JP4888689B2 - Surface polishing method for throated surface-coated cermet with a hard coating layer that exhibits excellent chipping resistance in high-speed cutting - Google Patents

Description

The present invention is a cutting throwaway tip made of a surface-coated cermet without a hole (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 steels and cast irons. ) Surface polishing method .

Conventionally, in general, as shown in a schematic perspective view in FIG. 4, a substrate composed of tungsten carbide (hereinafter referred to as WC) based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) based cermet (hereinafter referred to as these). On the entire surface of the rake face and flank including the cutting edge ridge line portion of the chip base)
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,
A coated cutting tip formed by vapor-depositing a hard coating layer composed of the lower layer and the upper layer is known, and this coated cutting tip is known.
Further, as shown in the schematic perspective view in FIG. 5, the above-mentioned coated cutting tip is placed through a sheet on the tip of the tool body, for example, the shank, and the tip of the crank piece is brought into contact with the upper surface of the tip. It is also well known that, for example, it is used for continuous cutting and intermittent cutting of various steels, cast irons, etc. in a state where the clamp screw provided at the rear of the crank piece is clamped and fixed in a replaceable manner.

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, the ratio of the wet blasting material to the total amount of water as a spraying abrasive is 15 When the polishing liquid containing -60 mass% aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) fine particles is sprayed and polished, the α-type Al ₂ O ₃ layer is based on the compliant standard JIS B0601-1994. (The following surface roughness indicates all measured values based on the standard), and Ra: 0.3-0.6 μm surface roughness is obtained. _Even when a coated cutting tip having a surface roughness of Ra: 0.3 to 0.6 μm smoothed by wet blasting on the surface of the ₂ O ₃ layer 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. A titanium nitride (hereinafter referred to as TiN) layer is formed on the entire surface using a normal chemical vapor deposition apparatus under normal conditions, for example, the conditions shown in Table 3 and an average layer thickness of 0.5 to 5 μm. With chemical vapor deposition formed,
As in the case of (a) above, when a polishing liquid containing 15 to 60% by mass of Al ₂ O ₃ fine particles is injected as a spray abrasive in the ratio of the total amount with water as a spray abrasive, the TiN layer is The α ₂ Al ₃ O ₃ layer constituting the upper layer of the hard coating layer acts as an abrasive in the coexistence of the Al ₂ O ₃ fine particles by being pulverized and atomized by the Al ₂ O ₃ fine particles. As a result, the surface of the α-type Al ₂ O ₃ layer after polishing is smoothed to a surface roughness of Ra: 0.2 μm or less, and this is the upper layer. When high-speed cutting was performed using a coated cutting tip in which the surface of the α-type Al ₂ O ₃ 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 that exceeds 1, the load applied to the cutting edge of the coated cutting tip becomes extremely high. Especially in the case of milling, when attaching the coated cutting tip to the tool body, the clamping force is extremely high. As a result, not only the compressive stress on the hard coating layer of the clamp piece abutting portion of the coated cutting tip is extremely high, but also the clamp piece abutting portion during cutting is correspondingly applied. In particular, the α-type Al ₂ O ₃ layer constituting the upper layer has a high hardness of about 3000 in terms of Vickers hardness (Hv). Cracks are likely to occur, and this causes peeling and chipping of the hard coating layer. As shown in the schematic perspective view of FIG. At this time, if the peripheral portion of the clamp piece abutting portion is not polished and the TiN layer of this portion is left, the TiN layer constituting the abrasive layer (hereinafter referred to as the TiN abrasive layer) Compared with the α-type Al ₂ O ₃ layer, the tool has a relatively very low Hv: about 1950 hardness and high strength. As shown in the schematic perspective view of FIG. When mounting the coated cutting tip with the clamp piece to the main body, it acts as a buffer layer with a high clamping force. As a result, the compressive stress on the α-type Al ₂ O ₃ layer is remarkably relieved, and the strength generated during cutting It acts as an anti-seismic layer that absorbs and mitigates the transmission of mechanical vibrations to the clamp piece, thereby mitigating the vibration attack by the clamp piece against the α-type Al ₂ O ₃ layer. Type Al ₂ The generation of cracks that cause peeling and chipping in the O ₃ layer should be prevented.
The research results shown in (a) to (c) above were obtained.

The present invention was made based on the above research results, and is composed of a WC-based cemented carbide or TiCN-based cermet, and includes the cutting edge ridge line portion of the chip base and the entire flank 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,
The surface coating method of the hole-less coated cutting tip , which is formed by chemical vapor deposition of the hard coating layer composed of the lower layer and the upper layer, and can be attached to the tool body in a replaceable manner by clamping with a clamp piece,
In a state where a TiN abrasive layer is formed by chemical vapor deposition on the entire surface of the α-type Al ₂ O ₃ layer that is the upper layer of the hard coating layer, with an average layer thickness of 0.5 to 5 μm
In wet blasting, as a spraying abrasive, a polishing liquid containing 15 to 60% by mass of Al ₂ O ₃ fine particles in a proportion of the total amount with water is sprayed,
And Al ₂ O ₃ milled TiN fine made by grinding atomized by atomization of injection is TiN abrasive layer is injection abrasive described above, in the presence of Al ₂ O ₃ fine as injection abrasive, the clamp Komato Grinding the surface of the α-type Al ₂ O ₃ layer that constitutes the upper layer of the hard coating layer, leaving the TiN abrasive layer around the contact portion , and cutting edge ridges of the α-type Al ₂ O ₃ layer The surface roughness of the rake face and the flank face including JIS B0601-1994 is measured by Ra: 0.2 μm or less, and the hard coating layer exhibits excellent chipping resistance in high-speed cutting. It has a feature in the surface polishing method of the coated cutting tip.

Hereinafter, in the surface polishing method of the coated cutting tip of the present invention, the reason why the hard coating layer, the TiN abrasive layer, and the Al ₂ O ₃ fine particles of the polishing liquid used in wet blasting are numerically limited as described above will be described. To do.
(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) TiN abrasive layer As described above, TiN abrasive layer during wet blasting, the Al ₂ O ₃ fine formulated as injection abrasive in the polishing liquid milled micronized, the Al ₂ O ₃ becomes TiN fine Acts as an abrasive in the presence of 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, if the average layer thickness is less than 0.5 μm, the wet When the ratio of the pulverized TiN fine particles at the time of blasting is too small, the polishing function cannot be sufficiently exerted. On the other hand, when the average layer thickness exceeds 5 μm, Al ₂ O blended in the polishing liquid as a jetting abrasive is used. ₃ The balance with the fine particles is lost and the amount is relatively too 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 Ra: 0.2 μm or less. Polish to a surface roughness of Therefore, the average layer thickness was set to 0.5 to 5 μm.
Furthermore, the average layer thickness of 0.5 μm or more is sufficient when the average layer thickness is less than 0.5 μm, and the clamping force buffering effect and the anti-seismic effect of the TiN abrasive layer around the clamp piece abutting part are fully demonstrated. It's also because you can't.

The Al ₂ O ₃ fine of Al ₂ O ₃ fine fraction polishing solution of (c) polishing liquid, in a state where at the time of wet blast coexists with pulverized TiN fine of TiN abrasive layer, the α type the Al ₂ O ₃ layer There is an action to polish the surface, but even if the ratio is less than 15% by mass or more than 60% by mass with respect to the total amount with water, the polishing function will rapidly decrease, so that ratio Was determined to be 15 to 60% by mass.

In the coated cutting tip surface-polished by the method of the present invention, the rake face and flank face including the cutting edge ridge portion of the α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer have a Ra: 0.2 μm or less. The TiN abrasive layer, which is polished to the surface roughness of the clamp piece and is present in the periphery of the clamp piece contact portion, serves as a buffer layer with high clamping force that is indispensable for high-speed cutting when attaching the coated cutting tip to the tool body. In addition to acting, it also acts as an anti-vibration layer for strong mechanical vibrations that occur during cutting, so the compressive stress on the α-type Al ₂ O ₃ layer is remarkably relieved, and vibration attacks by the clamp pieces are extremely becomes small, I result the α-type Al ₂ O ₃ cooperation with and be like crack is prevented to cause peeling and chipping in layers, cutting pressure of various kinds of steel and cast iron The cutting speed is 350m / 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 method for polishing the surface of the coated cutting tip according to 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. 4)
Next, a TiN abrasive material layer was formed by vapor deposition with the target layer thickness also shown in Table 5 under the TiN layer formation conditions shown in Table 3 (see FIG. 2).
Subsequently, the coated cutting tip for forming the TiN abrasive layer is subjected to wet blasting under the blast conditions shown in Table 4 and in the combinations shown in Table 5, and the TiN abrasive around the periphery of the clamp piece abutting portion In the state where the layer exists, the rake face and the 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 as well. Coated cutting tips 1 to 13 were produced (see FIG. 1).

For comparison purposes, as shown in Table 6, the same conditions except that the TiN abrasive layer is not formed and wet blasting is directly applied to the surface of the α-type Al ₂ O ₃ layer of the hard coating layer. Conventionally, the coated cutting chips 1 to 13 were manufactured.
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.

Further, the composition of the hard coating layer and the TiN abrasive layer of the present invention coated cutting tips 1 to 13 and the composition of the hard coating layer of the conventional coated cutting chips 1 to 13 are respectively set at the center in the thickness direction by an Auger spectrometer. As a result of measurement, 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, as for the various coated cutting tips of the present invention coated cutting tips 1 to 13 and the conventional coated cutting tips 1 to 13, respectively, as shown in FIGS. In a state where it is attached to the tip of the shank by clamping with the clamp screw of the clamp piece,
Work material: JIS · SCM420 lengthwise equal four round grooved round bars,
Cutting speed: 450 m / min,
Cutting depth: 2mm,
Feed: 0.2mm / rev,
Cutting time: 6 minutes
Dry interrupted high-speed cutting test of alloy steel under the above conditions (referred to as cutting condition A) (normal cutting speed is 200 m / min),
Work material: JIS / S50C lengthwise equal 4 round grooved round bars,
Cutting speed: 430 m / min,
Cutting depth: 2mm,
Feed: 0.3mm / rev,
Cutting time: 9 minutes
Dry intermittent high speed cutting test (normal cutting speed is 200 m / min) of carbon steel under the above conditions (referred to as cutting conditions B),
Work material: JIS / FC350 round bar,
Cutting speed: 550 m / min,
Cutting depth: 2mm,
Feed: 0.35mm / rev,
Cutting time: 12 minutes,
A dry continuous high-speed cutting test (normal cutting speed is 250 m / min) of normal cast iron 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, which were surface-polished by the method of the present invention, all have an α-type Al ₂ O ₃ layer cutting edge constituting the upper layer of the hard coating layer. The rake face and flank face including the ridge line part are polished to a surface roughness of Ra: 0.2 μm or less, and the TiN abrasive layer existing in the periphery of the clamp piece abutting part is used to apply the coated cutting tip to the tool body. When mounting, it acts as a buffer layer of high clamping force, which is indispensable for high-speed cutting processing exceeding 350 m / min, and also acts as a vibration-proof layer for strong mechanical vibration generated during cutting processing. compressive stress to the Al ₂ O ₃ layer is remarkably relaxed, and vibration attack by the clamp piece becomes extremely small, peeling or chipping occurred in a result the α type the Al ₂ O ₃ layer The upper layer of the hard coating layer is configured to prevent the occurrence of cracking, which shows excellent chipping resistance during high-speed cutting of steel and cast iron, and excellent cutting performance over a long period of time. In the conventional coated cutting tips 1 to 13 in which the surface roughness of the α-type Al ₂ O ₃ layer is Ra: 0.3 to 0.6 μm, all of them are used for tool attachment in high-speed cutting processing exceeding 350 m / min. It is clear that chipping occurs in the α-type Al ₂ O ₃ layer in combination with the need for a high clamping force, leading to a service life in a relatively short time.

As described above, the coated cutting tip of the present invention, which has been surface-polished by the method of the present invention, has a cutting speed of 350 m / min, in addition to continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron. It exhibits excellent chipping resistance even when performed at high speeds exceeding it, and exhibits excellent cutting performance over a long period of time. It can cope with cost reduction sufficiently.

It is the schematic perspective view which notched and showed a part of hard coating layer of this invention coated cutting chip surface-polished by the method of this invention . It is the schematic perspective view which notched and showed a part of TiN abrasive | polishing material layer of the covering cutting chip after TiN abrasive | polishing material vapor deposition formation in the method of this invention . It is a schematic perspective view which shows the attachment aspect to the tool main body of this invention cutting chip | tip surface-polished by the method of this invention . It is the schematic perspective view which notched and showed a part of hard coating layer of the conventional coated cutting chip . It is a schematic perspective view which shows the attachment aspect to the tool main body of the conventional coated cutting tip.

Claims (1)

On the entire rake face and flank face including the cutting edge ridge line portion of the chip base composed of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
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,
Surface polishing of a cutting throwaway tip made of surface-covered cermet without holes, which is formed by chemical vapor deposition of the hard coating layer composed of the lower layer and the upper layer, and can be attached to the tool body by clamping with a clamp piece. In the way
In a state where an abrasive layer composed of a titanium nitride layer having an average layer thickness of 0.5 to 5 μm is formed by chemical vapor deposition 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 15 to 60% by mass of aluminum oxide fine particles in a proportion of the total amount with water is sprayed,
In the presence of the pulverized titanium nitride fine particles formed by pulverizing and atomizing the aluminum oxide fine particles, which are spray abrasive materials, and the aluminum oxide fine particles as the spray abrasive material, the periphery of the clamp piece contact portion The surface of the aluminum oxide layer that constitutes the upper layer of the hard coating layer is polished, leaving the abrasive layer, and the surface roughness of the rake face and flank surface including the cutting edge ridge portion of the aluminum oxide layer is increased. The measurement based on JIS / B0601-1994, Ra: 0.2 μm or less, the hard coating layer is made of surface-coated cermet without hole that exhibits excellent chipping resistance in high-speed cutting. Surface polishing method for throwaway tip.

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