JP2005131739A - Cutting tool made of cermet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool made of a cermet having both of excellent chipping resistance and abrasion resistance. <P>SOLUTION: R honing 4 is formed on a cutting blade 3 of a TiCN based cermet base body 2 comprising a binding phase composed of Co and/or Ni and a hard phase composed of carbonitride of 4a, 5a, and 6a group metals in Periodic Table including Ti. The average particle diameter of the hard phase inside the cermet base body 2 is ≤ 1 μm. When a honing amount on the rake face 5 side of the R honing 4 is made as (a) and a honing amount on the flank 6 side of the R honing 4 is as (b), the cutting tool 1 made of a cermet is made to satisfy formula of a/b = 1.3-1.5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cutting tool made of TiCN-based cermet and having excellent fracture resistance and wear resistance.

  Conventionally, as a raw material for a throw-away tip for cutting, a hard phase composed of a composite metal carbonitride containing Ti and containing at least one of Group 4a, 5a and 6a metals in the periodic table is used. Alternatively, a TiCN group cermet bonded with a Ni bonded phase is known.

  In such cermet cutting tools, sudden chipping or chipping of the cutting edge is a problem, and there is a demand for improved wear resistance as well as improved wear resistance, and cermet cutting tools have excellent wear resistance. Therefore, the finish surface roughness and dimensional accuracy of the work material are strictly required because it is used mainly for finishing.

  Further, Patent Document 1 describes that the fracture resistance of the cutting edge is improved by controlling the honing amount on the rake face side and the flank face side of the cutting edge in the range of 1.5 to 4.0. Furthermore, Patent Document 2 describes that chipping and chipping can be prevented by forming a hardened surface layer with a small amount of binder phase on the honing surface of a cermet cutting tool.

On the other hand, in Patent Documents 3 and 4 and the like, as with a cermet as a cutting tool, the cement strength of a cemented carbide used for general purposes is improved by atomizing the particle size of tungsten carbide particles in the alloy. It describes that chipping resistance and wear resistance are improved.
Japanese Patent Laid-Open No. 10-71507 JP-A-5-212605 Japanese Patent Laid-Open No. 61-12847 Japanese Patent Laid-Open No. 7-157837

  However, applying the knowledge of atomization of cemented carbide as described in the above Patent Documents 3 and 4 to cermet to reduce the hardness of the hard phase will improve the alloy strength, but it will cause sudden chipping and chipping of the cutting edge. The generation was not improved and as a result was not satisfactory as a cutting tool.

  Moreover, even if the honing amount of the cutting edge is adjusted according to Patent Documents 1 and 2 for the fine cermet cutting tool, the cutting edge is improved when the cutting edge is subjected to a large cutting resistance, although the chipping resistance is improved. There was a risk that the dimensional accuracy of the work material processed by plastic deformation would be greatly shifted or that the wear would progress rapidly.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cermet cutting tool having excellent fracture resistance, plastic deformation resistance, and wear resistance. .

  As a result of studying the above problems, the present inventor has refined the average particle size of the hard phase of the cermet substrate to 1 μm or less, sets the honing amount on the rake face side of the cutting edge, and honing on the flank face side of the cutting edge. When the amount is b, by performing R honing of a / b = 1.3 to 1.5, the fracture resistance of the cutting tool made of fine cermet is greatly improved and the plastic deformation resistance is improved. And the wear resistance was also improved.

  That is, the cermet cutting tool of the present invention includes a TiCN group comprising a binder phase comprising Co and / or Ni and a hard phase comprising Ti and containing a carbonitride of Group 4a, 5a and 6a metals. A cutting tool in which R honing is formed on a cutting edge of a cermet base, the average particle size of the hard phase inside the cermet base is 1 μm or less, and the honing amount on the rake face side of the R honing is a, R When the honing amount on the flank side of the honing is b, a / b = 1.3 to 1.5.

Here, in at least R honing of the cermet substrate, the surface region in which the average particle size of the hard phase in the depth range of 50 to 200 μm from the surface of the cermet substrate is larger than the average particle size of the hard phase inside the cermet substrate In particular, the ratio (d ₁ / d) between the average particle diameter d ₁ of the hard phase at a depth of 30 μm from the surface of the cermet substrate and the average particle diameter d ₂ of the hard phase inside the cermet substrate. ₂ ) is 1.1 to 3.0, it is possible to suppress the plastic deformation in the cutting edge, improve the wear resistance as a cutting tool, and maintain the fracture resistance in the cutting edge.

Further, when the radius of curvature at the rake face side end portion of the R honing is R _a and the radius of curvature at the flank end portion of the R honing is R _b , R _a / R _b = 1.0 to 1.5 As a result, the cutting edge strength can be maintained to prevent chipping and abnormal wear, and the cutting edge can be prevented from being lost due to increased cutting edge resistance.

  In the cermet cutting tool of the present invention, the average particle size of the hard phase of the cermet substrate is atomized to 1 μm or less, the honing amount on the rake face side of the cutting blade is a, and the honing amount on the flank side of the cutting blade is When b is used, by performing R honing of a / b = 1.3 to 1.5, the fracture resistance of the cutting tool made of fine cermet is greatly improved and the plastic deformation resistance is improved. Abrasion resistance is also improved.

  The cermet cutting tool of the present invention will be described with reference to FIG.

  According to FIG. 1, a cermet cutting tool (hereinafter simply referred to as a tool) 1 is a carbonitriding of a periodic table 4a, 5a and 6a metal containing Ti and a binder phase composed of Co and / or Ni. An R honing 4 is formed on the cutting edge 3 of the TiCN-based cermet base 2 made of a hard phase made of a material, and the average particle size of the hard phase inside the cermet base 2 is 1 μm or less, and the rake face of the R honing 4 A / b = 1.3 to 1.5, where a is the honing amount on the 5 side and b is the honing amount on the flank 6 side of the R honing 4.

  As a result, it is possible to significantly improve the fracture resistance by suppressing the occurrence of sudden chipping, chipping and the like in the cutting edge 3, which was the biggest problem of the conventional cermet cutting tool, and the plastic resistance in the cutting edge 3 The wear resistance can be improved by improving the deformability.

  That is, it is important that the average crystal grain size of the hard phase (hard phase) in the cermet substrate 2 is 1 μm or less, particularly 0.5 to 0.9 μm, and further 0.7 to 0.9 μm. When the average crystal grain size of the phase exceeds 1 μm, the strength of the cermet is lowered and the chip resistance of the chip is lowered. In addition, it is desirable that the thickness is 0.5 μm or more from the standpoint of maintaining the sinterability of the cermet base 2 and maintaining the wear resistance of the cutting edge 3 and maintaining the impact resistance, hardness, and fracture resistance of the tool 1. .

  In addition, about the structure of the cermet base | substrate 2, the periodic table 4a, 5a containing Ti, and the composite metal carbonitride which consists of a 6a group metal are formed as a hard phase, and especially a hard phase is a core part which consists of TiCN. And at least one of composite carbide, composite nitride, composite carbonitride of Ti and periodic table 4a, 5a and 6a other than Ti, particularly one or more of W, Mo, Ta and Nb A double-core structure or a triple-core structure composed of a peripheral portion made of a cermet substrate having a grain growth control effect and a fine and uniform structure, It is desirable in that it has excellent wettability and contributes to increasing the strength of the cermet.

  In addition, it is desirable that the binder phase composed of Co and / or Ni is contained in a proportion of 5 to 30% by weight in order to maintain both fracture resistance and wear resistance.

Here, in at least the R honing 4 of the cermet substrate 2, the average particle diameter of the hard phase in the depth range A of 50 to 200 μm from the surface of the cermet substrate 2 is larger than the average particle diameter of the hard phase inside the cermet substrate 2. the ratio of the large surface area 9 is present, in particular, the average particle diameter d ₁ of the hard phase at a depth position of 30μm cermet substrate 2 surface, and the average particle size d ₂ of the cermet base body 2 inside of the hard phase When (d ₁ / d ₂ ) is 1.1 to 3.0, the plastic deformation in the cutting blade 3 is suppressed, the wear resistance as the tool 1 is improved, and the fracture resistance in the cutting blade 3 is improved. Can be maintained.

  The average particle size of the hard phase in the surface region 9 of the R honing 4 is preferably 0.6 to 2 μm from the viewpoint of satisfying both the wear resistance and the plastic deformation resistance of the cutting edge 3.

Further, when the curvature radius on the rake face 5 side end portion of the R honing 4 _R a, the radius of curvature on the flank surface 6 side end portion of the R honing 4 was _{R b, R a / R b} = 1.0~1 .5 can maintain the strength of the cutting edge 3 to prevent chipping and abnormal wear, and can also prevent the cutting edge 3 from being lost due to an increase in cutting edge resistance.

  Further, according to the present invention, (Tix, M1-x) (CyN1-y) (where M is the periodic table 4a, 5a and 6a group metals other than Ti, Al, Si) on the surface of the cermet substrate 2 Or a hard coating layer represented by 0.4 <x ≦ 1, 0 ≦ y ≦ 1) (hereinafter abbreviated as Ti-based coating layer), diamond, cubic boron nitride, alumina, Zr, Hf It is also possible to form another hard coating layer composed of one or more of Cr, Si carbide, nitride, carbonitride, and even when such a surface coating layer is formed, the wear resistance is improved and the plastic resistance is improved. Deformability and fracture resistance can be maintained.

In addition, the Ti coating layer is (Ti, M1) N (where M1 is one selected from the group of Al, Si, Zr and Cr), optimally in terms of heat resistance such as high hardness and high temperature stability. Is preferably made of (Tix, Al1-x) N.

(Production method)
To manufacture a cutting tool comprising the TiCN-based cermet of the present invention, first, as raw material powder, as a hard phase forming component, TiCN powder, and carbides, nitrides, and carbonitrides of periodic table 4a, 5a and 6a metals Using at least one kind of powder selected from the group, Ti is weighed so that the Ti amount is 55 to 80% by mass, particularly 65 to 77% by mass with respect to the total amount of the metals in Group 4a, 5a and 6a. Moreover, it mix | blends so that the ratio of N / (C + N) of carbon (C) and nitrogen (N) in the whole hard phase formation component may be 0.4-0.6.

  In addition, it is necessary that the TiCN powder used at this time is a fine powder having an average particle diameter of 1 μm or less. If the average particle size of the TiCN powder at this time is larger than 1 μm, it becomes difficult to make the average crystal particle size of the hard phase in the cermet 1 μm or less. Further, when the average particle size of the TiCN powder is 0.4 μm or more, the sinterability of the cermet substrate 2 can be maintained, and the average crystal particle size of the hard phase can be maintained without reducing the average crystal particle size of the hard phase. Desirable in terms.

  The average particle size of at least one powder selected from the group of carbides, nitrides, and carbonitrides of Group 4a, 5a, and 6a metals is suitably 0.5-2 μm. Further, Ni and / or Co powder having an average particle diameter of 0.3 to 4 μm is added at a predetermined ratio as a binder phase forming component.

  These weighed powders are mixed by a ball mill or the like, then formed into a predetermined cutting tool shape by a known forming method such as press molding, extrusion molding or injection molding, and then fired.

In firing, in order to form a hard phase with a cored structure and suppress the grain growth of the hard phase, a vacuum atmosphere with a vacuum degree of 0.01 Torr or less, or non-N ₂ , Ar, CO, CO ₂ gas, etc. In an oxidizing gas atmosphere, the temperature is raised from room temperature to around 950 ° C. at 5 to 15 ° C./min, and then raised to around 1400 ° C. at 1 to 5 ° C./min (heating rate b). The temperature is raised to a firing temperature of 1400 ° C. to 1600 ° C. at a rate of 43 ° C. to 15 ° C./minute (temperature increase rate C), and is allowed to cool to room temperature by cooling at a temperature of 10 ° C. to 15 ° C./minute within 1 hour. It is desirable to fire under conditions. Also, the cutting edge of the TiCN-based cermet substrate manufactured by the above method is controlled to the above-mentioned dimensions by controlling the material of the polishing member, the polishing method, the polishing pressure, the polishing time, etc. by brushing and grinding stone processing. The cermet cutting tool of the present invention can be manufactured by performing the R honing process.

  As raw material powder, TiCN (TiC / TiN = 50/50) powder having an average particle diameter shown in Table 1, TiN powder having an average particle diameter of 0.5 to 2 μm, TaC powder, NbC powder, WC powder, ZrC Using powder, VC powder, and Co powder, Ni powder, or alloy powder of Co and Ni having an average particle diameter of 2 μm, these raw material powders were blended into the blending composition shown in Table 1, and wet mixed and pulverized by a ball mill. The average particle diameter is measured by the microtrack method.

Next, the above mixed powder was press-molded into a chip shape of ISO standard CNMG120408 at a molding pressure of 98 MPa, and this molded body was heated to 950 ° C. in a vacuum of 0.01 Torr or less at a rate of 12 ° C./min. The temperature was raised from 1 ° C. to 1300 ° C. at 2 ° C./minute, raised to 5 ° C./minute up to the firing temperature shown in Table 1, held for 1 hour, and then cooled to room temperature at 12 ° C./minute in vacuum. A cermet having a shape of CNMG120408 was produced.

  Next, R honing of the dimensions shown in Table 2 was formed on each sample by brushing on the obtained cermet substrate. As for the shape of R honing, the honing amount on the rake face side and flank face side is estimated with a microscope, and the shape of the tool cross section is measured with a surface roughness meter. Was calculated. Further, the tool cross-section was mirror-polished, and the alloy structure was photographed with a scanning electron microscope to measure the average particle diameter, the presence / absence of a surface region, and the depth thereof.

  In addition, the cross section of the tool is observed with an electron microscope to confirm the presence or absence of the surface region, and the 7 mm × 7 μm observation region in the region of 1000 μm or more from the surface of the cermet substrate is intercepted to determine the crystal grain size of the hard phase. The average crystal grain size was measured as the average grain size of the hard phase inside the cermet substrate. Further, the average grain size of the hard phase was measured in two similar areas of the 7 × 7 μm observation region centered at a depth of 30 μm from the cermet substrate surface, and the average crystal grain size was determined as the average grain size of the hard phase on the cermet substrate surface. Measured as diameter.

Next, about the obtained sample,
Work material: S45C
Cutting speed: 200 m / min.
Feed: 0.3 mm / rev.
Cutting depth: 2.0mm
Under these conditions, an interval cutting test of 36 passes × 4 times was performed, and the amount of flank wear of the cutting blade was measured to evaluate the wear resistance. Further, the amount of honing at the cutting edge was calculated using a microscope and a projector. The results are shown in Table 2.

  As apparent from Table 2, the sample No. In No. 11, the plastic deformation resistance decreased. In addition, the sample No. In No. 10, many chippings occurred at the cutting edge, resulting in a large amount of flank wear and a short tool life. In addition, the sample No. In 8 and 12, the cutting resistance applied to the rake face was large, and a sudden defect occurred. In addition, sample No. 1 with a higher temperature rise rate b was used. In No. 9, the binder phase was ejected to the surface of the cermet substrate, resulting in poor sintering, and the tool characteristics could not be evaluated.

  On the other hand, according to the present invention, the average particle size of the hard phase inside the cermet substrate is 1 μm or less, and the ratio of the honing amount a on the rake face side of the R honing and the honing amount b on the flank face side a / b = sample No. in the range of 1.3 to 1.5. In Nos. 1 to 7, all were excellent in plastic deformation resistance and fracture resistance.

It is a principal part cross-sectional schematic diagram of the cermet cutting tool of this invention.

Explanation of symbols

1 Cermet cutting tool
2 Cermet substrate 3 Cutting edge 4 R honing a: Honing amount on the rake face side b: Honing amount on the flank face side Ra: Radius of curvature at the rake face side end part Rb: Curvature radius 5 at the flank face side end part Rake face 6 Escape Surface 9 Surface area

Claims (4)

R honing was formed on the cutting edge of a TiCN-based cermet substrate comprising a binder phase comprising Co and / or Ni, and a hard phase comprising Ti and containing a carbonitride of Group 4a, 5a and 6a metals of the periodic table. A cutting tool,
When the average particle size of the hard phase in the cermet substrate is 1 μm or less, the honing amount on the rake face side of the R honing is a, and the honing amount on the flank side of the R honing is b A cermet cutting tool characterized by being 1.3 to 1.5. In at least the R honing part of the cermet substrate, there is a surface region in which the average particle size of the hard phase in the depth range of 50 to 200 μm from the surface of the cermet substrate is larger than the average particle size of the hard phase inside the cermet substrate. The cermet cutting tool according to claim 1, wherein: A ratio (d ₁ / d ₂ ) between the average particle diameter d ₁ of the hard phase at a depth of 30 μm from the surface of the cermet substrate and the average particle diameter d ₂ of the hard phase inside the cermet substrate is 1.1 to The cermet cutting tool according to claim 2, wherein the cutting tool is 3.0. R _a / R _b = 1.0 to 1.5 where R _{a is} the radius of curvature at the rake face side end of the R honing and R _b is the radius of curvature at the flank end of the R honing. A cermet cutting tool characterized by that.

Images