JPH07195207A - Sintered body for tool and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a sintered body for tools to satisfy the features required for cutting tool materials, etc., that is, all of toughness, strength, workability, hardness, oxidation resistance at high temperature, reaction resistance, and wear resistance, etc. CONSTITUTION:A sintered body is made up of 10 to 65 volume % carbide, nitride, boride of transition metal of any of 4a, 5a, 6a groups of the perodic table, or a mixture of these substances, or a solid solution, 2 to 30 volume % iron group metal, 5 to 20 volume % of one kind or two or more kinds of Al2O3, Y2O3, MgO, ZrO2, 5 to 20 volume % cubic boron nitride with 10mum or less particle diameter, and 10 to 50 volume % fine-grained diamond of 1 to 40mum particle diameter. In the iron group metal constituting the sintered body, or on its surface, carbon is precipitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body suitable for use as a material for a cutting tool and a method for producing the same, and more particularly to a sintered body for a tool having excellent toughness, strength, wear resistance and the like. It relates to a manufacturing 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. Is requested. 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-grained diamond powder of about 2 to 20 μm and sintering it as a material for a cutting tool under 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, since commercially available diamond sintered bodies do not have sufficient high temperature oxidation resistance (heat resistance), they cannot be used for cutting accompanied by temperature rise, and diamond is an iron-based metal. Therefore, it has been a problem that wear easily progresses during cutting of iron-based metal.

Further, in the manufacturing process of the diamond sintered body, an ultrahigh pressure of 50 kb or more is usually required, and the manufacturing cost is remarkably increased, and therefore improvement in this point has been strongly desired.

[0006]

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

[0007]

A first invention is 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 10 to 65% by volume, iron group metal 2 to 30% by volume, Al
One or more of ₂ O ₃ , Y ₂ O ₃ , MgO, and ZrO ₂ 5 to 20% by volume, cubic boron nitride 5 to 20% by volume having a particle size of 10 μm or less, and fine particles having a particle size of 1 to 40 μm A sintered body for a tool, comprising 10 to 50% by volume of diamond, wherein carbon is deposited in or on the surface of an iron group metal constituting the sintered body [claim 1 ], The second invention is 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 10 to 65% by volume,
Iron group metal 2 to 30% by volume, Al ₂ O ₃ , Y ₂ O ₃ , Mg
One or more of O and ZrO ₂ 5 to 20% by volume, and cubic boron nitride 5 to 20% by volume having a grain size of 10 μm or less
And 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm are mixed at a temperature of 950 to 1150.
A method for producing a sintered body for a tool, which comprises sintering at a temperature of 1 ° C. and a pressure of 1 to 30 kb [claim 2], and a third invention is a raw material for a cemented carbide having a basic composition of WC-Co. On a substrate formed with or on a substrate formed with a cermet raw material composed of (Mo, W) C containing Mo as a main component and an iron group metal, and any of transitions of groups 4a, 5a, and 6a of the periodic table. Metal carbides, nitrides, borides or mixtures thereof or solid solutions thereof 10 to 65% by volume, iron group metals 2 to 30
1% or more of Al ₂ O ₃ , Y ₂ O ₃ , MgO, and ZrO ₂ of 5% to 20% by volume, 5 to 20% by volume of cubic boron nitride having a particle size of 10 μm or less, and a particle size of 1 ~ 40μ
m formed of a raw material mixture in which 10 to 50% by volume of fine diamond particles are mixed, and laminated at a temperature of 950 to 115.
This is a sintered body for a tool [claim 3] sintered and bonded at 0 ° C and a pressure of 1 to 30 kb.

These inventions will be further described below. The sintered body for a tool of the first invention is 4a, 5a of the periodic table,
Carbides, nitrides, borides or mixtures thereof of any of the Group 6a transition metals or solid solutions thereof, and Al _{2
O 3, Y 2 O 3,} MgO, 1 kind of ZrO ₂ or 2
More than seed, iron group metal, fine grained cubic boron nitride (cBN)
And fine diamond.

Among these, the substance constituting the binder phase is 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. Al ₂ O ₃ , Y ₂ O ₃ , MgO, Zr
One or more of O ₂ and an iron group metal.

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 hardness, strength, It has excellent thermal conductivity and chemical stability, and is essentially the same as that used in sintered compacts for tools such as cemented carbide and cermet. Of these, tungsten carbide is preferably used, but titanium carbide and the like can also be preferably used.

The content of these is 10 to 65% by volume. If this content is less than 10% by volume, the hardness, rigidity, and wear resistance of the binder phase will decrease, which is not preferable. Also, this is 65
When the content exceeds the volume%, the content of the iron group metal, the fine-grained diamond, etc. is relatively reduced, and the strength, toughness, and wear resistance of the sintered body are reduced, which is not preferable.

In addition to the above, iron group metal is contained in an amount of 2 to 30% by volume as a substance constituting the binder phase. This iron group metal is diamond, cBN and the periodic table 4a, 5a,
The group 6a transition metal has very good wettability with carbides, nitrides, and borides, promotes densification by viscous flow, and strengthens the retention of the dispersed fine diamond in the binding phase.

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 and strengthened. Further, if it exceeds 30% by volume, the hardness, rigidity, and wear resistance of the binder phase decrease, which is not preferable.

As another substance forming the bonded phase,
There are Al ₂ O ₃ , Y ₂ O ₃ , MgO, and ZrO ₂ . Each of these oxides has a high melting point and a high hardness, and is superior in high temperature oxidation resistance (heat resistance) to diamond and carbides, nitrides, and borides of group 4a, 5a, and 6a transition metals of the periodic table. Sex). Further, since these oxides are stable during sintering and cutting, they do not oxidize carbides, nitrides and borides of diamond and transition metals. Furthermore, since these oxides have low high temperature hardness as compared with cBN and diamond, they are easily deformed during high-pressure sintering, and snarling occurs between the particles, resulting in diamond particles, cBN particles and transition metal. The effect of improving the toughness by densely filling the spaces between the carbide, nitride, and boride particles. However, if the content rate is less than 5% by volume, the above-mentioned effects cannot be exhibited, so that the high temperature oxidation resistance is deteriorated. When the content is more than 20% by volume, the content of diamond, cBN or transition metal carbides, nitrides and borides becomes relatively small,
The high hardness of diamond and cBN cannot be sufficiently reflected in the sintered material, and as a result, wear resistance is not reduced, and toughness derived from carbides, nitrides and borides of transition metals is not achieved.

One of substances other than the binder phase is cBN. cBN is a substance that has hardness second only to diamond, is stable at higher temperatures than diamond, and is difficult to react with ferrous metals such as hardened steel and cast iron. Is less than 5% by volume, desired high temperature oxidation resistance and desired resistance to reaction with iron-based metals cannot be secured. On the other hand, if the content exceeds 20% by volume, the content of diamond and the binder phase forming substance becomes relatively small, and the high hardness of the diamond cannot be sufficiently reflected in the sintered material. As a result, the wear resistance is lowered, and the toughness and strength due to the binder phase forming substance cannot be obtained. The average particle size of cBN used here is 10 μm or less, preferably 3 μm.
m or less. If it exceeds 10 μm, it is difficult to uniformly disperse cBN between diamond particles, and desired toughness and strength cannot be obtained.

Outside of the above is fine diamond. Due to its inherent hardness, fine-grained diamond serves to improve the wear resistance of the sintered body and to strengthen the sintered body by being dispersed in the sintered body. 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 in the range of 1 to 40 μm. If the particle size is less than 1 μm, fine diamond particles tend to fall off, resulting in reduced wear resistance. If the particle size exceeds 40 μm, the strength of the tool cutting edge decreases, and the tool cutting edge becomes defective. The tool life of the tool obtained in step 3 will be shortened.

A second invention is a method for manufacturing a sintered body for a tool according to the first invention. The raw materials used here and their compounding ratios are set to the carbides, nitrides, borides or mixtures thereof of transition metals of any of Groups 4a, 5a and 6a of the Periodic Table, 10 to 65% by volume of solid solutions thereof, iron. Group metal 2-30
1% or more of Al ₂ O ₃ , Y ₂ O ₃ , MgO and ZrO ₂ or more and 5 to 20% by volume, 5 to 20% by volume of cubic boron nitride having a particle size of 10 μm or less, and a particle size of 1 ~ 40μ
The reason for setting 10 to 50% by volume of fine-grained diamond of m is
It is the same as that described above.

In a third aspect of the present invention, a raw material molded substrate of cemented carbide having a basic composition of WC-Co or Mo is a main component (M).
o, W) A raw material mixture used in the second invention is laminated and arranged on a cermet raw material molded substrate composed of C and an iron group metal,
Simultaneously, these are temperature 950 ~ 1150 ℃, pressure 1 ~ 30
It was sintered and joined at kb. Cemented carbide and cermet, which are substrates, are excellent in toughness, rigidity, thermal conductivity and corrosion resistance, and are suitable for use as cutting tools. This sintered body for tools has a sintering temperature of 950 to 1150.
Since it is obtained at a low temperature of ℃, the liquid phase observed in the sintering process of ordinary cemented carbide, cermet or commercially available diamond sinter does not appear in the cemented carbide or cermet substrate, but under high pressure. In this case, the solid phase sintering is sufficient, and the bonding strength with the hard layer containing diamond is also sufficient. When the hard layer containing diamond and the substrate layer are co-sintered in this manner, the strength of the substrate layer is higher than that of the hard layer, and therefore the transverse strength, that is, the strength of the integrated body can be further increased. Further, since the substrate layer is significantly easier to process than the hard layer containing diamond, it has an advantage that the cost for producing the tool can be reduced. The thicknesses of the hard layer containing diamond and the substrate layer may be determined in consideration of economical efficiency, tool specifications and strength, but it is sufficient if each is 0.5 mm or more.

These raw material mixtures are mixed by a mixer such as a ball mill, and are mixed as a powder or after embossing, and then at a high temperature and high pressure generating device such as a HIP device and a piston cylinder device at 950 to 1150 ° C. 30 kb
Solid-state sintering in the thermodynamically stable region of graphite. As a result, the fine-grained diamond dispersed in the raw material undergoes a slight amount of phase transition from the surface due to the catalytic action of the iron group metal, and a small amount of carbon is precipitated in or on the surface of the iron group metal to strengthen the bond phase.

Both the temperature and the pressure of this sintering condition are significantly lower than those of the commercially available diamond sintered body. Thermodynamic graphite stable regions and diamond stable regions related to pressure and temperature are as shown in FIG.

If the temperature is lower than 950 ° C., the sintered body will not be densified, and if it exceeds 1150 ° C., remarkable diamond phase transition will occur, a large amount of graphite will be generated, and the wear resistance inherent to diamond will be impaired. Absent.

When the pressure is less than 1 kb, 950 to 1150
Since the binder phase does not densify in the temperature range of ℃, a high-density sintered body cannot be obtained, and when it exceeds 30 kb, sintering occurs in the diamond stable region, and therefore the toughness of the binder phase accompanying the diamond phase transition. It is not preferable because it is not converted.

In the sintered body of the present invention, a graphite peak was hardly recognized by a method such as X-ray diffraction,
By observation with a transmission electron microscope (TEM) and Auger electron spectroscopy, very fine carbon of nanometer order is projected in or on the surface of the iron group metal close to the dispersed diamond forming the bonded phase. Was recognized. Such carbon is commercially available WC-C
o It is not observed at all in the iron group metals of cemented carbide, cermet and diamond sintered bodies or on the surface thereof. The reason why the binder phase is toughened in the sintered body of the present invention has not necessarily been clarified, but it is presumed as follows. That is, by the precipitation of fine carbon, it acts as a pin to suppress the movement of the transition existing in or on the surface of the iron group metal, macroscopically stopping the progress of microcracks, and as a whole sintered body. It is considered to be toughened. See also T
According to EM observation, the size of the iron group metal crystal grains in the commercially available WC-Co cemented carbide, cermet and diamond sintered body is several hundreds of microns in the submicron to large size, whereas the sintered body of the present invention. In the case of, it is recognized that the size of the iron group metal crystal grains is made to be subgrain due to the sintering at a low temperature in which a liquid phase does not occur, and the precipitation of fine carbon makes it extremely small and below submicron. It was It is thought that this disperses the stress concentration in the iron group metal or on the surface thereof, which also contributes to the toughness. further,
The sintering conditions are the sintering temperature (14
Since the temperature and the pressure are remarkably low as compared with the sintering pressure (50 ° C. or more) and the sintering pressure (50 kb or more),
It is also possible that the amount of strain generated in the sintering process is small. This is also considered to have contributed to strengthening.

[0024]

As described above, one or two of transition metal carbides, nitrides, borides or mixtures thereof or solid solutions thereof, iron group metals, Al ₂ O ₃ , Y ₂ O ₃ , MgO and ZrO ₂ are used. Bound phase type collecting material consisting of more than one kind, and fine particles c
When a raw material mixture in which BN and fine diamond particles are uniformly mixed at a predetermined ratio is sintered at a thermodynamically stable temperature and pressure of graphite, a part of the fine diamond particles undergoes a phase transition, resulting in the formation of fine carbon. It is possible to obtain a sintered body for a tool which is precipitated in or on the surface of an iron group metal and has a toughened and strengthened binder phase, and fine particles of cBN and Al ₂ O ₃ , Y ₂ O.
₃ , MgO, and ZrO ₂ provide a sintered body for tools that has excellent high-temperature oxidation resistance and resistance to iron-based metals.

[0025]

EXAMPLE Using a binder phase forming raw material having a particle size of 1 μm or less, fine diamond and fine cBN having a particle size of 2 μm were mixed,
Mold the raw material mixture obtained by thoroughly mixing with a pot mill,
A preform having a diameter of 30 mm and a thickness of 2 mm was obtained. This molded product, with a diameter of 30 mm and a thickness of 2 mm prepared in advance
Of the cemented carbide preform of WC-15 wt% Co, and heat-treated in a vacuum atmosphere at 800 ° C.,
It was inserted into a piston cylinder type high temperature and high pressure generator. A graphite heater was used as the heating element, and pyroxene and hexagonal boron nitride were used as the solid pressure medium. The raw material mixing ratios and sintering conditions are as shown in Tables 1 to 4, and the heating and holding time was 10 minutes. Further, Tables 1 and 2 show the test results of the inventive sintered bodies, and Tables 3 and 4 show the test results of the comparative sintered bodies.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

The obtained co-sintered body of the present invention was one in which the hard layer containing diamond and the cemented carbide portion were firmly integrated. This co-sintered body was cut by electric discharge machining to prepare a cutting tool and a bending strength test piece. The tool shape is ISO millimeter nominal TNGN160304, and the bending strength test piece shape is in accordance with JIS R 1601.
The size of the test piece is 2 mm x 1.5 mm due to the size of the sintered body.
× 20mm (± 0.05mm), span is 15mm
And For comparison, a commercially available K10 type cemented carbide (Comparative Example No. 15 in Table 4) and a commercially available diamond sintered body (Table 4)
Comparative example No. 16) was prepared and processed into a similar shape.

Using the above various cutting tools obtained as a result, the cast iron (FC30) was cut under the following conditions: cutting speed: 400 m / min, feed: 0.13 mm / revolution, depth of cut: 0.2 mm, cutting oil: none. Finished surface processing was performed, and the time required for the flank wear of the various cutting tools to reach 0.2 mm was measured. The transverse rupture strength test is based on JIS R 1601.
According to the above, the three-point bending strength (kg / mm ² ) was measured and examined.

As shown in Tables 1 and 2, the sintered material of the present invention has excellent strength, toughness, acid resistance and abrasion resistance, and composition and sintering conditions outside the scope of the present invention. It is clear that it shows extremely superior cutting characteristics as compared with the comparative sintered material and the conventional sintered material.

As described above, the sintered material of the present invention has excellent strength, toughness, high temperature oxidation resistance (heat resistance) and wear resistance, and therefore is excellent when used as a cutting tool material. It exhibits excellent cutting performance.

[0034]

According to the present invention, sintering for tools satisfying all of the toughness, strength, workability, hardness, high temperature oxidation resistance, reaction resistance, wear resistance, etc. required for cutting tool materials. Since the body can be sintered in the low-pressure region, which is a thermodynamically stable region of graphite, the manufacturing cost is greatly reduced compared to conventional diamond sintered bodies, and it is an excellent sintered body for tools. Is now possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a thermodynamic graphite stable region and a diamond stable region related to pressure and temperature.

Claims (3)

[Claims] 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 10 to 65% by volume and an iron group metal in an amount of 2 to 30% by volume. %, Al ₂ O ₃ , Y ₂ O ₃ , MgO, Z
Sintered body consisting of 5 to 20% by volume of one or more of rO ₂ and 5 to 20% by volume of cubic boron nitride having a particle size of 10 μm or less and 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm. A sintered body for a tool, wherein carbon is precipitated in or on the surface of an iron group metal constituting the sintered body. 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 10 to 65% by volume of a solid solution thereof, and 2 to 30 volumes of an iron group metal. %, Al ₂ O ₃ , Y ₂ O ₃ , MgO, Z
A raw material mixture in which 5 to 20% by volume of one or more of rO ₂ and 5 to 20% by volume of cubic boron nitride having a particle size of 10 μm or less and 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm are mixed. At a temperature of 950 to 1150 ° C and a pressure of 1
A method for manufacturing a sintered body for a tool, which comprises sintering at 30 kb. 3. 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) On a substrate obtained by molding a cermet raw material composed of C and an iron group metal, 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 These solid solutions are 10 to 65% by volume, iron group metals are 2 to 30% by volume, Al ₂ O ₃ , Y ₂ O ₃ , MgO, and Z.
A raw material mixture in which 5 to 20% by volume of one or more of rO ₂ and 5 to 20% by volume of cubic boron nitride having a particle size of 10 μm or less and 10 to 50% by volume of fine diamond particles having a particle size of 1 to 40 μm are mixed. The forming plates formed by
A sintered body for a tool, which is sintered and bonded at 0 to 1150 ° C. and a pressure of 1 to 30 kb.