JP3184774B2 - Continuous heating 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 heating furnace which is divided into a plurality of heating zones and uses preheated air of 800.degree. C. or more. Regarding what has been optimized.

[0002]

2. Description of the Related Art As shown in FIG.
For example, a heating zone 1P corresponding to the zone of the entrance of the slab 90, a heating zone 2H corresponding to a zone sandwiched between the zone of the entrance of the slab 90 and the zone of the exit, and a heating zone 3U corresponding to the zone of the exit of the slab. It is divided into a plurality of heating zones, and in recent years, in order to enhance its thermal efficiency, a type equipped with a burner 2 for burning fuel using preheated air at 800 ° C. or higher has been used. As shown in FIG. 12, for example, the burner 2 includes an air outlet 2a provided on the furnace wall 1a for injecting preheated air 2c of 800 ° C. or higher, and a plurality of fuel injection ports 2b provided therearound. And the primary fuel 2d and the secondary fuel 2e are supplied by the air injection port 2a and the fuel injection port 2a, respectively.
b, and the fuel injected from any of the ports is mixed with the preheated air 2c injected from the air outlet 2a, burns, forms a flame, and the generated heat heats the billet 90. It is configured as follows.

Further, in the conventional continuous heating furnace 1, the positional relationship between the air injection port 2a and the fuel injection port 2b constituting the burner 2 with respect to the billet 90 is the same in any zone. The fuel injection port 2 b is arranged so that the flame does not contact the billet 90. Besides, billet 9
The fuel is uniformly supplied to both the fuel injection ports 2b provided on the side closer to 0 and the side farther from 0.

[0004]

However, for the purpose of suppressing the formation of oxide scale on the surface of the billet 90, for example,
As a whole, the air ratio is 1 so that a reducing atmosphere is formed.
Since it is kept at a smaller value, the amount of unburned components in the exhaust gas increases, and if it is released into the atmosphere as it is, there is a problem that the environment is polluted. In order to avoid the environmental problem, it is necessary to separately provide a burner for burning unburned components.

On the other hand, when the air ratio is maintained at a value significantly higher than 1, the amount of flue gas due to excess air increases, the thermal efficiency decreases, and the generation of oxide scale on the surface of the billet 90 increases. There is a problem that.

[0006] Therefore, an object of the present invention is to provide a high thermal efficiency and a small amount of unburned components in exhaust gas.
Accordingly, to provide a continuous heating furnace configured to maintain an optimum atmosphere on the side close to the billet, which does not pollute the environment and substantially affects the billet in each zone. It is in.

[0007]

In order to achieve the above object, a continuous heating furnace according to the first aspect of the present invention is configured such that one furnace body is divided into a plurality of zones, for example, three zones, a billet (90). Heating zone 1 (P), which corresponds to the zone of the entrance, heating zone 2 (H), which is a zone sandwiched between the zone of the entrance of the billet (90) and the zone of the exit, and the zone of the exit for the billet (90). Assuming the case of the heating zone 3 (U), at least one burner (10) is disposed on the furnace wall of each zone, and each of the burners (10) has a preheated air (2c) of 800 ° C. or higher. )
Alternatively, an air outlet (20) capable of injecting preheated air (2c) and primary fuel (2d) at 800 ° C. or higher, and a side closer to the billet (90) with respect to the air outlet (20). A near fuel injection port (30) and a remote fuel injection port (40) provided on the far side and capable of injecting the secondary fuel (2e), respectively, and a first fuel injection port (30) provided on the close fuel injection port (30).
A control valve (35) and a second control valve (45) attached to the remote fuel injection port (40) are provided, and via the first control valve (35) and the second control valve (45), In the heating zone 1 (P) at the entrance of the billet (90), the amount of fuel supplied to the adjacent fuel injection port (30) is reduced by the remote fuel injection port (4).
0), and in the heating zone 2 (H) sandwiched between the zone of the entrance of the billet (90) and the zone of the exit, the fuel supply to the adjacent fuel injection port (30) is reduced. The slab (9) is set to heat the slab (90) in a larger and reducing atmosphere than to the remote fuel injection port (40).
In the heating zone 3 (U) at the carry-out port of (0), the amount of fuel supplied to the adjacent fuel injection port (30) is made smaller than that to the remote fuel injection port (40), and the billet (90) is oxidized. To be heated , and a plurality of zones (P, H,
U) Distance between the center of the burner (10) and the billet (90)
(L1, L2, L3) is changed to the zone of the entrance of the billet (90).
(P) to become larger from the carry-out exit band (U)
The position of the burner (10) of each band is set to (L1 <
L2 <L3) .

In the continuous heating furnace according to the second aspect of the present invention, one furnace is divided into a plurality of zones (P, H, U), and at least one zone is provided on a furnace wall of each zone (P, H, U). Burner (1
0) is arranged and each of its burners (10) is 800
The pre-heated air (2c) or higher at 800 ° C. or the pre-heated air (2c) at 800 ° C. or higher and the primary fuel (2d) can be injected into the air outlet (20). Proximity fuel injection holes (3) provided on the side closer to and farther from the piece (90) and capable of injecting the secondary fuel (2e), respectively.
0) and a remote fuel injection port (40), and a fuel supply rate control valve (55) attached to the close fuel injection port (30) and the remote fuel injection port (40). Through the control valve (55), in the zone (P) at the entrance of the billet (90), the proximity fuel injection port (30)
The fuel supply amount to the remote fuel injection port (40) is set substantially equal to that to the remote fuel injection port (40), and the zone (H) sandwiched between the zone (P) at the entrance of the billet (90) and the zone (U) at the exit. In the above, the fuel supply amount to the adjacent fuel injection port (30) is set to be larger than that to the remote fuel injection port (40), and the billet (90) is set to be heated in a reducing atmosphere. In the outlet zone (U), the fuel supply to the adjacent fuel injection port (30) is made smaller than that to the remote fuel injection port (40) to heat the billet (90) in an oxidizing atmosphere. Set and burner for each band (P, H, U)
The distance between the center of (10) and the billet (90) (L1, L2,
L3) is carried out from the zone (P) at the entrance of the billet (90).
Bars in each band to increase over the mouth band (U)
(L1 <L2 <L3)
It is characterized by the following. The primary fuel and the secondary fuel according to the first and second aspects include, for example, gas, heavy oil, and oil such as kerosene.

The symbols in parentheses described in the means for solving the above problems correspond to the symbols described in the drawings and the embodiments of the invention described later.

According to the present invention , first, in the zone of the entrance of the billet, for example, in the heating zone 1, the amount of fuel supplied to the adjacent fuel injection port is set substantially equal to that of the remote fuel injection port. Since the temperature of the flame on the side of the fuel injection port close to the slab is high and the temperature difference with the slab is large, the amount of heat transfer to the slab is high and the temperature of the slab rapidly rises. Next, in a zone sandwiched between the zone of the entrance of the billet and the zone of the exit, for example, in the heating zone 2, the fuel supply to the adjacent fuel injection port is larger than that to the remote fuel injection port. Since the temperature of the flame near the fuel injection port close to the billet is high and the temperature difference from the billet is large, the amount of heat transferred to the billet is high, and the billet temperature rises. In addition, the amount of air on the side of the fuel injection port close to the billet is insufficient, unburned components are generated, and the atmosphere becomes a reducing atmosphere, so that the generation of oxide scale on the surface of the billet is suppressed. Finally, in the zone of the exit of the billet, for example, in the heating zone 3,
Since the amount of fuel supplied to the adjacent fuel injection port is smaller than that to the remote fuel injection port, the temperature of the flame on the side of the close fuel injection port close to the billet is low, and the temperature difference with the billet is also small. The amount of heat transferred to the billet is low, and the temperature on the billet surface hardly rises, but the inside and outside temperatures become more uniform. The amount of air on the side of the adjacent fuel injection port becomes excessive, and the surroundings of the billet become an oxidizing atmosphere, and the thin, hard-to-peel oxide scale formed on the billet surface in the pre-tropical zone and the heating zone is oxidized, and its peelability is reduced. Enhanced.

The length of the flame is shortest when the fuel supply amount to the adjacent fuel injection port is in the zone of the loading port of the billet set to be substantially equal to that to the remote fuel injection port. The larger or smaller the fuel supply amount of the remote fuel injection port, the longer the fuel supply amount.

On the other hand, in each zone, the amount of air supplied from the air injection port is set so that the air ratio of the burner as a whole is slightly larger than 1. Although unburned components are once generated, mixing with air proceeds toward the tip of the flame, and eventually complete combustion occurs. Therefore, the amount of combustion exhaust gas is small,
It has high thermal efficiency and does not pollute the environment.

[0013] a high thermal efficiency since the air ratio is maintained slightly higher than 1. In addition, the distance between the center of the burner and the billet increases in the order of, for example, heating zone 1, heating zone 2, heating zone 3 from the zone of the entrance of the billet to the zone of the exit, and the heating zone 1 Since the distance between the flame formed on the side of the adjacent fuel injection port and the billet is small, the amount of heat transfer to the billet in the heating zone 1 increases, and the temperature rise rate increases. On the other hand, the flame formed on the side of the remote fuel injection port of the heating zone 3 is far from the steel slab and close to the ceiling, and the heat is reflected by the ceiling to the whole inside of the furnace. Transmission unevenness is reduced, and the temperature of the billet is made uniform.

[0014]

Embodiments of the present invention will be described with reference to the drawings. 1 is a longitudinal sectional view showing a continuous heating furnace according to a first embodiment of the present invention, FIG. 2 is a transverse sectional view showing a part of a heating zone 1P in FIG. 1, and FIG. 3 is a heating zone 2H in FIG. 1. FIG. 4 is a cross-sectional view showing a part of FIG.
It is a cross-sectional view which shows a part of U.

In the continuous heating furnace 80 according to the first embodiment of the present invention, a heating zone 1P for preheating the slab 90 and a slab 90 are heated in a reducing atmosphere in the moving direction of the slab 90. The heating zone 2H and the slab 90 are heated in an oxidizing atmosphere to
It is divided into three zones: a heating zone 3U for making the temperature within 0 uniform. Moreover, the furnace wall 81 and the billet 90 in each zone
A burner 10 configured as described below is provided above and below. That is, centering on the preheated air 2c at 800 ° C. or higher, or the air outlet 20 capable of injecting the preheated air 2c at 800 ° C. or higher and the primary fuel 2d (a plurality of air outlets may be provided at the same level). On the side close to the billet 90, the proximity fuel injection port 30 capable of injecting the secondary fuel 2e is provided.
Remote fuel injection ports 40 capable of injecting the same secondary fuel 2e are arranged on the side far from the billet 90, respectively. In addition, the proximity fuel injection port 30 (a plurality of proximity fuel injection ports may be provided at the same level) is provided with a first control valve 35 capable of adjusting the fuel supply amount, and the remote fuel injection port 40 (a plurality of proximity fuel injection ports are provided at the same level). May be provided with a second control valve 45 capable of adjusting the fuel supply amount. As the primary fuel and the secondary fuel, for example, oil such as gas, heavy oil, and kerosene is used. The preheated air 2c at 800 ° C. or higher can be obtained by using a regenerative burner, a regenerator, or a heat exchanger.

Further, the fuel supply amount Q1 to the adjacent fuel injection port 30 and the fuel supply amount Q2 to the remote fuel injection port 40 in each band are controlled via first and second control valves 35 and 45 which can be separately controlled. Is set as follows. That is, the heating zone 1P is the fuel supply amount Q to the adjacent fuel injection port 30.
1 is set to be substantially equal to the fuel supply amount Q2 to the remote fuel injection port 40, and in the heating zone 2H, the fuel supply amount Q1 to the adjacent fuel injection port 30 is changed to the fuel supply amount Q2 to the remote fuel injection port 40.
The heating zone 3U is set so that the fuel supply amount Q1 to the adjacent fuel injection port 30 is smaller than the remote fuel injection port 4.
It is set to be smaller than the fuel supply amount Q2 to zero. The opening degree setting (0 to 100) of the first and second control valves 35 and 45 may be automatic or manual, or may be controlled by a controller according to, for example, combustion conditions.

More specifically, first, on the inlet side of the heating zone 1P, the fuel supply amount Q
1 is set equal to Q2 to the remote fuel injection port 40 (for example, Q1: Q2 = 50: 50), so that the temperature of the flame on the side of the close fuel injection port 30 close to the billet 90 increases. Also, the temperature difference from the billet 90 is large. For this reason, the amount of heat transfer to the billet 90 is high, and the temperature of the billet 90 rises sharply. In this region, the temperature of the billet 90 is relatively low, so that the generation of oxide scale is small. Further, the length of the flame is shorter than the heating zone 2H and the heating zone 3U described later.

Further, on the side near the heating zone 2H where the temperature of the billet 90 has risen considerably, the fuel supply amount Q1 to the adjacent fuel injection port 30 is larger than that of the remote fuel injection port 40 (for example, Q1: Q2 = 100: 0), the amount of air on the side of the proximity fuel injection port 30 is insufficient, the combustion speed is reduced, the flame is lengthened, the temperature is reduced, and the fuel is reduced. Incomplete combustion occurs and unburned components are generated. Although this flame has a low temperature, its irradiance is high, and since it is close to the billet 90, the heat transfer amount is relatively high and reaches the desired temperature in a short time. However, since the flame temperature is low, the temperature reached is low, and there is no possibility of overheating and melting. Moreover, since the atmosphere is reducing,
The formation of oxide scale is also suppressed. However, the amount of air supplied from the air injection port 20 is supplied such that the air ratio is slightly larger than 1 as a whole with the burner 10, and therefore, the air amount is partially not supplied to the proximity fuel injection port 30. Although the combustion component is generated once, the mixing with the air proceeds toward the front end of the flame, and finally, the flame is completely burned. Therefore,
The amount of flue gas is small, the thermal efficiency is high, and the environment is not polluted. In order to stabilize the combustion, the air jet 20
May be supplied with a small amount of primary fuel. In FIG. 3, Q1: Q
The operation was performed with 2 = 100: 0, but 80:20, 70:
30 can be arbitrarily set. In addition, heating zone 1
As the heating zone changes from P to heating zone 2H, the ratio of Q1 and Q2 is changed from Q1: Q2 = 50: 50 to 60:40, 70:30,
The ratio may be gradually increased to 80:20, 90:10, and 100: 100.

Next, in the heating zone 2H, the fuel supply amount Q1 to the adjacent fuel injection port 30 is larger than that to the remote fuel injection port 40 (for example, Q1: Q2 = 100:
0) Therefore, the temperature and irradiance of the flame on the side of the proximity fuel injection port 30 close to the billet 90 are high, and the temperature difference from the billet 90 is large. The temperature of 90 rises. In addition, the proximity fuel injection port 30 close to the billet 90
Is insufficient, unburned components are generated, and the atmosphere becomes a reducing atmosphere, so that the generation of oxide scale on the surface of the billet 90 is suppressed. Also, the flame becomes longer.

Finally, in the heating zone 3U, the fuel supply amount Q1 to the adjacent fuel injection port 30 is smaller than that Q2 to the remote fuel injection port 40 (for example, Q1: Q2 = 0: 10).
0), the temperature of the flame on the side of the fuel injection port 30 close to the billet 90 is low, and the temperature difference with the billet 90 is small, so that the amount of heat transferred to the billet 90 is low, and the surface of the billet 90 Although the temperature hardly rises, the temperature inside and outside is made more uniform. In addition, the length becomes longer like the heating zone 2H. Moreover, the proximity fuel injection port 30
Side becomes excessive, the surroundings of the slab 90 become an oxidizing atmosphere, and the thin, hard-to-peel oxide scale formed on the surface of the slab 90 in the heating zone 1P and the heating zone 2H is oxidized. Enhanced. On the other hand, the flame formed on the side of the remote fuel injection port 40 is far from the steel slab 90 and close to the ceiling, and its heat is reflected by the ceiling to the whole inside of the furnace.
The heat transfer unevenness to zero is reduced, and the uniformity of the billet 90 is promoted.

As described above, in any of the zones, the amount of air supplied from the air outlet 20 is set so that the air ratio of the burner 10 as a whole is slightly larger than 1. In a region where the amount is large, unburned components are partially generated once, but mixing with air proceeds toward the front end of the flame, and eventually complete combustion occurs. Therefore, the amount of combustion exhaust gas is small, the thermal efficiency is high, and the environment is not polluted.

Next, a second embodiment will be described with reference to FIGS. 5 to 8. In addition to the configuration of the above-described second embodiment, as shown in FIG. The relationship of the distance L1 between the center of the burner 10 and the slab 90 in the heating zone 2H, the distance L2 between the center of the burner 10 and the slab 90 in the heating zone 2H, and the distance L3 between the center of the burner 10 and the slab 90 in the heating zone 3U is L1 < The position (height) of the burner 10 in each band is set so that L2 <L3. Thereby, in addition to the above-described operation and effect, the distance between the flame formed on the side of the proximity fuel injection port 30 of the heating zone 1P and the billet 90 is small, so that the heat transfer amount to the billet 90 in the heating zone 1P is small. Increases, the rate of temperature rise increases, and the time required for preheating or heating is reduced. Also,
On the contrary, the flame formed on the side of the remote fuel injection port 40 of the heating zone 3U is far from the billet 90, close to the ceiling,
Since the heat is reflected from the ceiling to the entire inside of the furnace, uneven heat transfer to the billet 90 is reduced, and the temperature of the billet 90 is made uniform.

Next, a third embodiment will be described with reference to FIG. 9. Referring to FIG. 9, opposing furnace walls 81, 81 parallel to the moving direction of the steel slab 90 of the continuous heating furnace 80 are opposed to each other. Burners 10, 10 are arranged so as to make it easier.
Moreover, the combustion heating conditions are set as follows so that the opposing burners 10, 10 are alternately operated and stopped at predetermined time intervals, that is, one of the burners 10 is operated alternately. . That is, one of the opposing burners 10, 10 operates for a certain period of time, and air and fuel are injected from one furnace wall 81 toward the other furnace wall 81, while the other is stopped. Then, on the contrary, one of the operating burners 10 is stopped for the same time, while the other is operating, and air and fuel are injected from the other furnace wall 81 toward the one furnace wall 81. The overall air ratio of each burner 10 is maintained at a value slightly higher than 1.

The flame formed by each burner 10 is:
The temperature, shape, atmosphere, and the like change from the furnace wall 81 on the side where air and fuel are injected toward the opposing furnace wall 81, and have a unique distribution. . For this reason, heating in the width direction of the steel slab 90 is not uniform, and uneven heating may occur.
On the other hand, by setting the opposing burners 10 and 10 to alternately operate and stop at predetermined time intervals, the distribution of the temperature, shape, atmosphere, and the like is changed at predetermined time intervals. The direction is reversed, and uneven heating in the width direction of the billet 90 is leveled, so that uneven heating of the billet 90 is eliminated. Note that the burners 10 and 10 are
Not only those arranged in pairs on the parallel furnace walls 81, 81 opposed to each other, but also the parallel furnace walls 81, 8
It may be arranged adjacent to any one of the furnace walls 81 (or both).

Finally, a fourth embodiment will be described with reference to FIG. In the first to third embodiments described above,
A first control valve 35 that can adjust the amount of fuel supplied to the adjacent fuel injection port 30 as needed, and a second control valve that can separately adjust the amount of fuel supplied to the remote fuel injection port 40 as needed The fuel supply amount ratio control valve 55 is used as shown in FIG. 10 to change the functions of the first control valve 35 and the second control valve 45 to one.
One valve may be used, and the ratio of the amount of fuel supplied to the proximity fuel injection port 30 and the remote fuel injection port 40 may be adjusted as needed. Thereby, the side close to the object to be heated 90 which substantially affects the object to be heated 90 can be adjusted to any oxidizing or reducing (including this intermediate) atmosphere. The opening degree setting (0 to 100) of the fuel supply amount ratio adjusting valve 55 may be automatic or manual, and may be controlled by a controller according to, for example, combustion conditions.

It is to be noted that the continuous heating furnace 80 of this embodiment
One furnace body is divided into a plurality of zones, for example, three zones, that is, a heating zone 1 corresponding to a zone of the entrance of the billet 90.
P, the heating zone 2H corresponding to the zone between the entrance zone and the exit zone of the billet 90 and the heating zone 3U corresponding to the exit zone of the billet 90 have been described. The present invention is not limited to this, and is applicable to two bands or four or more bands.

[0027]

As described above , according to the present invention, the ratio of the amount of fuel supplied to the adjacent fuel injection port to that of the remote fuel injection port is appropriately set for each zone according to the purpose of heating the billet. Therefore, a heat transfer amount corresponding to the purpose of heating the steel slab is obtained, and the atmosphere near the steel slab, which substantially affects the steel slab, is appropriately maintained. Moreover, in each zone, the amount of air supplied from the air ejection port is
By setting the air ratio slightly higher than 1 for the burner as a whole, unburned components are generated once in a region where the fuel supply is large, but mixed with air toward the tip of the flame. And eventually burn completely. Therefore, the amount of combustion exhaust gas is small, the thermal efficiency is high, and the environment is not polluted. The length of the flame can also be changed by changing the ratio of the fuel supply to the proximate fuel injection port to that of the remote fuel injection port. In particular, according to the second aspect of the present invention, since two control valves are replaced with one fuel supply ratio control valve, the number of parts is reduced.

In addition, since the distance between the center of the burner and the billet is appropriately set for each zone according to the purpose of heating the billet, the optimum heat transfer amount according to the purpose of heating the billet is set. Is obtained, and the atmosphere close to the billet, which substantially affects the billet, is optimally maintained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a continuous heating furnace according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a part of a heating zone 1P of FIG.

FIG. 3 is a cross-sectional view showing a part of a heating zone 2H of FIG.

FIG. 4 is a cross-sectional view showing a part of the heating zone 3U of FIG.

FIG. 5 is a longitudinal sectional view showing a continuous heating furnace according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a part of the heating zone 1P of FIG.

FIG. 7 is a cross-sectional view showing a part of the heating zone 2H of FIG.

FIG. 8 is a cross-sectional view showing a part of the heating zone 3U of FIG.

FIG. 9 is a cross-sectional view showing a part of a continuous heating furnace according to a third embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a part of a continuous heating furnace according to a fourth embodiment of the present invention.

FIG. 11 is a longitudinal sectional view showing a conventional example.

FIG. 12 is a cross sectional view showing a part of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous heating furnace 1a Furnace wall 2 Burner 2a Air injection port 2b Fuel injection port 2c Air 2d Primary fuel 2e Secondary fuel 10 Burner 20 Air injection port 30 Proximity fuel injection port 35 First control valve 40 Remote fuel injection port 45 2 control valve 55 fuel supply ratio control valve 80 continuous heating furnace 81 furnace wall 90 steel slab L1 distance L2 distance L3 distance Q1 fuel supply Q2 fuel supply P heating zone 1 H heating zone 2 U heating zone 3

Continuation of the front page (56) References JP-B 55-14966 (JP, B2) JP-B 54-13610 (JP, B2) JP-B 56-1371 (JP, B2) Jiko 57-7926 (JP , Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 9/00 101 C21D 1/52

Claims (2)

(57) [Claims] 1. A furnace body is divided into a plurality of zones, and at least one burner is disposed on a furnace wall of each zone.
Each of the burners is preheated air at 800 ° C. or higher, or
An air outlet capable of injecting preheated air and primary fuel at 800 ° C. or higher, and adjacent fuel provided on the side closer to and farther from the steel slab with respect to the air outlet, each of which can inject secondary fuel. An injection port and a remote fuel injection port, a first control valve provided to the proximity fuel injection port, and a second control valve provided to the remote fuel injection port, and a first control valve and a second control valve. In the billet inlet zone, the fuel supply amount to the adjacent fuel injection port is set substantially equal to that to the remote fuel injection port, and is sandwiched between the billet inlet and outlet zone. In the zone where the fuel is supplied to the adjacent fuel injection port is set to be larger than that to the remote fuel injection port and the slab is heated in a reducing atmosphere, and in the zone where the slab is discharged, the proximity fuel injection is performed. Fuel supply to the remote fuel injection It is smaller than is configured to heat the steel strip in an oxidizing atmosphere, moreover for each of the plurality of bands
Determine the distance between the center of the burner and the billet
Bar in each zone so that it increases from
A continuous heating furnace characterized in that the position of the furnace is set . 2. A furnace body is divided into a plurality of zones, and at least one burner is disposed on a furnace wall of each zone.
Each of the burners is preheated air at 800 ° C. or higher, or
An air outlet capable of injecting preheated air and primary fuel at 800 ° C. or higher, and adjacent fuel provided on the side closer to and farther from the steel slab with respect to the air outlet, each of which can inject secondary fuel. An injection port and a remote fuel injection port, and a fuel supply rate control valve attached to the adjacent fuel injection port and the remote fuel injection port. In the zone, the amount of fuel supplied to the adjacent fuel injection port is set substantially equal to that to the remote fuel injection port, and in the zone sandwiched between the billet inlet and outlet zones, the fuel supply to the adjacent fuel injection port is The fuel supply is set to be larger than that to the remote fuel injection port and the steel slab is set to be heated in a reducing atmosphere. Smaller than that to the mouth It is set so as to heat the steel strip in an oxidizing atmosphere, yet the center and steel of the burner for each of the plurality of bands
The distance from the slab to the slab entrance zone
The burner position of each band is set so that
Continuous heating furnace, characterized in that it is.