JPH04254561A - Sink roll for hot-dip metal coating - Google Patents

Abstract

PURPOSE:To simply and easily execute alloying of metal strip to be coated with coating metal by heating a sink roll in hot-dip metal coating bath from inner part at the time of executing a hot-dip metal coated layer on surface of the metal strip. CONSTITUTION:After executing galvernizing on surface of the steel strip 3 by dipping the metal strip 3 to be coated, of the steel strip, etc., while winding to the sink roll 1 supported with a supporting member 8 in the hot-dip metal coating bath of molten Zn, etc., in a coating vessel 2, the galvernized layer is alloyed with Fe in the steel strip 3 through an alloying furnace to form a Zn-Fe alloy coated layer having excellent corrosion resistance and stickness. In this case, hollow parts 1a and 9a are arranged in the sink roll 1 and this shaft 9 and the molten Zn heated with a heater 10 is supplied into the hollow part 1a in the sink roll 1 from the hollow part 9a in the shaft 9 through a communicating hole 9b with a pump P and the sink roll 1 is heated from inside and by heating the surface of steel strip 3, the galvernized layer and Fe are alloyed in good heat efficiency with the simple alloying furnace.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a sink roll for hot-dip metal plating, and in particular, a sink roll for hot-dip metal plating installed in a hot-dip metal plating facility where alloying treatment of the plating layer is performed after hot-dip plating. relates to a sink roll in which a heating means is provided inside the roll to heat the roll from the inside so that the metal material to be plated that comes into contact with the roll can be efficiently heated by the roll, and this sink roll By heating the metal material to be plated during hot-dip plating using rolls, the alloying treatment that is performed immediately thereafter can be performed efficiently.

The sink roll of the present invention uses a metal plate made of ferrous metals such as steel or nonferrous metals (including alloys) such as Ti, Ni, Cu, and Al to be plated, and uses zinc, lead, tin, Although it can be widely used for hot-dip plating of metals such as aluminum or alloys, the following explanation will focus on the case where it is applied to the production of galvanized steel sheets, which is the most versatile.

0003

2. Description of the Related Art Hot-dip galvanized steel sheets have been widely used in various fields since ancient times because they are easy to manufacture and have excellent corrosion resistance.

By the way, the most common method that has been put into practical use to obtain hot-dip galvanized steel sheets is to run a strip-shaped steel sheet along a guide sink roll provided in a hot-dip galvanizing tank and continuously immerse it. In this method, the steel sheet whose surface has been hot-dip galvanized by dipping is subsequently sent to a heating furnace, where the plating layer is alloyed.

For example, FIG. 4 is a longitudinal cross-sectional view illustrating a known hot-dip galvanizing treatment facility, in which molten zinc is charged into a hot-dip galvanizing tank 2 provided with a sink roll 1, and the sink roll 1 is guided. The strip steel plate 3 is run and immersed.

[0006] Galvanized steel sheet 3a exiting hot-dip galvanizing tank 2
is immediately sent to the alloying processing furnace 4, passes through a direct-fired heating zone 6 equipped with a burner 5, etc., and then passes through the direct-fired heating zone 6.
The alloy is alloyed by soaking in a convection heating zone 7 using combustion waste gas from the furnace as a heat source, and then passed through a cooling zone (not shown) and wound up as a galvanized product.

[0007]

[Problems to be Solved by the Invention] Temperature control for alloying treatment in the above method is an extremely necessary item to improve the quality of galvanized steel sheets, and according to the experience of the present inventors, It has been confirmed that the quality of plated products can be improved if the temperature is raised to a temperature suitable for oxidation and then heated slowly from a certain temperature.

[0008] To achieve gentle heating, it is desirable to make the alloying furnace as long as possible, but since the length of the existing alloying furnace is fixed, changing this requires a large economic burden. is forced. That is, increasing the length of the reactor requires a large amount of modification cost, and constructing a new reactor requires an even higher initial cost.

Moreover, the zinc on the surface of the galvanized steel sheet when it enters the alloying furnace is still in a molten state, and as it passes through the furnace it is heated and alloying gradually progresses. The emissivity of the surface is extremely small, and the emissivity will not increase unless alloying progresses to a certain extent.
There is also the problem that the radiant heat transfer efficiency of the alloying treatment furnace as a whole is poor, resulting in low thermal efficiency.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to focus on the alloying process performed after hot-dip metal plating, and to improve the heating used in the alloying process. A sink roll for hot-dip metal plating that is equipped with a heating means that can raise the temperature of the plated metal material sufficiently during the hot-dip galvanizing stage so that the alloying process can proceed efficiently without increasing the length of the furnace. This is what we are trying to provide.

[0011]

[Means for Solving the Problems] A sink roll according to the present invention that can solve the above problems is installed in a hot-dip metal plating facility where alloying treatment of the plating layer is performed after hot-dip plating. The gist of a sink roll for molten metal plating is that a heating means is provided inside the roll so that it can be heated from inside.

0012

[Operations and Examples] Under the above circumstances, the present inventors found that in order to shorten the length of the heating furnace for alloying treatment, the hot-dip galvanized steel sheet itself before being introduced into the heating furnace It is effective to keep the temperature high, and we thought that for this purpose, the preheating temperature of the steel plate to be plated and the molten zinc bath should be kept high.

However, even if the preheating temperature of the steel plate to be plated is increased, the heat retained in the steel plate is not only taken away by the molten zinc bath when the steel plate runs through the molten zinc bath, but also loses heat when it comes into surface contact with the sink roll. The temperature of the steel plate hardly rises because it is removed by heat transfer.

On the other hand, if the temperature of the entire hot-dip zinc bath is increased, both the steel sheet to be plated and the sink roll will be heated by the heat of the hot-dip zinc bath, so that the temperature of the hot-dip galvanized steel sheet introduced into the heating furnace will increase. is enhanced.

However, in this method, the entire molten zinc bath, which has a large heat capacity, must be maintained at a high temperature, so a large amount of thermal energy is required to maintain the temperature, and the amount of heat dissipated increases, resulting in a significant decrease in thermal efficiency. . Moreover, new environmental pollution and safety problems arise due to the evaporation of molten zinc.

Therefore, the present inventors have conducted extensive research in an attempt to develop a method that can efficiently increase the temperature of hot-dip galvanized steel sheets without causing the above-mentioned problems. It has become clear that by using a sink roll with a built-in sink roll, it is possible to efficiently raise the temperature of the steel plate to be plated by contact heat transfer from the sink roll.

That is, since the steel sheet to be plated is in surface contact with the outer peripheral surface of the sink roll in the plating bath, the heating efficiency is high, and since the method heats only the sink roll in contact with the steel sheet to be plated in the hot-dipping equipment, the equipment The total amount of heat input may be extremely small, and problems such as an increase in the amount of heat dissipated and an increase in the amount of zinc vapor generated do not occur.

In any case, it is essential to heat the hot-dip galvanizing bath according to the amount of heat released in order to maintain its temperature, but since the thermal energy given to the sink roll is also supplied to the hot-dip galvanizing bath. The amount of heat required to maintain the bath temperature can also be reduced, and as a result, the increase in the amount of heat consumed by the equipment as a whole can be suppressed to an almost negligible level.

[0019] In the present invention, the specific example of the heating mechanism built into the sink roll is not particularly limited, and it is also possible to adopt a resistance heating mechanism by embedding heat transfer wires, an electromagnetic induction heating mechanism, etc. In the present invention, which is used as a hot-dip galvanizing apparatus, the most preferred method is to use the hot-dip galvanizing metal itself as a heating medium, as detailed below.

That is, FIG. 1 is a cross-sectional explanatory view of a main part illustrating a plating apparatus equipped with a sink roll for hot-dip metal plating according to the present invention. has been done. The sink roll 1 is provided with a hollow portion 1a and openings 1 at appropriate locations on both side walls.
b, and the shaft 9 is also hollow to form a molten metal flow path 9.
a and communicates with the hollow portion 1a.
Open an appropriate number of holes.

[0021] On one side of the shaft 9, a molten metal feed pump P (M indicates a drive motor) and a heater H are disposed extending to the side of the sink roll 1, and at the tip thereof, a shaft is attached. An opening 10 is formed that communicates the molten metal flow path 9a of 9 with the inside of the plating tank 1.

When performing plating using this apparatus, the heater H heats the molten metal to an appropriate temperature, and the motor M drives the feed pump P to transfer the heated molten metal to the molten metal on the shaft 9. Metal flow path 9a
The sink roll 1 is heated from the inside by being fed from the inside to the hollow part 1a of the sink roll 1 through the communication hole 9b. Then, this molten metal is sequentially returned into the plating tank 2 through the opening 1b. In this case, replenishment commensurate with the amount taken out by plating may be performed by any method (not shown).

With this method, by controlling the heating temperature by the heater H, the surface temperature of the sink roll 1 and, by extension, the heating temperature of the steel plate 3 running in contact with the sink roll 1 can be freely adjusted. Moreover, think roll 1
The molten metal that enters the plating tank 2 from the opening 1b after heating is at a higher temperature than the molten metal in the plating tank 2.
The temperature drop of the molten metal due to heat radiation is also suppressed, and the opening 1
The molten metal flow discharged from b promotes stirring in the tank 2, and also has the effect of making the temperature in the plating tank 2 uniform.

FIG. 2 is a conceptual diagram showing another embodiment of the present invention, in which a heater H and a feed pump P are installed in a molten metal supply line L provided outside the plating tank 2, and the heated molten metal is This example is the same as the example shown in FIG. 1, except that it can be fed from the shaft portion of the sink roll 1. With this mechanism, it becomes possible to effectively use the molten metal for replenishment as a heating source.

FIG. 3 is a conceptual diagram showing still another embodiment of the present invention, in which molten metal tanks 11a and 11b for replenishment are provided, one of which is maintained at a high temperature and the other at a slightly low temperature, respectively.
The temperature of the molten metal supplied to the sink roll 1 can be controlled by adjusting the driving force of the feed pumps P1 and P2 and changing the feed ratio between the two.

In the case of an electromagnetic induction heating mechanism, both functions of the heater H and the molten zinc supply pump P (electromagnetic induction pump) can be achieved at the same time.

[0027] A sink roll 1 as shown in FIGS. 1 to 3 above.
If the plated steel plate 3 is heated by The thermal energy required for heating can be reduced, and the length of the alloying furnace can be shortened.

[0028]

[Effects of the Invention] The present invention is constructed as described above, and by providing an internal heating means in the sink roll for hot-dip metal plating to enable contact heating of the plated steel sheet, additional This makes it possible to reduce the amount of heat generated, and even when using an existing alloying furnace with a relatively short furnace length, alloying can be carried out efficiently under soft heating conditions.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of a main part illustrating a hot-dip metal plating apparatus equipped with a sink roll of the present invention.

FIG. 2 is a conceptual diagram showing another embodiment of the present invention.

FIG. 3 is a conceptual diagram showing still another embodiment of the present invention.

FIG. 4 is a schematic explanatory diagram illustrating a conventional facility equipped with a hot-dip plating apparatus and an alloying processing furnace.

[Explanation of symbols]

1 Sink roll for molten metal plating 2 Hot-dip plating tank 3 Steel strip 4 Heating furnace for alloying treatment 5 Burner 6 Direct-fire heating zone 7 Convection heating zone 8 Support member 9 Shaft 1a Hollow portion 1b Opening 9a Molten metal channel 9b Communication hole H Heater P Feed pump

Claims (2)

[Claims] Claim 1: In a sink roll for hot-dip metal plating installed in hot-dip metal plating equipment where alloying treatment of the plating layer is performed after hot-dip plating, a heating means is provided in the roll to heat the roll from the inside. A sink roll for hot-dip metal plating, which is characterized by being made to be able to do so. 2. The sink roll for molten metal plating according to claim 1, wherein the sink roll has a hollow part and heated molten metal is supplied to the hollow part to heat the sink roll.