JP2011005583A - Cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool which restricts peeling of a coating layer within the ridge of the cutting blade, is improved in chipping resistance in a cutting blade, and has a long service life.SOLUTION: In a throw-away tip 1 coated with a plurality of coating layers 9 including a lower layer 9L and an upper layer 9U on the surface of a base body 8, a nearly V-shaped lower layer chipped part 10 exists in the ridge 4 of the cutting blade in the lower layer 9L, and at least the surface of the lower layer chipped part 10 of the lower layer 9L is coated with the upper layer 9U.

Description

  The present invention relates to a cutting tool in which a coating layer is formed on the surface of a substrate.

  Conventionally, a cutting tool in which a surface of a substrate is coated with a coating layer is known, and the state of the coating layer on the cutting edge has been studied. For example, Patent Document 1 discloses a drill in which only a cutting edge ridge line portion is removed by secondary sputtering when a coating layer is formed by an arc ion plating method, thereby preventing defects and film peeling in the initial stage of cutting. It describes what you can do. Further, FIG. 4 of the same document describes that in the configuration in which two coating layers are formed, only the upper layer is removed at the cutting edge ridge portion and the lower layer is hardly affected.

  Further, in Patent Document 2, after coating the first hard film (lower layer) mainly composed of diamond or cBN, honing is performed so that the base material (substrate) is exposed at the cutting edge ridge (cutting edge line portion), and then Further, a cutting tool in which a second hard film (upper layer) is formed again is disclosed, and it is described that the peeling of the hard film and the fusion of the work material are suppressed at the cutting edge ridge line portion.

JP 2000-52118 A Japanese Patent Laid-Open No. 08-174309

  However, even in the configuration of the coating layer as in Patent Document 1 and Patent Document 2, the peeling resistance and fracture resistance of the coating layer at the cutting edge ridge line portion are insufficient, and further improvement in fracture resistance is required. It was.

  An object of the present invention is to provide a long-life cutting tool that improves the above-described conventional problems and has high peeling resistance and fracture resistance of the coating layer at the edge portion of the cutting edge.

  The cutting tool of the present invention covers a plurality of coating layers including a lower layer and an upper layer on the surface of the base, and when observed in a cross section orthogonal to the cutting edge ridge line, the lower layer is at the cutting edge ridge line. A substantially V-shaped lower layer lacking portion exists, and the upper layer covers at least the surface of the lower layer lacking portion of the lower layer.

Here, in the central portion of the rake face, the thickness t _{L of the} lower layer is 1 to 3 μm, the thickness t _{U of the} upper layer is 2 to 5 μm, and the ratio of the thickness t _L to the thickness t _U (t _U / t _L ) is preferably 1.5-3.

  Moreover, it is desirable that the depth of the substantially V-shaped lower layer lacking portion is 0.5 to 3 μm.

Furthermore, it is desirable that a ratio (t _E / t _U ) between the thickness t _{E of the} upper layer and the thickness t _U in the lower layer lacking portion is 1.2 to 1.5.

  According to the cutting tool of the present invention, when observed in a cross-section orthogonal to the cutting edge ridge line, a substantially V-shaped lower layer lacking part exists in the lower layer in the cutting edge ridge line part, and the lower layer lacking part Compared to the structure in which the upper layer covers the surface of the surface, the structure in which the lower layer is absent in the upper layer, and the structure in which the lower layer in the cutting edge ridge line portion is honed until the base is exposed and then the upper layer is covered again. Thus, it was found that the fracture resistance at the cutting edge ridge was high.

Here, in the central portion of the rake face, the thickness t _{L of the} lower layer is 1 to 3 μm, the thickness t _{U of the} upper layer is 2 to 5 μm, and the ratio of the thickness t _L to the thickness t _U (t _U / In the configuration in which t _L ) is 1.5 to 3, the chipping resistance at the cutting edge ridge is increased.

  Moreover, when the depth of the substantially V-shaped lower layer lacking portion is 0.5 to 3 μm, the fracture resistance particularly at the cutting edge ridge line portion is enhanced.

Furthermore, the ratio (t _E / t _U ) between the thickness t _{E of the} upper layer and the thickness t _U in the lower layer lacking portion is 1.2 to 1.5. It is desirable in that it is high and wear resistance is also improved.

It is a schematic perspective view which shows an example of the throw away tip which is a suitable example of the cutting tool of this invention. It is sectional drawing about the cutting edge of the throw away tip of FIG. It is the schematic diagram observed in the cross section orthogonal to the cutting-edge ridgeline part of the throw away tip of FIG. It is the schematic diagram observed in the cross section orthogonal to the cutting-edge ridgeline part of the throw away tip in the other embodiment of the cutting tool of this invention.

  FIG. 1 is a schematic perspective view of a throwaway tip which is a preferred example of the cutting tool of the present invention, FIG. 1 which is a schematic perspective view of the example, FIG. 2 which is a side view, and a cross-sectional view perpendicular to a cutting edge ridge line portion. This will be described with reference to FIG.

  According to FIG. 1, a throw-away tip (hereinafter simply referred to as a tip) 1 has a main surface 2 having a substantially flat plate shape with a polygonal shape, one main surface being a rake surface 2a, and a side surface being a flank. 3, the cutting edge 6 is formed including the nose part 5 of the cutting edge ridge line part 4 of the rake face 2a and the flank face 3. The main surface opposite to the rake surface 2a forms a seating surface 2b as shown in FIG.

  As shown in FIGS. 2 and 3, the chip 1 has a coating layer 9 including a plurality of layers including a lower layer 9 </ b> L and an upper layer 9 </ b> U formed on the surface of a base 8 so as to be deposited from at least the rake face 2 a to the flank face 3. In addition, according to FIG. 2, the screw hole 7 penetrated over the seating surface 2b is provided in the center part of the rake face 2a.

  Here, according to FIG. 3, in the chip 1, the lower layer 9 </ b> L has a substantially V-shaped lower layer lacking portion 10 in the cutting edge ridge line portion 4, and the surface of the lower layer lacking portion 10 of the lower layer 9 </ b> L is the upper layer 9 </ b> U. Is covered. With this configuration, the fracture resistance in the cutting edge ridge portion 4 is increased. In this configuration, the reason why the fracture resistance of the cutting edge ridge portion 4 is improved is unknown, but the crystal growth state in the cutting edge ridge portion 4 of the upper layer 9U becomes complicated and exists in the grown upper layer 9U. It is assumed that the residual stress is optimized.

  Note that the cross-sectional shape of the lower layer lacking portion (hereinafter abbreviated as the lower layer lacking portion) 10 of the lower layer 9L has at least one bent portion 11 as shown in FIG. It is desirable in that the residual stress of the coating layer 9 on the blade 6 can be efficiently and effectively reduced to suppress large chipping and chipping, and the wear resistance of the coating layer 9 on the rake face 2a and the flank face 3 can be maintained together. . According to the present invention, the cross-sectional shape of the lower layer lacking portion 10 may be a curved shape having no convex bent portion 11 as shown in FIG. As shown in FIG. 4B, the number of the convex bent portions 11 may be only one. However, as shown in FIG. May be.

Here, in the central part of the rake face 2a, the thickness t _L of the lower layer 9L is 1 to 3 μm, the thickness t _{U of the} upper layer 9U is 2 to 5 μm, and the ratio of the thickness t _L to the thickness t _U (t _{In the configuration in which (U} / t _L ) is 1.5 to 3, particularly 2 to 3, the chipping resistance at the cutting edge ridge portion 4 is increased.

Further, when the depth of the substantially V-shaped lower layer lacking portion 10 (average value d of d ₁ and d _{2 in} FIG. 3) is 0.5 to 3 μm, particularly 1.5 to 2.5 μm, it is particularly cut off. The chipping resistance in the edge line part 4 becomes high. In addition, it is desirable that the width w of the opening of the lower layer lacking portion 10 is 2 to 5 μm from the standpoint of maintaining a balance between chipping resistance and wear resistance in the cutting edge ridge line portion.

Further, the cutting edge ridgeline indicates that the ratio (t _E / t _U ) between the thickness t _E of the upper layer 9U in the lower layer lacking portion 10 and the thickness t _U in the central portion of the rake face 2a is 1.2 to 1.5. This is desirable in that the fracture resistance in the portion 4 is high and the wear resistance is improved.

  The covering layer 9 is composed of at least one carbide, nitride, carbonitride, diamond, diamond-like carbon (DLC), boron nitride (selected from the group of Periodic Tables 4, 5, and 6 metals, Al and Si. cBN). In the above configuration, the lower layer 9L and the upper layer 9U may be made of the same material type, or different material types so that the lower layer is made of a TiCN layer and the upper layer 9U is made of a (Ti, Al) N layer. The structure which becomes may be sufficient.

Here, according to the present invention, in forming the lower lack portion 10 as described above, cutting ridge 4 is sharp edge, i.e. the radius of curvature R _r of the cutting edge 6 cross section is in the following state 10μm substrate On the other hand, the coating layer 9 is formed by a method of forming the coating layer 9 by applying a bias voltage such as an arc ion plating method or a sputtering method. At this time, when forming the lower layer, the bias voltage is increased to 1.5 times or more of the steady film formation conditions, and then the bias voltage when forming the upper layer is the same as that when forming the lower layer. It can be manufactured by a method in which the bias voltage is lowered and the steady film formation conditions are restored.

Further, the cutting edge 6 is desirable in terms of improving the sharpness of the cutting edge 6 while being able to reliably form the lower layer lacking portion 10. The curvature radius R _r of the cross section of the cutting edge 6 is preferably 5 μm or less, and more preferably 3 μm or less.

  Moreover, in this invention, as shown in FIG. 2, you may form the concave-shaped or convex-shaped breaker part 12 in the rake face 2a side from the cutting blade 6 of the chip | tip 1, and, thereby, the chip | tip discharge property improves. As a result, the sharpness can be increased, chattering can be suppressed, and the roughness of the machined surface can be improved. In particular, the concave breaker portion 12 makes the cutting edge 6 sharper and the lower layer lacking portion 10 is reliably secured. Can be formed.

  Furthermore, according to the present invention, the arithmetic average roughness (Ra) of the rake face 2a and the flank face 4 is preferably 1 μm or less, particularly 0.5 μm or less from the viewpoint of improving the roughness of the machined surface and improving the sharpness. .

Grade A: 0.6% by mass of Cr ₃ C ₂ powder having an average particle size of 1.5 μm and 0.3% of VC powder having an average particle size of 1.2 μm with respect to the WC powder having an average particle size shown in Table 1. % By weight, Co powder having an average particle size of 0.5 μm was added in the ratio shown in Table 1,
Grade B: 15% by mass of TiN powder with an average particle size of 2 μm, 3% by mass of TaC powder with an average particle size of 2 μm, and NbC powder with an average particle size of 2 μm with respect to the TiCN powder with the average particle size shown in Table 1. 2% by mass, Co powder having an average particle diameter of 1 μm and Ni powder were added in the proportions shown in Table 1,
After mixing, forming into a TMMG chip shape and firing, polishing was performed so that the arithmetic average roughness (Ra) of the rake face and flank face was 0.5 μm or less. The cutting edge was machined so that the radius of curvature seen in the cross section was the value shown in Table 1. The tip angle θ of the nose portion was 60 °, and the positive angle α of the cutting edge was 11 °.

The base material is washed with alkali and evacuated at 1 × 10 ⁻² Pa. Then, the inside of the furnace is heated to 550 ° C. and both the lower layer and the upper layer are formed by the arc ion plating method (Ti , Al) N was formed under the conditions shown in Table 1 to produce a throw-away tip. In the table, sample No. Regarding No. 5, after forming the lower layer, it was once taken out and subjected to honing processing on the cutting edge, and then returned to the film forming apparatus again to form the upper layer.

In order to confirm the cross-sectional shape of the cutting edge of the obtained chip, the cross-section including the nose tip is cut by FIB processing (focused ion beam processing), and the cross-section of the cutting edge is observed by observing the cross-section with a scanning electron microscope. the shape and thickness of the rake face t _p at the boundary between the lower lack portion of the coating _layer, the flank face-side t _s were measured, and the average value was calculated. In addition, about the sample which does not have a lower layer lacking part, the film thickness in a cutting blade was described with the parenthesis writing. Further, the lower layer lacking portion was observed with a microscope while changing the angle from the upper oblique direction of the chip, and the maximum width of the lower layer lacking portion was measured.

In addition, the chip manufactured under the above conditions is subjected to cutting under the following conditions, and the chipping and chipping states at the time of performing 300 constant machinings are confirmed and indicated as chipping resistance. The number of workpieces processed was measured with the time when the arithmetic average surface roughness (Ra) of the cutting material exceeded 0.10 μm as the lifetime.
Cutting condition work material SUS430F
Machining form φ8mm Outer diameter end face finishing cutting cutting speed V = 150m / min
Notch 0.03mm
Feed 0.03mm / rev
Cutting state The wet results are shown in Table 1.

  As is apparent from the results in Table 1, the sample No. having no lower layer lacking portion was obtained. In No. 5, chipping and chipping occurred on the cutting edge, and the chipping resistance was low. Sample No. with no lower layer lacking part and upper layer lacking part present. 6 also chipped due to poor chipping resistance. Furthermore, sample No. which lacked both the lower layer and the upper layer. In No. 7, the progress of wear was fast and the number of processing was small.

  In contrast, Sample No. in which the cutting blade has a lower layer lacking portion and the upper layer covers the surface thereof. About 1-4, all became a chip | tip with a high chipping resistance and a long lifetime.

DESCRIPTION OF SYMBOLS 1 Throw away tip 2 Main surface 2a Rake surface 2b Seating surface 3 Relief surface 4 Cutting edge ridge part 5 Nose part 6 Cutting edge 7 Screw hole 8 Base body 9 Covering layer 10 Lower layer lacking part 11 Convex bending part 12 Breaker part t _L : Thickness of the lower layer at the center of the rake face t _U : Thickness of the upper layer at the center of the rake face t _E : Thickness of the upper layer at the edge of the cutting edge d ₁ : Depth on the rake face side of the substantially V-shaped lower layer missing part D ₂ : Depth on the flank side of the substantially V-shaped lower layer lacking portion

Claims (4)

  A cutting tool in which a surface of a substrate is coated with a plurality of coating layers including a lower layer and an upper layer, and the lower layer is substantially V-shaped at the cutting edge ridge when observed in a cross section perpendicular to the cutting edge ridge. A cutting tool in which the lower layer lacking portion is present, and the upper layer covers at least the surface of the lower layer lacking portion of the lower layer. In the central portion of the rake face, the thickness t _{L of the} lower layer is 1 to 3 μm, the thickness t _{U of the} upper layer is 2 to 5 μm, and the ratio of the thickness t _L to the thickness t _U (t _U / t _L ) The cutting tool according to claim 1, wherein is 1.5-3.   The cutting tool according to claim 1 or 2, wherein a depth of the substantially V-shaped lower layer lacking portion is 0.5 to 3 µm. The cutting tool according to claim 3, wherein a ratio (t _E / t _U ) between the thickness t _{E of the} upper layer and the thickness t _U in the lower layer lacking portion is 1.2 to 1.5.

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