JP5817689B2 - Secondary cooling method for continuous casting - Google Patents

Description

  The present invention relates to a secondary cooling method for continuous casting for uniformly cooling a slab in a continuous casting machine.

  In the iron and steel industry, when a molten steel is solidified to produce a slab, a continuous casting facility is generally used. As shown in FIG. 1, the continuous casting equipment draws the cast piece 3 that has been primarily cooled by the mold 2 and solidified on the surface little by little below the mold 2, and continuously feeds it while being sandwiched between the guide rolls 4. The slab 3 is produced continuously. While the slab 3 is fed out by the guide roll 4, cooling water is injected onto the surface of the slab 3 as secondary cooling. In this secondary cooling, for example, as shown in FIG. 8, in order to make the cooling performance in the width direction of the slab 3 uniform, the injection ports of a plurality of nozzles are formed so as to have an injection pattern having a uniform water density distribution. 21 is arranged.

  When such secondary cooling is performed, conventionally, a part of the cooling water sprayed on the surface of the slab 3 is drained as shown in FIG. Instead, it stayed between the upper part of the guide roll 4 and the slab 3, and became pooled water 13.

  In general, the accumulated water staying in the guide roll 4 is the smallest at the center in the width direction and shows a distribution that increases toward both sides. Thus, if the distribution of the accumulated water 13 is different in the width direction of the slab 3, it becomes a factor in which uniform cooling cannot be performed. Further, when it is necessary to strongly press the slab 3 with the guide roll 4, the guide roll 4 is divided in the width direction of the slab 3 as shown in FIG. 8 in order to increase the rigidity of the guide roll 4. . In such a case, the accumulated water due to the drainage of the cooling water is not generated at the position of the bearing portion 5 between the divided guide rolls 4. Therefore, the distribution of the accumulated water 13 is non-uniform between the position where the slab 3 is in contact with the guide roll 4 and the position of the bearing portion 5, and uneven cooling can occur in the width direction of the slab 3.

  Thus, it has been found that the accumulated water 13 of the guide roll 4 is a major factor that hinders uniform cooling of the slab 3. If the cooling becomes uneven, defects occur in the surface properties and internal quality of the slab 3. Therefore, it is necessary to prevent the deterioration of the quality of the slab 3 by eliminating the accumulated water 13 of the guide roll 4 or by controlling the influence of the accumulated water 13 to be uniform in the width direction.

  In order to reduce cooling unevenness, Patent Document 1 discloses a continuous casting apparatus provided with an injection nozzle for injecting high-pressure gas. Patent Document 2 discloses a continuous casting apparatus provided with a suction pipe for sucking residual water.

  Patent Document 3 discloses a cooling method in which an air mist injection surface is inclined.

JP 2010-253528 A JP 2010-253529 A JP 2009-255127 A

  However, both of Patent Documents 1 and 2 are provided with a new device such as an injection nozzle or a suction pipe, and there is a problem that a cost and a space for installation are required.

  Moreover, the said patent document 3 aims at uniform cooling so that the air mist sprayed from an adjacent nozzle may not mutually overlap, and is not considered about reducing the accumulated water of a guide roll part. Conventionally, for the problem of non-uniform cooling at the part where the air mist overlaps, the spray pattern of the nozzle is devised, and the water amount density (the amount of spray water per unit area) in consideration of the overlap between adjacent nozzles ) Nozzles designed in advance so that the distribution is uniform are used.

  The object of the present invention is to reduce the accumulated water at the guide roll position at a low cost without newly installing a device or the like, to uniformly cool the slab, and to produce an excellent quality slab. It is to provide a next cooling method.

  In order to solve the above problem, the present invention provides a secondary cooling method in which cooling water is sprayed toward a slab cast by a continuous casting apparatus to cool the slab during continuous casting. The injection direction of the nozzle for injecting the cooling water is rotated in the in-plane direction of the injection surface so that the long axis direction of the injection surface to the piece is inclined, and the inclination of the injection surface in the long axis direction is There is provided a secondary cooling method for continuous casting, characterized in that the direction is alternately reversed for each row in the width direction of the pieces.

Further, the present invention provides a secondary cooling method in which cooling water is sprayed toward a slab casted by a continuous casting apparatus, and the slab during continuous casting is cooled. The injection direction of the nozzle that injects the cooling water is rotated in the in-plane direction of the injection surface so that the major axis direction of the slab is inclined in the center in the width direction of the slab. A secondary cooling method for continuous casting, characterized in that the direction is symmetrical with respect to the boundary and is inclined so that the downstream side of the injection surface faces the side of the slab.

  In the secondary cooling method of continuous casting, it is preferable that the inclination angle of the jet surface in the major axis direction is in the range of 3 ° to 30 °.

  The nozzle may be a two-fluid nozzle, and the cooling water may be an air mist obtained by mixing air with water.

  According to the present invention, by inclining the major axis direction of the injection surface, the cooling water is injected in a direction for scooping out the accumulated water at the guide roll position and drained toward the side of the slab. In other words, since the accumulated water can be removed together with the cooling water injection, the cooling unevenness in the width direction of the slab is reduced and uniformly cooled without providing a dedicated device or the like, and an excellent quality slab can be obtained. Can be manufactured.

It is a side view which shows the outline | summary of a continuous casting installation. It is a side view which shows the mode of the cooling water injection of this invention. FIG. 3 is a partially enlarged front view of FIG. 2. It is a front view which shows embodiment of this invention. It is a graph which shows the temperature distribution of slab when the cooling method of FIG. 4 is implemented. It is a front view which shows different embodiment of this invention. It is a graph which shows the temperature distribution of slab when the cooling method of FIG. 6 is implemented. It is a front view which shows the example of the conventional secondary cooling method. It is a side view which shows the mode of the cooling water injection of FIG. It is a front view which shows the example of the secondary cooling method which inclined all the injection surfaces to the same direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 shows an outline of a continuous casting facility 1 according to the present invention. Molten steel in a tundish (not shown) is poured from the upper side of the mold 2, and the slab 3 in a state where the surface is first cooled by the mold 2 and solidified is pulled out little by little from the lower side of the mold 2. Below the mold 2, the slab 3 is continuously fed out while being sandwiched between a plurality of pairs of guide rolls 4 disposed to face each other, whereby a continuous slab 3 is produced. FIG. 1 shows an example of a continuous casting facility 1. After the slab 3 is pulled out substantially vertically below the mold 2 by the guide rolls 4 on both sides of the slab 3, the slab 3 is gradually bent by about 90 ° to be horizontal. It is a fold type that moves to. The present invention is not limited to a curved-type continuous casting facility, but can be similarly applied to a vertical type or the like.

  The slab 3 is continuously sent out by the guide roll 4 while being cooled by a secondary cooling means for injecting cooling water. As shown in FIG. 2, the secondary cooling means includes a two-fluid nozzle 11 that injects air mist 12 toward the slab 3 from the gap between the guide rolls 4. Air and water are mixed in the two-fluid nozzle 11. Then, the air mist 12 is injected. The two-fluid nozzle 11 applies to a plurality of slabs 3 having a width of about 2200 mm, for example, at appropriate intervals in the width direction of the slabs 3 so as to form an injection pattern having a uniform water density distribution in the width direction of the slabs 3. 7 to 8 lines are arranged in one row in the width direction. Usually, a water amount of about 5 to 20 liters / minute is ejected per one two-fluid nozzle.

  The air mist 12 spreads in a fan shape from the injection port 21 of the two-fluid nozzle 11 and is injected, and the injection surface 22 on which the air mist 12 collides with the slab 3 has an elliptical shape. As shown in FIG. 8, when the jet direction of the two-fluid nozzle 11 is not rotated, that is, when the direction of the major axis direction of the jet surface 22 is parallel along the gap between the guide rolls 4, as shown in FIG. The drainage of the air mist 12 stays on the upper portion of the guide roll 4 that is in contact with the slab 3 to form the accumulated water 13. When the guide roll 4 is divided in the width direction of the slab 3 as shown in FIG. 8, pooled water 13 is formed at the portion where the guide roll 4 and the slab 3 are in contact with each other, but the bearing part 5 Does not collect water. As a result, temperature unevenness occurs in the width direction of the slab 3, and uniform cooling cannot be performed.

  Therefore, in the present invention, the injection direction of the two-fluid nozzle 11 is rotated in the in-plane direction of the surface of the slab 3 so that the major axis direction of the injection surface 22 of the air mist is inclined. As a result, as shown in FIG. 2, the apparent vertical width of the air mist 12 in the traveling direction (arrow direction) of the slab 3 increases, and further, as shown in FIG. Therefore, the accumulated water 13 at the upper part of the guide roll 4 can be scraped out toward the side of the slab 3.

  The rotation angle in the injection direction is set according to the vertical distance between the guide rolls 4 and the distance between the injection port 21 of the two-fluid nozzle 11 and the cast piece 3. That is, the gap in the vertical direction of the guide roll 4 is normally about 40 to 50 mm, and the air mist 12 injected from the injection port 21 of the two-fluid nozzle 11 is not blocked by the upper and lower guide rolls 4 in the slab 3. The rotation angle in the injection direction is determined within the reachable range. Specifically, the inclination angle in the major axis direction of the ejection surface 22 is in the range of 3 ° to 30 °, preferably about 10 °. If the inclination angle is too small, the jet of the air mist 12 obliquely downward toward the accumulated water 13 is not sufficient, and the effect of discharging the accumulated water 13 becomes low. On the other hand, if the tilt angle is too large, a part of the air mist 12 hits the guide roll 4 and does not reach the slab 3, so that the cooling efficiency is lowered.

  FIG. 4 is an example of an embodiment of the present invention, and the inclination of the injection surface 22 in the major axis direction is alternately reversed for each column in the width direction of the slab 3. That is, the injection surface 22a in the first row from the top in FIG. 4 is inclined in the downstream direction (downward in FIG. 4) toward the left side in FIG. 4, and the injection surface 22b in the second row from the top is in the downstream direction. Tilt to the right. The third column is the same as the first column, and the fourth column is the same as the second column. The ejection surfaces 22 arranged in the same row are inclined in the same direction, and as shown in FIG. 4, a large amount of accumulated water 13 is discharged in the direction along the direction of the ejection surface 22 in each row. And by alternately making the inclination of the injection direction reverse for every row, the water 13 is uniformly collected as a whole. The solid line in the graph of FIG. 5 shows the temperature distribution in the width direction of the slab 3 when the secondary cooling method of FIG. 4 is performed. The broken line is the temperature distribution of the slab 3 when the secondary cooling is performed by inclining all the major axis directions of the injection surface 22 in the same direction as shown in FIG. 10, and not only simply inclining the injection surface 22. In this embodiment, which is alternately reversed for each column, a uniform cooling effect can be obtained.

  FIG. 6 shows a different embodiment of the present invention, in which the inclination in the major axis direction of the injection surface 22 is opposite to each other, that is, symmetrical with respect to the center in the width direction of the slab 3. The surface 22 is inclined so that the downstream side faces the side of the slab 3. That is, in FIG. 6, the injection surface 22 is tilted so that the accumulated water 13 is scooped out from the center in the width direction of the slab 3 toward both sides in each row. The solid line in the graph of FIG. 7 shows the temperature distribution in the width direction of the slab 3 when the secondary cooling method of FIG. 6 is performed. The broken line is the temperature distribution of the slab 3 when the secondary cooling is performed by inclining all the major axis directions of the injection surface 22 in the same direction as shown in FIG. 10, and not only simply inclining the injection surface 22. In this embodiment tilted in the left-right symmetric direction, a uniform cooling effect can be obtained.

  As described above, according to the present invention, the injection direction of the two-fluid nozzle 11 is rotated in the in-plane direction of the slab 3 and the major axis direction of the injection surface 22 of the air mist 12 is tilted. Air mist 12 is jetted toward the gap between the upper portion of the guide rolls 4 and the discharge of the accumulated water 13 is promoted. Therefore, the secondary cooling unevenness caused by the accumulated water is reduced, and an excellent quality slab can be manufactured. Moreover, the two-fluid nozzle 11 conventionally used as the secondary cooling means is used without providing a new device in the space where the gap between the guide rolls 4 arranged in the traveling direction of the slab 3 is limited. Thus, the accumulated water 13 can be discharged simultaneously with the secondary cooling.

  In addition, by alternately making the inclination of the injection surface 22 reverse in every row or inclining in the left-right symmetric direction, the accumulated water of the entire slab 3 can be discharged uniformly and a uniform cooling effect can be obtained. .

  In the above-described embodiment, the guide roll 4 is divided in the width direction and the guide rolls 4 are connected to each other by the bearing portion 5 in order to ensure high rigidity that strongly restrains the slab 3. However, when carrying out the present invention, even a guide roll having a width for pressing the entire width direction of the slab 3 can exhibit the effect of discharging the accumulated water in the same manner.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a cooling method in which cooling water is ejected by a nozzle while conveying a plate-shaped conveyed product by a roll in a continuous casting machine or the like.

DESCRIPTION OF SYMBOLS 1 Continuous casting apparatus 2 Mold 3 Slab 4 Guide roll 5 Bearing part 11 Two-fluid nozzle 12 Air mist 13 Pool water 21 Injection port 22 Injection surface

Claims (4)

In the secondary cooling method of injecting cooling water toward the slab cast by the continuous casting apparatus and cooling the slab during continuous casting,
Rotating the injection direction of the nozzle for injecting the cooling water in the in-plane direction of the injection surface so that the major axis direction of the injection surface to the slab of the cooling water is inclined;
The secondary cooling method for continuous casting, wherein the inclination of the injection surface in the major axis direction is alternately reversed for each row in the width direction of the slab. In the secondary cooling method of injecting cooling water toward the slab cast by the continuous casting apparatus and cooling the slab during continuous casting,
Rotating the injection direction of the nozzle for injecting the cooling water in the in-plane direction of the injection surface so that the major axis direction of the injection surface to the slab of the cooling water is inclined;
The inclination in the major axis direction of the injection surface is a bilaterally symmetric direction with the width direction center of the slab as a boundary, and is inclined so that the downstream side of the injection surface faces the side of the slab, Secondary cooling method for continuous casting.   The secondary cooling method for continuous casting according to claim 1 or 2, wherein an inclination angle in a major axis direction of the injection surface is in a range of 3 ° to 30 °.   The secondary cooling method for continuous casting according to any one of claims 1 to 3, wherein the nozzle is a two-fluid nozzle, and the cooling water is an air mist obtained by mixing air with water.

Images