KR20030054599A - Method for uniforming congelation speed of cast slab surface in continuous casting - Google Patents

Abstract

PURPOSE: A method for controlling solidification speed of the shell of cast slab during continuous casting is provided to prevent quality defects at both edge parts of the cast slab by properly controlling distance between nozzles and the upper surface of the cast slab, position of the nozzles and spray amount of cooling water. CONSTITUTION: In a method for cooling cast slab passing through a plurality of rolls mounted at both sides of continuous caster segments in continuous casting process using cooling water, the method comprises the processes of spraying cooling water onto the front of the cast slab using first series of nozzles(30) of odd number rows installed in a width direction between the rolls mounted at both sides of the cast slab; and spraying cooling water onto the front of the cast slab using second series of nozzles(40) of even number rows installed at a higher position than the first series of nozzles(30) in a width direction between the rolls mounted at both sides of the cast slab so that difference of solidification rate between the central part and both side parts of the cast slab is minimized, wherein the second series of nozzles(40) are spaced apart from the cast slab as much as 1.3α when the first series of nozzles(30) are spaced apart from the cast slab as much as α, wherein the second series of nozzles(40) are arranged between the first series of nozzles(30) in a width direction of the cast slab, and wherein spray angle(18) of cooling water of the first and second series of nozzles(30,40) is approximately from 100 to 120 degrees.

Description

METHOD FOR UNIFORMING CONGELATION SPEED OF CAST SLAB SURFACE IN CONTINUOUS CASTING}

The present invention, in the process of cooling the cast steel produced in the continuous casting process with the cooling water injected from the nozzles, by appropriately adjusting the distance and position of the nozzles from the upper surface of the cast steel and the injection amount of cooling water sprayed, the width direction of the cast steel It relates to a method of uniformity of the surface solidification rate of the cast during continuous casting to minimize the difference in the surface solidification rate generated by the quality defect in the two edges of the cast.

1 is a schematic diagram of a conventional continuous casting process.

Referring to FIG. 1, in the continuous casting process, molten steel is supplied from a tundish to a water-cooled copper mold 1 to form a solidification layer first, and then passes through a player segment 50 composed of a plurality of rolls 2. The solidification proceeds to the secondary by the cooling water sprayed from the installed nozzle (3) and is completely solidified, and the solidified slab is cut into a predetermined length by the cutter 5 at the segment end.

The player segment 50 is arranged from segment 1 to segment 9 downward from the mold 1. Segment 1 (foot roll part) 6 is a part integrated with the mold 1, segment 2 (bender part) 7 is a part in which the slab is subjected to bending stress in the vertical part and its lower end part, 3 to 5 (casting bow) 8 correspond to the bent cast portion, and segment 7 (straight portion) 9 is the portion to which the straightening stress is applied. The portion where the cast slab 25 is finally solidified corresponds to segments 8 to 10 (horizontal portion) 10.

2 shows the center and the edge of the slab 25 produced via the player segment 50. As shown in FIG. 2, the internal quality of the cast steel 25 produced through the player segment 50 is different depending on the cast steel position. That is, the incidence rate of the center segregation zone is not large in the center portion of the cast piece 25, but the incidence rate of the center segregation zone is high in the edge portion thereof.

On the other hand, Figure 3 is a width measurement result of the conventional slab, the temperature measurement results along the width direction of the slab 25 in the secondary cooling zone of the slab 25 corresponding to the segments 1 to 10 shown. do.

As shown in FIG. 3, the temperature of the cast steel 25 is the highest at 400 mm on both sides with respect to the center of the cast steel corresponding to 1280 mm from the left, and solidified at a point approximately 250 mm from the edge of the cast steel 25. The delay portion is generated, and thus the thickened molten steel immediately before the final solidification gathers at the edge of the cast piece 25 to form a severe central segregation zone. Here, the reason why the temperature is greatly reduced at the edge end of the cast piece 25 is that the rolling roll is a three-part roll, so that a pocket exists between the roll and the roll.

On the other hand, the cast piece 25 starts to move from the mold to initial solidification and moves to complete solidification through the secondary cooling zone. By the way, if the distribution of the cooling water in the width direction of the slab 25 of the secondary cooling stand is different, there is a difference in the solidification speed of the central portion and the edge portion of the slab 25 so that the overall non-uniform solidification occurs, the internal quality of the slab 25 Can cause differences.

4 is a schematic view of a nozzle arrangement of a conventional secondary cooling stand.

Referring to FIG. 4, nozzles in the secondary cooling stand that have been conventionally applied correspond to odd rows mounted between rollers 2 mounted on both sides of the player segment 50 through which the cast piece 25 passes. The first series nozzles 30 and the second series nozzles 40 corresponding to even numbers are formed.

The first series nozzles 30 are five, and the second series nozzles 40 are four. Here, the first and second series nozzles 30 and 40 are all installed at a position where the tip distance 15 from the slab 25 is approximately 220 to 240 mm apart, and more preferably 230 mm apart. Is installed in position. In addition, the first and second series nozzles 30 and 40 are installed with the nozzles 16 spaced apart from each other by approximately 380 to 400 mm, more preferably 390 mm. 17) the contact surface distance is approximately 725 mm, and the cooling water spray angle 18 of each nozzle is approximately 110 degrees.

5 is a result of measuring the amount of cooling water sprayed in the width direction of the slab 25 in the secondary cooling stand when the cooling action is performed by spraying the cooling water using the nozzle arrangement of the conventional secondary cooling stand shown in FIG. .

Referring to FIG. 5, as a result of measuring the widthwise cooling water injection amount of the slab 25 injected from the secondary cooling zone, it showed a relatively uniform distribution. Therefore, it can be seen that the non-uniformity of the surface solidification speed caused by the solidification delay of the slab 25 is not simply a result of the injection of the widthwise cooling water in the secondary cooling zone.

6 is the water vapor mobility on the cast steel.

Referring to FIG. 6, the cooling water injected from the secondary cooling zone is naturally vaporized in response to the slab surface 21 at a high temperature, and the vaporized water vapor is discharged through the high pressure vent installed in the player itself. At this time, the discharge path of the vaporized water vapor is moved from the high pressure state to the low pressure state based on the pressure injected from the nozzles 30 and 40 from the widthwise center portion of the slab 25 to the low pressure edge portion. The cooling water 20 injected into the cooling nozzles 30 and 40 by the path 22 of the water vapor is disturbed at the edge of the cast steel 25 so that the cast steel 25 is actually moved. Is reached, the amount of cooling water used for cooling is reduced.

Therefore, as the interference of water vapor increases toward the edge portion of the slab 25, as shown in FIG. 3, the edge portion of the slab 25 is subjected to less cooling action and thus the surface of the edge portion of the slab 25. As the temperature increases, a solidification delay occurs at the edge of the slab 25, causing a difference from the solidification speed with the central portion. As a result, there is a problem of deteriorating the internal quality of the slab 25 as a whole. have.

The present invention has been proposed in order to solve the above conventional problems, in the process of cooling the slabs produced in the continuous casting process with the cooling water sprayed from the nozzles, the distance and position of the nozzles spaced apart from the upper surface of the slab and It provides a method of uniformizing the surface coagulation speed of the slab during continuous casting to optimize the sprayed shot to minimize the difference in surface coagulation speed generated in the width direction of the slab to prevent quality coupling from occurring at both edges of the slab. There is that purpose.

1 is a schematic diagram of a conventional continuous casting process;

2 is a quality state diagram of the center portion and the edge portion of the playing cast;

3 is a width measurement result of the conventional cast steel;

4 is a schematic view of the nozzle arrangement of a conventional secondary cooling stage;

5 is a view of measuring the injection direction of the cooling water in the width direction of the slab in the conventional secondary cooling zone;

6 is the vapor mobility on the cast steel;

Figure 7 is a comparison of the actual measurement results and the calculation results of the surface temperature distribution of the cast when spraying the cooling water in a certain amount;

8 is a coolant amount distribution according to the interference of the vaporized water vapor on the slab during the cooling water injection in a certain amount;

9 is a comparison between actual measurement results and calculation results of the surface temperature distribution of cast steels in consideration of vaporized vapor on cast steels;

10 is a schematic view of the nozzle arrangement of the secondary cooling stage in the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention;

FIG. 11 is a result of measuring the widthwise cooling water injection amount of the cast steel when the nozzle spraying operation is performed when the nozzles are arranged in accordance with FIG. 10; FIG.

12 is a comparison between actual measurement results and calculation results of the surface temperature distribution in the width direction of the cast steel in the secondary cooling zone in the method of uniformizing the surface solidification rate of the cast steel during continuous casting according to the present invention; And

13 is a quality state diagram of the center portion and the edge portion of the cast in the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention.

Explanation of symbols on the main parts of the drawings

1 .... water cooled copper mold 2 .... rolls

3 .... Nozzle 4 .... Reduced iron discharge screw

25 .... Cast 30 .... The first series of nozzles

40 .... Second nozzles 50 .... Player segment

As a technical configuration for achieving the above object, the present invention provides a method for cooling a cast piece passed between a plurality of rolls mounted on both sides of a player segment in a continuous casting process with cooling water, the width between the rolls on both sides of the cast piece. Cooling water is sprayed on the front surface of the cast steel by the first row nozzles in the odd-numbered rows installed in the direction, and the front surface of the cast steel by the even-numbered second series nozzles installed in the width direction between the rolls on both sides of the cast steel. By spraying the cooling water to minimize the difference in the solidification rate of the central portion and the side portion of the cast steel by providing a method of uniformizing the surface solidification speed of the cast during continuous casting.

In the method of uniformizing the surface solidification speed of the cast during continuous casting according to the present invention, in the method of cooling the slab 25 passed between a plurality of rolls 2 mounted on both sides of the machine segment of the continuous casting process with a cooling water, (25) Cooling water is sprayed on the entire surface of the cast steel (25) with the first series nozzles (30) in odd rows provided in the width direction between the rolls (2) on both sides, and between the rolls (2) on both sides of the cast steel (25). Cooling water is sprayed on the entire surface of the cast steel (25) with even-numbered second series nozzles (40) installed higher than the first series nozzles (30) in the width direction of the solidification rate of the central portion and both sides of the cast steel (25) Minimize the difference.

Here, the first series nozzles 30 are provided five in the width direction of the slab 25 per odd row, and the second series nozzles 40 in the width direction of the slab 25 per even row. After installation, perform spraying work.

In addition, the second series nozzles 40 are installed to be spaced apart from the cast piece 25 by 1.3 a when the first series nozzles 30 are spaced apart from the cast piece 25 by a distance a. Spraying is performed on the front surface of the cast steel (25).

In addition, the second series nozzles 40 are respectively disposed to be disposed between the first series nozzles 30 in the width direction of the slab 25 to spray the entire surface of the slab 25.

On the other hand, the first and second series nozzles (30, 40) when the nozzles provided at both ends in the width direction of the slab 25 are respectively installed inwardly spaced apart from each other next to the nozzles installed next The nozzles disposed between the nozzles disposed at both ends of the first and second series nozzles 30 and 40 are spaced apart from each other by about 1.63b in the width direction, and then sprayed onto the front surface of the cast steel 25. Do the work.

In addition, the coolant spray angles of the first and second series nozzles 30 and 40 are sprayed with coolant while maintaining approximately 100 to 120 degrees, and more preferably, sprayed at 110 degrees. do.

In addition, the first and second series nozzles 30 and 40 are disposed on both sides of the slab 25 in the width direction than the amount of cooling water injected from the nozzles disposed in the center portion of the slab 25 in the width direction. Allow approximately 20 to 30% more coolant spray from the nozzles.

Hereinafter, the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention will be described in more detail according to the drawings and embodiments.

<Example>

Figure 7 is a comparison of the actual measurement results and the calculation results of the surface temperature distribution of the cast steel when spraying a certain amount of cooling water. That is, FIG. 7 shows the calculation result and the measured value using the heat transfer coagulation model assuming that the cooling water is injected in a constant amount in the secondary cooling zone in the slab 25 width direction.

Referring to FIG. 7, when the heat transfer coagulation model is used, the temperature of the center portion or the edge portion of the slab 25 is uniformly distributed at 884 degrees, which is quite different from the experimental measurement. Therefore, the condition that the cooling water injection amount is uniformly injected into the cast steel 25 does not affect the internal coagulation delay phenomenon and the internal quality of the cast steel 25 due to the uneven solidification generated in the actual cast steel 25.

Unlike the previous assumption, it is assumed that the amount of cooling water injected from the secondary cooling zone is unevenly injected. 8 is a distribution diagram of the amount of cold water according to vaporized water vapor on the slab 25 when spraying the cooling water in a predetermined amount. Referring to FIG. 8, the degree of interference of the amount of cooling water injected from the secondary cooling zone according to the vaporized water vapor has a sinusoidal curve as shown in FIG. 8, and the degree of interference of the amount of cooling water is 25% on both sides of the slab 25. It is assumed to decrease.

At this time, the results calculated using the heat transfer coagulation model is shown in FIG. Figure 9 is a comparison of the actual measurement results and the calculation results of the surface temperature distribution of the cast steel in consideration of vaporized water vapor on the cast steel. As shown in FIG. 9, it can be seen that the calculation result using the heat transfer coagulation model and the actual measurement result through the experiment are in good agreement. Accordingly, 20 to 30% more cooling water is provided at both edges of the cast piece 25 based on the calculation result using the heat transfer solidification model to solve the coagulation delay caused by uneven solidification of the surface of the cast piece 25. Experiments were conducted to spray, preferably 25% more.

In order to increase the width distribution of the coolant in the width direction of the secondary cooling zone to 25% at both edges of the slab 25, the installation positions of the first series nozzles 30 and the second series nozzles 40 are changed. I was.

10 is a schematic view of the nozzle arrangement of the secondary cooling stage in the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention. Referring to FIG. 10, a new nozzle arrangement in accordance with the present invention in the secondary cooling zone is characterized in that the first series nozzles 30 are arranged in the width direction of the slab 5 in odd rows on both sides of the player segment 50, respectively. The dogs were installed one by one, and four dogs were installed in even rows in the width direction of the cast piece 5, respectively.

In addition, the first series nozzles 30 are installed at a point where the distal end distance 15 of the slab 25 is separated by approximately 220 to 240 mm, and more preferably, at a point separated by 230 mm. It was made. In addition, the second series nozzles 40 are installed at a point where the distal end distance 15 of the slab 25 is spaced approximately 290 to 310 mm, and more preferably installed at a point spaced 300 mm. It was made.

In addition, the arrangement of the first series nozzles 30 and the second series nozzles 40 is approximately 290 to 310 mm in distance 16 from the nozzles in which nozzles disposed at both ends are disposed inward. It was to be installed in a spaced apart position, the interval between the nozzles disposed between the nozzles installed on both sides are to be spaced apart by approximately 480 ~ 500 mm.

Further, the arrangement of the first series nozzles 30 and the second series nozzles 40 is more preferably a distance 16 between the nozzles disposed at both ends of the first series nozzles 30 and the second array nozzles 40. It was set to be spaced apart by mm, and the distance between the nozzles disposed between the nozzles installed at both ends is to be spaced apart by 490 mm.

On the other hand, the first series nozzles 30 have a specific distance 17a of each nozzle about 725 mm, while the second series nozzles 40 have a specific distance 17b of each nozzle approximately 875 mm.

In addition, the first and second series nozzles 30 and 40 all set the cooling water injection angle 18 of the nozzles equal to 110 degrees, and then performed the cooling water spraying operation.

After the installation as described above, the result after spraying the cooling water from the nozzles 30 and 40 of the first and second series is shown in FIG. Referring to FIG. 11, when the nozzle spraying operation is performed in a state in which the nozzles 30 and 40 of the first and second series are arranged as described above, the amount of cooling water injected from both sides of the cast steel 25 is greater than that of the center portion. It can be seen that the increase is about 25%.

After arranging the first and second nozzles 30 and 40 as described above, in the process of producing the cast steel 25 by applying the distribution of the cooling water injection in the width direction of the cast steel 25 to the machine Surface temperature was measured and at the same time calculated using the heat transfer coagulation model for the same system.

12 is a comparison between actual measurement results and calculation results of the surface temperature distribution in the width direction of the slab in the secondary cooling zone in the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention.

Referring to FIG. 12, when cooling water is sprayed 20 to 30% more on the edge of the slab 25 in consideration of the interference of vaporized water vapor, the surface temperature of the slab 25 shows a uniform distribution. As a result, the calculations were predicted in a similar fashion. In addition, compared with FIG. 3, the surface temperature of the slab 25 was significantly reduced in the solidification delay portion due to non-uniform solidification.

13 is a quality state diagram of the center portion and the edge portion of the cast in the method of uniformizing the surface solidification rate of the cast during continuous casting according to the present invention.

Referring to FIG. 13, the solidification delay was reduced after using the method of uniformizing the surface solidification speed of the cast steel during continuous casting according to the present invention, and thus the difference between the surface segregation speed of the center segregation zone and the center portion and the edge portion of the cast steel 25 was reduced. Decreased significantly.

As described above, according to the method of uniformizing the surface solidification speed of the cast during continuous casting according to the present invention, in the process of cooling the cast produced in the continuous casting process with cooling water injected from the nozzles, the nozzles are spaced apart from the upper surface of the cast. By appropriately adjusting the distance, the position and the amount of sprayed coolant to minimize the difference in the surface solidification rate generated in the width direction of the cast steel, there is a useful effect of preventing the quality coupling is generated in both edges of the cast steel .

While the invention has been shown and described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit or scope of the invention as set forth in the claims below. I would like to clarify that knowledge is easy to know.

Claims (7)

In the method of cooling the cast steel passing between a plurality of rolls mounted on both sides of the machine segment of the continuous casting process with a coolant, Cooling water is injected onto the entire surface of the cast steel 25 by the first series nozzles 30 in an odd-numbered row installed in the width direction between the rolls 2 on both sides of the cast steel 25, and the rolls 2 on both sides of the cast steel 25. Cooling water is sprayed on the entire surface of the cast steel by the even-numbered second series nozzles 40 installed higher than the first series nozzles in the width direction between the first and second series nozzles. Uniformity of surface coagulation rate of cast steel during continuous casting characterized by minimization. The method of claim 1, The second series nozzles 40 may be installed to be spaced apart from the cast piece 25 by 1.3 a when the first series nozzles 30 are spaced apart from the cast piece 25 by a distance a. Uniformity of surface solidification rate of cast steel during continuous casting The method of claim 1, The second series nozzles (40) are respectively installed so as to be disposed between the first series nozzles (30) in the width direction of the slab (25) characterized in that the surface solidification rate uniformity of the cast during continuous casting. The method of claim 1, The first and second series nozzles 30 and 40 are each provided with nozzles installed at both ends in the width direction of the slab 25 inwardly spaced apart from each other by the next nozzles. The surface coagulation rate of the cast during continuous casting, characterized in that the nozzles disposed between the nozzles provided at both ends of the first and second series nozzles 30 and 40 are spaced apart by about 1.63b from each other in the width direction. Homogenization method. The method of claim 1, Cooling water injection angle of the first, second series nozzles (30) (40) is approximately 100 ~ 120 degrees, the surface solidification rate uniformity method of the cast during continuous casting. The method of claim 1, The first and second series nozzles 30 and 40 are nozzles disposed on both sides of the slab 25 in the width direction than the amount of cooling water injected from the nozzles disposed in the center portion of the slab 25 in the width direction. Method for homogenizing the surface solidification rate of the cast during continuous casting, characterized in that about 20 ~ 30% more cooling water is injected from the. The method of claim 1, Each of the first series nozzles 30 is installed in the width direction of the cast steel 25 per odd row, and the second series nozzles 40 are installed in the width direction of the cast steel 25 per even row. Uniformity of surface coagulation rate of cast steel during continuous casting.