JP4884261B2 - Injection tube for sub-ingot casting - Google Patents

Description

  The present invention relates to a pouring ingot for an ingot that reduces the inflow of a sealing gas into a mold and improves the surface of the steel ingot.

  In order to prevent the formation of oxide inclusions due to the reaction between oxygen in the atmosphere and the molten steel components when casting molten steel in the atmosphere, it is subtracted from the hood of 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 ingot-forming injection pipes to prevent contact between the molten steel and the atmosphere.

  A part of the sealing gas blown from the ladle hood is entrained in the flow of molten steel in the injection pipe for the pouring ingot, passes through the injection pipe and the runner, flows into the mold, and passes through the mold. Released into the atmosphere. When the gas bubbles for sealing do not flow into the mold, the surface of the molten steel is kept horizontal, and the molten metal surface rises gently as the casting progresses. However, if the gas bubbles for sealing flow into the mold, when the gas bubbles for sealing rise and separate from the surface of the molten steel, the bubbles lift or bounce the surface of the molten steel in the mold. As a result, a large fluctuation occurs on the surface of the molten steel. When large fluctuations occur on the surface of the molten steel, the molten steel wave and splash are applied to a position higher than the molten metal surface position on the inner wall of the mold and solidify in advance, then the molten metal surface rises and the main body solidifies, and the surface of the steel ingot The surface of the steel ingot is solidified by mixing the molten layer and unmelted layer of the coating material covering the surface of the molten steel and mixing the unmelted coating material between the mold and the molten steel. Deterioration of the surface skin of the steel ingot is likely to occur, such as dents and rough skin. 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 sealing gas, fluctuations in the surface of the molten steel in the mold due to entrainment of the sealing 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 mold due to the entrainment of gas for sealing is likely to occur particularly in the mold near the injection pipe.

  The conventional technique for preventing this phenomenon is to increase the gas flow in the molten steel by reducing the flow velocity in the injection pipe by increasing the diameter of the injection pipe, and the flow of the sealing gas into the mold. A method for reducing incoiling (see, for example, Patent Document 1) and a gas vent pipe between the injection pipe and the runner connecting the immediate mold so that the gas for sealing is introduced into the mold. There is an ingot casting method that prevents inflow (for example, see Patent Document 2).

  However, in the method of increasing the diameter of the injection tube described in Patent Document 1, even if the sealing body prevents the flow of air without flowing the sealing gas, the flow of gas into the mold is prevented. Thus, no surface skin defects can be eliminated, and more surface skin defects are generated in a state where there is an air entrainment without a sealing body than when there is a sealing body. From this, it can be said that a sufficient gas floating effect cannot be obtained because the entrainment of the gas in the injection pipe further increases in the state where the sealing gas is supplied. When the gas is floated in the injection tube in the state where the sealing gas is flowed or when the injection flow rate is increased, it is considered necessary to use a larger-diameter injection tube. Insufficient installation location is expected.

  In the method of setting up the vent pipe between the runner connecting the injection pipe and the immediate mold described in Patent Document 2, it is necessary to set up the vent pipe for each runner branched from the injection pipe. The more runways, the worse the casting yield, and the shortage of degassing pipe installation locations is expected. Further, if the degassing pipe is made thin in order to reduce the deterioration of the casting yield, the molten steel may be blown up along with the 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 reduce the inflow of bubbles of the sealing gas entrained in the injection pipe into the mold in the cast steel ingot means using the sealing gas. It is intended to provide an apparatus capable of preventing deterioration of the surface of the steel ingot and entrainment of the covering material covering the surface of the molten steel in the mold by preventing the large fluctuation of the surface of the molten steel.

  According to the first aspect of the present invention, the horizontal flow part 6 is provided in the lower part of the downflow part 4 of the injection pipe 1 into the casting mold for the sub-casting ingot. In addition to opening in the part 5, a partition 3 is provided in the injection pipe 1 to divide it into a downflow part 4 and a degassing part 5, and an upper end part of the degassing part 5 is used as an opening part 7, and an upper part of the downflow part 4 It is the injection tube 1 to the casting mold for the pouring ingot characterized by the above.

  The reason and principle of the above means of the present invention will be described. First, the reason why the bubbles of the sealing gas bubbles cannot be lifted up in the injection pipe 13 made of a conventional straight pipe for subcontracting is that the descending flow rate of the molten steel in the subfusion injection pipe 13 is higher than the rising speed of the bubbles. Because it is big. Therefore, in the means of the present invention, a partition 3 is provided inside the injection pipe 1 immediately below the inlet 8 of the injection pipe 1 for injecting molten steel from the ladle, and is divided into a downward flow portion 4 and a gas vent portion 5. The molten steel descending flow portion 4 is disposed, the lower portion of the descending flow portion 4 is closed to the bottom, the lower portion of the partition 3 is opened, and the horizontal flowing portion 6 that flows the molten steel in the horizontal direction is provided as the descending flow portion 4. The molten steel is laterally moved to the lower part of the gas vent part 5 directly above the runner opening 9 provided at the lower part. By using this means, the molten steel hits the bottom of the lower part of the downward flow part 4 and the downward flow stops, and when the molten steel flows to the lower part of the gas vent part 5 which is the upper part of the runner port 9, the sealing gas contained in the molten steel Are separated as bubbles and float up the degassing part 5. As a result, in the injection pipe 1 of FIG. 1, the gas floats and the remaining molten steel flows to the runner opening 9 in the direction directly below the gas vent 5. On the other hand, in the injection pipe 2 of FIG. 2, the gas floats up from the molten steel that has flowed to the degassing portion 5, and the remaining molten steel flows to the runway port 9 that faces further horizontally. By the way, the upper end of the degassing part 5 is closed, and the upper end part of the partition 3 is open on the downflow part 4 side above the injection pipe. Therefore, even if a large amount of sealing gas is wound and molten steel is injected into the injection tube 1 or the injection tube 2 from the injection port 8, the molten steel does not blow up to the outside together with bubbles from the upper end of the gas vent 5. It is safe and hot water can be injected well in terms of quality of cleanliness.

  By using the means of the present invention, when the molten steel descends at the lower part of the downflow part of the injection pipe and flows horizontally at the horizontal flow part and enters the gas vent part, bubbles of the seal gas contained in the molten steel are generated. As a result of being able to ascend and separate easily the degassing part, the molten steel surface rises in the mold poured down from the runway without swaying and blowing up, so that the resulting steel ingot Since the surface skin is not deteriorated and the coating material is not engulfed by the molten metal surface in the mold, a high-quality cleaned steel ingot without surface defects can be obtained.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the injection tube 1 of the present invention, and FIG. 2 schematically shows the injection tube 2 of the present invention in section. The injection pipe 1 shown in FIG. 1 has the runner port 9 facing in the direction immediately below the gas vent 5, and the injection pipe 2 shown in FIG. 2 has the runner port 9 in the horizontal direction in the direction of the horizontal flow part 6. It is the one that is suitable. 3 (a) is a side view and FIG. 3 (b) is a plan view showing a bottom casting ingot apparatus. Using the injection pipe 1 of the present invention, eight of the 5t steel ingots of SCr420 steel defined in JIS G 4053 Casting was performed by pouring, and visual inspection of the fluctuation of the surface of the molten steel in the mold and surface skin of the steel ingot were conducted. At the time of casting, argon was used as a sealing gas and was blown into the inlet 8 at a flow rate of 1 Nm ³ / min at the lower end of the hood 11 of the ladle 10. In this case, the molten steel was not blown out from the degassing portion 5 together with the seal gas bubbles at the upper end portion, and the molten steel could be safely agglomerated from the runner 12 into the mold.

Next, a comparative example will be described. Using the injection pipe 13 made of the conventional straight pipe shown in the schematic diagram of FIG. 4, eight 5t steel ingots of SCr420 steel are cast in the form of a bottom casting ingot of the explanatory view shown in FIG. 5, and the molten steel in the mold A visual survey of surface fluctuations and a surface skin of steel ingots were conducted. At the time of casting, argon was used as a sealing gas and was blown into the inlet 8 at the lower end of the hood 11 of the ladle 10 at a flow rate of 1 Nm ³ min. Next, the left and right molds were agglomerated from the runner 13 below the injection tube 13.

  Table 1 shows the results of visual inspection of the fluctuation of the surface of the molten steel in the mold in the ingot casting as an embodiment of the present invention and a comparative example. When the injection tube 1 or the injection tube 2 of the present invention was used, the fluctuation of the surface of the molten steel was not observed in all the molds with 10 charges. On the other hand, when the injection pipe 13 made of a conventional straight pipe is used, the fluctuation of the surface of the molten steel occurs in the mold A and the mold A ′ shown in FIG. confirmed.

  Table 2 shows the survey results of the surface skin of the cast steel ingot. In the steel ingot using the injection tube 1 or the injection tube 2 of the present invention, no defects were observed on the surface skin of all the 10 ingots. On the other hand, in the steel ingot using the conventional injection pipe 13 of the straight pipe, the surface skin of the steel ingot formed by the mold A and the mold A ′ closest to the injection pipe 13 is doubled by 5 charges out of 10 charges. Skin was confirmed. In addition, when the surface of the steel ingot in which the double skin has been confirmed is ground and removed with the steel ingot cast using the conventional straight pipe 13, a coating material for the molten metal surface in the mold is rolled up. Things were seen.

It is typical sectional drawing of the injection tube of this invention. It is typical sectional drawing of the other injection tube of this invention. The agglomeration apparatus using the injection tube of this invention is shown, (a) is a typical side view, (b) is a top view which shows the injection tube, runner, and casting_mold | template in (a). It is typical sectional drawing of the conventional injection tube. 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 pipe, runner, and casting_mold | template in (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection pipe 2 Injection pipe 3 Partition 4 Downflow part 5 Degassing part 6 Horizontal flow part 7 Opening part 8 Inlet 9 Hot water 10 Ladle 11 Hood 12 Runway

Claims (1)

The injection pipe into the casting mold for the lower casting is provided with a vertical partition inside to divide it into a downward flow part and a gas vent part, and a horizontal flow part is provided below the downward flow part to open the gas vent part. In addition, an injection pipe into the casting mold for the ingot casting, characterized in that the upper end part of the degassing part of the injection pipe is opened at the upper part of the downward flow part.

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