JPH075382B2 - Cubic boron nitride-containing sintered body - Google Patents

Description

The present invention relates to a cubic boron nitride suitable as a material for a cutting tool used for a drill, a milling tool or a turning tool, or a material for an abrasion resistant tool such as a slitter or a die. The present invention relates to a contained sintered body.

(Prior Art) Cubic boron nitride has the second highest hardness after diamond, and has the advantage that diamond has a high affinity with iron, whereas it has the advantage that it has a low affinity with iron. There is. For this reason, a cubic boron nitride-based sintered body obtained by adding a binder phase to cubic boron nitride has been put into practical use as one of the tool materials mainly for processing iron-based materials.
This cubic boron nitride-based sintered body that has been put into practical use is roughly classified into binder phase components. First, a binder phase is a so-called cermet-based binder phase composed of a ceramic component and a metal or an alloy, and secondly a binder phase. There is a so-called ceramic-based binder phase in which the phase is composed of a ceramic component.

Of these, as representatives of cubic boron nitride-based sintered bodies composed of a cermet-based binder phase, there are JP-B-57-49621 and JP-A-58-164750, which are composed of a ceramic-based binder phase. Typical examples of cubic boron nitride-based sintered bodies are JP-A-55-31517 and JP-A-58-1.
There is 76173 publication.

(Problems to be Solved by the Invention) Japanese Patent Publication No. 57-49621 discloses that cubic boron nitride is used in volume%.
80 to 20% and the balance is carbides, nitrides, borides, silicides of transition metals of groups 4a, 5a and 6a of the Periodic Table or a mixture thereof or a mutual solid solution compound as a first binder phase, and A
l, Si, Ni, Co, Fe, or an alloy or compound containing them as a second binder phase, and the first and second binder phases form a continuous binder phase in the sintered body structure. The cubic boron nitride-based sintered body is characterized in that the compound of the 5,5a, 6a group metal is 50% or more and 99.9% or less by volume in the binder phase. This cubic boron nitride based sintered body of JP-B-57-49621 is
Since the conventional cubic boron nitride-based sintered body is a binder phase composed of a metal or alloy, it is softened at a high level and is inferior in wear resistance and welding resistance, so that it is easily damaged when used as a tool material. However, although it was solved by forming a binder phase consisting of a compound of a transition metal of Group 4a, 5a, 6a of the periodic table and Al, Si, Ni, Co, Fe or an alloy or compound thereof, , A metal or a residual sintered body of an intermetallic compound such as TiAl ₃ , TiAl, Ti ₂ AlN, TiNi, Ti ₂ Ni, and from other binder phase components, for example, a tool material for high-speed cutting or high When it is used as a tool material for cutting a hard material, there is a problem that the mutual reaction between the binder phase and the work material, the oxidation of the binder phase or the softening of the binder phase progresses, and the wear resistance decreases. Further, the sintered body disclosed in JP-B-57-49621 has a problem that when a large amount of Al compound is contained, the adhesiveness between the cubic boron nitride and the binder phase is deteriorated and the chip tends to be lost.

JP-A-58-164750 discloses a Ti carbide, a nitride and a carbonitride, and one or more of Ti and W compound carbides and compound carbonitrides, 20 to 70 wt% and aluminum boride. 1
~ 10wt%, Al, Fe, Ni and Co, one or more
Composition containing 0.5 to 10 wt% and the balance consisting of cubic boron nitride and unavoidable impurities (however, cubic boron nitride 40 to 80
It is an ultra-high pressure sintered material for cutting tools, characterized by having (vol% content). The cubic boron nitride-based sintered body disclosed in JP-A-58-164750 is a compound of Ti that improves toughness and welding resistance, or a compound of Ti and W, and boride that improves thermal shock resistance. Aluminum and a binder phase containing a metal or alloy of Al, Fe, Ni and Co that improves the sintering property and toughness of a ceramic component consisting of aluminum nitride, which further improves welding resistance and thermal shock resistance, if necessary, and Sintered body consisting of cubic boron nitride, resulting in toughness,
Although it is a sintered body with excellent welding resistance and thermal shock resistance, it is inferior in oxidation resistance and chemical stability at high temperature, and when a large amount of metal or alloy is contained, Has a problem of poor wear resistance.

JP-A-55-31517 discloses a refractory metal compound of 5 to 50 vol% consisting of carbides, nitrides, carbonitrides, carbon oxides or carbonitride oxides of metals of groups 4a, 5a and 6a of the periodic table. , Aluminum oxide 10-70vol%, cubic boron nitride and unavoidable impurities 25-85xol%. The cubic boron nitride-based sintered body of JP-A-55-31517 is a sintered body excellent in both toughness and wear resistance, but since it does not contain aluminum nitride at the time of manufacture. The surface of the cubic boron nitride is easily reverse-converted to hexagonal boron nitride, and therefore the adhesion between the cubic boron nitride and the binder phase is likely to be reduced, or to be deficient, or with cubic boron nitride. There is a problem that the bonding strength between the cubic boron nitride and the binder phase is low because interdiffusion with the binder phase is difficult to occur.

JP-A-58-176173 discloses a high-pressure phase boron nitride with
80% by volume, 50 to 80% by weight of Al ₂ O ₃ in the residual binding phase, 15 to 40% by weight of one or more carbides, nitrides and carbonitrides of metals of groups 4a, 5a and 6a of the periodic table and Al It is a high hardness sintered body for tools containing 5 to 20 wt%. This JP-A-58-176173
Since it is disclosed that Al forms an Al compound of AlB ₂ or AlN, the sintered body in the publication is considered to be a sintered body obtained by sintering the above-mentioned components as a starting material. From this, the sintered body disclosed in JP-A-58-176173 is finally a sintered body composed of a ceramic binder phase, which is an excellent sintered body in consideration of strength, welding resistance, heat resistance and thermal conductivity. However, there is a problem that the bonding phase strength is low at a high temperature, so that the bonding is likely to occur, or the high-pressure phase boron nitride undergoes reverse conversion during the sintering process to reduce the bonding strength with the bonding phase, and thus the bonding is likely to be damaged. There's a problem.

The present invention has solved the above-mentioned problems, specifically, by controlling the binder phase composition and the content thereof in a sintered body composed of cubic boron nitride and a ceramic binder phase, Increases the bond strength between the binder phase compositions and between the binder phase and cubic boron nitride, resulting in strength, wear resistance, oxidation resistance, welding resistance, thermal shock resistance, thermal conductivity and chemistry The object is to provide a cubic boron nitride-based sintered body having excellent thermal stability.

(Means for Solving the Problems) The inventors of the present invention have studied to improve both the strength and the wear resistance of the cubic boron nitride-based sintered body, and in order to improve the wear resistance, The ceramic-based binder phase is superior to the cermet-based binder phase, and this ceramic-based binder phase contains both aluminum oxide and a refractory metal compound, especially a compound containing Ti within a certain ratio. The first finding that the wear resistance and strength tend to be excellent, and the second finding that the inclusion of aluminum oxide and aluminum nitrided aluminum boride among the ceramic binder phases has the effect of increasing the strength. In addition to the findings, the combination of the inclusion of both aluminum boride and titanium boride significantly improves the strength and wear resistance at high temperatures. It is intended to obtain a saw. The present invention has been completed based on the first finding, the second finding, and the third finding.

That is, the cubic boron nitride-containing sintered body of the present invention, cubic boron nitride 10 ~ 80vol%, aluminum oxide 7.5 ~
80 vol%, aluminum nitride 3-20 vol%, aluminum boride 1-5 vol%, titanium boride 1-5 vol%,
Sintered body consisting of 3.75-40 vol% of at least one refractory metal compound in Ti, Zr, Hf, Ta, Nb, V carbides, nitrides, W carbides and mutual solid solutions of these, and unavoidable impurities In addition, the volume ratio of the aluminum oxide to the high melting point metal compound is aluminum oxide: high melting point metal compound = 0.5 to 0.956: 0.5 to 0.044.

The cubic boron nitride in the cubic boron nitride-containing sintered body of the present invention preferably has an average particle size of 15 μm or less, and particularly preferably 1 μm to 5 μm in order to enhance both strength and wear resistance. Is. When the content of the cubic boron nitride is less than 10 vol%, the wear resistance is remarkably reduced, and conversely, when it is more than 80 vol%, the fracture resistance is remarkably reduced. Further, the content of cubic boron nitride is 10 to 43
In the case of vol%, fine cubic boron nitride having an average particle size of 0.5 μm to 2 μm is particularly suitable for a cutting tool material in dry cutting, and the content of cubic boron nitride is 43 to 80 vol.
In the case of%, cubic boron nitride having an average particle diameter of 2 to 5 μm is particularly suitable as a cutting tool material in wet cutting.

Aluminum oxide in the cubic boron nitride-containing sintered body of the present invention preferably has an average particle size of 1.0 μm or less, and particularly preferably 0.5 μm or less in order to obtain a particularly dense sintered body. The content of this aluminum oxide is
If it is less than 7.5 vol%, the wear resistance is remarkably deteriorated.
When it is more than 0.1%, the contents of cubic boron nitride and other binder phases become relatively small, and therefore wear resistance and chipping resistance are deteriorated and the life becomes extremely short.

Aluminum nitride in the cubic boron nitride-containing sintered body of the present invention prevents the reverse conversion of cubic boron nitride to hexagonal boron nitride at the time of temperature rise, and together with aluminum boride, cubic boron nitride and other binder phases. It acts as an intermediary for binding with, and its effect is weak when the amount is less than 3 vol%, and conversely 20
If it exceeds vol%, it becomes difficult to sinter.

Aluminum boride in the cubic boron nitride-containing sintered body of the present invention is composed of at least one of AlB ₂ and AlB ₁₂ , and when the content is less than 1 vol%, cubic boron nitride and a binder phase are formed. It lowers the bond strength and consequently the strength of the sintered body. Conversely, the content of aluminum boride is 5v
If it exceeds ol%, the sinterability is impaired and it becomes difficult to form a dense sintered body.

Titanium boride in the cubic boron nitride-containing sintered body of the present invention, the wear resistance and strength at high temperatures are remarkably excellent by combining with the above-mentioned aluminum boride in an appropriate amount, and especially when combined with AlB _2. It has a strong tendency to increase the strength, and when combined with AlB _12, it tends to increase the wear resistance. When the content of titanium boride is less than 1 vol%, the wear resistance at high temperature is significantly reduced, and when it is more than 5 vol%, the strength is significantly reduced.

The refractory metal compound in the cubic boron nitride-containing sintered body of the present invention is TiC, ZrC, HfC, TaC, NbC, VC, WC, TiN, ZrN, Ti.
(C, N), (Ti, Zr) (C, N), (Ti, Ta) (C, N), (Ti,
W) C, (Ti, W) (C, N), (Ti, Ta) C, (Ti, Ta, W) (C,
N) can be mentioned as a concrete example. This refractory metal compound is a compound containing Ti, for example,
TiC, TiN, Ti (C, N), (Ti, W) C, (Ti, W) (C, N), (T
It is preferable to use i, Ta) (C, N) as a main component because it has excellent wear resistance and fracture resistance. When the content of this refractory metal compound is less than 3.75 vol%, the effect of enhancing the wear resistance due to the interaction with aluminum oxide in the binder phase becomes weak, and conversely, when it exceeds 40 vol%, the strength decreases and the life becomes short. become.

In the cubic boron nitride-containing sintered body of the present invention, the binder phase composed of other components except the cubic boron nitride has an optimum bonding strength between the binder phases and between the binder phase and the cubic boron nitride. In addition to the composition of the binder phase, the composition ratio has a great influence on the wear resistance and the strength. In particular, the volume ratio of aluminum oxide to the refractory metal compound is aluminum oxide: refractory metal compound = 0.5. ~ 0.956: 0.55
It is important to be in the range of ~ 0.044.

The cubic boron nitride and the binder phase constituting the cubic boron nitride-containing sintered body of the present invention are a stoichiometric compound or a non-stoichiometric compound depending on manufacturing conditions including starting materials described later. It has become.

The cubic boron nitride-containing sintered body of the present invention can be produced by a conventional method for producing a cubic boron nitride-based sintered body. For example, for cubic boron nitride as a starting material, use a powder having an average particle size of 15 μm or less, preferably a powder having an average particle size of 5 μm or less, and use a finer submicron powder as the other binder phase. In particular, it is necessary to use a fine powder of Al ₂ O ₃ in order to promote sinterability.

The aluminum nitride contained in the sintered body must be mixed as aluminum nitride powder in the starting material in order to prevent the reverse conversion of cubic boron nitride at the time of heating in the sintering process. Al in addition to aluminum powder
The powder is contained in the starting material, and Al is used in the sintering process.
Alternatively, a method of precipitating a part of aluminum nitride from the mutual reaction between the boron nitride and cubic boron nitride may be used. In addition, aluminum boride contained in the sintered body, aluminum boride powder as a starting material, aluminum boride powder and
There is a method using Al powder as a starting material or a method using only Al powder as a starting material. Here, the use of Al powder as a starting material to form aluminum boride in the sintered body is due to the interaction between Al and cubic boron nitride in the sintering process, such as 3A.
It is formed by the reaction of l + 2BN → 2AlN + AlB ₂ . When Al powder is used as a starting material, although it has an effect of promoting sintering, it is subjected to a pretreatment such as a reduction treatment to remove oxygen attached or bonded to the surface of the Al powder, and Al It is important that the reaction between the powder and the compound containing Ti does not occur.

Furthermore, for the titanium boride and the refractory metal compound contained in the sintered body, it is preferable to use powders of the compounds to be contained in the sintered body as starting materials. This is preferable in terms of stability of characteristics.

After compounding these starting materials in a predetermined amount, mixing, drying, sieving and molding by the conventional powder metallurgy method, and then manufacturing a cubic boron nitride-containing sintered body by a conventional high pressure and high temperature apparatus. It can be performed by a method.

(Operation) The cubic boron nitride-containing sintered body of the present invention is
In particular, aluminum nitride acts to prevent the reverse conversion of cubic boron nitride to hexagonal boron nitride, and by combining aluminum boride and titanium boride in an appropriate amount, it is possible to combine the binder phases with each other and the binder phase and the cubic phase. It acts to increase the bond strength between the crystalline boron nitride and each other, and to increase the wear resistance and strength by optimizing the ratio of aluminum oxide to the refractory metal compound.

Example 1 Example 1 Cubic boron nitride (CBN) powder having an average particle size of 1 μm, Al ₂ O ₃ powder having an average particle size of 0.5 μm, and AlN having an average particle size of 1.0 to 1.5 μm
Powder, AlB ₂ powder, TiB ₂ powder, Al powder and refractory metal compound powder are used as starting materials, and each is mixed in a predetermined amount, and the mixed powder, balls and hexane are put in a mixing container lined with cemented carbide. Mixed and crushed. The mixing and grinding time was such that CBN as a starting material was shortened and Al ₂ O ₃ was mixed and ground for the longest time. The mixed powder thus obtained was dried, sieved and molded by the conventional powder metallurgical method, and then set in a high pressure and high temperature apparatus in the same manner as in the conventional method to obtain a pressure of 45 to 50.
A sintered body was prepared under the conditions of kb, temperature 1350 to 1550 ° C, and holding time 5 to 15 minutes. The sintered body composition thus obtained is shown in Table 1 as the sintered body composition of each sample as judged from the analysis by X-ray diffraction and the compounding composition. In Table 1, the product No. 3 of the present invention and the comparative product No. 2 out of the scope of the present invention use Al powder as a starting material, and the other components have the components shown in Table 1 as a starting material. . In addition, a commercially available sintered body made of 45 vol% CBN-ceramics-based binder phase and a sintered body made by the above method are cut and brazed so as to form a cemented carbide cutting edge, and then cut. Material SKD11 (HRC60 to 62), cutting speed 150m / mi
n, depth of cut 0.5 mm, feed rate 0.1 mm / rev, continuous dry turning test was conducted, and the cutting time until the average flank wear amount was 0.3 mm or the fracture life was calculated, and the results are shown in Table 1. I also wrote it down.

Example 2 A CBN powder having an average particle size of 4 μm and the starting material used in Example 1 were mixed in a predetermined amount, and then a sintered body was prepared in the same manner as in Example 1. This sintered body, a commercial product of 60 vol% CBN-ceramic binder phase, a commercial product of 80 vol% CBN-ceramic binder phase, and a commercial product of 90 vol% -CBN-metal binder phase were respectively superposed in the same manner as in Example 1. Brazing to hard alloy, work material,
A wet continuous turning test using cutting oil was conducted under the same conditions as in Example 1 for the cutting speed, the cutting depth, and the feed rate, and the cutting time until the end of the life was determined as in Example 1. Table 2 shows the composition and cutting test results of the sintered body prepared here.

(Effects of the Invention) From the above results, the cubic boron nitride-containing sintered body of the present invention is compared with the comparative product deviated from the sintered body composition of the present invention and the conventional cubic boron nitride-based sintered body. Since it has excellent wear resistance and fracture resistance, it has the effect of extending the life by about 2 to 23 times. From this, the cubic boron nitride-containing sintered body of the present invention is an industrially useful material that can be applied as, for example, a cutting tool material for NC machines or a processing tool material for automatic processing machines.

Claims (3)

[Claims] 1. Cubic boron nitride 10 to 80 vol%, aluminum oxide 7.5 to 80 vol%, and aluminum nitride 3 to 20 vol.
l%, aluminum boride 1-5vol%, titanium boride 1-5vol%, Ti, Zr, Hf, Ta, Nb, V carbides, nitrides, W
And a volume ratio of the aluminum oxide and the refractory metal compound, which is a sintered body composed of 3.75 to 40 vol% of at least one refractory metal compound among the carbides and their mutual solid solutions and unavoidable impurities. Is aluminum oxide:
Refractory metal compound = 0.5 to 0.956: 0.5 to 0.044, cubic boron nitride-containing sintered body. 2. The aluminum oxide has an average particle size of 1.0.
The cubic boron nitride-containing sintered body according to claim 1, wherein the sintered body contains cubic boron nitride. 3. The cubic boron nitride-containing sintered body according to claim 1, wherein the refractory metal compound has a compound containing Ti as a main component.