KR100929485B1 - Alloying hot dip galvanized steel sheet manufacturing equipment - Google Patents

Abstract

The present invention relates to an alloying hot dip galvanized steel sheet manufacturing apparatus,

An air knife is provided to control the plating amount of the steel sheet passing through the galvanizing bath, a heat treatment furnace for alloying treatment is provided on the upper portion thereof, and an alloyed hot dip galvanized plate provided with a sealing box for maintaining a non-oxidizing atmosphere during alloying. In the steel sheet manufacturing apparatus, an exhaust hood 9 for ash removal is provided at the lower portion of the air knife 5 in the sealing box 8, and a metal pump for removing ash existing on the surface of the galvanizing bath 3 is provided. 10) is installed,

When manufacturing alloyed hot-dip galvanized steel sheet, it prevents contamination of the inside of the sealing box and effectively controls the air knife in the sealing box, thereby preventing the occurrence of defects of the plated steel sheet, thereby making the alloyed hot-dip galvanized steel sheet with beautiful surface appearance. to provide.

Alloying, hot dip galvanizing

Description

Alloying hot dip galvanized steel sheet manufacturing apparatus {Manufacturing apparatus to produce galvannealing sheet steels}

1 is a configuration diagram showing an example of a conventional hot dip galvanizing process,

Figure 2 is a block diagram showing a hot dip galvanizing process according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

1: steel plate 2: snout

3: galvanized bath 4: sink roll

5: air knife 6: induction furnace

7: electric furnace 8: sealing box

9: exhaust hood 10: metal pump

11: observation window 12: top roll

The present invention relates to an apparatus for producing an alloyed hot-dip galvanized steel sheet, and more particularly, to discharge evaporation of zinc generated when maintaining the atmosphere during the alloying in a reducing atmosphere such as nitrogen-hydrogen, and to check the state of the air knife. The present invention relates to an apparatus for producing an alloyed hot-dip galvanized steel sheet, which provides an alloyed hot-dip galvanized steel sheet having excellent workability and excellent surface appearance by providing an observation window.

The alloyed hot-dip galvanized steel sheet is heated through the hot-dip zinc bath in a continuous hot dip plating process, and the plated layer is heated in an alloy heat treatment furnace installed directly on top of the hot-dip zinc bath before the zinc-coated layer on the surface is completely solidified. It is prepared by rapid cooling in an air cooling stand.

The plating layer of the alloyed hot-dip galvanized steel sheet has an iron content of about 10 to 12%, depending on the iron content, zeta phase (ζ, FeZn13), delta phase (δ, FeZn7), and capital gamma phase (Γ, Fe3Zn10). It is comprised, and workability and paintability vary greatly with these composition ratios.

In particular, the presence of the capital gamma phase is preferably suppressed as much as it causes powdering during molding.

In general, when manufacturing a hot-dip galvanized steel sheet, 0.14 to 0.2 wt% of aluminum is included in the plating bath, and a ternary alloy of iron-aluminum-zinc is present at the interface between the base iron and the plating layer to improve adhesion. .

However, in the production of alloyed hot-dip galvanized steel sheet, aluminum in the plating bath is managed to 0.14 wt% or less for smooth alloying reaction of zinc and iron.

The alloyed hot-dip galvanized steel sheet thus manufactured is widely used in automobiles, home appliances, etc. because the weldability and corrosion resistance after coating is superior to the galvanized steel sheet, and in recent years, demand for automotive exterior plates is increasing. In particular, strict surface quality is required for application to automotive exteriors.

The plating layer formation of the alloyed hot-dip galvanized steel sheet is first formed of zinc-iron intermetallic compound as zinc particles attached to the base iron are re-dissolved during the alloying process, and then the iron particles of the base iron diffuse into the zinc plating layer. To form.

However, since the zinc plating layer passing through the plating bath forms a thin oxide film by combining with atmospheric oxygen in the surface layer, the oxide coating layer does not dissolve and remains solid when the zinc plating layer is re-dissolved during the alloying process. As a result, the flow of re-dissolved zinc is not smooth.

That is, the zinc oxide layer of the surface layer hinders the flow of the molten zinc, and finally, when the alloying process is completed, the zinc oxide layer solidifies in a rough state and the surface appearance is not beautiful.

In Korean Patent Laid-Open Publication No. 2001-0058261 (published on July 05, 2001), in order to improve this point, a sealing box is installed until the alloying is completed in the plating bath, and nitrogen is introduced into the sealing box. A technique for maintaining the atmosphere in a non-oxidizing atmosphere has been proposed.

According to this technique, since no oxide film is formed on the surface layer, a hot-dip galvanized steel sheet having excellent surface appearance can be produced.

1 is a configuration diagram showing an example of a conventional hot dip galvanizing process.

When the steel sheet 1 enters into the galvanizing bath 3, the direction is turned upward by the sink roll 4, and the plating amount is controlled by the air knife 5.

The steel sheet (1) exiting the galvanizing bath (3) is alloyed through the induction furnace (6) and the electric furnace (7), after a slight cooling in the atmosphere, the direction is changed by the top roll (12) The alloying reaction is complete.

During alloying, the atmosphere is blocked from the outside by the sealing box 8, and the nitrogen is introduced by the air knife 5 to maintain the non-oxidizing atmosphere.

However, in this method, since the sealing box is installed from the plating bath to the alloying furnace and the inside is kept in a non-oxidizing atmosphere by introducing nitrogen, zinc has a problem that ash is generated very seriously.

These ashes have a problem of degrading workability by adhering to the air knife or the sealing box, and since the air knife is located inside the sealing box, an operator cannot grasp the state of the air knife.

In order to prevent evaporation of zinc, US Patent No. 4,557,952 proposed a method of preventing evaporation of zinc by adding 1-3 vol% of water vapor into the sealing box.

However, this technique has the disadvantage of impairing the fluidity of zinc because an oxide film is formed on the surface of the galvanizing bath, and since the air knife is also present inside the sealing box, the operator does not know the air knife condition accurately. there was.

The present invention is to solve the above problems, to discharge the evaporation of zinc generated when maintaining the atmosphere in a reducing atmosphere such as nitrogen-hydrogen during alloying, and the observation window so that the operator can check the state of the air knife It is an object of the present invention to provide an apparatus for producing an alloyed hot dip galvanized steel sheet which provides an alloyed hot dip galvanized steel sheet having excellent workability and excellent surface appearance.

In order to achieve the above object, the present invention is provided with an air knife for adjusting the plating amount of the steel sheet passed through the galvanizing bath, a heat treatment furnace for alloying treatment is provided on the upper portion, non-oxidizing atmosphere during alloying In the apparatus for producing alloyed hot-dip galvanized steel sheet provided with a sealing box for holding, an exhaust hood (9) for removing ash is provided in the lower portion of the air knife (5) in the sealing box (8), and a galvanizing bath (3). A metal pump 10 for removing ash present on the surface is installed.

More preferably, the present invention is characterized in that the observation window 11 for identifying the state of the air knife 5 is formed on at least one side of the sealing box (8).

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a block diagram showing a hot dip galvanizing process according to an embodiment of the present invention.

The hot-dip galvanized steel sheet manufacturing apparatus of this embodiment is provided with an air knife 5 for adjusting the plating amount of the steel sheet 1 passed through the galvanized bath 3, and a heat treatment furnace 6 for alloying treatment thereon. (7) is provided, and the basic structure is provided with a sealing box (8) in which nitrogen is added to maintain a non-oxidizing atmosphere during alloying is common to the conventional apparatus.

In addition to the basic structure, an exhaust hood 9 is installed at the lower end of the air knife to prevent ash from being generated by nitrogen emitted through the air knife 5, and contamination in the sealing box 8 due to evaporation of zinc. Will be prevented. The exhaust hood 9 is connected to the outside is installed so that the ash escapes.

In addition, since the ash present in the galvanizing bath 3 exits to the plating bath outside the sealing box 8 through the metal pump 10, the clean state is maintained in the sealing box 8. The metal pump 10 is a conventional one capable of pressurizing the molten metal.

Through this structure, contamination of the sealing box 8 generated by the ash is prevented, and defects in the plated steel sheet generated by the inflow of the ash can be suppressed.

In addition, since the state of the air knife 5 can be known through the observation window 11, the position, the angle of the air knife 5, the distance to the steel plate, and the like can be visually checked and controlled in real time.

The material of the observation window 11 is preferably a material such as quartz in consideration of a high temperature working environment.

<Example>

The alloyed hot-dip galvanized steel sheet was prepared while maintaining a reducing atmosphere by controlling the concentration of hydrogen and nitrogen when the hot-dip galvanized steel sheet was alloyed.

For the alloyed specimens as described above, the surface appearance, the degree of contamination in the sealing box, the paintability, the degree of air knife control and the like were evaluated and the results are shown in Table 1.

The coating amount was 45 to 60 g / m 2, the alloying time was 20 seconds, and the Fe content in the plating layer was 9 to 12%.

Test method for the surface appearance in Table 1 measured the visual and surface roughness. Surface roughness was measured based on Ra, and Wca value, which is a criterion for evaluating screening, was measured. The degree of contamination in the sealing box was visually evaluated and measured in the order of good, normal and poor.

division Atmosphere in the sealing box (Vol%) Sealing box contamination level (24 hours) Ash defect Surface appearance Ra (μm) Wca (μm) Remarks nitrogen Hydrogen Foot honor One 100 0 ◎ ◎ ◎ 0.82 0.41 Air knife status check 2 98 2 ◎ ◎ ◎ 0.80 0.40 3 96 4 ◎ ◎ ◎ 0.78 0.38 4 94 6 ◎ ◎ ◎ 0.78 0.38 5 90 10 ◎ ◎ ◎ 0.76 0.36 6 85 15 ◎ ◎ ◎ 0.75 0.35 7 80 20 △ ◎ ◎ 0.71 0.33 Existing example A 100 0 △ △ ◎ 0.81 0.40 Air knife status check impossible B 98 2 X △ ◎ 0.81 0.40 C 96 4 X △ ◎ 0.79 0.39 D 94 6 X △ ◎ 0.78 0.38 E 90 10 X X ◎ 0.75 0.36 F 85 15 X X ◎ 0.74 0.34 G 80 20 X X ◎ 0.71 0.32

As shown in Table 1, the surface appearance of both the existing examples (A-G) and the inventive examples (1-7) were all good because they were alloyed in a non-oxidizing and reducing atmosphere, and the roughness indexes Ra and Wca were similar.

However, ash defects are defects caused by evaporation of zinc, and when zinc is evaporated in a reducing or non-oxidizing atmosphere and adhered to the surrounding structure, it is sucked into the steel sheet to be introduced when it is dropped into the plating bath in a large sized state. In the case of Inventive Example (1-7), such ash defects did not occur, but in the case of the existing example, the hydrogen concentration was normal up to 6 vol%, but a large amount occurred when the volatility increased by 10 vol% or more.

In addition, when the pollution degree in the sealing box is operated for 24 hours, in the present invention, the contamination hardly occurs and the inside of the sealing box was kept very clean. However, in the existing case, severe sealing box contamination occurred when the hydrogen concentration was increased, and lip clogging of the air knife was also observed.

In the conventional case, since the sealing box surrounds the air knife, it is difficult to control the plating amount and it is difficult to control the distance and position of the air knife.

The present invention described above can be embodied in many different forms without departing from the spirit or main features thereof. Therefore, the above embodiments are merely examples in all respects and should not be construed as limiting.

As described above, the present invention, when manufacturing the alloyed hot-dip galvanized steel sheet to prevent contamination of the inside of the sealing box, and to effectively control the air knife in the sealing box. Accordingly, since the occurrence of defects in the plated steel sheet is prevented, an alloyed hot dip galvanized steel sheet having a beautiful surface appearance is provided.

Claims (2)

An air knife is provided to control the plating amount of the steel sheet passing through the galvanizing bath, and a heat treatment furnace for alloying is provided on the upper portion thereof, and a seal in which nitrogen is added to maintain a non-oxidizing atmosphere in the alloying process of the steel sheet. In the box-equipped hot-dip galvanized steel sheet manufacturing apparatus, An exhaust hood 9 for ash removal is installed at the lower portion of the air knife 5 in the sealing box 8, and a metal pump 10 for removing ash existing on the surface of the galvanizing bath 3 is installed. Alloying hot dip galvanized steel sheet manufacturing apparatus. The method of claim 1, Apparatus for producing an alloyed hot-dip galvanized steel sheet, characterized in that the observation window (11) for identifying the state of the air knife (5) is formed on at least one side of the sealing box (8).

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