KR100674615B1 - Method for controlling surface temperature of casting rolls in the twin rolls strip caster - Google Patents

Abstract

The present invention is a twin-roll thin plate casting process, measuring the surface temperature of the fixed roll and the movable roll, averaging the measured surface temperature of the fixed roll and the movable roll, filtering the average roll surface temperature Calculating a difference between the average roll surface temperature and a target roll surface temperature, and inputting the calculated difference of the roll surface temperature into a surface temperature / melt height controller to calculate a change amount of the molten steel height target value; And generating a new molten steel height target value by adding the output value of the roll surface temperature / molten steel height controller to the molten steel height target value, and controlling the height of the molten steel using the new molten steel height target value and the measured height of the hot water surface. If the actual height of the measured water surface is higher than the newly calculated molten steel height target value, the amount of incoming molten steel is reduced, and the actual water surface of the measured water surface is reduced. When it is lower than the newly calculated molten steel height target value, the surface temperature control of the casting roll in the twin-roll thin sheet manufacturing apparatus, characterized in that it comprises the step of increasing the amount of incoming molten steel, repeating the above process during the casting process Provide a method.

Double roll type sheet casting, control, hot water level, roll surface temperature

Description

Method for controlling surface temperature of casting rolls in the twin rolls strip caster}

1 is a schematic diagram of a thin sheet casting process,

Figure 2 is an illustration of the basic algorithm of the casting roll surface temperature control method,

3 is a flow chart of a control algorithm of the casting roll surface temperature control method.
4 is a flowchart illustrating an example of an algorithm for implementing a casting roll surface temperature control method.

Explanation of symbols on the main parts of the drawings

1-1: fixed roll 1-2: moving roll

1-3: Tundish 1-4: Immersion nozzle

1-5: stopper 1-7: sump

1-8: Surface height detection sensor 1-9: Roll gap

1-10: leader strip 1-11: discharge line

1-12: Coiler 1-13: Loop Pit

2-1: molten steel target height 2-2: new molten steel target height

2-3: molten steel height measurement value 2-4: molten steel target height error

2-5: Roll surface temperature / molten steel height controller 2-6: Roll surface temperature error

2-7: Roll surface temperature target value 2-8: Filtered roll surface temperature average value

2-9: Filter 2-10: Roll surface temperature average value

2-11: Average value calculator 2-12: Roll surface measuring thermometer

2-13: fixed roll 2-14: movable roll

2-15: Molten Steel Height Signal Detection Processor 2-16: CCD Camera

2-17: Stopper 2-18: Position Sensor (LVDT)

2-19: Stopper Actuator 2-20: Stopper Controller

2-21: Water level controller 2-22: Initial value of stopper height

The present invention relates to a control method that can be safely cast so as not to generate heat load in the casting roll by monitoring the surface temperature of the casting roll in the manufacturing method of twin-roll type thin sheet casting directly from the molten metal in case an abnormal situation occurs will be.

During casting, the surface temperature of the casting roll is constantly changed due to various surrounding conditions. And since the casting roll is generally coated with a special steel of a thin film on the surface, the rapid surface temperature change, in particular the temperature rise of the casting roll may affect the life of the casting roll itself. In addition, the rapid surface temperature change of the casting roll may affect the casting process itself.

Therefore, in such a case, if the surface temperature change of the casting roll can be grasped at all times, it will be a breakthrough method to protect the casting roll in advance and stabilize the casting process.

An important process of sheet casting takes place in the sump 1-7 between two rolls 1-1 and 1-2 rotating in opposite directions as shown in FIG. When the molten steel is first supplied from the tundish (1-3) via the stopper (1-5) to the sump between the two rolls through the immersion nozzle (1-4), the molten steel is within 0.2 seconds of the leader strip (1-10). It is solidified between the two rolls and pressed down. At this time, the molten steel and the leader strip (1-10) which solidify and the sheet which is solidified after that generate roll repulsion force (RSF). This pushing force is detected by a load cell mounted behind the roll. The sides of the two rolls are blocked by ceramic side dams to prevent the molten steel from spilling to the sides of the rolls. The solidification capacity of the molten steel is proportional to the cooling capacity of the casting rolls. The solidification capacity is also influenced by the distance between the two rolls, namely the roll gap 1-9, the casting speed (rotational speed) of the roll, and the height of the molten steel in the sump. The height of molten steel is measured using the water surface height detection sensor 1-8. In general, when molten steel solidifies, it causes a rolling force between the rolls. And the solidification reduction rate is affected by the roll gap and the casting speed. Roll gap is measured using a distance measuring device. For example, if the roll gap (1-9) is too large or the casting speed is too fast, the solidification point will be lower than the center line of the roll nip and the rolling force will become smaller, which causes unsolidification and plate breakage of the molten steel. Let's do it. In the opposite case, the freezing point rises upward and generates a high rolling force. Therefore, roll gap, casting speed, and rolling force are representative casting parameters that indicate the solidification of the sheet.

Unexplained 1-11 is the discharge line, 1-12 is the coiler and 1-13 is the loop fit.

In the casting process as described above, if the roll surface temperature is increased, that is, the heat flux of the roll surface is increased, the roll surface coating layer surface temperature is increased, the stress is increased, and the amount of deformation is increased. Cracks can cause significant economic losses that shorten roll life. In addition, the rapid surface temperature change of the casting roll may affect the casting process itself.

It is an object of the present invention to provide a method for protecting the roll and the peripheral equipment by detecting and dealing with disturbances that may occur during casting in order to solve the above problems.

In order to achieve the above technical problem, the present invention comprises the steps of measuring the surface temperature of the fixed roll and the movable roll in the twin-roll thin sheet casting process, averaging the measured surface temperature of the fixed roll and the movable roll, Filtering the average roll surface temperature, calculating a difference between the average roll surface temperature and a target roll surface temperature, and inputting a difference between the calculated roll surface temperatures into a surface temperature / melt height controller to obtain a molten steel height. Calculating a change amount of the target value, adding the output value of the roll surface temperature / melt height controller to the molten steel height target value to generate a new molten steel height target value, the new molten steel height target value and the measured height of the hot water surface Controlling the height of the molten steel by using a flow-inflowing flux when the actual height of the measured hot water surface is higher than a newly calculated molten steel height target value; Reducing the amount, and increasing the amount of molten steel flowing when the measured height of the hot water surface is lower than the newly calculated molten steel height target value, and repeating the above process during the casting process. Provided is a casting roll surface temperature control method in a twin roll thin plate manufacturing apparatus.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail with reference to drawings.

Figure 2 is an illustration of the basic algorithm of the casting roll surface temperature control method, Figure 3 is a flow diagram according to the algorithm of FIG.

The method of controlling the casting roll surface temperature can be described by referring to the following examples with reference to FIGS. 2 and 3.

One) The surface temperature of the roll during casting is measured using a thermometer (2-12) located at the rear of the fixed roll (2-13) and the movable roll (2-14) (S1).

2) The measured surface temperatures of the fixed rolls 2-13 and the movable rolls 2-14 are averaged using the average value calculator 2-11 (S2).

3) The average roll surface temperature (2-10) is filtered with a filter (2-9) to smooth the signal (S3). This minimizes the time delay of the signal.

4) The error 2-6 between the average roll surface temperature 2-8 and the target roll surface temperature 2-7 is calculated (S4).

5) The difference in the calculated temperature is input to the roll surface temperature / melt height controller 2-5 to calculate the change amount 2-4 of the molten steel height target value to compensate for the roll surface temperature change (S5).

6) A new molten steel height target value 2-2 is generated by adding the output surface 2-4 of the roll surface temperature / melt height controller 2-5 to the molten steel height target value 2-1 (S6).

7) Using the new calculated molten steel height target value (2-2), the molten steel height detection sensor (2-16) and the molten steel height signal detection processor (2-15), the actual height of the hot water surface (2-3) By controlling the height of the molten steel (S7).

8) If the actual height of the measured bath surface is higher than the newly calculated molten steel target value, lower the stopper (2-17) to reduce the amount of molten steel flowing into the roll summ from the tundish, and the actual height of the measured bath surface is newly calculated. If the molten steel height is lower than the target value, the stopper of the tundish is further opened to increase the molten steel flowing into the roll sump (S8).

9) The above process is repeatedly performed while casting is in progress.

Hereinafter, with reference to FIG . 3, the roll surface temperature / molten steel height controller 2-5 of FIG. 2 is demonstrated.

As described above, if the surface temperature of the casting roll exceeds a certain temperature during casting, the heat flux of the roll surface increases, which leads to an increase in the surface temperature of the roll coating layer, an increase in stress, and an increase in the amount of deformation. Cracks can cause significant economic losses that shorten roll life. Therefore, the temperature of the roll surface during casting should be measured on the back of the roll so as not to exceed the reference temperature.

The idea made for this is that the height of the molten steel in the roll sump is proportional to the roll surface temperature. Therefore, by utilizing this fact, if the roll surface temperature rises, the molten steel set point of the roll sump is lowered. On the contrary, if the roll surface temperature decreases, the roll height temperature of the roll sump is raised. Designed. To realize this idea, the roll surface temperature / melt height controller (2-5) was used. In other words, compare the target value of the roll surface temperature with the measured value, input the error to the controller, and then correct the appropriate set height of the molten steel surface using gain or weighting factor inside the controller. Minutes were generated.

4 is an example of an algorithm for implementing the casting roll surface temperature control method is an implementation example of the algorithm is as follows.
< Algorithm>

read (fcr_surface_temp);

read (mcr_surface_temp);

averaged_roll_surface_temp = average (fcr_surface_temp, mcr_surface_temp);

filtered_averaged_roll_surface_temp = filter (averaged_roll_surface_temp);

roll_surface_temp_error = roll_surface_temp_setpoint-filtered_ averaged_roll_surface_temp;

melt_level_setpoint_trim = roll_surface_temp / melt_level_controller ();

new_melt_level_setpoint = initial_melt_level_setpoint + melt_level_setpoint_trim;

roll_surface_temp / melt_level_controller ()

{

melt_level_setpoint_trim = gain_factor * roll_surface_temp_error;

}

From here,

fcr_surface_temp: Surface roll (2-13)

mcr_surface_temp: Movable Roll (2-14) Surface Temperature

averaged_roll_surface_temp: Roll surface temperature average value (2-10)

filtered_ averaged_roll_surface_temp: Averaged roll surface temperature filtered (2-8)

roll_surface_temp_error: Roll surface temperature error (2-6)

melt_level_setpoint_trim: amount of change in molten steel target value (2-4)

roll_surface_temp / melt_level_controller (): Roll surface temperature / melt height controller (2-5)

new_melt_level_setpoint: New molten steel target value (2-2)

initial_melt_level_setpoint: Molten steel height target value (2-1)

The process of the algorithm of FIG. 4 will be described as follows for each algorithm step by step.
read (fcr_surface_temp);
In order to implement the casting roll surface temperature control method, the temperature (fcr_surface_temp) of the surface of the fixed roll 2-13 is first read.
read (mcr_surface_temp);
Next, the temperature (mcr_surface_temp) of the surface of the movable roll 2-14 is read.
The process of the two algorithms (read (fcr_surface_temp); read (mcr_surface_temp);) is shown in Figure 3 the thermometer (2-12) located on the back of the fixed roll (2-13) and the movable roll (2-14) S1 step to measure the roll surface temperature during casting .
averaged_roll_surface_temp = average (fcr_surface_temp, mcr_surface_temp);
The average value (averaged_roll_surface_temp) of the surface temperature of the fixed roll 2-13 and the surface temperature of the movable roll 2-14 read in the above-mentioned step is calculated | required. This step becomes the step S2 of FIG. 3 which averages the surface temperatures of the fixed roll 2-13 and the movable roll 2-14 measured in FIG. 3 using the average value calculator 2-11.
filtered_averaged_roll_surface_temp = filter (averaged_roll_surface_temp);
After the temperature average value is obtained, the signal is smoothed by filtering the roll surface temperature (2-10) which averaged the temperature with a filter (2-9). This step becomes the step S3 of FIG.
roll_surface_temp_error = roll_surface_temp_setpoint-filtered_ averaged_roll_surface_temp; The error 2-6 (roll_surface_temp_error) between the average roll surface temperature 2-8 and the target roll surface temperature 2-7 is calculated and this step becomes the step S4 of FIG.
melt_level_setpoint_trim = roll_surface_temp / melt_level_controller ();
The difference of the calculated temperature is input to the roll surface temperature / melt height controller (2-5) to calculate the change amount (2-4) (melt_level_setpoint_trim) of the molten steel height target value to compensate for the roll surface temperature change. It becomes S5 step of three.
new_melt_level_setpoint = initial_melt_level_setpoint + melt_level_setpoint_trim;
The new molten steel height target value is added to the molten steel height target value (2-1) (initial_melt_level_setpoint) by adding the variation amount (melt_level_setpoint_trim) of the molten steel height target value as the output value (2-4) of the roll surface temperature / melt height controller (2-5). (2-2) (new_melt_level_setpoint) is generated and this step becomes the step S6 of FIG.
roll_surface_temp / melt_level_controller ()
{
melt_level_setpoint_trim = gain_factor * roll_surface_temp_error;
}
Next, the roll surface temperature / melt height controller (2-5) multiplies the roll_surface_temp / melt_level_controller () gain factor (gain_factor) by the roll surface temperature (2-7) error (2-6) (roll_surface_temp_error). The height of the molten steel is controlled by using the change value of the height target value (melt_level_setpoint_trim) (step S7). If the actual height of the measured hot water surface is higher than the newly calculated molten steel height target value, the stopper (2-17) is lowered to roll from the tundish. To reduce the amount of molten steel flowing into the sump, and if the actual height of the measured hot water surface is lower than the newly calculated molten steel height target value, open the stopper of the tundish to increase the amount of molten steel flowing into the roll sump (step S8). The process consisting of one of S1 to S8 steps is repeatedly performed during the casting process (step S9) to control the height of the molten steel during casting.

According to the present invention as described above, in case of temperature control of the surface of the casting roll in the twin roll type sheet casting method, if the temperature of the casting roll surface rises sharply due to an abnormal cause, it is monitored so as to prevent damage to the casting roll in advance. By extending the life of the casting rolls as well as ensuring the stability of the casting process can be cast safely.

According to the present invention, there is an advantage that the temperature of the surface of the casting roll can be controlled to a desired value by adjusting the height of the molten steel in the case of an abnormal cause while continuously monitoring the temperature of the surface of the casting roll in the twin roll type sheet casting method Therefore, by controlling the heat load of the casting roll constantly, the coating part of the casting roll surface is not damaged, thereby extending the life of the casting roll as well as economical advantages that can be safely cast.

Claims (1)

In the twin roll sheet metal casting process, Measuring surface temperatures of the fixed roll and the movable roll (S1); Averaging the measured surface temperatures of the fixed roll and the movable roll (S2); Filtering the average roll surface temperature (S3); Calculating a difference between the averaged roll surface temperature and a target roll surface temperature (S4); Calculating the change amount of the molten steel height target value by inputting the calculated difference of the roll surface temperature to a surface temperature / melt height controller (S5); Generating a new molten steel target value by adding the output value of the roll surface temperature / molten steel height controller to the molten steel height target value (S6); Controlling the height of the molten steel using the new molten steel height target value and the measured actual height of the hot water surface (S7); Reducing the amount of incoming molten steel when the actual height of the measured hot water surface is higher than the newly calculated molten steel height target value, and increasing the amount of molten steel flowing when the actual height of the measured hot water surface is lower than the newly calculated molten steel height target value. (S8); Repeating while the casting is in progress the above process (S1) to (S8) Step Casting roll surface temperature control method in a twin-roll thin plate manufacturing apparatus, characterized in that consisting of.

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