JPH0739613B2 - Device for dispersing bubbles in a metal melt - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus used for refining a metal melt, and more specifically, a refining gas is formed into fine bubbles in the metal melt, and the metal melt is melted into the metal melt. A metal melt capable of dispersing and discharging fine bubbles in the metal melt by giving a fluid force that moves forward, and further appropriately preventing a vortex flow generated on the surface of the metal melt by the flow force given to the metal melt. The present invention relates to a bubble dispersion device.

[0002]

2. Description of the Related Art For example, iron, copper, lead, zinc, aluminum,
A metal such as magnesium or an alloy thereof (in the present specification, unless otherwise specified, referred to as a metal) is once melted in a melting furnace and cast into various shaped products such as slabs, billets and castings. The slab and billet are rolled or extruded into a plate having a desired thickness or a shape member having a desired shape.
Castings are sometimes used as they are, but in many cases they are machined. It may also be forged.

In the metal melt melted in the melting furnace, there are fine particles of the lining of the melting furnace, metal oxides, foreign matters such as gas, and the metal melt in such a contaminated state is slab or billet. When cast into a plate or a shape material and cast into a sheet, it may cause surface scratches, or may cause swelling during heat treatment. Further, in the case of casting, when machining is performed, the cutting edge of the cutting tool is severely damaged or worn, and it is difficult to obtain a clean machined surface. Further, when forged, stress concentrates on the foreign matter and causes cracking.

As described above, the foreign matter in the metal melt is not preferable, and therefore various methods for removing the foreign matter have been proposed. For example, soothing metal melts. This method requires a long time and is poor in removal efficiency. Add flux. This method is difficult to uniformly add to the metal melt, has poor workability, and has poor removal efficiency. In recent years, generally, workability is improved, and a method of efficiently introducing a refining gas for a metal melt such as chlorine gas, nitrogen gas, or argon gas into the metal melt is performed. .

[0005]

Various methods have been proposed as a method for dispersing and introducing such a refining gas for a metal melt. For example, Japanese Examined Patent Publication No. 52-36487 has a rotor having a rotary blade at the end of a rotary shaft having a passage for purified gas introduced into a metal melt, and a non-rotating blade directly above the rotor. A stator is provided, and by introducing the refining gas while rotating the rotor, the refining gas is finely divided by the blades of the rotor, and further convection to the metal melt is caused by the rotating force of the blades. There is disclosed a refining gas dispersion device for carrying and distributing the refining gas finely divided by this convection over the entire metal melt. However, when the gas is conveyed and distributed over the entire metal melt by such a device, convection is generated around the device about the entire metal melt, and a downward metal melt flow is generated along the rotation axis, resulting in a large vortex flow. As a result, a new oxide is generated in the metal melt, and a large amount of oxides or floating substances (collectively referred to as dross in this specification) on the surface of the metal melt are generated and these are generated in the metal melt. It causes an unfavorable state such as re-mixing with.

A schematic explanation of this is considered to be as shown in FIG. That is, in FIG. 6, 1 is a container, 2 is a metal melt flow, 3 is a metal melt flow, 4 is a metal melt surface, 5 is a vortex flow generated around a rotation axis 6, 6 is a rotation axis, and 7 is a rotation axis. Is a blade, 8 is an inlet for introducing a refining gas, 9 is a refining gas passage, 10 is a rotor, and 11 is a refining gas bubble. When the refining gas passes through the refining gas passage 9 of the rotary shaft 6 and is ejected into the metal melt 2 from the refining gas ejection holes 12 of the rotary body 10 provided at the end of the rotary shaft 6, Due to the rotation of the blades, the refining gas is finely divided by the blades 7, and the thrust of the blades 7 causes the metal melt 2 to become a flow 3 of the metal melt and convey the refining gas bubbles 11.
It is considered that this rotation causes the surface 4 of the metal melt to undulate greatly, and at the same time, the flow 3 of the metal melt descends along the rotation axis 6 to generate a vortex 5 around the rotation axis 6.

In addition to the above, an improved device of the device described in Japanese Patent Publication No. 52-36487 has been proposed, but in any case, a downward flow of the metal melt is generated along the rotation axis, resulting in a large vortex flow. Then, the same unfavorable state as described above occurs. The present invention is an improvement of a device for dispersing fine refining gas bubbles in a metal melt, which substantially prevents the generation of a vortex formed around a rotation axis by the rotation of a rotor having blades. It is an object of the present invention to provide a device capable of appropriately preventing the generation of a large amount of dross caused by a vortex flow.

[0008]

Means for Solving the Problems As a result of various studies by the inventors, in order to introduce fine refining gas bubbles into a metal melt,
Rotating the blades to finely divide the introduced refining gas, generate convection in the metal melt, and convey the divided fine refining gas bubbles into the metal melt. The present invention has been completed by finding that, when a coating body covering the rotating body is provided at an appropriate distance from the blade of the above, it is possible to substantially prevent the generation of a vortex that causes a novel oxide in the above-mentioned metal melt. It was done.

That is, according to the present invention, there is provided a rotating shaft having a passage for the refining gas introduced into the metal melt, and an end portion of the rotating shaft, which is rotated by the rotation of the rotating shaft to produce the refining gas. And a rotor having a blade that gives a flow force to the metal melt to move the metal melt forward, while discharging the fine bubbles into the metal melt, and a blade of the rotor that covers the rotor. And a cover having a gap between the rotating body and a portion for sucking a part of the metal melt by rotation, and a device for dispersing bubbles in the metal melt.

[0010]

By covering the rotor, it is considered that the flow of replenishment of the metal melt from the rear of the rotor caused by the rotation of the blades of the rotor is changed as follows. That is, the metal melt is sucked from the gap portion and released again forward by the covering body covering the rotating body with a gap, and the metal melt flowing forward is replenished from the rear of the rotating body. It is considered that the eddy current generated by this is substantially prevented, and the large amount of dross generated by this eddy current is prevented.

The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a longitudinal main part for explaining an apparatus according to the present invention. Therefore, this does not limit the present invention. The rotary shaft 2 in FIG.
Reference numeral 1 is rotated by a driving means (a known means, which is not shown), and a rotary shaft 21 is provided with a gas passage 22. The rotating body 23 is screwed into one end of the rotating shaft 21 by the rotation opposite to the rotating direction of the rotating shaft 21, and is rotated by the rotation of the rotating shaft 21. The rotating body 23 has blades 24 which are rotated by the rotation of the rotating shaft 21, and the blades 24 have a flat surface or a three-dimensional curved surface and have an inclination angle with respect to the rotating shaft 21. The propulsive force to move the metal to the front is applied to the metal melt.

Reference numeral 25 denotes a refining gas discharge hole, and the refining gas passing through the refining gas passage 22 has this gas discharge hole 25.
Released into the melt. The released refining gas is wing 2
It is finely divided by the rotation of No. 4 and is dispersed in the entire metal melt by the metal melt moved forward by the rotation of the blade.

The cover 26, which is a feature of the present invention, is the ceiling portion 3.
8 and a skirt portion 32, and the skirt portion 32 and the blade 24 of the rotating body 23 have an appropriate distance, preferably 10 mm.
The above gap is provided. Further, the covering 26 is provided on the ceiling 3
8 has a hole in the center thereof and one end of the rotary shaft 21 is penetrated to be screwed into the rotary body 23 so that the jaw portion 28 of the rotary shaft 21 and the rotary body 2
It is sandwiched between the end faces 30 of the screwing portion 29 of the third screw. The skirt portion 32 may cover the blades 24 of the rotating body 23 even slightly, but it is preferable that the skirt portion 32 covers more than half of the blades 24. Skirt 32 of wing 24 and cover 26
The gap 27 is provided so that the metal melt flows into the place where the rear portion 31 of the rotor 23 has a negative pressure due to the forward movement of the melt by the rotation of the blades 24. As a result, no eddy current is generated around the rotation axis. Since the covering body 26 and the gap 27 have such a function, the rear portion 3
For the purpose of assisting the amount of the melt flowing into 1, the skirt portion 32 and the ceiling portion 38 of the covering body 26 may be provided with a slight hole.

As another example of the rotary shaft 21 described above, a sheath 33 for covering the rotary shaft 21 is provided as shown in FIG.
Can be screwed onto the sheath 33.

Next, a method of using the device of the present invention will be described. The refined gas is emitted from the refinement gas emission hole, and the rotor 2
Insert 3 into the metal melt while rotating. This is to prevent the metal melt from coming into contact with the rotating body and solidifying, and if there is no such a risk, the above-described operation may be performed after insertion. The insertion depth depends on the amount of metal melt, but is 10
-30 cm or more is sufficient. The rotation speed is the number of wings,
Depending on the size, the number of wings is 6, the height of wings is 60.
If the product is rotated at 200 rpm or more in mm, the refining gas is finely dispersed. Usually 300 to 600 rpm. The upper limit is determined by the strength of the device, which is 7 for the above devices.
A vortex does not occur even at 00 rpm. The rotating shaft 21 may be inserted in a vertical direction, and even if the rotating shaft 21 is obliquely inclined, a vortex does not occur. Particularly when the container of the metal melt is long, it is advantageous to direct the release direction of the refining gas toward the longitudinal direction of the container so that the gas reaches a long distance.

FIG. 2 and FIG. 3 are explanatory views expressed on the assumption of the flow state of the metal melt in the use state of the device according to the present invention. FIG. 2 shows the device according to the present invention used vertically inserted into the melt, and FIG. 3 shows the device used obliquely inserted into the melt. That is, the metal melt 34, which is finely divided by the blades 24 by the rotation of the rotor 23 passing through the rotary shaft 21 and moved forward by the blades 24, is caught from the rear portion of the rotor 23 due to the presence of the coating 26. Is not generated, and no eddy current is generated around the rotary shaft 23.

Next, an example of operation performed using the apparatus of the present invention will be shown.

EXAMPLE A metal melt was purified using the apparatus according to the present invention shown in FIG. The conditions are shown below. Purification conditions (1) Metal and amount ... Aluminum 25t, depth 75
0 mm (2) Temperature ... 730 ° C. (3) Gas for refining introduced ... 75% by volume of argon + 25% by volume of chlorine (4) Amount of gas for refining introduced ... 6 Nm ³ / Hr and processing time ... 25 minutes (5) Device The outer diameter of the rotor… 230mm Gap between the rotor and the skirt of the cover… 20mm Rotation speed of the rotor… 450rpm (6) Number of units used… 1 unit / furnace The surface of the metal melt was observed. No vortex was generated. As a result, the weight of the generated dross (slag after squeezing the aluminum melt) was 275 Kg.

As a comparative example, an apparatus having the same size as that of the example with the covering removed was used, and the conditions were the same. As a result of purification, a large eddy current was generated. The weight of the generated dross (after squeezing the aluminum melt) is 52.
It was 5 kg. As for the effect of removing magnesium, it took 13 minutes to reduce 500 ppm Mg in the melt to 400 ppm Mg in the example. Compared with the case where a degassing lance is used as a comparative example (the refining gas is blown from one end of the pipe and the gas is introduced into the melt from the other end), the time required in the example is 1/13 of that of the comparative example. there were. Regarding the effect of removing alkali or alkaline earth metals such as lithium, sodium and calcium, the time required to remove to the same extent is compared with the case where the degassing lance is used in the example, and the time required in the example is a comparative example. 1/5 to 1
It was / 10. The effect of removing the gas contained in the melt is as follows. Only argon is used as the gas for refining and the amount is 6 Nm ³ / H.
r and other conditions are the same as in the example, 0.
The 5ccH ₂ / 100g took 25 minutes to reduce the 0.3ccH ₂ / 100g. Compared with the case where the above degassing lance was used as a comparative example, the time required in the example was 1/5 of that in the comparative example. The gas content in the melt was analyzed by the Landsley method. In the case of the apparatus of the present invention, the dispersed bubbles are fine, and the total interfacial area of the dispersed gas bubbles with respect to the amount of the refining gas used increases. In particular, in the case of removing magnesium, almost 100% of the introduced chlorine gas can be consumed in the reaction for removing magnesium, which is expected to be good for the environment.

From the above results, it was found that the apparatus according to the present invention has a sufficient refining ability and the amount of dross generated is extremely small.

[0020]

As described above, as compared with the degassing lance, the apparatus according to the present invention requires less treatment time for demagnesium, dealkalizing or alkaline earth metal, degassing, and the amount of chlorine gas used. Environmental improvement due to reduction can be expected. Further, since the apparatus according to the present invention is provided with the covering body for covering the rotating body and sucks and replenishes the melt from the gap between the skirt portion of the rotating body and the covering body, it is possible to appropriately prevent the generation of the vortex around the rotation axis. The amount of dross generated thereby can be extremely reduced. Therefore, the work load of the dross treatment is reduced, the working environment is also improved, and the refining loss of the metal melt can be greatly improved, and the non-metal inclusions mixed in the metal melt from the dross, etc. And the effect of improving quality can be expected.

[Brief description of drawings]

FIG. 1 is a view showing an example of an apparatus according to the present invention, in which a rotary body is screwed onto an end of a rotary shaft and a covering body is sandwiched between the rotary shaft and the rotary body. FIG.

FIG. 2 is an explanatory view showing a state in which a refining gas is being released into a molten aluminum by using an apparatus showing an example of the present invention.

FIG. 3 is an explanatory view showing another state in which a refining gas is being released into molten aluminum using the apparatus showing an example of the present invention.

FIG. 4 is a view showing an example of a device according to the present invention, and is a longitudinal cross-sectional view of a main part of the device showing a state in which a covering body is screwed onto a sheath end portion covering a rotating shaft.

FIG. 5 is a perspective view showing an example of a rotating body used in the device of the present invention.

FIG. 6 is an explanatory view showing a state in which a refining gas is released into a molten aluminum by using a conventional apparatus.

Claims (3)

[Claims] 1. A rotary shaft having a passage for a refining gas introduced into a metal melt, and an end portion of the rotary shaft which is rotated by the rotation of the rotary shaft to rotate the refining gas into fine bubbles. As a result, the rotating body having a wing that gives a flow force to the metal melt, which discharges into the metal melt and causes the metal melt to move forward, and the rotation of the wing of the rotating body to cover the rotating body, And a cover having a gap between the blade of the rotating body for sucking a part of the metal melt, and a device for dispersing bubbles in the metal melt. 2. The device for dispersing bubbles in a metal melt according to claim 1, wherein the coating is fixed to a sheath that covers the rotating shaft. 3. The device for dispersing bubbles in a metal melt according to claim 1, wherein the gap between the blade of the rotating body and the covering body is at least 10 mm or more.