JP2012114451A - Transformer for power distribution and tank container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil-filled transformer, having improved corrosion resistance of a tank, capable of solving a problem of oil leakage and so on caused by tank corrosion in an oil-filled transformer.SOLUTION: The tank container, having excellent performances in weather resistance and processability, is provided by making material components of stainless steel appropriate using ferritic stainless steel for materials of the tank container to house a transformer body and to be filled with an insulation material, a tank, a cover, and the whole or a part of a metal fitting to be attached to a tank container body and the cover.

Description

  The present invention relates to a tank material and a manufacturing method for an oil-filled transformer for power distribution used outdoors and indoors.

  Fig. 1 shows a conceptual diagram of the structure of an oil-filled transformer in a metal tank so that it can be installed in an outdoor utility pole or indoor electrical room. A tank 1 contains a content structure composed of an iron core 2 and a coil 3, and a bushing 6 is attached to the tank. The tank is filled with insulating oil 5, and the upper part of the tank is sealed with a lid 2. The tank 1 has a structure in which steel plates are combined by welding, and the joint portions are connected by welding so that the insulating oil does not leak. In addition, in order to enhance the rust prevention performance of the tank and improve the finished appearance, the entire tank is painted with a paint having good weather resistance.

  Oil-filled transformer tanks for power distribution used outdoors and indoors, and transformer tanks using plain steel plates as the material are difficult to provide complete anti-corrosion performance. The occurrence of rust in each part is an unavoidable phenomenon, and if the progress of rust is significant, there is a possibility that the steel plate has a hole and the insulating oil inside leaks. In the case of transformers installed on outdoor utility poles, the bottom is often private land, and if oil leaks, the soil on general private land may be contaminated. In addition, if oil leaks from a transformer installed in the room, it is possible that the oil will flow out from the distribution pipe and cause water pollution in rivers and oceans. Both of these events have developed into major social problems, and transformer owners have to confirm the deterioration of the tank through periodic inspections in order to avoid such events.

  In view of the state of the prior art, the problem of the present invention is that, in oil-filled transformers for power distribution used outdoors and indoors, it is possible to manufacture the same as in the case of a transformer tank using ordinary steel plates. An oil-filled transformer having a transformer tank having a weather resistance such as a rust prevention performance up to the life of the transformer is provided.

  In order to solve the above-described problems, in the present invention, the transformer main body is stored, and ferritic stainless steel is used as the material of the tank container filled with the insulating material, and the material component of the stainless steel is made appropriate. An oil-filled transformer for power distribution comprising a tank container having excellent weather resistance and excellent workability.

  According to the present invention, since the transformer tank is manufactured using a material having excellent weather resistance, the transformer tank is improved in weather resistance, can be used for a long time, and the number of maintenance can be reduced. The owner of the transformer can reduce the maintenance cost of the transformer. Furthermore, since it is no longer necessary to depend on the corrosion resistance performance of the transformer tank for painting, the painting process can be simplified or the painting can be abolished, and the manufacturer can shorten the production time of the transformer, resulting in a cost reduction effect. In addition, by reducing the amount of paint used, it is possible to make products with less impact on the environment. Furthermore, in the manufacture of transformer tanks by manufacturers, new equipment investment and renovation of existing equipment are not required because they can be manufactured with the same equipment and work method as ordinary steel sheets.

The conceptual diagram of the structure of a transformer tank. Fig. 3 is a structural conceptual diagram of a transformer. Schematic diagram of corrosion diagnosis component placement on transformer tank. FIG. 3 is a diagram illustrating a configuration of a corrosion diagnostic component, and is an explanatory diagram of one surface of a corrosion diagnostic base material covered with a high corrosion resistance material. FIG. 3 is a diagram illustrating a configuration of a corrosion diagnostic component, in which one side of a corrosion diagnostic base material is coated with a highly corrosion resistant material and further organically coated. FIG. 3 is a diagram illustrating a configuration of a corrosion diagnostic component, in which one side of a corrosion diagnostic base material is covered with a highly corrosion resistant material and electrically insulated and installed. The structure of a corrosion diagnostic component is an explanatory diagram of a structure in which one side of a base material for corrosion diagnosis is coated with a high corrosion resistance material, further coated with an organic coating, and electrically insulated.

  Examples of the distribution transformer and tank container of the present invention will be described below. FIG. 1 is a structural conceptual diagram of a transformer tank, and FIG. 2 is a structural conceptual diagram of a transformer.

  The structure of the distribution transformer according to the first embodiment will be described with reference to FIGS. 1 and 2. A tank container 1 that contains a content structure consisting of a coil 4 and an iron core 3 and is filled with an insulating oil 5 comprises a side plate 11 formed into a flat plate in a cylindrical shape, and a disk-like bottom plate 12, and various types can be used depending on specifications and applications. Seats (13 etc.) are attached to the outer and inner surfaces of the tank container. The side plate 11 and the bottom plate 12 are made of ferritic stainless steel. Only the side plate 11 or only the bottom plate 12 may be made of ferritic stainless steel. Further, only specific portions of the side plate 11 and the bottom plate 12 may be made of ferritic stainless steel.

Unlike austenitic stainless steel typified by Fe-18Cr-8Ni, ferritic stainless steel has tensile and bending characteristics similar to those of ordinary steel sheets. For this reason, it is possible to drastically improve the perforated corrosion resistance without drastically remodeling existing manufacturing equipment or changing the shape of the tank container. In addition, ferritic stainless steel contains enough Cr to be self-passivated in the atmospheric environment, so it is high even when the surface treatment layer such as a coating film or plating is worn out or in these defective portions. Has perforation resistance. Furthermore, even if these surface treatment layers lose their anti-corrosion function and the ferritic stainless steel is corroded and red rust is generated, self-passivation easily occurs under the rust layer, and `` corrosion occurs but erosion due to pitting corrosion occurs. The characteristic of “very slow” appears. For this reason, it has the outstanding characteristic for preventing the situation of the leakage of the contents. Moreover, since ferritic stainless steel does not contain a large amount of Ni, it has excellent adhesion in coating and plating. For this reason, unlike austenitic stainless steel containing a large amount of Ni, it is easy to use rust prevention treatment by surface treatment such as painting or plating in combination. Furthermore, although austenitic stainless steel causes stress corrosion cracking due to chloride ions (Cl ⁻ ), ferritic stainless steel is extremely unlikely to cause stress corrosion cracking. For the above reasons, ferritic stainless steel is suitable as a tank container that may be used in an outdoor beach environment where sea breeze blows and sea salt adheres.

  Ferritic stainless steel is a steel containing 11 mass% or more of Cr, but when surface rusting is allowed or when the surface is coated to provide primary rust prevention treatment, the steel material cost is further reduced. When there is a need for this, it is assumed that 7.0% by mass or more of Cr is contained and 60% or more of the metal structure is composed of a ferrite phase.

  The structure of the power distribution transformer according to the second embodiment will be described with reference to FIGS. 1 and 2. The upper cover 2 of the transformer tank container has a structure in which various seats (22 and the like) are attached to the cover 21. The cover 21 is made of ferritic stainless steel. Only a specific part of the cover 21 may be made of ferritic stainless steel.

  The structure of the distribution transformer according to the third embodiment will be described with reference to FIGS. 1 and 2. In the distribution transformer described in Example 1 or Example 2, all or specific parts of the metal fitting (13 etc.) attached to the tank container body 1 and the metal fitting (22 etc.) attached to the upper lid 2 are manufactured from ferritic stainless steel. . Only specific parts of the parts may be made of ferritic stainless steel.

  A power distribution transformer according to a fourth embodiment will be described. In the distribution transformer described in any of Examples 1 to 3, the ferritic stainless steel used has an elongation at break of 30% or more when processed by uniaxial tension and a Rankford value (r value) of 1. Use one or more. If the elongation at break and the r value are small, it is difficult to perform the forming process even if the proof stress and tensile strength are the same as those of ordinary steel. For this reason, when it is necessary to keep the manufacturing cost low, it is effective to use ferritic stainless steel having the characteristic values in the above-mentioned range when manufacturing the same shape or complex shape as existing steel products. is there.

  The distribution transformer according to the fifth embodiment will be described. In the distribution transformer described in any of Examples 1 to 4, a ferritic stainless steel having a Vickers hardness (Hv) of 175 or less and a yield ratio (YR) of 80% or less is used. If the hardness and yield ratio are low, the forming process becomes easy. Moreover, when the yield ratio is low, the fracture resistance is excellent when an impact such as dropping on the ground is applied. For this reason, it is effective to make the Vickers hardness 175 or less and the yield ratio 80% or less when manufacturing a transformer container having a complicated shape or when fracture resistance is required.

  A power distribution transformer according to a sixth embodiment will be described. In the distribution transformer described in any of Examples 1 to 5, the ferritic stainless steel is manufactured using a component having a Cr content of 7.0 to 14.0% by mass. Cr added to ferritic stainless steel forms a dense passive film by air oxidation on the steel surface, and has the effect of improving the corrosion resistance against perforation corrosion. However, when added excessively, it not only increases the manufacturing cost, but also decreases the toughness of the steel. Moreover, since the adhesiveness decreases with respect to the primary rust prevention treatment by the surface treatment such as a coating film, pretreatment becomes difficult. Therefore, when toughness (especially low temperature toughness of the heat affected zone of the welded portion) is required or adhesion with the surface treatment layer is required, the Cr alloy amount is set to 7.0 to 14.0% by mass. It is effective.

  A power distribution transformer of Example 7 will be described. In the distribution transformer described in any of Examples 1 to 6, the components of the ferritic stainless steel are mass%, Ti: 0.08 to 2%, Nb: 0.08 to 2%, Al: 0.00. One containing at least one of 01 to 1% is used.

These Ti, Nb, and Al have the effect of improving the perforated corrosion resistance of ferritic stainless steel. In particular, in the state where the weld scale is still generated, the rust resistance against perforation chloride (Cl ⁻ ) and the perforation corrosion resistance are improved. For this reason, when used in an environment where the corrosiveness is severe, one kind of Ti: 0.08 to 2%, Nb: 0.08 to 2%, Al: 0.01 to 1% in mass%. It is preferable to use those including the above. If the content is small, the effect is weak, and if it is added excessively, performance corresponding to the cost cannot be obtained.

  The structure of the distribution transformer of Example 8 will be described. In the distribution transformer described in any one of Examples 1 to 7, the ferritic stainless steel includes, in terms of mass%, Ni: 0.08 to 2%, Cu: 0.08 to 2%, Mo: 0 Manufactured using one containing at least one of 0.08 to 2% and W: 0.08 to 2%.

These Ni, Cu, Mo, and W have the effect of significantly improving the perforated corrosion resistance of ferritic stainless steel. This action has the effect of reducing not only the depth of pitting corrosion but also the number of occurrences. In addition, it improves not only chloride ions (Cl ⁻ ) caused by sea breeze and snowmelt salt but also acid gas such as sulfurous acid gas and nitrous acid gas, acid rain and acid fog, and the effect of improving rust resistance and perforation resistance There is. For this reason, in particularly severe corrosive environments such as coastal areas and inside tunnels, ferritic stainless steels have a mass% of components, Ni: 0.08 to 2%, Cu: 0.08 to 2%, Mo: 0 It is effective to use one containing at least one of 0.08 to 2% and W: 0.08 to 2%. If the content is small, the effect is weak, and if it is added excessively, performance corresponding to the cost cannot be obtained.

  The power distribution transformer of Example 9 will be described. In the distribution transformer described in any one of Examples 1 to 8, it is manufactured so that the amount of the ferrite phase in the solidified structure of the weld metal portion is 10% or less. If there are many ferrite phases in the solidified structure of the weld metal, the toughness (especially the low temperature toughness) decreases. For this reason, when a tank container having excellent impact characteristics is required, it is effective to use an austenitic weld metal rod so that the amount of ferrite phase in the solidified structure of the weld metal is 10% or less.

  A power distribution transformer of Example 10 will be described. In the distribution transformer described in any one of Examples 1 to 9, the gap between the opposing metals formed on the outer surface of the tank container is manufactured as a structure that is closed by welding. Various metal fittings such as a tank mounting seat are joined to the outer surface of the tank by welding. At this time, the metal fitting and the side surface of the tank are joined by fillet welding. However, if the entire outer periphery of the contact surface is not welded and a non-welded portion remains, moisture and salt enter here, which becomes the starting point of rust generation and perforated corrosion. For this reason, when used in highly corrosive environments or when particularly high durability is required, it is effective to produce a structure in which the gaps between the metals formed on the outer surface of the tank container are closed by welding. is there.

  The power distribution transformer of Example 11 will be described. In the distribution transformer described in any one of Examples 1 to 10, the outer surface of the tank container is coated and manufactured. The painting may be a full-scale painting or a local painting. By coating ferritic stainless steel, rust resistance and perforation resistance can be significantly improved. Moreover, it can be set as the tank container which has the color which united with scenery by painting. Since the coating film in this application does not need high antirust ability in itself, the film thickness is not limited. In order to ensure only the color, the thickness may be several μm. Also, when ferritic stainless steel and coating are combined, unlike ordinary steel, ferritic stainless steel is superior in corrosion resistance and adhesion to the coating film, so there is no need for a preliminary coating layer such as rust-preventing undercoating as in ordinary steel. Yes, it can be applied directly to the stainless steel matrix.

  The power distribution transformer of Example 12 will be described. In the distribution transformer described in any one of Examples 1 to 11, it is manufactured by applying electrodeposition coating to the coating pretreatment. The electrodeposition coating site may be the entire surface or local. Since electrodeposition coating has an effect of suppressing corrosion under the coating film, high corrosion resistance performance can be exhibited by using it as a pretreatment when coating ferritic stainless steel. For this reason, when ultra-long durability is required in a severe corrosive environment, it is preferable to apply electrodeposition coating to the coating pretreatment.

  A power distribution transformer according to Example 13 will be described. In the power distribution transformer described in any one of Examples 1 to 12, it is manufactured by applying the Zn plating to the coating surface treatment. The plating site may be the entire surface or local. The Zn plating layer not only exhibits a sacrificial anticorrosive action on ferritic stainless steel, but also has an action in which the corrosion product of Zn suppresses rust generation and pitting growth of stainless steel. For this reason, when an extremely long-term durability is required in a harsh corrosive environment, it is effective to apply Zn plating to the coating base treatment.

  The power distribution transformer of Example 14 will be described. In the distribution transformer described in any one of Examples 1 to 13, for the parts to be pressed such as the cover 2 and the bottom plate 12, the anisotropy of the ferritic material is taken into account, depending on the rolling direction. Adjust the material shape before pressing. The part bent in parallel with the rolling direction shortens the original material dimension by 0.5 to 1% with respect to the bending length, and the part bent perpendicularly to the rolling direction has the original material dimension of 0 with respect to the bending length. .5-5% longer.

  Next, the reasons for limitation of claims 15 to 21 will be described. First, the component that performs corrosion diagnosis needs to have the same composition as the metal material that constitutes the target distribution transformer tank container. This is because if the composition of the material is different, the corrosion resistance changes, and the erosion amount of the device or the structure cannot be appropriately evaluated from the erosion amount of the corrosion diagnostic component. By the way, the same composition said in this application is a metal composition which shows equivalent corrosion resistance, and does not mean that it is numerically the completely same analysis value. As a guide, even if there is a difference in the composition range of various standard materials defined in JIS (Japanese Industrial Standards) or the like, the corrosion diagnostic component can be configured with the same composition. If it is chromium, a difference within 1% can be treated as the same composition.

  The part 7 that performs the corrosion diagnosis needs to have a portion 71 where the base material that is in direct contact with the corrosion-causing substance is exposed. This is because the reaction site (corrosion part) between the material and the environment is limited to a specific location. Even if the transformer tank container for power distribution is painted or plated, it is necessary to evaluate the corrosion resistance of minute defects that inevitably exist in these coating layers. The portion 71 where the base material directly contacting the corrosion-causing substance is exposed needs to be present.

  Further, in the parts for performing the corrosion diagnosis, it is necessary that the portion 72 covered with the high corrosion resistance material forms a pair with the metal exposed portion 71 as the front and back surfaces. This is to measure the amount of erosion of the exposed metal surface by bringing the sensor part of the ultrasonic plate thickness meter into close contact with the outer surface of the highly corrosion resistant material side and measuring the distance between the exposed metal portion 71 and the outer surface of the highly corrosion resistant material. It is to do. In order to ensure measurement accuracy, a sensor unit for ultrasonic plate thickness measurement needs to be in close contact with a measurement target. For this reason, the back surface of the exposed metal portion needs to suppress corrosion over a long period of time. For this reason, the back surface 72 of the exposed metal portion needs to be coated with a highly corrosion-resistant material.

  As the coating material, when the corrosiveness of the environment is weak, the organic coating is simple and inexpensive. When the environment is highly corrosive, the thickness of the organic coating is preferably 20 μm or more. Moreover, it can replace with organic coating | cover and can also be set as the plating layer which has zinc or aluminum as a main component. Since these plated metals have excellent corrosion resistance in the atmospheric environment, they are suitable for monitoring the degree of erosion of equipment and buildings used outdoors. Instead of plating, an organic coating containing fine particles of zinc or aluminum can be used. Zinc and aluminum dispersed in the organic coating film are suitable for the treatment of the non-corrosive surface of the erosion degree monitor because they enhance the excellent corrosion resistance.

  Furthermore, when the corrosive environment is severe or when it is necessary to accurately measure the amount of corrosion over a long period of time, high corrosion resistant materials such as stainless steel, nickel base alloy, pure titanium, titanium alloy, aluminum, aluminum alloy, copper, copper alloy are used. Either is desirable. The application of these metal materials is particularly effective in a severe coastal area where a sulfurous acid gas environment or seawater splash is applied. Furthermore, extremely high reliability is achieved by applying an organic coating 75 to the surface of these zinc or aluminum-based plating layers, stainless steel, nickel-base alloys, pure titanium, titanium alloys, aluminum, aluminum alloys, copper and copper alloys. Corrosion diagnostic parts with

  In addition, when used in an environment where the concentration of sea salt or sulfurous acid gas is high and the electrical conductivity of the water film formed on the surface of the corrosion diagnostic component is high, the outer surface of the highly corrosion-resistant material and the corrosion-causing substance It is desirable to electrically insulate the exposed portion of the base material that is in direct contact. This is to prevent the erosion rate of the exposed part of the base material from being affected by contact with different metals.

Examples corresponding to claims 15 to 21 will be described below.

  In various combinations shown in Table 1, a distribution transformer tank container and a corrosion diagnostic component for evaluating corrosion resistance were prepared, and artificial seawater (ASTM D 1141-90) concentrated four times was added at 9 am and 3 pm An accelerated atmospheric exposure test, sprayed twice a day, was conducted for one year. Then, using a commercially available ultrasonic thickness gauge, the ultrasonic thickness gauge sensor is brought into close contact with the high corrosion resistance material side of the corrosion diagnostic component, the remaining thickness is measured, and the distribution transformer that is the object of corrosion resistance evaluation. The amount of erosion of the container was compared.

  The tank container of the distribution transformer that was evaluated for corrosion resistance is schematically shown in FIG. 3 and is composed of Fe-10.5% Cr-0.4% Ni steel. The coating is 10 μm thick. Then, in view of coating film defects on the bottom surface 12, two crosscuts 8 having a width of about 1 mm and a length of 100 mm reaching the base metal were introduced (FIG. 3), and the erosion depth of this part was measured. The deepest erosion amount was taken as a representative value. Specifically, after the exposure test is completed, the periphery is cut out and the remaining coating film is removed with an organic solvent, followed by repeated immersion in 10% aqueous diammonium hydrogen citrate (50 ° C.) and rubbing with a nylon brush. The surface rust was removed. And using the optical microscope, the depth with the deepest erosion part was calculated | required with respect to the original surface where the coating film existed, and it was set as the erosion depth.

  In the accelerated atmospheric exposure test, the severity of the corrosive environment was changed by changing the amount of artificial seawater sprayed. The spray amount described below is a spray amount for each time at 9 am and 3 pm. In addition, as shown in FIG. 3, the attachment of the corrosion diagnosis component to the distribution transformer tank container was performed such that the position 200 mm from the bottom of the side surface of the tank container was the lower end of the corrosion diagnosis component. The size of the corrosion diagnostic component was 150 mm long × 100 mm wide. In the measurement of the remaining thickness of the corrosion diagnostic component, no special pretreatment such as rust removal on the exposed base material was performed. In order to ensure close contact between the ultrasonic sensor and the high corrosion resistance material, only the grease is applied to the sensor surface.

  Number 1 in Table 1 is an embodiment corresponding to claim 15 of the present application. A corrosion diagnostic component having the structure shown in FIG. 4 was manufactured and fixed to the distribution transformer tank container to be evaluated. That is, Fe-10.5% Cr-0.4% Ni steel was used as a base metal, and one surface was covered with acrylic resin as a high corrosion resistance material, and a corrosion diagnostic part was obtained. Artificial seawater was sprayed so that the adhesion amount of chloride ions (Cl- ions) was about 0.1 g / m2. As shown in Table 1, the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnosis parts are almost the same. It turns out that it is possible. A fixing base 73 and a fixing bolt 74 were used.

  Reference numeral 2 denotes an embodiment corresponding to claim 16. In this case, as shown in FIG. 4, corrosion diagnosis is made by using Fe-10.5% Cr-0.4% Ni steel as a base metal, acrylic resin as a high corrosion resistance material, and covering about 50 μm on one side. Parts were produced. Spraying was performed so that the adhesion amount of chloride ions (Cl- ions) was about 0.5 g / m2. As shown in Table 1, the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnosis parts are almost the same. It turns out that it is possible. Incidentally, in the corrosion diagnostic component (No. 1) where the acrylic resin is thin, corrosion under the coating film occurred in the acrylic resin, and it was impossible to measure the remaining thickness with ultrasonic waves. Thus, it can be seen that it is preferable to increase the thickness of the organic coating in an environment with strong corrosivity such as a high salt concentration.

  Reference numerals 3 and 4 are embodiments corresponding to claim 17. Also here, a Fe-10.5% Cr-0.4% Ni steel plate plated with hot dip galvanizing (adhesion amount 270 g / m 2) or hot dip aluminum plating (adhesion amount 200 g / m 2) so as to have the configuration shown in FIG. 4 is used. The corrosion diagnostic component was produced by removing the plating layer on one side with mechanical grinding and chemicals. Spraying was performed so that the adhesion amount of chloride ions (Cl- ions) was about 1 g / m2. As shown in Table 1, the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnosis parts are almost the same, and this method can diagnose the corrosion erosion degree of the distribution transformer tank container. It turns out that it is possible simply and accurately.

  Similarly, numbers 5 and 6 are embodiments corresponding to claim 18. As shown in FIG. 4, one side of Fe-10.5% Cr-0.4% Ni steel is coated with about 50 μm of zinc rich paint or acrylic resin paint mixed with aluminum fine particles. Corrosion diagnostic parts. Spraying was performed so that the adhesion amount of chloride ions (Cl- ions) was about 1 g / m2. As shown in Table 1, the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnosis parts are almost the same. It turns out that it is possible.

  Reference numerals 7 to 14 are embodiments corresponding to claim 19. Since this also has the structure shown in FIG. 4, stainless steel SUS304 (Fe-18% Cr-8% Ni), Ni-base alloy Alloy 600 (Ni -16% Cr-10% Fe), industrial pure titanium, Ti-6% Al-4% V alloy (titanium alloy), industrial pure aluminum, Al-1.0% Mg-0.5% Si-0 A corrosion diagnosis component was prepared by cutting a clad material in which 3% Cu (6061 aluminum alloy), industrial copper, and aluminum brass (Cu-22% Zn-2% Al alloy) were laminated by a rolling method. Spraying was performed so that the adhesion amount of chloride ions (Cl- ions) was about 5 g / m2. As shown in Table 1, even in a highly corrosive environment, it was confirmed that the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnostic parts were almost the same. It can be seen that it is possible to diagnose the degree of corrosion and erosion of distribution transformer tank containers in severe environments.

  Numbers 15 to 18 are embodiments corresponding to claim 20. As shown in FIG. 5, zinc rich paint coated with about 50 μm on one side of Fe-10.5% Cr-0.4% Ni steel (No. 15), Fe-10.5% Cr-0 .Stainless steel SUS304 (Fe-18% Cr-8% Ni), industrial pure titanium, Al-1.0% Mg-0.5% Si-0.3% Cu (6061) on one side of 4% Ni steel A clad material (numbers 16 to 18) obtained by laminating aluminum alloy) by a rolling method was cut, and an acrylic resin paint 75 was applied to about 10 μm on one side to obtain a corrosion diagnostic component. Spraying was performed so that the adhesion amount of chloride ions (Cl- ions) was about 10 g / m2. As shown in Table 1, even in a highly corrosive environment, it was confirmed that the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnostic parts were almost the same. It can be seen that it is possible to diagnose the degree of corrosion erosion of distribution transformer tank containers.

  Reference numerals 19 to 22 are embodiments corresponding to claim 20. In order to obtain the configuration shown in FIG. 6, a zinc rich paint coated with about 50 μm on one surface of Fe-10.5% Cr-0.4% Ni steel (No. 19), Fe-10.5% Cr-0. Stainless steel SUS304 (Fe-18% Cr-8% Ni), industrial pure titanium, Al-1.0% Mg-0.5% Si-0.3% Cu (6061 aluminum) on one side of 4% Ni steel After the clad material (numbers 20 to 22) obtained by laminating an alloy) is cut and processed into the shape of a corrosion diagnosis component, the end face and its surrounding width of about 20 mm are insulated with an acrylic resin paint 76 to diagnose corrosion. Parts were produced. Spraying was performed so that the adhesion amount of chloride ions (Cl− ions) was about 50 g / m 2. As shown in Table 1, it was confirmed that even in a highly corrosive environment, the erosion rate of the distribution transformer tank container and the erosion rate measured by the corrosion diagnostic component were almost the same. As a comparison, when the board surface was not covered with insulation, an error of erosion rate of + 25% in No. 7 and −16% in No. 14 occurred under this environmental condition.

  Reference numerals 23 to 26 are embodiments corresponding to claim 21. In order to obtain the configuration shown in FIG. 7, a zinc rich paint coated with about 50 μm on one side of Fe-10.5% Cr-0.4% Ni steel (No. 23), Fe-10.5% Cr-0. Stainless steel SUS304 (Fe-18% Cr-8% Ni), industrial pure titanium, Al-1.0% Mg-0.5% Si-0.3% Cu (6061 aluminum) on one side of 4% Ni steel The clad material (numbers 24 to 26) obtained by laminating an alloy) by a rolling method was cut and processed into the shape of a corrosion diagnostic component, and then the end surface and one surface were all covered with an acrylic resin paint 77. Moreover, spraying was performed so that the adhesion amount of chloride ions (Cl− ions) was about 100 g / m 2. As shown in Table 1, it is confirmed that the erosion rate of the metal container to be evaluated and the erosion rate measured by the corrosion diagnostic component are almost the same, and this method can diagnose the degree of corrosion erosion of metal equipment. It was proved that.

DESCRIPTION OF SYMBOLS 1 Tank 11 Side plate 12 Bottom plate 13 Tank mounting seat 2 Cover 21 Cover plate 22 Cover mounting seat 3 Iron core 4 Coil 5 Insulating oil 6 Bushing 7 Corrosion diagnosis part 71 Metal base material exposed part 72 High corrosion-resistant material 73 Fixing base 74 Fixing bolt 74 75 Organic coating 76 Insulating coating 77 Organic insulating coating 8 Cross cut

The distribution transformer according to the present invention is a distribution container composed of a tank container filled with insulating oil and filled with insulating oil, and a top cover, which is composed of a coil and an iron core, and the tank container is formed into a cylindrical plate. In order to increase the perforated corrosion resistance without making significant modifications to the existing manufacturing equipment or drastically changing the tank container shape, the side plate and the bottom plate are usually used. It is characterized by being made of a ferritic stainless steel having a Cr content of 7.0 to 14.0% by mass having tensile / bending characteristics similar to those of a steel plate.
Furthermore, the distribution transformer of the present invention is characterized in that the upper lid of the tank container is also made of the ferritic stainless steel.
Furthermore, the distribution transformer of the present invention is characterized in that all or a part of the metal fittings attached to the tank container main body and the upper lid are also made of the ferritic stainless steel.
As described above, in order to solve the above-described problems, in the present invention, ferritic stainless steel is used as the material of the tank container in which the transformer body is filled and the insulating material is filled, and the material component of the stainless steel is appropriate. Thus, an oil-filled transformer for power distribution comprising a tank container having excellent weather resistance and excellent workability.

In the present invention, a tank body and an upper lid of a distribution transformer are made of ferritic stainless steel having a Cr content of 7.0 to 14.0% by mass, which has tensile and bending properties similar to those of ordinary steel plates. Therefore, it is possible to drastically improve the perforated corrosion resistance without drastically remodeling existing manufacturing equipment or changing the shape of the tank container.
In addition, ferritic stainless steel contains enough Cr to be self-passivated in the atmospheric environment, so it is high even when the surface treatment layer such as a coating film or plating is worn out or in these defective portions. Has perforation resistance. Furthermore, even if these surface treatment layers lose their anti-corrosion function, the ferritic stainless steel is corroded and red rust is generated, self-passivation easily occurs under the rust layer, and `` corrosion occurs due to pitting corrosion. The characteristic of “very slow” appears. For this reason, it has the outstanding characteristic for preventing the situation of the leakage of the contents.
Moreover, since ferritic stainless steel does not contain a large amount of Ni, it has excellent adhesion in coating and plating. For this reason, unlike austenitic stainless steel containing a large amount of Ni, it is easy to use rust prevention treatment by surface treatment such as painting or plating in combination. Furthermore, although austenitic stainless steel causes stress corrosion cracking due to chloride ions (Cl ⁻ ), ferritic stainless steel is extremely unlikely to cause stress corrosion cracking. For the above reasons, ferritic stainless steel is suitable as a tank container that may be used in an outdoor beach environment where sea breeze blows and sea salt adheres.
Furthermore , according to the present invention, since the transformer tank is manufactured using a material having excellent weather resistance, the transformer tank is improved in weather resistance, can be used for a long time, and the number of maintenance can be reduced. Therefore, the owner of the transformer can obtain a reduction effect on the maintenance / maintenance cost of the transformer. Furthermore, since it is no longer necessary to depend on the corrosion resistance performance of the transformer tank for painting, the painting process can be simplified or the painting can be abolished, and the manufacturer can shorten the production time of the transformer, resulting in a cost reduction effect. In addition, by reducing the amount of paint used, it is possible to make products with less impact on the environment. Furthermore, in the manufacture of transformer tanks by manufacturers, new equipment investment and renovation of existing equipment are not required because they can be manufactured with the same equipment and work method as ordinary steel sheets.

Claims (22)

  A power distribution transformer comprising: a transformer main body made of a winding and an iron core; and a tank container that houses the transformer main body and is filled with an insulating material, and the tank container is made of ferritic stainless steel.   The power distribution transformer according to claim 1, wherein the upper lid of the tank container is made of ferritic stainless steel.   The distribution transformer according to claim 1 or 2, wherein all or part of the metal fittings attached to the tank container main body and the upper lid are made of ferritic stainless steel.   The distribution transformer according to any one of claims 1 to 3, wherein the elongation at break when ferritic stainless steel is processed by uniaxial tension is 30% or more, and the Rankford value (r value) is 1.1 or more. vessel.   The distribution transformer according to any one of claims 1 to 4, wherein the ferritic stainless steel has a Vickers hardness (Hv) of 175 or less and a yield ratio (YR) of 80% or less.   The distribution transformer according to any one of claims 1 to 5, wherein the ferritic stainless steel component has a Cr content of 7.0 to 14.0 mass%.   The ferritic stainless steel component contains at least one of Ti: 0.08 to 2%, Nb: 0.08 to 2%, and Al: 0.01 to 1% by mass%. The power distribution transformer according to any one of the above.   As a ferritic stainless steel component, in mass%, one of Ni: 0.08-2%, Cu: 0.08-2%, Mo: 0.08-2%, W: 0.08-2% The distribution transformer according to any one of claims 1 to 7, including the above.   The distribution transformer according to any one of claims 1 to 8, wherein an amount of a ferrite phase in a solidified structure of a weld metal part when a tank container is manufactured is 10% or less.   The distribution transformer according to any one of claims 1 to 9, wherein a gap formed by metal facing each other formed on the outer surface of the tank container is blocked by welding.   The distribution transformer according to any one of claims 1 to 10, which has a coating film on an outer surface of the tank container.   The distribution transformer according to any one of claims 1 to 11, wherein electrodeposition coating is applied as a pretreatment for coating.   The distribution transformer according to any one of claims 1 to 12, wherein Zn plating is performed as a coating ground treatment.   The distribution transformer according to any one of claims 1 to 13, wherein the shape before press processing is changed in accordance with the material characteristics of the ferritic stainless steel.   Corrosion diagnosis consisting of a metal with the same composition as the metal material that makes up the tank container, with the exposed part of the base material that directly contacts the corrosion-causing substance and the part covered with the highly corrosion-resistant material forming a pair as front and back surfaces The distribution transformer according to any one of claims 1 to 14, wherein the distribution transformer is provided with components.   The distribution transformer according to claim 15, wherein the high corrosion resistance material of the corrosion diagnostic component is an organic coating having a thickness of 20 μm or more.   16. The distribution transformer according to claim 15, wherein the high corrosion resistance material of the corrosion diagnostic component is a plating layer mainly composed of zinc or aluminum.   16. The distribution transformer according to claim 15, wherein the high corrosion resistance material of the corrosion diagnostic component is an organic coating layer containing zinc or aluminum fine particles.   16. The distribution transformer according to claim 15, wherein the high corrosion resistance material of the corrosion diagnostic component is any one of stainless steel, nickel-base alloy, pure titanium, titanium alloy, aluminum, aluminum alloy, copper, and copper alloy.   The distribution transformer according to any one of claims 15 to 19, wherein an organic coating is present on the surface of the highly corrosion-resistant material.   The distribution transformer according to any one of claims 15 to 20, wherein a boundary portion on an outer surface of the highly corrosion-resistant material and the metal base material exposed portion is electrically insulated. It is a tank container for a distribution transformer that houses a transformer body consisting of a winding and an iron core and is filled with an insulating material,
A tank container for a distribution transformer, characterized by being made of ferritic stainless steel.

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