JPH07238358A - Method for replenishing component to plating bath and device therefor - Google Patents

Abstract

PURPOSE:To unify the components in a plating bath in a snout part and prevent occurrence of unequal alloying in the transverse direction of a metallic sheet to be plated by simultaneously supplying a hot dip coating metal even to the parts of the metallic sheet exclusive of the parts where the hot dip coating metal infiltrates. CONSTITUTION:The hot dip coating alloy regulated in the components and temp. by a premelt pot 4 is transferred through a conduit 7 by a pump 6 and is supplied from plural hot dip coating metal replenishing ports 5 arrayed in the transverse direction of the sheet on both sides of the inside wall of the snout 3 when the amt. of the alloy in a plating tank 13 is short. This supply is executed by judging the timing by a proper method. As a result, the Al enriched layers uniform in the transverse direction of the steel sheet 2 are formed as the plating layers. The hot dip coated steel sheet having high quality is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying components to a plating bath in continuous hot metal plating and an apparatus which can be used for carrying out the method.

[0002]

2. Description of the Related Art In continuous hot dip plating, a continuously running metal plate or strip is dipped in a bath filled with molten metal for a predetermined time to deposit a desired plated metal on the surface of the metal plate. A hot-dip galvanized steel sheet is a typical example of the metal plate manufactured by the method.

By the way, when performing continuous hot dip galvanizing, pure zinc may be used in the plating bath, but it suppresses the growth of a hard and brittle Fe-Zn alloy layer formed at the interface between zinc and the base steel. In many cases, Al is added to improve the adhesion of the plated metal to the base. In addition to the above-mentioned addition of Al, the plating metal is usually in an alloy state by adding a small amount of Pb for forming a so-called flower pattern on the plating surface. When performing continuous hot dip plating with such an alloy, each alloy component in the plating bath is reduced as it is taken out as a plating layer adhering to the steel plate surface or due to the formation of floating dross. Need to replenish. Therefore, this replenishment technology has been researched and developed in the past, and the improvements thereof are still ongoing.

A conventional replenishment method is disclosed in, for example, Japanese Patent Laid-Open No. 62-2.
As disclosed in Japanese Patent No. 38358, pure Z is added to the plating bath.
It was to add an ingot of an Al—Zn alloy adjusted to n or one or more components as needed. However, with this replenishment method, it takes time for the ingot to melt and diffuse in the bath to form a uniform plating bath, and the ingot feeding interval is long, so fluctuations in the Al concentration in the bath cannot be prevented. However, there is a limit to satisfy the recent severe plating quality requirements, and a component replenishment method capable of achieving better plating quality has been desired.

Therefore, Japanese Patent Laid-Open No. 2-104649 discloses a plurality of premelt pots 4 as shown in FIG.
(See Fig. 4 (a)) Dissolve the supplementary supplementary components individually,
From there, the components are replenished and mixed in a mixing tank 12 separately provided in the plating bath so as to correspond to the required replenishment concentration and the reduction amount of the plating bath (FIG. 4 (b)), and then an injection nozzle is used. A method of spraying into a plating bath has been disclosed. Also,
As a method of preventing dross indentation by using a premelt pot and spraying a hot-dipped metal onto a steel sheet, there is also a method disclosed in JP-A-2-156054.

However, these Japanese Patent Laid-Open No. 2-1560
Although the method described in Japanese Patent Laid-Open No. 54-104649 and Japanese Patent Laid-Open No. 2-104649 also improved the plating quality of the product, the snout 3 (the cylinder at the entrance of the plating tank at which the steel plate is immersed in the plating bath). It takes time until the internal components become uniform, especially due to the flow of the bath generated by the progress of the steel plate, and the components in the snout and in the width direction. There was a problem that it was not possible to prevent the non-uniformity. In other words,
Since the position of -156054 plating metal spraying is before the sink roll or the snap roll in the latter half when the steel plate passes through the plating bath, in the width direction of the steel plate in the snout, which has a great influence on the plating quality. It was not intended to make the plating layer uniform.

Further, as a means for supplying molten metal into the snout from a pre-melt pot, see Japanese Utility Model Publication No. 57-138.
There is also a technique disclosed in Japanese Patent No. 78, but it aims to add an alloying suppressing element to non-alloyed hot dip plated steel sheets, and also mentions the necessity of uniform plating in the width direction of the steel sheet. However, the present invention is different from the object and method in the present invention.

[0008]

In view of such circumstances, the present invention provides a plating bath capable of preventing the unevenness of the alloy in the plate width direction by making the components of the plating bath uniform in the width direction of the metal plate inside the snout. It is an object of the present invention to provide a method for replenishing the ingredients and a device that can be used for the implementation.

[0009]

In order to achieve the above-mentioned object, the inventor has conducted experiments and studies, and in hot metal plating,
It was concluded that the plating layer formed at the beginning of plating is very important. In order to embody this conclusion, the metal plate to be plated usually has a plate width of 500 to 2000 mm, and in continuous hot-dip metal plating in which this plate passes through the plating bath at a considerably high speed, the plating bath containing a stable component at the beginning of plating. Recognizing that the point is exposure to the sun, we made every effort to achieve it. The present invention has been completed as a result, and in a component replenishment method for supplying the hot-dip plated metal from a pre-melt pot or a mixing tank of the hot-dipped metal to the plating bath, the metal plate to be plated is the plating bath. This is a component replenishing method for a plating bath, characterized in that the hot-dip galvanized metal is uniformly supplied to the entire invading portion in the plate width direction. In order to promote this effect, the present invention is also a method of supplying components to a plating bath according to claim 1, characterized in that the hot dip plated metal is simultaneously supplied to a portion other than the portion where the metal plate to be plated enters. Furthermore, as an apparatus that can be used for carrying out the present invention, the present invention is a plating tank provided with a tubular snout through which a metal plate to be plated passes, and a plurality of metal plates are provided in the snout along the plate width direction of the metal plate to be plated. The component supply device for a plating bath is characterized in that individual hot-dip metal supply ports are arranged in a row.

[0010]

In the present invention, a method for supplying components to a plating bath by supplying the hot-dip metal to the plating bath from a pre-melt pot or a mixing bath of the hot-dip metal is a metal plate to be plated Since the hot-dip galvanized metal is uniformly supplied to the entire part in the plate width direction of the invading part, the metal to be plated is immersed in the hot-dip galvanized metal of the desired component over the entire plate width in the snout, The Al-rich layer formed at the beginning of plating becomes uniform in the plate width direction, and uneven alloying in the width direction does not occur in the subsequent alloying treatment. This state is maintained from the start to the end of the plating operation, so that a hot-dip metal sheet with extremely little unevenness of alloy in the entire length and width direction of the plating layer can be manufactured. Further, in the present invention, since the hot dip plated metal is simultaneously supplied to a portion other than the invading portion of the metal plate to be plated, the above effect is promoted and the quality of the hot dip plated metal plate is further improved. There is also provided an apparatus capable of carrying out the component replenishing method of

The contents of the present invention will be described below with reference to FIGS.

[0012]

EXAMPLES FIG. 1 shows an example of equipment when the method of supplying components to a plating bath according to the present invention is carried out in the production of hot-dip galvanized steel sheets. (A) is a side sectional view and (b) is It is an AA arrow plane. There, thickness 0.8mm, width 1500m
m thin steel sheet for automobiles (hereinafter, simply referred to as a steel sheet) 2 as a metal sheet 2 to be plated, and 0.14% Al-
It was plated with a Zn alloy. First, the steel sheet 2 passes through an oxidation prevention tube (snout 3) of the steel sheet 2 provided on the upper surface of the plating bath 1, is immersed in the plating bath 1, and is changed in direction by a sink roll 8 near the bottom of the plating bath to perform stabilizing. Emit into the atmosphere via roll 9. After that, the excessively adhered plated metal is removed by the gas wiping nozzle 10, heated at 500 ° C. in the alloying furnace 11, and then wound up into a product. At that time, the speed of the strip was 100 m / min. The first hot-dip galvanized metal was supplied to the plating tank 13 from another pre-melt pot (not shown) and plated with the hot-dipped galvanized metal at the beginning of the operation. However, after 30 minutes, the amount of alloy in the plating tank 13 became insufficient, so the hot-dip zinc alloy whose components and temperature were adjusted in the premelt pot 4 shown in FIG. Transfer and 400 in the width direction on both sides of the inner wall of the snout.
It was supplied from a hot-dip galvanized metal replenishing port 5 arranged in five places at intervals of mm. The supply was performed at an average of 5 minutes with the timing determined by using a bath level meter as a sensor. As a result, a uniform Al-enriched layer was formed in the width direction of the steel sheet 2 as a plating layer, and a hot-dip galvanized steel sheet with good quality was obtained.

As a comparative example, the same steel sheet was plated by a method of using a mixing tank 12 in addition to the premelt pot 4 described in JP-A-2-104649 as a component supply method. As shown in FIG. 4, it uses equipment such as the present invention that does not have a supply port for plated metal in the width direction of the steel sheet. Both of these results are shown in FIG. 2 as variations in the Al enrichment amount (g / m ² ) in the plate width direction. According to FIG. 2, it can be seen that the method of supplying components to the plating bath according to the present invention is excellent. At this time, the total length of the steel plate 2 is 100
The result in FIG. 2 is an average value for almost the entire length. Further, FIG. 3 shows another result when the component replenishing method according to the present invention and the above comparative example are carried out. From FIG. 3, the degree of alloying of the steel plate 2 in the plate width direction is more uniform in the method according to the present invention,
Good implementation results. In the above example, the snout 4
Although the hot dip plating solution was replenished only in the case of No. 4, but when it was also replenished from the portion other than the snout 4 at the same time, the result becomes as shown by a mark in FIG. 3, and the uniform effect is further improved.

It is needless to say that the method of supplying components to the plating bath according to the present invention is not limited to the examples of the metal plate 2 to be plated and the hot-dip plated metal, and can be applied to many metals.

[0015]

As described above, according to the present invention, in the snout, which is the part where the metal plate to be plated penetrates into the plating bath, the components, the temperature of which is adjusted in the premelt pot or the mixing tank, the hot-dip metal is adjusted, By supplying from a plurality of replenishing ports arranged along the plate width direction, it becomes possible to manufacture a hot-dip metal plate without uneven alloying in the plate width direction.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of equipment for carrying out a method for supplying components to a plating bath according to the present invention, in which (a) is a side sectional view and (b) is
Is a view on arrow AA.

FIG. 2 is a comparison of the results of implementation by the method of the present invention and the comparison method, and is a diagram showing the amount of Al enrichment in the width direction of the steel sheet.

FIG. 3 is a comparison of implementation results by the method of the present invention and the comparison method, and is a diagram showing an alloying state in the width direction of the steel sheet.

FIG. 4 is a diagram showing a conventional component replenishing facility for a plating bath, in which (a) is a plan view and (b) is a side sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating bath 2 Metal plate (steel plate) to be plated 3 Snout 4 Premelt pot 5 Hot-dip plating metal supply port 6 Pump 7 Conduit 8 Sink roll 9 Stabilizing roll 10 Wiping nozzle 11 Alloying furnace 12 Mixing tank 13 Plating tank

Claims (3)

[Claims] 1. A component replenishment method for supplying the hot-dip plated metal to a plating bath from a pre-melt pot or a mixing tank of the hot-dipped metal, wherein the metal plate to be plated penetrates the whole of the plate width direction. A method for supplying components to a plating bath, which comprises uniformly supplying the hot-dip metal. 2. The method for replenishing components to a plating bath according to claim 1, wherein the hot-dip galvanized metal is simultaneously supplied to a portion other than the portion where the metal plate to be plated enters. 3. A plating tank having a tubular snout through which a metal plate to be plated passes, wherein a plurality of hot-dip metal supply ports are provided in the snout along the plate width direction of the metal plate to be plated. A component replenishing device for the plating bath.