JPS58107468A - Sintered material for high hardness tool and preparation thereof - Google Patents

Abstract

PURPOSE:To provide a sintered material for a high hardness tool having high tenacity and anti-wear property, obtained by preparing the sintered material consisting of a specific ratio of high pressure phase type boron nitride, Al2O3, a ferrous metal, Cu, Al, MgO and Y2O3. CONSTITUTION:A sintered material, wherein high pressure phase type boron nitride is contained in an amount of 30-85% by volume, the remainder bonding phase is constituted of a mixture or a compound consisting of one kind or more of Al2O3, AlN, SiC, Si3N4 and B4C, on the wt. basis to the bonding phase, 5- 30% ferrous metal, 1-15% Cu, 5-30% Al and 0.1-5% MgO and/or Y2O3, is prepared. The high pressure phase type boron nitride is cubic crystal boron nitride or wurtzite type boron nitride and said sintered material is obtained by a method wherein various stock material powders are mixed and molded and the resulting molded mixture is sintered under pressure of 20kg/cm<2> or more at 900 deg.C or more by an ultra-high pressure apparatus.

Description

[Detailed description of the invention] Cubic boron nitride (Cubic Boron N1tr)
IDE (hereinafter abbreviated as CBN) is a substance with the second highest hardness next to diamond, and is also a substance with excellent heat resistance and wear resistance, and is synthesized under ultra-high pressure and high temperature.

Various attempts have been made to sinter only this CBN, but
For this purpose, as described in Japanese Patent Publication No. 39-8948, for example, it is necessary to sinter about 70 kb or more under ultra-high pressure and high temperature of 190.0° C. or more. Although current ultra-high pressure and high temperature equipment can generate such high pressure and high temperature conditions,
When the equipment is enlarged to an industrial scale, the number of times the high pressure and high temperature generating section can be used is limited, making it impractical. Furthermore, although a sintered body made only of CBN has high hardness, it has poor toughness when used as a tool.

In addition, sintered bodies made of CBN bonded with metals such as Go are used in some parts. When this CBN sintered body is used as a whole-cutting tool, there is a drawback that the cutting edge of the tool is damaged at an early stage, especially when there is interrupted cutting. This seems to be because most of the binding metal CO reacts with CBN to form a brittle CO poride.

The present inventors did not create a sintered body bonded with such metals,
We have already applied for a patent for the complete specification of a CBN sintered body suitable for cutting tool applications, which uses a hard metal compound with high strength and excellent heat resistance as a binder phase. This application relates to carbides and nitrides of transition metals of groups 4a, 5a, and 6a of the periodic table.

CBN particles are bonded together in a continuous phase of succinic compounds, silicides, or mutual solid solution compounds of these, which have high strength and heat resistance, maintain high thermal conductivity even at high temperatures, and are particularly resistant to thermal shock. This provides a sintered body for high-hardness tools with rich properties.

In this invention, in order to make the most of the excellent thermal conductivity of CBN, the binder is also a heat-resistant compound with good thermal conductivity, and the sintered body as a whole has extremely excellent thermal conductivity. However, depending on the intended use of the tool, thermal conductivity may not be the first required characteristic, but rather strength or heat resistance may be the first required characteristic, and for such applications, the inventors have The bonded phase is A! go, , , AJN, SiC,S
i) A CBN sintered body consisting of one type or a mixture of two or more of BH3 and B4C, or a compound mainly composed of these compounds, which form a continuous phase in the sintered body structure, has been disclosed and a patent application has already been filed. .

The present inventors conducted various cutting tests using these sintered bodies and as a result confirmed innovative tool characteristics.

However, when milling a rigid material with a complicated shape, for example, the cutting edge of the tool still suffers from chipping, which is a problem. The reason for this is presumed as follows.

At the interface between CBN and the binder phase, the two react to generate a large amount of polide. This polide has high hardness but is a very brittle substance, which probably lowered the overall integrity of the CBN sintered body.

The present inventors considered that in order to improve the overall quality of the CBN sintered body, it would be best to suppress the formation of this polide and increase the toughness of the binder phase itself, and conducted various studies.

As a result, it has been found that by adding Cu to the binder, the formation of polide is suppressed, and the iron group metal of the binder remains as a compound with Cu, thereby improving toughness.

For example, when a metal such as Go is added to improve toughness, most of the CO forms a brittle polide and the toughness does not improve.

However, when Cu is added to the binder, even if a liquid phase is generated during sintering, the generation of polide is suppressed, and the iron group metal and Cu
was found to remain in the sintered body as a solid solution or compound. Utilizing this phenomenon, the inventors of the present invention conducted repeated research in order to produce an entire CBN sintered body with high toughness and excellent wear resistance. As a result, CBN received an A! =Oa, AJN, S
The sintered body combined with one or more mixtures or compounds of iC, Si3N4, 84C, iron group metals, Cu, AJ compounds, and MgO and/or Y2O3 has unprecedented high toughness and wear resistance. It turns out that it has sex.

The reason why the sintered body of the present invention exhibits excellent performance is presumed as follows. In the sintered body of the present invention, the formation of the polide phase is suppressed, so even if it exists, it is extremely thin.
Ano2o3A1N, SiC,5t
aN4. Although it appears to be bonded to B4C, the bonding strength between these phases is very high, and since the polide phase is thin, cracks rarely occur within this phase. This is probably due to its high toughness.

Further, the performance of the sintered body of the present invention is improved by adding AJ. This is because, for example, in liquid phase sintering of WC-Co cemented carbide, if there is a phenomenon of dissolution of hard particles into the binder phase and re-precipitation, a product with high bonding strength between the binder phase and the hard particles or between the hard particles can be obtained. , the sintered body of the present invention contains M in the binder phase.
Or A! This is probably because a phenomenon similar to this occurred due to the presence of the compound. Furthermore, since M has a low melting point, the addition of AJ improves sinterability, and a sintered body with high hardness can be obtained even when sintered at a low temperature. MgO and/or Yl
108 is AnoBOs, AJN, SiC, Si3N
4. Acts as a grain growth inhibitor for B4C crystals or crystals of two or more compounds.

The content of iron group metals is 596 or more and 30% by weight in the binder.
The following is good. If the content of iron group metals is less than 596, the strength of the compound of iron group metals, Cu, and AJ decreases, and if it exceeds 30%, the content of Cu in the binder decreases relatively, leading to the formation of polide. cannot be suppressed. The content of Cu in the binder is preferably 196 or more and 15% or less by weight. If the Cu content is less than 196%, the formation of polide cannot be suppressed, and if it exceeds 15%, the strength of the iron group metal, Cu, and M compound decreases. The effect of M inclusion appears when the M content is 596 or more by weight in the binder. Moreover, if the M content exceeds 8096% by weight in the binder, the strength of the iron group metal, Cu, and AJ compounds will decrease, which is not preferable. MgO and/or Y2O
The content of 3 is preferably 0.1% or more and 5% or less by weight, and 0.3% or more and 5% or less by weight.
Less than 1% has no effect, and more than 5% MgAJ20+
Spinel-type compounds such as these precipitate at grain boundaries, leading to a decrease in strength and cutting performance.

Various methods can be considered for adding iron group metals, Cu, and fiJ. For example, the simplest method is to add it as a metal powder or in the form of a compound powder before sintering.

Further, during sintering, the iron group metal and Cu can be melted and infiltrated from the outside of the sintered body.

The grain size of the CBN crystal used in the present invention needs to be 10 μm or less in view of the performance of the sintered body as a tool. If the crystal grains are coarse, the strength of the sintered body will be reduced, and when used as a cutting tool, finer crystal grains will provide a better machined surface.

In manufacturing the sintered body, we use an ultra-high pressure and high temperature equipment used for diamond synthesis, at a pressure of 20 kb or more and a temperature of 900 kb.
Perform at temperatures above °C. Particularly preferred sintering pressure and temperature conditions are a pressure of 30kb to 70kb and a temperature of 1100°C to 1500°.
It is C. The upper limits of these pressure and temperature conditions are both within the range of practical operating conditions for ultra-high pressure and high temperature equipment on an industrial scale. Further, the pressure and temperature conditions must be within the stable range of high-pressure phase type boron nitride shown in FIG.

When using such an excellent sintered body as a cutting tool, the high hardness sintered body only needs to be used in the part that will become the cutting edge.
This high hardness sintered body has strength and toughness.

Its performance can be fully demonstrated by bonding it to cemented carbide, which has excellent thermal conductivity.

However, if it is directly bonded to cemented carbide, the bonding strength may be weak and it may not be possible to use it for interrupted cutting, etc. if the CBN content is high. In order to obtain sufficient bonding strength, an intermediate layer containing less than 7096 CBN by volume and the remainder consisting of one of carbides, nitrides, carbonitrides of Ti, Zr, and Hf, or a mixture thereof or a mutual solid compound is used. It is enough to join it.

Similar studies were also conducted on wurtzite boron nitride, which is another form of high-pressure phase boron nitride, and results similar to those obtained using CBN were obtained.

Examples will be described below.

Example 1 A mixed powder containing 65% by volume of CBN powder with an average particle size of 3 μm and the remainder consisting of binder powder was prepared. The binder powder is AfflgOs, AiN, Ni, Cu
, An, and MgO by weight, respectively, 60%, 5%, and 15
%, 8%, 109/6, 2% were heat treated at 1000° C. for 30 minutes in a vacuum furnace, and then pulverized. This mixed powder of CBN powder and binder powder was
IuL inner diameter 10 whale M.

WC-6% Co cemented carbide (outer diameter 10U)
, height 2.55 IJL) and then filled with 0.4 g. Furthermore, on top of this is a cemented carbide (outer diameter IQa, height 2M)
Place M.

The entire container was placed in an ultra-high pressure apparatus used for diamond synthesis. The pressure was increased to 50 kb, then heated to 1300°C and held for 20 minutes.

The removed sintered body was ground using a diamond grindstone until a highly hard sintered body appeared, and further polished using diamond paste. When observed under an optical microscope, it was found to be a dense sintered body with no pores. As a result of investigating the product of this sintered body by X-ray diffraction, it was found that a trace amount of A7! B2 and Ni polides were detected. For comparison, a sintered body (see Table 1) with the above composition excluding Cu was also produced under the same conditions and examined by X-ray diffraction. As a result, large amounts of AlB2 and Ni polide were detected, but metallic Ni was not detected. These two types of sintered bodies and binding materials are Aj! 2
0. The sintered body (B) of the chisel was brazed onto one corner of a cemented carbide indexable tip, and then processed to create a cutting tip, and a cutting test was conducted. The work material is 5KDII die steel (HRC=
62), cutting speed 100 Tn/m I n +
When tested in a dry method with a depth of cut of 0.3 and a feed of 0.5υ, the sintered body of the present invention was tested for 20 minutes until the cutting edge broke.
However, the sintered bodies (A) and [F]
), the cutting edge broke off after cutting for 10 minutes and 5 minutes, respectively.

Example 2 CBN powder and binder powder were mixed in the composition shown in Table 1. The CBN powder used has an average particle size of 4μ. The binder powder was heat treated in the same manner as in Example 1.

Using the pulverized powder, the mixed powder was also sintered in the same manner as in Example. However, No., A, F, ) (are not the sintered bodies of the present invention.Next, cutting chips were prepared from these sintered bodies in the same manner as in Example 1, and a cutting test was conducted.Rigid material 5
The conditions are the same as in Example 1.

Table 1゜Speed 100m/min, depth of cut 0.2 flat, feed 0.1cm/
Cutting was performed using the rev dry method, and the flank wear width was measured after 10 minutes of cutting time. Table 1 also shows the surface cutting test results.

Example 8 Using wurtzite type boron nitride powder synthesized by the shock wave method with an average particle size of 1 μ or less, the same composition as No. and D of Example 2 was mixed, and this was sintered in the same manner as Example 1. After that, a cutting tip was made and a cutting test was conducted.
It was possible to cut for 20 minutes until the cutting edge broke.

[Brief explanation of the drawing]

FIG. 1 is for explaining the manufacturing conditions of the sintered body of the present invention, and shows the thermodynamically stable region on the pressure-temperature phase diagram of high-pressure phase type boron nitride. ■ = Cubic - hexagonal boron nitride equilibrium line I: High pressure phase boron nitride stability region ■: Hexagonal boron nitride stable

Claims (1)

[Scope of Claims] (1) Contains 80% or more and 8596 or less of high-pressure phase type boron nitride by volume, and the remaining binder phase is a mixture or compound of one or more of AnogQB and fiJ Convex 1BN484C. and the iron group metal is 5% or more and 80% of the binder phase by weight.
Hereinafter, a sintered body for a high hardness tool is characterized in that Cu is 1% or more and 15% or less, A is 5% or more and 80% or less, and MgO and/or ygos is 0.1% or more and 596 or less. . (Claim 1 characterized in that the high-pressure phase type nitride nitride is cubic boron nitride or wurtzite type boron nitride.
A sintered body for high-hardness tools as described in . (3) High-pressure phase type boron nitride powder and ANO2101 AIN,
Si sN4゜SiC, B4C powder or compound powder, iron group metal powder, Cu
High pressure, characterized by mixing powder, A powder, and MgO and/or Y2O3 powder, molding it into powder form or molding, and then sintering it using an ultra-high pressure device at a pressure of 20 kb or more and a temperature of 900°C or more. Volume of phase type boron nitride is 30
Contains 96 or more and 85% or less, with the remainder of the binder phase being k120s
. A mixture or compound of one or more of AItN, SiC, 5isN++ B4C, ferrous metal is 5% or more and 8096 or less of the binder phase by weight, and Cu is also 1%
1596 or more, A value is 596 or more and 30% or less, MgO and/or Y2O3 is o, i96 or more is 59
A method for manufacturing a sintered body for a high hardness tool having a hardness of 6 or less. (4) The method for producing a sintered body for a high-hardness tool according to claim 1, wherein the high-pressure phase boron nitride is cubic boron nitride or wurtzite boron nitride. (5) High pressure phase type boron nitride powder and Aj! 1to81A1N
, 5iBN4゜SiC, B4C, one or more powders or compound powders, Cu powder, A powder, and MgO and/or Y, O8 powder, and this is powdered or pressed and then subjected to ultra-high pressure. Pressure 2 using the device
0kb or more, sintered at a temperature of 900°C or more,
High-pressure phase type boron nitride, characterized by infiltrating into this powder a ferrous metal and Cu or an alloy of ferrous metal and Cu arranged so as to be in contact with the powder, in an amount of 30% or more by volume85
% or less, and the remaining binder phase is Ano208A7N,
A mixture or compound of one or more of SiC, 5iBN4.84C, and a ferrous metal is the binder phase by weight.
% or more and 30% or less, Cu is 196 or more and 15% or less, AJ is 5% or more and 80% or less, and MgO and/or Y2O3 is 0.1% or more and 5% or less. Method.