JP2006347850A - Cubic system boron nitride sintered compact and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cubic system boron nitride sintered compact having high hardness and high strength and further having excellent thermal characteristics and wear resistance and a method of manufacturing the same. <P>SOLUTION: The cubic system boron nitride sintered compact contains cubic system boron nitride and a binder, has Pickers hardness of ≥900 at 1,000°C temperature and 1 kgf load and is manufactured by the manufacturing method including a step for heat-treating cubic boron nitride powder as a raw material at 1,400-1,600°C under vacuum or a step for heat treating the cubic boron nitride powder as the raw material in an ammonia stream, a step for mixing the cubic boron nitride powder with the binder and a step for sintering the mixture under a condition of the prescribed pressure and temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cubic boron nitride sintered body and a method for producing the same, and more particularly relates to a cubic boron nitride sintered body having high hardness and high strength and excellent thermal characteristics, and a method for producing the same. .

  Cubic boron nitride (hereinafter referred to as “cBN”) has a hardness second to diamond and has high thermal chemical stability, and has been widely used as a cutting tool for iron-based materials.

  Since it is very difficult to directly sinter cBN particles (powder) alone, cBN sintered bodies generally used as cutting tools bind metals such as Al and Co, and ceramics such as TiC and TiN. It is manufactured by sintering cBN powder under high pressure as a material. For this reason, generally the commercially available cBN sintered compact contains the said binder about 10-40 volume%.

  For example, Patent Document 1 below discloses that a sintered body is obtained by bonding cBN together using a metal such as Co as a catalyst.

In the conventional cBN sintered body as disclosed in this document, the bonding strength between the cBNs is insufficient. In particular, in high-speed cutting of cast iron where the cutting edge temperature is high, cutting hardened steel, and the like, there has been a problem that cutting performance deteriorates due to a decrease in the hardness of the cutting edge.
Japanese Examined Patent Publication No. 57-59228

  The present invention has been made in order to solve the above-mentioned problems of the prior art, and the object thereof is a hexagonal boron nitride sintered material having high hardness and high strength, and excellent thermal characteristics and wear resistance. It aims at providing a body and its manufacturing method.

  According to one aspect of the present invention, there is provided a cubic boron nitride sintered body containing cubic boron nitride and a binder, and having a Vickers hardness of 900 or more at 1000 ° C. under a load of 1 kgf. A sintered boron nitride sintered body is provided.

  According to another aspect of the present invention, a cubic boron nitride sintered body containing cubic boron nitride and a binder, wherein the Vickers hardness at 1000 ° C. and a load of 1 kgf is 1200 or more. A cubic boron nitride sintered body is provided.

  Preferably, the binding material includes any one or more of a group VIII element of the periodic table, a simple element selected from the group consisting of W and Al, a solid solution, an intermetallic compound, a boride, a nitride, or a carbide. .

  Preferably, the binder is any one or more of a simple substance, a solid solution, a nitride, a carbide, a carbonitride, a boride, or a boronitride of an element selected from the group consisting of Group IV to VI metals of the Periodic Table including.

  Preferably, the cubic boron nitride is produced by heat-treating cubic boron nitride powder as a raw material within a range of 1400 ° C. to 1600 ° C. in a vacuum.

  Preferably, the cubic boron nitride is obtained by heat-treating cubic boron nitride powder as a raw material in an ammonia stream.

Preferably, the bending strength after the cubic boron nitride sintered body is treated with an acid is 100 kgf / mm ² or more.

  According to another aspect of the present invention, there is provided a method for producing a cubic boron nitride sintered body containing cubic boron nitride and a binder, wherein the cubic boron nitride powder as a raw material is heated in a vacuum at 1400 ° C. Cubic boron nitride sintering comprising a step of heat treatment within a range of 1600 ° C., a step of mixing cubic boron nitride powder and a binder, and a step of sintering the mixture under conditions of a predetermined pressure and a predetermined temperature. A method of manufacturing a body is provided.

  According to still another aspect of the present invention, there is provided a method for producing a cubic boron nitride sintered body containing cubic boron nitride and a binder, wherein the cubic boron nitride powder as a raw material is heat treated in an ammonia stream. There is provided a method for producing a cubic boron nitride sintered body comprising the steps of: mixing a cubic boron nitride powder and a binder; and sintering the mixture under conditions of a predetermined pressure and a predetermined temperature. The

  Preferably, the binder includes any one or more of an element selected from the group consisting of Group VIII elements of the periodic table, W and Al, a solid solution, an intermetallic compound, a boride, a nitride or a carbide.

  Preferably, the binder is any one or more of a simple substance, a solid solution, a nitride, a carbide, a carbonitride, a boride, or a boronitride of an element selected from the group consisting of Group IV to VI metals of the Periodic Table including.

  Preferably, the method further includes a step of adding a compound composed of carbon, nitrogen and hydrogen to the mixture after the mixing step and before the sintering step.

  According to the hexagonal boron nitride sintered body and the method for producing the same of the present invention, the bond between cBNs and the bond between cBN and the binder can be strengthened, so that the hardness is high even at high temperatures. Therefore, it shows excellent cutting characteristics in high-speed cutting of cast iron, cutting of hardened steel, and the like.

  The cubic boron nitride sintered body of the present invention is a cubic boron nitride sintered body containing cubic boron nitride and a binder, and has a Vickers hardness of 900 or more at 1000 ° C. and a load of 1 kgf. Preferably, the Vickers hardness at a load of 1 kgf at 1000 ° C. is 1200 or more.

  Thereby, in the high-speed cutting of cast iron and the cutting of hardened steel said that a tool blade edge temperature will be 600 to 1000 degreeC, since the blade edge can maintain high hardness, the outstanding cutting performance is exhibited.

  In the present invention, in order to obtain a cubic boron nitride sintered body having such characteristics, the following manufacturing method can be used.

  That is, according to the cubic boron nitride sintered body of the present invention, there is provided a method for producing a cubic boron nitride sintered body containing cubic boron nitride and a binder, wherein the cubic boron nitride powder as a raw material is vacuum-treated. Including a step of heat-treating within a range of 1400 ° C. to 1600 ° C., a step of mixing cubic boron nitride powder and a binder, and a step of sintering the mixture under conditions of a predetermined pressure and a predetermined temperature. .

  Further, in the above manufacturing method, the cubic boron nitride powder as a raw material can be subjected to a heat treatment in an ammonia stream.

  By manufacturing a cubic boron nitride sintered body using such a manufacturing method, the cubic boron nitride sintered body having the above-described excellent characteristics can be obtained.

Hereinafter, the cubic boron nitride sintered body of the present invention and the manufacturing method thereof will be described in detail.
<Cubic boron nitride powder>
In the present invention, the cBN powder used as a raw material in the cubic boron nitride (cBN) sintered body is not particularly limited, but a high-pressure synthetic cBN powder commercially available as an abrasive can be used.

<Binder>
In the present invention, the binder has an action of strongly sintering the cBNs. Such a binder includes any one or more of a group VIII element of the periodic table, an element selected from the group consisting of W and Al, a solid solution, an intermetallic compound, a boride, a nitride, or a carbide. A binder (first binder) can be used.

  Further, in the present invention, in addition to the above-mentioned binder, a simple substance, a solid solution, a nitride, a carbide, a carbonitride, a boride, or boronitride of an element selected from the group consisting of Group IV to Group VI metals A binder (second binder) containing any one or more of the objects can be used.

  In the present invention, when sintering using the first binding material, the material belonging to the first binding material has the same function and function of firmly bonding cBN to each other. The effect of the present invention can be achieved by using a binding material using.

  Specific examples of the first binder include Co, Fe, Ni, Al, WC, and CoAl.

  In the present invention, when sintering using the second binder, the material belonging to the second binder has the same function and function of increasing the melting point of the binder, so the material belonging to the second binder The effect of the present invention can be achieved by using a binding material using.

  Specific examples of the second binder include CrN, Ti, and ZrC, but are not limited thereto.

<Processing of cBN powder>
In the present invention, the cBN powder is pretreated before being mixed with the binder. Thereby, the oxygen of the surface of cBN can be removed and a coupling | bonding can be promoted.

  Specifically, such pre-processing is as follows. That is, the cBN powder as a raw material is heat-treated within a range of 1400 ° C. to 1600 ° C. in a vacuum. This is because it is possible to remove oxides present on the surface of the cBN powder that may inhibit sintering. Moreover, it is because the surface of cBN can be converted into hBN. By slightly converting the surface of cBN into hBN, it can be easily converted into cBN during sintering, and the bonding between cBN and the bonding between cBN and a binder can be promoted.

  Here, the reason why the temperature range is set within the range of 1400 ° C. to 1600 ° C. is that it is suitable for slightly converting the surface into hBN.

  In the present invention, the treatment of the cBN powder is also characterized in that the treatment is performed by heat-treating the cBN powder as a raw material in an ammonia stream. Thereby, the oxide which exists in the surface of cBN at low temperature can be removed by the reduction | restoration characteristic which ammonia has. Thereby, the coupling | bonding of cBN and the coupling | bonding of cBN and a binder can be promoted at the time of sintering.

  The temperature during the ammonia treatment is preferably 600 ° C. or higher and 1400 ° C. or lower. The reason is that the higher the temperature, the better the reduction effect, but if it is too high, reverse conversion to hBN occurs.

<Addition of compound>
Moreover, in this invention, the compound which consists of carbon, nitrogen, and hydrogen can be added to cBN powder with a binder, and it can mix and sinter to cBN powder as a raw material. As a result, oxides such as B ₂ O ₃ present as impurities on the cBN surface and oxygen in the adsorbed gas are reduced and removed by carbon contained in the compound, and nitrogen and hydrogen contained in the compound are catalysted. And can promote the bonding between cBN.

  The compound may be saturated or unsaturated, and may be lower or higher. Moreover, it may be linear or branched. However, the compound needs to volatilize during the sintering of cBN. The compound preferably contains an amino group and / or a cyano group.

  Here, the reason why it is necessary to be volatile during the sintering of cBN is that, if the compound is not present as a gas during the treatment, the oxygen impurity removal action on the cBN surface is not sufficient, Moreover, it is because catalyst substances, such as hydrogen and an amino group, do not fully act on the cBN surface.

  Preferably, the compound is present as carbon free radicals, hydrogen free radicals and nitrogen free radicals during cBN sintering. This is because the oxide removal action by carbon can be obtained more reliably, and the catalytic action by hydrogen or hydrogen and nitrogen can be obtained more reliably.

  In the present invention, examples of such a compound composed of carbon, nitrogen and hydrogen include melamine, dicyandiamide and cyanamide, and these can be used alone or in combination.

  In this invention, it is preferable that the addition amount of the compound which consists of carbon, nitrogen, and hydrogen is 3 mass% or less with respect to the mass of cBN powder. If the content exceeds 3% by mass, the carbon material remains at the grain boundaries, and the strength and hardness of the sintered body are greatly reduced. More preferably, it is 1 mass% or less.

<Sintering>
In the present invention, as described above, cBN powder as a raw material and a binder are mixed, and the mixture is sintered under a predetermined pressure condition and a predetermined temperature condition. Here, the predetermined pressure and the predetermined temperature are conditions under which cBN is thermodynamically stable.

  Specifically, the predetermined temperature is preferably in the range of 1000 ° C. or more and 2000 ° C. or less. This is because if the temperature is lower than 1000 ° C., the sintering of cBN may be insufficient. Moreover, it is because there exists a possibility that the problem that the cost at the time of mass production may become high will arise when it exceeds 2000 degreeC. More preferably, it is 1200 degreeC or more and 1600 degreeC or less.

  The predetermined pressure is preferably 4 GPa or more and 10 GPa or less. If it is less than 4 GPa, the sintering of cBN may be insufficient, and if it exceeds 10 GPa, mass production techniques are not generally established, which may be a problem. More preferably, it is 4 GPa or more and 6 GPa or less.

  In the present invention, the time required for sintering is not particularly limited, and is preferably set appropriately depending on the binder to be used and the above compound. For example, in order to obtain a stable sintered body, It is preferable to hold the above.

<Characteristics of sintered body>
The cubic boron nitride sintered body of the present invention has a Vickers hardness of 900 or more at a load of 1 kgf at 1000 ° C. Preferably, the Vickers hardness at a load of 1 kgf at 1000 ° C. is 1200 or more.

  The cBN sintered body having such characteristics is achieved by the materials, manufacturing methods and conditions as described above.

  In particular, in the present invention, when the Vickers hardness at a load of 1 kgf at 1000 ° C. is 900 or more, since the hardness of most steel materials is 200 or less at 1000 ° C., excellent wear resistance is exhibited.

  Such Vickers hardness can be measured by the method described in JIS R 1623 under conditions of 1000 ° C. and a load of 1 kg.

In the present invention, the cubic boron nitride sintered body produced by the production method of the present invention has a bending strength after being treated with an acid of 100 kgf / mm ² or more. Since the bending strength is 100 kgf / mm ² or more, the bonding between cBN is higher than that of general ceramics, and therefore, excellent wear resistance can be exhibited.

  In order to obtain such a bending strength, as described above, before cBN powder is sintered, it is obtained by treatment with ammonia and / or heat treatment in a range of 1400 ° C. to 1600 ° C. in a vacuum. It is something that can be done.

  Here, the treatment with an acid means that the binder and the cBN sintered body are sealed in a container in which the pressure in the container can be adjusted, and the treatment is performed by holding at a predetermined temperature for a predetermined time. This is a process for obtaining a component (hereinafter referred to as an acid-treated product) consisting mainly of cBN which has been eluted.

  The bending strength can be measured by setting the sample dimensions defined in JIS R 1601 to width 3 mm × length 6 mm × thickness 0.4 to 0.45 mm, and the distance between the lower fulcrums is 4 mm.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not necessarily limited to this.

(Examples 1-9; Comparative Examples 1-3)
As a raw material, cBN powder having an average particle diameter of 2 μm was heat-treated at a temperature in the range of 1300 to 1700 ° C. for 60 minutes under a vacuum of 1 × 10 ⁻³ Pa. The obtained cBN powder and the binder adjusted to the composition shown in Table 1 were filled in a cemented carbide container and sintered at 1500 ° C. under a pressure of 6 GPa.

  Next, the characteristics of the obtained cBN sintered body were evaluated. The results are shown in Table 2. The composition of the sintered body was identified using XRD. The high temperature hardness was measured at 1000 ° C. under vacuum using a high temperature microscope (QM-2 manufactured by Nippon Optical Industry Co., Ltd.).

  In addition, after processing into a thickness of 0.4 to 0.45 mm with a dimension of 6 mm × 3 mm, 40 ml of nitric acid having a concentration of 60% or more and less than 65 is diluted twice, and the concentration is 40% or more and 45%. The hydrofluoric acid mixed with 10 ml of the following hydrofluoric acid and the cBN sintered body were sealed in a pressure vessel and held at a temperature range of 120 ° C. or higher and lower than 150 ° C. for 48 hours to elute the binder component. .

  The bending strength test of the obtained acid-treated body mainly composed of cBN was performed by the above-described method. The results are shown in Table 2.

  Furthermore, ISO standard SNGN120408-shaped cutting tips were produced using the cBN sintered body produced as described above as a cutting edge, and a cutting test was performed under the conditions shown in Table 2. The results are also shown in Table 2.

  From the results in Table 2, it can be seen that the cBN sintered body of the present invention exhibits excellent cutting performance in order to exhibit excellent high temperature hardness.

(Examples 10 to 11)
A cBN powder having an average particle diameter of 2 μm as a raw material was subjected to a heat treatment at 1000 ° C. for 60 minutes while flowing 99 L of ammonia in an ambient atmosphere at a rate of 5 L / min. The obtained cBN powder and a binder adjusted to the composition shown in Table 3 were filled in a cemented carbide container and sintered at 1500 ° C. under a pressure of 6 GPa.

  This sintered body was subjected to the same test in the same procedure as in Example 1. The results are shown in Table 4.

  From the results in Table 4, it can be seen that even when the treatment with ammonia was performed before the cBN powder was sintered, it exhibited excellent high-temperature hardness and excellent cutting performance.

(Examples 12 to 14; Comparative Example 4)
A cBN powder having an average particle diameter of 2 μm as a raw material, a binder adjusted to the composition shown in Table 5, and additives are mixed, filled into a cemented carbide container, and at 1500 ° C. under a pressure of 6 GPa. Sintered.

  About the obtained sintered compact, the same test was done in the procedure similar to Example 1. FIG. The results are shown in Table 6.

  From the results shown in Table 6, it can be seen that the cutting performance is improved by the additive in the same manner as the powder treatment.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (12)

A cubic boron nitride sintered body containing cubic boron nitride and a binder,
A cubic boron nitride sintered body having a Vickers hardness of 900 or more at a load of 1 kgf at 1000 ° C. A cubic boron nitride sintered body containing cubic boron nitride and a binder,
A cubic boron nitride sintered body having a Vickers hardness of 1200 or more at a load of 1 kgf at 1000 ° C.   The binder includes any one or more of a group VIII element of the periodic table, an element selected from the group consisting of W and Al, a solid solution, an intermetallic compound, a boride, a nitride, or a carbide. Item 3. The cubic boron nitride sintered body according to Item 1 or 2.   The binder includes any one or more of an element selected from the group consisting of Group IV to Group VI metals of the periodic table, solid solution, nitride, carbide, carbonitride, boride, or boronitride. The cubic boron nitride sintered body according to any one of claims 1 to 3.   The cubic boron nitride is produced by heat-treating cubic boron nitride powder as a raw material in a range of 1400 ° C to 1600 ° C in a vacuum. A cubic boron nitride sintered body according to claim 1.   The cubic boron nitride sintered body according to any one of claims 1 to 4, wherein the cubic boron nitride is obtained by heat-treating cubic boron nitride powder as a raw material in an ammonia stream. . The cubic boron nitride sintered body according to any one of claims 1 to 6, wherein the bending strength after the cubic boron nitride sintered body according to claim 1 is treated with an acid is 100 kgf / mm ² or more. body. A method for producing a cubic boron nitride sintered body containing cubic boron nitride and a binder,
Heat-treating cubic boron nitride powder as a raw material in a range of 1400 ° C. to 1600 ° C. in vacuum;
Mixing the cubic boron nitride powder and the binder;
And a step of sintering the mixture under conditions of a predetermined pressure and a predetermined temperature. A method for producing a cubic boron nitride sintered body containing cubic boron nitride and a binder,
Heat treating cubic boron nitride powder as a raw material in an ammonia stream;
Mixing the cubic boron nitride powder and the binder;
And a step of sintering the mixture under conditions of a predetermined pressure and a predetermined temperature.   The binder includes any one or more of a group VIII element of the periodic table, an element selected from the group consisting of W and Al, a solid solution, an intermetallic compound, a boride, a nitride, or a carbide. The method for producing a cubic boron nitride sintered body according to claim 8 or 9, characterized in that   The binder includes any one or more of an element selected from the group consisting of Group IV to Group VI metals of the periodic table, solid solution, nitride, carbide, carbonitride, boride, or boronitride. The method for producing a cubic boron nitride sintered body according to claim 8 or 9, characterized by the above.   The cubic boron nitride firing according to any one of claims 8 to 11, further comprising a step of adding a compound comprising carbon, nitrogen and hydrogen to the mixture after the mixing step and before the sintering step. A method for producing a knot.