JP2001240932A - Wear resistant tool material and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wear resistant tool material suitable for high speed cutting work for a metallic material, and to provide its production method. SOLUTION: This tool material is a sintered body composed of superabrasive grain components containing (high pressure phase) boron carbonitride having a diamond type crystal structure as superhard substance and a binder, and the binder is contained by 5 to <80% by volume ratio to the whole of the sintered body. The tool material can effectively be obtained particularly by mixing the high pressure phase boron carbonitride powder and the binder and performing sintering under the static pressure of >=4 GPa at 1,200 to <=1,600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant tool material suitable for high-speed cutting of a metallic material and a method for producing the same.

[0002]

2. Description of the Related Art A diamond sintered body and a high-pressure phase boron nitride sintered body are widely used as cutting tool materials obtained by sintering superabrasive grains. Sintered diamond is used for processing a wide range of hard materials such as non-ferrous metals, ceramics, and stones, and enables highly productive processing operations utilizing the characteristics of diamond, which is the hardest material. On the other hand, the boron nitride sintered body is suitable for cutting iron-based materials, and has no reactivity with iron group metals. ing.

[0003]

The polishing tool made of a sintered diamond has a possibility of covering a wide range of applications in terms of hardness. However, the polishing of iron group (group 8) metal is not suitable for the processing of iron group metal, because the catalytic action of the workpiece at high temperature promotes the graphitization of diamond. There is.

On the other hand, in a boron nitride sintered body, the hardness (knoop) of boron nitride is as low as about 1/2 that of diamond,
Problems remain in terms of durability. That is, in the case of high-speed machining, there is an annoyance that the frequency of blade replacement is increased due to lack of hardness, and in the case of drilling and cutting a hard brittle composite material such as a reinforced concrete structure, the processing speed is increased. In many cases, a choice was made between using a boron nitride sintered body at the expense of sintering and using a diamond sintered body ignoring the tool cost.

[0005] Accordingly, by combining the hardness of diamond with the inertness to iron group metals such as boron nitride, it is possible to use the cutting tool for a long time and have high abrasion resistance, as well as iron and brittle materials. Development of a cutting tool (or polishing tool) material applicable to the simultaneous processing of a composite material (for example, cutting of reinforced concrete) with the above has been awaited.

[0006] In addition to diamond and boron nitride,
High-pressure phase boron carbonitride sintered bodies having a diamond-type crystal structure are also known. For example, in Japanese Patent Publication No. 62-20149,
A method of sintering this as a mixed powder with low-pressure phase boron carbonitride is described. However, to the knowledge of the inventors, there is no evidence that this material has been put to practical use, and it is presumed that a product of practically acceptable quality could not be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem by using boron carbonitride, which is a material comparable in hardness to diamond and inactive against iron group metals and equivalent to boron nitride. By providing it in the form of a sintered body for use, it is possible to facilitate high-load processing, particularly of iron group metals, and to improve productivity and reduce processing costs.

[0008] Boron carbonitride (BC) having a diamond type structure
N) is the first material successfully synthesized by the present inventors (JP-A-6-316411), and has the high hardness (bulk modulus of about 400 GPa) characteristic of diamond and the cubic boron nitride (c-B
N) has both heat resistance and non-reactivity with iron group metals, and is expected to exert its power particularly in the processing of iron-based materials.

[0009] Boron carbonitride having a diamond-type structure is a thermodynamically metastable substance, and is known to decompose and separate into a diamond phase and a c-BN phase at a temperature exceeding 1600 ° C. . Therefore, a method of synthesizing this substance using static ultrahigh pressure has not been completed to date, and a dynamic pressurization / heating method using a shock wave has been used for the synthesis. It has been recognized that the obtained boron carbonitride powder of the high-pressure phase is usually a spherical polycrystalline body having a particle diameter of 10 to 1000 °.

Although it is difficult to obtain such a fine powder with a binder for sintering, it has a fine and dense structure, high wear resistance and high toughness. It is convenient for body production.

As a sintering aid, a diamond sintered body,
The material is selected from various known materials used for manufacturing a c-BN sintered body. The sintering aid is required to have a large bonding force with the boron carbonitride particles and to exhibit a strong fixing action by being interposed between the particles. These are classified into liquid phase sintering and solid phase sintering according to the presence or absence of a liquid phase during sintering.
Generally, although the former requires a smaller amount of (required) sintering aid than the latter, it is considered that the direct bonding between boron carbonitride particles does not substantially occur.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, boron carbonitride having a diamond type structure is a metastable phase under normal pressure, and easily transitions to a low pressure phase BC ₂ N under normal pressure and high temperature, The sintering is performed under pressure because it decomposes into low pressure BN and graphite. The pressure during sintering is 4 GPa or more, preferably 6 GPa or more.

As a sintering aid for liquid phase sintering, a metal mainly composed of cobalt or nickel, or a WC-based cemented carbide is suitable. Since the main material, boron carbonitride, is a fine powder, and it is practically impossible to introduce a binder between the powders by infiltration, the sintering aid for liquid phase sintering is preliminarily carbonitrided. It must be uniformly mixed with the boron powder. When a WC cemented carbide is used as a binder, it is desirable to use a submicron powder and simultaneously add any of VC, TiC and TaC to prevent grain growth. Mixing 5 wt% or less of Cu in addition to the sintering aid for liquid phase sintering is effective for densification.

As the sintering aid for solid phase sintering, a structure mainly composed of carbides, nitrides, carbonitrides, and borides of Groups 4 to 6 of the periodic table is preferable. Preferred examples include (Ti, Z
Combinations of r, Hf, Ta, Cr, Mo)-(C, N, CN, B) can be mentioned, and TiC, TiN, TiCN can be mentioned as particularly preferred examples. These may be used alone or as a mixture if necessary, or may be used in combination.
Various combinations are possible, such as when other substances are added in addition to the types.

As described above, the boron-carbonitride having a diamond-type structure may change to a mixture of diamond and c-BN when exposed to a temperature of 1600 ° C. or higher. In the liquid phase sintering, the sintering aid is selected from materials that become molten under these temperature conditions. However, a sintering aid that generates a liquid phase at 1200 ° C. or lower is not preferred because it softens at high temperatures during cutting and may cause a decrease in blade edge strength.

On the other hand, since the sintering aid used for solid-phase sintering is generally a high melting point material, it is necessary to increase the reactivity and reduce the sintering temperature by using it in the form of fine powder. Further, since boron carbonitride as a main raw material is a fine powder, and it is necessary to sufficiently mix it with a sintering aid prior to the sintering operation, it is desirable to use a product having the same particle size as boron carbonitride. Therefore, as the powder for the auxiliary agent, a variety produced mainly by a CVD technique or a plasma application technique is used.

In addition to the above, sintering aids for solid-phase sintering include:
Al, Cu, Si, alumina and silicon carbide can be added as metal components to improve heat resistance and sinterability.

In order to further improve the heat resistance of the sintered body in the present invention, in addition to the high-pressure phase boron carbonitride used as a main component, fine powder of high-pressure phase boron nitride can be used as a superabrasive component. As the high-pressure phase, w- synthesized under impact pressure, having the same level of particle size as high-pressure phase boron carbonitride, than c-BN powder synthesized and pulverized by the static pressure method.
It is preferable to use BN because segregation of the structure can be reduced. However, as the ratio of the w-BN component increases, the hardness of the sintered body decreases and the durability decreases. Therefore, the ratio of the w-BN in the superabrasive component is 40 v
ol% or less is desirable.

The sufficiently mixed sintering raw materials are Ti, Ta, M
o, Zr, etc., filled in a high melting point metal capsule, degassed under high vacuum, remove water and oxygen adsorbed on the powder surface, perform pretreatment to improve sintering properties, and then fire Serve for closing. This metal capsule is not only a container for the powder material, but also functions as a getter for the gas desorbed from the powder surface under the high temperature of the sintering reaction.

A major feature of boron carbonitride is that it has both the hardness of diamond and the oxidation resistance of c-BN. Since this feature was maintained even in the sintered body, even when high-speed cutting in which the cutting edge was in a red-hot state was performed, the abrasion due to oxidation was slight. This phenomenon is understood to be the effect of covering the surface with boron oxide, as in the case of c-BN.

In order to facilitate handling as a cutting tool, in particular, brazing to a holder and sharpening of a blade, a sintered layer of boron carbonitride may be formed on a cemented carbide substrate during a sintering reaction. it can. In this case, the above-mentioned metal capsule is filled with a block of cemented carbide together with the sintering raw material, and the sintering operation and the bonding between the sintered layer and the base material are performed.

[0022]

Example 1 A sintered body was produced using diamond-type boron carbonitride synthesized by an impact pressure / heating method. This raw material powder has a deep blue color and B: C: N
Was about 1: 2: 1.

As a sintering aid, cobalt at a mass ratio of 8% to boron carbonitride was used in the form of cobalt chloride. The weighed boron carbonitride powder and cobalt chloride were wet-mixed in a planetary ball mill containing acetone and cobalt balls, taken out and dried, and then excess ammonia water was dropped to convert cobalt to hydroxide. The raw material powder in which metallic cobalt was uniformly dispersed was obtained by changing, drying and reducing with hydrogen.

This mixed powder is filled into a bottom of a tantalum container having a diameter of 13 mm and a depth of 5 mm to a thickness of about 1 mm, and a cemented carbide plate having a diameter of 13 mm and a thickness of 2.5 mm is placed on top of the tantalum container. The edge was bent and fixed.

For the sintering reaction, a belt-type high-pressure high-temperature apparatus was used, and kept at 6 GPa and 1400 ° C. for 5 minutes. The resulting sintered product is cut and polished to produce a cutting tip with a side of 6 mm and a tip angle of 60 °. The die is made of die steel (SKD-11, HRC
= 61). Processing conditions are 0.5m depth of cut
m, feed 0.2 mm / rev, cutting speed 100 m / min.

Under these conditions, the flank wear of the tip is 0.2 mm.
Processing time to reach was 30 minutes. On the other hand, for comparison, the cutting time in the case of a cutting tip similarly manufactured using c-BN powder was only 20 minutes.

[0027]

Example 2 A cemented carbide based bonding material was prepared using a boron carbonitride powder having an atomic ratio of B: C: N of about 1: 2.5: 1 and a sintering vessel having the same size as in Example 1. A sintered body was produced by Prepare a cemented carbide material in which 10% by mass of Co powder was added to a 9: 1 mass ratio of WC powder and TaC powder having a particle size of 0.6 micron, and 4 parts by volume of this cemented carbide material When,
Six parts of the boron carbonitride material was sufficiently mixed by wet mixing using a planetary ball mill containing acetone. A cemented carbide plate having the same size as that used in Example 1 was used as a backing material for the sintered layer. The sintering reaction conditions were 6 GPa and 1400 ° C., and the holding time was 10 minutes.

A 3 mm × 5 mm chip manufactured from the obtained sintered product through a cutting and polishing process was brazed to the cutting edge of a circular saw substrate and used as a dry cutter for concrete and tiles. In particular, it has been found to be useful for cutting concrete structures with reinforcing bars.

[0029]

Example 3 As a superabrasive, a mixture of the boron carbonitride raw material used in Example 2 and a wurtzite-type boron nitride of nominally 0-1 micron in a mass ratio of 7: 3 was used. By volume ratio, 3 parts of TiCN, 5 parts of TiN and Al ₂ O ₃ were added to 5 parts of the mixed powder.
Was added and wet-mixed in acetone using a planetary ball mill to prepare a sintering raw material powder.

In the same manner as in Example 1, the raw material powder and the cemented carbide plate were charged into a container made of tantalum, and kept at 6 GPa and 1500 ° C. for 10 minutes using a belt-type high-pressure high-temperature apparatus. Sintering.

In order to evaluate the performance, a die steel (SKD-11, HRC = 61) was cut by the same method as in Example 1, and as a result,
It was possible to use for 40 minutes before the flank wear of the tip reached 0.2 mm.

[0032]

Example 4 The same boron carbonitride raw material as in Example 1,
Using a sintered container of the same size, a sintered body using a Ti-based ceramics binder was manufactured. All of the ingredients listed in Table 1 were thoroughly mixed by wet mixing in a planetary ball mill using acetone. Sintering conditions are 6GPa, 15
The temperature was set to 00 ° C., and the holding time was set to 20 minutes.

[Table 1]

A cutting tip of 6 mm on a side and a tip angle of 60 ° is produced from a sintered product through a cutting and polishing process.
450). Processing conditions are 0.5m depth of cut
m, feed 0.2 mm / rev, cutting speed 230 m / min, and the processing time until flank wear reached 0.2 mm was evaluated.

In the case of processing with a commercially available c-BN sintered body tip (the binder is TiN-based) used for comparison, the processing time until the flank wear reached 0.2 mm was 6 minutes.

[0035]

According to the present invention, boron carbonitride in the high-pressure phase is replaced with the periodic table 4 to
By sintering using a group 6 carbide, nitride, carbonitride, boride, or a sintering aid containing Ni, Co, Cu, Al, Si, the hardness of diamond and the iron group of boron nitride It has become possible to produce a versatile cutting tool that is inert to metals and is suitable for processing hard materials including metals and ceramics.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C22C 29/04 C22C 29/04 D 29/12 29/12 C 29/14 29/14 C 29/16 29 / 16 A 32/00 32/00 QBZNP // B23B 27/14 B23B 27/14 B (72) Inventor Hiroshi Ishizuka 4-1-1, Joto, Oyama-shi, Tochigi Pref. ) Inventor Akatsuki Hosomi 4-5-1 Joto, Oyama-shi, Tochigi Pref. Tome Idia Co., Ltd. F-term (reference)

Claims (13)

[Claims] 1. A sintered body comprising a superabrasive component containing a diamond-type crystal structure (high-pressure phase) boron carbonitride as a superhard material and a binder. A wear-resistant tool material characterized by being contained in a volume ratio of 5% or more and less than 80% (based on the whole body). (2) The binder has a volume ratio of 10% or more and 60% or more.
The wear-resistant tool material according to claim 1, wherein the wear-resistant tool material contains less than. 3. The wear-resistant tool material according to claim 1, wherein said superabrasive component consists essentially of said high-pressure phase boron carbonitride. 4. The wear-resistant tool material according to claim 1, wherein said superabrasive component contains a second superhard material. 5. The wear-resistant tool material according to claim 4, wherein said second super-hard material consists essentially of high-pressure phase boron nitride. 6. The binder according to claim 1, wherein a main component of the binder is a carbide, nitride, carbonitride, or boride of an element of Groups 4 to 6 of the periodic table.
2. A wear-resistant tool material according to item 1. 7. The wear-resistant tool material according to claim 6, wherein the binder further contains at least one metal element selected from Al, Cu and Si, or alumina or silicon carbide. 8. The wear-resistant tool material according to claim 1, wherein a main component of the binder is one selected from Ni, Co, Cu, and an alloy containing these metals. 9. The high-pressure phase boron carbonitride having a composition of B _x C _y
In the representation of N _z , substantially x = z and x = 1
2. The wear-resistant tool material according to claim 1, wherein 0.5 ≦ y ≦ 4. 10. The composition of the high pressure phase boron carbonitride is substantially x = z and 2 ≦ y ≦ 3 for x = 1.
A wear-resistant tool material according to claim 9. 11. The wear-resistant tool material according to claim 1, wherein the high-pressure phase boron carbonitride comprises an impact-pressure synthesized polycrystalline fine powder having a primary particle size of substantially 10 to 1000 °. 12. The resistant material according to claim 5, wherein the second super hard material is wurtzite-type boron nitride (w-BN), which is contained in a volume ratio of not more than 40% with respect to the entire superabrasive component. Wear tool material. 13. A high-pressure phase boron carbonitride powder having a diamond-type crystal structure and a binder are mixed and subjected to a sintering at a static pressure of 4 GPa or more and a temperature of 1200 ° C. or more and not more than 1600 ° C. A method for producing a wear-resistant tool material, characterized by: