JPH09320573A - Dry battery manufacturing die member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the corrosion resistance to alkali component, and attain a long-term use without breakage by forming the part at least making contact with the mix of a dry battery of a die member by use of silicon nitride ceramics having a high bending strength. SOLUTION: A device for forming a mix of dry battery is formed of a die 1 provided on the inside of a metallic cylinder 2, an upper punch 3, and a lower punch 4. The part making contact with at least the mix of either one of these die members is formed by use of silicon nitride ceramics having a bending strength of 80kg/mm<2> or more. The silicon nitride ceramics preferably has an average crystalline particle diameter of 0.1-10μm, and contains 75% or more of silicon nitride particle having an aspect ratio of 3 or more. Even when a stress based on thermal expansion difference after shrinkage fitting is added when the die 1 is shrinkage fitted to the cylinder 2, the die is never broken since it is highly strong.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold member for manufacturing a dry battery, which is used when molding a mixture for a dry battery.

[0002]

2. Description of the Related Art A dry battery is constructed by arranging a molded body of a mixture around a carbon rod. This mixture is an important element that controls the characteristics of the battery, and is mixed in various ways depending on the intended use. For example, in a general manganese battery, manganese dioxide is used as a main component, acetylene black, graphite, ammonium chloride, etc. are mixed and press-molded into a predetermined shape with a die member, a die member such as an upper and lower punch, and the mixture is molded. Is being made.

On the other hand, in recent years, alkaline batteries have been widely used as long-life dry batteries.
For example, molten zinc with mercury, aluminum, nickel and / or
Alternatively, cobalt, alkali metal and / or alkaline earth metal, or those having a composition in which one or more kinds selected from indium, lead, cadmium, thallium, and gallium are mixed with these are used.

Stellite, hastelloy, titanium metal, etc. have been conventionally used as a mold member for molding these mixtures, but it has been proposed to use ceramics in order to enhance corrosion resistance and wear resistance. ing. For example, Japanese Patent Publication No. 4-58427 discloses the use of zirconia-based ceramics containing ZrO ₂ as a main component and a stabilizer, and Japanese Patent Publication No. 4-59268 discloses Si ₃ N 4.
It has been proposed to use sialon-based ceramics, which is a solid solution of ₄ and Al ₂ O ₃ .

[0005]

However, the mold member for producing a dry battery, which is made of sialon-based ceramics, has a problem that it is liable to be cracked or chipped during production or use because of its low strength. For example, if the die is made of sialon-based ceramics, when the die is fixed by shrink fitting inside the metal cylinder during the manufacturing process of the molding apparatus, stress is applied to the die due to the difference in thermal expansion after shrink fitting. It was easy to add and break. Alternatively, since a large impact is applied to the die and punch during use, these mold members are easily damaged.

On the other hand, the mold member for producing a dry battery, which is made of the zirconia-based ceramics, has high strength and toughness and thus is less likely to be damaged, but has a problem of poor corrosion resistance against alkaline components. Therefore, when a mixture for alkaline batteries, which has been widely used in recent years, is molded, there is a problem that the mold member is deformed due to corrosive wear, and as a result, the pressure during molding becomes uneven and cracking is likely to occur. It was

[0007]

Therefore, according to the present invention, a die member for molding a mixture of a dry battery, a die member such as an upper and lower punch, and the like are formed of silicon nitride ceramics having a bending strength of 80 kg / mm ² or more. Characterize.

Further, according to the present invention, the mold member for producing a dry battery is formed of silicon nitride ceramics having an average crystal grain size of 0.1 to 10 μm and containing 75% or more of silicon nitride grains having an aspect ratio of 3 or more. Is characterized by.

[0009]

EFFECTS OF THE INVENTION According to the present invention, since a mold member for manufacturing a dry battery is formed of a silicon nitride ceramic having high corrosion resistance to an alkaline component and high strength, even if it is used for manufacturing a mixture for an alkaline battery, it is damaged. It can be used satisfactorily for a long period of time.

[0010]

Embodiments of the present invention will be described below.

As shown in FIG. 1, the schematic structure of an apparatus for molding a mixture for a dry battery comprises a die 1 provided inside a metal cylindrical body 2, an upper punch 3 and a lower punch 4.
Then, the space inside the die 1 can be filled with a raw material forming a mixture for a dry battery, and pressed by the upper punch 3 and the lower punch 4 to be molded. Although the upper punch 3 and the lower punch 4 are provided in FIG. 1, it is possible to fix one and press only the other punch.

In the present invention, the members that come into contact with the mixture such as the die 1, the upper punch 3 and the lower punch 4 are referred to as mold members for producing a dry battery, and are in contact with at least the mixture in any one of these mold members. The bending strength of the part is 80 kg
/ Mm ² or more of silicon nitride ceramics.

That is, although silicon nitride ceramics is a material having excellent wear resistance, it has conventionally been low in strength,
When the mold member for producing a dry battery was formed, it was easily damaged. Therefore, as a result of various studies, a silicon nitride-based ceramic having a crystal structure as described later can have a very high bending strength of 80 kg / mm ² or more. Therefore, they have found that it can be suitably used as a mold member for producing a dry battery.

For example, when the silicon nitride ceramic die 1 is attached to the metal cylinder 2, the die 1 is fixed by shrink fitting, but the die 1 has high strength even if stress due to the difference in thermal expansion after shrink fitting is applied. Therefore, damage can be prevented. Also, die 1, upper punch 3, lower punch 4
Although a shock is applied during use, damage can be prevented if it is made of the above-mentioned high-strength silicon nitride ceramics.

In addition, since silicon nitride ceramics have high corrosion resistance against alkaline components, they can be used satisfactorily for a long time even when used for forming a mixture for an alkaline battery which has been widely used in recent years.

The bending strength in the present invention means JI
It is the three-point bending strength specified in SR1601, and can be measured by a three-point bending test method by cutting out a JIS test piece from a mold member for manufacturing a dry battery.

The silicon nitride ceramics forming the mold member for producing a dry battery has an average crystal grain size of 0.1 to 10.
75 μm and silicon nitride particles with an aspect ratio of 3 or more are 75
% Or more.

Here, the reason why the average crystal grain size is set within the above range is that the fracture toughness and the bending strength are significantly reduced when the average grain size exceeds 10 μm, while it is extremely difficult to produce the average grain size of less than 0.1 μm in manufacturing. is there.

The aspect ratio means the major axis of crystal grains /
This is the ratio of the minor axis, and in the present invention, the strength and toughness of the silicon nitride ceramics are improved by including many needle-shaped silicon nitride particles having an aspect ratio of 3 or more. The ratio of silicon nitride particles having an aspect ratio of 3 or more is set to 75% or more because the strength cannot be set to 80 kg / mm ² or more at less than 75% and is easily broken when used as a mold member for a dry battery. Is.

Regarding the average crystal grain size and aspect ratio and the content thereof, the fracture surface of the silicon nitride ceramics was measured by SEM (scanning electron microscope).
It is determined by taking a SEM photograph by enlarging it to 0 times and analyzing the SEM photograph with an image analyzer (Luzex). As for the aspect ratio in the present invention, the major axis and the minor axis are determined by the cross section of the crystal grain in the fracture surface, and the ratio of the major axis / minor axis is defined as the aspect ratio.

The composition of the silicon nitride ceramics having the above-mentioned characteristics is 90 to 96% by weight of Si ₃ N ₄ as a main component, and rare earth element oxides such as Y ₂ O ₃ and Yb ₂ O ₃ are used as sintering aids. 2 to 5% by weight of Al ₂ O ₃
What contains ~ 5 weight% is used.

In the case of manufacturing such a mold member for manufacturing a dry battery made of silicon nitride ceramics, raw materials having the above composition range are blended, a binder and a solvent are further added, and the mixture is ground by a rotary mill and then sprayed. Granulate with a dryer. The granules are filled in a mold and formed into a cylindrical shape by the cold isostatic pressing method. Vacuum degreasing the obtained compact, 1
A mold for producing a dry battery can be obtained by firing at a firing temperature of 750 to 1850 ° C. and polishing the obtained sintered body. Then, the silicon nitride ceramics having the above-described crystal structure can be obtained by adjusting the conditions during the firing.

The silicon nitride-based ceramics thus obtained, which constitutes the mold for producing a dry battery, has a main phase of β-Si ₃ N ₄
And having an average crystal grain diameter of 0.1 to 10 μm and containing 75% or more of silicon nitride particles having an aspect ratio of 3 or more, a density of 3.1 to 3.3 g / cm ³ , and a fracture toughness (K _1C ) 6.5 MPam ^1/2 or more, bending strength 8
It could be set to 0 kg / mm ² or more.

[0024]

Experimental Example 1 First, Si ₃ was used as the silicon nitride ceramics of the present invention.
A test piece was prepared from silicon nitride ceramics containing 91% by weight of N ₄ and the balance of Y ₂ O ₃ and Al ₂ O ₃ , 80% of silicon nitride particles having an average crystal grain size of 6 μm and an aspect ratio of 3 or more. On the other hand, as a comparative example, 3 mol%
Test pieces were made from partially stabilized zirconia ceramics containing Y ₂ O ₃ of
The corrosion resistance test was performed by measuring the weight reduction amount when immersed in each aqueous solution shown in.

The results are shown in Table 1. From these results, it can be seen that the weight reduction of the silicon nitride ceramics of the present invention is much smaller than that of the zirconia ceramics, especially in an alkaline aqueous solution (NaOH).

Therefore, when molding a mixture for an alkaline battery, it is understood that the mold member using the silicon nitride ceramics of the present invention is more durable than the zirconia ceramics.

[0027]

[Table 1]

Experimental Example 2 Next, using the silicon nitride ceramics of the present invention and the zirconia ceramics and sialon-based ceramics as comparative examples, a die 1 shown in FIG. 1 was produced and a usage test was conducted.

Ten pieces each were produced, and each piece was attached to a metal cylinder 2 by shrink fitting, and was used to form a mixture for an alkaline battery using a rotary press machine. When molding was performed 10,000 times, halfway Then, the numbers of the dies 1 damaged were compared.

The results are shown in Table 2. From these results, as shown in Experimental Example 1, the zirconia-based ceramics had low corrosion resistance to alkaline components, and therefore wear due to corrosion progressed and two samples were damaged. Further, since the sialon ceramics have low strength and toughness, two samples were damaged by the stress during shrink fitting and the impact during use.

On the other hand, since the one using the silicon nitride ceramics of the present invention has excellent corrosion resistance against alkali components, and has high strength and toughness, no damage occurs.

[0032]

[Table 2]

Experimental Example 3 Next, with respect to various other ceramics and the silicon nitride ceramics of the present invention, the average crystal grain diameter, the content of crystal grains having an aspect ratio of 3 or more, fracture toughness, and bending strength were measured. For silicon nitride ceramics, silicon nitrides A, B, and C can be prepared by changing the raw material particle size and firing conditions.
Created types.

As shown in Table 3, the silicon nitride ceramics have higher fracture toughness and strength than other ceramics. Above all, silicon nitride A having a content of crystal grains with an aspect ratio of 3 or more of 75% or more has a bending strength of 80 kg / mm ² or more and a fracture toughness (K _1C ) of 6.5MP.
It can be seen that it can be set to am ^1/2 or more.

For silicon nitrides A and B in Table 3,
When the other characteristics were compared, as shown in Table 4, the characteristics other than the strength were almost the same.

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

As described above, according to the present invention, a dry battery molding die member is made of silicon nitride ceramics having a strength of 80 kg / mm ² or more, or an average crystal grain diameter of 0.1 μm.
In addition, since it is formed of silicon nitride ceramics containing 75% or more of silicon nitride particles having an aspect ratio of 3 or more, damage during production or use is prevented, and particularly corrosion resistance to alkaline components is excellent. When it is used to mold the mixture, it can be used satisfactorily for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a dry battery molding die member of the present invention.

[Explanation of symbols]

 1: Dice 2: Cylindrical body 3: Upper punch 4: Lower punch

Claims (2)

[Claims] 1. A die member for molding a mixture for a dry battery, a die member such as upper and lower punches, wherein at least a portion in contact with the mixture is formed of silicon nitride ceramics having a bending strength of 80 kg / mm ² or more. A mold member for manufacturing a dry battery, comprising: 2. A die member for molding a mixture for a dry battery, a die member such as upper and lower punches, wherein at least a portion in contact with the mixture has an average crystal grain diameter of 0.1 to 10 μm and an aspect ratio of 3. A mold member for manufacturing a dry battery, comprising a silicon nitride ceramic containing 75% or more of the above silicon nitride particles.