KR100954797B1 - Method of edge dam load controlling in twin roll strip caster - Google Patents

Abstract

The present invention relates to a method for controlling edge dam reduction force in a twin roll sheet metal fabrication apparatus. The present invention relates to a method for controlling edge dam reduction force in a twin roll sheet metal fabrication apparatus capable of reducing as much as possible the reduction force applied to the edge dam at the start of casting. to provide. According to the present invention, in the method of controlling edge dam reduction force of a twin roll sheet metal fabrication apparatus, the pressure reduction force control immediately after the start of casting is changed to position control to turn on / off at a rate of 1000 times per second at a constant wear rate and a wear rate of "0". It is characterized by. By the above configuration, the present invention can improve the quality of the thin plate and at the same time can use the expensive edge dam can reduce the production cost.

Sheet Casting, Strip Casting, Edge Dam, Rolling Force

Description

Method for controlling edge dam reduction force of twin roll sheet metal fabrication equipment {Method of edge dam load controlling in twin roll strip caster}

The present invention relates to a method for controlling edge dam reduction force of a twin-roll thin plate manufacturing apparatus, and in particular, to change the pressure reduction force of the initial edge dam casting to position control to minimize the process load applied to the edge dam. The present invention relates to an edge dam reduction force control method of a twin roll sheet metal fabrication apparatus.

In general, a strip casting process is a method of continuously supplying molten steel to two rotating rolls and continuously producing a sheet of about several nm directly from the molten steel.

1 is a schematic diagram of a conventional thin sheet casting process.

As shown in Fig. 1, an important process of sheet casting is carried out on two rolls rotating in opposite directions, i.e. sump 9 between the fixed roll 1 and the moving roll 2, which is tundish The first molten steel from (4) is fed through the immersion nozzle (5) to the sump (9) between the two rolls (1,2) and the molten steel solidifies between the leader strip and the two rolls (1,2) within 0.2 seconds. To be pressed down.

At this time, the molten steel and the leader strip which solidifies, and the thin plate which is subsequently solidified, generate a roll repulsion force (RSF). This pushing force is sensed by the load cell 10 mounted behind the roll.

Here, the sides of the two rolls 1, 2 are blocked by the ceramic edge dam 8, in order to prevent the molten steel from flowing out to the sides of the rolls 1,2.

On the other hand, the solidification capacity of the molten steel is proportional to the cooling capacity of the casting roll. In addition, the solidification capacity is influenced by the distance between the two rolls 1 and 2, that is, the roll gap, the casting speed (rotation speed) of the roll, and the height of the molten steel in the sump 9. Here, the height of the molten steel is measured by using the hot water level detection sensor 7.

In general, when molten steel solidifies, it generates a rolling force between the rolls. And the solidification reduction rate is affected by the roll gap and the casting speed. The roll gap is measured using the distance measuring device 3.

For example, if the roll gap is too large or the casting speed is too fast, the solidification point will be lower than the center line of the roll nip, resulting in less pressing force, which causes unsolidification and plate breakage of the molten steel.

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 indicating the solidification of the sheet.

Basically, the height control of molten steel requires a high degree of precision and stability. Therefore, the height of molten steel is considered to maintain the target value immediately after the start of casting. Therefore, the reduction force can be seen as a result of the correlation between the roll gap and the casting speed.

On the other hand, in order to prevent the molten steel from leaking to the side of the roll (1,2) during the manufacture of twin-roll thin plate casting the thin plate directly from the molten metal, the edge dam (8) made of ceramic material is installed on the side of the two roll (1,2) In this case, there is a possibility that molten steel flows into the gap between the side surfaces of the rolls 1 and 2 and the edge dam 8 only by a few tens of micrometers.

Once the molten steel flows in, it degrades the lateral quality, ie the edge quality, of the cast strip to be produced, and consequently deteriorates the marketability, and abnormally wears the ceramic of the edge dam 8, making normal casting impossible.

In order to solve this problem, the effective position control of the edge dam is used to more effectively manage the wear and rolling force of the edge dam to prevent the molten steel from penetrating between the side of the roll and the edge dam.

Here, how to control the amount of wear of the edge dam 8 according to the casting time is an important factor in order to successfully achieve a long time casting and is one of the most important indicators in determining economic feasibility.

In addition, the efficient management of edge dams in the twin roll type sheet manufacturing process aimed at casting for a long time is not only an important goal for producing high quality sheet, but also plays a key role in reducing production cost through reduction of wear.

On the other hand, the edge dam is temporarily exerted due to disturbances such as molten steel solidifying on the leader strip mounted between the rolls and exiting between the rolls at the start of casting. All. This pressure also affects the edge dam and serves to damage the edge dam from the beginning of casting. When the edge dam is damaged in this way, it acts as an unstable element for the edge dam during the long casting process. Therefore, molten steel penetrates and damages the edge dam or generates a skull.

In order to reduce the amount of wear and to control the stable edge dam, the edge dam position control is used from the start of casting.

However, this conventional edge dam control method is performed from the start of the casting position control, which is essential for the wear of the edge dam at this time, due to the temporary increase in the pressing force applied to the edge dam at this time, the edge dam ceramic during casting There is a problem that there is a risk of breakage.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a method for controlling edge dam reduction force in a twin-roll thin sheet manufacturing apparatus capable of reducing as much as possible the reduction force applied to the edge dam at the start of casting. It is done.

In order to achieve the above object, the present invention provides a method for controlling the edge dam reduction force of a twin roll sheet metal fabrication apparatus, wherein the rolling force control immediately after the start of casting is changed to position control so as to maintain a constant wear rate and a wear rate of "0" 1000 times per second. It is characterized in that the on-off at a speed.

Preferably, the pressing force of the edge dam is measured during the position control, and if the measured pressing force is maintained for a predetermined time or less, the position control may be terminated and wear control by the pressing force may be performed.

Edge dam reduction force control method in the twin-roll thin plate manufacturing apparatus according to the present invention by changing the pressure reduction force control immediately after the start of casting to position control to improve the quality of the thin plate at the same time to improve the quality of the thin plate Since it can be used for a long time, there is an effect of reducing the production cost.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Edge dam reduction force control method in a twin-roll thin plate manufacturing apparatus according to an embodiment of the present invention by changing the pressure reduction force control performed immediately after the start of casting to position control of the position control and the wear rate "0" of the stationary state according to a certain wear rate Position control is controlled to be ON and OFF at a rate of 1000 times per second.

That is, before casting is started, the edge dam 8 is brought into close contact with the ends of the rolls 1 and 2, and then the reduction force control is performed at a constant pressure.

Next, when casting is started, the on-off wear control of the edge dam is performed by the position control at a predetermined wear rate, while immediately changing the edge dam control currently in progress from the reduction force control to the position control.

During the on-off wear control by the position control, the pressing force is measured for a certain time, and when the pressing force falls below the reference value, the pressing force is switched to the normal pressing force control and normal wear control is performed by the pressing force control according to the preset wear rate. .

Hereinafter, the edge dam reduction force control method of the twin-roll thin plate manufacturing apparatus according to an embodiment of the present invention with reference to FIGS. 2 and 3 in detail.

Figure 2 is a schematic diagram of a conventional edge dam, Figure 3 is a flow chart showing the edge dam reduction force control method of a twin-roll thin plate manufacturing apparatus according to an embodiment of the present invention.

First, before the casting is started, the edge dams 25 and 26 are brought into close contact with the ends of the casting rolls 21, and then the pressing force control is performed at a constant pressure (step S301).

As shown in FIG. 2, the seal plate 210 is formed on the drive side edge dam 25 and the work side edge dam 26 by the fixing roll 22 and the moving roll 23 by the upper shaft cylinder 24. It is in close contact with the upper (27, 28) and the lower (29).

Next, it is determined whether casting is started (step S302), and if it is determined that casting is not started, the rolling force control of step S301 is continuously performed.

As a result of the determination in step S302, when it is determined that casting has been started, the current pressing force control is switched to wear control by position control (step S303).

That is, the on-off of wear control by position control is performed at a high speed of about 1000 Hz at the start of casting. This means that the position control according to the predetermined wear rate and the position control of the wear rate " 0 ", ie, the position control in the stationary state, are repeated about 1000 times per second.

The reason for turning on and off the wear control by the position control in this way is to reduce the pressing force applied to the edge dams 25 and 26 at this point. The method to reduce the rolling force is to control the pressing force by setting a low pressure as the target value, but this is only used for controlling the edge dam wear because it only controls the pressing force but not the thickness of the worn edge dam. That's how you can't.

On the other hand, the wear control based on the position control increases the position value of the edge dam per unit time or unit distance at a constant rate, so that the amount of wear can be managed.

In this case, one way to reduce the reduction force is to keep the wear rate at "0" while maintaining the position control.

However, if the wear rate is maintained at " 0 " for a long time, there is a fear that molten steel penetrates because the adhesion state between the edge dams 25 and 26 and the ends of the casting rolls worsens.

Therefore, in the present embodiment, the wear control by the position control is turned on and off, that is, the wear rate is changed to a high speed with a constant value and "0". In particular, just before casting, the edge dams 25 and 26 are mechanically bent to some extent because the edge dams 25 and 26 are brought into close contact with the ends of the casting roll 21 at a constant pressure and the pressing force is controlled. .

When casting starts, a higher pressure than the normal is applied to the end of the casting roll 21 until this bending force disappears. Even though abrasion control is performed by controlling the position of wear rate "0" for a short period, penetration of molten steel Does not occur.

Next, while measuring the pressing force applied to the edge dams 25 and 26 for a predetermined time, for example, 10 seconds, it is determined whether the measured pressing force is kept below a reference value for a predetermined time (step S304). For example, when the pressing force applied to the edge dams 25 and 26 is not kept below the reference value for one second, the wear control by the position control in step S303 is continuously performed.

However, when it is determined in step S304 that the pressing force is maintained for a predetermined time or less, the wear control by the position control in step S303 is terminated, and the wear control by the normal pressing force control is switched.

As a result, overall wear control is performed while actively changing the wear rate according to the state of the cast strip edge and the thickness of the edge dams 25 and 26 during casting. In this way, it is possible to improve the quality of the thin plate and at the same time use the expensive edge dam to reduce the production cost.

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1 is a schematic view of a conventional sheet casting fixing.

2 is a schematic view of an edge dam.

Figure 3 is a flow chart showing the edge dam reduction force control method of the twin-roll thin plate manufacturing apparatus according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: fixed roll 2: moving roll

3: roll gap measuring device 4: tundish

5: immersion nozzle 6: stopper

7: Floor height detection sensor 8: Edge dam

9: molten steel sump 10: load cell

11: cylinder 12: strip

13: x-ray gauge 14: pinch roll

15: rolling mill 16: coiler

Claims (2)

In the edge dam reduction force control method of a twin-roll type sheet manufacturing apparatus, Immediately after the start of casting, the wear control by the pressure reduction force control is changed to the wear control by the position control, and the casting is performed by repeating the position control according to the predetermined wear rate and the position control of the stationary state of the wear rate "0" at a speed of 1000 times per second. A method for controlling edge dam reduction force of a twin-roll thin sheet manufacturing apparatus, characterized by reducing the reduction force applied to the edge dam at the start point. The method of claim 1, After measuring the pressing force of the edge dam during wear control by the position control, if the measured pressing force is maintained for a predetermined time or less, the wear control by the position control is terminated and the wear control by the pressing force control is terminated. Edge dam reduction force control method of a twin-roll thin plate manufacturing apparatus, characterized in that performed.

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