, and high thermal conductivity. It can be suitably used as a cutting tool, and particularly as a cutting tool for difficult-to-cut materials such as stainless steel.

Further, the cutting tool of the present invention provides a carbide, nitride, carbonitride, TiAlN, TiZrN, diamond and Al ₂ metal of metals of Groups 4a, 5a and 6a of the periodic table on the surface of the above-mentioned cemented carbide. A single layer or a plurality of layers of at least one kind of coating layer selected from the group of O ₃ may be used.

In order to form the coating layer on the cemented carbide, if necessary, the surface of the cemented carbide is polished and washed,
A conventionally known thin film forming method such as a PVD method or a CVD method may be used. Further, the thickness of the coating layer is desirably 0.1 to 20 μm.

[0029]

EXAMPLES (Examples) Tungsten carbide (WC) powder having an average particle size shown in Table 1, metal cobalt (Co) powder having an average particle size of 1.2 μm, and compound powder shown in Table 1 having an average particle size of 2.0 μm Was added and mixed at the ratios shown in Table 1, and formed into a cutting tool shape (SDK42) by press molding.
The temperature was raised at a rate of 10 ° C./min from a temperature 500 ° C. or more lower than the firing temperature and fired at 1500 ° C. for 1 hour to produce a cemented carbide.

The reflected electron image was observed with a scanning electron microscope at five arbitrary cross sections of the obtained cemented carbide.
The average particle size and content ratio of the Nb-Zr solid solution phase and the tungsten carbide phase in an arbitrary region of μm × 20 μm were calculated by Luzex image analysis. In addition, as a result of the EDS analysis, the sample No. 2-6
In both cases, the molar ratio of Zr / (Zr + Nb) is 0.3
~ 0.8 was confirmed to be satisfied. Similarly, the content ratios of the other solid solution phase and the binder phase were calculated. The results are shown in Table 1.

The three-point bending strength at 800 ° C. was measured in accordance with JISR1601, except that the thickness of the test piece was 2.5 mm and the three-point bending span was 10 mm. Furthermore, JIS was performed using a test piece of φ10 mm and thickness of 2.0 mm.
The thermal conductivity was measured by a laser flash method based on R1611. The results are shown in Table 1.

[0032]

[Table 1]

The surface of each of the obtained cemented carbides is coated with PV
A 2 μm-thick TiN film was formed by Method D to produce a cutting tool.

Using this cutting tool, stainless steel was cut for 15 minutes under the following conditions, and the flank wear and boundary damage of the cutting tool were measured. When the flank wear amount reached 0.2 mm or the boundary damage amount reached 0.5 mm during the cutting test, the cutting time was measured. Furthermore, the cutting edge of the tool after the cutting test was observed, and the presence or absence of deformation or damage was confirmed. The results are shown in Table 2. Work material: Stainless steel (SUS304) Tool shape: SDK42 Cutting speed: 200 m / min Feed speed: 0.2 mm / tooth Cutting depth: 2 mm Others: Use of water-soluble cutting fluid

[0035]

[Table 2]

From the results in Tables 1 and 2, Sample No. containing no Nb-Zr solid solution phase. In Nos. 1 and 2, abrasion resistance and fracture resistance were poor. The average particle diameter d ₁ and Nb-Zr ratio d ₂ / d ₁ between the average particle size d ₂ of the solid solution phase is less than 0.5 samples N of the tungsten carbide phase (WC)
o. In No. 7, the thermal conductivity decreased, the hardness decreased with an increase in the cutting temperature, and the wear resistance decreased. On the other hand, the average particle diameter d ₁ and Nb-Zr ratio d ₂ / d ₁ is greater than 2 sample N with an average particle size d ₂ of the solid solution phase of tungsten carbide phase (WC)
o. In No. 8, the alloy strength was reduced due to the coarse Nb-Zr solid solution phase precipitated, and defects occurred.

On the other hand, according to the present invention, Nb-Zr
Sample No. ₁ containing a solid solution phase and having a ratio d ₂ / d ₁ of 0.5 to ₂ between the average particle size d ₁ of the tungsten carbide phase (WC) and the average particle size d ₂ of the Nb—Zr solid solution phase. 2
No. 6 to No. 6 each had excellent wear resistance and fracture resistance with a flank wear of 0.15 mm or less.

[0038]

As described above in detail, according to the cemented carbide of the present invention, at least Zr and Nb
Include Zr-Nb solid solution phase containing, and the average particle diameter ratio of d ₂ of Zr-Nb solid solution phase to an average particle size d ₁ of the tungsten carbide phase (d ₂ / d ₁₎ is 0.5 to 2 As a result, the hardness and thermal conductivity of the cemented carbide can be increased, and by using this as a cutting tool, excellent wear resistance and plastic deformation resistance even when cutting difficult-to-cut materials such as stainless steel. It is possible to obtain a cutting tool having the property of resistance and fracture resistance.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cemented carbide according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbide tool 2 Tungsten carbide phase 3 Solid solution phase 4 Hard phase 5 Bonding phase 7 Nb-Zr solid solution phase 8 Other solid solution phases

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C23C 14/16 C04B 35/56 U F term (reference) 4G001 BA03 BA24 BA37 BA57 BA60 BA69 BB03 BB24 BB37 BB57 BB60 BB69 BC13 BC52 BC54 BC72 BD03 BD11 BD12 BD18 BE01 4K018 AD06 FA14 FA24 KA15 4K029 AA02 AA04 BA34 BA44 BA54 BA55 BA58 BA60 BB02 BD05

Claims (8)

[Claims] 1. A tungsten carbide phase and the fourth of the periodic table
a, a solid solution phase composed of at least two kinds of carbides, nitrides and carbonitrides selected from the group consisting of group 5a and 6a metals;
Consists binder phase and containing at least one iron group metal, as the solid solution phase comprises a Zr-Nb solid solution phase containing at least Zr and Nb, the relative average particle size d ₁ of the tungsten carbide phase Zr- cemented carbide ratio of the average particle size d ₂ of the Nb solid solution phase (d ₂ / d ₁₎ is characterized in that from 0.5 to 2. 2. The cemented carbide according to claim 1, wherein the content of the Zr—Nb solid solution phase is 1 to 10% by volume based on the total amount. 3. The total content of solid solution phases other than the Zr—Nb solid solution phase in the solid solution phase is 1 to 10% by volume based on the total amount.
The cemented carbide according to claim 1 or 2, wherein 4. The method according to claim 1, wherein the content of Ta in the metals of Groups 4a, 5a and 6a of the periodic table is 1% by weight or less in terms of TaC in the total amount. The cemented carbide described in the above. 5. The method according to claim 1, wherein said tungsten carbide phase is contained at a ratio of 60 to 95% by volume.
The cemented carbide according to any one of the above. 6. The cemented carbide according to claim 1, wherein the binder phase is contained at a ratio of 1 to 20% by volume. 7. A cutting tool comprising the cemented carbide according to any one of claims 1 to 6. 8. On the surface, a carbide, nitride, carbonitride, TiAlN, TiZ of a Group 4a, 5a, or 6a metal of the periodic table
rN, cutting tool according to claim 7, characterized by being formed of at least one single layer or multiple layers covering layer selected from the group consisting of diamond and Al ₂ O _3.