JPH1180843A - Device for continuously cooling steel sheet by gas jet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the flow-in and the flow-out of non-oxidizing gas into the other treating zone or treating device at the front and the rear parts of a cooling device, to reduce the supply of hydrogen and to easily and constantly hold the non-oxidizing gas concn. in the cooling device by arranging at least the outlet side seal part of a steel sheet at the lower part of the vertical type forcedly cooling device using the non-oxidizing gas having high hydrogen concn equal to or higher than a specific value. SOLUTION: In a continuous annealing line process, the heated, soaked and further, slow-cooled steel sheet is passed through the cooling zone from the inlet side seal part A of the steel sheet arranged at the lower part of the cooling zone. This cooling zone is provided with a cooler for cooling the non-oxidizing gas having >=50% hydrogen concn. in the inner part of the device and a blower for blowing the cooled gas to the steel sheet. The steel sheet is cooled to a prescribed temp. in the cooling zone and passed to a treating zone at the latter step from the outlet side seal part B arranged at the lower part of the cooling zone. In such a case, the seal device is constituted of one set of faced seal rolls, but any device for preventing the flow-out/in of the atmospheric gas in the inner part of the cooling zone is allowed to be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas jet cooling apparatus for a steel strip in a continuous annealing line.

[0002]

2. Description of the Related Art Conventional gas jet cooling with a low hydrogen concentration is not very suitable for rapid cooling of steel sheets because of its low heat transfer coefficient. For this reason, attempts have been made to increase the gas discharge flow rate and shorten the distance between the cooling nozzle and the steel plate in order to improve the heat transfer coefficient.However, fluttering and scratches on the steel plate are likely to occur, so a new presser foot is required. There was a problem that a roll had to be installed.

[0003] For example, Japanese Patent Application Laid-Open No. 6-346156 proposes a cooling method using a high hydrogen concentration for the purpose of rapid cooling by a high heat transfer coefficient and reduction of flapping of a steel sheet.

[0004]

However, when a steel sheet is cooled by using a high hydrogen concentration gas, if a new hydrogen gas is successively supplied and cooled, the amount of hydrogen used increases and the running cost increases. Becomes So, usually,
A gas jet cooling is performed by circulating the atmosphere gas by using the atmosphere gas having a high hydrogen concentration in the cooling device. But
In the vertical continuous processing line, the accompanying flow of the steel sheet, the inflow and outflow by the draft, the outflow of the atmospheric gas having a high hydrogen concentration from the gas jet cooling device to the processing zone or the processing device before and after the gas jet cooling device, or At the same time, an atmosphere gas of a treatment zone having a composition different from that of the atmosphere gas in the gas jet cooling device flows from the treatment zone before and after the gas jet cooling device or from the treatment device to the gas jet cooling device. Therefore, it is difficult to keep the hydrogen concentration in the gas jet cooling device constant, which hinders the control of the heat transfer rate and the cooling rate in rapid cooling.

[0005] An object of the present invention is to solve the above-mentioned problems by providing a vertical cooling device for gas jet cooling by circulation of an atmosphere gas having a high hydrogen concentration of 50% or more, which is provided before and after the cooling device. Gas jet cooling of a continuous steel plate that can suppress the inflow and outflow of non-oxidizing gas into the processing zone or processing equipment, reduce the amount of hydrogen supply, and easily maintain a constant non-oxidizing gas concentration in the cooling equipment It is to provide a device.

[0006]

In order to solve the above problems and achieve the object, the present invention uses the following means. (1) The apparatus of the present invention is a vertical forced cooling apparatus including means for cooling a steel sheet using a non-oxidizing gas having a hydrogen concentration of 50% or more in a continuous annealing line including a forced cooling step. A gas jet cooling apparatus for a continuous steel sheet, wherein at least a sealing portion on the outlet side of the steel sheet to the vertical cooling apparatus is provided at a lower portion of the apparatus.

(2) The apparatus according to the present invention is a vertical forced cooling apparatus having means for cooling a steel sheet using a non-oxidizing gas having a hydrogen concentration of 50% or more in a continuous annealing line including a forced cooling step. A gas jet cooling apparatus for a continuous steel sheet, wherein an inlet side seal part and an outlet side seal part for a steel sheet to the vertical cooling apparatus are provided at a lower part of the apparatus.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS To achieve the above-mentioned object, the present inventors have developed a vertical cooling device for gas jet cooling by circulation of an atmosphere gas having a high hydrogen concentration of 50% or more. The inflow and outflow of non-oxidizing gas into and from the treatment zone or treatment equipment is reduced, and the amount of hydrogen supplied is reduced.
As a result of intensive studies on a gas jet cooling device for a continuous steel plate that can easily keep the non-oxidizing gas concentration in the cooling device constant, the following findings have been obtained.

In general, in a vertical annealing facility, a draft force represented by the following equation (1) is generated in each processing apparatus. P = H (ρ _AIR −ρ _g ) (1) where H: furnace height (m), ρ _AIR : outside air density (kg / m)
³ ), ρ _g : gas density in the furnace (kg / m ³ ).

[0010] When the respective processing apparatuses are connected at the upper part of the apparatus, a pressure gradient is generated due to a difference in draft force between the processing apparatuses, and the inflow and outflow of the furnace gas represented by the following equation (2) occurs. Occur. ΔP = P ₁ −P ₂ = C · ρ _g · U ² / 2g (2) where C is a coefficient according to the fluid and the shape of the connection portion, and U is a gas outflow velocity in the furnace (m / sec).

In ordinary annealing equipment, there is no difference between the atmosphere gas in the cooling apparatus and the other processing apparatus, and a non-oxidizing gas having a hydrogen concentration of 3 to 7% is used. The atmosphere gas in the cooling device is the lowest.
Therefore, when the cooling device and another processing device are connected at the upper part of the device, the atmospheric gas in the processing device flows into the cooling device from the processing devices before and after the cooling device.

However, when the inside of the cooling device is filled with a non-oxidizing gas having a high hydrogen concentration and the inside of another processing device is filled with a non-oxidizing gas having a low hydrogen concentration of 3 to 7%, the cooling device and the other components are not used. Is connected at the top of the equipment,
The density is very low because of the non-oxidizing gas having a high hydrogen concentration, and the atmosphere gas (non-oxidizing gas having a high hydrogen concentration) in the cooling device flows out of the cooling device into the processing device before and after the cooling device.
Furthermore, as the hydrogen concentration increases, the outflow speed of the atmosphere gas in the cooling device increases, and the effect of offsetting the inflow of the atmosphere gas in the processing device due to the accompanying flow of the steel sheet cannot be expected. Therefore, the supply amount of hydrogen increases, which causes an increase in running cost. Also, when the hydrogen supply amount is large, the distribution of the atmospheric gas concentration tends to occur locally in the cooling device,
Control of heat transfer and cooling rate to the steel sheet is deteriorated.

FIG. 4 shows a simulation result of a pressure gradient due to a difference in draft force when the cooling device and the processing device are connected at the upper portion of the device under the conditions shown in Table 1.
In the figure, the hydrogen concentration of the atmosphere gas in the cooling device is 4
On the low hydrogen concentration side from the boundary of 5%, the pressure difference between the atmosphere gas of the cooling device and the other processing device becomes negative, and the gas flows from the other processing device to the cooling device. On the other hand, on the high hydrogen concentration side, the pressure difference between the atmospheric gas of the cooling device and the other processing device becomes positive, and the gas flows out of the cooling device to the other processing device.

[0014]

[Table 1]

The inventors of the present invention have studied various configurations and conditions based on the experience gained over many years. By providing the side seal portion also in the lower part of the vertical cooling device, the hydrogen supply amount can be reduced, and it has been found that the concentration of non-oxidizing gas in the cooling device can be easily kept constant, and the present invention has been completed. . That is, the present invention relates to a vertical forced cooling device that uses a non-oxidizing gas having a high thermal conductivity and a hydrogen concentration of 50% or more in a continuous annealing line, and a sealing portion on the inlet side of a steel sheet to the forced cooling device. And by providing the outlet side seal part at the bottom of the device,
The inflow and outflow of the non-oxidizing gas into and out of the other treatment zones or treatment units before and after the cooling device can be suppressed, the amount of hydrogen supply can be reduced, and the concentration of the non-oxidizing gas in the cooling device can be easily maintained constant. A gas jet cooling device for a continuous steel plate that can be provided.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is an explanatory view showing a cooling zone in a continuous annealing process of a steel sheet in a state where the configuration of the present invention is applied. (A) is a schematic diagram of an apparatus in which an inlet-side seal portion and an outlet-side seal portion of a steel plate are provided below a vertical cooling device, and (b) is a device in which an outlet-side seal portion of a steel plate is provided below a vertical cooling device. FIG. In the present invention, as described above, it is desirable to provide the inlet seal portion and the outlet seal portion of the steel plate at the lower part of the vertical cooling device. However, as shown in FIG. (The capacity and space), the number of passes becomes odd, and when the inlet side and the outlet side of the steel plate are divided into upper and lower sides of the cooling device, at least the outlet side seal portion is located at the lower portion of the cooling device.

As shown in FIG. 1 (a), the steel sheet which has been heated and soaked and then gradually cooled is passed through the cooling zone from the inlet side seal portion A of the steel sheet provided at the lower part of the cooling zone. . This cooling zone includes a cooler for cooling a non-oxidizing gas having a hydrogen concentration of 50% or more inside the apparatus and a blower for blowing the cooled gas to a steel plate outside the apparatus. It is cooled to a predetermined temperature in the cooling zone, and is passed through a processing zone at a later stage from an outlet side seal portion B provided at a lower portion of the cooling zone. In this drawing, the opposing 1
The seal device is composed of a set of seal rolls,
This may have any structure as long as it prevents the inflow and outflow of the atmospheric gas inside the cooling zone. Further, the outlet seal portion of the steel plate may be located slightly above the lower end of the vertical cooling device.

In the present invention, the reason why a non-oxidizing gas having a hydrogen concentration of 50% or more is used is to perform rapid cooling with a high heat transfer coefficient as described above. FIG. 2 shows Table 2.
In the case where the cooling device of the present invention is applied under the conditions of (1) (case 1 (the device of FIG.
3 (a) and (b)) and other cooling zone configurations as shown in FIGS. 3 (a) and 3 (b) (case 3 (the device of FIG. 3 (a) is applied), and case 4 (FIG. 3 (b) is applied))
The simulation result of the hydrogen supply amount in the steady state of FIG. In the figure, as the hydrogen concentration increases, Case 1,
Case 2 and 3 (Comparative Example)
The difference in the hydrogen supply amount becomes significant. Further, since the heat transfer coefficient with respect to the steel sheet is the maximum point and is outside the explosion limit range, the maximum value is obtained at the most desirable hydrogen concentration of 80% as the atmosphere gas composition in the cooling device.

This tendency becomes more remarkable as the temperature difference between the cooling device and the atmospheric gas in the processing device before and after the cooling device increases. This is evident from FIG. 5 which shows a simulation result of the hydrogen supply amount in each cooling device configuration under the conditions of Table 3 where the temperature difference of the atmosphere gas is even larger.
Also, in FIG. 2, case 2 (example of the present invention) and case 4
Comparing the hydrogen supply amounts of the (Comparative Example), it can be seen that the supply amount of hydrogen is reduced by providing the outlet seal portion of the steel plate at the lower part of the vertical cooling device.

[0020]

[Table 2]

[0021]

[Table 3]

The cooling device of the present invention may have a configuration as shown in FIGS. 6 (a), 6 (b) and 6 (c). That is, in the cooling devices of FIGS. 6A and 6B, the cooling zone is divided into a front stage and a rear stage, and the front stage or the rear stage of the cooling zone is a non-oxidizing device having a hydrogen concentration of 50% or more inside the device. A cooler for cooling the gas and a blower for blowing the cooled gas to the steel plate are provided outside the device, and the remaining cooling zone is provided with a cooling roll inside the device. FIG.
In the cooling device of (c), the cooling zone is set to a hydrogen concentration of 5 in the device.
Two sets of a cooler for cooling non-oxidizing gas of 0% or more and a blower for blowing the cooled gas to a steel plate are provided outside the apparatus,
Further, the cooling gas is also blown to the steel plate between the sealing device and the hearth roll.

[0023]

As described above, according to the present invention, in a vertical forced cooling device which uses a non-oxidizing gas having a high thermal conductivity and a hydrogen concentration of 50% or more in a continuous annealing process, By providing the sealing part of the steel plate to the forced cooling device at the lower part of the vertical cooling device and the sealing material of the steel plate at the lower part of the vertical cooling device, other treatment zones or treatments before and after the cooling device are provided. The inflow and outflow of the non-oxidizing gas into and from the device can be suppressed, the amount of hydrogen supply can be reduced, and the concentration of the non-oxidizing gas in the cooling device can easily be kept constant.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a cooling device according to an embodiment of the present invention. (A) is an apparatus schematic in which the entrance side seal part and the exit side seal part of the steel plate were provided in the lower part of the vertical cooling device. (B) is an apparatus schematic diagram in which a delivery side seal portion of a steel plate is provided below a vertical cooling device.

FIG. 2 is a diagram showing a calculation result of a hydrogen supply amount in each cooling device configuration according to the embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a configuration of a cooling device of a comparative example. (A)
FIG. 3 is a schematic diagram of an apparatus in which an inlet seal portion and an outlet seal portion of a steel plate are provided on an upper part of a vertical cooling device. (B) is an apparatus schematic diagram in which a delivery side seal portion of a steel plate is provided on an upper part of a vertical cooling device.

FIG. 4 is a diagram showing a calculation result of a pressure gradient due to a difference in draft force when a cooling device and a processing device are connected at an upper portion of a vertical cooling device.

FIG. 5 is a diagram showing a calculation result of a hydrogen supply amount (atmospheric gas temperature difference is large) in each cooling device configuration according to the embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a configuration of a cooling device according to an embodiment of the present invention. (A) is an apparatus schematic diagram provided with a cooling roll at the latter stage of a cooling zone. (B) is a schematic diagram of an apparatus in which a cooling roll is provided in a preceding stage of a cooling zone. (C) is a schematic diagram of an apparatus in which a cooling means is provided between a sealing device and a hearth roll.

Claims (2)

[Claims] 1. A vertical forced cooling device comprising: means for cooling a steel sheet using a non-oxidizing gas having a hydrogen concentration of 50% or more in a continuous annealing line including a forced cooling process, A gas jet cooling device for a continuous steel plate, wherein at least a sealing portion on the outlet side of the steel plate to the cooling device is provided at a lower portion of the device. 2. A vertical forced cooling apparatus comprising: means for cooling a steel sheet using a non-oxidizing gas having a hydrogen concentration of 50% or more in a continuous annealing line including a forced cooling step, A gas jet cooling apparatus for a continuous steel sheet, wherein a sealing part on an inlet side and a sealing part on an outlet side of a steel sheet to a cooling apparatus are provided at a lower part of the apparatus.