JP4319072B2 - Tundish with excellent inclusion levitation - Google Patents

Description

  The present invention relates to a tundish that is used for continuous casting of steel and is excellent in floatability of inclusions in which molten steel accommodated in a ladle is injected and the injected molten steel is discharged to a mold by an immersion nozzle.

  Inclusions in molten steel, especially non-metallic inclusions, are generated by reacting foreign inclusions mixed with refractory fine powder used as the inner wall material of furnaces and pans, and components in molten steel with solvents and air. Although there are raw inclusions, any of these inclusions causes nozzle clogging, slab defects, and the like during casting. Therefore, it is desirable to separate and remove inclusions as much as possible in the molten steel stage.

  In continuous casting of steel, a method is employed in which molten steel accommodated in a ladle is once poured into a tundish and then poured into a continuous casting mold through an immersion nozzle provided in the tundish. The tundish is a container that is used to float and separate non-metallic inclusions in the molten steel while stably supplying the molten steel from the ladle to the mold by once pooling the molten steel in the internal space.

  In order to improve the floatability of inclusions in the molten steel in the tundish, the floating upstream from the bottom of the tundish toward the molten steel bath surface is generated, the flow velocity of the molten steel flowing through the tundish is decreased, and the tundish It is said that it is effective to reduce the difference in the speed at which the molten steel flows at each of the locations.

  As a means for improving the floatability of inclusions in the molten steel in the tundish, for example, a porous plug is provided on the bottom surface of the tundish, and the molten steel pooled in the tundish from an inert gas blowing device connected to the porous plug is used. Floating upstream is generated by blowing an inert gas, or an induction heating coil is provided in the tundish, and power is supplied to the coil from a power source to heat the molten steel. However, such a method requires large-scale equipment, so that not only a large capital investment is required, but also when the inert gas is blown, pore defects are generated in the slab due to the blown gas. There are problems such as.

  It has also been proposed to increase the floatability of inclusions by increasing the capacity of the tundish to reduce the flow rate of the molten steel in the tundish. However, when different steel types are continuously cast, molten steels with different components are mixed in one tundish (this state is hereinafter referred to as a different hot pot molten steel). Since the mixed volume of the molten steel becomes large, there is a problem that a large yield reduction occurs when the hot pot molten steel cannot be used as any steel type before or after continuous casting.

  One means for improving the floatability of inclusions that can suppress the capital investment and suppress the yield reduction due to the molten steel in the pan is to provide a weir in the molten steel pool space of Tundish. For example, a tundish provided with a molten steel flow direction control stand (weir) made of a refractory having a downward slope of 20 to 60 degrees in the opposite direction to the hot water supply part to the molten steel mold in the molten steel receiving part in the tundish Has been proposed (see Patent Document 1).

  FIG. 14 is a cross-sectional view showing a simplified configuration of the conventional tundish 1. In the conventional tundish 1, the molten steel injected from the ladle 2 flows down the molten steel flow direction control table 3 (hereinafter referred to as the weir 3), collides with the bottom 4 and the end 5 of the tundish 1, It flows toward the upper part of the tundish 1 as indicated by reference numeral 6. The flow of the molten steel that has reached the vicinity of the surface of the hot water pool is reversed and flows toward the hot water supply section. Since the flow of the arrow 7 toward the hot water supply portion is blocked by the weir 3, it flows into the bottom of the tundish 1 while passing between the tundish side wall and the weir 3. In such a conventional tundish 1, a place where the molten steel is vigorously stirred or collided is formed, and in such a place, the minute oxides in the molten steel are likely to agglomerate and enlarge, and the enlarged oxide floats. Suppose that it is removed from the molten steel system after reaching the hot water supply part or after reaching the hot water supply part.

  However, in the prior art weir 3, a downward slope is formed in the direction opposite to the hot water supply part to the mold, and the flow rate is accelerated by the molten steel supplied from the ladle 2 flowing down the slope. Is done. By this acceleration, the flow velocity in the vertical direction and the flow velocity near the surface of the molten steel are increased and stirred vigorously, so that the fine inclusions agglomerate and enlarge. It also has the effect of winding into molten steel. Therefore, in the tundish 1 of the prior art, the inclusions are not sufficiently separated and removed, and the inclusions are caught in the intense flow of molten steel and flow into the continuous casting mold, and the slab quality cannot be sufficiently improved. There is.

  As described above, the weir has the advantage of not incurring high equipment costs, but the flow area of the molten steel in the tundish changes depending on the height of the weir, so it is difficult to control the local flow velocity, and the tundish In this case, the flow velocity may increase locally, and the floating property of the inclusions may be deteriorated.

  Even when weirs having the same dimensions and shape are provided, the flow path area may change according to the amount of molten steel in the tundish. For example, even if the weir is the same in the steady operation state (when the molten steel surface height is high) and the unsteady operation state (the state where the molten steel surface height is lowered after the pan is replaced), The flow area of the molten steel changes. In such a case, no specifications have been proposed for a weir that can exhibit good inclusion floating properties in any channel area in the steady operation state and the unsteady operation state.

JP 2000-117401 A

  An object of the present invention is an inclusion that can effectively levitate and separate inclusions in molten steel, particularly non-metallic inclusions, in both continuous and unsteady operation states in continuous casting of steel. It is to provide a tundish with excellent flying characteristics.

The present invention is used for continuous casting of steel, in molten steel contained in a ladle, and in a tundish that discharges the injected molten steel to a mold with an immersion nozzle.
A first member having a substantially flat plate shape;
A second member having a substantially flat shape, connected to the first member at one end of the first member, and provided to rise from the first member, and having a collision surface on which the injected molten steel collides; The cross-sectional shape consisting of comprises an L-shaped weir,
The weir is arranged so as to extend in a direction crossing the direction from the molten steel injection position where the molten steel is injected to the molten steel discharge position where the molten steel is discharged by the immersion nozzle,
In addition, the first member of the weir is in a direction parallel to the direction in which the molten steel is poured from the ladle, and the second member of the weir is the molten steel from the pouring position of the molten steel in the direction rising from the first member of the weir. It is arranged to be opposite to the direction toward the discharge position,
A flow path formed by the second member and a tundish bottom surface;
In the weir, the ratio (I / H) of the distance I between the other end of the first member and the bottom surface to the height H from the bottom surface to the bath surface of the molten steel is greater than 1.0 (I / H). > 1.0) ,
The ratio (D / H) of the distance D between the one end of the first member facing the bottom surface and the bottom surface to the height H from the bottom surface to the bath surface of the molten steel is greater than 0.3 (D / H> 0.3) is arranged such that a tundish excellent in inclusions flying characteristics, wherein Rukoto.

  The present invention is further characterized in that a lower weir is further provided between the weir and the molten steel discharge position so as to rise from the bottom surface.

According to the present invention, molten steel is injected from a ladle into a tundish impinges on the second member of the weir, the flow rate is diminished once after flow in the opposite direction to the molten steel discharge position, and the inner wall surface of the tundish Since it collides with the bottom surface and reverses and flows toward the molten steel discharge position, the difference in flow velocity at various locations in the tundish is reduced. The molten steel that has flowed toward the molten steel discharge position passes through a relatively narrow flow path below the weir and near the bottom formed by the bottom surface of the tundish and the weir. The molten steel pooled in the tundish flows with the entire cross section perpendicular to the direction connecting the molten steel injection position and the molten steel discharge position as the channel area.

  In this way, the molten steel flowing in the tundish rapidly passes through the lower part of the weir, and the flow passage area rapidly expands. Therefore, the flow velocity decreases and a floating upstream from the bottom surface toward the molten steel bath surface can be generated. it can. Therefore, the inclusions in the molten steel are made effective by arranging the second member of the weir so as to be under the bath surface of the molten steel to be pooled in both the steady operation state and the unsteady operation state of continuous casting. It is possible to produce an excellent quality slab by floating and separating. Furthermore, even when continuously casting steel types with different components, the difference in flow velocity at each location in the tundish is small and the flow velocity is slow, so that the molten steel in the tundish is not vigorously stirred and rectified. Therefore, the mixing volume of the hot pot molten steel is suppressed. Therefore, even when the steel types having different components are continuously cast in the same tundish, it is possible to suppress a decrease in yield due to the different hot pot molten steel.

Also, the height D to the lower end which is one end portion of the first member from the bottom of the dam, the ratio between the height H from the bottom surface to the bath surface of the molten steel (D / H) is 0.3 By placing the weir so that it becomes larger (D / H> 0.3), it collides with the second member of the weir, once flows in the direction opposite to the molten steel discharge position, and then collides with the inner wall of the tundish Thus, it is possible to cause the molten steel to flow toward the molten steel discharge position without excessively stirring the molten steel.

Also, the weir, the height I of up to an upper end which is the other end portion of the first member from the bottom of the dam, the ratio between the height H from the bottom surface to the bath surface of the molten steel (I / H) is, By arranging the weir so that it is larger than 1.0 (I / H> 1.0), the molten steel that collided with the second member of the weir overflows above the weir and flows toward the molten steel discharge position Therefore, rectification and floating upstream generation can be expressed more efficiently.
Also, by generating a flow of molten steel flowing into the second member is provided with molten steel discharge position direction opposite direction, slag floating on the molten steel bath surface is flowed into the molten steel by the injection flow from the injection nozzle Even in this case, it can be floated again on the molten steel bath surface.

According to the invention, the weir is formed so that the cross-sectional shape has an L shape, that is, the angle formed by the first member and the second member is approximately 90 degrees. When the angle formed by the first member and the second member is an extremely obtuse angle, the molten steel injected from the ladle collides with the second member and flows down to increase the flow velocity. An effect | action arises and the floating property of inclusions deteriorates. If the angle formed by the first member and the second member is an extremely acute angle, the receiving area of the second member that the molten steel injected from the ladle collides with becomes smaller, and the rectification action is reduced. Therefore, the weir is preferably formed so that the angle formed by the first member and the second member is approximately 90 degrees.

  Further, according to the present invention, since the lower weir is further provided between the weir and the molten steel discharge position so as to rise from the bottom surface, the flow path formed below the weir is directed toward the molten steel discharge position. Since the bottom flow of the molten steel that has flowed through can be reliably eliminated and a strong floating upstream can be generated, the floatability of inclusions can be further improved.

  FIG. 1 is a cross-sectional view showing a simplified configuration of a tundish 11 according to an embodiment of the present invention. The tundish 11 is a generally boat-shaped container, and has a refractory material such as a refractory brick lined on the inner wall of a steel outer shell. In FIG. 1, the outer shell and the refractory material lined are shown in a simplified manner. The tundish 11 is used for continuous casting of steel. Molten steel accommodated in the ladle 12 is injected into the accommodating space through an injection nozzle 13 provided in the ladle 12, and the injected molten steel 14 is immersed in the immersion nozzle 15. The continuous casting slab is manufactured by discharging the continuous casting mold 16.

  Although the tundish 11 of the present embodiment has a configuration in which one immersion nozzle 15 is provided, the configuration is not limited thereto, and a configuration in which a plurality of immersion nozzles are provided may be employed. However, in the case of a configuration in which a plurality of immersion nozzles are provided, the present invention consolidates a plurality of immersion nozzles only on one side with respect to a molten steel injection position where molten steel is injected from the injection nozzle 13 into the tundish 11. In other words, except for the local flow direction, the overall flow direction in the tundish is one direction from the molten steel injection position to the molten steel discharge position where the molten steel is discharged to the mold. It applies to.

  In the tundish 11 of the present embodiment, the first member 17 having a substantially flat plate shape and the substantially flat plate shape are connected to the first member 17 at one end 17a of the first member 17, A weir 19 comprising a second member 18 provided so as to rise from the first member 17 is provided. The weir 19 intersects the direction from the molten steel injection position 20 where molten steel is injected into the tundish 11 through the injection nozzle 13 from the ladle 12 to the molten steel discharge position 21 where the molten steel 14 is discharged by the immersion nozzle 15. The first member 17 of the weir 19 is arranged in a direction parallel to the direction in which the molten steel is poured from the ladle 12 and extends in the direction, that is, the width direction which is the short direction of the tundish 11 formed in a boat shape. In addition, the second member 18 of the weir 19 is arranged so that the direction in which the second member 18 rises with respect to the first member 17 of the weir 19 is opposite to the direction from the molten steel injection position 20 to the molten steel discharge position 21. In addition, the molten steel discharge | emission position 21 to the casting_mold | template 16, Comprising: The stopper which is the flow control member 22 of molten steel is provided in the inflow port of the molten steel to the immersion nozzle 15 provided in this position.

The first and second members 17 and 18 constituting the weir 19 are made of a refractory material such as alumina or magnesia, for example. The weir 19 may be configured as an integral member, or may be configured to connect the first member 17 and the second member 18. The weir 19 of the present embodiment is formed so that the cross-sectional shape parallel to the longitudinal direction of the tundish 11 has an L shape , and the angle θ formed between the first member 17 and the second member 18 is approximately 90 degrees. is there.

  The end of the weir 19 in the width direction is fixed to the inner wall on the side surface in the longitudinal direction of the tundish 11. At this time, the weir 19 is a bath surface of the molten steel 14 from the bottom surface 23 at a distance D between one end portion 17a (hereinafter referred to as the lower end portion 17a) of the first member 17 facing the bottom surface 23 of the tundish 11 and the bottom surface 23. It arrange | positions so that ratio (D / H) with respect to height H may be larger than 0.3 (D / H> 0.3). Further, the weir 19 has a ratio of the distance I between the other end 17b (hereinafter referred to as the upper end 17b) of the first member 17 and the bottom 23 to the height H from the bottom 23 to the bath surface of the molten steel (I / H) is larger than 1.0 (I / H> 1.0).

  FIG. 2 is a schematic diagram showing the flow direction of the molten steel 14 in the tundish 11 including the weir 19. The molten steel injected into the tundish 11 in the direction of the arrow 24 from the ladle 12 via the injection nozzle 13 first collides with the collision surface 25 facing the injection nozzle 13 of the second member 18 of the weir 19. The molten steel that has collided with the collision surface 25 of the second member 18 cannot flow in the direction of the molten steel discharge position 21 because the first member 17 serves as a barrier, and flows in the direction opposite to the direction of the molten steel discharge position 21.

  At this time, by arranging the weir 19 so that the ratio (I / H) is larger than 1.0, that is, the upper end portion 17b of the first member 17 is always on the molten steel bath surface, It is possible to prevent the molten steel that has collided with the collision surface 25 of the second member 18 from overflowing above the weir 19 and flowing toward the molten steel discharge position 21. Further, by providing the second member 18 and generating a flow of molten steel that flows in a direction opposite to the direction of the molten steel discharge position 21, the slag that floats on the molten steel bath surface flows into the molten steel by the injection flow from the injection nozzle 13. Even in this case, it can float again on the molten steel bath surface.

  The molten steel that has flowed in the direction opposite to the molten steel discharge position 21 direction collides with the inner wall surface 26 on one end surface in the longitudinal direction of the tundish 11 and in the direction opposite to the molten steel discharge position 21 direction. And flow toward the bottom surface 23 of the tundish 11. The molten steel flowing toward the bottom surface 23 further collides with the bottom surface 23 and turns in the flow direction, and flows in the flow path formed by the second member 18 and the bottom surface 23 toward the molten steel discharge position 21. At this time, by arranging the weir 19 so that the above-mentioned ratio (D / H) is larger than 0.3, it is possible to sufficiently secure the flow area of the turning flow toward the molten steel discharge position 21. Therefore, it is possible to prevent the molten steel from being excessively stirred.

  The area of the flow path formed below the weir 19 is a total cut in the width direction of the molten steel pooled in the tundish 11 that can be the flow path of the molten steel at a position closer to the molten steel discharge position 21 than the first member 17. Small compared to the area. Therefore, the molten steel that has passed through the flow path formed below the weir 19 toward the molten steel discharge position 21 is rapidly guided from the narrow flow path to the wide flow path.

  Therefore, the molten steel flowing in the tundish first collides with the collision surface 25 of the second member 18 of the weir 19 after the injection, whereby the flow velocity is reduced. Next, it collides with the inner wall surface 26 and the bottom surface 23 of the tundish 11 and reverses, and after passing through a relatively narrow channel below the weir 19, the channel area rapidly increases, so that the molten steel is While the floating upstream toward the bath surface is generated, the flow velocity is further reduced and the flow velocity difference in the depth direction of the molten steel can be reduced.

  Thus, the tundish 11 provided with the weir 19 slows down the speed at which the molten steel in the tundish 11 flows, reduces the difference in the flow velocity of the molten steel at various locations in the tundish 11, and effectively floats up the inclusions. Can be generated. Therefore, the inclusions in the molten steel injected into the tundish 11 can be effectively levitated and separated, and the outflow rate of the inclusions into the slab can be reduced, so that it is possible to manufacture a slab of excellent quality. . In addition, when continuously casting steel types having different components, the difference in flow rate at each location in the tundish 11 can be reduced and the flow rate can be reduced, so that the molten steel in the tundish 11 is not vigorously stirred. It is possible to reduce the mixing volume of the hot pot molten steel by rectification.

  Furthermore, in the tundish 11 provided with the weir 19 of the present invention, the second member 18 of the weir 19 has a steady operation state in which the bath surface height H of the molten steel pooled in the tundish 11 is high, and an unsteady state in which the bath surface height H is low. In both operating conditions, the inclusions in the molten steel can be effectively levitated and separated by placing them under the bath surface of the pooled molten steel, so that the steady operating state and the unsteady operating state Can produce slabs with little quality difference.

  FIG. 3 is a cross-sectional view showing a simplified configuration of the tundish 31 according to the second embodiment of the present invention. The tundish 31 of this embodiment is similar to the tundish 11 of the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  What should be noted in the tundish 31 is that a lower weir 32 is further provided between the weir 19 and the molten steel discharge position 21 so as to rise from the bottom surface 23 of the tundish 11. The lower weir 32 is made of a refractory material such as alumina or magnesia like the weir 19.

  In a general tundish used for continuous casting, a bottom flow that flows toward the immersion nozzle along the bottom surface of the tundish is generated, and inclusions are conveyed by this bottom flow and flow out of the immersion nozzle into the mold without rising. To do. Also in the above-described tundish 11 of the first embodiment, after the molten steel passes through the narrow flow path below the weir 19, the flow cross-sectional area of the molten steel expands, so that a strong floating upstream is generated. Although it can be almost eliminated, the bottom flow can be completely eliminated by providing the lower weir 32 as in the tundish 31 of the present embodiment.

  In the tundish 31, the molten steel that has passed through the flow path below the second member 18, particularly the molten steel that has passed near the bottom surface 23, collides with the lower weir 32 that rises from the bottom surface 23. The direction toward the surface, that is, the floating upstream. As a result, the floatability of inclusions in the molten steel can be further improved, and the outflow rate to the slab can be reduced.

Examples of the present invention will be described below.
Example 1
In the first embodiment, a tundish simulated container having the same dimensions as the tundish used for actual continuous casting is made of acrylic resin, and the same acrylic resin weir 19 and lower weir 32 are provided in the acrylic resin tundish simulated container. It was. Water is poured into the prepared tundish simulated container, and when the predetermined bath surface height H is reached, the discharge amount is adjusted so as to be the same amount as the injection amount, and pseudo inclusions are added. Was measured to determine the spill rate.

  4 to 13 show the arrangement conditions of the weirs provided in the acrylic resin tundish simulated container 35. FIG. FIG. 4 is a cross-sectional view showing the arrangement conditions of the weirs in test number 1. Of the both end faces in the longitudinal direction of the tundish simulated container 35, the position of the end face 36 near the water injection position is a base point (zero), and the weir is determined by the horizontal distance in the direction toward the water discharge position 37 simulating the immersion nozzle position. The arrangement position of was expressed. Test No. 1 was an arrangement condition in which the two first and second lower weirs 38H and 39H having a high height (400 mm) were respectively provided at the horizontal distances of 1300 mm and 3200 mm. FIG. 5 is a cross-sectional view showing the arrangement conditions of the weirs in test number 2. Test number 2 was set to the same arrangement condition as test number 1 except that the heights of the first and second lower weirs 38M and 39M were both medium (300 mm). FIG. 6 is a cross-sectional view showing the arrangement conditions of the weirs in test number 3. Test number 3 was set to the same arrangement condition as test number 1 except that the heights of the first and second lower weirs 38L and 39L were both low (150 mm).

  FIG. 7 is a cross-sectional view showing the arrangement conditions of the weirs in test number 4. Test number 4 was set to the same arrangement condition as test number 3 except that a horizontal weir 41 having a length of 500 mm extending in a direction parallel to the bottom surface 40 of the tundish simulated container 35 was provided at the position of the horizontal distance 4150 mm described above. . FIG. 8 is a cross-sectional view showing the arrangement conditions of the weirs in test number 5. Test No. 5 is provided near the bath surface in a state where water is injected into the tundish simulated container 35 at the position of the above-mentioned horizontal distance of 1700 mm, and is a height extending perpendicular to the bottom surface 40, that is, parallel to the lower weir. The same arrangement conditions as in test number 2 were set except that a 300 mm upper weir 42 was provided.

  FIG. 9 is a cross-sectional view showing the arrangement conditions of the weirs in test number 6. Test number 6 was set to the same arrangement condition as test number 1 except that the third lower weir 43 having a height of 200 mm was provided at the above-described horizontal distance of 800 mm. FIG. 10 is a cross-sectional view showing the arrangement conditions of the weirs in test number 7. Test number 7 was set to the same arrangement condition as test number 1 except that the third lower weir 43 having a height of 200 mm was provided at the above-described horizontal distance of 1000 mm. FIG. 11 is a cross-sectional view showing the arrangement conditions of the weirs in test number 8. Test number 8 was set to the same arrangement condition as test number 3 except that the flow control pipe 44 under injection was provided at a position immediately below the injection position.

FIG. 12 is a cross-sectional view showing the arrangement conditions of the weirs in test number 9. This is an arrangement condition simulating the tundish 11 according to the first embodiment of the present invention. At the injection position, the weir 45 having an L-shaped cross section is arranged such that the second member 47 is horizontal and the first member 46 is vertical. In addition, the second member 47 is disposed so as to rise from the first member 46 in the direction opposite to the direction toward the water discharge position 37. The weir 45 of this example is made of magnesia, the cross-sectional dimension of the first member 46 is 70 ^t × 540 ^L mm, and the cross-sectional dimension of the second member 47 is 100 ^t × 350 ^L mm. Moreover, the weir 45 was arrange | positioned so that the distance D of the lower end part of the 1st member 46 and the bottom face 40 might be 240 mm.

  FIG. 13 is a cross-sectional view showing the arrangement conditions of the weirs in test number 10. Test number 10 was set to the same arrangement condition as test number 9 except that the third lower weir 43 having a height of 200 mm was provided at the position of the horizontal distance of 1000 mm.

  Test numbers 9 and 10 are examples of the present invention, and test numbers 1 to 8 are comparative examples outside the scope of the present invention. The arrangement conditions of test numbers 1 to 10 are summarized in Table 1.

More specifically, the test was performed as follows. When water is poured into the tundish simulated container 35 at 230 L / min and the bath surface height H from the bottom surface 40 to the water surface becomes 700 mm imitating a steady operation state, or 400 mm imitating an unsteady operation state. At that time, the stopper 22 is opened and water is discharged from the tundish simulated container 35 from the water discharge position at 230 L / min which is the same as the injection amount. That is, the discharge amount is started so as to balance the injection amount and the discharge amount, and at the same time, hollow silica spheres that are pseudo inclusions are introduced into the tundish simulated container 35. The hollow silica spheres, which are pseudo inclusions, start being charged at the same time as the discharge of water is started, and the entire amount is charged in 4 minutes after the start. The water discharged from the tundish simulated container 35 was collected for 30 minutes after the start of the water discharge. Next, hollow silica spheres contained in the recovered water were extracted and dried, and the ratio of the recovered weight to the total weight charged was expressed as a percentage to determine the outflow rate of inclusions. The smaller the runoff rate, the better the tundish inclusion floating separation. The evaluation criteria are as follows.
A: Excellent floating separation of inclusions. Outflow rate 2% or less.
○: The inclusion floating property is good. Outflow rate exceeds 2% and 3% or less.
X: Inclusion floating separation property is poor. Outflow rate exceeds 3%.

  The ratio (D / H) of the distance D between the lower end portion and the bottom surface of the first member with respect to the bath surface height H under test conditions 9 and 10 according to the embodiment of the present invention is 240/700 = 0 in a steady operation state. .34, and 240/400 = 0.60 in the unsteady operation state. Further, the weir 45 is arranged such that the upper end portion of the first member 46 is positioned above the bath surface even when the bath surface height H imitating a steady operation state is 700 mm, that is, the ratio (I / H) was always arranged to exceed 1.0. Table 2 shows the diameters and amounts of hollow silica spheres, which are pseudo inclusions, and the capacity of the tundish simulated container 35.

  The evaluation results and the outflow rate of inclusions in the setting conditions of each test number are shown in Table 3 for the steady operation state where the bath surface height H is 700 mm and the unsteady operation state where the bath surface height H is 400 mm. Show.

  Under the setting conditions of test numbers 2 to 5 in the comparative example, the outflow rate exceeded 3% in both the steady operation state and the unsteady operation state, and the inclusion floating property was poor. In the setting conditions of test numbers 1 and 6 and 7 of the comparative example, the outflow rate in the steady operation state is 3% or less and over 2% and the inclusion floating property is good, but the outflow rate in the unsteady operation state is over 3%. The inclusion floatability is poor, and the difference between the steady operation state and the unsteady operation state is large. In the setting condition of test number 8 of the comparative example, in both the steady operation state and the unsteady operation state, the outflow rate is 3% or less and exceeds 2%, and the inclusion floating property is good, and the steady operation state and the unsteady operation state. However, the outflow rate was not 2% or less.

  On the other hand, in test numbers 9 and 10 which are the examples of the present invention, an outflow rate of 2% or less was achieved in both the steady operation state and the unsteady operation state, regardless of the steady operation state and the unsteady operation state. Excellent inclusion levitation was achieved.

(Example 2)
In Example 2, a tundish having the same configuration as the acrylic tundish simulated container and the weir used in the test in Example 1 is coated with a refractory material on a steel outer shell to form a refractory material weir. It was prepared by. Since the actual tundish has the same configuration as the tundish simulated container of Example 1, the same test number as each tundish simulated container, that is, test numbers 1 to 10 is used for the test number of each tundish in Example 2. It was.

  Melting stainless steel of chemical composition corresponding to SUS304 specified in Japanese Industrial Standards (JIS) G4305, and pouring the molten steel from the ladle into the tundish of test numbers 1 to 10 in the setting of the steady operation state, Further, a slab was formed by pouring into a continuous casting mold.

  From the slab cast using each tundish, a slab piece having a length of about 100 mm in the casting direction was collected. The central part of the collected slab piece was divided into 6 blocks having a size of 30 mm, the surface was polished, and the number of inclusions was measured by microscopic observation. In the microscopic observation, the inclusions having a size of 13 μm or more were counted, and the total number of inclusions obtained for each of the six blocks was taken as the representative value of the inclusion number of the slab. The object index was obtained and the inclusion floating property was evaluated. The inclusion index in the slab is a relative value with respect to test number 5 having the largest number of inclusions, and is given by the following equation (1).

Inclusion number index in slab = inclusion number of test number N / inclusion number of test number 5
... (1)
The smaller the inclusion index in the slab, the better the inclusion floating property. The evaluation results are shown in Table 4. Even in tests using actual tundish, in the tundish of test numbers 9 and 10 which are examples of the present invention, the inclusion number index in the slab is less than 0.20, the inclusion floating in the tundish is excellent, and the number of inclusions Was confirmed to be reduced.

It is sectional drawing which simplifies and shows the structure of the tundish 11 which is one Embodiment of this invention. It is a schematic diagram which shows the flow direction of the molten steel 14 in the tundish 11 provided with the weir 19. FIG. It is sectional drawing which simplifies and shows the structure of the tundish 31 which is the 2nd Embodiment of this invention. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 1. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 2. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 3. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 4. FIG. It is sectional drawing which shows the arrangement conditions of the weir in the test number 5. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 6. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in test number 7. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 8. FIG. It is sectional drawing which shows the arrangement conditions of the weir in the test number 9. FIG. It is sectional drawing which shows the arrangement | positioning conditions of the weir in the test number 10. FIG. It is sectional drawing which simplifies and shows the structure of the prior art tundish 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11,31 Tundish 12 Ladle 13 Injection nozzle 14 Molten steel 15 Immersion nozzle 16 Mold 17,46 1st member 18,47 2nd member 19,45 Weir 22 Stopper 32 Lower weir 35 Tandish simulated container 38 1st lower weir 39 2nd Lower weir 41 Horizontal weir 42 Upper weir 43 Third lower weir 44 Injection flow control pipe

Claims (2)

In the tundish used for continuous casting of steel, the molten steel contained in the ladle is injected, and the injected molten steel is discharged into the mold with an immersion nozzle.
A first member having a substantially flat plate shape;
A second member having a substantially flat plate shape, connected to the first member at one end of the first member, provided to rise from the first member, and having a collision surface on which the injected molten steel collides; The cross-sectional shape consisting of comprises an L-shaped weir,
The weir is arranged so as to extend in a direction crossing the direction from the molten steel injection position where the molten steel is injected to the molten steel discharge position where the molten steel is discharged by the immersion nozzle,
In addition, the first member of the weir is in a direction parallel to the direction in which the molten steel is poured from the ladle, and the second member of the weir is the molten steel from the pouring position of the molten steel in the direction rising from the first member of the weir. It is arranged to be opposite to the direction toward the discharge position,
A flow path formed by the second member and a tundish bottom surface;
In the weir, the ratio (I / H) of the distance I between the other end of the first member and the bottom surface to the height H from the bottom surface to the bath surface of the molten steel is greater than 1.0 (I / H). > 1.0) ,
The ratio (D / H) of the distance D between the one end of the first member facing the bottom surface and the bottom surface to the height H from the bottom surface to the bath surface of the molten steel is greater than 0.3 (D / H> tundish having excellent inclusions flying characteristics, wherein Rukoto disposed 0.3) so as to. Between the weir and the molten steel discharge position,
The tundish excellent in inclusion floating property according to claim 1, further comprising a lower weir so as to rise from the bottom surface.

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