EP1462530A1

EP1462530A1 - Apparatus for refining molten metal and method for refining molten metal using the same

Info

Publication number: EP1462530A1
Application number: EP04007604A
Authority: EP
Inventors: Tsutomu c.o. Nippon Light Metal Co Ltd Saito; Masayuki c.o. Nippon light metal co. ltd. Ozawa; Shouichi c.o. Nippon light metal co ltd. Kobayashi; Tsunehiko c.o. Nippon light metal co ltd Makino; Minoru c.o. Fukuoka Alumi Kogyo Co.Ltd. Fukuda
Original assignee: Nippon Light Metal Co Ltd
Current assignee: Nippon Light Metal Co Ltd
Priority date: 2003-03-28
Filing date: 2004-03-29
Publication date: 2004-09-29
Also published as: JP2004292941A

Abstract

An apparatus for refining a molten metal is characterized by a gas supply pipe 16 of inert gas G, a rotary feeder 6, a rotary shaft 32, and a rotator 36. The rotary feeder 6 supplies a flux powder P to the gas supply pipe 16. The rotary shaft 32 has a communication passage 34 provided therein so as to communicate with the gas supply pipe 16. In additions, the rotary shaft 32 is inserted into a molten metal M under the condition capable of rotating in one-way direction as well as normal and reverse directions. The rotator 36 is provided on an end portion of the rotary shaft 32 and includes a discharge port 38 to discharge the inert gas G or a compound of the inert gas G and the flux powder P into the molten metal M.

Description

FIELD OF THE INVENTION

The present invention relates to an apparatus for refining a molten metal and a method for refining the molten metal using the same. In addition, metals disclosed in the present specification relate to any one of aluminum, magnesium, and copper as well as the alloys based on any one of these three metals.

BACKGROUND OF THE INVENTION

A rotary degassing apparatus is disclosed as an apparatus to remove impurities in a molten aluminum. In the apparatus, an inert gas is blown into the molten aluminum through a nozzle, then the aluminum molten metal is stirred by a rotator provided on an end of the nozzle so that the inert gas is pulverized and discharged into the molten metal. (For example, P1 to 5, and Fig.1 to 4 of Japanese unexamined Patent Publication H07-233425)

Furthermore, a flux-diffusion rotator utilized in an apparatus for processing a molten metal is disclosed as an apparatus. In the apparatus, a flux carried by an inert gas is blown into an aluminum molten metal through a lance, the aluminum molten metal is stirred by a rotator provided on end of the lance so that the flux is diffused and discharged into the aluminum molten metal. (For example, P1 to 5, and Fig.1 to 3 of Japanese unexamined Patent Publication S63-183136)

Furthermore, a process for refining a molten light metal is disclosed, in which an inert gas in the molten metal is pulverized and bubbled by means of a rotation of a rotator inserted into the molten light metal to generate a convection in the molten light metal against a spiral flow before the spiral flow is generated in the molten light metal due to the rotation of the rotator. (For example, P1 to 5, and Fig.1 to 6 of Japanese unexamined Patent Publication H07-122106)

However, the following drawbacks have been risen in the above mentioned apparatus.

According to the rotary degassing apparatus disclosed in Japanese unexamined Patent Publication H07-233425, impurities in the molten metal can be physically removed by the inert gas, but the impurities cannot be efficiently removed.

Furthermore, according to the apparatus for processing a molten metal using flux-diffusing rotator disclosed in Japanese unexamined Patent Publication S63-183136, the inert gas and the flux can be pulverized by the rotator provided on the end of the lance to be discharged into stirred molten metal. However, pulverized inert gas cannot be uniformly diffused in the molten metal due to a whirlpool flow generated in the molten metal in accordance with a rotation of the rotator. Consequently, the pulverized inert gas and the flux are floated on or near the surface of the molten metal due to the whirlpool flow.

Furthermore, according to the process for refining the molten light metal disclosed in Japanese unexamined Patent Publication H07-122106, the inert gas is pulverized and bubbled by a rotation of the rotator to be diffused into the molten metal in spite of the fact that no flux is used. In addition, the rotator is alternately rotated in normal and reverse directions in such a manner that a direction of rotation is changed to a reverse direction from a normal direction and vice versa before the spiral flow is generated in the molten metal. The pulverized and bubbled inert gas can be thus efficiently rubbed against the molten light metal so that the impurities can be physically removed in an efficient manner. Accordingly, the refining process method can gain remarkable effects in comparison with a conventional refining process method in which the rotator is rotated in one-way direction. However, since the process is performed by only the inert gas, impurities cannot be efficiently removed in short time when impurities are abundant in the molten light metal.

Accordingly, in order to solve the aforementioned drawbacks of conventional apparatus, the purpose of the present invention is to provide an apparatus for refining the molten metal and a method for refining the molten metal using the same having the following the feature. Impurities, which are abundant in the molten metal, can be efficiently removed by means of a chemical reaction caused by the flux in combination with a physical action caused by the inert gas.

SUMMARY OF THE INVENTION

To solve aforementioned drawbacks, the present invention was made to provide the following two steps. The first step is a step to diffuse a flux, which is carried by an inert gas, into a molten metal so as to cohere with impurities in the molten metal. The second step is a step to pulverize and diffuse only the inert gas in the molten metal so as to float impurities on or near the surface of the molten metal. In the method of the present invention, the above two steps are performed in order. Or the above two steps are perform simultaneously.

Specifically, an apparatus for refining the molten metal of the present invention is comprised of a gas supply pipe for an inert gas, a powder supply means, a rotary shaft, and a rotator. Herein, the powder supply means is a means for supplying a flux powder to the gas supply pipe. The rotary shaft includes a communication passage provided therein so as to communicate with the gas supply pipe. In addition, the rotary shaft is inserted into the molten metal under the condition capable of rotating in one-way direction as well as normal and reverse directions. The rotator is provided on an end portion of the rotary shaft and has a discharge port to discharge only the inert gas or a compound of the inert gas and the flux powder into the molten metal.

According to the apparatus, a method for refining the molten metal is performed in the suitable condition in accordance with properties of the molten metal and kinds of impurities by taking the following two steps in arbitrary order. The first step is a flux-process step. The second step is a degassing-process step. The flux-process step is processed in the following manner. A compound of inert gas as carrier gas and the flux are pulverized by means of a rotation of the rotator rotating in one-way direction or normal and reverse directions to be uniformly diffused into the molten metal. Sequentially, any products gained by a chemical reaction of impurities and the flux are floated on the surface of the molten metal and is removed. On the other hand, the degassing-process step is performed in the following manner. Only the inert gas is pulverized and bubbled by means of a rotation of the rotator rotating in one-way direction or normal and reverse directions to be diffused into the molten metal. Sequentially, impurities and the remaining flux in the molten metal are floated on the surface of molten metal and are physically removed.

Especially, when only the inert gas is pulverized and bubbled by means of the rotator rotating in normal and reverse directions to be discharged into the molten metal, as described latter, the molten metal can be more efficiently refined by performing the degassing process under the state that a rotation of molten metal is mild so as not to generate a spiral flow in the molten metal

In addition, a kind of the flux is not specified in particular. For example, alkali, chloride of alkaline-earth metal, fluoride, carbonate, lead sulfate, nitrate, and the like can be utilized as said flux.

Furthermore, the apparatus for refining the molten metal of the present invention includes also a hopper as well as a rotary feeder or a screw feeder. Herein, the hopper has the flux powder stored therein. The rotary feeder or the screw feeder is constructed in such a manner that one side thereof is communicated with a lower end portion of the hopper while the other side thereof is communicated with the gas supply pipe.

According to the apparatus, the flux powder stored in the hopper is discharged every predetermined quantity and is mixed with inert gas, which is a carrier gas. Sequentially, a compound of flux powder and inert gas is diffused into the molten metal via the rotary shaft and the rotator. In addition, a required amount of flux powder can be certainly supplied into a gas supply pipe of the inert gas in a continuous manner or an intermittent manner in accordance with a kind of molten metal and a content of impurities.

Now, the rotary feeder and the screw feeder will be explained.

The rotary feeder includes a pair of rotor plates, which are relatively rotated around a coaxial shaft. Each rotary plate has a through hole in such a manner that the through hole of one rotary plate is lapped over that of the other rotary plate at one position. Thereby, flux powder can be certainly discharged from the hopper every predetermined quantity.

On the other hand, the screw feeder includes a horizontal screw shaft having a spiral-depressed groove in the longitudinal direction thereof. When the screw shaft is rotated, the flux powder can be continuously conveyed in the horizontal direction along the spiral-depressed groove of the screw shaft. In addition, it is preferable to install a vibrator on said hopper to prevent a bridge phenomenon of the flux powder from occurring in the vicinity of the outlet of the hopper.

What is more, a method for refining the molten metal of the present invention is used in the refining apparatus for the molten metal. The method includes a flux-process step and a degassing-process step. The flux-process step is performed in the following manner. The rotator inserted into the molten metal is rotated in one-way direction or normal and reverse directions, while a compound of pulverized inert gas and flux powder is diffused into the molten metal by means of the rotator. On the other hand, the degassing-process step is performed in the following manner. Only the inert gas is discharged into said molten metal from the rotator, while the rotator imparts a rotation to the molten metal in one-way direction or normal and reverse directions under the condition that a spiral flow does not occur in the molten metal.

According to the method, the flux process-step, which requires times for chemical reactions, is performed in advance by means of the rotator rotating in one-way direction or normal and reverse directions. Thereby, impurities and the flux in the molten metal are floated on the surface of molten metal and separated. Sequentially, only the inert gas is pulverized and bubbled by means of a rotation of the rotator rotating in one-way direction or normal and reverse directions under the condition that the spiral flow does not occur in the molten metal. Consequently, impurities and remaining flux in molten metal are certainly floated on the surface of molten metal and removed.

Therefore, since aforementioned two steps are efficiently performed, impurities in the molten metal can be efficiently removed. Herein, during the aforementioned two steps, the rotator is alternately rotated in normal and reverse directions. A rotation time of the normal direction is the same as that of the reverse direction.

Additionally, the present invention can also include a method for refining the molten metal having the following features. When only the flux-process step is performed, the degassing-process step can be also performed in parallel with the flux-process step. In the meantime, the rotator inserted into said molten metal is rotated in one way direction or normal and reverse directions under the condition that a spiral flows is not generated in the molten metal. In this case, the rotator is rotated in one-way direction or normal and reverse directions under the condition that a spiral flows is not generated in molten metal. In the meantime, a compound of the inert gas and flux can be pulverized and uniformly discharged into the molten metal. Thereby, the molten metal can be refined by means of a chemical agglutination reaction caused by the flux in the combination of a floating action caused by the inert gas as finely divided air bubbles. In a preferred embodiment, a degassing-process step is performed such that only the inert gas is blown into the molten metal over a period of from several minutes to ten minutes.

Also, a method for refining for the molten metal disclosed in the present invention can also include one of the following two steps. The first step is a step that molten metal is cast into ingots by means of a continuous casting method after the molten metal is refined by means of said each step. The second step is a step that the molten metal is poured into a required mold to be a casting product after the molten metal is refined by means of said each steps.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 is an elevation view showing an apparatus for refining a molten metal regarding the present invention.

Fig.2 is a vertical cross sectional view showing an apparatus for refining a molten metal of Fig.1.

Fig 3 is an elevation view showing an apparatus for refining a molten metal regarding the other embodiment.

Fig. 4 is a vertical cross sectional view showing an apparatus for refining the molten metal of Fig.1.

DETAILED EXPLANATION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will now be described with reference to the accompanied drawings. Fig.1 is an elevation view showing an apparatus 1 for refining a molten metal regarding the one embodiment of the present invention. Fig. 2 is a vertical cross sectional view showing the refining apparatus 1 of Fig.1.

As shown in Fig.1 and 2, the refining apparatus 1 for the molten metal is comprised of a gas supply pipe 16 of an inert gas G such as nitrogen or argon, a powder supply means, a rotary shaft 32. Herein, the powder supply means includes a rotary feeder 6 and a hopper 2 for supplying the powder P to the gas supply pipe 16. The rotary shaft 32 includes a communication passage 34 provided therein so as to communicate with the gas supply pipe 16. In addition, the rotary shaft 32 is inserted into the molten aluminum (the molten metal) M in a crucible 40.

Flux powder P is stored in the hopper 2 via an upper inlet 3 of the hopper 2. As shown by the arrow of the broken line in Fig.2, the flux powder P is fallen into a casing 7 of a rotary feeder 6 via an exhaust hole 4. The exhaust hole is provided on the lower portion of a corn. The casing 7 includes a rotator 8 and a disc 10 provided therein in such a manner that the rotator 8 and the disc 10 are located in a coaxial position. The rotator 8 can be rotated, while the disc 10 cannot be rotated.

A through hole 9 is provided away from the center of the rotator 8, while a through hole 11 is provided far from the center of the disc 10. A belt 13 is hooked on a circumference of the rotator 8 and a pulley 12 provided in the side of the casing 7 so as to bridge over the rotator 8 and the pulley 12. Thereby, when a motor M1 is rotated, the rotator 8 can be rotated in accordance with a rotation of the motor M1.

The exhaust hole 4 of the hopper 2 is located away from the center of the rotator 8. When the flux powder P is fallen on the rotator 8, Flux powder P is discharged from a fall hole 15 every predetermined quantity to be fallen into a mixing tank 14 as shown in Fig.2. However, the above process is performed in only the moment that the through hole 9 of the rotator 8 and the through hole 11 of the disc 10 are communicated with each other.

As shown by the arrow of broken line in Fig. 2, the flux powder P is fallen into an approximately conical mixing tank 14 from the inlet hole 15. On the other hand, as shown by the arrow of chain line in Fig.2, the inert gas G is supplied to the approximately conical mixing tank 14 from the gas supply pipe provided in the side of the conical mixing tank 14. At this time, the flux powder P and the inert gas G are mixed with each other to be supplied to a rotation controller 20 below the conical mixing tank 14 via an exhaust hole 17 and a rotary joint 18. However, when it is a condition to stop falling the flux powder G into the conical mixing tank 14, namely, the through holes 9 and 11 are not communicated with each other in the rotary feeder 6, the following process is performed. Only inert gas G is fallen into the conical mixing tank 14 to be supplied to the rotation controller 20 via the exhaust hole 17 and the rotary joint 18.

As shown in Fig.2, the rotation controller 20 includes a motor M2 and a control mean 22. Herein, the motor M2 rotates a rotary shaft 32. The control mean 22 is an inverter or and the like to control a number of rotations and a direction of rotation of the motor M2. The rotation controller 20 is supported by the upper portion of the crucible 40 via more than three horizontal members 25, a plurality of nuts 26, and a plurality of bolts 27. Herein, the horizontal member 25 is fixed to a bearing 24 vertically extending form the bottom surface of the rotation controller 20. The nut 26 is individually fixed to the end portion of the corresponding horizontal member 25. The bolt 27 is individually screwed in the corresponding nut 26 to join together. A supporting plate 28 is individually attached to a lower end portion of the corresponding bolt 27 and is individually provided on the edge of the opening portion of the crucible 40. Herein, the motor M2 is capable of alternately rotating in normal and reverse directions as well as one-way rotation.

As shown in Fig.2, flux powder P and inert gas G perpendicularly penetrated into the rotation controller 20 are supplied to a communication passage 34 in a carbon-made rotary shaft 32 via a hollow portion in a rotary shaft 29 equipped with a

joint parts

30 and 31. As shown in Fig.1 and Fig. 2, a disc shaped carbon rotator 36 is provided on the end portion of the rotary shaft 32. A plurality of discharge ports 38 are provided in the rotator 36 in such a manner that the discharge ports 38 are radially branched in a horizontal direction from a lower end portion of the communication passage 34. A plurality of recess portion 37 is symmetrically formed on the circumference of the rotator 36. Each discharge port 38 is provided on approximately center portion of the corresponding recess portion 37. Furthermore, the rotary shaft 32 and the rotator 36 are made of carbon. This is because the degradation of carbon by the chemical reaction with molten aluminum M is minimal at the relatively low temperature so that the molten aluminum M can not cause damage to them.

Next, a method for refining the molten metal using the refining apparatus 1 will be explained with reference to Fig.2. As shown by the arrow of one point chain line in Fig. 2, the inert gas G such as nitrogen or argon is supplied to the mixing tank 14 from the gas supply pipe 16. In the meantime, as shown by the arrow of broken line in Fig.2, the flux powder P stored in the hopper 2 is fallen into the mixing tank 14 every predetermined quantity via the rotary feeder 6. Thereby, a compound of the inert gas G and the flux gas is produced.

The compound goes through the rotation controller 20, then goes through the communication passage 34 in the rotary shaft 32. Herein, the rotary shaft 32 is rotated in one-way direction as shown by the arrow of real line in Fig.2 and the rotation speed thereof is approximately 300 rpm. Sequentially, the compound as finely divided air bubbles is discharged from the discharge port 38 of the rotator 36 into the molten aluminum M stored in the crucible 40. At this moment, the flux powder P and the inert gas as ultra fine air bubbles are discharged into the molten metal M. The flux powder P chemically reacts with impurities contained in the molten metal M so that the flux powder P and the impurities are cohered together to float on the surface of the molten metal M. When the above-mentioned flux-process step is performed for a predetermined time, impurities contained in the molten metal M can be separated and floated on the molten metal M.

Next, a rotation of the rotator 8 is stopped in the rotary feeder 6 under the condition that the through hole 9 of the rotator 8 is not communicated with the through hole 11 of the disc 10. In this case, only the inert gas supplied from the gas supply pipe 16 goes through the mixing tank 14, the rotation controller 20, and the communication passage 34 in the rotary shaft 32. Sequentially, only the inert gas as finely divided air bubbles is discharged from the discharge port 38 of the rotator 36 into the molten aluminum M. At this moment, the motor M2 is alternately rotated by approximately 450 rpm in normal and reverse directions for approximately 9 minutes. Thereby, the rotator 36 is rotated in normal and reverse directions. Additionally, when a rotation is switched to a reverse direction from a normal direction and vice versa, a switching operation must be done before a rotation flow as a spiral flow is generated in the molten metal M due to a rotation of the rotator 36.

Specifically, the inert gas G is turned into finely divided bubbles in the state that molten metal M is rotated and mildly stirred in accordance with a rotation of the rotator 36. Thereafter, the inert gas is gradually come to the surface of molten metal. At this moment, the inert gas physically blows up a remaining impurities and the flux powder P on or near the surface of the molten metal M so that the remaining impurities and the flux gas are removed. When above-mentioned degassing-process step is performed for approximately ten minutes, impurities (non-metal inclusion) are removed from the molten aluminum. This ensurely gives pure molten aluminum M.

In the case where the rotator 36 is rotated faster so as to bring about the rotation flow, a corotating phenomenon should occur in the molten aluminum M such that the molten aluminum M itself is rotated faster in proportion to a rotation flow as a spiral flow caused by a rotation of the rotator 36, which makes it difficult for the inert gas G to be uniformly diffused and floated on the surface of the molten metal M.

So, after each above-mentioned step is performed as a method for refining the molten metal disclosed in the present invention, the following two steps may also be preferably performed.

The one is a step that the pure molten metal is cast into ingots by means of a known semi-continuous casting method. The other is a step that the pure molten metal is poured into a required mold to be a casting product.

EXAMPLE

Now, specific examples of a method for refining the molten metal of the present invention will be described below.

Three sets of aluminum alloys were prepared as the following conditions. JIS No: AC2B (Al-Cu system), a ratio of new ingot to cut chip is 5:3. Weight is 400 kg.

The above three aluminum alloys were molten at 730°C to gain a molten aluminum M, respectively. Sequentially, each molten aluminum M was poured into the corresponding crucibles 40, respectively. Herein, the cut chip is a recycled material gained by cutting both edges of the above new ingot.

The refining apparatus 1 was individually installed into the three crucibles 40. Of these, in one of the three crucibles 40 as the first one, a flux-process step was performed, and then a degassing process step was performed in the method shown in table 1. The method of the flux-process step is as follows.

The rotator 36 is rotated by 300 rpm in one-way direction. In the meantime, a compound of a flux powder P and an argon gas G (the inert gas) are continuously discharged into the molten metal M for six minutes. After the above flux-process step was completed, the degassing process step was performed. The method of the degassing process step is as follows. The rotator 36 is alternately rotated by 450 rpm in normal and reverse directions for 8.8 minutes, respectively. In the meantime, only argon gas G is discharged into the molten metal M for ten minutes.

The method and the molten aluminum M gained by the above method are defined as the embodiment of the present invention. Herein, the molten aluminum M is classified into three classes. The first one is a molten aluminum that is before the above two steps were performed. The second one is a molten aluminum that is the way of performing the above two steps. The third one is a molten aluminum that is after the above two steps were performed. In addition, in the flux-process step, an amount of argon gas to be supplied was 1.5 l/min, while amount of supplying a flux was 90 g/min (0.13 weight percent of molten metal M). In the degassing process step, amount of supplying Argon gas was 1.8 l/min. Furthermore, it took approximately 0.8 seconds to switch a rotation direction of the rotator 36 form a normal direction to a reverse direction and vice versa.

Next, as shown in table 1, in the other crucibles 40 as the second one, a degassing process step was performed in the same method as that of the embodiment of the present invention. The method and the molten aluminum M gained by the method are defined as the example 1. Herein, the molten aluminum M is classified into three classes. The first one is a molten aluminum that is before the above degassing process step was performed. The second one is a molten aluminum that is the way of performing the above degassing process step was performed. The third one is a molten aluminum that is after the above degassing process step was performed

Next, as shown in Table 1, in the remaining crucibles 40 as the third one, the flux process step was performed in the same method as that of the embodiment of the present invention. Thereafter, a degassing process step was performed by means of one-way rotation of the rotator 36 for ten minutes. The above method and the molten aluminum M gained by the above method are defined as Example 2. Herein, the molten aluminum M is classified into three classes. The first one is a molten aluminum that is before the above two steps were performed. The second one is a molten aluminum that is the way of performing the above two steps. The third one is a molten aluminum that is after the above two steps were performed.

The above three molten aluminum M regarding the embodiment, Example 1, and Example 2 were individually molded to produce a plate shaped casting piece (240mm × 36mm × 6mm). Sequentially, each of the above casting pieces was cut at 25 positions along its width (the narrow side) to prepare 50 exposit surfaces (one side) of casting cut pieces. Thereby, number of non-metallic inclusions (impurities) on the exposit surface was counted by a watching observation. Herein, impurities having a size of nearly more than 100 µm can be identified by the watching observation.

As shown in Table 1, with regard to the embodiment, Example 1, and Example 2, the total number of impurities on the surface of the cut casting pieces and the average number per one surface of the cut casting pieces were counted, respectively. Each result is shown in Table 1. Additionally, a content of hydrogen gas in the casting piece was measured by means of Ransley method. Each result is also shown in Table 1.

According to the embodiment of the present invention shown in Table 1, a number of impurities (non-metal inclusion) were reduced by approximately 1/77 (1.3 percent) through the flux process step and the degassing process step. Especially, a number of impurities were reduced by 1/30 through the degassing process. This is because impurities were efficiently removed from the molten aluminum in the following manners. After the flux process is chemically performed in the molten aluminum, finely divided argon gas is discharged into the molten aluminum under the condition that the molten aluminum is mildly stirred by means of the rotator in normal and reverse directions so as not to generate a spiral flow.

On the other hand, according to Example 1 shown in Table 1, a number of impurities (non-metal inclusions) were reduced by approximately 1/14 (7 percent) through the degassing process step. It is a large number of impurities in comparison with the result of the embodiment. This is because only the degassing process step was performed to remove impurities.

According to Example 2 shown in Table 1, a number of impurities (non-metal inclusions) were decreased by approximately 1/11 (8.9 percent) through the flux process step and the degassing process step. This is the largest number in theses three methods (the embodiment, the example 1, and the example 2) in spite of the fact that the flux process step, which is the same as the embodiment, was performed. This is because the degassing-process was performed in such a manner that the molten aluminum was stirred by means of the rotator in only one-way direction. Additionally, with regard to a process to reduce a content of hydrogen gas in the casting piece, the result of effect was the following order as shown in table 1. The 1st was the embodiment, the 2nd was the example 2, and the 3rd was the example 1.

As described above, the results of the embodiment can prove that the method for refining molten metal and the apparatus 1 for refining the molten metal using the same regarding the present invention is effective to refine the molten metal.

Fig 3 is an elevation view showing an apparatus 1a for refining the molten metal regarding the other embodiment. Fig. 4A is a vertical cross sectional view showing the apparatus 1a refining the molten metal.

As shown in Fig.3 and Fig.4, the apparatus 1a for refining the molten metal includes a gas supply pipe 44 of inert gas G, a powder supply means, a rotation controller 20, a rotary shaft 32, and a rotator 36. Herein, the gas supply pipe 44 of inert gas G has an inlet 45 provided an upper portion thereof and an outlet 46 provided a lower portion thereof. The powder supply means has a hopper 2 for supplying flux powder P and a screw feeder 50 provided between the inlet 45 and the outlet 46 of the gas supply pipe 44. The rotation controller 20, the rotary shaft 32, and the rotator 36 are the same as the rotation controller 20, the rotary shaft 32, and the rotator 36 of Fig.1 and Fig.2.

As shown in Fig.4, the screw feeder 50 is comprised of a cylindrical casing 51 extending in a horizontal direction. The cylindrical casing 51 includes a substantially column shaped screw shaft 52 having a spiral groove as a conveyer passage 54 provided thereon along a longitudinal direction thereof. The screw shaft 52 is capable of rotating in the cylindrical casing 51.

The screw shaft 52 can be rotated by a motor M3. After flux powder P was supplied to the casing 51 from a discharge hole 4 of the hopper 2 provided on an upper portion of the casing 51, flux powder P is conveyed to the end portion 56 of the screw shaft 52 by the conveyer passage 54 due to a rotation of the screw shaft 52. Additionally, a vibrator 5 is installed on outside the hopper 2 to impart a vibration to the flux powder P so that a bridge phenomenon dose not occur in the vicinity of a corn portion of the hopper 2. As shown in Fig.4, after flux powder P was supplied to the end portion 56 of the screw shaft 52, flux powder P was combined with inert gas G at a joint part 48 of the casing 51 and the gas supply pipe 44, then a compound of the inert gas and the flux powder P is supplied to the rotation controller 20 via the outlet 46 of the gas supply pipe 44. Sequentially, the compound of the inert gas G and the flux powder P goes through a communication passage 34 of the rotary shaft 32 rotating in one-way direction by the motor M2, and then goes though a discharge port 38 of the rotator 36. Finally, the compound of the inert gas G and the flux powder P are uniformly diffused into the molten aluminum M (molten metal) in a crucible 40.

After the above flux process step was completed, the screw feeder 50 is stopped. Sequentially, a degassing process step can be performed in the following method. Only the inert gas G is pulverized and mildly discharged into the molten aluminum M in the state that the molten aluminum M is alternately rotated by the rotator 36 in normal and reverse directions.

Specifically, the aforementioned apparatus 1a for refining the molten metal can also refine the molten metal by certainly performing the above the method for refining the molten metal like the method by using the apparatus 1.

The present invention is not restricted to the aforementioned embodiments. For example, with regard to the flux process step, the rotator can be rotated in normal and reverse directions. With regard to the degassing process step, the rotator can be rotated in one-way direction under the state that a spiral flow is not generated in the molten metal. With regard to the inert gas, in addition to argon or nitrogen, a mixture of argon and nitrogen is available for the inert gas.

Furthermore, with regard to the rotation controller 20 including such as the motor M2 rotating the rotary shaft 32 and the rotator 36, it is not restricted that the rotation controller 20 is placed on right over the crucible 40. Specifically, the rotation controller 20 can be placed outside the crucible 40 in such a manner that it is connected to the rotary shaft 32 and the rotator 36 via a motive power communication means such as a chain and a gear.

Furthermore, with regard to the crucible storing molten metal M therein, the following furnaces can be utilized as the crucible as long as it is comprised of a cylindrical body made of a refractory material. One is a melting furnace or a holding furnace having a heater in the periphery thereof. The other is a melting furnace or a holding furnace having an inductance coil as a heating means wound around a furnace.

Finally, with regard to the molten metal according to the present invention, in addition to the aluminum and the alloy thereof, magnesium, copper or the alloy based on any one of these two metals is available for the molten metal of the present invention.

Claims

An apparatus for refining a molten metal being
characterized by:

a gas supply pipe for supplying an inert gas,

a powder supply means for supplying flux powder to the gas supply pipe,

a rotary shaft having a communication passage provided therein so as to communicate with said gas supply pipe,

the rotary shaft being inserted into the molten metal under the condition capable of rotating in one-way direction as well as normal and reverse directions,

a rotator being provided on an end portion of the rotary shaft and having a discharge port to discharge said inert gas or a compound of said inert gas and said flux powder into said molten metal.
The apparatus for refining the molten metal according to claim 1, wherein the powder supply means includes a hopper having said flux powder stored therein as well as a rotary feeder or a screw feeder in which one side thereof is communicated with an lower end portion of the hopper and the other side thereof is communicated with said gas supply pipe.
A method for refining the molten metal utilizing the apparatus for refining said molten metal according to claims 1 or 2 being characterized by:

a flux-process step to diffuse a compound of finely divided inert gas and flux powder into said molten metal under the state that said rotator inserted into said molten metal is rotated in one-way direction or normal and reverse directions,

a degassing-process step to discharge only said inert gas from said rotator into said molten metal under the state that said rotator inserted into said molten metal is rotated in one-way direction or normal and reverse directions so as not to generate a spiral flow in said molten metal.