JPS5927744B2 - High toughness ceramic cutting tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a material for cutting tools that has particularly excellent toughness and excellent fracture resistance due to thermal shock resistance and is suitable for applications such as turning of high-hardness materials and milling of cast iron materials. It is.

Ceramic cutting tools currently on the market can be roughly divided into two types: alumina ceramics and alumina-titanium carbide ceramics.

Alumina ceramic is suitable for ultra-high-speed finishing turning of cast iron materials, where the cutting edge temperature exceeds 1200°C, by taking advantage of the unique characteristics of alumina, which is its excellent wear resistance under high temperatures and oxidizing atmospheres. It is an indispensable existence.

However, alumina ceramics are unsuitable for use in turning high-hardness materials, milling cast iron materials, and wet turning because they lack toughness and have problems with fracture resistance due to thermal shock. On the other hand, alumina-titanium carbide ceramics contain approximately 30% by weight of T in alumina.
It is a material that improves fracture resistance due to thermal shock by compounding iO to make the crystal grains finer and at the same time compensate for the inherent characteristic of alumina, which is that the thermal conductivity decreases as the temperature increases.

Because this material is difficult to sinter, the hot press sintering method is used, and it has a fine composite structure, high hardness and toughness, and a transverse rupture strength of 80 to 90.
Because of its excellent value of ~/mTn2, it is also used for milling and wet turning of cast iron materials, for which alumina ceramics are unsuitable. The present inventor has developed a method using hot isostatic pressing (hereinafter referred to as HI) without using the hot pressing method, which has poor productivity.
Ae2O3- (nitride, boride) suitable for the method (denoted as P)
As a result of research on HIP-based ceramic tools, TiB2, which has comparable high-temperature hardness and thermal conductivity to TiC and has better oxidation resistance than TlC, has better sinterability than Al2O3-TiC. method can be applied, and Al2O3-Ti
We were able to develop a ceramic tool that is comparable to the C series.

However, in order to HIP the Al2O3-TiB2 system, it is necessary to achieve a relative density of 9501 or higher through preliminary sintering, and for example, in vacuum sintering, it is necessary to sinter at a temperature of 1500°C or higher, resulting in coarse grains. was unavoidable. Therefore, the present inventors investigated various additives to make Al2O3-TiB2-based crystal grains fine and found that AI
It has been found that N has the effect of refining crystal grains without significantly inhibiting sinterability.

The grain size of the ceramic sintered body in which AIN is blended with the Al2O3-TiB2 system is significantly finer than that of the ceramic sintered body that does not contain AIN, resulting in improved toughness and fracture resistance. can. The present invention was made based on the above findings, and αAl2
TlB2 powder 5-15% by volume A with O3 powder as the main component
This is a high toughness ceramic cutting tool characterized by comprising 0.2 to 2.0 volume % of IN powder. Further, in the present invention, MgO may be contained in an amount of 0.05 to 1.5% by volume, and further may contain MgO of 0.05 to 1.5% by volume. 0.05-1.5% NlO,C
A similar effect can be obtained by adding r2O3, TiO, TiO2, and Y2O3 in combination. The ceramic of the present invention could be obtained by pre-sintering a mixed powder having the above-mentioned composition range, followed by HIPing. The reason why TiB2 powder is limited to 5 to 15% by volume in the ceramics of the present invention is that if it is less than 5% by volume, it will lose its characteristics as a black ceramic, and if it is more than 15% by volume, the sinterability will be significantly reduced. TlB2 powder was limited to 5 to 15% by volume to avoid deterioration.

When the amount of AIN powder is less than 0.2 volume%, the grain refining effect disappears, and when it is more than 2.0 volume%, the sinterability deteriorates significantly, so the amount of AIN powder is 0.2 to 2.0 volume%. Limited. If MgO powder is less than 0.05 volume%, it has no effect on refining alumina crystal grains, and if it is more than 1.5 volume%, it reacts with alumina and forms a spinel layer at the grain boundaries, resulting in embrittlement. was set at 0.05 to 1.5% by volume. Furthermore, in the present invention, NiO, Cr2O3, T
The effect of grain refinement can also be obtained when one or more of iO, TlO2, Y2O3 is added.
If it is less than 0.05 volume %, there is no effect on refining alumina crystal grains, while if it exceeds 1.5 volume %, different phases will occur at the grain boundaries and embrittlement will occur. Therefore, the total amount of these components added is 0.
It is desirable that the content be within the range of 0.05 to 1.5% by volume. In the present invention, a part of TiB2 is 2% by volume or less of nitrides, borides, and B of groups 1va, va, and v1a of the periodic table.
A similar effect was obtained by substituting N, Si3N4.

A detailed explanation will be given below based on examples.

αAl2O3,T with average particle size 0.1μ and purity 99.9%
Mg was used to examine the effects of iB2 and grain refinement.
O and other oxides were blended in the proportions shown in Table 1 and wet mixed using ethyl alcohol in an alumina ball mill.

After mixing, vacuum drying, granulation and molding with 2T/(:Tn).
Sintering was carried out in a vacuum of 0 rr. The sintered body was heated at 1450℃, 10
HIP treatment was performed for 1 hour at 0.00 atm.

The hardness, bending strength and relative density of the obtained sintered body were
Shown in the table. From Table 1, in the Al2O3-TiB2 system,
All of the materials to which AIN was added in an amount of 0.5 to 2.0 volume % had a transverse strength of 90K9/ml or more, and the transverse strength was significantly improved compared to the other materials in Table 1.

In addition, AIN5. In case of O volume% combination, vacuum sintering
Since the relative density was 95% or less, the effect of HIP treatment was not apparent. Figures 1 to 4 are scanning electron micrographs showing the effect of AIN addition on the crystal structure. Figure 1 shows a volume ratio of 93.0A1203-5TiB2-
The second figure for 1.0AIN-1.0Mg0 material is 94.7A1.
203-5TiB2-0.3Mg0 material, Figure 3 is 93
．． 9A1203-5TiB2-1.0B203-0.1
The Mg0 material in Figure 4 is 93.8A1203-5TiB2.
Each structure of the -1.0Ni0-0.2Mg0 material is shown.

It is clear from the figure that the addition of AIN compared with other additives has a remarkable effect on grain refinement. As mentioned above, the ceramic of the present invention has excellent toughness due to the refinement of crystal grains, and is a ceramic that has better oxidation resistance than Al2O3-TiO type ceramics, and when used as a cutting tool, it can be used as a cutting tool for cast iron materials. Excellent cutting characteristics can be expected for milling.

[Brief explanation of drawings]

FIGS. 1 to 4 are scanning electron micrographs of fractured surfaces showing that AIN is effective in refining Al2O3-TiB2-based crystal grains.

Claims (1)

[Claims] 1 TiB_2 with αAl_2O_3 powder as the main component
Powder 5-15 volume%, AlN powder 0.2-2.0 volume%
A high-toughness ceramic cutting tool characterized by comprising: 2. A high-toughness ceramic cutting tool according to claim 1, characterized in that 0.05 to 1.5% by volume of MgO is added as a subcomponent. 3 With αAl_2O_3 powder as the main component, TiB_2
Powder 5-15 volume%, AlN powder 0.2-2.0 volume%
, and NiO, Cr_2O_3, B_2O_3, Ti
A high-toughness ceramic cutting tool comprising 0.05 to 1.5 volume % of one or more of O, TiO_2, and Y_2O_3. 4. A high-toughness ceramic cutting tool according to claim 3, characterized in that 0.05 to 1.5% by volume of MgO is added as a subcomponent.