JP6135616B2 - Uniform cooling casting method and continuous casting equipment for continuous cast slab in width direction - Google Patents

Description

  The present invention relates to a method for continuously cooling a continuous casting slab in the width direction and a continuous casting equipment, and more particularly, continuous casting capable of uniformly cooling a long side surface of a continuous casting slab during continuous casting of steel. The present invention relates to a method for uniformly cooling casting in the width direction of a slab and continuous casting equipment.

  In a vertical bending type continuous casting machine or a curved type continuous casting machine, a support roll that is a primary cooling means, for example, sandwiching a continuous cast slab drawn from a water-cooled mold, is spaced in the traveling direction of the continuous cast slab. A plurality of the nozzles are arranged and a spray nozzle or the like is disposed between the support rolls as secondary cooling means for cooling the continuous cast slab. In the continuous casting method of steel using such a vertical bending type continuous casting machine or a curved type continuous casting machine, the continuous cast slab drawn out from the mold is not completely solidified and has an unsolidified part inside. ing. For this reason, there exists a possibility that what is called a bulging deformation | transformation which deform | transforms so that a continuous cast slab may swell with the static pressure of molten steel may generate | occur | produce.

  As a means for suppressing this bulging deformation, a structure in which the above-described static pressure is reliably received by the support roll by narrowing the interval between the support rolls has been proposed. However, in order to reduce the roll interval, it is necessary to reduce the roll diameter of the support roll, and the roll length becomes relatively long with respect to the roll diameter, and the rigidity of the support roll cannot be secured. was there. For this reason, as shown, for example in patent document 1, as a support roll which supports the long side surface of a continuous casting slab, the continuous casting machine using the division | segmentation roll divided | segmented in the width direction (long side direction) of the continuous casting slab Has been proposed. By making the support roll into split rolls, the roll length is shortened, and the rigidity of the support roll can be secured even if the roll diameter is reduced.

  By the way, as described in Patent Document 1, when the split roll is used, a part of the secondary cooling water sprayed toward the continuous cast slab passes through the split portion of the split roll and hangs down. It becomes dripping water. Since the cooling capacity is greatly increased in the dripping water portion, there is a possibility that the temperature varies in the width direction of the continuous cast slab. In recent years, as described in Patent Document 2 in order to solve this problem, the division positions (bearing portions) of the division rolls are arranged so as to be shifted from each other in the width direction of the slab (so-called staggered arrangement). It has been proposed.

  Further, a space having a wedge-shaped cross section surrounded by the periphery of the roll and the surface of the slab is present immediately above the contact portion between the roll and the slab. The cooling water sprayed from the nozzle to the surface of the slab flows down along the surface of the slab, and then stays in the space for a while to become accumulated water. Even in this pooled water portion, the cooling capacity is greatly increased, and thus there is a risk of temperature variations in the width direction of the slab.

  When such temperature variation occurs, the final solidification position differs in the width direction, and the center segregation is deteriorated.

  In order to solve these problems of dripping water and accumulated water, a roll (hereinafter referred to as a slit roll) in which a slit for passing water is provided on the peripheral surface of the support roll as seen in Patent Document 3 has also been proposed. Yes. According to this, by letting the accumulated water on the roll flow from the water flow slit provided on the peripheral surface of the roll, not only the generation of the accumulated water is suppressed, but also the dripping that has been concentrated on the divided part of the divided roll in the past. Water can be dispersed throughout the roll, and local supercooling can also be suppressed.

Japanese Patent Laid-Open No. 08-290251 International Publication 2013 / 073593A1 Japanese Utility Model Publication No. 62-169750

  However, the vertical bending type continuous casting machine or the curved type continuous casting machine has a straightening band that bends the bent continuous casting slab. After this straightening band, dripping water stays on the upper surface of the slab. By doing so, the temperature variation in the width direction becomes more remarkable, and the deterioration of the above-mentioned center segregation becomes remarkable. In other words, simply dispersing the dripping water on the slab with the water flow slit has the problem that the dripping water cannot be removed in time and the amount of retained water increases, and a method of positively removing the dripping water from the slab is expected. ing.

  The present invention has been made in view of the above-described situation, and even in the case of using a vertical bending type continuous casting machine or a curved type continuous casting machine having a split roll, It is an object of the present invention to provide a continuous casting technology for steel that can suppress temperature variation and can produce a high-quality continuous cast slab by reducing residual water after the straightening band. .

In the present invention, the rotation of the support roll by drawing the slab so that the angle θ with respect to the casting direction is in the range of 45 ° or more and 90 ° or less on the support roll peripheral surface sandwiching the continuous cast slab in continuous casting of steel. Accordingly, as the spiral progresses in support rolls to central or et ends direction, when at least one of the spiral slit is provided, and providing a spiral slit into a plurality of support rolls, said plurality of By providing slits so that all the spiral slits of the support roll advance in the direction of both ends from the center of the support roll, and discharging the secondary cooling water on the continuous cast slab out of the short side machine, It has been solved.

  Here, the slit can be provided symmetrically with respect to the center in the width direction of the continuous cast slab.

  The width w of the slit can be in the range of 5 to 10 mm.

  Further, the depth d of the slit can be in the range of 2 to 5 mm.

  Further, the pitch L of the slits can be in the range of 10 to 50 mm.

The present invention also provides a curved band for bending a continuous cast slab having a rectangular cross-section drawn from a continuous casting mold, a correction band for bending back the curved continuous cast slab, and the continuous cast slab. A support roll that supports the long side surfaces of the continuous cast slabs arranged at intervals in the drawing direction, and a cooling fluid is ejected from between the support rolls toward the long side surfaces of the continuous cast slabs. A continuous casting facility provided with a secondary cooling means, wherein the support roll is rotated on the peripheral surface of the support roll so that an angle θ with respect to the casting direction is in a range of 45 ° or more and 90 ° or less and slab drawing is performed. Accordingly, as the spiral progresses in support rolls to central or al both ends, at least one spiral slit is provided, and the plurality of support rolls when spiral slits are provided The all plurality of support rolls spiral slits slit is provided so as spiral from the support roll center to both ends direction progresses, to discharge the secondary coolant on the strip cast continuously cast into shorter sides outside The present invention provides a continuous casting facility characterized by being configured as described above.

  In the conventional continuous casting method, when the support roll supporting the long side surface of the continuous cast slab is a split roll, a part of the cooling water ejected from the secondary cooling means is separated from the split part of the split roll. It drips and becomes dripping water. Here, by discharging the accumulated water on the roll to the short side of the continuous cast slab using the support roll according to the present invention, not only the retained water on the roll is suppressed, but also from the divided portion of the divided roll. Generation | occurrence | production of dripping water can also be suppressed and generation | occurrence | production of the temperature dispersion | variation in the width direction of a continuous cast slab can be suppressed.

  Further, after the straightening zone, temperature variation occurs in the width direction of the continuous cast slab due to the cooling water remaining on the upper surface of the continuous cast slab. Here, by draining the drooping water on the upstream side to the short side of the continuous cast slab by the support roll according to the present invention, the residual water on the upper surface of the slab can be reduced, The temperature variation in the width direction is eliminated. Therefore, temperature variation in the width direction of the continuous cast slab can be suppressed in all secondary cooling zones in the continuous casting machine, and a high quality continuous cast slab can be produced.

  According to the present invention, even when a vertical bending type continuous casting machine or a curved type continuous casting machine having a split roll is used, the accumulated water on the roll, drooping water from the roll split portion, continuous after the straightening band Steel continuous casting technology that can suppress the temperature variation in the width direction of the continuous cast slab due to residual water on the upper surface of the cast slab and can produce high quality continuous cast slab without vertical cracks Can be provided. In addition, by suppressing temperature variations in the slab width direction according to the present invention, it is possible to flatten the crater end (final solidification) position in the width direction and produce high-quality continuous cast slabs with less center segregation. Steel continuous casting technology can be provided.

Sectional drawing which shows an example of the vertical bending type continuous casting machine to which this invention is applied A perspective view showing an example of a conventional support roll group Cross-sectional view for explaining the problem The perspective view which shows the support roll shape which concerns on this invention, and the conceptual diagram which shows the definition of each variable of a slit The figure which shows the effect of this invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the content described in the following embodiment and an Example. In addition, the constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in the so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined or may be appropriately selected and used.

  First, the continuous casting equipment 1 which implements the continuous casting method of steel which is this embodiment is demonstrated.

  As shown in FIG. 1, the continuous casting equipment 1 includes a water-cooled mold 4 as a primary cooling means, and a support roll group 2 including a plurality of support rolls 7 positioned below the water-cooled mold 4. And a vertical band 11 for pulling downward a continuous cast slab (also simply referred to as a slab) 9 produced from the water-cooled mold 4, a curved band 12 for bending the continuous cast slab 9, and a curved continuous cast casting. The vertical bending type continuous casting machine has a straightening band 13 for bending the piece 9 back and a horizontal band 14 for conveying the continuous casting cast piece 9 in the horizontal direction.

  In the figure, 3 is an immersion nozzle for injecting molten steel into the water-cooled mold 4, 5 is an unsolidified portion inside the continuous cast slab 9, and 6 is a solidified shell formed on the surface of the continuous cast slab 9. Reference numeral 10 denotes, for example, a gas cutter for connecting the hardened continuous cast slab 9 to a predetermined length.

  The water-cooled mold 4 has a cylindrical shape having a rectangular hole, and a continuous cast slab 9 having a cross section matching the shape of the rectangular hole is produced. For example, the long side length of the rectangular hole (corresponding to the width of the continuous cast slab 9) is 700 to 2300 mm, and the short side length of the rectangular hole (corresponding to the thickness of the continuous cast slab 9) is 220 to 300. In this embodiment, the long side length is about 2100 mm and the short side length is about 250 mm.

  The water-cooled mold 4 is provided with a primary cooling means for cooling the molten steel in the rectangular hole.

  The support roll group 2 is bent with a pinch roll unit 11a positioned in a vertical band 11 that pulls the continuous cast slab 9 downward, and a bending roll unit 12a positioned in a curved band 12 that curves the continuous cast slab 9. The straightening roll unit 13a located in the straightening band 13 that bends the continuous cast slab 9 back, and the horizontal roll unit 14a located in the horizontal band 14 that conveys the continuous cast slab 9 in the horizontal direction are provided.

  Here, the support roll 7 of the support roll group 2 extends in the width direction of the continuous cast slab 9 and is configured to support the long side surface of the continuous cast slab 9.

  And the support roll 7 is set as the division | segmentation roll divided | segmented into 2 or more in the width direction of the continuous cast slab 9, as shown in FIG. More specifically, the support roll 7 has a roll main body 15 that is brought into contact with the long side surface of the continuous cast slab 9 and a smaller diameter than the roll main body 15 so as to be separated from the long side surface of the continuous cast slab 9. The intermediate bearing portion 16 is provided, and is divided in the longitudinal direction by the intermediate bearing portion 16.

  As shown in FIG. 2, such support rolls 7 have a position of the intermediate bearing portion 16 (position in the width direction of the continuous cast slab 9) between the support rolls 7 adjacent to each other in the traveling direction of the continuous cast slab 9. Arranged so as not to overlap.

  Here, between the support rolls 7 arranged at intervals in the traveling direction of the continuous cast slab 9, a spray nozzle 8 that jets cooling water to the long side surface of the continuous cast slab 9 is disposed. Has been. The cooling water ejected from the spray nozzle 8 flows along the long side surface of the continuous cast slab 9, but at the portion where the roll body 15 is in contact, as shown in FIG. The flow of the cooling water is stopped by the roll body portion 15 and becomes so-called accumulated water W1.

  On the other hand, in the portion where the intermediate bearing portion 16 having a diameter smaller than that of the roll body portion 15 is located, it flows along the long side surface of the continuous cast slab 9 as shown in FIG. W2.

  In the continuous casting equipment 1 having such a configuration, molten steel is injected into the water-cooled mold 4 through the immersion nozzle 3 inserted into the water-cooled mold 4, and this molten steel is the cold-cooled mold 4 as a primary cooling means. As a result of cooling from the surroundings, the solidified shell 6 grows and the continuous cast slab 9 is pulled out from below the water-cooled mold 4. At this time, the unsolidified portion 5 exists inside the continuous cast slab 9.

  The continuous cast slab 9 is pulled downward by the pinch roll unit 11a in the support roll group 2 and is bent by the bending roll unit 12a. And it is bent back by the correction | amendment roll unit 13a, and is conveyed in a horizontal direction by the horizontal roll unit 14a.

  At this time, cooling water is sprayed from the spray nozzle 8 provided as a secondary cooling means provided between the support rolls 7 toward the continuous cast slab 9, and the continuous cast slab 9 is cooled to further grow the solidified shell 6. I will do it.

  The continuous cast slab 9 is completely solidified in the horizontal belt 14 where the continuous cast slab 9 is pulled out in the horizontal direction, and is cut into product sizes by the gas cutter 10.

  Here, in the present invention, the width w is 5 to 10 mm, the depth d is 2 to 5 mm, as shown in FIG. 4 (including a conceptual diagram showing the definition of each variable of the slit) on the peripheral surface of the support roll 7. One in which one or a plurality of spiral slits 7a are symmetric in the center in the width direction of the slab so that the pitch L is 10 to 50 mm and the angle θ is in the range of 45 ° to 90 °. The accumulated water W1 on the roll is discharged to the short side of the continuous cast slab 9 by the rotation at the time of drawing the continuous cast slab. Here, the width w is set to a range of 5 to 10 mm, the depth d is set to 2 to 5 mm, and the pitch L is set to a range of 10 to 50 mm. Therefore, the cooling water does not flow into the groove but remains on the roll and remains as water W1, and the volume ratio of the groove portion is too large under condition 3, so that the cooling water is forced to be discharged from the slab. This is because it became clear that the cooling water could not be discharged outside the machine. The reason why the angle θ is set to 45 ° or more is that when the angle θ is less than 45 °, it is clear that the cooling water cannot be discharged outside the machine because the force in the direction of discharging from the slab does not work sufficiently. The reason why the angle is 90 ° or less is that if it is more than 90 °, the cooling water conversely collects in the center.

The “presence / absence of temperature unevenness” in Table 1 is defined as “temperature unevenness” when the variation index D calculated by the following equation (1) is 5% or more.
Variation index D = (dispersion of measured temperature) / (average temperature in the width direction) × 100 [%] (1)

  According to the steel continuous casting method of the present embodiment configured as described above, the secondary cooling water is discharged to the short side of the continuous casting slab by the support roll 7, and the accumulated water W1. It is possible to suppress the occurrence of temperature variation in the width direction of the continuous cast slab 9 due to the drooping water W2 and the residual water on the upper surface of the continuous cast slab, and it is possible to produce a high quality continuous cast slab 9 Become.

  As mentioned above, although the continuous casting method of steel which is one Embodiment of this invention was demonstrated, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.

  For example, although it demonstrated as a continuous casting method of steel using a vertical bending type continuous casting machine, it is not limited to this, You may use a curved type continuous casting machine.

  In addition, as illustrated in FIG. 4, it has been described as having a split roll divided by one intermediate bearing portion 16. However, the present invention is not limited to this, and the split roll is divided by two or more intermediate bearing portions. Or a non-divided roll. The slit arrangement may not be symmetrical with respect to the center of the continuous casting slab 9 in the width direction. The cross-sectional shape of the groove is not limited to a rectangle.

  Here, the result of the confirmation experiment carried out to confirm the effect of the present invention will be described.

  Casting was carried out using a vertical bending type continuous casting machine under the conditions shown in Table 2.

  The width of the continuous cast slab was 2100 mm and the thickness was 250 mm. The casting speed was 1.1 to 2.0 m / min.

  In the embodiment, a support roll having a width w = 5 mm, a depth d = 2 mm, a pitch L = 10 mm, and an angle θ = 45 ° of the slit 7a was used.

The conditions common to the conventional examples of Tables 1 and 2 and the examples of the present invention are as follows.
Support roll diameter: 230-270 mm
Body length: 2400mm
Number of divisions in the width direction: 2
Position in the drawing direction where the support rolls are installed in the continuous casting machine: A total of 60 are installed at positions 3 to 20 m from the meniscus (support rolls supporting the upper surface side of the slab are applicable)
Secondary cooling water conditions within the support roll installation range: specific water volume 1.3 L / kg

  An infrared radiometer was installed at 19.7 m from the meniscus to measure the surface temperature on the upper surface side of the slab in the slab width direction, and the surface temperature was measured. The surface temperature of the obtained continuous cast slab was measured at a plurality of points in the width direction (220 points at 10 mm intervals). An example of the measurement result is shown in FIG. And the dispersion | variation index D shown by (1) Formula was computed. The results are shown in Table 2. The “conventional example” in Table 2 is a support roll having no groove on the surface of the support roll as in the present invention and divided into two in the slab width direction. The support roll as shown in FIG. It is.

  In the example of the present invention, it is confirmed that the temperature variation in the width direction of the continuous cast slab is suppressed as compared with the conventional example. From this, according to the example of the present invention, it was confirmed that it was possible to reduce the temperature variation in the width direction of the produced continuous cast slab.

  For low carbon steel, the central segregation degree of continuous cast slabs was investigated. The center segregation degree is a surface average Mn obtained by analyzing the range of 10 mm × 10 mm of the cross section perpendicular to the slab drawing direction, which is surrounded by ± 5 mm from the width direction center to the width direction and ± 5 mm from the thickness center to the thickness direction. When the concentration is the numerator and half of the ladle amount of the molten steel charge is poured into the tundish, the sample taken from the molten steel in the tundish is a ratio using the Mn concentration obtained by spark emission analysis as the denominator. Asked.

  Table 2 shows the results. The center segregation degree at a casting speed of 1.1 m / min is marked as 1. From this, according to the example of the present invention, it was confirmed that the center segregation of the produced continuous cast slab can be reduced.

Furthermore, for medium carbon steel, we investigated the rate of occurrence of vertical cracks in continuous cast slabs. The rate of occurrence of vertical cracks is based on the results of cleaning surface flaws of thick plate products caused by vertical cracks in slabs by inspecting the surface of thick plates after rolling.
Longitudinal crack occurrence rate = Number of plate products that have been subjected to maintenance of vertical cracks for the relevant charge
÷ Number of plate products with appropriate charge (2)
As sought.

  Table 2 shows the results. From this, it was confirmed that according to the example of the present invention, it is possible to produce a continuous cast slab without vertical cracks.

DESCRIPTION OF SYMBOLS 1 ... Continuous casting equipment 2 ... Support roll group 3 ... Submerged nozzle 4 ... Water cooling mold 5 ... Unsolidified part 6 ... Solidified shell 7 ... Support roll 7a ... Slit 8 ... Spray nozzle 9 ... Continuous cast slab 10 ... Gas cutter 11 ... Vertical band 11a ... Pinch roll unit 12 ... Curved band 12a ... Bending roll unit 13 ... Straightening band 13a ... Straightening roll unit 14 ... Horizontal band 14a ... Horizontal roll unit 15 ... Roll main body part 16 ... Intermediate bearing part W1 ... Accumulated water W2 ... Dripping water

Claims (10)

In the continuous casting of steel, the support roll is sandwiched between the continuous rolls so that the angle θ with respect to the casting direction is in the range of 45 ° or more and 90 ° or less, and the support roll is rotated by drawing the cast slab. as spiral Chuo or we both end directions progresses, provided with at least one helical slit, and the case of providing a spiral slit to a plurality of support rolls, spirals of the plurality of support rolls Of the continuous cast slab characterized by providing a slit so that the spiral of all the slits advances from the center of the support roll toward both ends, and discharging the secondary cooling water on the continuous cast slab to the outside of the short side machine Uniform cooling casting method in the width direction.   The method of claim 1, wherein the slit is provided symmetrically with respect to the center in the width direction of the continuous cast slab.   The widthwise uniform cooling casting method for continuous cast slabs according to claim 1 or 2, wherein a width w of the slit is in a range of 5 to 10 mm.   The width direction uniform cooling casting method of the continuous casting slab according to any one of claims 1 to 3, wherein a depth d of the slit is in a range of 2 to 5 mm.   The width direction uniform cooling casting method of the continuous casting slab according to any one of claims 1 to 4, wherein the slit pitch L is in a range of 10 to 50 mm. A curved band that curves the continuous cast slab having a rectangular cross-section drawn from the continuous casting mold,
A straightening band that bends back the curved continuous cast slab, and
A support roll for supporting a long side surface of the continuous cast slab arranged at intervals in the drawing direction of the continuous cast slab, and
A continuous casting facility comprising secondary cooling means for ejecting a cooling fluid from between the support rolls toward the long side surface of the continuous cast slab,
The support roll circumferential surface, so that the angle θ is in the range of 45 ° to 90 ° with respect to the casting direction, and the rotation of the support roll caused by the slab withdrawal, helix progresses in support rolls to central or al both ends, So that at least one spiral slit is provided,
And when a spiral slit is provided in a plurality of support rolls, the slits are provided so that all the spiral slits of the plurality of support rolls advance in the direction of both ends from the center of the support roll,
A continuous casting facility characterized in that the secondary cooling water on the continuous cast slab is discharged outside the short side machine.   The continuous casting equipment according to claim 6, wherein the slit is provided symmetrically with respect to the center in the width direction of the continuous cast slab.   The continuous casting equipment according to claim 6 or 7, wherein a width w of the slit is in a range of 5 to 10 mm.   The continuous casting equipment according to any one of claims 6 to 8, wherein a depth d of the slit is in a range of 2 to 5 mm.   The continuous casting equipment according to any one of claims 6 to 9, wherein a pitch L of the slit is in a range of 10 to 50 mm.