JPS5843463B2 - High hardness sintered body for cutting tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a high-hardness sintered body in which boron is further contained in a composition consisting of high-pressure phase boron nitride, a ceramic material, and a metal. The present invention relates to a high-hardness sintered body for cutting tools that is excellent in both hardness and cutting performance.

High-pressure phase boron nitride is wurtzite-type boron nitride (hereinafter referred to as W
BN) and cubic boron nitride (hereinafter referred to as CBN) synthesized by static ultra-high pressure generated by press pressure.
These high-pressure phase boron nitrides are highly reactive with iron, as is the case with diamond, so they are suitable for cutting iron and its alloys. Since it is suitable for grinding, it has recently attracted attention as a high-performance iron processing material.

In order to use such useful high-pressure phase boron nitride for cutting applications, for example, it is necessary to sinter the high-pressure phase boron nitride at high temperature and pressure.

However, sintering under high temperature and high pressure is industrially difficult.

Therefore, it is necessary to sinter at a lower temperature and lower pressure.

However, since high-pressure phase boron nitride has high hardness, it is difficult to sinter at low temperatures.

Therefore, we added a material that can be easily sintered at a lower temperature to high-pressure phase boron nitride, and sintered it at a lower sintering temperature than high-pressure phase boron nitride alone. Efforts have been made to improve the cutting performance of sintered bodies containing only high-pressure boron nitride.

The materials added to the high-pressure phase boron nitride for this purpose include, for example, carbides and nitrides of IVa group and Va group metals.

There are ceramic substances such as borides.

Furthermore, by mixing and sintering the metal powder with the mixed powder of the high-pressure phase boron nitride and the ceramic substance, the metal is dissolved at high temperature in the interparticle spaces between the high-pressure phase boron nitride and the ceramic substance. A solid solution or compound was created between these particles and the metal, and the metal was solidified into a sintered body.

Conventional high-pressure phase boron nitride obtained in this way.

Sintered bodies containing ceramic materials and metals can be sintered more easily at relatively low temperatures and pressures than sintered bodies containing only high-pressure boron nitride, and they also have practical hardness and resistance to cutting. Although it is abrasive, it is also possible to ease the high temperature and high pressure conditions during sintering to facilitate industrial production, and for practical purposes, high pressure phase boron nitride has even higher hardness and excellent wear resistance during cutting. It has been desired to obtain a sintered body containing.

The present invention was obtained as a result of intensive research in search of a sintered body that could meet the requirements for industrial manufacturing as well as the requirements for practical quality and properties, as described above. By further adding boron to the raw material composition of a conventional sintered body containing high-pressure phase boron nitride, a ceramic substance, and a metal and sintering it, the sintered body can be sintered at a lower temperature than the conventional sintered body, and The properties of the obtained sintered body provide a high hardness sintered body for cutting tools which has higher hardness than conventional sintered bodies and is superior in transverse rupture strength and wear resistance during cutting.

That is, the high-hardness sintered body for cutting tools of the present invention contains one or two selected from the group consisting of high-pressure phase boron nitride with a volume ratio of 10 to 80, carbides, nitrides, and borides of group IVa and group Va metals. It is obtained by adding 10 to 300 parts by volume of boron per 100 parts by volume of the metal to a composition containing 19 to 80 parts by volume of the above ceramic material and 1 to 30 parts by volume of the metal mentioned below, and sintering the composition. This is a characteristic feature.

The high-pressure phase boron nitride used in the present invention is WB as described above.
There are two types, N and CBN, and either one or a mixture of both can be used.

The mixing ratio of WBN and CBN is arbitrarily set depending on the properties of the intended high-hardness sintered body and the types of other blended raw materials.

The content of high-pressure phase boron nitride in the raw material composition of the high-hardness sintered body for cutting tools of the present invention is in a volume range of 10 to 80, and 1
If the width is less than 0, it will not be possible to have sufficient properties as a high-hardness sintered body, and if the width exceeds 80, the content of other raw materials will be relatively small, making it difficult to obtain a good sintered body. Hard to get.

The ceramic materials used in the present invention include: (1) carbides, nitrides, and borides of titanium, zirconium, and hafnium, which are Mu group metals, and carbides, nitrides, and borides of Nadium, niobium, and tantalum, which are Va group metals; One or more ceramic materials selected from the group consisting of:

The content of ceramic material in the raw material composition of the high hardness sintered body for cutting tools of the present invention is 19 to 80 volume ratio,
If the width is less than 19 or more than 80, it is difficult to obtain a good sintered body.

In addition to the above-mentioned ceramic materials, other ceramic materials, i.e., metals other than Group A and Group Va, and carbides of metals such as magnesium, aluminum, silicon, chromium, yttrium, molybdenum, tungsten, and boron. , nitrides and oxides, IVa group and Va
Group metal oxides and the like may be added to improve the properties of the high hardness sintered body for cutting tools of the present invention.

The metals used in the present invention include magnesium, aluminum, silicon, copper, manganese, iron, cobalt, nickel,
Titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten, and one or more of these are used.

The content of the metal in the raw material composition of the high-hardness sintered body for cutting tools of the present invention is in the range of 1 to 30 by volume, and if the content is less than 1 volume, the toughness is sufficient to exhibit a strong bonding effect. −
It is desirable to achieve a sintered body with a high hardness when the volume width exceeds 30.

Next, the boron used as a feature of the present invention may be either amorphous or crystalline, and its content in the high hardness sintered body is 10 to 300 parts by volume per 100 parts by volume of the metals contained. and preferably 50 to 280 parts by volume.

If the content is less than 10 parts by volume, the following effects may be exhibited; if it exceeds 300 parts by volume, the bonding effect in the sintered body of the metals contained therein will be inhibited.

By adding boron to the composition of the high-hardness sintered body for cutting tools of the present invention, it has higher hardness and superior transverse rupture strength and wear resistance during cutting than conventional high-pressure phase boron nitride sintered bodies. It has an extremely advantageous effect in terms of manufacturing technology, in that it can be made into a sintered body, and a sintered body with good hardness can be obtained even when sintered at a lower temperature than conventional sintered body compositions that do not contain boron. are doing.

The above excellent properties and effects are thought to be due to the physicochemical properties of boron.

That is, the melting point of many metals is lowered by adding boron.

This phenomenon is noticeable, for example, in the case of high-pressure phase boron nitride, diamond, or iron group metals commonly used in the sintering of cemented carbides.

In the case of cobalt, its melting point is said to be 1495° C. under normal pressure, but when about 13% by volume of boron is added, the melting point decreases to 1095° C.

Similarly, in the case of iron, the addition of about 12 parts by volume of boron lowers the melting point from 1534°C to 1150°C, and in the case of nickel, the addition of about 13 parts by volume of boron lowers the melting point from 1453°C to 1070°C. .

Thus, in addition to the advantage that boron lowers the melting point of the metal, making it fluid at lower temperatures and allowing sintering to proceed with flow of the metal in the sintered body at lower temperatures, Boron has the advantage that it combines with the IVa group metal to form a metal boride with high hardness and melting point, thereby improving the properties of the sintered body.

In other words, in carbides, nitrides, and borides of group IVa metals, strictly speaking, the chemical equivalent ratio of metal to carbon, nitrogen, or boride deviates from the value theoretically calculated from the composition of 70, and the actual value is Since the metal is in excess, the added boron combines with the unbonded Group A metal to form the above-mentioned boride with high hardness and high melting point, and at the same time, when the chemical bond is further strengthened, the sintered body Closer organization.

Furthermore, boron can be eutectic with metals such as pre-distributed metals to lower the melting point of the metal, and even without forming a compound with IVa group metals, boron itself has a high melting point and high hardness, so it can form a eutectic. However, if an excessive amount is added to a plate necessary for preparing or preparing a compound, there will be no inconvenience.

In addition, the composition of the high hardness sintered body for cutting tools of the present invention is as follows:
The metal to be added is not limited to the metal whose melting point decreases due to the addition of boron, but also a metal whose melting point increases, such as aluminum, for example.

In this case, for example, aluminum has 660
℃, so if each powder is added without forming a eutectic with boron in advance, the melted aluminum will improve the wetting of the high-pressure phase boron nitride, and the overall sintered body composition will be It is expected that it will help sintering and dissolve boron, ultimately creating a eutectic with a higher melting point in the sintered body and coexisting therein. There will be no inconvenience.

In addition, not only does it generate a eutectic of metal and boron,
Depending on the sintering conditions and the type of additive metal, adding boron may generate metal boride during sintering, which may improve the sintered strength, heat resistance, and hardness of the sintered body.

In the present invention, the advantages of adding boron to the sintered body composition are not limited to the above-mentioned effects, but also lower temperature,
Manufacturing advantages include the possibility of sintering at low pressures.

That is, when high-pressure phase boron nitride is sintered, a high-pressure phase boron nitride is not stable at high temperatures under normal pressure and undergoes a phase transformation into a soft low-pressure phase boron nitride, so a highly hard sintered body cannot be obtained.

Therefore, in order to obtain a sintered body with high hardness, it is necessary to sinter the high-pressure phase boron nitride under stable high pressure and high temperature.

As shown in Figure 1, in the stable high-pressure, high-temperature region of high-pressure phase boron nitride, the pressure increases as the temperature rises, so when sintering at a high temperature, it must be sintered at a high pressure.
On the other hand, when sintering at a low temperature, a lower pressure is sufficient.

Therefore, in the present invention, the addition of boron lowers the temperature at which the metal melts and becomes fluidized, so the sintering temperature may be lower than when boron is not added.At the same time, the load pressure during sintering also decreases. It turns out that I don't care if it's low.

This reduces the need for sophisticated technology to generate high pressures and has the benefit of extending equipment life due to reduced stress loads on the high pressure equipment.

As described above in detail, the present invention provides a sintering raw material for a sintered body containing high-pressure phase boron nitride, one or more of carbides, nitrides, and borides of group IVa and group Va metals, and a metal. By adding boron to the sintered body, a high-hardness, high-performance sintered body can be obtained under a wide range of sintering conditions. This is an industrially extremely useful invention.

Next, the present invention will be specifically explained with reference to Examples.

Example I WBN50 volume ratio, titanium carbide volume ratio, titanium nitride 17 volume ratio, nickel 2.4 volume width, molybdenum 1.6
volume%, aluminum 4 volume width, amorphous boron 8 volume width (
That is, a total of 10 g (added at a ratio of 100 parts by volume of boron to 100 parts by volume of metal) was placed in a cemented carbide Beaufret mill, 50 m of acetone was added, and the mixture was mixed for 24 hours.

All of the raw material powders used have an average particle size of 3 μm or less (the same applies to each side below unless otherwise specified).

After mixing, the raw material powder is dried to remove acetone, and then 5 parts by weight of nitrocellulose is added to give a thickness of 2 mm and a diameter of 1 mm.
The thickness of the mixed powder made of tungsten carbide 90% by weight and cobalt 10% by weight was formed into a disk shape of 0m7IL and placed in a molybdenum capsule with an outer diameter of 11mm, a height of 5.5mm, and a thickness of 0.5mm. 3 m 7 IL 1 After placing the molded body with a diameter of 101 m on top of each other, it was heated to 10" torr, 70
Degassing was performed at 0°C for 1 hour.

Immediately after the degassing treatment, the molybdenum capsule containing the raw material powder was placed in a belt-type ultra-high pressure device and heated to 155
Sintering was performed by maintaining the temperature and pressure of 0° C. and 55 kb for 15 minutes.

In this way, a sintered body in which a tungsten carbide-cobalt sintered body part (hereinafter referred to as a cemented carbide base) is firmly adhered to a high hardness sintered body part for cutting tools of the present invention containing WBN is obtained. Obtained.

Next, the surface of the sintered body part containing WBN of this sintered body was polished with a diamond grindstone to make it smooth, and the Vickers hardness was measured with a micro Vickers hardness meter, and it was found to be 3800.
It was Ky/iA.

Further, this sintered body was cut with a diamond cutting blade to create a cutting tip, and a cutting test was conducted by silver brazing the cemented carbide base side to a steel tool handle.

5KH9 grade steel heat-treated to HRC60 hardness was used as the work material, and the cutting speed was 96 m/mjn.

Depth of cut 0.2 mm, feed 0.11 mrn/rev
When it was cut as follows, it took several minutes for the flank wear to reach 0.2 mtn.

Comparative Example 1 Sintering was performed in the same manner as in Example 1 except that boron was removed from the sintering raw material composition in Example 1.

The obtained sintered body was subjected to hardness measurements and cutting tests in the same manner as in the examples.

As a result, the Vickers hardness was 9/- to 3400,
The time required for flank wear to reach 0.2 mm is 1
It was 4 minutes.

Comparative Example 2 The sintering raw material composition was the same as Comparative Example 1, and the sintering conditions were set to a pressure of 6.
Sintering was carried out in the same manner as in Example 1 except that the weight was 5 kb and the temperature was 1650°C.

The resulting sintered body was tested in the same manner as in Example 1, and the Vickers hardness was 36 ooK/-, the flank wear was Q, and the time to reach 2 mm was 22 minutes.

In other words, is it carried out with a sintering raw material composition that does not contain boron? l
Comparative Examples 1 and 2 showed that in order to obtain a sintered body with performance close to the test result of the sintered body of Example 11, higher temperature and pressure than the sintering conditions of Example 1 were required.

Example 2 The sintering raw materials were WBN 30 volume, CBN 30 volume, titanium disulfide 15 volume, tantalum carbide 10 volume, cobalt 1.2 volume, tungsten 0.8 volume, aluminum 2 volume, amorphous. Boron 11 volume factor (i.e. metal 1
The experiment was repeated in the same manner as in Example 1, except that the ratio of 275 parts by volume of boron to 00 parts by volume was used.

The resulting sintered body has a Vickers hardness of 3900 K.
g/ynm, the time required to reach flank wear of 0.2 mm was 30 minutes.

Comparative Example 3 The same experiment as in Example 2 was conducted except that the sintering raw material composition of Example 2 except that amorphous boron was removed.

The obtained sintered body has a Vickers hardness of 3500 kg/mi
So, the time it takes for flank wear to reach 0.2 mx is 14
It was a minute.

Example 3 CBN 70 volume width, tantalum carbide 12 volume ratio, vanadium nitride 9 volume ratio, nickel 2.4 volume ratio, manganese 1 volume %, molybdenum 0.6 volume %, aluminum 4 volume ratio, amorphous boron 1 volume ratio (That is, a ratio of 12.5 parts by volume of boron to 100 parts by volume of metal) was used as the sintering raw material, and an experiment was conducted under the same sintering conditions and subsequent test conditions as in Example 1.

The hardness of the obtained sintered body was Vickers hardness 3600 odor/self, and the time required for flank wear to reach 0.2 mm was 24 minutes.

Comparative Example 4 An experiment similar to Example 3 was conducted except that the composition of the sintered body of Example 3 except that amorphous boron was removed.

The hardness of the resulting sintered body was 330 Vickers hardness.
At 0 Kg/m11, the time required for flank wear to reach 0.2 urn was 18 minutes.

Example 4 The sintering experiment of Example 1 was repeated.

However, the temperature during sintering was 1400°C.

The resulting sintered body has a Vickers hardness of 3100 kg.
/vta, cutting speed 96 m/lTl1lIL, 5KDII grade steel heat treated to hardness HRC60, depth of cut 0.51
! 711. When cutting was performed at a feed rate of 0.11 ram/rev, the time required for flank wear to reach 0.2 urn was 23 minutes.

Comparative Example 5 The experiment of Example 4 was conducted using a sintered body composition excluding amorphous boron.

The obtained sintered body has a Vickers hardness of 1900 Ky/7I2
As a result of the same cutting test as in Example 4, the cutting edge broke off in a few seconds and could not withstand cutting.

Example 5 WBN 12 volumes, titanium carbide 40 volumes, aluminum 3 volumes, nickel 8 volumes, molybdenum 3 volumes,
An experiment similar to Example 1 was conducted using crystalline boron with an average grain size of 2 μm and a volume ratio of 34 (ie, a ratio of 242.9 parts by volume of boron to 100 parts by volume of metal) as a sintering raw material. went.

However, the pressure during sintering is 52'kb and the temperature is 1370''
It was quiet.

The obtained sintered body has a Vickers hardness of 2300 kVmyA, and is made of 5UJ type 2 steel heat-treated to a hardness of HRC58 at a cutting speed of 96 m/1 TILL, a cutting depth of 0.5 mm, and a feed rate of 0 and 11 mm.
When cutting with turn/rev, it took 16 minutes for flank wear to reach 0.2 mm.

Comparative Example 6 An experiment similar to Example 5 was conducted using a composition other than crystalline boron.

The resulting sintered body has a Vickers hardness of 1800 kg.
/-, the same cutting test as in Example 5 was conducted, and the time required to reach flank wear of 2 mm was less than 1 minute.

Example 6 A sintering experiment similar to that in Example 1 was conducted.

However, aluminum was removed from the sintering raw material composition of Example 1.

The Vickers hardness of the resulting sintered body is 3900K.
He was g/i♂.

When the sintered body was subjected to an X-ray diffraction test, WBN, CBN
.

In addition to titanium carbide, titanium nitride, nickel, and molybdenum, nickel boride (BNi2 tNi2BINiBNi4B
3) and molybdenum boride (BMo2).

The presence of MO82, M o B, M o B4) was observed.

Examples 7 to 11 Each sintered body was obtained by sintering using the sintering raw material composition and manufacturing conditions shown in Table 1 below.

Table 1 shows the Vickers hardness and cutting test results of each of the obtained sintered bodies.

Comparative Examples 7 to 11 Each sintered body was obtained by sintering using the sintering raw material composition and manufacturing conditions that do not contain amorphous boron as shown in Table 1 below.

Table 1 shows the Vickers hardness and cutting test results of each of the obtained sintered bodies.

Reference example 1 Sintering raw materials are WBN 30 volume, CBN 30 volume, titanium disulfide 15 volume, aluminum oxide 10 parts by volume, cobalt 1.2 parts by volume, tungsten 0.8 volume width, aluminum 2 volume width, amorphous. The experiment was repeated in the same manner as in Example 1, except that 11 parts by volume of boron (ie, a ratio of 275 parts by volume of boron to 100 parts by volume of metal) was used.

The resulting sintered body has a Vickers hardness of 4000 kg.
/mri' The time required for flank wear to reach 0.2 mm was 26 minutes.

Reference example 2 CBN 70 volume ratio, tantalum carbide 12 volume width, boron carbide 5 volume width, vanadium nitride 4 volume ratio, nickel 2.4 volume part, manganese 1 volume ratio, molybdenum 0.6 volume part, aluminum 4 volume part, non 1 part by volume of crystalline boron (ie, 12.5 parts by volume of boron per 100 parts by volume of metal) was used as the sintering raw material, and the sintering conditions and subsequent test conditions were as described in Example 1.
An experiment was conducted in the same manner.

The hardness of the obtained sintered body was 9/9 Vickers hardness 3600.
-, the time required for flank wear to reach 0.2 mm was 22 minutes.

[Brief explanation of the drawing]

FIG. 1 is a temperature-pressure relationship diagram showing the stable region of high-pressure phase boron nitride.

Claims (1)

[Scope of Claims] 1 High-pressure phase boron nitride 10 to 80 volume fraction, one or more ceramic materials selected from the group consisting of carbides, nitrides, and borides of IVa group and Va group metals 19
To a composition containing 1 to 30 parts by volume of ~80 parts by volume and one or more metals selected from the following metals, 10 to 300 parts by volume of boron is further added to 100 parts by volume of the above metals, and sintered. A high-hardness sintered body for cutting tools, which is characterized by: Metals: Magnesium, aluminum, silicon, copper, manganese, iron, cobalt, nickel, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten.