JPS6213536A - Device for sealing exit of atmospheric furnace - Google Patents

Abstract

PURPOSE:To prevent the entering of air from a seal roll part and to operate an atmospheric furnace stably, by providing a seal roll at the steel strip exit of the atmospheric furnace following a direct fire heating furnace, and providing a seal chamber at the upstream side. CONSTITUTION:The seal roll 12 is provided to the steel strip 1 exit of the atmospheric furnace 4 following the direct fire heating furnace 3, and the seal chamber 13 is provided to the upstream side thereof. A seal gas blowing device 11 is provided to the chamber 13 and a furnace inside pressure gauge 15 is set in the furnace 4. If the pressure of the furnace 4 is decreased by the variation, etc., of combustion condition, this is detected by the gauge 15 and seal gas is blown into the chamber 13 from the device 11 to prevent the entering of the air into the furnace 4.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a copper band continuous heat treatment furnace having a direct-fired heating furnace. The purpose is to prevent air from entering the interior.

(Prior art and its problems) In a steel strip continuous heat treatment furnace equipped with a direct-fired heating furnace, the steel strip is first heated to 500 to 800°C without oxidation or reductively in the direct-fired heating furnace, and then further heated in a subsequent atmospheric furnace. , soaking,
After performing heat treatment such as rapid cooling to a temperature below about 150°C where oxidation in the atmosphere is not a problem, it is released into the atmosphere.

The inside of this atmospheric furnace is maintained at a positive pressure of approximately +5 to 15 s + sWc to prevent air from entering, and the furnace is filled with atmospheric gas (3 to 20% H1, remaining Nz) to reduce and prevent oxidation. I am doing it.

In such an atmospheric furnace, the following conventional sealing mechanisms are available for taking out the material into the atmosphere after heat treatment, but each of them has its own problems.

■Seal roll method As shown in Figure 2, the copper strip 21 is clamped by a pair of rolls at 20°20. A complete mechanical seal is not possible due to the unavoidable gaps 23, 24 between the two.

Normally, a small amount of furnace atmosphere gas is blown out from here to prevent atmospheric air from entering the furnace, but if the combustion state of the direct-fired heating furnace on the entrance side changes, the pressure inside the furnace suddenly becomes negative. There is a risk of atmospheric intrusion.

(2) Water-sealing system As shown in FIG. 3, this is a system in which the outlet 26 of the atmospheric furnace 25 is sealed with a water-sealing tank 27, and the steel strip 21 is passed through this tank 27. However, with this method, there is a risk of water vapor intruding into the furnace, and the same problem as atmospheric intrusion remains.

The present invention was proposed as a result of studies to solve the above-mentioned problems.

(Means for Solving the Problems) As shown in FIG.
2 is provided, and a seal chamber 13 is provided upstream of the seal roll 12. In addition, a seal gas blowing device 11 is provided in this seal chamber 13, and an atmospheric furnace 4 is provided.
A furnace pressure gauge 15 is installed.

(Function) When the furnace pressure of the atmosphere furnace temporarily decreases when the combustion conditions are changed, the furnace pressure gauge 15 detects this and the seal chamber 1
A sealing gas is blown into the sealing chamber 3 by a blowing device 11 to make the pressure inside the sealing chamber 13 higher than the outside air to prevent atmospheric air from entering.

(Example) A specific embodiment of the present invention will be described below with reference to FIG.

This figure shows an overall schematic diagram of the copper strip continuous heat treatment equipment, in which a preheating furnace 2, a direct-fired heating furnace 3, and an atmosphere furnace 4 are arranged in sequence.

After passing through a preheating furnace 2, the steel strip 1 is heated in a direct-fired heating furnace 3 at 50%
Non-oxidizing or reductive heating is performed to 0 to 800°C, followed by further heating to a high temperature in the atmospheric furnace 4, soaking, rapid cooling,
After undergoing over-aging treatment, it is cooled to about 150°C or less, where oxidation in the atmosphere is not a problem, and then the seal roll 1
2 and then taken out of the furnace.

In the direct-fired heating furnace 3, fuel gas 5 and combustion air 6
high temperature combustion gas is supplied to the burner section. This combustion gas directly collides with the steel strip 1 and heats the steel strip 1 to a predetermined temperature, and then becomes furnace exhaust gas 7, which heats the steel strip 20 in the preheating furnace 2.
After preheating to 0-450°C, the furnace pressure control damper 9. It passes through the exhaust fan 8 and is exhausted from the chimney.

The passage between the direct-fired heating furnace 3 and the atmosphere furnace 4 is narrowed to prevent combustion exhaust gas from entering the atmosphere furnace, but the passage is quite large in order for the steel strip 1 to pass through without any hindrance. A passageway is required (100 layers x 2000m of fat),
There is no function as a gas seal here, so the furnace pressure fluctuation of the direct-fired heating furnace 3 directly becomes the furnace pressure fluctuation of the atmospheric furnace 4.

Therefore, the atmospheric gas l is transferred from the atmospheric furnace 4 to the direct-fired heating furnace 3.
A furnace pressure needle 14 is placed at the part where the O waves wave, and the furnace pressure control damper 9 is used to control the pressure there to be between +5 and 15 -C.

Such furnace internal pressure can be maintained at a constant pressure during steady-state conditions, but when the combustion conditions of the direct-fired heating furnace 3 are changed, for example when one zone out of multiple zones is extinguished, the furnace pressure control damper 9 cannot be closed in time. The pressure inside the atmosphere furnace 4 may become negative for a short period of time (about 5 to 10 seconds). In this case, a seal roll 12 is provided at the part where the steel strip l exits the atmospheric furnace 4, but as shown in FIG. 2, there is a large gap 23 in this part.
24, making it easy for the atmosphere to enter.

Therefore, in the present invention, in order to prevent this air from entering, a seal chamber 13 is provided upstream of the seal roll 12, and a throttle is provided between the seal chamber 13 and the atmospheric furnace 4 to reduce the pressure of the atmospheric furnace 4 (for example, 5 mat from pressure
e low) is detected by the furnace pressure needle 15, while the seal chamber 1
A sealing gas is blown into the inside of 3 from a blowing device 11. This seal gas can be used alone or with HL of 3 to 2.
0% atmospheric gas may be used.

Since it is necessary to continue blowing a small amount of N or atmospheric gas into the seal chamber 13 even during normal operation, it is better to provide the cutoff valve 16 with a small diameter bypass pipe or to connect a separate pipe to the seal chamber.

The amount of seal gas blown depends on the size of the orifice, but is 300
~60ONm2 is enough, and the blowing time is 10~2
It is about 0 seconds.

(Effects) According to the present invention described above, even if the furnace pressure of the atmospheric furnace temporarily decreases, it is possible to prevent air from entering through the seal roll portion at the outlet of the steel strip, and to maintain stability in the atmospheric furnace. Operation becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram showing an embodiment of the present invention, FIG. 2 is a perspective view of a conventional seal roll, and FIG. 3 is a schematic diagram of the same conventional water seal system. In the figure, 1 is a copper strip, 3 is a direct-fire heating furnace, 4 is an atmospheric furnace, 11 is a sealing gas supply device, 12 is a seal roll, 13 is a sealing chamber, and 15 is a furnace pressure needle of the atmospheric furnace.

Claims (1)

[Scope of Claims] An atmospheric furnace provided subsequent to a direct-fired heating furnace, a sealing chamber provided upstream of an exit seal roll of the atmospheric furnace, and means for detecting the furnace pressure of the atmospheric furnace; An atmospheric furnace outlet sealing device characterized in that means is provided for blowing sealing gas into the sealing chamber when the atmosphere is lowered.