JP5025312B2 - Method of pouring into casting mold for ingot casting to improve the surface of steel ingot by generating swirling flow in runner - Google Patents

Description

  In the present invention, an inert sealing gas for sealing the connection portion so that the atmosphere does not enter the connection portion of the injection pipe to the ladle and the mold for ingot casting is dropped from the connection portion through the injection pipe and the runner. It flows into the casting ingot mold, but the amount of seal gas flowing into each casting mold is reduced by dispersing the flowing seal gas in multiple casting molds connected to the runner. It is related with the pouring method to the mold for undercast ingot which improves the surface skin of the steel ingot obtained by doing this.

  In order to prevent the formation of oxide inclusions due to the reaction between oxygen and molten steel components in the atmosphere when casting molten steel in the mold for casting ingots in the atmosphere, it is provided at the molten steel opening and closing gate of the ladle. An inert gas such as argon or nitrogen is blown as a sealing gas between the hood and the upper inlet of the injection tube to prevent contact between the molten steel and the atmosphere.

  The seal gas blown from the hood part of the ladle is wound into the molten steel flow in the injection pipe, passes through the injection pipe and the runner, becomes a bubble, and flows into the casting mold for the lower casting ingot. Released into the atmosphere through the lump mold. In the case where the seal gas bubbles do not flow into the lower casting ingot mold, the molten steel surface rises gently with the progress of casting while the surface of the molten steel remains horizontal in the lower casting ingot mold. However, if the seal gas bubbles flow into the mold for ingot casting, the bubbles will rise to the surface of the molten steel in the mold for ingot casting when the bubbles rise and leave the surface of the molten steel. A large fluctuation (boiling) is generated on the surface of the molten steel by raising or flipping the steel. When large fluctuations occur on the surface of the molten steel, the molten steel wave and splash solidify at a position higher than the position of the molten steel surface of the inner wall of the mold for casting ingot, and the surface of the molten steel is formed on the inner wall portion at the position where the solidification has occurred earlier. Rises and the body solidifies. As a result, the surface of the steel ingot has a double skin, or the molten layer and unmelted layer of the coating material covering the molten steel surface are mixed and the unmelted coating material is wound between the mold and the molten steel. The surface of the steel ingot is liable to deteriorate, for example, the surface of the steel ingot is solidified and the surface of the steel ingot is dented or rough. In addition, the coating material covering the surface of the molten steel is wound into the molten steel, and the wrapped coating material may not float and separate from the molten steel and may solidify while trapped in the initial solidification shell of the steel ingot surface layer. . In particular, when argon gas is used as the seal gas, fluctuations in the surface of the molten steel in the casting for ingot casting due to the entrapment of the seal gas are significantly generated as compared with the case where nitrogen gas is used. In this case, the fluctuation of the surface of the molten steel in the casting for ingot casting due to the entrapment of the seal gas is likely to occur particularly in the casting for casting ingot in the immediate vicinity of the injection pipe.

  The conventional technique for preventing this phenomenon is to increase the diameter of the injection pipe and reduce the flow velocity in the injection pipe to promote the rising of the seal gas in the molten steel, and the inside of the casting gas casting mold Boiling suppression ingot-making method (see, for example, Patent Document 1) for reducing the inflow into the pipe, and a degassing pipe standing between the injection pipe and the casting mold for the immediate ingot-making ingot. There is a lower casting ingot method that prevents gas from flowing into the casting mold (see, for example, Patent Document 2).

  However, in the method of increasing the diameter of the injection tube described in Patent Document 1, the inside of the mold for casting the ingot is not produced even if the seal body prevents the inflow of the atmosphere without flowing into the injection tube of the seal gas. It is not possible to prevent the surface gas from flowing into the surface and eliminate any surface defects. On the other hand, when there is an air entrainment without a sealing body, more surface skin than when there is a sealing body A defect has occurred. From this, it can be said that when the seal gas is flowed, the entrainment of the gas in the injection pipe further increases, so that a sufficient seal gas floating effect cannot be obtained. When the gas is floated in the injection tube with the seal gas flowing or when the injection flow rate is increased, it is considered necessary to use a larger diameter injection tube, which deteriorates the casting yield and places the injection tube. The shortage is predicted.

  In the method of standing a degassing pipe between the injection pipe described in Patent Document 2 and the runner connecting the immediate casting ingot casting mold, it is necessary to set up the degassing pipe for every runway branched from the injection pipe. The more runners branched from the injection pipe, the worse the casting yield, and the shortage of the location for installing the gas vent pipe is also predicted. Further, if the degassing pipe is made thin in order to reduce the deterioration of the casting yield, molten steel may be blown up along with bubbles from the upper end of the degassing pipe when a large amount of sealing gas is wound.

JP 2000-233260 A JP 2002-219556 A

  The problem to be solved by the present invention is to provide a plurality of sub-casting ingots for inflow of molten steel from one runway to a plurality of molds for sub-casting ingots. When casting in the form of branching to the casting mold, the molten steel flowing in the runner is turned into a swirling flow to collect the sealing gas bubbles in the injection pipe at the center of the runner, and the mold for the ingot casting Dispersing the inflow into multiple molds for ingot casting ingots reduces fluctuations in the surface of the molten steel in the ingot casting molds, worsens the surface of the steel ingot, and molds for ingot casting It is providing the method of preventing the envelopment of the coating | covering material which has covered the surface of the molten steel in the inside.

  According to the first aspect of the present invention, the injection pipe arranged vertically when flowing the molten steel from the ladle through the injection pipe to the runner for the ingot casting The molten steel is poured from the upper entrance of the steel and dropped. In this case, a step portion is provided at the lower end portion of the injection pipe, and the flow of the molten steel is switched from the vertical drop toward the end portion of the step portion at the step portion. The flow of the molten steel is directed to the lower part in the direction of the downpipe pipe part in the pipe part, and the outlet provided on the side wall of the downpipe pipe part at the end of the step part located lower and closest to the extension line of the bottom face of the step part This is a method for pouring molten steel into a horizontal runner to create a swirling flow in the runner and pouring it into a casting mold for ingot casting. The flow of molten steel in the runner to the casting mold for the conventional ingot casting was a horizontal flow facing the runner direction. However, in the means of claim 1 of the present invention, a swirl flow is generated in the runner. This is a pouring method in which the surface of the steel ingot is improved by pouring it into the casting mold for the pouring ingot in a state where the bubbles of the sealing gas are located at the center of the runner.

  In the invention of claim 2, the position of the outlet provided on the side wall of the drop tube portion at the end of the step portion is shifted from the central axis of the injection tube in the horizontal direction by 1/2 to 3 times the thickness of the injection tube, and The upper end surface of the outlet is deviated from 0 to 300 mm below the extension line of the bottom surface of the stepped portion, and the molten steel is caused to flow from the outlet to the horizontal runner. This is a method of pouring a mold for undercast ingots that generates a flow to improve the surface of the steel ingot.

  According to a third aspect of the present invention, a stepped portion provided at the lower end portion of the injection pipe is disposed in the horizontal direction, and molten steel is caused to flow through the stepped portion. It is a pouring method to the mold for undercast ingot which improves the surface skin of a steel ingot.

  According to a fourth aspect of the present invention, the step portion provided at the lower end portion of the injection pipe is disposed obliquely downward and the molten steel is caused to flow through the step portion. This is a pouring method for a mold for ingot casting to improve the surface of the steel ingot.

  The reason and principle of the method of the present invention will be described. First, in the conventional ingot casting method, the molten steel flow in the runner is a mere horizontal flow. First, when flowing molten steel from the ladle to the pouring pipe, the upper inlet of the pouring pipe is covered with a hood provided at the molten steel opening / closing gate portion of the ladle, and this inlet is shielded with a sealing gas such as argon or nitrogen. However, when this seal gas is entrained in the molten steel flow from the ladle, enters the injection pipe together with the molten steel, flows from the outlet to the runner, and when the molten steel flows as a horizontal flow, the seal gas contained in the molten steel is bubbled It easily separates from the molten steel and rises as bubbles on the upper wall of the runway. That is, in one horizontal runner in which a large number of casting molds are arranged in series on the injection pipe, the sealing gas is formed in the runway from the injection pipe to the nearest casting mold. Becomes bubbles and accumulates on the horizontal upper surface wall of the runner, and most of the accumulated bubbles are drawn into the casting mold for the ingot and cast into the casting tube. For this reason, there has been a problem that the coating material on the surface of the molten steel is caught in the molten steel on the surface of the molten steel in the casting mold for the last ingot.

  However, in the means of the present invention, a step portion is provided at the lower end portion of the injection tube, a drop tube portion is provided at the end portion of the step portion, and the step located lower and closest to the extension line of the bottom surface of the step portion. By disposing the outlet on the side wall that forms the drooping pipe portion at the terminal end of the section, the upper end surface of the outlet to the runner is shifted downward from the extension line of the bottom surface of the stepped portion, and this By shifting the position of the outlet in the horizontal direction from the position of the longitudinal central axis of the injection pipe, the molten steel flowing through the injection pipe flows into the runner extending horizontally from the outlet as a swirling flow. Thus, centrifugal force acts on the molten steel flowing in the runner as the molten steel turns into a swirling flow and flows into the runner. Further, the molten steel that has turned into a swirling flow has a specific gravity greater than that of the contained sealing gas bubbles, so that the molten steel on which the centrifugal force has acted expands to the peripheral wall portion of the runner. On the other hand, since the bubbles of the seal gas have a smaller specific gravity than the molten steel, the force gathered at the center of the runner acts on the bubbles. Since the force of the bubbles of the seal gas trying to collect in the center of the runway is greater than the force of floating and separating in the runway due to buoyancy, the action of the seal gas bubbles in the runway floating and separating is hindered. It is done. As a result, the molten steel is sequentially injected into the casting mold for the ingot casting in a state where the bubbles of the sealing gas are present in the center of the runner. Therefore, the molten steel that has air bubbles in the center of the runner and flows into the casting mold for casting is used not only for casting casting molds closest to the injection pipe but also for casting castings that are farthest from the casting pipe. Bubbles are evenly dispersed in the mold and poured down. As described above, since the bubbles of the seal gas are dispersed and flow into the casting mold for the lower casting ingot, the amount of the bubbles of the sealing gas flowing into each casting mold for the lower casting ingot is substantially uniform. The amount of air bubbles per lower casting ingot mold is reduced. Therefore, the molten metal surface rising in the casting for ingot casting is gently raised and does not fluctuate due to bubbles, and the coating material on the surface of the molten steel in the casting for casting ingot is not caught in the molten steel.

  Since the present invention is the above-mentioned means, the molten steel that has entered the horizontal runner from the lower part of the step portion at the lower end of the injection pipe is swirling, so that the sealing gas contained in the molten steel in the runner The bubbles are caused by centrifugal force, and the seal gas having a small specific gravity becomes the central part of the swirl flow, is uniformly distributed and carried into the respective casting molds for lower casting, and is poured downward. As a result, the amount of the seal gas bubbles to be poured together with the molten steel per one mold for casting ingots is reduced as a result of averaging regardless of the distance from the injection tube. In the casting mold, the molten steel surface rises calmly and does not blow up. Therefore, the surface skin of the obtained steel ingot is not roughened, and further, the coating material is not caught on the molten metal surface in the mold for ingot casting. Therefore, the method of the present application is an excellent pouring method that has never been obtained.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an injection tube 1 used in an example of an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing an injection tube 1a used in another embodiment of the present invention. FIG. 3 is a schematic diagram showing the inflow state of the swirl flow 13 of the molten steel 11 and the seal gas bubbles 15 that flow evenly from the injection pipe 1 through the runner 7 to each of the castings 10 for ingot casting in the embodiment of the present invention. It is sectional drawing. FIG. 4 is a schematic cross-sectional view showing an example of an injection tube 1b that is inconvenient for the implementation of the present invention. FIG. 5 is a schematic cross-sectional view showing the horizontal flow 14 and the flow of the seal gas bubbles 15 in the runner 7 produced by the inconvenient injection pipe 1b of FIG. Further, FIG. 6 is a schematic cross-sectional view showing a casting casting ingot casting facility to which the method of the embodiment of the present invention is applied. 6 (a), the molten steel 11 is poured from the ladle 8 through the injection pipe 1 and the runner 7 into a plurality of casting ingot casting molds 10 arranged in series in the runner 7. It is a typical side view which shows arrangement | positioning of the ladle 8 at the time of casting, the injection pipe 1, the runner 7, and the some casting mold 10 for ingot casting. Further, FIG. 6B is a schematic plan view shown by an arrow XX in FIG. FIG. 7 shows an ingot forming apparatus using a conventional injection tube, (a) is a schematic side view, and (b) shows the injection tube 1, runner 7, and lower casting ingot mold 10 in (a). FIG. Further, FIG. 7B is a schematic plan view indicated by an arrow XX in FIG. FIG. 8 is a graph showing the results of investigating the surface defects of the steel ingot surface of the method of the present invention and the conventional example.

  First, the equipment used in the first embodiment of the present invention will be described with reference to FIG. The injection pipe 1 in this facility has an upper inlet 4 through which the molten steel 11 flows from the ladle 8 at the upper end, and a step 3 at the lower end 2 of the injection pipe 1. And in the method of 1st Embodiment, this level | step-difference part 3 has the direction of a horizontal direction, and is the means of Claim 3. Further, a drop tube portion 5 is provided at the end portion 3 a of the step portion 3. The downpipe portion 5 is formed below the extension of the horizontal bottom surface 3 b of the step portion 3. Of the side walls of the droppipe portion 5, the wall surface is on the same side as the side wall of the horizontal step portion 3. As shown in FIG. 6, left and right outlets 6 are arranged on the side wall 5 a at right angles to the direction of the stepped portion 3 and in the horizontal direction. The runners 7 are connected in the horizontal direction from the left and right outlets 6, and the molten steel 11 is poured into the casting mold 10 for the lower casting ingot via the left and right runners 7. Note that the lower end 5 b of the drop tube portion 5 of the end portion 3 a of the step portion 3 of the injection tube 1 is closed at the nearest position below the outlet 6.

  Furthermore, the equipment used in the first embodiment of the present invention has a horizontal step 3 at the bottom of the injection tube 1. In this injection tube 1, as an embodiment of claim 2 of the present application, the outlet 6 opened on the side wall 5 a of the drop tube portion 5 disposed at the terminal end 3 a of the step portion 3 is the center of the outlet 6. 1 is displaced in the horizontal direction from the central axis of 1 within a range of a displacement width 3d that is 1/2 to 3 times the thickness of the injection tube 1. Further, the runway 7 is formed so that the extension line of the bottom surface 3a of the stepped portion 3 is positioned so as to be shifted to a position higher by 0 to 300 mm above the horizontal upper surface wall 7a of the runway 7. Form the position of the outlet 6.

  A method for pouring the casting into the mold 10 for the ingot casting in the first embodiment of the present invention will be described. First, the refined molten steel 11 is poured from the hood 9 of the pan 8 into the upper inlet 4 of the vertically downward injection pipe 1 and dropped downward. Subsequently, the flow of the dropped molten steel 11 is turned to the terminal end portion 3 a of the step portion 3 by the step portion 3 provided at the lower end portion 2 of the injection pipe 1. Further, the downwardly descending pipe portion 5 disposed at the terminal end portion 3a of the stepped portion 3 turns the flow of the molten steel 11 downward so that the drooping is lower than the bottom surface 3b of the stepped portion 3 and close to the bottom surface 3b. The pipe 5 is turned to the outlet 6 disposed at the side wall 5a in the direction perpendicular to the direction of the stepped portion 3 in the horizontal direction. Further, the molten steel 11 flows from the outlet 6 to the runner 7 disposed horizontally. In this way, the direction of the flow of the molten steel 11 is changed from the lower end portion 2 of the injection tube 1 to the step portion 3, and the direction is again changed at the terminal portion 3 a of the step portion 3 by the downpipe tube portion 5 to be in the horizontal direction. The swirling flow 13 shown in FIG. 3 is applied to the molten steel 11 that has flowed into the downpipe section 5. By flowing the molten steel 11 that has become the swirl flow 13 from the outlet 6 to the runner 7, the molten steel 11 flows in the runner 7 in the swirl flow 13, and the lower mold inlet of each lower casting ingot mold 10. No. 12 is poured into the casting mold 10 for ingot casting. The step portion 3 in the first embodiment is disposed in the horizontal direction at the lower end portion 2 of the injection tube 1 in the means of the invention of claim 3.

  By the way, in the method of the means of claim 2 of the present invention, the size of the horizontal displacement width 3d at which the center position of the outlet 6 to the runner 7 is displaced from the central axis of the injection tube 1 is such that the injection tube 1 If it is smaller than ½ times the thickness, the swirl flow 13 generated in the runner 7 is too weak to be a sufficient swirl flow 13. On the other hand, even if the horizontal displacement width 3d to be displaced is larger than three times the thickness of the injection pipe 1, the swirling flow 13 generated in the runner 7 is not different from that of three times. The strength is saturated. Therefore, if the size of the horizontal deviation width 3d is larger than three times the thickness of the injection tube 1, the installation space will be increased by that amount, and the yield will not improve even if it is increased. This is a demerit such as a worsening of the yield. Therefore, the position where the outlet 6 is disposed on the side wall 5a of the drop tube portion 5 is such that the position of the central axis of the drop tube portion 5 at the outlet 6 is equal to the thickness of the injection tube 1 in the horizontal direction from the central axis of the injection tube 1. It is assumed that it is arranged at a position displaced by a displacement amount 3d in the range of / 2 to 3 times. Furthermore, the reason for determining the position of the outlet 6 to the runner 7 so that the upper wall 7a of the runner 7 is located at a position 0 to 300 mm lower than the position of the bottom face 3a of the step portion 3 is that the bottom face 3a of the step portion 3 If the position is too lower than the position of the upper surface wall 7a of the runner 7 leading to the outlet 6, the swirl flow 13 cannot be generated in the runner 7. On the other hand, the bottom surface 3a of the step 3 This is because if the position is too higher than the position of the upper surface wall 7a of the runner 7 following the outlet 6, the swirl flow 13 formed in the runner 7 will be too weak.

  An injection tube 1a shown in FIG. 2 which is equipment used in the second embodiment of the present invention will be described. The injection tube 1a of the present invention has a stepped portion 3 at the lower end portion 2a thereof disposed obliquely downward, and has a downwardly descending tube portion 5 at the terminal end portion 3a of the stepped portion 3. As shown in FIG. 6, of the side wall 5 a of the downpipe pipe portion 5, the wall surface is on the same side as the side wall of the stepped portion 3 in the obliquely downward direction, perpendicular to the protruding direction of the stepped portion 3 and horizontally. Left and right outlets 6 are provided. Similar to the equipment of the first embodiment, the runners 7 are connected in the horizontal direction from the left and right outlets 6, and the molten steel 11 passes through the left and right runners 7 and is used as a casting mold for lower casting. 10 is injected. In addition, the lower end 5b of the drooping pipe part 5 of the terminal part 3a of the step part 3 of the injection pipe 1a is closed at the nearest position below the outlet 6.

  Furthermore, in the equipment used for the second embodiment of the present invention, in the injection pipe 1a having the step portion 3 obliquely downward at the lower portion, as an embodiment of claim 4 of the present application, the terminal portion of the step portion 3 is used. 3a, the outlet 6 of the opening on the side wall 5a of the drop tube portion 5 has a position of the central axis of the drop tube portion 5 at the outlet 6 of the thickness of the injection tube 1a in the horizontal direction from the central axis of the injection tube 1a. It is displaced by a displacement amount 3d in a range of / 2 to 3 times. Furthermore, the horizontal upper surface wall 7a of the runner 7 is arranged to be deviated from 0 to 300 mm below the extension line 3c of the bottom surface 3b of the stepped portion 3, and the molten steel 11 flows from the outlet 6 to the runner 7. Yes. In this way, by arranging the position of the outlet 6 to the runner 7 below the extension line 3c of the bottom surface 3b of the stepped portion 3, as shown in FIG. Occurs. In this case, the swirling flow 13 causes the molten steel 11 having a large mass to be around the swirling flow 13 due to centrifugal force, and the bubbles 15 of the seal gas entrained in the molten steel 11 from the upper inlet 4 of the injection pipe 1 b become the swirling flow 13. Since it flows to each mold inlet 12 connected to the runner 7 at the center, it is substantially uniform not only in the immediate vicinity of the injection pipe 1a but also in the casting mold 10 for the lower casting ingot located in the far part of the mold inlet 12. Since the molten steel 11 and the entrained sealing gas bubbles 15 are distributed, the amount of the sealing gas bubbles 15 per one ingot casting ingot mold 10 is small, resulting in the infusion casting ingot. The upper surface of the molten steel in the mold 10 does not fluctuate due to bubbles, so that the series of ingots becomes a homogeneous clean steel.

  On the other hand, in the injection tube 1b shown in FIG. 4, when the outlet 6 and the upper wall 7a of the runner 7 of FIG. 5 are positioned above the extension line 3c of the bottom surface 3b of the step portion 3, as shown in FIG. Even if the swirl flow 13 is generated, the swirl flow 13 is not generated in the molten steel 11 flowing into the runner 7, or the swirl flow 13 is weak. For this reason, the seal gas bubble 15 entrapped in the molten steel 11 from the upper inlet 4 of the injection pipe 1 b easily floats and separates in the runner 7 to form a floating bubble 16, and the hot water close to the injection pipe 1 b in the runner 7. It accumulates on the upper surface wall 7 a of the road 7. As a result, most of the bubbles 15 of the sealing gas flow into the lower casting ingot mold 10 in the immediate vicinity of the injection tube 1b. Further, even if the swirl flow 13 can be formed in the runner 7, even if it is too weak as in the above paragraph 0020, the bubble 15 of the seal gas separates and floats in the runner 7 to become the floating bubble 16, and the injection pipe The bubble 15 of the seal gas will almost flow into the mold inlet 12 closest to 1b. Therefore, in the lower casting ingot mold 10 into which the bubbles 15 of the sealing gas have flowed, fluctuations due to the bubbles are generated on the upper surface of the molten steel in the lower casting ingot mold 10 and the covering material is entrained. Since the bubble 15 of the sealing gas does not flow into the lower casting ingot mold 10 which is far from the lower casting ingot mold 10, fluctuations due to the bubbles do not occur on the upper surface of the molten steel in the lower casting ingot mold 10. In this way, the quality of the steel ingot formed by the series of the ingot casting mold 10 varies.

1 has a horizontal step portion 3 at the lower end portion 2 of the injection tube 1 shown in the schematic diagram of FIG. 1, and the molten steel 11 flows out from an outlet 6 disposed on the side wall 5a of the downpipe portion 5 to the end portion 3a of the step portion 3. Then, using the method of the present invention in which the swirling flow 13 is generated in the runner 7, in the form of the lower casting ingot shown in FIG. 6, eight 5t steel ingots of SCR 420 steel of JIS G 4104 are used for the lower casting ingot. Ten charge castings were performed using the mold 10. At the time of casting, argon was used as the sealing gas and was blown from the hood 9 of the ladle 8 at a flow rate of 1 Nm ³ / min. The visual inspection of the fluctuation of the molten steel surface in the casting 10 for the ingot casting and the surface of the obtained steel ingot were conducted. As a result, 10 charges are averaged and shown in Table 1.

2 has a stepped portion 3 inclined at the lower portion of the lower end portion 2 of the injection tube 1a shown in the schematic view of FIG. 2, and a molten steel 11 from an outlet 6 disposed on the side wall 5a of the downpipe tube portion 5 at the end portion 3a of the stepped portion 3. 4 and using the method of the present invention in which the swirling flow 13 is generated in the runner 7, in the form of the lower casting ingot shown in FIG. 4, eight 5t steel ingots of SCR 420 steel of JIS G 4104 are prepared by lower casting. Ten charge castings were performed using the lump mold 10. At the time of casting, argon was used as the sealing gas and was blown from the hood 9 of the ladle 8 at a flow rate of 1 Nm ³ / min. The visual inspection of the fluctuation of the molten steel surface in the casting 10 for the ingot casting and the surface of the obtained steel ingot were conducted. As a result, 10 charges are averaged and shown in Table 1.

As a comparative example, in the form of the lower casting ingot by the injection pipe 1 having no conventional stepped portion shown in FIG. 7, eight SCR 420 steel 5t steel ingots of JIS G 4104 are charged by the casting 10 for the lower casting ingot. Casted. In the same manner as in Example 1 above, argon was used as the sealing gas during casting, and the hood 9 in the ladle 8 was blown at a flow rate of 1 Nm ³ / min. The visual inspection of the fluctuation of the molten steel surface in the casting 10 for the ingot casting and the surface of the obtained steel ingot were conducted. As a result, 10 charges are averaged and shown in Table 1.

  In each method of Example 1 and Example 2 of the present invention, four casting molds 10a to 10d and 4 casting molds 10a 'to 10d for each of the injection pipe 1 and the injection pipe 1a are provided. In FIG. 8, as shown in Table 1, the fluctuations of the surface of the molten steel in the casting for ingot casting 10 are small for the four casting casting molds 10a, 10b, 10a ′, 10b ′, and are shown in FIG. Thus, the obtained steel ingot surface skin defect index is both less than 0.2, and the other four casting molds 10c, 10d, 10c ′ to 10d ′ are as shown in Table 1. There was no fluctuation, and the obtained steel ingot surface skin defect index was 0 as shown in FIG. Thus, in the method of the present invention, even if there is a fluctuation in the mold 10 for the ingot casting, the surface defect of the steel ingot is slight and has no substantial effect, The steel ingot by the mold 10 was also practically unproblematic.

  On the other hand, in the apparatus shown in FIG. 7 using the conventional injection pipe consisting of only a straight pipe, the left and right ingot casting molds 10a to 10d and the lower casting ingot casting mold of each of the injection pipe 1 are provided. In 10a ′ to 10d ′, as shown in Table 1, the fluctuation of the molten steel surface in the casting ingot casting mold 10 is large in the two right and left casting casting molds 10a and 10a ′. As shown in FIG. 8, the obtained steel ingot surface skin defect index was 1. In the other 6 pieces of the ingot casting molds 10b to 10d and the casting ingot casting molds 10b ′ to 10d ′ in total, there was no fluctuation as shown in Table 1, and as shown in FIG. The steel ingot surface skin defect index was both 0. Thus, in the conventional injection tube 1, the steel ingot by the left and right ingot casting molds 10 immediately adjacent to the injection tube 1 has a large defect on the surface of the steel ingot and cannot be used as it is. Was bad.

It is typical sectional drawing of the injection tube of one form used for a method of the present invention. It is typical sectional drawing of the injection tube of the other form used for the method of this invention. It is typical sectional drawing which shows the inflow state of the swirling flow of the molten steel and the bubble of seal gas which equally flow in into each casting mold for ingot casting from the injection pipe through the runner in the embodiment of the present invention. It is typical sectional drawing which shows the example of the injection tube which is inconvenient to implementation of this invention. FIG. 5 is a schematic cross-sectional view showing a horizontal flow in a runner caused by the inconvenient injection pipe of FIG. 4 and a state of inflow of seal gas bubbles into a sub-ingot casting mold. It is typical sectional drawing which shows the casting equipment for lower casting ingots to which the method of embodiment of this invention is applied. The agglomeration apparatus using the conventional injection | pouring pipe | tube is shown, (a) is a typical side view, (b) is a top view which shows the injection | pouring pipe | tube in the (a), a runner, and the casting mold for ingot casting. It is a graph which shows the investigation result of the steel ingot surface skin defect of the method of this invention, and a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection pipe 1a Injection pipe 1b Injection pipe 2 Lower end part 3 Step part 3a Termination part 3b Bottom face 3c Extension line 3d Deflection width 4 Upper inlet 5 Drop pipe part 5a Side wall 5b Lower end 6 Outlet 7 Runway 7a Upper surface wall 8 Ladle 9 Hood 10 Mold for casting ingot 11 Molten steel 12 Mold inlet 13 Swirling flow 14 Horizontal flow 15 Seal gas bubbles 16 Floating bubbles

Claims (4)

When flowing the molten steel from the ladle through the injection pipe to the runway for lower casting, the molten steel was injected and dropped from the upper inlet of the injection pipe arranged vertically, and provided at the lower end of the injection pipe. Change the flow of the molten steel at the stepped portion toward the terminal end of the stepped portion, and further direct the molten steel flow from the terminal end to the lower portion at the dropping tube provided at the terminal end of the stepped portion. The surface of the steel ingot surface by generating a swirling flow in the runway characterized by flowing molten steel from the outlet disposed on the side wall of the drop pipe part at the end of the stepped portion located at the lower and nearest position to the horizontal runway Method of pouring into casting molds for lower casting ingots. The position of the outlet disposed on the side wall of the drop tube portion at the end of the step portion is shifted from the central axis of the injection tube in the horizontal direction by 1/2 to 3 times the thickness of the injection tube, and the bottom surface of the step portion is extended. 2. The steel ingot by generating a swirling flow in the runner according to claim 1, wherein the upper end surface of the exit is deviated from 0 to 300 mm below the wire and the molten steel is caused to flow from the exit to the horizontal runner. A pouring method for casting molds for lower casting to improve the surface skin. 3. A stepped portion provided at a lower end portion of an injection pipe is disposed in a horizontal direction so that molten steel flows through the stepped portion, and a swirling flow is generated in the runner to create a steel ingot surface skin. An improved method of pouring into casting molds for ingot casting. 3. A step surface provided on a lower end portion of the injection pipe is disposed obliquely downward to allow molten steel to flow through the step portion. Method of pouring into casting molds for lower casting ingots.

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