JP2007118104A - Surface coated cermet throwaway cutting tip having hard coating layer exhibiting excellent chipping resistance in high speed cutting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated cutting tip having a hard coating layer exhibiting excellent chipping resistance in high speed cutting. <P>SOLUTION: In the coated cutting tip having a hard coating layer which is composed of a lower Ti-compound layer and an upper α-type Al<SB>2</SB>O<SB>3</SB>layer and is formed by vapor deposition on the surface of a tip base body, an abrasive layer composed of chromium oxide is formed by vapor deposition over the whole surface of the upper α-type Al<SB>2</SB>O<SB>3</SB>layer with a mean layer thickness of 0.5 to 5 μm. After that, the polishing fluid mixed with fine particles of SiC serving as an injection abrasive material is jetted by wet blasting in order to polish the surface of the upper α-type Al<SB>2</SB>O<SB>3</SB>layer leaving the abrasive layer around a tool mounting hole intact so as to achieve a surface roughness Ra of 0.2 μm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface-coated cermet cutting throwaway tip (hereinafter referred to as a coated cutting tip) that exhibits excellent chipping resistance with a hard coating layer, particularly when used for high-speed cutting of various types of steel and cast iron. Is.

Conventionally, generally, as shown in a schematic perspective view in FIG. 3, it is composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet, and a tool at the center. On the entire surface of the rake face and the flank face including the cutting edge ridge line portion of the base body (hereinafter collectively referred to as a chip base body) having mounting holes,
As a lower layer, a titanium carbide (hereinafter referred to as TiC) layer, a titanium nitride (hereinafter also referred to as TiN) layer, a titanium carbonitride (hereinafter referred to as TiCN) layer, a titanium carbonate (hereinafter referred to as TiCO) layer And a Ti compound layer comprising one or more of titanium carbonitride oxide (hereinafter referred to as TiCNO) layers and having an overall average layer thickness of 3 to 20 μm,
As an upper layer, an aluminum oxide layer (hereinafter referred to as an α-type Al ₂ O ₃ layer) having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition,
It is well known that a coated cutting tip formed by vapor-depositing a hard coating layer composed of is used for continuous cutting and intermittent cutting of, for example, various types of steel and cast iron. Yes.

In the above-mentioned coated cutting tip, the constituent layer of the hard coating layer generally has a granular crystal structure, and the TiCN layer constituting the Ti compound layer as the lower layer is intended to improve the strength of the layer itself. In a normal chemical vapor deposition apparatus, a gas mixture containing organic carbonitrides is used as a reaction gas, and it is formed by chemical vapor deposition at an intermediate temperature range of 700 to 950 ° C. so that it has a vertically grown crystal structure. It is also known to do.
Furthermore, it is also known that the surface of the α-type Al ₂ O ₃ layer (upper layer) constituting the hard coating layer of the above-described coated cutting tip is smoothed by wet blasting for the purpose of improving cutting performance. Yes.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010 JP-A-8-276305

In recent years, the performance of cutting equipment has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and along with this, cutting tends to be faster. The cutting tip has no problem when it is used for continuous cutting or intermittent cutting under normal conditions such as steel or cast iron, but the cutting speed is 350 m / min. When it is used for cutting at a high speed exceeding 1, the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer is likely to chip (small chipping), and as a result, in a relatively short time. At present, the service life is reached.

The present inventors have, from the viewpoint as described above, focuses on coated cutting tip α type the Al ₂ O ₃ layer described above constituting the upper layer of the hard coating layer, in particular the α-type the Al ₂ O ₃ layer As a result of research to improve chipping resistance of
(A) On the surface of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer in the above-mentioned conventional coated cutting chip, 20% as a proportion of the total amount with water as a sprayed abrasive by wet blasting When a polishing liquid containing -80 mass% silicon carbide (hereinafter, referred to as SiC) fine particles is sprayed and polished, the α-type Al ₂ O ₃ layer is measured based on the compliant standard JIS B0601-1994 ( The following surface roughness is a measured value based on such a compliant standard), and Ra: 0.3-0.6 μm surface roughness is exhibited. As a result, the α-type Al ₂ O ₃ Even when a coated cutting tip whose surface was smoothed to a surface roughness of Ra: 0.3 to 0.6 μm by wet blasting was used, the cutting speed was 350 m / min. High-speed cutting that exceeds the limit cannot effectively suppress chipping at the cutting edge.

(B) On the other hand, as shown in the schematic perspective view of FIG. 2, the rake face and clearance including the cutting edge ridge line portion of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer in the conventional coated cutting tip described above. In a state where a chromium oxide (hereinafter referred to as Cr ₂ O ₃ ) layer is vapor-deposited on the entire surface using a normal chemical vapor deposition apparatus under normal conditions, for example, the conditions shown in Table 3.
As in the case of (a) above, when a polishing liquid containing 20 to 80% by mass of SiC fine particles as a spraying abrasive in a ratio to the total amount of water is sprayed by wet blasting, the Cr ₂ O ₃ layer ( Hereinafter, the Cr ₂ O ₃ abrasive layer) is pulverized and pulverized by the SiC fine particles, becomes Cr ₂ O ₃ fine particles and acts as an abrasive in the presence of the SiC fine particles, and constitutes the upper layer of the hard coating layer will be polishing the surface of the α-type the Al ₂ O ₃ layer to the α-type the Al ₂ O ₃ layer surface after the results polishing, Ra: is smoothed to a surface roughness of not more than 0.2μm When the high-speed cutting was performed using the coated cutting tip in which the surface of the α-type Al ₂ O ₃ layer as the upper layer was smoothed to a surface roughness of Ra: 0.2 μm or less, 350 m / min. Chipping at the cutting edge is prevented even at a cutting speed exceeding 1, and the hard coating layer exhibits excellent wear resistance over a long period of time.

(C) As described above, the cutting speed is 350 m / min. In high-speed cutting processing exceeding 1, the load applied to the cutting edge of the coated cutting tip becomes extremely high. Therefore, especially in the case of milling, when mounting the coated cutting tip to the tool body, it is attached with a very high clamping force. As a result, the compressive stress on the hard coating layer around the tool mounting hole of the coated cutting tip becomes extremely high. In particular, the α-type Al ₂ O ₃ layer constituting the upper layer has a Vickers hardness. In combination with having a high hardness of about 3000 at the height (Hv), cracks are likely to occur in this, and this causes peeling and chipping in the hard coating layer. As shown in the perspective view, in the wet blasting, the peripheral portion of the tool mounting hole is not polished, and the Cr ₂ O ₃ abrasive layer of this portion is left, Since the Cr ₂ O ₃ abrasive layer is relatively low in hardness (Hv: around 1150) compared to the α-type Al ₂ O ₃ layer, the coated cutting tip is attached to the tool body. Since it acts as a buffer layer with a high clamping force, and as a result, the compressive stress on the α-type Al ₂ O ₃ layer becomes extremely small, it is possible to prevent the occurrence of cracks that cause peeling and chipping. To become a.
The research results shown in (a) to (c) above were obtained.

The present invention has been made on the basis of the above research results, and includes a cutting edge ridge portion of a chip base made of a WC-based cemented carbide or TiCN-based cermet and having a tool mounting hole in the center. On the entire surface and flank,
As a lower layer, a Ti compound layer composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer and having an overall average layer thickness of 3 to 20 μm,
As an upper layer, an α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm,
In a coated cutting chip formed by vapor-depositing a hard coating layer composed of
With the Cr ₂ O ₃ abrasive layer deposited on the entire surface of the α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer,
In wet blasting, as a spraying abrasive, a polishing liquid containing 20 to 80% by mass of SiC fine particles in a proportion of the total amount with water is sprayed,
In the presence of the pulverized Cr ₂ O ₃ fine particles by wet blasting of the Cr ₂ O ₃ abrasive layer and the SiC fine particles as a spray abrasive, the abrasive layer around the tool mounting hole is left, and the hard layer is left. The surface of the α-type Al ₂ O ₃ layer constituting the upper layer of the coating layer is polished, and the surface roughness of the rake face and the flank face including the cutting edge ridge line portion is measured based on the compliant standard JIS B0601-1994. Ra: 0.2 μm or less, the hard coating layer is characterized by a coated cutting tip that exhibits excellent chipping resistance in high-speed cutting.

The reason why the numerical values of the hard coating layer and the Cr ₂ O ₃ abrasive layer of the coated cutting chip of the present invention and the SiC fine particles of the polishing liquid used in wet blasting are limited as described above will be described below.
(A) Hard coating layer (a-1) Ti compound layer of lower layer The Ti compound layer exists as a lower layer of the α-type Al ₂ O ₃ layer, and the high temperature strength of the hard coating layer is high due to its excellent high-temperature strength. In addition to contributing to strength improvement, it has a function of firmly adhering to both the chip base and the α-type Al ₂ O ₃ layer, thereby improving the adhesion of the hard coating layer to the chip base, but the overall average layer thickness is If the thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation particularly in high-speed cutting accompanied by generation of high heat. Since it becomes a cause, the whole average layer thickness was set to 3-20 micrometers.

(A-2) α-type Al ₂ O ₃ layer of the upper layer The α-type Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and contributes to improving the cutting performance of the coated cutting tip. If the average layer thickness is less than 1 μm, the desired excellent cutting performance cannot be exhibited over a long period of time. On the other hand, if the average layer thickness exceeds 15 μm, chipping tends to occur. The average layer thickness was set to 1 to 15 μm.

(B) Cr ₂ O ₃ abrasive material layer As described above, the Cr ₂ O ₃ abrasive material layer is pulverized and atomized into SiC ₂ O ₃ fine particles by SiC fine particles blended in the polishing liquid as an injection abrasive during wet blasting. It acts as an abrasive in the presence of the SiC fine particles and polishes the surface of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer. In this case, the average layer thickness is less than 0.5 μm In the wet blasting, the ratio of the pulverized Cr ₂ O ₃ fine particles is too small to sufficiently exhibit the polishing function. On the other hand, when the average layer thickness exceeds 5 μm, the abrasive is injected into the polishing liquid. As a result, the balance with the SiC fine particles blended as follows is lost and becomes relatively large. In this case as well, the polishing function suddenly decreases. In either case, the surface of the α-type Al ₂ O ₃ layer is made Ra: 0. .Surface roughness of 2 μm or less Because it is can not be polished, it determined the average layer thickness and 0.5 to 5 [mu] m.

(C) Ratio of SiC fine particles of polishing liquid The SiC fine particles of the polishing liquid include an α-type Al ₂ O ₃ layer coexisting with the pulverized Cr ₂ O ₃ fine particles of the Cr ₂ O ₃ abrasive layer during wet blasting. There is an action to polish the surface, but even if the ratio is less than 20% by mass or more than 80% by mass with respect to the total amount with water, the polishing function will be drastically deteriorated. Was determined to be 20 to 80% by mass.

In the coated cutting tip of the present invention, the rake face and flank face including the cutting edge ridge line portion of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer are polished to a surface roughness of Ra: 0.2 μm or less. In addition, the Cr ₂ O ₃ abrasive layer present in the periphery of the tool mounting hole acts as a buffer layer having a high clamping force that is indispensable in high-speed cutting when the coated cutting tip is attached to the tool body. Combined with the fact that the compressive stress on the α-type Al ₂ O ₃ layer becomes extremely small, and as a result, cracks that cause peeling and chipping are prevented, cutting various steels and cast iron, etc. The cutting speed is 350 m / min. Even when used for high-speed operation exceeding the above, excellent chipping resistance is exhibited, and the service life can be further extended.

  Next, the coated cutting tip of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By processing, chip bases A to F made of a WC-based cemented carbide having a throwaway tip shape defined in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. TiCN base cermet chip bases a to f having a standard / CNMG12041 chip shape were formed.

Next, each of these chip bases A to F and chip bases a to f is charged into a normal chemical vapor deposition apparatus,
First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically grown crystal structure described in JP-A No. 6-8010, and other than that, a normal granular crystal structure is shown. The Ti compound layer and the α-type Al ₂ O ₃ layer having the target layer thicknesses shown in Table 5 are vapor-deposited as the lower layer and the upper layer of the hard coating layer under the conditions shown in FIG. (See Fig. 3)
Next, a Cr ₂ O ₃ abrasive layer was formed by vapor deposition at a target layer thickness also shown in Table 5 under the Cr ₂ O ₃ layer formation conditions shown in Table 3 (see FIG. 2).
Subsequently, the coated cutting tip for forming the Cr ₂ O ₃ abrasive layer was wet-blasted under the blasting conditions shown in Table 4 and in the combinations shown in Table 5, and Cr ₂ was formed around the tool mounting hole. The rake face and flank face including the cutting edge ridge line portion of the α-type Al ₂ O ₃ layer (upper layer) are polished to the surface roughness shown in Table 5 in the presence of the O ₃ abrasive layer. Thus, the coated cutting chips 1 to 13 of the present invention were manufactured (see FIG. 1).

For comparison purposes, as shown in Table 6, without forming the Cr ₂ O ₃ abrasive layer, wet blasting is directly performed on the surface of the α-type Al ₂ O ₃ layer of the hard coating layer. Conventionally coated cutting chips 1 to 13 were manufactured under the same conditions.
Table 6 shows the surface roughness after wet blasting of the α-type Al ₂ O ₃ layer constituting the hard coating layer of the conventional coated cutting chips 1 to 13 obtained as a result.

  In addition, the composition of the hard coating layer and the abrasive layer of the above-described coated cutting chips 1 to 13 of the present invention, and the composition of the hard coating layer of the conventional coated cutting chips 1 to 13 are each measured with an Auger spectroscopic analyzer at the center in the thickness direction. When measured, all showed substantially the same composition as the target composition, and when the thickness of the same constituent layer was measured using a scanning electron microscope (longitudinal section measurement), both were substantially the same as the target layer thickness. The same average layer thickness (average value of 5-point measurement) was shown.

Next, for the various coated cutting chips of the present invention coated cutting chips 1 to 13 and the conventional coated cutting chips 1 to 13 described above, all of them are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / SNCM447 round bar,
Cutting speed: 410 m / min,
Incision: 2.5mm,
Feed: 0.25mm / rev,
Cutting time: 7 minutes
Wet continuous high-speed cutting test (normal cutting speed is 250 m / min) of alloy steel under the following conditions (referred to as cutting condition A),
Work material: JIS / FCD550 lengthwise equal length 4 round bar with groove,
Cutting speed: 420 m / min,
Incision: 2.5mm,
Feed: 0.2mm / rev,
Cutting time: 8 minutes
Wet intermittent high-speed cutting test (normal cutting speed is 250 m / min) of ductile cast iron under the above conditions (referred to as cutting conditions B),
Work material: JIS / SCr420H round bar,
Cutting speed: 480 m / min,
Incision: 3mm,
Feed: 0.25mm / rev,
Cutting time: 10 minutes,
Wet continuous high-speed cutting test (normal cutting speed is 250 m / min) of alloy steel under the above conditions (referred to as cutting condition C), and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 7.

From the results shown in Tables 5 to 7, the coated cutting tips 1 to 13 of the present invention each have a rake face and a flank face including the cutting edge ridge line portion of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer. However, Ra: polished to a surface roughness of 0.2 μm or less, and the Cr ₂ O ₃ abrasive layer present around the tool attachment hole exceeds 350 m / min when the coated cutting tip is attached to the tool body. It acts as a buffer layer with high clamping force, which is indispensable in high-speed cutting, and prevents cracks that can cause peeling and chipping. It exhibits excellent chipping resistance in high-speed cutting of steel and cast iron. Conventionally, the surface roughness of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer is Ra: 0.3 to 0.6 μm, while exhibiting excellent cutting performance over a wide range Cutting tip 1-1 In, in both high-speed cutting of over 350 meters / min, I coupled with the fact that require high clamping force to the tool mounting, chipping occurs in the α-type the Al ₂ O ₃ layer, a relatively short period of time It is clear that the service life is reached.

  As described above, the coated cutting tip of the present invention can be used not only for continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron, but also when cutting is performed at a high speed exceeding 350 m / min. Because it shows excellent chipping resistance and exhibits excellent cutting performance over a long period of time, it can sufficiently satisfy the high performance of cutting equipment, labor saving and energy saving of cutting work, and further cost reduction. Is.

It is a schematic perspective view of this invention coating cutting tip shown notching a part of hard coating layer. Is a schematic perspective view of a coated cutting tip Cr ₂ O ₃ abrasive layer deposition form shown cut away a portion of the abrasive layer. It is a schematic perspective view of the conventional coated cutting tip shown by cutting out a part of a hard coating layer.

Claims (1)

It is composed of a tungsten carbide base cemented carbide or a titanium carbonitride base cermet, and the entire rake face and flank face including the cutting edge ridge line part of the chip base having a tool attachment hole in the center part,
The lower layer is composed of one or more of a titanium carbide layer, a titanium nitride layer, a titanium carbonitride layer, a titanium carbonate layer, and a titanium carbonitride oxide layer, and has an overall average layer thickness of 3 to 20 μm. Having a Ti compound layer,
As an upper layer, an aluminum oxide layer having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition,
In the cutting throwaway tip made of surface-covered cermet formed by vapor-depositing a hard coating layer composed of
In a state where an abrasive layer composed of a chromium oxide layer having an average layer thickness of 0.5 to 5 μm is deposited on the entire surface of the aluminum oxide layer which is the upper layer of the hard coating layer,
In wet blasting, as a spraying abrasive, a polishing liquid containing 20 to 80% by mass of silicon carbide fine particles in a proportion of the total amount with water is sprayed,
The upper layer of the hard coating layer in the presence of the abrasive layer around the tool mounting hole in the coexistence of the pulverized chromium oxide particles by wet blasting of the abrasive layer and the silicon carbide particles as the spray abrasive The surface roughness of the rake face and the flank face including the cutting edge ridge line portion was polished, and the surface roughness Ra was set to 0.2 μm or less in accordance with the standard JIS / B0601-1994. A surface-coated cermet cutting throwaway tip with a hard coating layer that exhibits excellent chipping resistance in high-speed cutting.

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