JP2009174054A - Metal refining method and apparatus, refined metal, cast metal, metallic product and electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal refining method and apparatus, etc., by which the refining efficiency can be improved and the obtained refined metal weight is increased by preventing the metal crystallized under state of high solidified speed from being exfoliated from a cooling body after growing to some extent. <P>SOLUTION: In the method for refining the metal, crystallizing a high purity metal on the cooling body surface while rotating the cooling body 3 by dipping the cooling body 3 into molten metal 2 to be refined; the maximum rotating speed of the cooling body 3 at the front-half of the initial stage of the refining, is set at higher than the average rounding speed after the initial stage of the refining and the average rounding speed of the cooling body at the rear-half of the initial stage of the refining, is set at lower than the average rounding speed after the initial stage of the refining to perform the refining. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal purification method and apparatus, and more specifically, the content of eutectic impurities from metals such as aluminum, silicon, magnesium, lead, and zinc containing eutectic impurities using the principle of segregation solidification. The present invention relates to a method and an apparatus for producing a high-purity metal with a smaller amount than the original metal, and further relates to a metal purified by the above-described method, a cast product using the metal, a metal product, and an electrolytic capacitor.

  As a method for purifying this kind of metal, a rotating cooling body is immersed in a molten metal containing eutectic impurities placed in a refined molten metal holding furnace, and the cooling body is rotated while supplying a cooling fluid to the rotating cooling body. A method of crystallizing a purified metal having a high purity on the peripheral surface is known (for example, see Patent Document 1).

  In this method, it has been found that the slower the solidification rate on the peripheral surface of the cooling body, the higher the purity of the crystallized metal. By the way, when the cooling body is immersed in the molten metal to be purified while the temperature of the peripheral surface of the cooling body is low, the solidification rate to the peripheral surface increases, and as a result, the purity of the crystallized metal is as shown in FIG. There is a problem that it becomes low. Further, the metal crystallized at such a high solidification rate has poor adhesion to the cooling body, and is very easily peeled off by centrifugal force due to rotation. There is no problem if it is peeled off at the initial stage of purification, but if it peels after growing to some extent, the weight of the purified metal obtained is reduced.

As a method for coping with such peeling, it has been proposed to provide a groove for preventing peeling on the circumferential surface of the rotating cooling body (see Patent Document 2).
Shoko Sho 61-3385 JP 62-280334 A

  However, the method of providing a groove for preventing peeling on the peripheral surface of the rotating cooling body is not sufficient, and it cannot prevent peeling. Therefore, if it peels after growing to some extent, the weight of purified metal decreases. I still couldn't solve the problem.

  The present invention has been made in view of such circumstances, and avoids a situation where a metal crystallized at a high solidification rate grows to some extent and then peels off from the cooling body, thereby improving the purification efficiency. It is possible to provide a metal refining method and apparatus capable of obtaining a large amount of purified metal, and to provide a metal purified by the above method, a cast product using the metal, a metal product, and an electrolytic capacitor. And

The above problem is solved by the following means.
(1) In a metal refining method in which a cooling body is immersed in a molten metal to be purified and a high purity metal is crystallized on the surface of the cooling body while rotating the cooling body, the maximum peripheral speed of the cooling body in the first half of the refining initial stage Is set larger than the average peripheral speed after the initial stage of purification, and the average peripheral speed of the cooling body in the latter half of the initial purification stage is set smaller than the average peripheral speed after the initial stage of purification. Is performed so as not to exceed the average peripheral speed after the initial stage of purification.
(2) The metal purification method according to item 1, wherein the first half of the purification is from the start of purification to the total purification time × 0.1, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.1.
(3) The metal purification method according to item 1, wherein the first half of the purification is from the start of purification to the total purification time × 0.05, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.05.
(4) The relationship between the maximum peripheral speed V1 of the cooling body in the first half of the refining initial stage, the average peripheral speed V2 of the cooling body in the second half of the refining initial stage, and the average peripheral speed V4 after the initial stage of refining is V1 ≧ V4 × 1.1. The metal refining method according to any one of items 1 to 3, wherein V2 ≦ V4 × 0.9 is set.
(5) The metal purification method according to any one of items 1 to 4, wherein the metal to be purified is aluminum.
(6) A refined metal lump whose impurity element composition distribution is in the range of 70% to 130% of the average impurity concentration.
(7) A furnace body containing the molten metal to be refined, a cooling body immersed in the molten metal contained in the furnace body, a rotary drive device for rotating the cooling body, and a cooling body in the first half of the refining initial stage So that the maximum peripheral speed is higher than the average peripheral speed after the initial stage of purification and the average peripheral speed of the cooling body in the latter half of the initial stage of purification is smaller than the average peripheral speed after the initial stage of purification. And a control means for controlling the rotational speed of the cooling body by the rotary drive device so that the maximum peripheral speed of the cooling body does not exceed the average peripheral speed after the initial stage of purification.
(8) The metal purification apparatus according to item 7, wherein the first half of the purification is from the start of purification to the total purification time × 0.1, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.1.
(9) The metal purification apparatus according to item 7, wherein the first half of the purification is from the start of purification to the total purification time × 0.05, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.05.
(10) In the control means, the relationship between the maximum peripheral speed V1 of the cooling body in the first half of the refining initial stage, the average peripheral speed V2 of the cooling body in the second half of the refining initial stage, and the average peripheral speed V4 after the initial stage of refining is V1 ≧ 10. The metal refining device according to any one of items 7 to 9, wherein the rotational speed of the cooling body by the rotational drive device is controlled so that V4 × 1.1 and V2 ≦ V4 × 0.9.
(11) A purified metal purified by the method according to any one of claims 1 to 5.
(12) A casting manufactured from the refined metal according to claim 11.
(13) A metal product obtained by rolling the cast product according to claim 12.
(14) An electrolytic capacitor in which the metal product according to claim 13 is used as an electrode material.

  According to the invention described in the preceding item (1), since the maximum peripheral speed of the cooling body in the first half of the purification initial stage is set to be larger than the average peripheral speed thereafter, the cooling body is placed in the molten metal to be purified. Crystallized metal having a high solidification rate and low purity, which occurs in the first half of the purification when immersed, can be positively separated from the rotating cooling body and re-dissolved in the molten metal. In this way, the crystallized metal with poor adhesion to the cooling body is removed at an extremely early stage, so that it is possible to avoid the situation where the crystallized metal with a high solidification rate grows to some extent and then peels off from the cooling body. In addition, the average peripheral speed of the cooling body in the second half of the refining stage is set smaller than the average peripheral speed in the first half of the refining stage, and further, the maximum peripheral speed of the cooling body in the second half of the refining stage does not exceed the average peripheral speed after the initial stage of refining. Since it is set and refined, the centrifugal force of the rotating cooling body acting on the crystallized metal can be reduced in the latter half of the early stage of purification, so that the refined metal after aggressive peeling in the first half of the early stage of purification can be grown without peeling. Therefore, it is possible to purify a large amount of crystallization metal with high purification efficiency.

  According to the invention described in item (2) above, stable improvement in purification efficiency and stable increase in purified weight can be expected.

  According to the invention described in item (3) above, it is possible to expect a more stable improvement in purification efficiency and a more stable increase in purified weight.

  According to the invention described in (4) above, the relationship between the maximum peripheral speed V1 of the cooling body in the first half of the refining initial stage, the average peripheral speed V2 of the cooling body in the second half of the refining initial stage, and the average peripheral speed V4 after the initial stage of refining. Since V1 ≧ V4 × 1.1 and V2 ≦ V4 × 0.9 are set, the initial positive peeling effect of the crystallized metal having a high solidification rate and poor adhesion to the cooling body, and then crystallization The effect of preventing the peeled metal can be effectively exhibited.

  According to the invention described in item (5) above, a high-purity metal lump can be obtained.

  According to the invention described in item (6) above, crystallized aluminum having a high solidification rate and poor adhesion to the cooling body can be peeled off from the cooling body at the initial stage of purification, thereby improving the purification efficiency of the aluminum lump.

  According to the invention described in the preceding item (7), the crystallized metal having a high solidification rate and poor adhesion to the cooling body can be positively peeled off at the initial stage of purification, and then the crystallized metal is peeled off. It can be a purification device that can be prevented.

  According to the invention described in the preceding item (8), a purification apparatus that can be expected to stably improve the purification efficiency and stably increase the purified weight can be obtained.

  According to the invention described in item (9) above, it can be a purification apparatus that can be expected to further improve the purification efficiency and to increase the purified weight more stably.

  According to the invention described in the above item (10), the initial positive peeling effect of the crystallized metal having a high solidification rate and poor adhesion to the cooling body and the effect of preventing the subsequent crystallized metal from peeling off are effectively exhibited. And a purification apparatus that can be made to operate.

  According to the invention described in the above item (11), it can be a purified metal with high purity.

  According to the invention described in item (12), a cast product with high purity can be obtained.

  According to the invention described in item (13), a rolled metal product with high purity can be obtained.

  According to the invention described in the preceding item (14), an electrolytic capacitor using an electrode material made of a rolled metal with high purity can be obtained.

  An embodiment of the present invention will be described below.

  FIG. 1 is a diagram for explaining a schematic configuration of a metal refining apparatus according to an embodiment of the present invention and a metal refining method using the same.

  In FIG. 1, reference numeral 1 denotes a molten metal holding furnace, and a molten metal 2 is accommodated and held in the molten metal holding furnace 1. A rotating cooling body 3 is disposed above the holding furnace 1 so as to be movable up and down, left and right. At the time of metal refining, the cooling body 3 moves downward and is immersed in the molten metal 2 in the molten metal holding furnace 1. Has been made. Moreover, although illustration was abbreviate | omitted, the refined metal scraping apparatus is installed by the arrangement | positioning parallel to the molten metal holding furnace 1, and the metal crystallized in the cooling body 3 can be scraped off and collect | recovered. Furthermore, the molten metal 2 in the molten metal holding furnace 1 is arranged in the heating furnace so as to have a constant temperature, and is heated from the outside of the holding furnace 1.

  A rotation driving device 4 such as a motor is connected to the cooling body via a rotating shaft 31 so that a rotational force can be applied to the cooling body 3. The rotational speed of the rotary drive device 4, in other words, the rotational speed of the cooling body 3 can be variably controlled by the control unit 5, so that, as will be described later, the maximum peripheral speed of the cooling body 3 in the first half of the purification initial stage is set. The average peripheral speed of the cooling body 3 in the latter half of the purification initial stage can be set to be smaller than the average peripheral speed in the initial stage of the purification.

  As shown in FIG. 1 (a), the rotary cooling body 3 is immersed in the molten metal 2 in the molten metal holding furnace 1 and rotated while supplying a cooling fluid therein, and the purified metal 6 is disposed on the peripheral surface of the cooling body 1. Crystallize slowly. This order is not particularly limited, and there is no problem even if the rotating cooling body 3 is immersed in the molten metal 2 while rotating. The eutectic impurities are discharged into the liquid phase to form a common impurity impurity concentration layer in the liquid phase near the solidification interface. The impurities in the impurity concentration layer are formed by the relative speed between the rotating cooling body 3 and the molten metal 2. Is dispersed throughout the liquid phase. When solidification proceeds in this state, a metal lump 6 having a purity much higher than that of the original molten metal 2 is obtained on the peripheral surface of the cooling body 3 as shown in FIG.

  The high-purity metal lump 6 on the peripheral surface of the rotary cooling body 3 is pulled up together with the cooling body 3 from the molten metal 2 after a certain period of time, and is scraped off and recovered from the cooling body 3. After that, the cooling body 3 is again crushed in the molten metal 2 in the molten metal holding furnace 1 and used for metal refining. This process is repeated and metal purification is continuously performed.

  In this step, the cooling body after scraping off the purified metal has a temperature clearly lower than the temperature of the molten metal. Therefore, the molten metal 2 that is in contact with the same surface of the cooling body 3 when dipped in the molten metal 2 abruptly solidifies due to thermal diffusion to the cooling body 3. Since the solidified metal is rapidly cooled at this time, the eutectic impurities are hardly discharged, and the purity is poor. In addition, since the close contact with the cooling body 3 is poor, the purified metal lump 6 often peels off during purification, and in this case, the weight of the purified lump obtained after purification for a certain time is reduced. In this way, the purification process becomes very unstable, resulting in poor production efficiency.

  Therefore, the present invention increases the centrifugal force acting on the metal refined mass 6 by deliberately increasing the peripheral speed of the rotary cooler 3 for the low purity metal refined mass 6 crystallized immediately after the cooling body 3 is immersed. By doing so, it is made to peel off positively in a short time in the initial stage of purification. That is, purification is performed by setting the maximum peripheral speed of the cooling body in the first half of the purification initial stage to be larger than the average peripheral speed after the initial stage of purification.

  Thus, by setting the maximum peripheral speed of the cooling body in the first half of the purification initial stage higher than the average peripheral speed after the initial stage of purification, the purified metal with low purity crystallized immediately after the immersion of the cooling body 3 Since the peripheral speed of 3 is high, it receives a large centrifugal force and peels off in a short time. Moreover, since the crystallized metal with low purity solidified by rapid cooling is positively separated, the purification efficiency of the entire refined mass is improved. Then, in the latter half of the initial purification stage, the average peripheral speed of the cooling body is made smaller than the average peripheral speed after the initial stage of purification, and the maximum peripheral speed of the cooling body in the latter half of the initial purification stage does not exceed the average peripheral speed after the initial stage of purification. By doing so, as shown in FIG. 1 (c), the newly purified metal refining lump 6 can be grown without being peeled off after active peeling, and stable purification can be achieved. The resulting purified metal weight also increases.

  Here, the first half of the purification means, for example, from the start of purification to the total purification time × 0.1. Even if the maximum peripheral speed of the cooling body is increased after the elapse of the total purification time × 0.1, the separation timing of the crystallized metal refining mass 6 is too late and the production efficiency may be deteriorated. Desirably, the first half of the purification should be from the start of purification to the total purification time × 0.05.

  Specifically, the maximum peripheral speed V1 of the cooling body from the start of purification to the total purification time × 0.05 is set to V1 ≧ V4 × 1.1 with respect to the average peripheral speed V4 after the initial stage of purification. In order to obtain a more reliable effect, the maximum peripheral speed V1 of the cooling body 3 from the start of purification to the total purification time × 0.1 is set to V1 with respect to the average peripheral speed V4 after the initial stage of purification. It is preferable to carry out purification by setting ≧ V4 × 1.1.

  On the other hand, the latter half of the initial purification refers to, for example, the time from the end of the first half of the initial purification to the total purification time × 0.1. Even if the average peripheral speed is reduced to a time exceeding the total refining time × 0.1, not only does the anti-peeling effect of the purified metal newly crystallized after the positive exfoliation saturate, it also causes a decrease in productivity. There is a possibility that the final refined metal weight cannot be increased. In order to ensure the effect of preventing the new purified metal from being peeled off after positive peeling, it is preferable to ensure at least the end of the first half of the purification from the end of the first half of the purification to the total purification time × 0.05.

  Specifically, the average peripheral speed V2 of the cooling body 3 from the start of purification to the total purification time × 0.05 is set to V2 ≦ V4 × 0.9 with respect to the average peripheral speed V4 thereafter. In order to obtain a more reliable effect, the average peripheral speed V2 of the cooling body 3 from the start of purification to the total purification time × 0.1 is set to V2 ≦ the average peripheral speed V4 thereafter. It is preferable to carry out purification by setting V4 × 0.9.

  Further, if the maximum peripheral speed V3 of the cooling body 3 in the second half of the purification initial stage is equal to or higher than the average peripheral speed V4 in the second half of the purification initial stage, the average peripheral speed V1 of the cooling body 3 in the second half of the purification initial stage is greater than the average peripheral speed V4 thereafter. Even if it is set to a small value, the purified metal crystallized after the aggressive peeling operation in the first half of the refining process may peel again due to the centrifugal force generated by the maximum peripheral speed. It is necessary to set the peripheral speed V3 so as not to exceed the average peripheral speed V4 thereafter. Preferably, the maximum peripheral speed V3 of the cooling body 3 in the latter half of the refining stage is set to 0.95 times or less of the average peripheral speed V4 thereafter.

  In this metal refining apparatus, the molten metal holding furnace 1 may be a single one, or a plurality of holding furnaces may be connected to each other by a connecting rod. In the case of a single substance, when the purification is repeated, the impurity concentration of the molten metal increases, so that the purity of the purified metal is deteriorated. Therefore, it is better to replace the molten metal regularly. When they are connected to each other by a connecting rod, if a new molten metal is poured from one end, the molten metal 2 flows out to the adjacent molten metal holding furnace 1 and the high concentration molten metal stays in the molten metal holding furnace 1 as it is. Therefore, it is not necessary to replace the molten metal. Further, the molten metal that has flowed out of the most downstream molten metal holding furnace 1 is discharged because it has a concentration that is not suitable for purification.

  The rotary cooling body 3 is preferably made of graphite or ceramics, but is not limited thereto. Since the rotary cooling body 3 also becomes high temperature due to contact with the high-temperature molten metal, it may be any metal as long as it does not melt at this high temperature and does not cause an extreme decrease in strength.

  The refrigerant for cooling the rotary cooling body 3 is not particularly limited, and nitriding gas, carbon dioxide gas, argon gas, compressed air, and the like can be used, but compressed air is recommended in terms of cost.

  The refined metal may include metals such as aluminum, silicon, magnesium, lead, and zinc containing eutectic impurities. In particular, when aluminum is purified, if impurities that generate peritectic crystals with aluminum are contained, boron addition and stirring are preferably performed. By adding boron and stirring, boron reacts with peritectic impurities such as Ti, V, and Zr contained in the molten metal, and insoluble borides such as TiB2, VB2, and ZrB2 are generated. Excess boron is removed as eutectic impurities. The boride is separated from the cooling body 3 by the centrifugal force generated by the rotation of the cooling body 3 in the molten metal holding furnace 1 and is not contained in the aluminum crystallized on the peripheral surface of the cooling body 3. In addition, when the molten metal holding furnaces 1 are connected to each other by connecting rods, it is preferable to arrange a boron addition crucible in the uppermost stream. Boron is generally supplied into the molten metal as a master alloy rod added to aluminum.

  Since the metal refine | purified by the above is high purity, the outstanding characteristic and function can be exhibited by using it for various processes and uses. For example, a refined metal may be used for casting to produce a cast product, or the cast product may be rolled and used as various metal plates or metal foils. Moreover, you may use this metal foil as an electrode material of an aluminum electrolytic capacitor, for example.

  The refined metal block has an impurity element composition distribution as shown in FIG. 2 that falls within the range of 70% to 130% of the average impurity concentration. Is desirable in that there are few.

[Example]
A molten aluminum containing mainly Fe: 500 ppm and Si: 400 ppm as impurities is placed in a refining holding furnace, and the power of the refining furnace heater is adjusted and maintained at a temperature of 665 ° C. Then, a tapered rotating cooling body with an outer diameter of 150 mm at the upper end adjusted for temperature is immersed in the molten metal, and purified aluminum is crystallized on the peripheral surface of the rotating cooling body for 7 minutes while rotating at the speed shown below. I let you. The rotating cooling body was cooled by directly applying compressed air.
(1) The rotational speed of the cooling body was changed from the start of purification to the total purification time x 0.025, the peripheral speed V1: 3.5 m / sec, and then the total purification time x 0.05, the average peripheral speed V2: 2.7 m / sec. The maximum peripheral speed V3 was set to 2.9 m / sec, and thereafter the peripheral speed was set to 3.1 m / sec (therefore, the average peripheral speed V4 was also set to 3.1 m / sec). The lump weight averaged 6.16 kg. Further, the number of peelings that occurred during the purification was investigated with the passage of time after the start of purification, as shown in Table 1, and the rate of peeling occurred within the total purification time × 0.05 from the start of purification.

  In addition, the average composition of the refined lump of Experiment No. 3 was Fe: 101 ppm, Si: 121 ppm, the composition in the vicinity of the rotating cooling body contact portion was investigated, Fe: 130 ppm, Si: 153 ppm, the composition in the vicinity of the lump outer periphery was investigated. However, Fe; 98 ppm, Si: 112 ppm.

(2) The rotational speed of the cooling body was changed from the start of purification to the total purification time × 0.05, the peripheral speed V1: 3.5 m / sec, and then to the total purification time × 0.1, the average peripheral speed V2: 2.7 m / sec. The maximum peripheral speed V3 was set to 2.9 m / sec, and thereafter the peripheral speed was set to 3.1 m / sec (therefore, the average peripheral speed V4 was also set to 3.1 m / sec). The lump weight averaged 6.18 kg. Further, the number of peelings that occurred during purification was investigated with the passage of time after the start of purification, as shown in Table 2. The number of peelings within the total purification time × 0.1 from the start of purification decreased.

[Conventional example]
A molten aluminum containing mainly Fe: 500 ppm and Si: 400 ppm as impurities is placed in a refining holding furnace, and the power of the refining furnace heater is adjusted and maintained at a temperature of 665 ° C. After that, a tapered cooling cooling body having an outer diameter of 150 mm whose temperature is adjusted at the upper end is crushed in the molten metal and rotated at a constant speed of 3.1 m / sec. Purified aluminum was crystallized. The rotating cooling body was cooled by directly applying compressed air.

  As a result of conducting the purification experiment five times, the weight of the purified lump was 6.0 kg on average. Further, the number of peelings that occurred during the purification was investigated along with the passage of time after the start of purification. As shown in Table 3, peeling occurred in all purifications from the start of purification to the total purification time × 0.05.

  When the composition in the vicinity of the rotating cooling body contact portion of the purified mass of Experiment No. 13 was investigated, it was extremely poor in purity: Fe: 200 ppm, Si: 240 ppm.

It is a figure for demonstrating the schematic structure of the metal purification apparatus which concerns on one Embodiment of this invention, and the metal purification method using the same. It is a graph which shows the composition distribution of the impurity element of the refined metal lump.

Explanation of symbols

1 Molten metal holding furnace 2 Molten metal (molten metal)
3 Cooling body 4 Rotation drive device 5 Control unit 6 Refined metal block

Claims (14)

In a metal purification method in which a cooling body is immersed in a molten metal to be purified, and a high-purity metal is crystallized on the surface of the cooling body while rotating the cooling body.
The maximum peripheral speed of the cooling body in the first half of the purification is set larger than the average peripheral speed after the initial stage of purification, and the average peripheral speed of the cooling body in the second half of the initial purification stage is set smaller than the average peripheral speed after the initial stage of purification. A metal refining method, wherein the refining is performed such that the maximum peripheral speed of the cooling body in the latter half of the refining initial stage does not exceed the average peripheral speed after the refining initial stage.   The metal purification method according to claim 1, wherein the first half of the purification is from the start of purification to the total purification time × 0.1, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.1.   2. The metal purification method according to claim 1, wherein the first half of the purification is from the start of purification to the total purification time × 0.05, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.05.   The relationship between the maximum peripheral speed V1 of the cooling body in the first half of the purification initial stage, the average peripheral speed V2 of the cooling body in the second half of the initial purification stage, and the average peripheral speed V4 after the initial stage of purification is V1 ≧ V4 × 1.1, V2 ≦ The metal purification method according to any one of claims 1 to 3, which is set to V4 x 0.9.   The metal purification method according to claim 1, wherein the metal to be purified is aluminum.   A metal refined mass in which the impurity element composition distribution is in the range of 70% to 130% of the average impurity concentration. A furnace body containing the molten metal to be refined;
A cooling body immersed in the molten metal contained in the furnace body;
A rotation drive device for rotating the cooling body;
The maximum peripheral speed of the cooling body in the first half of the refining process is larger than the average peripheral speed after the initial stage of refining, and the average peripheral speed of the cooling body in the second half of the refining stage is smaller than the average peripheral speed after the initial stage of refining. Further, a control means for controlling the rotational speed of the cooling body by the rotary drive device so that the maximum peripheral speed of the cooling body in the latter half of the refining initial stage does not exceed the average peripheral speed after the initial stage of refining,
A metal refining apparatus characterized by comprising:   The metal purification apparatus according to claim 7, wherein the first half of the purification is from the start of purification to the total purification time × 0.1, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.1.   The metal purification apparatus according to claim 7, wherein the first half of the purification is from the start of purification to the total purification time × 0.05, and the second half of the purification is from the end of the first half of the purification to the total purification time × 0.05.   The control means is such that the relationship between the maximum peripheral speed V1 of the cooling body in the first half of the purification initial stage, the average peripheral speed V2 of the cooling body in the second half of the purification initial stage, and the average peripheral speed V4 after the initial stage of purification is V1 ≧ V4 × 1. The metal refining device according to any one of claims 7 to 9, wherein the rotational speed of the cooling body by the rotational drive device is controlled so that .1 and V2 ≦ V4 × 0.9.   A purified metal purified by the method according to claim 1.   A casting manufactured from the refined metal according to claim 11.   A metal product obtained by rolling the cast product according to claim 12.   An electrolytic capacitor in which the metal product according to claim 13 is used as an electrode material.

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