KR20040097552A - An apparatus for preventing strip from attaching dross thereon in zinc plating process - Google Patents

Abstract

PURPOSE: To produce a plated product having good surface quality by preventing dross formed of impure zinc formed in the plating pot from adhering to the surface of the strip in a process of performing plating by passing a cold rolled strip through a plating pot in a hot dip galvanizing line. CONSTITUTION: In an apparatus for preventing defects from forming on the surface of the strip by preventing upper dross of molten zinc contained in a plating pot (100) and iron dross from adhering to the surface of strip when manufacturing a hot dip galvanized strip (S), the apparatus comprises a subsidiary pot (5) which is installed in the plating pot, and through which the strip passes; and a pump (20) mounted on the subsidiary pot to fill high purity molten zinc having good quality in the subsidiary pot by supplying molten zinc of a part having the least impurities in the plating pot into the subsidiary pot so that plating operation is performed by passing the strip through the upper dross and iron dross removed plating pot.

Description

AN APPARATUS FOR PREVENTING STRIP FROM ATTACHING DROSS THEREON IN ZINC PLATING PROCESS}

The present invention relates to an apparatus for preventing the occurrence of product defects due to the upper dross and iron dross generated in the manufacture of hot-dip galvanized steel sheet stuck to the surface of the steel sheet, more specifically hot dip galvanized Cold rolled steel sheet is plated as it passes through the plating bath in the facility, and in this process, the dross made of impurity zinc in the plating bath is prevented from adhering to the surface of the steel sheet, and improved hot-dip galvanized to produce a plated product having good surface quality. It relates to a dross adhesion preventing device of the process.

In general, the hot-dip galvanized steel sheet (S) of the steel mill passes through the hot-dip galvanized bath 100 as shown in Figure 1 while maintaining the annealing heat-treated strip (S ') at an appropriate temperature (about 460 ℃), In the process, the molten zinc 110 is attached to both surfaces of the steel sheet (S), and when passed through this, an air spray is made from the air knife 120 on the upper side thereof, and the amount of plating deposition is adjusted according to the spraying strength. After passing through the air knife 120, the steel sheet (S) is cooled to produce a finished product.

In this process, the molten zinc 110 is the temperature of the air generated in the air knife 120 is relatively lower than the temperature of the molten zinc, the zinc plating is attached to the steel sheet (S) to rise along the steel sheet (S) and then air In the process of being cut down by the air blowing pressure of the knife 120, a large amount of O2 is contained in the components, and as the temperature is lowered, oxidation is promoted, and the surface of the molten zinc is always exposed to the atmosphere so that molten zinc ( Oxidation of 110 occurs

In addition, the production of such continuous molten plated steel sheet (S) is 97% or more pure molten zinc 110 is plated in the bath 100, the steel plate (S) heat-treated in the furnace 130 is snout 134 When the ash is introduced into the molten plating bath 100 and passes through the sink 136, the ash ASH and the iron component are introduced together into the bath 100, and the inside of the bath 100. It reacts with zinc 110 and aluminum to form intermetallic compounds (FeZn7, Fe2Al5, ZnO).

In this process, the intermetallic compound 140 maintaining the iron powder is heavy, so that the specific gravity is precipitated down the tub 100, the intermetallic compound of the aluminum component is lower than the zinc plating to rise to the top, such a process Solidified as a floating upper dross 150 present at the top of the plating bath 100. In addition, the upper dross 150 is solidified while being oxidized at the upper surface of the zinc plating bath 100 in combination with the air.

On the other hand, the small pieces of the solidified upper dross 150 forming the upper layer of the plating bath 100 is attached to the surface of the steel sheet (S) is not removed even in the air knife 120, the steel sheet (S) When it adheres to the surface of) and solidifies, it exists as a big defect of the steel plate S. Therefore, in order to remove such defects, the worker must continuously perform a work to prevent the dross 140 and 150 from accessing the surface of the steel sheet S passing through the plating bath 100, and at the same time, In the meantime, the dross 140 and 150 had to be removed by the operator at all times.

Therefore, the dross 140 collected at the edges of the plating bath 100 needs to be periodically removed and collected. This operation is very cumbersome, which greatly reduces the productivity of the galvanizing operation. In addition, as shown in FIG. 1, the high specific gravity iron dross (FeZn7) 140 is present in the upper portion of the steel sheet S, and the iron contained in the dross is formed in the upper portion of the sink roll 136 along the steel sheet traveling direction. In the presence of a lot, iron dross 140 is buried in the steel sheet (S) to cause surface defects. Therefore, the defective product is mixed in the finished product, causing a problem of lowering the error rate of the galvanized product.

The present invention is to solve the above conventional problems, the purpose is to prevent the cause of the intermetallic compound (FeZn7, Fe2Al5, ZnO) present in the hot-dip galvanizing bath buried in the surface of the steel sheet causing defects, High-quality molten zinc is always overflowed to the auxiliary port so that the upper dross and iron dross (FeZn7) do not exist, thereby preventing the adhesion to the steel sheet and reducing the occurrence of surface defects. It is to provide a dross adhesion preventing device of the hot dip galvanizing process to achieve the maximum quality.

1 is a cross-sectional view showing a hot dip galvanizing process according to the prior art;

2 is a cross-sectional view showing a hot dip galvanizing process equipped with a dross adhesion preventing device of a hot dip galvanizing process according to the present invention;

3 is a detailed view in which the dross adhesion preventing device of the hot dip galvanizing process according to the present invention is mounted in a plating bath;

4 is a detailed view of the auxiliary port and the pump provided in the dross adhesion preventing device of the hot dip galvanizing process according to the present invention;

5 is a cross-sectional view of the auxiliary port and the pump provided in the dross adhesion preventing device of the hot dip galvanizing process according to the present invention;

6 is a detailed view of a control unit provided in the dross adhesion preventing device of the hot dip galvanizing process according to the present invention;

7 is a flowchart showing a control operation by a controller provided in the dross adhesion preventing device of the hot dip galvanizing process according to the present invention;

8 is a diagram illustrating an experiment of the optimum level of the molten zinc overflow outlet in the auxiliary port provided in the dross adhesion preventing device of the hot dip galvanizing process according to the present invention.

<Description of the symbols for the main parts of the drawings>

5 ... Auxiliary port 10 ..... Synchro support

12 .... steel plate inlet 15 ..... outlet

17 .. Pump support 20 ..... Pump

23 ..... motor 25 .... screw member

29 ..... guide pipe 31 ..... bearing

35 .... induct heater 40 ..... gear connection

42 .... driven gear 44 ..... drive gear

50 .... Auxiliary port water level sensor

60 ... control 62 .... toggle switch

64 ..... level setting and input section 66 ..... comparison section

68 ..... Output 100 ..... Plating Bath

110 .... Molten Zinc 120 .... Air Knife

130 .... Furnace 134 .... Snout

136 .... Think 140 ..... Intermetallic Compound

150 .... upper dross S .... galvanized steel

In order to achieve the above object, the present invention, in the manufacture of hot-dip galvanized steel sheet, the upper dross and iron dross of the molten zinc contained in the plating bath is stuck to the surface of the steel sheet to generate a surface defect In the prevention device,

An auxiliary port installed in the hot dip bath and having a steel sheet passing therein; And a pump mounted to the auxiliary port to supply molten zinc having the smallest impurities in the hot dip bath to the auxiliary port to fill the inside of the auxiliary port with high-purity molten zinc. It is to provide a dross attachment preventing device of the hot dip galvanizing process characterized in that the steel plate passes through the plating bath from which the dross and the iron dross are removed.

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

The dross attachment preventing device 1 of the hot dip galvanizing process according to the present invention locates an auxiliary port 5 made of heat-resistant steel having a desired shape in which paper milk packs are placed upside down inside the plating bath 100. It is installed on the top of the sink roll 136, so that the top is installed on the sink roll support 10 so that the top is located above the molten zinc level of the plating bath 100. And, the lower end of the auxiliary port (5) to form a steel plate inlet 12 by cutting the lower end of the auxiliary port (5) so as to pass through, the size is approximately 40mm long, 1500mm wide and The steel sheet S is passed through the steel sheet inlet 12.

That is, in the present invention, the auxiliary port 5 made of heat-resistant steel 60 mm above the average level of the molten zinc 110 contained in the plating bath 100 is installed, and the horizontal length of the auxiliary port 5 is approximately 1800 mm, The longitudinal direction is made of approximately 900mm, the lower portion is made narrower so that the heavy iron dross 140 exits under the steel sheet inlet 12 by the difference in specific gravity, the overall shape of the milk peck It is upside down.

In addition, the outlet port 15 overflowing the molten zinc 110 at the center of the back and forth at a height of approximately 45 mm and a length of 300 mm for the molten zinc 110 flowing over the auxiliary port 5 is formed thereon. When the water level of the port 5 is increased, the molten zinc 110 of the auxiliary port 5 flows out through the portion. In addition, as shown in FIG. 5, the pump 20 fixed to the upper pump support 17 of the auxiliary port 5 has a length of the screw member 25 rotated by the motor 23. It has a length that can reach from the upper end of the auxiliary port (5) to a plurality of induct heaters 35 located in the middle portion of the plating bath 100 to assist the molten zinc 110 of high temperature and high quality To the port (5).

Accordingly, the auxiliary port 5 divides a part of the space in the plating bath 100 so as to partition the molten zinc 110 inside and the molten zinc 110 outside thereof.

In addition, the auxiliary port 5 is formed with a plurality of outlets (15) overflowing from the inner space to the molten zinc 110 flows from the inner space to the upper edge, respectively, as shown in detail in FIG. It is provided with a plurality of pumps 20 of appropriate capacity for pumping and supplying the molten zinc 110 from the outside of the 5).

The pumps 20 are mounted on an auxiliary pump support 17 which is fixed to the upper end of the auxiliary port 5, the pumps 20 being respectively mounted on the auxiliary pump support 17 with a motor 23 body. It is fixed, and the rotation axis of the motor 23 is connected to rotate the screw member 25 through the gear connecting portion 40.

The screw member 25 is mounted to be rotatable through the bearing 31 at the lower end in the cylindrical inclined guide pipe 29, respectively, the upper end of the screw member 25 forms a driven gear 42 The gear connecting portion 40 is configured by gear coupling to the drive gear 44 connected to the rotation shaft of the motor 23.

In addition, each of the induction pipes 29 has a lower end portion thereof drawn out of the auxiliary port 5 to extend to the induct heater 35 provided in the plating bath 100, and the inductor heater 35 The suction zinc is sucked out at the portion where the molten zinc 110 is circulated, and is positioned to supply the inside of the auxiliary port 5 through the zinc outlet 49 provided at the upper end of the induction pipe 29. In the auxiliary port 5, the molten zinc 110 of high purity flows.

As described above, around the inductor heater 35 disposed at the center of the plating bath 100 by the pump 20, there is usually a high quality molten zinc 110 free of impurities in the plating bath 100. When the molten zinc 110 drawn out from this portion is supplied to the auxiliary port 5, some of it is pulled down through the steel plate inlet 12 of the auxiliary port 5, while the other part is melted. The upper dross 150 generated by the molten zinc 110 combined with oxygen flows out toward the zinc outlet 15 and exits from the inside of the auxiliary port 5 through the molten zinc outlet 15 to the outside. To do that.

Therefore, since the upper dross 150 does not exist on the surface of the molten zinc 110 in the auxiliary port 5, the dross does not adhere to the surface of the steel sheet S.

In addition, the iron dross 140 is present between the sink roll 136 and the collect roll 170, which is to block the portion by the auxiliary port (5). Therefore, the iron dross 140 coming up along the steel sheet S has a specific gravity greater than that of zinc 110 when its weight is increased, so that the iron dross 140 escapes downward through the steel sheet inlet 12 of the auxiliary port 5. Therefore, only the high quality molten zinc 110 remains in the auxiliary port 5 to prevent the surface quality deterioration by the dross.

On the other hand, the motor 23, which is the power of the pump 20, the rotation speed is reduced through the gear connection portion 40, the pump 20 has to pump the molten zinc 110 heavy gravity specific gravity, screw type When the shaft is rotated and the screw member 25 is rotated, the pumping operation occurs.

On the other hand, the amount pumped by the pump 20 is the auxiliary port water level level sensor 50 is formed as an ultrasonic sensor on the upper side of the auxiliary port 5 is always driven by driving the motor 23 of the pump, In (5) it is controlled so that the water level of the molten zinc 110 flows can be stably discharged to remove the upper dross (150).

6 is a block diagram provided in the control unit 60 for adjusting the water level of the auxiliary port (5), the automatic operation and manual operation is first determined by the automatic or manual switching switch 62.

The control unit 60 corresponds to a small computer or controller, and includes a level setting and input unit 64, a comparator 66, an output unit 68, and the like.

Manual operation by the control unit 60 is used when the operator sees the water level of the auxiliary port 5 visually when the auxiliary port water level sensor 50 has failed, and manually adjusts the water level of the auxiliary port 5. In the case of automatic switching, the level setting value and the sensor level value provided in the control unit 60 are compared with each other in the comparison unit 66, and if the range is out of the level management or more, the output is output from the comparison unit 66. While the value from section 66 passes through output 68, the rotational speed of each motor 23 of pump 20 is controlled by the rotational speed command. Accordingly, the molten zinc 110 can always maintain the preset level level in the auxiliary port 5, and the upper dross 150 can always be removed from the auxiliary port (5).

7 is a control flow chart illustrating a series of operations of the controller 60 provided in the dross adhesion preventing device 1 of the hot dip galvanizing process according to the present invention.

First, it is divided into automatic operation and manual operation by the mode selected by the operator. And, in the case of manual operation, while the operator visually sees the level of the molten zinc 110 in the auxiliary port 5, the motor 23 is driven and pumped at a constant speed so that the molten zinc 110 always overflows. In this case, the level is read by the water level sensor 50, and when the water level differs by ± 10 mm or more from the previously set level value, the speed of the pump 20 in the comparator 66 of the controller 60 is increased. Give an increase or deceleration command.

By such a command, the rotation speed of the motor 23 is determined, and the rotation of the motor is increased or decreased. Therefore, the molten zinc 110 in the auxiliary port 5 is composed of an electrical circuit so as to always maintain a quantitative level.

Hereinafter will be described the effect of the present invention configured as described above.

The dross adhesion preventing device 1 of the hot dip galvanizing process according to the present invention will be described below with reference to the operation of the water level control device of the auxiliary port 5, as shown in FIGS. 6 and 7. First, the operator selects during manual and automatic operation in step 72 through the selection switch 62 provided in the control unit 60. In general, when operating in the automatic mode in step 74, the level sensor 50 ) Is composed of the ultrasonic sensor 50, and uses the principle of measuring the distance by measuring the reflection time to project the ultrasonic wave to the object to be measured and return.

In this case, the level sensor 50 is installed on the upper part of the auxiliary port 5 to measure and operate the level of the auxiliary port 5, and if a failure occurs in the auxiliary port 5 level sensor 50, step Switching to the manual mode at 76 maintains the level control of the molten zinc 110 inside the auxiliary port 5 by hand.

In the manual mode, the operator always monitors the molten zinc level of the auxiliary port 5, and if the level rises too much, the pump 20 speeds down, and if the level goes too low, the inconvenience of having to increase the speed of the pump 20 increases. In addition, the automatic mode automatically adjusts the level of molten zinc, thereby eliminating the burden on the worker.

Looking at the automatic level adjustment mode of the control unit 60, as in step 78, the value of the level set value 47 is approximately 25mm higher than the outlet 15, the zinc level is in advance to the comparison unit 66 Is entered. Then, as in step 80, the water level is measured by the auxiliary port water level sensor 50 and the value is input as the sensor level value 45, and as in step 82, the sensor 50 Compare the two values, sensor level and level setpoint, obtained from

Then, as in step 84, it is determined whether the sensor level value is low or high compared to the level setting value, and if it is low, the motor 23 is operated as in step 86 so that the power is connected to the gear connecting portion 40. Rotating the screw member 25 through the), the molten zinc 110 is pushed by the driving force of the screw member 25 by the rotational force of the screw member 25 to rise upward along the induction pipe (29).

Then, the molten zinc 110 in the vicinity of the induct heater 35 in which the high-quality molten zinc 110 of high purity is concentrated in the plating bath 100 is pumped into the auxiliary port 5. The pumped molten zinc 110 partially escapes through the auxiliary port 5 steel plate inlet 12, and when a larger amount of molten zinc 110 is pumped than the escaped portion, the molten zinc 110 is pumped outward from the inside of the auxiliary port 5. It will overflow. The overflow portion flows to the outlet 15 formed by cutting 300 mm in height and 50 mm in width from the front and rear of the middle portion of the auxiliary port 5.

If high, then as in step 88, the rotational speed of the motor 23 is reduced to reduce the amount of pumped molten zinc.

Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

8 plots the optimum level of outlet 15 overflowing molten zinc 110 at auxiliary port 5. As a result of testing the level in several cases as shown in Table 1 of FIG. 8, the height of the zinc 110 at the outlet 15 is 0 mm and 5 mm, so that the upper dross 150 cannot be pulled out. The level of 10mm was found that some of the upper dross of the edge portion did not escape and remained partially, and the speed of the pump 20 was increased to raise the level to 25 mm. Started to exit through. The motor 23 of the pump 20 was further increased to 30 mm, and the upper dross flowed out to the outlet 15 at the upper part, and only the high quality molten zinc was present at the upper part. Then, the pump speed is increased to raise the level to 40 mm, and the flow rate of the flowing zinc zinc 110 is increased, and if the control is unstable for a while, the flow of the molten zinc 110 flows not only to the outlet 15 but also to the upper side of the auxiliary port 5 as a whole. It may be possible, and sometimes a motor trip occurs due to capacity problems during long-term operation.

Therefore, in view of the efficiency of control and defect prevention of the product, the reference level is set to 25 mm, and if the absolute value differs from 25 mm to 10 mm, the number of revolutions of the motor 23 is controlled to the molten zinc 110 in the auxiliary port 5. It is desirable to control so as to maintain the proper level.

As shown in the flowchart shown in FIG. 7, when the operator selects the automatic mode by the mode selection step 72, since the level setting value is 25 mm, the sensor level measurement is read to see if the deviation value of the two values exceeds 10 mm. In comparison, if the value is a positive value, the speed is increased, and if the value is a negative value, the pump 20 is adjusted by the motor 23 to maintain the proper level of the molten zinc 110 in the auxiliary port 5. Control to prevent the defect caused by the dross.

Comparative material 1 in Table 1 has a large amount of dross generation of foreign matter combined with oxygen because there is no flow of zinc 110 through the outlet 15 of zinc 110 in the auxiliary port 5, comparative material 2 Since the flow height of the molten liquid at the silver outlet 15 was set to 5 mm and the width (length) of the outlet 15 was 200 mm, dross was slightly attached to the surface of the steel sheet because the flow rate of dross removal on the surface of the zinc 110 was slow.

However, in the present invention 1, when the height of the zinc 110 flowing from the outlet 15 of the auxiliary tank is set to 10 mm and the length of the outlet 15 is 250 mm, the outlet 15 on the upper surface of the auxiliary port 5 The flow rate of was small so that the dross was not completely removed (a trace amount) at the corners.

In addition, the present invention 2, 3 is the upper surface of the auxiliary port (5) by installing the height of the molten zinc 110 flowing from the outlet 15 of the auxiliary tank 20 to 30mm and the length of the outlet 15 to 300 ~ 350mm At the flow rate of the outlet 15 is appropriate, dross on the zinc surface is completely removed, so that dross is completely removed on top of the zinc 110 solution.

In comparison 3, the flow rate of the outlet 15 on the upper surface of the auxiliary port 5 is set by the height of the molten zinc 110 flowing from the outlet 15 of the auxiliary tank 40 mm and the length of the outlet 15 400 mm. Since the dross on the molten zinc surface is completely removed, no dross adheres to the surface of the steel sheet. However, the flow rate is fast, and the load of the pump motor is increased so that the trip is broken due to the overload of the motor 23.

Therefore, in the present invention, it is optimal to set the height of the zinc 110 flowing from the outlet 15 to 10 to 30 mm and the length of the outlet 15 to 250 to 350 mm as in 1,2,3 of the invention. Able to know.

As described above, according to the present invention, in order to prevent dross generated during hot dip galvanization from adhering to the surface of the steel sheet, an auxiliary port 5 is provided inside the plating bath 100 to remove dross around the steel sheet. Dross is stuck to the surface of the steel sheet (S) to prevent the occurrence of product defects.

Therefore, it is possible to prevent the adhesion of the dross to improve the surface quality of the galvanized steel sheet (S), thereby improving the error rate of the finished product is obtained.

Claims (4)

In the manufacture of the hot-dip galvanized steel sheet (S), the upper dross (150) and the iron dross (140) of the molten zinc 110 contained in the plating bath 100 is different on the surface of the steel sheet (S) In the device which prevents a surface defect from sticking, An auxiliary port 5 installed inside the hot dip bath 100 and having a steel plate S therethrough; and It is mounted to the auxiliary port 5 to supply the molten zinc 110 having the smallest impurities in the hot dip bath 100 to the auxiliary port 5 to supply the inside of the auxiliary port 5 with high purity and high quality. Steel plate (S) is passed through a plating bath in which the upper dross 150 and the iron dross 140 are removed, including a pump 20 filling the molten zinc 110. Dross sticking prevention device of the hot dip galvanizing process characterized in that. According to claim 1, wherein the auxiliary port (5) is installed on the top of the sink roll 136, the upper end is installed on the sink roll support 10 so that the upper end is located above the level of molten zinc level of the plating bath (100) The lower end of the auxiliary port 5 is formed by cutting the lower end of the auxiliary port 5 so as to pass through the steel plate S to form a steel plate inlet 12, and the upper side of the auxiliary port 5 Dross sticking prevention device of the hot dip galvanizing process, characterized in that the outlet 15 is formed in the front and back center for the molten zinc (110) flowing up. 2. The pump (20) according to claim 1, wherein the pumps (20) are mounted on an auxiliary pump support (17) which is fixed to the upper end of the auxiliary port (5), each of which has a motor (23) body fixed on the auxiliary pump support (17). The rotating shaft of the motor 23 is connected to rotate the screw member 25 through the gear connecting portion 40, while the screw members 25 are respectively in the cylindrical inclined guide pipe 29 It is mounted so as to be rotatable through the lower bearing 31, the induction pipes 29 are each of the lower end is drawn out of the auxiliary port 5, the induct heater 35 of the plating bath 100 By extending to, dross adhesion prevention device of the hot dip galvanizing process, characterized in that the supply of high purity molten zinc (110). According to claim 3, The pump 20 is an auxiliary port level level sensor 50 is formed as an ultrasonic sensor on the upper side of the auxiliary port (5) to drive the motor 23 of the pump, thereby always the auxiliary port In (5) the dross adhesion prevention device of the hot dip galvanizing process, characterized in that the water level of the molten zinc 110 is controlled to flow over to stably discharge the upper dross (150).