JP2001079456A - Method and apparatus for producing designed precoat steel panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the uniformity of a pattern in the lateral direction of a steel panel by applying topcoating to a primary coating film formed by primary coating and curing treatment and subsequently adjusting the discharge height of a rotary atomizing sprayer to uniformly apply a design pattern to the steel panel in the lateral direction thereof before curing the coating films by the induction heating of the steel panel. SOLUTION: A steel panel 2 is coated with a primary coating material by a first coater 4 through a pretreatment apparatus 3 and the coated steel panel is cured in a first oven 5 to be coated with a topcoating material by a second coater 6. Subsequently, a rotary atomizing sprayer 7 having a coating material discharge part provided thereto in a liftable manner is arranged between the second coater 6 and a second oven 8 and the topcoating film and a pattern coating film are backed in the second oven 8 at the same time. The coating material discharge part may be arranged at any position between the second coater 6 and the second oven 8 if it is provided at the central part in the lateral direction of the steel panel but the height thereof is made possible to set arbitrarily. The movable range of the coating material discharge part in a height direction is not especially restricted but can be adjusted to the range of 30-200 cm from the surface of the steel panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a precoated steel sheet,
A method for producing a decorative pre-coated steel sheet (painted steel sheet) with a fine spot-like pattern by spraying a paint of a different color on the wet top coating so that the paint particles are dispersed. The present invention relates to a manufacturing apparatus suitable for use in a manufacturing method.

[0002]

2. Description of the Related Art Recently, housing exterior walls, interior materials,
Precoated steel sheets used for doors, roofs, and the like are required to have higher designability.
Conventionally, to manufacture steel sheets that meet these needs,
There were techniques such as laminating a printed film on a steel plate or printing directly on a steel plate. However, none of these methods has been practically used because the cost of the product is high or the pattern is too artificial. In recent years, pre-coated steel sheets with improved design have been used for these manufacturing technologies by spraying a paint of a different color from the paint on the top coat to form a fine spot-like pattern. It is getting.

In order to form such a spot-like pattern,
There is a method of manufacturing a pre-coated steel sheet, forming a sheet, and performing air spraying on another line. Further, in a continuous line of a two-coat two-bake process used for manufacturing a precoated steel sheet, a first coater for a base coat and a second coater for a top coat disposed downstream of a first oven (baking furnace). If an air spray device is installed between the second ovens, continuous production can be performed in-line. However, when applying patterns by air spraying in any process, the pattern size is not uniform and the design is inferior, and the spray width is narrow and multiple devices are required to spray over the entire width of steel plate (hereinafter including steel strip). There are drawbacks such as necessity.

Accordingly, as a technique for compensating for such a drawback caused by the air spray, recently, Japanese Patent Application Laid-Open No. 8-216331,
JP-A-9-290211, JP-A-11-612, JP-A-11-290
Japanese Patent Application Laid-Open No. 76934 and Japanese Patent Application Laid-Open No. 11-77895 have proposed a manufacturing technique using a rotary atomizing spray device. In each of these methods, a rotary atomizing spray device is installed between a second coater and a second oven in a continuous line, spray coating is performed before baking a top coat, and then both paints are baked at the same time. At this time, the size and distribution density of the pattern is affected by the number of revolutions of the paint discharger of the rotary atomizing spray device, the amount of paint discharge, the viscosity of the paint, etc.
In order to obtain a desired design property, it has been common practice to carry out spraying by appropriately combining these conditions. By the way, needless to say, how to design a pattern uniformly in the width direction of the steel sheet is required in the design steel sheet. The rotary atomizing spray device has a wider spray width than the air spray device, and a single rotary atomizing spray device can perform spray coating over the entire width of a steel sheet.

[0005]

However, in this rotary atomizing spray device, the fine particles of the paint, which generally scattered horizontally due to the centrifugal force from the paint discharge section (nozzle) rotated at a high speed, are easily affected by the air resistance. Therefore, the following problems occur. In other words, the larger the steel sheet width and the smaller the paint particle diameter, the more difficult it is for the paint to reach the steel sheet edge, so that the pattern is not formed. In the direction, it is difficult to form a uniform pattern. Further, in the second oven, a hot-air oven has been generally used conventionally, and since hot air of several tens of meters / second is blown onto the steel sheet surface, each spot should originally have a circular shape. There is also a problem that the pattern shape is disturbed, such as an oval shape or a linear shape, and in some cases, the linear patterns are overlapped with each other, so that the design property is greatly reduced.

Accordingly, the present invention is to solve the above-mentioned problems of the prior art when manufacturing a pre-coated steel sheet, and particularly to manufacture a pre-coated steel sheet having a base coat and a top coat formed thereon. It is an object of the present invention to propose a method for producing a designable precoated steel sheet capable of forming a uniform spot-like pattern in the width direction of the steel sheet in a continuous line of 2 coats and 2 bake, and a production apparatus used for this method. Another object of the present invention is to propose a manufacturing technique of a designable precoated steel sheet that does not disturb the pattern shape in the heating and baking step when manufacturing the precoated steel sheet.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made by sequentially forming a base coat, a top coat and a design coat on a steel sheet surface in a continuous line. In the method of manufacturing pre-coated steel sheet, a base coat is formed by base coating and curing treatment, after overcoating, and by adjusting the discharge height of the rotary atomizing spray device, the design pattern is uniform in the width direction of the steel sheet And then hardening these coating films by induction heating of the steel sheet.
In addition, the first coater, the first coater,
An oven, a second coater, and a second oven are arranged in this order, and in a two-coat, two-baked continuous precoated steel sheet manufacturing apparatus, the discharge position of the paint is directly above the center of the steel sheet in the width direction between the second coater and the second oven. The present invention provides an apparatus for producing a designable pre-coated steel sheet, characterized in that a rotary atomizing spray device that can be set to an arbitrary height is provided. Further, in this apparatus, it is preferable that the second oven is an induction heating furnace.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present invention provides a two-coat, two-bake continuous coating and baking line for producing a pre-coated steel sheet in order to form a spot-shaped pattern uniformly in the width direction of the steel sheet and enhance the design. In between, a rotary atomizing spray device that can adjust the height of the paint discharge section to an arbitrary height by being able to move up and down just above the center in the width direction of the steel plate is installed.

In general, a rotary atomizing spray device has a configuration in which fine particles of a paint which are ejected in a horizontal direction by a centrifugal force from a discharge portion (nozzle) of a paint rotating at a high speed are subjected to gravity and air resistance to form a parabolic shape on the steel sheet surface. To form a speckled pattern. In the conventional rotary atomizing spray device, the smaller the particle size of the paint particles, and the smaller the specific gravity of the same particle size, the shorter the flight distance in the width direction due to the influence of air resistance,
In addition, since the influence of the flow of the surrounding air is liable to occur, there is a problem that the density of the pattern becomes small at the edge portion of the steel sheet, and the pattern becomes uneven. In such a state, it is usually necessary to remove the non-uniform portion of the pattern at the edge of the steel plate, so that an increase in cost due to a decrease in yield cannot be avoided. Such a problem seems to be reduced by reducing the effect of air resistance by increasing the size of the large pattern, that is, by increasing the particle diameter of the paint. It is necessary to reduce the number, which means that the horizontal distance of the paint particles decreases, and the pattern uniform portion in the width direction of the steel sheet does not spread as expected.

As a result of intensive studies to solve these problems, the inventors have found that the uniformity of the pattern in the width direction has been reduced.
The fact that the height from the steel plate of the paint discharge section of the rotary atomizing spray device has a great effect, and when using a predetermined paint to obtain a pattern of a predetermined size, the uniform portion in the width direction becomes the maximum. It has been found that the height of the paint discharge section (nozzle) exists. In other words, in order to use various paints in the production line of pre-coated steel sheet and to form patterns of various particle sizes uniformly in the width direction of the steel sheet, the height of the paint discharge nozzle of the rotary atomizer should be It has been found that setting the optimum height according to the type is extremely effective.

FIG. 1 shows an apparatus for producing a precoated steel sheet by a two-coat two-bake process according to the present invention. In the continuous line shown in FIG. 1, the steel sheet 2 unwound from the uncoiler 1 passes through a pretreatment device 3 for a chemical conversion treatment provided as necessary, and is coated with a base paint by a first coater 4. The composition is cured in one oven, and the top coat is applied in the second coater 6. Next, the second coater 6 and the second coater
A rotary atomizing spray device 7 is provided between the ovens 8 so that the paint discharge section can be raised and lowered, and the top coat and the patterned coating film are simultaneously baked and cured in the second oven 8. The position of the paint discharger may be any position between the second coater and the second oven as long as it is the center in the width direction of the steel sheet, but it is essential that the height can be set arbitrarily. The movable range in the height direction is not particularly limited, but it is necessary that the movable range can be adjusted at least from 30 cm to 200 cm from the steel sheet surface. As long as the height adjustment method of the paint discharge part can be set to any height,
It may be automatic or any.

In order to obtain a precoated steel sheet having a higher design quality, it is necessary to install a plurality of rotary atomizing spray devices and discharge different paints. In such a case, all the paint discharge sections may be positioned at the center in the width direction of the steel sheet, and each paint discharge section may be independently set at an arbitrary height. When a plurality of nozzles are installed in the line running direction, it is desirable that the nozzles are separated from each other so that the discharged paint particles do not collide with each other, and in order to further reduce air resistance, a rotary atomizing spray device is used. It is desirable to cover the peripheral area until the paint discharged from the nozzle drops on the steel plate with a draft or the like. When a decorative precoated steel sheet is manufactured using the apparatus according to the present invention, a rotary atomizing spray that maximizes the uniformity in the width direction of the steel sheet in advance for each target pattern size and properties of the paint to be used is used. The height of the paint discharge portion of the apparatus may be determined in advance, and the height of the discharge nozzle may be set so as to meet the condition, and spraying may be performed.

[0013] A uniform design pattern can be formed by spray coating using the above-described method using a rotary atomizing spray device. However, in order to further improve the quality of precoated steel sheet products, it is necessary to use an oven. It is also necessary to suppress disturbance of the pattern of the pattern as much as possible. The inventors have found that if the second oven is an induction heating furnace, since hot air is not blown onto the steel sheet surface, individual spot-like patterns can be baked while maintaining their original circle without being disturbed. . As described above, by using the induction heating method for the second oven, it is possible to suppress the deterioration of the design property due to the collapse of the shape of the spot pattern such as in a hot blast stove. Therefore, in order to further exert the effects of the present invention and further enhance the design, the second
Preferably, the oven is an induction heating furnace.

[0014]

【Example】Invention Example 1  Pre-coated steel consisting of the two-coat two-bake process shown in FIG.
In the continuous line for plate manufacturing, the second coater and the second
Paint is discharged in the center of the moving direction of the oven and just above the center of the steel plate width.
The height of the part can be set at any position between 30cm and 200cm
A rotary atomizing spray device was provided. Width 1
After painting and baking on a steel sheet of m, finish coating
(Polyester white) and subsequently different from the top coat
Color paint (polyester black paint, viscosity: four
Cup No. 4 for 20 seconds) using a rotary atomizing spray device.
Sprayed. Then, the second oven (induction heating furnace)
Was baked. The spray condition is: discharge amount = 20
0 ml / min and the number of rotations = 1000 rpm. Ma
In addition, the height of the paint discharge section was previously set at 50, 75,
100, 125cm, and change the pattern in the width direction
The height at which the uniform part is widened is determined, and the optimum conditions
Produced a precoated steel sheet with design. The appearance of this steel plate
Investigate pattern uniformity, pattern shape and pattern size.
Was.Invention Examples 2 and 3  Let the number of rotations of the nozzle be 2000 rpm and 4000 rpm
And gradually reduce the size of the handle,
A steel sheet was manufactured in the same manner as in Example 1.

[0015]Comparative Examples 1 and 2  Time when the height of the nozzle was fixed at 60 cm outside the appropriate range
Paint with a spray atomizer and other conditions
Steel sheets were manufactured in the same manner as in Invention Examples 1 and 2, respectively.Comparative Example 3  Time when the height of the nozzle was fixed at 60 cm outside the appropriate range
Paint with a spray atomizer and
Steel plate under the same conditions as in Invention example 3 except that
Was manufactured.

The results are shown in Table 1 together with the manufacturing conditions. From Table 1, in the invention example, the height of the paint discharge portion was set so that the uniform portion of the pattern in the width direction of the steel sheet became the largest, so that a uniform pattern could be formed over the entire width of the steel sheet. In addition, since the second oven was an induction heating furnace, the shape of the handle was circular and good. On the other hand, in the comparative example in which the height of the paint discharge portion was out of the appropriate range, the width of the steel plate having a uniform pattern was limited to 80 to 90. And the second
The pattern shape of Comparative Example 3 in which the oven was a hot blast stove was disturbed by hot air and became an ellipse or a line, which was defective.

[0017]

[Table 1]

[0018]

As described above, according to the present invention,
Since the height of the discharge part (nozzle) of the rotary atomizing spray device can be set arbitrarily, the size of the design pattern,
By optimizing the height in accordance with the viscosity of the design paint, a design-precoated steel sheet having improved pattern uniformity in the width direction of the steel sheet can be manufactured. In addition, by using the second oven as an induction heating furnace, a precoated steel sheet with further improved design can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an apparatus for manufacturing a pre-coated steel sheet provided with a rotary atomizing spray apparatus refining apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Uncoiler 2 Steel plate 3 Pretreatment apparatus 4 1st coater 5 1st oven 6 2nd coater 7 Rotary atomizing spray device 8 2nd oven

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D073 AA01 BB03 CA15 CB12 4D075 AA08 AE06 BB35Z CB36 DA06 DB03 DC02 EA05 4F034 BA21 CA02 CA22

Claims (3)

[Claims] 1. A method for manufacturing a designable precoated steel sheet by sequentially forming a base coat, a top coat and a design coat on the steel sheet surface in a continuous line, wherein the base coat is formed by base coat and curing treatment. After top coating, the design pattern is uniformly painted in the width direction of the steel sheet by adjusting the discharge height of the rotary atomizing spray device, and then these coating films are cured by induction heating of the steel sheet. And
A method for producing colored steel sheets with decorative design. 2. A two-coat, two-baked continuous precoated steel sheet manufacturing apparatus in which a first coater, a first oven, a second coater, and a second oven are arranged in this order.
A rotary atomizing spray device capable of setting a paint discharge position to an arbitrary height immediately above the center in the width direction of the steel sheet, between the coater and the second oven; . 3. The apparatus for producing a decorative precoated steel sheet according to claim 2, wherein the second oven is an induction heating furnace.