JPH08296052A - Production of coated chromate steel sheet having excellent appearance - Google Patents

Abstract

PURPOSE: To make the coating weight of chromate on a steel sheet uniform and to obtain the coated chromate steel sheet having excellent appearance by adequately controlling the shape of the steel sheet by utilizing a gap sensor at the time of forming chromate films on the surfaces of the perpendicularly rising steel sheet. CONSTITUTION: The cold rolled steel sheet 1 is pulled up in a perpendicular direction by a sink roll 4 and after the shape defect of the steel sheet 1 is corrected by a moving shift roll 5 and a stationary shift roll 6, a chromate liquid is injected from a chromate liquid discharge port 7 and is applied on the steel sheet surfaces at the time of chromating the surface of the cold rolled steel sheet. The coating weight of the chromate is controlled by the air ejected from slit nozzles 8 and thereafter, the chromate liquid is dried and baked by a drier 9. In such a case, the spacings between the slit nozzles 8 and the steel sheet 10 are measured by a gap sensor 10 disposed in the upper part of the slit nozzles 8 and, by this result, the steel sheet 10 is positioned and corrected to the center of the slit nozzle 8 by the moving shift roll 5, by which the coating weight of the chromate to be applied is made uniform and the coated chromate steel sheet having the excellent appearance is stably produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating chromate treatment method for a steel sheet, and more particularly to a method for producing a coated chromate steel sheet having an improved appearance by achieving uniform coating chromate adhesion amount. .

[0002]

2. Description of the Related Art A coating chromate treatment in which a treatment liquid containing chromic acid as a main component is applied to a steel sheet and dried to form a chromate film is an effective means for improving the corrosion resistance and coatability of cold-rolled steel sheet and plated steel sheet Is. In the coating chromate treatment, the squeeze roll method and the gas wiping method are generally used as a method for controlling the amount of the chromate film deposited, but the gas wiping method is advantageous in terms of processing under high-speed threading.

The coating chromate treatment method by the gas wiping method has been conventionally performed by the method shown in FIG. That is, the steel sheet 1 moves upward through the deflector roll 2 and the chromate treatment tank sink rolls 3 and 4, and the chromate liquid ejected from the chromate liquid discharge port 7 is applied thereto. The steel plate 1 moves further upward, and the amount of chromate attached is controlled by the air jetted from the slit nozzle 8. After that, the steel plate 1 passes through the dryer 9 and the chromate solution is dried and baked to form a chromate film. The amount of chromate adhered is controlled by the distance between the slit nozzle 8 and the steel plate 1 and the pressure of the air jetted from the slit nozzle 8.

[0004]

In the conventional coating chromate treatment method using the gas wiping method, the gap between the slit nozzle 8 and the steel plate 1 becomes non-uniform in the width direction depending on the shape of the steel plate, so that the slit nozzle 8 ejects the gas. Distribution of the generated air pressure, resulting in non-uniform adhesion,
In addition, there is a problem that a defective appearance is likely to occur. SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to provide a method for producing a coated chromated steel sheet having an excellent appearance by using a gap sensor to make the coating chromate adhesion amount uniform.

[0005]

The present invention achieves the above object and has the following features. That is, the steel plate 1 is moved upward via the deflector roll 2 and the chromate treatment tank sink rolls 3 and 4, and the movable shift roll 5, which is controlled by feedback from the gap sensor 10 disposed above the slit nozzle 8, After correcting the shape with the fixed shift roll 6, apply the chromate liquid ejected from the chromate liquid discharge port 7,
A method for producing a coated chromated steel sheet having an excellent appearance, characterized in that the amount of chromate adhered is controlled by air jetted from a slit nozzle 8.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an embodiment according to the present invention. The steel sheet 1 to be treated in the present invention is a cold-rolled steel sheet or a hot-rolled steel sheet, or Z formed by electroplating, hot dipping, vapor phase plating, chemical plating or the like using these as a base.
It is a plated steel sheet having a plating layer such as n plating, Zn alloy plating, and Al plating.

The steel sheet 1 moves upward through the deflector roll 2 and the sink rolls 3 and 4 in the chromate treatment tank, and the movable shift roll 5 and the fixed shift roll 6 correct the defective shape of the steel sheet 1. The movable shift roll 5 is
It is controlled by feedback from the gap sensor 10 which measures the shape of the steel sheet. After that, the chromate solution ejected from the chromate solution discharge port 7 is applied to the steel plate 1, wiped by the air ejected from the slit nozzle 8, and the amount of chromate solution film is adjusted so that a predetermined amount of chromate film is obtained after drying. To be done. Then, after passing through the drier 9, the chromate solution on the surface of the steel sheet is dried and baked to form a chromate film.

The gap sensor 10 is a slit nozzle 8
The gap between the slit nozzle 8 and the steel plate 1 is arranged at the upper portion and is measured. The shape of the steel plate 1 is recognized from the measurement result, and the amount of pushing is automatically adjusted by feeding back to the movable shift roll 5 so that the steel plate becomes flat. The shape of the steel plate is corrected by pushing the movable shift roll 5 toward the steel plate side, and the fixed shift roll 6 restores the position of the steel plate to the center position.

In order to exert the effects of the present invention in a wide range of conditions, the movable shift roll 5 is pushed into the steel sheet side at a maximum of 100 mm, and the distance between the centers of the movable shift roll 5 and the fixed shift roll 6 is 100 to 100 mm. 500 mm, the distance between the center of the movable shift roll 5 and the slit nozzle 8 is 1500 mm
Hereinafter, it is desirable that the distance between the centers of the slit nozzle 8 and the gap sensor 10 be 300 mm or less. By doing so, the moving speed of the steel sheet is 10 to 300 m / min,
The present invention can be applied under a wide range of conditions such as a plate thickness of 0.3 to 2.5 mm and a plate width of 600 to 2100 mm.

The chromate treatment liquid applicable to the present invention contains, as a main component, chromic acid and, if necessary, one part thereof is reduced, and silica, phosphoric acid, a fluorine compound, a water-soluble resin, and a surfactant are used. An aqueous solution containing the above can be used.

FIG. 2 shows the relationship between the chromate adhesion amount difference and the chromate appearance when the movable shift roll is used by the feedback of the gap sensor, when the movable shift roll is manually used, and when the movable shift roll is not used. It is the figure shown. The steel plate material, size, and plate passing speed are random, and the processing conditions are as follows. Chromate treatment liquid: Chromic acid 10 g / l Silica 3
0 g / l Chromate adhesion amount: Aim for 50 mg / m ² as Cr Further, the evaluation method is as follows. Chromate adhesion amount difference: Maximum and minimum difference when measuring 5 points at equal intervals in the width direction Chromate appearance: Visual inspection, 5 grades (the larger the number, the better the appearance)

Table 1 is a table in which 50 samples of the chromate adhesion difference and the chromate appearance were measured at random under the same conditions as in FIG.

[Table 1]

It can be seen from FIG. 2 and Table 1 that the smaller the chromate adhesion difference, the better the chromate appearance, and that pushing the movable shift roll 5 improves the chromate appearance. Further, it can be seen that the movable shift roll control by feedback from the gap sensor has a better chromate appearance and is more stable than the manual movable shift roll control. This is because the control by feedback from the gap sensor can increase or decrease the pushing amount of the shift rolls successively as compared with the manual operation.

[0014]

INDUSTRIAL APPLICABILITY As described above, it is possible to make uniform the amount of chromate adhered by the coating chromate treatment method of the present invention and to produce a chromate-treated steel sheet having an excellent appearance.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a chromate adhesion amount difference and a chromate appearance.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Steel Plate 2 Deflector Roll 3,4 Sink Roll 5 Movable Shift Roll 6 Fixed Shift Roll 7 Chromate Liquid Discharge Port 8 Slit Nozzle 9 Dryer 10 Gap Sensor

Claims (1)

[Claims] 1. A movable shift controlled by feedback from a gap sensor 10 arranged above a slit nozzle 8 by moving a steel plate 1 upward through a deflector roll 2 and sink rolls 3 and 4 in a chromate treatment tank. After the shape is corrected by the roll 5 and the fixed shift roll 6, the chromate solution ejected from the chromate solution discharge port 7 is applied, and the amount of chromate adhered is controlled by the air ejected from the slit nozzle 8. Manufacturing method of coated chromated steel sheet with excellent appearance.