Degassing apparatus for aluminum alloy and degassing method for aluminum alloy

Abstract

To reduce the concn. of gas contained in the cast block of an aluminum alloy having ≥ 99. 99wt% impurity.SOLUTION: The length of the trough 3 between the in-line degassing device 4 and the casting device 2 is made to be not longer than the 6500mm. In the in-line degassing device 4, the temperature of the molten metal of the aluminum alloy is controlled to ≤ 780 °C, and also, the hydrogen gas concentration is controlled to ≤ 0.1 14ppm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy degassing device and an aluminum alloy degassing method, and more particularly to an aluminum alloy degassing device and an aluminum alloy degassing method that can suppress the generation of voids in the process of manufacturing a sputtering target. [Background technology]

[0002] For example, sputtering targets are required to have a chemical composition that contains few impurities, to be free of foreign matter such as non-metallic inclusions, to have a low rate of defects such as voids, and to have uniform and fine crystal grain sizes across the entire sputtering surface, and similar properties are also required of the ingots that are the raw materials for such targets.

[0003] When manufacturing a sputtering target, raw materials meeting a specified purity are first melted so as not to be contaminated by other metal elements. Next, the composition is adjusted by adding specified metals to the molten metal, and then a slag removal process is carried out to remove foreign matter, including non-metallic inclusions, from the molten metal. The molten metal is then passed through a filter to remove foreign matter before being poured into a casting machine.

[0004] The molten metal is cooled in the casting machine and solidified into a cylindrical or rectangular prism to obtain the raw material, the ingot. The ingot has coarse crystals with a size of 3 mm or more, and an anisotropic crystalline structure that is elongated in the solidification direction, so the structure is modified.

[0005] In other words, to ensure uniformity in sputtering, the crystal structure of the sputtering target must be uniform, fine, equiaxed grains with a grain size of several hundred microns. Random crystal orientation is also sometimes desired. Therefore, the ingot undergoes plastic processing and heat treatment to modify the structure.

[0006] In order to prevent the occurrence of voids due to this structural modification (plastic processing and heat treatment), specifically, the expansion and aggregation of hydrogen gas in the ingot caused by the "plastic strain" resulting from the plastic processing and the "heat" during heat treatment occurs, which results in the occurrence of voids. In order to prevent this, a degassing process is carried out to remove the hydrogen gas (see, for example, Patent Document 1).

[0007] Patent Document 1 discloses a technique for reducing hydrogen gas by blowing inert gas such as nitrogen, argon, or carbon dioxide into the molten metal in the form of fine bubbles. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-97529 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the technology described in Patent Document 1 was insufficient to stably maintain the quality of materials for sputtering targets.

[0010] In sputtering targets, the occurrence of voids can cause uneven sputtering, resulting in arcing and splashing, which can lead to product defects.

[0011] The present invention has been devised in view of the above points, and aims to provide an aluminum alloy degassing apparatus and an aluminum alloy degassing method that can sufficiently reduce the gas concentration in an aluminum ingot. [Means for solving the problem]

[0012] As a result of various studies by the inventors of the present application, the following findings have been reached.

[0013] That is, as described above, the expansion and aggregation of hydrogen gas in the ingot occurs due to "plastic strain" and "heat" during the structural modification of the ingot, resulting in the generation of voids. The generation of voids was confirmed when the hydrogen gas concentration in the aluminum alloy ingot was 0.15 ppm or higher, but was not confirmed when the concentration was lower than that.

[0014] For this reason, in order to suppress the generation of voids, it is necessary to control the hydrogen gas content of the aluminum alloy ingot to 0.14 ppm or less.

[0015] Additionally, oxygen, nitrogen, and carbon (which form gaseous compounds with oxygen) have a high saturation content relative to aluminum and do not cause the voids mentioned above. However, oxygen, nitrogen, and oxygen-carbon compounds are released during sputtering and can contaminate the sputtering gas, so their content must be reduced.

[0016] Furthermore, while vacuum casting, in which the melting furnace, molten metal flow path, and casting equipment (casting machine) are placed in a vacuum, is theoretically an effective method for reducing oxygen, nitrogen, and carbon, it is not realistic in terms of cost and mass production capacity. Therefore, it is necessary to consider atmospheric casting as a prerequisite.

[0017] Furthermore, to prevent the contamination of oxygen or nitrogen from the degassing gas (e.g., argon gas) used to degas aluminum alloys, the degassing gas used must be guaranteed to have a specified purity. To achieve this, it is necessary to select a high-purity "degassing gas," and it is also effective to treat the "degassing gas" with a molecular sieve and dehydrate it to reduce oxygen.

[0018] Furthermore, as a method for degassing aluminum alloys, it is difficult to apply a degassing process using a flux, since this leads to a decrease in the purity of the aluminum due to compounds of the metals that make up the flux.

[0019] When attempting to reduce the amount of gas contained in an aluminum alloy by degassing using a "degassing gas" alone, without using a flux, it is effective to set the rotation speed of the rotor that refines the bubbles of the "degassing gas" to a predetermined rotation speed or higher, thereby improving the degassing ability by refining the bubbles.

[0020] However, if the rotor rotation speed is too high, the surface of the molten aluminum alloy will ripple or swirl, resulting in oxygen being taken into the aluminum alloy, and therefore an upper limit must be set for the rotor rotation speed.

[0021] Furthermore, in order to suppress the uptake of hydrogen gas, oxygen gas, and nitrogen gas from the atmosphere, as well as carbon derived from carbon dioxide gas, into the molten metal that has completed the degassing process, it is necessary to purge the opening surface of the trough, which is the molten metal flow path, to the atmosphere with a "degassing gas" of a specified purity, or to keep the molten metal temperature below a specified temperature, limit the opening area to a specified value, and limit the molten metal residence time to a specified time or less.

[0022] [1] Based on this knowledge, in order to achieve the above object, the aluminum alloy degassing device of the present invention is an aluminum alloy degassing device that is installed in a molten metal flow path between an aluminum alloy melting furnace and a casting device that casts the molten aluminum alloy melted in the melting furnace, and degasses the molten metal using a specified degassing gas, wherein the distance of the molten metal flow path to the casting device is 6500 mm or less, the temperature of the molten metal discharged is 780°C or less, and the hydrogen gas concentration is 0.14 ppm or less.

[0023] Here, by making the distance of the molten metal flow path to the casting device 6,500 mm or less, moisture absorption by the molten metal discharged from the degassing device until it reaches the casting device can be suppressed, and the molten aluminum alloy that has completed degassing can be prevented from absorbing hydrogen gas, oxygen gas, and carbon derived from carbon dioxide from the atmosphere.

[0024] In addition, by keeping the temperature of the molten metal discharged from the degassing device below 780°C, the reaction rate between "aluminum" and "oxygen in the atmosphere" is slow, which reduces the amount of oxides produced. It also prevents the molten aluminum alloy from absorbing hydrogen gas from the atmosphere.

[0025] Furthermore, by keeping the hydrogen gas concentration of the molten metal discharged by the degassing device at 0.14 ppm or less, it is possible to suppress the occurrence of voids caused by "plastic strain" and "heat" during structural modification of aluminum alloy ingots.

[0026] [2] In the aluminum alloy degassing apparatus of the present invention, the molten metal to be discharged preferably has an oxygen gas concentration of 20 ppm or less, a nitrogen gas concentration of 20 ppm or less, and a carbon concentration of 40 ppm or less.

[0027] In this case, the target material contains a small amount of gas components, and it is possible to prevent the sputtering gas from being contaminated by gases released from the target material during sputtering.

[0028] [3] In the aluminum alloy degassing device of the present invention, it is preferable that the depth of the molten metal flow path to the casting device is H (mm) and the width is W (mm), and that H / W ≧ 0.75 is satisfied.

[0029] Here, when the volume of the molten metal is constant, the larger the ratio of the width to the depth, the larger the ratio of the area of ​​the molten metal that is in contact with the air relative to the volume of the molten metal, making it easier for hydrogen gas to be absorbed from the atmosphere.In addition, the heat dissipation area to the atmosphere becomes larger, making it necessary to raise the temperature of the molten metal, which also makes it easier for hydrogen gas to be absorbed. Furthermore, when "H / W ≧ 0.75", the hydrogen gas concentration can be kept low, and the generation of voids caused by "plastic strain" and "heat" during structural modification of aluminum alloy ingots can be suppressed.

[0030] [4] In order to achieve the above object, the present invention provides a method for degassing an aluminum alloy, which uses a predetermined degassing gas to degas the molten metal at a point in a molten metal flow path between an aluminum alloy melting furnace and a casting device that casts the molten aluminum alloy melted in the melting furnace, where the distance to the casting device is 6,500 mm or less, and the temperature of the molten metal is set to 780°C or less and the hydrogen gas concentration of the molten metal is set to 0.14 ppm or less.

[0031] Here, by degassing the molten metal at a point in the molten metal flow path between the melting furnace and the casting device where the distance to the casting device is 6,500 mm or less, moisture absorption by the degassed molten aluminum alloy metal until it reaches the casting device can be suppressed, and the absorption of hydrogen gas, oxygen gas, and carbon derived from carbon dioxide from the atmosphere can be suppressed.

[0032] Furthermore, by keeping the temperature of the molten metal below 780°C, the reaction rate between "aluminum" and "oxygen in the atmosphere" is slowed down, which reduces the amount of oxides produced. It also prevents the molten aluminum alloy from absorbing hydrogen gas from the atmosphere.

[0033] Furthermore, by keeping the hydrogen gas concentration in the molten metal at 0.14 ppm or less, it is possible to suppress the occurrence of voids caused by "plastic strain" and "heat" during the structural modification of aluminum alloy ingots.

[0034] [5] In the aluminum alloy degassing method of the present invention, it is preferable to set the oxygen gas concentration of the molten metal to 20 ppm or less, the nitrogen gas concentration to 20 ppm or less, and the carbon concentration to 40 ppm or less.

[0035] In this case, the target material contains a small amount of gas components, and it is possible to prevent the sputtering gas from being contaminated by gases released from the target material during sputtering.

[0036] [6] In the degassing method for aluminum alloys of the present invention, it is preferable to use argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas as the degassing gas, to blow in the degassing gas at a rate of 2.5 L / min or more per kg of molten metal, and to rotate the rotor at a rotation speed of 480 rpm or more and 600 rpm or less.

[0037] In this case, the flow rate of the degassing gas is sufficient and the rotor rotation speed conditions are optimal, so that the bubbles in the degassing gas can be sufficiently broken down, thereby improving the degassing ability of the degassing gas and providing a sufficient degassing effect.

[0038] On the other hand, when the degassing gas is blown at a rate of less than 2.5 L / min per 1 kg of molten metal, the flow rate of the degassing gas is too low to generate sufficient bubbles. Furthermore, if the rotor rotation speed is less than 480 rpm, the bubbles of the degassing gas cannot be sufficiently broken down, and if the rotor rotation speed exceeds 600 rpm, the surface of the molten aluminum alloy will ripple or swirl, trapping oxygen gas.

[0039] [7] In the aluminum alloy degassing method of the present invention, it is preferable to use argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas as the degassing gas, and to blow in the degassing gas at a rate of 16 L / min or more per ton of molten metal into the melting furnace and rotate the rotor at a rotation speed of 600 rpm or more and 700 rpm or less.

[0040] In this case, degassing is carried out not only at the point where the distance to the casting device is 6500 mm or less, but also at the melting furnace, so that the amount of contained gas can be further reduced.

[0041] Furthermore, since the flow rate of the degassing gas is sufficient and the rotor rotation speed conditions are optimal, the bubbles in the degassing gas can be sufficiently broken down, thereby improving the degassing ability of the degassing gas and providing a sufficient degassing effect.

[0042] On the other hand, if the degassing gas is blown in at a rate of less than 16 L / min per ton of molten metal, the flow rate of the degassing gas is too low to generate sufficient bubbles. Furthermore, if the rotor rotation speed is less than 600 rpm, the bubbles of the degassing gas cannot be sufficiently broken down, and if the rotor rotation speed exceeds 700 rpm, the surface of the molten aluminum alloy will ripple or swirl, trapping oxygen gas.

[0043] [8] In the degassing method for aluminum alloys of the present invention, argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas is used as the degassing gas, and it is preferable to blow in 2.5 L / min or more of degassing gas per 1 kg of molten metal on the melting furnace side of the molten metal flow path closer to the "point where the distance to the casting device is 6500 mm or less," and rotate the rotor at a rotation speed of 480 rpm or more and 600 rpm or less.

[0044] In this case, degassing is performed not only at the "point where the distance to the casting device is 6500 mm or less" but also at the "point closer to the melting furnace than the 'point where the distance to the casting device is 6500 mm or less,'" thereby achieving a further reduction in the amount of gas contained.

[0045] Furthermore, since the flow rate of the degassing gas is sufficient and the rotor rotation speed conditions are optimal, the bubbles in the degassing gas can be sufficiently broken down, thereby improving the degassing ability of the degassing gas and providing a sufficient degassing effect.

[0046] On the other hand, when the degassing gas is blown at a rate of less than 2.5 L / min per 1 kg of molten metal, the flow rate of the degassing gas is too low to generate sufficient bubbles. Furthermore, if the rotor rotation speed is less than 480 rpm, the bubbles of the degassing gas cannot be sufficiently broken down, and if the rotor rotation speed exceeds 600 rpm, the surface of the molten aluminum alloy will ripple or swirl, trapping oxygen gas.

[0047] [9] In the method for degassing an aluminum alloy of the present invention, the degassing gas is preferably argon gas having a purity of 99.999% or more, which has been treated with a molecular sieve.

[0048] In this case, it is possible to prevent the inclusion of oxygen and nitrogen from the argon gas, and the amount of gas contained in the molten aluminum alloy can be reduced even more sufficiently.

[0049]

[10] In the method for degassing an aluminum alloy of the present invention, the purity of the aluminum alloy may be 99.99 wt% or more.

[0050] According to the present invention, even in the case of high-purity aluminum alloys with a purity of 99.99 wt% or more, the amount of gas contained can be sufficiently reduced, and quality that meets the specified standards can be stably maintained. [Effects of the Invention]

[0051] The aluminum alloy degassing apparatus and method of the present invention can sufficiently reduce the gas concentration in an aluminum ingot. [Brief explanation of the drawings]

[0052] [Figure 1] FIG. 1 is a schematic diagram for explaining an example of a method for degassing an aluminum alloy to which the present invention is applied. [Figure 2] FIG. 2 is a schematic diagram for explaining another example of the method for degassing an aluminum alloy to which the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0053] Hereinafter, a mode for carrying out the invention (hereinafter referred to as "embodiment") will be described. The explanation will be given in the following order. 1. First embodiment 2. Second embodiment 3. Variations

[0054] <1. First embodiment> FIG. 1 is a schematic diagram for explaining an example of a method for degassing an aluminum alloy to which the present invention is applied.

[0055] In the first embodiment, an aluminum alloy melting furnace 1, a casting device 2 that casts the molten aluminum alloy melted in the melting furnace 1, and an in-line degassing device 4 are provided. The in-line degassing device 4 is provided between the melting furnace 1 and the casting device 2.

[0056] In addition, a gutter (molten metal flow path) 3 is provided for supplying molten metal from the melting furnace 1 to the casting device 2. More specifically, a "first gutter 3a" is provided between the melting furnace 1 and the in-line degassing device 4, and a "second gutter 3b" is provided between the in-line degassing device 4 and the casting device 2.

[0057] Furthermore, the length of the second gutter 3b is 6500 mm or less. In addition, when the depth of the gutter 3 (first gutter 3a, second gutter 3b) is H (mm) and the width is W (mm), it is designed to satisfy the condition "H / W ≧ 0.75".

[0058] The melting furnace 1 is also provided with a degassing rotor 5 . The degassing rotor 5 has a hollow rotary shaft 51 and rotary blades 52 attached to the tip of the rotary shaft 51, and both the rotary shaft 51 and the rotary blades 52 are made of carbon or ceramics.

[0059] The rotary vanes 52 are provided with vents (not shown) for blowing out the degassing gas, and the vents are in communication with the hollow part of the rotary shaft 51. That is, the degassing gas supplied to the hollow part of the rotary shaft 51 passes through the vents provided in the rotary vanes 52 and is blown into the molten metal.

[0060] The rotary shaft 51 is provided so as to be rotatable by a motor (not shown), and rotates at a rotation speed of 600 to 700 rpm. As the rotary shaft 51 rotates, the rotary vanes 52 also rotate, and the rotation of the rotary vanes 52 atomizes the degassing gas (bubbles) that has been blown into the molten metal from the vent hole.

[0061] The in-line degassing device 4 is also provided with a degassing rotor 6 . The degassing rotor 6 has a hollow rotary shaft 61 and rotary blades 62 attached to the tip of the rotary shaft 61, and both the rotary shaft 61 and the rotary blades 62 are made of carbon or ceramics.

[0062] The rotary vanes 62 are provided with vents (not shown) for blowing out the degassing gas, and the vents are connected to the hollow part of the rotary shaft 61. That is, the degassing gas supplied to the hollow part of the rotary shaft 61 passes through the vents provided in the rotary vanes 62 and is blown into the molten metal.

[0063] The rotary shaft 61 is rotatable by a motor (not shown), and rotates at a rotation speed of 480 to 600 rpm. As the rotary shaft 61 rotates, the rotary vanes 62 also rotate, and the rotation of the rotary vanes 62 atomizes the degassing gas (bubbles) that has been blown into the molten metal from the vent hole.

[0064] [Degassing in Melting Furnace 1] In the melting furnace 1, aluminum raw materials (aluminum ingots, scrap aluminum alloy products, etc.) are melted, and predetermined metals are added to the molten metal to adjust the composition. The purity of the aluminum alloy in the first embodiment is 99.99 wt% or more.

[0065] Thereafter, a degassing process (first degassing process) is performed. Specifically, while the motor is driven to rotate the rotary shaft 51 (rotation speed: 600 to 700 rpm), argon gas is blown into the hollow part of the rotary shaft 51 at a rate of 16 L / min or more per ton of molten metal.

[0066] The argon gas (degassing gas) used here has a purity of 99.999% or more and has been subjected to molecular sieve treatment.

[0067] The argon gas bubbles that are blown into the molten metal in the melting furnace 1 and atomized by the rotary blades 52 can remove hydrogen gas and the like from the molten aluminum alloy.

[0068] [Degassing in inline degasser 4] After the degassing treatment (first degassing treatment) in the melting furnace 1 is completed, the molten metal is supplied to the in-line degassing device 4 through the first trough 3a and is further subjected to a degassing treatment (second degassing treatment).

[0069] Specifically, in the in-line degassing device 4, the motor is driven to rotate the rotary shaft 61 (rotation speed: 480 to 600 rpm), while argon gas is blown into the hollow part of the rotary shaft 61 at a rate of 2.5 L / min or more per kg of molten metal.

[0070] The argon gas bubbles that are blown into the molten metal in the in-line degassing device 4 and atomized by the rotary blades 62 can remove hydrogen gas and the like from the molten aluminum alloy.

[0071] The temperature of the molten metal discharged from the in-line degassing device 4 is 780°C or less. Degassing is performed so that the hydrogen gas concentration is 0.14 ppm or less, the oxygen gas concentration is 20 ppm or less, the nitrogen gas concentration is 20 ppm or less, and the carbon concentration is 40 ppm or less.

[0072] After the degassing in the in-line degasser 4 is completed, the molten aluminum alloy is supplied to the casting device 2 through the second trough 3b.

[0073] <2. Second Embodiment> FIG. 2 is a schematic diagram for explaining another example of the method for degassing an aluminum alloy to which the present invention is applied.

[0074] The second embodiment includes an aluminum alloy melting furnace 1, a casting device 2 for casting the molten aluminum alloy melted in the melting furnace 1, a first inline degassing device 4A, and a second inline degassing device 4B. The first in-line degassing device 4A and the second in-line degassing device 4B are provided between the melting furnace 1 and the casting device 2.

[0075] In addition, a trough (molten metal flow path) 3 is provided for supplying molten metal from the melting furnace 1 to the casting device 2. More specifically, a "third trough 3c" is provided between the melting furnace 1 and the first in-line degassing device 4A, a "fourth trough 3d" is provided between the first in-line degassing device 4A and the second in-line degassing device 4B, and a "fifth trough 3e" is provided between the second in-line degassing device 4B and the casting device 2.

[0076] Furthermore, the length of the fifth gutter 3e is 6500 mm or less. In addition, when the depth of the gutters 3 (third gutters 3c, fourth gutters 3d, fifth gutters 3e) is H (mm) and the width is W (mm), they are designed to satisfy the condition "H / W ≧ 0.75".

[0077] The first in-line degassing device 4A is also provided with a degassing rotor 7. The degassing rotor 7 has a hollow rotary shaft 71 and rotary blades 72 attached to the tip of the rotary shaft 71, and both the rotary shaft 71 and the rotary blades 72 are made of carbon or ceramics.

[0078] The rotary vanes 72 are provided with vents (not shown) for blowing out the degassing gas, and the vents are in communication with the hollow part of the rotary shaft 71. That is, the degassing gas supplied to the hollow part of the rotary shaft 71 passes through the vents provided in the rotary vanes 72 and is blown into the molten metal.

[0079] The rotary shaft 71 is rotatable by a motor (not shown), and rotates at a rotation speed of 480 to 600 rpm. As the rotary shaft 71 rotates, the rotary vanes 72 also rotate, and the rotation of the rotary vanes 72 atomizes the degassing gas (bubbles) that has been blown into the molten metal from the vent hole.

[0080] Similarly, the second in-line degassing device 4B is also provided with a degassing rotor 8. The degassing rotor 8 has a hollow rotary shaft 81 and rotary blades 82 attached to the tip of the rotary shaft 81, and both the rotary shaft 81 and the rotary blades 82 are made of carbon or ceramics.

[0081] The rotary vanes 82 are provided with vents (not shown) for blowing out the degassing gas, and the vents are connected to the hollow part of the rotary shaft 81. That is, the degassing gas supplied to the hollow part of the rotary shaft 81 passes through the vents provided in the rotary vanes 82 and is blown into the molten metal.

[0082] The rotary shaft 81 is rotatable by a motor (not shown), and rotates at a rotation speed of 480 to 600 rpm. As the rotary shaft 81 rotates, the rotary vanes 82 also rotate, and the rotation of the rotary vanes 82 atomizes the degassing gas (bubbles) that has been blown into the molten metal from the vent hole.

[0083] [Degassing in the first in-line degasser 4A] In the melting furnace 1, aluminum raw materials (aluminum ingots, scrap aluminum alloy products, etc.) are melted, and predetermined metals are added to the molten metal to adjust the composition. Thereafter, the molten metal is supplied to the first in-line degassing device 4A through the third trough 3c, and is subjected to a degassing treatment (first degassing treatment). The purity of the aluminum alloy in the second embodiment is 99.99 wt% or more.

[0084] Specifically, in the first in-line degassing device 4A, the motor is driven to rotate the rotary shaft 71 (rotation speed: 480 to 600 rpm), while argon gas is blown into the hollow part of the rotary shaft 71 at a rate of 2.5 L / min or more per 1 kg of molten metal.

[0085] The argon gas bubbles that are blown into the molten metal in the first in-line degassing device 4A and atomized by the rotary blades 72 can remove hydrogen gas and the like from the molten aluminum alloy.

[0086] [Degassing in the second in-line degasser 4B] After the degassing treatment (first degassing treatment) in the first in-line degassing device 4A is completed, the molten metal is supplied to the second in-line degassing device 4B through the fourth trough 3d and further subjected to a degassing treatment (second degassing treatment).

[0087] Specifically, in the second inline degassing device 4B, the motor is driven to rotate the rotary shaft 81 (rotation speed: 480 to 600 rpm), while argon gas is blown into the hollow part of the rotary shaft 81 at a rate of 2.5 L / min or more per 1 kg of molten metal.

[0088] The argon gas bubbles that are blown into the molten metal in the second in-line degassing device 4B and atomized by the rotary blades 82 can remove hydrogen gas and the like from the molten aluminum alloy.

[0089] The temperature of the molten metal discharged from the second in-line degassing device 4B is 780°C or less. In addition, degassing is performed so that the hydrogen gas concentration is 0.14 ppm or less, the oxygen gas concentration is 20 ppm or less, the nitrogen gas concentration is 20 ppm or less, and the carbon concentration is 40 ppm or less.

[0090] After the degassing in the second in-line degassing device 4B is completed, the molten aluminum alloy is supplied to the casting device 2 through the fifth trough 3e.

[0091] [effect] In the aluminum alloy degassing method to which the present invention is applied, in both the first and second embodiments, the gas content in the molten metal can be reduced, and as a result, the gas concentration in the aluminum alloy ingot cast by the casting apparatus 2 can also be sufficiently reduced. Therefore, no voids were generated during the structural modification of the aluminum alloy ingot.

[0092] Furthermore, the contents of oxygen, nitrogen, and carbon contained in the aluminum alloy ingot can be sufficiently reduced, and the sputtering gas will not be contaminated.

[0093] <3. Modifications> In both the first and second embodiments described above, the explanation is given using examples in which not only the "first degassing treatment" but also the "second degassing treatment" is performed, but if the gas content can be sufficiently reduced by a single degassing treatment, it is not necessarily necessary to perform multiple degassing treatments.

[0094] For example, the "first degassing process" in the first embodiment may be omitted, and only the "second degassing process" in the first embodiment may be performed. [Explanation of symbols]

[0095] 1 Melting furnace 2 Casting equipment 3a First Gutter 3b Second gutter 3c Third Gutter 3d Fourth Gutter 3e The Fifth Gutter 4 In-line degasser 4A First in-line degasser 4B Second in-line degasser 5 Degassing rotor 51 Rotation axis 52 Rotating blades 6 Degassing rotor 61 Rotation axis 62 Rotor blades 7 Degassing rotor 71 Rotation axis 72 Rotating blades 8 Degassing rotor 81 Rotation axis 82 Rotating blades

Claims

1. 1. An aluminum alloy degassing device that is provided in a molten metal flow path between an aluminum alloy melting furnace and a casting device that casts molten aluminum alloy melted in the melting furnace, and that degasses the molten metal using a predetermined degassing gas, The distance of the molten metal flow path to the casting device is 6500 mm or less, and The temperature of the molten metal to be discharged is 780°C or less, and the hydrogen gas concentration is 0.14 ppm or less. Aluminum alloy degassing equipment.

2. The discharged molten metal has an oxygen gas concentration of 20 ppm or less, a nitrogen gas concentration of 20 ppm or less, and a carbon concentration of 40 ppm or less. The degassing apparatus for aluminum alloys according to claim 1.

3. When the depth of the molten metal flow path to the casting device is H (mm) and the width is W (mm), H / W≧0.75 3. The degassing apparatus for aluminum alloys according to claim 1 or 2.

4. A method for degassing an aluminum alloy, comprising: degassing the molten metal using a predetermined degassing gas at a point in a molten metal flow path between a melting furnace for an aluminum alloy and a casting device that casts the molten metal of the aluminum alloy melted in the melting furnace, the point being 6,500 mm or less away from the casting device; The temperature of the molten metal is set to 780°C or less, The hydrogen gas concentration in the molten metal is set to 0.14 ppm or less. A method for degassing aluminum alloys.

5. The oxygen gas concentration of the molten metal is set to 20 ppm or less, the nitrogen gas concentration is set to 20 ppm or less, and the carbon concentration is set to 40 ppm or less. The method for degassing an aluminum alloy according to claim 4.

6. As the degassing gas, argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas is used, and The degassing gas is blown in at a rate of 2.5 L / min or more per 1 kg of the molten metal, and the rotor is rotated at a rotation speed of 480 rpm or more and 600 rpm or less. The method for degassing an aluminum alloy according to claim 4 or 5.

7. As the degassing gas, argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas is used, and In the melting furnace, the degassing gas is blown in at a rate of 16 L / min or more per ton of the molten metal, and the rotor is rotated at a rotation speed of 600 rpm or more and 700 rpm or less. The method for degassing an aluminum alloy according to claim 4 or 5.

8. As the degassing gas, argon gas or a mixed gas obtained by mixing argon gas with chlorine gas in an amount of 3% or less relative to the amount of argon gas is used, and The degassing gas is blown into the molten metal flow path at a rate of 2.5 L / min or more per kg of the molten metal on the melting furnace side of the point, and the rotor is rotated at a rotation speed of 480 rpm or more and 600 rpm or less. The method for degassing an aluminum alloy according to claim 4 or 5.

9. The degassing gas is argon gas with a purity of 99.999% or more that has been treated with a molecular sieve. The method for degassing an aluminum alloy according to claim 4 or 5.

10. The purity of the aluminum alloy is 99.99 wt% or more. The method for degassing an aluminum alloy according to claim 4 or 5.

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