JPS6246510B2 - - Google Patents

Description

[Detailed description of the invention]

Cubic boron nitride (Cubic BN, abbreviated as CBN) is a material with the second highest hardness after diamond.
Synthesized under ultra-high pressure and high temperature. Currently, CBN is already used as an abrasive grain for grinding, and CBN is also used for cutting purposes.
Sintered bodies made by bonding metals such as Co with metals are used in some cases. When this sintered body of CBN bonded with metal is used as a cutting tool, the wear resistance decreases due to the softening of the bonded metal phase at high temperatures, and the workpiece metal easily adheres to the tool, resulting in damage to the tool. There are some drawbacks. The present invention is a new material suitable for cutting tools in which a binder phase is a hard metal compound with high strength and excellent heat resistance, rather than a sintered body bonded with such metals.
This relates to CBN sintered bodies. The inventors first developed CBN into carbides, nitrides, and boron of group 4a, 5a, and 6a metals of the periodic table as a sintered body for tools that takes advantage of CBN's characteristics of high hardness and extremely high thermal conductivity. We have developed a highly hard sintered body for tools bonded with compounds consisting of oxides and silicides, and have applied for patents (Japanese Patent Application No. 154570, 1983).
No. 54666). The inventors further prototyped sintered bodies with a wide range of compositions and conducted performance tests on tool materials particularly suitable for cutting high-hardness steel and cast iron. As a result, we have arrived at the present invention. Conventionally, hardened steel with a hardness of HRc45 or higher was mainly cut using a grindstone using Al ₂ O ₃ or SiC-based abrasive grains.
CBN was developed as an abrasive grain for cutting such high-hardness materials, and is used for grinding already hardened tool steel. Grinding generally removes less workpiece per unit time than cutting, and processing efficiency is low. Further, when comparing processing machines such as lathes and grinders, grinders are generally more expensive, and combined with lower processing efficiency, the overall processing cost is higher. However, until now there has been no tool that can cut workpieces with a hardness of HRc45 or higher under practical conditions. The aforementioned commercially available sintered bodies made by bonding CBN with metals such as Co can be used to machine high-hardness materials that conventionally rely on cutting, but when actually tested, It still lacks heat resistance and wear resistance, and cannot be said to have sufficient practical performance as a cutting tool for high-hardness steel or cast iron. The inventors have developed CBN, which was disclosed in a previous application (Japanese Patent Application No. 154570/1982), as a tool for cutting high-hardness steel and cast iron, using various compounds of metals in groups 4a, 5a, and 6a of the periodic table. As a result of prototype bonded sintered bodies and performance tests, we found that among these compounds, carbides and nitrides are suitable as bonding materials, and in particular Ti, Zr, which are group 4a metals of the periodic table, It has been found that a material mainly composed of Hf carbide, nitride, or a mutual solid solution or mixture of these has the best wear resistance. These compounds are used as the main wear-resistant components of cermets for cutting tools currently on the market, and in the present invention they are used as binders for CBN with even higher hardness. When cutting a highly hardened material such as hardened steel, the stress applied to the tool edge is higher than when cutting ordinary steel under the same conditions, and the temperature of the tool edge also becomes higher.
When cutting with a tool material such as WC-based cemented carbide or TiC-based cermet that has a metal binder phase such as Co, these tool materials lack high-temperature hardness and the cutting edge deforms and breaks. Ceramic tools, which are mainly composed of Al ₂ O ₃ and do not contain any bonding metals, are relatively suitable for cutting such high-hardness steel and cast iron, but they lack toughness.
If the stress applied to the cutting edge changes during cutting, the tool will be severely damaged. Furthermore, when machining hardened steel or the like, generally the dimensional accuracy and surface roughness of the workpiece are required to have an accuracy comparable to machining. In particular, in order to improve the machined surface roughness, it is advantageous to sharpen the cutting edge angle of the tool so that it has good cutting quality, but Al ₂ O ₃ ceramics lack toughness, so it is difficult to sharpen the cutting edge. If used as a base, it will break and it will be difficult to obtain a good machined surface roughness. The sintered body of the present invention improves the drawbacks of conventional tool materials, and is made of a tough sintered body for tools that combines CBN, a highly hard and wear-resistant component, with a compound that is highly heat resistant and wear resistant. It provides unity. Furthermore, the inventors conducted detailed experiments on the relationship between CBN content in the sintered body, grain size, and cutting performance, and found that when cutting high-hardness steel, cast iron, etc.
It was found that CBN content and particle size greatly affect cutting performance. Figure 1 shows CBN using TiN as a bonding material.
The graph shows the correlation between the content of and the wear resistance when cutting hardened steel with a hardness of HRc60. The CBN grain size in the sintered body has an average grain size of 3μ, and Al is added to the binder for the reason described later to form a compound containing Al such as an Al-Ti intermetallic compound. CBN has higher hardness than TiN and is thought to have better wear resistance. Therefore, it is thought that the higher the CBN content, the better the wear resistance of tools for cutting hardened steel, etc. However, in reality, as shown in Figure 1, when TiN is used as a binder, CBN
The one with a content of 60% by volume has the best wear resistance, and if the content is more than 60%, the wear resistance becomes worse. The reason for this is still not fully elucidated, but
One reason is that when the CBN content exceeds 70% by volume, the CBN grains come into contact with each other, and in this case, it is good if the bonding strength of the CBN grain boundaries is sufficiently strong, but if this is not the case, the shear stress applied during cutting It is thought that this causes cracks in the grain boundaries and the CBN particles fall off. In the sintered body of the present invention, Ti, Zr, and Hf are used as binders.
The bonding strength between carbide, nitride crystals and CBN particles is
This is thought to be stronger than the bond strength between CBN grains,
It is thought that the maximum value of wear resistance occurs in the composition range where these binders can exist as a continuous binder phase between CBN particles. Furthermore, commercially available CBN sintered bodies made of Co-based metal as a binder are estimated from the structure to be approximately 85
% by volume of CBN, the sintered body of the present invention has significantly improved wear resistance. Note that when the CBN content is less than 30%, the wear resistance is comparable to that of commercially available CBN sintered bodies. Figure 2 shows a sintered body using TiN as a binder with a constant CBN content of 60% by volume, and the wear resistance was evaluated when only the particle size of CBN was changed. The finer the average particle size of CBN in the sintered body, the smaller the amount of wear. The particle size of CBN affects not only the wear resistance but also the machined surface roughness of the workpiece. As a result of experiments, it was found that when the particle size of CBN is coarse, the machined surface roughness of the workpiece becomes rough. When the sintered body of the present invention is used to cut hardened steel, which is currently being processed by grinding, the roughness of the machined surface naturally becomes a problem. According to experiments conducted by the inventors, the average particle size of CBN is 10% in terms of the required performance for both wear resistance and machined surface roughness of the workpiece.
There is no practical problem if it is less than μm, but if it is less than 3 μm,
It has been found that extremely excellent performance can be achieved if it is less than m. Now, the method for manufacturing a sintered body of CBN and a heat-resistant compound selected in this way is to first start with CBN.
powder and one or two of these heat-resistant compound powders
The seeds or more are mixed using means such as a ball mill, and this is pressed into powder form or molded into a predetermined shape at room temperature, and sintered under high pressure and high temperature using an ultra-high pressure device. 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,
Pack an insulating material such as NaCl and wrap the CBN mixed powder embossed body. A pressure medium such as pyrofluorite is placed around the graphite heating element. It is desirable that the sintering pressure and temperature conditions be within the stable region of cubic boron nitride shown in FIG. 3, but this equilibrium line is not always accurately determined and is only a guideline.
Further, conditions can be changed depending on the type of heat-resistant compound to be combined with CBN. A very noteworthy feature of the sintered body according to the invention, which makes the invention useful, is that the heat-resistant compound 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 bond, just like the metal Co phase that is the binding phase in WC-Co cemented carbide. exhibits a state of phase,
This imparts toughness to the sintered body. One of the reasons why carbides, nitrides, and their mutual solid solutions of Ti, Zr, and Hf are particularly excellent as the binder phase heat-resistant compound of the present invention is that, taking nitrides as an example, nitrides of these metals is expressed in the form MN ₁ ±x (M indicates a metal such as Ti, Zr, or Hf, and x means the presence of an atomic vacancy or a relative excess of atoms) on the MN phase diagram. It has a wide range of existence. As a result of trial production of sintered bodies using materials with various values of x in MN ₁ ±x as raw materials for the sintered bodies, it was found that the sintering properties were particularly excellent when the value of x was within a certain range. The reason for this will be discussed below. When considered as a tool material, especially for cutting tools, it is desirable that the crystal grain size of the sintered body is several microns or less, and in order to obtain such a crystal grain size,
The CBN particle size of the raw material must be finer than this. Micron or sub-micron fine powder contains a fairly large amount of oxygen. Generally, most of this oxygen exists on the powder surface in the form of a compound approximately in the form of hydroxide. This hydroxide-like compound decomposes when heated and comes out as a gas. When the material to be sintered is not sealed, it is not difficult to get this gas out of the system. However, when sintering is performed under ultra-high pressure as in the present invention, it is almost impossible for the generated gas to escape outside the heating system. Generally, in such cases, it is common practice in the powder metallurgy industry to perform a degassing treatment in advance, but this becomes a problem if the degassing treatment temperature cannot be made high enough. This case corresponds to exactly that. That is, when considering the transformation of CBN into a low-pressure phase, there is an upper limit to the heating temperature. The degassing process of fine powder involves the following stages depending on the temperature. First, at low temperatures, physically adsorbed substances and hygroscopic water are removed. Decomposition of chemisorbed substances and hydroxides then occurs. At the end, oxide remains. In the case of CBN, it is stable up to about 1000℃, so
It can be preheated to at least this temperature. 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, since it is desired that gas components remain in the sintered body as little as possible, it is preferable to remove all water and hydrogen as a preliminary treatment. In the present invention, all degassing treatments at temperatures of 1000° C. or higher are performed in vacuum based on this idea. The reason why a good sintered body can be obtained when MN ₁ ±x is added is considered as follows. That is, oxides, probably in the form of B ₂ O _{3 ,} are present on the CBN powder surface. When this B ₂ O ₃ reacts with M corresponding to the (-x) portion of MN ₁ ±x, the reaction is B ₂ O ₃ +4M→MB ₂ +3MO, and no gas is generated. MO has the same crystal structure as MN and forms a mutual solid solution. This is thought to be the reason why Ti, Zr, and Hf nitrides represented by MN ₁ ±x exhibit particularly excellent sinterability.
This is true not only for nitrides but also for carbides represented by MC ₁ ±x, carbonitrides represented by M(C,N) ₁ ±x, or the above-mentioned compounds containing two or more metals as M. The same can be said about The inventors are MN ₁ ±x, MC ₁ ±x, M(C,N) ₁ ±x
When a compound of Ti, Zr, and Hf is shown in the form ( ₁ ±
It was confirmed that the sinterability is excellent when these compounds having a value of x) of 0.97 or less are used as raw materials. The sintered body according to the present invention uses the above-mentioned heat-resistant compound as a binder for CBN, but may also contain a metal phase other than the heat-resistant compound such as Ni, Co, Fe, etc. as a third phase if necessary. It's okay. However, the main component of the binder phase is a heat-resistant compound phase, and the volume ratio of these metal phases in the sintered body must be equal to or less than the amount of the heat-resistant compound phase. If it exceeds this range, the heat resistance and wear resistance of the sintered body will decrease, and the performance as a tool will be lost. In addition, the sintered body of the present invention contains elements that are used in the synthesis of CBN and are believed to have solubility in hexagonal boron nitride and CBN at high temperatures and high pressures, such as alkali metals such as Li, alkalis such as Mg, etc. Earth metals, Pb, Sn, Sb,
It may also contain Al, Cd, Si, etc. 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. In addition, even when sintering under ultra-high pressure, the CBN particles do not receive external pressure hydrostatically until the binder penetrates between the individual CBN particles, and the heating during this time causes them to form hexagonal crystals. There is also the possibility of metamorphosis to boron nitride. In such a case, it is thought that if an element having a dissolvating effect on the above-mentioned hexagonal boron nitride is added to the mixed powder, there is an effect of preventing this reverse transformation. Based on this idea, the inventors conducted experiments to confirm the effect particularly on Al and Si. As an example of a method for adding Al and Si, using a group 4a nitride, in this compound MN ₁ ±x, ( ₁ ±x) is 0.97.
Add a predetermined amount of Al or Si or both to the following, mix, and then heat to 600℃ or higher in a vacuum or inert atmosphere to remove a relative excess of M of MN ₁ ±x.
Intermetallic compounds that exist on the M-Al, M-Si phase diagram by reacting Al or Si (for example, when M is Ti)
TiAl ₃ , TiAl, etc.) was produced, and this powder was used as a binder material to be mixed with CBN. In this method, the added Al and Si are uniformly dispersed in the binder, and the effect can be achieved even with a small amount of addition. Another method is to use M-
Al, M--Si intermetallic compound powder may be prepared and added at the time of mixing the raw materials, or Al and Si powder may be added. This also applies when the binder compound is a carbide or carbonitride. We compared the sintered body created in this way to which Al and Si were added and the sintered body that did not contain these. When a sintered body is polished and its structure is observed, it is found that the sintered body containing Al and Si has less peeling of CBN particles on the polished surface than the sintered body, and the bond strength between the CBN particles and the binder phase is stronger. it is conceivable that. Also, when comparing the performance as a cutting tool,
The steel containing Al and Si was superior in both wear resistance and toughness. Incidentally, such an effect appeared when the sintered body contained Al or Si in an amount of 0.1% or more by weight. In particular, when Al is included, the M--Al intermetallic compound formed in the binder phase has high heat resistance and toughness, and has the effect of improving the toughness of the sintered body. However, wear resistance is inferior to CBN and carbides and nitrides of Ti, Zr, and Hf, which are the main components of the binder phase. Abrasion resistance decreases. When using the sintered body bonded to the cemented carbide base material of the present invention as a cutting tool, the high-hardness sintered body made of CBN and a heat-resistant compound may be brazed directly to a steel tool support, or It can be used by brazing the tip of a manufactured throw-away tip. CBN itself has poor wettability with ordinary silver or copper solder. Therefore, the higher the CBN content, the more difficult it is to braze. The sintered body of the present invention has a CBN content of 30% by volume.
% or more and less than 70%, and the bonded phase is 4a of the periodic table,
It is mainly composed of carbides, nitrides, and carbonitrides of group 5a and 6a metals, which form a continuous binder phase in the structure. This binder phase has good wettability to silver solder and copper solder, and therefore, the sintered body of the present invention can be brazed by a conventional method. However, when the sintered body of the present invention is used as a cutting tool, it is only necessary that a CBN-containing hard layer with high wear resistance forms the cutting edge of the tool. Therefore, it is more advantageous in terms of economy and strength of the tool to form this hard layer into a composite sintered body made of cemented carbide as a base material and bonded thereon. The thickness of the hard layer in the composite sintered body needs to be changed depending on the conditions of use of the cutting tool and the corresponding tool shape, but generally speaking, if the thickness is 0.5 mm or more, the sintering of the present invention will be effective. In the case of the body, it is sufficient. The cemented carbide used as the base material is preferably a WC-based cemented carbide, which has high rigidity, good thermal conductivity, and excellent toughness. The method for obtaining such a composite sintered body is to first prepare a base alloy in a predetermined shape using cemented carbide, and then use CBN and a heat-resistant compound to form a hard layer that forms the cutting edge of the tool. The resulting mixed powder is placed in powder form or pressed and molded, and the whole is hot-pressed in an ultra-high pressure device to sinter the hard layer, and at the same time, bond this to the base cemented carbide. At this time, the cemented carbide base material contains a metal such as Co as a binder phase, and when the limit of the liquid phase of the binder metal is exceeded during hot pressing, the binder metal melts. The content of CBN in the hard layer-forming powder is higher than that in the sintered body of the present invention, for example, when it consists only of CBN, the CBN particles have extremely high rigidity and are difficult to deform. It has a gap, into which the liquid phase of the base cemented carbide mentioned above enters. However, in the sintered body of the present invention, CBN binders are those of 4a, 5a, and 6a of the periodic table.
Group metal carbides, nitrides, and carbonitrides are mainly used, and these form a continuous binder phase during sintering.
It has lower rigidity than CBN, and under ultra-high pressure, it deforms during processing and becomes a compact with almost no gaps before a liquid phase forms in the base cemented carbide. For this reason, in the sintering of the present invention, the liquid phase generated in the base cemented carbide during hot pressing under ultra-high pressure invades the hard layer, changing the composition of the hard layer and reducing wear resistance. There's nothing to do. In addition, carbides, nitrides, and carbonitrides of metals from groups 4a, 5a, and 6a of the periodic table, which are the binder phase of the sintered body of the present invention, are used as the main hard wear-resistant components of cemented carbide and cermet. As can be seen from the above, it is a bonding metal in cemented carbide.
It has high affinity for iron group metals such as Co,
In the sintered body of the present invention, since these compounds form a continuous binder phase in the sintered body, strong adhesive strength can be obtained at the bonding interface with the base cemented carbide. As mentioned above, the sintered body of the present invention has excellent performance as a cutting tool for hardened steel, high hardness cast iron, etc. In particular, the hardness of structural carbon steel, alloy steel, case hardening steel, bearing steel, etc. used for machine parts, etc.
High hardness component materials heat treated to HRc45~65,
It is suitable for cutting of carbon tool steel, alloy tool steel, high-speed steel, and other materials that have been heat treated to a hardness of HRc45 to HRc 66, which are used for molds and tool materials, and can replace the conventional grinding process. It is possible to cut with efficiency and high precision. Furthermore, rolls of chilled cast iron, ductile cast iron, cast steel, forged steel, and hardened materials used for rolling wire rods and plates, as well as rolls of adamite and grain rolls with a hardness of approximately HRc40 or more, are cut using conventional cemented carbide or ceramic tools. When applied to items that have been previously machined, it has extremely superior performance, allowing several times higher efficiency than conventional tools, and tool life being 20 to 50 times longer. The present invention will be specifically explained below using examples. Example 1 TiN _0.73 powder with an average particle size of ₁ μm by ball milling using cemented carbide balls and an average particle size of 30 μm
Al powders were blended at a weight ratio of 90% and 10%, respectively, and mixed using a V-type blender. This mixed powder was pressed into a beret at a pressure of 1 t/cm ³ , heated to 1000° C. in a vacuum furnace, and held for 30 minutes. When this was crushed into powder and examined by X-ray diffraction, diffraction peaks that appeared to be TiAl ₃ , TiAl, and Ti ₂ AlN were obtained in addition to TiN, and no metal Al was detected. This TiN powder containing the Al compound and CBN powder with an average particle size of 3 μm were mixed in the proportions shown in the table below.

[Table] Among the mixed powders, 2% camphor was added to powders D and E, and the mixture was pressed to have an outer diameter of 10 mm and a height of 1.5 mm. This was inserted into a stainless steel container. This container was placed in a vacuum furnace at a vacuum of 10 ^-4 mmHg.
Degassed by heating to 1100°C for 20 minutes. This was loaded into a guardrail type ultra-high pressure device. Pyrofluorite was used as the pressure medium, and a graphite cylinder was used as the heater. Note that NaCl was filled between the graphite heater and the sample. First, apply pressure
The temperature was raised to 55 Kb, and later the temperature was raised to 1100°C and held for 20 minutes, then the temperature was lowered and the pressure was gradually lowered. The obtained sintered body has an outer diameter of approximately 10 mm and a thickness of approximately 1 mm.
It was hot. This was ground to a flat surface using a diamond grindstone, and further cut using a diamond cutting blade to create a cutting chip, which was brazed to a steel support and used as a comparison material. Furthermore, a cemented carbide disk of WC-10% Co composition with an outer diameter of 9.8 mm and a thickness of 3 mm was placed in a stainless steel container, and powders A to I in Table 1 were filled on top of the disk. After degassing by heating at 1100°C in vacuum for 20 minutes, it was sintered at a pressure of 50 Kb and a temperature of 1200°C for 15 minutes. As a result, a sintered body with an outer diameter of 10 mm and a thickness of 1 mm bonded to the cemented carbide was obtained. Next, this sintered body was cut using a diamond cutting blade, the cemented carbide surface of this was brazed to a steel support, and bits A to I for cutting were made. Cutting steel with hardness HRc60 with SCM21 type at 100m/min, depth of cut 0.3mm, feed 0.15mm/
Cutting with rev for 30 minutes. For comparison, chips having compositions D and E that were not bonded to a cemented carbide base material were also tested. Table 1 shows the results obtained in the Examples of the present application. In addition, the brazed part of D, which was tested as a comparative example, came off in 10 minutes, and the brazed part of E came off in 15 minutes. Sintered body C
When the surface of the CBN sintered body was examined by X-ray diffraction, in addition to CBN and TiN, small amounts of TiAl, TiAlN,
AlN and _TiB2 were detected. Example 2 A mixed powder was prepared using CBN raw material powders having different average particle sizes and having the composition shown in Table 2. The TiN--Al compound powder mixed with CBN was the one obtained in Example 1.

[Table] As in Example 1, a cemented carbide disk was placed in a stainless steel container, and the mixture was filled therein and hot pressed under ultra-high pressure to obtain a sintered body. A cutting chip was made from this and its performance was investigated using SNCM grade 9 steel. The hardness of the work material is HRc60, and the cutting conditions are cutting speed 150m/min, depth of cut 0.2mm,
The feed was set to 0.12 mm/rev. Figure 2 shows the tool flank wear width after cutting for 15 minutes. In addition, the average particle size of 3 μm prepared in Example 1
Sintered body F using CBN raw material was also tested at the same time. As shown in Figure 2, the finer the CBN particle size, the better the wear resistance. Furthermore, after polishing the sintered bodies using diamond paste, we observed their structures with an optical microscope, and found that both the F and JKL sintered bodies had a structure in which CBN particles were bonded with TiN containing an Al compound. The phase formed a continuous phase in the structure, and the particle size of the CBN particles in the sintered body was approximately the same as that of the raw CBN particles. Using sintered body K as an example, the behavior of Al in the sintered body was investigated in more detail. Figures 4, 5, and 6 are photographs of a portion of a typical structure of the polished surface of the sintered body K, analyzed using an X-ray microanalyzer. First of all, Figure 4 is a reflected electron beam image magnified 4000 times, and the individual particles that appear black in the photograph are clearly visible.
It is CBN. The TiN-Al compound, which is the bonding phase of CBN, appears gray. Note that there is a white region in the outer periphery of the CBN particles and in the binder phase, but as will be described later, this is the W element, which was contained in the raw material TiN. Figure 5 shows Al (B--
This is the result of analyzing the relative concentration distribution of B' line) and Ti (CC' line). For both lines B-B' and C-C', the upper direction of the photograph is the direction in which the density is higher. This shows that Al and Ti are distributed in the binder phase of CBN particles with almost similar concentration trends. This Al―Ti
It is more characteristic X-ray than a compound, and Ti is TiN and Al-Ti
It is a more characteristic X-ray than a compound. Figure 6 shows Al (B-B' line) on line A-A', which is the same location as Figures 4 and 5, and the same position as Figure 5;
It shows the distribution of W (C-C' line). W was contained in the raw material TiN powder, and was contained in the sintered body in an amount of about 1% by weight. What is noteworthy is that the concentration of W increases near the CBN particles. In order to study this phenomenon, we used the same CBN raw powder as the sintered body K.
CBN by volume without adding Al using TiN raw material powder
We prototyped a sintered body containing 60%. Although it was heated to 1100°C for 20 minutes at the same pressure as sintered body K at 55 Kb, a dense sintered body could not be obtained in this case, so the sintering temperature was raised to 1300°C to create a sintered body. This material was analyzed in the same way as sintered K, and the results are shown in Figures 7 and 8.
It is a diagram. FIG. 7 is a reflected electron beam image corresponding to FIG. 4, and the black particles are CBN. W is dotted in white in the gray TiN bonded phase. Figure 8 is the 7th
W(C-
The concentration distribution was investigated using characteristic X-rays of C' line) and Ti (B-B' line), and as seen in Figure 6 in sintered body K, the W contained in TiN was found near the CBN particles. There is no phenomenon of enrichment. When Al is included, the W element migrates at low temperatures (1100°C), and it is presumed that a liquid phase was partially formed during sintering. This is thought to improve sinterability when Al is included. Example 3 Using CBN powder with an average particle size of 3μ, each powder was blended into the composition shown in the table below.

[Table] These respective powders were mixed, and as in Example 1, the cemented carbide disk and powder were placed in a stainless steel container and sintered under a pressure of 55 Kb at a temperature range of 1200 to 1300°C. . This sintered body was cut to make a cutting chip and a performance test was conducted. The work material used was hardened steel equivalent to die steel SKD11 with a hardness of HRc65. Cutting conditions are speed 80
m/min, depth of cut 0.2mm, feed 0.06mm/rotation. The flank wear width for each composition of sintered body is
The cutting time to reach 0.2 mm was as follows.

[Table] The results show that those with TiN or TiC as the main component of the binder had excellent wear resistance. Example 4 TiN powder containing CBN and Al compound corresponding to F described in Example 1 was mixed, and this mixed powder was
It was molded into pellets of 10 mm and 1.5 mm thick. Separately, a disk made of WC-6% Co cemented carbide with an outer diameter of 10 mm and a thickness of 3 mm was prepared. This cemented carbide disk and the pellets were placed one on top of the other and inserted into a stainless steel container. After performing vacuum degassing treatment on the whole in the same manner as in Example 1, pressure was applied using an ultra-high pressure device.
Hot pressed at 55Kb and 1100℃ for 20 minutes.
The obtained sintered body was a layer of a hard sintered body containing CBN with an outer diameter of about 10 mm and a thickness of about 1 mm, which was firmly bonded to a WC-6% Co cemented carbide disk. This composite sintered body was ground with a diamond grindstone to obtain a disc-shaped cutting chip. This was placed in a steel support and a performance test was conducted. The work material used was a chilled cast iron roll material with a hardness of HRc56, an outer diameter of 735 mm, and a width of 650 mm. For comparison, a sintered body made of commercially available CBN bonded with a metal mainly composed of Co, and an Al ₂ O ₃ containing TiC.
Cutting tips made of ceramic and cemented carbide equivalent to JIS classification KO1 were tested at the same time. Cutting conditions were determined to be suitable for each tool, and the cutting conditions were as shown in the table below.

[Table] The results are shown in the table above, and the sintered body of the present invention had no defects and had a performance 50 times better than that of KO1 cemented carbide. Example 5 Using CBN with an average particle size of 1 μm, each powder was blended into the composition shown in the table below.

[Table] Using this mixed powder and following the method of Example 4, a sintered body having a 1 mm thick CBN-containing hard layer bonded to a WC-6% Co cemented carbide base material was produced. After cutting this, it was brazed to one end of a throwaway chip made of cemented carbide. This chip was used to mill hardened steel using a face milling machine. The workpiece material is a powder press mold made of hot die steel equivalent to SKD 11 grade with a hardness of HRc64. The end face of this mold was milled with a single blade at a cutting speed of 143 m/min, depth of cut of 0.4 mm, and feed rate of 0.07 mm/rotation. Sintered bodies of the present invention R, S, T, U
Both were able to be machined under these conditions without chipping the cutting edge. Further, the surface roughness of the machined mold surface was 2 to 3 μm in maximum height roughness, and the machined surface was extremely good. Example 6 CBN powder with an average particle size of 3μ and Ti with an average particle size of 3μ
(C _{0.80 N 0.15 ) 0.95 powder} and Si powder each in volume _% 68
%, 30%, and 2%. Example 4 below
A disk-shaped sintered body having a 1 mm thick CBN-containing hard layer bonded to a WC-6% Co cemented carbide base material was obtained according to the method described in . This was ground to create a cutting chip with a circular cutting edge. This was used to cut a rolling roll made of cast steel with a hardness of HRc55. For comparison, the same roll was cut using a cemented carbide cutting chip equivalent to JIS classification KO1. The conditions are as follows.

[Table] In the sintered body of the present invention, the machining efficiency in terms of cutting speed x depth of cut x feed was three times that of KO1 cemented carbide, and the volume of workpiece material machined until the tool life was reached was approximately 50 times.

[Brief explanation of the drawing]

Figure 1 is for explaining the composition range of the sintered body of the present invention, which shows CBN with a TiN-based binder phase.
Hardened steel with hardness HRc60 is made of sintered bodies with different contents.
This shows the tool flank wear width when cutting for minutes. Figure 2 shows CBN in the sintered body of the present invention.
This is to explain the relationship between grain size and wear resistance, and shows the tool flank wear width when hardened steel of HRc60 is cut for a certain period of time using sintered bodies with different CBN grain sizes. FIG. 3 is a diagram relating to the manufacturing conditions of the sintered body of the present invention, and shows the stable existence region of cubic boron nitride on the pressure and temperature phase diagram. Fourth,
Figures 5, 6, 7, and 8 are all microscopic structure photographs for explaining the microstructure and distribution of component elements of the sintered body of the present invention. Figures 4, 5, and 6 show the backscattered electron beam image and the distribution of component elements analyzed using an X-ray microanalyzer for a sintered body with a TiN-Al compound as the binder phase, and Figures 7 and 8 show the distribution of component elements. This is a micrograph of a similarly distributed microstructure of a sintered body with TiN as a binder phase.

Claims (1)

[Scope of Claims] 1 Contains 30% or more but less than 70% by volume of cubic boron nitride with an average particle size of 3μ or less, with the remainder being carbides or nitrides of transition metals from groups 4a, 5a, and 6a of the periodic table. This compound forms a continuous binder phase in the structure of the sintered body, and the layer of the sintered body with a thickness of 0.5 mm or more is the cemented carbide base material. A sintered body for cutting tools made of high hardness steel such as hardened steel and high hardness cast iron, characterized by being joined to. 2 Compounds that form a continuous bonded phase are listed in Periodic Table 4a.
A sintered body for a cutting tool according to claim 1, characterized in that the sintered body is mainly made of carbides, nitrides, and carbonitrides of Group metals Ti, Zr, and Hf. 3 Compounds forming a continuous bonded phase are listed in the periodic table.
It is mainly composed of carbides, nitrides, and carbonitrides of group 4a metals Ti, Zr, and Hf.
0.1% by weight of Al or Si or both
A sintered body for a cutting tool according to claim 1 or 2, characterized in that the sintered body contains the above. 4 Mix cubic boron nitride powder with an average particle size of 3μ or less and powder mainly composed of carbides, nitrides, or mixtures thereof or mutual solid solution compounds of group 4a, 5a, and 6a transition metals of the periodic table. Cubic boron nitride is produced by placing it in contact with a cemented carbide base material in powder form or after molding, and sintering the entire body under high pressure and high temperature using an ultra-high pressure device. Contains 30% or more and less than 70% by volume, with the remainder mainly consisting of carbides, nitrides, or mixtures thereof, or mutual solid solution compounds of group 4a, 5a, and 6a transition metals of the periodic table, This compound forms a continuous binder phase in the structure of the sintered body, and a layer of the sintered body with a thickness of 0.5 mm or more is bonded to a cemented carbide base material.High hardness steel such as hardened steel, high hardness cast iron. A method for producing a sintered body for cutting tools. 5 Cubic boron nitride powder with an average particle size of 3μ or less and carbides, nitrides, and carbonitrides of Ti, Zr, and Hf from Group 4a of the periodic table are MC ₁ ±x and MN ₁ ±xM, respectively.
(C,N) When expressed in the form of ₁ ±x, ( ₁ ±
Mix powders mainly composed of these compounds with a value of Volume % of cubic boron nitride, which is characterized by being sintered under high pressure and high temperature using
Contains 30% or more and less than 70%, and the remainder is from periodic table 4a
This compound mainly consists of compounds mainly composed of carbides, nitrides, and carbonitrides of Ti, Zr, and Hf of the group Ti, Zr, and Hf, and these compounds form a continuous binder phase in the structure of the sintered body. A method for manufacturing a sintered body for cutting tools of high hardness steel such as hardened steel or high hardness cast iron, in which a layer with a thickness of 0.5 mm or more is bonded to a cemented carbide base material. 6 Carbides, nitrides, and carbonitrides of Ti, Zr, and Hf in Group 4a of the periodic table are MC ₁ ±x, MN ₁ ±x, respectively.
When expressed in the form of M(C,N) ₁ ±x, ( ₁
For these compound powders whose value of ±x) is less than 0.97,
Al powder, Si powder, or compound powder containing these is added, and the two are reacted in advance in a vacuum or inert gas atmosphere at a temperature of 600°C or higher. Either by generating a compound, or by mixing Al, Si powder or a compound powder containing these, cubic boron nitride powder with an average particle size of 3μ or less, and powder mainly composed of the above-mentioned Ti, Zr, Hf compound powder. The cubic boron nitride is produced by placing it in powder form or in contact with a cemented carbide base material after molding, and then sintering the entire product under high pressure and high temperature using an ultra-high pressure device. The compound contains 30% or more and less than 70% by volume, with the remainder forming a continuous binder phase in the structure of the sintered body, and the compound is composed of Ti, Zr,
It is mainly composed of carbides, nitrides, and carbonitrides of Hf, and the sintered body contains 0.1% or more of Al or Si, or both by weight, and the thickness of the sintered body is 0.5%.
A method for manufacturing a sintered body for cutting tools of high hardness steel such as hardened steel or high hardness cast iron, in which a layer of mm or more is bonded to a cemented carbide base material.