JP2010058161A - Machine and method for continuously casting molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machine and a method for continuously casting molten metal, which prevent adhesion of nonmetallic inclusions to the inside of a continuous casting nozzle. <P>SOLUTION: The continuous casting machine includes a sliding nozzle and a movable plate driving device 6 for driving movable plates 3. Among the portions in openings 4 of fixed plates 2, portions which are not covered with the movable plates 3, become a runner 5 through which molten metal passes. The movable plate driving device 6 oscillates the movable plates 3 in the range of ≥0.5 mm and ≤15 mm of amplitude while restraining the variations of an area S<SB>1</SB>of the runner 5 in the range of ±5%, and the oscillation frequency is in the range of ≥1/sec and ≤100/sec. The movable plates 3 preferably comprise two movable plates. By continuously casting molten metal while oscillating movable plates, adhesion of nonmetallic inclusions to the inner wall of a cylindrical inner hole of an immersion nozzle is greatly reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a continuous casting apparatus and a continuous casting method capable of preventing adhesion of non-metallic inclusions into a continuous casting nozzle in continuous casting of molten metal, particularly molten steel.

  In the continuous casting of molten metal, the molten metal that has been refined is accommodated in a ladle and further transferred to a tundish. A continuous casting nozzle is installed at the bottom of the tundish, and the molten metal in the tundish is injected into the mold via the continuous casting nozzle. The molten steel in the mold forms a solidified shell by the primary cooling by the mold, and then the solidification is promoted by the secondary cooling by the water spray from the cooling nozzle laid on the support segment installed under the mold. Manufacture pieces.

  In order to adjust the amount of molten metal to be injected through the continuous casting nozzle, the continuous casting nozzle is provided with a sliding nozzle or stopper, and the injection of molten metal is controlled by opening and closing these. In general, when a sliding nozzle is used, the controllability of the molten metal injection amount is superior to that of a stopper. Further, in the case of a continuous casting nozzle using a sliding nozzle, the continuous casting nozzle has a divided structure composed of an upper nozzle 13, a sliding nozzle 1, a lower nozzle 14, and an immersion nozzle 15, as shown in FIG. The immersion nozzle 15 has a bottomed cylindrical shape and usually has two discharge ports 17 below. Here, the inner space of the cylinder is referred to as a cylindrical inner hole 16.

Among the continuous casting nozzles, particularly non-metallic inclusions such as Al ₂ O ₃ suspended in the molten metal are likely to adhere to the portion of the immersion nozzle that is immersed in the molten metal in the mold. This is remarkable when casting Al killed steel having a high Al content. Of the inner wall of the immersion nozzle, non-metallic inclusions are likely to be deposited on the portion corresponding to the vicinity of the molten metal meniscus in the mold or near the molten metal discharge port at the tip of the immersion nozzle. If non-metallic inclusions accumulate on the inner wall of the nozzle, the flow of molten metal is hindered and casting becomes difficult. Moreover, if non-metallic inclusions adhere to the inner wall of the nozzle, the controllability of the injection amount following the fluctuation of the molten metal surface height in the mold deteriorates, and the continuous casting flux that covers the molten metal in the mold (Powder for continuous casting) is entrained in the molten metal, and a part thereof is trapped by the solidified shell of the molten metal, which may become a starting point of defects.

  Usually, an inert gas such as argon gas is blown into a continuous casting nozzle to reduce adhesion of non-metallic inclusions to the inner wall of the continuous casting nozzle. Although this reduces the adhesion of non-metallic inclusions, the effect is not sufficient, and the blown inert gas is trapped in the slab as bubbles, which may cause bubble defects.

Patent Document 1 discloses a technique for reducing the adhesion of non-metallic inclusions on the inner wall of a continuous casting nozzle by blowing the inert gas into the continuous casting nozzle while increasing or decreasing the back pressure or flow rate of the inert gas. It is disclosed. Thereby, the molten steel flow flowing down the immersion nozzle is disturbed, and the stagnation in the immersion nozzle is eliminated, so that the adhesion of Al ₂ O _{3 on} the inner wall of the immersion nozzle can be efficiently prevented.

  In Patent Document 2, a pulsed alternating current is applied to an electromagnetic coil disposed on the outer periphery of an immersion nozzle to cause pulsation in the molten metal flow flowing through the immersion nozzle, and alumina or the like is formed on the inner wall of the immersion nozzle. A continuous casting method is disclosed that prevents adhesion and growth of non-metallic inclusions, prevents clogging of the immersion nozzle, and prevents drift of molten metal in the mold.

  The sliding nozzle is usually composed of one or two fixed plates and one movable plate. Both the fixed plate and the movable plate have openings through which molten metal flows. By sliding the movable plate, the area of the overlapping portion (runner) of the opening of the fixed plate and the movable plate is adjusted, and the flow rate of the molten metal is adjusted. When the opening area of the runner is narrowed, the runner opening is located at the end of the opening of the fixed plate.

  According to Patent Document 3, when the opening area of the runner is small, the molten metal flow flowing in the immersion nozzle is deviated with respect to the center of the nozzle hole, and the discharge port flow rate of the immersion nozzle is not uniform and the flow direction is not uniform. It is said that stability and the like will be difficult to control the flow rate, and that the inclusion of non-metallic inclusions in the product will be promoted. Therefore, in this document, the movable plate in the sliding nozzle of the continuous casting nozzle is divided into two parts, the center of the runner opening formed by the opening of the fixed plate and the two movable plates, and the continuous casting nozzle. The center of the inner wall is made coincident to prevent the continuous casting nozzle and the molten metal in the mold from drifting.

JP 2007-237246 A Japanese Patent Laid-Open No. 9-277034 JP-A-5-277678

  With respect to the problem of non-metallic inclusions adhering to the molten metal flow path of the continuous casting nozzle, a sufficient effect cannot be obtained simply by blowing an inert gas into the nozzle. Moreover, since the blown inert gas is trapped in the slab as bubbles, it also causes bubble defects. The same applies to the invention described in Patent Document 1.

  If it is going to arrange | position an electromagnetic coil in the outer periphery of an immersion nozzle as described in patent document 2, a large-scale electromagnetic installation will be arrange | positioned between a tundish and a casting_mold | template, and it is not easy. Moreover, the adhesion of non-metallic inclusions to the immersion nozzle could not be sufficiently prevented only by the electromagnetic force generated by the electromagnetic coil.

  The invention described in Patent Document 3 is not intended to prevent non-metallic inclusions from adhering to the continuous casting nozzle, and, similarly to conventional nozzles, non-metallic inclusions are attached to the nozzle. Problems occur.

  An object of the present invention is to provide a molten metal continuous casting apparatus and a molten metal continuous casting method capable of preventing adhesion of non-metallic inclusions into a continuous casting nozzle.

The present invention has been made to solve the above problems, and the gist thereof is as follows.
(1) A continuous casting apparatus having a stationary plate 2 having an opening 4 having a cross-sectional area S ₀ and a sliding nozzle having a movable plate 3 that slides along the fixed plate 2. The portion of the opening 4 of the fixed plate 2 that is not covered by the movable plate 3 is a runner 5 through which molten metal passes, and the variation of the area S ₁ of the runner 5 is ± 5%. The movable plate driving device 6 oscillates the movable plate 3 within an amplitude range of 0.5 mm or more and 15 mm or less, and the oscillation frequency of the oscillation is 1 to 100 times / second. An apparatus for continuously casting molten metal, characterized in that:
(2) The movable plate 3 is composed of two movable plates, and the movable plate driving device 6 synchronizes the two movable plates while suppressing the variation of the area S ₁ of the runner 5 within a range of ± 5%. The continuous casting apparatus for molten metal according to the above (1), wherein the apparatus is rocked in the same direction within an amplitude range of 0.5 mm or more and 15 mm or less.
(3) a movable plate drive unit 6, increased to the runner area S ₁ is 1.25 times or more of the cast initial stage runner area S _10, the range of 2 times or less in the case where the passing amount i.e. throughput constant molten metal The molten metal continuous casting apparatus according to the above (1) or (2), wherein the movable plate 3 starts to swing when the molten metal is moved.
(4) A continuous casting method using a fixed plate 2 having an opening 4 having a cross-sectional area S ₀ and a sliding nozzle having a movable plate 3 that slides along the fixed plate 2. of the four, next runner 5 portion which is not covered by the movable plate 3 to pass through the molten metal, while suppressing the area S ₁ variation in the runner 5 in the range of ± 5%, the amplitude of the movable plate 3 0 .. A continuous casting method of molten metal characterized by oscillating in a range of 5 mm to 15 mm and setting the oscillation frequency to 1 to 100 times / second.
(5) The movable plate 3 is composed of two movable plates, and the amplitude of each of the two movable plates is synchronized in the same direction while suppressing the variation of the area S ₁ of the runner 5 within a range of ± 5%. The molten metal continuous casting method as described in (4) above, wherein the rocking is performed in the range of 0.5 mm or more and 15 mm or less.
(6) When the molten metal passage amount, that is, when the throughput is constant, the runner area S ₁ increases to a range of 1.25 times or more and 2 times or less of the initial runner area S _{10 at} the start of casting. The method for continuously casting molten metal according to the above (4) or (5), characterized in that swinging of the molten metal is started.

The present invention provides a continuous casting using a sliding nozzle, of the opening of the fixed plate becomes the runner that portion which is not covered by the movable plate passes the molten metal, the area S ₁ variation in the runner ± 5% For continuous casting, the movable plate is oscillated within the range of amplitude 0.5 mm or more and 15 mm or less, and the oscillation frequency is 1 to 100 times / second. Non-metallic inclusions can be prevented from sticking into the nozzle.

  When a sliding nozzle is used to adjust the flow rate of the molten metal, the continuous casting nozzle often has a divided structure composed of an upper nozzle 13, a sliding nozzle 1, a lower nozzle 14, and an immersion nozzle 15, as shown in FIG. . The immersion nozzle 15 has a bottomed cylindrical shape and usually has two discharge ports 17 below.

  A second meniscus 20 is present at a position higher than the surface of the molten metal 18 in the mold (herein referred to as “first meniscus 19”) in the cylindrical inner hole of the immersion nozzle, and the second meniscus 20 in the cylindrical inner hole. The region below is a molten metal filling region 21, and above the second meniscus 20, the molten metal that has passed through the opening of the sliding nozzle 1 falls in the cylindrical inner hole (FIG. 10 ( b)). The height of the second meniscus 20 fluctuates. When the non-metallic inclusion adhesion to the cylindrical inner hole 16 and the discharge port 17 of the immersion nozzle increases, the pressure loss during the flow of the molten metal increases, so the second meniscus rises. The inside of the cylindrical hole including the sliding nozzle portion becomes a molten metal full region 21 (FIG. 10C).

  In the sliding nozzle having one movable plate, as described above, when the opening area of the runner 5 of the sliding nozzle 1 is narrowed, the runner 5 is positioned at the end portion of the opening 4 of the fixed plate 2. It will be. When the molten metal falls from the sliding nozzle 1 to the second meniscus 20 in the cylindrical inner hole of the immersion nozzle 15 and enters the molten metal full region 21 from the second meniscus 20, the runway 5 of the sliding nozzle is It flows in at the open end (hereinafter referred to as “downstream side 22”) (FIGS. 10B and 10C). As a result, in the molten metal filling region 21 below the second meniscus in the cylindrical inner hole, the molten metal flow rate is low on the side where the molten metal flow enters (downflow side 22), whereas the molten metal flow is fast. On the opposite side (hereinafter referred to as “flowing opposite side 23”), the phenomenon that the molten metal flow rate becomes slow occurs.

  Using molten steel as the molten metal, a numerical simulation was performed on the flow state of the molten steel in the immersion nozzle of the continuous casting nozzle.

  In the conventional sliding nozzle 1 composed of the fixed plate 2 and one movable plate 3, the area of the overlapping portion (runner channel 5) of the opening of the fixed plate 2 and the movable plate 3 is adjusted. When the opening area of the runner is narrowed, the position of the runner 5 is located at the end of the opening 4 of the fixed plate. The molten steel flow flowing downward from the runner 5 descends vertically and merges with the molten metal filling region 21 at the position of the second meniscus 20. The position where the molten steel flows merge is not centered in the cylindrical inner hole 16, but is biased toward the side where the runner 5 of the sliding nozzle is opened (downstream side 22) (FIG. 10B). As a result of the numerical simulation, in the molten metal filling region 21 below the second meniscus 20, the molten steel flow velocity is high on the flow side 22 in the radial direction of the cylindrical inner hole 16, whereas the flow velocity is about 1 m / sec. It has been found that the flow rate opposite side 23 has a slow molten steel flow velocity, which is only about 0.05 m / sec.

  And when the state of inclusion attachment of the immersion nozzle used in actual continuous casting was investigated, among the inner walls of the cylindrical inner hole 16, there was little non-metallic inclusion attachment on the flow-down side 22, and on the flow-flow opposite side 23 It was found that there were many nonmetallic inclusions.

  Here, 100 kg of molten steel was prepared in a crucible using an atmospheric melting furnace, and the rotating surface was immersed in the molten steel for 30 minutes while rotating a refractory having a diameter of 10 cm at 60 rpm. As a result, adhesion of non-metallic inclusions having a thickness of 2 mm was observed on the rotating surface of the refractory immersed in the molten steel. Next, the same refractory is vibrated in the direction of the rotation axis, the frequency is 10 times / second, the amplitude is 3 mm, and the refractory is immersed in molten steel while rotating at 60 rpm in the same manner while applying vibration. It was. Then, on the rotating surface of the refractory immersed in the molten steel, the adhesion thickness of nonmetallic inclusions was less than 0.1 mm. From this, it was found that when some vibration is applied to the molten steel in contact with the refractory, the amount of non-metallic inclusions can be greatly reduced.

  Therefore, in order to apply vibration to the molten metal in the molten metal filling region 21 in the cylindrical inner hole of the immersion nozzle, the movable plate of the sliding nozzle was shaken. The swinging of the movable plate means that the movable plate is slid along the fixed plate, and a reciprocating motion is performed to reverse the sliding direction at a constant frequency and a constant amplitude. When the molten metal was continuously cast while the movable plate was swung in this manner, it became clear that non-metallic inclusion adhesion to the inner wall of the cylindrical inner hole of the immersion nozzle can be greatly reduced.

  A sliding nozzle that is normally used has one or two fixed plates 2 and one movable plate 3. In the example shown in FIGS. 1 and 2, two fixed plates (2 a and 2 b) and one movable plate 3 are provided. The swinging of the movable plate means that the movable plate 3 is moved to the position shown in FIGS. 1A and 2C (the movable plate 3 swings to the rightmost position) and FIGS. 1B and 2D. ) Position (movable plate 3 swings to the leftmost position). 1 corresponds to the swinging amplitude of the movable plate.

  In order to reduce adhesion of non-metallic inclusions to the inner wall in the cylindrical inner hole of the immersion nozzle, it is necessary to impart sufficient vibration to the molten metal in the molten metal filled region 21. It has been found that when the movable plate is swung to impart vibration to the molten metal, the non-metallic inclusion adhesion can be effectively reduced as the swirling frequency is increased. If the oscillation frequency is 1 time / second or more, the molten metal can be effectively vibrated and non-metallic inclusion adhesion can be reduced. On the other hand, if the oscillation frequency exceeds 100 times / second, the oscillation effect is saturated, so the upper limit is made 100 times / second or less. Further, the larger the swing amplitude, the more effectively non-metallic inclusion adhesion can be reduced. By swinging the movable plate with an amplitude of 0.5 mm or more, the molten metal can be vibrated effectively and non-metallic inclusion adhesion can be reduced. On the other hand, if the swing amplitude exceeds 15 mm, the swing of the molten metal becomes too large, so the upper limit of the amplitude is set to 15 mm or less.

When the runner area S ₁ fluctuates greatly when the movable plate 3 swings, the molten metal injection amount (ton / hour) from the sliding nozzle 1 fluctuates, and the molten metal level in the mold (first meniscus 19). ), And the continuous casting flux (powder for continuous casting) covering the molten metal surface in the mold is entrained in the molten metal, and part of it is captured by the solidified shell of the molten metal, which becomes the base point of the defect Therefore, it is not preferable. In order to prevent such a problem from occurring, it is preferable to keep the runner area S ₁ constant. However, if the fluctuation margin of the runner area S ₁ is within ± 5%, casting can be performed without any problem. Therefore, in the present invention, the variation of the runner area S ₁ is controlled within ± 5%. As shown in FIGS. 1 and 2, in the sliding nozzle having one movable plate, the range of the amplitude in which the movable plate can be oscillated is the runner area S before reaching the upper limit of 15 mm. It will be limited by the requirement that the fluctuation margin of ₁ is within ± 5%.

  Next, a case where a sliding nozzle having two movable plates (3a, 3b) is used as shown in FIGS. 4A is an exploded view of members constituting the sliding nozzle, and FIG. 4B is a view showing the fixed plate 2 and the opening 4. As shown in FIG. 4 (c), the opening 4 of the fixed plate 2 is partially covered by the two movable plates (3 a, 3 b), so that the uncovered portion becomes the runner 5. FIG. 6 is a diagram showing the position of the movable plate and the open / close state of the runner. 6A shows a runner fully closed state, FIG. 6B shows a runner half-open state, and FIG. 6C shows a runner fully opened state.

The position of the movable plate 3 is determined so that the portion of the opening 4 of the fixed plate 2 that is not covered by the two movable plates (3a, 3b) becomes the runner 5 through which the molten metal passes. while the area S ₁ of is held constant, and to perform the swing in conjunction with the two movable plates 3. The swinging of the movable plate means that the movable plates (3a, 3b) are moved to the positions shown in FIGS. 3 (a) and 4 (c) (the movable plate 3 swings to the rightmost position) and FIGS. This means that reciprocal movement is performed during the position (d) (the movable plate 3 swings to the leftmost position). And Aa and Ab shown in FIGS. 3 and 4 correspond to the swing amplitudes of the movable plates 3a and 3b. Since it has two movable plates, it can swing while keeping the runner area constant during swinging. Therefore, it is possible to increase the amplitude A of the movable plate to the upper limit of 15 mm while keeping the fluctuation margin of the runner area S ₁ within ± 5%, and to effectively remove non-metallic inclusions. Is possible. 3 shows the case where the second meniscus 20 is present at a position close to the height of the first meniscus 19 in the mold, whereas FIG. 5 shows that the second meniscus rises and the cylindrical inner hole of the immersion nozzle 15 The case where all 16 become the molten metal filling area | region 21 is shown.

Also, during casting, throughput of molten steel which is determined from the template sectional area and the casting speed or with the throughput M, is determined runner area S _1. Further, the runner area S ₁ changes when the throughput is kept constant due to the fluctuation of the non-metallic inclusion adhesion state in the immersion nozzle. When the opening area of the fixed plate opening 4 is S ₀ as shown in FIG. 2B and FIG. 4B, the runner area S ₁ is the cross section S of the fixed plate opening due to the large throughput. _When it is larger than 0.9 times ₀ , the flow rate of the molten metal can be kept high on the inner wall of the immersion nozzle, so that non-metallic inclusions hardly adhere to the inner wall of the immersion nozzle. In addition, when the runner area S ₁ becomes larger than 0.9 times the fixed plate opening cross-sectional area S ₀ due to adhesion of non-metallic inclusions, the effect of swinging the runner position is little. Absent. Further, when the runner area S ₁ is smaller than 0.2 times the cross-sectional area S ₀ of the fixed plate opening, the flow rate of the molten metal is kept low on the inner wall of the immersion nozzle, and the non-metallic inclusions on the inner wall of the immersion nozzle are maintained. Although there is concern about adhesion, there is no such operation mode in the first place. That is, the present invention is applied in the range where the runner area S ₁ is 0.2 to 0.9 times the cross-sectional area S ₀ of the fixed plate opening.

  The movable plate 3 of the present invention may be oscillated at all times during continuous casting, but it is more preferable that the oscillating plate 3 is oscillated only when the oscillation is necessary.

Even if the runner area S ₁ is kept constant due to adhesion of non-metallic inclusions to the inner wall of the immersion nozzle during casting, the amount of molten metal passing through the immersion nozzle, that is, the throughput M is reduced. Alternatively, in order to keep the throughput M constant, the runner area S ₁ must be increased.

In the present invention, while the amount of molten metal passing, that is, when the throughput is constant, the runner area S ₁ is less than 1.25 times the initial runner area S _{10 at} the start of casting, nonmetallic inclusions are present on the inner wall of the immersion nozzle. Since it is not adhered or slightly adhered, the movable nozzle 3 does not have to be oscillated. Throughput constant at the runner area S ₁ is 1.25 times or more of the cast initial stage runner area S ₁₀ when, in any of the 2 times or less, since the adhesion of non-metallic inclusions is considered to have progressed to some extent, It is preferable that the movable nozzle 3 is swung. At the time when the adhesion of the non-metallic inclusion has progressed to this extent, the non-metallic inclusion has adhered to the portion that was on the opposite side 23 while the movable nozzle 3 was not rocked. The molten metal in the immersion nozzle is vibrated by the swinging of the non-metallic inclusions, and the non-metallic inclusions are peeled off from the inner wall of the immersion nozzle by the vibrations, and the adhering non-metallic inclusions can be satisfactorily removed.

On the other hand, when the runner area S ₁ when the throughput is constant is expanded to more than twice the initial runner area S _{10 at} the start of casting, the non-metallic inclusions adhere to the inner wall of the immersion nozzle, and the movable plate is It is difficult to detach the non-metallic inclusion from the inner wall of the immersion nozzle even if it is swung.

Therefore, when the runner area S ₁ when the amount of molten metal passing, that is, the throughput is constant, increases to a range of 1.25 times to 2 times the initial runner area S _{10 at} the start of casting, the two movable It is better to start the rocking of the plate.

The molten metal continuous casting apparatus of the present invention has a movable plate driving device 6 for driving the movable plate regardless of whether the number of movable plates is one or two. FIG. 8 shows the case of having two movable plates. As shown in FIG. 8, the movable plate drive device 6 includes a control device 7 and a drive mechanism 8, and the drive mechanism 8 drives the movable plate 3 based on a command from the control device 7. An air cylinder or a hydraulic cylinder can be used as the drive mechanism 8. The movable plate driving device 6 performs operation control for swinging the two movable plates 3 while suppressing the fluctuation of the runner area S ₁ within ± 5%. Further, the molten metal passing amount i.e. throughput constant and runner area S ₁ when the casting start initial runner area S ₁₀ 1.25 times more, when increased to the range of 2 times or less, the two movable Control to start rocking the plate.

  In the sliding nozzle 1 applied in the present invention, the two movable plates 3 can be configured such that the two movable plates (3a, 3b) do not overlap as shown in FIGS. In this case, the runway 5 is a space formed by the gap 10 formed between the two movable plates (3a, 3b) and the opening 4 of the fixed plate. When the two movable plates come into contact with each other, the gap 10 disappears (FIG. 6A), and the runner 5 is closed.

  Moreover, as shown in FIGS. 7 and 8, the two movable plates (3a, 3b) can be configured to overlap each other. In this case, as shown in FIG. 8C, movable plate openings (11a, 11b) are provided in the two movable plates (3a, 3b), respectively. A space formed by the movable plate opening 11 of the two movable plates and the opening 4 of the fixed plate is a runner 5. FIG. 8D shows the case where the two movable plates are positioned at the right end of the swing, and FIG. 8E shows the case where the two movable plates are positioned at the left end of the swing.

  The sliding direction of the movable plate 3 may be either the thickness direction of the mold or the width direction of the mold.

  The present invention was applied when continuously casting low-carbon Al-killed steel using a steel slab continuous casting apparatus having a ladle molten steel amount of 350 tons. The continuous casting apparatus is a 2-strand slab continuous casting apparatus, and the slab thickness is 250 mm. As the continuous casting nozzle 12, a nozzle composed of an upper nozzle 13, a sliding nozzle 1, a lower nozzle 14, and an immersion nozzle 15 was used. The immersion nozzle 15 is made of a bottomed cylindrical alumina graphite refractory, has an inner diameter of 70 mm, and has two discharge ports 17 on the side of the lowermost part. No inert gas is blown into the continuous casting nozzle.

As the sliding nozzle 1, the one shown in FIGS. 1 and 2 was used when there was one movable plate, and the one shown in FIG. 7 was used when there were two movable plates. Both have two fixed plates 2. The fixed plate 2 has a circular opening 4, and the sectional area S ₀ of the opening 4 is 3850 mm ² . The movable plate driving device 6 that drives one or two movable plates 3 includes a driving mechanism 8 that uses an air cylinder and a control device 7 that controls the movement of the driving mechanism 8. The direction in which the movable plate 3 slides is the mold thickness direction.

Casting was started at the casting speed shown in Table 1, using the width shown in Table 1 as the mold width. Adjust the runner area S ₁ by the movable plate driving unit 6, to achieve a casting speed as a target. The runner area at the start of casting was defined as S ₁₀ , and the S ₁₀ / S ₀ ratio performance is shown in “Casting initial runner area ratio” in Table 1.

After starting casting, the movable plate 3 starts to swing from a predetermined timing. When having two movable plates, upon swinging the movable plate 3, the movable plate driving unit 6 drives the movable plate 3 so as to keep the runner area S ₁ constant. The fluctuation of the runner area S ₁ can be kept within ± 5%. The runway area fluctuation results are shown in “Runway area fluctuation” in Table 1. The frequency and amplitude of the movable plate swing are shown in Table 1.

A runner area S ₁ in the timing was started swinging of the movable plate 3, the ratio of runner area S ₁₀ at the start of casting (S ₁ / S ₁₀₎ shown in Table 1. In the example indicated as S ₁ / S ₁₀ = 1.0, it means that the rocking is performed from the start of casting. For the other examples, casting was performed while maintaining the casting speed constant without swinging at the start of casting. When non-metallic inclusions adhere to the continuous casting nozzle, control is performed to increase the runner area S _{1 in} order to maintain the casting speed. As a result, the swing of the movable plate was started when S ₁ / S ₁₀ reached a predetermined value (the value shown in “ratio of S ₁ and S ₁₀ at the start of swing” in Table 1).

  After the casting in the tundish was completed, the adhesion amount of non-metallic inclusions adhered in the continuous casting nozzle was evaluated. Table 1 shows the evaluation values of the adhesion thickness evaluated with the adhesion amount of Comparative Example 2 in Table 1 as 1. Moreover, the cast slab was hot-rolled and cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.9 mm, and the number of ridges (hege, sliver) per unit length of the steel sheet was evaluated. Table 1 shows the evaluation values obtained by evaluating the number of wrinkles in Comparative Example 2 in Table 1 as 1.

For Examples 1 to 11 in Table 1, the movable nozzle started to swing from the start of casting. Examples 1 to 10 are cases where there are two movable plates, and the runner area variation, oscillation frequency, and oscillation amplitude are all within the scope of the present invention, and good quality can be obtained. In Example 10, the fluctuation of the runner area S ₁ during rocking was intentionally increased to ± 5% which is the upper limit of the present invention, but the quality evaluation result was good. Example 11 is an example of the present invention having one movable plate.

In Examples 12 to 19, the movable nozzle is not oscillated at the start of casting, non-metallic inclusion adheres to the continuous casting nozzle, the runner area S ₁ increases, and S ₁ / S ₁₀ After reaching a predetermined value, the movable nozzle started to swing. S ₁ / S ₁₀ at the start of swinging was changed to 1.18, 1.25, 2, and 2.5. Although the quality evaluation decreases as S ₁ / S ₁₀ at the start of oscillation increases, the quality evaluation is “good but slightly inferior” if S ₁ / S ₁₀ is in the range of 1.25 to 2. It is a good range. In addition, the effect of not starting oscillation from the start of casting can reduce wear due to oscillation of the movable plate 3 and eliminates the need to always guarantee precise control of the movable plate drive device 6. I was able to get it.

In Comparative Example 1, since the mold width was wide and the casting speed was high, the casting initial runner area ratio S ₁₀ / S ₀ was as large as 0.95, which was outside the scope of the present invention. Since the flow rate of molten steel in the continuous casting nozzle was high from the beginning of casting, the quality evaluation result was good despite no rocking.

In Comparative Example 2, although the casting initial runner area ratio S ₁₀ / S ₀ was 0.5 and was within the scope of the present invention, no swinging was performed. As a result, both the non-metallic inclusion adhesion in the continuous casting nozzle and the failure occurrence rate in the cold-rolled steel sheet were the worst results.

In Comparative Example 3, although the movable nozzle was oscillated, the control of the movable nozzle driving device was intentionally changed to increase the variation of the runner area S ₁ during oscillation to ± 7%. As a result, the incidence of rejection in cold-rolled steel sheets increased. As the runner area S ₁ fluctuates greatly, the flow rate of molten steel discharged from the nozzle for continuous casting fluctuates, which fluctuates the surface position of the molten steel in the mold, inducing powder entrainment and increasing non-metallic inclusions in the slab It is estimated that

  In Comparative Example 4, the oscillation frequency was less than the lower limit of the present invention, and the quality was slightly inferior. In Comparative Examples 5 and 6, the oscillation frequency exceeded the upper limit of the present invention, and although the quality was good, it was saturated. In Comparative Example 7, the vibration amplitude was less than the lower limit of the present invention, and the quality was slightly inferior. In Comparative Examples 8 and 9, the oscillation amplitude exceeded the upper limit of the present invention, and although the quality was good, it was saturated.

It is a fragmentary sectional view showing one form of the present invention, and (a) shows the case where a runner is located in the rocking right end, and (b) shows the case where the runner is located in the rocking left end. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic explaining this invention, (a) is a disassembled sectional view of the nozzle for continuous casting, (b) is a figure explaining a fixed nozzle, (c) is a runner swinging right end, (d) is hot water. The case where the road is located at the left end of the swing is shown. It is a fragmentary sectional view showing one form of the present invention, and (a) shows the case where a runner is located in the rocking right end, and (b) shows the case where the runner is located in the rocking left end. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic explaining this invention, (a) is a disassembled sectional view of the nozzle for continuous casting, (b) is a figure explaining a fixed nozzle, (c) is a runner swinging right end, (d) is hot water. The case where the road is located at the left end of the swing is shown. It is a fragmentary sectional view showing one form of the present invention, and (a) shows the case where a runner is located in the rocking right end, and (b) shows the case where the runner is located in the rocking left end. It is a fragmentary sectional view showing one form of the present invention, (a) shows a runner fully closed state, (b) shows a runner half-opened state, and (c) shows a runner fully opened state. It is a fragmentary sectional view showing one form of the present invention, and (a) shows the case where a runner is located in the rocking right end, and (b) shows the case where the runner is located in the rocking left end. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic explaining this invention, (a) is a disassembled sectional view of the nozzle for continuous casting, (b) is a figure explaining a fixed nozzle, (c) is a figure explaining a movable plate, (d) is hot water. The road is at the right end of the swing, and (e) shows the case where the runner is at the left end of the swing. It is sectional drawing of the nozzle for continuous casting of this invention. It is a fragmentary sectional view showing the conventional nozzle for continuous casting, (a) shows a runner fully closed state, and (b) and (c) show a runner half open state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sliding nozzle 2 Fixed plate 3 Movable plate 4 Opening part 5 Runway 6 Movable plate drive device 7 Control apparatus 8 Drive mechanism 9 Tundish 10 Gap 11 Movable plate opening part 12 Continuous casting nozzle 13 Upper nozzle 14 Lower nozzle 15 Immersion nozzle 16 Cylinder inner hole 17 Discharge port 18 Molten metal 19 in mold 1st meniscus 20 2nd meniscus 21 Molten metal filling area 22 Flowing side 23 Flowing opposite side A Swing amplitude

Claims (6)

A fixed plate having an opening cross-sectional area S _0, a continuous casting apparatus having a sliding nozzle having a movable plate to slide along the fixed plate, has a movable plate driving device for driving the movable plate, fixed among the openings of the plate becomes a runner that portion which is not covered by the movable plate passes the molten metal, while suppressing the area S ₁ variation of the runner within the range of ± 5%, the movable plate driving device Is a continuous casting apparatus for molten metal, wherein the movable plate is swung within a range of amplitude of 0.5 mm or more and 15 mm or less, and the vibration frequency is 1 to 100 times / second. The movable plate is composed of two movable plates, and the movable plate driving device synchronizes the two movable plates in the same direction while suppressing the variation of the runner area S ₁ within a range of ± 5%. The molten metal continuous casting apparatus according to claim 1, wherein the apparatus continuously swings within an amplitude range of 0.5 mm to 15 mm. The movable plate driving device is configured such that when the molten metal passage amount, that is, the throughput is constant, the runner area S ₁ increases to a range of 1.25 times or more and 2 times or less the casting start initial runner area S _10. 3. The molten metal continuous casting apparatus according to claim 1, wherein the movable plate starts to swing. A fixed plate having an opening cross-sectional area S _0, a continuous casting method using a sliding nozzle having a movable plate to slide along the fixed plate, out of the openings of the fixed plate, is covered by movable plate becomes runner which portions not pass the molten metal, the while suppressing runner area S ₁ varies within the range of ± 5%, to oscillate the movable plate in the following range of amplitude 0.5 mm 15 mm, A continuous casting method of molten metal, wherein the oscillation frequency is 1 to 100 times / second. The movable plate is composed of two movable plates, and the fluctuation of the area S _{1 of the} runner is suppressed within a range of ± 5%, and the two movable plates are synchronized in the same direction in the same direction with an amplitude of 0.5 mm. 5. The molten metal continuous casting method according to claim 4, wherein the rocking is performed within a range of 15 mm or less. When the molten metal passage amount, that is, the runner area S ₁ when the throughput is constant, increases to a range of 1.25 times to 2 times the initial runner area S _{10 at} the start of casting, the movable plate is swung. 6. The molten metal continuous casting method according to claim 4, wherein the method is started.

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