JP2016125070A - Lid for overhead hardware material excellent in maintainability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lid for an overhead hardware material whose indication of corrosion can be observed before a hole is made due to corrosion in a lid upper part of the overhead hardware material installed on a utility pole by means of visual inspection from the ground, which does not require costly inspection such as inspection by climbing the pole, and which is excellent in corrosion resistance and maintainability and inexpensive, and to provide an overhead transformer and an overhead switch applying the same.SOLUTION: Provided is a coated or uncoated metal lid applied to an overhead hardware material, which is molded by using a plated steel sheet having both surfaces applied with hot-dip zinc plating or hot dip aluminum plating having a total content of Al and Mg of less than 6 mass% or 6 mass% and more. When an adhesion amount of a hot-dip zinc plating film on the lid outer surface side is tA(g/m), and an adhesion amount thereof on the lid inner surface side is tB(g/m), tA is less than 300-500 g/m, tB is 30-100 g/mand more, and tA/tB is a constant value and more. Also provided are an overhead transformer and an overhead switch applying the lid.SELECTED DRAWING: None

Description

  The present invention relates to a lid applied to an aerial equipment such as a transformer or a switch erected on a utility pole, and more specifically, corrosive damage of an aerial base material can be easily detected by visual inspection from the ground. The present invention relates to a painted or unpainted metal lid with excellent corrosion resistance and maintainability, which facilitates maintenance that can be maintained before reaching the point of view.

  Currently, electrical distribution equipment such as aerial transformers and switches that require hermeticity must be visually inspected by workers from the ground and from aerial work vehicles in order to avoid failure due to holes due to corrosion. Ascending pillars are being inspected. In particular, corrosion on the upper side of the lid cannot be discriminated from the ground, and periodic climbing column inspections using an aerial work vehicle, etc., or observation of the upper part of the lid using special jigs are performed. It has become.

  Many of the lids currently used have a specification in which a steel plate is molded into a lid and then hot dip galvanized. In this case, since the inner and outer surfaces of the lid have the same rust-proof specifications, there is a possibility that the upper part of the lid that is exposed to rainwater will be preferentially perforated. Become. Moreover, since it is the specification which performs hot dipping after shaping | molding, a conveyance expense and an inventory management expense generate | occur | produce and a cost becomes high.

  Some of the lids currently in use are made of hot-dip galvanized steel sheet to reduce the transportation and inventory management costs compared to the case of hot-dip plating after molding. Some lids are cost effective. However, in this case as well, the inner and outer surfaces of the lid have the same rust-proof specification, so there is a possibility that the upper part of the lid may be perforated, and it is necessary to periodically inspect the climbing column at the upper part of the lid, which is expensive. Become. In addition, there are lids designed to reduce the cost as no coating, but due to the deterioration of the anticorrosion performance due to the absence of coating, there is a cost problem such as the inspection interval of the upper portion of the lid must be shortened.

  As a management method for corrosion degradation of aerial equipment, surface management by corrosive environment monitoring has also been proposed, but even if the height of the power pole is the same, whether it is easily affected by salt damage, etc. Since the corrosive environment fluctuates greatly depending on topography, individual inspection is still essential. In Patent Document 1, in order to solve the same problem, when colored liquid is sealed in the hollow part of the high-pressure switch and the upper part of the high-pressure switch deteriorates to form a hole, the colored liquid flows out from the hole. It has been proposed that it is possible to notify that there is a possibility of failure in the high-voltage switch by flowing down from the upper surface to the side surface of the high-voltage switch, but this method cannot prevent perforation.

JP 2014-75891 A

Quantitative evaluation of degradation environment for electrical equipment materials Vol. 69, No. 3 (Electric cooperative research group, published in 2013)

  As mentioned above, maintenance of aerial equipment that does not allow perforation of the lid is likely to be perforated on the top of the lid. Since the inner and outer surfaces have the same specifications, there is a possibility that all parts of the lid will be perforated.

  The present invention has been made in view of the above circumstances, and by visual inspection from the ground, it is possible to detect signs of corrosion before the perforation due to corrosion of the lid upper part of the overhead equipment installed on the utility pole, etc. The purpose of the present invention is to provide a cover for an inexpensive overhead equipment that does not require any costly inspection such as inspection and has excellent corrosion resistance and maintainability.

  In order to achieve the above object, the present inventors have intensively studied and investigated the function of the lid of the aerial base material in detail. As a result, the part where the hole resistance of the lid is required is the inner part of the hermetic seal part at the upper part of the lid, and the side or end of the lid that protrudes from the seal part on the side of the equipment has holes due to corrosion. However, it was found that the sealing inside the equipment was not affected.

  Therefore, it is possible to visually inspect from the ground, and the anticorrosion performance of the lid side and end, which is harmless to the lid sealability, is moderately reduced from the anticorrosion performance of the upper lid, and corrodes ahead of the upper lid. In addition, the above-mentioned purpose can be achieved, and an appropriate reduction in the corrosion resistance of the side of the lid can be realized by molding the lid using a plated steel sheet with a difference thickness plating on the outer surface and the inner surface. As a result, the present invention has been completed.

  That is, the present invention is as follows.

(1) Applicable to aerial equipment formed using plated steel sheets with hot-dip galvanized coating on which both the Al and Mg content is less than 6% by mass and the Mg content is 3% by mass or less A painted metal lid,
The amount of adhesion of the hot dip galvanized film on the outer surface side of the lid is tA (g / m ² ),
When the adhesion amount of the hot dip galvanized film on the inner surface side of the lid is tB (g / m ² ),
A painted metal lid, wherein tA is less than 500 g / m ² , tB is 50 g / m ² or more, and tA / tB is 1.8 or more.

(2) Applicable to aerial equipment formed using plated steel sheets with hot-dip galvanized aluminum plating on both sides, with a total content of Al and Mg of 6% by mass or more and 3% by mass or less. A painted metal lid,
TA (g / m ² ), the adhesion amount of the hot-dip galvanized aluminum plating film on the lid outer surface side,
When the adhesion amount of the hot dip aluminum plating film on the inner surface side of the lid is tB (g / m ² ),
A painted metal lid, wherein tA is less than 300 g / m ² , tB is 30 g / m ² or more, and tA / tB is 1.4 or more.

(3) Applicable to aerial equipment formed using plated steel sheets with hot dip galvanizing on both sides, where the total content of Al and Mg is less than 6% by mass and the Mg content is 3% by mass or less. Unpainted metal lid,
The amount of adhesion of the hot dip galvanized film on the outer surface side of the lid is tA (g / m ² ),
When the adhesion amount of the hot dip galvanized film on the inner surface side of the lid is tB (g / m ² ),
tA is less than 500 g / ^{m 2,} unpainted metal lid, wherein tB is 100 g / ^{m 2} or more, and tA / tB is 1.4 or more.

(4) Applicable to aerial equipment molded using plated steel sheets with hot-dip galvanized aluminum plating on both sides, with a total content of Al and Mg of 6% by mass or more and 3% by mass or less. An unpainted metal lid that
TA (g / m ² ), the adhesion amount of the hot-dip galvanized aluminum plating film on the lid outer surface side,
When the adhesion amount of the hot dip aluminum plating film on the inner surface side of the lid is tB (g / m ² ),
An unpainted metal lid, wherein tA is less than 300 g / m ² , tB is 50 g / m ² or more, and tA / tB is 1.2 or more.

(5) Painted or unpainted metal lid applied to aerial equipment, formed using hot dip galvanized or hot dip galvanized steel sheet with differential pressure plating on both sides, with a large amount of plating coating A metal lid formed with the side as the lid outer surface side and the side with a small amount of adhesion as the lid inner surface side.
(6) Futagaimen the coating weight of plating film serving as the side tA (g / m ^2), when the tB (g / m ²⁾ the coating weight of plating film serving as the lid inner side, when the coated metal lid The metal lid according to (5) above, wherein tA / tB is in the range of 1.2 to 2.0, and in the case of an unpainted metal lid, tA / tB is in the range of 1.4 to 5.0.
(7) An aerial transformer or an aerial switch characterized by applying the painted metal lid or the unpainted metal lid according to any one of (1) to (6) above.

  According to the present invention, it is possible to detect signs of corrosion at the top of the lid of the aerial equipment by visual inspection from the ground, by forming a plated steel sheet having different plating adhesion amounts on both sides of the steel sheet. An inexpensive metal lid that does not require maintenance costs can be provided.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Unless otherwise specified, in the present specification, “%” in the composition means “% by mass”.

  When a lid is formed using a plated steel plate, there is a concern about the anticorrosion performance of the non-plated portion on the side surface that is the cut surface of the plated steel plate. In general, it is considered that rusting is likely to occur because the unplated area increases, especially when there is no coating and the plate thickness is large. However, when the unpainted lid of the present invention having a thickness of 2.3 mm and 3.2 mm was evaluated in a corrosive environment, the end face of the lid faces the lower end and is eluted from the outer surface of the lid by rain water hitting the top of the lid. It has been found that it is covered with a white product of zinc or aluminum and is anticorrosive.

  Based on the above knowledge, the optimal plating range and plating specifications for the inner and outer surfaces applied to the steel sheet depend on the degree of damage to the plating film that the lid side receives during molding, the appearance defect due to the increase in film thickness, the composition of the plating film, and the presence or absence of coating. It is determined.

As the plated steel sheet for forming a lid, a hot-dip plated steel sheet having differential thickness plating on both sides is desirable. In the method in which hot dipping is performed after the lid is formed, it is difficult to control the amount of adhesion on the inner surface of the lid, but the amount of adhesion can be easily controlled by molding a steel plate that has been previously hot dipped. In addition, it is not necessary to transport the molded lid to the hot dipping process, and transportation costs are greatly reduced.
Moreover, since the steel material may be deformed and cracks may occur in the plating film by molding the lid, the basic composition of the plating film is preferably mainly composed of zinc, aluminum, and magnesium that can sacrifice and prevent the steel material. Chromium and nickel that do not have sacrificial anticorrosive action are not preferable.

  The average composition of the plating film of the hot-dip plated steel sheet for forming the lid has an Al content of 0 to 56% in both cases where the total content of Al and Mg is less than 6% and in the case of 6% or more. The Mg content is 0 to 3%, and the balance is Zn and inevitable impurities. Inevitable impurities (such as Si) composed of other impurity elements are in the range of 1% or less in total. Since Al is an element that imparts high corrosion resistance to the plated surface, and Zn is an element that imparts sacrificial anticorrosive action, considering the balance of their characteristics, depending on whether to paint or not paint The Al content is determined within the above range. Accordingly, a hot-dip galvanized steel sheet that does not contain Al or Mg can also be used.

  In general, Mg in hot dipping has an anticorrosive effect. The anticorrosion effect can be expected by including Mg in the plating film. On the other hand, if Mg is contained in the hot dip galvanizing bath, the plating property may be reduced due to the generation of Mg oxide dross. Therefore, it is preferable that the Mg content in the hot dip coating is 3% or less. Since the generation of dross is suppressed by containing Al in the hot dip galvanizing bath, a hot dip galvanized steel sheet containing Mg and Al can be used from the viewpoint of preventing deterioration of the plating property. It is. In this case, by making the Mg content less than the Al content, the plating property is improved, and a film having an excellent anticorrosion effect is formed.

  As the average composition of the plating film of the hot-dip plated steel sheet for forming, the plating film not containing Al or Mg cannot be expected to have an anticorrosive effect due to Al or Mg. -Zn plating film <Al-Zn plating film <Zn plating film It is preferable to increase the entire size in this order.

  In addition, the amount of the optimum plating film to be applied to a metal lid formed using a plated steel sheet that has been subjected to hot dip galvanization or hot dip galvanized aluminum plating varies depending on the presence or absence of coating. When providing a coating film, since the coating film has a rust-preventing effect, the amount of plating film deposited may be small.

In the present invention, the molten plating film tA (g ^{/ m} 2) the adhesion amount of the Futagaimen side, when the coating weight of the molten plating film serving as the lid inner surface side was ^{tB (g / m 2),} Al and Mg Depending on the content and the presence or absence of coating, there is an optimum amount of adhesion. When realizing such an embodiment, using a hot dip galvanized steel sheet or a hot dip galvanized aluminum plated steel sheet that has been subjected to differential pressure plating on both sides of the steel sheet, the side with the larger coating film adhesion amount is the lid outer surface side, and the adhesion amount It is easy to mold the lid with the smaller side as the inner surface side of the lid. When the adhesion amount of the plating film on the outer surface side of the lid is tA (g / m ² ) and the adhesion amount of the plating film on the inner surface side of the lid is tB (g / m ² ), tA / tB in the case of a painted metal lid. Is in the range of 1.2 to 2.0, and in the case of an unpainted metal lid, tA / tB is in the range of 1.4 to 5.0, and particularly good results are obtained.

In the case of a coated metal lid formed from a plated steel sheet coated on both sides with a hot-dip galvanized aluminum alloy with a total content of Al and Mg of less than 6%, tA is less than 500 g / m ² and tB is It is preferable that 50 g / m ² or more and tA / tB is 1.8 or more. In hot dip galvanizing with tA of 500 g / m ² or more, the anticorrosion performance is saturated and the appearance deteriorates. Further, when tB is less than 50 g / m ² , rusting on the inner surface of the lid is quick in coastal areas where the corrosive environment is severe, and even when ground inspection is performed, the frequency of inspection increases in the salt damage area and maintenance costs increase. Moreover, when tA / tB is less than 1.8, the case where the upper surface of the lid is corroded first is recognized. tA is more preferably in the range of 100 to 500 g / m ² , particularly preferably in the range of 150 to 300 g / m ² . tB is more preferably in the range of 50 to 200 g / m ² , particularly preferably 60 to 150 g / m ² . tA / tB is more preferably in the range of 1.8 to 5.0.

In the case of a coated metal lid formed from a plated steel sheet coated on both sides with a hot dip galvanized aluminum plating having a total content of Al and Mg of 6% or more according to claim 2, Al and Mg have an anticorrosive effect. The desired performance can be achieved with a smaller amount of adhesion. That is, it is preferable that tA is less than 300 g / m ² , tB is 30 g / m ² or more, and tA / tB is 1.4 or more. tA is more preferably in the range of 80 to 300 g / m ² , particularly preferably in the range of 80 to 200 g / m ² . tB is more preferably in the range of 45 to 150 g / m ² , particularly preferably in the range of 50 to 100 g / m ² . tA / tB is more preferably in the range of 1.4 to 4.0.

In the case of an unpainted metal lid formed from a plated steel sheet coated on both sides with a hot-dip galvanized coating with a total content of Al and Mg of less than 6% according to claim 3, tA is less than 500 g / m ² , tB Is preferably 100 g / m ² or more and tA / tB is preferably 1.4 or more. In hot dip galvanizing with a tA of 500 g / m ² or more, the anticorrosion performance is already saturated, and the appearance is deteriorated, so that it is not suitable for practical use. In addition, when tB is less than 100 g / m ² , rusting on the inner surface of the lid is quick in coastal areas where the corrosive environment is severe, and even when ground inspection is performed, the frequency of inspection increases and maintenance costs increase. Moreover, when tA / tB is less than 1.4, the case where the upper surface of the lid is corroded first is recognized. tA is more preferably in the range of 150 to 500 g / m ² , particularly preferably in the range of 200 to 450 g / m ² . tB is more preferably in the range of 100 to 400 g / m ² , particularly preferably in the range of 100 to 320 g / m ² . tA / tB is more preferably in the range of 1.4 to 2.5.

In the case of an unpainted metal lid formed from a plated steel sheet coated on both sides with a hot-dip galvanized aluminum plating having a total content of Al and Mg of 6% or more according to claim 4, Al or Mg has an anticorrosive effect. Therefore, the desired performance can be achieved with a smaller amount of adhesion. That is, it is preferable that tA is less than 300 g / m ² , tB is 50 g / m ² or more, and tA / tB is 1.2 or more. In hot dip galvanizing with tA of 300 g / m ² or more, not only the anticorrosion performance is already saturated, but also the appearance is deteriorated, so that it is not suitable for practical use. Further, when tB is less than 50 g / m ² , rusting on the inner surface of the lid is quick in coastal areas where the corrosive environment is severe, and even when ground inspection is performed, the frequency of inspection increases in the salt damage area and maintenance costs increase. Moreover, when tA / tB is less than 1.4, the case where the upper surface of the lid is corroded first is recognized. tA is more preferably in the range of 80 to 300 g / m ² , particularly preferably in the range of 80 to 200 g / m ² . tB is more preferably in the range of 50 to 150 g / m ² , particularly preferably in the range of 60 to 100 g / m ² . tA / tB is more preferably in the range of 1.2 to 2.0.

  A chemical conversion treatment film can also be provided on the surface of the unpainted hot-dip coating film of the present invention by a conventionally known method. Even if the chemical conversion film is damaged due to the deformation of the steel plate at the time of lid molding, the effect of the present invention is not impaired.

As the thickness of the coating film, an epoxy resin coating film is provided by electrodeposition or spraying of about 30 to 60 μm, and if necessary, a top coating film having a weather resistance of about 30 μm such as melamine, fluorine, polyurethane, urethane, etc. The specifications with Moreover, although baking coating of powders, such as polyester and urethane, is applicable, when a film thickness exceeds 200 micrometers, the difference in the anticorrosion performance by metal plating will become unclear, and there exists a possibility that a lid outer surface may corrode preferentially.
In the coated metal lid, coating is preferably performed after molding in order to prevent damage to the coating film, but the effect of the present invention is not impaired even if the coated plated steel sheet is molded.

  The painted metal lid and the unpainted metal lid of the present invention are applied to aerial equipment such as a transformer and a switch installed on a utility pole. It is economical because it can be used in the same way as a conventional transformer or switch by simply covering the open end of the case body of a transformer or switch with a hermetic seal.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited only to a following example.

(Examples 1-14 and Comparative Examples 1-13)
[Plated steel sheet]
As the hot-dip plating base material, a plain steel material of SS400 having a plate thickness of 2.3 mm was used. In part, a hot dip plated steel sheet having a thickness of 3.2 mm was used.
The above-mentioned base material was evaluated using 6-section plated steel sheets having different plating compositions, which were subjected to hot dip galvanization and hot dip galvanized aluminum plating (both were differential pressure plating).
Table 1 shows the average coating film composition of the plated steel sheet. Zinc plating contains a total of 1% or less of inevitable impurity elements in the plating film.

[Molding]
The case where a predetermined hot-dip steel sheet was molded into a can lid shape and the molded product was evaluated was described as “pre-plating”.
A case where a predetermined hot-dip plating was performed on a molded product obtained by forming a base steel plate into a can lid shape was described as “post-plating”.

[Painting]
An epoxy resin electrodeposition coating film with a film thickness of 30 μm was formed as an undercoat layer on the inner and outer surfaces of the can lid after molding, and a urethane resin coating film with a film thickness of 25 μm was formed as an overcoat layer (see “ Paint specification A ”). For comparison, a urethane-based powder coating with a film thickness of 220 μm was applied to the inner and outer surfaces of the lid after molding (“Coating Specification B” in Table 1).

Table 1 shows the types of hot-dip plated steel sheets subjected to the test, the plating method, the average composition of the plating film, and the presence or absence of coating.
Examples 1-3: Painted metal lids coated with a metal lid formed with a plated steel plate subjected to hot dip galvanizing Examples 4-5: Metal lids formed of a plated steel plate subjected to hot dip zinc aluminum plating Painted painted metal lids Examples 6 to 9: Metal lids formed from plated steel sheets with hot dip galvanized on both sides (no paint)
Examples 10 to 14: Metal lid (unpainted) formed from a plated steel sheet on both sides of hot-dip galvanized aluminum plating

  The characteristics of the can lid were evaluated by the following methods.

(1) Evaluation A (comparative corrosion test): In this test, the rusting times on the outer surface of the can lid and the inner surface of the side surface of the can lid are compared and confirmed that the rusting on the outer surface of the lid is slower than the rusting on the side surface of the lid. did.
The lid is molded using a hot-dip plated steel sheet with a plating coating amount on the outer surface of the lid tA (g / m ² ) and a plating coating amount on the back surface of the lid tB (g / m ² ). A test piece (150 × 70 mm) was cut out from the end of the lid for evaluation of the inner side of the lid side surface and from the center of the lid for evaluation of the outer surface of the lid. About a part of the cut-out test piece, the lid molded from the plate material whose inner side plating thickness was reduced by polishing the inner side plating film on the side surface of the lid and used as a simulated test piece was used. Some test lids were painted after polishing the plating film.

The cut surface of the cut specimen was sealed with an epoxy resin.
Thereafter, a composite cycle test defined in JIS K 5621: “General anticorrosion paint” was performed on the test piece, and the rusting time (Time− on the inner side of the lid side surface) was determined based on the rusting time on the outer surface of the lid (Time−outer surface). Inner surface) was measured.
If (Time-outer surface / Time-inner surface) was 1 or less, it was evaluated as "X", and if (Time-outer surface / Time-inner surface) exceeded 1, it was evaluated as "Good".

(2) Evaluation Method B (Absolute Corrosion Test): In this test, if the anti-corrosion performance on the side of the lid is too low, corrosion spreads from the rusting holes and the loss of airtightness in the seal part of the overhead equipment is more than the corrosion on the outside of the lid. Since it becomes remarkably quick, the lower limit of the anticorrosion performance of the lid side surface was confirmed and evaluated.
The lid is molded with a hot-dip plated steel sheet having a plating coating amount on the outer surface of the lid of tA (g / m ² ) and a plating coating amount of the back surface of the lid on the inner surface of tB (g / m ² ). The initial plating film thickness of each section on the inner side of the lid side surface was measured. After that, the plating film on the inner side of the lid side is polished stepwise for some sections, the plating film thickness is reduced locally, and a lid molded from a plate with reduced inner plating thickness is used as a simulated test piece did. Some test lids were painted after polishing the plating film.

  The test lid was attached to the actual equipment, and the equipment was installed in the salt damage area. After two years, the corrosion state of the inner side surface and the edge of the lid side surface was observed. A case where red rust reaching the ground iron was observed was evaluated as “x”, and a case where no red rust was observed was evaluated as “good”.

(3) Evaluation method C (appearance test): In this test, when the amount of plating adhesion increases, unevenness occurs on the plating surface, which affects deformation and finish during lid molding. The glossiness was measured as an evaluation corresponding to the irregularities on the outer surface side.
With hot dip galvanizing, tA is 250 g / m ² , and with hot galvanized aluminum plating, tB is 90 g / m ^2, and the standard glossiness is GB, the measured glossiness is GM, and GM / GB is 0.7 or more. Was evaluated as “◯”, assuming that the change in glossiness was within the allowable range, and “X” as less than 0.7, assuming that the change in unevenness was large and outside the allowable range.

  The evaluation results are summarized in Table 1.

From the comparison of Examples 1-3 of the present invention and Comparative Examples 1-2, in the coated hot-dip galvanized lid of the present invention, the coating coating amount of the pre-molded plated steel sheet on the inner surface side of the lid must be 50 g / m ² or more to prevent corrosion. If the performance is insufficient and the ratio of the coating amount of the pre-molded plated steel sheet (tA / tB) is 1.8 or more, the rusting times on the outer surface of the can lid and the inner surface of the side surface of the can lid cannot be comparatively evaluated. I understand that. From these results, it is understood that the minimum value of the coating amount of the pre-molded plated steel sheet on the lid outer surface side is about 90 g / m ² .

From the comparison of Invention Examples 4-5 and Comparative Examples 3-4, in the coated hot-dip galvanized aluminum plating lid of the present invention, the coating film adhesion amount of the pre-molded plated steel sheet that is the inner surface of the lid is not 30 g / m ² or more. Insufficient anti-corrosion performance, and the ratio of the coating thickness of the pre-molded plated steel sheet (tA / tB) is 1.4 or higher, the rusting times on the outer surface of the can lid and the inner surface of the side surface of the can lid cannot be comparatively evaluated. It turns out that it becomes. From these results, it is understood that the minimum value of the coating amount of the pre-molded plated steel sheet on the outer surface side of the lid is about 50 g / m ² .

From the comparison between Invention Examples 6-9 and Comparative Examples 5-8, in the unpainted hot-dip galvanized lid of the present invention, the coating amount of the pre-molded plated steel sheet on the inner surface side of the lid is not 100 g / m ² or more. Insufficient anti-corrosion performance, and the ratio of the coating thickness of the pre-molded plated steel sheet (tA / tB) is 1.4 or higher, the rusting times on the outer surface of the can lid and the inner surface of the side surface of the can lid cannot be comparatively evaluated. It turns out that it becomes. From these results, it can be seen that the minimum value of the coating amount of the pre-molded plated steel sheet on the outer surface side of the lid is about 140 g / m ² .

From the comparison between Invention Examples 10 to 14 and Comparative Examples 9 to 11, in the unpainted hot dip galvanized aluminum plating lid of the present invention, the coating amount of the pre-molded plated steel sheet on the inner surface side of the lid is 50 g / m ² or more. Otherwise, the anticorrosion performance will be inadequate, and the ratio of the coating amount of the pre-molded plated steel sheet (tA / tB) will not be 1.2 or more. It turns out that it becomes impossible. From these results, it is understood that the minimum value of the coating amount of the pre-molded plated steel sheet on the outer surface side of the lid is about 60 g / m ² .

  From Examples 8 and 11 of the present invention, it can be seen that, even if the cover is uncoated at least up to a plate thickness of 3.2 mm, the end face of the cover where there is no plating is protected against corrosion.

  From Comparative Example 12, when the coating thickness exceeds 200 μm, there is a possibility that the outer surface of the lid is preferentially corroded without the difference in the anticorrosion performance between the inner and outer surfaces even with the plating specifications of the present invention. From Comparative Example 13, a lid that has been hot dip galvanized by post-plating is not preferred because the difference in the anticorrosion performance of the inner and outer surfaces of the lid is small and the lid outer surface may corrode preferentially. In addition, the cost increases due to the cost of transporting the lid for hot dipping.

  For painted or unpainted metal lids applied to the aerial equipment of the present invention, a sign of corrosion on the top of the aerial equipment lid should be detected by visual inspection from the ground by comparative evaluation between the lid outer surface side and the lid side inner surface side. As a result, maintenance costs can be significantly reduced. Therefore, the industrial contribution by the present invention is significant.

Claims (7)

Painted metal lid applied to aerial equipment, formed using plated steel sheets with hot dip galvanizing on both sides, the total content of Al and Mg being less than 6% by mass and the Mg content being 3% by mass or less Because
The amount of adhesion of the hot dip galvanized film on the outer surface side of the lid is tA (g / m ² ),
When the adhesion amount of the hot dip galvanized film on the inner surface side of the lid is tB (g / m ² ),
A painted metal lid, wherein tA is less than 500 g / m ² , tB is 50 g / m ² or more, and tA / tB is 1.8 or more. Painted metal applied to aerial equipment, formed using plated steel sheet with hot-dip galvanized aluminum plating, the total content of Al and Mg being 6% by mass or more and Mg content being 3% by mass or less A lid,
TA (g / m ² ), the adhesion amount of the hot-dip galvanized aluminum plating film on the lid outer surface side,
When the adhesion amount of the hot dip aluminum plating film on the inner surface side of the lid is tB (g / m ² ),
A painted metal lid, wherein tA is less than 300 g / m ² , tB is 30 g / m ² or more, and tA / tB is 1.4 or more. Unpainted metal applied to aerial equipment, formed using galvanized steel sheets with hot-dip galvanizing on both sides, with a total content of Al and Mg of less than 6% by mass and a Mg content of 3% by mass or less A lid,
The amount of adhesion of the hot dip galvanized film on the outer surface side of the lid is tA (g / m ² ),
When the adhesion amount of the hot dip galvanized film on the inner surface side of the lid is tB (g / m ² ),
tA is less than 500 g / ^{m 2,} unpainted metal lid, wherein tB is 100 g / ^{m 2} or more, and tA / tB is 1.4 or more. Non-painting applied to aerial equipment formed using plated steel sheets with hot-dip galvanized aluminum plating on both sides, with a total content of Al and Mg of 6 mass% or more and Mg content of 3 mass% or less A metal lid,
TA (g / m ² ), the adhesion amount of the hot-dip galvanized aluminum plating film on the lid outer surface side,
When the adhesion amount of the hot dip aluminum plating film on the inner surface side of the lid is tB (g / m ² ),
An unpainted metal lid, wherein tA is less than 300 g / m ² , tB is 50 g / m ² or more, and tA / tB is 1.2 or more.   Painted or unpainted metal lid that is applied to aerial equipment, and is formed using hot-dip galvanized or hot-dip galvanized steel sheet with differential pressure plating on both sides. A metal lid formed on the outer surface side, and the side with a small amount of adhesion is formed on the inner surface side of the lid. When the adhesion amount of the plating film on the outer surface side of the lid is tA (g / m ² ) and the adhesion amount of the plating film on the inner surface side of the lid is tB (g / m ² ), tA / tB in the case of a painted metal lid. Is a range of 1.2 to 2.0, and in the case of an unpainted metal lid, tA / tB is a range of 1.4 to 5.0.   An aerial transformer or aerial switch, wherein the painted metal lid or the unpainted metal lid according to any one of claims 1 to 6 is applied.