JP4841201B2 - Throwaway tip - Google Patents

Description

  The present invention relates to a throw-away tip in which a hard coating layer having excellent fracture resistance and wear resistance is formed on the surface.

  2. Description of the Related Art Conventionally, throw-away tips that are widely used for metal cutting work are often used in which a single layer or multiple layers of a hard coating layer are formed on the surface of a base made of cemented carbide.

  With regard to such a throw-away tip, for example, in Japanese Patent Application Laid-Open No. H10-260260, the applicant of the present invention has a land surface having the same height as the center surface in order to increase the restraining force of the throw-away tip under cutting conditions where a strong impact is applied. It is proposed that it is effective to design it to be a constraining surface.

  In addition, regarding the cemented carbide substrate, Patent Document 2 discloses a so-called debonding in which the bonding phase concentration is high in the honing portion of the substrate surface by adding Zr and Hf to the cemented carbide substrate and controlling the honing process conditions. A method for reducing the de-β-free region from which the β layer (bonded phase enriched layer) has been removed is described. Further, Patent Document 3 discloses that a growth-inhibiting hard layer is formed in advance and then honing is performed to remove the de-β layer in the honing portion, which is then heat-treated to remove the de-β layer in the honing portion. The method to revive is described. Furthermore, Patent Document 4 discloses that the de-β layer disappears at the honing part as in the case where the honing process is performed on the sintered body by firing after performing the honing process at the molded body stage. It is described that can be prevented. And these patent documents 2-4 describe that the defect resistance in the honing part which is a cutting edge can be improved by making a de-beta layer exist also in a honing part, and the fracture resistance of a tool can be improved. Has been. Further, in each of the rake face including the land surface following the honing portion and the flank face, a de-β layer having a uniform thickness is formed.

Further, in Patent Document 5, in a throw-away tip in which a land surface and a breaker groove are formed inside a ridge line of a blade edge, a de-β layer that has low hardness and improved toughness is formed on the surface portion of the base body, and the de-β By setting the thickness of the layer so that it is thicker at the breaker groove than at the land surface, it is possible to increase the fracture resistance in the breaker groove that is liable to break due to the load during cutting and to increase the plastic deformation resistance at the land surface. Are listed. This document also describes that the de-β layer on the land surface and the flank surface has the same thickness.
JP 2004-98251 A JP 7-113180 A JP-A-10-225804 JP-A-7-185909 JP 2003-145212 A

  However, in a throw-away tip having a land surface as an installation surface as in Patent Document 1, a configuration in which a de-β layer having a predetermined thickness exists on the land surface and the flank surface as described in Patent Documents 2 to 5 Then, in the cutting form in which chips are extended and guided to the breaker groove, plastic deformation occurs on the land surface and the height of the land surface is lowered, and the land surface is disposed on the seating surface and In this case, there is a problem that the restraining force on the land surface is weakened, chatter vibration is generated during cutting, and the finished surface roughness of the work material is lowered. In addition, chips generated during cutting collide with the breaker groove and are curved, but are rarely divided here, and since the curved chips collide with the flank and are often divided, When the thickness of the layer is reduced as a whole, there arises a problem that when the chips collide and divide on the flank face of the throw-away tip, defects are easily generated due to the impact of the chips. In particular, this phenomenon was conspicuous at the time of cutting steel in which chips easily extend.

  The present invention has been made in order to solve the above-mentioned problems, and the purpose of the present invention is to provide a throw-away tip that can obtain a strong restraining force even in a double-sided throw-away tip and has excellent fracture resistance on the flank. It is to provide.

  In the present invention, with respect to the above-mentioned problems, the height of the land surface is the same as the height of the central surface, and when it is disposed on the seating surface, it is configured to be an installation surface, and the honing portion that becomes the cutting edge during cutting is used. In the subsequent land surface, there is no de-β layer to prevent plastic deformation during cutting, or the de-β layer is thin, and the de-β layer is thick on the flank. This makes it possible to maintain a strong restraining force on any land surface against a throw-away tip that can be used on both sides, and to exhibit stable cutting performance without chipping even if chips collide with the flank. .

That is, the throw-away tip of the present invention has a substantially flat plate shape, the two main surfaces are polygonal, and are used as a rake surface and a seating surface, respectively, and the side surfaces are used as flank surfaces. And the flank face is used as a cutting edge, a land surface is provided on the peripheral edge of the main surface, and a center surface is provided on the inside from the land surface with a breaker groove interposed therebetween. The throw-away tip can be used, and when the one main surface is the seating surface, the center surface and the land surface on the main surface side are both installation surfaces, and the carbonization tip is carbonized. A hard coating layer is formed on the surface of a cemented carbide substrate in which tungsten and cubic carbides of metals of the periodic tables 4a, 5a and 6a are bonded with a binding phase of an iron group metal. The concentration B of the binder phase on the surface of the cemented carbide substrate at the flank surface is higher than the concentration A of the binder phase inside the alloy substrate (B> A), and the inside of the cemented carbide substrate. The ratio (B / A) between the concentration A of the binder phase and the concentration B of the binder phase on the surface of the cemented carbide substrate at the flank surface is determined by the concentration A of the binder phase inside the cemented carbide substrate. wherein the ratio of the concentration C of the binder phase in the surface of the cemented carbide substrate in the land surface (C / a) much larger than the,
Further, the breaker groove has a wall surface on the center surface side formed of a two-step rising wall surface including a first step forming an angle α with the center surface and a second step forming an angle β (where β <α). The concentration D of the binder phase at the groove bottom in the breaker groove is defined as the concentration B of the binder phase at the surface of the cemented carbide substrate at the flank, and the binder phase at the surface of the cemented carbide substrate at the land surface. With respect to the density C, B>D> C.

  Here, the ratio (C / A) of the concentration C of the binder phase on the surface of the cemented carbide substrate at the land surface to the concentration A of the binder phase inside the cemented carbide substrate is 0.95 to 1. .05, that is, the surface of the land surface has the same binder phase concentration as the inside of the cemented carbide substrate within the range of variation, and there is no binder phase enriched layer. This is desirable in that crater wear can be reduced while maintaining fracture resistance on the land surface.

  Further, in the flank, a region where the binder phase concentration B on the surface of the cemented carbide substrate is higher than the binder phase concentration A inside the cemented carbide substrate is 10 μm from the surface of the cemented carbide substrate. The thickness of 50 μm or less is desirable in that the wear resistance and fracture resistance on the flank can be optimized.

  The width of the land surface in the vicinity of the corner portion is narrower than the width of the land surface in other portions, so that the cutting resistance due to the land surface in the corner portion that mainly functions as a cutting edge can be reduced, and the corner portion It is desirable in that the restraining force of the throw-away tip can be increased at other portions.

  Further, in the breaker groove, the wall surface on the central surface side is a two-stage rising wall surface composed of a first step forming an angle α with the central surface and a second step forming an angle β (where β <α). However, it is desirable in that the chips are easily bent and can be divided easily.

  According to the configuration of the first aspect of the present invention, the shape of the land surface arranged on the seating surface plays a role of increasing the binding force of the chip, that is, the height of the land surface is designed to be the same as the height of the central surface. Has been. Then, by optimizing the concentration of the binder phase on the surface of the cemented carbide substrate at each part, that is, by making the B / A on the flank larger than the ratio C / A on the land surface, It is possible to suppress plastic deformation of the land surface, which is a passage of chips, during cutting, and a high restraining force can be stably obtained even when the land surface becomes an installation surface. Moreover, although the chip | tip can be divided efficiently and the chip | tip discharge | emission property can be improved with the said breaker groove | channel, even if a chip collides with a flank, stable cutting performance can be exhibited, without missing.

  According to the configuration of claim 2 of the present invention, crater wear can be reduced while maintaining the fracture resistance on the land surface. According to the configuration of claim 3 of the present invention, the wear resistance and resistance to flank are reduced. Defectability can be optimized. Furthermore, according to the structure of Claim 4 in this invention, while being able to reduce the cutting resistance in the corner part used most frequently as a cutting blade, the strong restraint force of a throw away tip can be maintained. Furthermore, according to the structure of Claim 5 in this invention, the division | segmentation of a chip becomes easy.

  FIG. 1 is a schematic cross-sectional view of an example of the throw-away tip of the present invention, FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1, the Y-Y cross-section of the throw-away tip of FIG. The binder phase concentration distribution (B / A, C / A) in the cemented carbide substrate will be described with reference to FIG.

  According to FIG. 1, a throw-away tip (hereinafter also simply referred to as a tip) 1 has a substantially flat plate shape, two main surfaces are polygonal, and are used as a rake surface 2 and a seating surface 3, respectively. The chip 1 is a double-sided chip 1 used as a flank 4. And at least the corner part 5 of the crossing edge part of the said main surface, ie, each of the rake face 2 and the seating surface 3, and the flank 4, is used as a cutting edge, and the land surface 6 is on the peripheral part of the said main surface, and A center surface 8 is provided on the inner side from the land surface 6 with a breaker groove 7 interposed therebetween. Further, a screw hole 9 is provided at the center of the center surface 8 of the throw-away tip 1.

  Further, as shown in FIG. 2, the chip 1 of the present invention has a configuration in which a hard coating layer 13 is deposited on the surface of a cemented carbide substrate 11 in which tungsten carbide is bonded with a binding phase of an iron group metal. And according to the chip 1 of the present invention, as shown in FIG. 3, when one main surface becomes the seating surface 3, both the central surface 8 on the main surface side and the land surface 6 become the installation surface, The concentration B of the binder phase on the surface of the cemented carbide substrate 11 at the flank 4 is higher than the concentration A of the binder phase inside the cemented carbide substrate 11 (B> A), and inside the cemented carbide substrate 11. The ratio (B / A) between the binder phase concentration A and the binder phase concentration B at the surface of the cemented carbide substrate 11 at the flank 4 is determined as follows. 6 is larger than the ratio (C / A) of the binder phase concentration C on the surface of the cemented carbide substrate 11.

  Thereby, the wear resistance on the land surface 6 is increased, and plastic deformation of the land surface 6 can be suppressed. Moreover, since the density | concentration B of a binder phase is high in the surface of the flank 4, it can suppress that the flank 4 lose | disappears when the chip | tip which generate | occur | produces at the time of cutting collides with the flank 4 and is divided | segmented. As a result, the chip 1 as a whole exhibits fracture resistance and stable cutting performance.

  In addition, if the land surface 6 and the center surface 8 are formed by double-head grinding so that they have the same height, the honing portion 10 formed at the intersection ridge portion of the rake surface 2 and the flank surface 4 and continuing to the land surface 6. Compressive residual stress can be imparted to the honing part 10, and the honing part 10 is used as a cutting edge, so that the chipping resistance of the cutting edge is also improved. Here, the ratio (C / A) of the binder phase concentration C on the surface of the cemented carbide substrate 11 on the land surface 6 to the binder phase concentration A inside the cemented carbide substrate 11 is 0.95 to 1.05. In other words, the concentration of the binder phase in the cemented carbide substrate 11 is the same as that of the cemented carbide substrate 11 within a range of local variation. The presence of the binder phase enriched layer 12 on the surface can increase the wear resistance of the land surface 6 so that the restraint force of the chip 1 can be increased when the land surface 6 becomes the installation surface, and the escape is performed. The surface 4 is desirable in that it has chipping resistance that can withstand chip collision.

  In the present invention, the binder phase concentration A inside the cemented carbide substrate 11 refers to the average value of the binder phase concentration in the region where the depth from the surface of the cemented carbide substrate 11 is 1000 to 1100 μm. Furthermore, the concentration of the binder phase on the surface of the cemented carbide substrate 11 is such that the concentration of the binder phase on the surface of the cemented carbide substrate 11 is within the cemented carbide substrate 11 in order to eliminate variation in concentration measurement. It is determined that the binder phase enriched layer 12 exists when the concentration is 1.06 times or more compared to the concentration of. The thickness of the binder phase-enriched layer 12 refers to the thickness from the surface of the cemented carbide substrate to a depth position where the binder phase concentration is the same value as the inside of the cemented carbide substrate 11.

  The binder phase concentration ratio (B / C) is 1.05 to 1.3, and particularly preferably 1.1 to 1.2, so that plastic deformation of the land surface 6 can be suppressed. And it is desirable at the point which can improve the fracture resistance of flank 4.

  Further, as shown in FIG. 3, in the flank 4, a region where the binder phase concentration B on the surface of the cemented carbide substrate 11 is higher than the binder phase concentration A inside the cemented carbide substrate 11, so-called binder phase richness. It is desirable that the layer 12 has a thickness t of 10 μm or more and 50 μm or less from the surface of the cemented carbide substrate 11 in that the wear resistance and fracture resistance on the flank 4 can be optimized. Further, in the flank 4, it is desirable that the binder phase concentration ratio (B / A) is 1.1 to 1.3 in terms of enhancing the fracture resistance of the flank 4. A particularly desirable range of this binder phase concentration ratio (B / A) is 1.1 to 1.2.

  The cemented carbide substrate 11 includes tungsten carbide as a main component and includes cubic carbides of Group 4a, 5a, and 6a metals in the periodic table, so-called β layers, and bonded with iron group metals, particularly cobalt. It is. Here, with respect to the entire cemented carbide substrate 11, the content ratio of the cubic carbides of the periodic tables 4a, 5a and 6a group metals is 1 to 15% by mass in total, and the inclusion of iron group metals It is desirable that the ratio is 5 to 10% by mass in that the thickness of the binder phase enriched layer 12 can be reliably controlled. A particularly desirable range of the content ratio of the iron group metal is 6 to 9% by mass.

  Moreover, it is desirable to provide the TiCN layer 14 as the hard coating layer 13. In particular, the TiCN layer 14 is preferably made of streaky TiCN particles extending perpendicularly to the surface of the cemented carbide substrate 11.

Further, according to the example shown in FIGS. 1 and 2, the Al ₂ O ₃ layer 15 is formed on the upper surface of the TiCN layer 14. It is desirable that the Al ₂ O ₃ layer 15 has an α-type crystal structure because it is structurally stable and can maintain excellent wear resistance even at high temperatures. Incidentally, Al ₂ a part of Al ₂ O ₃ crystal as a κ-type crystal structure other than α-type crystal structure, i.e. the crystal structure of the Al ₂ O ₃ layer 15 as a mixed crystal of α-type crystal structure and κ-type crystal structure It is also possible to adjust the adhesion of the O ₃ layer 15.

Further, when the Al ₂ O ₃ layer 15 has an α-type crystal structure, TiC _x N _y O _z (x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 <z ≦ 1, particularly z It is effective to form an intermediate layer (not shown) composed of ≧ 0.1) between the TiCN layer 14 and the Al ₂ O ₃ layer 15, thereby stably growing the α-type crystal structure. be able to.

Further, according to FIG. 2, a lowermost TiN layer 17 is formed as a first layer immediately above the surface of the cemented carbide substrate 11. This has the effect of suppressing the diffusion of the components of the cemented carbide substrate 11 into the hard coating layer 13 and the effect of easily controlling the particle shape of the TiCN layer 14. Furthermore, according to the example shown in FIGS. 1 and 2, the uppermost TiN layer 18 is formed on the Al ₂ O ₃ layer 15 as the uppermost layer of the hard coating layer 13. As a result, since the chip 1 exhibits a gold color, it is desirable that when the chip 1 is used, it is easy to determine whether the uppermost TiN layer 18 is worn and used, and the progress of wear can be easily confirmed. The uppermost layer is not limited to the uppermost TiN layer 18, and a DLC (diamond-like carbon) layer or a CrN layer may be formed in order to improve slidability.

Further, according to the present invention, as shown in the enlarged view of the main part in FIG. 1B, the width w ₁ of the land surface 6 following the corner portion 5 in the vicinity of the corner portion 5 is the same as that of the land surface 6 of the other portion. The fact that it is narrower than the width w ₂ can reduce the cutting resistance at the corner portion 5 that mainly functions as a cutting edge, and can increase the binding force of the chip 1 at the land surface 6 other than the corner portion 5. desirable.

Further, as shown in FIG. 2, the breaker groove 7 is such that the wall surface on the side of the central surface 8 forms a first step that forms an angle α with the central surface 8 from the groove bottom, and an angle β (where β <α) 2 It is important that the wall is a two-step rising wall composed of a step because it makes it easy to divide chips. At this time, the concentration D of the binder phase at the groove bottom of the breaker groove 7 is as follows with respect to the binder phase concentration B on the surface of the flank 4 and the binder phase concentration C on the surface of the cemented carbide substrate 2 of the land surface 6. B>D> C enhances chipping resistance at the bottom of the breaker groove 7, and the breaker groove 7 is not easily worn, and even if cutting progresses, the flow of the chip does not change and stable and stable chip disposal is possible. It is important in that .

(Production method)
In order to manufacture the above-described throw-away tip 1, first, an inorganic powder such as a metal carbide, nitride, carbonitride, oxide or the like that can be formed by firing the above-mentioned cemented carbide is added to a metal powder, a carbon powder. Etc. are added and mixed as appropriate, and after forming into a predetermined chip shape by a known molding method such as press molding, casting molding, extrusion molding, cold isostatic pressing, etc., the rate of temperature rise from 1000 ° C. to the firing temperature Is heated at a rate of 2 to 5 ° C./min, and is fired in vacuum or in a non-oxidizing atmosphere at 1400 ° C. to 1500 ° C. for 1 to 1.5 hours. In the present invention, in order to form the above-described binder phase enriched layer 12, it is necessary to add a nitride or carbonitride powder as a raw material, or to fire in a nitrogen atmosphere. As a result, the base body 11 having the binder phase enriched layer 12 having a predetermined thickness in which the binder phase content is larger than the inside of the base body 11 is obtained on the surface of the base body 11.

Next, double-head grinding using a grindstone is performed on both main surfaces so as to remove the binder phase-enriched layer 12 present on the surface of the rake face 4 of the substrate 11. According to the present invention, at this time, the land surface 6 as well as the center surface 8 of the rake face 2 needs to be controlled to be ground by 100 μm or more. As a result, the binder phase content existing on the surface of the center surface 8 and land surface 6 of the cemented carbide substrate 11 and the surface of the flank 4 can be made different so that the required performance can be exhibited. can do. In addition, honing using a brush or an elastic grindstone is applied to the cutting edge of a normal throw-away tip, whereas in the present invention, the land surface 6 is processed by the same double-head grinding as the center surface 8. In addition, compressive residual stress can be applied to the honing portion 10 serving as a cutting edge during double-head grinding, and the chipping resistance of the cutting edge is also improved. Note that the intersecting ridge line portion following the land surface 6 is honed by double-head grinding. The shape of the honing portion 10, that is, the polishing amount is such that the ratio (p ₁ / p ₂ ) of the polishing amount p ₁ on the rake face side and the polishing amount p ₂ on the flank side is 1.0 to 1.5. However, it is desirable in that it can reduce the cutting resistance and suppress chatter.

  At this time, as shown in the enlarged cross-sectional view of the main part of the cemented carbide substrate 11 before polishing in FIG. 4, the sintered body shape before polishing is landed in the vicinity of each corner portion 5 of the central surface 8. It is possible to confirm whether or not the rake face 2 has been double-head ground in parallel by grinding this surface so that the convex portion 20 does not remain after grinding as a shape provided with the convex portion 20 higher than the height of the surface 6. Thus, the height of the entire circumference of the land surface 6 and the height of the central surface 8 can be reliably controlled to the same height. In addition, the convex portion 20 has an effect of preventing the cemented carbide substrate 11 from contacting and reacting with the firing base plate when the cemented carbide substrate 11 is fired.

  In addition, when the TiCN layer 14 described later is formed by the grinding step, the crystal growth state of the TiCN particles on the center surface 8, the land surface 6, and the flank 4 side can be controlled.

Then, the hard coating layer 13 is formed on the surface of the cemented carbide substrate 11 by chemical vapor deposition or physical vapor deposition. For example, the lowermost TiN layer 17 is first formed, then the TiCN layer 14, the Al ₂ O ₃ layer 15, and then the uppermost TiN layer 18 as desired. Furthermore, it is desirable to polish at least the land surface 6 on the surface of the hard coating layer 13 after film formation, if desired, in that the slip of the chips becomes smooth.

  Add tungsten carbide (WC) powder with an average particle size of 1.5 μm, metallic cobalt (Co) powder with an average particle size of 1.2 μm, and raw material powder shown in Table 1 with an average particle size of 2.0 μm in the ratio shown in Table 1. After mixing, it was formed into a throw-away tip shape (CNMG120408) by press molding. Then, a binder removal treatment is performed, and the temperature is increased at a rate of 1000 ° C. or higher at a rate of 3 ° C./minute, and is baked in a vacuum of 0.01 Pa under the conditions shown in Table 1. A sintered body of cemented carbide was prepared.

Then, after grinding this sintered body under the conditions shown in Table 1, by a CVD method, TiN layer: 0.1 μm-TiCN layer: 8 μm-TiCNO layer: 0.1 μm-Al ₂ O ₃ layer : 2 μm-TiN layer: A hard coating layer having a layer structure of 0.5 μm was formed, and honing polishing was performed from the rake face side to produce a throw-away tip having the shape shown in Table 1. The height of the land surface described in Table 1 is the difference in height between the center surface of the rake face and the land surface, that is, the land surface and the holder when the land surface to be measured is arranged on the seating surface side. It is the distance from the mounting surface.

  The obtained throwaway tip was measured with a wavelength dispersive X-ray microanalyzer (EPMA) to measure the concentration distribution of the binder phase in the vicinity of the surface of the cemented carbide substrate on the land surface, breaker groove, and flank surface. The concentration of the binder phase on the surface of the alloy substrate and the thickness of the binder phase-enriched layer were determined and shown in Table 2.

  And after processing with the following conditions once using this throw away tip, the cutting test was similarly performed with the following conditions in the state which has arrange | positioned the used corner part on the seating surface, and the cutting performance was evaluated. The results are shown in Table 2.

(Abrasion test)
Work material: Chromium molybdenum steel (SCM435)
Tool shape: CNMG120408
Cutting speed: 300 m / min Feeding speed: 0.3 mm / rev
Cutting depth: 2mm
Others: Use of water-soluble cutting fluid Evaluation item: Number of machining until the end of the chip life

  From the results shown in Tables 1 and 2, sample Nos. Within the scope of the present invention. In Nos. 1 to 6, chattering was small and defects on the flank surface were small.

  On the other hand, the sample No. 1 whose land surface was designed to be lower than the center surface was used. Even in No. 7, crater wear progressed on the land surface of the used corner arranged on the seating surface, the binding force of the tip was weak, and chatter vibration occurred during cutting. Further, Sample No. in which a binder phase enriched layer is not formed on the surface of the cemented carbide substrate. In 8, it was missing early on the flank. Further, the sample No. 1 was obtained by grinding the entire surface of the cemented carbide substrate. 9 also caused a lot of chipping on the flank.

It is (a) schematic perspective view and (b) principal part enlarged plan view of the throw away tip of this invention. It is XX sectional drawing of the throw away tip of FIG. It is a figure which shows ratio (B / A, C / A) of the density | concentration of the binder phase of the cemented carbide base in the YY part of the throwaway chip | tip of FIG. 2, and ZZ part. It is a principal part expanded sectional view which shows the shape of the sintered compact before double-headed grinding at the time of manufacturing the throw away tip of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Throw away tip 2 Rake face 3 Seating face 4 Relief face 5 Corner part 6 Land surface 7 Breaker groove 8 Central surface 9 Screw hole 10 Honing part 11 Cemented carbide base body 12 Bonded phase enriched layer 13 Hard coating layer 14 TiCN layer 15 Al ₂ O ₃ layer 17 Lowermost layer TiN layer 18 Uppermost layer TiN layer 20 Convex portion

Claims (4)

The two main surfaces are polygonal, and are used as a rake surface and a seating surface, and the side surfaces are used as flank surfaces, and each of the main surfaces and the flank surface A corner portion is used as a cutting edge, a land surface is provided at a peripheral portion of the main surface, and a center surface is provided with a breaker groove inward from the land surface, and the two main surfaces are sequentially used as a seating surface. A throw-away tip that can be used on both sides, and the throw-away tip has an installation surface in which both the central surface and the land surface on the principal surface side when the one principal surface becomes the seating surface. And a hard coating layer is deposited on the surface of the cemented carbide substrate in which tungsten carbide and cubic carbides of the periodic table groups 4a, 5a, and 6a are bonded with an iron group metal binder phase, Above The concentration B of the binder phase on the surface of the cemented carbide substrate at the flank surface is higher than the concentration A of the binder phase inside the hard alloy substrate (B> A), and the inside of the cemented carbide substrate. The ratio (B / A) of the binder phase concentration A to the binder phase concentration B on the surface of the cemented carbide substrate at the flank is the concentration A of the binder phase inside the cemented carbide substrate. wherein the ratio of the concentration C of the binder phase in the surface of the cemented carbide substrate in the land surface (C / a) much larger than the a,
Further, the breaker groove has a wall surface on the center surface side formed of a two-step rising wall surface including a first step forming an angle α with the center surface and a second step forming an angle β (where β <α). The concentration D of the binder phase at the groove bottom in the breaker groove is defined as the concentration B of the binder phase at the surface of the cemented carbide substrate at the flank, and the binder phase at the surface of the cemented carbide substrate at the land surface. A throw-away chip , wherein B>D> C with respect to concentration C.   The ratio (C / A) of the binder phase concentration C on the surface of the cemented carbide substrate at the land surface to the binder phase concentration A inside the cemented carbide substrate is 0.95 to 1.05. The throw-away tip according to claim 1, wherein the throw-away tip is within a range.   In the flank, the region where the binder phase concentration B on the surface of the cemented carbide substrate is higher than the binder phase concentration A inside the cemented carbide substrate is 10 μm to 50 μm from the surface of the cemented carbide substrate. The throw-away tip according to claim 1, wherein the throw-away tip is present in the following thickness.   The throw-away tip according to any one of claims 1 to 3, wherein a width of the land surface in the vicinity of the corner portion is narrower than a width of the land surface in another portion.

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