JPS63201064A - Cubic boron nitride base superhigh pressure sintering material for cutting tool - 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] This invention has excellent wear resistance (resistance to particle drop-off) and is particularly useful as a cutting tool for finishing of high-hardness steel such as carburized and hardened steel. The present invention relates to a cubic boron nitride (hereinafter referred to as CBN)-based ultra-high pressure sintered material suitable for

[Conventional technology]

In recent years, the development of ultra-high pressure sintered materials based on CBN, which has high hardness, has progressed as material for cutting tools of high-hardness steel such as carburized and hardened steel. Group 4a, Group 5a, Group 6a, metal carbides, nitrides, borides, silicides, M203, MgO1A1. N%5
A CBN-based sintered material has been proposed that has a composition consisting of one or more of i5N4: 20 to 80% by weight, and the remainder: CBN and unavoidable impurities (see Japanese Patent Publication No. 57-3631). .

[Problem that the invention seeks to solve]

However, among the above conventional CBN-based sintered materials, T
C consisting of nitride of 1, CBN and unavoidable impurities
When using a BN-based sintered material as a cutting tool for finishing, for example, when turning carburized and hardened steel with a hardness of HRC: 60 or more, the H7 tolerance (when the outer diameter dimension is 20 discs, O~ The limit is to obtain a dimensional accuracy of 21μ) and a surface roughness of 3 to 4S, which falls short of the dimensional accuracy and surface roughness conventionally obtained in grinding of high-hardness steel. In the current situation where there is a shift from grinding to cutting with higher processing efficiency, the above CBN-based sintered material has satisfactory dimensional accuracy and surface roughness when used as a cutting tool for finishing high-hardness steel. Therefore, the conventional CBN-based sintered materials mentioned above have a problem in that the scope of their use as cutting tools is limited. In order to be able to use this technology, for the time being, materials that can finish the workpiece to a dimensional accuracy of at least H6 tolerance (0 to 13 μ for rigid materials with outer diameter class 20) and a surface roughness of 2S are required. There is.

[Findings based on research]

Therefore, as a result of various studies to solve these problems, the inventors of the present invention discovered that (1) Ti nitrides and carbonitrides (hereinafter referred to as TiN and T1CN, respectively) have been summarized. % in a sintered material consisting of T1 compound) and CBN.
Where T1 compound particles and CBN particles come into contact with each other, a glass phase with weak bonding strength is likely to be formed at the interface, and this glass phase reduces grain boundary strength by increasing the temperature of the cutting edge during cutting. Therefore, the glass phase-rich material was used as a cutting tool because the particles could not be retained sufficiently on the cutting edge surface, and as a result, the particles would fall off the surface prematurely, creating relatively large depressions there. (2) On the other hand, stable TiB2 is formed at the interface between Ti compound particles and CBN particles, and this stable TiB2 phase, contrary to the above, Even when the temperature of the cutting edge increases, sufficient grain boundary strength is maintained to firmly hold the particles, so that the particles do not fall off the cutting edge surface and are gradually worn away, so that the above-mentioned recesses do not occur on the surface. , the cutting edge surface remains relatively smooth during the cutting process, and therefore, when the TlB2 phase-rich material is used as a cutting tool, the dimensional accuracy and surface roughness of the product improve; (3) at the particle interface; In order to reduce the formation of the glass phase and increase the formation of the TlB2 phase, it is necessary to make the particle sizes of the Ti compound particles and the CBN particles the same, and to make the blending ratios of both particles as equal as possible based on their capacities. (4) In order to satisfy the requirements described in item (3) above without impairing the properties of the sintered material consisting of the Ti compound and CBN, the average particle diameters of both the Ti compound and CBN must be 0.5 ~ 5 μ, the average particle size ratio between them is within the range of 0.5 to 2.0, and the blending ratio of both is 40 to 60:60 to 40 (volume ratio). (5) One of the impurities contained in the sintered material described in item (4) above, for example, iron group metals and W that are mixed in by mixing with a mixing device such as a ball mill, or from other causes. In the sintered material, the content of impurities consisting of 0.
If the capacity is kept below 5, the toughness of this sintered material will improve, as well as its welding resistance and therefore wear resistance at high temperatures. We have discovered that excellent dimensional accuracy and surface roughness can be maintained even during high-speed cutting.

[Failure to solve the problem]

This invention was invented based on the above-mentioned knowledge, and has excellent "resistance to particle drop-off", which improves dimensional accuracy and surface roughness of products, especially in finishing of high-hardness steel such as carburized and hardened steel. The purpose is to provide a CBN-based ultra-high pressure sintered material for cutting tools that can improve the
N (7) One or two of these: 4o~60%, CBN having an average particle size: 0.5~5μ, and impurities: the remainder, and having a composition (volume %) consisting of: Ti
N, and one or two of T1CN and the CB
It is characterized in that the average particle size ratio with N is within the range of 0.5 to 2.0.

[Detailed description of the invention]

Next, the reason why the component composition range, average particle size, and average particle size ratio are limited to the above range in this invention will be described.

A. Component composition range T1 Compounds have the effect of imparting welding resistance and abrasion resistance to materials, but when their content decreases by 40% (capacity CH, the same applies hereinafter), the abrasion resistance decreases. As it becomes insufficient, the amount of T1 compound relative to CBH becomes too small, and the contact between CBN particles increases, thereby increasing the formation of the glass phase and further reducing the wear resistance of the sintered material. , and when the content increases by as much as 60%.

If the amount of CBH is too small, the thermal conductivity of the material is insufficient, welding is more likely to occur at the cutting edge, and the contact between the T1 compounds increases, which also significantly inhibits the formation of the glass phase. This reduces the wear resistance of the material, and in any case, when used for finishing high-hardness steel such as carburized and hardened steel, the dimensional accuracy and surface roughness of the product will decrease. Therefore, the content is 40 to 6
It was set as 0%.

Among the impurities, impurities consisting of iron group metals and W combine with KB during sintering to partially form a liquid phase, thereby promoting grain growth of the T1 compound and reducing the toughness of the material. At the same time, B contained in the sintered material in combination with the above components is difficult to diffuse into the rigid material when exposed to high temperatures during cutting, resulting in a decrease in the welding resistance of the cutting edge. Therefore, if it is desired to impart exceptional heat resistance and strength to the CBN-based sintered material of this invention and make it suitable for high-speed cutting, the inclusion of this impurity is necessary. It is important to keep the amount below 0.5%.

B, average particle size The average particle size of CBN particles or T1 compound particles is 0.5μ
If the particles become smaller than
Contact between N particles or T1 compound particles increases to prevent the formation of a glass phase that reduces grain boundary strength.On the other hand, if the average particle size of CBN particles exceeds 5μ, the particles themselves become brittle and are susceptible to sintering. The strength and abrasion resistance of the bonding material decreases, and the dimensional accuracy and surface roughness of the product deteriorate.In order to avoid the formation of the glass phase, the average particle size of the T1 compound particles must be equal to that of the CBN particles. Since it is necessary to make them uniform, the average particle diameters of both the Ti compound and CBN were determined to be 0.5 to 5 μm.

C1 average particle size ratio T1 Even if the average particle sizes of the compound and CBN are within the above range, if their mutual average particle size ratio is less than 0.5 or exceeds 2.0, these components will be removed. In the sintered material, the contact interface between the T1 compound and the CBN compound decreases, and the ratio of the glass phase formed at the interface between particles of the same type increases, causing the above-mentioned disadvantages. The average particle size ratio of the T1 compound and CBN was determined to be 0.5 to 2.0.

Note that the CBN-based sintered material of the present invention is produced using a normal ultra-high pressure sintering method, that is, first as a raw material powder.

All CBs have an average particle size within the range of 0.5 to 2.0.
N powder, TiN powder, and T1CN powder are prepared, and those having an average particle size ratio of T1 compound to CBN in the range of 0.5 to 2.0 are appropriately selected from these raw material powders to form a predetermined powder. The compounded composition is mixed, and then the mixed powder state or green compact state is inserted into a metal container together with a WCC cemented carbide plate as required, and heated at 800 to 1200°C. The sealed container is heated to a temperature of
70, humidity temperature: 200 to 16 oo Celsius, maintained at a pressure and temperature within the range of several minutes to several tens of minutes, cooled, and finally released the pressure. Can be done.

In addition, the CBN-based sintered material of the present invention, in which the content of impurities consisting of iron group metals and W is reduced to 0.5% or less, has impurities consisting of iron group metals and W in the mixed powder or green compact. For example, by adding or adopting a suitable method for removing the impurities during or after the preparation of the mixed powder, or by adding or adopting a suitable method to prevent the impurities from being mixed in the mixed powder, It can be manufactured by applying the above-mentioned ultra-high pressure sintering method to the mixed powder or green compact while employing the above-mentioned method. To remove impurities 1. For example, gently rotate a magnet in a mixed powder that is still in the form of a slurry after being mixed with a solvent such as acetone.
A method of adsorbing iron group metals and W combined with them to a magnet, or after drying the mixed powder,
A method of selectively dissolving the impurities by pickling it can be used.

Furthermore, when using the CBN-based sintered material of the present invention as a cutting tool, it can also be used as an indexable tip, either alone or in combination with a high-rigidity material such as WCC cemented carbide cermet. Furthermore, these tips may be used in a state where they are attached by brazing to the tip of a holder made of WCC cemented carbide hardened steel or the like.

〔Example〕

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

As raw material powder, CBN powder having average particle diameters of 0.8μ, ■, 5μ, and 3μ, 04μ and 1μ.

and TiN powder with 3 μ, and 1.5 μ, 3
Prepare T I C0,5NO,5 powders with μ and 6μ, and mix these raw powders with the blending ratio of the components shown in Table 1, excluding impurities consisting of iron group metals and W. After mixing with each other in diacetone using a ball mill for 5 hours and drying,
Mixed powders were formed, each having a blending composition shown in Table 1, and each containing two impurities mainly consisting of iron group metals and W originating from the mixing device.

Then, the mixed powder thus prepared was heated to 2 torrL/C.
After molding into a disc-shaped powder compact with dimensions of diameter: 13w x thickness: 1.5u at a pressure of IIL2, these compacts were inserted into a container of an ultra-high pressure and high temperature generator, and heated with a pressure crab of 50K.
b. By performing ultra-high pressure sintering under the conditions of temperature: 150CIC1 holding time: 5 minutes, a Ti compound having substantially the same component composition as the blended composition and substantially the same average particle size as the raw material powder is produced. Invention C consisting of particles and CBN particles
Each of BN-based sintered materials 1 to 8 was produced, and while the mixed powder was still mixed with acetone and turned into a slurry, the surface was covered with a Teflon sheet (Teflon is a trademark of DuPont, USA). A round bar-shaped permanent magnet was gently rotated in the slurry for 2 hours to separate the iron group metal and W.
The CBN-based sintered material of the present invention was prepared using the same procedure as the above-mentioned method, except that the impurities consisting of were adsorbed and removed, thereby reducing the impurity content as shown in the m1 table. 9 to 11 were produced, respectively.

Further comparison, component composition range, T1 compound and CBH
Any one of the average particle diameters of the particles and the ratio of these average particle diameters to each other falls outside the scope of the present invention (deviating conditions are referred to as the first condition).
Comparative CBN-based sintered materials 1 to 5 (indicated by * in the table) were each produced in the same manner as above.

Next, the resulting CBN-based sintered materials 1 to 1 of the present invention
8. For comparative CBN-based sintered materials 1 to 5, transverse rupture strength was measured for the purpose of evaluating toughness, welding resistance and wear resistance at high temperatures were evaluated, and dimensional accuracy obtained in finishing of high-hardness steel. For the purpose of evaluating the surface roughness, cutting chips were cut from each of the above sintered materials, brazed to a we-based cemented carbide holder, and polished. (Surface hardness: HR
C60±1, carburizing depth: 07u or more) round bar (diameter:
150ruL), cutting speed: 100m/fox, depth of cut: 0.05m.

Send 1! ) 20, 24 mt/rev
, .

A continuous cutting test was carried out under the conditions of cutting time: 2o, and the flank wear width of the cutting edge was measured, and the surface roughness of the cut product was measured using a surface roughness meter. Regarding CBN-based sintered materials 9 to 11, the same properties as above were investigated, and the same cutting tests were performed under the same conditions as above, except that only the cutting speed was increased to 15 Qm/miu, and the same results were obtained. The flank wear width of the cutting edge and the surface roughness of the product were measured, and these results are also shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, the CBN-based sintered material 1 of the present invention
-11 all have high toughness and wear resistance, so they exhibit excellent cutting performance and produce products with excellent dimensional accuracy and surface roughness in finishing of carburized and hardened steel. You can also out of these sintered materials.

CBN-based sintered materials 9 to 11 of the present invention all have improved heat resistance due to the removal of impurities consisting of iron group metals and W. Comparative CBN-based sintered materials 1 to 5 exhibit performance equivalent to that of CBN-based sintered materials 1 to 5, but any of the component composition range, average particle size, and average particle size ratio are outside the scope of this invention.
It can be seen that the dimensional accuracy and surface roughness are inferior.

As mentioned above, the CBN-based sintered material of the present invention has particularly excellent "particle dropout resistance", so when used as a cutting tool for finishing of high-hardness steel such as carburized and hardened steel. , it is possible to manufacture products with improved dimensional accuracy and surface roughness, and in addition, the impurities of the sintered material, especially those consisting of iron group metals and W, are reduced to below a specified amount, resulting in improved heat resistance and toughness. The CB of this invention is excellent.
The N-based sintered material also has the effect of being able to withstand high-speed cutting and improving processing efficiency.

Claims (2)

[Claims] (1) Ti nitride having an average particle size of 0.5 to 5 μ;
and one or two carbonitrides: 40-60%
, cubic boron nitride having an average particle size of 0.5 to 5 μm and the remainder impurities (volume %), and the Ti
nitride, and one or two of carbonitrides,
The average particle size ratio with the cubic boron nitride is 0.5 to
A cubic boron nitride-based ultra-high pressure sintered material for cutting tools, characterized in that the pressure is within the range of 2.0. (2) Among the impurities, Fe, Co, Ni, and W
The sintered material according to claim 1, wherein the content of one or more impurities selected from the following is 0.5% by volume or less.