JP2735702B2 - Fiber reinforced ceramic tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, iron, nickel,
The present invention relates to a ceramic tool material useful for cutting an alloy such as cobalt or various materials.

[0002]

2. Description of the Related Art Conventionally, as a ceramic tool, a tool mainly composed of aluminum oxide (Al ₂ O ₃ ) has been widely used, but various improvements have been made due to insufficient strength and toughness of Al ₂ O ₃ itself. Has been done. A typical material is titanium carbide (TiC) in an Al ₂ O ₃ sintered body.
The material itself has been toughened by dispersing and incorporating particles and zirconium oxide (ZrO ₂ ) particles into a composite.

[0003] However, cutting conditions and the like as tools have become more severe, and higher strength and higher strength have been required for tool materials.
High toughness and wear resistance are required. Therefore, in recent years, fiber-reinforced ceramics to which a fibrous substance made of various ceramics has been added instead of TiC or ZrO ₂ have attracted attention. Among these, silicon carbide (SiC) whisker reinforced materials are particularly attracting attention as materials for cutting difficult-to-cut materials because of their excellent properties.

[0004]

However, this SiC whisker has a problem that, when cutting an iron-based metal, the reactivity between SiC and the work material is high and abrasion increases. For this purpose, whisker addition systems of compounds other than SiC, particularly carbides and oxides, have been studied, but at present, whisker mass production technology has not been established, and whiskers having good characteristics have not been obtained. Therefore, SiC
In whisker-added systems, how to suppress the reactivity of the SiC whiskers with the work material and increase the wear resistance is a major issue in achieving practical application as tool materials and expanding the field of application. ing.

The inventors of the present invention have studied the mechanism that causes wear of a tool when a material containing SiC is used as a tool and a ferrous metal is cut.
Because iC has high reactivity with iron, the added SiC is preferentially eroded by the metal as the work material at the tool edge, which becomes high temperature during cutting, and the wear of the tool material is increased. It became clear. And this phenomenon is
This was particularly noticeable for tool materials containing SiC whiskers. This is because the whisker has a thin and long shape, and the whisker uniformly dispersed in the cutting tool material is eroded along the whisker at the time of cutting, so that a wedge is applied to the tool material, especially on the rake face of the cutting tool. This is because you will be struck.

The present invention is directed to a SiC whisker-added tool material which prevents wedge-shaped erosion and prevents destructive wear even when cutting an iron-based material.
It is an object to provide a tool strengthened by whiskers.

[0007]

Means for Solving the Problems In the above-mentioned SiC whisker-added system, the present inventors studied a method for suppressing the erosion effect due to the reaction with the iron-based metal and preventing the wedge-shaped erosion phenomenon. As a result of the superposition, it was considered that the direction of erosion can be controlled by controlling the arrangement of the particles of the SiC whiskers themselves. When the particles are arranged so that the SiC whiskers are parallel to the rake face of the tool, the erosion during cutting of the iron-based material does not progress in a wedge shape as described above, so that destructive wear can be prevented. And found the present invention.

That is, the fiber reinforced ceramic tool of the present invention is characterized in that, in a tool material reinforced using SiC whiskers, the SiC whiskers are oriented parallel to the tool rake face. It is characterized in that the ratio of the number of whisker particles having an aspect ratio of 2 or less on the tool flank to the number of whisker particles having an aspect ratio of 2 or less on the tool rake surface is controlled to be 10 or more.

Hereinafter, the present invention will be described in detail. The fiber reinforced ceramics tool of the present invention has a composition in which Al ₂ O ₃ is a main component and SiC whiskers are added as a reinforcing material.
% By volume, in particular 20 to 40% by volume. If the addition amount of this whisker is more than 50% by volume, tool wear is large, and it is not suitable for practical use.
The effect of improving toughness is reduced.

The Al ₂ O ₃ and SiC whiskers are usually uniformly dispersed as a sintered body, and the whiskers, which are acicular particles, are also randomly dispersed in the direction. It is characterized in that the whisker particles are arranged anisotropically on the rake face and the flank face of the cutting edge in the shape, and the whiskers are arranged so as to be parallel to the rake face. As a result, a difference occurs between the rake face and the flank in the shape of the whisker in the electron microscope photograph of the mirror surface.

FIGS. 1 and 2 are simulated views of a rake face and a flank of a fiber-reinforced ceramic tool of the present invention taken by a scanning electron microscope. As is clear from the drawing, the needle-like form of the SiC whisker is remarkably observed on the rake face, whereas the needle-like form, particularly the length, is shorter on the flank face than on the rake face. This indicates that the surface of the whisker in the longitudinal direction is exposed on the rake face, whereas the cross section of the whisker is exposed on the flank face.

According to the present invention, the anisotropy of the whisker was considered in detail from the viewpoint of the tool performance. As a result, the aspect ratio (major axis length / minor axis length) between the flank and the rake face in the photomicrograph was taken. When the number of whisker particles having a particle size of 2 or less was defined as N ₁ and N ₂ , respectively, excellent cutting characteristics were exhibited when the ratio represented by N ₁ / N ₂ was 10 or more, particularly 30 or more.

Further, according to the fiber reinforced ceramic tool of the present invention, the above Al ₂ O ₃ —SiC whisker is used as a main component, and further, a rare earth element oxide such as Y ₂ O ₃ , Nd ₂ O ₃ , CeO ₂ or the like is removed. The sinterability of the system can be enhanced by containing 0.1 to 3% by weight.

Next, a method for producing the ceramic tool of the present invention will be described. Usually, in the case of manufacturing the Al ₂ O ₃ -SiC whisker-based material, an Al ₂ O ₃ raw material powder and SiC whiskers were mixed well in a liquid, the mixture after feed drying is sintered by a hot press method. Since the hot press method is uniaxial pressing, it is known that whiskers may be oriented on a plane perpendicular to the pressing axis. However, this tendency is unsatisfactory, and SiC whisker particles are usually arranged in random directions in a sintered body that has been hot-pressed.

According to the present invention, Al ₂ O ₃ raw material and S
The iC whisker raw material and other additives, if necessary, are blended in a desired mixing ratio, and this is thoroughly mixed with a solvent by a known method to prepare a slurry. Next, the obtained slurry is poured into a mold made of metal, plastic, gypsum, or the like in which, for example, a large number of continuous vents having an average diameter of 100 μm or less are formed at the bottom, and the solvent is reduced to 30% from the mixture.
Filter and separate until:

At this time, SiC whisker particles and Al ₂ O ₃ particles are deposited in the mold material to form a molded body. Inside the molded body, the whiskers are oriented in a direction perpendicular to the direction of gravity or the direction of suction. It will be. According to the present invention, the shape of the mold is formed into a tool shape, and the whisker-oriented side is formed as a rake face.

In the above molding step, water is the cheapest solvent and is easy to handle, but other organic solvents can also be used. In the step of removing the solvent from the mixture of the raw materials, it is also effective to suction-filter the solvent through the communication holes by reducing the pressure or the vacuum on the opposite side of the communication holes. At this time, 2kg / cm
^Two or more pressures may be applied. The pressure at this time is 1
The pressure is preferably 0 to 200 kg / cm ^2, but can be increased within the allowable range of the strength of the mold.

In addition, it is effective that the continuous ventilation holes of the mold used in molding are provided only on the bottom surface or two parallel surfaces of the mold, and the whisker is deposited in one direction.

After the solvent is sufficiently filtered in this way, the molded body is removed from the mold, and the molded body is dried, and then placed in, for example, a carbon mold and subjected to hot pressing. In hot press sintering, a temperature of 1700 to 1950 ° C. in a reducing atmosphere containing Ar, vacuum, or
By firing for about 3 hours, it is possible to make the relative density 99% or more. As another firing method, 175 in a vacuum or an inert gas or a reducing atmosphere is used.
After baking at a temperature of 0 to 2000 ° C., hot baking at 1650 to 1900 ° C. in an inert atmosphere can further increase the density.

[0020]

[Action] In the Al ₂ O ₃ -SiC addition system tool, tool wear material is preferentially eroded by metal is work material is expanded in tool tip having a high temperature during cutting. This phenomenon occurs because, in a tool material containing SiC whiskers, since the whiskers have a thin and long shape, this portion is preferentially eroded during cutting, and wedge-shaped erosion occurs at the cutting edge. This wedge-shaped erosion is most pronounced on the rake face of the tool where the cutting temperature is highest. The wedge-shaped erosion is not so remarkable on the tool flank because the cutting temperature is lower than on the rake face. According to the tool of the present invention, the whiskers are arranged in parallel with the rake face in comparison with the conventional tool on the rake face, so that when the SiC whiskers react with the work material and erosion progresses, However, since erosion proceeds in the direction of the rake face and not in the depth direction, it is possible to prevent the occurrence of wedge-shaped erosion. As a result, wear can be prevented even when cutting an iron-based material, and the life of the tool can be prolonged, as is clear from the examples described later.

[0021]

The present invention will be described below with reference to the following examples. Al ₂ O ₃
Powder (average particle size: 0.4 μm), SiC whiskers (short axis length: 0.8 μm, aspect ratio: 30) and Y ₂ O ₃ powder as a sintering aid are added at the ratio shown in Table 1, and distilled water is used as a solvent. The mixture was sufficiently mixed in a rotary mill to prepare a slurry. Next, the slurry was poured into a tool having a tool shape made of a porous resin, and the mold was pressed at a pressure of 100 kg / cm ² while adjusting the suction force with a vacuum pump to perform molding. The obtained compact was hot-pressed at 1900 ° C. under a pressure of 300 kg / cm ² to obtain a relative density of 9%.
A sintered body of 9% or more was produced.

In addition, as a comparative example, the slurry was not formed by suction, the slurry was dried, filled in a carbon mold, and hot pressed to prepare samples No. 9 and No. 10 in the table.

Further, as another embodiment, Al ₂ O ₃ and SiC whiskers are formed by the method described above,
Furthermore, after cold isostatic pressing at a pressure of 4000 kg / cm ² , it is baked at 1900 to 2000 ° C. for 6 hours in a vacuum, and further heated in Ar under a pressure of 2000 kg / cm ² for 1900 hours.
C. and hot isostatic sintering was performed.
2 was obtained.

For each of the obtained tool sintered bodies, JISR
Based on 1601, the four-point bending strength was measured. Also, the rake face and flank face of each tool sintered body are mirror-finished with diamond powder of 3 μm or less and etched, and then the silicon with an aspect ratio of 2 or less is obtained by a scanning electron microscope (SEM) photograph.
The number of particles of the C whiskers was counted, and the ratio of N ₁ / N ₂ was calculated with the number of particles on the flank being N ₁ and the number of particles on the rake face being N ₂ .

Next, a cutting test was performed under the following cutting conditions, and crater wear was examined. Cutting condition 1 Work material Inconel 718 Cutting speed 250m / min Cutting depth 1.5mm Feed 0.2mm / rev Cutting time 5min

Cutting condition 2 Work material SUS304 Cutting speed 250 m / min Cutting depth 1.5 mm Feed 0.2 mm / rev Cutting time 10 minutes

[0027]

[Table 1]

[0028]

[Table 2]

According to Table 1, the toughness is improved by increasing the added amount of SiC whiskers. However, when the added amount of SiC whiskers is 60% by volume, a large number of voids are present in the sintered body, and the toughness cannot be measured. could not. Further, the strength and toughness of the sintered body did not significantly correlate with the orientation of the SiC whiskers.

According to Table 2, as the amount of SiC whiskers added to the tool increases, the amount of wear during cutting tends to increase. In particular, the samples prepared by the conventional method and having almost no orientation of the SiC whiskers In No.9,10,
In all cases, wedge-shaped erosion was observed and abrasion was large. On the other hand, the sample in which the SiC whiskers are oriented according to the present invention is also apparent from the comparison of the samples No. 5 and No. 9 and the samples No. 6 and No. 10 with the same SiC whisker addition amount. Thus, it can be seen that the wear amount can be significantly reduced as compared with the conventional product.

[0031]

As described in detail above, the Al ₂ O _{3 of the} present invention
The SiC whisker-based fiber reinforced ceramic tool can prevent wedge-shaped erosion that occurs when an iron-based material is used as a work material. Therefore, it is possible to impart cutting stability to the iron-based work material and to extend the life of the tool.

[Brief description of the drawings]

FIG. 1 is a schematic drawing of a scanning electron micrograph of a rake face of a tool of the present invention.

FIG. 2 is a schematic drawing of a scanning electron micrograph of the flank of the tool of the present invention.

Claims (1)

(57) [Claims] In a ceramic tool mainly composed of aluminum oxide and containing silicon carbide whiskers, the ratio of the number of whisker particles having an aspect ratio of 2 or less on a tool flank to the number of whisker particles having an aspect ratio of 2 or less on a tool rake face is reduced. A fiber-reinforced ceramic tool, wherein the number is 10 or more.