KR20160058021A - Device for Hot-Dop Metal Coated Steel Sheet - Google Patents

Device for Hot-Dop Metal Coated Steel Sheet Download PDF

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KR20160058021A
KR20160058021A KR1020150156559A KR20150156559A KR20160058021A KR 20160058021 A KR20160058021 A KR 20160058021A KR 1020150156559 A KR1020150156559 A KR 1020150156559A KR 20150156559 A KR20150156559 A KR 20150156559A KR 20160058021 A KR20160058021 A KR 20160058021A
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South Korea
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steel sheet
nitrogen
coated steel
plating bath
gas discharge
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KR1020150156559A
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Korean (ko)
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문병선
임병문
송용근
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동국제강주식회사
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C23C2/18—Removing excess of molten coatings from elongated material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C23C2/18—Removing excess of molten coatings from elongated material
    • C23C2/20—Strips; Plates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

The present invention provides an apparatus for manufacturing a hot-dip metal coated steel sheet, allowing the lower end of an air knife to pass through a nitrogen curtain section easily suppressing oxidation to restrict oxide generated on the upper part of a plating bath and block absorption on the surface of a plating layer, thereby improving the quality of the exterior appearance of the surface. The apparatus for manufacturing a hot-dip metal coated steel sheet comprises a lower end gas discharge bar, a lateral surface cover and an upper end gas discharge bar. The lower end gas discharge bar is spaced from the surface of the plating bath at a predetermined distance and discharges nitrogen gas in the surface direction of the plating bath along the periphery of the coated steel sheet. The lateral cover is diagonally extended upward from the lateral surface of the lower end gas discharge bar in the direction of the hot-dip coated steel plate. The upper end gas discharge bar is formed on the upper end of the lateral surface cover and discharges nitrogen gas to the downside.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a device for manufacturing a hot-dip coated steel sheet having excellent corrosion resistance and surface quality,

The present invention relates to an apparatus for manufacturing a hot-dip coated steel sheet excellent in corrosion resistance and surface quality.

Hot-Dop Metal Coated Steel Sheet is widely used for securing corrosion resistance of base steel sheet. As a representative example, the galvanized steel sheet (GI) is widely used based on economy and abundant resources, and is one of the most commonly used coated steel sheets. In addition, 55% Al-Zn (aka Galvalume) aluminum-plated steel sheet was proposed in the late 1960s to improve the corrosion resistance of these galvanized steel sheets.

These aluminum-coated steel sheets are superior in corrosion resistance and heat resistance to zinc-coated steel sheets, and are thus widely applied to automobile mufflers, household appliances, and heat-resistant materials.

For example, an aluminum-coated steel sheet containing Ti in the iron of Japanese Unexamined Patent Publication No. 57-47861, an aluminum-coated steel sheet containing C, Si, Cu, Ni and a small amount of Cr in the steel of Japanese Patent Publication No. 63-184043.

In addition, 10% or less of Si is added to the aluminum plating bath to suppress the growth of the Fe - Al alloy layer due to the reaction of aluminum with iron and the rapid diffusion of aluminum metal into iron. Since the coated steel sheet produced by this method is relatively excellent in workability and heat resistance, it is widely used in heat-resisting parts such as a muffler of a car, a water heater, a radiator, and an inner end of an electric rice cooker.

However, the silicon added to suppress the formation of the alloy layer has a problem that the appearance of the surface of the coated steel sheet is disrupted, resulting in an unclear appearance. Such a damage of the surface appearance due to the addition of silicon causes a small amount of magnesium (US Patent No. 3,055,771 to Sprowl). ≪ RTI ID = 0.0 >

Recently, a steel sheet containing Cr is developed on a steel sheet plated with aluminum in accordance with prolonged service life of parts used in automobile exhaust gas systems. For example, a coated steel sheet containing 1.8 to 3.0% of chromium in Japanese Patent Laid-Open No. 63-18043 or a steel sheet containing 2-3% of Cr as disclosed in Japanese Patent Application No. 63-47456.

On the other hand, in the case of the Zn-Al alloy plated steel sheet as described above, there is a disadvantage in that the machined cutting portion can not sufficiently exhibit corrosion resistance. This phenomenon is attributed to the fact that the exposed surface of the cutting section has a corrosion resistance due to reduction of sacrificial zinc which prevents corrosion of iron due to the zinc-aluminum alloy layer. In addition, the Zn-Al alloy plated steel sheet has a disadvantage in that since the plating layer is formed in a form that does not have a different kind of alloy phase, the interface is weakened when used after bending or drawing, and corrosion resistance after processing is reduced.

In order to improve the above characteristics, the steel of the Zn-Al-Mg-Si alloy coated steel sheet having excellent corrosion resistance of Korean Patent No. 10-0586437 contains 45 to 70 wt% of Al, 3 to 10 wt% of Mg, 3 to 10 wt% , And the remainder is Zn and inevitable impurities. In Korean Patent No. 10-0928804, a Zn-Al-Mg alloy plated steel sheet excellent in corrosion resistance and workability has been proposed.

In the hot-dip galvanized steel sheet, the surface quality depends not only on the composition of the plating bath but also on the technique of controlling the surface of the steel sheet coming from the plating bath. The components of the molten plated layer, such as Zn, Al, Mg, etc., combine with oxygen in the atmosphere to form an oxide film, which degrades the surface quality of the coated steel sheet. In particular, plated steel sheet products in which Mg is added to the plating bath often cause a problem in the appearance quality of the surface as compared with general GI and GL plating baths, which is a problem caused by the oxidizing property of the Mg element. Mg is a highly oxidative element. In a plating bath having a high temperature, oxidation reactivity is particularly high. As a result, oxides or Mg micro-oxides bonded with other elements are stuck to the strip, resulting in quality deterioration of the surface of the coated steel sheet.

In order to solve such a problem, a method in which a strip immersed in a molten metal coming out of a plating bath (port) is exposed to the atmosphere to form an oxidizing atmosphere for preventing oxidation in a zone where cooling progresses, It is known.

For example, International Publication Nos. WO2011 / 102434 (D1), Japanese Patent Application Laid-Open Nos. 55-141554 (D2), 2010-202951 (D3), and 2002-348651 (D4).

However, in the method or apparatus for forming an anoxic atmosphere in a zone where the strip is immersed in the molten metal and then goes out to the atmosphere, there are many problems in the conventional method or apparatus.

That is, in the conventional apparatus for the non-oxidizing atmosphere, as shown in the drawing of the prior art (D1 of FIG. 2, D2 of FIG. 2, D3 of FIG. 2, D3 of FIG. And a box type which surrounds the box type.

The temperature of the plating bath is about 460 ° C. (general zinc-aluminum-plated steel plate bath), 600 ° C. (galvanized steel plate bath) 650 ° C. (aluminum-plated steel plate bath) , The internal hot air can not be properly discharged into the atmosphere and the temperature inside the box is raised.

This conventional method or structure causes many problems in the actual process as follows.

- Structural deformation due to heat in confined spaces

     : Air Knife Rip, Rip, Sink roll arm and other structures.

- Malfunction of airknife driven electric devices such as sensors, motors, etc. attached to air knife

     : To prevent this, a cooling device must be separately provided to prevent the temperature rise of various electric devices. Thereby reducing the lifetime of various electric devices.

- Spangle control after plating and deposition amount control is not easy

   : Spangle size fineness on the surface of coated steel sheet affects the product quality. In order to miniaturize the spangle, fast cooling is required after controlling the adhesion amount, but in the case of the box type, the cooling efficiency is lowered due to the latent heat inside. In order to increase the cooling speed of the strip after plating, various other techniques such as mist spraying and metal powder spraying are actually used in addition to the cooling technique of spraying the air. The box type structure is a structure or a method which hinders cooling after plating.

- It is not easy to remove the surface oxide (top dross) that occurs on the plating bath.

   : The purpose of forming a non-oxidizing atmosphere by spraying nitrogen gas is to prevent oxidation from occurring on the surface of the molten metal and to prevent the generated oxide from adsorbing to the strip. In the case of the box type, the surface oxide Dross) It is not easy to remove

   : Oxidation occurs on the surface of the strip actually in a non-oxidizing atmosphere. It should be periodically removed by using a manpower or a robotic device, but the box type structure is a closed type. In order to remove oxides on the surface of the strip, There is a problem that the opening and closing must be repeated. In this case, it is difficult to maintain stable nitrogen atmosphere inside the box due to repeated opening and closing.

- Nitrogen gas cost increase

   Box Type There are two ways to fill the inside with nitrogen. In Air Knife, it is a method to fill by using injected nitrogen for control of plating amount and supply from other supply line from the outside.

   : The actual amount of nitrogen injected from continuous kneading line is usually 3000 ~ 6000m3 / hr, which is insufficient to fill the box type internal oxygen with nitrogen. As mentioned above, In addition to the nitrogen supplied from Air Knife, additional nitrogen should be supplied at the level of 3000 ~ 4000m3 / hr, which is more than twice the amount of nitrogen used. .

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a hot-dip coated steel sheet having excellent corrosion resistance and surface quality by forming an oxidizing atmosphere on a steel sheet coming from a surface of a hot- .

In order to achieve the above object, the present invention provides a device for effectively forming an oxidizing atmosphere around a plated steel plate installed between a surface of a plating bath for producing a plated steel sheet and an air knife installation, Lt; / RTI >

The apparatus of the present invention comprises a lower gas discharge bar for discharging a non-oxidizing gas toward a surface of the plating bath along a periphery of a coated steel plate at a distance from a surface of the plating bath; A side cover extending upward from the side of the lower end gas discharge bar in an upward direction toward the coated steel sheet; And an upper gas discharge bar formed at the upper end of the side cover and discharging the non-oxidizing gas downward.

The non-oxidizing gas is for preventing the surface of the steel sheet from forming an oxide film by binding with oxygen in the atmosphere, and includes an inert gas or a gas having a very low reactivity. Typically, in the embodiment of the present invention, the nitrogen gas is exemplified by the gas.

According to the present invention, suppressed from being Zn, Al, Mg oxide surrounding the periphery of the plated steel sheet to the tent collapsed oxidizing gas to the surface of the coated steel strip coming up from the plating bath to form an effect of improving the plating surface quality.

Fig. 1 is an enlarged photograph of the surface of a GI plating bath base Mg-Al-Ba-added coated steel sheet produced by the apparatus of the present invention 5,000 times,
Fig. 2 is an enlarged photograph of a 2,000 times magnification of the cross section of the coated plate of the GI plating bath base Mg-Al-Ba produced in the apparatus of the present invention.
3 is a plan schematic view of the nitrogen dam facility (nitrogen screen forming apparatus) of the present invention,
FIG. 4 is a diagram schematically illustrating a cross section taken along the line A-A 'in FIG. 3,
Fig. 5 is a diagram schematically showing a front view of Fig. 3. Fig.

Hereinafter, the present invention will be described in more detail.

The present invention creates an oxidation-inhibiting atmosphere through the installation of a non-oxidizing gas (nitrogen) curtain at the lower end of the air knife of the plating bath and prevents the TOP DROSS suspension from adsorbing to the steel sheet. It is possible to suppress the oxide generated when the base steel strip (Strip) is immersed in the plating bath to the oxygen interface by minimizing the reaction with oxygen and prevent the generated oxide from approaching the base steel sheet to prevent surface adsorption . In case of manufacturing with Air Knife integrally, it is easy to control the plating amount by minimizing the gap between the molten metal and the knife when controlling the coating amount of plating, and the additional effect of reducing the temperature of the lower part by a certain amount, Effect can be realized.

The apparatus for forming a nitrogen film according to an embodiment of the present invention is an apparatus for producing a coated steel sheet having excellent corrosion resistance and surface appearance characteristics while solving the aforementioned problems in the production of a hot dip galvanized steel sheet, Aluminum-plated steel sheet, galvanized steel sheet, molten aluminum-plated steel sheet, and the like.

Figs. 3 to 5 schematically show the device of the present invention.

The apparatus of the present invention is configured to be spaced apart from the surface of the plating bath 3 and movable up and down between the air knife 2 from the surface of the plating bath 3 by the lifting means 5. [

The apparatus of the present invention includes bottom nitrogen discharge bars 41, 42 formed in a rectangular shape along the periphery of the coated steel sheet 1 rising from the surface of the plating bath 3. The lower nitrogen discharge bars 41 and 42 receive nitrogen from the nitrogen supply pipe 46 on the side and discharge the nitrogen gas toward the surface of the plating bath 3. Although not shown, a plurality of holes (nozzles) for ejecting nitrogen gas are formed on the lower surface of the lower nitrogen discharge bars 41 and 42 at predetermined intervals.

The lower nitrogen discharge bars 41 and 42 may be integrally formed as rectangular pipes. However, the lower nitrogen discharge bars 41 and 42 may be formed integrally with the first and second bars 41 and 42, And the second bar 42 may be spaced apart from each other in the width direction (in the vertical direction in the drawing).

The apparatus of the present invention further includes a side cover 43 extending upward from the sides of the lower nitrogen discharge bars 41 and 42 in the direction of the coated steel plate 1 and a lower cover 43 formed at the upper end of the side cover 43, And upper nitrogen discharge bars 44 and 45 for discharging the nitrogen gas 10.

The upper nitrogen discharge bars 44 and 45 are formed in the shape of a pipe in which nitrogen discharge holes (not shown) are formed in the surface direction of the plating bath and are formed facing each other at the upper end of the side cover 43, . The upper nitrogen discharge bar (44, 45) is supplied with nitrogen from the nitrogen supply pipe (46).

The side cover 43 is formed to be inclined upwards from the lower nitrogen discharge bars 41 and 42 to the upper nitrogen discharge bars 44 and 45 in the direction of the coated steel plate 1, (10) is not scattered but is caught around the plated steel plate (1).

The advantages of the nitrogen film forming apparatus of the present invention described above will be described below in comparison with the conventional apparatuses (D1-D4).

1) In the apparatus of the present invention, the nitrogen curtain is formed in only a part of the space at the lower end of the air knife, and there is no element to prevent the spangle refinement due to the deformation of the structure and the cooling ability after plating due to the latent heat generated in the conventional box type.

   : The method or apparatus of the present invention is not a box type such as the invention cited for covering the entire Air Knife which controls the deposition amount of the plating from the surface of the molten metal bath, but the air knife And a nitrogen curtain (nitrogen curtain) is formed by using a nozzle in the lower end portion to form nitrogen DAM. Instead of filling the sealed space with nitrogen, the nitrogen gasket (47) is formed by using a nitrogen nozzle at the upper and lower portions of the lower part of the air knife, and the inside is maintained in a nitrogen atmosphere, Do not keep latent heat.

   : Since the nitrogen screen 47 of the present invention is formed only in a part of the lower part of the air knife as shown in the drawing, it does not affect any structure (parts) other than the surface of the molten metal bath and the strip on which plating is proceeding. Therefore, it is also less likely to cause errors due to the heat generated in the conventional box type and the heat of the electric device for driving the air knife such as various sensors and motors.

2) Top Dross Removal is easy.

   : In the case of the manufacturing apparatus of the present invention, not a direct contact or immersed atmosphere on the surface of the molten metal bath, but a certain distance from the surface of the molten metal bath, so that there is no interference when removing the dross through the space. In addition, even when inserting a device or a tool into the space for removing the top dross, it is effective to maintain the nitrogen atmosphere because the nitrogen curtain type thin film sprayed through the nozzle is always maintained.

3) Prevention effect of strip drip on top of plating molten metal top

   : In the production of the Mg-doped alloyed steel sheet, even though the potting portion of the molten metal pot is filled with nitrogen, it is impossible to completely prevent the fine oxide film formed by some top dross and oxidizing Mg. However, since the amount can be remarkably reduced, a manufacturing method of spraying nitrogen gas is applied.

   : In the present invention, a nitrogen atmosphere is formed in order to suppress the fine oxidation film on the top dross and the top of the molten metal bath, and the effect of physically preventing the top dross and the fine oxidation film from being adsorbed on the strip is also included.

   : The present invention forms a nitrogenous membrane in the lateral direction of the plating port when injecting nitrogen downward from the lower nitrogen discharge bars 41 and 42 (refer to FIG. 4-6). This is because the top Dross and fine The oxidation of the oxide film to the vicinity of the strip is physically prevented so that the oxide film can not be adsorbed to the strip.

   : The method of the present invention, which has the effect of preventing the adsorption on the strip after plating simultaneously with the formation of nitrogen atmosphere, differs from the conventional apparatus in which oxides are suppressed by forming only the existing nitrogen atmosphere.

4) Nitrogen gas cost reduction

   : Since the apparatus of the present invention forms a nitrogen atmosphere only for a part of the space required at the lower end of the air knife, it is possible to maintain the nitrogen film even with only a small amount of nitrogen coming out from the lower nitrogen discharge bars 41 and 42, But it is more efficient than the box type that supplies nitrogen.

   : Therefore, the manufacturing method according to the present invention can also reduce the amount of nitrogen used compared to a method of filling the inside of a conventional box type with nitrogen. Also, even if the same amount of nitrogen is used, the present invention is a manufacturing method capable of exhibiting a more effective oxide formation suppression and adsorption prevention effect than the conventional method.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples. The present invention will be further described by way of examples, but the present invention is not limited by the following examples.

A degreased cold rolled steel sheet having a steel sheet thickness of 0.8 mm, a width of 120 mm and a length of 250 mm was plated using a hot-dip simulator. The composition (% by weight) of the plating bath was changed as shown in Table 1 to prepare a zinc-aluminum alloy-plated steel sheet. Further, a nitrogen film was formed through the nitrogen film forming apparatus shown in Figs. 3 to 5.

The plating adhesion amount was adjusted with an air knife, and the evaluation results based on the adhesion amount of the single-sided plating of the zinc-aluminum-based alloy coated steel sheet produced are shown in Table 1.

The corrosion resistance was evaluated by 5% according to the KSD 9504 test method and the initial red rusting time (5%) in the 35 ° C NaCl salt spray test atmosphere. The magnesium oxide on the surface of the plating layer was observed by an optical microscope and the EDAX component Analysis equipment and X-ray diffraction (XRD) equipment were used.

The results of evaluation according to specific test evaluation methods are as follows.

1. Degree of occurrence of dross: It is the result of measuring the amount of dross generated on the plating bath after preparing the dissolution plating specimen according to the plating composition.

◎: Dross generation amount less than 5%

DELTA: Dross generation amount relative to the plating bath 10 to 20%

X: More than 20% of dross generated from plating bath

2. Surface appearance: The visual appearance of the sequin appearance and the degree of formation of the outer surface of the plating layer were visually observed.

◎: Consistent sequin formation and high gloss

△: Sequin formation is not clear

X: Spangle formation is weak and appearance is poor

3. Cross-sectional corrosion resistance: The degree of redness after 1000 hours of saline spray test was evaluated.

⊚: Red emission rate less than 5%

DELTA: Occurrence rate of red rust was 10 to 20%

X: Red emission rate 30% or more

4. Plate corrosion resistance: Salt spray test The degree of redness after 2,500 hours was evaluated.

⊚: Red emission rate less than 5%

DELTA: Red emission ratio of 20 to 30%

X: Red emission rate 30% or more

(Table 1)

Figure pat00001

* Based on weight%, the balance is zinc.

As shown in Table 1, it can be seen that the production example to which the apparatus of the present invention is applied is excellent in surface appearance and corrosion resistance.

1: Plated steel strip (STRIP) 3: Plated molten metal (Plating bath)
5: Lifting means (moving the whole equipment up and down)
41: Lower nitrogen discharge nozzle bar 42: Upper nitrogen discharge nozzle bar
43: side cover 44: side nitrogen discharge nozzle bar
45: Nitrogen film 46: Nitrogen supply pipe

Claims (4)

An apparatus for forming a non-oxidizing atmosphere around a plated steel sheet which is installed between a surface of a plating bath for producing a hot-dip coated steel sheet and an air knife installation,
Lower gas discharge bars (41, 42) for discharging the non-oxidizing gas toward the surface of the plating bath (3) along the circumference of the coated steel strip (1) at a distance from the surface of the plating bath (3);
A side cover 43 extending upward from the side of the lower end gas discharge bars 41 and 42 in the direction of the coated steel strip 1;
And an upper gas discharge bar (44, 45) formed at an upper end of the side cover (43) and discharging a non-oxidizing gas downward. The method for producing a non-oxidizing atmosphere for manufacturing a hot- . 2. The method according to claim 1, wherein a plurality of holes (nozzles) for ejecting non-oxidizing gas are formed at a predetermined interval on the lower surface of the lower gas discharge bar (41, 42) And discharging the non-oxidizing gas in the direction of the surface of the plating bath (3). The method of claim 1, wherein the lower gas discharge bar (41, 42) is divided into a first bar (41) and a second bar (42) so that the first bar (41) And the steel sheet is made to be able to spread in the width direction. The apparatus according to any one of claims 1 to 3, characterized in that the apparatus is configured to be movable up and down between the air knife (2) from the surface of the plating bath (3) by the lifting means An apparatus for forming a non-oxidizing atmosphere for producing a hot dip galvanized steel sheet.










KR1020150156559A 2014-11-13 2015-11-09 Device for Hot-Dop Metal Coated Steel Sheet KR20160058021A (en)

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