JP2002266060A - Vertical alloying furnace and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical alloying furnace not causing the fluttering of steel plate while securing the sealing property even in the case of applying alloying treatment or no alloying treatment to a steel plate using the vertical alloying furnace. SOLUTION: In the vertical alloying furnace having a plating bath for applying plating on the steel plate and having, above the plating bath, a wiping nozzle for adjusting the coating weight of the steel plate drawn up from the plating bath, a touch roll, a heating zone, a holding zone and a cooling zone in this order, a pair of gas jetting boxes are provided to face each other across the steel plate in the middle stage part of the holding zone, another gas jetting box is provided above or below one of the pair of the gas jetting boxed, and further, a pair of gas jetting boxes are provided to face each other across the steel plate in the boundary part between the holding zone and cooling zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloyed plated steel sheet by dipping a steel sheet in a hot-dip plating bath, pulling it up, gas wiping, heating, retaining and cooling, and immersing it in a plating bath for gas wiping. The present invention relates to a vertical alloying furnace for producing a non-alloyed plated steel sheet which is cooled without heating and holding, and is not alloyed, and a method of operating the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for galvanized steel sheets as a material for automobiles and the like, and a demand for enhancement of rust prevention has been increasing. As this alloying furnace for producing an alloyed galvanized steel sheet, for example, a vertical type as shown in FIG. 3 is known. In this vertical alloying furnace, the annealed steel sheet 1 is immersed in a hot-dip galvanizing bath 2 to plate the steel sheet 1 with molten zinc, and is plated through a gas wiping process by a wiping nozzle 4 while being pulled up through a sink roll 3. It is sent to the heating zone 5 while adjusting the basis weight, where it is heated by induction heating or direct heating type heating means 6. In the case of induction heating, in the next holding zone 7, for example, by a tube heater, or by direct heating heating In the case, an alloying reaction is generated by holding the fuel gas in the holding zone 7 to generate an alloying reaction.
After cooling the obtained alloyed galvanized steel sheet 1 in a cooling zone 12 with a cooling device 8 such as a steam-water cooling device, a conveying roller 9 is provided.
To carry it out of the furnace.

[0003] At the rear end of the retaining zone 7, a flue 10 capable of adjusting the air volume is provided. At the boundary between the holding zone 7 and the cooling zone 12, a pair of gas injection boxes 11-1, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, is set in order to suppress the draft of the gas inside the furnace accompanying the unloading of the galvanized steel sheet 1. -2 are opposed to each other. In addition, a pair of gas injection boxes 13-1 and 13-2 are opposed to each other with the steel plate 1 interposed therebetween in a rising gas flow passage extending from the heating zone 5 to the retaining zone 7, that is, in the middle of the retaining zone 7. In particular, the pressure loss to the steel sheet 1 is controlled, and in particular, the infiltration of air from the lower part in the heating zone 5 is suppressed, and the draft of the gas in the holding zone 7 is suppressed, so that the steel sheet 1 can be rapidly heated. Improving efficiency. Moreover, these two pairs of gas injection boxes 11-1, 11-2, 13-1,
13-2 also has a function of preventing fluttering of the steel sheet 1, and prevents fluttering of the steel sheet together with the touch roll 14 installed above the wiping nozzle 4.

[0004]

By the way, in such a vertical alloying furnace, after galvanizing,
In some cases, heating and holding are performed to produce an alloyed plated steel sheet, and in other cases, after hot-dip galvanizing, non-alloyed plated steel sheets are manufactured by cooling without heating and holding. For the production of steel sheets, a vertical alloying furnace is used in common. A vertical alloying furnace is generally about 70 m
Since the steel plate 1 has a height of about the same, the steel plate 1 vibrates greatly during transportation, that is, causes so-called fluttering. Therefore,
As shown in FIG. 3, the heat treatment is performed while supporting the steel sheet 1 by the touch roll 14 and the two pairs of gas injection boxes 11-1, 11-2, 13-1, and 13-2. When an alloyed plated steel sheet is manufactured, the touch roll 14 needs to be used because the plating weight is generally small and the accuracy of the weight variation is strict. In addition, since the plating is alloyed by heating and retaining after passing through the plating bath, even if the touch roll 14 comes into contact with the steel plate 1 after passing through the plating bath 2, there is a particular problem in the plating appearance quality. Hateful.

On the other hand, when no alloying treatment is performed, the steel sheet 1 after passing through the plating bath 2 is cooled without being heated and held after passing through the plating bath 2. Further, the basis weight of the non-alloyed plated steel sheet is generally larger than that of the alloyed plated steel sheet. Therefore, since the plating is not dried before reaching the cooling zone 12, if the steel plate 1 is supported by the touch roll 14, the plating on the surface of the steel plate 1 is flawed, which causes a problem in appearance quality. The steel sheet 1 cannot be supported by the touch roll 14 like an alloyed plated steel sheet. Gas injection boxes 11-1, 1 arranged opposite to each other
Although 1-2, 13-1, and 13-2 also have a fluttering prevention function, when the steel sheet 1 has a shape such as C warp, the balance of the holding force between the front and back of the steel sheet 1 is lost, so that the gas injection box is used. It is difficult to prevent fluttering. Therefore, when a non-alloyed plated steel sheet which is not alloyed is manufactured by a conventional vertical alloying furnace, the steel sheet 1 may cause fluttering depending on the shape of the steel sheet 1, and the gas wiping nozzle 4 or the heating device 6 In addition, there are problems such as collision with the cooling device 8 and the like and unevenness in the basis weight of plating.

The present invention has been made in order to solve such a problem. The present invention is applicable to a case where a steel plate is subjected to an alloying treatment using a vertical alloying furnace and a case where the alloying treatment is not performed. Another object of the present invention is to provide a vertical alloying furnace in which a steel sheet does not cause fluttering regardless of the shape of the sheet.

[0007]

SUMMARY OF THE INVENTION The present invention provides a plating bath for plating a steel sheet, a wiping nozzle above the plating bath, a wiping nozzle for adjusting a plating weight of the steel sheet pulled up from the plating bath, a touch roll, a heating zone, In a vertical alloying furnace having a retaining zone and a cooling zone in order, a pair of gas injection boxes are provided opposite to each other with a steel plate interposed therebetween in the middle stage of the retaining zone, and one of the pair of gas injection boxes is provided above the gas injection box. Or, below, install another gas injection box,
Further, a pair of gas injection boxes are provided opposite to each other at a boundary between the retaining zone and the cooling zone with a steel plate interposed therebetween.

In the operating method of the vertical alloying furnace having the above-mentioned structure, when the steel sheet is subjected to the alloying treatment, the fluttering of the steel sheet is prevented by the touch roll, and the steel sheet is installed so as to face the middle part of the retaining zone. Each seal is performed by gas injection from the gas injection box and the gas injection box installed opposite to the boundary between the retaining zone and the cooling zone, and when the steel plate is not subjected to alloying treatment, it is not opposed to the middle section of the retaining zone. The gas injection from the installed gas injection box prevents the fluttering of the steel plate, and the sealing is performed by the gas injection from the gas injection box installed opposite to the boundary between the retaining zone and the cooling zone.

[0009]

FIG. 1 shows an embodiment of a vertical alloying furnace according to the present invention. Above the hot-dip galvanizing bath 2, a wiping nozzle 4 for adjusting the basis weight of the steel sheet 1 pulled up from the plating bath 2 and a touch roll 14 for preventing fluttering of the steel sheet 1 are provided. The heating zone 5, the holding zone 7, and the cooling zone 12 are installed in this order to constitute a vertical alloying furnace. A pair of gas injection boxes 13-1 and 13-2 are opposed to each other with the steel plate 1 interposed therebetween in the middle stage of the retaining zone 7, and a gas injection box 15 is provided above the gas injection box 13-1. . This gas injection box 15 has a gas injection box 13-
2 is installed in a non-opposite manner. The gas injection boxes 13-1, 13-2, and 15 are movable in parallel.

At the rear end of the retaining zone 7, a flue 10 for adjusting the air volume is provided. A pair of gas injection boxes 11-1 and 11-2 sandwich the steel plate 1 at the boundary between the retaining zone 7 and the cooling zone 12 in order to suppress the draft of the furnace atmosphere gas accompanying the carry-out of the plated steel plate 1. Are installed facing each other. And this gas injection box 11-
1 and 11-2 can also be translated.

Next, a description will be given of an operation method for producing an alloyed plated steel sheet subjected to an alloying treatment and for producing a non-alloyed plated steel sheet not subjected to an alloying treatment. When manufacturing an alloyed plated steel sheet, the annealed steel sheet 1 is immersed in a hot-dip galvanizing bath 2 (about 470 ° C.) to be coated with hot-dip zinc, and is subjected to gas wiping by a wiping nozzle 4 while being pulled up through a sink roll 3. After that, the basis weight of plating is adjusted. Thereafter, the steel sheet 1 is sent to the heating zone 5, and is heated directly from both sides thereof by a burner flame to a temperature of about 520 ° C., for example, by a direct-fire type heating means 6 arranged in close proximity to the steel sheet 1 with the steel sheet 1 interposed therebetween. Rapidly heated.

Next, the steel sheet 1 is held in the holding zone 7 by the combustion exhaust gas from the burner to generate an alloying reaction, and the obtained alloyed plated steel sheet 1 is cooled in the cooling zone 12 by, for example, a steam-water cooling device or the like. After being cooled by the cooling device 8 of FIG. 7 for vertical alloying furnace
Since it has a height of about 0 m, the gas wiping process and the alloying process are performed while supporting the steel plate 1 with the touch roll 14 so that the steel plate 1 does not cause fluttering.

FIG. 2 is an enlarged view of the gas injection box installed facing the middle stage of the retaining zone 7. In the case of the alloyed plated steel sheet 1 which has been subjected to the alloying treatment, the shut-off valve of FIG. 16 is closed, the shut-off valves 17 and 18 are opened, and the gas injection boxes 13-1 and 13-2 opposed to each other with the steel plate 1 interposed therebetween.
From the heating zone 5 to the steel sheet 1 to generate a static pressure, giving a pressure loss resistance to the gas flow from the heating zone 5,
The gas flow that rises from is sealed. The gas injection box is provided with a plurality of slit-shaped gas injection nozzles 19 for injecting gas, and the nozzles 19 inject furnace gas sucked from the holding zone 7 by a blower to both sides of the steel plate 1. ing. The flow rate is adjusted by the blower speed.

Further, the gas is also supplied from a pair of gas injection boxes 11-1 and 11-2, which are provided opposite to each other with the steel plate 1 interposed therebetween, between the retaining band 7 and the cooling zone 12, ie, between the retaining band 7 and the cooling zone 12. And the above-described gas injection boxes 13-1, 13-
A double seal is performed together with 2. The configuration of the gas injection boxes 13-1 and 13-2 is the same as that of the gas injection box 1.
Same as 1-1 and 11-2. The gas to be injected is room temperature air. In this way, by performing double sealing by gas injection at the middle stage and the outlet side of the holding zone 7, the retention of combustion gas in the heating zone 5 is improved, rapid heating is enabled, and high-temperature combustion from the heating zone 5 is performed. Gas rises,
It is possible to prevent the gas from flowing into the cooling zone 12 and increase the cooling effect.

Next, a case of manufacturing a non-alloyed plated steel sheet in which the steel sheet 1 is not subjected to alloying treatment will be described. The annealed steel sheet 1 is immersed in a hot-dip galvanizing bath 2 (about 470 ° C.) to be coated with hot-dip zinc, and is pulled up through a sink roll 3 while being subjected to a gas wiping process by a wiping nozzle 4 to adjust a plating weight. . Then steel sheet 1
Passes through the heating zone 5 and the holding zone 7, but only passes therethrough, and does not perform the heating process until reaching the cooling zone 12. When alloying is not performed, the plating adhered to the surface of the steel sheet 1 is not dried, so that the steel sheet 1 cannot be supported by the touch roll 14. Therefore, the touch roll 14 above the wiping nozzle 4 is retracted from the steel plate 1. Therefore, instead of the touch roll 14, in the present invention, fluttering of the steel plate 1 is prevented by the gas injection box installed in the middle stage of the retaining band 7.

That is, here, in FIG.
Is closed, the shutoff valves 16 and 18 are opened, and gas is injected toward the steel plate 1 from the gas injection boxes 13-2 and 15 arranged non-opposed with the steel plate 1 interposed therebetween. By injecting gas non-oppositely from the front and back of the steel sheet 1, a bending force is applied in the longitudinal direction of the steel sheet 1, the rigidity of the steel sheet 1 is improved, and even in the case of a poorly shaped steel sheet 1 such as a C-warped steel sheet, fluttering is prevented. This can be prevented. This gas injection box 13
-2 and 15 can be moved in parallel, and the prevention of the fluttering is more effective as the distance from the steel plate 1 is smaller.

Even when the alloying treatment is not performed, since the high-temperature gas rises due to the draft caused by the heat dissipated from the steel plate 1, the gas injection box 11 provided at the boundary between the holding zone 7 and the cooling zone 12 is formed. By injecting normal-temperature air from -1, 11-2 toward the steel plate 1 and sealing it, high-temperature gas is prevented from flowing into the cooling zone 12. However, when the alloying treatment is not performed, since there is no combustion exhaust gas from the heating device 6 of the heating zone 5 as in the case of performing the alloying treatment, the gas injection seal is provided only at the boundary between the holding zone 7 and the cooling zone 12. It is possible to obtain a sufficient sealing effect. Steel plate 1 cooled by cooling device 8 in cooling zone 12
Is carried out of the furnace by the transfer rollers 9.

In the present embodiment, the gas injection box 15 is disposed above the gas injection box 13-1 of the retaining zone 7, but may be installed below the gas injection box 13-1. Further, the gas injection box 15 may be installed above or below the gas injection box 13-2. In short, the present invention can be implemented as long as the gas injection box is arranged so as to be opposed to and not opposed to each other with the steel plate 1 interposed therebetween, and can be switched between opposed injection and non- opposed injection.

Although the embodiment has been described by taking a burner as an example of a heating device in the heating zone 5, the present invention can be similarly applied to an induction heating device instead of a burner.
In this case, it is preferable to heat the gas in the furnace using a tube heater in the holding zone 7. In addition, in the case of the induction heating device, since the combustion exhaust gas is not generated unlike the burner, the gas generated by the hot air generator provided outside the system is blown from the gas injection boxes 13-1, 13-2, and 15 into the temperature of the steel plate 1. Prevent descent. Further, a switching shutoff valve may be used instead of the shutoff valves 16 and 17.

[0020]

According to the present invention, a gas injection box capable of switching gas spraying between facing and non-facing is installed with a steel plate interposed in the middle portion of the holding zone, and gas is also provided at the boundary between the holding zone and the cooling zone. A configuration and operation that can be performed by switching the method of spraying the gas injection box in the middle part of the Baoding zone between the case where the injection box is installed facing and the case where an alloyed plated steel sheet is manufactured and the case where a non-alloyed plated steel sheet that is not alloyed is manufactured And how to do it.
Therefore, during the production of alloyed plated steel sheets, a double seal is formed by injecting gas from the gas injection box located opposite to the boundary between the holding zone interruption part and the holding zone / cooling zone, resulting in high temperature from the heating zone and the holding zone. The gas can be prevented from flowing into the cooling zone to increase the cooling efficiency, and the invasion of air from below in the heating zone can be suppressed to enable rapid heating. In addition, there is no problem of fluttering because the touch roll is supported.

When a plated steel sheet that is not alloyed is manufactured, gas is injected non-oppositely from the gas injection box in the middle part of the holding zone, so that the steel sheet can be stably conveyed and the steel sheet having a C-warped shape or the like can be formed. Even during processing, fluttering can be reliably prevented, and high-temperature gas in the holding zone flows into the cooling zone by gas injection from a gas injection box arranged opposite to the boundary between the holding zone and the cooling zone. And cooling efficiency can be increased. As described above, according to the present invention, a C-warped steel sheet or the like is processed with a very simple apparatus configuration and operating method while ensuring the sealing property in both cases of manufacturing an alloyed plated steel sheet and a non-alloyed plated steel sheet. Even in this case, it is possible to reliably prevent fluttering.

[Brief description of the drawings]

FIG. 1 is a view showing a vertical alloying furnace of the present invention;

FIG. 2 is a view showing an arrangement of gas injection boxes in a retaining zone according to the present invention;

FIG. 3 is a view showing a conventional vertical alloying furnace.

[Explanation of symbols]

 Reference Signs List 1 steel sheet 2 hot-dip galvanizing bath 3 sink roll 4 wiping nozzle 5 heating zone 6 heating means 7 holding zone 8 cooling device 9 transport roller 10 flue 11-1, 11-2 gas injection box 12 cooling zone 13-1, 13- 2 Gas injection box 14 Touch roll 15 Gas injection box 16, 17, 18 Shut-off valve 19 Gas injection nozzle

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 2/40 C23C 2/40 F term (Reference) 4K027 AA02 AA05 AA22 AB42 AC52 AC73 AD15 AD23 AD25 AD26 AE24 4K043 AA01 CA01 CB03 EA05 FA12 FA13 GA03 GA06 HA04

Claims (2)

[Claims] 1. A plating bath for plating a steel sheet, a wiping nozzle for adjusting a plating weight of the steel sheet pulled up from the plating bath, a touch roll, a heating zone, a holding zone, and a cooling zone in order above the plating bath. In the vertical alloying furnace, a pair of gas injection boxes are provided opposite to each other with a steel plate interposed in the middle part of the retaining zone, and another gas injection box is provided above or below one of the pair of gas injection boxes. A vertical alloying furnace, wherein an injection box is installed, and a pair of gas injection boxes are installed opposite to each other at a boundary between the retaining zone and the cooling zone with a steel plate interposed therebetween. 2. A plating bath for plating a steel sheet, and a wiping nozzle, a touch roll, a heating zone,
Baoding zone, a pair of gas injection boxes are provided opposite to each other with a steel plate interposed therebetween in the middle stage of the holding zone of the vertical alloying furnace having a cooling zone in order, and either one of the pair of gas injection boxes is located above or below. A method for operating a vertical alloying furnace in which another gas injection box is installed, and a pair of gas injection boxes are installed opposite to each other at a boundary between the retaining zone and the cooling zone, with a steel plate interposed therebetween. When performing alloying treatment on the steel sheet, the fluttering of the steel sheet was prevented by the touch roll, and the gas injection box was installed to face the middle part of the retaining zone and the gas injection box was installed to face the boundary between the holding zone and the cooling zone. Sealing is performed by gas injection from the gas injection box, and when alloying is not performed on the steel sheet, the steel sheet is injected by gas injection from the gas injection box installed in the middle part of the retaining zone. Thereby preventing Ttaringu, the coercive Condition and operation method of the vertical alloying furnace, characterized in that for sealing the gas injection from the cooling zone of the opposing installing the gas injection box boundary.