JP2007169107A - Cubic bn ultra-high pressure sintered compact and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cubic BN ultra-high pressure sintered compact which is most suitable for high-speed cutting or intermittent cutting of high hardness steel such as carburized material or hardened material of steel; and a method for producing the same. <P>SOLUTION: The cubic BN ultra-high pressure sintered compact comprises 30-80 vol% of cubic BN and the balance composed of a binding phase, formed of at least one kind selected from carbides, nitrides, borides and oxides of group 4a, 5a and 6a elements of the periodic table, nitrides and oxides of Al, and carbides and nitrides of Si, and mutual solid solutions thereof, and inevitable impurities. The binding phase contains (1) at least one kind of complex compound of complex nitrides and complex carbonitrides containing at least one of Zr and Hf and Ti, (2) a complex boride containing at least one of Zr and Hf and Ti, (3) AlN, and (4) Al<SB>2</SB>O<SB>3</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cBN-based ultrahigh-pressure sintered body that is optimal for high-speed cutting and intermittent cutting of high-hardness steel such as a carburized steel and a hardened steel, and a method for producing the same.

For cutting high hardness steel such as carburized steel and hardened steel, a cBN-based ultrahigh pressure sintered body composed of 40 to 70% by volume of cBN and the balance of TiN as a main component is generally used. . Examples of the binder phase other than TiN include AlN and Al ₂ O ₃ generated from metal Al added as a sintering aid, and TiB ₂ generated by reaction of cBN and TiN.

  Recently, high-efficiency is required by high-speed cutting or high-feed cutting at the machining site, and improvement of wear resistance, fracture resistance, and chipping resistance, which are basic required performances even in cBN-based ultra-high pressure sintered bodies. Is required. Therefore, many studies have been made on the components of the binder phase in order to improve the performance.

(Ti, M) (N, C, O) (where M is Zr, Hf, V, Nb, Ta, Cr, Mo, W) as a conventional technique regarding the components of the binder phase of the cBN-based ultra-high pressure sintered body (See, for example, Patent Document 1), titanium carbonitride with N / C ≦ 0.15, Al, W, Content and particle size of an intermetallic compound with at least one metal of Co and Zr (see, for example, Patent Document 2), TiCN, WC, AlN, TiB ₂ , Al ₂ O ₃ (See, for example, Patent Document 3), Ti, Zr, Hf, Ta carbide, nitride, carbonitride, Al compound, Al ₂ O ₃ content, and cBN particles Containing a structure bonded through an Al compound (for example, see Patent Document 4) .) There is.

  Among these prior arts, those containing nitrides of Zr and Hf improve the heat resistance and chemical stability of the binder phase and improve the wear resistance, but the toughness, thermal conductivity, etc. Insufficient wear resistance and chipping resistance are inferior, and there is a problem that wear resistance is insufficiently improved because hardness decreases.

JP-A-7-172924 JP-A-7-286229 JP-A-8-81270 JP-A-8-253837

  The present invention solves the above-described problems. Specifically, at least one of a composite nitride containing at least one of Zr and Hf and Ti and a composite carbonitride is used as a raw material powder. In addition, by reacting with cBN during sintering to include a composite boride containing at least one of Zr and Hf and Ti, the hardness, toughness, heat resistance, chemical stability, and thermal conductivity of the binder phase It is an object of the present invention to provide a cBN-based ultra-high pressure sintered body that is improved in wear resistance, fracture resistance, and chipping resistance by improving the above.

  The present inventor has been studying the improvement in the life of a cBN-based ultrahigh-pressure sintered body for cutting high-hardness steel. When the binder phase contains at least one nitride of Zr and Hf, the heat resistance and steel The chemical stability against wear is improved and wear resistance is improved, and the inclusion of at least one boride of Zr and Hf increases the hardness, toughness and thermal conductivity to increase wear resistance and chipping resistance. In order to improve the property, and to contain at least one nitride and boride of Zr and Hf, a composite nitride with Ti can be used as a starting material and sintered with cBN (cubic boron nitride). The present inventors have obtained knowledge that it is better to complete the present invention.

That is, the cBN-based ultrahigh-pressure sintered body of the present invention has cBN: 30 to 80% by volume, and the remainder is a carbide, nitride, boride, oxide, or Al nitride of the periodic table 4a, 5a, and 6a group elements. In a cBN-based ultrahigh pressure sintered body composed of a binder phase consisting of at least one of oxides, oxides, Si carbides, nitrides and their mutual solid solutions and inevitable impurities, the binder phases are (1) Zr and Hf (2) a composite boride containing at least one of Zr and Hf and Ti, and (3) AlN. And (4) Al ₂ O ₃ .

Specifically, the composite compound which is an essential component (1) of the binder phase in the cBN-based ultrahigh pressure sintered body of the present invention includes (Ti, Zr) N, (Ti, Hf) N, (Ti, Zr, Hf) N, (Ti, Zr, Hf) (C, N) and the like. These composite nitrides and composite carbonitrides are referred to as (Ti _1-a M _a ) (C _1-b N _b ) (where M represents at least one of Zr and Hf). Where a represents the atomic ratio of M to the sum of Ti and M, b represents the atomic ratio of N to the sum of C and N, and a and b are 0.1 ≦ a ≦ 0, respectively. .6, 0 ≦ b ≦ 0.7 is satisfied. If the value of a is less than 0.1, the wear resistance is inferior, and if it exceeds 0.6, the chipping resistance decreases. If the value of b exceeds 0.7, the chemical stability with respect to the steel decreases rapidly and the wear resistance decreases. Further, the content of the composite compound such as composite nitride or composite carbonitride is preferably 40 to 75% by volume with respect to the entire binder phase. When the amount is less than 40% by volume, the effect of improving the wear resistance is small. When the amount exceeds 75% by volume, the amount of the composite boride is relatively reduced and the chipping resistance is lowered.

Specific examples of the composite boride which is an essential component (2) of the binder phase include (Ti, Zr) B ₂ , (Ti, Hf) B ₂ , and (Ti, Zr, Hf) B ₂ . Here, since the composite boride is a compound in which the composite compound of the essential component (1) is changed to a boride by a sintering reaction, the ratio of Ti, Zr, and Hf substantially matches the composite compound. When these composite borides are expressed as (Ti _1-c M _c ) B ₂ (where M is at least one of Zr and Hf), c is M relative to the sum of Ti and M. It is preferable that c satisfies 0.1 ≦ c ≦ 0.6. If the value of c is less than 0.1, the wear resistance is inferior, and if it exceeds 0.6, the chipping resistance decreases. Moreover, 10-40 volume% is preferable with respect to the whole binder phase content of a composite boride. If it is less than 10% by volume, the effect of improving the chipping resistance is small, and if it exceeds 40% by volume, the amount of complex compounds such as complex nitrides and complex carbonitrides is relatively reduced and wear resistance is lowered.

AlN, which is an essential component (3) of the binder phase, is produced by a reaction between metal Al, which is a sintering aid, and cBN, and the amount thereof is preferably in the range of 10 to 30% by volume with respect to the whole binder phase. If it is less than 10% by volume, the sinterability is inferior, and if it exceeds 30% by volume, the hardness and toughness are lowered and both the wear resistance and chipping resistance are inferior. The essential component (4), Al ₂ O _3, is produced by a reaction between metal Al, which is a sintering aid, and oxygen in the raw material powder or mixed in the process. % Is preferred.

In addition to the above four essential components, carbides, nitrides and borides of periodic table 4a, 5a and 6a elements such as ZrC, HfN, VB, TaB, CrB, WC, ZrO ₂ , SiC and Si ₃ N ₄ , Oxide, Si carbide, and nitride may be contained. The total content of these compounds is preferably 20% by volume or less with respect to the entire binder phase.

  If the content of cBN in the cBN-based ultra-high pressure sintered body of the present invention is less than 30% by volume, the strength and toughness tend to decrease and chipping easily occurs. Conversely, if the content exceeds 80% by volume, the reaction between cBN and steel occurs. In order to increase wear, the volume was determined to be 30 to 80% by volume.

  One of the methods for producing a cBN-based ultrahigh-pressure sintered body of the present invention is a composite nitride, composite carbonitride and composite carbonitride containing cBN powder, at least one of Zr and Hf, and Ti. A first step of mixing and pulverizing at least one kind of powder and a metal aluminum powder; a second step of sintering the mixed powder obtained in the first step at a pressure of 3 to 7 GPa and a temperature of 1300 to 1600 ° C. under a high pressure and high temperature It includes a process. One of the methods for producing a cBN-based ultrahigh-pressure sintered body of the present invention is a composite nitride, composite carbonitride, and composite carbonitride containing cBN powder, at least one of Zr and Hf, and Ti. Among at least one kind of powder, metallic aluminum powder, and carbides, nitrides, borides, oxides, Al nitrides, oxides and Si carbides and nitrides of Group 4a, 5a, and 6a elements of the periodic table First step of mixing and pulverizing at least one kind of binder phase forming powder, and second step of sintering the mixed powder obtained in the first step under a pressure of 3 to 7 GPa and a temperature of 1300 to 1600 ° C. Is included.

As the starting material, at least one powder of composite nitride and composite carbonitride containing at least one of Zr and Hf and Ti, for example, a mixed powder of ZrN, HfN and TiN, TiCN and TiH ₂ is used. It is a solid solution by vacuum heating. When the composition formula of this powder is represented by (Ti, M) (C, N) _x (where x represents the atomic ratio of C and N to the total of Ti and M), the value of x Is preferably in the range of 0.6 to 0.9. This is because if the value of x is less than 0.6, the ratio of the composite boride produced by the sintering reaction is high, and conversely if it exceeds 0.9, the ratio of the composite boride decreases.

  The cBN-based ultrahigh-pressure sintered body of the present invention is a composite nitride containing at least one of Zr and Hf and Ti, and the composite carbonitride acts to increase heat resistance and chemical stability against steel, The resulting composite boride containing at least one of Zr and Hf and Ti acts to increase the hardness, toughness and thermal conductivity, and as a result, the wear resistance of the resulting cBN-based ultrahigh pressure sintered body It works to improve the chipping resistance at the same time.

  The cBN-based ultrahigh-pressure sintered body of the present invention has an effect that it can achieve a life that is approximately twice that of conventional cBN-based ultrahigh-pressure sintered tools, particularly with high-speed intermittent turning of high-hardness steel.

First, commercially available ZrN having an average particle diameter of 1.7 μm, HfN having an average particle diameter of 2.3 μm, TiN having an average particle diameter of 1.5 μm, TiC having an average particle diameter of 1.5 m, and TiH _{2 having} an average particle diameter of 5 μm. Each powder was weighed to the composition shown in Table 1, and 0.2% by weight of paraffin wax and hexane solvent were inserted into a stainless steel pot together with a cemented carbide ball, and the ball mill for 24 hours. Thereafter, it was dried to obtain a mixed powder. These mixed powders were lightly filled into a zirconia crucible and inserted into a heating furnace, and then heated in a vacuum of about 5 Pa and subjected to heat treatment at 1600 ° C. for 1 hour. The treated powder was crushed and pulverized for 48 hours by the ball mill to obtain composite carbonitride powders (A) to (D). Table 1 also shows the composition formula obtained by calculation from the average particle size (FSSS) of the obtained powder and the measurement results of nitrogen content, carbon content, and oxygen content. X-ray diffraction confirmed that all the powders were almost uniform solid solutions.

The obtained composite carbonitride powders (A) to (D), the aforementioned ZrN, HfN, TiC, and commercially available cBN having an average particle diameter of 3.0 μm, TiN _{0.7 having} an average particle diameter of 1.2 μm, an average Table 2 shows each powder of metal Al having a particle diameter of 0.9 μm, WC having an average particle diameter of 0.5 μm, and ZrO ₂ having an average particle diameter of 0.2 μm in which 3 mol% of Y ₂ O ₃ is dissolved. The composition was weighed and inserted into a stainless steel pot lined with urethane together with a cemented carbide ball, hexane solvent, and paraffin, and dried in nitrogen to obtain a mixed powder.

  Next, the obtained pressed powder compact was placed on a cemented carbide base metal, embedded in a zirconium capsule, inserted into a vacuum heating furnace, and degassed at 800 ° C. for 1 hour. Thereafter, the capsules were set in an ultra-high pressure and high temperature generator, sintered under the conditions of a pressure of 5.5 GPa, a temperature of 1450 ° C., and a holding time of 30 minutes. CBN-based ultra-high pressure sintered body was obtained. And the sample for a measurement was produced by cutting by electric discharge machining, grinding by diamond, and lapping, and Knoop hardness (load: 4.8 N) was measured. The results are also shown in Table 2.

  Moreover, after identifying the component of each sample by X-ray diffraction method, the content of each component was calculated | required by collating the image analysis result of the structure | tissue photograph image | photographed with the scanning electron microscope, and the quantitative analysis result by X-ray diffraction method. And about the binder phase component, the ratio was computed. These results are shown in Table 3. When the amounts of Ti, Zr, and Hf in the composite nitride, composite carbonitride, and composite boride contained in the product of the present invention were analyzed by EDS, the composition formula of the composite carbonitride powder used in the blending (Table 1).

From the results of Table 3, the product of the present invention using composite carbonitride as the starting material for the binder phase contains composite boride, whereas the comparative product using TiN, ZrN, and HfN separately. It can be seen that the boride formed is TiB ₂ and does not form a composite nitride.

The sintered bodies of the present invention products 2, 3, 5, 8, 9 and comparative products 1, 3, 4, 5 obtained in Example 1 were cut by electric discharge machining and applied to chip tips made of cemented carbide. The chip shape for cutting test: TNMA160408 was produced through grinding with a diamond grindstone. And the cutting test by the following conditions was done and the result was shown in Table 4.
(A) Peripheral intermittent wet cutting; Work material: Carburizing and quenching material of SCM415 (with two grooves, HRC = 61), Cutting speed: 200 m / min, Cutting amount: 0.5 mm, Feeding amount: 0.1 mm / rev, evaluation criteria: average flank wear amount VB = 0.2 mm or cutting time until chipping and chipping.
(B) End face intermittent dry cutting; Work material: FC30 (HB210-230), Cutting speed: 400 m / min, Cutting amount: 0.5 mm, Feeding amount: 0.20 mm / rev, Evaluation criteria: Average flank wear amount Cutting time until VB = 0.2mm or chipping and chipping.

  From the results in Table 4, the product of the present invention has an average life of 1.9 times in high-speed intermittent turning of carburized and hardened steel and 1.4 times in high-speed turning of casting, compared with the comparative product. It turns out to be effective for high-speed cutting.

Claims (4)

cBN: 30 to 80% by volume, and the remainder is periodic table 4a, 5a, 6a group element carbide, nitride, boride, oxide, Al nitride, oxide, Si carbide, nitride and these In a cBN-based ultrahigh-pressure sintered body composed of at least one binder phase and inevitable impurities in the mutual solid solution, the binder phase is (1) a composite nitride and composite containing at least one of Zr and Hf and Ti CBN containing at least one complex compound of carbonitride, (2) a complex boride containing at least one of Zr and Hf and Ti, (3) AlN, and (4) Al ₂ O ₃ Super high pressure sintered body. The bonded phase is (Ti _1-a M _a ) (C _1-b N _b ) (wherein M represents at least one of Zr and Hf, and a represents a combination of Ti and M with respect to the entire bonded phase. B represents the atomic ratio of N to the sum of C and N, and a and b satisfy 0.1 ≦ a ≦ 0.6 and 0 ≦ b ≦ 0.7, respectively. Compound compound represented by: 40 to 75% by volume and (Ti _1-c M _c ) B ₂ (wherein M represents at least one of Zr and Hf, and c represents the sum of Ti and M) M represents the atomic ratio of M to C, and c satisfies 0.1 ≦ c ≦ 0.6.) Composite boride represented by: 10 to 40% by volume, AlN: 10 to 30% by volume, Al ₂ O ₃ : cBN-based ultrahigh-pressure sintered body composed of 2 to 20% by volume.   First step of mixing and crushing cBN powder, at least one of composite nitride containing at least one of Zr and Hf and Ti, composite carbonitride and composite carbonitride, and metal aluminum powder A method for producing a cBN-based ultrahigh-pressure sintered body comprising a second step of sintering the mixed powder obtained in the first step at a pressure of 4 to 6 GPa and a temperature of 1400 to 1600 ° C. under high pressure and high temperature. cBN powder, composite nitride containing at least one of Zr and Hf, and Ti, at least one of composite carbonitride and composite carbonitride, metallic aluminum powder, periodic table 4a, 5a , A first step of mixing and grinding the carbide, nitride, boride, oxide, Al nitride, oxide and Si carbide of the group 6a element, and at least one binder phase forming powder in the nitride, A method for producing a cBN-based ultrahigh-pressure sintered body comprising a second step of sintering the mixed powder obtained in the first step at a pressure of 4 to 6 GPa and a temperature of 1400 to 1600 ° C under an ultrahigh pressure and high temperature.