JPS64344B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is useful as a cutting tool for high-speed cutting _of steel or cast _iron . Al ₂ O _3- based ceramics containing a high melting point titanium compound or a solid solution in which the titanium of the high melting point titanium compound is partially replaced with one or more metals from group 4a (excluding titanium), 5a and 6a group metals. This is a new manufacturing method, which has improved toughness compared to the Al ₂ O _3- based ceramics obtained by conventional manufacturing methods.
This invention relates to a manufacturing method for obtaining Al ₂ O _3- based ceramics. [Prior art] Ceramics for tools require the highest toughness, oxidation resistance, and wear resistance among ceramics, and currently there are three types of ceramics: Al ₂ O ₃ based, zirconia based, and silicon nitride based. Ceramics have been put into practical use as tools. In particular, for high-speed cutting of steel and cast iron, tools made of Al ₂ O _3- based ceramics, which have a low affinity with iron, have excellent wear resistance, so it is necessary to improve the toughness of Al ₂ O _3- based ceramics. It is industrially important to be able to use it for wet cutting, interrupted cutting, etc., and various improvements have been made. One of the Al ₂ O _3- based ceramics with improved toughness has a high melting point compound or solid solution with higher hardness than Al ₂ O ₃ as a second dispersed phase in the Al ₂ O ₃ matrix (first dispersed phase). There are some things that are dispersed. Specifically, 95 to 60% by weight of Al ₂ O ₃ powder is mixed with 5 to 40% by weight of titanium carbide (hereinafter referred to as TiC) or titanium carbonitride (hereinafter referred to as TiC).
TiCN), or titanium in other 4a, 5a and 6a
A mixture of carbide solid solution or carbonitride solid solution powder partially substituted with one or more of the group metals and sintered has been put into practical use as Al ₂ O _3- based ceramics for cutting tools. . In the production of the above-mentioned improved Al ₂ O _3- based ceramics, the starting materials Al ₂ O ₃ and TiC or Titanium nitride (hereinafter referred to as TiN) and the like are pulverized into as fine a powder as possible for use. Furthermore, when sintering a mixture of Al ₂ O ₃ powder and titanium compound powder, if sintered in an oxidizing atmosphere, the titanium compound will be oxidized, and conversely, if sintered in a strongly reducing atmosphere, Al ₂ O ₃ will be reduced. It will be done,
In addition, in normal sintering in an inert atmosphere, sintering does not proceed sufficiently even with the use of sintering aids, and only ceramics with a low density ratio and low toughness are obtained, so conventionally, hot pressing is rarely used. It is carried out by [Problems to be solved by the invention] However, because titanium compounds such as TiC or TiN have high hardness, it is difficult to reduce the average particle size to 0.5 μm or less and the maximum particle size to 3 μm or less by pulverization. difficult and therefore obtainable
There was a limit to the improvement in toughness of Al ₂ O _3- based ceramics. In addition, as mentioned in the section on conventional technology, sintering is carried out by the hot press method in the conventional method. There are problems such as increased cost. Therefore, the object of the present invention is to obtain a powder that can be obtained without making the raw material powder extremely fine by the pulverization method.
Al ₂ O ₃ in the first dispersed phase and a high melting point titanium compound or titanium in the high melting point titanium compound in the second separated phase in Al ₂ O ₃ group ceramics are partially 4a (excluding titanium), 5a and 6a group Production of _{Al 2} O _3- based ceramics in _which the particle size of the solid solution substituted with one or more metals is fine and the toughness is therefore greatly improved. The goal is to establish a method. Furthermore, another object of the present invention is to develop _{Al 2} O _3- based ceramics that have a high density ratio and high toughness even when not by the hot pressing method but by the _normal sintering method. The goal is to establish a manufacturing method. [Means for solving the problem] As a result of various studies, the present inventors found that Al ₂ O ₃ powder and
If necessary, a solid solution powder in which a portion of the titanium of a high melting point titanium compound or a high melting point titanium compound is replaced with one or more metals from group 4a (excluding titanium), 5a and 6a group metals, and dititanium. When the temperature is raised to sinter a green compact made from a blended composition containing aluminum nitride (hereinafter referred to as Ti ₂ AlN) powder, etc., the temperature in the green compact is first increased at 1100 to 1450°C.
Since Ti ₂ AlN is decomposed into fine Al ₂ O ₃ and fine TiN, it is possible to finely and uniformly disperse the second dispersed phase of which TiN is a part or whole, and furthermore, Decomposition of TiN
Ti ₂ AlN powder suppresses grain growth of blended Al ₂ O ₃ and decomposed Al ₂ O ₃ , making it possible to make the particle size of the first dispersed phase and second dispersed phase in the obtained ceramics finer. When blended, sinterability is promoted, so ceramics with a high density ratio can be obtained even without the hot pressing method, that is, even with a normal sintered body, and in the case of the hot pressing method, the density ratio is even higher than that of the conventional method. As a result of the above, ceramics with high toughness can be obtained.
It has been discovered that Al ₂ O _3- based ceramics can be obtained. This invention was invented based on the above knowledge, and uses alumina powder and, if necessary, a high melting point titanium compound or a portion of titanium in a high melting point titanium compound.
4a (excluding titanium), solid solution powder substituted with one or more metals of group 5a and 6a metals;
A method for producing alumina-based ceramics, characterized in that the blended composition further contains Ti ₂ AlN powder.
Alumina as the first dispersed phase, a high melting point titanium compound as the second dispersed phase, or a portion of the titanium in the high melting point titanium compound replaced with one or more metals from group 4a (excluding titanium), 5a and 6a group metals This is a method for producing alumina-based ceramics containing a solid solution of The configuration of this invention will be explained below. () High melting point titanium compounds etc. High melting point titanium compounds include TiC, TiN and
There are TiCN etc. Then, some of the high melting point titanium compounds are 4a (excluding titanium) and 5a.
Solid solutions in which Ti is substituted with one or more metals from group 6a metals include TiC, TiN, and TiCN.
It is a solid solution substituted with one or more of Zr, Hf, V, Nb, Ta, Cr, Mo, and W. These are blended as necessary, but the blending amount is preferably 30% by weight or less. When these are blended, they react with most of the TiN produced by the decomposition of Ti ₂ AlN during sintering and form a solid solution, but the uniformly dispersed TiN is still a mixture of Al ₂ O ₃ particles. This suppresses growth and maintains the effect of producing fine-structured Al ₂ O _3- based ceramics. () Ti ₂ AlN As mentioned in the findings section, Ti ₂ AlN is a result of the refinement of the first and second dispersed phases in ceramics based on the decomposition of Ti ₂ AlN into Al ₂ O ₃ and TiN. and has the effect of promoting sinterability. The content of Ti ₂ AlN is preferably 1.0 to 12.0% by weight. If it is less than 1.0% by weight, the above-mentioned effect cannot be obtained, while if it exceeds 12.0% by weight, the amount of oxygen and nitrogen will be insufficient, which will actually impede sinterability. Note that Ti ₂ AlN decomposes into Al ₂ O ₃ and TiN when the temperature rises, and the oxygen in the decomposed Al ₂ O ₃ is supplied from the oxygen in the blended Al ₂ O ₃ and the oxygen in the atmosphere. considered to be a thing. That is, it is considered that the ceramics produced by the method of the present invention are mainly composed of oxygen-deficient Al ₂ O ₃ . On the other hand, most of the nitrogen in TiN produced by decomposition is supplied from N in Ti ₂ AlN, but it is thought that nitrogen in the atmosphere or nitrogen from high melting point titanium compounds is also a part of it. () Other compounding components If necessary, add 2% by weight of other oxides such as MgO, Cr ₂ O ₃ , etc. that promote the sintering of Al ₂ O ₃ .
The following may be blended. () Sintering In the method of the present invention, ceramics with a high density ratio can be obtained not only by the hot pressing method but also by the ordinary sintering method. The final sintering temperature in the method of this invention is 1550
Temperatures within the range ˜1700° C. are preferred. The atmosphere for sintering is normally a reduced pressure or normal pressure atmosphere that does not oxidize the high melting point compound. Due to the temperature increase for this sintering, as mentioned in the findings section, fine particles due to the decomposition of Ti ₂ AlN are generated.
The generation of Al ₂ O ₃ and fine TiN and the resulting suppression of grain growth of Al ₂ O ₃ by the TiN, as well as the reaction between the TiN and a high melting point titanium compound, etc., as described in the configuration () are also possible. sintering occurs. Further, it is preferable to perform hot isostatic pressure sintering after normal sintering because ceramics with a higher density ratio can be obtained. [Example] Hereinafter, the configuration and effects of the present invention will be explained in detail by Examples as well as Reference Examples. Example 1 Al ₂ O ₃ powder with an average particle size of 0.6 μm: 80% by weight,
0.6μm MgO powder: 0.5% by weight, 0.8μm TiC
Powder: 14.5% by weight, 1.0μm Ti ₂ AlN powder: 5
% by weight, mixed in a wet ball mill for 48 hours, and dried after mixing to obtain a mixed powder. This mixed powder
It was press-molded at a pressure of 1 t/cm ² and sintered at 1640° C. for 1 hour in a nitrogen atmosphere (nitrogen gas pressure: 10 torr). The produced ceramic has a first dispersed phase of Al ₂ O ₃
and a second dispersed phase, the density ratio was 98.8%, the Rockwell A hardness was 93.5, and the transverse rupture strength was 90 Kg/mm ² . For comparison, ceramics were manufactured as follows without using Ti ₂ AlN powder. That is, a mixed powder having a composition of Al ₂ O ₃ powder: 80% by weight, MgO powder: 0.5% by weight, and TiC powder: 19.5% by weight was similarly press-molded and sintered under the same conditions, but the sintering was not sufficient. The density ratio of the ceramics obtained was 91.
%, transverse rupture strength was 15 Kg/mm ² , and many fine pores were observed. Reference Example 1 Using the ceramics of the present invention obtained in Example 1, a throw-away chip having a shape conforming to JIS standard SNP432 was manufactured and high-speed turning of cast iron was performed.
The conditions are shown below. Work material: FC25 (Brinell hardness: 180) Cutting speed: 400 m/min Feed: 0.4 mm/rev. Depth of cut: 0.5 mm Commercially available Al ₂ O ₃ -1 wt% MgO ceramics and Al ₂ O ₃ were used for comparison purposes. A similar cutting test was conducted using a hot-pressed throw-away tip made of -30% by weight TiC ceramics. The indexable insert made of the ceramics of the present invention had flank wear of 0.20 mm after 15 minutes of cutting time, whereas the insert made of Al ₂ O ₃ -1% by weight MgO ceramics broke in 12 minutes. In addition, the one made of Al ₂ O ₃ -30% by weight TiC ceramics had flank wear of 0.25 mm after cutting time of 15 minutes. Example 2 Al ₂ O ₃ powder with an average particle size of 0.6 μm, MgO with an average particle size of 0.6 μm
powder, 0.8μm TiC powder, 0.8μm TiN powder,
1.0 μm TiC _0.5 N _0.5 powder, 1.0 μm (Ti _0.4 ,
Ta _0.1 , W _0.5 ) C powder, 1.0 μm (Ti _0.4 , W _0.6 )
Prepare C _0.5 N _0.5 powder and 1.0 μm Ti ₂ AlN powder, mix them according to the composition shown in Table 1, and mill them in a ball mill at 48 µm.
Wet mixing was performed for hours. After drying, it is press-formed at a pressure of 1 t/cm ² and then sintered using the normal sintering method (N ₂ gas pressure: 3 torr).
Sintering at 1650℃ for 1 hour in _N2 atmosphere), hot isostatic pressure sintering (hereinafter abbreviated as HIP, 1000Kg/mm2 ⁾
Ar gas pressure, sintering at a temperature of 1600℃ for 30 minutes) or hot press method (hereinafter abbreviated as HP; 1620℃)
Ceramics No. ¹ to 12 of the present invention produced by blending Ti ₂ AlN powder and produced without blending Ti ₂ AlN powder. Comparative ceramics Nos. 1 to 4 were manufactured. Rockwell A hardness of these ceramics,
The density ratio and transverse rupture strength were measured and the results are shown in Table 1. Reference Example 2 Ceramics No. 1 of the present invention obtained in Example 2
12 and Comparative Ceramics No. 1 to 4, Reference Example 1
A similar throw-away chip was manufactured and a cutting test was conducted under the following cutting conditions, and the flank wear width was measured. The results are also shown in Table 1. Work material: FC25 (Brinell hardness: 180) Cutting speed: 450 m/min Feed: 0.30 mm/rev. Depth of cut: 1.0 mm Cutting time: 10 minutes [Effects of the invention] From Example 1 and Reference Example 1, Ti ₂ By using AlN powder as part of the raw material powder, sinterability is promoted, ceramics with a high density ratio can be obtained even by ordinary sintering, and when this ceramic is used as a cutting tool, It can be seen that despite its high toughness, it also has excellent cutting performance such as wear resistance. Furthermore, as can be seen from Example 2 and Reference Example 2, ceramics Nos. 1 to 12 of the present invention all have excellent Rockwell A hardness, density ratio, and transverse rupture strength.

【table】

[Table] The cutting performance was also good when used as a cutting tool. On the other hand, among the comparative ceramics, Nos. 1 and 2 made by the normal sintering method have extremely small transverse rupture strengths and cannot be cut when used as cutting tools.
In addition, comparative ceramics No. 3 made by hot pressing method
No. 4 and No. 4 have sufficiently high hardness, but are slightly inferior in transverse rupture strength and cutting performance. This seems to be due to the particle size of the latter dispersed phase being coarser than that in the case of using Ti ₂ AlN. As described above, according to the method of the present invention, Al ₂ O _3- based ceramics with improved toughness can be produced using the ordinary sintering method instead of the hot pressing method.

Claims (1)

[Scope of Claims] 1. A green compact from a blended composition is sintered to contain alumina as a first dispersed phase, a high melting point titanium compound as a second dispersed phase, and a portion of titanium of the high melting point titanium compound 4a ( However, in the method for producing an alumina-based ceramic containing either or both of a solid solution substituted with one or more metals of group 5a and group 6a metals (excluding titanium), the blended composition further comprises: 1. A method for producing alumina-based ceramics, comprising using a blended composition containing titanium aluminum nitride powder.