JP2012076219A - Tool jointing body, cutting tool using the same and method of manufacturing tool jointing body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength tool jointing body which can process a hard-to-cut material such as heat resistant metal and ductile iron.SOLUTION: A first layer formed of an alumina quality sintered body and a second layer formed of cemented carbide or cermet are integrally joined, and the ratio of a thickness of the first layer to a thickness of this second layer is set to 0.03-0.50. A difference in a thermal expansion coefficient between the first layer and the second layer is set within 1.0 ppm/K. As a result of this, the tool jointing body 10 having higher flexural strength than an SiC whisker including alumina quantity sintered body by itself, can be provided.

Description

  The present invention relates to a bonded assembly for a tool, a cutting tool using the same, and a method for manufacturing the bonded assembly for a tool.

Conventionally, an alumina sintered body has been used for the purpose of use in a cutting tool or the like. This is because the alumina sintered body is excellent in chemical stability and maintains high hardness even at high temperatures, and is therefore suitable as a material for a cutting tool for high-speed machining. Among alumina-based sintered bodies, alumina ceramics containing zirconium oxide (hereinafter simply referred to as ZrO ₂ ) and titanium carbide (hereinafter simply referred to as TiC) are excellent in resistance to iron, and therefore are mainly used for cutting cast iron. It is used for.

  In such a cutting tool, various ideas have been made in order to further increase the strength and reduce the cost of the sintered body. For example, in order to further increase the strength of an alumina sintered body, it has been proposed to include silicon carbide (SiC) whiskers in the alumina sintered body to provide a cutting tool for difficult-to-cut materials such as ductile cast iron. Yes. On the other hand, since SiC whiskers are expensive, a cutting tool is also proposed in which SiC whiskers are included only in the cutting edges, and the base material other than the cutting edges is an alumina sintered body that does not include SiC whiskers (for example, , See Patent Document 1 below).

Japanese Patent Laid-Open No. 11-10409

  However, if the thickness of the cutting edge is reduced in order to reduce the amount of SiC whisker used, the strength of the cutting edge will be insufficient. For this reason, there has been a demand for an alumina sintered body for tools having sufficient strength while reducing the cost.

  The present invention has been made to solve at least a part of the above-described problems, and an object thereof is to realize a high-strength tool material without necessarily using SiC whiskers. For this reason, this invention is realizable as the following forms or an application example.

[Application Example 1]
A first layer formed of an alumina sintered body and a second layer formed of cemented carbide or cermet are integrally joined,
The bonded assembly for a tool, wherein a ratio of the thickness of the first layer to the thickness of the second layer is 0.03 to 0.50.
In this joined body for tools, the strength can be made higher than that using a single SiC whisker-containing alumina sintered body.

[Application Example 2]
The bonded assembly for a tool according to application example 1, wherein a difference in coefficient of thermal expansion between the first layer and the second layer is within 1.0 ppm / K.
In this tool assembly, the difference in thermal expansion coefficient between the first layer and the second layer is 1.0 ppm / K or less, so that the occurrence of cracks due to a temperature rise during use can be suppressed. .

[Application Example 3]
The bonded assembly for a tool according to application example 2, wherein the content of the metal binder phase in the cemented carbide forming the second layer is 25 to 40% by volume.
Thus, by adjusting the content of the metal binder phase in the cemented carbide binder phase, the difference in thermal expansion coefficient between the first and second layers can be made 1.0 ppm / K or less. For example, in the case of a WC-Co cemented carbide, the metal binder phase has a cobalt (Co) content, and in the case of a WC-Co-Ni-Cr cemented carbide, the content of Co-Ni-Cr, In the case of a WC-Ni-Cr cemented carbide, if the Ni-Cr content is 25 to 40% by volume, the difference from the thermal expansion coefficient with the first layer which is an alumina sintered body. Can be made 1.0 ppm / K or less.

[Application Example 4]
Application Example 1 in which the alumina sintered body is any one of ZrO ₂ -containing alumina ceramic, SiC whisker-containing alumina ceramic, SiC particle-containing alumina ceramic, TiC-containing alumina ceramic, and 99.5 mass% or more high-purity alumina ceramic. To a tool assembly according to any one of Application Examples 3 to 4.
In such a joined tool body, the strength can be further increased.

[Application Example 5]
The bonded assembly for a tool according to any one of application examples 1 to 4, wherein the first and second layers are integrally bonded by brazing or hot pressing.
By joining the first and second layers together by brazing or hot pressing, it is possible to easily form a bonded assembly for a tool having sufficient strength that can be used for a tool. Further, by integrally forming by brazing or hot pressing, the alumina layer (the first layer formed of an alumina-based sintered body) can be made thicker than the coated carbide.

[Application Example 6]
The bonded assembly for a tool according to any one of application examples 1 to 5, wherein the first and second layers are integrally bonded by brazing using an Ag-based brazing material.
Such a bonded assembly for a tool can improve fracture resistance.

[Application Example 7]
The bonded assembly for a tool according to any one of Application Example 1 to Application Example 6, wherein a ratio of thermal expansion coefficients of the first layer and the second layer is within 1.11.
In this tool joined body, since the ratio of the thermal expansion coefficients of the first layer and the second layer is within 1.11, generation of cracks due to a temperature rise during use can be suppressed. Here, the “ratio of thermal expansion coefficients” is (larger thermal expansion coefficient) ÷ (smaller thermal expansion coefficient).

[Application Example 8]
A cutting tool comprising the tool assembly according to any one of Application Example 1 to Application Example 7.
With this configuration, it is possible to provide a cutting tool having practical high strength at low cost.

[Application Example 9]
Prepare a surface layer material having a first thickness formed of an alumina sintered body,
Preparing a substrate having a second thickness formed of cemented carbide or cermet;
Adjusting the ratio of the first thickness of the surface layer material to the second thickness of the substrate from 0.03 to 0.50;
A method for manufacturing a bonded body for a tool, wherein the surface layer material is integrally bonded to the base material by brazing or hot pressing.

  According to such a method for manufacturing a bonded assembly for a tool, a bonded assembly for a tool having sufficient strength can be easily manufactured by a simple manufacturing process.

It is explanatory drawing which shows the structure of the joined body 10 for tools as an Example. It is explanatory drawing which shows the raw material used for the joined body for tools. It is explanatory drawing which shows an Example and a comparative example. 3 is a graph showing the fracture behavior of Example 1 and Comparative Example 1. 1 is an explanatory diagram showing an appearance of a cutting tool 100. FIG. It is explanatory drawing which shows the result of a fracture resistance test and an abrasion resistance test. It is explanatory drawing which illustrates the other structural example of the joined body for tools.

[Composition of joined body]
The embodiment of the present invention will be described with reference to examples. FIG. 1 is a structural diagram of a bonded assembly for a tool for carrying out the present invention. This tool assembly 10 is a cutting tip attached to the tip of a cutting tool, and includes a surface layer 20 that is a first layer made of an alumina sintered body, and a base material layer 30 that is a second layer. It is configured. The surface layer 20 is bonded to the base material layer 30 by the bonding layer 40. As the surface layer 20, as will be described later, ZrO ₂ -containing alumina ceramic, SiC whisker-containing alumina ceramic, SiC particle-containing alumina ceramic, TiC-containing alumina ceramic, or the like can be used. In addition to the alumina sintered body, the same effect can be obtained with an alumina sintered body containing a Ti-based carbonitride such as TiN or TiCN. Moreover, as the base material layer 30, a cemented carbide, a cermet, etc. can be used. As the bonding layer 40, a brazing material or the like can be used.

  In the tool bonded body 10 shown in FIG. 1, the thickness T1 of the alumina sintered body as the surface layer 20 is set to 0.10 to 0.50 mm. The thickness of the bonding layer 40 was 10 to 30 μm. Then, the ratio T1 / T2 of the thickness T1 of the surface layer 20 to the thickness T2 of the base material layer 30 was adjusted.

[Production method]
Next, the manufacturing method of the Example and comparative example of the joined body 10 for tools is demonstrated.
<1> Production of the material of the surface layer 20:
The materials of the surface layer 20 used for the tool assembly 10 are shown as materials A, B1, B2, C, G, and H in FIG.
A: ZrO ₂ -containing alumina ceramic (product name HC1)
B1: Alumina ceramic containing SiC whiskers (Product name WA1)
B2: Alumina ceramic containing SiC particles (Product name SE1)
C: TiC particle-containing alumina ceramic (product name HC2)
G: 99.5% by mass high-purity alumina ceramic H: 30% by volume Partially stabilized zirconia-containing alumina ceramic The product names are those of Nippon Special Ceramics.

  These materials A to C were formed into a square shape with a side of 15 mm, and the thickness was set to a predetermined dimension T1 + 0.50 mm by polishing. The thickness T1 of each material will be described later as examples and comparative examples.

<2> Production of base material layer 30:
The base material layer 30 of the bonded assembly 10 for a tool was mainly made of a cemented carbide (as a comparative example, there is one using another material). The materials of the base material layer 30 used in Examples and Comparative Examples are shown as materials D to F in FIG.
D: Cemented carbide 1 (Co content 40% by volume)
E: Cemented carbide 2 (Co content 32% by volume)
F: Cemented carbide 3 (Co content 24% by volume)
The cemented carbides 1 to 3 were manufactured by a normal manufacturing method, but the amount of Co was adjusted at the stage of preparing cemented carbide powder. Specifically, the tungsten carbide (WC) and Co were blended so that the powder had a desired volume ratio of Co in the cemented carbide finally obtained. Then, it was ground for 90 hours by a ball mill using acetone as a solvent and a stainless steel pot and a cemented carbide cobblestone. Thereafter, acetone was removed to obtain cemented carbide powder, and the materials of cemented carbides 1 to 3 were manufactured.

  Each of the materials D to F thus obtained was the same as the materials A to C, and had a square shape with a side of 15 mm, and the thickness was adjusted to T2 + 0.50 mm by polishing. The thickness T2 of each material will be described later as examples and comparative examples.

<3> Thermal expansion coefficient of each material:
The thermal expansion coefficients of the cemented carbides 1 to 3 and alumina ceramic thus obtained are shown in FIG. As shown in the figure, the thermal expansion coefficient of each material is 7.6 ppm / K for material A, 7.4 ppm / K for material B1, 6.8 ppm / K for material B2, and 7.8 ppm / K for material C. D is 7.5 ppm / K, Material E is 7.1 ppm / K, Material F is 6.5 ppm / K, Material G is 7.5 ppm / K, and Material H is 8.4 ppm / K. The reason why the thermal expansion coefficients of the cemented carbides 1 to 3 are different is that the volume percentage of Co is different.

<4> Joining:
The materials A to F obtained by the above method were combined and joined by brazing or hot pressing. Brazing was performed by installing a foil piece of brazing material (Copper-ABA (L) manufactured by WESGO) between the materials and heating to 1080 ° C. In addition to the Cu-based Copper-ABA (L) manufactured by WESGO, an Ag-based brazing material (Tanaka Kikinzoku TKC911 or the like) may be used as the brazing material. When this brazing material is used, the brazing temperature can be lowered to about 890 ° C., and damage to the material of the surface layer 20 and the material of the base material layer 30 can be reduced. In the case of hot pressing, each material was placed in a graphite furnace, and each material was joined at a temperature of 1300 ° C., a pressure of 30 MPa, and a holding time of 1 hour. Moreover, you may join the raw material which mixed the raw material which comprises the surface layer 20 and the base material layer 30 as an intermediate | middle layer. Thereby, the reliability of joining can be made higher. The intermediate layer may be a so-called functionally graded material in which the mixing ratio of both raw materials is changed stepwise.

  After joining the materials, the surface layer 20 is polished to a predetermined dimension T1 and the base material layer 30 is polished to T2 so that the total thickness of the joined body is 3 mm. To 15). The configuration and various characteristics of the example and the comparative example are shown in FIG. In the figure, numbers 1 to 4 and 6 to 13 indicate examples, and numbers 5, 14, and 15 indicate comparative examples.

[Strength test and results]
A test piece was manufactured from the bonded assembly for tool 10 manufactured by the above method, and a bending strength test was performed. The test piece was manufactured by cutting out each of the above-mentioned joined bodies into a predetermined width, polishing to a width of 4 mm, and chamfering. The length of the test piece is 15 mm. This test piece is installed in a bending test apparatus so that the alumina sintered body side becomes a tensile surface. The span was 10 mm and 3-point bending. The numerical value obtained by measuring the bending strength in this state is the value in the “strength” column of FIG.

When the strengths of FIG. 3 are compared, the example is superior to the comparative example in the following points.
(A) The ratio T1 / T2 of the thickness T1 of the surface layer 20 (ZrO ₂ -containing ceramic) of the tool assembly 10 to the thickness T2 of the base material layer 30 (hard metal 1) is 0.03 to 0.00. If it is set to 50, as can be seen from Examples 1 to 4 and 11, it is possible to achieve higher strength than Comparative Example 5 and the like. Moreover, the intensity | strength more than a single SiC whisker containing alumina sintered compact (comparative example 15) is realizable. Therefore, it is possible to obtain the tool bonded body 10 having high strength at low cost. Note that this point varies depending on whether the surface layer 20 and the base material layer 30 are joined by brazing (Examples 1 to 4) or by hot pressing (Example 11). There is no.
(B) About the base material layer 30, the direction made from a cemented carbide (Example 6) may make intensity | strength higher than the case where the base material layer 30 is made into an alumina sintered body (Comparative Examples 14 and 15). As a result, higher strength can be achieved than when a single SiC whisker-containing alumina sintered body is used.
(C) When the difference in thermal expansion coefficient between the surface layer 20 and the base material layer 30 is 1.0 ppm / K or less, or the ratio of thermal expansion coefficients is 1.11 or less (Examples 7, 8, and 9), heat Cracks due to stress are not observed, but when the difference in thermal expansion coefficient is 1.1 ppm / K or the ratio of thermal expansion coefficients is 1.17, cracks due to thermal stress are observed (Example 10). . In Example 10, the result of measuring the strength is 1240 MPa, which is higher than the strength of the SiC whisker-containing alumina alone. However, in Example 10, cracks occurred in the surface layer 20 (external inspection is x determination).

(D) As seen in Examples 3, 12, and 13, even if the material of the surface layer 20 is changed, the difference from the thermal expansion coefficient of the base material layer 30 by the cemented carbide is within 1.0 ppm / K, or If the ratio of the thermal expansion coefficients is within 1.11, a strength higher than that of a single SiC whisker-containing alumina sintered body can be realized. In order to make the difference in thermal expansion coefficient between the surface layer 20 and the base material layer 30 within 1.0 ppm / K, or the ratio of the thermal expansion coefficients within 1.11, according to the thermal expansion coefficient of the surface layer 20, Although the thermal expansion coefficient of the base material layer 30 was adjusted, the thermal expansion coefficient can be adjusted by adjusting the content of the metal binder phase contained in the cemented carbide in the range of 25 to 40% by volume. Specifically, in the case of a WC-Co based cemented carbide, the Co content, in the case of a WC-Co-Ni-Cr based cemented carbide, the Co-Ni-Cr content, and the WC-Ni-Cr content. In the case of a cemented carbide, the content of Ni—Cr may be 25 to 40% by volume.
(E) From the analysis of the examples and comparative examples described above, the tool bonded body 10 of the example has a single SiC whisker-containing alumina-based sintered body even when the surface layer 20 does not include a SiC whisker-containing alumina sintered body. A strength higher than that of the ligature can be realized. For this reason, the joined body 10 for tools suitable for cutting difficult-to-cut materials such as heat-resistant alloys and ductile cast iron can be obtained.

  In the joined body 10 for a tool of this example, the ratio T1 / T2 between the thickness T1 of the surface layer 20 and the thickness T2 of the base material layer 30 is set to 0.03 to 0.50, and the surface layer 20 and the base material layer. The difference in thermal expansion coefficient from 30 is within 1.0 ppm / K, or the ratio of thermal expansion coefficient is 1.1 or less. In this case, it was found that the fracture behavior in the bending test was clearly different from that of the conventional joined body. This point will be described with reference to FIG.

FIG. 4 is a graph showing the result of a bending test in the joined body of Example 3 shown in FIG. 3 and a comparative example (not shown) in which cermet is used for the base material layer 30 and the surface layer 20 is ZrO ₂ -containing alumina ceramic. It is. In Example 3, the difference in thermal expansion coefficient is about 0.1 ppm / K, or the ratio of thermal expansion coefficients is 1.01. In the comparative example, since the thermal expansion coefficient of the cermet of the base material layer 30 is 8.1 ppm / K, the difference in thermal expansion coefficient is about −0.5 ppm / K, or the ratio of the thermal expansion coefficients is 1.07. .

  As can be seen from FIG. 4, the strength test graph J1 of Example 3 showed a strength of 1620 MPa by the bending test, but the strength test graph R1 of the comparative example broke at a stretch between 800 and 1000 MPa. In FIG. 4, an enlarged view around 800 MPa is shown in a circle. As shown in the figure, in Example 3 (J1), a change is observed in the stress-displacement curve. It can be inferred that this is a change that occurs due to the occurrence of cracks in the surface layer 20 with the observation with the naked eye. However, in Example 3, the difference in thermal expansion coefficient between the surface layer 20 and the base material layer 30 is small, and both layers are firmly bonded by brazing, so that cracks generated in the surface layer 20 are bonded to the bonding surface. However, the entire tool assembly 10 has not been destroyed. This is considered to be one of the reasons why the joined body for tool 10 of the example showed higher strength than the single body of the SiC whisker-containing alumina sintered body.

  FIG. 5 shows a cutting tool configured using such a bonded assembly 10 for a tool. FIG. 5 is an external view of a cutting tool using the bonded assembly 10 for a tool which is an embodiment of the present invention. As illustrated, the cutting tool 100 includes the joined body of the above-described embodiment as a cutting insert 120 at the tip of the tool. The cutting insert 120 is a disposable cutting edge having a substantially rectangular parallelepiped shape that is attached to a cutting tool 100 used for cutting heat-resistant alloy. The cutting insert 120 is normally detachably attached to the attachment portion 112 at the tip of the main body 110 called a holder of the cutting tool 100.

  Since this cutting tool 100 includes the joined body (see FIG. 3) of the embodiment that achieves high strength as a cutting insert, it can be used for cutting of heat-resistant metal, ductile cast iron, and the like.

[Fracture resistance test and wear resistance test and their results]
A chipping resistance test and an abrasion resistance test in cutting were performed on the above cutting tool. FIG. 6 shows the characteristics and test results of the cutting tip subjected to these tests. Numbers (No.) 17 to 21, 23 to 25 are examples, and numbers 16, 22, 26 to 29 are comparative examples.

In the surface layer 20, Examples 17 to 21 and 25 and Comparative Examples 16 and 22 are ZrO ₂ -containing alumina ceramics (HC1), Example 23 is 99.5% high-purity alumina ceramic, and Example 25 is 30% by volume partially stable. Zirconia-containing alumina ceramic was adopted. As the base material layer 30, cemented carbide 1 (WC-40 vol% Co) was used for all examples (Examples 17 to 21, 23 to 25 and Comparative Examples 16 and 22) in which the material was not single. All of Comparative Examples 26 to 29 employ a single material.

Comparative Example 26 is a ZrO ₂ -containing alumina ceramic, Comparative Example 27 is a SiC whisker-containing alumina ceramic, Comparative Example 28 is a 99.5 mass% high-purity alumina ceramic, and Comparative Example 29 is a 30 vol% partially stabilized zirconia-containing alumina. Ceramic was adopted.

  Joining was performed by brazing. As for the brazing material, in Examples 17 to 21, 23, and 24 and Comparative Examples 16 and 22, Tanaka precious metallic Ag-based brazing material TKC911 was used, and in Example 25, Cu-based brazing material Cu-ABA (L) manufactured by WESGO was used. Was used. The pattern shown in FIG. 6 was prepared for the dimensional ratio between the surface layer 20 and the base material layer 30 in the cutting tip.

The fracture resistance test was carried out by a dry turning test under the following conditions on the above cutting tip.
Chip shape: SNGN432-TN
Cutting speed: 200 m / min.
Feed amount: 0.4 to 0.6 mm / rev. (0.05mm / rev. Increments, 5 patterns)

As shown in FIG. 6, the cutting tips of Examples 17 to 21 were fed at a feed rate of 0.5 mm / rev. Was not missing. In contrast, the cutting tip of Comparative Example 26 (single ZrO ₂ -containing alumina ceramic (HC1)) has a feed rate of 0.45 mm / rev. Deficient by. Therefore, it can be said that the cutting tips of Examples 17 to 21 have improved fracture resistance than the cutting tip of Comparative Example 26. The difference between the cutting tips of Examples 17 to 21 and the cutting tip of Comparative Example 26 is that Examples 17 to 21 employ cemented carbide 1 as the base material layer 30, whereas Comparative Example 26 has It is a point which does not employ | adopt the base material layer 30 but is single. Therefore, adopting the cemented carbide 1 as the base material layer 30 contributes to improvement in fracture resistance.

  On the other hand, as shown in FIG. 6, the cutting tip of Comparative Example 16 has a feed amount of 0.5 mm / rev. Deficient by. Feed amount 0.5 mm / rev. The difference from the cutting tips of Examples 17 to 21 that were not lost due to the difference was that Comparative Example 16 had a T1 / T2 of 0.021, whereas Examples 17 to 21 had a T1 / T2 of 0.033 or more. It is a point. Therefore, making T1 / T2 0.033 or more contributes to the improvement of fracture resistance. Therefore, it is desirable to set T1 / T2 from 0.033 to 0.46.

  On the other hand, as shown in FIG. 6, the cutting tips of Examples 17 and 21 were fed at a feed rate of 0.55 mm / rev. Deficient by. Further, the cutting tip of Example 18 has a feed amount of 0.6 mm / rev. Deficient by. On the other hand, the cutting tips of Examples 19 and 20 have a feed amount of 0.6 mm / rev. Was not missing. The difference between Examples 19 and 20 and Examples 17, 18, and 21 is that Examples 19 and 20 have T1 / T2 of 0.12 to 0.27, whereas Examples 17, 18, and 21 differ. Is a point where T1 / T2 is 0.055 or less or 0.46. Therefore, T1 / T2 being from 0.12 to 0.27 contributes to improvement in fracture resistance. Therefore, it is desirable to set T1 / T2 from 0.12 to 0.27.

  In addition, as shown in FIG. 6, the improvement in fracture resistance obtained by the above T1 / T2 being 0.27 is an example in which a 99.5% high-purity alumina ceramic is used for the surface layer 20. 23 and Example 24 using 30% by volume partially stabilized zirconia-containing alumina ceramic for the surface layer 20 are the same.

  On the other hand, as shown in FIG. 6, the cutting tip of Example 19 was 0.6 mm / rev. Was not missing. On the other hand, the cutting tip of Example 25 was 0.6 mm / rev. Deficient by. The difference between Example 19 and Example 25 is that Example 19 is an Ag-based brazing material while Example 25 is a Cu-based brazing material. Therefore, the cutting tip that employs the Ag-based brazing material has improved fracture resistance than the cutting tip that employs the Cu-based material.

  The reason why the chipping resistance is improved in this way is presumed that the Ti-rich layer was formed at the bonding interface between the surface layer and the brazing material, and at the bonding interface between the base material layer 30 and the brazing material. The appearance of this Ti-rich layer was confirmed by experiments. On the other hand, when Cu-based brazing material was used, it was confirmed by experiments that a Ti-rich layer was not formed on any joint surface, or a Ti-rich layer was formed on only one of the joint surfaces.

  As described above, when the Ag-based brazing material is used, the Ti-rich layer is formed on both joint surfaces because the Ti component in the brazing material is excessive at the joining temperature of the Ag-based brazing material (920 ° C.). It is assumed that it becomes difficult to diffuse into the hard alloy and the Ti—Co intermetallic compound or the like segregates. On the other hand, when a Cu-based brazing material is used, the reason why a Ti-rich layer is not formed on both joint surfaces is that at the bonding temperature of the Cu-based brazing material (1080 to 1140 ° C.), the Ti in the brazing material It is presumed that the components easily diffuse into the cemented carbide and Ti-Co intermetallic compounds do not segregate.

Next, the abrasion resistance test will be described. The abrasion resistance test was performed by a dry turning test under the following conditions.
Chip shape: SNGN432-TN
Cutting speed: 500 m / min.
Feed amount: 0.3 mm / rev.

  As shown in FIG. 6, the wear amounts of the cutting tips of Examples 17 to 21, 23, and 24 are equivalent to those of Comparative Examples 26, 28, and 29 and are better than Comparative Example 27. That is, if the surface layer is an alumina ceramic, good wear resistance can be obtained without depending on the base material layer 30.

  Therefore, if alumina ceramic is used for the surface layer, the fracture resistance can be improved while maintaining the wear resistance by employing the base material layer 30 of any of the embodiments. Wear amount is 0.08 mm or less, and feed rate is 0.6 mm / rev. The T1 / T2 of Examples 19, 20, 23, and 24 that were not lost by is from 0.12 to 0.27. Therefore, it is desirable to set T1 / T2 from 0.12 to 0.27 in terms of improving the fracture resistance while maintaining the wear resistance.

  Although the present invention has been described with reference to the examples, it is needless to say that the joined body for a tool of the present invention can be realized in various modes. FIG. 7 is an explanatory view showing another configuration example of such a joined body. FIG. 7A shows an example in which the surface layer is composed of not only alumina ceramic but also a thin layer of cermet. In this example, the alumina ceramic and the cermet are integrated by hot pressing, and further joined to the cemented carbide as the base material layer 30 by brazing. FIG. 7B shows an example in which alumina ceramic is used for the flank cover 150. Also in this case, the ratio T1 / T2 between the thickness T1 of the alumina ceramic and the thickness T2 of the base material layer 30 is set in the range of 0.03 to 0.50, and the difference in thermal expansion coefficient between the two is 1.0 ppm / Within K, or the ratio of thermal expansion coefficients may be within 1.11. FIG. 7C shows a configuration example in which a surface layer 200 of alumina ceramic is brazed to the four corners of the tool assembly. The thickness ratio and the difference in coefficient of thermal expansion are the same as in the above-described embodiment. In this case, the amount of alumina ceramic used can be reduced. Of course, it may be divided into two instead of being divided into four. Further, it can be divided into a large number. It should be noted that the alumina ceramic surface layer 200 need not be provided at all the divided corners.

DESCRIPTION OF SYMBOLS 10 ... Assembly for tools 20 ... Surface layer 30 ... Base material layer 40 ... Joining layer 100 ... Cutting tool 110 ... Main-body part 112 ... Mounting part 120 ... Cutting insert 150 ... Flank cover 200 ... Surface layer

Claims (9)

A first layer formed of an alumina sintered body and a second layer formed of cemented carbide or cermet are integrally joined,
The bonded assembly for a tool, wherein a ratio of the thickness of the first layer to the thickness of the second layer is 0.03 to 0.50.   The bonded assembly for a tool according to claim 1, wherein a difference in thermal expansion coefficient between the first layer and the second layer is within 1.0 ppm / K.   The bonded assembly for a tool according to claim 2, wherein the cemented carbide forming the second layer has a metal binder phase content of 25 to 40% by volume. 2. The alumina sintered body is any one of ZrO ₂ -containing alumina ceramic, SiC whisker-containing alumina ceramic, SiC particle-containing alumina ceramic, TiC-containing alumina ceramic, and high purity alumina ceramic of 99.5% by mass or more. The joined body for a tool according to claim 3.   The joined body for a tool according to any one of claims 1 to 4, wherein the first and second layers are joined together by brazing or hot pressing.   The tool joined body according to any one of claims 1 to 5, wherein the first and second layers are joined together by brazing using an Ag-based brazing material.   The bonded assembly for a tool according to any one of claims 1 to 6, wherein a ratio of a thermal expansion coefficient between the first layer and the second layer is within 1.11.   A cutting tool comprising the tool assembly according to any one of claims 1 to 7. Prepare a surface layer material having a first thickness formed of an alumina sintered body,
Preparing a substrate having a second thickness formed of cemented carbide or cermet;
Adjusting the ratio of the first thickness of the surface layer material to the second thickness of the substrate from 0.03 to 0.50;
A method for manufacturing a bonded body for a tool, wherein the surface layer material is integrally bonded to the base material by brazing or hot pressing.

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