Tundish and manufacturing method of ingot

Abstract

To provide a tundish that can be used multiple times while effectively suppressing residual hot water in the tundish and that is compatible with a uniaxial tilting furnace, and a manufacturing method of an ingot using the tundish.SOLUTION: A tundish for manufacturing an ingot includes: a hot water outlet port communicating with a cast, in a center part of the tundish when the tundish is viewed from a casting direction; an inclined surface inclined by 10 to 30 degrees toward the hot water outlet port; and an inner wall formed continuously to the inclined surface. It is preferable that the tundish is for a uniaxial tilting furnace.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a tundish for casting ingots and a method for manufacturing an ingot. [Background technology]

[0002] When producing an ingot by casting molten metal melted in a melting furnace into a mold, a tundish for ingot casting is used, and the molten metal is first received in the tundish, and then poured into the mold through a tapping hole formed in the tundish that leads to the mold. A typical shape of a tundish used when casting this ingot is a structure having a tapping port formed on a flat bottom surface, as shown in FIG. 1 of JP 63-247589 A (Patent Document 1) and FIG. 1 of JP 2013-032247 A (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 63-247589 [Patent Document 2] JP 2013-032247 A Summary of the Invention [Problem to be solved by the invention]

[0004] The molten metal is poured into the mold through a tap hole formed in the tundish, but after casting is completed, there is an issue that the solidified molten metal (hereinafter referred to as the residual molten metal in the tundish) remains on the inner bottom surface of the tundish. Since the residual molten metal in the tundish is not included in the ingot, the weight ratio of the ingot to the molten material charged, i.e., the material yield, decreases, and a loss of molten material occurs. In particular, when the inner bottom surface of the tundish is flat, the molten metal begins to solidify due to a drop in temperature before it has completely flowed to the tap hole, so the amount of residual molten metal in the tundish increases and the material yield decreases. Furthermore, in a small melting furnace, the weight of the molten material that can be charged at one time is small, so the weight of the ingot is inevitably small, and the decrease in material yield due to the residual molten metal in the tundish increases production costs to an unacceptable level. In addition, if the amount of molten metal remaining in the tundish increases, the tapping port after casting is completed becomes clogged with solidified molten metal, making it extremely difficult to use the same tundish multiple times. If the number of times that a tundish can be used decreases in this way, the number of tundishes used increases, which not only increases the cost of producing ingots but also increases the environmental load due to the increased amount of used tundishes that are discarded.

[0005] In addition, when casting an ingot, the melting furnace needs to be tilted toward the tundish in order to pour the molten metal into the tundish. Therefore, the melting furnace body has a tilting axis for tilting the furnace toward the tundish. A melting furnace with such a tilting axis is called a tilting furnace. A melting furnace with a single tilting axis is called a single-axis tilting furnace. In the case of a single-axis tilting furnace, when the molten metal starts pouring into the tundish, the drop from the furnace body to the tundish is high, and the molten metal falls at a position far from the furnace body. On the other hand, when the pouring ends and the tilting angle reaches 90° or more, the speed at which the molten metal flows out of the furnace body slows down, and the molten metal falls at a position close to the furnace body. Therefore, in order for the tundish to receive the molten metal without spilling it, the position at which the molten metal falls, which changes from the start to the end of pouring, must all be contained within the tundish. When the drop from the furnace body to the tundish is large, as in a single-axis tilting furnace, the molten metal splashes onto the bottom and inner walls of the tundish, and onto the surface of the molten metal inside the tundish, and can fly out of the tundish and contaminate the inside of the melting furnace. The above problems have not been addressed in the prior art. An object of the present invention is to provide a tundish which can be reused multiple times while effectively suppressing residual molten metal in the tundish and which is also compatible with a single-axis tilting furnace, and a method for manufacturing an ingot using the tundish. [Means for solving the problem]

[0006] The present invention has been made in view of the above-mentioned problems. That is, the present invention is a tundish for producing an ingot, which, when viewed from the casting direction, has a tapping port in the center of the tundish leading to a mold, has a sloping surface of 10 to 30 degrees toward the tapping port, and has an inner wall surface formed continuously with the sloping surface. The tundish is preferably for a single-axis tilting furnace. More preferably, the thickness of the inclined surface is uniform, or the ratio of the diameter of the cylindrical through hole forming the tapping port to the length of the straight portion is 1:1.

[0007] The present invention also provides a method for producing an ingot using the tundish, comprising the steps of: This method for producing an ingot includes a melting process in which a molten metal is obtained using a melting furnace installed in a vacuum vessel, and a casting process in which the molten metal is cast to obtain an ingot, and in the casting process, the tundish is used to obtain an ingot when the molten metal is cast into a mold. Effect of the Invention

[0008] According to the present invention, a tundish that can be used multiple times while effectively suppressing residual molten metal in the tundish and can be used in a single-axis tilting furnace can be provided. In particular, since it is possible to avoid a decrease in the yield of raw materials caused by residual molten metal in the tundish, it is particularly useful for producing ingots using expensive raw materials. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram showing an example of a tundish as viewed from the casting direction. [Diagram 2] FIG. 2 is a partial cross-sectional schematic view showing an example of a tundish. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a tundish as viewed from the outside of the bottom surface. [Figure 4] 1 is a photograph of the appearance of a tundish after multiple uses. [Diagram 5] FIG. 2 is a schematic partial cross-sectional view showing an example of a tundish provided with a filter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First, the tundish for producing an ingot according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a tundish 21 as viewed from the casting direction. The tundish 21 has a tapping hole 1 at the center of its inner bottom surface. FIG. 2 shows a partial cross section of the tundish. As shown in FIG. 2, the tundish has an inclined surface 2 at an angle of 10 to 30 degrees toward the tapping hole 1. The reason for providing the inclined surface 2 is that, for example, the molten metal obtained in a melting furnace for a single-axis tilting furnace is not always poured in the same path to the tapping hole on the inclined surface, so that the molten metal that moves along the long inclined surface loses heat to the tundish side, solidifies, and becomes residual molten metal in the tundish. In other words, no matter where the molten metal falls on the inner bottom surface of the tundish, it is possible for the molten metal to flow quickly toward the tapping hole 1, and the molten metal is cast into a mold (not shown) through the tapping hole 1. If the angle of the inclined surface 2 is less than 10 degrees, the speed of the molten metal flowing on the inner bottom surface of the tundish decreases, so solidification due to the drop in temperature advances and the amount of molten metal remaining in the tundish increases. Also, if the angle of the inclined surface 2 exceeds 30 degrees, it becomes necessary to provide a long inclined surface in order to accommodate all of the falling positions of the molten metal, which change from the start to the end of pouring, within the tundish. Therefore, the angle of the inclined surface 2 is set to 10 degrees to 30 degrees. The preferable lower limit of the angle of the inclined surface 2 is 15 degrees, and the preferable upper limit of the angle of the inclined surface 2 is 25 degrees.

[0011] In the present invention, a filter 7 may be provided at the tap port 1 as shown in Fig. 5. By providing the filter 7, it is possible to prevent oxidized impurities such as slag from being mixed into the ingot being cast. The material of the filter shown in Fig. 5 is not particularly limited, but it is sufficient to select a material that is unlikely to react with the molten metal and that is easy to collect the desired impurities from high melting point materials such as oxides and carbides such as zirconia, alumina, magnesia, and silicon carbide.

[0012] The angle of the inclined surface of the tundish 21 referred to in the present invention is the angle of the inclined surface when a straight line is drawn horizontally with reference to the entrance of the tapping hole 1 as shown in Fig. 2. In addition, since this is a casting tundish, the tapping hole 1 is provided with a through hole 4 having a straight portion 6 facing the mold. As shown in Figs. 1 to 3, it is preferable that the tapping hole 1 is located in the center of the tundish 21 and provided with a through hole 4 leading to the mold. The diameter 5 of the through hole 4 formed from the tap hole 4 toward the mold may be changed depending on the weight of the ingot to be cast. For example, for a small ingot weighing about 5 to 30 kg, the diameter may be 15 mm to 35 mm. The tundish 21 of the present invention has an inner wall surface 3 formed continuously with the inclined surface 2. This allows the inner wall surface to block splashes of the molten metal that are generated, making it possible to suppress the splashes from scattering outside the tundish. The above-described configuration of the present invention can reduce the amount of molten metal remaining in the tundish, and at the same time, it also reduces the risk of the tap hole being clogged with solidified molten metal after casting, making it possible to use the tundish multiple times.

[0013] The tundish 21 of the present invention is suitable for use in a uniaxial tilting furnace. As described above, in the case of a uniaxial tilting furnace, the position at which the molten metal falls changes significantly from the start to the end of pouring into the tundish. In the present invention, since the inner bottom surface of the tundish has an inclined surface, the molten metal can flow quickly toward the tapping hole 1 no matter where the molten metal falls on the inner bottom surface of the tundish.

[0014] In the present invention, it is preferable that the thickness of the inclined surface on the inner bottom surface of the tundish is uniform, as shown in FIG. The tundish 21 expands thermally from the portion in contact with the molten metal due to the heat, and a change in dimension occurs. For example, if the thickness of the inclined surface 2 becomes thicker toward the outer periphery of the tundish 21, the inside of the tundish expands thermally, but the temperature of the outside does not rise and the dimensions do not change, so that the tundish may crack in order to eliminate the distortion between the two. Therefore, it is preferable that the thickness of the inclined surface 2 described above is uniform (thickness does not change) so that local distortion is not generated in the cross section of the tundish. Note that, even if the thickness is uniform, thickness variations to the extent of manufacturing variations are allowed. For example, a thickness variation of 5 mm or less falls within the range of uniformity. A thickness variation of 3 mm or less is preferable, and a thickness variation of 2 mm or less is more preferable.

[0015] In the tundish 21 of the present invention, as shown in FIG. 2, the through hole 4 having a cylindrical cavity forming the tapping port 1 preferably has a ratio of its diameter 5 to the length of the straight portion 6 of 1:1. If the straight portion 6 is longer than this ratio, the flow resistance and temperature drop are likely to be significant when the molten metal passes through the tapping port 1, and the risk of solidification and clogging in the tapping port may increase. Conversely, if the diameter is larger than this ratio, the flow of the molten metal after passing through the tapping port 1 may be disturbed and the straightness may be likely to decrease, and the risk of the molten metal not entering the mold arranged below the tundish 21 may increase. These risks are influenced by physical properties such as the viscosity and density of the molten metal itself, and chemical properties such as the "wettability" and reactivity between the molten metal and the tundish, but in order to avoid clogging of the tapping port 1 while dealing with molten metals of a wide variety of alloy compositions and to repeatedly use the tundish, it is preferable that the cylindrical through hole 4 forming the tapping port 1 has a ratio of its diameter 5 to the length of the straight portion 6 of 1:1. However, even if the ratio is 1:1, some variation in the ratio due to manufacturing variability is allowed. For example, a variation of plus or minus 10% is within the range of 1:1. By combining the preferred embodiments described above, it is possible to prevent cracking of the tundish, to prevent solidification blockage in the tap hole, and to more reliably pour the molten metal into the mold.

[0016] Next, a method for producing an ingot using the tundish of the present invention will be described. The ingot to be produced is a 10 kg ingot for research purposes that contains expensive alloying elements. The melting furnace used is a melting furnace with one tilting axis (single-axis tilting furnace) installed in an empty vessel. The tundish used has the structure shown in Figures 1 to 3, and is a tundish for a uniaxial tilting furnace, having a tapping port 1 leading to a mold in the center of the tundish 21, a sloping surface 2 at an angle of 25 degrees toward the tapping port, and an inner wall surface 3 formed continuous with the sloping surface. The sloping surface of the tundish 21 has a uniform thickness of about 40 mm, and the straight portion 6 and diameter 5 of the through hole 4 formed from the tapping port provided in the tundish 21 toward the mold are each about 20 mm, with the ratio of the length of the diameter 5 to the straight portion 6 being 1:1.

[0017] The ingot can be produced by the following procedure. As the dissolution process, (1) The vacuum chamber is evacuated using a vacuum pump, and a vacuum is maintained inside the chamber. (2) A melting furnace installed inside the vacuum vessel is used to melt the metals that will be used to make the ingots. As a casting preparation process, (3) A mold that fits the shape of the ingot to be produced and the tundish of the present invention described above are placed on top of it. (4) The pressure inside the vacuum vessel and the location where the tundish and mold of the present invention are placed are adjusted to the same pressure. As a casting process, (5) The melting furnace is tilted toward the tundish, and the molten metal is poured into the tundish of the present invention. (6) After pouring all the molten metal, wait until the metal in the mold solidifies. The ingot extraction process is as follows: (7) Remove the tundish and mold of the present invention. (8) Remove the ingot from the mold.

[0018] A photograph of the tundish after 20 repetitions of the above-mentioned ingot production is shown in Figure 4. Figure 4 is a photograph of the tundish's appearance as seen from the casting direction. As can be seen from Figure 4, there was no cracking in the tundish after multiple uses, and it can be seen that the residual molten metal in the tundish was effectively suppressed. From the above, it was possible to safely cast without spilling the molten metal from the mold. In addition, the present invention makes it possible to suppress the amount of molten metal remaining in the tundish, and thus makes it possible to avoid a decrease in the yield of raw materials due to the remaining molten metal in the tundish, which is particularly useful for producing ingots using expensive raw materials. In the above-mentioned melting process, the present invention is not limited to a melting furnace installed in a vacuum vessel. For example, the tundish of the present invention can be applied to a casting process in which melting is performed in an atmosphere other than a vacuum, such as an air atmosphere or a gas atmosphere. [Explanation of symbols]

[0019] 1. Tap hole 2 Slope 3. Inner wall surface 4 Through holes 5 diameter 6 Straight section 7 Filters 21 Tundish

Claims

1. A tundish for producing an ingot, the tundish being viewed from a casting direction, The tundish has a tapping hole at its center that leads to a mold, A surface having an inclination of 10 to 30 degrees toward the tap hole, The tundish has an inner wall surface formed continuously with the inclined surface.

2. 2. The tundish of claim 1, wherein the tundish is for a single-axis tilting furnace.

3. 3. The tundish according to claim 1, wherein the thickness of said inclined surface is uniform.

4. 3. The tundish according to claim 1, wherein the ratio of the diameter of the cylindrical through hole forming the tapping port to the length of the straight portion is 1:

1.

5. A method for producing an ingot using the tundish according to claim 1 or 2, a melting step of obtaining molten metal using a melting furnace installed in a vacuum vessel; A casting step of casting the molten metal to obtain an ingot, A method for producing an ingot, characterized in that, in the casting step, when the molten metal is cast into a mold, an ingot is obtained using the tundish.

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