JPH082461B2 - Cooling control method for hot rolled steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cooling control method for a hot rolled steel sheet by a cooling device provided between a hot finish rolling mill and a winding machine.

[Conventional technology]

Conventionally, in the hot rolling step, cooling performed to wind the hot-rolled steel sheet after finish rolling with a winder is performed with the temperature of the hot-rolled steel sheet leaving the hot finish rolling machine (hereinafter referred to as rolling end temperature). Considering the material surface of the hot-rolled steel sheet that is cooled between the temperature of the hot-rolled steel sheet when it is wound up on the winding machine (hereinafter referred to as the winding temperature), the cooling device This is done by controlling the amount of cooling water injected.

For example, in Japanese Patent Laid-Open No. 53-91009, as a conventional technique, a cooling device provided between a hot finish rolling mill and a winding machine is divided into a plurality of water injection control units. The cooling control of the hot-rolled steel sheet mainly consisting only of the coiling temperature, which consists of a relatively simple water injection pattern by the water injection control unit, is increased, and the cooling control for each water injection control unit described in the related art is as described above. When controlling the cooling process from the rolling end temperature to the coiling temperature, it was pointed out that the water injection pattern was very large and complicated, and this was improved to improve the hot rolling mill and the coiling machine. The required cooling capacity is estimated by assuming that there is always air cooling during water cooling in order to calculate the water cooling capacity of each water injection control unit assigned to one or more of these calculation zones by dividing the space into multiple calculation zones. Subtract this air cooling capacity from And Mel so, and for calculating the required number of water injection control units for each computation zone from the water-cooling capability, at least (A) a basic cooling capacity i.e. basic heat flux q ₀ common to all irrigation control units, (B) upstream It is determined from the sum of the actual water cooling capacity of each water cooling water injection control unit, that is, the sum of the actual heat flux q ₁ , which is obtained as the product of the correction coefficient K ₁ according to the water injection state on the side and (C) the correction coefficient K ₂ peculiar to each water injection control unit. Further, a cooling control method for a hot-rolled steel sheet is disclosed in which the cooling capacity of each water injection control unit in each calculation zone is controlled by obtaining it as the sum of the air cooling capacity and the water cooling capacity.

[Problems to be Solved by the Invention]

By the way, in recent years, the range of the cooling capacity has been expanded due to the requirement from the material side of the hot-rolled steel sheet, and it is necessary to improve the temperature control accuracy, and the water injection control unit is becoming finer in terms of equipment. In the cooling control method for hot-rolled steel sheet described in JP-A-53-91009, the number of calculation zones or the water injection control unit in each zone is large, and the case of the correction coefficient depending on the upstream water injection situation is enormous. In addition, since the water injection control unit is small, it is difficult to obtain the correction coefficient, and there are many practical difficulties. On the other hand, since the water injection control unit becomes finer, there is a water injection control unit that is used less frequently, and the opening / closing valve and / or the nozzle of the water injection control unit that is used less frequently causes trouble, and sufficient water injection control cannot be performed. Or, it is inevitably replaced with the one that is frequently used while keeping the life of the one that is frequently used.

[Means for solving the problem]

The present invention has been made in view of the above circumstances, and its gist is a method for cooling and controlling a hot-rolled steel sheet by a cooling device provided between a hot finish rolling mill and a winding machine. Therefore, a large number of nozzle headers provided in the cooling device are configured as a water injection control unit in which one or several nozzle headers are opened and closed by one opening / closing valve, and a plurality of these water injection control units are set as a group unit. On the other hand, a water injection pattern corresponding to the cooling capacity required from the material aspect of the hot-rolled steel sheet is set for each group, and the opening / closing valve of the water injection control unit is determined by the set water injection pattern. When the hot-rolled steel sheet is cooled and controlled by opening and closing, and when there is a water injection pattern with the same number of water injection control units where the valves are open among the water injection patterns for each group. Their water injection pattern periodically cycled hot-rolled steel sheet is a cooling control method for hot-rolled steel sheet for controlling the cooling.

[Action]

Since the present invention is configured as a water injection control unit in which one to several nozzle headers provided in the cooling device are opened / closed by one opening / closing valve, it is determined from the material aspect of the hot rolled steel sheet. It is possible to realize strong cooling and improve the temperature control accuracy of the hot rolled steel sheet. Further, since a plurality of the water injection control units are configured as a group unit in a plurality of group units, the cooling capacity of each group can be easily grasped and can be reflected in the temperature control of the hot rolled steel sheet. Becomes Furthermore, among the water injection patterns in the group unit, when there are water injection patterns with the same number of water injection control units with the valves opened, the water injection patterns are periodically cycled to control the cooling of the hot rolled steel sheet. , The water injection control unit is used on average, and it is possible to make the changes over time in the equipment uniform, and it is less likely that the on-off valve and / or nozzle of the water injection control unit will cause trouble, and Since the lifespan of these devices are averaged, the overall lifespan is longer than in the past. In addition, it is desirable to switch the cycle time at intervals of 0.5 to 24 hours.If it is shorter than 0.5 hours, the control of cooling the hot-rolled steel sheet will be insufficient, and if it exceeds 24 hours, an on-off valve will be provided. Since the environment in which it is hot is a bad environment, it will be difficult for the on-off valve to operate smoothly, or water stains in the cooling water will cling to the inside of the nozzle, resulting in nozzle clogging, or if the lower nozzle is hot Trouble such as the scale falling from the rolled steel sheet and adhering to it easily occurs.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

FIG. 1 is a schematic diagram centering on an outlet side equipment of a hot finish rolling mill according to a cooling control method for a hot rolled steel sheet according to the present invention. In the figure, 1 is a hot-rolled steel sheet, 2 is a hot finish rolling mill, 3 is a cooling device, 4 is a table roller, 5 is a winder, and 6 is a thermometer provided on the outlet side of the hot finishing mill 2. , 7 are thermometers provided immediately before the winder 5. Further, in the figure, 8 is a head tank, 9 is a water storage pit, 10 is a water supply pump, 11 is a main water supply pipe, 12 is a drain pipe for flowing overflow water from the head tank 8, 13 is a through spit, and 14 is a cooling water return pipe. Piping, 15 nozzle header, 16 opening / closing valve for each water injection control unit, 17 flow meter, 18 branch pipe, 19 main pipe, 20
Indicates a valve, which constitutes the cooling device 3.

The hot-rolled steel sheet 1 is rolled by a hot rolling mill (not shown) and finally rolled by the hot finish rolling mill 2 to a predetermined size. After that, the plate is passed on the table roller 4, and the winding machine 5
To be wound up. Meanwhile, the hot-rolled steel sheet 1 is cooled by the cooling device 3 in a cooling pattern as shown in FIG. 2, for example, at the cooling rate CR required for manufacturing the material from the exit-side steel sheet temperature FDT of the hot finish rolling mill 2. Cooling is controlled so that the coiling temperature CT can be obtained. By the way, recently, the range of the cooling rate CR and the coiling temperature CT required from such a material aspect has expanded as compared with the conventional one.
Equivalent to 4 mm, cooling rate CR is 10 to 100 ° C / sec, winding temperature CT
Is 200-600 ℃.

Under such circumstances, the water density is huge in terms of equipment, and in order to cope with this, a method of using the head tank 8 as the cooling device 3 as shown in FIG. 1 is adopted on the water supply side. Further, in the cooling control unit, the water injection control unit is subdivided, and one to several nozzle headers 15 are
An on-off valve 16 is provided as a group to serve as a water injection control unit.

Fig. 3 shows the upper group by collecting a plurality of water injection control units.
U1 to U7 and lower groups L1 to L7 are illustrated for each seven groups, and S1 to S13 denote calculation sections between the hot finish rolling mill 2 and the winder 5. In this figure, the calculation section length and the group length are the same, but they do not necessarily have to be the same. Note that setting the calculation sections S1 to S13 divided into equal pitches is necessary for predicting the temperature drop amount of the steel sheet in the cooling zone in cooling control of the hot rolled steel sheet. This is because the temperature of the steel sheet is predicted at the same time as the temperature of the steel sheet is predicted based on S13.

FIG. 4 is an explanatory diagram for explaining the cooling control method according to the present invention, and FIG. 4 (a) is the nozzle header 15 described above.
1 water injection control unit consisting of 1 and open / close valve 16
The water injection patterns of the groups are shown, and there are seven water injection patterns from the water injection pattern (a) in which the open / close valves 16 are all opened to the water injection pattern (g) in which all the on-off valves 16 are closed. Further, FIG. 4 (b) shows the same water injection pattern as the water injection pattern (b) shown in FIG. 4 (a). Thus, when the same water injection pattern exists in the group unit, When the water injection pattern of is periodically cycled, the nozzle (not shown) attached to the nozzle header 15 and the opening / closing valve 16 are used on average, and these changes over time can be made uniform, and The trouble caused by can be reduced.

FIG. 5 is a block diagram of a control system relating to a cooling control method for hot-rolled steel sheet according to the present invention. In the figure, initial information is
It means initial information such as steel type, plate thickness, strip running speed, predicted hot finish rolling temperature, water injection pattern, target winding temperature and the like. In the initial setting, the control unit to be water-poured for each group unit is determined based on the initial information and the information obtained by the learning control described later, and the water pouring command is issued. The dynamic control turns on the control unit for water injection based on the information on the measured sheet thickness, sheet passing speed, hot finish rolling temperature and coiling temperature, and the information obtained by learning control and feedback control described later.・ Off control. When there is an error between the target coiling temperature and the measured coiling temperature, the learning control corrects the steel plate temperature prediction based on the calculation section based on the measured hot finish rolling temperature, the measured coiling temperature, and the water injection record. . In the feedback control, when an error occurs between the target winding temperature and the actually measured winding temperature, a part of the water injection control unit closer to the winder 5 is injected by the steel plate temperature prediction based on the calculation section. ON / OFF control is performed independently of the control unit. In addition to the initial information, the actual value collection includes the temperature of the steel plate,
The learning coefficient etc. are collected and stored.

Based on the control system related to the cooling control method for hot-rolled steel sheet described above, a steel sheet with a thickness of 4 mm (coil length of 710 m) with a hot rolling finish temperature of about 900 ° C. was passed at a striping speed of 610 m / min. acceleration
When cooling control was performed with a target of a winding temperature of 600 ° C. at 0.1 m / s ² , the state in the middle of the cooling control was the result shown in FIG. 6, and accurate cooling control was performed.
In the figure, FDT is the hot rolling finish temperature, CTN is the temperature during cooling, and CT is the coiling temperature. The meandering hot rolling finish temperature is a skid mark generated during heating.

〔The invention's effect〕

As described above, according to the present invention, a large number of nozzle headers provided in the cooling device are configured as a water injection control unit that opens and closes one to several nozzle headers by one opening / closing valve. It is possible to realize strong cooling that is determined from the material aspect of the steel sheet, and improve the temperature control accuracy of the hot rolled steel sheet. Further, since a plurality of the water injection control units are configured as a group unit in a plurality of group units, the cooling capacity of each group can be easily grasped and can be reflected in the temperature control of the hot rolled steel sheet. Becomes Furthermore, among the water injection patterns in the group unit, when there are water injection patterns with the same number of water injection control units with the valves opened, the water injection patterns are periodically cycled to control the cooling of the hot rolled steel sheet. , The water injection control unit is used on average, and it is possible to make the changes over time in the equipment uniform, and it is less likely that the on-off valve and / or nozzle of the water injection control unit will cause trouble, and Since the lifespan of these devices is averaged, the overall lifespan is longer than in the past.

[Brief description of drawings]

FIG. 1 is a schematic diagram centering on the outlet side equipment of a hot finish rolling mill according to the cooling control method for hot rolled steel sheet according to the present invention, and FIG. 2 is an example diagram of a cooling pattern required from the material side of the steel sheet, 3 and 4 are explanatory views for explaining the cooling control method according to the present invention, FIG. 5 is a block diagram of a control system related to the cooling control method for the hot rolled steel sheet according to the present invention, and FIG. 6 is the present invention. It is a cooling control state diagram by the cooling control method of the hot rolled steel sheet. 1 ... Hot rolled steel plate, 2 ... Hot finishing rolling mill 3 ... Cooling device, 4 ... Table roller 5 ... Winding machine, 6, 7 ... Thermometer 8 ... Head tank, 15 ... Nozzle Header 16 …… Opening / closing valve, 17 …… Flowmeter 18 …… Spring pipe, 19 …… Main pipe 20 …… Valve FDT …… Outside steel plate temperature of hot finish rolling mill CR …… Cooling speed, CT …… Coiling temperature CTN …… Temperature during cooling U1 to U7 …… Upper group unit L1 to L7 …… Lower group unit S1 to S13 …… Calculation section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-50122 (JP, A) JP-A-60-213308 (JP, A)

Claims (1)

[Claims] 1. A method for controlling cooling of a hot-rolled steel sheet by a cooling device provided between a hot finish rolling mill and a winder, wherein a plurality of nozzle headers provided in the cooling device are provided. One to several units are configured as a water injection control unit that opens and closes with a single on-off valve, and a plurality of these water injection control units are configured as one group unit into a plurality of group units. A water injection pattern corresponding to the cooling capacity required from the material side of the steel sheet is set, and the opening / closing valve of the water injection control unit determined by this set water injection pattern is opened / closed to control the cooling of the hot-rolled steel sheet. Of the unit watering pattern,
When there are water injection patterns with the same number of water injection control units where the valves are open, the hot water rolled steel sheet cooling control method is characterized in that those water injection patterns are periodically cycled to cool and control the hot rolled steel sheet. .