JP2502303B2 - Edge heating method for slab - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a direct hot rolling process in which a slab of continuous casting is directly or auxiliary heated without cooling and then hot-rolled. The present invention relates to an edge heating method for heating an edge portion of a slab.

[Prior Art] A so-called direct hot rolling process is known in which a slab after continuous casting is conveyed to a hot rolling step, and continuous casting is followed by hot rolling of the slab. As described above, by directly connecting the steelmaking and the rolling, it is possible to reduce the energy required for heating the slab necessary for the hot rolling step. In such a direct hot rolling process, a slab after continuous casting is cut into a slab shape, and then the slab is directly placed on a roller table and conveyed to a hot rolling factory. Then, after rolling the slab to a predetermined plate thickness, it is wound around a coil.

By the way, during the transportation of the slab to the hot rolling step, the temperature of the slab, particularly the temperature of the edge portion of the slab, is reduced due to heat dissipation. Therefore, the roller table that conveys the slab from the continuous casting machine to the hot rolling process is provided with an edge heating device for heating the edge portion of the slab in the middle thereof.

[Problems to be Solved by the Invention] However, in the conventional edge heating method, since the inside of the edge heating furnace is uniformly heated by the burner and the slabs are conveyed at intervals, there is no slab. In some cases, the slab is heated with the same heating power as when heating it. Therefore, there is a problem that energy is wasted and the fuel consumption rate is high. Further, even if there is no slab, the inside of the heating furnace is constantly heated at a high temperature, and since the state of being cooked in the air continues, there is a problem that the life of the refractory of the roll and the heating furnace is short.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a heating method for an edge heating device capable of preventing waste of energy and extending the life of rolls and refractories.

[Means for Solving Problems] A method for edge heating of a slab according to the present invention is provided in the middle of conveyance of a roller table that conveys a continuously cast slab in a hot rolling process, and removes an edge portion of the slab. In the heating method by the edge heating device for heating, the heating device is divided into a plurality of heating regions, and in each heating region, the tip end portion of the slab is heated in response to the forward movement of the slab, and the rear end portion thereof is heated. It is characterized in that it is heated at a temperature higher than that in the case of heating, and when there is no cast piece, it is heated at a lower temperature than in the case of heating the rear end.

[Operation] According to the present invention, the slab that has been conveyed to the edge heating device is heated to a higher temperature at the front end portion than at the rear end portion, and if there is no slab, it is kept warm. The inside of the heating device is being heated. Moreover, the inside of the edge heating device is divided into a plurality of heating regions, and as the cast piece progresses, by strengthening the heating power only in the area corresponding to the tip portion of the cast piece, only the tip portion of the cast piece is Heat the temperature to a higher temperature.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2 of the accompanying drawings.

As shown in FIG. 2, an edge heating device 14 for heating the edge portion of the slab before hot rolling is arranged between the continuous casting machine 10 and the hot rolling device 12. A heating furnace 16 is disposed between the edge heating device 14 and the hot rolling device 12, and the slab that requires heating during the transportation is selectively heated by the heating furnace 16. The steel sheet after rolling in the hot rolling apparatus 12 is a coiler 18
It is designed to be wound into a coil.

As shown in FIG. 1, the edge heating device 14 is provided on a roller table 26 that conveys the continuously cast slabs 20 and 22 to the hot rolling device 12, and heats the edge portion of the conveyed slab. There is. The roller table 26 has a plurality of rollers.
27 are arranged at equal intervals, and between each roller 27, three gas burners 29 are arranged at positions corresponding to the edge portions on one side of the slab. This heating device 14 has a plurality of heating zones (heating regions). ) That is, from the inlet side, sequentially from the first heating zone
28, a second heating zone 30, a third heating zone 32 and a fourth heating zone 34, each heating zone comprising:
A gas burner group is provided corresponding to each. That is, the first gas burner group 36 is formed in the first heating zone 28, and the second gas burner group 38 is formed in the second heating zone 30.
Is formed, a third gas burner group 40 is formed in the third gas zone 32, and a third gas burner group 42 is formed in the fourth gas zone 34. Each gas burner group is connected to the control device 43, and the combustion of the gas burner 27 is controlled. In this case, the burn rate of the gas burner 27 is 80%, 70%, and 20% at full open independently for each gas burner group.
It is controlled by various ratios.

40 to 50 in front of the roller table edge heating device 14
Around the cm, a pair of first photosensors 45 for detecting the front end and the rear end of the conveyed slab are provided,
By blocking the light between the first photosensors 45, the tip portion is detected, and when the blocked light is received again, the rear end portion is detected. The first photosensor 45 is connected to the control device 43 described above, and when it detects the front end portion and the rear end portion of the slab, it outputs a detection signal thereof.

In addition, each of the first heating zones 28 has about 30 to 40 in the vicinity of the exit side of the first heating zone 28 and before the second heating zone 30.
A pair of second sensors for detecting the front and rear edges of the slab at the position of cm
Photo sensor 44 is provided, and the tip of the photo sensor 44 is detected by blocking the light between the second photo sensors 44,
When the blocked light is received again, the rear end is detected. The second photo sensor 44 is connected to the control device 43 in the same manner as the first photo sensor 45 described above, and emits a detection signal when the front end and the rear end of the slab are detected. Similarly, a third photosensor 46 is provided in the second heating zone 30, and a fourth photosensor 48 is provided in the third heating zone 34.

 Next, the operation of this embodiment will be described.

As shown in FIG. 2, the slab continuously cast by the continuous casting machine 10 is cut into slabs 20 and 24, placed on a roller table 26, and conveyed to the hot rolling apparatus 12. Hot rolling equipment
In 12, the slab is rolled into a predetermined thickness by a mill and then wound into a coil in a coiler 18. By the way, when the slabs 20 and 24 are conveyed by the roller table 26 between the continuous casting machine 10 and the hot rolling apparatus 12, the slabs 20 and 24 radiate heat, but a temperature decrease particularly at the edge portion occurs. Therefore, the edge portion of the slab is heated by the edge heating device 14 provided in the middle of the conveyance path of the roller table 26. When the temperature of the entire slab is not suitable for rolling, the slab is taken out to the heating furnace 16, where the entire slab is heated, and then returned to the roller table 26 again.

Here, a heating method in the edge heating device 14 will be described. The edge heating device 14 heats the inside of the edge heating device 14 at a constant temperature (when the combustion coefficient is 0.8) and when there is no slab. In this case, the gas burners 29 in the edge heating furnace 14 are all supplied with fuel gas and combustion air so as to burn about 20% (100% when the fuel gas supply of the gas burner is fully opened). Is controlled.

When the slab 20 is conveyed from the continuous casting machine 10 and reaches before the edge heating device 14, the first photosensor 45 detects the tip portion of the slab 20. This detection signal is sent to the control device. The control device raises the combustion rate of the first gas burner group 36 to 60% based on the detection signal at the tip of the slab. As a result, the tip of the slab that has subsequently entered the first heating zone 28 is strongly heated. This intense heating heats the slab to about 1200 ° C. Next, the first photo sensor 45
When the rear end of the slab 20 is detected, the first gas burner group 36 reduces its combustion rate to about 40% medium heating. In this case, in the first heating zone 28, the front end of the slab 20 has finished passing, and the central part and the rear end of the slab are in the middle of passing, so this part is heated with a weaker heat than the front part of the slab, Heat to about 1100 ° C. Then, when the second photosensor 44 detects the passage of the slab 20, that is, when the slab passes the first heating zone 28, the combustion rate of the first gas burner group 36 is reduced to 20% and the first heating is performed. The zone 28 is kept warm.

Similarly, in the second heating zone 30, the second photosensor
The detection of 44 controls the combustion of the second gas burner group 38. That is, when the second photo sensor 44 detects the tip, the burning rate of the second gas burner group 38 is raised from 20% to 60% to heat the tip strongly, and then lowered to 40% to the center of the slab. When the third photosensor 46 detects the passage of the slab by heating the rear end portion and the rear end portion, 20% of heat retention heating is performed. As described above, in each heating zone, the combustion rate is independently controlled according to the passage of the slab.

If the slabs 20 and 24 pass through the edge heating device 14 in about 8 minutes and the slabs are continuously conveyed, about 2
It is transported at minute intervals.

In the above-mentioned embodiment, the case where the combustion efficiency is 0.8 has been described, but the present invention is not limited to this, and when the combustion efficiency is 1.0 (when the normal heating device is immediately after starting up), the slab is heated at 75% and the slab is heated. The rear end is heated at 60% and the heat is heated at 20%. When the combustion efficiency is 0.5, the slab is heated at 50% at the front end, 40% at the rear end, and 20% at the heat retention heating.

According to this embodiment, the inside of the edge heating furnace is divided into a plurality of heating zones, and the gas burner group in each heating zone is independently controlled to heat the leading end portion of the passing slab at its rear end portion. The slab is heated efficiently with a higher burning power or higher burning rate than the case, and the heat retention heating when there is no slab is heating with a weaker heating power than when heating the rear end, so that the slab is heated efficiently without wasting energy. be able to. For example, the conventional energy consumption of 150,000 Kcal per ton of slab is 45,000 Kcal in this embodiment, and it is possible to save about 1/3 of energy, and refractory materials and Table roll life is about 3
It can be extended twice.

The present invention is not limited to the above-described embodiment and can be variously modified without departing from the scope of the present invention.

For example, in the above-described embodiment, the heating zone is divided into four, but the number is not limited to this, and any number such as three or five may be used.

In the above-described embodiment, the tip of the slab or the position of the slab is detected by the photosensor and the combustion of each gas burner group is controlled according to the detection signal, but the invention is not limited to this, and the edge heating device is passed. Depending on the speed of the slab to
Similar effects can be obtained even if the combustion of each gas burner group is controlled.

The heating of the slab is not limited to the use of a gas burner, and the same effect can be obtained by heating with an electromagnetic heater.

[Effect of the Invention] According to the present invention, when heating the edge of a slab, the front end is heated to a higher temperature than the rear end, and when there is no slab, the rear end is heated. Is heated at a temperature lower than the case of heating. Moreover, the inside of the edge heating device is divided into a plurality of heating regions, and as the cast piece progresses, by strengthening the heating power only in the area corresponding to the tip portion of the cast piece, only the tip portion of the cast piece is Since the temperature is raised to a high temperature, waste of energy can be prevented and the life of the roll and the refractory can be extended.

[Brief description of drawings]

FIG. 1 is a schematic side view illustrating an edge heating method according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a direct hot rolling process according to an embodiment of the present invention. 14 …… Edge heating device, 28 …… First heating zone (heating area), 30 …… Second heating zone (heating area), 32 ……
Third heating zone (heating area), 34 ... Fourth heating zone (heating area), 36 ... First gas burner group, 38 ... Second gas burner group, 40 ... Third gas burner group, 42 ……
Fourth gas burner group.

Claims (1)

(57) [Claims] 1. A heating method using an edge heating device which heats an edge portion of a slab, which is provided during the transportation of a roller table for transporting a continuously cast slab to a hot rolling step,
The heating device is divided into a plurality of heating regions, and in each heating region, the tip of the slab is sequentially corresponding to the advance of the slab,
A method for edge heating of a slab, comprising heating at a higher temperature than a case of heating the rear end, and heating at a lower temperature than a case of heating the rear end when there is no slab.