JPH04325632A - Method and device for maintaining furnace pressure in continuous annealing furnace - Google Patents

Abstract

PURPOSE:To prevent lowering of inner pressure in a cooling zone due to the reduction of heat quantity transferred with a metal strip from heating zone to the cooling zone. CONSTITUTION:At the time of continuously annealing a thick metal strip S1 and a thin metal strip S2 connected with the strip at a connected point W, the connecting point W and strip speed are obtd. with a detector 36 and based on this information, a blower 32 is started with a controller 38, and by circulating gas in the cooling zone 24 between a heat exchanger 28 and the cooling zone, the inside of this cooling zone 24 is heated. The strip passing in the cooling zone 24 becomes a thin strip S2 and even if the heat quantity transferred from the heating zone 22 is reduced, by making this cooling zone the fixed temp., the inner pressure in the furnace is maintained.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method and apparatus for maintaining pressure in a continuous annealing furnace, and in particular to a method and apparatus for maintaining pressure in a continuous annealing furnace, which is suitable for maintaining pressure in a cooling zone constituting a continuous annealing furnace. This invention relates to a method and device for maintaining pressure in a furnace.

0002

2. Description of the Related Art As shown in FIG. 3, a continuous annealing furnace for metal strips is usually equipped with a preheating zone 10, a heating zone 12, and a cooling zone 14, each of which has a sealing section 16A on its inlet and outlet sides. ~16D are provided, and each band is divided. The metal strip S is annealed by passing the metal strip S continuously through a continuous annealing furnace, preheating it in a preheating zone 10, heating it to a specified temperature in a heating zone 12, and holding it for a predetermined time. , by cooling in the cooling zone 14.

[0003] In the above-mentioned continuous annealing furnace, various metal strips having different plate thicknesses, plate widths, or processing conditions are continuously processed. At this time, the tip of the metal strip to be processed next is It is connected by welding to the rear end of the strip to provide an uninterrupted process.

[0004] Therefore, the thickness of the preceding metal strip and the following metal strip may be different, or the plate speed may be changed.

For example, when sequentially annealing a thin plate next to a thick plate, if the processing temperatures for the thick plate and the thin plate are the same, the amount of heat carried from the heating zone 12 to the cooling zone 14 by the strip S will be greater for the thin plate. Therefore, when the thin plate is introduced into the cooling zone 14, the ambient temperature of the cooling zone 14 will decrease.

[0006] When the ambient temperature in the cooling zone 14 decreases as described above, the atmospheric gas in the cooling zone 14 undergoes volumetric contraction.
The pressure inside the furnace becomes negative. Therefore, such a cooling zone 14
In order to alleviate pressure fluctuations in the metal strip, air is allowed to enter from the inlet seal part 16C and the outlet seal part 16D of the cooling zone 14, and this air forms an oxide film on the surface of the strip, resulting in a deterioration in the quality of the metal strip. become.

[0007] This phenomenon occurs in the same way even if the thickness of the metal strip is the same, because the amount of heat supplied to the cooling zone 14 decreases as the strip speed decreases.

[0008] Furthermore, the above-mentioned phenomenon becomes more conspicuous, especially as the temperature of the heating zone 12 is higher and as the heat capacity of the furnace itself is smaller.

[0009] Techniques that can be applied to prevent the occurrence of the above-mentioned phenomenon include, for example,
There is a technology proposed in 6252 that compensates for the depressurization by supplying atmospheric gas in the event of an emergency shutdown, etc., but this technology not only requires a large-scale equipment configuration, but also causes a large change in the furnace temperature itself. There are drawbacks.

The present invention has been made to solve the above-mentioned conventional problems, and when annealing is carried out by passing a metal strip through a continuous annealing furnace having at least a heating zone and a cooling zone, there is a difference between the heating zone and the cooling zone. An object of the present invention is to provide a method and apparatus for maintaining pressure in a continuous annealing furnace, which can effectively prevent the pressure in the furnace in the cooling zone from decreasing even when the amount of heat carried by the metal strip decreases.

[0011]

Problems to be Solved by the Invention The present invention aims to reduce the amount of heat carried by the metal strip from the heating zone to the cooling zone when the metal strip is annealed by passing through a continuous annealing furnace having at least a heating zone and a cooling zone. The above object is achieved by supplying heat to the cooling zone and maintaining the furnace pressure in the cooling zone when the furnace pressure in the cooling zone decreases due to a decrease in the furnace pressure.

The present invention also provides a continuous annealing furnace having at least a heating zone and a cooling zone, a heat exchanger installed in the heating zone, and a gas circulating furnace between the heat exchanger and the cooling zone. A circulation means, a gas control means for controlling the amount of gas to be circulated, a connection point detection means for detecting the connection point of the metal strip passing through the furnace, and a plate speed measurement means for measuring the passing speed of the metal strip. By adopting this configuration, the above-mentioned problem has been achieved as well.

[0013]

[Function] In the present invention, when the amount of heat supplied from the heating zone to the cooling zone is reduced by the metal strip, for example, the amount of heat possessed by the heating zone is forcibly supplied to the cooling zone, so that the atmospheric gas in the cooling zone is Because it is possible to prevent the inside of the cooling zone from becoming negative pressure due to a decrease in the temperature of the cooling zone,
Air infiltration can be reliably prevented. Therefore, it is possible to effectively prevent the surface of the metal strip from being oxidized and deteriorating the quality of the strip, such as discoloration, which would occur when air enters the cooling zone.

[0014] The metal strip to which the present invention can be applied is not particularly limited, and various steel plates such as general cold-rolled steel plates, electromagnetic steel plates, and stainless steel plates can be used.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an in-furnace pressure maintaining device for a continuous annealing furnace according to an embodiment of the present invention.

The apparatus of this embodiment has a preheating zone 20 and a heating zone 22.
and a continuous annealing furnace consisting of a cooling zone 24,
At the entrance of the pre-preparation zone 20, between the pre-preparation zone 20 and the heating zone 22, between the heating zone 22 and the cooling zone 24, and at the outlet of the cooling zone 24, the pre-preparation zone 20, the heating zone 22 and the cooling Seal portions 26A to 26D are provided for dividing the band 24.

A heat exchanger 28 made of a coiled pipe is installed in the heating zone 22, and the heat exchanger 28 and the cooling zone 24 are connected to each other.
An outgoing pipe line 30A and a returning pipe line 30B for circulating the atmospheric gas in the cooling zone 24 are disposed between the cooling zone 24 and the cooling zone 24.

The outbound pipe line 30A is provided with a blower (gas circulation means) 32 for sending atmospheric gas in the cooling zone 24 to the heat exchanger 28, and the return pipe line 30B is provided with a blower (gas circulation means) 32 for sending atmospheric gas from the cooling zone 24 to the heat exchanger 28. A control valve (gas control means) 34 is provided to adjust the flow rate of the heated gas.

Further, near the entrance of the cooling zone 24 in the heating zone 22, there is a plate thickness/plate speed detection device having a function of detecting the connection point W of the metal strip and a function of measuring the passing speed of the metal strip. A device 36 is installed, and the detection device 36 and the blower 32 are connected to a control device (gas control means) 38.
The air blower 32 is connected to the air blower 32 via a detection signal, and it is possible to control the air blowing amount and air blowing timing of the air blower 32 based on the detection signal from the detecting device 36. After detecting the connection point W, the detection device 36 detects the air blower 32 so that the air blower 32 can be activated before the connection point W is introduced into the cooling zone.
It will be installed at a location where there is sufficient time, taking into account the fan system GD2 that makes up the system.

Furthermore, a thermometer 40 for measuring the ambient temperature is installed in the cooling zone 24, and the operation of the blower 32 and the gas flow rate of the control valve 34 are controlled based on the measured value of the thermometer 40. is adjustable.

Next, the operation of this embodiment will be explained.

As shown in FIG.
With the thin plate strip S2 connected to the rear end of 1,
Consider the case where these are passed through a continuous annealing furnace to undergo annealing treatment.

Regarding the metal strip that passes continuously, the plate thickness and plate speed detection device 36 detects the connection point W, measures the passing speed, and inputs this information as a signal to the control device 38. As a result, the blower 32 is activated immediately before the atmospheric temperature in the cooling zone 24 is predicted to decrease due to a decrease in the thickness of the metal strip, that is, immediately before the connection point W passes through the seal portion 26C. .

With the activation of the blower 32, the cooling zone 24
The atmospheric gas inside is introduced into the heat exchanger 28 through the outgoing pipe line 30A, heated, and then passed through the returning pipe line 30B as high-temperature gas.
and is returned to the cooling zone 24 again. At that time, the ambient temperature in the cooling zone 24 is measured with the thermometer 40, and based on the information, the control device 38 adjusts the amount of air blown by the blower 32 or the flow rate of the control valve 34. As a result, the atmospheric temperature within the cooling zone 24 is controlled to be kept constant at all times.

As described in detail above, according to this embodiment, when a metal strip is continuously annealed, the metal strip changes from a thick plate to a thin plate midway through, so the strip is cooled from the heating zone 22. It is possible to effectively prevent a decrease in the ambient temperature of the cooling zone 24 due to a decrease in the amount of heat carried into the zone 24. Therefore, it is possible to always maintain the furnace pressure in the cooling zone 24 constant. This situation is shown in FIG.

FIG. 2(A) schematically shows the apparatus shown in FIG. 1, and FIG. 2(B) shows the thickness (t) of the metal strip as it passes through the continuous annealing furnace. The graph shows the relationship between the change and the furnace pressure (P) in the cooling zone 24 over time.

That is, in the case of the conventional method in which only the furnace temperature of the cooling zone 24 is controlled, when the connection point W passes through the inlet A of the cooling zone 24, as shown by the dashed line, the strip thickness decreases and the strip The amount of heat carried from the heating zone 22 to the cooling zone 24 decreases, and conversely, the amount of heat left in the heating zone 22 remains. However, this excess heat can be quickly reduced, so heating zone 2
Although the pressure increase in the cooling zone 24 is small, the pressure decreases to below atmospheric pressure (negative pressure) in the cooling zone 24, and as a result, outside air is sucked in in the shaded area.

On the other hand, in the case of this embodiment, the cooling zone 2
After the atmospheric gas of No. 4 is sent to the heat exchanger 28 of the heating zone 22 and heated, rapid heating is performed by circulating the gas back to the original state as high-temperature gas, and the furnace temperature of the cooling zone 24 is also controlled. As shown by the solid line, it can be seen that the furnace pressure within the cooling zone 24 is maintained approximately constant.

As described above, according to this embodiment, even when the thickness of the strip passing through the furnace at a constant speed decreases, the pressure inside the furnace in the cooling zone 24 is maintained almost constant, and the negative pressure is maintained. This prevents oxidation of the strip caused by outside air flowing into the cooling zone 24, thereby preventing deterioration in the quality of the strip.

Although the present invention has been specifically explained above, the present invention is not limited to what is shown in the above embodiments.
Various changes can be made without departing from the gist of the invention.

For example, in the above embodiment, the case where the metal strip changes from a thick plate to a thin plate has been described, but the present invention can be similarly applied even when the thickness of the metal strip is the same but the speed of the metal strip is reduced.

Further, in the above embodiment, 30A is the outgoing pipe, and 30A is the outgoing pipe.
The case where 0B is the incoming pipe is shown, but 30B is the outgoing pipe,
30A can also be used as a return pipe.

Furthermore, since the flow rate of the circulating gas can be adjusted by controlling the blower 32, the control valve 34
does not necessarily have to be present.

Further, although the plate thickness/plate speed detecting device 36 has been shown in which the connecting point detecting means and the plate speed measuring means are integrated, each of these means may be provided separately.

Furthermore, although the above-mentioned embodiment has shown how to maintain the pressure inside the furnace in the cooling zone, the device of the above-mentioned embodiment has been proposed, for example, in JP-A No. 63-149323.
It can also be used as a furnace temperature adjustment device in a heating zone.

Furthermore, the heat source for heating the cooling zone is not limited to the heat exchanger installed in the heating zone, but may also be a burner installed outside the furnace or other heating devices such as an electric heater. good.

[0038]

As explained above, according to the present invention, when a metal strip is annealed by passing through a continuous annealing furnace having at least a heating zone and a cooling zone, the metal strip is transported from the heating zone to the cooling zone. Even when the amount of heat decreases, it is possible to effectively prevent the furnace pressure in the cooling zone from decreasing.

[0039] Therefore, since air can be prevented from entering the inside of the cooling zone due to the negative pressure in the furnace, it is possible to prevent the metal strip from being oxidized by the air, and the strip can be oxidized. Deterioration in quality can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an in-furnace pressure maintenance device for a continuous annealing furnace according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram showing the effects of the embodiment.

FIG. 3 is a schematic explanatory diagram showing conventional problems.

[Explanation of symbols]

20...Preliminary zone, 22...Heating zone, 24...Cooling zone, 26A to 26D...Seal part, 28... Heat exchanger, 30A...outbound pipe, 30B...return pipe line, 32...Blower, 34...control valve, 36...Plate thickness/plate speed detection device, 38...control device, 40...Thermometer, S...Metal strip.

Claims (2)

[Claims] Claim 1: When a metal strip is annealed by passing through a continuous annealing furnace having at least a heating zone and a cooling zone, the amount of heat carried by the metal strip from the heating zone to the cooling zone is reduced, and the furnace in the cooling zone is A method for maintaining furnace pressure in a continuous annealing furnace, characterized in that when the internal pressure decreases, heat is supplied to the cooling zone to maintain the furnace pressure in the cooling zone. 2. A continuous annealing furnace having at least a heating zone and a cooling zone, a heat exchanger installed in the heating zone, and gas circulation means for circulating gas between the heat exchanger and the cooling zone; It is equipped with a gas control means for controlling the amount of gas to be circulated, a connection point detection means for detecting the connection point of the metal strip passing through the furnace, and a plate speed measurement means for measuring the passing speed of the metal strip. An in-furnace pressure maintenance device for a continuous annealing furnace characterized by: