JPH03218968A - Sintered body for tool and production thereof - Google Patents

Abstract

PURPOSE:To obtain a sintered body for a tool which simultaneously has heat resistance and wear resistance by sintering mixed powder which consists of TiN and Al2O3, ZrO2 and SiC whisker, etc., at the specified rate. CONSTITUTION:Mixed powder of >=40vol.% TiN and the balance one or more kinds of Al2O3, ZrO2, AlN and SiO whisker is molded. Thereafter the molded body is pressurized and sintered at <=1600 deg.C in vacuum or the inert gas atmosphere. For example, by vol.% 60.0 TiN powder having 1.5mum mean particle diameter, 22.8 Al2O3 powder having 0.37mum mean particle diameter, 1.2 ZrO2 powder partiality stabilized by 3 mol% Y2O3 having 0.3mum mean particle diameter, 4.0 SiC whisker having 2mum mean length and 12.0 AlN powder having 0.3mum mean particle diameter are blended. This blended material is mixed by a wet method and the mixture is dried. The obtained powdery raw material is hot-pressed at 1500 deg.C in vacuum and sintered. When the blending rate of TiN is regulated to <=40vol.%, generation of chipping is not prevented and the roughness of the worked face is impaired.

Description

[Detailed Description of the Invention] Industrial Applications The present invention relates to a sintered body for tools and a method for manufacturing the same, and is particularly suitable for use in high-speed cutting of high-hardness materials such as bearing steel. be.

Conventional technology In the past, the hardness of the workpiece was determined by the rock-well hardness (
In H, c), machining of high hardness materials with a hardness of 60 or more is difficult, so grinding is mainly performed using diamond abrasive grains or the like. However, since the grinding process has a slow processing speed, the process cannot be shortened as expected.

In order to solve the problem of WRll, as a tool for cutting high hardness materials, ■sl whose main component is WC-Co! Alloy tool, ■TiC
-TiN-Ni-Mo based cermet tool, ■Aj20
, CBN sintered tools made by sintering CBN particles at high temperature and high pressure have been extensively developed, and a new field of machining is being developed.

Tools for cutting this high-hardness material are required to have the following performance characteristics: (1) Small amount of tool wear, and (2) Good surface roughness of the cut workpiece.

Problems to be Solved by the Invention> However, among the above-mentioned tools for use with high-hardness materials, cemented carbide tools and cermet tools suffer from plastic deformation of the metal binder due to heat generated during machining, resulting in rapid wear. The problem is that it cannot be applied.

In addition, ceramic tools are more likely to break than cemented carbide or cermet, and are more likely to cause chipping (a peeling crack phenomenon in a minute area), resulting in poor machined surface roughness, making them unsuitable. There is +aui.

Furthermore, although the CBS sintering machine meets the performance requirements for cutting high-hardness materials, high temperatures of over 1,600°C and high pressures of over 50,000 atmospheres are required to sinter CBN. At the same time, the manufacturing equipment is special and expensive, and the CB
The problem is that N sintered tools are very expensive to manufacture.

Means for Solving the Problems〉 The structure of the sintered body for tools of the present invention for solving the above problems is as follows: 40% by volume or more of TiN, and the balance is Aj203, Z
It is characterized in that it is made by sintering a mixed powder with one or more selected from rq, AjN, and SiC whiskers, and on the other hand, this method for producing a sintered body for tools uses TiN of 40% by volume or more and the balance of Aj20l, ZrO2, AIN
, SiC whisker, and a mixed powder of one or more selected from SiC whiskers is molded and then pressure sintered at a temperature of 1600° C. or lower in a vacuum or an inert gas atmosphere.

Hereinafter, the configuration of the present invention will be explained in detail.

The present invention uses titanium nitride (TiN) as the main component, and Aj'203 and ZrO as other components. , A
#N, one or more selected from SiC whiskers.

Here, the blending ratio of TiN is 40% by volume or more in powder form. This is because if the TiN powder content is less than 40%, it is impossible to prevent the occurrence of chipping, which is a drawback of ceramic tools. In addition, TiN powder was added to 9
Although sintering is possible when the content is 0% by volume or more, it is not suitable for use as a tool because it cannot be sufficiently densified.

Therefore, a suitable blending amount for use as a tool is 40 to 90% by volume, more preferably 60 to 80% by volume.

Incidentally, attempts have been made to use TiN in tools that use a metal binder such as cermet or powdered high speed steel as a binding material. These tools are mainly aimed at improving Yasu (the general name for high-speed tool steel) and are intended for soft work materials with HPLC hardness of 30 or less, improving finishing accuracy, Effects such as increased efficiency were confirmed.

However, it is difficult to sinter TiN without a metal binder, and a tool sintered only with ceramics as in the present invention has not been developed.

In addition, the inventor considered the problem of thermal conductivity as a cause of chipping that occurs in conventional ceramic tools mainly composed of AI203. The thermal conductivity of Aj203 is high near room temperature, but rapidly decreases at relatively low temperatures of 100° C. or higher. To improve the toughness of At20, Z r O
If 2 is added, the thermal conductivity will further decrease. If the thermal conductivity of the material is poor, when it is made into a tool, the heat generated at the interface with the workpiece material is transferred, resulting in a temperature difference between the tool surface and the inside, resulting in large thermal stress.

Due to this thermal stress, extreme welding causes defects, and even if no defects occur, chipping occurs in which crystal grains fall off. In the present invention, the main component of TiN is TiN, which has high thermal conductivity, and the lower limit value is set to 40% by volume to prevent chipping of the fitting used as a tool.

The remaining other components added to the TiN powder as the main component are Aj, O, , ZrO2, AIN,
One can mention SiC whiskers.

Here, AN, O, are the main components of the remaining components,
It also has high chemical stability and has the property of not easily reacting with workpiece materials when made into tools.

It is also effective because its hardness is relatively high.

Z r O2 has the effect of improving sinterability by adding a large amount. This effect is due to the presence of A
It is possible to sinter at a low temperature of about 1500° C. even when components that inhibit sintering such as jN, SiC whiskers, and TiN are added.

In addition, the ZrO powder partially stabilized by adding about 3 moj% Y203 to l(DZrO) is the same as the above-mentioned AI
It can be used as the main component of the remaining component instead of 20I. In this case, compared to the case where Aj,03 is used as the main material, wear increases slightly, but a tool with high strength can be obtained, so it is less likely to break.

AIN and SiC whiskers as the remaining components are added for the purpose of improving thermal conductivity. This is TiN
If there is a large amount of TiN, it will not have a big impact on the heat transfer vehicle as a worker, but if there is a small amount of TiN, the remaining components are likely to chip or peel off, so AIN and S
We are trying to improve these by using iC whiskers. Note that the addition of SiC whiskers does not affect the various properties of the tool, but the addition of AjN has the disadvantage of reducing the strength, so it is better not to add it when there is a large amount of TiN.

Here, in the present invention, pressure sintering means, for example, hot sintering,
X method and H I P (Hot Isostatic P
Using a sintering method using hot isostatic pressing (res: hot isostatic pressing), in a vacuum or inert gas atmosphere, and at a firing temperature of 16
This means firing at a temperature of 00°C or lower. Above firing temperature 1 6
0 0' (The reason for the following limitations is that the steady wear of the tool is desirable because the finer the grain size after firing, the smaller it is desirable. If the temperature is 1600°C or higher, abnormal growth of the grain size becomes noticeable. This is because when used as a cutting tool, the life span is significantly reduced.

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

(Example of manufacturing method of sintered body) Commercially available TiN powder with an average particle size of 1.5 μm as the main component and commercially available Al with an average particle size of 0.3 μm as the remaining component.
203 powder; 3mo/% Y20 with an average particle size of 0.3μm
, Partially stabilized z '02 powder; SiC whiskers with an average diameter of 0.3 μm and an average length of 2 μm; A with an average particle size of 0.3 μm
Using IN powder as a raw material, it was blended into the composition shown in Table 1 below, further ethanol was added, wet mixed, and then dried to obtain a raw material powder.

This raw material powder is heated to a specified temperature in a vacuum. Hot press (pressure 400 kgf/cjlt, sintering).

After that, the throw-away tip (ISO symbol SNMN
432 (Dimensions after processing: 12.7 m x 12.7 m x 4.7
It was processed into a shape with a corner radius of 0.8 cm) and was made into a tool.

Using the obtained tool, a cutting test was conducted under breath conditions.
Each was evaluated.

o @ Cutting material: SVJ 2 (H, C6 about 2), 0
Cutting speed: 100n/min, 0 depth of cut:
O. lm / r ev, O feed: 0.
2m/r ev, 0 Tool wear amount: Cutting distance 4
Flank wear width after 000m.

0 Machined surface roughness: Machined surface roughness of the workpiece material after cutting distance of 4000 m.

The results of this cutting test are shown in Table 1. Note that the CBN sintered tool used as a comparison material here is a commercially available product from another company.

Table 1 From the results shown in Table 1, ceramic tools containing 40% by volume or more of TiN exhibited superior cutting performance compared to comparative examples outside the range, and equivalent performance compared to CBN sintered tools. showed that.

Effects of the Invention> As described above with the embodiments, according to the present invention, it is possible to provide a sintered body for tools that has both excellent heat resistance and wear resistance, and is particularly suitable for cutting high-hardness materials such as bearing steel. When used for processing, etc., it has the effect of exhibiting excellent performance.

Claims (1)

[Claims] 1) 40% by volume or more of TiN, the balance being Al_2O_3
, ZrO_2, AlN, and SiC whisker. 2) 40% by volume or more of TiN and the balance is Al_2O_3
, ZrO_2, AlN, and SiC whiskers, is molded and then pressure sintered at a temperature of 1600°C or less in a vacuum or inert gas atmosphere. A method for manufacturing a sintered body for tools.