KR100333069B1 - Method for uniformly cooling cast slab in twin roll strip caster - Google Patents

Abstract

PURPOSE: A method for uniformly cooling cast slab in twin roll strip caster is provided to produce cast slab of good quality by preventing the cast slab from being inclined to any one casting roll out of two casting rolls even after solidification shell slips away from roll nip, thereby preventing thermal strain of the cast slab. CONSTITUTION: In an ordinary strip casting method for directly casting thin cast slab by injecting molten metal into a space between casting rolls which are rotated oppositely to each other, the method for uniformly cooling cast slab(15) in twin roll strip caster comprises the processes of detecting difference between current values generated at driving motor for rotating the two casting rolls(13) by using a pair of idle rolls(20) which are installed directly under the casting rolls(13), through which cast slab slipping away from the casting rolls(13) passes, and which are back and forth movably installed; and moving position of the idle rolls(20) to a casting roll(13) having a detected lower current value in the two casting rolls(13) when the detected difference between the current values is a certain amount or more so that the difference between the current values becomes zero.

Description

Uniform Cooling Method of Cast Steel in Twin Roll Type Sheet Casting Machine

The present invention can prevent the phenomenon that the thickness of the cast is produced unevenly due to the heat deformation of one side cast roll by the heat dissipation generated in the cast produced during the sheet casting process to produce the cast (hot coil) directly from molten steel without making slabs. The present invention relates to a method for cooling a slab uniformly in a twin roll sheet casting device.

In general, a twin-roll sheet caster has a molten metal 14 between a ladle 10 and a pair of casting rolls 13 rotating through a tundish 11 and a molten steel supply nozzle 12, as shown in FIG. It is a device which supplies and manufactures the thin plate 15 product of about several mm directly from the molten metal 14 according to the proximity point space | interval between the casting rolls 13.

On the other hand, on both sides of the pair of casting rolls 13, edge dams 16 made of refractory plate are installed to prevent the supplied molten metal 14 from flowing out, and a pair of casting rolls 13 and a pair of casting rolls 13 are formed during casting. The molten metal 14 is supplied to the space formed by the edge dam 16 by the molten metal supply nozzle 12.

In order to obtain a high quality cast 15 during thin sheet casting by the twin roll method, the molten metal is precisely controlled so that the molten metal 14 supplied between the casting rolls 13 can be maintained at a constant height during the normal casting. The molten metal 14 supplied through the discharge port of the supply nozzle 12 is uniformly supplied over the full width of the casting roll 13, and stable molten metal should be supplied so that the surface may not fluctuate.

Therefore, the molten metal injected between the two casting rolls 13 loses heat from the surface of the casting roll 13 which is cooled by the internal cooling water, thereby solidifying. When the two casting rolls 13 are closest to each other and the two solidification angles 17 are combined with each other and are pulled out of the roll, the cast piece 15 is formed. Lose.

The thickness of the solidification angle 17 is determined by the length of the contact arc in which the solidification angle 17 is in contact with the casting roll 13 surface.

The most important point when the two solidification angles 17 are combined at the point where the two casting rolls 13 are closest to each other is that the thickness of each solidification angle 17 should be the same. Thus, the internal structure of the cast piece 15 that passes between the casting rolls 13 is uniform.

In the related art, as shown in FIG. 2, the slab 15 exiting the casting roll 13 tends toward the slab drawing device 21. In this case, the cast piece 15 exiting the roll 닢 18 is biased toward the drawing device 21, so that the contact time of the solidification angle 17 which contacts the surface of the casting roll 13 located on the drawing device 21 side is The longer the contact time of the opposite solidification angle 17, the greater the thickness of the solidification angle 17 in contact with the surface of the casting roll 13 located toward the drawing device.

In this way, a difference in thickness between the two solidification angles 17 occurs in the internal structure of the cast slab 15, which causes a problem that the properties of the cast slab 15 become nonuniform.

In addition, since the cooling capacity of the pair of casting rolls 13 cooled by the internal cooling water of the casting rolls 13 rotating opposite to each other is exerted by the contact with the solidification angle 17 to be cast, each casting roll 13 The amount of heat absorbed should be the same.

As described above, when both solidification angles 17 asymmetrically contact the surfaces of each casting roll 13, a difference in the amount of heat absorbed by each casting roll 13 may occur, thereby causing a surface temperature of the casting roll 13. Are different from each other, and thus the degree of thermal expansion of the surface of the casting roll 13 is different because each casting roll 13 is different, resulting in uneven thickness of the cast piece 15 to be cast.

The present invention has been invented to solve this problem in view of the above problems, and even after the solidification angle exits the roll 닢 so that the cast steel is not biased to either one of the two casting rolls to prevent thermal deformation of the cast steel It is an object of the present invention to provide a method for uniformly cooling the cast steel in a twin roll sheet casting device to produce a.

1 is a schematic view of a general twin roll sheet casting device

Figure 2 is a schematic diagram showing the production process of a typical cast

Figure 3 is a schematic diagram showing the production process of the cast steel of the present invention

Figure 4 is a graph showing the difference between the present invention and the conventional method

<Description of the code | symbol about the principal part of drawing>

10: ladle 11: tundish

12: nozzle 13: casting roll

14 molten metal 15 cast

16: edge dam 17: solidification angle

18: roll 닢 20: two rolls

21: cast steel drawing device 22: casting roll drive motor

The present invention having such an object is provided in the ordinary sheet casting method of directly casting a thin cast by injecting molten metal between casting rolls which are rotated opposite to each other. A cast piece 13 that exits the casting roll 13 passes, and a pair of idle rolls 20 are installed so as to be able to move forward and backward, and is generated in the drive motor 22 for rotating the two casting rolls 13. Detecting the difference between the current value, when the difference between the detected current value is a certain amount or more casting roll detected the position of the idle roll 20 as the current value of the two casting rolls 13 ( 13) to make the difference in the current value to zero.

In the present invention, even after the two solidification angles 17 exit the roll 18 18, a pair of the cast pieces 13 under the casting roll 13 is not biased so that the casted pieces 15 are not biased toward either of the two casting rolls 13. An idle roll 20 (Idle Roll) is provided to pass the cast piece 15 therebetween.

The pair of idle rolls 20 may be moved forward and backward. The reason for the retraction is that the unsolidified molten steel can be lowered through the two casting rolls 13 at the start and the end of the casting. To protect.

If the length of the contact arc where the two solidification angles 17 are in contact with each casting roll 13 is different, the current value of the drive motor 22 rotating the two casting rolls 13 is the respective casting roll 13. ), A difference occurs.

The current value of the drive motor 22 is continuously collected during casting, and the difference between the drive motor current values of each roll is detected, and when a difference of more than a predetermined amount occurs, the position of the idle roll 20 located below the casting roll is low. By moving toward (13), the current value difference of each casting roll 13 driving motor can be made zero.

Hereinafter, the present invention will be described through Examples.

<Example>

Shown by the small circle in Fig. 4 is that each casting roll when cast in a biased state toward the cast slab 15 drawing device 21 without installing the idle roll 20 under the casting roll 14 of the present invention ( 13) The difference between the current value of the driving motor 22 and the heat extraction amount of the two casting rolls 14 is shown, and the current value of the driving motor 22 of the casting roll 13 on the drawing device 21 side is larger. The heat extraction amount is also larger.

In FIG. 4, the large circle is a case in which the idle roll 20 is installed below the casting roll 13 of the present invention, and the difference in current value and heat extraction amount of the driving motor 22 of each casting roll 13 is almost different. You can see that it is zero.

In the present invention, by installing an idle roll below two casting rolls to allow the cast slab to pass between the two idle rolls, the thickness of the solidification angle generated between the two casting rolls is uniform, so that the inside of the cast slab The structure becomes uniform and the endothermic amount of the two casting rolls is the same, and the thermal expansion amount of the casting roll is also the same, so that the thickness of the cast slab becomes uniform.

Claims (1)

In the conventional sheet casting method of injecting molten metal between casting rolls which rotate opposite to each other to directly cast a thin cast steel, While using a pair of idle rolls 20 installed below the casting roll 13 and passed through the cast roll 13, the cast piece 13 is installed to enable forward and reverse, Detecting a difference between current values generated in a drive motor (22) rotating the two casting rolls (13). When the difference between the detected current values becomes a certain amount or more, the position of the idle roll 20 is moved toward the casting roll 13 in which the current value among the two casting rolls 13 is detected to be low, thereby providing the current value. The uniform cooling method of the slab in the twin-roll thin plate casting apparatus comprising a process of making a difference of zero.

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