JP5534567B2 - Hard materials and cutting tools - Google Patents

Description

  The present invention relates to a hard material containing a compound containing Ti in a hard phase, and a cutting tool. In particular, the present invention relates to a cutting tool having high thermal conductivity and excellent heat resistance, and a hard material capable of constructing a cutting tool excellent in heat resistance.

  Conventionally, a hard material called cermet has been used as a main material of a cutting tool. Cermets typically use Ti-containing compounds such as Ti carbide (titanium carbide: TiC) and Ti carbonitride (titanium carbonitride: TiCN) as the hard phase and bond iron group metals such as Co and Ni. It is a sintered body as a phase. Patent Document 1 discloses a cermet having TiC as a main hard phase, and Patent Document 2 discloses a cermet having TiCN as a main hard phase. Cermet is 1. Compared with cemented carbide with tungsten carbide (WC) as the main hard phase, 1. Can reduce the amount of W, a rare resource, 2. Excellent wear resistance, 3. Cutting of steel It has the advantage that the finished surface is beautiful and light weight.

  In a general cermet, a composite compound containing TiC and TiCN as a central structure (core) and both Ti and another metal element other than Ti (for example, W) is used as a particle constituting the hard phase. It contains particles called a core rim structure that surrounds the surrounding structure (rim) (see FIGS. 1 and 2 of Patent Document 2).

Japanese Patent Laid-Open No. 06-172913 JP 2010-031308

  Conventional cermets have low thermal conductivity and are desired to improve heat resistance.

  As a result of investigation by the inventors, Ti composite compounds containing Ti and periodic table Group 4, Group 5 and Group 6 metal elements (excluding Ti), such as carbonitrides of Ti and W, are WC. It was found that the thermal conductivity is significantly lower than that of TiC and TiN, and that the thermal conductivity is lower than that of TiC and TiN. The Ti composite compound that mainly constitutes the rim is considered to be inferior in thermal conductivity because it takes a solid solution structure and scatters phonons that govern thermal conduction. And the knowledge that the heat conductivity of a cermet falls significantly by including many such low thermal conductivity complex compounds was acquired. In particular, when TiC powder is used as a raw material in producing a cermet containing TiC as a main hard phase, a Ti composite compound is easily generated, and the core rim structure particles tend to be thick (large). Further, even in a cermet containing TiCN as a main hard phase, if the Ti composite compound is large, the thermal conductivity is lowered.

  In a cutting tool made of cermet with a large amount of Ti composite compound, the heat of the cutting edge at the highest temperature cannot be radiated through the inside of the cutting tool, and the heat tends to be trapped in the cutting edge and the vicinity thereof. Therefore, for example, rake face wear (crater wear) and thermal cracks that are greatly affected by the temperature of the blade edge, and cracks due to these are likely to increase, resulting in performance degradation. Therefore, even in cutting conditions where the cutting edge temperature tends to be high, such as when performing high-speed cutting (for example, cutting speed of 200 m / min or more), and cutting conditions where heating and cooling are repeated, wear resistance and chipping resistance It is desired to develop a cutting tool that can suppress deterioration in performance such as heat resistance and is excellent in heat resistance. Moreover, development of the material which can construct | assemble the cutting tool which is excellent in such heat resistance is desired.

  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. In addition to the large amount of Ti composite compound and the absence or small amount of WC, the thermal conductivity of the cermet is lowered.

  Then, one of the objectives of this invention is providing the hard material which can construct | assemble the cutting tool excellent in heat resistance. Another object of the present invention is to provide a cutting tool having excellent heat resistance.

  The inventors of the present invention have studied a configuration excellent in heat resistance for a hard material containing a compound containing Ti as a hard phase, such as cermet. As a result of preparing and studying hard materials with various structures by adjusting the raw materials, the heat conductivity of hard materials is suppressed by keeping the ratio of Ti composite compound phases with very low thermal conductivity within a specific range. We obtained knowledge that the rate could be greatly 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 hard material of the present invention includes a compound containing Ti as a hard phase, and includes the following Ti compound phase and Ti composite compound phase as the 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. Where the area ratio of the Ti compound phase relative to this cross section is a, and the area ratio of the Ti composite compound phase is b, 0.5 ≦ (a / b) is satisfied.

  In the hard material of the present invention, the area ratio of the Ti composite compound phase having a low thermal conductivity is not more than twice the area ratio of the Ti compound phase, and more or less equivalent (preferably less than the Ti compound). Increases sex. Therefore, the cutting tool composed of the hard material of the present invention has 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, the target is cut). Even when milling, end milling, or the like in which contact with the cutting material and cooling with the cutting fluid are repeated, the heat at the cutting edge and its vicinity can be released well. Therefore, this cutting tool can effectively suppress heat accumulation in the cutting edge and the vicinity thereof. As described above, the hard material of the present invention constructs a cutting tool having excellent heat resistance, in which the cutting edge and the vicinity thereof are kept at a high temperature for a long time and the cutting performance is not easily deteriorated due to repeated cooling and heating cycles. Can do. In particular, in the form containing WC, it is easier to increase the thermal conductivity.

  As one form of the present invention, there is a form in which, as the hard phase, containing WC and taking a cross section of the hard material, 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 thermal conductivity by fully containing WC with high thermal conductivity. In addition, the above-described embodiment reduces the amount of WC used as a raw material to a certain extent so that the amount of WC deposited satisfies the above-mentioned specific range. (1) Ti containing Ti and W even though WC is sufficiently present It is possible to suppress excessive formation of the composite compound, (2) to reduce the amount of WC used as a raw material, and to reduce the amount of W used as a rare resource.

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

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

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

When a Mo-containing compound such as Mo ₂ C is used as the raw 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 excessively contained, a Ti composite compound containing Ti and Mo is likely to be generated, which causes an increase in the rim and a decrease in thermal conductivity. The said form can reduce the content rate of Ti composite compound by restrict | limiting content of the compound containing Mo used for a raw material, and can suppress the heat conductive fall.

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

The said form can be manufactured by using TiN abundantly as a raw material, adjusting sintering conditions, and depositing TiN. By using a large amount of TiN as a raw material, the production of Ti composite compounds such as TiWC ₂ can be easily reduced, and the above form has relatively few Ti composite compounds with low thermal conductivity and is excellent in heat resistance.

  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.

  In the above embodiment, the Ti compound phase is large, so that the thermal conductivity can be improved as compared with the case of fine particles. Moreover, since the said form is manufactured by using Ti compound powder large to some extent as a raw material, compared with the case where fine powder is used, melt | dissolution and precipitation of a compound are hard to be performed at the time of sintering. Therefore, the said form can reduce the presence rate of Ti complex compound, and can suppress the heat conductive fall. Also from this point, the said form is excellent in heat resistance.

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

  In addition to containing WC having a high thermal conductivity, the above form can improve the thermal conductivity 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, compared with the case of using a fine powder, dissolution of WC and precipitation of a composite compound containing W during sintering are performed. It is hard to be done. Therefore, the said form can reduce the presence rate of Ti composite compound containing Ti and W, 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 said cross section is mentioned.

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

  As an embodiment of the present invention, the hard phase may include a core rim structure 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.

  As an aspect of the present invention, the hard phase includes a form containing 20% or less of a single Ti compound phase in which the outer periphery of the Ti compound phase is not surrounded by the Ti composite compound phase.

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

  As one form of this invention, the said hard phase includes the form which contains 20% or less of the simple substance Ti compound compound phase which does not contain the said Ti compound phase inside the said Ti compound compound phase.

  The said form is excellent in sinterability 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, since the content of the single Ti composite compound phase having a low thermal conductivity is in a specific range, the above form can suppress a decrease in thermal conductivity due to the inclusion of the single Ti composite compound phase.

  The cutting tool of this invention is comprised from the hard material of the above-mentioned this invention.

  Since the cutting tool of the present invention is composed of the hard material of the present invention having excellent heat resistance, the cutting tool is excellent in heat resistance and can have a good sharpness over a long period of time.

  The hard material of the present invention can construct a cutting tool having excellent heat resistance. The cutting tool of the present invention is excellent in heat resistance.

(A) is a schematic diagram illustrating the structure of the hard material of the present invention, and (B) is a schematic diagram illustrating the structure of a general cermet.

Hereinafter, embodiments of the present invention will be described in more detail.
[Hard material]
The hard material of the present invention is a sintered body that includes a hard phase made of ceramics and a binder phase that combines an iron group metal as a main component and bonds the hard phase, and the balance is composed of inevitable impurities. The hard phase includes at least two phases of a Ti compound phase and a Ti composite compound phase.

<Hard phase>
(Ti compound phase)
The Ti compound 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 sintered body is low in TiC (20% by mass or less with the sintered body 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 is at least one of TiN and TiCN.

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

Further, when X-ray diffraction was performed, it had a TiN (220) peak and a TiWC ₂ (220) peak, and the integrated intensity of the TiN (220) peak: α was the peak of TiWC ₂ (220). It is preferable that the integrated intensity 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.

  For the measurement of hard phase, binder phase, and element content, for example, identify compounds and metal elements using XRD and analyze the composition using EDX, EPMA, X-ray fluorescence, IPC-AES, etc. You can do it.

(Ti compound phase)
The Ti composite compound is composed of Ti, one or more metal elements selected from Group 4, Group 5 and Group 6 (except Ti), carbon (C), nitrogen (N), and oxygen (O 1) or more selected from compounds with one or more elements selected from 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 taking the cross section of the hard material and calculating the total area of the Ti compound phase and Ti composite compound phase existing in this cross section 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 hard material, 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. Since there are few Ti composite compound phases with low heat conductivity, the fall of heat conductivity can be suppressed. Ratio of the above-mentioned area ratio: The larger the value of a / b, the smaller the Ti composite compound phase, the lower the thermal conductivity can be suppressed, 1 ≦ (a / b), and further 2 ≦ (a / b) It is preferable to satisfy. 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 hard material using a technique that enables 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) is obtained. , 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 measurement of the area ratio is performed on the internal region excluding the surface layer region in the cross section of the hard material. The surface layer region is the smaller of the region from the outermost surface of the hard material up to a thickness of 1 mm and the region from the outermost surface of the hard material to the inside up to 10% of the average thickness of the hard material. And Depending on the raw materials used and sintering conditions, a modified layer may be formed on the surface of the hard material and in the vicinity thereof. Therefore, the measurement region is selected from the region excluding at least the surface layer region in the cross section = the internal region. It is preferable that a location located sufficiently inside such as the center of the hard material in the cross section and the vicinity thereof is set as the measurement region. 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 hard material are determined (estimated) from the mass ratio of each element and X-ray diffraction. 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)
A form containing WC having a high thermal conductivity as the hard phase is preferable because the thermal conductivity is enhanced. As the WC content increases, the thermal conductivity can be increased. However, as described above, the amount of W, which is a rare resource, is increased, and a Ti composite compound is easily generated. Accordingly, 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 hard material 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 is preferably 80% by mass or more of an iron group metal with the binder phase being 100% by mass, and particularly Co, which is less liable to cause liquid phase transfer 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 to 20% by mass with 100% by mass of the hard material.

<Other contents>
In addition, hard materials include 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 in total 20% by mass 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. Accordingly, the Mo content in the hard material 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 composition, the content of each phase, and the thermal conductivity described later are desired.

<Thermal conductivity>
In the present invention, the thermal conductivity is high because the Ti composite compound phase is relatively small. Although depending on the composition, content and particle size of the hard phase, for example, a form satisfying a thermal conductivity of 20 W / m · K or more can be mentioned. The higher the thermal conductivity, the easier it is to transfer the heat from the cutting edge and its vicinity to the outside, and it is possible to prevent the heat from being trapped in the cutting edge and its vicinity, and it is possible to construct a cutting tool with excellent heat resistance. Accordingly, the thermal conductivity is preferably 30 W / m · K or more, more preferably 40 W / m · K or more. However, the thermal conductivity has a correlation with the content of WC in the hard material, and the higher the amount of WC, the higher the thermal conductivity, but the amount of W used as a raw material increases, so 70 W / m K or less is preferable.

<Application>
The hard material of the present invention can be suitably used for various cutting tool materials as described later.

[Cutting tools]
The cutting tool of this invention is comprised from the hard material of this invention which provides the above-mentioned specific hard phase. This cutting tool can have various shapes and sizes. Representatively, there are a cutting edge exchangeable tip for milling, a cutting edge exchangeable tip for turning, a drill, a milling cutter, an end mill, a metal saw, a gear cutting tool, a reamer, a tap, and the like.

[Production method]
The hard material of the present invention can be produced by the same production method as that for general cermets. Specifically, after preparing and mixing raw material powders, granulation is performed as appropriate, and the granulated powder is supplied to a mold and pressed to produce a press-molded body having a desired shape. Obtained by sintering.

  When the total amount of Ti-containing compounds such as TiN, TiCN, and TiC is 100% by mass, the raw material powder has a thermal conductivity of 50% by mass or more, more than 70% by mass, especially 75% by mass or more. It is preferable that a Ti composite compound having a low rate is difficult to form. 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, when a composite compound containing Ti and W (typically carbonitride) is used as the raw material powder, the Ti composite compound is easily formed and the thermal conductivity of the sintered body is likely to be lowered. Therefore, it is preferable not to use a composite compound containing Ti and W as the raw material powder.

When a hard material containing WC is used, a relatively large amount of WC powder is used as a 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, and the total amount of the raw material powder 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, 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 about 2 to 15 hours. 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.

  Examples of the sintering condition include holding at 1300 ° C. to 1500 ° C. for 0.5 hours to 3.0 hours in a vacuum atmosphere.

  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, sintered bodies containing phases composed of compounds containing Ti as hard phases were prepared, and the structure was observed. 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. Sample No. 1-200 is a comparative sample, which is a sintered body made of only a WC-Co based cemented carbide. The average particle diameters of the prepared powders are WC: 3 μm, TiCN: 3 μm, TiN: 2 μm, and TiC: 3 μm. 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%.

Powders having the respective compositions shown in Table 1 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 to obtain a granulated powder having an average particle size of 100 μm. The granulated powder is weighed, each powder is supplied to a mold (model number: SNGN120408), and press-molded at a pressure of 1 ton / cm ² to produce a press-molded body. The obtained press-molded body is sintered under a vacuum atmosphere at 1430 ° C. for 60 minutes to obtain a sintered body.

About each obtained sintered compact, the composition 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. .1-110 was substantially free of Ti compound phase. In addition, WC was present in samples No. 1-1 to No. 1-5, No. 1-7, and No. 1-8 except for sample No. 1-6. Furthermore, in all of Samples No. 1-1 to No. 1-8, the Mo content was 5% by mass or less, which was equal to or less than the addition amount of Mo ₂ C used as a raw material.

  Each obtained sintered body was cut, and the cross section of the sintered body was observed by SEM. As a result, all of the sintered bodies (hard materials 1) of Samples No. 1-1 to No. 1-8, as shown in FIG. 1 (A), have a Ti compound phase 12 as a central structure as a hard phase. In addition, there are core rim structured particles 10 having the Ti composite compound phase 13 as a surrounding structure. Each of these sintered bodies has a large core: Ti compound phase 12 and a thin rim: Ti compound compound phase 13 in the core rim structure particle 10. Samples No.1-1 to No.1-8 have some particles of the single Ti compound phase 20 consisting of only the Ti compound phase 12 and some particles of the single Ti compound compound phase 30 consisting of only the Ti composite compound phase 13. To do. On the other hand, the sintered bodies (hard material 100) of samples No. 1-100 and No. 1-110 using TiC without using TiN as a raw material are rim: Ti composite compound as shown in FIG. In addition to the presence of the core rim structure particles 110 having a thick phase 13, there are a relatively large amount of the simple Ti composite compound phase 30.

  Using the SEM image of the cross section of the sintered body described above, each of the Ti compound and the Ti composite compound was extracted, and the area ratio of the Ti compound phase in each cross section was a, and the area ratio of the Ti composite compound phase was b, 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 a cross section was calculated | required. The results are also shown in Table 3.

  Furthermore, WC was extracted using the SEM image of the cross section of the sintered body, and the area ratio (%) of WC in the cross section was obtained. The results are shown in Table 3.

  Furthermore, using the SEM image of the cross section of the sintered body 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 phase relative to the total area of the Ti compound phase (%) Was calculated. These results are also shown in Table 3.

  Further, the average particle size (μm) of the extracted Ti compound phase and the average particle size (μm) of WC were determined. These results are also shown in Table 3. The average particle diameter is determined by using the SEM image (5000 times) of the cross section of the sintered body described above and an image analyzer: Mac-VIEW (manufactured by Mountec Co., Ltd.) for each particle (n ≧ 30) in the horizontal direction. Each of the feret 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 sintered body, and the presence or absence of the TiN (220) peak and 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 object of X-ray diffraction was the cross section of the sintered body, but the surface of the sintered body may be used.

Test pieces for measuring thermal properties were prepared from the obtained sintered bodies, and the thermal conductivity (W / m · K) was examined. The results are shown in Table 3. 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 .

  Each of the obtained sintered bodies is subjected to grinding processing (planar polishing), and then subjected to blade edge processing to obtain a cutting tool. 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, the presence or absence of defects after a 10-minute cutting test was confirmed visually and using a microscope as cutting performance.

  As shown in Table 3, the ratio between the area ratio of the Ti compound phase and the area ratio of the Ti composite compound: Samples No. 1-1 to No. 1-8 composed of a hard material having a / b of 0.5 or more This cutting tool is excellent in wear resistance, hard to chip, and tough even when performing cutting that causes the cutting edge to become hot (here, cutting speed is 200 m / min or more). I understand that. It can also be seen that Samples No. 1-1 to No. 1-8 have a lower thermal conductivity than Sample No. 1-200, which is a WC—Co based cemented carbide, but are somewhat higher. Specifically, samples No. 1-1 to No. 1-8 have a thermal conductivity of 20 W / m · K or more, and the thermal conductivity is higher depending on the composition. Further, it can be seen that Samples No. 1-1 to No. 1-8 also have a small amount of the single Ti composite compound phase. From these facts, the reason why the cutting tools of Sample No. 1-1 to No. 1-8 had excellent cutting performance even under the cutting conditions in which the cutting edge becomes high temperature as described above is that Because there are few Ti composite compounds with low conductivity, it is possible to suppress the decrease in the thermal conductivity of hard materials, escape the heat of the cutting edge generated at the time of cutting to the outside, it is possible to suppress the accumulation of heat in the cutting edge and its vicinity, Conceivable.

  In particular, when WC is contained in Samples No. 1-1 to No. 1-8, the greater the WC content, the higher the thermal conductivity of the hard material, and the area ratio is 10% or more. It can be seen that those with m · K or more can also be obtained. In Samples No. 1-1 to No. 1-8, it can be seen that the larger the average particle size of Ti compound phase and WC, the higher the thermal conductivity. Furthermore, since Samples No. 1-1 to No. 1-8 have both a simple Ti composite compound phase and a simple Ti compound phase, most of both phases exist as core rim structured particles. It can be said that the Ti composite compound phase is thin.

  Samples No. 1-1 to No. 1-8 having excellent heat resistance do not use TiC or Ti composite compounds as raw materials but use TiN or TiCN, and preferably use a lot of TiN (specifically In particular, it can be said that the TiN ratio can be 50% by mass or more, and further 70% by mass or more). The more TiN is used as the raw material, and the shorter the mixing time of the raw material, the larger the area ratio of TiN in the sintered body (for example, the area ratio of TiN is 50% or more), TiN in the sintered body ( 220) The peak integrated intensity ratio: α / β is increased (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 a raw material, if the amount used is small (here, 20% by mass or less based on the whole raw material), the WC phase hardly exists in the sintered body, and W in the raw material powder is Ti composite. It is believed that it can exist as a 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 raw material powder and more than 30% by mass). By adjusting the composition of the raw material powder in this manner, it can be said that the thermal conductivity can be further increased by changing the structure of the sintered body and suppressing the formation of the Ti composite compound.

  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]
As raw material powders, powders having different average particle diameters were prepared, and sintered bodies were produced in the same manner as in Test Example 1 to examine the structure.

  In this test, a powder having an average particle diameter shown in Table 4 was prepared, and a sintered body was produced in the same manner as in Test Example 1 except that the blending ratio shown in Table 4 was used. The obtained sintered body was cut in the same manner as in Test Example 1, and the structure was observed by SEM. The results are shown in Table 5.

  As shown in Table 5, even if it is a raw material powder of the same composition, it is a large powder, and by shortening the mixing time, a sintered body with a large hard phase (for example, the average particle size of the Ti compound phase is It can be seen that a sintered body having 1 μm or more and an average particle diameter of WC of 2 μm or more is obtained. Moreover, it turns out that the sintered compact with a large average particle diameter of a hard phase has high heat conductivity. Furthermore, it can be seen that the average particle diameter of WC greatly affects the thermal conductivity of the sintered body. Even when a large powder is prepared as a raw material, it can be seen that if the mixing time is long, the hard phase in the sintered body becomes fine and the thermal conductivity decreases. Therefore, in order to produce a hard material with a hard phase consisting of a compound containing Ti and a high thermal conductivity, use a large amount of TiN powder as a raw material and make a relatively large powder, mixing time It can be said that shortening is preferable.

  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, a tool shape, a composition, etc. can be changed suitably.

  The hard material of the present invention can be suitably used as a cutting tool material. In particular, the cutting tool of the present invention can be suitably used for cutting under conditions where the cutting edge is hot (for example, high-speed cutting) or under conditions where a thermal cycle is performed.

1,100 Hard material 10,110 Core rim structure particles
12 Ti compound phase 13 Ti compound phase
20 Single Ti compound phase 30 Single Ti compound phase

Claims (11)

A hard material comprising a compound containing Ti as a hard phase,
As the 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,
Said taking a cross-section of hard material, the area ratio of the Ti compound phase for this section a, wherein, when the area ratio of Ti composite compound phase to is b, meets 0.5 ≦ (a / b),
A hard material in which 50% or more of the total area of the Ti compound phase in the cross section is Ti nitride . As the hard phase, containing WC,
2. The hard material according to claim 1, wherein when the cross section of the hard 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. 3. The hard material according to claim 1, wherein the thermal conductivity of the hard material is 20 W / m · K or more and 70 W / m · K or less. 4. The hard material according to claim 1, wherein the Mo content is 5% by mass or less. When X-ray diffraction was performed, the peak of TiN (220) and the peak of TiWC ₂ (220) were detected,
The integrated intensity of the peak of the TiN (220) α, when the integrated intensity of the peak of TiWC ₂ (220) β, any one of claims 1 to 4 satisfying (α / β) ≧ 0.3 Hard material as described in 1. 6. The hard material according to claim 1, wherein an average particle diameter of the Ti compound phase is 1 μm or more. As the hard phase, containing WC,
7. The hard material according to claim 1, wherein the average particle diameter of the WC is 2 μm or more. 8. The hard material according to claim 1 , wherein the hard phase includes particles having a core rim structure in which the Ti compound phase is a central structure and the Ti composite compound phase is a peripheral structure. 9. The hard material according to claim 8 , wherein the hard phase 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. The hard phase, a hard material as claimed in claim 8 or claim 9 containing elemental Ti composite compound phase does not include the Ti compound phase in the interior of the Ti complex compound phase 20% or less. 11. A cutting tool composed of the hard material according to claim 1 .

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