JP2922713B2 - Zirconia sintered body for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zirconia sintered body for a tool used for a knife such as a kitchen knife or a slitter knife, a die such as a drawing die, and a tool for abrasion resistance.

[0002]

2. Description of the Related Art Metals such as iron have conventionally been used for knives such as kitchen knives and slitter knives, dies such as drawing dies, and tools for wear resistance.

[0003] However, tools using such a metal such as iron have the problems of low hardness and rust and the like. Therefore, in recent years, tools made of ceramics that have high hardness and do not generate rust and the like have been recently used. Tools are being used.

However, in such a ceramic tool, a stress acting portion (for example, a cutting edge of a knife such as a kitchen knife or a slitter knife) to which a stress acts during use tends to be chipped and chipping is likely to occur. A (ZrO ₂ ) sintered body is used (for example, see Japanese Patent Application Laid-Open No. 3-93668).

[0005]

However, even with a tool using a high-toughness ZrO ₂ -based sintered body, chipping may occur in the stress acting portion when a large impact occurs, and such chipping is minimized. It was necessary to suppress.

The inventor of the present invention has thoroughly studied such problems, and as a result, a large amount of monoclinic ZrO ₂ (m-ZrO ₂ ) has been formed in the stress acting portion of the tool. It was found that tetragonal ZrO ₂ (t-ZrO ₂ ) was small. Incidentally, toughening of ZrO ₂ from t-ZrO ₂ m-Z
Since the change is performed by a change of volume expansion at the time of transition to rO ₂ , there is a problem that it is difficult to perform toughening with a conventional tool in view of the fact that t-ZrO ₂ is small as described above. As a result, even if a crack is to be generated in the stress acting portion, the transition from t-ZrO ₂ to m-ZrO ₂ is not performed so much, the toughness due to volume expansion is hard to be performed, and the crack may develop and chipping may occur. was there.

The present inventor has further examined this point. As a result, the fact that t-ZrO ₂ is small in the stress acting portion is a necessary polishing process in the tool manufacturing process. _The transition from ₂ to m-ZrO ₂ was made, and it became clear that t-ZrO ₂ in the stress acting portion was reduced. In order to remove the influence of such polishing, various investigations, for example, heat treatment of the tool was performed,
No significant effect was observed.

[0008]

[Means for Solving the Problems] The present inventor has studied the above problems, and as a result, found that flaky A was contained in ZrO _2.
The inventors have found that by adding l ₂ O ₃ , the stress acting portion of the tool can be toughened, and have reached the present invention.

That is, the zirconia sintered body for a tool according to the present invention contains partially stabilized zirconia as a main component, and further has a thickness of at least 2 μm and a diameter of 10 μm.
It contains the following flaky alumina at a ratio of 3 to 40% by volume.

Here, the average thickness of the flaky alumina is 2 μm.
The reason why the average diameter is not more than 2 μm and the average diameter is more than 10 μm is that the effect of improving the toughness is small and the sinterability is deteriorated. The flaky alumina preferably has an average thickness of 0.5 μm or less and an average diameter of 2 μm or less. This is because within this range, the effect of strengthening toughness is large.

The reason for adding flaky alumina in an amount of 3 to 40% by volume is that if it is less than 3% by volume, the effect of toughness is small, and if it exceeds 40% by volume, it is difficult to obtain a dense sintered body. It is. The optimum amount of flaky alumina varies depending on the firing method.

That is, 3 to 20% by volume is preferable in normal firing, and 3 to 25% in hot isostatic firing after normal firing.
%, More preferably 3 to 40% by volume for hot isostatic pressing (HIP) using glass capsules, and preferably 3 to 35% by volume for hot pressing.

The partially stabilized zirconia which is the main component of the present invention contains t-ZrO ₂ in a proportion of 60% or more in zirconia, and includes m-ZrO ₂ and cubic ZrO ₂ (c
—ZrO ₂ ) may be present at 40% or less.

As a method for producing the zirconia sintered body for a tool of the present invention, for example, first, ZrO ₂ contains 2.5 to 3 mol% of Y ₂ O ₃ as a stabilizer. The partially stabilized ZrO ₂ is prepared, ₃ to 40% by volume of flaky Al ₂ O ₃ is added to the partially stabilized ZrO ₂ , and firing of Y ₂ O ₃ , Er ₂ O _3, etc. is performed to improve sinterability. A predetermined amount of binder, further, a binder or the like is added, desired molding means,
For example, after being formed into an arbitrary shape by a die press, a cold isostatic press, an extrusion molding, or the like, firing is performed at 1350 to 1500 ° C.

For the firing, a normal firing method, a hot press method, a hot isostatic firing method, or the like is applied. To improve the compactness, a hot isostatic firing method (HIP) is performed after the normal firing. Is preferred.

[0016]

In the zirconia sintered compact for a tool according to the present invention, for example, in a polishing step in a tool manufacturing process, a stress acting portion is changed from t-ZrO ₂ to m-ZrO _2, and t-ZrO ₂ in the stress acting portion is changed. even if _{the 2} is running low, the toughness is greatly improved for two reasons:.

That is, chipping in ceramic is
First, cracks are formed on the ceramic surface, and the cracks are generated by gradually expanding the cracks.
If O ₂ is added scaly Al ₂ O _3, as shown in FIG. 1, scaly Al ₂ O ₃ 11 to withstand sufficiently against external shock, for so-called anchor effect, to improve toughness, Crack growth in the initial stage is suppressed, and chipping is suppressed.

In the zirconia sintered body for a tool according to the present invention, as shown in FIG. 1, when a crack is to be generated in the sintered body 13, a tensile force acts on the flaky Al ₂ O ₃ 11. ,
T- existing around the flaky Al ₂ O ₃ 11
ZrO ₂ is transferred to the m-ZrO _2, the amount of transition to m-ZrO ₂ is greatly improved, the volume of the sintered body 13 around the scaly Al ₂ O ₃ 11 is expanded, the expansion of cracks suppression And
BR> Toughness improves.

Hereinafter, the present invention will be described with reference to the following examples.

[0020]

EXAMPLE As a raw material powder, a partially stabilized ZrO ₂ co-precipitated raw material powder (average crystal grain size: 0.5 μm) mainly composed of t-ZrO ₂ containing 3 mol% of Y ₂ O ₃ as a stabilizer was used. Mix, pulverize and mix well. A predetermined amount of scaly Al ₂ O ₃ and a sintering aid were added to the partially stabilized ZrO ₂ so as to obtain a sintered body as shown in Table 1, and then mixed and pulverized for 30 minutes using an attrition mill. After adding and mixing paraffin wax as a binder to the mixed powder, it was dried and press-molded at a pressure of ² ton / cm ² . The molded body was fired in the atmosphere at a temperature of 1450 ° C. for one hour.

[0021]

[Table 1]

Then, JISR160 is applied to each sintered body.
According to 1, the three-point bending strength and Vickers hardness were measured. Further, the sample was polished to a mirror surface state, and the fracture toughness was measured by the IF method. Further, each sample was polished with a diamond grindstone, processed into a blade shape, and used for 100 hours. After that, an inspection was performed to determine whether chipping had occurred.
The results are shown in Table 2.

[0023]

[Table 2]

From Table 2, it can be seen that all of the samples of the present invention have high strength, toughness, and hardness, and that no chipping occurs even after a certain period of use, or that the chipping is extremely small.

[0025]

As described in detail above, in the zirconia sintered body for a tool of the present invention, when flaky Al ₂ O ₃ is added to ZrO ₂ , the flaky Al ₂ O ₃ is resistant to external impact. Because of the so-called anchor effect, the toughness is improved, crack propagation in the initial stage is suppressed, and chipping is suppressed. Further, when a crack is to be generated in the sintered body, a tensile force acts on the flaky Al ₂ O ₃ , and this flaky A ₂ O ₃ is formed.
t-ZrO ₂ existing around l ₂ O ₃ is changed to m-ZrO
₂ , the volume around the flaky Al ₂ O ₃ expands, and the expansion of cracks is suppressed. Therefore, when the zirconia sintered body for a tool of the present invention is applied to a tool, the stress acting portion is t-Z in the polishing step in the tool manufacturing process.
Even when the transition from rO ₂ to m-ZrO ₂ and the amount of t-ZrO ₂ is reduced, the toughness can be greatly improved, and thereby chipping can be largely suppressed.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing the effect of the addition of scaly Al ₂ O ₃ .

[Explanation of symbols]

11 Scale-like Al ₂ O ₃ 13 sintered body

Claims (1)

(57) [Claims] 1. A zirconia sintered material for a tool, comprising partially stabilized zirconia as a main component and 3 to 40% by volume of flaky alumina having an average thickness of 2 μm or less and an average diameter of 10 μm or less. body.