JP4289182B2 - Tundish injection tube - Google Patents

Description

  The present invention relates to an injection pipe used when pouring molten metal from a ladle into a tundish that is an intermediate container in continuous casting of molten metal, and more specifically, a swirl flow is formed in the molten metal flowing down in the injection pipe. By this, it is related with the injection pipe which can clean a molten metal simply and effectively.

  In the case where molten metal is poured from a ladle through a tundish, which is an intermediate container, into a mold to produce a slab, a typical method for pouring molten metal from a ladle into the tundish is a system that uses a long nozzle and There is a method using an injection tube.

  FIG. 10 is a schematic cross-sectional view showing a situation in which molten metal is poured from a ladle into a tundish using a long nozzle and continuous casting is performed. As shown in the figure, the method using the long nozzle is that a literally long and slender long nozzle 62 is attached to the bottom of the pan 6, and the tip of the nozzle is immersed in the molten metal 72 in the tundish 4. In this method, the molten metal 71 is supplied.

  FIG. 11 is a schematic cross-sectional view showing a situation in which molten metal is poured from a ladle into a tundish using a tundish injection pipe and continuous casting is performed. As shown in the figure, in the method using the injection tube, the cylindrical injection tube 1 having a relatively large diameter is immersed in the molten metal 72 in the tundish 4 in the tundish lid 5. The bottom of the ladle 6 is brought into close contact with the upper end of the injection pipe 1 through a seal structure, and the inside of the injection pipe 1 is filled with an inert gas 8 such as Ar, so that the molten metal from the short ladle nozzle 61 is filled. In this method, the falling flow 7 is poured so as to strike the molten metal in the injection pipe.

  Compared to the method using a long nozzle, the method using an injection tube involves an inert gas in the atmosphere when the falling flow from the ladle is struck against the molten metal surface, and an inert gas such as Ar Is considered to be advantageous for cleaning the molten metal because it forms an upward flow while capturing non-metallic inclusions in the molten metal. However, no attempt has been made to further enhance the function of cleaning the molten metal.

  The present invention promotes the mixing of the inert gas and the molten metal by forming a swirl flow in the molten metal in the injection tube, thereby facilitating the trapping of the nonmetallic inclusions in the molten metal by the inert gas. It is intended to highly clean molten metal.

  The installation of a swirl flow forming mechanism in the molten metal transfer nozzle is known, for example, as disclosed in Patent Document 1. Patent Document 1 discloses a molten steel transfer nozzle that prevents intrusion of air from a peripheral portion of a sliding nozzle, which is provided with a twisted tape-like component for imparting swirl to the molten steel flow in the nozzle. ing. However, in the pouring from the ladle to the tundish, the provision of the swirl flow forming mechanism in the nozzle has the following problems.

The first problem is that it becomes difficult to discharge packed sand mainly composed of, for example, SiO ₂ component in the nozzle on the ladle. Filled sand is filled in the upper nozzle above the nozzle at the bottom of the ladle so that the molten metal in the ladle flows out without solidifying in the upper nozzle. A part of the stuffed sand is sintered into a lump by receiving the heat of the molten metal. When the swirl flow forming mechanism is provided in the nozzle having a small inner diameter, there is a high possibility that the massive sintered sand is clogged in the nozzle.

  The second problem is that the flow resistance of the molten metal increases due to the installation of the swirl flow forming mechanism, and the flow rate of the molten metal from the ladle decreases. In particular, at the end of casting when the pressure head (static pressure) of the molten metal in the ladle is lowered, there is a possibility that a necessary flow rate of the molten metal cannot be secured. Thus, installing the swirl flow forming mechanism in the nozzle attached to the bottom of the ladle involves the risk of hindering stable casting operations.

  These problems described above can be solved by arranging a mechanism for imparting a swirling flow to the molten metal inside the tundish injection pipe as in the present invention. That is, in the present invention, by providing a swirl flow forming mechanism in the injection pipe having a relatively large inner diameter as compared with the nozzle, it is possible to secure a flow path for easily passing even massive sintered sand. became. Also, the energy required for swirling is not from the pressure head in the ladle, but from the ladle nozzle to the hot water surface in the injection pipe, or from the difference in height between the hot water surface in the injection pipe and the hot water surface in the tundish. Therefore, the influence of the increase in flow resistance due to the presence of the swirl flow formation mechanism on the flow rate of molten metal from the ladle can be eliminated.

  As a method of mixing the molten metal and the inert gas using the swirling flow in the tundish, there are the following apparatuses and methods.

  Patent Document 2 is a tundish having a hot water receiving part for molten steel, a hot water supply part for supplying the received molten steel into the mold, and a flow path connecting the hot water receiving part and the hot water supply part, An electromagnetic force generator that applies a rotational force for turning molten steel to the outer periphery of the flow path and a tundish in which a gas blowing port is disposed at a predetermined position of the flow path are disclosed. Further, in Patent Document 3, the same tundish as disclosed in Patent Document 2 is used, and the axial cross-sectional average of the molten steel obtained from the maximum turning speed of the molten steel in the flow passage and the flow speed of the molten steel is obtained. A continuous casting method is disclosed in which casting is performed so that the speed satisfies a predetermined relationship.

  However, since these techniques require a dedicated tundish with a complicated shape, the operation becomes complicated, and it is not easy to increase productivity, and further, the burden of equipment cost increases.

  As described above, in order to impart a swirling flow to the molten metal by a simple method and to effectively clean the molten metal at a low equipment cost, there still remains a problem that must be solved. ing.

JP-A-11-90593 (Claims and paragraph [0005])

JP 2002-205154 A (claims and paragraph [0008]) JP 2003-80351 A (Claims and paragraph [0009])

  As described above, the conventional pouring technique for tundish has the following problems. That is, (1) If a swirl flow forming mechanism is provided in the nozzle between the ladle and the tundish, it will be difficult to discharge the packed sand in the nozzle on the sintered ladle, and it will melt due to an increase in flow resistance. The metal discharge rate also decreases. (2) If a swirl flow forming mechanism is provided in the tundish, the equipment cost increases and the operation becomes complicated.

  The present invention has been made in view of the above-mentioned problems, and the problem is that a swirl force is applied to the molten metal flowing down the tundish injection pipe to form a swirl flow, thereby effectively and effectively. An object of the present invention is to provide an injection tube capable of cleaning molten metal.

  In order to solve the above-mentioned problems, the present inventor, based on the conventional problems, forms a swirling flow by applying a swirling force to the molten metal, and non-metallic inclusions in the bubbles gathered at the center of the swirling flow The present invention was completed by studying a tundish injection tube capable of trapping and purifying an object and obtaining the following findings (a) to (f).

  (A) A swirl flow forming mechanism for forming a swirl flow inside the injection pipe is provided, and further, the inner diameter of the lower outlet portion of the injection pipe is reduced, so that it is stable without being affected by the molten metal head in the ladle. Strong swirl flow. This is because the flow rate of the molten metal in the circumferential direction increases at the lower outlet of the injection tube due to the law of conservation of angular momentum.

(B) In the injection pipe of the above (a), there is no clogging of clogged sand sintered body mainly composed of SiO ₂ of the ladle nozzle and clogging with solidified metal, and the injection pipe is easy. Therefore, it is appropriate that the inner diameter of the main body of the injection tube be in the range of 200 mm to 1500 mm. In addition, the inner diameter of the lower outlet portion of the injection tube is obtained from the viewpoint of obtaining a uniform swirling flow of the molten metal and facilitating the capture of nonmetallic inclusions by gas bubbles by increasing the circumferential flow velocity. It is appropriate to set it to 1/2 or less of the inner diameter of the main body.

(C) The length in the injection tube axial direction of the lower outlet portion of the injection tube of (a) is sufficient to ensure sufficient time for bubbles to collect at the center of the injection tube and capture non-metallic inclusions. It shall be the 100mm or more.

(D) When an inert gas is blown between the swirling flow forming mechanism of (a) and the lower end of the lower outlet portion of the injection tube, more inert gas bubbles are formed to capture nonmetallic inclusions. you promote.

(E) Blowing the inert gas of (d) above is an inner wall portion of the lower outlet portion having an inner diameter of 1/2 or less of the inner diameter of the injection tube main body portion, at a position separated by 100 mm or more from the lower end of the outlet portion. Doing the gas blowing section disposed circumferentially continuous, is stable reverse conical bubble film formation, capture of non-metallic inclusions Ru is further promoted.

  (F) When the inner diameter of the lower end portion of the lower outlet portion of the injection tube is increased from the inside of the injection tube toward the lower end of the outlet, the swirling molten metal flow flows out while spreading in the tube diameter direction of the injection tube by centrifugal force. Therefore, after flowing out from the injection tube, it is easy to form an upward flow in the tundish. Therefore, the floating separation of bubbles and non-metallic inclusions entrained in the molten metal is promoted.

The present invention has been completed based on the above findings, and the gist thereof resides in the tundish injection tube shown in the following (1) and (2) .

(1) A tundish injection pipe used for pouring water into a tundish, which is an intermediate container between a ladle and a mold, the injection pipe having an atmosphere adjustment in a space formed by its inner wall and molten metal The inert gas is used in a state of being blown at a blowing rate of 200 NL / min to 1300 NL / min, and a swirling flow is generated by applying a swirling force to the molten metal flowing down in the pouring tube. A swirl flow forming mechanism made of a refractory for forming is disposed, and the swirl flow forming mechanism is disposed at a position lower than the molten metal surface in the injection pipe, and the swirl flow forming mechanism is disposed at a lower outlet portion of the injection pipe. Between the lower end, an inert gas blowing portion for blowing an inert gas into the flowing molten metal is continuously arranged in the circumferential direction on the inner wall portion of the lower outlet portion of the injection pipe, and the inert gas From the blowing part Length to the lower end of the lower outlet portion of the pipe is not less 100mm or more, the amount of blowing inert gas from the inert gas blowing unit is 2NL / min~100NL / min, the inner diameter of the body portion of the infusion pipe is 200 mm to 1500 mm, the length of the lower outlet portion of the injection tube in the injection tube axial direction is from 100 mm to 1000 mm upward from the lower end of the lower outlet portion, and the inner diameter of the lower outlet portion is 60 mm or more An injection tube for tundish (hereinafter referred to as “first invention”), characterized in that it is ½ or less of the inner diameter of the main body of the injection tube.

( 2 ) In the tundish injection tube according to (1 ), the inner diameter of the lower end portion of the lower outlet portion of the injection tube is expanding toward the lower end of the outlet (hereinafter referred to as “first” 2 ) ".

  In the present invention, the “swirl flow forming mechanism” means a mechanism that forms a swirl flow in the molten metal by applying a swirl force in the circumferential direction to the molten metal flowing down in the tundish injection pipe. As described later.

  The “main part of the injection tube” means a main part having a sufficiently large inner diameter of the injection tube, for example, a part A in FIGS.

  The “inner diameter of the main body portion of the injection tube” means the inner diameter (D1) of the main body portion of the injection tube.

  The “lower outlet part” means an outlet part located at the lower part of the injection tube main body part, for example, a part B in FIGS.

  In addition, the “inner diameter of the lower outlet portion” means the inner diameter (D2) of the portion where the inner diameter is most reduced in the lower outlet portion.

  The injection tube for tundish according to the present invention includes a swirl flow forming mechanism that forms a swirl flow by applying a swirl force to the molten metal flowing down the injection tube, and regulates the inner diameter of the injection tube main body within an appropriate range. Further, by reducing the inner diameter of the lower outlet portion, it is possible to obtain a stable strong swirling flow while capturing and removing non-metallic inclusions, and to clean the molten metal effectively, even though it is a simple apparatus.

  As described above, the present invention is a tundish injection pipe used for pouring from a ladle to a tundish, and the space formed by the inner wall of the injection pipe and the molten metal has an amount within a predetermined range. A swirl flow forming mechanism is arranged at a position lower than the molten metal surface inside the injection pipe to form a swirl flow in the molten metal flowing down in the injection pipe. This is a tundish injection tube in which the inner diameter of the main body, the length of the lower outlet portion of the injection tube in the axial direction of the injection tube, and the inner diameter range of the lower outlet portion are respectively defined.

  The present inventor provides a mechanism for forming a swirling flow inside a cylindrical injection tube used for pouring from a ladle to a tundish in continuous casting, and further reducing the inner diameter of the lower outlet part, It was found that a stable strong swirling flow that is not affected by the molten metal head in the ladle can be obtained at the lower outlet of the injection tube.

In the molten metal in the injection tube, an inert gas, which is an atmospheric gas in the injection tube in which a falling flow from the ladle is entrained, is suspended in a number of bubbles. By swirling the molten metal containing the bubbles of the inert gas, the bubbles having a small density and a small centrifugal force gather at the center of the swirling flow. The bubbles gathered at the center of the swirling flow in this way capture non-metallic inclusions such as Al ₂ O ₃ while swirling. Since these bubbles flow out from the injection tube and then float in the tundish together with the trapped nonmetallic inclusions, the molten metal is effectively cleaned as compared with the case where no swirl flow is formed.

  FIG. 1 is a schematic cross-sectional view showing a situation in which molten metal is poured from a ladle into a tundish using the injection tube for tundish according to the present invention and continuous casting is performed. In the figure, the molten metal 71 in the ladle 6 is injected into the tundish 4 as a molten metal injection flow 7 through a ladle nozzle 61 attached to the bottom of the ladle 6. The molten metal 72 injected into the tundish 4 is further injected into the mold 11 via the immersion nozzle 10 attached to the bottom of the tundish, and is drawn down and solidified while being cooled to form a metal casting. It becomes a piece 12.

  The molten metal injection flow 7 entrains the inert gas 8 blown for adjusting the atmosphere in the injection tube in the injection tube main body indicated by A in FIG. Many bubbles are suspended. This molten metal injection flow is given a flow velocity component in the circumferential direction in the injection pipe while passing through the swirl flow forming mechanism 2 arranged in the injection pipe main body A, and flows down while forming a swirl flow. The molten metal injection flow 7 further flows down to the injection tube lower outlet portion indicated by B in the figure, whose inner diameter is reduced to ½ or less of the inner diameter of the main body portion. Is further accelerated to form a strong swirling flow.

  As a result of the formation of the swirling flow in this way, the bubbles accumulated at the center of the swirling flow according to the centrifugal force action capture non-metallic inclusions and flow out from the lower end of the lower outlet portion to the tundish. To go. Then, the bubbles that have captured these non-metallic inclusions float on the molten metal bath surface in the tundish, so that the non-metallic inclusions are separated from the molten metal body, and the molten metal is cleaned. The reason why the present invention is limited to the above range and the preferable range will be described below.

1) Inner diameter of injection tube When the inner diameter of the injection tube main body A (D1 in FIG. 1) is less than 200 mm, the ladle-packed sand sintered product is likely to clog the swirl flow forming mechanism 2 and the solidified ground. Blocking with gold is also likely to occur. On the other hand, when the inner diameter of the injection tube main body A is larger than 1500 mm, the injection tube 1 becomes enormous and the handling becomes difficult and the refractory cost also increases. Therefore, the inner diameter range of the injection tube main body A is set to 200 mm to 1500 mm. In addition, the preferable range of the internal diameter of the injection pipe main-body part A is 300 mm-1000 mm.

  The inner diameter (D2 in FIG. 1) of the lower outlet B of the injection tube obtains a uniform swirling flow and increases the circumferential flow velocity of the swirling flow, and thus the swirling angular velocity, according to the law of conservation of angular momentum. From the viewpoint of increasing the collision frequency between the non-metallic inclusions and the inert gas bubbles, the smaller the inner diameter of the main body portion A, the better. In order to form a sufficiently uniform swirling flow in the molten metal and to obtain a sufficient trapping effect of non-metallic inclusions by the inert gas, the inner diameter of the lower outlet portion B of the injection tube is set to 1 of the inner diameter of the injection tube main body A. It is necessary to reduce it to less than / 2. Therefore, the inner diameter of the lower outlet portion B of the injection tube is set to ½ or less of the inner diameter of the injection tube main body A.

  Note that if the inner diameter of the lower outlet portion B of the injection tube is significantly reduced compared to the inner diameter of the main body portion A, the necessary head increases according to the strength of the swirling flow to be obtained. Depending on the specifications of the casting machine, that is, the size of the head formed in the injection tube and the flow rate (throughput) of the molten metal per unit time, the reduction degree of the inner diameter is limited. For example, if an injection tube with a significantly reduced inner diameter of the lower outlet is used under a condition with a high throughput, a strong swirl flow can be obtained, but a large head (depending on the strength of the swirl flow (angular kinetic energy)) ( Therefore, when the height from the surface level in the tundish to the upper end of the injection pipe is not sufficient, the molten metal may overflow from the upper end of the injection pipe.

  Further, when the inner diameter after reduction is less than 60 mm, there is a high possibility that the molten metal is blocked at the lower outlet portion B of the injection tube. Therefore, the inner diameter of the lower outlet portion B is preferably 60 mm or more. A more preferable range of the inner diameter of the lower outlet portion B is 100 mm or more.

2) In the first invention wherein the length of the injection tube, the length of the injection tube bottom outlet B (L2 in FIG. 1), and 100mm or more in the axial direction of the tube from the lower end of the injection tube bottom outlet. In the inner diameter reduced portion of the lower outlet portion of the injection tube, the action of centrifugal force has a strong action of gathering bubbles in the center of the swirl motion while capturing the inclusions. In this case, if the length in the tube axis direction of the lower outlet portion of the injection tube is short, the time margin for the bubbles to sufficiently collect at the center is reduced, and the effect of capturing non-metallic inclusions is not sufficiently exerted. . Therefore, the length of the lower outlet portion of the injection tube in the tube axis direction is set to 100 mm or more.

Incidentally, good preferable length of the injection tube bottom outlet is 150mm or more. Further, even if the length of the lower outlet portion of the injection tube is increased to 1000 mm or more, the effect of capturing non-metallic inclusions is saturated with respect to an increase in equipment cost, and the handling of the equipment becomes difficult. Therefore, the length of the lower outlet section shall be the following 1000 mm.

  Next, a preferable range of the total length of the injection tube (L1 in FIG. 1) will be described. The total length of the injection tube is limited within a certain range depending on the bath depth of the tundish, the distance from the tundish lid 5 to the tundish inner hot water surface, or the distance from the bottom of the ladle to the injection tube lid, but from 600 mm to Generally, the range is about 1700 mm. In the present invention, since the swirl flow forming mechanism is disposed in the injection tube, the total length of the injection tube is preferably in the range of 800 mm to 1700 mm.

3) Swirling flow forming mechanism As the swirling flow forming mechanism, for example, as disclosed in Patent Document 2 and Patent Document 3 described above, there is a method using a rotating magnetic field. However, the method using the electromagnetic force is not an effective means in the present invention because it requires a large facility and a high facility cost.

  Therefore, as the swirl flow forming mechanism in the present invention, as described in detail in the embodiment, a structure made of a refractory is arranged inside the injection pipe, and a molten metal head (potential energy) is used to make the molten metal. It is appropriate to apply a swirling force to form a swirling flow.

Also, the installation position of the swirling flow forming mechanism, placed lower location than the water surface of the injection tube. Then, it is possible to prevent troubles due to the solid metal solidified metal adhering to the swirl flow forming mechanism and growing upward, and the impact caused by the molten metal falling flow from the ladle nozzle. This is because damage and melting damage can be reduced.

  Here, the difference between the molten metal surface level in the injection tube and the molten metal surface level in the tundish depends on the flow resistance of the molten metal in the injection tube, the angular kinetic energy of the swirling flow, and the molten metal throughput. It is determined. Therefore, experimentally grasp the influence of the structure of the swirl flow formation mechanism, the reduction ratio of the inner diameter of the lower part of the injection pipe and the throughput on the difference in the molten metal level between the injection pipe and the tundish. Thus, the level of the molten metal surface in the injection pipe can be predicted, and the preferred installation position of the swirl flow forming mechanism can be determined.

4) Position and amount of inert gas blown into the injection pipe As shown in FIG. 1, the inert gas 8 is blown into the injection pipe for adjusting the atmosphere, so that the molten metal in the injection pipe is injected. Inert gas 8 bubbles entrained during the flow down are included. In addition to this, if the inert gas 9 is blown between the swirl flow forming mechanism and the lower end of the lower outlet portion, more inert gas bubbles are contained in the molten metal. The molten metal can be cleaned by trapping with gas bubbles. For this purpose, for example, the inert gas is introduced to a predetermined height position of the injection pipe by the inert gas introduction flow path 13 provided in the pipe wall of the injection pipe, and blown into the injection pipe from the inert gas blowing section 3. That's fine. Therefore, the first invention is an injection tube provided with an inert gas blowing portion between the swirl flow forming mechanism and the lower end of the lower outlet portion.

For a period from the swirling flow mechanism 2 as a position for blowing inert gas 9 to the lower end of the lower outlet section B for the following reason.

  That is, when an inert gas is blown from the injection tube main body A having a large inner diameter and a low flow rate of the molten metal in the injection tube, most of the injected inert gas 9 is heated in the injection tube in a short time. Since it floats to the level, it is difficult to be entrained as an inert gas bubble in the molten metal, and therefore, it is difficult to obtain an effect of suspending a large amount of the inert gas in the molten metal. On the other hand, between the swirl flow forming mechanism 2 and the lower end of the injection tube lower outlet portion B, for example, as shown in FIG. When the active gas blowing portion 3 is provided and the inert gas 9 is blown, the flow rate of the molten metal is relatively large. Therefore, the effect of drawing the bubbles into the swirling flow and accumulating it at the center of the swirling flow by the action of centrifugal force is great. The blown inert gas 9 is efficiently entrained in the molten metal, suspended and non-metallic inclusions. It is because it is easy to capture.

Incidentally, blowing of the inert gas shall be the following ranges. That is, blowing of the inert gas 8 for atmosphere adjustment of the injection tube is in the range of 200NL / min~1300NL / min. If the blowing amount is less than 200 NL / min, the atmosphere is likely to be mixed into the injection pipe, and non-metallic inclusions are likely to increase due to atmospheric oxidation. On the other hand, if the blowing amount exceeds 1300 NL / min, excessive inertness is caused. This is because the use of gas causes an increase in metal casting costs.

Further, blowing amount of the inert gas 9 blown from a position between the swirling flow forming mechanism to the lower end of the lower outlet section, the range of 2NL / min~100NL / min. If the blowing rate is less than 2 NL / min, the amount of bubbles is small and the effect of capturing non-metallic inclusions is not sufficient. On the other hand, if the blowing rate exceeds 100 NL / min, the amount of bubbles becomes excessive and the flow of molten metal This is because the molten metal scatters due to an increase in resistance and rising bubbles in the tundish.

5) Blowing of inert gas from the blowing section continuously arranged in the circumferential direction and the blowing position FIG. 7 shows a ring-shaped arrangement continuously arranged in the circumferential direction on the inner wall of the lower outlet portion of the injection pipe It is the schematic for demonstrating formation of the bubble film | membrane at the time of blowing inactive gas from the blowing part. As shown in the figure, when a ring-shaped blowing portion 31 is arranged in the circumferential direction on the inner wall portion of the lower outlet portion B of the tundish injection pipe 1 and the inert gas 9 is blown from the blowing portion, the blowing is blown. The bubbles of inert gas are drawn into the center of the swirl flow while drawing a spiral trajectory as shown by the solid line, broken line, alternate long and short dash line, and dot line in the figure. It moves to form an inverted conical bubble film 14.

When the inert gas is blown in this way, the conical bubble film is stably formed if the length from the inert gas blowing portion to the lower end of the lower portion of the injection tube is 100 mm or more. This conical cell membrane has a filter action to trap non-metallic inclusions in the molten metal, and the molten metal is effectively cleaned. Therefore, in the first invention, the inert gas blowing portion is arranged circumferentially on the inner wall portion of the lower outlet portion of the injection tube, and the length from the inert gas blowing portion to the lower end of the lower outlet portion of the injection tube is The injection tube was 100 mm or more.

  The length (L4) of the ring-shaped blowing portion in the injection tube axial direction is not particularly defined. The ring-shaped blowing portion may be constituted by, for example, a thin ring-shaped porous refractory having a thickness of about 10 mm in the tube axis direction, or a thick ring-shaped porous refractory having a thickness of about 100 mm in the tube axis direction. May be. Alternatively, a plurality of ring-shaped refractories of about 20 mm in the tube axis direction may be arranged in the tube axis direction with an interval of about 50 mm. Furthermore, it can replace with these porous refractories, and can also use the refractory which has many through-holes about 0.2 mm-1 mm in diameter.

6) In the first shot bright injection tube in the form of injection tube bottom outlet, when the inner diameter of the lower end portion 101 of the lower outlet section to expand toward the outlet lower end, molten metal stream swirling motion centrifugal force As a result, the gas flows out while spreading in the radial direction of the injection tube, so that it is easy to form an upward flow in the tundish after flowing out from the injection tube. Therefore, floating separation of bubbles and non-metallic inclusions entrained in the molten metal is promoted. Further, it is difficult for stagnation and vortex to occur in the flow around the lower end of the outlet, and adhesion of non-metallic inclusions is also suppressed. Therefore, the second invention is an injection tube in which the inner diameter of the lower end portion 101 of the lower outlet portion of the injection tube expands toward the lower end of the outlet portion.

  The enlarged shape of the inner diameter may be a shape that linearly expands, or may be a rounded shape in which the cut surface of the lower end portion 101 in the injection tube axial direction has a radius of curvature (R). However, it may have a parabolic shape, or may have any shape (progressively enlarged shape) in which straight lines are combined to approximate a trumpet shape. Among these shapes, the most preferable shape is a trumpet shape in which the inner diameter changes in a parabolic shape and the rate of change (increase rate) gradually increases toward the lower end of the outlet portion. The reason why such a shape is preferable is that the flow of molten metal flowing out from the injection tube is difficult to peel off from the inner wall of the outlet of the injection tube, and the flow is less likely to stagnate or vortex, thereby further suppressing the adhesion of non-metallic inclusions. Because it is done.

  Moreover, when the cut surface in the injection tube axial direction has a shape with a rounded curvature radius (R), the size of the curvature radius (R) is preferably about 40 mm to 120 mm. If the value of R is less than 40 mm, the inner diameter of the outlet end portion expands rapidly, and the flow of the molten metal flowing out from the injection tube is easily separated from the end wall surface of the injection tube outlet portion. On the other hand, if the value of R exceeds 120 mm, the thickness of the refractory at the outlet end becomes thin, and the strength of the outlet end decreases, which is not preferable.

7) Sealing between injection pipe and ladle lower part A preferable sealing method between the upper part of the injection pipe and the lower part of the ladle for maintaining the atmosphere in the injection pipe will be described.

FIG. 8 is a schematic diagram showing a longitudinal section in the vicinity of the seal member between the upper portion of the injection tube and the lower portion of the ladle. For example, a hole having a thickness of about 100 mm and a diameter of about 550 mm and a diameter of about 150 mm through which the ladle nozzle 61 passes in the center is formed in the lower part of the sliding gate hardware 20 that is a flow rate adjusting mechanism installed at the lower part of the ladle 6. And a sealing member 24 in which the periphery, side surfaces and upper surface of the Al ₂ O ₃ —SiO ₂ porous refractory 23 are covered with an iron plate 22. The gap between the central hole and the ladle nozzle 61 is filled with Al ₂ O ₃ —SiO ₂ cotton refractory 25 and sealed, and the lower surface is made of Al ₂ O ₃ —SiO ₂ cotton refractory. It is preferable to closely contact the upper surface of the injection tube 1 through the cushion material 26.

  The tundish injection pipe of the present invention will be described in more detail with reference to examples, and the results of a casting test conducted to confirm the effect of the tundish injection pipe of the present invention will also be described.

Example 1
First, an embodiment of a tundish injection tube will be described. FIG. 1 is a longitudinal section showing a situation where molten metal is poured from a ladle into a tundish using the injection tube for tundish according to the present invention that satisfies the conditions specified in the present invention, as described above, and continuous casting is performed. It is the schematic of a surface.

  An example of the dimensions of the injection tube (hereinafter referred to as “infusion tube of injection tube number 1”) in FIG. The inner diameter (D1) of the main body portion A of the injection tube is 480 mm, the inner diameter (D2) of the lower outlet portion of the injection tube is 120 mm, the total length (L1) of the injection tube is 1350 mm, and the length (L2) of the lower outlet portion B of the injection tube is 350 mm, and the length (L3) from the lower end of the lower outlet portion of the injection tube to the inert gas blowing portion is 250 mm. The inert gas blowing portion 3 is composed of a ring-shaped porous refractory blowing portion embedded in the inner wall of the lower portion of the injection tube, and the length (L4) in the injection tube axial direction is 25 mm. Furthermore, the shape of the lower end portion of the injection tube outlet portion is a shape in which the cut surface in the injection tube axial direction of the lower end portion has a roundness with a radius of curvature (R) of 90 mm and expands toward the lower end of the outlet portion. .

The wall thickness (t) of the injection tube 1 is 35 mm, the portion 800 mm from the upper part is made of Al ₂ O ₃ —C refractory, the lower part is made of MgO—C refractory, and the porosity of the gas blowing portion is lower than 800 mm. The refractory is composed of Al ₂ O ₃ —C refractory. The swirl flow forming mechanism 2 is made of an Al ₂ O ₃ —C refractory having a thickness of 40 mm.

  FIG. 2 is an outline of a longitudinal section showing a situation in which molten metal is poured from a ladle into a tundish using a tundish injection pipe of another example of the present invention that satisfies the conditions specified in the present invention, and continuous casting is performed. FIG. The main points of the injection tube (hereinafter referred to as “injection tube of injection tube number 2”) different from the injection tube of injection tube number 1 are as follows.

  That is, in the injection pipe of the injection pipe number 1 shown in FIG. 1, a swirl flow forming mechanism shown in FIG. 4 to be described later is installed as a swirl flow forming mechanism, and the blowing portion 3 of the inert gas 9 into the injection pipe is provided. Is provided at the lower outlet portion B of the injection tube whose diameter is reduced, and the inner diameter of the lower end portion 101 of the lower outlet portion of the injection tube is rounded with a constant radius of curvature (R) toward the lower end of the outlet. Is expanding. On the other hand, a swirl flow forming mechanism shown in FIG. 5 described later is installed in the injection tube of the injection tube number 2 shown in FIG. 2, and the blowing portion 3 of the inert gas 9 is connected to the swirl flow forming mechanism 2. They are different from each other in that they are provided in the lower injection tube main body portion A and the lower end portion 101 of the lower injection tube outlet portion is rapidly expanded. Further, the injection tube of the injection tube number 2 is composed of two parts: an upper injection tube 102 located above the tundish lid 5 and a lower injection tube 103 located below.

  An example of the dimensions of the injection tube with the injection tube number 2 is as follows. The inner diameter (D1) of the main body A of the injection tube is 600 mm, the inner diameter (D2) of the lower injection tube outlet is 200 mm, the total length (L1) of the injection tube is 1500 mm, and the length (L2) of the lower injection tube outlet B is (L2). 300 mm, and the length (L3) from the lower end of the lower outlet portion of the injection tube to the inert gas blowing portion is 500 mm. The inert gas blowing portion 3 is composed of six porous plugs (cylindrical porous refractories) embedded in the inner wall of the injection tube main body A in the circumferential direction.

The injection tube of the injection tube number 2 has a lower injection tube 103 made of Al ₂ O ₃ —C refractory with a thickness (t) of 30 mm, and a porous plug of the inert gas blowing portion 3 made of Al ₂ O ₃ —C refractory. The upper injection tube 102 is made of a MgO refractory having a thickness of 30 mm and having an outer peripheral portion covered with an iron plate. The swirl flow forming mechanism 2 is made of an Al ₂ O ₃ —C refractory having a thickness of 30 mm.

FIG. 3 is a schematic vertical cross-sectional view showing a situation in which molten metal is poured from a ladle into a tundish using a tundish injection pipe according to a reference example of the present invention and continuous casting is performed. Injection tube shown in FIG. (Hereinafter referred to as "injection tube of the injection tube No. 3"), as a swirling flow forming mechanism, but the swirling flow forming mechanism shown in FIG. 6 described later Ru is installed, defined in the present invention There is no blowing portion of the inert gas 9 into the injection tube, and only the inert gas 8 for maintaining the atmosphere in the injection tube is blown. Further, the inner diameter of the lower end portion 101 of the lower outlet portion of the injection tube is linearly expanded toward the lower end of the outlet.

  An example of the dimensions of the injection tube with the injection tube number 3 is shown below. The inner diameter (D1) of the main body portion A of the injection tube is 540 mm, the inner diameter (D2) of the lower outlet portion of the injection tube is 100 mm, the total length (L1) of the injection tube is 1500 mm, and the length (L2) of the lower outlet portion B of the injection tube is 380 mm. The shape of the lower end portion of the outlet portion is such that the cut surface in the injection tube axis direction of the lower end portion linearly expands with an opening angle (θ) on one side of 30 degrees with respect to the tube axis.

The injection tube of injection tube number 3 is made of a lower injection tube 103 made of MgO-C refractory having a thickness (t) of 30 mm, and an upper injection tube 102 made of high alumina refractory having a thickness of 30 mm whose outer periphery is covered with an iron plate. and swirling flow forming mechanism 2, the wall thickness is constituted by Al ₂ O ₃ -C refractory material 25Mm～60mm.

  On the other hand, FIG. 11 is a schematic diagram showing a situation in which molten metal is poured from a ladle into a tundish using a conventional tundish injection pipe as a comparative example, and has already been described. The injection tube shown in the figure (hereinafter referred to as “infusion tube of injection tube number 4”) is composed of an upper injection tube 102 and a lower injection tube 103, and the inner diameter (D1) of the injection tube is 400 mm. The total length (L1) is 1000 mm. The atmosphere adjusting inert gas 8 is blown in, but the inert gas 9 is not blown in.

  The injection tube of the above injection tube number 4 has a lower injection tube 103 made of MgO-C refractory having a thickness of 30 mm, and the upper injection tube 102 is made of a high alumina material having a wall thickness of 30 mm covered with an iron plate. It is composed of refractories.

As described above, the injection pipes of the injection pipe numbers 1 and 2 are both the injection pipes of the present invention that satisfy the conditions specified in the first invention, and the injection pipe of the comparative example in which the swirling flow of the molten metal cannot be obtained. Compared with the case of using the injection tube of No. 4, the effect of capturing and separating non-metallic inclusions by obtaining a stable and strong swirling flow is excellent.

Injection tube of the injection tube number 1, have a ring-shaped inert gas blowing unit, also has a shape expanding along with the rounded inner diameter of the lower end 101 of the outlet portion has a constant radius of curvature, the 2 Since the conditions specified in the invention are also satisfied, it has an extremely excellent effect of levitating and separating non-metallic inclusions and cleaning molten metal.

In addition, since the injection tube of injection tube number 3 does not have an inert gas blowing portion, it is a reference example of the present invention. The effect of trapping non-metallic inclusions by the bubble film is the injection tube of injection tube numbers 1 and 2. Compared with the injection pipe of the injection pipe number 4 which is a comparative example, it has a high cleaning effect of non-metallic inclusions.

The injection tube of injection tube number 3 has a shape in which the inner diameter of the lower end portion 101 of the outlet portion linearly expands sequentially, and satisfies the conditions specified in the second invention. Therefore, the flow of the molten metal that has flowed out of the outlet portion can easily form an upward flow smoothly in the tundish as compared with the injection tube of the injection tube number 2 having a shape in which the lower end portion of the outlet rapidly expands.

  Next, an embodiment of a swirl flow forming mechanism installed inside the tundish injection pipe will be described. The following swirl flow forming mechanism is an example, and the swirl flow forming mechanism used in the present invention is not limited to these.

FIG. 4 is a perspective view of a swirl flow forming mechanism used in the present invention. The swirl flow forming mechanism shown in the figure (hereinafter referred to as “swirl flow forming mechanism of mechanism number 1”) is provided with cuts pq and sr in a disk, and an opposing semicircular portion having an arbitrary diameter qr. The shafts have shapes twisted in opposite directions. The molten metal flowing down from the upper part of the injection pipe for tundish is swirled in the direction indicated by arrows F1 and F2 by this swirl flow forming mechanism, and passes through the openings pqp ₁ and srs ₁ to the lower part of the swirl flow forming mechanism. It turns into a swirling flow and flows down to the lower part of the tundish injection pipe.

FIG. 5 is a perspective view of another swirl flow forming mechanism used in the present invention. The swirl flow forming mechanism shown in the figure (hereinafter referred to as “swirl flow forming mechanism of mechanism number 2”) is provided with cuts along the generatrices Om and On on the side surface of the cone, and does not separate the apex O portion. In addition, the two conical side faces that are opposed to each other have a shape twisted in the opposite directions around the horizontal line passing through the vertex O around the horizontal line perpendicular to the bus line mOn. The molten metal flowing down from the upper part of the tundish injection pipe is swirled in the direction indicated by arrows F1 and F2 by this swirl flow forming mechanism, and the swirl flow forming mechanism of the swirl flow forming mechanism mm ₂ m ₁ and nn ₂ n ₁ It goes down to the lower part and turns into a swirling flow and flows down to the lower part of the tundish injection pipe.

  FIG. 6 is a view showing still another swirl flow forming mechanism used in the present invention, where FIG. 6 (b) is a plan view, and FIG. 6 (a) is a longitudinal section in the DD section in FIG. 6 (b). The figure, and (c) in the same figure, show development views of the longitudinal section along the circumferential curve efghijkl in (b) of the figure. The swirl flow forming mechanism (hereinafter referred to as “swirl flow forming mechanism of mechanism number 3”) shown in the figure has four openings in the circumferential direction on the side surface of the cone having a thickness. The conical side surface is twisted by rotating the upper surface of the side surface counterclockwise around the central axis of the cone and the lower surface of the conical side surface clockwise.

  In FIG. 6 (b), the curved surface Iroheho shows the upper surface of the conical side surface, and the curved surface Ironiha shows the downward surface inclined in the circumferential direction from the generating line Ilo on the upper surface of the conical side surface toward the generating line Hani on the lower surface of the conical side surface. Represents the lower surface of the conical side surface, and the curved surface has an upward surface inclined in the circumferential direction from the generatrix of the upper surface of the conical side surface toward the generatrix of the lower surface of the conical side surface. The compartment totinuri is an opening.

  In addition, the curved surface Rinkawa is the upper surface of the conical side surface, the curved surface Rinuol is the downward surface inclined in the circumferential direction from the generatrix line of the upper surface of the conical side surface toward the generatrix Luo of the lower surface of the conical side surface, and the curved surface Luo Tayo is the lower surface of the conical side surface The curved surface Wakayo represents an upward surface inclined in the circumferential direction from the generatrix waka of the upper surface of the conical side surface toward the generatrix Yota of the lower surface of the conical side surface. The section Yotasole is an opening. Similarly, a curved surface is formed for the remaining semicircular portion of the conical side surface.

  Therefore, when the longitudinal section along the circumferential curve efhijkl in FIG. 6B is developed in the circumferential direction, as shown in FIG. 6C, it opens between the longitudinal sections efhg and ijlk on the conical side. The hole ghji is disposed.

  When the molten metal flowing down from the upper part of the injection pipe for tundish passes through the opening ghji and the like in FIG. 6C, a turning force is applied in the directions indicated by arrows F1 and F2 (that is, FIG. 6). In (b), a clockwise swirl force is applied), and after passing through the swirl flow forming mechanism, it turns into a swirl flow and flows down to the lower part of the tundish injection pipe.

  The structure of the swirl flow forming mechanism having mechanism numbers 1 to 3 has been described above. The requirements required for the swirl flow forming mechanism are the following three points. That is, (1) strength and durability that do not cause breakage such as cracking even when the molten metal falling flow from the ladle directly collides with the swirling flow forming mechanism when the position of the inner surface of the tundish is low, such as in the early stage of casting. (2) Sintered sand and slag flowing out of the ladle, a flow passage cross-sectional area that is not blocked by non-metallic inclusions in the molten metal, and (3) early casting, etc. This is that the molten metal is less scattered when the falling flow from the ladle directly collides with the swirling flow forming mechanism when the position of the inner surface of the tundish is low. Among the above, in order to satisfy the requirement (2) in particular, it is preferable to secure a flow path having a size that allows passage of a sphere having a diameter of at least about 100 mm in the initial use state.

(Example 2)
In order to confirm the effect of the injection tube for tundish according to the present invention, a casting test was conducted and the result was evaluated.

  A continuous casting test was conducted using the injection tube for tundish of the example of the present invention having the injection tube number 1 shown in FIG. 1 and using molten steel as the molten metal. In addition, a swirl flow forming mechanism having a mechanism number 1 shown in FIG. 4 (an angle formed by a disk constituting the swirl flow forming mechanism and a horizontal plane is 35 degrees) was installed in the injection tube.

  Continuous casting is a 6-strand curved continuous feed while supplying Al killed molten steel with a carbon content of 0.45% by mass having a composition shown in Table 1 below to a tundish with a molten steel amount of 40 tons (t). Using a casting machine, molten steel was poured into a circular section mold having a diameter of 360 mmφ, and a slab having a circular section was cast at a drawing speed of 0.8 m / min.

  Perform continuous casting with the same ladle refining conditions so that the non-metallic inclusion content in the ladle does not fluctuate, and (1/2) r part (here) from the center on the top side of the round slab in the steady casting part , R is the radius of the slab) and the content of non-metallic inclusions in the sample taken from the sample was measured and compared.

  FIG. 9 is a diagram showing test results of continuous casting while pouring molten metal from a ladle into the tundish using an injection tube for tundish, and FIG. 9 (a) shows the injection tube shown in FIG. The test result using the No. 1 tundish injection pipe (installed with the swirl flow forming mechanism No. 1) is shown. FIG. 5B shows the tundish injection pipe No. 3 shown in FIG. The test result using the swirl flow forming mechanism of mechanism number 3 is shown.

  The inclusion content was evaluated by the following method. That is, the injection tube of the injection tube number 5 having the same shape as the conventional injection tube number 4 and the same inner diameter (D1) and overall length (L1) of the injection tube as the injection tube number 1 (L1 = 1350 mm, D1 = 480 mm) The content of inclusions in the steel of the comparative example cast by using the total oxygen content (T. [O]) was determined, and this value was used as the reference (100), and the inclusion content in the steel of the present invention was indexed. And is shown in FIG. 9 as the total oxygen content index (T. [O] index).

Here, in the test (reference) of the comparative example using the injection tube of the injection tube number 5, casting was performed while flowing the atmosphere adjusting Ar gas 8 at 500 NL / min, and the injection tube of the injection tube number 3 of the reference example was used. In the test, casting was performed while flowing Ar gas 8 for atmosphere adjustment at 480 NL / min. In the test using the injection pipe of the injection pipe number 1 of the present invention, casting was performed while Ar gas was further blown from the gas blowing portion 3 of the injection pipe in addition to the atmosphere adjusting Ar gas 8.

From the results shown in FIG. 9, the injection tube No. 5 of the comparative example is used for both the test using the injection tube No. 1 of the present invention and the test using the injection tube No. 3 of the reference example. The total oxygen content index (T. [O] index) in the steel was lower than that of the conventional test, and the effect of capturing and removing non-metallic inclusions in the steel was confirmed. In particular, in the test using the injection tube of the injection tube number 1, a further excellent cleaning of the steel was achieved, and a slab having a much lower inclusion content was obtained.

  The injection tube for tundish according to the present invention includes a swirl flow forming mechanism that forms a swirl flow by applying a swirl force to the molten metal flowing down in the injection tube, and defines an inner diameter of the injection tube main body within an appropriate range. Further, by reducing the inner diameter of the lower outlet portion, it is possible to obtain a stable strong swirling flow with a simple apparatus, capture and remove non-metallic inclusions, and effectively clean the molten metal. Therefore, the injection tube of the present invention is an apparatus that can be widely applied in the field of continuous casting of molten metal, which requires the production of a highly clean slab with inexpensive equipment.

It is the schematic of the longitudinal cross-section which shows the condition which pours molten metal from a ladle to a tundish using the injection pipe for tundish of this invention, and performs continuous casting. It is the schematic of the longitudinal cross-section which shows the condition which pours molten metal from a ladle to a tundish using another injection pipe for tundish of this invention, and performs continuous casting. It is the schematic of the longitudinal cross-section which shows the condition which pours molten metal from a ladle to a tundish using the injection pipe for tundish of the reference example of this invention, and performs continuous casting. It is a perspective view of the swirl flow formation mechanism used by this invention. It is a perspective view of another swirl flow formation mechanism used by the present invention. It is a figure which shows another swirl | vortex flow formation mechanism used by this invention, the figure (b) is a top view, The figure (a) is a longitudinal cross-sectional view in the DD cross section in the figure (b), and FIG. 4C shows a circumferential development of the longitudinally cut surface by the circumferential curve efghijkl in FIG. It is the schematic for demonstrating formation of the bubble film | membrane at the time of blowing inactive gas from the ring-shaped blowing part arrange | positioned in the circumferential direction at the inner wall part of the injection pipe lower part outlet part. It is the schematic showing the longitudinal cross-section of the sealing member vicinity between an injection pipe upper part and a ladle lower part. It is a figure which shows the test result which performed continuous casting, pouring a molten metal from a ladle to a tundish using the injection pipe for tundish, The figure (a) shows the injection pipe for tundish shown in FIG. The test results used are shown, and FIG. 3B shows the test results using the tundish injection tube shown in FIG. It is the schematic of the longitudinal cross-section which shows the condition which pours molten metal from a ladle to a tundish using a long nozzle, and performs continuous casting. It is the schematic of the longitudinal cross-section which shows the condition which pours molten metal from a ladle to a tundish using the conventional injection pipe for tundish, and performs continuous casting.

1: Tundish injection pipe 101: Injection pipe lower outlet lower end 102: Upper injection pipe 103: Lower injection pipe 2: Swirl flow forming mechanism 3: Inert gas blowing part to flowing molten metal 31: Ring-shaped blowing part
4: Tundish 5: Tundish lid 6: Ladle 61: Ladle nozzle 62: Long nozzle 7: Molten metal injection flow 71: Molten metal in ladle 72: Molten metal in tundish 8: Not for adjusting atmosphere in injection tube Active gas 9: Inert gas for blowing into flowing molten metal 10: Immersion nozzle 11: Mold 12: Metal slab 13: Inert gas introduction channel 14: Inverted conical bubble film 20: Sliding gate hardware 21: Sliding Hydraulic cylinder for gate operation 22: Iron plate 23: Porous refractory 24 Seal member 25: Cotton-like refractory 26: Cushion material

Claims (2)

An injection tube for tundish used for pouring to a tundish that is an intermediate container between a ladle and a mold,
The injection tube is used in a state where an inert gas for adjusting the atmosphere is blown into the space formed by the inner wall and the molten metal at a blowing rate of 200 NL / min to 1300 NL / min,
A swirl flow forming mechanism made of a refractory for forming a swirl flow by applying a swirl force to the molten metal flowing down in the injection tube is arranged inside the injection tube,
The swirl flow forming mechanism is disposed at a position lower than the molten metal surface in the injection pipe,
Between the swirl flow forming mechanism and the lower end of the lower outlet portion of the injection pipe,
An inert gas blowing portion for blowing an inert gas into the flowing molten metal is continuously arranged in the circumferential direction on the inner wall portion of the lower outlet portion of the injection pipe,
The length from the inert gas blowing part to the lower end of the lower outlet part of the injection tube is 100 mm or more,
The inert gas blowing amount from the inert gas blowing portion is 2 NL / min to 100 NL / min,
The inner diameter of the main body of the injection tube is 200 mm to 1500 mm,
The length in the injection tube axial direction of the lower outlet portion of the injection tube is 100 mm or more and 1000 mm or less upward from the lower end of the lower outlet portion,
An infusion tube for tundish, wherein the inner diameter of the lower outlet is 60 mm or more and is ½ or less of the inner diameter of the main body of the infusion tube. 2. The tundish injection tube according to claim 1, wherein an inner diameter of a lower end portion of the lower outlet portion of the injection tube is enlarged toward a lower end of the outlet.

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