JPH0610621Y2 - Continuous hot dip plating equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a continuous hot dip galvanizing apparatus in which a duct called a snout is used to shut off the entrance path of a steel strip entering the plating bath from the outside air. .

[Conventional technology]

When producing a plated steel sheet with a continuous hot dip coating device, in order to remove the work hardening of the cold rolled steel sheet, which is the raw material, and to reduce and purify its surface, the raw steel sheet is treated in an annealing furnace in a reducing atmosphere before plating. Is customary.

In such a continuous hot dip coating apparatus, as shown in FIG. 3, the steel plate 2 discharged from the continuous annealing furnace 1 passes through the snout 3 and is immersed in the plating bath 7, and then the sink roll 4 and the snap roll 5 are inserted. After that, the extra plating bath adhered to the surface is blown off by the nozzle 8 outside the bath, and the surface of the steel plate 2 is plated with a predetermined thickness. The snout 3 has its upper end connected to the outlet of the annealing furnace 1 and its lower end immersed in the plating bath, thereby blocking the entrance path of the steel strip 2 entering the plating bath 7 from the outside air, and The same reducing atmosphere is maintained to prevent surface oxygenation of the steel strip 2.

By the way, conventionally, in hot dip galvanizing, a slight amount of Al is added to the plating bath in order to improve the adhesion of zinc to the steel strip. This Al reacts with Fe precipitated from the steel strip to form Fe ₂ Al ₅ and floats on the bath surface as so-called top dross. Further, on the bath surface, foreign substances carried from the furnace by the steel strip, zinc vapor in the snout, etc. are also present as floating foreign substances.

In the absence of snout, these contaminants diffuse on the bath surface and can be easily removed, even if they are concentrated near where the steel strip enters the plating bath. However, in the presence of snout, all these foreign matters concentrate near the position where the steel strip enters the plating bath and adhere to the steel strip immediately before plating, or when the steel strip enters the bath, It is caught and adheres to the steel strip in the bath. As a result, plating defects such as non-plating and indentation due to dross adhesion occur. Therefore, in order to maintain quality, it is necessary to remove these foreign substances from inside the snout to the outside as appropriate.

Techniques for removing this foreign matter include, for example, Japanese Patent Publication No. 63-
Japanese Patent No. 49743 discloses a method for removing foreign matter in a snout to remove the foreign matter accumulated on the bath surface in the snout to the outside while slightly lifting the snout from the bath surface and circulating an inert gas in the snout. . According to this, it is not necessary to replace the inside of the snout with outside air conditions, there is no suction of oxygen into the annealing furnace, and the removal work is easy,
The working time is certainly reduced.

[Problems to be solved by the device]

However, it is necessary to stop the line in order to remove the foreign matter, and the line stop for removing the foreign matter is often twice a week, which is a major factor that hinders the productivity. In addition, it is necessary to replace the inside of the snout with an inert gas each time foreign matter is removed, and the foreign matter is frequently removed. Therefore, the cost required for this gas replacement is enormous.

On the other hand, as a device for removing foreign matter without stopping the line, the plating bath in the snout is sucked by a pair of suction ducts provided on both sides in the width direction of the steel strip, and discharged to the outside of the snout through the duct, A device is known in which a flow in the width direction of a steel strip is generated in a plating bath in a snout, and along the flow, suspended foreign matters in the snout are continuously discharged and removed to the outside of the snout.

However, in this device, the floating foreign matter in the snout moves toward the duct in the snout along the plating bath flowing in the width direction of the steel strip, so that a flaw called "horizontal stripe" is formed on the plating surface of the steel strip. There was a risk of it occurring. The foreign matter floating near the central portion of the steel strip often cannot be removed because the suction forces of the suction ducts located on both sides of the steel strip are balanced.

The present invention has been made in view of such a situation, and the plating operation can be continued for a long time without removing the foreign matter from the outside of the snout, and the surface flaws such as "horizontal stripes" do not occur and the foreign matter remains. It is an object of the present invention to provide a continuous hot-dip galvanizing apparatus that does not occur.

[Means for Solving the Problems]

The plating apparatus of the present invention is a continuous hot dip plating apparatus equipped with a snout that shuts off the entrance path of the steel strip entering the plating bath from the outside air. And a plating bath supply means for supplying a plating bath into the weir and discharging foreign substances in the weir together with the plating bath between the weir and the snout.

[Action]

In the plating apparatus of the present invention, foreign substances generated in the weir during the plating operation are eliminated between the weir and the snout during the plating operation by supplying the plating bath into the weir. As a result, the vicinity of the steel strip entry position on the plating bath surface is kept clean, so that the plating operation can be continued for a long time without discharging the foreign matter in the snout to the outside.

Further, due to the overflow of the steel strip side plating bath, a plating bath flow that flows from the steel strip side to the outside thereof, that is, toward the snout side plating bath is generated in the steel strip side plating bath. Foreign matter floating on the steel strip side plating bath surface is discharged to the snout side plating bath along this plating bath flow.
It does not flow in the width direction of the steel strip. Therefore, "horizontal streak" flaws do not occur on the plated surface of the steel strip, and no floating foreign matter is discharged and remains in the plating bath surface of the steel strip.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional side view showing an essential part (snout portion) of an example of a plating apparatus embodying the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG.

In the plating apparatus of this embodiment, the snout 11 is arranged at a predetermined inclination angle. The snout 11 has its lower end immersed in the plating bath, and its upper end connected to the outlet of the annealing furnace. The lower end 12 of the snout 11 is connected to the snout body 14 via a heat-resistant bellows 13, and a drive mechanism 1 including a screw jack, a rack pinion, a cylinder, etc.
By means of 5, it can move up and down with a predetermined inclination angle. By this vertical movement, the lower end of the snout 11 is dipped in the plating bath and pulled up onto the bath surface. The steel strip 2 that has left the annealing furnace advances in the snout 11 and enters the plating bath.

In the lower end portion 12 of the snout 11, two weirs 16, 16 parallel to the steel strip 2 are provided. These weirs 1
6 and 16 are steel strip facing surfaces 110 of the steel strip 2 and the snout 11.
In between, the plating bath is divided into the steel strip 2 side and the snout 11 side in the vicinity of the bath surface, and both side ends thereof are fixed to both side surfaces of the snout lower end portion 12.

A pipe 17 is inserted between the steel strip 2 and the weir 16 from below, and its tip is located below the plating bath surface and above the lower end of the weir 16. The pipe 17 has a base end connected to a pump 18 disposed outside the snout 11 via a lower portion of the lower end of the snout 11. The pipe 17 and the pump 18 constitute a plating bath supply means, and the pump 18
Is driven to supply the plating bath from outside the snout 11 through the pipe 17 between the steel strip 2 and the weir 16 in the snout 11. As shown in FIG. 2, this plating bath supply means is provided in two stages in the width direction of the steel strip on each side with the steel strip 2 interposed therebetween.

To perform the plating operation in the plating apparatus of this embodiment,
The lower end 12 of the snout 11 is lowered, and the lower end is immersed in a plating bath for sealing. In this state, the upper end of the weir 16 projects from the plating bath surface. With the inside of the snout 11 kept in the same reducing atmosphere as in the annealing furnace, the steel strip 2
Enters the plating bath from the annealing furnace through the inside of the snout 11. Snout 1 as the plating operation progresses
A top dross is generated on the plating bath surface in the No. 1, and foreign matters which are carried from the furnace or generated from the metal vapor in the snout 11 also float on the plating bath surface in the snout 11.
These foreign matters mainly collect between the steel strip 2 and the weirs 16, 16, that is, inside the weirs 16, 16.

However, in the plating apparatus of the present embodiment, the plating bath outside the snout 11 is driven by the pump 18 so that the pipe 17
Then, it is discharged from below between the steel strip 2 and the weirs 16, 16. By this discharge, the plating bath surface rises between the steel strip 2 and the weirs 16, 16, and the weirs 16, 16 and the snout 1
The plating bath overflows between the first steel strip facing surface 110 and the first steel strip facing surface 110. Due to this overflow, a plating bath flow that flows from the steel strip side toward the snout side plating bath is generated in the steel strip side plating bath. Foreign substances floating on the plating bath surface between the steel strip 2 and the weirs 16, 16 are discharged between the weirs 16, 16 and the steel strip facing surface 110 of the snout 11. The foreign matter discharged here does not affect the plating quality of the steel strip even in the snout 11. Therefore, snout 11
It is possible to continue the plating operation for a long time without discharging it to the outside. The supply of the plating bath into the weirs 16, 16 may be continuously performed during the plating operation or may be intermittently performed.

In the above embodiment, the weir is installed between both side surfaces of the snout, but it is also possible to provide the weir so as to surround the steel strip within the snout by installing an appropriate supporting member between the weir and the snout. Is.

[Effect of device]

INDUSTRIAL APPLICABILITY The plating apparatus of the present invention can continue the plating operation for a long period of time without removing foreign matter outside the snout. Therefore, the number of foreign substances discharged to the outside of the snout is drastically reduced, and the number of line stoppages and gas replacements due to the foreign substances discharged to the outside of the snout are drastically reduced, which enables a significant reduction in plating cost.

In addition, the surface of the plated steel strip is free from flaws such as "horizontal stripes" due to foreign matter, and does not remain due to insufficient foreign matter removal capability.
Therefore, a high-quality plated steel strip can be stably obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing an essential part of an example of a plating apparatus embodying the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 shows a general structure of the plating apparatus. It is a schematic side view shown. In the figure, 11: snout, 16: weir, 17, 18: plating bath supply means.

Claims (1)

[Scope of utility model registration request] 1. A continuous hot dip galvanizing apparatus equipped with a snout for shutting off an entrance path of a steel strip entering a plating bath from the outside air, wherein a bottom surface of the snout immersed in the plating bath is parallel to both sides of the steel strip. A weir that is provided to partition the plating bath surface in the snout into a steel strip side and a snout side in the vicinity of the plating bath, and a plating bath outside the snout is supplied from below to the steel strip side plating bath in the weir. A continuous hot dip plating apparatus comprising: a plating bath supply means for overflowing foreign matter inside the plating bath onto the weir and discharging the foreign matter to the surface of the snout side plating bath outside the weir.