JPH01279769A - Method for continuously plating metallic sheet - Google Patents

Abstract

PURPOSE:To continuously plate a metallic sheet in a uniform plating amt. by bringing a plating metal into contact with the moving sheet heated at a specified temp. to melt the metal, and continuously measuring the sheet temp. to hold the sheet at a constant temp. CONSTITUTION:A band steel 1 heated to a temp. higher than the m.p. of a plating metal is moved in direction of the arrow, and a plating metal 2 is brought into contact with the surface. As a result, the metal 2 is melted, the formed molten metal 3 is deposited as a film 4, and the metal 2 is continuously supplied to the band steel 1. In the plating method for the band steel 1, the temp. of the band steel 1 immediately before being plated is continuously measured, and the band steel is held at a constant temp. By this method, the variance in the plating amt. can be effectively controlled, and the uniform plating film 4 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for continuously plating the surface of a metal plate without using a molten metal bath.

[Conventional technology]

Conventionally, as a method of forming a plating film on the surface of a copper strip,
Hot-dip plating is a widely used method in which a steel strip is immersed in pre-molten plated metal.

In continuous hot-dip galvanizing, which is a typical example of this type of plating method, the steel strip is heat-treated and surface-cleaned in a pre-treatment furnace, and then immersed in a hot-dip zinc bath to form a plating film.
The copper strip pulled out of the bath is subjected to plating deposition amount adjustment using gas aperture, and surface conditioning such as galvanealing.

The hot-dip plated steel sheet thus obtained has a relatively beautiful surface and excellent corrosion resistance, so it is widely used in practical applications.

However, conventional hot dip galvanizing methods have various problems associated with the use of plating baths. Particularly recently, plated steel strips are required to have a more uniform, smooth, and beautiful surface than ever before, mainly for use in home appliances, automobile exterior panels, etc. There is also a high demand for new products such as, and as a result, problems with the quality of plated steel strips and the plating process itself using conventional hot-dip plating methods have become apparent. Some of such problems are discussed below.

1) Fe from the surface of the steel strip is eluted during the plating bath, and so-called dross is often generated due to the oxidation of the plating metal, and this must be pumped up and removed. A loss of plated metal occurs.

2) Impurities tend to get mixed into the plating bath, such as dross being generated in the plating bath and debris from the bricks that make up the pot getting mixed into the bath, which adhere to the copper strip and deteriorate its appearance.

3) Since the components of the plating metal ingot put into the bath are different from the trace elements in the components that adhere to the steel strip and the components that are discharged outside the bath as by-products such as dross, the necessary elements are contained as per the target. It is difficult to adjust and control the plating bath components.

As a result, various plating defects occur, such as poor plating adhesion and poor alloying of the galvanic material.

4) It is necessary to immerse steel mechanical parts such as rolls for passing the steel strip, roll support arms, bearings, etc. into a high temperature, highly corrosive plating metal bath.

This causes problems such as erosion of these members, generation of dross accompanying this, and deterioration of the appearance of the plating surface due to erosion of the surface of the roll in the bath.

Furthermore, operation downtime is required to periodically repair or replace eroded or damaged parts of these mechanical parts, making it impossible to effectively and maximally utilize the production capacity of the equipment.

5) By using a passing roll in the plating bath, the group grooves of the roll are likely to be transferred to the plating surface, resulting in deterioration of the appearance.

6) Discharge of bottom dross that accumulates at the bottom of the tower, top dross that accumulates on the bath surface, initial threading of steel strip into the bath, maintenance of rolls in the plating bath, etc. at high temperatures and in large quantities. Working near the plating bath places a heavy burden on the worker and is dangerous.

7) Pot - Since only one type of plating can be done per group,
When performing various types of dissimilar plating, it is necessary to carry out routine practice by pumping out a bath, or to prepare in advance a pot in which dissimilar plating metals are melted, and to move the pot.

8) When producing double-sided plated materials and single-sided plated materials in a single facility, it is necessary to change the plating equipment for the pot section, which requires a lot of time and effort in addition to the equipment burden. .

9) It is difficult to perform special plating such as double-sided dissimilar plating, multilayer plating, and double-sided differential thickness plating.

As described above, conventional hot-dip plating methods have various problems.

In contrast to such conventional hot-dip plating methods, the present inventors have devised a new plating method that can solve all of the above-mentioned problems.

As shown in Fig. 1, this method involves melting a plated metal material (2) by bringing it into contact with a moving steel strip (1) that is heated to a temperature higher than the melting point of the plated metal. By continuously supplying 2) to the steel strip (1), the molten plated metal (3) is continuously deposited as a plating film (4) on the surface of the moving steel strip. It is. Further, in this method, in order to ensure melting of the plated metal material (2), the plated metal material (2) can be preheated by a preheating device (5) as shown in FIG.

In this plating method, plating metal material of the same phase is fed toward the steel strip, and the sensible heat of the steel strip melts it on the surface of the steel strip by the amount of plating area, and this molten metal is deposited as plating metal. Since it does not require a molten metal bath at all, it can solve the conventional problems associated with the use of a plating bath at once.Moreover, by controlling the feeding speed of the solid plated metal material, it is possible to reduce the amount of plating deposited. Control can also be performed with high precision.

[Problem to be solved by the invention]

However, according to studies conducted by the present inventors, it has been found that such a plating method has a problem of variations in the amount of plating deposited due to fluctuations in the temperature of the steel strip. To explain this based on the schematic diagram in Figure 5, in the single plating method,
A molten layer (3) of plating metal exists between the plating metal material (2) and the copper strip (1), and this molten layer (3) is necessary to stably obtain the thickness of the plating film (4). ) must be maintained at a certain appropriate thickness. However, the interface B between the solid phase and the liquid phase of the plated metal changes its position depending on the penetration temperature of the steel strip to be plated, and as the plate temperature increases, it moves from the position of the solid line in the figure to the position of the upper broken line. Further, this interface becomes higher on the downstream side of the line, and the molten layer (3) becomes thicker. When the plate temperature increases, this molten layer (3) becomes thicker and the shape of the liquid phase becomes unstable, which causes the amount of plating to change over time. On the other hand, if the penetration temperature of the steel plate is too low, the plated metal will not be melted enough to ensure the desired thickness of the plated film, and in extreme cases, the plated metal will become unplated.

In conventional continuous hot-dip galvanizing, the temperature of the copper strip typically fluctuates by about 30°C around 460°C. If this occurs, the plating amount is 20
g/n? This results in variations in diameter.

[Means to solve the problem]

The present invention was created in view of these problems, and its characteristics include: melting a plated metal material by bringing it into contact with a moving metal plate that is heated to a temperature higher than the melting point of the plated metal; By continuously supplying the plated metal material to the metal plate, the plate temperature of the metal plate immediately before plating can be continuously controlled while the molten plated metal is continuously deposited as a plating film on the surface of the moving metal plate. By controlling the steel strip temperature to a constant value in this way, variations in coating weight can be effectively suppressed. be able to.

FIG. 6 shows an investigation of the effect of variation in steel strip temperature on variation in plating amount in the plating method shown in FIG. 1, using zinc plating as an example.

By suppressing fluctuations in plate temperature and controlling it to a constant level,
Fluctuations in the amount of plating deposited can be made small.

In the present invention, in order to keep this plate temperature constant, the plate temperature is detected before plating, and the plate temperature is controlled based on this detected temperature. Generally, before plating, a steel strip is subjected to direct flame heating and reduction heating for the purpose of burning off surface oil and removing surface oxide film, etc., and is therefore in a heated state before plating. Therefore, gas cooling is normally performed to adjust the heated steel strip to a predetermined temperature. However, there are variations in the temperature obtained by temperature adjustment performed in this manner. Therefore, in the present invention, temperature control is further performed after the gas cooling. Specifically, a plate temperature adjustment furnace equipped with a heating and cooling mechanism is installed upstream of the plating equipment, and a plate temperature meter is installed just before the plating equipment, and the plate temperature adjustment furnace adjusts the temperature based on the detected value of the plate temperature meter. The copper strip is heated or cooled to keep the plate temperature constant.

It should be noted that the plating film formed by the plating method of the present invention may still have some unevenness in the amount of coating. processing can be performed. As this surface conditioning device, for example, an ultrasonic vibration type device (so-called ultrasonic iron) having an ultrasonic vibrator is used. This device is held by a ricinder device (not shown) having a buffer mechanism, and its diaphragm is brought into light contact with the surface of the steel strip on which the plating film is formed, and ultrasonic vibrations are applied to the plating film. , the thickness of the plating metal film is made uniform. Furthermore, in order to prevent uneven plating adhesion due to vibration of the copper strip, the steel strip (1) can be pinched by pinch rolls (7) upstream of the plating metal material supply section, as shown in FIG.

As a means (pinch means) for preventing uneven adhesion due to vibration of the steel strip, not only the above-mentioned pinch roll but also an air action method, an electromagnetic force method, or other appropriate means can be used.

Furthermore, in the present invention, it is also possible to run the steel strip (1) in a direction other than the horizontal direction; for example, the steel strip (1) may be run in a vertical direction.

In the case of this vertical line, the running direction may be either up or down. Further, the present invention can be applied to both double-sided and single-sided plating methods.

The present invention as described above can be applied to various metal platings or alloy platings (for example, Zn plating, Zn-Al1 alloy plating, etc.).

〔Example〕

Figure 7 shows an example in which the present invention is applied to continuous hot-dip galvanizing of steel strips, and (8) shows that oil and dirt on the steel strips are burned off and the copper strips are heated to a predetermined temperature. (9) is a reduction furnace that reduces the oxide film on the surface of the steel strip in a reducing atmosphere and performs annealing; (10) is a cooling furnace that cools the copper strip according to a predetermined heat cycle; (11) )
is a plate temperature adjustment furnace for controlling the temperature of the copper strip at a constant level.

(12) is a plate thermometer (usually a radiation thermometer), and (13) is a plating device.

The steel strip (1) passes through a direct-fired heating furnace (8) and a reduction furnace (9), and then is heated to approximately the temperature for plating (for example, 46°C) in a cooling furnace (10).
The plate is cooled down to a temperature of around 0° C.), then finally adjusted to a constant temperature in a plate temperature adjustment furnace (11), and then sent to a plating device (13). Then, the plate temperature immediately before plating is detected by the plate thermometer (12), and the steel strip is heated or cooled in the plate temperature adjustment furnace (11) so that the detected value becomes constant.

FIG. 8 shows an example of the internal mechanism of the plate temperature adjustment furnace (11), and (14) is a cooling device equipped with a slit nozzle (16) for injecting cooling gas (for example, N2 gas). , (15) is a heating device (heater), and these devices are used depending on the plate temperature of the copper strip.

Moreover, FIG. 9 shows the plating situation in the plating apparatus (13), in which the plating metal material (2) is fed to the surface of the steel strip by the feed rollers (17) on both sides of the copper strip, and plating is performed. Note that such double-sided plating does not necessarily have to be performed at the same position in the line direction as shown in the figure, but can be performed at different positions in the line direction on each side.

〔Effect of the invention〕

According to the present invention described above, solid plated metal material is melted by the plating area weight on the surface of the copper strip by the sensible heat of the metal plate passing through it, and this is attached to the metal plate as a plating film. Hot-dip metal plating of metal sheets can be carried out without the need for any baths, eliminating all the conventional problems caused by the use of molten metal baths, and reducing the feed rate of solid plated metal materials. Through control, the amount of plating deposited can also be controlled with high precision. In addition, by controlling the plate temperature to a constant value, it is possible to uniformly form the plating film without changing the amount of the plating film deposited.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams schematically showing the principle of the plating method that is the basis of the present invention. FIG. 3 is an explanatory diagram showing a case where a surface conditioning device is provided in the method of the present invention, and FIG. 4 is an explanatory diagram showing a case where a pinch roll is provided on the upstream side. FIG. 5 is an explanatory diagram showing the state of formation of a molten layer by melting the plated metal material. FIG. 6 shows the influence of variations in steel strip temperature on variations in the amount of zinc plating deposited. FIG. 7 is an explanatory diagram showing one implementation situation of the present invention, FIG. 8 is an explanatory diagram showing the internal mechanism of the plate temperature adjustment furnace in FIG. 7, and FIG.
The figure is an explanatory view showing the plating situation in FIG. 7. In the figure, (1) is a steel strip, and (2) is a plated metal material. (3) is molten metal, (4) is plating film, (5) is preheating device, (6) is surface conditioning device, (11) is plate temperature adjustment furnace,
(12) is a plate thermometer, (13) is a plating device, (14)
(15) is a cooling device, and (15) is a heating device. Fig. 1 Copper strip traveling direction Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 7 Fig. 6 Variation in plate temperature (0C) Fig. 9

Claims (1)

[Claims] By bringing a plated metal material into contact with a moving metal plate that is heated to a temperature higher than the melting point of the plated metal, it is melted, and by continuously supplying the plated metal material to the metal plate, the molten plating is When continuously depositing metal as a plating film on the surface of a moving metal plate, the plate temperature of the metal plate immediately before plating is continuously measured and the plate temperature is controlled so that the plate temperature remains constant. A continuous plating method for metal plates characterized by: