JP2735919B2 - Sintered body for tool and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sintered body for a tool and a method for manufacturing the same, and is particularly suitable for use in high-speed cutting of high-hardness materials such as, for example, bearing steel. .

<Conventional technology> Conventionally, since the hardness of the work material is Rockwell hardness ( _HRC ) and the machining of high hardness material of 60 or more is difficult, the grinding is mainly performed by diamond abrasive grains or the like. We are processing. However, since the grinding is performed at a low processing speed, it is difficult to shorten the tool.

In order to solve this problem, WC-Co-based cemented carbide tools, TiC-TiN-Ni
-Mo cermet tool, ceramic tool mainly composed of Al ₂ O _3, CBN sintered tools were sintered CBN particles at high temperatures and pressures have been developed in the field of new machining it is being expanded.

 Cutting tools made of this high-hardness material are required to have performances such as (i) a small amount of tool wear and (ii) good machined surface roughness of the machined material.

<Problems to be Solved by the Invention> However, among the tools for high-hardness materials described above, cemented carbide tools and cermet tools are applied because the metal binder undergoes plastic deformation due to heat generated during processing, and wear progresses in a short time. There is a problem that can not be.

In addition, since ceramic tools are more susceptible to chipping and more likely to chipping (peeling cracking phenomenon in a minute area) than carbide alloys and cermets, the roughness of the machined surface is poor and cannot be applied. There's a problem.

Furthermore, although CBN sintering tools meet the performance requirements for cutting hard materials,
A high temperature of 0 ° C. or more and a high pressure of 50,000 atm or more are required, and the production equipment is special and expensive, so that the production of the CBN sintered tool is very expensive.

<Means for Solving the Problems> A first invention of a sintered body for a tool for solving the above problems is Ti
In a sintered body for a tool, which is obtained by sintering a mixed powder of N powder 40% by volume or more and a binder whose main component is Al ₂ O ₃ , the remainder is selected from ZrO ₂ , AlN and SiC whiskers. And one or more other binders are added.

The second invention of the sintered body for a tool is a sintered body for a tool which is obtained by sintering a mixed powder of a TiN powder of 40% by volume or more and a binder whose main component is a ZrO ₂ powder. To Al
It is characterized by adding one or more other binders selected from N and SiC whiskers.

The third invention relates to a method for producing a sintered body for a tool, which comprises forming a mixed powder of 40% by volume or more of TiN powder and a binder whose main component is Al ₂ O ₃ , followed by forming a vacuum. Alternatively, pressure sintering is performed at a temperature of 1600 ° C. or lower in an inert gas atmosphere.

In a fourth aspect based on the third aspect, the remaining part is
It is characterized by adding one or more other binders selected from ZrO ₂ , AlN and SiC whiskers.

The fifth invention relates to a method for manufacturing a sintered body for a tool, and comprises forming a mixed powder of a TiN powder of 40% by volume or more and a binder containing ZrO ₂ powder as a main component, followed by vacuum forming. Alternatively, in a method of producing a sintered body for a tool that is sintered under pressure at a temperature of 1600 ° C. or less in an inert gas atmosphere,
It is characterized by adding one or more other binders selected from AlN and SiC whiskers.

Here, the mixing ratio of TiN is set to 40% by volume or more in a powder state. This is because if the TiN powder content is less than 40% by volume, the occurrence of chipping, which is a drawback of ceramic tools, cannot be prevented. Further, if the TiN powder is made to be 90% by volume or more, it can be sintered, but it cannot be sufficiently densified, so that it is not suitable for use as a tool.

Therefore, the preferred compounding amount used as a tool is 40 to 90% by volume.
More preferably, the content is 60 to 80% by volume.

Attempts to use TiN as a tool have been made using a metal binder such as cermet or powdered high speed steel as a binder. These tools, primarily to improve the high-speed steel (common Designation of high speed tool steel) for the purpose are those intended for the H _RC hardness of 30 or less soft workpiece, improving the finishing accuracy,
The effects such as high efficiency were confirmed. However, TiN
It is difficult to sinter without a metal binder, and a tool sintered only with ceramics as in the present invention has not been developed.

Further, the present inventor considered the problem of thermal conductivity as a cause of chipping generated in a conventional ceramics tool containing Al ₂ O ₃ as a main component. The thermal conductivity of Al ₂ O ₃ is high near room temperature, but drops sharply at relatively low temperatures of 100 ° C. or higher. A
If ZrO ₂ is added to improve the toughness of l ₂ O ₃ , the thermal conductivity will further decrease. If the thermal conductivity of the material is poor, when a tool is used, the heat generated at the interface with the work material is difficult to transfer,
A temperature difference occurs between the tool surface and the inside, causing a large thermal stress. Due to this thermal stress, in extreme cases, defects occur,
Even if no defects occur, chipping occurs in which crystal grains fall off. In the present invention, TiN is mainly composed of TiN having a high conductivity, and the lower limit is set to 40% by volume to prevent chipping when used as a tool.

Examples of the remaining other components to be added to the TiN powder as the main component include Al ₂ O ₃ , ZrO ₂ , AlN, and SiC whiskers.

Here, Al ₂ O ₃ is a main component of the remaining components, has high chemical stability, and has characteristics that it is difficult to react with a work material when used as a tool. It is also effective because the hardness is relatively high.

ZrO ₂ has the effect of improving sinterability by adding a small amount. This effect is achieved by using AlN, SiC
Even when components that inhibit sintering, such as whiskers and TiN, are added, sintering can be performed at a low temperature of about 1500 ° C.

Furthermore, the ZrO ₂ powder partially stabilized by the addition of Y ₂ O ₃ of about 3 mol% to ZrO ₂ may be a subject of the remainder ingredients in place of the Al ₂ O ₃ mentioned above. In this case, although abrasion is slightly increased as compared with the case where Al ₂ O ₃ is mainly used, a tool having high strength can be obtained, so that there is a feature that the chip is hardly broken.

AlN and SiC whiskers as the remaining components are added for the purpose of improving thermal conductivity. This does not have a significant effect on the thermal conductivity as a tool when the TiN content is large, but when the TiN content is low, it is easy to cause chipping or peeling from the remaining components, so using AlN and SiC whiskers We are trying to improve these. In addition, SiC
Whiskers do not affect the various properties of the tool due to the addition, but AlN has the disadvantage that the strength is reduced by the addition, and it is better not to add it when the TiN content is high.

Here, the pressure sintering in the present invention means, for example, a sintering method by a hot press method or a HIP (Hot Isostatic Press: hot isostatic pressure press) method, and is performed in a vacuum or an inert gas atmosphere, and It means firing at a temperature of 1600 ° C. or less.
The above firing temperature is limited to 1600 ° C. or lower, because the constant wear of the tool is desirable as the grain size after firing is smaller and smaller, and if it is 1600 ° C. or higher, abnormal growth of the grain size becomes remarkable, This is because when used as a cutting tool, the life is significantly reduced.

<Embodiment> Hereinafter, a preferred embodiment of the present invention will be described in detail.

(Example of manufacturing method of sintered body) Commercially available TiN powder having an average particle diameter of 1.5 μm as a main component and commercially available Al ₂ O ₃ powder having an average particle diameter of 0.3 μm as a residual component;
3 mol% Y ₂ O ₃ partially stabilized ZrO ₂ powder having an average particle size of 0.3 μm;
SiC whiskers having an average diameter of 0.3 μm and an average length of 2 μm; AlN powder having an average particle diameter of 0.3 μm was used as a raw material, blended into the composition shown in Table 1 below, further added with ethanol, wet-mixed, and then dried. Raw material powder was obtained.

This raw material powder was hot-pressed (pressure 400 kgf / cm ² ) in a vacuum at a predetermined temperature and sintered.

After that, the indexable insert (ISO symbol SNMN432 (after processing 12.7mm × 12.7mm × 4.76mm, corner radius 0.8m)
m)) and processed into a tool.

Using the obtained tools, cutting tests were performed under the following conditions, and each evaluation was performed.

Workpiece: SVJ2 (about H _RC 62), Cutting speed: 100 m / min, cut: 0.1 mm / rev, Feed: 0.2 mm / rev, tool wear amount: flank wear width after cutting distance 4000 m.

Machining surface roughness: Machining surface roughness of work material after cutting distance of 4000m.

Table 1 shows the results of the cutting test. Here, the CBN sintered tool used as the comparative material is a commercial product of another company.

From the results shown in Table 1, the ceramic tool containing 40% by volume or more of TiN showed excellent cutting performance as compared with the comparative example out of the range, and showed the same performance as compared with the CBN sintered tool.

<Effects of the Invention> According to the present invention, as described above with reference to the embodiments, a sintered body for a tool having both excellent heat resistance and wear resistance can be provided. When used for processing or the like, an effect that excellent performance can be exhibited.

Claims (5)

(57) [Claims] 1. A tool sintered body obtained by sintering a mixed powder of at least 40% by volume of TiN powder and a binder whose main component is Al ₂ O ₃ , wherein ZrO ₂ , AlN and A sintered body for a tool, characterized by adding one or more other binders selected from SiC whiskers. 2. A tool sintered body obtained by sintering a mixed powder of at least 40% by volume of TiN powder and a binder having ZrO ₂ powder as a main component, wherein the remaining portion is selected from AlN and SiC whiskers. A sintered body for a tool, characterized by adding one or more other binders. 3. A TiN powder 40% by volume or more, the mixed powder of the balance was mainly composed of Al ₂ O ₃ binder, after molding, vacuum or inert gas atmosphere, pressurized at 1600 ° C. below the temperature A method for producing a sintered body for a tool, comprising performing pressure sintering. 4. The method for producing a sintered body for a tool according to claim 3, wherein one or more other binders selected from ZrO ₂ , AlN and SiC whiskers are added to the remainder. A method for producing a sintered body for a tool, comprising: 5. After molding a mixed powder of TiN powder 40% by volume or more and a binder whose main component is ZrO ₂ powder,
In a method for producing a sintered body for a tool, which is pressure-sintered at a temperature of 1600 ° C. or less in a vacuum or an inert gas atmosphere, the remaining part includes one or more other binders selected from AlN and SiC whiskers. A method for producing a sintered body for a tool, characterized by adding: