JP2008132570A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool having long service life in cutting a hard-to-cut material. <P>SOLUTION: This cutting tool is made of a cemented carbide formed by binding a hard phase including tungsten carbide and one of the carbide, nitride, and carbonitride of group 4, 5, 6 metals to each other with a binding metal made of at least one of iron group metals. The surface of the cemented carbide has a β phase formed of the solid solution of one of the carbide, nitride, and carbonitride including at least one of Ti, Ta, Nb, and Zr and W. Since cavities are present in the β phase, the chipping and the elastic deformation of the edge of the cutting tool can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cutting tool, and forms a hard coating layer on the surface of a cemented carbide having excellent fracture resistance and wear resistance, or the surface of the cemented carbide for cutting difficult-to-cut materials such as stainless steel. It is related with the cutting tool formed.

  Conventionally, as a cemented carbide widely used for metal cutting, a WC-Co alloy composed of a hard phase mainly composed of tungsten carbide and a binding phase of an iron group metal such as cobalt, or the above WC-Co. A technique using a system in which solid solution phases such as carbides, nitrides, and carbonitrides of Group 4, 5, and 6 metals of the periodic table are dispersed in the system is known.

  These cemented carbides are excellent in wear resistance and fracture resistance, and are used as cutting tools mainly for cutting of carbon steel, alloy steel, and the like.

  Further, a technique for forming a hard coating layer made of a carbide, nitride, carbonitride, carbonitride oxide, etc. of Ti on the surface of the above-mentioned cemented carbide is also known. It is used for continuous cutting and intermittent cutting of cast iron or the like (see, for example, Patent Document 1 or Patent Document 2).

  However, in recent years, the field of processing difficult-to-cut materials such as heat-resistant alloys such as stainless steel, titanium alloys, and nickel-based alloys has increased, and the demand for cutting tools suitable for difficult-to-cut materials processing has increased. For example, stainless steel When cutting is performed, there is a problem that the cutting temperature of the cutting edge becomes high, and the cutting edge tends to be damaged due to thermal shock or cutting resistance.

Here, in Patent Document 1 and Patent Document 2, a porous zone portion in which 5 to 30% of voids are present in the area of the entire cross section in a depth region of 2 to 100 μm from the surface of the base material is formed. Techniques to do this are disclosed. Thereby, mechanical and thermal strength can be improved.
JP 2003-048106 A JP 2003-071612 A

  However, as described in Patent Documents 1 and 2, if many holes are provided on the surface of the base material in the vicinity of the cutting edge, chipping resistance and wear resistance at the high temperature of the cutting edge are reduced, and the cutting edge is plastically deformed. And the tool life is shortened. In addition, if there are many voids in tungsten carbide or the binder phase portion, the generated cracks are likely to propagate, resulting in a decrease in fracture resistance.

  The present invention has been made to solve the above problems, and its purpose is to suppress plastic deformation caused by high-speed and intermittent cutting, and to exhibit excellent wear resistance and fracture resistance. It is an object to provide a tool having a long life.

  In cemented carbide, the more the solid solution phase (β phase) component (TiC, TaC, NbC, ZrC, MoC, etc.) is added, the worse the thermal conductivity, but in order to maintain the hardness at high temperatures, etc. It is necessary to add a β phase component. Therefore, the applicant improves the thermal conductivity of the β phase by providing pores in the β phase of the alloy, suppresses the deterioration of fracture resistance and wear resistance due to diffusion of heat cracks and work materials, performance It has been found that can be improved.

  That is, the cutting tool according to the present invention includes a hard phase containing any one of tungsten carbide and carbides, nitrides, and carbonitrides of group 4, 5, and 6 metals, and a bonded metal composed of at least one of iron group metals. And a solid solution of at least one of carbide, nitride, and carbonitride containing at least one of Ti, Ta, Nb, and Zr and W on the surface of the substrate made of a cemented carbide bonded by It has the beta phase which consists of, The void | hole exists in the said beta phase, It is characterized by the above-mentioned.

  In the above invention, the abundance ratio of the vacancies existing in the β phase is desirably 2 to 10% when the area of all β phases in the cross section perpendicular to the thickness direction is 100%.

  Moreover, in the said invention, it is desirable for the magnitude | size of a void | hole to be in the range of 0.1 micrometer-2.0 micrometers in diameter converted into a circle.

  In the above invention, it is desirable that the β phase contains at least Zr. In particular, the content of the Group 4, 5, 6 metal gradually decreases from the inside of the substrate toward the surface, and the rate of decrease of the Zr content from the inside of the substrate toward the surface is It is desirable that the rate of decrease in the content of other Group 4, 5, 6 metals is smaller.

  In addition, the cemented carbide is a raw material having a WC of 70 to 93% by weight, a group 4, 5 and 6 metal carbide, nitride, carbonitride 2 to 15% by weight and an iron group metal 3 to 15% by weight. It is desirable to consist of what was formed from.

  Further, a hard coating layer made of a metal of Group 4, 5, 6 in the periodic table, aluminum, silicon carbide, nitride, oxide, and a composite compound of two or more of these compounds is formed on the surface of the substrate. It is desirable.

  The structure of the present invention improves the conductivity of heat generated by cutting, and is resistant to chipping that can withstand high-temperature dry cutting, high-speed cutting, high-feed cutting, or cutting of difficult-to-cut materials such as stainless steel. Can have sex.

  In other words, the presence of vacancies in the β phase makes it less likely to become a fracture source than when the vacancies exist in the hard phase, and it is possible to suppress a decrease in fracture resistance. Further, when the crack reaches the hole, it is possible to suppress the progress of the crack or to deflect the progress direction, so that the toughness of the tool is improved and the fracture resistance can be improved.

  Further, the abundance ratio of the vacancies existing in the β phase is 2 to 10% when the area of all β phases in the cross section perpendicular to the thickness direction is 100%, so that the fracture resistance is not lowered. Sufficient thermal conductivity can be obtained.

  When the size of the pores is in a range of 0.1 μm to 2.0 μm in diameter in terms of a circle, the thermal conductivity of the cemented carbide can be improved without reducing the fracture resistance. This is desirable.

  It is desirable that the β phase contains at least Zr, so that high temperature hardness and thermal shock resistance can be improved.

  The content of the Group 4, 5, 6 metal contained in the cemented carbide gradually decreases from the inside toward the surface portion, and the decrease rate of the Zr content is the content of other Group 4, 5, 6 metals. By making the amount smaller than the rate of reduction of the amount, it is desirable because high fracture resistance can be obtained, and Zr remaining in the vicinity of the surface can improve wear resistance and toughness at high temperatures during cutting.

  A cross-sectional view of a cutting tool according to an embodiment of the present invention is shown in FIG. In this example, the cutting tool is mirror-polished from the rake face side to expose the cross section, and the cross section is observed with a scanning electron microscope (SEM).

  The cemented carbide of the present invention includes a hard phase 1 mainly composed of tungsten carbide (WC), a compound layer composed of any one of carbides, nitrides, and carbonitrides of Group 4, 5, and 6 elements, or 2 It has a composition comprising a solid solution phase (hereinafter referred to as β phase) 2 composed of seeds or more, a binder phase mainly composed of an iron group metal, and inevitable impurities.

Examples of the β phase include (W, Ti) C and (W, Ti, Ta) C. The starting material for producing the β phase composed of (W, Ti) C is a combination of a carbide of W and Ti or a combination of oxide and C (W and TiC and C, W and TiO ₂ and C, WO ₃ and TiO ₂ and C). In addition, there is a β phase composed of a quaternary solid solution such as (W, Ti, Ta, Nb) C.

  Here, according to the present invention, voids (voids) 3 exist in the β phase, and the heat conductivity generated by cutting is improved by using such a configuration. Thus, excellent chipping resistance can be obtained in dry cutting, high-speed cutting, high-feed cutting, or cutting of difficult-to-cut materials such as stainless steel.

  Here, the said hole 3 points out what has a hole diameter in the range of 0.01-3.0 micrometers.

  When the hole diameter is 0.01 μm or more, cracks are likely to advance on the holes 3, so that the crack deflection action is sufficiently exerted, and the fracture resistance is increased. Moreover, when the diameter of the holes is 3.0 μm or less, the holes are less likely to be a source of destruction, and therefore, it is preferable that no sudden defects occur during cutting.

  In addition, if the size of the holes 3 is in a range of 0.1 μm to 2.0 μm in diameter in terms of a circle, the thermal conductivity of the cemented carbide can be improved without reducing the fracture resistance. This is desirable because it can be done.

  Further, the abundance ratio of vacancies existing in the β phase is 2 to 10%, particularly 2.5 to 5%, assuming that the area of all β phases is 100%. Can be optimized for cutting.

  Here, the composition of β phase 2 is composed of one or more compounds or composite compounds selected from carbides, nitrides, and carbonitrides of Group 4, 5, and 6 elements in the periodic table. For example, Ti, Nb, Ta, Mo, Cr, V, etc. are preferably used. Among these, inclusion of at least a Zr element in the β phase 2 is desirable because high temperature hardness and thermal shock resistance can be improved.

  Further, the content of the Group 4, 5, 6 metal contained in the cemented carbide gradually decreases from the inside toward the surface portion, and the decrease rate of the Zr content is the same as that of other Group 4, 5, 6 metals. By making the content smaller than the rate of decrease of the content, it is desirable because high fracture resistance can be obtained and wear resistance and toughness at high temperature during cutting can be improved by Zr remaining in the vicinity of the surface.

  Further, the cemented carbide has a WC of 70 to 93% by weight, particularly 85 to 90% by weight, carbides, nitrides, carbonitrides of Group 4, 5, 6 metal, that is, 2 to 15% by weight of β phase component, In particular, the composition comprising 5 to 10% by weight and iron group metal of 3 to 15% by weight, particularly 6 to 12% by weight, has sufficient wear resistance and fracture resistance in cutting stainless steel and the like. A cemented carbide cutting tool having performance can be obtained.

  Further, a hard coating layer made of carbide, nitride, oxide, or a composite compound of an element selected from Group 4, 5, 6 elements, aluminum, silicon, boron in the periodic table is coated on the surface of the cemented carbide. As a result, the wear resistance and fracture resistance can be improved.

  Materials for the hard coating layer include titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), titanium carbonitride oxide (TiCNO), aluminum oxide (Al2O3), zirconium carbide (ZrC), zirconium nitride (ZrN), composite nitride of titanium and aluminum (TiAlN), and the like.

  In particular, it is desirable to use TiCN, Al2O3, or TiAlN because the cutting performance is particularly improved.

(Production method)
An example of the manufacturing method of the cemented carbide which comprises the cutting tool of this invention mentioned above is demonstrated. First, the metal cobalt (Co) powder is 5.0 to 15.0 mass% with respect to the tungsten carbide (WC) powder, and the niobium carbide powder is 0.8 to 4 as a compound powder for forming the β phase. 0.5% by mass, 0.5% by mass to 1.5% by mass of tantalum carbide powder, and 14.0% by mass or less of the compound powder for forming the β phase. At this time, the average particle diameter of the niobium carbide powder that is the compound raw material powder for forming the B1-type solid solution phase is set to 0.4 to 0.7 μm.

  Then, a solvent is added to the prepared powder and mixed and pulverized for a predetermined time to obtain a slurry. Then, a binder is added to the slurry and further mixed, and a mixed powder is produced while drying the slurry using a spray dryer or the like. Do the grain. At this time, the pulverization is preferably wet pulverization using acetone, methanol, isopropyl alcohol, water or the like as a solvent.

  When a predetermined particle size is obtained by pulverization, a metal carbide such as TiC, NbC, ZrC, TaC, or MoC is added and mixed with stirring. Since these metal carbides are not pulverized, it is desirable to use those having a particle size smaller than that of the WC raw material. This stirred and mixed slurry is dried and granulated to produce granules.

  When the process of mixing to granulation is performed by the above method, since WC and Co are pulverized, a new particle cross section is formed at the time of pulverization, and the state is very active. On the other hand, since the post-added component such as TiC is merely stirred and mixed without being pulverized, the particles themselves are not rich in activity. Therefore, when fired at the above temperature, vacancies can be present only in the β phase.

  Thereafter, it is molded into a predetermined shape and fired. The firing temperature is desirably fired at a firing temperature of 1350 to 1500 degrees so that fine pores exist in the β phase.

  And about the produced cemented carbide alloy, the surface of a cemented carbide alloy is grind | polished as needed, and a honing process is given to a cutting blade part.

  Furthermore, if desired, a known hard coating layer may be formed on the surface of the cemented carbide by a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method to form a cutting tool.

(Example)
Powders were mixed with the composition described in Table 1, and further molding aids such as paraffin were added, stirred for several hours, and dried and granulated to obtain granules.

  At this time, sample no. In 1-6, after mixing only WC and Co by wet mixing using methanol as solvent, add TiC, ZrC, TaC, NbC, Mo2C3, TiN powder, stir, and granulate using spray dryer Granules were obtained.

  Sample No. In Nos. 7 to 9, all raw materials were mixed by wet mixing and granulated with a spray dryer to obtain granules.

Next, the granules were formed into a shape of CNMG120408 by uniaxial press molding and fired at the firing temperature shown in Table 1.

  After firing, burrs were removed, thickness correction and blade edge honing were performed, and then a film was formed in the order of TiN, TiCN, Al2O3, and TiN by a chemical vapor deposition method to produce a cutting tool.

  Then, the rake face of the prepared sample is ground from the surface to a depth of 500 μm, mirror lapping is performed with diamond paste, a cross section perpendicular to the thickness direction of the cutting tool is exposed, and then the secondary of the scanning electron microscope The cross section was observed with an electron image at a magnification of 3000, and the presence or absence of vacancies in the β phase was confirmed, and the area ratio and size of the vacancies were measured.

  The hole area ratio and diameter were measured after being converted into a circle using a Luzex image analyzer.

  In addition, the composition of the β phase was analyzed using energy dispersive spectroscopy (EDS). Further, the content of Zr and other Group 4, 5, 6 elements from the surface of the cemented carbide and from the surface to the inside of 500 μm were measured by the previous analysis.

  A cutting test was performed under the following conditions using the prepared sample.

(Abrasion resistance test)
Cutting method: Turning work material: SCM435 Round bar cutting speed: V = 250 m / min
Feeding: f = 0.3mm / rev
Cutting depth: d = 2.0mm
Cutting state: wet cutting time: 10 minutes Evaluation item: flank (side) simple wear width Vb and maximum wear width Vbmax after 10 minutes cutting
(Defect resistance test)
Cutting method: Turning work material: SCM440 Round groove with four grooves Cutting speed: V = 200 m / min
Feeding: f = 0.2mm / rev
Cutting depth: d = 1.0 mm
Cutting condition: Wet evaluation item: Number of impacts leading to breakage
The state of the cutting edge was observed with a microscope when the number of impacts was 1000. The measurement results are shown in Table 2.

  As shown in Tables 1 and 2, sample no. In Nos. 7 to 9, the tool life was short due to sudden chipping of the cutting edge due to chipping, rapid progress of wear, and plastic deformation of the cutting edge.

  On the other hand, the sample No. which is within the scope of the present invention in which vacancies exist in the β phase. In Nos. 1 to 6, no chipping occurred at the cutting edge, and no plastic deformation of the cutting edge was observed.

In addition, in an Example, it grinds to the depth of 500 micrometers from the surface of the rake face of a cutting tool, the cross section orthogonal to the thickness direction of a cutting tool is exposed, and the area ratio and magnitude | size of a void | hole are made into arbitrary places. Although it measured, if it is a cross section orthogonal to the thickness direction, it will not specifically limit. Further, when measuring a plurality of arbitrary locations in the cross section, the average value of the present invention is as long as the area of the pores is in the range of 2 to 10% when the area of all β phases is 100%. In particular, the chipping resistance and the thermal conductivity can be optimized for cutting.

It is a scanning electron microscope (SEM) photograph in the section of the cutting tool concerning one example of the present invention.

Explanation of symbols

1: Hard phase 2: β phase 3: Void

Claims (7)

Tungsten carbide and a cemented carbide in which a hard phase containing any one of carbides, nitrides and carbonitrides of Group 4, 5, and 6 metals is bonded with a bonding metal consisting of at least one of iron group metals. A cutting tool,
The surface of the cemented carbide has a β phase composed of a solid solution of at least one of Ti, Ta, Nb, and Zr and at least one of carbide, nitride, and carbonitride containing W,
A cutting tool characterized in that pores exist in the β phase. 2. The cutting according to claim 1, wherein the abundance ratio of vacancies existing in the β phase is 2 to 10% when the area of all β phases in a cross section perpendicular to the thickness direction is 100%. tool. 3. The cutting tool according to claim 1, wherein a size of the hole is in a range of a diameter of 0.1 μm to 2.0 μm in terms of a circle. The cutting tool according to any one of claims 1 to 3, wherein the β phase contains at least Zr. The content of the Group 4, 5, 6 metal gradually decreases from the inside of the substrate toward the surface; and
5. The reduction rate of the content of the Zr from the inside to the surface of the cemented carbide is smaller than the reduction rate of the content of other Group 4, 5, 6 metals. Cutting tools.   The cemented carbide is formed from a raw material of 70 to 93% by weight of WC, 2 to 15% by weight of carbides, nitrides and carbonitrides of Group 4, 5, 6 metals and 3 to 15% by weight of iron group metals. The cutting tool according to any one of claims 1 to 5, wherein the cutting tool is made.   Forming a hard coating layer comprising a metal of Group 4, 5, 6 of the periodic table, aluminum, silicon carbide, nitride, oxide, and a composite compound of two or more of these compounds on the surface of the substrate. The cutting tool according to any one of claims 1 to 6, characterized in that:

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