JP2006266008A - Manufacturing method for excavating tool, and excavating tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an excavating tool, which enables a cutting-edge tip to be firmly fixed to a mounting part of a tool body, even if a cutter, constituted of a diamond-sintered body, is arranged in a part on the side of the outer periphery of the top surface of the cutting-edge tip, and to provide the excavating tool. <P>SOLUTION: In this manufacturing method for the excavating tool, wherein a plurality of cutting-edge tips 11 formed like a circular flat plate are mounted on the mounting part 3 provided on the leading end surface of the tool body, the cutting-edge tip 11 comprises a cutting-edge base body 12 and the cutter 14; the top-surface side of the cutter 14 serves as a cutter body 16 which comprises the diamond-sintered body; the undersurface side thereof serves as a seating part 15 which comprises cemented carbide; and the ratio of the outer periphery of the top surface of the cutting-edge tip 11 occupied by the cutter 14 is set in a range of ≥20% and <50%. The manufacturing method comprises a first jointing step of making the cutting-edge base body 12 and the mounting part 3 brazed to each other, and a second jointing step of making the cutter 14 and the cutting-edge base body 12 brazed to each other, after the first jointing step. The brazing temperature of the first jointing step is set higher than that of the second jointing step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an excavation tool used for excavation of a well or the like and an excavation tool.

As a drilling tool used for drilling oil wells and other wells, a post made of tungsten carbide base cemented carbide (hereinafter referred to as a tungsten carbide based cemented carbide) Carbide posts) are fixed by brazing or shrink fitting in a predetermined arrangement, and each of these carbide posts is equipped with a cutting edge tip having a cutter composed of a diamond sintered body, or a tool It is known that the cutting edge tip is directly attached to a matrix part made of tungsten carbide alloy provided at the tip of the main body.
The above excavation tool is attached to an excavation machine, connected to a rotary drive body such as a motor, rotated around the rotation axis of the tool main body, and fed into the excavation material on the tip side of the excavation tool, whereby the tool Drilling is performed by excavating a rock or the like to be excavated with a cutting edge tip attached to the tip of the main body.

  In general, the cutting edge tip brazed to the tip of the above-mentioned excavation tool is formed in a substantially circular flat plate shape in order to cope with an impact load when excavating, and the outer periphery of the upper surface of the cutting edge tip is entirely PCD. Those composed of a diamond sintered body such as (polycrystalline diamond) are widely used. In an excavation tool in which such a cutting edge tip is brazed to a carbide post or matrix part, only a part of the outer periphery of the upper surface of the cutting edge tip is used for excavation, and there is an unused portion of a sintered diamond body. Resulting in.

  Since the diamond sintered body is manufactured by sintering at an ultrahigh pressure, the cost is very high, and the unused diamond sintered body is often reused. In the above excavation tool, the blade tip once brazed is removed, rotated and brazed again, but the tool body must be heated to a temperature at which the brazing material melts. It took a lot of time and effort to attach and detach. In addition, since the tool body and carbide post that have been used once are reused, if the tool body or carbide post is deformed or damaged during excavation work, the cutting edge tip cannot be brazed accurately and reused. There was a problem that it was impossible.

In view of the above situation, Non-Patent Document 1 aims to reduce the manufacturing cost of a drilling tool equipped with a cutting edge tip composed of a diamond sintered body having a circular flat plate shape using Co metal as a sintering aid. Therefore, for example, a drilling tool is disclosed in which a cutting edge tip having a sector diamond sintered body having a central angle of 120 ° is directly joined to a matrix portion.
In an excavation tool equipped with such a cutting edge tip, the unused portion of the diamond sintered body is eliminated, and it is not necessary to attach and detach the cutting edge tip. it can. Moreover, since the usage-amount of a diamond sintered compact is small, the manufacturing cost of this cutting-edge chip | tip can be reduced.
T. Ohno, et al. “Cost reduction of compressing diamond compact bits through improved durability” Geothermics, vol.31, pp.245-262,2002

By the way, a general diamond sintered body using Co as a sintering aid is sintered by applying a heat treatment held at 1500 ° C. for 30 minutes under a high pressure of 5 to 6 GPa. Used exclusively for drilling oil wells that can offset costs.
When the cutter is composed of the above general diamond sintered body, the diamond sintered body deteriorates at 800 ° C. and its hardness is remarkably lowered, so the brazing temperature must be 800 ° C. or lower. There is.

In general, since a high melting point brazing material has a higher bonding strength than a low melting point brazing material, the bonding strength between the cutting edge tip and the carbide post or the matrix portion increases as the brazing temperature increases. The lower the value, the lower the value, so there was a problem that the cutting edge tip was likely to fall off due to excavation resistance.
Also, when the fan-shaped cutter itself is brazed directly to a carbide post or matrix part, the joining area is small, so it cannot be firmly joined, and the cutter will fall off and be damaged and used as a drilling tool. There was a problem that it was impossible.
From such a situation, when a cutter is formed of a general diamond sintered body, there has been a problem that it is not possible to stably provide an excavation tool equipped with a cutting edge tip with a part of the outer periphery of the upper surface as a cutter.

  The present invention has been made in view of the above-described circumstances, and even a cutting edge chip in which a cutter made of a diamond sintered body is arranged on a part of the outer peripheral side of the upper surface is firmly attached to the attachment portion of the tool body. An object of the present invention is to provide a method of manufacturing a drilling tool that can be fixed and a drilling tool.

In order to achieve the above object, the present invention proposes the following means.
The manufacturing method of an excavation tool according to claim 1 has a cylindrical tool body, and a cutting edge tip formed in a circular flat plate shape is attached to a tip portion of the tool body. A method for manufacturing a drilling tool, wherein a plurality of tools are mounted in such a manner that the surfaces cross each other in the rotational direction, and the workpiece is excavated by the cutting blade tip. A blade base and a cutter supported by a recess formed in a part of the outer peripheral side of the upper surface of the cutting blade base, the upper surface side of the cutter being a cutter body made of a diamond sintered body, and the lower surface side being a cemented carbide And the ratio of the cutter to the outer periphery of the upper surface of the cutting edge tip is 20% or more and less than 50%, and the cutting blade base and the mounting portion are brazed. One joining step and after the first joining step A second joining step in which the cutter and the cutting blade base are brazed, and a brazing temperature in the first joining step is higher than a brazing temperature in the second joining step. It is characterized by.

  In the excavation tool manufacturing method having the above-described configuration, a first joining step in which the cutting blade base and the attachment portion of the tool body are brazed, and a second joining step in which the cutting blade base and the cutter are joined after the first joining step. In the first joining step, brazing can be performed at a temperature exceeding the deterioration temperature of the diamond sintered body. Moreover, since the seat part which consists of a cemented carbide is provided in the lower surface side of the cutter, in the 2nd joining process, joining of a cutting blade base | substrate and a cutter turns into the same cemented carbide.

In the method for manufacturing an excavating tool according to claim 2, the brazing temperature in the first joining step is set to 800 ° C. or more and 1000 ° C. or less, and the brazing temperature in the second joining step is set to 600 ° C. or more and 800 ° C. or less. It is characterized by.
In the excavation tool manufacturing method having the above configuration, the brazing temperature in the first joining step is set to 800 ° C. or higher, so that the cutting blade base and the tool body can be firmly fixed. Moreover, since the brazing temperature in the second joining step is set to 800 ° C. or lower, it is possible to prevent the cutter body from deteriorating even when the cutter body is made of a general diamond sintered body.

  The excavation tool according to claim 3 has a cylindrical tool main body, and a cutting edge tip formed in a circular flat plate shape on a mounting portion provided on a tip surface of the tool main body is a rotation direction of the tool main body. A drilling tool for drilling a work material with the cutting edge tip, the cutting edge tip comprising a cemented carbide cutting blade base having a circular flat plate shape, A cutter supported by a recess formed in a part of the outer peripheral side of the upper surface of the cutting blade base, the upper surface side of the cutter is a cutter body made of a diamond sintered body, and the lower surface side is a seating portion made of cemented carbide. In addition, the ratio of the cutter to the outer periphery of the upper surface of the cutting blade tip is 20% or more and less than 50%, and a first brazing material layer is formed between the cutting blade base and the mounting portion. And between the cutter and the cutting blade base Second brazing material layer is formed, the first brazing material layer, characterized in that it is constituted by a brazing material having a melting point higher than the brazing material constituting the second brazing material layer.

  Since the first brazing material layer is made of a brazing material having a melting point higher than that of the second brazing material layer, the first brazing material layer is formed when forming the second brazing material layer. There is no risk of melting. Moreover, since the seat part which consists of a cemented carbide is provided in the lower surface side of a cutter, joining of a cutting blade base | substrate and a cutter becomes the same cemented carbide.

The excavation tool according to claim 4, wherein the first brazing material layer is composed of a brazing material having a melting point of 750 ° C or higher and 900 ° C or lower, and the second brazing material layer has a melting point of 500 ° C or higher and 700 ° C or lower. It is composed of brazing material.
In the excavation tool having the above-described configuration, the first brazing material layer is composed of a brazing material having a melting point of 750 ° C. or more, and the second brazing material layer is composed of a brazing material having a melting point of 700 ° C. or less. When forming the two brazing filler metal layers, there is no possibility that the first brazing filler metal layer melts.

According to the first aspect of the present invention, since the brazing can be performed at a temperature exceeding the deterioration temperature of the diamond sintered body in the first joining step, the joining strength between the cutting blade base and the attachment portion of the tool body can be increased. In addition, it is possible to prevent the cutting blade base body from dropping off due to the impact force during excavation of the work material.
In addition, a seating part made of cemented carbide is provided on the lower surface side of the cutter, and the cemented carbide between the cutting blade base and the cutter is the same cemented carbide, so the bonding strength between the cutting blade base and the cutter is increased. The cutter can be prevented from falling off from the cutting blade base.

  According to invention of Claim 2, a cutting blade base | substrate and a tool main body can be fixed firmly, and it can prevent reliably that a cutting blade base | substrate falls out from a tool main body. Moreover, since the deterioration of the general diamond sintered body is prevented in the second joining step, even if the cutter body is made of the general diamond sintered body, it is possible to prevent the cutter hardness from being significantly lowered, and as a drilling tool. Can be used.

  According to the third aspect of the present invention, when the second brazing filler metal layer is formed, the first brazing filler metal layer is not likely to melt, so that the cutting blade base and the tool body are firmly joined to each other. Can be provided. Moreover, since the cemented carbide of the cutting blade base and the cutter is the same, the bonding strength between the cutting blade base and the cutter is high, and the cutter can be prevented from falling off the cutting blade base.

  According to the fourth aspect of the present invention, when the second brazing material layer is formed, there is no possibility that the first brazing material layer is melted. Therefore, the first brazing material layer is formed between the cutting blade base and the tool body. The brazing filler metal layer is not melted, and the cutting blade base can be prevented from falling off from the tool body. In addition, since the deterioration of the general diamond sintered body is prevented when forming the second brazing material layer, the hardness of the cutter may be significantly reduced even if the cutter body is composed of the general diamond sintered body. Can be used as a drilling tool.

  Therefore, according to the present invention, a method for manufacturing an excavation tool and excavation that can be firmly fixed to a mounting portion of a tool body even with a cutting edge tip in which a cutter composed of a diamond sintered body is disposed on a part of the outer peripheral side of the upper surface. A tool can be provided.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an excavation tool according to an embodiment of the present invention, and FIG. 2 shows a carbide post and a cutting edge tip provided at the tip of the excavation tool.

  The excavation tool 1 includes, for example, a tool body 2 made of alloy steel or the like defined in JIS / SCH415 and having an outer shape formed in a columnar shape, and a plurality of carbide posts 3 provided in a predetermined arrangement on the tip surface of the tool body 2. And have. In this embodiment, as shown in FIG. 1, four are arranged at equal intervals in the radial direction and four are arranged at equal intervals in the circumferential direction. The carbide post 3 is attached to the tool body 2 by means such as brazing or shrink fitting.

  The cemented carbide post 3 is formed in a columnar shape as shown in FIG. 2 and is made of a tungsten carbide based cemented carbide. The upper surface of the carbide post 3 is provided with an inclined surface that approaches the radial inner side of the carbide post 3 as it goes above the carbide post 3, and this inclined surface is the mounting surface of the cutting edge tip 11. 3A. The cemented carbide post 3 is mounted so that the axis M of the cemented carbide post 3 is parallel to the rotation axis L of the tool body 2 and the mounting surface 3A faces the front side in the rotation direction T of the tool body 2. ing.

3 and 4 show the cutting blade base and the cutting blade tip mounted on the above-mentioned carbide post 3.
The cutting blade tip 11 includes a cutting blade base 12 made of cemented carbide and a cutter 14 supported by the recess 13 of the cutting blade base 12, and the cutting blade tip 11 as a whole is a circular flat plate having a substantially constant thickness. It has a shape.
The cutting blade base 12 is formed in a circular flat plate shape as shown in FIG. 3, and its lower surface 12A is a brazing surface to be brazed with the mounting surface 3A of the carbide post 3, and an upper surface facing the lower surface 12A. 12B is a surface facing the excavation direction.

  A concave portion 13 for supporting the cutter 14 is formed in a part of the outer periphery of the upper surface 12B. The concave portion 13 has the same shape as the outer shape of the cutter 14 and is brought into contact with the work material at the cutting edge tip 11 during excavation work. In the present embodiment, in the present embodiment, it is formed in a sector shape having the center of the cutting blade base 12 as the center in plan view, and the bottom surface of the recess 13 is formed with the lower surface 12A and the upper surface 12B of the cutting blade base 12. It is formed to be parallel. The recess 13 is formed by electric discharge machining of a sintered flat plate cemented carbide material.

  And this recessed part 13 has a pair of support surface 13A, 13B which makes | forms the V shape where a space | interval gradually spreads toward an outer peripheral side, and the impact force at the time of excavation which these support surfaces 13A, 13B apply to the cutter 14 Will receive. Since the recess 13 has the wedge-shaped support surfaces 13A and 13B, the impact force applied to the cutter 14 is widely dispersed in the cutting blade base 12, and the strength against the impact force of the cutting blade tip 11 is increased. become.

Further, the cutting blade base 12 is integrally formed of a general cemented carbide, for example, a tungsten carbide based cemented carbide using Co as a binder. In the present embodiment, the cutting blade base 12 contains 9.5% by mass of Co as a binder, and the remainder is integrally formed of a cemented carbide made of tungsten carbide and inevitable impurities. The above cemented carbide is manufactured as follows. As the raw material powder, 9.5% by mass of Co powder, 0.5% by mass of TiC, and WC powder having an average particle size of 3 μm are used. These raw material powders are wet mixed in a ball mill for 84 hours, dried, pressed into a green compact at a pressure of 100 MPa, and the green compact is sintered at 1400 ° C. for 1 hour in a vacuum of 6 Pa. The above cemented carbide is obtained.
The above cemented carbide has high strength and high toughness, and the cutting blade base 12 serves as an impact absorber that absorbs thermal shock and mechanical shock applied to the cutting blade tip 11 during excavation work.

  The cutter 14 is provided at a portion of the cutting edge tip 11 that comes into contact with the work material during excavation work. In the present embodiment, the cutter 14 is arranged so as to occupy 1/4 of the outer periphery of the upper surface of the cutting edge tip 11. Has been. That is, the cutter 14 is formed in a fan shape when viewed from above as shown in FIG. 3, and an angle formed by two straight lines of the fan shape is 90 °.

The lower surface side of the cutter 14 is a seating portion 15, and the seating portion 15 is made of a cemented carbide made of substantially the same material as the cutting blade base 12.
On the other hand, the upper surface side of the cutter 14 is a cutter main body 16, and the cutter main body 16 is made of a general diamond sintered body using Co as a sintering aid.

  The cutter 14 is manufactured as follows. Diamond powder having an average particle diameter of 25 μm is formed as a raw material powder on a tungsten carbide-based cemented carbide base material using cobalt (Co) as a binder formed in a disk shape. Using a generator, pressurize and heat to the diamond stable region (5.5 GPa, 1500 ° C., hold for 30 minutes). During the ultrahigh pressure / high temperature treatment, Co on the cemented carbide side is infiltrated on the diamond powder side, and finally, a circular flat plate-like sintered body in which diamond and cemented carbide are integrally formed is obtained.

  Thereafter, the sintered body is subjected to roughing by polishing with a diamond grindstone, and further cut into a desired shape by laser processing or wire electric discharge processing, whereby the fan-shaped cutter 14 can be obtained. Here, the cutter 14 includes a seating portion 15 made of a cemented carbide and a cutter body 16 made of a diamond sintered body. In the present embodiment, the cutter 14 is formed in a fan shape, and the angle formed by the two fan-shaped straight lines is 90 °. Therefore, by cutting the circular flat plate-like sintered body into 1/4, Four cutters 14 can be created from the sintered body.

Here, a method of joining the above-mentioned cutting blade tip 11 and the carbide post 3 and a method of joining the cutting blade base 12 and the cutter 14 will be described.
First, as a first joining step, the attachment surface 3A of the carbide post 3 and the brazing surface (lower surface 12A) of the cutting blade base 12 are brazed using a Ti active brazing material. The composition of this Ti active brazing material is Ag 70%, Cu 28%, Ti 2%, and the melting point is 780 ° C to 800 ° C. This Ti active brazing material is used for brazing at 850 ° C. At this time, the mounting surface 3A of the carbide post 3 is inclined so as to face the front side in the rotation direction T of the tool body 2 and to recede inward in the radial direction of the carbide post 3 as it goes upward of the carbide post 3. Therefore, the cutting blade base 12 is arranged so as to face the front side in the rotation direction T of the tool body 2 and to move backward toward the rear side in the rotation direction T toward the tip end side of the excavation tool 1. Further, the recess 13 of the cutting blade base 12 is brazed so as to face the tip side of the excavation tool 1.

  Next, as a second joining step, the concave portion 13 of the cutting blade base 12 and the seating portion 15 of the cutter 14 are brazed using a silver brazing material. The composition of this silver brazing material is Ag 45%, Cu 15%, Zn 16%, Cd 24%, and the melting point is 605 ° C. to 620 ° C. This silver brazing material is used for brazing at 650 ° C. Here, since the recess 13 of the cutting blade base 12 is brazed so as to face the front end side of the excavation tool 1, the cutter body 16 made of a diamond sintered body is arranged so as to face the front end side of the excavation tool 1. Is done.

  By the first joining step, the first brazing filler metal layer 21 made of Ti active brazing material is formed between the attachment surface 3A of the carbide post 3 and the brazing surface (lower surface 12A) of the cutting blade base 12. Further, a second brazing material layer 22 made of a silver brazing material is formed between the recess 13 of the cutting blade base 12 and the seating portion 15 of the cutter 14 by the second joining step. Therefore, the first brazing material layer 21 is composed of a brazing material having a melting point higher than that of the brazing material constituting the second brazing material layer 22.

  The excavation tool 1 having the above-described configuration is attached to an excavation machine, connected to a rotary drive body such as a motor, rotated about the rotation axis L of the tool body 2, and in the excavation material on the tip side of the excavation tool 1. By being fed, the rock body or the like to be excavated is excavated and drilled by the cutting edge tip 11 attached to the carbide post 3 at the tip of the tool body 2. Here, in the excavation tool 1, the cutter main body 16 made of a diamond sintered body is disposed toward the tip of the excavation tool 1, so that the material to be excavated is excavated by the cutter main body 16.

  In the excavation tool 1 described above, the first brazing filler metal layer 21 is composed of a brazing filler metal having a melting point higher than that of the brazing filler metal constituting the second brazing filler metal layer 22, so that the second joining step performs the first brazing filler metal layer 21. When the two brazing filler metal layers 22 are formed, the first brazing filler metal layer 21 is prevented from melting, and the cutting blade base 12 can be prevented from falling off the carbide post 3. Moreover, since brazing can be performed at a high temperature of 800 ° C. or higher in the first joining step, the joining strength between the cutting blade base 12 and the carbide post 3 can be increased, and the cutting blade base 12 is made of the carbide post by the excavation resistance. 3 can be prevented from falling off or being damaged.

  Further, in the second joining step, the concave portion 13 of the cutting blade base 12 and the seating portion 15 of the cutter 14 are composed of cemented carbides of substantially the same material and are joined with the same kind of materials, so that the joining strength can be increased. The cutter 14 can be prevented from falling off the cutting blade base 12 due to the excavation resistance. Further, since the cutter main body 16 made of a diamond sintered body is arranged so as to occupy 1/4 of the outer periphery of the upper surface of the cutting edge tip 11, the amount of expensive diamond sintered body used is small and the cutting edge tip 11 is manufactured. Cost can be reduced.

  Furthermore, in the second joining step, the cutter body 16 is composed of a general diamond sintered body using Co as a sintering aid by brazing at a temperature lower than 800 ° C., which is a deterioration temperature of the general diamond sintered body. Even so, the hardness of the cutter body 16 can be prevented from being significantly reduced by the second joining step, and can be used as the excavation tool 1.

In the present embodiment, the cutter main body 16 has been described as being composed of a general diamond sintered body using cobalt (Co) as a sintering aid. However, the present invention is not limited to this. It may be composed of a diamond sintered body using ceramics such as SiC as a binder, or a diamond sintered body obtained by removing Co used as a sintering aid by chemical treatment. .
Moreover, although the cemented carbide post 3 is provided as an attachment part and the cutting edge chip | tip 11 is mounted | worn with this carbide post 3, it is not limited to this, For example, the matrix part made from a cemented carbide is used as an attachment part. It may be provided and the cutting edge tip 11 is directly joined to the matrix portion.

Moreover, although the cutter 14 has been described with the cutting edge tip 11 occupying ¼ (25%) of the outer periphery of the upper surface of the cutting edge tip 11, the present invention is not limited to this. %). In what occupies 1/3 of the outer periphery of the upper surface, three cutters can be formed from a circular flat plate-like sintered body.
Further, the cutter 14 and the recess 13 of the cutting blade base 12 have been described as having a fan shape, but the cutter main body 16 may be disposed on a part of the outer peripheral side of the upper surface of the cutting blade tip 11. For example, the concave portion 13 may be formed in a crescent shape.

  Further, the excavation tool 1 in which four cutting edge tips 11 are arranged in the circumferential direction and four in the radial direction has been described, but the present invention is not limited to this. For example, the tool body 2 is formed in a cylindrical shape. An excavation tool such as a core bit having a cutting edge tip 11 attached to the tip of the tool body 2 may be used. Further, it is preferable that the arrangement of the cutting edge tips is determined in consideration of the shape and size of the excavating tool, the size of the cutting edge chip, the material of the material to be excavated, and the like.

It is a perspective view of the front-end | tip part of the excavation tool which is embodiment of this invention. FIG. 2 is a side view of a cemented carbide post and a cutting edge tip provided at the tip of the excavation tool in FIG. 1. It is explanatory drawing of the cutting blade base | substrate brazed to the cemented carbide post of FIG. It is explanatory drawing of the cutting blade chip | tip with which the excavation tool of FIG. 1 is mounted | worn.

Explanation of symbols

1 Drilling tool 2 Tool body 3 Carbide post (mounting part)
11 Cutting Blade Tip 12 Cutting Blade Base 13 Recess 14 Cutter 15 Seating Section 16 Cutter Main Body 21 First Brazing Material Layer 22 Second Brazing Material Layer

Claims (4)

A plurality of cutting edge tips formed in a circular flat plate shape are mounted in a posture that crosses the surface in the rotation direction of the tool body on a mounting portion provided on the tip surface of the tool body. , A method for manufacturing an excavation tool for excavating a work material with the cutting edge tip,
The cutting edge tip has a cutting blade base made of cemented carbide having a circular flat plate shape, and a cutter supported by a recess formed in a part of the outer peripheral side of the upper surface of the cutting blade base, and the upper surface of the cutter The side is a cutter body made of a diamond sintered body and the lower surface side is a seating portion made of cemented carbide, and the ratio of the cutter to the outer periphery of the upper surface of the cutting edge tip is 20% or more and less than 50%. And
A first joining step in which the cutting blade base and the attachment portion are brazed, and a second joining step in which the cutter and the cutting blade base are brazed after the first joining step,
The method for manufacturing an excavating tool, wherein a brazing temperature in the first joining step is higher than a brazing temperature in the second joining step.   2. The excavation according to claim 1, wherein the brazing temperature in the first joining step is 800 ° C. or more and 1000 ° C. or less, and the brazing temperature in the second joining step is 600 ° C. or more and 800 ° C. or less. Tool manufacturing method. A plurality of cutting edge tips formed in a circular flat plate shape are mounted in a posture that crosses the surface in the rotation direction of the tool body on a mounting portion provided on the tip surface of the tool body. , An excavation tool for excavating a work material with the cutting edge tip,
The cutting edge tip has a cutting blade base made of cemented carbide having a circular flat plate shape, and a cutter supported by a recess formed in a part of the outer peripheral side of the upper surface of the cutting blade base, and the upper surface of the cutter The side is a cutter body made of a diamond sintered body and the lower surface side is a seating portion made of cemented carbide, and the ratio of the cutter to the outer periphery of the upper surface of the cutting edge tip is 20% or more and less than 50%. And
A first brazing filler metal layer is formed between the cutting blade base and the mounting portion, and a second brazing filler metal layer is formed between the cutter and the cutting blade base,
The excavation tool, wherein the first brazing material layer is made of a brazing material having a melting point higher than that of the brazing material constituting the second brazing material layer.   The first brazing material layer is composed of a brazing material having a melting point of 750 ° C. or more and 900 ° C. or less, and the second brazing material layer is composed of a brazing material having a melting point of 500 ° C. or more and 700 ° C. or less. The excavation tool according to claim 3.

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