JPH0253923B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a voltage nonlinear resistor, and in particular to a method for manufacturing a voltage nonlinear resistor suitable for a lightning arrester element with little variation in electrical characteristics. (Prior art) Conventionally, in manufacturing a voltage nonlinear resistor in which a sintered body is obtained by granulating, molding, and firing a raw material powder consisting of additives and zinc oxide, a raw material powder in which each component is uniformly dispersed is used. In order to obtain the raw material powder, the additives were once calcined and pulverized, and then mixed with zinc oxide powder to obtain the raw material powder. When calcining this, additives were simply placed in a refractory crucible-shaped container and calcined at a temperature of, for example, 900°C. (Problems to be Solved by the Invention) However, in the above-mentioned conventional calcination method, since the calcination container during calcination is not a closed container, the Bi ₂ O ₃ and Sb ₂ O ₃ components among the additives are particularly sensitive. There was a drawback that the components of the calcined product obtained as a result were not uniform. In addition, when filling the firing container with additives, the surface of the filling inside the container is flat, so the reaction of the additives is delayed in the center of the filling in the firing container.
In this case as well, there was a drawback that the components of the obtained sintered body were not uniform. Therefore, when creating voltage nonlinear resistors using these raw material powders, there is a drawback that various electrical properties such as voltage nonlinearity, energized life, and lightning surge resistance vary between each voltage nonlinear resistor. It was hot. An object of the present invention is to eliminate the above-mentioned problems and provide a method for manufacturing a voltage nonlinear resistor with good electrical characteristics such as voltage nonlinearity, energized life, and lightning surge resistance, and with little variation. It is. (Means for Solving the Problems) The method for manufacturing the voltage nonlinear resistor of the present invention involves calcining the additives that form the grain boundary phase to react in advance, and finely pulverizing the additives to form zinc oxide powder. In addition, in a method for manufacturing a voltage nonlinear resistor in which a sintered body is obtained by obtaining a raw material mixture, this raw material mixture is granulated, molded, and fired, additives are placed in a refractory container in the calcination step. It is characterized by being baked at a temperature of 750 to 850°C in a sealed state with a lid on. (Function) In the above-mentioned configuration, by placing the additive in a closed container and performing calcination at a temperature of 750 to 850°C, preferably with at least 30% by volume open in the center of the filled additive, The ingredients of the additive after calcination become uniform, and as a result, the voltage nonlinearity, energized life, lightning surge resistance, etc. of the voltage nonlinear resistor made using the raw material powder obtained by the present invention are improved. It is possible to obtain products with good characteristics and little variation. In addition, the reason why the calcination temperature is limited to 750 to 850°C in the present invention is that if it is lower than 750°C, the effect of calcination cannot be sufficiently exhibited and the components will not be uniform.
This is because if the temperature exceeds 850°C, the reaction of the additives will proceed too much, making pulverization difficult. Hereinafter, a method for producing a voltage nonlinear resistor using the raw material powder obtained by the method of the present invention will be described. First, for example Bi ₂ O ₃ 0.1-2.0 in mol%,
_{Co2O3 0.1} ~2.0%, MnO2 _0.1 ~2.0%, _{Sb2O3 0.1} ~
2.0%, _Cr2O3 , 0.1~2.0%, _Ni0.1 ~2.0%,
After pulverizing a mixture of SiO ₂ 1.0 to 11.0% and, if necessary, additional additives such as Al ₂ O ₃ 0.001 to 0.05% and bismuth borosilicate glass to a size of 2 μm or less, preferably using a wet ball mill. , drying,
Crush to obtain finely ground additives. Next, the finely ground material is filled into a refractory container preferably made of magnesia or mullite. At this time, it is preferable to provide a space of about 30% by volume or more in the center of the packed finely pulverized material, since sufficient calcination can be carried out. Furthermore, if containers of the same shape are stacked and calcined, it is sufficient to cover only the topmost container. Next, the sealed container is placed in a furnace, heated to an appropriate temperature of 750 to 850°C at a heating rate of 150 to 250°C/hr, held for a predetermined period of time, and further heated to an appropriate temperature of 750 to 850°C at a cooling rate of 50 to 150°C.
Calcination is performed by cooling at °C/hr. The calcination time is 2
About 7 hours is preferable. Thereafter, the calcined additive is pulverized, preferably by a wet pot mill, and mixed with zinc oxide powder. At this time, a predetermined amount of a polyvinyl alcohol aqueous solution is added as a binder. This mixing operation preferably uses a disper mill. The obtained slurry is degassed under reduced pressure and then granulated into fine particles, preferably using a spray dryer, and then the granulated product is molded into a predetermined shape under a molding pressure of 800 to 1000 kg/cm ² . The molded body is held at 800 to 1000℃ for 1 to 5 hours at a heating/cooling rate of 50 to 70℃/hr.
The binder is scattered and removed by pre-firing under certain conditions. Next, an insulating coating layer is formed on the side surface of the calcined body. This insulating coating layer consists of Bi ₂ O ₃ , Sb ₂ O ₃ ,
Ethyl cellulose as an organic binder to SiO ₂ , etc.
It is an oxide paste containing butyl carbitol, n-butyl acetate, etc., and is applied to the side surface of the calcined body to a thickness of 60 to 300 μm. Next, change this to the temperature increase/decrease rate
40-60℃/hr, 1000-1300℃ preferably 1200℃3
Main firing is performed for ~7 hours. Then, a glass paste made by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied onto the insulating coating.
Apply to a thickness of 100 to 300 μm, heat up and cool down in air at a rate of 100 to 200°C/hr, and hold at 400 to 600°C for 0.5 to 2
It is preferable to form the glass layer by heat treatment under the condition of time. Finally, both end faces of the voltage nonlinear resistor are polished smooth, and aluminum electrodes are provided by thermal spraying to obtain a voltage nonlinear resistor. Example 1 A voltage nonlinear resistor with a diameter of 47 mm and a thickness of 20 mm produced by the method described above was manufactured using raw material powder obtained by calcining additives in a magnesia container with a lid of magnesia sealed. Invention samples No. 1 to 4
Comparative Examples Nos. 1 and 2 were prepared using raw material powder obtained by calcining additives in an open state without a lid.
Furthermore, samples No. 1 to 4 of the present invention and comparative example No.
Among Examples 1 and 2, the porosity at the center of the container was changed as shown in Table 1. For calcination, all samples were heated to 800°C at a heating/cooling rate of 200°C/hr, held at 800°C for 5 hours, and then heated at a cooling rate of 100°C/hr.
It was carried out on a cooling schedule of hr. The thickness of the insulation coating layer of all these samples is 300~
Within the range of 100μm and on the insulation coating layer
A glass layer with a thickness of 50-100 μm was provided. Thereafter, the voltage nonlinearity index, ΔV _1nA after lightning surge, and leakage current ratio were measured for each of the obtained voltage nonlinear resistors, and their average value and standard deviation were determined. The results are shown in Table 1. In Table 1, the voltage nonlinearity index α is I=KV〓(I: current, V: voltage,
K: constant of proportionality) was calculated from the values of V _1nA and V ₁₀₀ 〓 _A. Also, ΔV _1nA after lightning surge is 4×10μs
After applying a current of 40KA 10 times with a current waveform of
The rate of decrease in V _1nA is shown. Furthermore, the leakage current ratio is calculated by applying a current to the element at an ambient temperature of 130°C and a current application rate of 95%, and the current ratio after 100 hours of application to the current immediately after application: I ₁₀₀ hours/I ₀
I asked for it from time.

[Table] As is clear from Table 1, Samples Nos. 1 to 4 using raw material powder obtained by calcining the additive of the present invention in a closed container are different from Comparative Examples Nos. 1 and 2. It is possible to achieve a higher voltage nonlinearity index, lower ΔV _1nA after lightning surge, and lower leakage current compared to the previous model, resulting in better electrical characteristics such as voltage nonlinearity, energized life, and lightning surge withstand capacity. It was found that the standard deviation value of was also small and there was little variation in characteristics. Furthermore, among Samples Nos. 1 to 4 of the present invention, if the center part of the additive filled in the container is made to have a space of 30% or more by volume, a voltage nonlinear resistor with even better characteristics and less fluctuation in characteristics can be obtained. I found out that it can be done. Example 2 Diameter 47 mm and thickness made in the same manner as described above
In a 20 mm voltage nonlinear resistor, the influence of the calcination temperature of additives was investigated using sample Nos. 1 to 5 using raw material powders obtained by varying the calcination temperature. At this time,
Calcination was performed for all samples in a sealed state with a lid on the container, and the void space in the center of the firing container for additives was kept constant at 40% by volume. Thereafter, in the same manner as in Example 1, the voltage nonlinear index and the ratio of ΔV _1nA leakage current after lightning surge were measured for each of the obtained voltage nonlinear resistors, and their average value and standard deviation were determined. . The results are shown in Table 2.

[Table] As is clear from Table 2, even in samples using raw material powder obtained by calcining the additive of the present invention in a closed container, the voltage becomes non-linear when the calcining temperature is less than 750°C. It was found that the ΔV _1nA and leakage current after a lightning surge increased. Furthermore, it was found that when the temperature exceeds 850°C, although various properties are good, the reaction progresses too much and pulverization becomes difficult. (Effects of the Invention) As is clear from the detailed explanation above, according to the method for manufacturing a voltage nonlinear resistor of the present invention, the additives are calcined in a sealed state, and the temperature during calcining is controlled. By specifying the temperature to be 750 to 850°C, it is possible to obtain a voltage nonlinear resistor with good electrical properties such as voltage nonlinearity, charging life, and lightning surge resistance, and with little fluctuation.

Claims (1)

[Claims] 1. Additives that form a grain boundary phase are calcined and reacted in advance, and this is pulverized and added to zinc oxide powder to obtain a raw material mixture. This raw material mixture is then granulated, In a method for manufacturing a voltage nonlinear resistor in which a sintered body is obtained by molding and firing, in the calcination step, additives are placed in a refractory container and fired at a temperature of 750 to 850°C in a sealed state with a lid. A method for manufacturing a voltage nonlinear resistor characterized by: 2. The method of manufacturing a voltage nonlinear resistor according to claim 1, wherein the additive is a predetermined amount of bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, nickel oxide, or silicon oxide. 3. The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein a space of 30% by volume or more is provided in the center of the container when filling the additive into the container.