KR20190076754A - Method for manufacturing hot dip aluminum plated steel sheet - Google Patents

Abstract

Provided is a method for manufacturing a hot dip aluminum plated steel sheet, comprising the following steps of: forming a first hot dip aluminum plated layer on a surface of a steel strip by allowing the steel strip to pass through a first hot dip aluminum plating bath; cooling the hot dip aluminum plated steel sheet on which the plating layer is formed at temperature of 400-550°C; forming a second hot dip plated layer on a surface of the cooled hot dip aluminum plated steel sheet by allowing the cooled hot dip aluminum plated steel sheet to pass through a second hot dip plating bath; and cooling the hot dip plated steel sheet on which the plating layer is formed at temperature of 400°C or less.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a hot-dip galvanized steel sheet,

The present invention relates to a method of manufacturing an aluminum-plated steel sheet using two plating baths, and more particularly, to a method of manufacturing an aluminum-plated steel sheet using two plating baths, And a manufacturing method thereof.

Conventionally, a method of plating with zinc, a method of plating with aluminum, a method of plating with aluminum-zinc have been used.

Among them, the zinc plating method is classified into hot-dip galvanizing and electro-galvanizing according to the method, and the galvanized steel is excellent in corrosion resistance due to the sacrificial property of zinc. It is widely used in general industrial fields such as home appliances, interior and exterior materials for construction.

 However, under the corrosive environment, zinc is decomposed and destroyed by the sacrificial method, so that corrosion resistance is lost over time and the steel is not sufficiently protected. In addition, zinc has a melting point of 460 deg. C, which is relatively low in metals, and can not be used for parts requiring high temperature stability.

Next, an aluminum-plated steel material has been used as an alternative to overcome the above disadvantages of the zinc-plated steel material, and a dense passive film of aluminum oxide is formed on the surface of the plating layer to exhibit excellent corrosion resistance over a long period of time. ℃, it can be applied to heat-resistant parts such as automobile exhaust system and household electric heating equipment.

However, in the case of molten aluminum plating, since the maximum plating amount is not sufficient, there is a problem in that the corrosion resistance and the thermal conductivity are higher than that of the aluminum sheet material, so there is a restriction in replacing the aluminum sheet material.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method of manufacturing a molten aluminum-plated steel sheet capable of providing a sufficient plating amount by applying a double plating method.

According to an aspect of the present invention,

Passing the steel strip through a first molten aluminum plating bath to form a first molten aluminum plated layer on the surface thereof;

A step of cooling the molten aluminum plated steel sheet on which the plating layer is formed to a temperature range of 400 to 550 캜;

Passing the cooled molten aluminum plated steel sheet through a second molten plating bath to form a second molten plated layer on the surface thereof; And

And cooling the hot-dip coated steel sheet having the plated layer formed thereon to 400 DEG C or less.

The first molten aluminum plating bath may be composed of 7.0 to 12.0% of silicon, 0.1 to 2.0% of iron (Fe), and the balance aluminum (Al) in weight percent.

Wherein the second molten bath comprises a molten aluminum bath containing 7.0 to 12.0% of silicon (Si), 0.1 to 2.0% of iron (Fe), and the balance aluminum (Al) (Si), 0.1 to 2.0% of iron (Fe), 0.1 to 3.0% of aluminum (Al), 0.1 to 3.0% of magnesium (Mg) A molten zinc bath comprising; A molten aluminum-zinc plating bath containing 40.0 to 45.0% of zinc (Zn), 0.1 to 2.0% of silicon (Si), and the remainder aluminum (Al) can be used.

When the coated steel sheet obtained in the above-described manufacturing process is a molten aluminum-coated steel sheet, the coating amount is 20 to 600 g / m ² ; In the case of molten aluminum and hot-dip galvanized steel, the coating amount is 100 to 700 g / m ² ; In the case of molten aluminum and molten aluminum-zinc plated steel, the plating amount may be 50 to 600 g / m ² .

The present invention having the above-described constitution has an advantageous effect in manufacturing a molten aluminum-plated steel sheet which can increase the plating amount through double hot-dip plating in the process of manufacturing a hot-dip aluminum-coated steel sheet and further can impart properties to the plating layer .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of a double-molten aluminum plating apparatus according to an embodiment of the present invention; FIG.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of a double-molten aluminum plating apparatus according to an embodiment of the present invention; FIG.

The dual molten aluminum plating apparatus of the present invention roughly comprises a first molten aluminum plating bath 2, a second molten plating bath 5, a first cooling device 4, a second cooling device 7, (3), a second air knife (6), and a final cooling device (8). 1, reference numeral 1 denotes an annealing apparatus.

As shown in Fig. 1, a steel strip introduced from the annealing apparatus 1 and passed through the first molten aluminum plating bath 2 is passed through the first air knife 3 and the first cooling apparatus 4. The steel strip introduced from the first cooling device 4 passes through the second hot dip galvanizing bath 5 and then passes through the first air knife 6 and the second cooling device 7 to the final cooling device 8).

That is, the method for producing a molten aluminum-coated steel sheet according to the present invention comprises the steps of: passing a steel strip through a first molten aluminum plating bath to form a first molten aluminum plating layer on the surface thereof; A step of cooling the molten aluminum plated steel sheet on which the plating layer is formed to a temperature range of 400 to 550 캜; Passing the cooled molten aluminum plated steel sheet through a second molten plating bath to form a second molten plated layer on the surface thereof; And a step of cooling the hot-dip coated steel sheet having the plated layer formed thereon to 400 DEG C or less.

First, in the present invention, a steel strip is passed through a first molten aluminum plating bath to form a first molten aluminum plated layer on its surface. That is, the steel strip discharged from the annealing apparatus 1 is charged into the first molten aluminum plating bath 2 and passed therethrough to form a first molten aluminum plating layer on the surface thereof.

At this time, in the present invention, the first molten aluminum plating bath may be composed of 7.0 to 12.0% of silicon, 0.1 to 2.0% of iron (Fe), and aluminum (Al)

The steel sheet having the plated layer formed on its surface as described above can then control the amount of plating formed on the surface thereof while passing through the first air knife 3. Specifically, the first air knife 3 is a device for adjusting the amount of plating by spraying high-pressure air, whereby the plating amount can be adjusted to 10 to 300 g / m ² , and 600 g / m 2 ² plating is possible.

Next, in the present invention, the hot-dip coated steel sheet on which the plating layer is formed is cooled to a temperature range of 400 to 550 ° C.

That is, in the present invention, when the plating bath process is completed, the plated steel sheet is subjected to a cooling process in a cooling process section. At this time, the cooling is performed in the first cooling device 4, and any cooling device that can cool a normal steel sheet can be used as the cooling device.

In the first cooling device (Pre-Cooler) 4, it is preferable to cool to 400 to 550 ° C, which is a suitable temperature range for subsequent secondary hot-dip coating. At this time, it is preferable that the jetting pressure of the air cooling air is in the range of 500 to 1000 mmH2O. If the cooling air is blown too hard, it is preferable that the plating layer is hardened to prevent double plating, and if it is weakly blown, the primary melted aluminum melts in the second hot-dip plating step, so that the proper temperature is maintained.

In the present invention, the cooled molten aluminum-plated steel sheet is passed through a second molten-plating bath to form a second molten-plated layer on its surface.

That is, the steel plate having passed through the first cooling device 4 is charged into the second hot-dip galvanizing bath 5 and passed therethrough to form a first molten aluminum plated layer on its surface.

At this time, in the present invention, the second molten bath includes a molten aluminum bath containing 7.0 to 12.0% of silicon (Si), 0.1 to 2.0% of iron (Fe) and aluminum (Al) (Si), 0.1 to 2.0% of iron (Fe), 0.1 to 3.0% of aluminum (Al), 0.1 to 3.0% of magnesium (Mg) A molten zinc bath comprising; A molten aluminum-zinc plating bath containing 40.0 to 45.0% of zinc (Zn), 0.1 to 2.0% of silicon (Si), and the remainder aluminum (Al) can be used.

In the present invention, when the molten aluminum plating bath is used in the first molten aluminum plating bath 2 and the molten aluminum plating bath is used again in the second molten plating bath 5, Can be obtained.

When a molten aluminum plating bath is used in the first molten aluminum plating bath 2 and a molten zinc plating bath is used in the second molten plating bath 5, a molten aluminum galvanized steel sheet having molten aluminum and a molten zinc plated layer Can be obtained.

When a molten aluminum plating bath is used in the first molten aluminum plating bath 2 and a molten aluminum-zinc plating bath is used in the second molten plating bath 5, molten aluminum and molten aluminum having a molten aluminum- Aluminum and a molten aluminum-zinc plated steel sheet can be obtained.

When the plated steel sheet obtained in the above-described manufacturing process is a molten aluminum-plated steel sheet, the plating amount is 20 to 600 g / m ² ; In the case of molten aluminum and hot-dip galvanized steel, the coating amount is 100 to 700 g / m ² ; In the case of molten aluminum and molten aluminum-zinc plated steel, the plating amount may be 50 to 600 g / m ² .

Thereafter, the steel sheet having the plating layer formed on its surface as described above can control the plating amount formed on the surface of the steel sheet after passing through the second air knife 6. Specifically, the second air knife 6 is a device for adjusting the plating amount by injecting high-pressure air, thereby adjusting the plating amount to 10 to 300 g / m ^{2. When} the plating is performed at the maximum value, ² plating is possible.

Finally, in the present invention, the molten aluminum plated steel sheet on which the plating layer is formed is cooled to 400 캜 or lower.

That is, in the present invention, it is preferable that cooling is performed in a range of 400 ° C or less, which is difficult to cause re-melting of the surface of the plating layer in the second cooling device 7.

At this time, the jetting pressure of the air cooling air is preferably in the range of 1000-1600 mmH2O. If the cooling air is blown too hard, molten aluminum, which has a lower specific gravity than zinc, is easily damaged and leaves a crater-like mark on the surface. On the other hand, if the pressure of the cooling air is lowered too much, the hot heat that has cooled the plated steel sheet is not efficiently discharged, but stays around the steel plate, thereby deteriorating the cooling effect. Therefore, the air pressure of the cooling device in the present invention is preferably limited to 1000-1600 mmH2O.

The molten aluminum-plated steel sheet having completed the above-described cooling can then be produced through the final cooling device 8 to produce a molten aluminum-plated steel sheet having excellent adhesion between the steel sheet and the plated layer.

Hereinafter, the present invention will be described in detail by way of examples.

(Example)

After the annealing process in the continuous hot-dip plating line, a hot-dip coated steel sheet was prepared for each of the above-mentioned hot-dip coated steel sheets using a double plating apparatus.

At this time, a steel sheet having a thickness of 0.2 to 5.0 mm, a width of 500 to 1500 mm, a yield point of 60 kgf / mm ² or more, a tensile strength of 60 kgf / mm ² or more, and an elongation of 0.1 to 5.0% was used as the base steel sheet for the production of the hot- To prepare respective hot-dip coated steel sheets.

Thereafter, the plated and plated amount was formed on the hot-dip coated steel sheet using different conditions. In Inventive Example 1-1, Inventive Examples 1-2 and Inventive Examples 1-3, aluminum plating baths were used for the first and second molten bathtubs 2 and 5 respectively, In the first molten steel bath 2, the aluminum bath is used for the second molten bath bath 5 and the zinc bath is used for the first molten bath bath 2, while the aluminum bath is used for the first molten bath 2 and the second molten bath bath 5 An aluminum-zinc bath was used.

In the case of Example 1-1, the air amount of 800 mmH ₂ O was injected from the first cooling device 4 after the amount of plating was adjusted to 200 g / m ² by the first air knife 3, / m < ² > and then cooled through the cooling devices 7 and 8 to prepare a plated steel sheet.

Inventive example 1-2 was adjusted to a coating amount of 200 g / m ² in the first air knife 3 and then sprayed with air 800 mmH ₂ O in the first cooling device 4 and a coating amount 150 g / m ² and then cooled through cooling devices 7 and 8 to prepare a coated steel sheet.

Inventive Examples 1-3 were prepared by spraying the first air knife 3 with a plating amount of 250 g / m ² followed by air pressure of 900 mmH ₂ O in the first cooling device 4 and 200 g / m ² and then cooled through cooling devices 7 and 8 to prepare a coated steel sheet.

Inventive Example 2, the first air knife and then (3) adjusting the coating weight 200g / m ² in the first was pressure 800mmH ₂ O injected from the cooling apparatus 4, the second air in the knife (6) coating weight 100g / m ² And then cooled through the cooling devices 7 and 8 to prepare a coated steel sheet.

Example ₃ was adjusted to a coating amount of 200 g / m ² by the first air knife 3 and then an air pressure of 800 mm H ₂ O was injected from the first cooling device 4 and a coating amount of 150 g / m ² And then cooled through the cooling devices 7 and 8 to prepare a coated steel sheet.

The thus-prepared hot-dip coated steel sheet was subjected to a lock-forming test to evaluate the plating tightness, and the results are also shown in Table 1 below.

division Type of steel plate Plating amount (g / m 2) evaluation Inventory 1-1 Molten aluminum - Molten aluminum coated steel plate 240 ○ Inventory 1-2 Molten aluminum - Molten aluminum coated steel plate 350 ○ Inventory 1-3 Molten aluminum - Molten aluminum coated steel plate 550 ○ Inventory 2 Molten aluminum - Hot-dip galvanized steel sheet 300 ○ Inventory 3 Molten aluminum - Hot-dip galvanized steel sheet 350 ○

As shown in Table 1, all of the coated steel sheets produced by the double hot dip coating method of the present invention show excellent plating adhesion.

That is, it can be confirmed that the present invention can prepare a molten aluminum-plated steel sheet capable of controlling the amount of plating adhered upward through double hot-dip plating and capable of imparting properties to the plating layer.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. Of course it is possible. Therefore, the scope of the present invention should not be limited to the above-described embodiments but should be defined by the following claims as well as equivalents thereof.

1: annealing apparatus 2: first molten aluminum plating bath
3: first air knife 4: first cooling device
5: second hot dip bath 6: second air knife
7: Second cooling device 8: Final cooling device

Claims (4)

Passing the steel strip through a first molten aluminum plating bath to form a first molten aluminum plated layer on the surface thereof;
A step of cooling the molten aluminum plated steel sheet on which the plating layer is formed to a temperature range of 400 to 550 캜;
Passing the cooled molten aluminum plated steel sheet through a second molten plating bath to form a second molten plated layer on the surface thereof; And
And cooling the hot-dip coated steel sheet having the plated layer formed thereon to 400 DEG C or less.
The method according to claim 1, wherein the first molten aluminum plating bath is composed of 7.0 to 12.0% of silicon, 0.1 to 2.0% of iron (Fe) and aluminum (Al) A method for manufacturing an aluminum-plated steel sheet.
The method according to claim 1, wherein the second molten bath comprises a molten aluminum bath containing 7.0 to 12.0% of silicon (Si), 0.1 to 2.0% of iron (Fe) and aluminum (Al) (Si), 0.1 to 2.0% of iron (Fe), 0.1 to 3.0% of aluminum (Al), 0.1 to 3.0% of magnesium (Mg) A molten zinc bath comprising; Zinc-plated bath containing 40.0 to 45.0% of zinc (Zn), 0.1 to 2.0% of silicon (Si), and the remainder aluminum (Al), in terms of weight% A method for manufacturing a molten aluminum plated steel sheet.
The method according to claim 1, wherein when the coated steel sheet obtained in the above manufacturing process is a molten aluminum-coated steel sheet, the amount of coating is 20 to 600 g / m ² ; In the case of molten aluminum and hot-dip galvanized steel, the coating amount is 100 to 700 g / m ² ; And in the case of molten aluminum and molten aluminum-zinc plated steel sheet, the plated amount is 50 to 600 g / m ² .

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