JP3044286B2 - Continuous annealing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous annealing furnace used for continuous annealing equipment for steel strip such as a thin steel strip (for example, about 0.2 to 2 mm).

[0002]

2. Description of the Related Art Conventionally, as a heating device for a continuous annealing furnace, for example, Japanese Patent Publication No. 59-12729 has been proposed in order to increase the heating efficiency.
The direct fire type is used as described in the publication. Also,
Japanese Unexamined Patent Publication (Kokai) No. 64-52025 proposes a direct-fire type reduction apparatus using a burner having a special structure.

[0003]

However, in the direct-fired heating furnace described in Japanese Patent Publication No. 59-12729, even if the air ratio is set to 1 or less, at a certain temperature (for example, 700 ° C.) or more. However, there is a problem that the steel sheet cannot be used because the steel sheet is highly oxidized. For this reason, 7
When it is necessary to heat to a temperature of 00 ° C. or higher, an indirect heating device using a radiant tube is further used, so that there is a problem that the overall heating efficiency is poor. When the direct-fired reduction apparatus described in JP-A-64-52025 is used for the heating portion of the continuous annealing furnace, it is possible to heat the steel strip to a higher temperature range, but it is possible to stabilize the steel strip. Special burners are required to form the reduction zone, which is a very expensive facility. Furthermore, since the atmosphere is reductive, it becomes difficult to incinerate rolling oil and the like adhering to the steel strip, and there is a problem that the surface treatment of the steel strip in a subsequent plating line or the like is hindered. The present invention has been made in view of the above circumstances, and performs annealing by heating to a high temperature, is compact, has low equipment costs, is economical in operating costs, and is capable of incinerating rolling oil and the like adhering to a steel strip. It is a first object to provide a possible continuous annealing furnace.
A second object of the present invention is to improve the thermal efficiency of the entire continuous annealing furnace including the reduction direct-fired heating device.

[0004]

According to the present invention, there is provided a semiconductor device comprising:
The continuous annealing furnace according to the present invention is a continuous annealing furnace in which a steel strip is continuously conveyed and annealed, and in a continuous annealing furnace, a heating zone of the steel strip is weakly oxidized and directly fired using a regenerative burner. A regenerative burner configured with a direct-fired heating device and using all or a part of the exhaust gas generated from the weakly-oxidized direct-fired heating device and the reduced direct-fired heating device in the weakly-oxidized direct-fired heating device; And the combustion air of the weak oxidation direct-fired heating device and the reduction direct-fired heating device was supplied to the air supply system of the regenerative burner, and was preheated by the regenerator of the regenerative burner. A part of the high-temperature air is used as combustion air for the reducing direct-fired heating device. And
The continuous annealing furnace according to claim 2 is the continuous annealing furnace according to claim 1, wherein a part of cold air is supplied to the high-temperature air preheated by the heat storage body to lower the temperature to a predetermined temperature, and the reduced direct-heating type heating apparatus is used. To supply.

[0005]

In the continuous annealing furnace according to the first and second aspects, the heating zone is constituted by a weak oxidizing direct heating type heating device and a subsequent reducing direct heating type heating device. It is heated to about 600 to 650 ° C. by a weak oxidation direct-fired heating device, and then further reduced to 65 ° C. by a reduced direct-fired heating device.
Heat to a temperature above 0 ° C. As a result, the weakly oxidized direct heating type heating device can incinerate and remove oil, carbon, etc. attached to the surface of the steel strip, and the reduced direct heating type heating device heats the steel strip surface without generating scale. Can be heated to a predetermined high temperature. In addition, since a regenerative burner is used for the weak oxidation direct-fired heating device, the flow rate of exhaust gas exhausted from the flue is reduced or eliminated,
As a result, the pre-tropical zone in the front part of the heating zone can be shortened or the pre-tropical zone can be eliminated, and the size of the continuous annealing furnace can be reduced. Furthermore, since the heat sent to the pre-tropical zone is effectively used for heating, the overall thermal efficiency is improved. Furthermore, not only the exhaust gas of the weak oxidation direct fire type heating device but also the exhaust gas discharged from the reduction direct fire type heating device is used for preheating the regenerator of the regenerative burner used in the weak oxidation direct fire type heating device. Uses the air preheated by the heat accumulator as combustion air for the weak oxidation direct heating type heating device and the reduction direct heating type heating device, so that the retained heat of the exhaust gas generated from the reduction direct heating type heating device is also reduced. Actively used. In the continuous annealing furnace according to the second aspect, the preheated combustion air has a temperature of about 1000 ° C. and is taken out from the weak oxidizing direct-fired heating device, so that there is a distance to the burner of the reduced direct-fired heating device. In this case, cold air is supplied to the combustion air at 1000 ° C. to lower the temperature to a predetermined temperature (for example, 800 ° C.) at which the heat insulating material can be used, and use the combustion air as the combustion air. In this case, if a large amount of cold air is supplied, the thermal efficiency of the entire continuous annealing furnace is reduced. Therefore, it is necessary to determine the amount of the cool air to be supplied by examining the balance between the facility cost and the fuel cost in each facility.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is an explanatory view of the continuous annealing furnace according to the first embodiment of the present invention, FIG. 2 is a temperature graph of the continuous annealing furnace, and FIG. 3 is a graph showing the relationship between the temperature of the steel strip and the generated oxide film amount ratio. FIG. 4 is a graph showing the relationship, FIG. 4 is an explanatory diagram of a continuous annealing furnace according to a second embodiment of the present invention, FIG. 5 is an explanatory diagram of the continuous annealing furnace, and FIG. 6 is a diagram of a third embodiment of the present invention. FIG. 7 is an explanatory view of such a continuous annealing furnace, FIG. 7 is a sectional view of a weak oxidation direct-fired heating device constituting the continuous annealing furnace, and FIG. 8 is an operation explanatory view of the continuous annealing furnace.

As shown in FIG. 1, a continuous annealing furnace 10 according to a first embodiment of the present invention is a vertical continuous annealing furnace having a portal furnace body 11, one of which is provided with a pre-tropical PH. The other is a heating zone HF. The heating zone HF has a weak oxidation direct-fired heating device 1HF on the inlet side and a reduced direct-fired heating device 2HF on the outlet side. Hereinafter, these will be described in detail.

[0008] The pre-tropical PH is passed through a steel strip 12 passing at a speed of about 150 m / min using the exhaust gas from the heating zone HF.
Is preferably heated to about 250 ° C., thereby improving the thermal efficiency of the continuous annealing furnace 10. As described below, when a regenerative burner is used for the weak oxidation direct-fired heating device 1HF, even if the heating temperature in the pre-tropical PH is lowered, the weak oxidation direct-fired heating device 1HF is sufficient. Therefore, the length of the pre-tropical PH can be made shorter than before.

The weak oxidation direct fire type heating device 1HF constituting the preceding stage of the heating zone HF uses a regenerative burner and burns in a range where the air ratio is slightly smaller than 1, and passes through the steel strip 1 passing therethrough.
2 was heated to a temperature below about 650 ° C. Since the atmosphere is weakly oxidizing, carbon, rolling oil, and the like adhering to the steel strip 12 are burned almost completely at this portion to be removed. FIG. 3 shows an oxide film (mainly Fe) formed when a thin steel plate (steel strip) is heated using such a weakly oxidizing direct-fired heating device 1HF and the air ratio is 1 or less.
_The amount of ₃ O ₄ ) is shown. The amount of the oxide film is small up to 600 ° C., but increases sharply when the temperature exceeds 700 ° C., so that the temperature that can be heated by the weak oxidation direct-fired heating apparatus 1HF is about 650.
It shows that it is about ° C.

[0010] A reduced direct-heating type heating device 2HF constituting the latter stage (ie, the outlet side) of the heating zone HF is disclosed in, for example, Japanese Patent Application Laid-Open No.
As described in JP-A-52025, a burner is used, the air ratio is adjusted to 0.7 to 0.9, and the steel strip 12 is heated by a reducing flame blown on the steel strip 12. The temperature of the steel strip 12 heated by the reduced direct-heating type heating device 2HF is about 850 ° C. Each point A of the continuous annealing furnace 10
FIG. 2 shows the temperatures of C to C and the heating state thereof. In this embodiment, the steel strip 1
2, the temperature is about 250 ° C., about 650 ° C. at the point B that has passed through the weak oxidation direct-fired heating apparatus 1HF, and the reduced direct-fired heating apparatus 2HF
Is about 850 ° C. at the point C passing through. FIG.
In the figure, 13 is an inlet side roll, 14 is a guide roll,
14a shows a flue.

Next, FIG. 4 and FIG. 5 show a continuous annealing furnace 15 according to a second embodiment of the present invention.
Reference numeral 5 denotes a horizontal continuous annealing furnace in which a passing steel strip 16 is horizontally conveyed, and a pre-tropical PHa from the inlet side, a weak oxidation direct-fired heating device 1HFa and a reduced direct-fired heating device 2HFa constituting a heating zone. Have. A regenerative burner composed of a pair of burners 18a and 18b for switching between combustion and exhaust is used in the weak oxidation direct-fired heating device 1HFa, and the length of the pre-tropical PHa is made as short as possible. Reference numeral 17 denotes an exhaust gas flue, reference numerals 19 to 22 denote fans, and reference numerals 23 and 24 denote exhaust gas chimneys. The temperatures of the points A to C in the continuous annealing furnace 15 are the same as those in FIG. 2 and the operation and effect are the same, so that the description thereof will be omitted.

Next, when further studying the continuous annealing furnace 15 according to the second embodiment (the same applies to the continuous annealing furnace 10 according to the first embodiment), the weak oxidation direct-fired heating apparatus 1H
Pre-tropical PHa is installed before Fa. in this case,
As shown in FIG. 5, if a recuperator 25 for preheating the combustion air of the reduction direct heating type heating device 2HFa using the exhaust gas sensible heat exhausted from the front of the pre-tropical PHa, that is, from the inlet of the steel strip 16, is installed. Although the sensible heat of the exhaust gas can be recovered to some extent, such recovery of the exhaust heat by the recuperator 25 cannot achieve such a large thermal efficiency as can be achieved by the regenerative burner of the weak oxidation direct fire type heating device. Then, the inventor further studied diligently and completed the continuous annealing furnace 30 according to the third embodiment.

A continuous annealing furnace 30 according to a third embodiment of the present invention shown in FIGS. 6 to 8 will be described. As shown in FIG. 6, a regenerative burner having combustion exhaust units 31 and 32 that alternately emit and burn a pair is used for the weak oxidation direct-fired heating device 1HFb.
Is provided with a direct fire type burner 33. When one of the combustion exhaust sections 31 performs the combustion operation and the other combustion exhaust section 32 performs the exhaust, the exhaust gas from the direct fire burner 33 of the reduction direct heating type heating device 2HFb is returned to the direct combustion burner 33. The heat storage body 3 of the combustion exhaust part 32 passes from the furnace body of the fire heating device 2HFb through the furnace body of the weak oxidation direct fire heating device 1HFb.
2a, the valve 34, the flow control valve 35, and the fan 36 are exhausted. On the other hand, the combustion air of the combustion exhaust portion 31 is supplied with a flow control valve 37, a fan 38, a valve 39,
It is supplied through the heat storage body 31a of the combustion exhaust part 31. Part of the combustion air preheated to about 1000 ° C. by the heat storage body 31 a is supplied to the direct-fire burner 33 through the valve 41. The combustion exhaust section 3
In the case where 2 performs the combustion operation and the combustion exhaust unit 31 performs the exhaust operation, the valve 39 is closed and the valve 42 is opened, and the valve 34 is closed and the valve 43 is opened, and the same operation is performed. On the other hand, the combustion exhaust parts 31 and 32
By switching valves 44 and 45,
It is supplied to the burning burner side. The valves 41 and 46 for switching the combustion air to the direct-fired burner 33 may be switching valves, or may be check valves in some cases.

FIG. 7 shows the details of the structure of the regenerative burner composed of the combustion exhaust sections 31 and 32. Assembled, each combustion exhaust part 3
1, 32 are provided with burner tubes 48 for supplying fuel,
Heat storage body 31 made of ceramics etc. inside on both sides
Heat storage chambers 49 and 50 having a and 32a, respectively, are provided. Exhaust ports 51 and 52 for sending combustion air to the direct-fired burner 33 are provided above the heat storage chambers 49 and 50, and air is supplied to the heat storage chambers 49 and 50 below the heat storage chambers 32 and 31a.
When preheating is performed, connection ports 53 and 54 for exhausting air are provided. The continuous annealing furnace 30 is not provided with a pre-tropical zone. However, if necessary, a steel strip can be used by a part of the exhaust gas generated from the weak oxidation direct heating type heating device 1HFb and the reduction direct heating type heating device 2HFb. It is free to provide a pre-tropical zone for heating 16 in front of the weak oxidation direct-fired heating device 1HFb.

Next, the operation of the continuous annealing furnace 30 will be described with reference to FIGS. 7A and 7B, which show the flow of each fluid at the time of each combustion switching separately, and FIG. To explain, when the combustion exhaust portion 31 of the regenerative burner performs a combustion operation as shown in FIG.
The combustion air is sent from the fan 38 to the connection port 53 of the combustion exhaust unit 31, and is heated to about 1000 ° C. by the internal heat storage body 31 a to burn the fuel from the burner tube 48.
Part of the combustion air heated to about 1000 ° C. is discharged from the upper exhaust port 51 and is used as preheating air for the direct-fired burner 33. The exhaust gas burned by one combustion exhaust part 31 and the exhaust gas from the direct fire type burner 33 are supplied to the other combustion exhaust part 32 to heat the heat storage body 32 a in the heat storage chamber 50 and to connect the lower connection port 54. Is exhausted to the outside through the fan 36. Next, when the combustion exhaust portion 32 of the regenerative burner performs a combustion operation, FIG.
As shown in (B), the combustion air from the fan 38 is supplied from the connection port 54 of the heat storage chamber 50, is heated to about 1000 ° C. by the heat storage body 32a, and burns the fuel supplied from the burner tube 48. Some of the air is used as combustion air for the direct-fired burner 33 from the upper exhaust port 52. As a result, the temperature of the exhaust gas exhausted from the heat storage chambers 49 and 50 becomes a low temperature of about 200 ° C. or less, and the sensible heat contained in the exhaust gas is efficiently recovered.

As described above, if the air heated by the heat accumulators 32a and 31a is used as the combustion air of the direct-fire type burner 33, the temperature becomes about 1000 ° C. Direct fire type heating device 2HF
If the distance to b is long, it is necessary to provide a pipe that can withstand a high temperature of about 1000 ° C., which may increase the equipment cost. In this case, as shown in FIG.
8 is diverted through the regulating valve 56,
The temperature of the combustion air can also be lowered by mixing and diluting the combustion air leaving 1, 46 with the air. However, if a large amount of cold air is mixed, the temperature of the combustion air becomes too low, and the thermal efficiency of the entire continuous annealing furnace 30 decreases. You need to air.

[0017]

As is clear from the above description, the continuous annealing furnace according to claims 1 and 2 divides the heating zone into a weak oxidation direct-fired heating device and a reduced direct-fired heating device. In addition to being able to efficiently incinerate carbon and oil, etc. attached to the steel strip, and heating in the high-temperature range, the steel strip is heated by a reducing direct-fired heating device that has a reducing ability, without oxidizing the steel strip. It can be heated to a predetermined high temperature. As compared with the case where the entire heating zone is formed by a reduction direct-fired heating apparatus, the equipment cost is lower and the attached carbon, oils and fats are burned and removed, so that the treatment can be performed with high efficiency. In addition, since a regenerative burner is used, the length of the pre-tropical zone can be reduced, and the overall thermal efficiency can be improved. Furthermore, since the combustion air heated by the regenerative burner used for the weak oxidation direct fire type heating device is used for the combustion air of the direct fire type burner of the reduction direct heating type heating device, the regenerative burner is used. The thermal efficiency of the reduction direct-fired heating device can be improved to the same extent as that of the weak oxidation direct-fired heating device used, and the thermal efficiency of the entire continuous annealing furnace can be improved. In the continuous annealing furnace according to the second aspect, since cool air can be mixed into a part of the combustion air from the regenerative burner, if the temperature is adjusted to an appropriate temperature, the equipment cost and the operating cost are balanced. It is possible to operate the continuous annealing furnace economically.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a continuous annealing furnace according to a first embodiment of the present invention.

FIG. 2 is a temperature graph of the continuous annealing furnace.

FIG. 3 is a graph showing a relationship between a temperature of a steel strip and a produced oxide film amount ratio.

FIG. 4 is an explanatory view of a continuous annealing furnace according to a second embodiment of the present invention.

FIG. 5 is an explanatory view of the continuous annealing furnace.

FIG. 6 is an explanatory view of a continuous annealing furnace according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view of a weak oxidation direct-fired heating device constituting the continuous annealing furnace.

FIG. 8 is a diagram illustrating the operation of the continuous annealing furnace.

[Explanation of symbols]

10: continuous annealing furnace, 11: furnace body, 12: steel strip, 13: inlet side roll, 14: guide roll, 14a: flue, 1
5: continuous annealing furnace, 16: steel strip, 17: flue, 18a: burner, 18b: burner, 19: fan, 20: fan, 21: fan, 22: fan, 23: chimney, 24:
Chimney, 25: recuperator, 30: continuous annealing furnace, 3
1: combustion exhaust unit, 31a: heat storage unit, 32: combustion exhaust unit,
32a: regenerator, 33: direct fire burner, 34: valve, 35: flow control valve, 36: fan, 37: flow control valve, 38: fan, 39: valve, 41: valve, 4
2: valve, 43: valve, 44: valve, 45: valve, 46: valve, 47: refractory, 48: burner tube,
49: heat storage chamber, 50: heat storage chamber, 51: exhaust port, 52: exhaust port, 53: connection port, 54: connection port, 56: regulating valve, P
H: Pre-tropical, PHa: Pre-tropical, HF: Heating zone, 1HF:
Weak oxidation direct flame heating device, 1HFa: weak oxidation direct flame heating device, 2HF: reduced direct flame heating device, 2HFa: reduced direct flame heating device, 1HFb: weak oxidation direct flame heating device, 2HF
b: Reduction direct-fired heating device

Continuation of the front page (56) References JP-A-63-130718 (JP, A) JP-A-4-72023 (JP, A) JP-A-51-16211 (JP, A) JP-B-58-83608 (JP) , B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 9/56 101 C21D 1/52

Claims (2)

(57) [Claims] In a continuous annealing furnace for continuously conveying and annealing a steel strip, a weak oxidation direct-fired heating device using a regenerative burner in a heating zone of the steel strip, and a subsequent reduction direct fire And a heat storage type burner used for the weak oxidation direct fire type heating device, wherein all or a part of the exhaust gas generated from the weak oxidation direct fire type heating device and the reduction direct fire type heating device is used. While discharging from the system, the combustion air of the weakly oxidizing direct fire type heating device and the reducing direct fire type heating device is supplied to the air supply system of the regenerative burner, and the high temperature air preheated by the regenerator of the regenerative burner is supplied. A continuous annealing furnace characterized in that a part of the furnace is used as combustion air for the reduced direct-fired heating device. 2. The continuous annealing furnace according to claim 1, wherein cold air is partially supplied to the high-temperature air preheated by the heat storage body to lower the temperature to a predetermined temperature, and then supplied to the reduced direct-fired heating device.