JPS5910948B2 - Materials for cutting tools and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ceramic-based high speed cutting tool materials.

Ceramic high-speed cutting tool materials have recently been used in a wider range of applications due to advances in manufacturing methods that have resulted in more uniform and finer structures, and improvements in machine tools that have increased spindle speed, horsepower, and rigidity. It's on.

Up until now, the focus of ceramic tools has been to improve strength and toughness through finer grain size, and to improve wear resistance through increased density. However, when a compact composed of Al2O3 and carbide or carbonitride powder is sintered in a high-temperature vacuum, a point such as 15Al203+3C (carbide or carbonitride) = nA1+3CO is formed. be.

Incidentally, in the case of Al2O3-3CTiC, even if it is sintered in vacuum (10-2 TOrr) at 1600 DEG C. for 1 hour, the sintering progresses only to 70% of the theoretical density20.
Therefore, in order to densify Al2O3-carbide or carbonitride, etc., put the mixed powder of the material to be sintered into a graphite mold for about 20 minutes.
It is necessary to hot-press at a pressure of 1500 to 1700°C at a pressure of kg/cm, and in fact, all A1203=3CWt%25TiC black ceramics currently on the market are produced by the hot-pressing method. However, the hot press method cannot process large quantities due to the graphite mold, and is difficult to achieve continuous production, and the process of cutting and grinding into the shape of the throwaway chip is unavoidable, resulting in high production costs. There are drawbacks such as having no choice but to do so. As a countermeasure to the above-mentioned drawbacks, we obtained a calcined body with a throw-away shape from the beginning, eliminated the cutting process, and adjusted the dimensions to reduce the grinding allowance, and then used the hot isostatic pressing method (hereinafter referred to as "HIP"). It is conceivable to process 35 large quantities. However, in the above-mentioned HIP, if the density of the calcined body is not 95% or more of the theoretical value, the inert gas or high-temperature molten glass that is the pressure medium will penetrate into the inside of the calcined body, and the shrinkage will not be sufficient. There is a drawback that a high-density sintered body cannot be obtained because of the high density. Therefore, the density is theoretically 9
When HIPing a sintered body of 5% or less, the usual methods include vacuum sealing it in a metal capsule or glass capsule that softens at the sintering temperature, or coating the surface of the sintered body with a metal or compound. However, the above-mentioned advantage of reducing production costs by HIP may not be fully utilized. However, recently, a new Al2O3-based ceramic composition that overcomes the drawbacks of the above-mentioned prior art and has a relative density of 95% under normal sintering conditions has been developed.
A material containing 5 to 15 wt% of N has been proposed (see JP-A-53-130208).

This material produces a sintered body suitable for mass processing by HIP, so the manufacturing cost is less than half that of conventional materials.At the same time, since it is a high-density sintered body, its hardness and bending strength are comparable to commercially available black ceramics. It is an excellent material that has the following properties. On the other hand, the inventor of the present invention has independently studied various types of Al2O3-based ceramic materials with a new composition that have a relative density of 95% or more under normal sintering conditions, and as a result, the present invention was developed.

In the present invention, the final composition of the sintered body obtained by HIP is Ta.
less than N2OvOl%, NbNl5vOl% or less, and the sum of TaN<15NbN is 5 to 20v01%, the remainder Al
It is characterized by consisting of 2O3.

Furthermore, the novel composition of the present invention, which includes one or more of Sl3N4, AIN, and BN in an amount of 5v01% or more in the above composition, is a sintered body suitable for mass processing by HIP, and the manufacturing cost is low. It has the advantage of being less than half the amount of conventional material, and because it is a high-density sintered body, it is an excellent material with hardness and bending strength that are comparable to commercially available black ceramics. Hereinafter, the present invention will be explained in detail based on Examples.

α-Al2O3 with a purity of 99.9% and an average particle size of 0.5μ,
TaN, NbN, O.P. with a purity of 9.9% and an average particle size of 1 μm. 5
Wt% MgO, Si3N4, AIN, and BN were blended at each blending ratio shown in Table 1 to obtain a raw material powder.

After pulverizing this powder in ethyl alcohol for 72 hours, wax was added and granulated to give a weight of 2000 kg/(17
The compacts formed at a pressure of 7i were presintered at various temperatures in a nitrogen atmosphere. Next, pressure sintering was performed at each HIP temperature shown in Table 1 under a high pressure Ar gas pressure of 1500 atmospheres for 60 minutes. Table 1 shows the hardness, bending strength and relative density of the obtained sintered body. From Table 1, if TaN2OvOl% or less, NbNl5vOl% or less, and the total content of TaN and NbN is 5 to 20v01%, the relative density should be 95% or more when the preliminary sintering temperature is in the range of 1400 to 1700℃. 1400-1700 after that.
It can be seen that a ceramic composition having a relative density of 99.8% or more and excellent hardness and bending strength can be obtained by performing the HIP treatment in the temperature range of .degree. Also TaN. l5
The NbN content is 101% for each, and the sum is 2
In the case of v01%, the crystal grains of Al2O3 become large and the bending strength is poor, while on the other hand, the content of TaN and NbN is
In the case of 5v01%, the relative density is at most 91.0% even if the preliminary sintering temperature is 1700°C, and it is therefore clear that even if HIP treatment is performed, high densification is not achieved and the bending strength is low. Therefore, in the present invention, the content of TaN and NbN may be less than TaN2OvOl% and less than NbNl5vOl%, and the content of TaN and NbN may be 5 to 15v02% in total even if the content of either one is 1% or less. , both 2.
It is more preferable that the content is 5% or more, and the pre-sintering temperature and HIP temperature may be arbitrarily selected within the range of 1400 to 1700°C depending on the content of TaN and NbN.

In addition, in the present invention, carbides of metals in Groups 1 and 1 of the periodic table are used at 5v0! ? The following elements can be included to improve characteristics.

Claims (1)

[Claims] 1. The final composition of the sintered body after hot isostatic sintering is TaN20.
less than vol%, NbN 15 vol% or less, and TaN
The sum of the contents of and NbN is 5 to 20 vol%, the balance is Al_
A cutting tool material characterized by consisting of 2O_3. 2 Si_3N_4, AlN,
The cutting tool material according to claim 1, containing 5 vol% or less of one or more types of BN. 3. Sinter the compact in vacuum, in an inert gas, or in a hydrogen atmosphere at 1,400 to 1,700°C to a relative density of 95% or more, and then sinter at a temperature of 1,400 to 1,700°C, 5
TaN, NbN and A characterized by being densified to 99.8% or more of the relative density by hot isostatic sintering under gas pressure of 00 to 2000 kg/cm^2.
A method for producing a cutting tool material containing l_2O_3 as a main component.