JP4345181B2 - Transporting and storing metal products - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a method for transporting and storing a metal product, and more particularly, to a method for preventing the occurrence of rust due to condensation locally generated on a metal product when the metal product is transported and stored in an open-air environment.
[0002]
[Prior art]
Metal products having a bare metal surface such as polished steel bars and steel tire cords tend to rust. For this reason, these products are required to pay full attention not to cause rust in the process of transportation and storage after production until they are used by the user. Generally, these products are transported in open air. In some cases, a double waterproof sheet is applied to the inner and outer hooks to prevent rusting due to dew and rainwater.
[0003]
On the other hand, the surface-treated steel sheet is a steel sheet in which a surface coating layer according to the application is provided on the surface of the cold-rolled steel sheet, and rust preventive oil is applied in the final plating process. In particular, surface-treated steel plates used for food containers (cans, etc.) are manufactured by plating Sn, Ni, Cr, etc. harmless to humans on steel plates, but (1) the plating metal is expensive, 2) High plating cost, 3) To increase the corrosion resistance of the inner surface of the can, the inner surface is painted or coated with a resin film, so expensive plating metal is economical and resource-saving. As much as possible from the aspect of. Therefore, compared with surface-treated steel sheets for automobiles and surface-treated steel sheets for home appliances, the plating amount is very thin, 1/40 to 1/60, and is highly sensitive to rust. Every effort is made against rusting.
[0004]
For example, in order to prevent rusting in the process of transporting or storing thin tin-plated steel sheets, which are the above-mentioned surface-treated steel sheets for cans, efforts are made to increase the coating rate of the surface of the plated metal sheet, that is, pinholes in the plating layer. While striving for eradication, rust preventive oil is applied to the steel sheet surface. Furthermore, when transporting and storing the product, generally the coiled product is wrapped with rust-proof paper and buffer paper (for example, corrugated cardboard) coated with a vaporizable rust-proofing agent, and then a waterproof film-laminated paper is used on it. A method of packaging and covering with a waterproof sheet is employed. Moreover, the method of storing in an indoor warehouse after conveyance is adopted as necessary.
[0005]
[Problems to be solved by the invention]
By these means, it has been considered that rust in the transportation or storage process has been eradicated. However, recently it was found again that rust was found as a discolored part in the can manufacturing process. When such rust occurred, a large amount of products had to be disposed of.
[0006]
Therefore, the present invention eliminates local rusting of metal products, which has been a problem in transportation and storage of conventional surface-treated steel sheets from this viewpoint, and rust found in the can-making process of surface-treated steel sheets for cans. The purpose is to propose means that can be prevented.
[0007]
[Means for Solving the Problems]
The inventors have conducted a thorough investigation on the causes of rusting of metal products, and the above-mentioned local rusting is caused by direct direct exposure in the process of transporting and storing metal products under conditions of direct sunlight. We found that the part where the temperature rise is large when exposed to sunlight and the part where the temperature rise behind it is extremely small coexist in the coil. It has been found that the metal product may be covered with a radiant heat shielding sheet for transportation and storage below.
[0009]
That is, the present invention, when transporting and storing a metal product packed so as to be shielded from the outside air by a rust preventive paper coated with a vaporizable rust preventive agent, a buffer paper and a waterproof film laminated paper, in the open air, This is a method for transporting and storing a metal product, in which the packaged metal product is further covered with a radiant heat shielding sheet, and local rusting due to condensation is prevented by suppressing a local temperature rise of the metal product. In this case, it is preferable to apply the above method to a surface-treated steel sheet, particularly a thin tin-plated steel sheet or a tinted steel sheet.
[0010]
In the above invention, it is preferable to use a radiation heat shielding sheet having a radiation rate of 0.7 or less.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described based on embodiments. Examples of the metal product that is an object of the present invention include a steel plate having a surface that easily rusts , in particular, a thin tin-plated steel plate or a tin plate steel plate .
[0012]
These metal products, multiplied inner dew or rain, the outer seat and by applying a waterproof sheet double, proof technique rusting by dew or rain, further volatile corrosion inhibitor coated with anti-corrosion paper, buffer It is packed so as to be shielded from the outside air by paper and waterproof film laminated paper. Therefore, they do not lead to rusting in the normal transportation / storage process. However, according to what the present inventors have observed, rusting occurs locally by the following mechanism.
[0013]
In other words, when the product is exposed to direct sunlight, the temperature around the metal product rises only in the part that has been exposed to direct sunlight, and moisture contained in the packing paper is released into the packaging or moisture contained in the waterproof sheet is exposed to the surroundings. Is released and increases the relative humidity of the surroundings. In parts where the temperature is increased due to direct sunlight, the temperature of the metal product is higher than the dew point of the atmosphere, so condensation does not occur, but the part where the temperature did not rise due to direct sunlight, such as the lower side of the coil In part, the temperature of the metal product is lower than the dew point of the surrounding atmosphere, so condensation occurs and is localized at that location, so even if the amount of condensed water is small as a whole, it becomes large water droplets locally. It spreads and becomes rust that can be observed with the naked eye. Thus, normally, rust is generated at a site where rust caused by condensation does not occur.
[0014]
Therefore, in order to prevent the occurrence of rust due to such a cause, it is only necessary to prevent a local temperature increase due to the direct sunlight. For example, the following means can be considered.
(1) Transport and store metal products at night. This confirmed that rusting can be prevented. However, it is impossible to supply steel materials smoothly to consumers having a continuous high production line, and there are problems such as extreme reduction in productivity or working conditions, which is not practical.
(2) It is conceivable to provide a heat insulating layer between the metal product and the waterproof sheet. However, this means has many problems such as the strength of the heat insulating layer and the disposal of the heat insulating layer material at the time of unpacking.
(3) Further, it is conceivable to cool a portion that receives direct sunlight at the time of transportation / storage, for example, with an electric fan, but a wet cooler is required, which makes the equipment large and industrially impossible. Moreover, an effect is not necessarily recognized.
[0015]
In the present invention, in place of these means, the metal product is covered with a radiant heat shielding sheet when the metal product is transported and stored in the open air. Here, the radiant heat shielding sheet refers to a protective sheet such as a conveyed product having a characteristic of an emissivity of 0.7 or less. For example, a surface of a truck exclusive sheet marketed under the trade name Permcare (registered trademark) is coated with a metallic coating. Those that reflect radiant heat can be suitably used.
[0017]
The present invention is suitably applied to thin tin-plated steel sheets, particularly can steel sheets. In steel plates for cans, it is most effective to apply to this because defects such as rust should not occur over the entire length of the entire width except for the final end of about 1 mm before the can is finished. In particular, conventional tinplate with Sn of 11.2 g / m ² or less and Cr hydrated oxide of 20 mg / m ² or less, Sn of 2 g / m ² or less, metal Cr of 30 mg / m ² or less and Cr hydrated oxide of It is most effective to apply the present invention to a thin tin-plated steel sheet (LTS) of 20 mg / m ² or less, and further to a steel sheet obtained by subjecting these steel sheets to Ni plating as a base treatment.
[0018]
Taking such surface-treated steel sheet as an example, such metal products that are sensitive to rust are packed with rust-proof paper and buffer paper coated with a vaporizable rust-proofing agent. Wrapped and transported / stored. Rustproof paper coated with a vaporizable rust inhibitor is a packaging paper coated with a vaporizable rust inhibitor generally called VCI paper, where the atmosphere inside the package is filled with the vaporizable rust inhibitor. It has a function to prevent rusting of steel plates. The buffer paper refers to a packing member having a buffering function against external force such as corrugated cardboard or pressboard paper, and has a function of enabling the sheet to be transported without attaching a wrinkle (push bar) to an internal steel plate or the like by the buffering action. The waterproof film-laminated paper refers to paper on which a waterproof film such as a vinyl film is laminated, and has an action of blocking the packaging material from the outside air and moisture (humidity).
[0019]
The outline of the packing state is shown in FIG. 1 and FIG. 2, and the surface-treated steel sheet for can 1 wound in a coil shape is packed so as to be shielded from the outside air by the rust-proof paper 2 that is folded, and buffered from above. It is packed with paper 3 and further packed with waterproof film laminate paper 4 from above. Therefore, it is considered that the surface-treated steel sheet 1 for cans is usually protected from the external atmosphere by the action of these packing materials and does not rust.
[0020]
However, it has been found that the surface-treated steel sheet 1 for can actually rusts by the following mechanism.
(1) The buffer paper 3 generally has a high hygroscopic property, and retains a large amount of water during storage. (Moisture retention increases the weight of the buffer paper by about 10%.) When exposed to high temperatures, this moisture is released around the surface-treated steel sheet coil, causing an increase in the absolute humidity of the environment around the coil.
(2) When the surface-treated steel sheet coil is exposed to direct sunlight on a transport vehicle such as a truck after shipment from the factory, the temperature locally rises on the upper surface. For example, the surface temperature of the packaging material is 10 ° C. Rise to 15 ° C.
(3) As a result, moisture is released as water vapor from the buffer paper 3 and further the rust preventive paper 2 and is sealed by the waterproof film laminated paper 4, so that water vapor penetrates around the surface-treated steel sheet coil. In some cases, water vapor may enter the coil periphery from an incompletely folded portion of the rust-proof paper 2. The invading water vapor diffuses into the space around the coil by convection.
(4) The surface-treated steel sheet coil has a part where the temperature is increased by direct sunlight and a part where the temperature is low without being affected by this, and the latter part has a high relative humidity and condensation occurs. It will rust.
[0021]
Even in this case, in order to cut off the mechanism leading to dew condensation, a means for suppressing the temperature rise in the environment around the surface-treated steel sheet coil, particularly a local temperature rise, may be taken. Specifically, the radiant heat of direct sunlight may be blocked. This suppresses the release of water vapor from rust-proof paper, buffer paper, etc. that occurs during transportation and storage, and the humidity is set to a level that does not cause condensation even if water vapor enters the coil through the rust-proof paper. As a result, local rusting can be prevented.
[0022]
Specifically, the packaged metal product is further covered with a radiant heat shielding sheet. In the present invention , since the metal product has already been strictly packaged, it is only necessary to cover the metal product with a radiant heat blocking sheet for its transportation and storage, and use a normal waterproof sheet or the like. There is no need.
[0023]
FIG. 3 shows a steel strip coil having an emissivity of a radiant heat shielding sheet using an experimental apparatus in which a steel strip coil 12 packed in a gantry 11 is placed and covered with a radiant heat shielding sheet 13 as shown in FIG. Although it is a figure which shows the result of investigating the influence on the surface temperature, as shown here, the maximum rising temperature of the surface of the inner packaging material is part A (part affected by direct sunlight) under the condition where the emissivity is 0.7 or less. It can be seen that the temperature is less than 10 ° C. Therefore, the absolute humidity is low and no condensation occurs. For example, if the absolute humidity is 30 (g / kg dry air), dew condensation is not expected even if the temperature of the low temperature portion B of the steel strip coil is 30 ° C. or lower. By repeating such experiments, the present inventors have found that the emissivity of the characteristic value of the sheet for conveying and storing metal products is 0.7 or less. The emissivity refers to the ratio ε = W / W ₀ between the radiation divergence W of the heat radiator and the radiant divergence W ₀ of the complete black body at the same temperature.
[0024]
In this way, the present invention suppresses local temperature rise due to radiant heat of direct sunlight during transportation and storage of metal products, and even when moisture is released from waterproof sheets and packaging materials, This is to prevent local condensation in the section. In light of this purpose, the characteristic value of the radiant heat shielding sheet should basically satisfy only a radiation rate of 0.7 or less. However, if the heat insulating property represented by the heat transfer coefficient is satisfied at the same time, an increase in the coil surface temperature is further suppressed, and a preferable result is obtained. Therefore, it is preferable that the radiation heat shielding sheet according to the present invention has high heat insulation.
[0025]
【Example】
Example 1
As shown in Fig. 1, 6 coils of thin tin-plated steel sheet (LTS) coil are packed with VCI paper and buffer paper (kraft paper), and then packed on a cardboard laminated with vinyl film and loaded on a transport truck. Then, it was covered with a truck-specific sheet permanent care (trademark) manufactured by Unitika Co., Ltd. having an emissivity of 0.6, and conveyed for a long distance. During the transfer period, direct sunlight from above the coil continued for about 6 hours. The weather during the transport was clear and the average relative humidity was 50%. When the emissivity of the truck-specific sheet was 0.9, the same test was conducted for 6 coils.
[0026]
After being transported, the packaging was unwound and the side of the coil was observed to investigate the presence of condensation. As a result, when the emissivity was 0.9, rusting due to condensation was observed on the lower surface of the coil for 2 out of 6 coils, but when the emissivity was 0.6, no dew condensation was observed on the 6 coils tested. Did not occur.
[0027]
( Reference example)
As shown in Fig. 5 and Fig. 6, 9 bundles of deformed bar products 21 are loaded and held on the truck bed 20, wrapped with an inner sheet (fabric sheet) 22, and from above, Unitika stock with an emissivity of 0.6 is used as an outer sheet 23 Covered with company-made truck seat perm care for long distance transportation. The weather during transportation was fine, and the direct sunlight from above the truck continued for about 5 hours. A test for transporting nine bundles of deformed bar products was performed under the same conditions as described above except that a sheet having an emissivity of 0.9 was used as the outer sheet 23.
[0028]
After the transportation, the dew condensation state on the surface of the deformed bar product was investigated. As a result, when the emissivity was 0.9, sweating (water droplets) was observed on the side surface and end surface of the deformed bar product for 3 bundles out of 9 bundles, and it was confirmed that some of them progressed to rust. When the emissivity was 0.6, no sweating (water droplets) was observed on the 9 bundles tested, and no rust was generated.
[0029]
【The invention's effect】
In the present invention, the metal product is covered with the radiant heat shielding sheet as described above, and the metal product is transported and stored while suppressing the temperature rise locally due to direct sunlight. Condensation in the storage process and rusting based on it could be prevented. In particular, it was possible to almost completely suppress rusting due to condensation on a thin tin-plated steel plate or tinplate steel plate that easily rusts, and the production of cans and the like could be stabilized.
[Brief description of the drawings]
FIG. 1 is a partially cutaway cross-sectional view showing a packaging state of a surface-treated steel sheet.
FIG. 2 is an enlarged view of FIG.
FIG. 3 is a relationship diagram showing the effect of emissivity on the surface temperature of a packing coil.
FIG. 4 is a schematic view of an experimental apparatus for investigating an increase in the surface temperature of a packing coil.
FIG. 5 is a schematic view of a method for transporting and storing a metal product in a reference example.
6 is an A-A sectional view of a transport and storage method of a metal product shown in FIG.

Claims (3)

When transporting and storing metal products that have been packaged so that they are shielded from outside air by rust-proof paper, buffer paper, and waterproof film-laminated paper coated with a vaporizable rust preventive agent, A method for transporting and storing a metal product, characterized in that the metal product is further covered with a radiant heat shielding sheet to prevent local rusting due to condensation by suppressing a local temperature rise of the metal product.   The method for transporting and storing a metal product according to claim 1, wherein the metal product is a thin tin-plated steel plate or a tin plate steel plate. The method for transporting and storing a metal product according to claim 1 or 2, wherein a radiation heat shielding sheet having an emissivity of 0.7 or less is used.

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