JPH0817123B2 - Method of manufacturing voltage non-linear resistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a voltage nonlinear resistor containing zinc oxide as a main component.

(Problems to be Solved by the Related Art and Invention) A voltage non-linear resistor containing zinc oxide as a main component is a surge arrester or surge for the purpose of voltage stabilization or surge absorption because of its excellent non-linear voltage-current characteristics. Widely used for absorbers. This voltage non-linear resistor is obtained by adding a small amount of metal oxide such as bismuth, antimony, cobalt, manganese, etc. expressing voltage non-linearity to zinc oxide as the main component,
It is configured by mixing, granulating, shaping, and then firing, applying an inorganic substance to the side surface to form a side surface high resistance layer, firing, and attaching electrodes to both end surfaces of the fired body.

When the voltage nonlinear resistor obtained in this way is applied to a lightning arrestor for the purpose of absorbing large surges, it is desirable that the voltage nonlinear resistor has a large switching surge and lightning surge discharge withstand capability. It is desired that the resistance layer has high adhesion strength to the element body.

In JP-A-60-74403, bismuth, cobalt,
Manganese, antimony, nickel, boron, and aluminum are converted into Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , NiO, B ₂ O ₃ , and Al ³⁺ , respectively, and Bi ₂ O ₃ 0.1-5. Mol%, Co ₂ O ₃ 0.1-5 mol%, MnO 0.1-5 mol%, Sb ₂ O ₃ 0.1-5 mol%, NiO 0.1-5 mol%, B ₂ O ₃ 0.002-0.2 mol%, Al ³⁺ A method is disclosed in which a mixture containing 0.001 to 0.05 mol% is molded and then sintered, and the sintered body is heat-treated. However, this voltage non-linear resistor has a low gap discharge characteristic, and the switching surge (2m
S) Since the withstand capacity is low, the characteristics are not satisfactory.

Further, in JP-A-61-204902, a method of applying a predetermined glass frit to the side surface of the resistor element and simultaneously performing heating to form a side surface high resistance layer and conversion of bismuth oxide into body-centered cubic crystal is disclosed. It is disclosed. However, this voltage non-linear resistor has low lightning surge discharge withstand capability and low adhesion strength of the lateral high-resistance layer.

An object of the present invention is to reduce the limiting voltage in a large current region,
A voltage non-linear resistor that can improve the gap discharge characteristics when used as a lightning arrester, can stabilize the resistor element against surges, can prolong the life, and can improve surge withstand capability. Is to manufacture.

(Means for Solving the Problems) The present invention contains zinc oxide as a main component, and bismuth oxide as an additive component is converted into Bi ₂ O ₃ in an amount of 0.1 to 2.0 mol%, and amorphous silica is converted into SiO ₂ . Converted to 0.5 to 9 mol%, aluminum nitrate converted to Al ₂ O ₃ 0.001 to 0.05 mol%,
And bismuth borosilicate glass converted to B ₂ O ₃ 0.005
A mixture containing at least 0.1 mol% is molded and calcined to form a calcined body, and the calcined body is coated with an oxide paste and then calcined to form a calcined body with a lateral high resistance layer formed. Then, the maximum temperature of this fired body is 520 to 650 ℃, and the heating rate is 200.
The present invention relates to a method for producing a voltage non-linear resistor, which is characterized by performing heat treatment at a temperature lowering rate of 20 to 150 ° C./hour or less.

(Operation) In the present invention, by limiting the additive components and performing heat treatment under specific conditions after the main firing, the limiting voltage ratio in the large current region is reduced, the lightning surge discharge withstand capability is improved, and the stability against surge is ensured. We were able to achieve a dramatic improvement in sex.

By adjusting the amount of bismuth oxide added to Bi ₂ O ₃ to 0.1-2.0 mol% (more preferably 0.5-1.5 mol%), the lightning surge discharge withstand capability is improved, the limiting voltage ratio is reduced, and the voltage is reduced. The life characteristics can be improved. If this content is less than 0.1 mol%, the lightning surge discharge withstand capability and the life span of voltage application are deteriorated, and if it exceeds 2 mol%, the limiting voltage ratio increases.

By setting the addition amount of the amorphous silica to 0.5 mol% to 9 mol% (more preferably 1.0 to 3.0 mol%), it becomes possible to improve the lightning surge discharge withstand capacity and reduce the limiting voltage ratio. If it is less than 0.5 mol%, the lightning surge discharge withstand capability decreases, and the limiting voltage ratio increases, and if it exceeds 9 mol%, the lightning surge discharge withstand capability also decreases.

By reducing the amount of aluminum nitrate (preferably added as an aqueous solution) to 0.001 to 0.05 mol% (more preferably 0.002 to 0.02 mol%) in terms of Al ₂ O ₃ , it is possible to reduce the limiting voltage ratio. It is possible to improve the electric life characteristics. If this content is less than 0.001 mol%, the limiting voltage ratio increases, and if it exceeds 0.05 mol%, the leakage current increases and the electrical life characteristics deteriorate.

Convert the added amount of bismuth borosilicate glass to B ₂ O ₃
0.005-0.1 mol% (more preferably 0.01-0.08 mol%)
The reduction of the limiting voltage ratio and V _1mA after lightning surge application
It is possible to reduce the rate of change of. If this value is less than 0.005 mol, the limiting voltage ratio is increased and the voltage life characteristic is also deteriorated.
On the other hand, if it exceeds 0.1 mol%, the electric surge discharge withstand capability decreases and the limiting voltage ratio also increases.

The heat treatment temperature of the fired body is 520 ℃ ~ 650 ℃ (more preferably
550-600 ℃) is also important, and the heat treatment temperature is 52
Below 0 ° C, bismuth oxide at the grain boundaries hardly undergoes phase transition, so the electrical life characteristics are not improved and the effect of heat treatment does not appear. Above 650 ° C, all bismuth oxide becomes body-centered cubic and lightning surge occurs. The discharge withstand capability decreases.

The rate of temperature rise during heat treatment is 200 ° C / hour or less, but 50
More preferably, it is set to 150 ° C./hour. Temperature rising rate is 200 ℃
If the time exceeds / hour, thermal distortion occurs in the resistor element and the lightning surge discharge withstand capability decreases.

The rate of temperature decrease during heat treatment is 20 to 150 ° C./hour, more preferably 50 to 100 ° C./hour. The cooling rate is 2
If the temperature is less than 0 ° C / hour, most of the bismuth oxide crystals become body-centered cubic crystals and the lightning surge discharge withstand capability decreases, resulting in 150 ° C / hour.
When the time is exceeded, the bismuth oxide becomes a monoclinic system, the life characteristics of charging is not improved, and the lightning surge discharge withstand capability is also reduced.

(Example) In order to obtain a voltage nonlinear resistor containing zinc oxide as a main component, first, a zinc oxide raw material adjusted to a predetermined particle size is contained as a main component, and bismuth oxide is converted into Bi ₂ O ₃ as an additive component. 0.1-2.0 mol%, and convert the amorphous silica to SiO _2.
0.5-9 mol%, aluminum nitrate converted to Al ₂ O ₃ of 0.
A mixture containing at least 001 to 0.05 mol% and at least 0.005 to 0.1 mol% of bismuth borosilicate glass converted to B ₂ O ₃ is prepared. In this mixture, other than cobalt oxide, manganese oxide, antimony oxide, chromium oxide, nickel oxide,
You may contain silver oxide, silver nitrate, etc. Alternatively, the above additives may be calcined at 800 to 1000 ° C. and then pulverized to adjust the particle size to a predetermined value, and the zinc oxide raw material may be mixed. On this occasion,
A predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw material powders.

Next, vacuum degassing is performed preferably at a vacuum degree of 200 mmHg or less. The water content of the mixed slurry is preferably about 30 to 35 wt%, and the viscosity of the mixed slurry is preferably 100 ± 50 cp. Next, the mixed sludge obtained was fed to a spray dryer to give an average particle size of 50-
150μm, preferably 80-120μm, water content 0.5-2.0
Granules of wt%, more preferably 0.9-1.5 wt%, are granulated. Next, the obtained granulated powder is molded into a predetermined shape under a molding pressure of 800 to 1000 kg / cm ^{2 in} a molding step.

Next, the molded body is heated at a temperature raising / lowering rate of 50 to 70 ° C./hour and temperature.
Pre-baking is performed under the conditions of 800 to 1000 ° C. and holding time of 1 to 5 hours. It should be noted that the temperature rising / falling rate of the molded body is 10 to 100 before the preliminary firing.
It is preferable that the binder is scattered and removed at 400 to 600 ° C. at a temperature of 100 ° C./hr and a holding time of 1 to 10 hours.

Next, a high resistance layer is formed on the side surface of the calcined body. In this example
A mixture paste for insulation coating with a predetermined amount of Bi ₂ O ₃ , Sb ₂ O ₃ , ZnO, SiO ₂ , etc., added with ethyl cellulose, butyl carbitol, n-butyl acetate as an organic binder to a thickness of 60-300 μm Apply to the side of the calcined body.

Next, this is main-baked under conditions of a temperature rising / falling rate of 20 to 100 ° C./hour and a maximum holding temperature of 1000 to 1300 ° C., preferably 1050 to 1250 ° C. for 3 to 7 hours.

After the main firing, the obtained fired body, the maximum temperature 520 ~ 650 ℃,
Heat treatment is performed at a temperature rising rate of 200 ° C./hour or less and a temperature lowering rate of 20 to 150 ° C./hour.

At this time, a glass paste in which ethyl cellulose, butyl carbitol, n-butyl acetate, etc. were added to the glass powder as an organic binder was added to the high resistance layer on the side surface at 100 to 300 μm.
It is more preferable that the glass layer is formed by applying a coating having a thickness of m and heat treating.

After that, both end surfaces of the obtained voltage nonlinear resistor are
Polishing is performed using water, preferably oil, as a polishing liquid with an abrasive corresponding to # 400 to # 2000 such as ₂ O ₃ and diamond.
Next, after cleaning the polished surface, electrodes are provided, for example, by thermal spraying, on both polished end surfaces by, for example, aluminum or the like to obtain a voltage nonlinear resistor.

Hereinafter, the results of actually measuring various characteristics of the voltage nonlinear resistor within and outside the range of the present invention will be described.

Example 1 Bi ₂ O ₃ , SiO ₂ and Al were added to bismuth oxide, amorphous silica, aluminum nitrate and bismuth borosilicate glass, respectively.
Converted into ₂ O ₃ and B ₂ O ₃ and contained only the addition amount shown in Table 1 below,
And Co ₃ O ₄ 0.66 mol%, MnO ₂ 0.5 mol%, Sb ₂ O ₃ 1.0 mol%, C
r ₂ O ₃ 0.5 mol%, NiO 1.0 mol% as an additive,
Mixing the raw material whose balance is ZnO according to the method described above,
Granulation, molding, and calcination were performed to form a high resistance layer, and main firing was performed. Next, the temperature is raised at a rate of 150 ° C / hour, heat-treated at 500 ° C, and lowered at a rate of temperature decrease of 100 ° C / hour. V _1A = 6.8kV (diameter 47mm, thickness 22.5mm, element area 47mm in diameter) Voltage non-linear resistors of the present invention example and comparative example having a shape of 47 mm in diameter and 22.5 mm in thickness, which are required to apply a current of 1 A to both end faces) were prepared. Then, with respect to the obtained voltage non-linear resistor, the limiting voltage ratio (V _40KA / V _1A ), the lightning surge discharge withstanding capacity and the V _1mA change rate after lightning surge application were measured, and the results are shown in Table 1. .

The lightning surge discharge withstand voltage destruction rate of the voltage ratio linear resistor is n =
50 specimens were prepared, and impulse currents (90KA, 100KA, 110KA, 120KA) with a waveform of 4/10 μs were repeatedly applied twice, and the number of elements destroyed by the application was divided by the number tested (50) ( %).

From the results shown in Table 1, by limiting the addition amounts of bismuth oxide, amorphous silica aluminum nitrate and bismuth borosilicate glass according to the present invention, the limiting voltage ratio in the large current region can be reduced and the lightning surge discharge withstand capability can be improved. However, it can be seen that the stability against lightning surge is also improved.

Example 2 In the same manner as in Example 1, the voltage non-linear resistors of Examples and Comparative Examples were produced. However, the amount of bismuth oxide added is Bi ₂ O.
1.0 mol% when converted to ₃ , the amount of amorphous silica added is 2.0 mol% when converted to SiO ₂ , and the amount of aluminum nitrate added is Al ₂ O ₃
The amount of bismuth borosilicate glass added was 0.005 mol%, and the addition amount of bismuth borosilicate glass was 0.02 mol% converted to Bi ₂ O ₃ . In the heat treatment after the main calcination, the rate of temperature increase was 150 ° C./hour, and the maximum temperature and rate of temperature decrease were variously changed. And
With respect to the voltage non-linear resistors of Examples and Comparative Examples, the characteristic life pattern of voltage application, the lightning surge discharge withstand breakdown rate, and the V _{1 mA} change rate after application of lightning surge were measured. Table 2 shows the results.

In addition, as the life characteristics of the applied voltage, an accelerated deterioration test was performed at a charge rate of 95% and a temperature of 150 ° C, and the resistance component current flowing in the zinc oxide element was measured. Pattern b in which the current value starts to increase from several hours to several tens of hours after the start of the test, leading to thermal runaway, and a pattern in which the current value increases and then tends to decrease for several tens of hours after the start of the test c. The electric charge life characteristics can be broadly classified into four types of patterns, which are the most preferable pattern d in which the current value tends to decrease immediately after the start of the test and which then stably changes.

As shown in the drawing,
It was classified into 4 patterns of c and d, and this classification is shown in Table 2.

As can be seen from Table 2, the maximum temperature during heat treatment is 520-650.
If the temperature is set to ℃ and the cooling rate is set to 20 to 150 ℃ / hour, the characteristic life pattern of charging becomes c and d, and the increase of the resistance component current,
Runaway does not occur, lightning surge discharge withstand breakdown rate can be lowered,
The stability of the element against lightning surge is also improved.

Example 3 A voltage non-linear resistor was prepared in the same manner as in Example 2.
However, the maximum temperature during heat treatment is 560 ° C, and the cooling rate is 100 ° C /
Each time, the voltage heating rate was changed variously, each voltage non-linear resistor of the example and the comparative example was created, and the lightning surge discharge withstand breakdown rate was measured for each. The results are shown in Table 3.

As can be seen from the results in Table 3, the lightning surge discharge withstand rate is significantly improved by setting the heating rate to 200 ° C./hour or less.

(Effects of the Invention) As described above, according to the method for manufacturing a voltage non-linear resistor of the present invention, the life characteristics of voltage application, the lightning surge discharge withstand capability, and the stability of the element against lightning surge are significantly improved, and the large current It is possible to reduce the limiting voltage ratio in the region.

[Brief description of drawings]

 The drawing is a graph showing an example of a charging life characteristic pattern.

Claims (1)

[Claims] 1. Zinc oxide as a main component, and bismuth oxide as an additive component is converted into Bi ₂ O ₃ in an amount of 0.1 to 2.0 mol%, and amorphous silica is converted into SiO ₂ in an amount of 0.5 to 9 mol%. , 0.001 to 0.05 mol% of aluminum nitrate converted to Al ₂ O ₃ ,
And bismuth borosilicate glass converted to B ₂ O ₃ 0.005
A mixture containing at least 0.1 mol% is molded and calcined to form a calcined body, and the calcined body is coated with an oxide paste and then calcined to form a calcined body with a lateral high resistance layer formed. Then, the maximum temperature of this fired body is 520 to 650 ℃, and the heating rate is 200.
A method for producing a voltage non-linear resistor, which comprises performing heat treatment at a temperature lowering rate of 20 to 150 ° C./hour or less at a temperature of not higher than ° C / hour.