JP5472659B2 - Composite structure tool - Google Patents

Description

  The present invention relates to a composite structure tool composed of a sintered body having a composite structure including both a cemented carbide containing WC as a main hard phase and a hard material containing a compound containing Ti in the hard phase. In particular, the present invention relates to a composite structure tool having excellent heat resistance.

  Conventionally, cemented carbides and cermets that use ceramic particles as the hard phase and iron group metals such as Co and Ni as the binder phase have been used as the main material of cutting tools. The hard phase is typically a Ti compound such as WC (tungsten carbide) for cemented carbide and TiCN (titanium carbonitride) for cermet.

  Patent Document 1 discloses a cutting tool made of a composite structure sintered body having a surface layer made of cemented carbide on the surface of a base material made of cermet containing a Ti compound and WC in a hard phase. This cutting tool is excellent in toughness by providing a surface layer made of a cemented carbide excellent in toughness on a hard cermet surface.

International Publication No. 2009/034716

  For the purpose of improving the productivity of cutting objects, cutting conditions that increase the cutting edge temperature, such as increasing the cutting speed, are desired. Therefore, it is desired to develop a cutting tool in which cutting performance such as wear resistance and toughness is not easily lowered even under cutting conditions in which the cutting edge temperature is high, that is, a cutting tool having excellent heat resistance.

  In a general cermet, a Ti compound such as TiCN is used as a central structure (core), and a Ti composite compound containing both Ti and another metal element other than Ti, such as (Ti, W) CN, is surrounded by a surrounding structure ( It has a hard phase called a core rim structure. As a result of investigations by the present inventors, it was found that a Ti composite compound mainly existing as a rim has a significantly lower thermal conductivity than WC, and a lower thermal conductivity than TiC or TiN. It was. The Ti composite compound is considered to be inferior in thermal conductivity because it takes a solid solution structure and scatters phonons that govern thermal conduction. Since many Ti composite compounds of such low thermal conductivity were included, the knowledge that the thermal conductivity of a cermet fell significantly was acquired. On the other hand, WC generally has a high thermal conductivity. Therefore, it is conceivable to use WC as a raw material for cermet to reprecipitate WC in the sintered body. However, even if WC is used as a raw material, this WC decomposes and a Ti composite compound containing W is produced. Depending on the amount of WC added, W may be contained in the Ti composite compound, WC may not be substantially precipitated, and WC may not be present or small in the sintered body. The absence or small amount of WC does not sufficiently improve the thermal conductivity of the cermet.

  In such a cutting tool with a large amount of Ti composite compound and cermet with little or no WC, the heat of the cutting edge that has the highest temperature cannot be dissipated through the inside of the cutting tool, and heat accumulates in the cutting edge and its vicinity. It becomes easy. For this reason, rake face wear (crater wear), thermal cracks, and the like, which are greatly affected by the cutting edge temperature, are likely to increase, and performance may be degraded. Therefore, it is possible to suppress performance degradation even under cutting conditions where the cutting edge temperature tends to be high, such as when performing high-speed cutting (for example, at a cutting speed of 200 m / min or more), or cutting conditions where heating and cooling are repeated. Development of cutting tools with excellent heat resistance is desired. Moreover, since the cutting tool which consists only of cermets is inferior to toughness, the cutting tool which is excellent also in toughness is desired.

  As described in Patent Document 1, the surface of the cutting tool is made of cemented carbide, so that it has excellent toughness, and there are many WCs in the blade edge and its vicinity, improving the heat dissipation of the blade edge and its vicinity. It is done. However, when the base material is composed of cermets with a large amount of Ti composite compound and little or no WC as described above, depending on the cutting conditions as described above, the heat of the blade edge and its vicinity is used for the cermet part. As a result, it cannot be fully escaped, and the performance of the cutting edge may be degraded.

  Then, the objective of this invention is providing the composite structure tool which is excellent in heat resistance.

  The present inventors are excellent in heat resistance for a sintered body having a composite structure in which a hard material containing a Ti-containing compound such as cermet as a hard phase is used as a base and a cemented carbide is provided on this surface. The configuration was examined. Compared to cemented carbide, by improving the structure of the base material with less W content (especially WC content), the thermal conductivity of the base material itself can be increased, and the cutting edge tends to be hot. It is considered that good performance can be obtained even under cutting conditions or cutting conditions in which a cooling / heating cycle is repeated. Therefore, as a result of preparing and examining base materials of various structures by adjusting the raw materials, the heat conductivity of the base material is suppressed by suppressing the existence ratio of the Ti composite compound phase having a very low thermal conductivity to a specific range. It was found that the thermal conductivity of the sintered body of the composite structure can be increased significantly, and that the thermal conductivity of the composite structure can be increased. Moreover, the knowledge that the abundance ratio of the Ti composite compound phase can be suppressed to a specific range by adjusting the composition used for the raw material was obtained. The present invention is based on the above findings.

The composite structure tool of the present invention includes a base material composed of a hard material comprising a compound containing Ti as a hard phase, and a surface layer material formed integrally with the base material and constituting at least a part of the cutting edge. With The surface layer material is composed of a cemented carbide having WC as a main hard phase. The base material contains W in an amount exceeding 0% by mass and 80% or less of the W content in the surface layer material. Moreover, the said base material is provided with the following Ti compound phases and Ti composite compound phases as a hard phase.
Ti compound phase: a phase composed of at least one Ti compound of Ti nitride and Ti carbonitride
Ti composite compound phase: a phase composed of a Ti composite compound containing Ti and one or more metal elements (excluding Ti) selected from Group 4, Group 5 and Group 6 of the periodic table and the composite structure of the present invention The tool takes a cross section of the base material, and satisfies 0.5 ≦ (a / b) where a is the area ratio of the Ti compound phase relative to the cross section and b is the area ratio of the Ti composite compound phase.

  The composite structure tool of the present invention has a surface layer material made of a cemented carbide on a base material made of a hard material having a Ti compound phase, and is a cemented carbide containing a large amount of WC having high toughness and high thermal conductivity. Since at least a part of the cutting edge is made of an alloy, it has high toughness and excellent heat dissipation.

  In the composite structure tool of the present invention, the area ratio of the Ti composite compound phase having a low thermal conductivity in the hard material satisfies a specific range. Specifically, the Ti composite compound phase is not more than twice the area of the Ti compound phase and more preferably equal to or less than the Ti compound phase (preferably less than the Ti compound), so that the thermal conductivity of the substrate itself is also improved. Therefore, the composite structure tool of the present invention is a cutting condition in which the cutting edge becomes high temperature (for example, high-speed cutting with a cutting speed of 200 m / min or more) and a cutting condition in which a cooling cycle is performed (for example, contact with a work material). In the case of using milling, end milling, etc. in which the cooling with the cutting fluid is repeated, the cutting edge and the heat in the vicinity thereof can be satisfactorily released using both the cutting edge itself and the substrate. Therefore, the composite structure tool of the present invention can effectively suppress heat accumulation in the blade edge and the vicinity thereof. As a result, the composite structure tool of the present invention is excellent in heat resistance because the cutting edge and the vicinity thereof are kept at a high temperature for a long time and the cutting performance is not lowered due to repeated cooling and heating cycles. In particular, in the form in which the base material also contains WC, the base material itself can easily increase the thermal conductivity, and the difference from the thermal expansion coefficient of the surface layer material tends to be small, and the deformation of the surface layer material based on the difference in the thermal expansion coefficient And peeling can be suppressed. Therefore, this form is more excellent in heat resistance.

  As one embodiment of the present invention, the base material contains WC, and when the cross section of the base material is taken, the area ratio of the WC with respect to the cross section is 10 area% or more and 60 area% or less. .

  The said form is easy to raise the heat conductivity of a base material by fully containing WC with high heat conductivity. In addition, in the above-described embodiment, by reducing the amount of WC used as a raw material to some extent so that the amount of WC deposited satisfies the above-described specific range, (1) Ti and W are sufficiently present while WC is sufficiently present in the base material. It is possible to suppress excessive generation of a Ti composite compound containing: (2) the amount of WC used as a raw material can be reduced, and the amount of W used as a rare resource can be reduced.

  As one form of this invention, the form whose heat conductivity of the said surface layer material is higher than the heat conductivity of the said base material is mentioned.

  The above-mentioned form has high heat conductivity of the surface layer material constituting at least a part of the blade edge, so that the surface layer material itself is excellent in heat dissipation, can prevent heat from being trapped in the blade edge and its vicinity, and is excellent in heat resistance. .

  As an embodiment of the present invention, an embodiment in which the thermal conductivity of the substrate is 20 W / m · K or more and 70 W / m · K or less can be given.

  The said form has the heat conductivity of a base material high enough, and is excellent in heat resistance. Moreover, the said form can reduce the quantity of WC used for a raw material, and can reduce the usage-amount of W which is a scarce resource by making the thermal conductivity of a base material into the above-mentioned specific range.

  As one form of this invention, the said surface layer material has a form whose average thickness is 0.1 mm or more and 1.5 mm or less.

  The said form is high toughness because surface layer material excellent in toughness exists sufficiently, and can reduce the usage-amount of W which is a scarce resource by making the thickness of surface layer material into a specific range.

As one embodiment of the present invention, the thermal expansion coefficient of the surface material is lower than the thermal expansion coefficient of the base material, and the difference is 0.5 × 10 ⁻⁶ / K or more and 3 × 10 ⁻⁶ / K or less. A form is mentioned.

  The said form can give a compressive stress to a surface layer material based on the difference of thermal expansion amount, and can anticipate the improvement of a fracture resistance by presence of a compressive stress. Moreover, the said form can prevent that a surface layer material peels or a crack generate | occur | produces after sintering by making the difference of a thermal expansion coefficient into a specific range.

  As one form of this invention, the form whose content of Mo in the said base material is 5 mass% or less is mentioned.

When a compound containing Mo, such as Mo ₂ C, is used as the raw material of the base material, for example, the wettability between the Ti compound phase and the binder phase can be improved, the sinterability can be improved, and a dense sintered body can be easily obtained. However, when Mo is contained excessively, a Ti composite compound containing Ti and Mo is likely to be generated, resulting in an increase in the rim, resulting in a decrease in the thermal conductivity of the base material and hence the thermal conductivity of the composite structure tool. The said form can reduce the content rate of Ti composite compound by restrict | limiting content of the compound containing Mo used for the raw material of a base material, and can suppress the heat conductive fall of a base material.

As one aspect of the present invention, when X-ray diffraction is performed on the substrate, a peak of TiN (220) and a peak of TiWC ₂ (220) are detected, and the integrated intensity of the peak of TiN (220) is α, When the integrated intensity of the peak of TiWC ₂ (220) is β, a form satisfying (α / β) ≧ 0.3 can be mentioned.

The said form can be manufactured by using TiN extra for the raw material of a base material, adjusting sintering conditions, and depositing TiN. By using a large amount of TiN as the raw material of the base material, it is easy to reduce the production of Ti composite compounds such as TiWC _2, and the above form has relatively few Ti composite compounds with low thermal conductivity in the base material, and heat resistance Excellent.

  As one form of this invention, the form whose average particle diameter of the said Ti compound phase is 1 micrometer or more is mentioned.

  The said form can raise the thermal conductivity of a base material rather than the case of a fine particle because the Ti compound phase in a base material is large. In addition, since the above form is manufactured by using a somewhat large Ti compound powder as a raw material for the base material, the compound is dissolved and precipitated during sintering as compared with the case of using a fine powder. hard. Therefore, the said form can reduce the presence rate of Ti complex compound in a base material, and can suppress the fall of the heat conductivity of a base material. Also from this point, the said form is excellent in heat resistance.

  As an embodiment of the present invention, there is an embodiment in which the substrate contains WC as the hard phase, and the average particle diameter of the WC is 2 μm or more.

  The above-described form contains WC having a high thermal conductivity, and can improve the thermal conductivity of the base material due to the large WC, and is more excellent in heat resistance. In addition, since the above form is manufactured by using a certain amount of WC powder as a raw material of the base material, compared with the case of using a fine powder, a composite compound containing WC dissolved and W during sintering Is difficult to deposit. Therefore, the said form can reduce the presence rate of Ti compound compound containing Ti and W in a base material, and can suppress the heat conductive fall. Also from this point, the said form is excellent in heat resistance.

  As one form of this invention, the form whose 50% or more is a nitride of Ti (TiN) with respect to the total area of the said Ti compound phase in the cross section of the said base material is mentioned.

  The said form can be manufactured by using TiN more than a fixed amount for the raw material of a base material (it is using more), and precipitating TiN by adjusting sintering conditions. By using a large amount of TiN as a raw material for the base material, it is easy to reduce the production of Ti composite compounds, and the above form can reduce the proportion of Ti composite compounds with low thermal conductivity in the base material, and is heat resistant. Excellent in properties.

  As an embodiment of the present invention, the hard phase in the substrate may include a core rim-structured particle having the Ti compound phase as a central structure and the Ti composite compound phase as a peripheral structure.

  The particles of the core rim structure include a Ti composite compound phase that is excellent in wettability with the binder phase, so that the wettability with the binder phase can be enhanced and the sinterability can be improved. The said form can be set as a precise | minute sintered compact because the particle | grains of a core rim structure exist in a base material.

  As one form of this invention, the said hard phase in the said base material has the form which contains 20% or less of single-piece | unit Ti compound phases in which the outer periphery of the said Ti compound phase is not enclosed by the said Ti compound compound phase.

  The said form can improve thermal conductivity by containing the simple substance Ti compound phase which does not have a rim | limb: Ti composite compound with low heat conductivity in a base material. Moreover, the said form can suppress the fall of the sinterability of a base material because content of a simple substance Ti compound phase is a specific range.

  As one form of this invention, the said hard phase in the said base material has the form which contains 20% or less of single-piece | unit Ti compound compound phases which do not contain the said Ti compound phase inside the said Ti compound compound phase.

  The said form is excellent in the sinterability of a base material by including the single-piece | unit Ti compound compound phase excellent in the wettability with a binder phase, and it is easy to make it a precise | minute sintered compact. Moreover, the said form can suppress the fall of the heat conductivity of the base material by containing a single-piece | unit Ti composite compound phase because content of the single-piece | unit Ti composite compound phase with low heat conductivity is a specific range.

  The composite structure tool of the present invention is excellent in heat resistance.

It is a perspective view which shows typically the form of the composite structure tool of this invention. (A) is a schematic diagram explaining the structure of the base material provided in the composite structure tool of the present invention, and (B) is a schematic diagram explaining the structure of a general cermet.

Hereinafter, embodiments of the present invention will be described in more detail.
[Composite structure tool]
The composite structure tool of the present invention is a cutting tool composed of a hard phase made of ceramics, a binder phase that binds a hard phase mainly composed of an iron group metal, and the balance unavoidable impurities. This tool is composed of a sintered body in which a surface layer material constituting at least a part of the cutting edge and a base material made of a material different from the surface layer material are integrally sintered. Typical tool forms include a cutting edge exchangeable tip for milling and a cutting edge exchangeable tip for turning.

  The integrated state of the surface layer material and the base material is, for example, a two-layer form including a plate-shaped surface material 10 on one surface of a columnar base material 20 as in the composite structure tool 1A shown in FIG. Like the composite structure tool 1B shown in FIG. 1 (B), a multilayer structure form such as a three-layer form having plate-like surface layers 11 and 13 on one surface of the columnar substrate 20 and the other surface facing each other, FIG. (C) Composite structure tool 1C as shown in FIG. 1 (D), the inner form of the surface layer material 15 so as to cover the entire circumference of the columnar base material 20, as shown in FIG. 1 (D) composite structure tool 1D The surface layer material 17 is provided so as to cover a part of the surface of the base material 20 (here, the outer peripheral surface), and the other shape (both end surfaces here) of the base material 20 is exposed from the surface layer material 17 Is mentioned. In FIG. 1, the surface layer material is shown thick for easy understanding. FIG. 1 is an example, and the surface layer material shown in FIG. 1 can be made thinner or thicker.

  As described above, the composite structure tool of the present invention is the same as the cutting tool described in Patent Document 1 in appearance. The feature of the tool of the present invention resides in the structure of the base material. Hereinafter, the composition and structure of the surface layer material and the base material, the thermal characteristics of both, and the method for manufacturing the tool will be described in order.

<Surface material>
Examples of the cemented carbide constituting the surface layer material include WC-based cemented carbide having a known composition and structure as described in Patent Document 1. The surface layer material preferably contains 80% by area or more, and more preferably 85% by area or more when the cross section of the surface layer material is taken. (The method for measuring the area ratio is a method for measuring the content of WC in the substrate described later. The same). In addition, the content of W in the surface layer material is preferably 60% by mass or more, and more preferably 70% by mass or more. This W is preferably present in a substantially WC state. Further, the WC in the surface layer material is preferably as the particle size is larger because the thermal conductivity of the surface layer material is enhanced. Specifically, the average particle diameter of WC in the surface layer material is preferably about 1 μm to 3 μm. The surface layer material preferably contains an iron group metal (preferably Co) in an amount of 3% by mass to 20% by mass, and more preferably 5% by mass to 15% by mass. In addition, in anticipation of the effect of suppressing excessive grain growth of WC, metals such as Cr, Ta, Ti, Nb, Zr, V, (Ta, Nb) C, VC, Cr ₃ C ₂ , NbC, TiCN, etc. These metal compounds can be contained in a total amount of 10% by mass or less.

  If the surface layer material exists so as to constitute at least a part of the cutting edge, the covering region of the surface layer material on the substrate and the shape thereof are not particularly limited. When the surface layer material is plate-shaped as shown in FIG. 1 (A) to FIG. 1 (C), by adjusting the thickness of the surface layer material, the shape of the blade edge can be reduced to the form in which the entire blade edge is composed of the surface layer material. Only a part of the surface layer material can be easily adjusted. In the form shown in FIG. 1 (D), the entire cutting edge is made of a surface layer material made of cemented carbide.

  If the surface material is too thin, the effect of improving toughness due to the provision of cemented carbide will not be sufficiently obtained, and the heat resistance will decrease due to the relatively small number of parts having WC with high thermal conductivity. It becomes easy to invite. On the other hand, if the surface layer material is too thick, the toughness and heat resistance are excellent, but the amount of W that is a scarce resource increases. Accordingly, the average thickness of the surface layer material is preferably 0.1 mm or more and 1.5 mm or less, and if it is 0.2 mm or more and 1 mm or less, the productivity is excellent. The average thickness of the surface layer material is as shown in FIG. 1 (A) to FIG. 1 (C). In the case of a plate shape), the thickness of the surface layer material is measured at 5 points or more on the cross section or the laminated surface of the surface layer material and the base material, and the average of these measurement points is obtained.

<Base material>
The hard material constituting the base material contains W (greater than 0% by mass). This W mainly constitutes a WC or Ti composite compound phase described later. As the W content increases, the WC content tends to increase, and as described later, it is possible to increase the thermal conductivity and reduce the difference in thermal expansion coefficient of the surface layer material. However, since the use amount of W, which is a rare resource, is increased, the W content in the base material is preferably 80% or less, more preferably 70% or less of the W content in the surface layer material in mass ratio. . The content of W in the substrate can be adjusted by the addition amount of a compound containing W such as WC used as a raw material.

  Moreover, the hard material which comprises a base material contains at least 2 phase of Ti compound phase and Ti compound compound phase as a hard phase.

(Ti compound phase)
The Ti compound in the base material is at least one of Ti nitride: TiN and Ti carbonitride: TiCN, and preferably contains substantially no TiC. As a result of investigations by the present inventors, when TiC is used as a raw material, it is easier to form a Ti composite compound such as a composite compound containing Ti and W than when TiN or TiCN is used, and the existence ratio of the Ti composite compound increases. It was easy to do. Therefore, the amount of TiC used as a raw material is reduced as much as possible, preferably not used. As a result, the TiC obtained after sintering is low in TiC (20% by mass or less with the substrate being 100% by mass) or substantially absent. On the other hand, when TiN was used as a raw material, it was found that if TiN is used in a large amount, it is difficult to form the Ti composite compound described above, and rim formation is easily suppressed. Moreover, the knowledge that TiCN was preferable other than TiN was obtained. Therefore, the Ti compound phase actively present as the hard phase of the substrate is at least one of TiN and TiCN.

  In particular, when taking a cross-section of the substrate and extracting the Ti compound phase (TiN, TiCN, TiC) and taking the total area as described later, this total area is taken as 100%, 50% or more, and further 70% The form in which the above is TiN is preferable.

Further, when X-ray diffraction was performed on the substrate, it had a TiN (220) peak and a TiWC ₂ (220) peak, and the integrated intensity of the TiN (220) peak: α is TiWC ₂ (220) It is preferable that the integrated intensity of the peak is larger than β, specifically, (α / β) ≧ 0.3 is satisfied. TiWC ₂ is one of Ti composite compounds described later. As a result of investigating the Ti composite compounds having various compositions, it was found that even if the composition ratio of the Ti composite compounds slightly changed, the TiWC ₂ peak was detected at a close position (substantially the same position). Therefore, TiWC ₂ is adopted as an index of the Ti composite compound. As the peak intensity ratio: α / β is larger, it can be said that TiWC ₂ having a lower thermal conductivity is relatively less, and the thermal conductivity is superior. (α / β) tends to increase when the TiN content is high, and is preferably 0.5 or more, more preferably 1.0 or more.

  In addition, the measurement of the content of the hard phase, the binder phase, and the element in the surface layer material and the substrate described above is performed by, for example, identifying compounds and metal elements by XRD or the like, EDX, EPMA, fluorescent X-ray, IPC-AES This can be done by analyzing the composition using, for example.

(Ti compound phase)
Ti composite compound in the base material is Ti, one or more metal elements selected from Group 4, Group 5 and Group 6 (except Ti), carbon (C), nitrogen (N), And one or more selected from compounds with one or more elements selected from oxygen (O). Typically, at least one selected from carbides, nitrides, oxides, carbonitrides, and carbonitrides containing Ti and the above metal elements can be given. Specifically, (Ti, W, Mo, Ta, Nb) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Ta) (C, N), (Ti, W, Mo, Zr) (C, N), (Ti, W, Mo) (C, N), (Ti, W, Mo) N, TiWC _{2 and the} like. In particular, carbonitride is mentioned.

(Existence form)
The Ti compound phase and the Ti composite compound phase typically exist in a core rim structure in which a Ti composite compound serving as a rim exists so as to surround the periphery of the Ti compound serving as a core. The particles having the core rim structure are provided with a rim having excellent wettability with the binder phase, so that the sinterability can be enhanced and a dense sintered body can be obtained. Moreover, since the core rim structure particles enclose a Ti compound phase that is relatively excellent in thermal conductivity, the thermal conductivity is also excellent. Therefore, when the cross section of the substrate is taken and the total area of the Ti compound phase and Ti composite compound phase existing in the cross section is determined as described later, the total area is 100% and the core rim structure particles are 60% or more. It is preferable to contain. Depending on the manufacturing conditions, the Ti compound phase may exist even as a single phase (single Ti compound phase) exposed without being covered with the Ti composite compound. The Ti composite compound phase may exist even as a single phase that does not include the Ti compound phase (single Ti composite compound phase). Since the simple Ti compound phase is excellent in thermal conductivity but inferior in sinterability, its content is the total area of the Ti compound phase in the above cross section (the area of the Ti compound phase in the core rim structure particles and the simple Ti compound phase). 20% or less, more preferably 10% or less (including 0%), where 100% is the total area with the area of the compound phase. Since the single Ti composite compound phase is excellent in sinterability but inferior in thermal conductivity, its content is the total area of the Ti composite compound phase in the above-mentioned cross section (the area of the Ti composite compound phase in the core rim structure particles) And the area of the elemental Ti composite compound phase) as 100%, it is preferably 20% or less, more preferably 10% or less (including 0%).

(Existence ratio of Ti compound phase and Ti compound phase)
In the present invention, the content of the Ti composite compound phase is somewhat low. Specifically, in the cross section of the substrate, the ratio of the area ratio of the Ti compound phase: a and the area ratio of the Ti composite compound phase: b: a / b satisfies 0.5 or more. A decrease in the thermal conductivity of the substrate can be suppressed by having a small Ti composite compound phase having a low thermal conductivity. The ratio of the above-mentioned area ratios: The larger the value of a / b, the smaller the Ti composite compound phase, and the lowering of the thermal conductivity of the substrate can be suppressed. 1 ≦ (a / b), and further 2 ≦ (a It is preferable to satisfy / b). However, if a / b is too large, there will be many simple Ti compound phases that are inferior in wettability with the binder phase, leading to a decrease in sinterability, so (a / b) ≦ 10 must be satisfied. Is preferred.

  The measurement of the area ratio is performed as follows. After taking a cross-sectional image of the cross-section of the substrate using a technique that allows observation of the structure, such as an electron microscope or an optical microscope, the obtained image is analyzed using a commercially available image analysis software, and the hard phase (mainly the Ti compound phase) , Ti composite compound phase, WC etc. as appropriate) and binder phase. The area of each extracted phase is obtained, and the area ratio is obtained using the obtained area. In particular, when an image obtained by a scanning electron microscope (SEM) is used, it is easy to perform image analysis and excellent workability. The magnification at the time of observation can be appropriately selected depending on the particle size of the hard phase, but it is easy to use 1000 to 5000 times. In the SEM image, typically, the WC is white, the Ti compound is black, and the Ti composite compound and the binder phase are gray. Therefore, it may be difficult to separate the Ti composite compound phase and the binder phase. In this case, the area ratio of the Ti composite phase is calculated by subtracting the compounding ratio of the binder phase from the area ratio including both the Ti composite compound phase and the binder phase. The compounding ratio of the binder phase can be obtained by using the composition analysis such as EDX, EPMA described above. For example, in the acquired image, the area ratio of the black area (Ti compound phase) is a, the area ratio of the gray area (total area of the Ti composite compound phase and the binder phase) is x, the compounding ratio (area ratio) of the binder phase is Assuming c, the area ratio of the Ti composite compound phase: b is obtained as b = xc, and a / b is obtained.

  The area ratio is measured for a region located sufficiently inside in the cross section of the substrate. Specifically, when a part of the base material constitutes the outer surface of the composite structure tool (for example, the form shown in FIG. 1 (A), FIG. 1 (B), FIG. 1 (D)), the measurement region Is a region excluding the surface layer region including the outer surface. The surface layer region is the smaller one of the region from the outermost surface of the substrate up to 1 mm in thickness and the region from the outermost surface of the substrate toward the inside up to 10% of the average thickness of the substrate. And When the entire surface of the base material is covered with the surface layer material (for example, the form shown in FIG. 1C), the measurement region is a region excluding the region near the boundary between the base material and the surface layer material. The region in the vicinity of the boundary is defined as the smaller one of the region up to 1 mm thick from the boundary to the inside and the region up to 10% of the average thickness of the base material from the boundary to the inside. Depending on the raw materials used and the sintering conditions, a modified layer may be formed on the outer surface of the substrate and its vicinity, or on the boundary with the surface layer material and its vicinity. Therefore, a measurement region is selected from a region excluding at least a surface layer region or a region near the boundary in the cross section = an internal region. It is preferable to make the measurement region a location located sufficiently inside such as the center of the substrate and its vicinity in the cross section. The above-mentioned area ratio of the binder phase is equivalent to the volume ratio obtained by determining the volume ratio of the binder phase as follows. The mass ratio of each element is obtained by composition analysis, and the composition and mass ratio of the compound in the substrate are determined (estimated) from the mass ratio of each element, X-ray diffraction, and the like. And the volume ratio of a binder phase is computed using the mass ratio and density of a binder phase, and the mass ratio and density of a compound.

(Other hard phases)
The form containing WC having a high thermal conductivity as the hard phase of the base material can improve the thermal conductivity and reduce the difference in thermal expansion coefficient from the surface layer material made of cemented carbide to reduce the heat after sintering. The deformation due to the difference in shrinkage can be reduced, which is preferable. The higher the WC content, the higher the thermal conductivity of the substrate. However, as described above, the amount of W, which is a rare resource, is increased, and a Ti composite compound is easily generated, which is not preferable. Therefore, the content of WC is preferably 10 area% or more and 60 area% or less, and more preferably 20 area% or more and 50 area% or less when the cross section of the substrate is taken.

(Particle size)
In general, the larger the particle size of the particles constituting the hard phase, the easier it is to increase the thermal conductivity, and the more preferable. In particular, the average particle size of the Ti compound phase (in the case of a core rim structure, the average particle size of the core) is preferably 1 μm or more, and more preferably about 1 μm to 4 μm. The average particle size of the Ti composite compound phase (in the case of the core rim structure, the average particle size of the rim including the core) is preferably about 1.5 μm to 4.5 μm. When WC is contained, the average particle diameter of WC is preferably 2 μm or more, and more preferably about 2 μm to 6 μm.

(Binder phase)
The binder phase in the substrate is preferably iron group metal, with 80% by mass or more of the binder phase being 100% by mass, and particularly preferably Co which hardly causes liquid phase movement during sintering. In addition, it is allowed to contain (solid solution) an element considered to be caused by the raw material. The content of the binder phase is 8% by mass or more and 20% by mass or less, based on 100% by mass of the base material.

(Other contents)
In addition, the base material is 20% by mass in total of metals such as Cr, Ta, Nb, Zr, V, and Mo, and metal compounds such as (Ta, Nb) C, VC, Cr ₃ C ₂ , NbC, and Mo ₂ C. It can contain in the following ranges. The form containing these metals and metal compounds can be expected to have an effect of suppressing grain growth and an effect of improving toughness due to solid solution in the binder phase. However, if a large amount of a compound containing Mo such as Mo ₂ C is used, a Ti composite compound is likely to be generated, and the rim tends to be thick. Therefore, the Mo content in the substrate is preferably 5% by mass or less, and more preferably 3% by mass or less. It does not have to contain Mo or a compound containing Mo.

  The composition, content, and average particle size of the raw materials are adjusted so that the thermal properties such as the composition of the surface layer material and the base material, the content of each phase, the thermal conductivity and the thermal expansion coefficient described later are desired.

<Thermal conductivity>
Since the surface layer material contains more WC having a higher thermal conductivity than the base material, the surface layer material typically has a higher thermal conductivity than the base material. The thermal conductivity of the surface layer material may be 60 W / m · K or more and 140 W / m · K or less, depending on the WC content. Since the surface layer material constituting at least a part of the cutting edge has a high thermal conductivity, the heat of the cutting edge generated during cutting can be easily released to the outside. In the present invention, since the Ti composite compound phase is relatively small, the thermal conductivity of the base material can be increased to some extent. Although depending on the composition, content and particle size of the hard phase, for example, a form in which the thermal conductivity of the substrate satisfies 20 W / m · K or more can be mentioned. The higher the thermal conductivity of the substrate, the easier it is to transfer the heat from the blade edge and its vicinity to the outside through the inside of the substrate, and it is possible to suppress heat accumulation in the blade edge and its vicinity, and it is excellent in heat resistance. m · K or more, more preferably 40 W / m · K or more. The thermal conductivity of the base material has a correlation with the content of WC in the base material, and although the thermal conductivity of the base material increases as the amount of WC increases, the amount of W used for the raw material increases. 70 W / m · K or less is preferable.

<Coefficient of thermal expansion>
Since the surface layer material and the base material are composed of different compositions, a form in which the thermal expansion coefficients of both are different is representative. When the thermal expansion coefficient of the surface layer material is lower than the thermal expansion coefficient of the base material, compressive stress can be applied to the surface layer material having a small amount of thermal shrinkage due to thermal shrinkage after sintering. When the surface layer part which comprises at least one part of a blade edge | tip has a compressive stress, fracture resistance can be improved and the improvement of cutting performance can be anticipated. In order to obtain this effect, the difference in thermal expansion coefficient between the two is preferably 0.5 × 10 ⁻⁶ / K or more. On the other hand, if the difference in thermal expansion coefficient between the two satisfies 3 × 10 ⁻⁶ / K or less, both raw materials are sintered together, and then cracking, peeling, and deformation are caused by the difference in the amount of thermal shrinkage between the two. It is preferable that a sintered body having a composite structure excellent in dimensional accuracy and shape accuracy is obtained.

[Production method]
The composite structure tool of the present invention can be manufactured using the technique described in Patent Document 1. Specifically, the raw material powder for manufacturing the cemented carbide which comprises surface layer material, and the raw material powder for manufacturing the hard material which comprises the above-mentioned base material are each prepared. And after mixing each raw material powder separately, it granulates suitably. It is obtained by supplying granulated powder of each raw material to a mold in order to obtain a desired composite structure and pressing it to produce a press-formed body having a composite structure and sintering the press-formed body.

  In particular, the raw material powder for producing the Ti compound phase provided in the base material is 50% by mass or more, further 70% by mass or more, when the total of compounds containing Ti such as TiN, TiCN, and TiC is 100% by mass, In particular, it is preferable that 75% by mass or more of the powder is made of TiN because it is difficult to form a Ti composite compound having low thermal conductivity. The raw material powder made of a compound containing Ti is preferably a mixed powder of TiN powder and TiCN powder, or TiN powder alone, and TiC that easily forms a Ti composite compound is preferably not used. The more TiN used as a raw material, the easier it is to produce a form in which more TiN exists. Further, a composite compound containing Ti and W (typically carbonitride) is also preferably not used for the raw material powder because it easily forms a Ti composite compound having a low thermal conductivity as described above.

When the substrate contains WC, a relatively large amount of WC powder is used as the raw material (preferably more than 20% by mass in the raw material powder). As shown in the test examples to be described later, when the WC powder used for the raw material is small, WC is not substantially present in the sintered body, and the WC powder of the raw material tends to be used only for the formation of the Ti composite compound phase. . In addition, one or more compounds selected from carbides, nitrides, and carbonitrides of one or more metal elements selected from Group 4, Group 5, and Group 6 of the periodic table (TiN, TiCN, TiC described above) And WC) can be added to the raw material. As described above, the addition amount of Mo compound such as Mo ₂ C is preferably small. The total amount of the raw material powders of the base material is 100% by mass, preferably 5% by mass or less, and may not be used.

  Furthermore, in the process of mixing the raw material powders weighed in a predetermined amount, it was found that the shorter the mixing time of the base material, the easier the generation of the Ti composite compound is suppressed. By shortening the mixing time, the metal compound constituting the raw material powder can be prevented from being excessively pulverized. As a result, the fine powder of the metal compound can be reduced, and the dissolution (solid solution) and reprecipitation of the fine powder can be suppressed in the sintering step, and thus the formation of the Ti composite compound can be easily suppressed. Also, by shortening the mixing time, it becomes easy to maintain the particle size of the raw material powder, the hard phase can be made relatively large (average particle size: about 1 μm to 4.5 μm), and heat dissipation can be improved. When a ball mill or the like is used for mixing, the specific mixing time is, for example, half or less of the mixing time of the raw material powder of the cemented carbide for the surface layer material. More specifically, the mixing time of the raw material powder for the surface layer material: about 20 hours to 30 hours and the mixing time of the raw material powder for the base material: about 2 hours to 15 hours can be mentioned. Or if it is medialess mixing which does not use a grinding | pulverization media, it will be easier to maintain the particle size of raw material powder. Medialess mixing includes, for example, a method in which raw material powder is mixed with an organic solvent such as ethanol or acetone to form a slurry, and the slurry is mixed without pulverizing media while being irradiated with ultrasonic waves. In addition, the predetermined amount of the raw material powder for the surface layer material and the raw material powder for the base material is determined based on the desired shape and thickness, the specific gravity of each raw material powder, and the shrinkage rate of each raw material powder, respectively. calculate.

  The above-mentioned sintering also serves as integral bonding of the surface layer material and the substrate together with the formation of the sintered body. As the sintering conditions, general ones can be used, for example, holding at 1300 ° C. to 1500 ° C. in a vacuum atmosphere for 0.5 hours to 3.0 hours.

  In addition, blade edge processing such as honing, and formation of a coating film by a CVD method or a PVD method can be appropriately performed.

[Test Example 1]
Using raw material powders of various compositions, a composite structure sintered body comprising a surface layer material made of cemented carbide and a base material containing a phase made of a compound containing Ti as a hard phase was prepared, and the structure was observed. Went. Further, cutting performance was examined using this sintered body as a cutting tool.

  In this test, a powder having the composition shown in Table 1 was prepared as a raw material powder. The average particle diameters of the prepared powders are WC: 3 μm, TiCN: 3 μm, TiN: 2 μm, and TiC: 3 μm. Samples No.1-1 to No.1-8, and Samples No.1-100 and No.1-110 were prepared using the powder having the composition shown in Table 1 for the production of the base material. The powder having the composition shown in -200 was used for producing the surface layer material. Sample No. 1-200 is a comparative sample produced using only the powder having the composition shown in Table 1, and is a sintered body made of cemented carbide only.

  The powders of each composition shown in Table 1 were weighed, and the powders of each composition were mixed in ethanol by a ball mill. The mixing time was the time (time) shown in Table 1. After mixing, the powder of each composition is granulated, and the powder for the surface layer material (granulated powder) having an average particle diameter of 100 μm, the powder for the base material (granulated powder), and the powder for the comparative sample (granulated powder) obtain. Table 1 shows the mass ratio (%) of TiN when the total of Ti-containing compounds: TiN, TiCN, and TiC used as the raw material powder is 100 mass%.

The surface layer material powder and the base material powder were weighed out so that the surface layer material and the base material had a desired thickness (here the target thickness of the surface layer material: 0.3 mm), and the mold (model number: SNGN120408 (Thickness: 4.76 mm)) is sequentially supplied and press-molded at a pressure of 1 ton / cm ² to produce a multi-layer press-molded body. Here, in the rectangular parallelepiped made of the base material powder, a laminated press-molded body having a three-layer structure in which a rectangular plate-like layer made of the surface layer material powder is present so as to cover two opposing surfaces. The obtained laminated press-molded body is sintered under a condition of 1430 ° C. × 60 min in a vacuum atmosphere to obtain a sintered body.

  The sintered body obtained as described above (excluding sample No. 1-200) includes a layer composed of a cemented carbide and a layer composed of a hard material having a composition different from that of the cemented carbide. This is a three-layer structure in which a surface layer material made of a cemented carbide of a rectangular plate shape is integrated so as to sandwich two opposing surfaces of a base material made of a cuboidal hard material (see FIG. 1 (B)). When the average thickness of the surface layer material was measured, all the samples were 0.3 mm (total of two layers: 0.6 mm).

About each obtained sintered compact, the composition of the base material was investigated using the SEM-EDX apparatus. As a result, samples No. 1-1 to No. 1-8 have at least one of TiN and TiCN: a Ti compound phase and a composite compound containing Ti and W: a Ti composite compound phase. .1-100 was substantially free of Ti compound phase. In addition, WC was present in the sintered bodies of Samples No. 1-1 to No. 1-5, No. 1-7, and No. 1-8 except Sample No. 1-6. Furthermore, for samples No.1-1 to No.1-8, No.1-100, No.1-110, we investigated the amount of W in the surface material and the amount of W in the base material using the SEM-EDX equipment. The mass ratio (%) of the amount of W in the base material to the amount of W in the surface layer material was determined. The results are shown in Table 3. In addition, samples No. 1-1 to No. 1-8 all have a Mo content of 5% by mass or less in the base material, which is equal to or less than the addition amount of Mo ₂ C used as a raw material. It was.

  The base material was cut | disconnected about each obtained sintered compact, and the cross section of the base material was observed by SEM. As a result, as shown in FIG. 2 (A), each of the base materials 20 of samples No. 1-1 to No. 1-8 has a hard structure, a Ti compound phase 22 as a central structure, and a Ti composite compound phase. There are core rim-structured particles 21 having 23 as a surrounding tissue. Each of these base materials 20 has a large core: Ti compound phase 22 and a thin rim: Ti composite compound phase 23 in the core rim structure particle 21. Samples No. 1-1 to No. 1-8 also have a single Ti compound phase 220 particle consisting of only the Ti compound phase 22 and a single Ti compound compound phase 230 particle consisting of only the Ti compound compound phase 23. To do. On the other hand, the base material (cermet 200) of sample No. 1-100 using TiC without using TiN as a raw material is a core rim structure particle with a thick rim: Ti composite compound phase 23, as shown in FIG. In addition to the presence of 210, there are relatively many simple Ti composite compound phases 230.

  Using the SEM image of the cross section of the base material described above, each of the Ti compound and the Ti composite compound was extracted, and the area ratio of the Ti compound phase in the cross section of the base material was a, and the area ratio of the Ti composite compound phase was b, The ratio: a / b was determined. The results are shown in Table 3. Moreover, the area ratio (%) of TiN with respect to the total area of the Ti compound phase in the cross section of the substrate was determined. The results are also shown in Table 3.

  Furthermore, WC was extracted using the SEM image of the cross section of the base material described above, and the area ratio (%) of WC in the cross section of the base material was determined. The results are shown in Table 3. In addition, using the powder for the comparative sample, molding and sintering in the same manner as described above to produce a sintered body (hard metal) of comparative sample No. 1-200, and the area of WC in the same manner The rate (%) was determined. The results are shown in Table 3. In addition, the area ratio of WC of the surface layer material in samples No. 1-1 to No. 1-8, No. 100, and No. 110 is equivalent to the area ratio of WC in comparative sample No. 1-200.

  Furthermore, using the SEM image of the cross-section of the substrate described above, the area ratio of the single Ti compound phase relative to the total area of the Ti compound phase (%), the area ratio of the single Ti compound compound phase relative to the total area of the Ti compound compound phase ( %). These results are also shown in Table 3.

  Furthermore, the average particle diameter (μm) of the Ti compound phase extracted from the substrate and the average particle diameter (μm) of WC were determined. These results are also shown in Table 3. The average particle size is determined by using the SEM image (5000 times) of the cross-section of the base material described above and an image analyzer: Mac-VIEW (manufactured by Mountec Co., Ltd.), and the horizontal feret for each particle (n ≧ 30). Each of the diameter and the vertical feret diameter was measured, and the average of the measured horizontal feret diameter and the vertical feret diameter was taken.

Further, X-ray diffraction was performed on the cross-section of the above-mentioned substrate, and the presence or absence of a TiN (220) peak and a TiWC ₂ (220) peak was examined. Then, a ratio α / β when the integrated intensity of the peak of TiN (220) is α and the integrated intensity of the peak of TiWC ₂ (220) is β was obtained. The results are also shown in Table 3. In this test, the target of X-ray diffraction was the cross section of the base material, but the outer surface of the base material may be used.

A test piece for measuring thermal characteristics was prepared from each of the obtained sintered bodies. In addition, a test piece was similarly prepared for the cemented carbide of Comparative Sample No. 1-200. And the thermal conductivity (W / m * K) and the thermal expansion coefficient (10 ^<-6 > / K) were measured using the produced test piece. The results are shown in Table 3. Samples No.1-1 to No.1-8, No.1-100, No.1-110 show the thermal properties of the substrate, and Sample No.1-200 shows the thermal properties of the cemented carbide (= The thermal properties of the surface material are shown. Here, the thermal conductivity is calculated by thermal conductivity = specific heat × thermal diffusivity × density. A commercially available measuring instrument can be used for the measurement of specific heat and thermal diffusivity. For example, when using TC-7000 manufactured by ULVAC-RIKO, a sample for measurement (8 mm × 8 mm × 1.5 mm) can be cut out from each sintered body, and specific heat and thermal diffusivity can be measured by a laser flash method. The density is determined by the Archimedes method. In the case of a sintered body having a shape or size that makes it difficult to cut out the measurement sample, for example, the thermal permeability is measured with a commercially available thermal microscope, or the specific heat is measured using differential scanning calorimetry (DSC). Or the thermal conductivity can be calculated using the thermal permeability = (thermal conductivity × density × specific heat) ^1/2 . The coefficient of thermal expansion was measured in the range of 30 ° C to 200 ° C.

  Note that the surface layer (corresponding to the surface layer material here) and the intermediate layer (corresponding to the base material here) covered with the surface layer are divided from the sintered body of the composite structure by cutting, etc. After processing into a shape, physical property values such as thermal characteristics may be evaluated for each. Or, after evaluating the physical property values in the state of the composite structure, the surface layer or the intermediate layer is removed, and the physical property values of the surface layer or the intermediate layer are obtained again from the results of the physical property evaluation of the surface layer or the intermediate layer. May be calculated.

  Each of the obtained sintered bodies was ground (planar polishing), and then subjected to cutting edge processing.In samples No.1-1 to No.1-8, No.1-100, No.1-110 In addition, a cutting tool made of cemented carbide is obtained with a composite structure cutting tool, sample No. 1-200. The obtained cutting tool was subjected to a cutting test (turning) under the conditions shown in Table 2 to examine the cutting performance. The results are shown in Table 3. In this test, crater wear width (mm) was measured as cutting performance.

  As shown in Table 3, it is composed of a sintered body having a composite structure of a surface layer material made of a cemented carbide and a base material made of a hard material having a Ti compound phase and a Ti composite compound phase in the hard phase, and a Ti compound. The ratio of the area ratio of the phase to the area ratio of the Ti composite compound: Samples No.1-1 to No.1-8, which have a base material with a / b of 0.5 or more, are cut so that the cutting edge becomes hot. It can be seen that even when performing (high speed cutting such as a cutting speed of 200 m / min or more) here, crater wear is small, it is difficult to break, and excellent toughness. In addition, it can be seen that the base materials included in samples No. 1-1 to No. 1-8 have a somewhat higher thermal conductivity than the surface layer material (here, equivalent to the characteristics of sample No. 1-200). . Specifically, the thermal conductivity of the base materials included in Sample Nos. 1-1 to 1-8 is 20 W / m · K or more, and the thermal conductivity is higher depending on the composition. Further, it can be seen that the base materials included in Samples No. 1-1 to No. 1-8 have few simple Ti composite compound phases. From these facts, the reason why Samples No. 1-1 to No. 1-8 had excellent cutting performance even under cutting conditions in which the cutting edge as described above becomes high temperature is that the thermal conductivity is Because there are few low Ti compound compounds, it was possible to suppress a decrease in the thermal conductivity of the base material, and the heat of the blade edge generated during cutting was released to the outside of the base material, and it was possible to suppress the heat trapping in the blade edge and its vicinity, it is conceivable that. In addition, all of the samples No. 1-1 to No. 1-8 were provided with a surface layer material having a higher thermal conductivity than the base material, so that it was possible to suppress heat accumulation in the blade edge and the vicinity thereof, it is conceivable that.

In particular, Samples No. 1-1 to No. 1-8 contain W in the base material. When this W is present as WC, the greater the WC content, the greater the thermal conductivity of the base material. It can be seen that crater wear is low. In particular, it can be seen that when the area ratio of WC is 10% or more, a product having a thermal conductivity of 25 W / m · K or more can be obtained. In Samples No. 1-1 to No. 1-8, it can be seen that the larger the average particle size of the Ti compound phase and WC in the base material, the higher the thermal conductivity. Furthermore, it can be seen that the greater the WC content in the base material, the smaller the difference in thermal expansion coefficient between the base material and the surface layer material (sample No. 1-200) made of cemented carbide. Here, the difference satisfies 3 × 10 ⁻⁶ / K or less. In addition, since the base materials of Samples No. 1-1 to No. 1-8 are small in both the single Ti composite compound phase and the single Ti compound phase, many of both phases exist as core rim structure particles, It can be said that the core rim structure particles have a thin Ti composite compound phase.

  Samples No. 1-1 to No. 1-8 having such a heat-resistant substrate do not use TiC or a Ti composite compound, but use TiN or TiCN, preferably TiN. It can be said that it can be produced by using a large amount (specifically, the TiN ratio is 50 mass% or more, and further 70 mass% or more). The more the TiN is used as the raw material, and the shorter the mixing time of the base material powder in the raw material mixing step, the less the time required for the surface layer material powder (hard metal powder) is, The area ratio of TiN in the (base material) increases (for example, the area ratio of TiN is 50% or more), the ratio of the integrated intensity of the peak of TiN (220) in the sintered body (base material): α / β (For example, α / β is 0.3 or more). Further, α / β can be increased even when the amount of Mo or Mo compound added is 5 mass% or less, preferably not used. Furthermore, when WC powder is used as the base material powder, if the amount used is small (here, 20% by mass or less based on the entire raw material), the WC phase hardly exists in the sintered base material. It is considered that W of can exist as a Ti composite compound phase. On the other hand, when the amount of WC powder used is large to some extent, it can be said that the WC phase is precipitated and the thermal conductivity is excellent. Therefore, when WC powder is used as a raw material, it can be said that it is preferable to make it at least an amount capable of precipitating the WC phase (more than 20% by mass of the substrate powder, and more than 30% by mass). Thus, by adjusting the composition of the powder for the base material, changing the structure of the base material and suppressing the formation of the Ti composite compound, the thermal conductivity can be further increased or the thermal expansion coefficient of the surface layer material can be increased. It can be said that the difference can be reduced.

  For samples No. 1-1 to No. 1-8, the average particle size of the Ti composite compound in the substrate was determined in the same manner as the average particle size of the Ti compound phase (for the core rim structure particles, The outer diameter of the rim was measured), Ti composite compound: 1.5 μm to 2.5 μm.

[Test Example 2]
Using the powder for the base material of sample No. 1-3 used in Test Example 1 and the powder for the surface layer material (the composition is Sample No. 1-200 in Table 1), the same as in Test Example 1, a hard material A cutting tool made of a sintered body having a three-layer structure including a surface layer material made of a cemented carbide was prepared on the surface of the base material made of and the cutting performance was examined.

  This test was performed in the same manner as in Test Example 1 except that the thickness of the surface layer material (thickness of one layer) was changed to the thickness (mm) shown in Table 4. Then, the multilayer structure sintered body was processed into a cutting tool in the same manner as in Test Example 1, and the cutting test (turning) was performed under the same cutting conditions as in Test Example 1 (Table 2) to determine the cutting performance. I investigated. The results are shown in Table 4. In this test, crater wear width (mm) and flank wear amount (Vb wear amount (mm)) were measured as cutting performance.

  Moreover, in the produced composite structure cutting tool, the ratio of the two-layer surface material: the occupation ratio was obtained. The results are also shown in Table 4. The occupation ratio was defined as a ratio (%) of the total thickness of the two-layer surface material with respect to the thickness of the cutting tool: 4.76 mm.

  As shown in Table 4, it can be understood that both the crater wear and the flank wear are small when the thickness of the surface layer material made of the cemented carbide is 0.1 mm or more. However, if the surface material is thick and the occupancy rate is high, the amount of W used will increase, and if the surface material is between 1 mm and 2 mm, it will be less affected by the base material and there will be a difference in cutting performance. None (here, the amount of wear is almost constant when the thickness of the surface layer> Vb wear amount). Therefore, considering the amount of W used, it can be said that the thickness of the surface layer material is preferably 1.5 mm or less.

  Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention. For example, the tool shape, the composition and thickness of the surface layer material, the composition of the base material, and the like can be appropriately changed.

  The composite structure tool of the present invention can be suitably used for cutting, particularly for processing under conditions where the cutting edge is hot (for example, high-speed cutting) or conditions where a cooling cycle is performed. The composite structure tool of the present invention can be expected to be used for a drill, an end mill, a milling cutter, a metal saw, a gear cutting tool, a reamer, a tap, and the like in addition to the above-described blade tip replacement type tip.

1A, 1B, 1C, 1D Composite structure tool 10, 11, 13, 15, 17 Surface material 20 Base material
21,210 Corerim structure particles 22 Ti compound phase 23 Ti compound phase
220 Single Ti compound phase 230 Single Ti compound phase 200 Cermet

Claims (14)

A composite structure tool comprising a base material composed of a hard material comprising a compound containing Ti as a hard phase, and a surface layer material formed integrally with the base material and constituting at least a part of the cutting edge. And
The surface layer material is composed of a cemented carbide having WC as a main hard phase,
The substrate is
W is contained in a range of more than 0% by mass and 80% or less of the content of W in the surface layer material,
As a hard phase,
Ti compound phase composed of at least one Ti compound of Ti nitride and Ti carbonitride, and
Containing Ti and a Ti composite compound phase composed of a Ti composite compound containing one or more metal elements selected from Group 4, Group 5 and Group 6 (excluding Ti) of the periodic table,
A composite structure tool satisfying 0.5 ≦ (a / b), where a cross-section of the substrate is taken and the area ratio of the Ti compound phase relative to the cross-section is a and the area ratio of the Ti composite compound phase is b. The base material contains WC,
2. The composite structure tool according to claim 1, wherein when the cross section of the base material is taken, the area ratio of the WC relative to the cross section is 10 area% or more and 60 area% or less.   3. The composite structure tool according to claim 1, wherein a thermal conductivity of the surface layer material is higher than a thermal conductivity of the base material.   The composite structure tool according to any one of claims 1 to 3, wherein the base material has a thermal conductivity of 20 W / m · K or more and 70 W / m · K or less.   The composite structure tool according to any one of claims 1 to 4, wherein the surface layer material has an average thickness of 0.1 mm to 1.5 mm. The thermal expansion coefficient of the surface material is lower than the thermal expansion coefficient of the base material, and the difference is 0.5 × 10 ⁻⁶ / K or more and 3 × 10 ⁻⁶ / K or less. A composite structure tool according to claim 1.   The composite structure tool according to any one of claims 1 to 6, wherein the Mo content in the substrate is 5 mass% or less. When X-ray diffraction was performed on the substrate, TiN (220) peak and TiWC ₂ (220) peak were detected,
The integrated intensity of the TiN (220) peak is α, and the integrated intensity of the TiWC ₂ (220) peak is β, wherein (α / β) ≧ 0.3 is satisfied. Composite structure tool.   The composite structure tool according to any one of claims 1 to 8, wherein an average particle diameter of the Ti compound phase is 1 µm or more. The base material contains WC as the hard phase,
The composite structure tool according to any one of claims 1 to 9, wherein an average particle diameter of the WC is 2 µm or more.   The composite structure tool according to any one of claims 1 to 10, wherein 50% or more of the Ti compound phase in the cross section of the base material is Ti nitride.   The composite structure tool according to any one of claims 1 to 11, wherein the hard phase in the base material includes core rim structure particles having the Ti compound phase as a central structure and the Ti composite compound phase as a peripheral structure. .   13. The composite structure tool according to claim 12, wherein the hard phase in the base material contains 20% or less of a single Ti compound phase in which an outer periphery of the Ti compound phase is not surrounded by the Ti composite compound phase.   14. The composite structure tool according to claim 12, wherein the hard phase in the base material contains 20% or less of a single Ti composite compound phase that does not include the Ti compound phase inside the Ti composite compound phase.

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