JPH0585826A - Sintered ceramics - Google Patents

Abstract

PURPOSE:To improve the chipping resistance of a ceramic tool composed mainly of TiN in the high-speed cutting or intermittent cutting of a hard material by forming a binary phase texture consisting of TiN and a Y-type Si-Al-O-N binder. CONSTITUTION:The raw material powder for the subject ceramic is produced by mixing 40-80vol.% of TiN used as a main component with Al3O3 to improve the sinterability and further AlN and SiC fine powder or whisker to prevent the lowering of chipping resistance caused by the unreacted Al2O3 remaining after sintering. When the raw material powder is sintered, reaction of the AlN, SiC and Al2O3in the binder takes place to form a Y-type Si-Al-O-N having high heat-conductivity. In the above process, the SiC, AlN and Al2O3 are compounded in such a manner as to form a binary texture consisting of TiN and Y-type Si-AlO-N. The heat-conductivity is improved by this process to suppress the generation of thermal stress. The tool made of the sintered ceramic has remarkably improved chipping resistance in the high-speed cutting and intermittent cutting of a hard material such as bearing steel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sintered body for tools, and is particularly suitable as a tool for high speed cutting and interrupted cutting of high hardness materials such as bearing steel.

[0002]

2. Description of the Related Art Conventionally, a work material having a Rockwell hardness (HRC) of 60 or more and a hard material of 60 or more is difficult to cut. It is carried out. However, in the grinding process, since the processing speed is slow, the process cannot be shortened.

As a tool for cutting a high hardness material to solve this problem, a cemented carbide tool containing WC-C ₀ as a main component, a TiC-TiN-Ni-M ₀ series cermet tool,
For CBN, which is a ceramics tool containing Al ₂ O ₃ as a main component, various CBN sintering tools in which particles are sintered at high temperature and high pressure have been developed. As a tool for cutting these high hardness materials,
Performance such as small tool wear and good work surface roughness of the work material after cutting is required, especially CBN
The importance of sintering tools is increasing.

[0004]

However, among the above-mentioned tools, in the cemented carbide tools and cermet tools, the metal binder causes plastic deformation due to heat generation during processing, so that wear progresses in a short time and Not applicable as a tool. On the other hand, the Al ₂ O ₃ -based ceramics tool is superior in hardness, but is more susceptible to chipping as compared with cemented carbide and cermet, and chipping (peeling crack phenomenon in a minute area) Since it is liable to occur, the machined surface becomes rough and it is difficult to apply it to cutting of high hardness material mainly for finishing. Although the CBN sintered tool meets the required performance for cutting of high hardness materials,
To sinter N, a high temperature of 1600 ° C. or higher and a high pressure of 50,000 atmospheres or higher are required, and the manufacturing equipment is also special, so the manufacturing cost becomes very high.

Therefore, in recent years, a ceramic tool mainly composed of TiN (titanium nitride) has been proposed. This has 40 to 80% by volume of TiN as a main component,
A remarkable improvement is seen in the improvement of the surface roughness of the work material. The reason why TiN is limited to 40 to 80% by volume is that the surface roughness is reduced by fine chipping at 40% or less, and at 80% or more, sintering is possible but densification is insufficient and defects occur. This is because it becomes easier.

Some of these ceramic tools
Those mainly used as a binder₂O ₃Has been adopted.
Generally Al₂O₃Surface roughness of ceramics tools
Is thought to be due to the loss of crystal grains, and
Then Al₂O₃The poor thermal conductivity of is considered. Material heat
If the conductivity is poor, the heat generated will be transferred at the interface with the work material.
Temperature difference between the tool surface and the inside
Power is generated. Defects in extreme cases due to this thermal stress
Chipping that causes crystal grains to fall off even if there is no defect
Occurs. Then, whether the hardness of the work material becomes higher,
As the cutting speed increases,₂O₃But
When used as an inder, the thermal stress is
Becomes larger and is likely to be lost.

Therefore, in another type, the occurrence of chipping is reduced by applying AlN having excellent heat transfer property as a binder. Also, depending on the work material,
It has been confirmed that the addition of SiC whiskers is effective, though intermittent cutting is required and a large physical or thermal shock is applied in this case. However, in the case of application to intermittent cutting, it was necessary to further increase the transverse rupture strength in order to prevent chipping.

The present invention has been made in view of the above circumstances,
It is intended to provide a ceramics sintered body suitable for a cutting tool made of a high hardness material, which can be manufactured by an ordinary ceramics sintering method.

[0009]

Therefore, in the present invention, the following constitution of the sintered body is adopted. That is, TiN is made 40 to 80% by volume for the above-mentioned reason, and AlN is added to enhance the thermal conductivity and prevent chipping. And
The gist of the present invention is that fine-grained (whisker) SiC
In order to improve the sinterability at this time, Al ₂ O ₃ is added. After sintering, the binder AlN, Si
C, Al ₂ O ₃ reacts with Y-type Si-A having good thermal conductivity.
However, if Al ₂ O ₃ remains unreacted at this time, the fracture resistance is greatly reduced. That is, in the ceramic sintered body of the present invention, TiN is set to 40 to 80% by volume, and SiC, AlN, and Al ₂ O are formed so as to have a two-phase structure of TiN and Y-type Si—Al—O—N after sintering. _It is a mixture of ₃ . If a small amount of ZrO ₂ or Y ₂ O ₃ is added, a small amount of ZrO ₂ or Y ₂ O ₃ improves the difficulty of sintering due to the addition of SiC and does not adversely affect the transverse rupture strength. Further, SiM ₂ as an impurity is allowed.

[0010]

In the TiN ceramics suitable for cutting high hardness materials, Al ₂ O ₃ is added to improve the sinterability, but if Al ₂ O ₃ remains after the sintering, the fracture resistance decreases. Therefore, AlN and SiC are also added to form a two-phase structure of TiN and Y-type Si-Al-O-N having a good heat transfer coefficient to improve the thermal conductivity, that is, to reduce the generation of thermal stress.
Greatly improves fracture resistance during high-speed cutting and intermittent cutting.

[0011]

The preferred embodiments of the present invention will be described in detail below. In this embodiment, TiN powder having an average particle size of 1.5 μm, AlN powder having an average particle size of 0.3 μm, and S having an average diameter of 0.3 μm and an average length of 2 μm are used as main components.
iC whiskers, Al ₂ O ₃ powder having an average particle size of 0.3 μm, 3 mol% Y ₂ O ₃ partially stabilized ZrO ₂ powder having an average particle size of 0.3 μm were added to the following composition, and ethanol was further added. Wet-blending was performed and then dried to obtain raw material powder.
In addition, a raw material powder in which the volume% other than TiN powder was changed as follows was used as a comparative example. Then, these raw material powders are hot-pressed in a vacuum at a predetermined temperature (pressure 400 kgf / cm
² ) and sintered. Sample Raw material composition (vol /%) Firing temperature TiN AlN SiC whisker Al ₂ O ₃ ZrO ₂ Example 60 20 10 7 3 1500 ℃ Comparative example 60 12 4 23 1 1500 ℃

FIG. 1 shows the results of X-ray diffraction of Examples and Comparative Examples.
And FIG. 2 respectively. As is clear from these figures, in the examples, TiN, Y-type Si—Al—O—N and Si ₂ M as an impurity are used, whereas in the comparative example, in addition to these compounds, , Al ₂ O ₃ is present.

The inventor and the like then used the throw-away tip (ISO symbol SNMN432 (size after processing 12.7 mm).
× 12.7 mm × 4.76 mm, corner radius 0.8 m
m)) and processed into a tool. Then, using the obtained tool, a continuous cutting test was performed under the following conditions, and each evaluation was performed. Work Material: SUJ2 (HRC about 62) Cutting Speed: 100 m / min and 150 m / min Cutting Depth: 0.1 mm / rev Feed: 0.1 / rev Cutting Speed 100 m / min In both Example and Comparative Example,
A good result is shown. At a cutting distance of 6000 m, the flank wear amount is about 0.3 mm, and the finished surface roughness is 3 μm, which is C currently used as a high hardness cutting tool.
It showed the same characteristics as the BN sintering tool.

Next, the inventors increased the cutting speed to 15
A cutting test was performed at 0 m / min. As a result, the comparative example was damaged immediately and could not be cut, but the example did not damage up to a cutting distance of 2000 m as shown in FIG. 3, and the finished surface roughness was good at 3 μm or less, and cutting at high speed. It turned out that the sex is greatly improved.

The inventors next conducted an intermittent cutting test using the test piece shown in FIG. 4 under the following conditions. In this example, the test piece had a diameter of 54 mm and a length of 128 mm. Work material: SUJ2 (HRC 62) Cutting speed: 100 m / min Depth of cut: 0.1 mm Feed: 0.1 mm 1 pass: 217 m Intermittent frequency: 10204 times As a result, the comparative example was defective in 1 pass, In the example, it was found that the chipping occurred at the 7th time, and the interrupted machinability was greatly improved. In this case, the finished surface roughness is also 3
It was good at about μm. This test shows that ZrO ₂ ,
If Y ₂ O ₃ is added in a small amount, it improves the sintering resistance due to the addition of SiC and does not adversely affect the transverse rupture strength, and SiM ₂ as an impurity is allowed. Was confirmed.

Under the above conditions, Al ₂ O ₃ ceramics (including TiC) and C, which are currently used for cutting high hardness materials, are used.
As a result of cutting test performed on the BN sintered tool, Al ₂ O
_{While 3} ceramics were damaged in one pass,
The CBN sintering tool was not broken even after 11 times.

[0017]

As described above in detail based on the examples, by using the ceramic sintered body of the present invention,
It is possible to inexpensively manufacture a ceramic tool for high-hardness steel, which is excellent in high-speed machinability and intermittent machinability and is substantially equivalent to a CBN sintered tool.

[Brief description of drawings]

FIG. 1 is a graph showing a result of X-ray diffraction of a ceramics sintered body according to an example of the present invention.

FIG. 2 is a graph showing a result of X-ray diffraction of a ceramic sintered body of a comparative example.

FIG. 3 is a graph showing a result of a cutting test of a ceramics sintered tool according to an example of the present invention.

FIG. 4 is a front view and a side view showing the shape of a ceramics tool according to an embodiment of the present invention.

Claims (1)

[Claims] 1. TiN of 40 to 80% by volume and Y-type Si
A ceramics sintered body characterized by forming a two-phase structure with a binder containing —Al—O—N as a main component.