JPS61183167A - Crack-resistant cubic boron nitride base sintering material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention has particularly excellent fracture resistance, as well as excellent wear resistance, heat resistance, oxidation resistance, and chemical stability at high temperatures. A cubic boron nitride (hereinafter referred to as CBN) based cutting tool suitable for high-speed cutting of high-hardness steel such as cast iron, die steel, and high-speed steel, and heavy-duty cutting with high depth of cut and high feed. It concerns sintered materials.

[Conventional technology]

In recent years, in the field of metal cutting, the speed of cutting cast iron has increased, and the switch from grinding to cutting of high-hardness steels such as die steel and high-speed steel has progressed rapidly. Sintered materials have attracted attention, and a large number of CBN-based sintered materials have been proposed.

Among these CBN-based sintered materials, especially high-grade materials consisting of carbides, nitrides, carbonitrides, carbonates, or carbonitrides of metals from groups 4a*, 5a*, and 6a of the periodic table. Melting point compound: 5-50%, aluminum oxide (hereinafter A
(denoted as Z, O,) = 10 to 70 も.

CBN-based sintered material (Japanese Patent Publication No. 59-2
7303) has excellent wear resistance, heat resistance,
It is useful as a cutting tool because of its oxidation resistance and chemical stability at high temperatures.

[Problem that the invention seeks to solve]

However, the conventional CBN-based sintered material described above is, for example, die steel (S
When used as a throw-away tip for cutting KD-1i), at a cutting speed of 150 m/min,
When the depth of cut is set to 0.3 or more, or the feed is set to 0.3 W or more, even though the wear of the chip cutting edge is in the early stages, peeling occurs parallel to the rake face (in a two-shell shape) from the nose of the cutting edge. This caused the product to reach the end of its service life.

The causes of this are the high temperature of the cutting edge that occurs when cutting high-hardness steel, which causes minute thermal cracks and microchips, and in addition, high-load cutting (especially high-feed cutting) that causes excessive cutting resistance (especially back force and This is thought to cause cracks to easily propagate in the direction parallel to the rake face, resulting in peeling and chipping.

Furthermore, to examine the cause in detail, the above-mentioned conventional CBN-based sintered material is heated to a high temperature using an ultra-high pressure container, and as shown in the schematic longitudinal cross-sectional view in FIG. The sample S is inserted into the center via a solid pressure medium 4 while being sandwiched between the upper and lower anvils 2.3, and is manufactured by pressurizing the sample by moving the upper and lower anvils 2.3 in the vertical direction, respectively. Therefore, the force applied to the sample S is relatively larger in the vertical direction than in the horizontal direction. Therefore, when the manufactured sintered material is observed microscopically, it shows the structure as shown in the schematic diagram in Figure 2. The CBN particles, which are the dispersed phase forming component, are distributed in a flattened state in the direction of pressure.

This is because when considering the solid phase reaction in the state of contact between CBN particles and the binder, the solid phase reaction is more accelerated in the plane perpendicular to the pressurizing direction, and the CBN particles move in the pressurizing direction. It is thought that due to plastic deformation, the CBN grain boundaries take on an elongated shape in the horizontal direction, as shown in Figure C21.
As a result, the sintered material has a type of flow line structure that flows along a plane (horizontal direction) perpendicular to the pressing direction, and when the sintered material in this state is used as a cutting tool,
CBN particles have a flow line parallel to the back force and feed force direction during cutting, and when a high load is applied, cracks parallel to the rake face start from small thermal cracks and microchipping. It is thought that this can easily propagate and lead to peeling.

[Means for solving problems]

Therefore, the inventors of the present invention conducted research to solve the problems of the conventional CBN-based sintered materials from the above-mentioned viewpoints.

(2) The distribution of CBN particles as a dispersed phase-forming component in the conventional CBN-based sintered material is shown in Figure 3 (2). -70% by volume, 30-70% by volume of fine particles with a particle size of less than 1-5 μm
If a mixed grain structure is created in which , ,
The pressure applied to the material itself becomes uniform and averaged, and as a result, selective promotion of the solid phase reaction on the plane perpendicular to the pressurizing direction of each CBN particle is prevented, and
The CBN particles are compressed in the pressurizing direction (: the frequency of crushing is significantly reduced (second), the formation of a flow line structure of the CBN particles is suppressed, and the fracture resistance is dramatically improved. To become.

(b) As seen in Figure 2, relatively coarse CB
If only N particles are present, the CBN particles form bridges with each other more frequently, and if pressure sintering is performed in this state, the edges of the CBN particles forming the bridges will become stressed (secondarily destroyed). In addition, during the sintering process, microvoids are formed in areas where pressure transmission is insufficient due to bridges between CBN particles (:), so it is difficult to obtain a high-strength sintered material, but as shown in Figure 3 (= So that you can see it (
=Mixed grain structure (with this, the formation of bridges between CBN particles and the formation of microvoids are significantly suppressed, making it possible to obtain a high-strength sintered material.

The findings shown in (2) and (c) above were obtained.

This invention was made based on the above findings, and includes carbides, nitrides, and carbonitrides of Ti, Zr, and Ta, as well as carbides of W, borides of Ti (hereinafter referred to as
Tie, TiN, T1CN*Zr respectively
C*ZrN + ZrCN.

TaC, TaN, TaCN, W C, and T
iB).

Further (= one or more of these two or more solid solutions (hereinafter collectively referred to as high melting point compounds)) = 10 to 40 range.

CBN-based sintered material containing A4-Ol: 3 to 30%, and the remainder consisting of CBN (containing 50 to 80%) and unavoidable impurities (the above is the capacity range, and the following is the capacity range). In materials,
The particle size distribution of CBN particles as a dispersed phase forming component is as follows: coarse particles with a particle size of 5 to 18 μm: 30 to 70%, and particle size of 1 to 18%.
Fine particles less than 5 μm: 30 to 70% of the CBN-based sintered material has improved fracture resistance and strength.

Next, in the CBN-based sintered material of this invention.

The reason why the component composition and the particle size distribution of CBN particles are limited as described above will be explained.

(2) Content of high melting point compounds These components themselves have high high temperature hardness, elastic modulus, and thermal conductivity, and have a small coefficient of thermal expansion, and therefore improve the heat resistance and wear resistance of the material. As a result, when cutting high-hardness steel, it has the effect of suppressing as much as possible the occurrence of minute thermal cracks and microchips, which are the starting points of peeling and chipping, and when sintering, it forms a skeleton structure and strengthens the material. However, if the content is less than 101, the desired effect cannot be obtained in this effect, while if the content exceeds 40, the content of CBN will be relatively low and the material Since the wear resistance of
~404.

In addition, when manufacturing the material, especially as a raw material powder, T
When using T1□A/, N produced by reacting iN and a Ti-At intermetallic compound, this T
i, AtN reacts with CBN which rapidly splits at a sintering temperature of 1200°C or higher to produce TiB, and this T
I B * is CBN, a high melting point compound, and ht t
Since the sintered material precipitates by going around into the voids existing between the Os, the obtained sintered material has even better toughness.

(c) Content of At, O, AA, O, component gives the material excellent oxidation resistance and chemical stability at high temperatures, especially serves as an interface between the cutting edge and the rigid material, and Suppresses boundary wear on the front cutting edge and side cutting edge, which are exposed to sharp thermal gradients, and crater wear on the rake face, which is scraped by high-temperature chips, thereby preventing damage to the cutting edge, which is the starting point for chipping. However, if its content is less than 3%, not only will the desired effect not be obtained, but also a skeleton structure rich in toughness cannot be sufficiently formed during sintering. If the content exceeds the CBH content, the CBH content becomes relatively too small and it becomes impossible to secure the desired excellent wear resistance, so the content was set at 3 to 30 parts.

(c) Content of CBN The CBN component has the effect of imparting high hardness, excellent chemical stability, and high thermal conductivity to the material due to its own properties, but its content is less than 50%. However, if the content exceeds -80,000 yen, the sinterability deteriorates significantly and the CBN particles tend to fall off, resulting in a significant deterioration of the wear resistance. The content was set at 50% to 80% since it would lead to a large amount of carbon.

tD Particle size distribution of CBN particles The particle size and distribution ratio of coarse and fine CBN particles were determined empirically based on the results of numerous experiments. Coarse particles with a particle size of 5 to 18 μm: 30 to 70 blood.

When distributed in the ratio of 30 to 70% fine particles with a particle size of less than 1 to 5 μm, the above particles have excellent fracture resistance and high strength. When coarse grains and fine grains do not exist in the above ratio, crack propagation resistance decreases, the fracture toughness value of the CBN particles themselves decreases, the frequency of bridges between CBN particles increases, and CBH
Due to at least one of the formation of a flow line structure, it becomes impossible to provide excellent fracture resistance and high strength.

〔Example〕

Next, the CBN-based sintered material of the present invention will be specifically explained using examples.

As raw material powder, average particle size: 0.5 μm.

3 laces me 7 laces m, 15 laces, and 5 with 30 μm
Types of CBN powder, 0.2 am ultrafine At5O
S powder, TIC powder with an average particle size within the range of 0.1 to 5 μm, ZrC powder, TaC powder, TEN powder, Z
rN powder, TaN powder, T1CN powder, ZrCN powder, TaCN powder, Ni powder, Ti*kl N powder, (
Ti, Ta) C powder, (Ti, Zr) N powder, (Ti
, W) CN, and (Ti, Ta, W) CN
After preparing powders, blending these raw material powders into a predetermined composition, and mixing in a ball mill for 5 hours.

It is press-molded into a green compact at a pressure of 1,5 tonz-, and then this green compact is subjected to ultra-high pressure using an ultra-high pressure device under the conditions of a pressure crab of 60,000 atm, temperature: 1500°C, and holding time: 60 minutes. By sintering, sintered materials 1 to 18 of the present invention and conventional sintered materials 1 to 3, each having the composition shown in Table 1, were produced.

Next, the particle size distribution of CBN particles was measured for the resulting sintered materials 1 to 18 of the present invention and conventional sintered materials 1 to 3.
To braze the C cemented carbide holder, a cutting tool with the shape of 5NP432 M was created through a series of processing, grinding, and polishing steps, and this cutting tool was used.

Work material: High speed steel (SKD-11, hardness: HRC60)
, Cutting speed: 170 m/min.

Depth of cut: 0.5m.

Continuous high-speed/heavy cutting tests were conducted on high-hardness steel under the conditions of feed: 0.3 tone/rev.
The cutting time until the rake face wear depth of the cutting edge reached 100 μm was measured. The results of these measurements are shown in Table 1.

〔Effect of the invention〕

As is clear from the results shown in Table 1, all of the sintered materials 1 to 18 of the present invention exhibit excellent wear resistance and chipping resistance, and exhibit excellent cutting performance throughout their service life. On the other hand, conventional sintered materials 1 to 3 all have C
Since the BN particles were mainly composed of coarse particles crushed into flat shapes, the cutting edge was damaged within 8 minutes after the start of cutting, and the service life was reached.

As mentioned above, the CBN-based sintered material of the present invention has particularly excellent fracture resistance and high strength, and also has excellent wear resistance and
It has excellent heat resistance, oxidation resistance, and chemical stability at high temperatures, so it is suitable for high-speed cutting of high-hardness steel such as cast iron, die steel, steel, and high-speed steel, as well as high depth of cut and high feed. When used as a cutting tool for heavy cutting, it exhibits excellent cutting performance over an extremely long period of time, making it industrially useful.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing the main parts of a manufacturing apparatus for CBN-based sintered material, FIG. 2 is a schematic organization diagram of a conventional CBN-based sintered material, and FIG. 3 is a schematic diagram of a CBN-based sintered material of the present invention. This is an organizational chart. In the drawings, 1... cylinder, 2...
...Upper anvil. 3... Lower anvil, 4-... Solid pressure medium, S
···sample.

Claims (1)

[Claims] One or more of carbides, nitrides, and carbonitrides of Ti, Zr, and Ta, carbides of W, borides of Ti, and solid solutions of two or more of these. :10
~40%, aluminum oxide: 3~30%, and the rest is cubic boron nitride (50~80%).
In a cubic boron nitride-based sintered material having a composition (volume %) consisting of unavoidable impurities, of the cubic boron nitride as a dispersed phase forming component, coarse grains with a particle size of 5 to 18 μm are used. 30 to 70% by volume, and 30 to 70% by volume of fine particles with a particle size of less than 1 to 5 μm.
A cubic boron nitride-based sintered material with excellent fracture resistance, characterized by improved fracture resistance by having a particle size distribution that occupies .