KR20030038222A - APPARATUS AND METHOD FOR REMOVAL OF DROSS IN Zn-POT - Google Patents

Abstract

PURPOSE: An apparatus and a method for removing dross in galvanizing pot are provided to solve surface defects of strip due to dross by injecting nitrogen gas into dead zone to collect dross, thereby floating the collected dross to the upper part of the pot before removing the floated dross. CONSTITUTION: In a hot dip galvanizing facility, the apparatus comprises nitrogen gas pipes (30) which are respectively installed at the front end part of sink roll and stabilizing roll according to a proceeding direction of strip inside plating pot, and at the end part of which a nozzle (34) is formed; a gas supply pipe (32) which is connected to the side part of the nitrogen gas pipes (30), and on which a pressure regulation valve is mounted to supply nitrogen gas having an appropriate pressure; a rotation shaft (20) installed inside the nitrogen gas pipes (30) so that the rotation shaft (20) is supported by a rotary joint (26); a driving motor (22) mounted on the upper part of the rotation shaft (20) to drive the rotation shaft (20); and rotation blades (24) installed at the lower part of the rotation shaft (20) so that the rotation blades (24) split bubbles of nitrogen gas ejected through the nozzle (34) to small bubbles.

Description

Dross removal apparatus in galvanized bath and its method {APPARATUS AND METHOD FOR REMOVAL OF DROSS IN Zn-POT}

The present invention relates to an apparatus and a method for removing dross in a plating bath of a hot dip galvanizing plant. More particularly, the present invention relates to a dross removal device between a steel plate and a sink roll in a plating bath, and injects nitrogen gas into a stagnant dross. The dross removal apparatus in the plating bath which can manufacture the galvanized steel sheet having excellent surface quality by preventing the dross from adhering to the plating layer of the steel plate by reducing the Fe component of the dross in the plating bath and floating the dross. It is about.

In general, hot-dip galvanized steel sheet has better corrosion resistance than electro-galvanized steel sheet, but the surface quality is poor because dross generated during the plating process adheres to the steel sheet and forms a flaw on the surface of the coated steel sheet.

As shown in FIG. 1, in the hot dip galvanizing facility, the sink roll 4 is installed in the zinc plating solution 2 contained in the plating bath 1, and the steel sheet 3 passes through the sink roll 4. Plated via a galvanizing solution (2), and consists of a snout (7) wrapped to shield the steel plate (3) entering the galvanizing solution (2) from the outside air.

The reason why impurities such as Fe, upper dross and lower dross are generated in the hot dip galvanizing bath 1 is explained as follows. That is, as the steel plate 3 passes through the snout 7 and is immersed in the zinc plating solution 2, Fe eluted from the surface of the steel plate to the zinc plating solution 2 reacts with Zn in the zinc plating solution 2 to form a lower portion. The dross (Fe ₂ Zn ₇ ) 9 is formed, and when the steel sheet 3 passes the galvanizing solution 2 and passes the air knife 6 for adjusting the plating amount, the molten zinc is oxidized to form the steel sheet 3. It flows downward to cover the plating bath surface, which is the upper dross (ZnO) 8.

Since the upper dross 8 floats on the surface of the galvanizing solution 2 and can be removed mechanically, the lower dross 9 is difficult to remove because it is present in the galvanizing solution 2.

In particular, in the dead zone 10 in which the flow of the zinc plating solution 2 between the snout 7 and the steel plate 3 is stagnant, an appropriate amount (0.17 to 0.23 wt%) of aluminum, which is a component of the zinc bath, is The Fe component is excessively eluted from the steel sheet 3 in a state in which it is not formed, so that the equilibrium state of zinc, aluminum, and iron components is broken, and the lower dross (Fe ₂ Zn ₇ ) 9 having a specific gravity is excessively generated.

Accordingly, the lower dross (Fe ₂ Zn ₇ ) 9 generated excessively in the dead zone 10 is attached to the steel plate surface at the same time as the roll in the plating bath 1 rotates while flowing in the advancing direction of the steel plate 3. It causes surface quality problems.

Conventionally, the inclined plate 12 is installed in front of the sink roll 4 and the stabilizing roll 5 in the dead zone 10 section of the plating bath 1 to switch the flow of the dross. And dross was prevented from adhering to the steel plate 3.

However, the above method cannot solve the quality problem of the surface of the steel sheet by the lower dross 9 having a high specific gravity generated in the dead zone 10, and if the line speed is increased, despite the installation of the inclined plate 12, The dross is introduced between the steel sheet 3 and the rolls 4 and 5, so that the surface defects of the steel sheet and the dent increase.

In order to solve the above problems, the present invention is a dross in a galvanized bath that can solve the defects on the surface of the steel sheet by the dross by trapping the dross by ejecting nitrogen gas in the dead zone area to remove the float on the upper portion of the bathtub It is an object of the present invention to provide a removal device and method thereof.

1 is a perspective view of an installation state of an inclined plate according to the present invention;

Figure 2 is a perspective view of the installation state of the nitrogen gas bubbler in the plating bath according to the present invention,

3 is a cross-sectional view of the nitrogen gas bubbler according to the present invention.

Explanation of symbols on the main parts of the drawings

1: plating bath 2: zinc plating solution

3: steel sheet 4: sink roll

5: stabilizing roll 6: air knife

7: snout 8: upper dross

9: Lower Dross 10: Dead Zone

12: inclined plate 20: rotation axis

22: drive motor 24: rotary wing

26: rotary joint 30: nitrogen gas pipe

32: gas supply pipe 34: nozzle

36: pressure regulating valve

In order to achieve the above object, the present invention is installed in the dead zone between the steel plate and the sink ball in the plating bath and the lower end of the nitrogen gas pipe consisting of a nozzle; A rotating shaft installed inside the nitrogen gas pipe; A drive motor mounted to an upper end of the rotating shaft; The dross removal device in the plating bath and the dross removal device in the plating bath by ejecting nitrogen gas at a pressure of 0.6 to 1.4 kg / cm 2 through the dross removal device in the plating bath, characterized in that the rotary blade is mounted on the lower end of the rotating shaft. It provides a dross removal method in the plating bath, characterized in that to remove the floating.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Figure 2 is a perspective view of the installation state of the nitrogen foam in the plating bath according to the present invention, Figure 3 is a cross-sectional view of the nitrogen foam in accordance with the present invention.

As shown in FIG. 2, the first nitrogen gas bubbler is installed on the upper portion of the portion where the steel sheet 3 flows into the sink roll 4, and the second nitrogen gas bubbler is formed of the stabilizing roll 5 of the steel plate front portion. It is installed in the lower portion, and the third nitrogen gas foamer is installed in the lower portion of the stabilizing roll (5) of the steel plate rear portion.

The reason for the installation in this position is to prevent the dross from flowing between the steel sheet and the roll to cause steel sheet surface defects.

The nitrogen gas foamer is a long cylindrical nitrogen gas pipe 30 connected to the nitrogen gas supply pipe 32 is immersed and fixed in the plating bath (1) as shown in Figure 3 and nitrogen gas in the nitrogen gas supply pipe (32) Pressure control valve 36 is installed to control the pressure of.

In addition, the lower end exit side of the nitrogen gas pipe 30 is composed of a nozzle 15 so as to generate bubbles of nitrogen gas.

The rotating shaft 20 is installed inside the nitrogen gas pipe 30, and a driving motor 22 is installed on the upper portion of the rotating shaft 20, and the nitrogen gas pipe ( The rotary joint 26 supports the rotating shaft in the center of 30).

Rotating blades 24 are connected to the lower end of the rotating shaft 20 so that the nitrogen gas ejected through the nozzle 34 of the nitrogen gas pipe is pulverizable into small air bubbles.

Example 1

In order to compare the method of injecting nitrogen gas into the plating bath according to the present invention and the method of not introducing nitrogen gas according to the conventional invention, a plating bath having the following conditions is made, and the nitrogen gas is ejected at a predetermined pressure in the plating bath. As a result of measuring the change in the Fe component every 10 minutes, there was almost no change in the Fe component in the plating bath when nitrogen gas was not added.However, when nitrogen gas was added, the Fe component was changed according to the time. Decreased.

The conditions of the plating bath are as follows.

Plating bath temperature: 450 ℃

Nitrogen gas pressure: 0.8 kg / ㎠

Composition of components in bath: Al 0.2wt%, Fe 0.013wt% Zn and other impurities

Table 1. Variation of Fe Components in Plating Baths

Table 2. Changes in the Fe component of the dross floating on the plating bath

division Fe content of suspended dross (wt%) Fe content in the plating bath (wt%) Deviation of components Primary harvesting analysis 0.091 0.013 0.078 Second collection analysis 0.084 0.013 0.071

As a result of this embodiment, the Fe component in the bath was reduced from 0.013wt% to 0.005wt% by blowing nitrogen gas into the plating bath, and the Fe component in the floating dross floated on the bath was 0.013wt% to 0.078wt%. It can be seen that the increase. Therefore, it can be seen that the Fe component, which is the cause of dross in the galvanizing solution, is rapidly reduced in the zinc plating solution by releasing nitrogen gas into the plating bath to float foreign substances to the upper part of the bath.

Example 2

As shown in FIG. 2, after the nitrogen gas expander according to the present invention is installed in the plating bath while continuously performing the hot dip plating operation, the surface of the steel plate is used to detect defects in the steel plate surface by Fe content and dross in the plating bath. Measured.

The surface detector used here is a device for measuring the position and number of dents on the surface of the attached dross and the steel sheet having a size of 1.5 mm or more.

As the working conditions, a cold rolled steel sheet having a thickness of 0.4 to 2.0 mm and a width of 900 to 1500 mm was continuously operated for 10 days, followed by hot dip plating, and compared with the conventional technology.

Table 3.

division Nitrogen gas pressure (kg / ㎠) With dross Dent Fe component injury Conventional example - 5 5 5 - 4 4 5 Inventive Example 0.4 4 4 3 0.6 2 2 3 0.8 One 2 3 1.0 One One 2 1.0 One One One 1.1 2 2 One 1.2 One One 2 1.2 2 3 One 1.4 3 3 One 1.6 4 4 2 * Score: Excellent 1 ~ 13

When the nitrogen gas pressure is low below 0.6 kg / cm 2, the nitrogen gas is not sufficiently foamed in the plating bath, and the collection function of Fe and dross is reduced. On the other hand, when the nitrogen gas pressure is higher than 1.4kg / ㎠, the fluidity in the plating bath is rapidly increased, and the collection function of Fe and dross is improved, but the variation of the plating amount is severely caused by the vibration of the steel sheet, and the dent caused by dross Secondary defects occur.

In addition, by installing a rotary blade at the lower end of the nitrogen gas pipe to further finely crush the nitrogen gas to increase the total surface area of the gas bubbles, the reaction with the dross is more effectively progressed to facilitate the rise of the dross.

As described above, the apparatus for removing dross by the nitrogen gas expander in the plating bath according to the present invention, and the method of the present invention provide a Fe component and ash by installing a nitrogen gas expander at the leading end of the steel sheet in the hot-dip galvanizing bath. By collecting the dross generated from the gas snout and floating it in the upper portion of the bathtub, the steel sheet surface defect caused by the dross is drawn between the steel sheet and the roll is suppressed, thereby producing a steel sheet having excellent surface quality.

Claims (2)

In hot-dip galvanizing equipment, A nitrogen gas pipe (30) installed at the distal end portions of the sink roll (4) and the stabilizing roll (5) along the moving direction of the steel plate (3) in the plating bath (1) and having an end portion (34); A gas supply pipe 32 connected to the side of the nitrogen gas pipe 30 and equipped with a pressure regulating valve 36 to supply nitrogen gas at an appropriate pressure; A rotating shaft 20 installed to be supported by the rotary joint 26 in the nitrogen gas pipe 30; A drive motor 22 mounted on the top of the rotation shaft 20 for driving the rotation shaft 20; Dross removal apparatus in a galvanized bath, characterized in that consisting of a rotary blade (24) installed at the lower end of the rotating shaft 20 so that the bubbles of nitrogen gas ejected through the nozzle 34 can be crushed small. Supplying nitrogen gas at a pressure of 0.6 to 1.4 kg / cm 2 by the pressure regulating valve 36 of the nitrogen gas supply pipe 32; Three nitrogen gas pipes 30 connected to the nitrogen gas supply pipe 32 and installed at the distal ends of the sink roll 4 and the stabilizing roll 5 along the moving direction of the steel plate 3 in the plating bath 1. Nitrogen gas is ejected through the nozzle 34; Ejected into the zinc plating solution through the nozzle 34 by the operation of the rotary blade 24 installed on the lower end of the rotary shaft 20 is mounted inside the nitrogen gas pipe 30 and rotated by the drive motor 22. Pulverizing the bubbles of nitrogen gas to be small; The dross removal method in the galvanizing bath, characterized in that to remove the dross in the galvanizing bath by collecting and floating the dross in the dead zone (10) area by the nitrogen gas bubble.