JPS63270350A - Ceramic cutting tool and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled cutting tool having excellent abrasion resistance and mechanical properties, etc., by mixing Al2O3 powder with SiC whisker and boron (compound) powder at specific weight ratios, forming the mixture and sintering at a specific temperature in non-oxidizing atmosphere. CONSTITUTION:(A) 1-40wt.% of SiC whisker having an average diameter of 0.1-2mum, a length of 10-100mum and an aspect ratio of >=10 and preferably having beta-type structure is mixed with (B) 0.1-2wt.% of boron or a boron compound (e.g. B4C or TiB2) and (C) the remaining part of Al2O3 powder. The mixed powder is formed and sintered in a non-oxidizing atmosphere at 1,500-1,900 deg.C to obtain the objective ceramic cutting tool. Since boron (compound) is added to Al2O3 reinforced with SiC whisker, a composite material having high strength and dense texture can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement of an A1□03 cutting tool, and is an Al2O3 cutting tool with improved sinterability, high wear resistance, and mechanical strength. and the improvement of its manufacturing method.

Conventional technologyThe material of ceramic cutting tools has traditionally been high-purity AhO*.
, or add a small amount of carbide etc. to it and sinter it A.
It is a l2O3 ceramic, and its wear resistance allows high-speed cutting of steel, and a high-quality machined surface was obtained. However, due to its weak mechanical strength such as toughness,
It lacked reliability and stability when working with impact forces.

Therefore, in order to improve mechanical strength, especially bending strength and impact resistance, we made A1zOs crystal grains uniform and fine, densified by sintering at the same time as forming, dispersion strengthened by 1r02, TiC, etc., and by SiC whiskers. Compositeization is taking place.

Problems to be Solved by the Invention Particularly in the case of composite SiC whiskers, SiC whiskers significantly impair the sinterability of Al2O3 due to the reaction between the SiC whiskers and the matrix during the manufacturing process and uneven interfacial adhesion. Therefore, it was not possible to sufficiently improve properties such as mechanical strength.

The present invention solves the problem of poor sinterability when compounding Al2O3 with SiC whiskers, and provides an Al2O3 ceramic cutting tool with excellent mechanical strength and a long service life, and a method for manufacturing the same. purpose.

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors conducted various experiments focusing on the additives used when compounding SiC whiskers, and found that boron or boron compounds were added. As a result, it was discovered that the sinterability of A1□03 was significantly improved, and mechanical strength characteristics superior to those of conventional products were obtained. That is, the present invention was completed based on the knowledge that addition of boron or a boron compound prevents deterioration in sinterability due to SiC whiskers in Al2O and improves mechanical strength.

A1□03 may normally contain impurities such as MgO that cannot be removed, but the upper limit is 0.9% based on Al2O3.
That's it.

The SiC whisker used is a known one, and has a length of 1
0 μm to 100 μm, diameter of 0.1 μm to 2 μm, and aspect ratio of 10 or more are preferred, but the most desirable type is β-type SiC whiskers with a length of 15 to 30 μm, e.g., about 20 μm, and an aspect ratio of 15 to 70, e.g., 20 to 50. be.

The material of this ceramic cutting tool is 1% to 40% by weight of SiC whiskers that meet the above conditions, boron, or one selected from the group consisting of B4C, TiB2, B2O3, and BN, or a mixture thereof. The compound is mixed with ceramic powder in a proportion of 0.1% to 2% by weight and manufactured using a powder method.

Although the powder method is convenient for mixing, it is difficult to achieve unidirectionality and high density, so it is also effective to use extrusion method or liquid phase press method in combination. Sintering is performed at a temperature of 1500℃ in a non-oxidizing atmosphere.
Hot press sintering at a temperature of ~1900°C has a great effect on densification. Furthermore, hot isostatic pressing is also highly effective in improving sinterability.

Function The present invention shows that the addition of boron or a boron compound is
A I 203 compositely strengthened with whiskers significantly improves the sinterability of ceramic cutting tools, and based on the discovery of particle densification, this improvement in sinterability has improved mechanical strength properties compared to conventional ones. Become something excellent. Examples of boron compounds include B and C.

One selected from the group consisting of TlB2, B2O3, and 8N or a mixture thereof improved sinterability.

At this time, if the amount of boron added is less than 0.1% by weight, the effect of addition will be small, and if it is more than 2% by weight, the sinterability will deteriorate. However, the same effect can be obtained by adding a boron compound in an amount of 0.1% to 2% by weight in terms of boron.

The effect of adding SiC whiskers is small if it is not 1% by weight or more, and the sinterability is poor if it is 40% by weight or more.
Significant reduction in reinforcement due to whiskers. Furthermore, SiC whiskers cannot be used if they have a diameter of 2 μm or more and a length of 100 μm or more because the strength of the sintered body decreases.

Example α-type Al2O3 powder with an average particle size of 0.4 μm and an average particle size of 0.4 μm.
β-type SiC whiskers with a length of 3 μm and a purity of 99
．． 9% metallic boron having an average particle size of 0.1 μm or less was mixed in the composition shown in Table 1, and after molding, hot press sintering was performed at 1750° C. for 2 hours. A cutting tip specified in JIS 5NG432 was prepared from the sintered body thus obtained and subjected to a cutting test, and the performance shown in Table 1 was obtained.

Table 1 also shows the bending strength of the sintered bodies.

However, the cutting test was conducted under the following conditions.

Work material 545CHB 320 Diameter 300m + nφ x Length 600mm Machine Ikegai NC lathe 25HP Cutting conditions
Speed 800Tn/min Cutting depth 2111111 Feed 0.3mm/min Table 1 In Table 1, the amount of metal boron added is 0.1% by weight ~
All the samples in which the SiC whisker content was in the range of 2% by weight and the amount of SiC whiskers added was in the range of 1% to 40% by weight showed excellent results in both life time and bending strength.

On the other hand, in sample number 1, the amount of added SiC whiskers used was too small, so in sample number 5.

Because the amount of SiC whiskers used was too large,
Satisfactory results were not obtained in terms of life time and bending strength.

In addition, since metallic boron was not mixed in sample number 6,
Satisfactory results were not obtained in terms of life time and bending strength.

In sample No. 9, the amount of metal boron added was too large, so both the life time and the bending strength were insufficient.

Sample No. 10 did not use either SiC whiskers or metallic boron, so it was not possible to obtain satisfactory results in terms of both life time and bending strength.

Effects of the Invention As mentioned above, in the composite strengthening of Al2O3 ceramics using SiC whiskers, high strength and dense A1203-3i C can be obtained by adding boron or a boron compound.
A whisker composite material is obtained, which also achieves a significant improvement in performance as a cutting tool, as shown in Table 1. Furthermore, in addition to the excellent thermal properties inherent in ceramics, its mechanical properties have also been significantly improved, so it can be used as a structural material with an extremely wide range of applications.

Claims (11)

[Claims] (1) A ceramic cutting tool mainly composed of Al_2O_3 and containing 1 to 40% by weight of SiC whiskers and 0.1 to 2.0% by weight of boron or a boron compound. (2) the SiC whiskers are β-type, have an average diameter of 0.1 μm to 2 μm, and a length of 10 μm to 100 μm;
The ceramic cutting tool according to claim 1, having an aspect ratio of 10 or more. (3) The SiC whisker has a length of 15 to 30 μm,
The ceramic cutting tool according to claim 2, which is a β-type SiC whisker with an aspect ratio of 20 to 50. (4) The above boron compounds include B_4C, TiB_2, B
The ceramic cutting tool according to any one of claims 1 to 3, characterized in that it is one selected from the group consisting of _2O_3 and BN, or a mixture thereof. (5) 1 to 40% by weight of SiC whiskers and 0.1 to 40% by weight of SiC whiskers;
After molding a mixed powder containing 2.0% by weight of boron or boron compound powder and the balance being Al_2O_3 powder, it is sintered at a temperature in the range of 1500 to 1900°C and in a non-oxidizing atmosphere. A method for manufacturing a ceramic cutting tool. (6) the SiC whiskers are β-type, have an average diameter of 0.1 μm to 2 μm, and a length of 10 μm to 100 μm;
The method for manufacturing a ceramic cutting tool according to claim 5, wherein the aspect ratio is 10 or more. (7) The method for manufacturing a ceramic cutting tool according to claim 6, wherein the SiC whisker is a β-type SiC whisker having a length of 20 μm and an aspect ratio of 20 to 50. (8) The above boron compounds include B_4C, TiB_2, B
The method for manufacturing a ceramic cutting tool according to any one of claims 5 to 7, characterized in that the cutting tool is one selected from the group consisting of _2O_3 and BN or a mixture thereof. (9) The method for manufacturing a ceramic cutting tool according to any one of claims 5 to 8, characterized in that sintering is performed by pressureless sintering. (10) The method for manufacturing a ceramic cutting tool according to any one of claims 5 to 8, characterized in that hot press sintering is used. (11) A method for manufacturing a ceramic cutting tool according to any one of claims 5 to 8, characterized in that a hot isostatic press is used.