JP2003130557A - Molten metal ventilating and stirring device and operation method for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent solidification of molten metal in slits in a molten metal ventilating and stirring device having the slits formed in a disc part serving as a stirring means. SOLUTION: This molten metal ventilating and stirring device 1 is equipped with a hollow rotating shaft 2 rotatable around the axis, a gas jetting part 3 provided in an opening part of the lower end of the hollow rotating shaft 2, and an impeller part 4 provided at the lower end of the hollow rotating shaft 2. The disc part 8 constituting the impeller part 4 is provided with a plurality of slits 13 extended in the radial direction. The slits 13 are split grooves penetrating the upper and lower surfaces of the disc part 8, with width gradually increased radially toward the outside to open at the outer peripheral edge of the disc. Thus, when the disc part 8 is raised and rotated above the molten metal, the molten metal remaining in the slits 13 can be surely removed from its expanded shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal aeration and stirring device having a function of injecting a gas into a molten metal and stirring the molten metal, and a method of operating the same.

[0002]

2. Description of the Related Art Molten metals such as aluminum, magnesium, and alloys thereof contain dissolved harmful gases such as hydrogen gas and innumerable minute inclusions (mainly oxide particles). If the molten metal is directly used for casting, dissolved harmful gas, minute inclusions, etc. will remain in the final product, causing various adverse effects. For this reason, it is necessary to remove dissolved harmful gas, minute inclusions, etc. in the molten metal before casting.

As a method of removing dissolved harmful gas, minute inclusions, etc. from the molten metal, gases such as argon, nitrogen and chlorine in the molten metal (in the present invention, the gas injected into the molten metal is referred to as "fluxing gas"). ).) To remove dissolved harmful gas and minute inclusions in the molten metal by contact with the fluxing gas (aeration and stirring method), that is, the fluxing gas is dispersed in the molten metal in the form of bubbles. Then, in the process of the bubbles floating toward the surface of the molten metal, they diffuse and rise while expanding, and at the same time, the dissolved harmful gas and minute inclusions are taken into the bubbles to remove them and clean the molten metal. It was being done.

As an apparatus for realizing this type of aeration and stirring method, for example, as shown in FIG. 7, an impeller (stirring blade) 53 is provided at the lower end of a hollow shaft 52 arranged in the molten metal treatment tank 51. A molten metal aeration stirring device 50 is configured to inject the fluxing gas from the lower end through the hollow shaft 52 and to disperse the bubbles of the fluxing gas in the molten metal while atomizing the bubbles of the fluxing gas by the rotation of the impeller (stirring blade) 53. Was known.

However, in this type of aeration and stirring method, the impeller 53 is put into the molten metal at a temperature higher than 700 ° C. without preheating, or the impeller 53 is suddenly pulled out from the molten metal after use. In the conventional molten metal aeration and agitation apparatus 50 as described above, the impeller 53, particularly the disk portion 54 thereof, may be cracked by thermal shock or the like.

Therefore, Japanese Patent Laid-Open No. 7-11350 discloses an impeller 53 made of silicon nitride or sialon-based ceramic, as shown in FIG. 8, in order to provide an impeller resistant to thermal shock.
In addition to the above, it is proposed to provide a slit (cracking groove) 56 extending in the radial direction in the impeller disk portion 54 and opening at the outer peripheral edge 55.

[0007]

As described above, the impeller 5 is used.
If the slit 56 is provided in the disk portion 54 of 3, even if the impeller 53 is suddenly put into the molten metal at high temperature without preheating, or if the impeller 53 is suddenly pulled out from the molten metal or the impeller 53 is rotated at high speed, Since the slits 56 can absorb the strains generated by these impacts, it is possible to prevent the disk portion 54 from being cracked as in the conventional case. However, on the other hand, the molten metal may enter the slit 56 and solidify as it is,
It has recently become clear that the disk portion 54 of the impeller may be cracked due to the thermal contraction and thermal expansion of the metal.

In view of the above, the present invention provides a molten metal aeration and stirring apparatus having a disk portion as a stirring means at the lower end of a hollow rotary shaft, and a slit provided in the disk portion. It is intended to provide a molten metal aeration stirrer and a method of operating the same so as not to solidify as it is.

[0009]

In order to solve the above problems, the present invention relates to a hollow rotary shaft, a gas injection portion provided at a lower end opening of the hollow rotary shaft and having a gas injection port, and a hollow rotary shaft. And a disc portion as a stirring means provided at the lower end of the disc portion, and a slit formed in the disc of the disc portion, the width of which widens in the radial direction and which is open at the outer peripheral edge of the disc. We propose a molten metal aeration stirrer with a structure.

In the molten metal aeration and stirring apparatus having such a structure, the fluxing gas is supplied into the hollow of the hollow rotary shaft, and the fluxing gas is injected into the molten metal from the gas injection port, and at the same time, the hollow metal is hollow. The stirring gas can be dispersed in the molten metal in the form of fine bubbles by rotating the rotating shaft to stir the disc. At this time, since the slits provided in the disk portion can absorb the strain generated by the impact such as heat and rotation, the disk portion is not damaged such as cracked. Moreover, in the present invention, since the slit is formed so as to widen its width in the radially outward direction, not only is the molten metal less likely to enter and remain in the slit, but a disk is formed on the molten metal. By raising the portion and rotating the disk portion, it is possible to reliably remove the residual molten metal due to the expanded shape.
Therefore, it is possible to prevent the disk portion from being damaged by the solidification of the molten metal remaining in the slit as in the conventional molten metal ventilation stirring device.

The present invention also provides a method of operating the molten metal aeration and stirring apparatus having the above-mentioned structure, after immersing the disk portion in the molten metal to inject and stir the fluxing gas, and then as necessary. It is proposed to periodically raise the disc part on the molten metal and rotate the disc part to remove the molten metal adhering to the disc part. By operating in this way, the molten metal remaining in the slit can be reliably removed by centrifugal force. At the same time, since the molten metal attached to or remaining on the disc portion other than the slit can be removed at the same time, it is possible to prevent damage to the disc portion that occurs when peeling off the molten metal attached to or remaining on the disc portion. .

The molten metal aeration stirrer and its operating method of the present invention are for removing dissolved harmful gas such as hydrogen gas and fine inclusions dissolved in the molten metal, or for accelerating the refining rate, or The present invention can be applied to an apparatus in which a fluxing gas is blown into a molten metal and stirred to disperse the fluxing gas in the molten metal for various purposes such as for crystal grain refining treatment. In other words, it can be applied to all devices having a function of dispersing a gas in a molten metal, and a powder mixed gas in which flux powder is mixed with fluxing gas is blown into a molten metal. It can also be applied to a diffusion device.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The molten metal aeration stirrer 1 jets and distributes a bubble-like fluxing gas into the molten metal in order to remove gas components such as hydrogen gas dissolved in the molten metal and minute inclusions. As shown in FIG. 1, a hollow rotary shaft 2 that can rotate about an axis, a gas injection part 3 provided in a lower end opening of the hollow rotary shaft 2, and a hollow The rotary shaft 3 and the impeller portion 4 provided at the lower end of the rotary shaft 3 are provided.

The hollow rotary shaft 2 has a hollow cylindrical shape having a gas flow portion 5 inside, and a flange 6a is projectingly provided on an upper end portion of the outer peripheral surface of the hollow rotary shaft 2 and a lower end portion of the outer peripheral surface of the hollow rotary shaft 2. Is provided with a screw portion 6b.

The impeller portion 4 has a short tubular portion 7 having the same diameter as that of the hollow rotary shaft 2, a disc portion 8 projecting outward near the lower end of the short tubular portion 7, and a lower surface of the disc portion 8. The projecting plate portions 9 (six in the figure) formed in a radial shape are provided.

A screw portion 1 is provided on the upper end of the outer surface of the short tubular portion 7.
2, the lower end portion of the hollow rotary shaft 2 and the upper end portion of the short tubular portion 7 are joined to each other, and the connecting member 11 is screwed to the screw portion 6b and the screw portion 10 on the outer side of the joined portion. The hollow rotary shaft 2 and the impeller portion 4 are connected to each other to form a single hollow rotary shaft 12 that is in communication with each other.

The disk portion 8 has an annular plate shape protruding outward from a portion slightly above the lower end portion on the outer peripheral surface of the short tubular portion 7, and the disk portion, that is, the annular plate shape, has a radial direction. There are provided a plurality of slits 13 (six in the figure) extending in the direction.

The slit 13 is formed as a crack groove penetrating the upper and lower surfaces of the disk portion 8 and is formed so as to gradually widen its width in the radially outward direction and open at the outer peripheral edge of the disk. There is. The extent to which the slit 13 is widened is preferably 1 to 30 degrees, and particularly preferably 3 to 10 degrees in terms of achieving both hot water shortage and stirring efficiency. If it is less than 1 degree, it is difficult to obtain the effect of expanding and molten metal may remain in the slit 13. On the other hand, if it is significantly larger than 30 degrees, the stirring effect becomes poor. The opening width of the slit 13 is preferably 3 to 20%, and more preferably 5 to 10%, with respect to the diameter of the disc portion, from the viewpoint of hot water shortage and stirring efficiency. As shown in FIG. 3, the slit 13 can be formed starting from the vicinity of the inner peripheral edge of the disk portion 8, that is, the vicinity of the rising edge of the short tubular portion 7, but as shown in FIG. It is also possible to form near the middle part of 8 as a starting point. The number of slits 13 is not particularly limited, but is 2 to 10, especially 4 to 8,
Of these, 6 is the most preferable. The slit 13
In addition to being formed so as to extend straight from the center toward the radially outer side as in the present example, it is also possible to form so as to be linearly or curvedly displaced from the radial direction in the rotational reverse direction.

The projecting plate portion 9 has a trapezoidal plate-shaped portion or a triangular plate-shaped portion protruding downward with a slight gap 14 between the gas injection portion 3 and, more specifically, the gas injection port 15, and an outer peripheral edge portion of the disk portion 8. The protrusion height is gradually reduced toward the outer radial direction. However, the projecting plate portion 9 is not limited to such a shape, and the protruding height is formed to be constant, only the intermediate portion of the disk portion 8 is formed, or the peripheral edge is slightly deflected downward. Then, it may be formed into a screw blade shape, or the protruding plate portion 9 may be formed so as to function as a stirring blade.

The gas injection part 3 is constructed by attaching a bottom cover part 16 having a plurality of gas injection ports 15 to the lower end opening of the short tubular part 7, that is, the lower end opening of the hollow rotary shaft 12. is there. The bottom lid portion 16 has a bottomed tubular shape including a peripheral side surface 16a and a bottom surface 16b, and has gas injection ports 15 (six in the figure) in the lateral direction on the peripheral side surface 16a at a height along the peripheral edge of the bottom surface 16b. Further, each of them is opened so as to face each slit 13. The number of gas injection ports 15 is not limited to six, and even if it is about 1 to 10, the function is sufficiently exhibited.
The position of the gas injection port 15 may be provided in the peripheral side surface 16a other than the position along the peripheral edge of the bottom plate 16b, but the gas bubbles injected from the gas injection port 15 are effectively provided by the projecting plate portion 9. Since it is cut into pieces, it is desirable to form it at a position inside the projecting plate portion 9. The diameter of the gas injection port 15 is 0.
5 to 5.0 mm is preferable. If the diameter is smaller than 0.5 mm, the injection port 15 may be blocked during continuous use, while if the diameter is larger than 5.0 mm, the gas flow section 5
It is not preferable because the molten metal splash penetrates into the interior and adheres to the wall surface.

The materials for the molten metal aeration and stirring apparatus 1 having the above-described structure, that is, the hollow rotary shaft 2, the gas injection portion 3 and the impeller portion 4 are eroded by the molten metal such as silicon nitride, sialon, silicon carbide, carbon and carbon ceramics. It is preferably formed from a material that is difficult and heat resistant. In particular, when forming as a molten metal aeration stirring device for molten metal such as aluminum or aluminum alloy which reaches a high temperature, it is preferable to use ceramics such as silicon nitride and sialon which are resistant to erosion and excellent in heat resistance.

The molten metal aeration and stirring apparatus 1 having the above structure
In the above, the gas injection part 3 and the impeller part 4 are formed separately, but it is also possible to integrally form them.

Next, as an application example of the molten metal aeration and stirring apparatus 1, as shown in FIGS.
The operation method in that case will be described together with the configuration example installed in 0. However, the apparatus to which the molten metal aeration and stirring apparatus 1 is applied is not limited to the molten metal purification apparatus 20 having such a configuration.

The molten metal purification apparatus 20 has a refractory furnace 21 surrounded by a peripheral wall and a bottom wall made of a refractory material, and a molten metal processing chamber 22 and a separation / extraction connected to the molten metal processing chamber 22. The chamber 23, a molten metal inlet 24 that communicates with the molten metal treatment chamber 22 to supply molten metal, and an outlet 25 that communicates with the molten metal treatment chamber 22 and sends the treated molten metal out of the furnace. At the center of the molten metal processing chamber 22, a molten metal aeration and stirring device 1 is installed so as to be able to move up and down.

The molten metal aeration stirrer 1 comprises a hollow rotary shaft 2
The hollow rotary shaft 2 is rotatably and vertically movably supported by being connected to a supporting means (not shown) via a flange 6a of the same, and a fluxing gas supply means (not shown) is provided at the upper end of the gas flow section 5. To connect the hollow rotating shaft 2 with the fluxing gas. The supporting means of the hollow rotary shaft 2 is arbitrary, but usually, the hollow rotary shaft 2 can be rotated and lifted by an electric motor. Further, the gas supply means is also optional, and is usually provided with a gas supply tube, a tank, a pump and the like, but the pump can be omitted if the gas pressure in the tank is a predetermined value or higher.

In the molten metal purifying apparatus 20 having the above structure, a molten metal such as aluminum is supplied from the inlet 24 into the molten metal processing chamber 22, where the molten metal aeration and stirring apparatus 1 purifies the molten metal, and hydrogen gas is supplied. Dross such as dissolved harmful gas and minute inclusions is discharged from the separation and extraction chamber 23, while purified metal melt is discharged from the tap 25. At this time, in the molten metal processing chamber 22, the molten metal aeration and agitation device 1 is immersed in the molten metal, and the hollow rotating shaft 2 is rotated while the gas is injected from the gas injection port 15 into the molten metal through the gas flow portion 5. Inject bubbling xing gas.
The bubbles of the fluxing gas ejected from the gas ejection port 15 are further atomized by the agitation by the projecting plate portion 9 and dispersed in the molten metal, and thereafter float toward the molten metal surface. In this floating process, the bubbles diffuse and rise while expanding, and at the same time, the dissolved harmful gas in the molten metal, minute inclusions, etc. are taken into the bubbles and float on the surface of the molten metal.
Emitted from. The fluxing gas blown into the molten metal may be nitrogen, carbon monoxide, chlorine, argon, helium, krypton, xenon, or any other gas that is inert or has a reducing property with respect to the metal.

In such purification treatment, the temperature of the molten metal such as aluminum is preferably higher than 700 ° C., and the hollow rotating shaft 2 is preferably rotated at a speed of 300 rpm to 800 rpm. Since the impeller part 4 may be immersed or pulled out without preheating, the impeller part 4 and especially its disk part 8 are thermally or mechanically heavily loaded.
In this case, since the slit 13 is provided in the disk portion 8 and the distortion generated in the disk portion 8 is absorbed by the slit 13, the disk portion 8 is not cracked.

Moreover, since the slit 13 is formed so as to widen its width in the radially outward direction, the hollow rotary shaft 2 is raised to raise the disk portion 8 on the molten metal, and By rotating the rotary shaft 2 and the disk portion 8, it is possible to reliably remove the molten metal that has adhered to or remains in the slit 13. At the same time, the disk portion 8 outside the slit 13
It is possible to remove the molten metal adhering to the etc. In the conventional molten metal aeration and agitation device, when the molten metal adhering to the impeller part 4 was tried to be removed, the material of the impeller part 4 was also peeled off. Driving can solve such problems.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a molten metal ventilation stirring device according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view showing a lower side portion of the molten metal aeration and stirring device of FIG.

3 is a plan view of an example of a disk portion of the molten metal aeration and agitation device shown in FIG. 1, that is, a disk portion as a stirring means provided at the lower end of a hollow rotating shaft, as viewed from the bottom side.

FIG. 4 is a plan view of a disc portion of an example different from that of FIG. 3 when viewed from the bottom side.

FIG. 5 is a plan view showing an example of a molten metal purification device provided with a molten metal aeration and stirring device.

6 is a sectional view of the molten metal purification apparatus shown in FIG.

FIG. 7 is a cross-sectional view showing an example of a conventional molten metal purification device (including a molten metal ventilation stirring device).

FIG. 8 is a plan view of an example of a disk portion (impeller) as a stirring means provided at the lower end of a hollow rotary shaft of a conventional molten metal aeration stirring device when viewed from the bottom side.

[Explanation of symbols]

1 Molten metal aeration stirrer 2 Hollow rotating shaft 3 Gas injection section 4 Impeller section 5 Gas distribution section 6a flange 6b screw part 7 Short tubular part 8 discs 9 Veneer 10 screw part 11 Coupling member 12 hollow rotating shaft 13 slits 14 Gap 15 Gas injection port 16 Bottom cover 20 Molten metal purification equipment 21 Refractory furnace 22 Molten metal processing chamber 23 Separate extraction room 24 Bath entrance 25 tap

Claims (2)

[Claims] 1. A hollow rotary shaft, a gas injection part provided at a lower end opening of the hollow rotary shaft and having a gas injection port, and a disk part as a stirring means provided at the lower end of the hollow rotary shaft. A molten metal aeration stirrer having a structure in which a slit is formed in the disc of the disc portion so as to widen in the radial direction and open at the outer peripheral edge of the disc. 2. The molten metal aeration stirrer according to claim 1, wherein the disk portion is immersed in the molten metal to inject and stir the fluxing gas, and then as needed or periodically. A method for operating a molten metal aeration and stirring apparatus, comprising: raising a disc part on a molten metal to rotate the disc part to remove the molten metal adhering to the disc part.