JP2005256055A - Consecutive hot dip metal coating method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a consecutive hot dip coating method with which the adjustment of coated thickness is easily performed and the uniformity of the coated thickness is high in comparison with the conventional method using a gas-wiping nozzle. <P>SOLUTION: At the upper part of a hot dip galvanizing bath 2, two flat-like blades 3, 4 are disposed so as to be in contact with a running course of a steel sheet 1 drawn up from the hot dip galvanizing bath 2. These blades 3, 4 have the width having not narrower than the width of the steel sheet 1 and in the respective blades 3, 4, respective vibrators 5, 6 are fitted. A part of the molten zinc stuck to the surface of the steel sheet 1 is scraped down by bringing the tip parts of the blades into contact with the surface of the running steel sheet 1 in a state of vibrating the blades 3, 4. At this time, the coated thickness is controlled by adjusting the pushing amounts of the blades 3, 4 to the running path of the steel sheet 1. Desirably, two blades 3, 4 are disposed in a zigzag state while holding the running path of the steel sheet 1 between the blades. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for continuous hot metal plating, such as continuous hot dip galvanizing.

  2 and 3 show an example of a conventional continuous galvanizing apparatus.

  The steel strip 1 is continuously supplied into the molten zinc bath 2 (plating tank), and the steel strip 1 is pulled upward via the sink roll 22. Next, by blowing gas from the gas wiping nozzle 23 onto the surface of the steel strip 1 above the molten zinc bath 2, the molten zinc adhering to the surface of the steel sheet is scraped off, and the amount of adhesion (ie plating thickness) To control.

However, the gas wiping method may cause the following problems. That is:
(A) In order to reduce the plating thickness, it is necessary to reduce the traveling speed of the steel strip or increase the collision pressure of gas wiping, that is, the gas pressure. However, lowering the running speed of the steel sheet directly leads to a decrease in productivity, and increasing the gas pressure induces splash of molten metal, so there is a limit to reducing the plating thickness.

  (B) It is very sensitive to the vibration and warpage of the steel sheet and is easily affected. For this reason, vibration and warpage are often corrected by installing a roll or the like before and after the gas wiping nozzle. However, installation of a roll or the like causes an increase in equipment cost and running cost. Moreover, since such a roll itself generates defects such as chatter, there is a problem in quality.

  (C) In gas wiping, defects called “ripple waves” occur. This is caused by turbulence of the wiping gas (jet vortex), and becomes a problem particularly when a hot-dip galvanized plate that is not subjected to alloying treatment is manufactured.

  (D) Since the gas is used, the steel sheet is inevitably cooled during wiping. However, it is disadvantageous in terms of thermal energy when producing an alloyed hot-dip plating in which an alloying treatment is performed following wiping.

  (E) Molten metal splash may enter the gas ejection port of the nozzle, resulting in uneven adhesion amount (nozzle clogging).

  (F) Generally, the amount of adhesion is changed by changing the gas pressure. However, the change in the amount of adhesion is not always easy because splash and nozzle clogging are likely to occur.

  These problems are rooted in the use of gas for wiping. As a method for solving this problem, for example, Japanese Patent Application Laid-Open No. 2000-212714 discloses a method for controlling the amount of adhesion using electromagnetic force. However, this method has a problem that, in principle, an induced current flows through the steel strip, so that there is a problem that the steel strip is heated, and there is a problem that the adhesion amount is strongly influenced by warpage and vibration of the steel plate. It is not easy.

  Japanese Patent Application Laid-Open No. 09-209101 discloses a method of sandwiching a steel strip with a blade and controlling the amount of adhesion. However, this method is not practical because the amount of adhesion is uneven when the steel sheet is warped or vibrated.

Japanese Laid-Open Patent Publication No. 01-147049 discloses a continuous hot dipping apparatus in which electromagnets are arranged in front (FIG. 2), after (FIG. 1), or before and after (FIG. 3) a gas wiping nozzle. According to these apparatuses, vibration is applied to the steel strip pulled up from the hot dipping bath using an electromagnet, and the amount of plating is adjusted by blowing gas from a gas wiping nozzle onto the surface. However, in this method, since the effect of shaking off the molten metal by vibration is insufficient, it is not possible to expect an excessively large reduction in the flow rate of airflow, and the effect is limited.
JP 2000-212714 A JP 09-209101 A Japanese Patent Laid-Open No. 01-147049

  The present invention has been made in view of the problems with the plating thickness control method in the conventional continuous molten metal plating as described above, and the object of the present invention is to provide a conventional method using a gas wiping nozzle. In comparison, an object of the present invention is to provide a continuous molten metal plating method and apparatus in which the adjustment of the plating thickness is easy and the uniformity of the plating thickness is high.

The continuous molten metal plating method of the present invention comprises:
In a continuous molten metal plating method in which a metal band is passed through a molten metal bath and a plating layer is attached to the surface of the metal band,
A flat blade with a width equal to or greater than the width of the metal strip is brought into contact with the surface of the metal strip pulled up from the molten metal bath with vibration applied thereto, and a part of the molten metal is scraped off at the tip of the blade. And the adhesion amount of a molten metal is controlled by adjusting the relative position of the vibration center of the blade with respect to the travel path of the metal strip.

  Preferably, the frequency of vibration applied to the blade in the direction perpendicular to the traveling path of the metal band is 1 kHz or more.

  Preferably, the amplitude of vibration applied to the blade in the direction perpendicular to the traveling path of the metal strip is set to 1 μm or more and 100 μm or less.

  Preferably, the pushing amount of the blade with respect to the travel path of the metal strip is 0.1 t or more and 10 t or less, expressed as a distance from the track of the center thickness of the metal strip to the vibration center position of the blade. Where t is the thickness of the metal strip.

The continuous molten metal plating apparatus of the present invention is
In a continuous molten metal plating apparatus in which a metal strip is passed through a molten metal bath and a plating layer is attached to the surface of the metal strip,
A vibrator for scraping off a portion of the molten metal on the surface of the metal band, disposed close to the travel path of the metal band pulled up from the molten metal bath;
An oscillating device for vibrating the vibrating body to contact the molten metal on the surface of the metal band;
A pushing device for adjusting the relative position of the vibrating body with respect to the travel path of the metal strip;
It is provided with.

  Preferably, a flat blade having a width equal to or larger than the width of the metal band is used as the vibrator.

  Preferably, the blades are arranged in a staggered manner with a metal strip travel route in between.

  According to the continuous molten metal plating method and apparatus of the present invention, since the molten metal is scraped off by bringing the vibrating body into contact with the surface of the metal strip, the control of the plating thickness is excellent and the uniformity of the plating thickness is high. . Further, according to the method and apparatus of the present invention, there is no occurrence of quality defects such as splash, which becomes a problem when the gas wiping nozzle is used.

  FIG. 1 shows an example of the arrangement of blades for controlling the plating thickness in a continuous molten metal plating apparatus according to the present invention. Note that the overall configuration of the continuous molten metal plating apparatus is the same as that of FIG.

  In the figure, 1 is a steel strip (metal strip), 2 is a molten zinc bath (molten metal bath), 3 is a blade (vibrating body), 5 and 6 are vibrators (oscillators), and 7 and 8 are oscillators. (Oscillator), 9 and 10 represent pushing devices.

  In this example, as shown in FIG. 1, two flat blades 3 and 4 are arranged above the molten zinc bath 2 so as to contact the traveling path of the steel strip 1 pulled up from the molten zinc bath 2. Has been. These blades 3 and 4 have a width slightly larger than the width of the steel strip 1 and are arranged in a staggered manner (that is, shifted in height from each other) with the travel path of the steel strip 1 in between. . Vibrators 5 and 6 are attached to the blades 3 and 4, and the vibrators 5 and 6 are connected to the oscillators 7 and 8, respectively. Further, the vibrators 5 and 6 are connected to the pushing devices 9 and 10.

  The tip of the blades 3 and 4 is brought into contact with the surface of the traveling steel strip 1 in a vibrating state, and a part of the molten metal adhering to the surface of the steel strip 1 is scraped off. At this time, the plating thickness can be controlled by adjusting the pushing amount of the blades 3 and 4 with respect to the travel path of the steel strip 1. In addition, as a pushing amount, the protrusion amount of the vibration center of the blades 3 and 4 with respect to the track | orbit of the sheet thickness center of the steel strip 1 when the blades 3 and 4 are not contacted can be used, for example.

  In this way, by applying vibration to the blades 3 and 4 and bringing them into contact with the surface of the steel strip 1, the amount of adhesion can be controlled stably without degrading the quality of the plating. This is because, when a vibration is applied to an object, a levitation force is generated. From a microscopic viewpoint, since the blade and the steel strip (base material) are in a non-contact state, it is considered that the adhesion amount of the molten metal can be controlled. .

  Further, as a result of the tests by the inventors of the present application, it has been found that the vibration frequency needs to be 1 kHz or more, and more preferably 10 kHz or more. This is because a pattern corresponding to this vibration appears on the plating surface. When the frequency is low, the pattern due to vibration is recognized by the human eye as a defect, but when the frequency is high, the pattern pitch is high. This is because it becomes smaller and is not recognized by human eyes.

  The amplitude applied to the blade is preferably 1 μm or more and 100 μm or less. This is because the non-contact effect cannot be obtained when the thickness is 1 μm or less, and the difference in adhesion amount due to vibration becomes significant when the thickness is 100 μm or more.

  Preferably, the pushing amount of the blade with respect to the travel path of the steel strip is 0.1 t or more and 10 t or less, expressed by the distance from the center of thickness of the steel strip to the vibration center position of the blade. Where t is the thickness of the steel strip. This is because when the indentation amount is 0.1 t or less, it is difficult to ensure the uniformity of the adhesion amount. Because.

  It is desirable to change the height of the blade on the front and back of the steel plate. This is because if the height of the blade is changed, the pushing amount can be secured in the opposite direction on the front and back sides, so that the adhesion amount can be easily controlled and at the same time, the warpage and vibration can be corrected. In this way, it is possible to eliminate rolls in the bath that often cause quality defects such as chatter marks and intrusion of foreign matter (dross). The difference in height between the front and back blades only needs to be about 10 mm larger than the thickness of the edge of the blade used.

  The amount of adhesion is controlled by adjusting the push-in amount. However, the relationship between the push-in amount and the adhesion amount varies depending on the frequency, amplitude and output of the vibration to be added. For example, when the amount of adhesion is desired to be smaller than the current value, the amount of pressing is increased. However, when the amount of pressing is simply increased, scratches may occur. Such a case can be solved by increasing the output of the vibration oscillator and increasing the vibration amplitude. Similarly, when the warpage of the steel plate is severe or when the vibration is severe, it may be necessary to increase the pushing amount. Even in such a case, according to the embodiment of the present invention, if the output of the oscillator is increased, it is possible to operate in a state where warpage and vibration are suppressed and no scratches are generated.

In order to investigate the performance of the plating thickness control by the method of the present invention, a test was conducted under the following conditions using the apparatus shown in FIG. The cold-rolled steel strip used for the test had a thickness of 0.75 mm and a width of 1000 mm, and the blade had a thickness of 25 mm (d = 25 in the figure), a width of 1200 mm, and a depth of 400 mm. It was. The blades were arranged in a staggered manner, and the height of the blades was shifted by 150 mm between the front and back of the steel strip (h = 150 in the figure). The line speed was 90 mpm and the tension was 2 kg / mm ² . The vibration applied to the blade was 19.5 kHz with a frequency of 30 μmp-p. The power required for vibration was 2.5 kW on one side and 5 kW on both sides in total.

Table 1 shows the results. In this table, the oscillator output, the push-in amount from the pass line (mm), the average deposit amount (g / m ² ), the maximum deposit amount difference in the width direction (five observation points, 50 each from the left and right edges) , 250 and 500 mm positions).

  As can be seen from Table 1, by adjusting the blade push-in amount based on the method of the present invention, it is possible to control the plating adherence amount and improve the uniformity of the adherence amount.

The figure which shows an example of arrangement | positioning of the blade for controlling the plating thickness in the continuous molten metal plating apparatus based on this invention. The figure which shows an example of the conventional continuous hot dip galvanizing apparatus. The figure explaining the gas wiping nozzle for controlling the plating thickness in the conventional continuous zinc metal plating apparatus.

Explanation of symbols

1 ... steel strip (metal strip),
2 ... Molten zinc bath (molten metal bath),
3, 4 ... blade (vibrating body),
5, 6 ... vibrator (oscillator),
7, 8 ... Oscillator (oscillator),
9, 10 ... pushing device,
22 ... Sink roll,
23: Gas wiping nozzle.

Claims (7)

In a continuous molten metal plating method in which a metal band is passed through a molten metal bath and a plating layer is attached to the surface of the metal band,
A flat blade with a width equal to or greater than the width of the metal strip is brought into contact with the surface of the metal strip pulled up from the molten metal bath with vibration applied thereto, and a part of the molten metal is scraped off at the tip of the blade. And the continuous molten metal plating method characterized by controlling the adhesion amount of a molten metal by adjusting the relative position of the vibration center of a braid | blade with respect to the travel path | route of a metal strip.   2. The continuous molten metal plating method according to claim 1, wherein a frequency of vibration applied to the blade in a direction perpendicular to a traveling path of the metal strip is set to 1 kHz or more.   2. The continuous molten metal plating method according to claim 1, wherein the amplitude of vibration applied to the blade in a direction perpendicular to the traveling path of the metal strip is 1 μm or more and 100 μm or less.   The pushing amount of the blade with respect to the travel path of the metal strip is expressed by a vibration center position of the blade and is 0.1 t or more and 10 t or less (where t is the thickness of the metal strip). 2. The continuous molten metal plating method according to 1. In a continuous molten metal plating apparatus in which a metal strip is passed through a molten metal bath and a plating layer is attached to the surface of the metal strip,
A vibrator for scraping off a portion of the molten metal on the surface of the metal band, disposed close to the travel path of the metal band pulled up from the molten metal bath;
An oscillating device for vibrating the vibrating body to contact the molten metal on the surface of the metal strip;
A continuous molten metal plating apparatus comprising: In a continuous molten metal plating apparatus in which a metal strip is passed through a molten metal bath and a plating layer is attached to the surface of the metal strip,
A flat blade that is disposed close to the travel path of the metal strip pulled up from the molten metal bath, has a width equal to or greater than the width of the metal strip, and scrapes off a portion of the molten metal on the surface of the metal strip;
An oscillation device for vibrating the blade to bring the tip into contact with the molten metal on the surface of the metal strip,
A pushing device for adjusting the relative position of the vibration center of the blade with respect to the travel path of the metal strip;
A continuous molten metal plating apparatus comprising:   The continuous molten metal plating apparatus according to claim 6, wherein the blades are arranged in a staggered manner with a traveling path of a metal strip interposed therebetween.

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