JPH06306525A - Sintered compact for tool and its production - Google Patents

Abstract

PURPOSE:To produce a sintered compact for a tool having excellent toughness, strength, wear resistance or the like by mixing the carbides or the like of transition metals, iron-group metals and fine-grained diamond in specified ratios and executing sintering at a specified temp. under a specified pressure. CONSTITUTION:By volume, 20 to 85% carbides, nitrides or sulfides of any transition metal of the 4a, 5a and 6a group in a periodic table or their mixture or solid solution (such as WC), 2 to 30% iron-group metals (such as Co) and 10 to 50% fine-grained diamond having 10 to 40mum grain size are mixed by a ball mill or the like. As it is or after being subjected to die extrusion, this mixture is subjected to solid phase sintering at 950 to 1150 deg.C under 1 to 30kb by a hot hydrostatic pressing device to produce a sintered compact in which fine carbon is precipitated in the iron group metals or on the surface thereof. In this way, the sintered compact for a tool excellent in workability, hardness or the like can be produced at a remarkably reduced producing cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered body suitable for use as a material for cutting tools, etc., and particularly to a sintered body for tools having excellent toughness, strength, wear resistance and the like. Regarding the method.

[0002]

2. Description of the Related Art Cutting tools made of non-ferrous metals such as aluminum alloys and copper alloys, non-metallic materials such as ceramics, concrete, rubber and plastics have excellent toughness, strength,
Workability, hardness and wear resistance are required. Cermet, which is widely used as a material for cutting tools at present, is a composite material of ceramics and metal, and has considerable wear resistance and excellent toughness, strength, and workability. Even so, it cannot be said that the recent severe requirements for high-speed cutting have been sufficiently satisfied.

Due to the recent tendency toward high-speed cutting, a diamond sintered body obtained by adding a small amount of a binder such as Co to a fine diamond powder of 2 to 20 μm and sintering it as a material for a cutting tool under an ultrahigh pressure. Despite its extremely high price due to its manufacture, it has attracted attention due to its high wear resistance.

However, the diamond sinter cutting tool cannot be said to have sufficient toughness and strength as compared with cemented carbide, and depending on the work material, chipping wear,
There was a problem that the blade edge was damaged. further,
In the manufacturing process of a diamond sintered body, an ultrahigh pressure of 50 kb or more is usually required, which significantly raises the manufacturing cost.
There has been a strong demand for improvement in this respect.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a diamond sintered body for a tool sintered body which satisfies all of the required properties as a material for a cutting tool, such as toughness, strength, workability, hardness and wear resistance. It is intended to be economically obtained by sintering under a low pressure as compared with the bonded body.

[0006]

The present invention is directed to a carbide of a transition metal of any one of Groups 4a, 5a and 6a of the periodic table,
Nitride, boride or mixture thereof or solid solution thereof 20 to 85% by volume, and iron group metal 2 to 30% by volume
And 10 to 50% by volume of fine-grained diamond having a particle size of 1 to 40 μm, wherein carbon is deposited in or on the surface of the iron group metal constituting the sintered body. A sintered body for a tool (claim 1), a carbide, a nitride, a boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume. And 2 to 30% by volume of iron group metal,
10-50% by volume of fine diamond with a particle size of 1-40 μm
A raw material mixture obtained by mixing and is sintered at a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 kb (claim 2), wherein an iron group metal is used instead of the iron group metal. The oxide is mixed in an amount of 2 to 30% by volume in terms of an iron group metal, and the raw material mixture is subjected to reduction treatment in a reducing atmosphere at a temperature of 500 to 900 ° C., and then a temperature of 950 to 1150 ° C. and a pressure of 1 to 1.
The method for producing a sintered body for a tool according to claim 2 (claim 3) and the basic composition is W, wherein the sintering is performed at 30 kb.
Substrate or M molded from a raw material of C-Co cemented carbide
On a substrate on which a cermet raw material composed of (Mo, W) C containing o as a main component and an iron group metal is molded, a carbide of a transition metal of any one of Groups 4a, 5a, and 6a of the periodic table, 20 to 85% by volume of a nitride, a boride or a mixture thereof or a solid solution thereof, and 2 to 30% by volume of an iron group metal;
10-50% by volume of fine diamond with a particle size of 1-40 μm
Laminating a molding plate molded with a mixture of raw materials mixed with and
The sintered body for a tool according to claim 1 (claim 4), characterized by being sintered and joined under high temperature and high pressure. Hereinafter, these inventions will be further described.

A sintered body for a tool according to claim 1 is a carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, a mixture thereof, a solid solution thereof, an iron group. It is composed of a sintered body of metal and fine-grained diamond.

Among these, the substance constituting the binder phase is a carbide, nitride, boride or mixture of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a solid solution thereof and an iron group metal. is there.

Carbides, nitrides, borides or mixtures thereof of transition metals of any of Groups 4a, 5a and 6a of the Periodic Table or solid solutions thereof, when used as a tool, have high temperature hardness, strength, It has excellent thermal conductivity and chemical stability, and is essentially the same as that used in tool sintered bodies such as cemented carbide and cermet. Among these, tongue ten carbide is preferably used, but titanium carbide and the like can be preferably used as well.

The content of these is 20 to 85% by volume. If this content is less than 20% by volume, the hardness, rigidity and wear resistance of the binder phase will be reduced, which is not preferable. Also, this is 85
When the content exceeds the volume%, the content of iron group metal, fine diamond, etc. is relatively decreased, and the toughness and wear resistance of the sintered body are reduced, which is not preferable.

In addition to the above, the iron group metal is contained in an amount of 2 to 30% by volume as a substance constituting the binder phase. The iron group metal promotes densification by viscous flow mechanism.
Further, the iron group metal has a very good wettability with diamond, so that the retention of the dispersed fine-grained diamond on the bonding phase becomes strong.

If the content of the iron group metal is less than 2% by volume, the binder phase cannot be densified, and the binder phase cannot be toughened or strengthened. Further, if it exceeds 30% by volume, the hardness, rigidity and wear resistance of the binder phase decrease, which is not preferable.

Outside the above is fine diamond. Due to its inherently high hardness, fine-grained diamond serves to improve the wear resistance of the sintered body and toughen the sintered body by dispersing it in the sintered body, and its content is 10 to 50% by volume. If it is less than 10% by volume, a sintered body having sufficient wear resistance cannot be obtained, and the toughness cannot be improved by dispersing fine diamond particles. If it exceeds 50% by volume, the densification of the binder phase is hindered and a dense sintered body cannot be obtained. The fine-grained diamond used here has an average grain size of 1 to 40 μm. If the particle size is less than 1 μm, the wear resistance decreases, and if it exceeds 40 μm, the strength of the tool cutting edge decreases, the tool cutting edge is damaged, and the tool life of the tool obtained from this sintered body is shortened, which is not preferable.

A second invention of the present application is a method for manufacturing a sintered body for a tool of the first invention. The raw materials used here are carbides, nitrides, borides or mixtures thereof of transition metals of any of Groups 4a, 5a and 6a of the periodic table or 20 to 85% by volume of solid solution thereof, and iron group metal 2 ˜30% by volume and 10 to 50 fine diamond particles with a particle size of 1 to 40 μm
The capacity is%. The reason for blending these in the above proportions is the same as described above.

These raw material mixtures are mixed by a ball mill or the like, and the raw material mixture is powdered or pressed and then is subjected to hot isostatic pressing (HIP) device, high temperature and high pressure generating device such as piston cylinder device and the like at 950 to 1150. ℃,
Solid-phase sintering is performed in a thermodynamically stable region of graphite of 1 to 30 kb. As a result, the fine-grained diamond dispersed in the raw material undergoes a minute amount of phase transition from the surface to be graphitized by the catalytic action of the iron group metal, and fine carbon particles are precipitated in the iron group metal or on the surface thereof to strengthen the binder phase. The sintering conditions are significantly lower in temperature and pressure than the sintering conditions of commercially available diamond sintered bodies.

Thermodynamic graphite stable regions and diamond stable regions with respect to pressure and temperature are shown in FIG. If the temperature is lower than 950 ° C., the sintered body will not be densified, and if it exceeds 1150 ° C., a remarkable diamond phase transition will occur, a large amount of graphite will be generated, and abrasion resistance peculiar to diamond will be deteriorated, which is not preferable.

When the pressure is less than 1 kb, 950 to 1150
Since the binder phase is not densified in the temperature range of ° C, a high density sintered body cannot be obtained. On the other hand, if the pressure exceeds 30 kb, sintering will occur in the diamond stable region, and the binder phase will not be toughened due to the phase transition of diamond, which is not preferable.

In the sintered body for a tool of the present invention, the peak of graphite was hardly recognized in the X-ray diffraction, but by observing with a transmission electron microscope (TEM) and Auger electron spectroscopy, it was confirmed that It was confirmed that very fine carbon of nanometer order was deposited in the iron group metal forming the binder phase or on the surface thereof. Such carbon is not found in or on the surface of the iron group metal of commercially available WC-Co cemented carbide, cermet and diamond sintered body.

The reason why the binder phase is toughened in the sintered body for a tool of the present invention is not necessarily clear, but it is presumed as follows. In other words, by the precipitation of fine carbon, it acts as a pin to suppress the movement of transition in the iron group metal or on the surface thereof, and by these, the progress of microcracks is macroscopically stopped and the overall sintered body is tough. It is considered to have been converted.

According to TEM observation, the commercially available WC-C
o If the iron group metal crystal grains in the cemented carbide, cermet or diamond sintered body are submicron or larger and are as large as several hundreds of microns, in the case of the sintered body for tools of the present invention, It was found that the size of the iron group metal crystal grains was very small and less than submicron due to the sintering at a low temperature which does not occur and the precipitation of the fine carbon particles described above. As a result, there is no stress concentration in the iron group metal or on the surface thereof, which is considered to be one of the reasons for strengthening.

Furthermore, since the sintering conditions are significantly lower with temperature and pressure than when commercially available diamond is sintered (pressure of 50 kb or more, temperature of 1400 ° C. or more), it is produced inside the sintered body of the present invention during the sintering process. It is also considered that the strain is small, which is also considered to contribute to strengthening.

A third invention is to replace the iron group metal in the raw material described in the preceding paragraph with an oxide of the iron group metal in the range of 2 to 30 in terms of the iron group metal.
% By volume, and mix this raw material mixture at a temperature of 500 to 900 ° C.
In the reducing atmosphere, the material is reduced and then sintered. As a result, the transverse rupture strength, that is, the strength of the sintered body can be further increased. The reason why the mixing ratio of the iron group metal is set to 2 to 30% by volume in terms of the iron group metal is the same as the reason described in claim 1.

The reducing atmosphere is preferably a hydrogen atmosphere, and the processing temperature is 500 to 900 ° C. If it is less than 500 ° C., the oxide of the iron group metal is not reduced, and if it exceeds 900 ° C., a remarkable phase transition occurs from the surface of the raw material diamond, and a large amount of graphite is generated, which is not preferable. The following reaction proceeds by this reduction treatment.

M−O + H ₂ → M + H ₂ O Here, M is an iron group metal. This iron group metal oxide is
In consideration of dispersibility in the binder phase, those having a particle size of 1 μm or less are preferable. The reason why the strength of the sintered body is improved by using the iron group metal oxide instead of the iron group metal is considered as follows.

In a conventional mixing method using a ball mill or the like, some mixing is performed at the same time as the raw materials are mixed. However, the iron group metal such as Co has a unique malleability and ductility, so that the metal particles are likely to be like water candy during mixing. There was a problem that it was easy to adhere to. On the other hand, when an oxide of an iron group metal is used during mixing, the oxide has good friability, so that the oxides are mixed uniformly without adhering to each other, and the iron group metal that has undergone the reduction treatment is uniformly dispersed in the structure. It will be. It is considered that this improves the strength of the sintered body. The raw material particle size of the iron group metal oxide used here is 3 μm or less in average particle size, and preferably 0.5 μm or less.

A fourth invention is a substrate obtained by molding a raw material of cemented carbide having a basic composition of WC-Co, or a raw material of cermet consisting of (Mo, W) C containing Mo as a main component and an iron group metal. A substrate formed by molding and a molding plate formed by molding the raw material mixture used in claim 2 are laminated and arranged, and these are simultaneously sintered and bonded under high temperature and high pressure.

The former substrate is a substrate formed by molding a raw material of cemented carbide whose basic composition is WC-Co, or a raw material of cermet consisting of (Mo, W) C containing Mo as a main component and an iron group metal. The formed substrates are all excellent in toughness, rigidity, thermal conductivity and corrosion resistance, and are suitable for use as a cutting tool.

The sintering temperature of this tool sintered body is from 950 to 950.
It can be obtained at low temperature of 1150 ℃
The liquid phase does not appear as observed in the sintering process of the cermet or the commercially available diamond sintered body, and the solid phase sintering is sufficient. Moreover, since the hard layer containing diamond and the other substrate layer are simultaneously sintered and the substrate layer has a higher strength than the hard layer, the strength can be further increased as an integrated body.

Further, since the substrate layer is significantly easier to process than the hard layer containing diamond, there is an advantage that the cost can be reduced because the tool is manufactured. The thickness of the hard layer containing diamond may be determined in consideration of economical efficiency, tool specifications and strength, and 0.5 mm or more is sufficient for each.

The raw material mixture ratio, fine diamond particles, sintering temperature, sintering pressure, etc. of the present invention will be further described below with reference to experimental examples. The raw materials for forming the binder phase are
Tungsten carbide (WC) having an average particle size of 0.8 μm and high-purity cobalt (Co) having an average particle size of 1.0 μm were used.

Further, the raw material compounding ratios of WC, Co, and fine-grained diamond were partially weighted for convenience of notation in the figure. The true specific gravity measured values of the powders of WC, Co and diamond are as follows. From these true specific gravity measured values,
The weight ratio and volume ratio of each are converted.

WC: 15.60 g / cm ³ , Co: 8.9
0 g / cm ³ , diamond; 3.5 g / cm ³ Experimental Example 1 In this experiment, the relationship between the Co blending ratio (vol%) in the raw material blend and the relative density (%) of the sintered body was examined. is there.
The compounding ratio of WC-Co forming the binder phase and the fine-grained diamond is 3 kinds, and the weight ratio is 95.0: 5.0.
0.5: 9.5, same, 86.4: 13.6. The fine diamond particles each had a particle size of 7 μm.

A raw material mixture obtained by thoroughly mixing the above raw materials with a pot mill was used, and the sintering pressure was 10 kb and the sintering temperature was 1050.
A sintered body was obtained at a temperature of 10 ° C. for 10 minutes. The results are shown in FIG. From FIG. 2, it is clear that the compounding ratio of Co is required to be 2% by volume or more for any compounding ratio of fine diamond.

Experiment 2 In this experiment, the obtained sintered body was processed into a cutting tip, and cement mortar was cut with the cutting tip. From the result, the relationship between the Co compounding ratio (volume%) and the tool life (minute) was shown. This is what I examined.

The composition ratio of WC-Co forming the binder phase and fine diamond was set to the same three kinds as in Experiment 1, and the Co composition ratio was variously changed as in Experiment 1. Similar to Experiment 1, the raw material mixture obtained by thoroughly mixing the raw materials with a pot mill was used, and the sintering pressure was 10 kb, the sintering temperature was 1050 ° C., and the heating holding time was 10
Sintered in minutes. The shape of the cutting tip produced from the sintered body is ISO millimeter nominal TNGN 160304.

The work material was cement mortar, which was prepared by mixing standard sand with Portland cement 1 at a volume ratio of 2 and adding 65% by weight of water to the cement, followed by curing in water for 28 days.

Cutting speed 50 m / min, depth of cut 0.5 m
m, feed was 0.13 mm / revolution, and life was determined when the average flank wear width was 0.3 mm. The result was as shown in FIG. As is clear from FIG. 3, a cutting tool having an excellent tool life can be obtained from this sintered body by setting the compounding ratio of Co to 2 to 30% by volume. In combination with Experiment 1 described above, it is found that the iron group metal is preferably in the range of 2 to 30% by volume.

Experiment 3 In this experiment, the relationship between the compounding ratio of fine diamond particles (vol%) and the relative density (%) of the sintered body was investigated.

The compounding ratio of WC: Co is 94.
7: 5.3, ibid, 89.5: 10.5, ibid, 84.2:
There are 3 types of 15.8. Capacity ratio of fine diamond (v
ol%) was changed as shown in FIG. The grain size of fine diamond was 7 μm.

This raw material mixture was thoroughly mixed with a pot mill, and this was sintered at a sintering pressure of 10 kb, a sintering temperature of 1050 ° C., and a heating and holding time of 10 minutes. The relative density (%) of the obtained sintered body was measured and determined in relation to the diamond volume ratio (vol%). The result is as shown in FIG. From FIG. 4, it is clear that the sintered body is densified only when the volume ratio of the fine-grained diamond is 50% or less.

Experiment 4 In this experiment, the relationship between the fine diamond blending ratio (vol%) and the tool life (min) was investigated when a cutting tip was processed from a sintered body and cement mortar was cut with this. is there.

The WC: Co of the raw material mixture is 8 by weight.
It was fixed at 9.5: 10.5. The volume ratio of fine diamond was changed variously. The particle size of the fine-grained diamond was 7 μm. The raw material mixture was thoroughly mixed and sintered in a pot mill as in Experiment 1. Sintering pressure is 5 kb, 10
There were 3 types of kb and 20 kb. The sintering temperature is 10
The temperature was 50 ° C. and the heating and holding time was 10 minutes in each case.

The shape of the cutting tip was ISO as in Experiment 2.
Cement mortar obtained in the same manner as in Experiment 2 was used as the work material. Cutting speed is 5
The life was determined when the average flank wear width was 0.3 mm at 0 m / min, the depth of cut was 0.5 mm, the feed was 0.13 mm / revolution, and these were the same as in Experiment 2. The result was as shown in FIG. As is clear from FIG. 5, it is clear that good results are obtained when the volume ratio of the fine-grained diamond is 10 to 50% by volume.

The volume ratio of fine diamond is 10%.
Below, damage to the cutting edge of the tool was recognized in addition to steady mechanical wear. It is understood that this is because when the volume ratio of fine-grained diamond is less than 10%, the sintered body is not dispersed and strengthened by the diamond particles, and the toughness of the cutting edge is lowered. When combined with Experiment 3, the volume ratio of fine diamond is 10 to 10.
A good sintered body can be obtained with 50% by volume.

Experiment 5 In this experiment, the relationship between the fine diamond particle size (μm) and the tool life (min) was investigated. In this experiment, the ratio of WC: Co: fine diamond in the raw material mixture was 81.0: 9.5: 9.5 by weight and 57.8: 1 by volume.
The particle size of the fine-grained diamond used here was variously changed while keeping the ratio constant at 2.0: 30.2.

Using this raw material mixture, a sintered body was obtained in the same manner as in Experiment 2, and a cutting tip was produced therefrom. The same work material as in Experiment 2 was used, and the tool life was examined. The results are shown in Fig. 6. As is clear from FIG. 6, when the sintering pressure is all in the range of 5 to 20 kb, the fine grain diamond has a grain size in the range of 1 to 40 μm, and it is clear that the tool life is good.

The grain size of fine diamond is 40 μm.
It is understood that the tool life is shortened when the value exceeds 0.1 because the fine diamond particles are too large and the cutting edge strength is reduced.

Experiment 6 In this experiment, the sintering temperature (° C.) was kept constant with the raw material mixture ratio kept constant.
And the relative density (%) of the sintered body was investigated.
That is, the raw material mixing ratio was WC: Co: fine-grained diamond 81.0: 9.5: 9.5 by weight and 57.
8: 12.0: 30.2. The fine diamond used had a grain size of 7 μm.

The sintering pressure is 5 kb, 10 kb, 20 kb.
And the heating and holding time was set to 10 minutes. The results are shown in Fig. 7. As shown in the figure, it is recognized that the sintered body is densified only at the sintering temperature of 950 to 1150 ° C. even if the sintering pressure is changed. If the sintering temperature is lower than 950 ° C, the binder phase will not be densified.
It is clear that at a temperature above 150 ° C., the density was reduced due to the remarkable graphitization of fine-grained diamond.

Experiment 7 In this experiment, the relationship between the sintering temperature and the relative density was examined with the sintering pressure kept constant for the materials having different raw material mixing ratios. The sintering pressure is 10 kb and the heating and holding time is 1
It was set to 0 minutes.

Three kinds of raw material compounding ratios are used, and a weight ratio of WC: Co: fine-grained diamond is 85.0: 10.0 :.
5.0 (volume ratio 68.1: 14.1: 17.8), weight ratio 81.0: 9.5: 9.5 (volume ratio 57.8:
12.0: 30.2), 77.3: 9.1: 1 by weight.
It was set to 3.6 (50.2: 10.4: 39.4 in volume ratio). The fine diamond used had a grain size of 7 μm. The results are shown in Fig. 8. From FIG. 8, even if the compounding ratio of the fine-grained diamond in the raw material mixture was changed, the sintering temperature was 950 to 11
It is clear that the most densified sintered body can be obtained in the range of 50 ° C.

Experiment 8 In this experiment, the sintering pressure was kept constant and the sintering temperature (° C.) and the Vickers hardness (kg / mm) were obtained with the raw material mixture ratio changed.
^This is a study of the relationship in ² ). The sintering pressure is 10
The heating time was 10 minutes.

Three raw material mixing ratios were used, and the weight ratio of WC: Co: fine-grained diamond was 85.7: 4.8: 9.
5 (volume ratio 62.9: 6.1: 31.0), weight ratio 81.0: 9.5: 9.5 (volume ratio 57.8: 12.
0: 30.2), and the weight ratio is 76.2: 14.3: 9.5.
(The volume ratio is 53.1: 17.4: 29.5). The fine diamond used was 7 μm. The results are shown in Fig. 9. As is clear from FIG. 9, even if the composition ratio of WC, Co and diamond is changed, the sintering temperature is 950 to 1150.
It is possible to obtain a sintered body having a high Vickers hardness in the range of ° C. When combined with the results of Experiments 5 to 7, it is found that the sintering temperature is preferably in the range of 950 to 1150 ° C.

Experiment 9 In this experiment, the relationship between the sintering pressure (kb) and the relative density (%) was investigated under the condition that the sintering temperature was constant and the mixing ratio of the raw materials was changed. The sintering temperature was 1050 ° C. and the heating and holding time was 10 minutes.

Three raw material mixing ratios were used, and the weight ratio of WC: Co: fine-grained diamond was 85.0: 10.0 :.
5.0 (volume ratio 68.1: 14.1: 17.8), weight ratio 81.0: 9.5: 9.5 (volume ratio 57.8:
12.0: 30.2), 77.3: 9.1: 1 by weight.
It was set to 3.6 (50.2: 10.4: 39.4 in volume ratio). The fine diamond used had a grain size of 7 μm. The results are shown in FIGS. 10 and 11. Note that FIG. 11 is similar to FIG.
FIG. 6 is an enlarged partial view showing the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. As is clear from FIGS. 10 and 11, it is understood that a dense sintered body can be obtained only when the sintering pressure is 1 kb or more even if the compounding ratio of the fine-grained diamond changes.

Experiment 10 In this experiment, the relationship between the sintering pressure (kb) and the relative density (%) was examined when the sintering temperature was kept constant and the particle size of the fine diamond particles was changed. The sintering temperature was 1050 ° C. and the holding time was 10 minutes.

The raw material mixture has a compounding ratio of WC: Co: fine grain diamond of 81.0: 9.5: 9.5 by weight.
(The volume ratio was 57.8: 12.0: 30.2). The particle size of fine diamond is 2 μm, 7 μm, 14
Three types of μm were used. The results are shown in FIGS. 12 and 13.
Note that FIG. 13 is an enlarged partial view showing the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. As is clear from FIGS. 12 and 13, even if the particle size of the fine-grained diamond changes, a dense sintered body can be obtained only when the sintering pressure is 1 kb or more.

Experiment 11 In this experiment, the sintering pressure (k
The relationship between b) and the relative density (%) of the sintered body was investigated. That is, the raw material mixing ratio is WC: Co: fine-grained diamond 81.0: 9.5: 9.5 by weight, and 5 by volume.
7.8: 12.0: 30.2. The fine diamond particles used had an average particle size of 7 μm.

The sintering temperature is 1000 ° C., 1050 ° C., 1
The heat retention time was set to 10 minutes for each of the three types at 100 ° C. The results are shown in FIGS. 14 and 15. Note that FIG. 15 is an enlarged view of the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. 14 and 15
It is recognized that even if the sintering temperature is changed within the range of the present invention, a dense sintered body can be obtained only when the sintering pressure is 1 kb or more, as shown in FIG.

Experiment 12 In this experiment, the relationship between the sintering pressure (kb) and the transverse rupture strength of the sintered body was investigated with the sintering temperature kept constant with the raw material mixture ratio changed. The sintering temperature was 1050 ° C., and the heating and holding time was 10 minutes.

The mixing ratio of the raw materials is as follows: WC: Co: fine-grained diamond by weight 85.7: 4.8: 9.5 (volume ratio 6
2.9: 6.1: 31.0), and the weight ratio is 81.0: 9.
5: 9.5 (volume ratio 57.8: 12.0: 30.
2) and 76.2: 14.3: 9.5 by weight (53.1: 17.4: 29.5 by volume). The fine-grained diamond used had an average grain size of 7 μm.
Three-point bending strength (kg / mm ² ) according to JIS R 1601
Was measured and investigated. However, the size of the test piece is 2 mm x 1.5 mm x 20 mm (10.05 mm) due to the limitation of the size of the sintered body,
The span was 15 mm.

The results are shown in FIGS. 16 and 17. Note that FIG. 17 is an enlarged view of the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. As shown in FIG. 16 and FIG. 17, even if the raw material mixture ratio changes within the range of the present invention, the bending strength of the sintered body, that is, the strength is the highest in the sintering pressure range of 1 to 30 kb. Is recognized.

Experiment 13 In this experiment, the sintering pressure (k
The relationship between b) and transverse rupture strength (kg / mm ² ) was investigated.
The raw material mixing ratio was WC: Co: fine-grained diamond 81.0: 9.5: 9.5 by weight, and the volume ratio was 57.
8: 12.0: 30.2 with a fine diamond grain size of 7
The thing with a micrometer was used.

The sintering temperature is 1000 ° C., 1050 ° C., 1
The heat retention time was set to 10 minutes for each of the three types at 100 ° C. The results are shown in FIGS. 18 and 19. Note that FIG. 19 is an enlarged view of the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. 18 and 19
As shown in, even if the sintering temperature changes, the sintering pressure is 1 to
It is recognized that the bending strength, that is, the strength of the sintered body is the highest in the range of 30 kb.

Experiment 14 In this experiment, the relationship between the sintering pressure (kb) and the tool life (min) was investigated. The raw material mixture was mixed with WC: Co: fine-grained diamond in a weight ratio of 81.0: 9.5: 9.
5, the volume ratio was 57.8: 12.0: 30.2, the particle size of diamond was kept constant at 7 μm, and the sintering pressure was variously changed to obtain a sintered body. Cutting chips were produced from these sintered bodies in the same manner as in Experiment 4.

The same work material as in Experiment 4 was used.
The tool life was examined in the same manner as in. The result is shown in FIG.
21 and FIG. Note that FIG. 21 is an enlarged view of the range of 0 to 5 of the sintering pressure (kb) on the horizontal axis of FIG. As is clear from FIGS. 20 and 21,
Good tool life can be obtained when the sintering pressure is in the range of 1 to 30 kb. From the results of the above Experiments 9 to 14, it is understood that good results can be obtained at a sintering pressure of 1 to 30 kb.

Experiment 15 In this experiment, the sintering temperature (° C.) was kept constant with the raw material mixture ratio kept constant.
And the relationship between the X-ray graphitization degree (%) of the obtained sintered body.

Here, the X-ray graphitization degree is a value (%) obtained by the following equation. That is, in the powder X-ray diffraction intensity of the obtained sintered body, X-ray graphitization degree (%) = X-ray diffraction intensity (graphite) / (X-ray diffraction intensity (graphite) + X-ray intensity (diamond) × 100 It is qualitatively understood that the higher the X-ray graphitization degree is, the more graphite is present in the sintered body.

The raw material mixing ratio was WC: Co: fine-grained diamond 81.0: 9.5: 9.5 by weight, and 5 by volume.
7.8: 12.0: 30.2. The fine diamond used had a grain size of 7 μm. Sintering pressure is 5 kb, 1
Three kinds of 0 kb and 20 kb were used, and the heating and holding time was 10 minutes in all cases. The results are shown in Fig. 22. As shown in the figure, at any sintering pressure in the present invention, the presence of graphite is recognized when the sintering temperature is 500 ° C. or higher.
In the temperature range of 950 to 1150 ° C, the existence of graphite is hardly recognized. The fact that the presence of graphite is hardly observed in this temperature range is understood to be that carbon generated during heating or heating and holding was precipitated in the iron group metal or on the surface thereof. Then, the carbon deposited in the iron group metal or on the surface thereof contributes to the strengthening of the binder phase. 1150
It is clear that a large amount of graphite was detected by X-ray because the graphitization of diamond was remarkable when the temperature was higher than ° C.

Experiment 16 This experiment was conducted in connection with the third invention of the present application, and the iron group metal oxide used here had an average particle size of 0.2.
It is high-purity cobalt oxide (Co ₃ O ₄ ) of μm. Here, when iron group metals were mixed in the form of metallic Co for each of the following various raw material compositions, the difference in transverse rupture strength (Kg / mm ² ) when mixed in the form of Co oxide (Co ₃ O ₄ ) was compared. . These raw material mixtures were subjected to reduction treatment in a hydrogen atmosphere at 800 ° C. and then subjected to high temperature and high pressure treatment. Sintering pressure is 10 kb, sintering temperature is 1
The heating and holding time was 050 ° C. and 10 minutes.

Three kinds of raw materials were used, and the weight ratio of WC: Co: fine diamond was 85.0: 10.0:
5.0 (volume ratio 68.1: 14.1: 17.8), weight ratio 81.0: 9.5: 9.5 (volume ratio 57.8:
12.0: 30.2), by weight 17.3: 9.1: 1.
3.6 (50.2: 10.4: 39.4 by volume ratio),
The fine diamond used had a grain size of 7 μm. The results are shown in Table 1. As is clear from this table, Co (Co
It was confirmed that in the case of mixing in the form of ₃ O ₄ ), the transverse rupture strength was improved by 20% or more as compared with the case of mixing in the form of metallic Co.

[0072]

[Table 1]

[0073]

As described above, a binder phase forming material composed of a carbide, a nitride, a boride of a transition metal, or a mixture thereof, or a solid solution thereof and an iron group metal, and fine diamond are uniformly blended at a predetermined ratio. When the raw material mixture is thermodynamically sintered at a stable temperature and pressure of graphite, a part of the fine-grained diamond undergoes a phase transition and carbon precipitates in the iron group metal or on the surface thereof, resulting in a significantly high binder phase. A toughened and high-strength sintered body for tools can be obtained.

[0074]

【Example】

(Examples 1 to 16) Using the binder phase forming raw materials shown in Table 2,
A raw material mixture obtained by mixing fine diamond particles and thoroughly mixing with a pot mill was molded to obtain a preform having a diameter of 30 mm and a thickness of 2 mm. This compact and a preformed cemented carbide preform of WC-15wt% Co having a diameter of 30 mm and a thickness of 2 mm were laminated and subjected to a reduction treatment in a hydrogen atmosphere at 800 ° C., and then a piston cylinder type high temperature and high pressure. It was inserted into the generator. Graphite heater was used as the heating element, and pyroxene and hexagonal boron nitride were used as the solid pressure medium. The sintering conditions are as shown in Table 2 and the heating and holding time is 1
It was set to 0 minutes.

When an iron group metal oxide is used,
It was converted to the compounding ratio when reduced. The recovered sintered body was one in which the hard layer containing diamond and the cemented carbide portion were firmly integrated.

The simultaneous sintered body was cut by electric discharge machining to prepare a cutting tool and a bending strength test piece. The tool shape was ISO millimeter nominal TNGN 160304 similar to Experiment 2, and the bending strength test piece shape was in accordance with JIS R 1601. Due to the size of the sintered body, the test size is 2mm x 1.5mm x 20mm (± 0.0
5 mm) and the span was 15 mm.

For comparison, a commercially available K10 type cemented carbide and a commercially available diamond sintered body were prepared and processed into the same shape. The same cement mortar as in Experiment 2 was used as the work material. The work material had a cutting speed of 50 m / min, a depth of cut of 0.5 mm, a feed of 0.13 mm / revolution, and the life was reached when the average flank wear width was 0.3 mm. Flexural strength is in accordance with JIS R 1601, 3-point bending strength (kg / mm ² )
Was measured and investigated. The results of the cutting test and the transverse rupture strength test are shown in Table 2.

In the case of the commercially available cemented carbide chip and the commercially available diamond sintered body chip, the tool edge was broken and the tool life was reached when the flank wear width was about 0.1 mm, whereas the sintered body of the present invention was used. In the case of chips, the wear state of the tool flank was steady wear and the tool life was also significantly superior (Table 3).

[0079]

[Table 2]

[0080]

[Table 3] (Examples 17 to 25) Using the binder phase forming raw materials shown in Table 3, raw material mixtures obtained by blending fine diamond particles and thoroughly mixing them in a pot mill were obtained to obtain preforms having a diameter of 30 mm and a thickness of 2 mm. It was This molded product and (Mo ₇ W ₃ ) -20 wt% with a diameter of 30 mm and a thickness of 2 mm prepared in advance
A cermet preform made of Co is laminated to obtain 80
The reduction treatment was performed in a hydrogen atmosphere at 0 ° C. This laminated compact was sandwiched between 80 mm square and 0.1 mm thick stainless steel thin plates to be capsules, and hexagonal boron nitride powder was applied between the compact and the stainless plate for mold release. These were placed in a vacuum container, a stainless plate was welded in a vacuum, and the molded body was enclosed. Then, the capsule encapsulating this compact was inserted into a hot isostatic press (HIP) device, and the HI was held for 30 minutes under the sintering conditions shown in Table 3 in the simultaneous temperature rising and pressurizing pattern.
P treatment was performed. When the iron metal oxide was used, it was converted to the compounding ratio when it was reduced.

After the HIP treatment, the stainless capsule and the hexagonal boron nitride used for the mold release were removed, and the sintered body was recovered. As a result, the hard layer containing diamond and the cemented carbide portion were firmly integrated. Met.

Tools and test pieces were prepared from this co-sintered body in the same manner as in Examples 1 to 16 and subjected to a cutting test and a bending strength test. The results are shown in Table 3. In the case of the chip using the sintered body of the present invention, the wear state of the tool flank is steady wear, and similar to Experimental Examples 1 to 16,
The tool life was significantly longer than that of the commercially available superalloy chips and commercially available diamond sintered body chips.

[0083]

According to the present invention, a sintered body for a tool satisfying all of the toughness, strength, workability, hardness and wear resistance required as a cutting tool material is thermodynamically made of graphite. Since it is possible to sinter in a low pressure region which is a stable region, the manufacturing cost is significantly reduced as compared with the conventional diamond sintered body, and an excellent sintered body for tools can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing thermodynamically graphitic and diamond stable regions with respect to pressure and temperature.

FIG. 2 is a diagram showing the relationship between the Co blending ratio (vol%) in the raw material mixture and the relative density (%) of the sintered body, while changing the raw material blending ratio.

FIG. 3 is a diagram showing a relationship between a Co blending ratio (vol%) in a raw material mixture and a tool life (min) while changing the raw material blending ratio.

[Fig. 4] Mixing ratio of fine-grained diamond in the raw material mixture (vol%)
FIG. 6 is a diagram showing the relationship between the relative density (%) of the sintered body and the raw material mixture ratio.

[Fig. 5] Compounding ratio of fine diamond in the raw material mixture (vol%)
FIG. 6 is a diagram showing the relationship between the tool life (minutes) of a cutting tip manufactured from a sintered body and the sintering pressure varied.

FIG. 6 is the particle size (μ of fine diamond in the raw material mixture.
m) and a tool life (minutes) of a cutting tip produced from a sintered body obtained by using the raw material, with the sintering pressure being changed.

FIG. 7 is a diagram showing the relationship between the sintering temperature (° C.) when obtaining a sintered body and the relative density (%) of the obtained sintered body, while changing the sintering pressure.

FIG. 8 is a diagram showing the relationship between the sintering temperature (° C.) when obtaining a sintered body and the relative density (%) of the obtained sintered body, while changing the raw material mixture ratio.

FIG. 9 is a diagram showing the relationship between the sintering temperature (° C.) when obtaining a sintered body and the Vickers hardness (kg / mm ² ) of the obtained sintered body while changing the raw material mixing ratio.

FIG. 10 is a diagram showing the relationship between the sintering pressure (kb) when obtaining a sintered body and the relative density (%) of the obtained sintered body, while changing the raw material mixing ratio.

FIG. 11 is a partially enlarged view showing a sintering pressure range of 0 to 5 kb in FIG. 10 in an enlarged manner.

FIG. 12 is a diagram showing the relationship between the sintering pressure (kb) for obtaining a sintered body and the relative density (%) of the obtained sintered body while changing the grain size of fine diamond.

FIG. 13 is a partially enlarged view showing the sintering pressure range of 0 to 5 kb in FIG. 12 in an enlarged manner.

FIG. 14 is a diagram showing the relationship between the sintering pressure (kb) when obtaining a sintered body and the relative density (%) of the obtained sintered body, while changing the sintering temperature.

FIG. 15 is a partially enlarged view showing a sintering pressure range of 0 to 5 kb in FIG. 14 in an enlarged manner.

FIG. 16 is a diagram showing the relationship between the sintering pressure (kb) for obtaining a sintered body and the transverse rupture strength (kg / mm ² ) of the obtained sintered body, while changing the raw material mixing ratio.

FIG. 17 is a partially enlarged view showing a sintering pressure range of 0 to 5 kb in FIG. 16 in an enlarged manner.

FIG. 18 is a diagram showing the relationship between the sintering pressure (kb) for obtaining a sintered body and the transverse rupture strength (kg / mm ² ) of the obtained sintered body, while changing the sintering temperature.

FIG. 19 is a partially enlarged view showing the sintering pressure in the range of 0 to 5 kb in FIG. 18 in an enlarged manner.

FIG. 20 is a diagram showing a relationship between a sintering pressure (kb) for obtaining a sintered body and a tool life (min) of a cutting tip manufactured from the sintered body.

FIG. 21 is a partially enlarged view showing an enlarged range of sintering pressure of 0 to 5 kb in FIG. 20.

FIG. 22 is a diagram showing the relationship between the sintering temperature (° C.) for obtaining a sintered body and the X-ray graphitization degree (%) of the obtained sintered body, while changing the sintering pressure.

Claims (4)

[Claims] 1. A carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume,
A sintered body composed of 2 to 30% by volume of an iron group metal and 10 to 50% by volume of fine-grained diamond having a particle size of 1 to 40 μm, wherein carbon is present in the iron group metal constituting the sintered body or on the surface thereof. A sintered body for tools, which is characterized by being precipitated. 2. A carbide, nitride, boride of a transition metal of any one of Groups 4a, 5a and 6a of the Periodic Table, or a mixture thereof or a solid solution thereof in an amount of 20 to 85% by volume,
A tool characterized by sintering a raw material mixture obtained by mixing 2 to 30% by volume of an iron group metal and 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm at a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 kb. For manufacturing sintered body for automobile. 3. An oxide of an iron group metal in place of the iron group metal,
It is characterized in that the raw material mixture is mixed in a reducing atmosphere at a temperature of 500 to 900 ° C. and then sintered at a temperature of 950 to 1150 ° C. and a pressure of 1 to 30 kb. The method for manufacturing a sintered body for a tool according to claim 2. 4. A substrate formed by molding a raw material of a cemented carbide having a basic composition of WC-Co or having Mo as a main component (Mo,
W) Carbide, nitride, boride of transition metals of any one of Groups 4a, 5a, and 6a of the Periodic Table, or these on a substrate on which a raw material for cermet composed of C and an iron group metal is formed. 20-85% by volume of a solid solution or a solid solution thereof,
Formed plates formed by mixing a raw material mixture in which 2 to 30% by volume of an iron group metal and 10 to 50% by volume of fine-grained diamond having a particle size of 1 to 40 μm are laminated, and sintered and joined under high temperature and high pressure. The sintered body for a tool according to claim 1, wherein: