JPH06128656A - Combustion control method for heating furnace - Google Patents

Abstract

PURPOSE:To precisely heat a material to be heated to an aimed extracting temp. by controlling the combustion at one or more zones in a preheating zone, a heating zone and a soaking zone based on the information of continuous casting and tracking information relating to the material in a heating furnace. CONSTITUTION:In the operation synchronously executing the continuous casting, heating and hot-rolling, based on the information of the continuous casting and the tracking information relating to the material in the heating furnace, the combustion of one or more zones of the preheating zone, the heating zone and the soaking zone in the heating furnace is controlled. The cracking information denotes the information relating to the passing timing of a steel slab. The combustion in the heating zone is controlled by the ignition and the extinction of each burner in the preheating zone, the heating zone and the soaking zone and the lowering of combustion load of the burner, etc. Thus, the energy loss is reduced and the material can precisely be heated to the aimed extracting temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct hot charge (DHC) system in which continuous casting, heating and hot rolling are synchronized.
R), a combustion control method for a heating furnace.

[0002]

2. Description of the Related Art Usually, a hot rolled steel sheet is manufactured by a process including a continuous casting machine, a heating furnace and a rolling machine in this order.
Among these, temperature control in the heating furnace is important for heating the steel slab to be rolled to a predetermined temperature and conserving energy. By the way, in recent years, as a part of rationalization such as process simplification and energy saving, a direct mounting hot charge (DHCR) process in which a steel making process and a hot rolling process are synchronized has attracted attention, and is used in this direct mounting hot charge. In the heating furnace to be used, direct operation or synchronized operation with the continuous casting machine is aimed. The term "synchronization" does not mean that a plurality of processes or apparatuses are operated independently of each other, but that the respective operation timings are associated with each other in order to achieve a certain purpose.

FIG. 4 schematically shows an outline of steps up to charging of a direct-equipped hot charge furnace, which is a synchronized operation of steelmaking-hot rolling, up to charging of a heating furnace. In the figure, the slab cast by the continuous casting machine 1 is cut into a predetermined size by the cutting machine 2 to form a slab, and then directly in front of the heating furnace 5 by the roller table 3 (may be a track). The steel piece 6 is loaded into the heating furnace 5 by the charger 4, for example.

In the conventional general process in which steelmaking-hot rolling is asynchronous, the cut steel pieces are once gathered in a yard, and these steel pieces are set at a constant pitch corresponding to a substantially rolling pitch or an extraction pitch. Although it was operated by continuously transferring it into the heating furnace, the directly installed hot charge directly charges the cut steel pieces into the heating furnace without collecting them in the yard.

However, comparing the average production capacities of continuous casting and hot rolling, hot rolling is generally superior. Further, the ability of continuous casting is regulated by steel type (casting speed) and casting width, and the ability of hot rolling is regulated by rolling thickness and rolling width, and these abilities often do not match. Therefore, in order to synchronize the continuous casting and the hot rolling, it is necessary to provide a timing adjusting function in the process between them, for example, the heating process by the heating furnace. Conventionally, a charger or a split-driving type walking beam has been introduced as such equipment, but according to the results of studies by the present inventor, these techniques alone cannot deal with direct hot charging.

On the other hand, in addition to the provision of the timing adjusting function in the transfer equipment as described above, more flexible response is required to the combustion equipment of the heating furnace. For example, Japanese Patent Publication No. 2-17611 or Japanese Laid-Open Patent Publication No. 61-70319 discloses a technique of sequentially igniting and extinguishing a plurality of burners installed in the heating furnace in the furnace length direction in order to cope with the material to be heated that is intermittently charged. Proposed.

[0007]

The technique proposed in Japanese Examined Patent Publication No. 2-17611 or Japanese Patent Laid-Open No. 61-70319 recognizes a change in charging pitch as a change in charging temperature.
Since the burner of the heating furnace is controlled to be turned on / off to reduce the variation of the final extraction temperature, the burner is ignited and extinguished sequentially over time in both the heating zone and the soaking zone. , A heating furnace with a charger and a split-drive walking beam,
The pre-tropics and heating zones are used to absorb the production capacity difference between continuous casting and hot rolling.

By the way, in the case of direct hot charging, the material to be heated usually needs to pass through the heating furnace in 30 to 60 minutes in the process. Therefore, in the above-mentioned conventional technique, it is extremely difficult for a skilled operator to set the furnace temperature of each combustion zone, and it becomes impossible for the heating furnace to absorb the production capacity difference between the pre-heat zone and the heating zone. In this case, heating failure such as insufficient burning or overburning occurs, which causes quality deterioration and energy loss.

It is an object of the present invention to automatically control the ignition timing and extinguishing timing of the preheating zone, heating zone and soaking zone of the heating furnace in direct hot charging in accordance with the information of continuous casting. Accordingly, it is an object of the present invention to provide a combustion control method for a heating furnace, which can reduce energy loss as much as possible and accurately heat a material to be heated to a target extraction temperature.

[0010]

SUMMARY OF THE INVENTION Here, a gist of the present invention is a combustion control method for a heating furnace in an operation in which continuous casting, heating and hot rolling are performed in synchronization with each other.
Combustion of a heating furnace characterized by controlling combustion of at least one of preheating zone, heating zone, and soaking zone of the heating furnace based on information of continuous casting and tracking information on a material to be heated in the heating furnace It is a control method.

Here, the tracking information means information relating to the passage timing of the billet. Further, as a specific mode of controlling combustion, a mode of igniting and extinguishing the burners of the pre-tropical zone, the heating zone and the soaking zone can be exemplified, but in addition to this, for example, the combustion load of the burner is reduced. It also includes an embodiment.

FIG. 1 is an explanatory diagram showing an example of the flow of a steel slab (material to be heated) according to the present invention when a manufacturing opportunity is changed in a direct hot charge operation. In FIG. 1 (a), the continuous casting machine 1 completes casting of the A chance, the hot rolling mill 7 rolls the billet A 0, and the heating furnace 5 casts at this chance and the cutting machine 2 performs the casting. There are cut steel pieces A1 to A5, and the steel pieces A6 to A9 are conveyed in a process upstream of the heating furnace 5. At this time, since steel slabs exist in all zones in the heating furnace 5,
(Pre-Tropical, Heated Zone, Soaking) burners are lit.

In FIG. 1 (b), in the continuous casting machine 1,
Tundish exchange (A → B) is being carried out, during which the steel pieces are transported from the state shown in Fig. 1 (a), and there are steel pieces A4 to A8 in the heating furnace 5, which are rolled by the rolling mill 7. Piece A3 is being rolled. The burner in the heating furnace 5 is ignited in all zones. In FIG. 1 (c), in the continuous casting machine 1, the exchange of the tundish is completed, during which the billet is further transported, the billet A9 is in the heating zone, and the preheat zone is vacant. Therefore, at this time, the pre-tropical zone of the heating furnace 5 is extinguished to keep it warm. It should be noted that the rolling mill 7 is rolling the billet A5.

In FIG. 1 (d), the continuous casting machine 1 uses B
Chance casting is started, and billet A6 is rolled by rolling mill 7. Since the steel strip A9 exists in the heating zone, the combustion in the heating furnace 5 is the same as the state shown in FIG. 1 (c). In FIG. 1 (e), the steel slab B1 is cut, and the rolling mill 7 rolls the steel slab A7. In the heating furnace 5, the vacant heating zone is extinguished and becomes warm, but here, the charging time of the bill B1 to be conveyed next is predicted by calculation, and this charging time is calculated. In order to raise the temperature of the furnace to a predetermined temperature, the timing for starting the temperature rise in the pre-tropical zone is determined, and the temperature rise in the pre-tropical zone is started in accordance with this timing.

Further, in FIG. 1 (f), the steel piece B4 is cut by the cutting machine 2 and the steel piece B1 is loaded into the heating furnace 5. In addition, the rolling mill 7 performs rolling of the billet A8,
After the rolling of the billet A9 is completed, the roll of the rolling mill 7 is changed. Also in the heating furnace 5, the heating zone is heated to the elevated furnace temperature.

That is, in the present invention, since the heating furnace adjusts the timings of the continuous casting process and the hot rolling process which have different production capacities, they function as a timing buffer for synchronizing them to minimize energy loss. In addition to the constant pitch operation of the heating furnace that has been performed conventionally, combustion of the heating furnace can be performed in a timely manner even when the supply of steel slabs that constantly occurs, such as tundish exchange in the steelmaking process, is stopped. Can be controlled.

[0017]

The present invention will be described in detail below with reference to the accompanying drawings together with its function and effect. 2 is similar to FIG. 4 described above,
It is explanatory drawing which shows an example of the direct mounting hot charge process which this invention applies to, code | symbol 8 is a ladle, and code | symbol 9 is a ladle 8.
The reference numeral 10 is a mold, the reference numeral 11 is a cutting machine for cutting the continuously cast slab into a predetermined length, and the reference numeral 12 is the charging furnace 13 for charging the cut steel slab. Indicate the charger to be used. In FIG. 2, the estimated time t _{C of} charging the first steel piece in the heating furnace after the tundish replacement is represented by the following equation.

[0018]

[Equation 1] t _C = t _s1 + θ _TG + θ _GF ·····, where t _{s1 is} the casting start time of the first steel piece after tundish replacement θ _TG : The time from tundish to completion of cutting θ _GF : Time from completion of cutting to charging of heating furnace Here, θ _TG can be treated as a function of drawing speed and is represented by the following equation.

[0019]

[Formula 2] θ _TG = f (VC ^* ) ······································································· However, however, VC ^* : drawing speed, θ _GF can be treated as a constant determined by the equipment layout and the transportation method. Therefore, in the present invention, the expected heating furnace charging time of the first steel piece after the tundish replacement can be calculated easily and accurately.

Further, in the present invention, the combustion of the heating furnace is controlled according to the situation of the steel slab in the furnace. FIG. 3 is a graph showing an example of changes in the furnace temperature of the preheating zone of the heating furnace controlled by the present invention. In FIG. 3, t _e is the time when the furnace is heated in the heating zone, t _o is the current time, t _c is the scheduled charging time of the next billet, Ts is the furnace temperature during operation, and Th is the heat retention. The furnace temperature at
Is the time from the start of temperature decrease to the completion of temperature increase, θh is the (temperature decrease + heat retention) time, θu is the temperature increase time, α is the temperature increase rate, and β is the part of the pretropical zone as the buffer zone. Each time is shown. Further, although the example shown in FIG. 3 is performed in the pre-tropical zone as an example, it goes without saying that the same can be applied to the heating zone and the soaking zone.

Point a in FIG. 3 corresponds to the state shown in FIGS. 1 (a) and 1 (b), and the operation is performed at the furnace temperature Ts. Also in the present invention, the furnace temperature Ts may be determined by a general fuel control calculation, and no limitation is required. Point b in Fig. 3 corresponds to the state shown in Fig. 1 (c), and it was confirmed from the tracking information in the furnace that the billet passed through the pre-tropical zone. Next chance to show (Fig. 1
3) Predict the charging start time of B chance)
Points c, d, e, and f are determined. (i) Determination of heating time θu

[0022]

[Mathematical formula-see original document] θu = ΔT / α = Ts −Th / α ····················· Here, α is determined by Ts and Th and thermal inertia of the furnace wall, It can be decided from. For example, when θu = 30 minutes and α = 200 ° C / H,
According to the equation, ΔT = 100 ° C. (Ts = 1200 ° C.), the temperature should be kept at 100 ° C. lower than the operating furnace temperature Ts, and the temperature rise should be started 30 minutes before the start of charging. (ii) Next, when the current time and t _o, the current time t _o, kept at the temperature of the preheating zone is determined by the following equation and.

[0023]

[Formula 4] When t _o <(t _C + β) −θu, the pre-tropical heat retention temperature Th = Ts −ΔT is set to the heat retention state by: t _o ≧ (t _C + β) when -Shitau, is from the time of incubation preheating zone temperature _{Th = Ts -α (t C +} β-t o) ······· the temperature increase start or NoboriAtsushichu.

As described above, according to the present invention, based on the information of continuous casting and the tracking information on the material to be heated in the heating furnace, one or more of preheating zone, heating zone and soaking zone of the heating furnace are provided. By controlling the furnace temperature of, the energy loss can be reduced as much as possible and the material to be heated can be accurately heated to the target extraction temperature during direct hot charging. This control can be performed completely automatically by inputting it into the computer in advance. Further, the present invention will be described with reference to examples.

[0025]

[Example] Combustion control of the heating furnace shown in the graph of FIG. 3 (ON / OFF control of each burner in the pretropical zone) was performed as an example of the present invention.
The direct hot charge operation shown in FIG. 1 was performed. On the other hand, the operator performed control to appropriately change the furnace temperature setting value of the heating furnace based on experience and intuition as a comparative example, and compared the present invention with the comparative example.

In the example of the present invention, Ts: 12 in FIG.
The temperature was set to 00 ° C, Th: 1100 ° C, and θu: 30 minutes, and the combustion in the pretropical zone was controlled using the above formula and formula. According to the invention,
Compared with the conventional example, the predicted variations in the charging time of the heating furnace and the excess / deficiency of the set furnace temperature are reduced, so that the fuel consumption can be reduced by 3% and the heating failure of the billet can be eliminated. It has become possible.

[0027]

As described in detail above, according to the present invention, the ignition timing and the extinction timing of the preheat zone, the heating zone and the soaking zone of the heating furnace in the direct hot charge are
By controlling according to the information of continuous casting, the energy loss can be reduced as much as possible, and the material to be heated can be accurately heated to the target extraction temperature.

[Brief description of drawings]

FIG. 1 (a) to FIG. 1 (f) show the manufacturing opportunity change in the direct hot charge operation, respectively.
FIG. 3 is an explanatory diagram showing an example of a flow of a steel slab (material to be heated) according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a direct mounting hot charging process to which the present invention is applied.

FIG. 3 is a graph showing an example of changes in the pre-tropical furnace temperature of the heating furnace controlled by the present invention.

FIG. 4 is an explanatory view schematically showing an outline of steps up to charging of a direct-equipped hot charge (DHCR), which is a synchronized operation of steelmaking-hot rolling, into a heating furnace.

[Explanation of symbols]

 1: Continuous casting machine 2: Cutting machine 3: Roller table 4: Charger 5: Heating furnace 6: Steel billet 7: Rolling machine 8: Ladle 9: Tundish 10: Mold 11: Cutting machine 12: Charger 13: Heating furnace

Claims (1)

[Claims] 1. A combustion control method for a heating furnace in an operation in which continuous casting, heating and hot rolling are performed in synchronization with each other,
A heating furnace that controls combustion of one or more of preheating zone, heating zone and soaking zone of the heating furnace based on the information of the continuous casting and the tracking information about the material to be heated in the heating furnace. Combustion control method.