JPS6060977A - Sintered body for high hardness tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Cubic boron nitride (Cubic Boron N1tr)
icle (hereinafter abbreviated as CBN) has high hardness and excellent thermal conductivity (because it has little reactivity with iron group metals, its light viscous material is used for cutting) as an abrasive material. Attention has been paid.

The present inventors have already invented a tool sintered body that can maximize the excellent features of this CBH, and have filed a patent application for the invention.

The first of these is the periodic table IVa, Vt1+
Carbides, nitrides, borides, silicides of Via group transition metals.

Or these mutual solid solution compounds form a continuous phase and C
It combines BN crystals, and has excellent heat resistance and wear resistance, as well as high thermal conductivity even at high temperatures. This provides a sintered body for use.

In addition, the inventors conducted a single cutting test using each of these annealed axes, and found that CBN's excellent head melting resistance even in low-speed cutting where high-speed steel is used. Therefore, it was discovered that it was an extremely excellent substance, and based on this discovery, ite A I 2031 A I N+ S r c+
A patent application has been filed for a +1A hardness tool sintered body in which CBN crystals are bonded together in a continuous phase consisting mainly of S13N4°B2O, a mixture thereof, or a partner or compound thereof.

Now, the inventors, based on this second invention, < CBN+A
As a result of more detailed research using l2O3 sintered bodies,
Not only the CBN and Al2O3 content in the sintered body, but also the Cu ka line X of the Al2O3 (IIG) plane in the sintered body.
We found that the half-width in line diffraction has a close relationship with tool performance.

The present invention is filed based on this discovery.

Generally, in X-ray diffraction, the half-width of a substance depends on the crystal grain size, strain, bonding state with other substances, etc. of the substance.

Now, Figure 1 shows CB sintered under a pressure of 50 to GOkb.
N-A] Al2O3 in 203 sintered body (+'1lli)
The half width of the surface is 3ft! The half width is constant up to point B, but decreases thereafter as the sintering temperature increases. That is, between A and B, CBN-
Since almost no Al2O3 or Al2O3 reaction takes place, no decrease in the half value width is observed, but between B-0, the CBN-Al2O3 or Al2O3 reaction takes place and sintering progresses, so the half value width decreases. It is thought that the width will continue to decrease. However, when the temperature rises above point C, CBN-
AhO3 Aruiha AI 203 Comrade's Reaction Kaushi Shirumono N1 hardly shows any decrease in half value width.

On the other hand, when the same sintered body shown in Fig. 1 was ground and formed into a cutting tool, various work materials were cut. 1' 1° is o, and the one about 65° is a baked x111 body R' (is the wear condition such that the child falls off in pieces? The amount of wear after cutting for a certain period of time also increases. Ta.

Also, those of B-C (that is, half width o, 6 degrees or less)
Compared to this, the amount of wear is small.
No evidence of particles falling off after a while was observed. However, when we examine the B-C 1liij I Kawauchi in a little more detail, we find that the half-value width is 0.3° → 0.2
As the angle decreases, 11iI't[ increases, and in particular, when 1'11° is 0.14° or less, the amount of wear and tear is greater than when 1'11° is 0.2°. Next, using an Al2O3 raw material t1 powder which has the same half width as the sintered body (a) in Fig. 1 but is different from that in Fig. 1, it was also sintered under a pressure of 50 kb. When the cutting performance of the sintered body (1) was compared, both had almost the same performance.

Although it is not necessarily clear what causes the relationship between the half width and the tool performance, it can be estimated as follows.

As mentioned earlier, the half width between A and B, which has a half width of about 0.65° and does not change depending on the sintering temperature, is Al203-Al.
Since the sintering between 2O3, Al203 and CBH has hardly progressed, even if it is used as a cutting tool, it exhibits a thickness of 1 which causes particles to fall off, and the thickness increases by 1ρtL. On the other hand B-
As sintering progresses between C, the half width decreases and becomes 0.
．． When the temperature is below GOO°, good tool performance can be obtained in practice. On the other hand, since grain growth of Al2O3 progresses at the same time as the sintering phenomenon, it is thought that tool performance deteriorates when the half width is less than 0.200°. In addition, in this CBN-A 120311 structure, CBN-Al2O
It is also possible that reaction products (for example, AlB2゜AIBOx, etc.) are generated at the 3-interface, and as the sintering temperature increases by 1, the amount of these reactants increases, and because this is brittle, CBN particles are likely to fall off during cutting. .

Therefore, in order to fully exhibit the viscous ability of the iJt compact of the present invention, it is necessary to
The half width by X-ray diffraction of r-ray is o, Boo° ~ 0.20
Must be within the 0° range. Furthermore, it is a well-known fact that in order to improve the performance of a sintered body, it is necessary to make the sintered body as grainy as possible, but for this purpose it is necessary to make the grain size of the raw material powder fine. In particular, sintered bodies of various grain sizes of CBH were prepared and tested, and it was found that CBN grain sizes of 5 μm or less always exhibited good tool performance for U14. Furthermore, among the cutting performance tests for various work materials,
For cast iron material 11, the sintered body having a CBN content of 2θ to 55% by volume was particularly excellent.

When the sintered body of the present invention is used as a cutting tool, it is sufficient that the upper cutting edge is formed of a CBN-containing hard layer that is highly resistant to wear.

Therefore, it is more advantageous in terms of economy and strength of the tool to form this hard layer into an integrated composite molded metal layer made of super-alloy and bonded thereon. The thickness of the hard layer in the composite sintered body needs to be changed depending on the usage conditions as a cutting tool and the corresponding tool shape, but it is generally 0.
．． A thickness of 5 cm or more is sufficient for the sintered body of the present invention.

The cemented carbide used as the base material is preferably WCC cemented carbide, which has high rigidity, good thermal conductivity, and excellent toughness. The method for obtaining such a composite sintered body is to prepare a base alloy in a predetermined shape using cemented carbide in advance, and then add a mixed powder of CBN and Al2O3 to form a hard layer that will become the cutting edge of the tool. The hard layer is sintered and the hard layer is simultaneously bonded to the base cemented carbide.

At this time, the cemented carbide metal contains a metal such as Go as a binder phase, and when the temperature at which the binder metal appears in a liquid phase is exceeded during hot pressing, the binder metal melts. If the hard layer-forming powder contains more CBH than the sintered body of the present invention, for example, if it is made only of CBN, the CBN particles have extremely high rigidity and are difficult to deform. There are gaps between the particles, and the liquid phase of the base cemented carbide mentioned above enters into these gaps. However, in the sintered body of the present invention, A I 203 is used as a binder for CBH, and this forms a continuous binder phase in the sintered body, but Al2O3 has lower rigidity than CBN. Under ultra-high pressure, the compact becomes a compact with almost no gaps before it is deformed during pressurization and a liquid phase is generated in the base cemented carbide. For this reason, in the sintered body of the present invention, the liquid phase generated in the base cemented carbide during hot pressing under ultra-high pressure infiltrates into the hard layer, causing changes in the composition of the hard layer and 1V wear resistance. There is no decline in sexuality.

Now, the method for manufacturing this composite sintered body of Al2O3 and CBN is to first mix CBN powder and this Al2O3 powder using a means such as a ball mill, and then mold this into a predetermined shape in powder form or at room temperature. It is pressed and molded and sintered under high pressure and high temperature using ultra-high pressure equipment. The ultra-high pressure equipment used is a girdle type, belt type, etc. equipment used for diamond synthesis. A graphite cylinder is used as the heating element, and talc,
The CBH mixed powder molded body is wrapped with an insulating material such as NaCl. A pressure medium such as pyroferrite is placed around the graphite heating element. It is desirable that the sintering pressure and temperature conditions be within the stability region of cubic boron nitride shown in Figure 2, but this equilibrium line is not always known accurately and is only a guideline. . In FIG. 2, (A) shows the stability region of cubic boron nitride, and (B) shows the stability region of hexagonal boron nitride.

A very noteworthy feature of the sintered body according to the present invention, which also makes the present invention effective, is that the heat-resistant compound of Al2O3 forms a continuous phase on the structure of the sintered body. That is, in the sintered body of the present invention, the tough heat-resistant compound penetrates into the gaps between the high-hardness CBN particles and forms a continuous structure, just like the fully bent Co phase that is the binder phase in WC-Co cemented carbide. It exhibits the state of a binder phase, which gives the sintered body toughness.

The lower limit of the amount of CBN phase in the sintered body according to the present invention is 20 by volume.
It says up to %. If it is less than this, the performance as a tool that takes advantage of the characteristics of CBH will not be exhibited. Particularly, in cutting cast iron, a CBN containing amount of 55 to 20% by volume shows very excellent performance.

When considered as a tool material, particularly in a cutting tool, the crystal grain size of the sintered body is desirably several microns or less, as described above. Fine powder of several microns or less than a micron contains a considerably large amount of oxygen. Generally, most of this oxygen exists on the powder surface in the form of a compound similar to hydroxide. This hydroxide-like compound comes into contact with the gas during heating and comes out as a gas. jf&#
When the substance to be treated is not sealed, it is not difficult to vent this gas to the outside of the system.

However, when sintering is carried out under ultra-high pressure as in the present invention, it is almost impossible for the generated gas to escape out of the rEJj system. Generally, in such cases, it is common knowledge in the powder metallurgy industry to perform degassing treatment in advance, but if the degassing treatment lKk +U cannot be made sufficiently high, it is only necessary. This case corresponds to exactly that. That is, when considering the transformation of CBN into a low pressure phase, there is a limit to the applied fJζ temperature.

The degassing process of fine powder involves various stages of υ as well as temperature. First, at low temperatures, physically adsorbed substances and endothermic moisture are removed. Then the chemisorbed and hydroxide fraction M occurs. At the end, oxide remains. In the case of CBH, it is stable up to about 000°C in summer, so it can be heated to at least this temperature in advance.

Therefore, it can be considered that if the gas is degassed and heated in advance, the residual gas components remain in the form of oxides. Conversely, it is preferable to leave as much of the gas component as possible in the sintered body (since there is none), it is preferable to remove all water and hydrogen as a preliminary treatment.

In the present invention, based on this idea, all degassing treatments are carried out in vacuum at temperatures above 1000°C. In addition, the cup according to the present invention is used in the synthesis of CBN in the form of a viscous substance, and it is also possible to use elements believed to be soluble in hexagonal boron nitride and CBN at high temperatures and high pressures, such as alkali metals such as Li, 9Mg, etc. alkaline earth metals, P, Sn, Sl).

It may also contain compounds such as AI+Cd, Si, MgO, and AIN as additives.

CBN used as a raw material for the sintered body of the present invention is synthesized under ultra-high pressure using hexagonal boron nitride as a raw material. Therefore, there is a possibility that hexagonal boron nitride remains as an impurity in the CBN powder.

Furthermore, even when sintering under ultra-high pressure, the CBN particles are subjected to external pressure hydrostatically until the &+-joints penetrate between the individual particles of CBH. There is also a possibility that reverse transformation to type boron nitride occurs. In such cases, it is believed that the addition of an element that has a catalytic effect on the hexagonal boron nitride as described in 1111 to the mixed material has the effect of preventing this reverse transformation.

The sintered body according to the present invention has high hardness and strength.
It has excellent heat resistance and abrasion resistance, and is suitable for IV↓ applications such as wire drawing dies, leather 9-diameter dies, drill pits, etc. in addition to cutting tools.

Examples will be described below.

In all of the examples, cubic boron nitride (CBN) is used as the base material, but a part of the CBN is made of wurtzite boron nitride (WB
N) or by replacing i& with diamond, the same result as wa can be obtained.

Example 1 CBN powder with an average particle size of 2μ and Al2 with an average particle size of 1/l
O3 powder was blended at a volume ratio of 45% and 55%, respectively, and thoroughly mixed in a mortar. This powder was filled into a stainless steel container with an inner diameter of 10.0 W and an outer diameter of 14.0 mm, and a WC-15%C with an outer diameter of 9.91 mm and a thickness of 3W.
A disk of O alloy was placed on top of it. Furthermore, 1100 on top of that
Mesh + 200 menonyu iron powder embossed outer diameter 10.
Place a molded body with air permeability with a thickness of 0 mm and 2 mm, plug a stainless steel cylinder, place a pure copper plate on the cylinder, and place the whole body in a vacuum furnace under a vacuum of 10-'torr for 1000 m
°C and held for 1 hour to degas, then reduce the temperature to 1
The temperature was raised to 100°C and held for 10 minutes to impregnate the green compact with copper and keep the raw powder in an airtight state.

This was charged into a Girl type ultra-high pressure device. Pyroferrite was used as the pressure medium and a graphite cylinder was used as the heater. Note that NaCl was used between the graphite heater and the sample.
The IQ level was increased. First, the pressure was increased to 55 kb, and then the temperature was increased to 41 λ degrees to 1100 degrees Celsius, held for 20 minutes, and then the temperature was lowered and the pressure was gradually lowered. The obtained sintered body had an outer diameter of about IO+im-, a thickness of about 1 ml, and was WC-1.
It was firmly attached to the 5% CO cemented carbide.

This is Diasen 1! The back surface was ground with a whetstone and polished using diamond paste. When the sample before polishing was observed using an optical microscope, it was found that Al2O3 had penetrated between the CBHs, forming a completely dense structure. The half-value width of the Al2O3 (JIG) surface of the sintered body was measured by diffraction of Cu Ka rays and was found to be 0.525'. In addition, the hardness of the sintered body was measured at 1ltl using a microbi-Nocas hardness tester.
+ Established. The average value of hardness was 3400.

The sintered body was cut using a diamond cutting blade to create a cutting tip, which was brazed to a copper support.

For comparison, a JIS classification I (cutting of the same shape with 10 cemented carbide) was created.The workpiece H was Fe12 (iTj
I used Tano 1υ. The hardness of the work material is H+u+220
It is.

The cutting strip 11 has a lino cutting speed of 100 m/mm, depth of cut of 0.2 mm + feed of 0, I n + Il / I' e
It was set to V. In this article, the cutting test was carried out using KIO.
The roughness of the machined surface was I 5 thn Rmax, whereas the roughness of the alloy according to the present invention was 4 um Rmax, and even after 120 minutes of cutting, the roughness of the machined surface was 6 μm R + aX, which was slightly worse. Further, when the cutting edge of the tool after cutting was observed, there was a strong residue on the cutting edge of the tool on the rake face of the tool with KIO, but this was not observed at all with the sintered body of the present invention.

Example 2 CBN powder and Al2O3 powder were mixed in the composition shown in Table 1. The average particle size of the Al2O3 powder used was 1μ.

These mixed powders were pretreated in the same manner as in Example 1, and then sintered under the conditions shown in Table 1 using an ultra-high pressure device. The heating holding time was 20 minutes in both cases.

Table 1 Table 2 shows the results of measuring the half-width by diffraction of Cu Ka rays on the Al203 (grain 6) surface of these sintered bodies and the results of the cutting test. In addition, for the cutting test, the work material FC2
Five types of cast iron materials with hardness HR [1250, outer diameter +50cm, inner diameter 70+1111] were used, and the cutting speed was 4.
00m7 mm, depth of cut 0.111111. Feed 0.
15111111 / r eV for 15 minutes For comparison, a commercially available ceramic tool mainly composed of Al2O3 (autoceramic) and an Al2O3 ceramic tool containing TiC (
The test results for black ceramics have also been added to Table 2. A(
The half width of the 203(IIG) plane is o, e o o'~
It was found that the sintered body of the present invention at an angle of 0.200° has excellent cutting performance.

Example 3 2% by weight of MgO powder with an average particle size of 1 μm was added to Al2O3 powder with an average particle size of 1 μm, and 5θ% by volume of CBN powder with an average particle size of 4 μm was added thereto. 2% camphor was added to this mixture f5), and the outer diameter was 10 mm and the crystallinity was 1.5+++i.
Embossed and molded. After putting this in a Mo container and degassing, it was sintered in the same manner as in Example 1, and the outer diameter was 10 m.
A sintered body having a thickness of 1 mm and a thickness of 1 mm was obtained.

However, the pressure during sintering was 50 kb and the temperature was 1300°C. At this time, the half width of the Al2O3 (118) plane is 0.3
It was 80. The sintered body was cut using a diamond cutting blade to prepare cutting chips, and the cutting performance was compared with that of a commercially available cold-pressed ceramic squeegee mainly composed of A'1203. FC20 was used as the work material, and the cutting speed was 400 m/
min, depth of cut 2 +1111. Cutting was performed for 30 minutes at a feed rate of 0.36 mm/rotation. The flank wear width of commercially available ceramics is 0.
30, whereas that of the sintered body of the present invention was 0.2.
It was 0 Sesaku.

Example 4 An average particle size of 0.5 by weight was added to Al2O3 powder with an average particle size of 1μ.
Add 10% of μ AIN powder and add C of average particle size 5μ.
45% by volume of BN powder was blended. After putting this in a Mo container and degassing it, the pressure was 55°C in the same manner as in Example 1.
kb, i'U degree Sintered at 1250°C. Al in the sintered body
The half width of the 2O3(II[i) plane was determined to be 0.400° by diffraction of Cu Ka rays. This sintered body was cut using a diamond cutting blade to prepare a cutting tip, and FC35 was cut for 15 minutes at a cutting speed of 30 G+n/min, a depth of cut of 1 step, and a feed rate of 0.36 mm/rotation.

For comparison, a cutting test was also conducted on Al2O3 ceramic containing TiC. As a result, while the flank wear width of the Ichi 1u ceramic was 0.45 mm, that of the sintered body of the present invention was O, IOn+11.

[Brief explanation of drawings]

Figure 1 is baked under a pressure of 50 ~ Go kb! -, Shita CB
N-Al2O3 (J'6 quenching temperature and A in the sintered body
This figure shows the relationship between the F411i width in the Cu Ka line X-ray diffraction of the l203 (116) plane, in which (a) shows the 1200″Cift, and (b) shows the Al2O3 raw material powder used. Fig. 2 shows the manufacturing conditions of the sintered body of the present invention.
Figure # Temperature (6C)

Claims (1)

[Claims] 1. Contains 55 to 20% by volume of cubic boron nitride,
In a sintered body in which the remainder consists of Al2O3 and this remainder forms a connected phase in an anti-viscous Ill weave, the Al in the sintered body
(+1[
i) The half width of the surface is 0. 11. A high-hardness viscous material for use in hardened steel tools, characterized in that the particle size of cubic boron nitride is in the range of GOO° to 0.200° and is 5 microns or less. 2. Claim 1 or 2, which has a thickness of 0.5+im or more and is directly joined to an alloy made of cemented carbide.
A sintered body for high-hardness tools as described in .