JPH0512428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to continuous hot-melt plating of metal strips,
In particular, it relates to continuous hot-melt plating of metal strips in which two or more different types of plating are performed using the same plating line.

Already today, continuous hot-dip plating of metal strips, such as continuous hot-dip galvanizing, is widely used as a surface treatment method for thin steel sheets for building material applications or for applications such as household appliances and automobiles.

Generally speaking, hot-dip plating of metal strips is not limited to one type, but various types of plating are appropriately selected and carried out by changing the type of plating metal or changing the proportion of the plating bath composition depending on the application. There is. However, preparing multiple dedicated plating pots to produce different plating products depending on the type of plating or changes in the plating bath composition not only increases equipment costs, but also complicates operations and increases productivity. It was also not desirable from the standpoint of sexual improvement.

Therefore, in the prior art, several methods have been proposed for performing two or more different types of plating using the same plating line, but these methods are not always satisfactory. .

As a method for changing the composition of the plating bath itself, for example, in JP-A No. 49-41234, a plurality of plating bath pots (hereinafter simply referred to as pots) are used.
Disclosed is a method in which pots are installed independently, and pots selected according to the type of plating are moved to predetermined positions on the plating line. However, such a method also requires a large capital investment in order to implement it, and the number of pots depending on the type of plating must be prepared independently, which inevitably increases production costs. There is also a known method that allows the composition of added metals in the plating bath to be changed (Japanese Patent Application Laid-open Nos. 51-15494 and 52-113331), but this only makes it possible to change some of the components. Therefore, it cannot be applied to the preparation of plating baths that have completely different components.

Thus, the general purpose of the present invention is to solve the above-mentioned drawbacks of the prior art, namely, to minimize the cost of modification and downtime of equipment when modifying and applying existing equipment;
It can also be applied to the above types of plating,
It is also applicable to plating baths with greatly different ingredients, and is based on a completely new idea.
The objective is to realize fusion plating that allows switching of plating baths using a multi-pot method.

In connection with this purpose, the present inventors previously proposed a continuous melt plating method and an apparatus therefor that enabled plating bath switching using a double pot system in Japanese Patent Application No. 57-227792. The purpose is to make further improvements.

Here, what is shown in Figure 1 is patent application No. 57-227792.
This is a continuous melt plating device 1 using the double pot method disclosed in the above patent, in which an inner pot 3 is immersed and housed in an outer pot 2.

Inner and outer pots 3, as shown in FIG.
In the case of the double pot method, which uses a double pot consisting of two pots, when plating is performed using the inner pot 3, the plating bath of the outer pot 2 requires the rotation of the sink roll in the inner pot and the strip bathing. Flow of the plating bath due to moving movement cannot be expected. That is,
Even when an induction type groove furnace is adopted as the type of outer pot, the flow of the bath from induction heating in the heating groove to the entire pot is due to thermal convection, and the bath has a viscosity. There is no great hope for heat transfer due to the flow of the bath, and furthermore, when a direct heating method from the outside is adopted, such as when using an iron pot, there is no fluidity of the bath due to the action applied from the outside. Therefore, in both cases, in the double pot system, the only heat transfer is the natural convection of the bath. On the other hand, in the plating bath in the inner pot, the sink roll immersed in the bath receives rotational force due to the tension of the strip, and due to the rotation of the sink roll and the movement of the strip itself in the bath, the plating bath in the inner pot is considerably It flows at a flow rate of , and the bath temperature is kept uniform. Also, the inner pot bath (hereinafter referred to as the inner pot bath)
Considering the heat balance of the bath, the heat input from the outer pot is used for natural dissipation from the bath surface and for heating the strip. Since the amount of heat required for heating the latter strip constantly changes depending on the size and line speed at that time, it can be easily estimated that the bath temperature in the inner pot will change minutely, and the heat input from the outer pot will If this cannot be handled, the bath temperature in the inner pot will change, making it impossible to maintain constant plating conditions, which will have a negative impact on plating quality. However, it seems that heat was conducted from the outer pot to the inner pot only by natural convection.
There may be cases where it is not possible to respond to the above-mentioned change in the bath temperature of the inner pot.

Therefore, in the present invention, a forced flow phenomenon other than natural convection is caused in the outer pot using various methods described below, and the plating bath in the outer pot (hereinafter referred to as the outer pot bath) is drained from the inner pot. The purpose is to improve the heat transfer to the bath, and its main points are: (1) In a continuous melt plating method for metal strips in which two or more different types of plating are performed by switching the plating bath, 1. Plating is performed continuously using a composite plating tank equipped with a plating bath pot and one or more other plating bath pots immersed and housed in the plating bath pot, and continuous melt plating is performed in the other plating bath pots. The plating bath described in 1 above is forcibly stirred while the plating bath is being heated.
continuous melt plating method; and (2) a composite plating tank comprising one plating bath pot and one or more other plating bath pots accommodated therein, wherein the one or more other plating bath pots are the same as the first plating bath pot. The pot is detachably attached to the plating bath pot and immersed in the plating bath to a sufficient depth, so that the heating energy for melting and keeping the plating bath heated is transferred from the heat source of the plating bath pot to the plating bath of the first plating bath. In a continuous melt plating device configured to be transmitted to the one or more other plating bath pots via the plating bath in the bath pot, a device for forcibly stirring this one plating bath is connected to the first plating bath pot. This is a continuous melt plating device characterized by being installed in the

In the present invention, the means for forcibly agitating and fluidizing the plating bath in the outer pot, that is, the outer pot bath, include all means for forcibly agitating ordinary liquids. In other words, although the present invention does not place any restrictions on the method of forced stirring itself, generally known methods include (1) using mechanical rotary blades, and (2) using gas in the bath. (3) A method in which the bath itself is circulated by a pump. In the case of mechanical rotor blades, rotation is applied to the rotor blade immersed in the bath from an external power source such as an electric motor through its rotating shaft.
There is no particular limit to the rotation speed, and it can be determined as appropriate based on operational needs. Regarding the material of the part to be immersed, stainless steel, surface-sprayed metal, ceramic, or the like is used in consideration of corrosion resistance. As a means for blowing gas into the bath, an inert gas such as N ₂ is suitable in order to prevent overoxidation of the molten metal, but there is no particular restriction. Furthermore, in the method of circulating the plating bath itself using a pump, there is no particular problem as long as a material that can withstand molten metal is selected, as in the case of using the rotary blades described above.

It should be noted that stirring using an electromagnetic pump may be considered as a method other than the one explained above, and it is clear to those skilled in the art from the above explanation that any of these methods can be selected as appropriate without departing from the purpose of the present invention. Will.

Next, the present invention will be further explained with reference to drawings showing embodiments of the present invention.

2 to 4 are side views, partially in section, of a plating device for carrying out the present invention. In addition, the same members are indicated by the same reference numerals in each drawing, including the case of FIG. 1.

2 to 4, the plating device 1 according to the present invention is comprised of a large outer pot 2 for melting and keeping the molten plating metal warm, and one or more small inner pots 3 accommodated inside the large outer pot 2. Consists of a composite plating tank. In the illustrated example, only one small inner pot 3 is provided, but a plurality of small inner pots 3 may be provided. The inner pot 3 is accommodated and held in a plating bath formed in the outer pot 2, that is, an outer pot bath, in a immersed state.

In the plating bath housed in the inner pot 3, that is, in the inner pot bath, a sink roll 4 supported by a suitable support device is disposed, and a metal strip 6 supplied to the inner pot bath via a snout 5 is placed in the sink roll. It passes through the roll 4 and is taken out of the plating tank from a pair of guide rolls (not shown). Therefore, when the metal strip is running, the metal strip 6
The inner pot bath is constantly stirred and fluidized by the moving movement of the sink roll 5 and the rotating movement of the sink roll 5.

On the other hand, the outer pot bath is appropriately heated and kept warm by heating means 7 (high-frequency induction heating in the illustrated example). This heating means is not particularly limited, and heating may be performed using, for example, a gas burner, electric heating, or the like. However, the inner pot bath is not provided with any particular heating means, and is heated and kept warm by the heat of the outer pot bath.

According to the present invention, the outer pot plating bath is appropriately provided with a stirring mechanism 8, which generates a forced stirring flow and transmits the heat from the heating means 7 to the inner pot bath.

FIG. 2 shows a case where the stirring mechanism 8 employs a system in which the outer pot bath is stirred by mechanical rotary blades. In the illustrated example, rotary blades 10 are attached to the tip of the rotating shaft 9, and are driven by an electric motor or other power source 11.

FIG. 3 shows a method in which gas is blown into the bath. In the illustrated example, a preferably inert gas 13 is introduced into the outer pot bath via a gas blowing device 12 consisting of a pipe immersed in the bath by an air supply device 14 which increases the pressure with a compressor or the like if necessary. Send it in.

FIG. 4 shows a case where the stirring mechanism 8 employs a system in which the bath itself is circulated by a pump. In particular, the circulation suction side 15 is preferably placed in a high temperature part of the bath, as shown in the figure, and the circulation pump 1
6 is preferably made of a material with good corrosion resistance against molten metal. Exposed side of circulation path 17
It is particularly preferable to direct it to a location with poor convection, such as the bottom of an inner pot.

Although the invention has been described above in relation to its specific embodiments, according to the invention the transfer of heat from the outer pot bath to the inner pot bath takes place rapidly and therefore the inner pot bath can be used. It has been found that even when plating with a hot pot, the plating conditions, especially the temperature of the inner pot bath, can be kept constant regardless of fluctuations in operating conditions, making it possible to perform high-quality plating.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a double-pot type melt plating apparatus; and FIGS. 2 to 4 are schematic side views, partially in cross-section, of the apparatus according to the present invention. 1... plating device, 2... outer pot, 3...
Inner pot, 4... sink roll, 5... snout, 6... metal strip, 7... heating means, 8
...Agitation mechanism.

Claims (1)

[Claims] 1. In a continuous melt plating method for metal strips in which two or more different types of plating are performed by switching plating baths, one plating bath pot and one or more other plating baths immersed and housed in the plating bath pot are used. Plating is performed continuously using a composite plating tank equipped with a plating bath pot, and while continuous melt plating is being performed in the other plating bath pot, the first plating bath is forcibly stirred. Continuous melt plating method. 2 1 plating bath pot and 1 housed in it
said one or more other plating bath pots are removably attached to said first plating bath pot and have a sufficient depth within said plating bath. The heating energy for melting and heat-insulating the plating bath is transmitted from the heat source of the one plating bath pot to the one or more other plating bath pots through the plating bath in the one plating bath pot. 1. A continuous melt plating device configured to allow the first plating bath to be forcibly stirred, wherein the first plating bath pot is provided with a device for forcibly stirring the first plating bath.