JP2548095Y2 - Gas wiping nozzle - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas wiping nozzle for controlling a coating weight in a continuous hot-dip plating facility, and more particularly to a gas wiping nozzle suitable for producing thin-coated products at a high speed.

[0002]

2. Description of the Related Art In recent years, demand for surface-treated steel sheets having excellent corrosion resistance has been rapidly increasing for use in steel sheets for automobiles, civil engineering, construction, and household electric appliances. In addition, hot-dip galvanizing and hot-dip aluminum plating are frequently used.

FIG. 1 is a schematic configuration diagram of a continuous hot-dip galvanizing facility. The steel strip 1 in which the mechanical properties and the penetration temperature into the plating bath are adjusted in the continuous furnace enters the plating bath 4 in the plating pot 3 via the snout 2. The steel strip 1 that has penetrated into the plating bath 4 has its direction changed by a non-driven sink roll or so-called pass roll 5 immersed and arranged in the plating bath 4, and a support roll also immersed and arranged in the plating bath 4. 6 and is lifted from the plating bath 4. The steel strip 1 pulled up from the plating bath 4 is cooled to room temperature via the wiping nozzle 7 and the top roll 8.

[0004] The function of the wiping nozzle 7 is to spray compressed air such as air or N ₂ from a slit provided over the entire width of the plated steel sheet onto the surface of the plated steel sheet, thereby pulling up the plated steel sheet from the plating bath. The purpose is to control the amount of metal plating on the belt surface.

Conventionally, as a method of controlling the amount of plating metal deposited by a wiping nozzle, a method of adjusting a slit gap of the nozzle (Japanese Patent Laid-Open No. 57-200588),
A method of adjusting the distance between a plated steel strip and a nozzle (Japanese Patent Laid-Open No.
JP-A No. 1-111430), by setting the angle between the front portion of the wiping nozzle body and the plated steel strip to a specific angle, it is possible to prevent the generation of a vortex due to turbulence of the wiping gas between the nozzle and the plated steel strip to perform plating. A method of controlling the amount of adhesion (Japanese Patent Laid-Open No. 2-57953) and the like have been proposed.

[0006] In addition to the above, common methods employed in actual operations include a method of adjusting the pressure or flow rate of the wiping gas, a method of adjusting the spray angle of the wiping gas, and a method of adjusting the nozzle height from the plating bath. There is a method of performing adjustment and the like.

[0007]

Recently, attempts have been made to produce thin-walled products equivalent to electroplated products in a continuous hot-dip galvanizing line. That is, by passing a steel strip through a hot-dip zinc bath at a high speed of, for example, 100 m / min or more, and by strongly gas-wiping the hot-dip zinc adhering to the surface of the steel strip to reduce the amount of the hot-dip zinc, the same as an electroplated product It produces thin-walled products.

In general, it is considered effective to increase the slit gap of the wiping nozzle and increase the wiping gas pressure for thinning. That is, the larger the slit gap of the wiping nozzle, the higher the wiping gas pressure, the greater the drawing force of the hot-dip metal of the nozzle,
The coating weight is limited.

However, by increasing the amount of wiping gas or increasing the pressure, scatter of plating metal called splash caused by collision between wiping gases at the edge of the coated steel strip, and molten metal on the plating bath surface due to similar causes. Splash splash occurs, and as a result, the occurrence of steel strip surface defects due to
This has caused an increase in the amount of plating metal oxide scattered on the plating bath surface, and further caused environmental pollution and safety problems due to the plating metal scattered around the plating pot.

[0010] In addition, due to the increase in the amount of wiping gas, the hot-dip metal on the surface of the steel strip is cooled to exhibit a solidification phenomenon. As a result, the fluidity of the adhered plated metal is reduced, and it is difficult to reduce the amount to the target amount. Was also happening.

[0011] Such adverse effects associated with an increase in the amount of wiping gas and an increase in pressure are particularly remarkable in the production of thin-walled products at high speeds, and the problems as disclosed in Japanese Utility Model Laid-Open No. 2-57953 are disclosed. It was difficult to produce a product of electroplating equivalent of satisfactory quality only by the above-mentioned measures against splash.

An object of the present invention is to provide a gas wiping nozzle capable of producing high-quality thin products at a high speed.

[0013]

Means for Solving the Problems In order to achieve the above object, the present inventors have investigated in detail the drawing behavior of hot-dip metal by a wiping nozzle when manufacturing thin-walled products at a high speed. As a result, in the case of thinning at a high speed, such as when manufacturing an electroplating equivalent, the biggest obstacles to the drawability are the cooling and splashing of the surface of the plated steel strip by the wiping gas. It was concluded that the main factor was in increasing gas volume.

That is, increasing the gas flow rate is an effective means for ensuring the metal drawing ability of the gas wiping nozzle, and this has been proved particularly in the case of manufacturing thick-walled products. However, in the production of thin-walled products, rather than improving the drawability of the plated metal by increasing the gas amount, the cooling effect of the plated metal adhered to the steel strip surface is greater, resulting in impaired drawability, or It has been found that a splash due to collision between gases due to an increase in the amount of gas is generated.

From these facts, the inventors of the present invention effectively reduce the gas flow rate by narrowing the slit of the wiping nozzle and thereby increase the gas flow rate in order to secure the squeezing property in thinning at high speed. As a result of various tests, the present invention was completed.

The wiping nozzle of the present invention is a gas wiping nozzle for hot-dip metal plating which controls the amount of plating applied to the surface of a steel sheet by spraying a wiping gas onto the surface of the steel sheet to which the hot-dip metal is deposited. The central part in the width direction was a parallel part with a constant slit gap, the slit gap was not less than 0.3 mm and less than 1.0 mm, and a tapered part where the slit gap gradually increased laterally was provided on both sides of the parallel part. It is characterized by the following.

[0017]

FIG. 2 is a front view showing the nozzle slit of the wiping nozzle of the present invention.

The central portion of the slit 10 in the plate width direction is the parallel portion 1.
The left and right sides are symmetrical tapered portions 12, 12 whose slit gap gradually increases toward the side.

The total width L of the slit 10 is the maximum plate width Wmax
The width l of the parallel portion 11 is set to a minimum plate width Wmi.
It is slightly smaller than n.

The slit gap g of the parallel portion 11 which is important in the present invention is not less than 0.3 mm and less than 1.0 mm. When the slit gap g is 1.0 mm or more, in thinning at a high speed, an increase in the amount of wiping gas causes the cooling of the plated metal on the surface of the coated steel strip to proceed, so that the drawing effect of the hot-dip plated metal is rather reduced. . Also, the collision between the wiping gases at the steel strip edge becomes remarkable, and a splash occurs. On the other hand, with a slit gap g of less than 0.3 mm, the wiping capacity is limited.
The wiping pressure for securing the wiping capacity increases.

That is, in the wiping nozzle of the present invention, the slit gap g of the parallel portion 11 is narrowed to 0.3 mm or more and less than 1.0 mm, so that the amount of wiping gas can be reduced at the time of producing thin-walled products at a high speed. By reducing
By suppressing the cooling of the plated metal on the surface of the plated steel strip and by mitigating the collision between the wiping gases at the edge of the steel strip, it is possible to suppress the occurrence of splash.
Further, with the decrease in the amount of wiping gas, the amount of oxidation of the wiped plating metal also decreases, and the amount of top dross floating on the plating metal bath surface can be suppressed.

Desirably, the slit gap is less than 1.0 mm over the entire width of the slit 10.

The function of the tapered portion 12 is to increase the wiping force on the edge portion by widening the slit gap corresponding to the edge portion of the steel strip, and to prevent the build-up of the edge portion, thereby making the amount of adhesion uniform in the width direction. It is.
The slit gap is desirably not less than 1.1 times and not more than 1.4 times the slit gap g of the parallel portion 11 as represented by the maximum slit gap G at the side end. When G <1.1 g, build-up occurs at the edge, and when G> 1.4 g, the edge is excessively wiped.

The operating conditions in which the wiping nozzle of the present invention is particularly effective are high-speed thinning with a line speed of 100 m / min or more and a basis weight of 40 g / m ² or less per side.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.

In the slit shown in FIG. 2, the slit gap g of the parallel portion is set to 1.0 mm, 0.8 mm, 0.6 mm, 0.3 m.
m, 0.2 mm. The width l of the parallel portion is 800 mm, and the total width L of the slit gap is 2000 m
m, the width l ′ of the tapered portion is 600 mm, and the maximum slit gap G of the tapered portion is the slit gap g of the parallel portion.
1.3 times of The steel strip width is 1000 mm.

FIG. 3 shows the relationship between the wiping pressure and the amount of single-sided adhesion at each slit gap, and FIG. 4 shows the relationship between the wiping pressure and the nozzle height at which the splash occurs.
The plating is hot-dip galvanized, and the line speed is 12
0 m / min.

At a high speed of 120 m / min, when the slit gap was 1.0 mm, the coating metal deposition amount was limited to 35 g / m ^{2 on} one side even if the wiping gas pressure was increased. However, by the slit gap and 0.8 mm, it enables with diluted about 25 g / m ² on one side, squeezed up with thin of about 20 g / m ² and electroplating article corresponds on one side at 0.6mm or less Nature was secured.

At the same time, the generation of the splash can be suppressed, and the surface defect of the plated product due to the splash is almost completely prevented. In addition, the amount of oxidation of the plating metal due to the decrease in gas amount was reduced, and the amount of generated top dross was reduced.

[0030]

[Effects of the Invention] As is clear from the above description, the wiping nozzle of the present invention exhibits excellent drawability in thinning at a high speed by narrowing the slit gap.
This has an industrially significant effect of enabling the manufacture of thin-walled products equivalent to electroplating. In addition, the yield can be improved by preventing the occurrence of surface defects, and the amount of top dross can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a continuous hot-dip galvanizing facility.

FIG. 2 is a schematic view showing an example of a slit configuration of the wiping nozzle of the present invention.

FIG. 3 is a graph showing an effect of a slit gap on a plating adhesion amount.

FIG. 4 is a graph showing the effect of a slit gap on splash generation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel strip 4 Plating bath 7 Wiping nozzle 10 Slit 11 Parallel part 12 Tapered part

Claims (2)

(57) [Scope of request for utility model registration] In a gas wiping nozzle for hot-dip metal plating for controlling the amount of plating on the surface of a steel sheet by spraying a wiping gas onto the surface of the steel sheet to which the hot-dip coated metal has been applied, the central part of the nozzle slit in the width direction of the nozzle is controlled. The slit gap is a constant parallel part, and the slit gap is
A gas wiping nozzle characterized in that it has a taper portion of 0.3 mm or more and less than 1.0 mm and a slit gap gradually increasing laterally on both sides of a parallel portion. 2. The gas wiping nozzle according to claim 1, wherein a maximum slit gap of the tapered portion is set to be 1.1 to 1.4 times a slit gap of the parallel portion.