JPH07113154A - Method and device for hot-dipping - Google Patents

Abstract

PURPOSE:To provide a method and device in which the adhesion of foreign matters on the surface of the steel sheet at a snout part of the hot-dipping is prevented and a plated steel sheet with excellent appearance is obtained. CONSTITUTION:In the hot-dipping method, a box 3 to surround a steel sheet 1 is formed at the part where the steel sheet 1 is dipped in a plating tank at a snout part of the hot-dipping, and the hot-dipping liquid is overflowed from an upper opening part of the box 3 by feeding the plating liquid into the box. The hot-dipping device is provided with a discharging device 6 of foreign matters which are deposited between the box 3 and the inner wall of the snout part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for hot dip galvanizing, hot dip galvanizing, hot dipping aluminum, hot dipping zinc-aluminum alloy plating and the like.

[0002]

2. Description of the Related Art As is well known in the hot metal plating method, after the steel sheet to be plated is heated and annealed, the upper end is connected to an annealing furnace and the lower end is immersed in a plating bath through the inside of a snout immersed in the molten metal plating bath. The method is to obtain a hot-dip metal-plated steel sheet by controlling the amount of hot-dip metal plating adhered by a gas squeezing method by changing the traveling direction by a pot roll in a bath and pulling it upward. When the steel sheet is immersed in the plating bath through the snout part, dust, scum,
When foreign matter such as dross, fragments of refractory bricks in an annealing furnace, and powder adheres, problems such as plating surface defects and abnormal alloying reaction occur.

In order to solve this problem, various methods have been conventionally proposed, for example, the following methods. (1) A method of preventing the generation of scum by adjusting the hydrogen and oxygen concentrations in the atmosphere introduced into the snout to below a specific concentration. (Japanese Patent Publication No. 2-25981, Japanese Patent Publication No. 3-4
(9981 gazette) (2) Foreign matter such as scum on the bath surface is wiped off by discharging molten metal from one end side to the other end side in the width direction of the steel sheet immersed in the snout, and at the other end side Method for preventing foreign matter from adhering to the steel plate by discharging the powder to the outside of the snout (JP-A-61-186463)

(3) Foreign matter such as scum on the bath surface is wiped by blowing an inert gas onto the plating bath surface from one end side to the other end side in the width direction of the steel sheet dipped in the snout, and A method of preventing foreign matter from adhering to the steel plate by discharging foreign matter outside the snout at the end. (JP-A-4-276051 and JP-A-4-276052)

(4) Foreign matter on the bath surface is provided by providing a slit nozzle over the entire width of the steel sheet below the surface of the molten metal plating bath and jetting the molten plating solution toward the steel sheet in the vicinity where the steel sheet enters the plating bath. How to prevent sticking. (JP-A-60-
No. 2654) (5) A method of preventing foreign matter from adhering to the steel sheet by providing a weir that partitions the steel sheet and the snout wall in the snout, and supplying a molten plating solution into the weir to discharge the foreign matter. (Japanese Patent Laid-Open No. 2-66666)

However, each of the methods has drawbacks and cannot prevent foreign matter from adhering to the steel sheet. That is,
In the method (1), for example, foreign substances adhering to the steel plate and falling onto the plating bath surface from the inner wall of the snout cannot be removed merely by controlling the atmospheric gas composition in the snout. The methods (2) and (3) have the effect of reducing the amount of foreign matter on the bath surface, but part of them adhere to the steel plate during the process of wiping foreign matter from one end side to the other end side in the snout. However, there was a problem that it could not completely prevent the adhesion of foreign matter.

In the method (4), since it is necessary to eject the plating bath with a strong pressure in order to remove the foreign matter in the vicinity of the steel sheet, not only the running cost is required, but also the steel sheet end portion is discharged from the slit nozzles on both sides. Due to the collision of the plating solution flow, the effect of eliminating foreign matter was lost, and defects such as entrainment of foreign matter due to waviness of the plating bath surface occurred. Method (5) is
In order to supply zinc to the weir whose bottom is open and discharge foreign matter, it is necessary to increase the flow rate of zinc, which not only requires running cost, but also disturbs the plating bath and entrains foreign matter. Problems such as foreign matter adhering to the steel sheet occurred.

[0008]

DISCLOSURE OF THE INVENTION The present invention, in hot dip metal plating, when a steel sheet is immersed in a plating bath through a snout portion, dust on the steel sheet surface or the plating bath surface,
The purpose is to prevent problems such as plating surface defects and alloying reaction abnormalities due to foreign substances such as scum, dross, fragments of refractory bricks in an annealing furnace, and powders adhering to them.

[0009]

In order to solve the above problems, the present invention provides the following means. (1) By forming a box surrounding the steel sheet in the portion where the steel sheet is immersed in the plating bath in the snout portion of the molten metal plating and feeding the plating bath into the box, the plating solution is caused to flow out from the upper opening of the box. A method and an apparatus for hot-dip plating of molten metal. (2) A method and an apparatus for hot-dip metal plating, comprising a device for discharging foreign matter deposited between the box according to (1) and the inner wall of the snout.

[0010]

The device of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view of an apparatus used in the present invention, and FIG. 2 is a horizontal sectional view of a snout portion. In the figure, 1 is a steel plate, 2 is a snout,
3 is a box, 4 is a pot roll, 5 is a plating solution delivery device, 6
Is a foreign substance discharging device, 7 is a foreign substance on the plating bath surface, 8 is a foreign substance discharging device suction port, and 9 is a wiping nozzle. According to the method of the present invention, a box 3 surrounding the steel sheet 1 is formed in the portion where the steel sheet 1 of the snout portion 2 is immersed in the plating bath, and the plating solution is fed from the plating solution delivery device 5 to the inside of the box 3 and the upper portion of the box 3 By flowing out the plating solution from the open portion, the foreign matter 7 on the plating bath surface is discharged between the box 3 and the inner wall of the snout 2 without adhering to the steel plate. The discharged foreign matter 7 is discharged outside the system by the foreign matter discharging device.

The metals applied in the present invention include zinc and zinc-based alloys, zinc-aluminum based alloys, aluminum and aluminum-based alloys. The material of the box is Fe-based alloy such as stainless steel, Ni such as Hastelloy and Vitalium, Co-based alloy, ceramic such as alumina and zirconia, and composite material such as metal coated with ceramic, corrosion resistance, oxidation resistance and heat resistance. A material with good properties and thermal shock resistance can be applied. The shape of the box is such that the upper end is located near the plating bath surface inside the snout. A function of correcting the position may be added to the fluctuation of the plating bath surface. In order to reduce the outflow of the plating bath from the steel plate passage portion at the bottom of the box, a shielding plate, a seal roll, etc. may be arranged. The structure of the box may be a divided structure so that the box can be attached and detached in the molten metal plating without cutting the steel plate.

A metal pump, an electromagnetic pump or the like can be applied as the plating solution delivery device. A flow rate adjusting function may be added. The flow rate is not particularly limited, but in order to flow out the plating solution from the upper opening of the box, it is necessary to supply more than the amount leaking from the steel plate passage section at the bottom of the box.
As the foreign matter discharge device, a suction type discharge using a metal pump, an electromagnetic pump, or the like, or a mechanical discharge having a double-type opening / closing door or the like in the snout portion can be applied. A device for blowing an inert gas from the bath surface, a scraping jig, or the like may be used to scrape and collect foreign matter between the box periphery and the inner wall of the snout to the discharge device.

[0013]

EXAMPLES Next, examples of the present invention will be described. In a continuous hot-dip galvanizing line capable of passing steel sheets up to a maximum sheet width of 1219 mm, the device of the present invention was installed in the portion where the steel sheet in the snout portion is immersed in the plating bath. The box was made of a material obtained by spraying ceramic on stainless steel, and the upper opening had a size around 50 mm from the steel plate, and the position was at the same level as the bath surface. A rotary metal pump was used as the plating solution delivery device. The flow rate of the plating solution was adjusted so that the surface of the Snout bath was observed while the plate was running and zinc was gently discharged from the upper opening of the box. When observing the plating bath surface condition when a steel plate having a plate thickness of 0.8 mm and a plate width of 1219 mm was passed at a speed of 80 m / min, foreign matter such as dust from the plating bath surface scum and the inner wall of the snout was found in the box. It was eliminated without adhering to the steel plate by the plating bath flowing out from the upper opening of the. At that time, a product with good appearance was obtained with almost no foreign matter adhering to the plated steel plate surface.

[0014]

EFFECTS OF THE INVENTION By applying the present invention, it is possible to manufacture a plated steel sheet having a good appearance and free of foreign matter.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an apparatus used in the present invention,

FIG. 2 is a cross-sectional view of the snout portion of the device used in the present invention.

[Explanation of symbols]

 1 Steel plate 2 Snout 3 Box 4 Pot roll 5 Plating solution delivery device 6 Foreign matter discharge device 7 Foreign matter on the plating bath surface 8 Foreign matter discharge device Suction port 9 Wiping nozzle

Claims (2)

[Claims] 1. A plating bath is formed from a top opening of the box by forming a box surrounding the steel sheet in a portion where the steel sheet is immersed in the plating bath in the snout portion of the molten metal plating and feeding the plating bath into the box. A molten metal plating method, characterized in that the molten metal is discharged. 2. A hot-dip galvanizing apparatus comprising a device for discharging foreign matter accumulated between the box according to claim 1 and the inner wall of the snout.