JP6350199B2 - Slab support apparatus and slab support method for continuous casting - Google Patents

Description

  The present invention relates to a slab support device and a slab support method for continuous casting having a slab support roll and a backup roll.

  In continuous casting of metals such as steel, a solidified shell is formed on the outer periphery of the molten metal supplied into the mold and is drawn at a constant speed from the lower end of the mold. Solidification proceeds while being supported by the slab support roll, solidification is completed, and the solid casting is drawn out from the continuous casting apparatus.

  As the slab having the unsolidified portion is pulled out and moved downward, the static pressure of the molten metal applied to the solidified shell increases, so that bulging that pushes the solidified shell outward occurs. In order to reduce the occurrence of bulging, it is effective to reduce the roll pitch in the casting direction, and the slab support roll is reduced in diameter to shorten the roll pitch. On the other hand, by reducing the diameter of the slab support roll, the flexural rigidity of the roll is lowered, so that there is a concern that the roll itself bends outward due to the molten metal static pressure.

  At the end of solidification during continuous casting, the molten metal, which is attracted to the crater end as the solidified shrinkage of the unsolidified metal at the center of the slab, is concentrated, may accumulate to form center segregation. The center segregation is reduced by lightly reducing the slab at the end of solidification and reducing the thickness of the slab by an amount corresponding to the solidification shrinkage of the unsolidified metal. In addition, a void called center porosity is formed at the center of the slab. The center porosity is also reduced by reducing the unsolidified portion at the end of solidification or the slab immediately after complete solidification. When the slab is rolled down by the roll, the roll is deflected by the rolling reaction force. If a large-diameter roll is used to reduce roll deflection, the roll pitch widens and causes bulging. Therefore, the slab is reduced using a small-diameter split roll.

  By providing a backup roll on the side of the slab support roll that is in contact with the slab, the deflection of the slab support roll due to the reaction force from the slab can be reduced. Patent Documents 1 to 3 disclose a slab support device having a backup roll. In any case, in order to prevent bulging of the slab, a backup roll is used for the purpose of reducing the diameter of the slab support roll and densifying the roll pitch.

  Since the slab support roll contacts the high temperature slab while rotating, it receives a large heat input and repeats heating and cooling. Usually, a cooling water channel is provided at the center of the roll, and the cooling of the roll is achieved by passing the cooling water through the cooling water channel. Patent Document 4 discloses an invention in which a mist nozzle or a spray nozzle dedicated to roll cooling is installed on a slab support roll, and water is sprayed from the nozzle to the roll. Patent Document 2 discloses an invention in which a contact point between a slab support roll (support roll) and a backup roll is a water channel for cooling the support roll.

JP 55-33817 A JP-A-10-328799 JP 11-291007 A Japanese Patent Laid-Open No. 2002-126859

  Conventionally, split rolls have been used for rolls for rolling down the slab for the purpose of improving center segregation and center porosity of the slab. In this case, the bearing of the split roll is exposed to a high temperature. Even with split rolls, the deflection of the entire roll system may not be negligible when the slab is reduced. On the other hand, it is preferable to install a backup roll behind the slab support roll (one roll). If a single roll having a small diameter is used as the slab support roll and a split roll is disposed as a backup roll behind the roll, the thermal load on the bearing of the split roll can be reduced. Further, the deflection of the entire roll system due to the reaction force of rolling can be greatly reduced.

  As described above, the slab support system having the slab support roll and the backup roll is an effective means for both reducing the diameter of the slab support roll for reducing bulging and optimizing the roll for reducing the slab. It is.

  Here, in the situation where the slab support roll rotates while in contact with the slab during casting, an angle θ is defined in the roll rotation direction around the center of rotation of the slab support roll. The slab contact position of the slab support roll is set to θ = 0 °.

  As described above, the slab support roll is usually provided with a cooling water channel at the center of the roll, and the cooling water is passed through the cooling water channel to cool the roll. When continuous casting is performed at a constant casting speed, the roll also rotates at a constant rotational speed while contacting the slab. The circumferential temperature distribution on the roll surface shows a steady temperature distribution in which the portion in contact with the slab is the hottest temperature and the temperature decreases sequentially in the roll rotation direction. Since the cooling water channel is arranged at the center, the temperature distribution in the radial direction inside the roll is a temperature distribution in which the temperature decreases as approaching the center. Since the roll temperature distribution is in a steady state, the roll bending due to thermal stress is also in a steady state, and the deflection direction of the roll does not move with time. Usually, the deflection direction of the roll due to thermal stress is oriented in the direction in which the defined angle θ is approximately 90 °.

  During continuous casting, the casting speed may decrease significantly unsteadyly. In the case where the continuous casting apparatus has a breakout prediction device, a breakout prediction signal is generated before the breakage proceeds and breaks out when a breakage due to restraint occurs in the solidified shell in the mold. At this time, in order to prevent the occurrence of breakout, the casting speed is temporarily greatly reduced to repair the broken portion of the solidified shell. In addition, there is a case where the casting speed is reduced or temporarily reduced to zero at the time of changing the type of casting during continuous casting (dissimilar steel type seam) or when changing the tundish. After that, when the casting speed returns to the steady state and the rotation speed of the roll returns to the steady rotation speed, a large deflection occurs in the roll, and a phenomenon is observed in which the direction of deflection rotates with the rotation of the roll. This phenomenon is referred to herein as “swinging”.

  In the slab support device having a backup roll behind the slab support roll, when the above-mentioned "swinging" of the slab support roll occurs, the deflection direction rotates with the rotation of the roll and the backup roll comes into contact. When the same direction is met, a large reaction force is generated between the slab support roll and the backup roll, which increases the bending moment of the body and neck of each roll and supports each roll. This increases the load on the bearing.

  A scale is generated on the surface of a high-temperature slab during continuous casting by an oxidation reaction. When the grown scale peels off, it adheres to the surface of the slab support roll. In a slab support device that has a backup roll behind the slab support roll, the scale adhering to the surface of the slab support roll bites into the contact area with the backup roll as the roll rotates, causing wear on the roll surface. Promoted, resulting in reduced roll life.

  The first object of the present invention is to reduce the load on the roll and the roll support device caused by the swing of the roll in the continuous cast slab support device having a slab support roll and a backup roll. The second object of the present invention is to prevent roll wear and roll life from being reduced due to the scale peeled from the slab.

That is, the gist of the present invention is as follows.
(1) A slab support device for continuous casting having a slab support roll in contact with a slab during continuous casting and a backup roll in contact with the slab support roll on the side opposite to the slab,
The angle θ is defined in the roll rotation direction during casting around the center of rotation of the slab support roll, and the slab contact position of the slab support roll is θ = 0 °,
A fluid injection nozzle that directly injects fluid onto the surface of the slab support roll, and a position where the fluid from the fluid injection nozzle collides with the surface of the slab support roll is within a range of θ = 0 to 180 °; Continuous casting characterized in that, among the fluids ejected from the fluid ejection nozzle, the water density of water colliding with the slab support roll surface can be 50 L / min · m ² or more per roll surface area. Slab support device.
(2) The slab support roll is a single roll in the slab width direction, and the backup roll is one or more in the slab width direction, and a part of the slab support roll in the slab width direction. The continuous casting according to (1), wherein the fluid ejected from the fluid ejecting nozzle collides with the slab support roll at least at a position where the backup roll is disposed in the slab width direction. Slab support storage.
(3) A slab support method using a slab support device for continuous casting having a slab support roll that contacts a slab during continuous casting, and a backup roll that contacts the slab support roll on the side opposite to the slab. There,
The angle θ is defined in the roll rotation direction around the slab support roll rotation center, the slab contact position of the slab support roll is θ = 0 °,
The fluid is directly sprayed on the surface of the slab support roll, and the position where the fluid collides with the surface of the slab support roll is within the range of θ = 0 to 180 °. The method for supporting a slab for continuous casting, wherein the density of the amount of water impinging on the surface is 50 L / min · m ² or more per area of the roll surface.
(4) The slab support roll is one roll in the slab width direction, and the backup roll is one or more in the slab width direction, and a part of the slab support roll in the slab width direction. The slab support for continuous casting according to the above (3), wherein the jetted fluid collides with the slab support roll at a position where the backup roll is disposed at least in the slab width direction. Method.

  The present invention relates to a slab support roll for continuous casting having a slab support roll in contact with a slab during continuous casting and a backup roll in contact with the slab support roll on the side opposite to the slab. An angle θ is defined in the roll rotation direction during casting around the center, the slab contact position of the slab support roll is set to θ = 0 °, and a fluid injection nozzle is provided to inject fluid directly onto the surface of the slab support roll. The position where the fluid from the fluid injection nozzle collides with the surface of the slab support roll is within the range of θ = 0 to 180 °, so that the load on the roll and the roll support device caused by the roll swinging Can be prevented, and roll wear and roll life reduction due to the scale peeled from the slab can be prevented.

It is a side view which shows an example of the slab support apparatus for continuous casting of this invention. It is a front view which shows an example of the slab support apparatus for continuous casting of this invention, (a) is a case where a backup roll is one roll, (b) is a case where a backup roll is a division | segmentation roll.

  The present invention will be described with reference to FIGS.

  The present invention includes a slab support roll 1 that contacts a slab during continuous casting, and a slab support device 1 for continuous casting having a backup roll 3 that contacts the slab support roll 2 on the side opposite to the slab. The slab support method used is the object. By providing the backup roll 3 on the anti-slab side of the slab support roll 2, the deflection of the slab support roll 2 due to the reaction force from the slab 10 can be reduced. Since the slab support roll 2 is densely arranged in the casting direction and the gap between the adjacent rolls is narrow, when a plurality of roll pairs having the backup roll 3 are installed adjacent to each other, the backup roll also includes the slab support roll and A roll having the same or smaller diameter will be arranged. When the backup roll width (axial length) is small, the backup roll having a diameter larger than the diameter of the slab support roll is arranged by staggering the axial arrangement position of the backup roll between adjacent rolls. It is also possible (see Patent Document 3).

  In the present invention, as described above, in the situation where the slab support roll 2 rotates while being in contact with the slab during casting, the angle θ is defined in the roll rotation direction 12 during casting with the slab support roll rotation center as the center. . The slab contact position 14 of the slab support roll 2 is set to θ = 0 °. As shown in FIG. 1, if the drawing is a horizontal portion roll and the casting direction 11 flows from the left to the right in the drawing, the slab support roll 2L on the upper side of the slab is θ = 0 ° on the lower side of the roll. Yes, since the roll rotation direction 12 is counterclockwise during casting, θ increases counterclockwise. The slab support roll 2F on the lower side of the slab has θ = 0 ° on the upper side of the roll, and since the roll rotation direction 12 is clockwise during casting, θ increases clockwise. In other words, θ = 0 to 180 ° can be said to be a surface facing the downstream side in the casting direction 11 of the slab support roll 2.

  As described above, during continuous casting, when there is a casting speed change (hereinafter referred to as “recovery of casting speed reduction”) after the casting speed is significantly reduced once, and the roll rotational speed returns to the steady rotational speed, A large deflection occurs in the roll, and a phenomenon occurs in which the direction of deflection rotates with the rotation of the roll (running around). And this invention makes it the 1st objective to reduce the load to the roll and roll support apparatus resulting from the whirling of a roll.

  When the casting speed decreases during continuous casting, and when the casting speed becomes zero, the surface of the slab support roll that is in contact with the hot slab has a temperature higher than that at the steady rotational speed. Rises. As a result of the temperature increase, roll bending due to thermal stress also increases. In the circumferential direction of the roll, the roll bending due to thermal stress is also increasing in the direction in which the temperature rises locally. That is, the roll bending direction seen from the roll rotation center coincides with the direction of the surface where the temperature has increased. After that, when the casting speed is increased to a steady speed, the roll portion whose temperature has been locally increased in contact with the slab for a long time moves with the rotation of the roll. Therefore, it moves with the rotation of the roll also in the direction in which the roll bending increases. This phenomenon has been found to be the cause of “runout” that occurs during recovery of casting speed reduction.

In order to achieve the first object, the continuous casting slab support device of the present invention has a fluid ejection nozzle 4 that directly ejects fluid onto the surface of the slab support roll, and the fluid from the fluid ejection nozzle 4 is cast into the slab. The position of collision with the surface of the support roll (fluid collision position 5) is in the range of θ = 0 to 180 °. Further, the slab support method of the present invention using the slab support device for continuous casting injects the fluid directly onto the surface of the slab support roll, and the position where the fluid collides with the surface of the slab support roll (fluid collision position 5). Is in the range of θ = 0 to 180 °. In FIG. 1, the fluid ejected from the fluid ejecting nozzle 4 faces the roll within the fluid ejecting range 6 and collides with the fluid collision position 5 on the surface of the slab support roll 2. With regard to both ends of the fluid collision position 5, the smaller θ side is described as θ ₁ , and the larger θ side is described as θ ₂ .

  When the casting speed is recovered, the temperature of the surface of the slab support roll that has been in contact with the slab when the casting speed decreases is greatly increased, and the temperature increasing portion moves with the rotation of the roll after the recovery of the casting speed. In the conventional continuous casting, since the fluid is not directly jetted and cooled in the range of θ = 0 to 180 °, the roll that has risen until the roll of the slab support device makes a half rotation. A large reaction force is applied to the backup roll when the surface temperature is not sufficiently lowered and the roll is rotated halfway and the temperature rising portion turns to the backup roll side. On the other hand, in the present invention, since the fluid is directly injected onto the surface of the slab support roll in the range of θ = 0 to 180 °, the roll surface at the position where the fluid collides is rapidly cooled and the temperature is lowered. Steady roll bending is also reduced rapidly. And since roll bending has fully reduced at the time of a half rotation of a roll after recovery of casting speed, reaction force concerning a backup roll can be reduced reliably.

If the position where the fluid collides with the slab support roll surface (fluid collision position 5) is in the range of θ = 0 to 180 °, that is, if the angles θ ₁ and θ ₂ are both in the range of 0 to 180 °, The fluid may directly collide with the roll surface at any position within this range. In the present invention, the fluid is preferably jetted directly onto the surface of the slab support roll in the range of θ = 10 to 90 °. More preferably, the fluid is directly sprayed onto the surface of the slab support roll in the range of θ = 10 to 45 °.

  In the said invention, the fluid directly injected by the slab support roll becomes object. When the fluid is ejected from the fluid ejecting nozzle, the fluid ejecting nozzle that directly ejects the fluid onto the surface of the slab support roll is a target. For example, fluid is directly ejected from a fluid ejection nozzle onto a slab, and fluid that collides with the slab and rebounds and reaches the slab support roll is excluded from the target. And the position where the fluid collides with the slab support roll surface is in the range of θ = 0 to 180 °. As long as the fluid collides in the range of θ = 0 to 180 °, there is a fluid that directly collides with the slab without preventing the fluid from directly colliding in the other range of θ = 180 to 360 °. It does not prevent you from doing.

  As a fluid that is directly sprayed onto the slab support roll, only water may be sprayed, or water and air may be sprayed and sprayed in a steam spray state.

The amount of fluid sprayed onto the slab support roll is not particularly limited. However, as the amount of fluid increases, the roll cooling effect increases, which is preferable. In the present invention, among the fluids to be jetted, the density of water that collides with the surface of the slab support roll is preferably 50 L / min · m ² or more per roll surface area, and exhibits a sufficient roll bending reduction effect. can do. More preferably, it is 100 L / min · m ² or more.

If the water density of water colliding with the slab support roll surface is 50 L / min · m ² or more, regardless of the angular range (θ ₂ −θ ₁ = Δθ) of the region where water collides in the circumferential direction of the roll, The effect of the present invention can be sufficiently exerted as a measure against swinging. However, as the nozzles to be actually used, those having a circumferential range where water collides are often used with an angle of Δθ = 5 ° or more, and further, nozzles with an angle of Δθ = 10 ° or more are used more frequently. .

  The good range of the effect of countermeasures against swinging can be defined by the amount of water. If the amount of water impinging on the surface of the slab support roll per unit time in the width direction unit length of the roll is 50 L / m · min or more, the anti-swaying effect of the present invention can be achieved. More preferably, it is 100 L / m · min or more.

  As described above, the present invention provides a continuous casting slab support device having a slab support roll and a backup roll, which prevents the roll wear and roll life from being reduced due to the scale peeled from the slab. Objective.

As described above, in the present invention, as a countermeasure against the run-out generated when the casting speed is reduced and recovered, the fluid is directly sprayed on the surface of the slab support roll, and the position where the fluid collides with the surface of the slab support roll is θ = 0 to 0. Within the range of 180 °. And it turned out that the scale adhering to the slab support roll surface can be removed as a result of injecting the fluid to the slab support roll surface in such a position. It has also been found that the scale can be removed if the density of water colliding with the surface of the slab support roll is 50 L / min · m ² or more per area of the roll surface. The scale adheres to the surface of the slab support roll at the portion (θ = 0 °) where the slab support roll is in contact with the slab. Thereafter, if the scale can be removed by colliding the fluid in the range of θ = 0 to 180 °, the scale is removed before the scale attachment position reaches the contact position with the backup roll. It is possible to prevent the scale from being pushed into the roll by the pressure between the backup rolls. It is more preferable that the water density of the water colliding with the surface of the slab support roll is 100 L / min · m ² or more.

Similar to the anti-swaying effect of the present invention, as for the scale peeling effect, the angle of the area where water collides in the circumferential direction of the roll as long as it is 50 L / min · m ² or more per roll surface area. The effect is exhibited regardless of the range (Δθ).

  The backup roll behind the slab support roll is arranged for the purpose of preventing the phenomenon that the slab support roll bends due to the reaction force from the slab even if the slab support roll has a small diameter. For this purpose, for example, when the slab support roll is a single roll, it is not necessary to press the entire axial length of the slab support roll with the backup roll. Even if only the central part in the axial direction of the slab support roll is pressed by a backup roll having a small roll width (axial length), a great effect can be exhibited. Actually, for example, as shown in FIG. 2B, the slab support roll 2 can be a single roll, and three rolls having a small roll width (axial length) can be arranged as the backup roll 3. . A portion where the backup roll 3 is not disposed in the axial direction (slab width direction) of the slab support roll is formed. In such a case, in the present invention, the fluid sprayed directly onto the surface of the slab support roll exerts an effect by colliding with the slab support roll at least at the position where the backup roll 3 is disposed in the slab width direction. (FIG. 2B). In such a case, in the width direction of the slab, since the scale is removed by the fluid injection at the portion where the slab support roll and the backup roll are in contact with each other, the second object of the present invention of preventing scale biting is sufficient. Has been achieved. In addition, although fluid is not directly sprayed on the surface of a part of the slab support roll in the slab width direction, the roll surface temperature is lowered at the part where the fluid is directly sprayed. The effect is also demonstrated.

  The present invention was applied to a vertical bending type steel slab continuous casting apparatus. The slab to be cast has a width of 1900 mm and a thickness of 300 mm. A slab support device with a backup roll as shown in FIGS. The diameter of the slab support roll and the backup roll is 250 mm, and the length of the slab support roll in the slab width direction is 2000 mm. The roll is cooled by having a hole penetrating the rotation center of the slab support roll and flowing cooling water through the hole.

As shown in FIGS. 1 and 2, a fluid ejection nozzle 4 was installed. The fluid to be ejected is water. By adjusting the installation position and the injection angle of the fluid injection nozzle 4 and the flow rate (L / min) of the water to be injected, as shown in Table 1, the injection angle θ range (θ ₁ , θ ₂ ) and the slab support roll The water density (L / min · m ² ) of water colliding with the surface was adjusted.

  A numerical calculation was performed on the occurrence of run-out that occurred when the casting speed decreased. As the casting speed fluctuation, the casting speed was lowered from the steady casting speed of 1 m / min to 0.3 m / min, two slab support rolls passed as it was, and then the casting speed was increased to 1 m / min. The heat supply from the slab to the roll, cooling by water jet from the fluid jet nozzle, and roll deformation due to thermal stress were calculated numerically, and the load from the slab support roll on the backup roll was calculated. The maximum value of the load was observed in the vicinity after the ¼ rotation of the roll from the rise of the casting speed. The maximum value of the load in “no injection” in Comparative Example 1 was normalized to 1, and the magnitude of the load in each Example was evaluated and entered in the “Backup Roll Load Ratio” column of Table 1. Further, at the time when the casting speed is rotated 90 ° from the re-increase of the casting speed, the difference between the surface temperature of the θ = 90 ° portion of the slab support roll and the surface temperature of the θ = 270 ° portion is shown as “roll temperature deviation” in Table 1. Described.

Examples 1 to 9 are examples of the present invention, and the position where the fluid collides with the surface of the slab support roll is in the range of θ = 0 to 180 °, and the water density is 50 L / min · m ² or more. As a result, in all of Examples 1 to 9, the load ratio is 0.9 or less, and the load on the backup roll is reliably reduced. In Comparative Examples 2 to 4, the fluid collision position was in the range of θ = 180 to 360 °, and the load ratio could not be reduced. In Comparative Examples 11 and 12, the water density was 10 L / min · m ^2, which was less than the preferred range, but the load on the backup roll could be reduced. However, as described later, the scale indentation evaluation results were all “x”.

  In the continuous casting apparatus, continuous casting was performed using the slab support device provided with the backup roll, and the state of scale indentation on the surface of the slab support roll was investigated when 20 charges were cast. Table 1 shows “◯” when there was no scale indentation, and “x” when there was a scale indentation.

In Examples 1 to 9, the position where the fluid collided with the surface of the slab support roll was in the range of θ = 0 to 180 °, and the scale indentation evaluation results were all “◯”. In particular, in Example 9, the fluid collision position was only in the 1 ° range of θ = 90 to 91 °, but the scale indentation evaluation result was “◯”. On the other hand, Comparative Examples 1 to 4 did not perform liquid injection, or even if it was performed, the injection range was in the range of θ = 180 to 360 °, and the scale indentation evaluation results were all “x”. In Comparative Examples 11 and 12, the water density was as low as 10 L / min · m ^2, and the scale indentation evaluation results were both “x”.

1 slab support device 2 slab support roll 2F slab support roll (lower side)
2L slab support roll (upper side)
3 Backup roll 3F Backup roll (lower side)
3L backup roll (upper side)
4 Fluid injection nozzle 5 Fluid collision position 6 Fluid injection range 10 Slab 11 Casting direction 12 Roll rotation direction 13 Slab width direction 14 Slab contact position

Claims (4)

A slab support device for continuous casting having a slab support roll in contact with a slab during continuous casting and a backup roll in contact with the slab support roll on the side opposite to the slab,
The angle θ is defined in the roll rotation direction during casting around the center of rotation of the slab support roll, and the slab contact position of the slab support roll is θ = 0 °,
A fluid injection nozzle that directly injects fluid onto the surface of the slab support roll, and a position where the fluid from the fluid injection nozzle collides with the surface of the slab support roll is within a range of θ = 0 to 180 °;
Continuous casting characterized in that, among the fluids ejected from the fluid ejection nozzle, the water density of water colliding with the slab support roll surface can be 50 L / min · m ² or more per roll surface area. Slab support device.   The slab support roll is a single roll in the slab width direction, and the backup roll is one or more in the slab width direction, and is disposed in a part of the slab support roll in the slab width direction. The slab support for continuous casting according to claim 1, wherein the fluid ejected from the fluid ejection nozzle collides with the slab support roll at a position where a backup roll is disposed at least in the slab width direction. Storehouse. A slab support method using a slab support device for continuous casting having a slab support roll in contact with a slab during continuous casting and a backup roll in contact with the slab support roll on the side opposite to the slab,
The angle θ is defined in the roll rotation direction around the slab support roll rotation center, the slab contact position of the slab support roll is θ = 0 °,
The position at which the fluid collides with the slab support roll surface and the fluid collides with the slab support roll surface is within a range of θ = 0 to 180 °,
The method for supporting a slab for continuous casting, wherein the density of water colliding with the surface of the slab support roll in the jetted fluid is 50 L / min · m ² or more per area of the roll surface.   The slab support roll is a single roll in the slab width direction, and the backup roll is one or more in the slab width direction, and is disposed in a part of the slab support roll in the slab width direction. The slab support method for continuous casting according to claim 3, wherein the fluid to be ejected collides with the slab support roll at a position where the backup roll is disposed at least in the slab width direction.

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