JP6992828B2 - Manufacturing method and equipment for surface-treated metal strips - Google Patents

Description

The present invention relates to a method and equipment for producing a surface-treated metal band, specifically, a method and equipment for producing a surface-treated metal band, which is characterized by a method for drying a surface-treated liquid applied to the metal band, and in particular, galvanizing. This is a manufacturing technique suitable for producing a surface-treated galvanized steel sheet by subjecting a steel sheet or a hot-dip galvanized steel sheet to a chromate-free surface treatment.

Conventionally, chromate treatment has been widely used as a surface treatment method for imparting properties such as corrosion resistance, heat resistance, fingerprint resistance, and paintability to the surface of a metal material such as a steel strip (hereinafter, a steel strip will be described as an example). It has been done. However, in recent years, chromate-free surface treatments that do not use chromate have been developed because chromate treatment has a large environmental load.

When the film thickness after drying is the same, the chromate-free surface-treated film has lower required properties such as corrosion resistance than the chromate-treated film, so that it is necessary to form a thicker film in the chromate-free surface treatment. To form a thick film, there are methods of (i) increasing the coating amount of the treatment liquid to increase the coating film thickness, and (ii) increasing the solid content concentration of the treatment liquid. However, in the former method, the amount of heat required for drying increases, so that the manufacturing cost increases. On the other hand, in the latter method, the risk of film defects increases when painting with a roll such as a roll coater.
Further, in the past, an organic solvent was often used as a solvent for paints (surface treatment liquids), but in recent years, there has been a strong tendency to use an aqueous solvent in order to reduce the environmental load.

Hereinafter, a conventional method for drying and baking a coating film and its problems will be described by taking as an example a case where a water-based paint (water-based surface treatment liquid) is applied to a steel strip.
When the water-based paint is applied to the steel strip in a continuous line, the water-based paint is applied to the steel strip with a continuous coating device such as a roll coater to form a coating film, and then the coating film is dried and baked by a dry baking device. Conventionally used drying and baking apparatus include a hot air heating furnace, an induction heating furnace, an infrared heating furnace, and the like, and a combination of these heating furnaces is also used.
For example, in Patent Document 1, as a method of baking a coated steel sheet using a drying and baking apparatus including a hot air heating furnace and an induction heating furnace, the coating film is first dried in the hot air heating furnace in the first stage, and the induction heating furnace in the latter stage. Discloses a method for final drying and baking of a coating film.

Japanese Unexamined Patent Publication No. 63-190681

In the induction heating furnace, the coating film is dried and baked by inductively heating the steel strip, and the drying and baking speed of the coating film is increased by heating the steel strip to a high temperature. Further, in other heating furnaces such as a hot air heating furnace, the steel strip becomes a high temperature state to some extent during the drying and baking process.
In the steel strip coating line, the paint film is inspected by the operator in the final process, so the steel strip needs to be cooled to near room temperature for the inspection. As a cooling method after drying and baking the coating film, water cooling has a problem that the coating film deteriorates, so gas cooling or air cooling with compressed air is usually performed, but such cooling also requires extra energy cost. It takes. Further, when the film thickness is thick, the amount of water that must be evaporated increases, and there is also a problem that the energy required for drying increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a surface-treated metal band, which can carry out a process including drying after applying a surface-treating liquid at low cost. It is in.

As a result of repeated studies to solve the above problems, the present inventor, as a method of drying the surface treatment liquid applied to the surface of the metal band in a continuous line, applies a metal band to a pressure lower than the atmospheric pressure, preferably a surface treatment liquid. A new method was devised in which the surface treatment liquid was dried by introducing it into a decompression chamber whose pressure was reduced below the vapor pressure of the solvent and volatilizing the solvent of the surface treatment liquid in this decompression chamber.
That is, the gist of the present invention for solving the above problems is as follows.

[1] A method for manufacturing a surface-treated metal band in a continuous line.
The surface treatment process of applying the surface treatment liquid (x) to the surface of the metal band,
It has a drying step of drying the surface treatment liquid (x) applied to the surface of the metal strip in the surface treatment step.
In the drying step, the metal band is passed through a decompression chamber (A) decompressed to less than atmospheric pressure, and the solvent of the surface treatment liquid (x) adhering to the surface of the metal band is volatilized in the decompression chamber (A). A method for manufacturing a surface-treated metal band.
[2] In the production method of the above [1], when the decompression chamber (A) is equal to or lower than the vapor pressure of the solvent of the surface treatment liquid (x) (however, when the solvent consists of two or more liquids having different vapor pressures), A method for producing a surface-treated metal band, which is characterized in that the vapor pressure is reduced to the vapor pressure of the liquid having the lower vapor pressure or less).
[3] In the production method of the above [2], the main component of the solvent of the surface treatment liquid (x) is water, and the pressure reducing chamber (A) is reduced to 605 Pa or more and 101 kPa or less. How to make a metal band.

[4] In any of the above-mentioned manufacturing methods [1] to [3], the decompression chamber (A) is the main decompression chamber (a) and the preliminary decompression chambers (b) provided on the entry side and the exit side thereof, respectively. It has ₁ ) and (b ₂ ), and is characterized by passing the metal band through the main decompression chamber (a) through both preliminary decompression chambers (b ₁ ) and (b ₂ ) decompressed to less than atmospheric pressure. A method for manufacturing a surface-treated metal strip.
[5] In any of the above-mentioned manufacturing methods [1] to [4], a roll coater is provided on the entrance side of the decompression chamber (A), and the surface treatment liquid (x) is applied to the surface of the metal strip by the roll coater. A method for manufacturing a surface-treated metal band.
[6] In any of the above-mentioned manufacturing methods [1] to [5], the inside of the decompression chamber (A), the position immediately before the entry side of the decompression chamber (A), and the position immediately after the exit side of the decompression chamber (A). A method for producing a surface-treated metal band, which comprises providing a heating device at at least one of the heating devices and heating the metal band by the heating device.
[7] In any of the above-mentioned manufacturing methods [1] to [6], the inside of the decompression chamber (A), the position immediately before the entry side of the decompression chamber (A), and the position immediately after the exit side of the decompression chamber (A). A method for manufacturing a surface-treated metal band, which comprises providing a vibration damping device at at least one of the vibration damping devices and suppressing the vibration of the metal band by the vibration damping device.

[8] In the manufacturing method of the above [4], a roll coater is provided on the entrance side of the decompression chamber (A), the surface treatment liquid (x) is applied to the surface of the metal strip by the roll coater, and the main decompression chamber (a). A method for manufacturing a surface-treated metal band, which comprises providing a vibration damping device in a preliminary decompression chamber (b ₂ ) provided on the exit side of) and suppressing the vibration of the metal band by the vibration damping device.
[9] In the manufacturing method of the above [5] or [8], a pair of upper and lower coating rolls constituting the roll coater is sent out toward the inlet of the decompression chamber (A) while restraining the metal band, thereby causing the metal band. A method for producing a surface-treated metal strip, which comprises guiding the metal strip to be horizontally passed through the decompression chamber (A).
[10] In the manufacturing method of the above [7] or [8], the vibration damping device is one or more selected from a suppression roll and a non-contact electromagnetic vibration damping device. How to make a metal strip.
[11] In the manufacturing method of the above [4] or [8], a heating device is provided in the preliminary decompression chamber (b ₁ ) provided on the entrance side of the main decompression chamber (a), and the metal band is formed by the heating device. A method for producing a surface-treated metal strip, which comprises heating.
[12] In the production method of the above [6] or [11], the surface-treated metal band is characterized in that the vapor pressure of the solvent of the surface-treated liquid (x) is adjusted by heating the metal band with a heating device. Manufacturing method.
[13] In any of the above-mentioned manufacturing methods [1] to [12], it is possible to control the pressure in the decompression chamber (A) according to the temperature of the metal band when passing through the decompression chamber (A). A method for manufacturing a characteristic surface-treated metal strip.

[14] A manufacturing facility for surface-treated metal strips using a continuous line.
Surface treatment equipment that applies surface treatment liquid (x) to the surface of the metal strip,
The surface treatment equipment has a drying equipment for drying the surface treatment liquid (x) applied to the surface of the metal strip.
The drying facility has a decompression chamber (A) through which the metal band passes, and the decompression chamber (A) is characterized in that the solvent of the surface treatment liquid (x) adhering to the surface of the metal band is volatilized. Surface-treated metal strip manufacturing equipment.
[15] In the manufacturing equipment of [14] above, the decompression chamber (A) is the main decompression chamber (a) and the preliminary decompression chambers (b ₁ ) and (b ₂ ) attached to the entrance and exit sides thereof, respectively. A surface-treated metal strip manufacturing facility characterized in that the metal strip is allowed to pass through the main decompression chamber (a) through both preliminary decompression chambers (b ₁ ) and (b ₂ ).

According to the present invention, the surface treatment liquid applied to the surface of the metal strip in the continuous line can be dried without heating the metal strip to a high temperature. Therefore, the cooling step after drying becomes unnecessary, and the manufacturing cost of the surface-treated metal band can be reduced.

Explanatory drawing schematically showing one embodiment of the manufacturing method and manufacturing equipment of the present invention. Explanatory drawing schematically showing the manufacturing method of the present invention and other embodiments of manufacturing equipment. Explanatory drawing which shows an example of the roll seal mechanism using the holding roll for vibration damping of a steel strip in embodiment of this invention.

The present invention is a method for manufacturing a surface-treated metal band in a continuous line, in which a surface treatment step of applying a surface treatment liquid x to the surface of the metal band and a surface treatment liquid applied to the surface of the metal band in this surface treatment step. It has a drying step of drying x, in which the metal band is passed through a decompression chamber A decompressed below the atmospheric pressure, preferably below the vapor pressure of the solvent of the surface treatment liquid, in the decompression chamber A. It volatilizes the solvent of the surface treatment liquid x adhering to the surface of the metal strip. Hereinafter, the case where the metal strip is a steel strip will be described as an example, but the present invention can be applied to the surface treatment of various metal strips other than the steel strip.

In general, when a substance in a liquid state is placed under a reduced pressure of less than atmospheric pressure, particularly under a reduced pressure of vapor pressure or less, it becomes difficult to be in a liquid state and vaporization is promoted. When the solvent of the surface treatment liquid x is water, the vapor pressure of water is about 101 kPa at 100 ° C. and about 2 kPa at 20 ° C. Water, which is the solvent of the surface treatment liquid x, can be vaporized under a reduced pressure of less than atmospheric pressure even if the pressure exceeds the vapor pressure, and the surface treatment liquid x can be dried. If the temperature of the band is 20 ° C, the temperature of the solvent of the surface treatment liquid x adhering to the surface is also about 20 ° C. Therefore, drying is further promoted by placing the band under a reduced pressure of 2 kPa or less, which is lower than the vapor pressure. Can be made to.

In the surface treatment step, the method of applying the surface treatment liquid x to the steel strip is not particularly limited, and any method such as coating with a roll coater or a bar coater, dipping, or spray coating can be applied, but the surface can be applied in the surface treatment step. In order to stably guide the steel strip coated with the treatment liquid x into the decompression chamber A in which the drying process is performed without contacting with other members, it is advantageous to use a roll coater as described later. , Application with a roll coater is particularly preferable.
The type and composition of the surface treatment liquid x applied to the steel strip are not particularly limited, and a commonly used one can be used. The solvent of the surface treatment liquid x may be water, an organic solvent, or a mixed solvent of water and an organic solvent, but in general, a solvent containing water as a main component (including a solvent consisting only of water) is used (including a solvent consisting only of water). That is, there are many aqueous surface treatment liquids x). Here, when the organic solvent is mixed with water which is the main component of the solvent, it is preferable that the ratio of the organic solvent is up to about 10% by mass in the whole solvent. Examples of the aqueous surface treatment liquid x include an aqueous solution containing a silane coupling agent, a surfactant, and the like.

In the surface treatment step, the steel strip coated with the surface treatment liquid x on the surface is depressurized to less than the atmospheric pressure, preferably less than the vapor pressure of the solvent of the surface treatment liquid x (more preferably less than the vapor pressure of the solvent of the surface treatment liquid). It is introduced into the decompression chamber A, and in this decompression chamber A, a drying step of volatilizing the solvent of the surface treatment liquid x adhering to the surface of the steel strip is performed. Here, it is better to reduce the pressure in the decompression chamber A to the vapor pressure of the solvent of the surface treatment liquid x or less (more preferably less than the vapor pressure of the solvent of the surface treatment liquid x) to further promote the drying. For the vapor pressure of the solvent of the surface treatment liquid x, for example, the temperature of the steel sheet immediately before or immediately after the surface treatment liquid x is applied and introduced into the decompression chamber A is measured, and usually this steel plate temperature ≈ surface treatment. Since it is the liquid x temperature, it can be obtained based on this steel sheet temperature.
When the pressure reducing chamber A is reduced to a pressure equal to or lower than the vapor pressure of the solvent of the surface treatment liquid x, and the solvent is composed of two or more liquids having different vapor pressures (for example, the solvent is a mixture of water and an organic solvent). In the case of a solvent), it is preferable that the pressure is reduced to the vapor pressure of the liquid having the lower vapor pressure or less.
In order to reduce the pressure inside the decompression chamber A, the room is exhausted using a vacuum pump or the like.

In the drying step in the decompression chamber A, the steel strip having the surface treatment liquid x adhered to the surface is dried to the extent that at least the surface treatment film component does not adhere to the transport roll, and in this state, the steel strip leaves the decompression chamber A and is lined up. It is sent to the downstream side. The surface-treated film of the surface-treated steel strip immediately after leaving the decompression chamber A may not be completely dried to the product level, but in a normal continuous line, a looper or the like is long on the downstream side of the decompression chamber A. Since there is a line, drying (natural drying) proceeds further in the process of being transported to the downstream side of the line, and a desired surface treatment film at the product level can be obtained. Therefore, it is not necessary to perform the baking treatment (heat treatment) of the surface treatment film after the drying step.
The amount of adhesion of the surface-treated film (the amount of adhesion after drying) varies depending on the type of film and cannot be specified uniformly. However, for example, in the case of a film containing a component as shown in Examples, corrosion resistance is achieved. It is preferably about 0.2 to 1.0 g / m ² from the viewpoint of ensuring the above. If the adhesion amount is less than 0.2 g / m ² , the corrosion resistance may be insufficient, while if it exceeds 1.0 g / m ² , the film may be partially peeled off.

Since the method of the present invention can dry the surface treatment liquid x required only in the drying step in the decompression chamber A, the steel strip does not become hot in the drying step, and therefore the cooling step after drying is performed. It is basically unnecessary, and the manufacturing cost can be reduced accordingly.
In addition, in the method of the present invention, the following problems in the case of drying and baking the coating film in the induction heating furnace as in the conventional method can be basically avoided. That is, in the induction heating furnace used for drying and baking the coating film, the induction heating coil is arranged so as to surround the steel strip through which the plate is passed. When the coating film is dried and baked in this induction heating furnace, steam is generated, but since the induction heating coil is cooled by the cooling water circulating inside the induction heating coil, the steam generated in the induction heating furnace becomes the induction heating coil. There is a problem that dew condensation and agglomerated water droplets drip and adhere to the surface of the coated steel strip, impairing the quality of the coated steel strip. In particular, when a thick coating film is dried and baked, the amount of evaporated water increases and dew condensation is likely to occur, so that there is an increased risk that water droplets will fall on the coated steel strip and cause deterioration of surface quality. Therefore, the drying and baking method in which the hot air heating furnace and the induction heating furnace are used in combination as in Patent Document 1 also has the same problem. In the method of the present invention, since the problem of dew condensation of water vapor due to the drying of such a surface treatment liquid basically does not occur, a surface treatment metal band having excellent surface quality can be stably formed even when a thick coating film is formed. Can be manufactured.

FIG. 1 schematically shows an embodiment of the manufacturing method and manufacturing equipment of the present invention.
In the present embodiment, the roll coater 1 and the decompression chamber A are sequentially provided from the upstream side between the upstream side and downstream side bridle rolls 2a and 2b for applying tension to the steel strip S in the continuous line.
The decompression chamber A has an inlet 4 and an outlet 5 through which the steel strip S passes, and a vacuum pump 3 is connected. The vacuum pump 3 exhausts the air in the decompression chamber A to reduce the pressure. .. Normally, it is economical to use at least a high-pressure pump and a low-pressure pump in combination as the vacuum pump 3, and to use these properly according to the degree of decompression. In this embodiment as well, the high-pressure pump 30 (as the vacuum pump 3) For example, an oil rotary pump or the like) and a low pressure pump 31 (for example, a mechanical booster pump or the like) are provided and used properly.

The roll coater 1 itself may be the one that has been used conventionally, but in the present embodiment, the roll coater 1 is installed close to the entrance side of the decompression chamber A, and the roll coater 1 puts the steel strip S in the decompression chamber. It also serves as a guide for passing the board horizontally in A. That is, on the front surface of the inlet 4 of the decompression chamber A, a pair of upper and lower coating rolls 12 constituting the roll coater 1 restrain the steel strip S and send it out in the direction of the inlet 4, so that the steel coated with the surface treatment liquid x. The band S can be stably and horizontally passed through the decompression chamber A without coming into contact with other members (for example, members such as the inlet 4 and the outlet 5 of the decompression chamber A). Therefore, it is preferable that the roll coater 1 is installed as close as possible to the entrance side of the decompression chamber A, and in particular, the most downstream side position of the roll coater 1 (outside of the coating roll 12) and the inlet 4 of the decompression chamber A. It is preferable that the distance is 1 m or less.

Further, although not shown, in order to more reliably prevent the steel strip S from vibrating and coming into contact with other members (for example, members such as the inlet 4 and the outlet 5 of the decompression chamber A), the inside of the decompression chamber A, Immediately before the entry side of the decompression chamber A (preferably within 1 m on the upstream side of the inlet 4 of the decompression chamber A), and immediately after the exit side of the decompression chamber A (preferably within 1 m on the downstream side of the outlet 5 of the decompression chamber A). It is preferable to provide a vibration damping device at at least one of them and suppress the vibration of the steel strip S by this vibration damping device. Examples of the vibration damping device include a suppression roll, a non-contact electromagnetic vibration damping device (electromagnetic support device), and one or more of these can be used.
As the holding roll, for example, a known roll device for restraining the steel strip S by sandwiching it between upper and lower rolls can be used. Further, as a non-contact electromagnetic vibration damping device, there is a known known method for damping a steel strip S by applying a magnetic force (attractive force or repulsive force) to the steel strip S from electromagnets arranged on both sides of the steel strip passing line. An electromagnetic vibration damping device or the like can be used.

Further, depending on the surface treatment liquid x, sufficient film characteristics may not be obtained because the film component and the steel strip do not react unless heated to a predetermined temperature. Therefore, although not shown, the inside of the decompression chamber A and the decompression chamber are not shown. Of the positions immediately before the entrance side of A (preferably within 1 m on the upstream side of the inlet 4 of the decompression chamber A) and immediately after the exit side of the decompression chamber A (preferably within 1 m on the downstream side of the outlet 5 of the decompression chamber A). A heating device may be provided at at least one place so that the steel strip (surface treatment liquid x) can be heated by this heating device. The type of the heating device is not particularly limited, but the induction heating device is particularly preferable from the viewpoint of controllability of the heating temperature. Further, as described above, a heating device is provided in the decompression chamber A (position near the inlet 4 of the chamber) or immediately before the entrance side of the decompression chamber A, and the steel strip S (surface treatment liquid x) is heated by this heating device. Therefore, the vapor pressure of the solvent of the surface treatment liquid x can be adjusted, and thereby the degree of decompression of the decompression chamber A can be reduced.
Even if the steel strip is heated by the induction heating device installed in the decompression chamber A, the generated water vapor is sucked by the vacuum pump 3 and exhausted, so that there is no possibility of dew condensation on the induction heating device.

The inlet 4 and the outlet 5 of the decompression chamber A are usually composed of slit-shaped openings. In order to reduce the inflow of air as much as possible, it is preferable that these openings have a small gap with the steel strip S through which the plate passes, but if the gap with the steel strip S is too small, the steel strip S may come into contact with the steel strip S. be. Therefore, the inlet 4 and the outlet 5 of the decompression chamber A can be provided with an appropriate sealing mechanism for suppressing the inflow of air, if necessary. For this sealing mechanism, for example, a known sealing mechanism such as a roll seal or an air seal (air curtain) can be used.
Further, in order to enable the widths of the inlet 4 and the outlet 5 to be changed according to the plate width of the steel strip S, the inlet 4 and the outlet 5 of the decompression chamber A can be partially closed in the width direction. It is preferable to attach a movable mask.

In the embodiment of FIG. 1, the pressure inside the decompression chamber A is reduced to less than the atmospheric pressure by the vacuum pump 3, preferably to be less than the vapor pressure of the solvent of the surface treatment liquid x (more preferably less than the vapor pressure of the solvent of the surface treatment liquid x). Ru.
The surface treatment liquid x is applied to the surface of the steel strip S by the roll coater 1 (surface treatment step), and the steel strip S coated with the surface treatment liquid x is immediately introduced into the decompression chamber A and passes through the decompression chamber A. The surface treatment liquid x is dried in the process (drying step).

When the inside of the decompression chamber A is depressurized below the vapor pressure of the solvent of the surface treatment liquid x, for example, the temperature of the steel strip S (surface treatment liquid x) is measured on the entrance side of the decompression chamber A with a radiation thermometer or the like. The vapor pressure of the solvent of the surface treatment liquid x may be obtained based on the measurement temperature, and the pressure in the decompression chamber A may be controlled. Further, when the steel strip S (surface treatment liquid x) is heated by the heating device in the decompression chamber A or immediately before the entry side of the decompression chamber A, the temperature of the steel strip S (surface treatment liquid x) after heating is set. It may be measured with a radiation thermometer or the like, the vapor pressure of the solvent of the surface treatment liquid x may be obtained based on the measured temperature, and the pressure in the decompression chamber A may be controlled.
In the present embodiment, the roll coater 1 is installed close to the entrance side of the decompression chamber A so that the steel strip S does not come into contact with the member at the inlet 4 or the outlet 5 of the decompression chamber A. If necessary, the tension of the steel strip between the bridle rolls 2a and 2b may be increased, or the vibration damping device as described above may be installed to suppress the vibration of the steel strip S.

Further, when decompression is performed only in a single decompression chamber as in the embodiment of FIG. 1, air is sucked from the gap between the inlet 4 and the outlet 5 of the decompression chamber A, so that the pressure is exhausted to reduce the pressure to a required level. An expensive vacuum pump with high capacity is required. Therefore, it is preferable to provide spare chambers before and after the main decompression chamber to reduce the pressure difference between the main decompression chamber and the outside so that air suction from the outside to the main decompression chamber is suppressed.
FIG. 2 schematically shows an embodiment of the manufacturing method and manufacturing equipment of the present invention in such a form.

In the embodiment of FIG. 2, the roll coater 1 and the decompression chamber A are sequentially provided from the upstream side between the upstream side and downstream side bridle rolls 2a and 2b for applying tension to the steel strip S in the continuous line. Is the same as in FIG. 1, but the decompression chamber A is composed of the main decompression chamber a and the preliminary decompression chambers b ₁ and b ₂ provided on the entry side and the exit side thereof, respectively, and the steel strip S is less than the atmospheric pressure. The main decompression chamber a is passed through both pre-decompression chambers b ₁ and b ₂ that have been decompressed. Here, in the main decompression chamber a, the surface treatment liquid x is dried as in the decompression chamber A of the embodiment of FIG. 1, and the preliminary decompression chambers b ₁ and b ₂ are the main decompression chamber a and the outside. It reduces the pressure difference and suppresses the suction of air from the outside to the main decompression chamber a.

Vacuum pumps 3a, 3b ₁ , and 3b _{2 are} connected to the main decompression chamber _a and the preliminary decompression chambers b ₁ and b ₂ , respectively. The air in ₁ and b ₂ is exhausted and depressurized. Also in this embodiment, a high pressure pump 30 (for example, an oil rotary pump) and a low pressure pump 31 (for example, a mechanical booster pump) are provided as the vacuum pump 3 and are appropriately used.
In order to further enhance the effect of the preliminary decompression chamber, the preliminary decompression chamber b ₁ and the preliminary decompression chamber b ₂ are composed of a plurality of preliminary decompression chambers adjacent to each other in the line direction, and each preliminary decompression chamber is depressurized by a vacuum pump. You may try to do it.

The inlet 6 of the preliminary decompression chamber b ₁ , the outlet 7 of the preliminary decompression chamber b ₂ , the entrance / exit 8 between the preliminary decompression chamber b ₁ and the main decompression chamber a, and the entrance / exit 9 between the main decompression chamber a and the preliminary decompression chamber b ₂ are usually used. , Consists of a slit-shaped opening. In order to reduce the inflow of air as much as possible, it is preferable that these openings have a small gap with the steel strip S through which the plate passes, but if the gap with the steel strip S is too small, the steel strip S may come into contact with the steel strip S. be. Therefore, at the inlet 6 of the preliminary decompression chamber b ₁ , the outlet 7 of the preliminary decompression chamber b ₂ , the entrance / exit 8 between the preliminary decompression chamber b ₁ and the main decompression chamber a, and the entrance / exit 9 between the main decompression chamber a and the preliminary decompression chamber b ₂ . Can be provided with an appropriate sealing mechanism for suppressing the inflow of air, if necessary. As this sealing mechanism, a known sealing mechanism such as a roll seal (see, for example, FIG. 3) or an air seal (air curtain) can be applied.

Similar to the embodiment of FIG. 1, in this embodiment as well, the roll coater 1 is installed close to the entrance side of the decompression chamber A (preliminary decompression chamber b ₁ ), and the roll coater 1 decompresses the steel strip S. It also serves as a guide for allowing the board to pass horizontally in Room A. As a result, the steel strip S coated with the surface treatment liquid x is placed between other members (for example, the inlet 6 of the preliminary decompression chamber b ₁ , the outlet 7 of the preliminary decompression chamber b ₂ , the preliminary decompression chamber b ₁ and the main decompression chamber a). (Members such as the doorway 8 and the doorway 9 between the main decompression chamber a and the preliminary decompression chamber b ₂ ), so that the plate can be stably and horizontally passed through the decompression chamber A. Also in this embodiment, the roll coater 1 is preferably installed as close as possible to the entry side of the decompression chamber A (preliminary decompression chamber b ₁ ), and in particular, the most downstream position of the roll coater 1 (the exit of the coating roll 12). It is preferable that the distance between the side) and the inlet 6 of the preliminary decompression chamber b ₁ is 1 m or less.

Further, similarly to the embodiment of FIG. 1, in the structure of the decompression chamber as in the embodiment of FIG. 2, at least one of the decompression chamber A (main decompression chamber a, preliminary decompression chamber b ₁ , and preliminary decompression chamber b ₂ ) is used. Inside, just before the entrance side of the decompression chamber A (preferably within 1 m on the upstream side of the inlet 6 of the preliminary decompression chamber b ₁ ), immediately after the exit side of the decompression chamber A (preferably the outlet 7 of the preliminary decompression chamber b ₂ ). A vibration damping device and a heating device can be provided at least one of the positions (within 1 m on the downstream side of the steel), and the significance of providing them and the details of the vibration damping device are as described in the embodiment of FIG. However, in the present embodiment, a heating device 10 such as an induction heating device is provided in the preliminary decompression chamber b ₁ provided on the entrance side of the main decompression chamber a so that the steel strip S can be heated by the heating device 10. At the same time, a suppression roll 11 which is a vibration damping device is provided in the preliminary decompression chamber b ₂ provided on the exit side of the main decompression chamber a, and the suppression roll 11 suppresses the vibration of the steel strip S. As the vibration damping device, a non-contact electromagnetic vibration damping device or the like may be used.

In the embodiment of FIG. 2, the inside of the main decompression chamber a of the decompression chamber A is less than the atmospheric pressure by the vacuum pump 3a, preferably equal to or less than the vapor pressure of the solvent of the surface treatment liquid x (more preferably, the vapor pressure of the solvent of the surface treatment liquid x). The pressure is reduced to less than 1), and the pressure inside the preliminary decompression chambers b ₁ and b ₂ is also reduced to less than atmospheric pressure by the vacuum pumps 3 b ₁ and 3 b ₂ . Here, as the depressurization state of the main decompression chamber a and the preliminary decompression chambers b ₁ and b ₂ , it is preferable that the pressure of the preliminary decompression chambers b ₁ and b ₂ is higher than the pressure of the main decompression chamber a.
The surface treatment liquid x is applied to the surface of the steel strip S by the roll coater 1 (surface treatment step), and the steel strip S coated with the surface treatment liquid x is immediately introduced into the decompression chamber A to reduce the pressure chamber A (main decompression chamber A). The surface treatment liquid x is dried in the process of passing through the chamber a) (drying step). At that time, since the preliminary decompression chambers b ₁ and b ₂ are regions that buffer the pressure difference with the outside, air suction from the outside to the main decompression chamber a is suppressed, and therefore an expensive vacuum pump with high exhaust capacity. The decompression of the main decompression chamber a can be performed relatively easily without using the above.

In the present embodiment, the steel strip S is the inlet 6 of the preliminary decompression chamber b ₁ , the outlet 7 of the preliminary decompression chamber b ₂ , the entrance / exit 8 between the preliminary decompression chamber b ₁ and the main decompression chamber a, and the main decompression chamber a and the preliminary decompression chamber. A roll coater 1 is installed close to the entrance side of the decompression chamber A and a vibration damping device (suppressing roll 11) is installed in the preliminary decompression chamber b ₂ so as not to come into contact with the member at the entrance / exit 9 between b ₂ and the like. This prevents the steel strip S from coming into contact with the members in the decompression chamber A, but if necessary, the tension of the steel strip between the bridle rolls 2a and 2b is increased. You may take action.

Further, in the case of the surface treatment liquid x that needs to be heated in order to obtain predetermined film characteristics by heating the steel strip S (surface treatment liquid x) with the heating device 10 provided in the preliminary decompression chamber b ₁ . Can also be dealt with appropriately. Further, by heating the steel strip S (surface treatment liquid x) with the heating device 10, the vapor pressure thereof can be adjusted by controlling the temperature of the solvent of the surface treatment liquid x, whereby the vapor pressure of the decompression chamber A can be adjusted. It is also possible to reduce the degree of decompression.
When the inside of the main decompression chamber a is depressurized below the vapor pressure of the solvent of the surface treatment liquid x, for example, the temperature of the steel strip S (surface treatment liquid x) is measured in the preliminary decompression chamber b ₁ with a radiation thermometer or the like. The vapor pressure of the solvent of the surface treatment liquid x may be obtained based on this measured temperature and the vapor pressure curve, and the pressure in the decompression chamber A may be controlled. When the steel strip S is heated by the heating device 10 in the preliminary decompression chamber b ₁ , the temperature of the steel strip S (surface treatment liquid x) after heating is measured with a radiation thermometer or the like, and the measured temperature is measured. And the vapor pressure of the solvent of the surface treatment liquid x may be obtained based on the vapor pressure curve, and the pressure in the decompression chamber A may be controlled.

In the present invention, a roll seal mechanism can be configured by using a restraining roll for vibration damping of a steel strip at the outlet of the decompression chamber A or the like. FIG. 3 shows an example of the roll sealing mechanism, in which a holding roll 11 (vibration damping device) is incorporated at the outlet of the decompression chamber A, and the holding roll 11 constitutes the roll sealing mechanism 13. The member on the decompression chamber A side constituting the outlet may have a small gap with the holding roll 11 as much as possible, and may be brought into contact with the holding roll 11 via an appropriate sliding member in some cases. The roll sealing mechanism using such a holding roll 11 can be applied to, for example, the outlet 5 of FIG. 1, the outlet 7 of FIG. 2, the entrance / exit 9, and the like.

As described above, the method of the present invention can dry the surface treatment liquid x required only in the drying step in the decompression chamber A, so that the steel strip does not become hot in the drying step. The cooling process after drying is basically unnecessary. However, in some cases, it can be used in combination with a known drying method such as hot air heating or induction heating. For example, hot air heating (first stage) + the method of the present invention (second stage), the method of the present invention (first stage) + induction It is also possible to adopt an embodiment such as heating (second stage). Further, depending on the type of the film, in order to promote the film forming reaction and the curing reaction, an ultraviolet irradiation step may be provided as necessary and carried out in combination with the method of the present invention.

When the surface treatment liquid is dried in the decompression chamber, it is important to eliminate the gap between the decompression chamber and the outside in order to reduce the pressure in the decompression chamber to a state close to vacuum (for example, about 100 Pa), but the method of the present invention is continuous. Since it is performed on the line, there is always a gap for the metal band to pass through the decompression chamber A. In order to depressurize the inside of the decompression chamber A having such a gap to a state close to vacuum, it is necessary to discharge a large amount of gas by a large-scale equipment and a vacuum pump, which requires a huge cost.
The main component of the solvent of the general surface treatment liquid x is water, and the vapor pressure of water is 605 Pa at 0 ° C. and 101 kPa at 100 ° C. In the method of the present invention, it is sufficient that the decompression chamber A can be depressurized to the vapor pressure or less of water. Therefore, when the main component of the solvent of the surface treatment liquid x is water, the decompression chamber A is depressurized to 605 Pa or more and 101 kPa or less. It is preferable that the pressure is not reduced to a pressure lower than that (for example, about 100 Pa) from the viewpoint of the equipment cost of the vacuum equipment (vacuum equipment including a vacuum pump). In addition, the degree of decompression required in the decompression chamber A is determined by the vapor pressure of water, and the vapor pressure of water can be controlled by adjusting the metal band temperature with a heating device. It is also possible to reduce the equipment cost by designing the drying equipment while balancing the above.

A hot-dip galvanized steel sheet (GI) was used as a metal strip to be treated (hereinafter referred to as "steel strip"), and a chromate-free surface treatment was applied to the metal strip to produce a surface-treated steel strip.
In the example of the invention, in the equipment as shown in FIG. 2, the surface treatment liquid was applied to the surface of the steel strip with the roll coater 1, and then the surface treatment liquid was dried in the decompression chamber A. In Comparative Examples 1 and 2, the surface treatment liquid was applied to the surface of the steel strip according to the conventional method with a roll coater, and then the surface treatment liquid was dried in an induction heating furnace. Further, in Comparative Example 3, in the equipment as shown in FIG. 2, the pressure in the decompression chamber A was intentionally made higher than the atmospheric pressure, and the steel strip coated with the surface treatment liquid was passed.

The surface treatment solution was a chemical solution containing 3-glycidoxypropyltrimethoxysilane, organosilicon compound, Zrfluoro compound, phosphoric acid, vanadium oxysulfate, and polyethylene oxide diluted with pure water to a predetermined solid content concentration. I used the one. This surface treatment liquid had a viscosity of 10 mPas, a surface tension of 40 mN / m, and a specific gravity of 1.
In this example, the dry state and the steel strip temperature of the surface-treated film immediately after the completion of the drying process were investigated, and the corrosion resistance, blackening resistance, and appearance of the manufactured surface-treated steel strip were evaluated as follows. .. The amount of film adhered after drying was measured by fluorescent X-ray analysis calibrated by a gravimetric method using a test piece cut out from a surface-treated steel strip as a sample. The results are shown in Table 1 together with the manufacturing conditions.

(1) Evaluation of the dry state of the coating film immediately after the completion of the drying process The dry state of the coating film was evaluated by visually observing the surface condition of the surface-treated steel strip (for one coil) immediately after the completion of the drying process on the inspection table. .. That is, before the surface-treated liquid is sufficiently dried, the surface-treated steel strip is formed in the holding roll 11 in the preliminary decompression chamber b ₂ (in the equipment in which Comparative Examples 1 and 2 were carried out, the holding roll provided on the outlet side of the induction heating furnace). As a result of contact with the film, it was visually determined whether or not "blurring" occurred in the film. Since the quality of drying is also affected by the transport speed of the surface-treated steel strip, the judgment criteria were subdivided as follows according to the transport speed of the surface-treated steel strip.
⊚: No “blurring” occurred even when the transport speed was 150 mpm or more ○: No “blurring” occurred when the transport speed was 125 mmp or more but less than 150 mmp ●: The transport speed was 100 mmp or more If it is less than 125 mpm, "blurring" does not occur. Δ: If the transport speed is 75 mmp or more, "blurring" does not occur if it is less than 100 mmp. If there is, "blurring" did not occur ×: “blurring” occurred even if the transport speed was less than 50 mpm

(2) Evaluation of the temperature of the steel strip immediately after the completion of the drying process The temperature of the surface-treated steel strip (for one coil) immediately after the completion of the drying process was measured with a radiation thermometer on the inspection table. A test piece was cut out from the surface-treated steel strip immediately after the completion of the drying process, the temperature was measured with a thermocouple, and the emissivity was calibrated by comparison with this measured value. A steel strip temperature of less than 60 ° C. immediately after the measured drying process was completed was regarded as acceptable (◯), and a steel strip temperature of 60 ° C. or higher was regarded as rejected (×).
(3) Appearance evaluation Regarding the appearance of the surface-treated steel strip (for one coil), visually check for the presence or absence of film defects (the above-mentioned "smearing" of the film and other film defects), and which steel strip transfer speed is used. However, the case where the film defect was confirmed was regarded as a failure (×), and the case where the film defect was not confirmed at least in a part of the steel strip transport speed was regarded as a pass (○).
It was also investigated whether the film was "rubbed" by contacting the constituent members (excluding the holding roll 11) of the surface-treated steel strip while passing through the drying equipment.

(4) Evaluation of corrosion resistance A salt spray test conforming to JIS Z2371 was carried out for 24 hours on the test piece cut out from the surface-treated steel strip, and the rust generation area ratio was measured. A case where the rust generation area ratio was less than 10% was regarded as a pass (◯), and a case where the rust generation area ratio was 10% or more was a failure (x).
(5) Evaluation of blackening resistance The test piece (size 50 x 150 mm) cut out from the surface-treated steel strip was held in a constant temperature bath at 80 ° C. and 98% RH for 24 hours, and the color tone of the test piece before and after this holding was spectrally colored. It was measured with a meter and evaluated by the difference (ΔL) in the L value of the Lab color system. The judgment criteria are as follows.
◯: ΔL ≧ -3
Δ: -3> ΔL ≧ -5
×: ΔL <-5
The steel strip temperature before the drying step was measured using a radiation thermometer installed on the downstream side of the heating device 10 (induction heating device) in the preliminary decompression chamber b ₁ .

In Table 1, in Invention Examples 1 to 4 and 10, the pressure in the decompression chamber A (main decompression chamber a) was set to a pressure lower than the atmospheric pressure and higher than the vapor pressure of the solvent of the surface treatment liquid. In Invention Example 10, the steel strip was cooled to 0 ° C. with a coolant at the entry side position of the roll coater 1 so that the surface treatment liquid applied by the roll coater 1 became 0 ° C. In Invention Example 5, the pressure in the decompression chamber A (main decompression chamber a) was set to a pressure equal to or lower than the vapor pressure of the solvent of the surface treatment liquid. In Invention Examples 1 to 5 and 10, the heating device 10 (induction heating device) installed in the preliminary decompression chamber b ₁ was not used. Further, in Examples 6 to 8, the vapor pressure of the solvent of the surface treatment liquid is increased by heating the steel strip using the heating device 10 installed in the preliminary decompression chamber b ₁ , and the pressure of the decompression chamber is changed to the vapor. It was set to be less than or equal to the pressure. Therefore, the vapor pressure of the solvent of the surface treatment liquid was obtained based on the measurement result of the temperature of the steel strip immediately after being heated by the heating device 10, and the pressure in the decompression chamber was controlled so as to be equal to or lower than this vapor pressure. Further, in Invention Example 9, the drying conditions were the same as those in Invention Example 5, but the suppression roll 11, which is a vibration damping device, was not used.

In Comparative Examples 1 and 2, the produced surface-treated steel strip satisfied the characteristics such as corrosion resistance and appearance, but the temperature was 60 ° C. or higher on the inspection table, and the inspection by the operator could not be performed for safety reasons.
In Comparative Example 2, since the amount of film adhered is large and the amount of water evaporated in the drying step is also large, the vaporized steam condenses in the induction heating furnace, and water droplets fall on the steel strip to produce the surface. The treated steel strip had a poor appearance.
In Comparative Example 3, the drying was poor, and the surface-treated steel strip produced accordingly was inferior in film characteristics and appearance.

On the other hand, in Invention Examples 1 to 10, the inspection table temperature is less than 60 ° C. (40 ° C. or lower), there is no problem in the operator inspection, and the manufactured surface-treated steel strip satisfies the characteristics such as corrosion resistance and appearance. rice field. In particular, in Invention Examples 5 to 9 in which the pressure in the decompression chamber was set to less than the vapor pressure of the solvent of the surface treatment liquid, the dry state of the film was particularly good.
Further, in Invention Example 9, since the holding roll 11 which is a vibration damping device was not used, the surface-treated steel strip came into contact with the constituent members (excluding the holding roll 11) of the same equipment while passing through the drying equipment. “Rubbing” of the film occurred, and this film defect was observed at a ratio of about 1 to 5 in 100 coils. On the other hand, in Invention Examples 1 to 8 and 10 using the suppression roll 11 which is a vibration damping device, such a film defect was not observed.
Further, an alloyed hot-dip galvanized steel sheet (GA) was used as a metal strip to be treated, and a chromate-free surface treatment was applied to the metal strip to produce a surface-treated steel strip. By doing so, a surface-treated steel strip having excellent corrosion resistance and appearance was obtained.

A decompression chamber
a Main decompression chamber
b ₁ , b ₂ preliminary decompression chamber 1 roll coater 2a, 2b bridle roll 3, 3a, 3b ₁ , 3b ₂ vacuum pump 4 inlet 5 outlet 6 inlet 7 outlet 8, 9 inlet / outlet 10 heating device 11 restraining roll 12 coating roll 13 roll Seal mechanism 30 High pressure pump 31 Low pressure pump S Steel strip

Claims (12)

A method for manufacturing a surface-treated metal strip in a continuous line.
The surface treatment process of applying the surface treatment liquid (x) to the surface of the metal band,
It has a drying step of drying the surface treatment liquid (x) applied to the surface of the metal strip in the surface treatment step.
In the drying step, the metal band is passed through a decompression chamber (A) decompressed to less than atmospheric pressure, and the solvent of the surface treatment liquid (x) adhering to the surface of the metal band is volatilized in the decompression chamber (A). Dry the surface treatment liquid (x) with
Further, an induction heating device is provided inside the decompression chamber (A) and at least one of the positions immediately before the entry side of the decompression chamber (A), and the metal band is heated by the induction heating device, and the metal band is heated. A method for producing a surface-treated metal band, which comprises adjusting the vapor pressure of the solvent of the surface-treated liquid (x) by heating . The decompression chamber (A) is below the vapor pressure of the solvent of the surface treatment liquid (x) (however, if the solvent consists of two or more liquids with different vapor pressures, the vapor pressure of the liquid with the lower vapor pressure or less) The method for producing a surface-treated metal band according to claim 1, wherein the vapor pressure is reduced. The temperature of the metal band after heating by the induction heating device is measured, the vapor pressure of the solvent of the surface treatment liquid (x) is obtained based on this measured temperature, and the pressure in the decompression chamber (A) is controlled based on this vapor pressure. The method for producing a surface-treated metal band according to claim 2, wherein the surface-treated metal band is made. The production of the surface-treated metal band according to claim 2 or 3 , wherein the main component of the solvent of the surface-treating liquid (x) is water, and the decompression chamber (A) is depressurized to 605 Pa or more and 101 kPa or less. Method. The decompression chamber (A) has a main decompression chamber (a) and preliminary decompression chambers (b ₁ ) and (b ₂ ) attached to its entry side and exit side, respectively, and the metal band is less than atmospheric pressure. The method for producing a surface-treated metal band according to any one of claims 1 to 4 , wherein the main decompression chamber (a) is passed through both preliminary decompression chambers (b ₁ ) and (b ₂ ) decompressed. .. The surface-treated metal according to any one of claims 1 to 5 , wherein a roll coater is provided on the entrance side of the decompression chamber (A), and the surface treatment liquid (x) is applied to the surface of the metal strip by the roll coater. How to make an obi. A vibration damping device is provided at least one of the inside of the decompression chamber (A), the position immediately before the entrance side of the decompression chamber (A), and the position immediately after the exit side of the decompression chamber (A). The method for producing a surface-treated metal band according to any one of claims 1 to 6, wherein the vibration of the band is suppressed. A roll coater is provided on the entrance side of the decompression chamber (A), the surface treatment liquid (x) is applied to the surface of the metal band by the roll coater, and a preliminary decompression chamber (preliminary decompression chamber) is provided on the exit side of the main decompression chamber (a). b ₂ ) The method for manufacturing a surface-treated metal band according to claim 5 , wherein a vibration damping device is provided in the vibration damping device, and the vibration of the metal band is suppressed by the vibration damping device. A pair of upper and lower coating rolls constituting the roll coater guides the metal strip to be horizontally passed through the decompression chamber (A) by sending the metal strip toward the inlet of the decompression chamber (A) while restraining the metal strip. The method for producing a surface-treated metal band according to claim 6 or 8, wherein the surface-treated metal band is characterized by the above. The method for manufacturing a surface-treated metal band according to claim 7 or 8, wherein the vibration damping device is one or more selected from a suppression roll and a non-contact electromagnetic vibration damping device. The fifth or eighth aspect of claim 5 or 8, wherein an induction heating device is provided in a preliminary decompression chamber (b ₁ ) provided on the entrance side of the main decompression chamber (a), and the metal band is heated by the induction heating device . How to manufacture surface-treated metal strips. The surface-treated metal band according to any one of claims 1 to 11 , wherein the pressure in the decompression chamber (A) is controlled according to the temperature of the metal band when passing through the decompression chamber (A). Production method.

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