JP3003062B2 - Heating method of billet in 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 method of heating a steel slab in a continuous heating furnace, wherein the extraction temperature of some steel slabs is made different from the extraction temperature of other steel slabs.

[0002]

2. Description of the Related Art As is well known, when operating a continuous heating furnace in a hot rolling line, the heat extraction temperature of some steel slabs is set to the same as that of other steel slabs in order to obtain different material properties. Different temperatures are used. Conventionally, such a heating method is performed by changing the furnace temperature of the zone where the slab is located, and the influence is exerted on the slabs before and after, so that the heating temperature does not affect the product performance. A method of inserting a piece as a dummy material or changing the extraction pitch (Japanese Patent Laid-Open No. 62-240717), a method of scheduling the loading order of the steel pieces so that the extraction temperature smoothly changes in the passing order ( JP-A-63-5321
No. 6) or a method in which a plurality of heating furnaces are selectively used, and the heating temperature is changed by changing the furnace time for each furnace (Japanese Patent Laid-Open No. 58-48626).

[0003]

However, these methods require a large stock of billets (,),
Since the loading order and extraction order of the billet are different, complicated scheduling work taking into account the restrictions on the rolling schedule is required (). In addition, there was a problem that the productivity was not always sufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a continuous method capable of efficiently extracting some steel slabs to different extraction temperatures by a simple method and efficiently. An object of the present invention is to provide a method for heating a billet in a heating furnace.

[0005]

Means for Solving the Problems A method for heating a steel slab in a continuous heating furnace according to the present invention has the following constitution. That is, a part of the billet group continuously charged in the continuous heating furnace is heated and extracted to a temperature higher or lower than the extraction temperature of the other steel bill without changing the charging interval. In the method of heating a billet, first, a steady fuel injection amount pattern F1 consisting of a fuel injection amount per zone of the heating furnace when heating all the billets to an extraction temperature θ1, and an extraction temperature θ2 And a steady fuel input pattern F2 comprising the fuel input per zone of the heating furnace when heating is continuously performed to the heating furnace, and F1 when heating the partial steel slab from the extraction temperature θ1 to the extraction temperature θ2. Zone fuel input change ratio ΔR ( 0 <ΔRe, ΔRn <1, where ΔRe ≠) with respect to the difference between the total fuel input and the total fuel input of F2.
ΔRn, the subscript e is the zone where the target billet exists,
n is the field of the adjacent zone before and after the zone where the target billet exists.
Previously obtained a slip). Therefore, when the heating and extracting temperatures of the steel slabs present in the furnace are all θ1, the fuel input amount in each zone is set to the fuel input amount in the steady fuel input pattern F1. Next, with the progress of the operation, when the steel slab to be heated to the extraction temperature θ2 is charged into the heating furnace, the burner system in the zone where the steel slab is present is moved in accordance with the movement of the steel slab in the furnace. Fuel input to the pattern F1 by increasing or decreasing the difference between the total fuel input of F1 and the total fuel input of F2 by the zone fuel input change ratio (ΔRe) with respect to the pattern F1. Set and control. Further, the fuel input amount to the burner system in the adjacent zone before and after the zone is calculated by comparing the fuel input amount in the front and rear zones in the pattern F1 with F
The fuel injection amount is reduced or increased by an amount obtained by multiplying the difference between the total fuel injection amount of F1 and the total fuel injection amount of F2 by the above-mentioned zone fuel injection amount change ratio (ΔRn). The fuel input amount to the pattern F1
The fuel injection amount of each zone is controlled while maintaining the fuel injection amount of the other zone.

Further, the continuous heating furnace in the present invention has a regenerative alternating combustion burner system.

[0007]

According to the method of heating a billet according to the fuel supply control method of the present invention, the amount of fuel supplied to each zone is sequentially changed as the billet is moved in the furnace without changing the charging interval of the billet. Now, if the steel slab to be heated and extracted to a temperature θ2 higher (or lower) than the heating and extraction temperature θ1 of most steel slabs is successively charged into the majority of the steel slabs, it will be heated to a high (or low) temperature θ2. Set to increase (or decrease) the fuel input of the zone where the billet to be extracted exists by a certain amount,
As controlled, the heat transfer to the billet is higher (or lower) and higher (or lower) than most other billets
It becomes possible to heat to a predetermined temperature. In addition, the billet to be set to the heating extraction temperature θ1 located in the adjacent zone before and after that increases or decreases the fuel input amount in the zone where the billet to be heated and extracted to the high (or low) temperature θ2 exists.
As a result, the amount of heat transferred from the zone increases (or decreases) under the influence of the influence, but the fuel input amount in the adjacent zone is changed according to the zone fuel input pattern of the fuel input amount pattern for heating the steel slab to the full amount θ1. Reduced by a certain amount (or
Is increased and increased, so that even if this effect exists, it is heated to a predetermined temperature θ1. As a result, the charging interval billet part that was continuously charged into the continuous heating furnace
It is possible to heat extract (burn) to a temperature different from other billets without changing .

In the present invention, the reason why a continuous heating furnace provided with a regenerative alternating combustion burner system is used is that in the regenerative alternating combustion burner system, most of the combustion gas generated by combustion is exhausted outside the furnace through the regenerator. So
This is because the amount of gas flowing out from each zone to other zones is small, the correlation between the furnace temperature in each zone and the fuel input is strong, and the interference between the zones is small, so that the effect of the fuel input control of the present invention is large. Therefore, the method of the present invention can be applied to a continuous heating furnace having a conventional burner (not a regenerative alternating combustion burner system) although the degree of burning is somewhat deteriorated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a fuel supply amount control method for a continuous heating furnace according to one embodiment of the present invention.
2 and 3 are schematic structural views showing a regenerative alternating combustion burner system provided for each unit furnace of the continuous heating furnace. FIG. 2 is a side sectional view of the unit furnace, and FIG. 3 is a unit furnace. It is also a front view.

The continuous heating furnace 1 is constituted by connecting a plurality of unit furnaces 2 each having an inlet 3 for a billet W and an outlet 4. The embodiment consists of eight unit furnaces 2 and therefore has eight zones for continuously heating the billet. In the unit furnace 2, a pair of regenerative combustion burners 9 are installed on the upper and lower parts of the furnace body and on the left and right of each part, respectively, facing the furnace length direction. Each of the burners 9 has a space 10 for mixing fuel and preheated combustion air supplied through a heat storage body 11 provided in the burner main body, as shown in FIGS. Periodically and alternately performs combustion and exhaust, while one burner 9 stops combustion and exhaust gas is drawn out of the furnace through the regenerator 11 of the burner by one four-way valve 14. The other burner 9 starts burning and blows out high-temperature combustion gas toward the inside of the furnace. Note that FIG.
, 12 is an air supply system for supplying combustion air by a pushing fan 15, and 13 is an exhaust gas exhaust system for exhausting exhaust gas by an induction fan 16. The four-way valve is provided to the air supply system 12 and the exhaust gas exhaust system 13. 14 are provided. 1
Reference numeral 8 denotes a fuel supply system that supplies fuel through one three-way valve 17. In FIGS. 1 and 2, reference numeral 5 denotes furnace pressure control means provided for each unit furnace 2. The furnace pressure control means 5 adjusts the opening degree of a damper 6 provided in a duct 7 communicating with a collecting chimney 8, and reduces the furnace pressure in each zone. It is controlled to be constant.

At least one pair of the regenerative alternating combustion burner systems 100 configured as described above is installed for each unit furnace 2 to constitute a continuous heating furnace 1 as shown in FIG. Therefore, each zone of the continuous heating furnace 1 is a unit furnace 2
Exhaust gas hardly flows out to adjacent zones before and after by the regenerative alternating combustion burner 9, and interference between zones is reduced. Further, a fuel flow control device 101 for controlling the fuel supplied to the burner 9 for each zone is provided for each regenerative alternating combustion burner system 100. The fuel flow control device 101 is configured to output a fuel flow control signal to the regenerative alternating combustion burner system 100 based on a control signal from the fuel input setting means 102.

The fuel input setting means 102 includes a fuel input pattern calculating means 103 and a billet furnace position calculating means 104.
And a set fuel flow rate calculating means 105. When the information 106 of the steel slab to be heated and extracted to the normal temperature θ1 is given to the fuel injection pattern calculation means 103, the fuel injection amount and the fuel injection pattern prediction formula model for estimating the relationship between the pattern and the transition of the steel slab temperature are obtained by the fuel injection pattern calculation formula model. A steady fuel injection amount pattern F1 for heating the billet to the target extraction temperature θ1 is obtained. Each zone of the continuous heating furnace 1 is changed to the fuel injection amount pattern F1 based on a signal from the billet furnace position calculating means 104. It is sequentially set to the fuel input amount based on this.

When the information of the billet having different heating extraction temperature θ2 is given to the fuel injection pattern calculation means 103, a steady fuel injection amount pattern F2 for heating the steel billet to the target extraction temperature θ2, and a total fuel injection amount of F1. Then, a zone fuel input change ratio .DELTA.R for extracting a different temperature based on the difference between the total fuel input of F2 and F2 is determined. The fuel input setting means 102 is periodically activated and outputs a fuel flow control signal based on a signal from the in-slab furnace position calculating means 104. If the different hot-extraction temperatures are higher (or lower) than the normal hot-extraction temperature, the fuel input of the zone where the billet with different hot-extraction temperatures θ2 is located will be the total fuel input of F1 with respect to F1. The fuel input amount is increased (or decreased) by a certain ratio of the difference between the total fuel input amount of F2 and the fuel input amount of ΔR (zone fuel input change ratio) ΔR. With respect to the fuel input amount based on the amount pattern F1, the fuel input amount of a constant ratio (zone fuel input change ratio) ΔR of the difference between the total fuel input amount of F1 and the total fuel input amount of F2 is reduced (or increased). Changed) to the amount.

Further, a specific example will be described. Billet 22
0 mm x 1125 mm x 8800 mm is charged at normal temperature of 30 ° C, and heating operation is performed at a heating extraction temperature of 1230 ° C with a heating efficiency of 200 T / Hr.
6 mm, 8 zones), without changing the heating efficiency, after heating and extracting eight steel slabs (corresponding to 2 zones) to 1270 ° C., and then heating again to the heating and extracting temperature of 1230 ° C. based on the method of the present invention. FIG. 6 shows the transition of the billet extraction temperature in the test performed. At this time, F estimated by the fuel injection pattern prediction formula model
1 and F2 are as shown in FIGS. 4 and 5, and the total fuel input amounts are 54.6 × 10 ⁶ kcal / Hr and 57.0 ×, respectively.
Was 10 ⁶ kcal / Hr.

The fuel input amount in the two zones where the steel slab to be heated to 1270 ° C. is located is determined as follows. From the relationship between the billet heating extraction temperature difference ΔT and zones fuel input amount change rate ΔR of FIG 7, of the two zones located billet heating to 1270 ° C., when the spout side of the zone (● mark), Zone The change rate of the fuel injection amount is ΔR = 0.57, and ΔR = 0.49 in the zone near the extraction port (indicated by a circle). At this time, the change amount of the fuel input amount of the zone is a difference of 2.4 × 10 ⁶ kca between the total fuel input amount of F1 and the total fuel input amount of F2.
1 / Hr multiplied by ΔR, each being 1.4 × 1
0 ⁶ kcal / Hr, a 1.2 × 10 ⁶ kcal / Hr. Therefore, the setting of the fuel injection setting means 102 is changed to the fuel injection amount obtained by increasing this change amount to the fuel injection amount of the zone of F1. Simultaneously heating to 1270 ° C. 2
The fuel input amount in one zone near the charging port adjacent to the zone is expressed by F1 according to ΔR = −0.47 indicated by a mark in FIG.
1.1 × 10 ⁶ kcal /
The fuel input setting means 102 is set so as to reduce by Hr. Similarly, one zone near the extraction port adjacent to the two zones where the steel slab to be heated to 1270 ° C. is located is 0.7 × 10 ⁶ by ΔR = −0.31 indicated by the square in FIG.
The fuel injection setting means 102 was set to a fuel injection amount that was subtracted from the fuel injection amount of the zone of F1 by kcal / Hr, and the fuel injection amount was controlled. The result is as shown in FIG.
It can be seen from FIG. 6 that the billet was burnt to two different temperatures.

Further, eight steel slabs were heated and extracted at 1230 ° C. without changing the heating efficiency in a continuous heating furnace operating at a heating and extraction temperature of 1270 ° C. at a heating efficiency of 200 T / Hr, and then heated again. FIG. 8 shows the transition of the billet extraction temperature when the setting and control according to the present invention are performed to heat the billet to the extraction temperature of 1270 ° C. Also, the billet is heated as intended. As described above, in the present invention, heating and extraction at different temperatures can be realized only by increasing or decreasing the fuel input amount by a certain amount in accordance with the movement of the billet in the furnace without performing complicated control.

[0017]

As described above, according to the present invention, when some of the steel slabs are heated and extracted to a temperature θ2 higher (or lower) than the heating extraction temperature θ1 of the other steel slabs, all the steel slabs are subjected to θ.
The fuel input pattern F1 to be heated to 1 and the fuel input pattern F2 to be heated to θ2 are determined, and the steel slab heated to a higher temperature (or lower temperature) than the other steel slabs is moved in the furnace.
The fuel input amount to the burner system in the zone where the billet is present is calculated as follows with respect to the zone fuel input amount according to the pattern F1.
In addition to increasing (or decreasing) a certain percentage of the difference between the total fuel input amount of F1 and the total fuel input amount of F2, the fuel input amount to the burner system in the adjacent zone before and after that is determined by the pattern F
1 is reduced (or increased) by a certain percentage of the difference between the total fuel input of F1 and the total fuel input of F2, and the fuel input of the other zones is reduced by that of the other zones of F1. By setting and controlling the amount of fuel input in each zone so as to obtain the amount of fuel input, some steel slabs continuously charged into the continuous heating furnace are heated and extracted to a temperature different from other steel slabs. can do. In addition, by using the regenerative alternating combustion burner system as the burner system, the interference between the zones of the exhaust gas is reduced, and the effect of the present invention is sufficiently exhibited.

Further, according to the present invention, since only the fuel injection amount in each zone is controlled as described above, there is no change in the extraction pitch or the decrease in the heating efficiency, and the scheduling operation is extremely simple. Therefore, it has an excellent effect on the operation of the hot rolling line.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a fuel injection amount control method of a continuous heating furnace according to one embodiment of the present invention.

FIG. 2 is a sectional side view of a unit furnace of a continuous heating furnace provided with a regenerative alternating combustion burner system.

FIG. 3 is a front view of the unit furnace.

FIG. 4 is a diagram showing a fuel input amount pattern at a heating extraction temperature of 1230 ° C.

FIG. 5 is a diagram showing a fuel input amount pattern at a heating extraction temperature of 1270 ° C.

FIG. 6 is a transition diagram of an extraction temperature of a billet.

FIG. 7 is a diagram showing a relationship between a difference in extraction temperature of a billet and a change rate of a fuel input amount.

FIG. 8 is a transition diagram of an extraction temperature of a billet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous heating furnace 2 Unit furnace 3 Loading 4 Loading / unloading 9 Regenerative combustion burner 100 Regenerative alternating combustion burner system 101 Fuel flow control device 102 Fuel input setting means

Continued on the front page (72) Inventor Munehiro Ishioka 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Ryoki Fujii 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Ryoichi Tanaka 2-1-153 Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Inside (72) Inventor Mamoru Matsuo 2-1-153 Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Furnace Industry Inside the Company (72) Inventor Atsushi Sudo 2-1-153 Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Inside the Furnace Industry Co., Ltd. (56) References JP 4-78691 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) C21D 11/00 102 C21D 9/00 101 C21D 1/52 C21D 1/00 112

Claims (2)

(57) [Claims] 1. A method in which a part of a group of billets continuously charged into a continuous heating furnace is heated to a temperature higher or lower than an extraction temperature of other billets without changing a charging interval. In the heating method of the steel slab to be heated and extracted, the fuel input pattern F1 for each zone of the heating furnace when all the steel slabs are heated to the extraction temperature θ1 and the fuel injection pattern when all the steel slabs are heated to the extraction temperature θ2 The fuel input pattern F2 for each zone of the heating furnace and the difference between the total fuel input of F1 and the total fuel input of F2 when heating a part of the steel slab from the extraction temperature θ1 to the extraction temperature θ2. Zone fuel input change rate ΔR ( 0 <ΔRe, ΔRn <1, where
ΔRe ≠ ΔRn, subscript e is the zone where the target billet exists
In the case of n, adjacent zones before and after the zone where the target billet exists
In the case of the burner system, the amount of fuel input to the burner system in the zone where the billet is present is determined in accordance with the pattern F in accordance with the movement of the billet in the furnace.
For the fuel input of No. 1, the difference between the total fuel input of F1 and the total fuel input of F2 is calculated as the zone fuel input change ratio (Δ
Re) is increased or decreased by the amount multiplied by Re), and the amount of fuel input to the burner system in the adjacent zone before and after the zone is calculated based on the total fuel input of F1 and the total fuel input of F2 with respect to the fuel input of pattern F1. Continuous heating, wherein the fuel injection amount to the burner system in the other zones is set to the fuel injection amount of the pattern F1 by increasing or decreasing the difference between the fuel injection amount and the zone fuel injection amount change ratio (ΔRn). How to heat the billet in the furnace. 2. The method for heating a steel slab in a continuous heating furnace according to claim 1, wherein a continuous heating furnace having a regenerative alternating combustion burner system is used.