JPH06264154A - Method for removing slag from molten al or al alloy and method for recovering metal content from slag - Google Patents

Abstract

PURPOSE:To reduce metal loss accompanied with slag removal and to efficiently recover the metal content by applying stirring force in the whole thickness direction of the slag layer floated up on the surface of molten Al and removing the slag after separating the metal in the slag. CONSTITUTION:At the time of melting an Al or Al alloy raw material, preceding to casting, the slag floated up on the surface of the molten metal 1 is removed. At this time, the stirring force is given in the whole thickness direction of the slag layer 2 and the metal content 3 which is contained in the slag and is difficult to separate is separated and, after recovering by flowing down in the molten metal 1, the slag is removed. The stirring of the slag layer 2 is desirable to execute by removing the slag while rotating a rotary blade 4 for rotating in the slag removing direction in the almost vertical direction to the slag layer 2. The rotary blade 4 to be used is suitable if cast iron-made, ceramic-made, graphite-made blade, etc. It is desirable to promote the recovery of the metal content 3 by arranging an inclining surface in the downgrade toward the direction in the melting furnace to the lower surface of a slag removing hole. Further, it is desirable to remove the slag after heating the slag by adding refining agent into the slag layer 2 to burn a part of the metal content 3 in the slag.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In the present invention, when smelting Al or an Al alloy (hereinafter represented by an Al alloy), the slag floating on the surface of the molten metal and the metal loss associated with the slag are removed as much as possible. The present invention relates to a method of efficiently reducing and removing metal, and a method of efficiently recovering a metal content from a slag.

[0002]

2. Description of the Related Art Since Al alloys are lighter in weight, have higher specific strength and are more excellent in corrosion resistance than steel materials, they are used as outer panel materials and parts materials for vehicles such as automobiles and trains, building materials, and household electrical appliances. It is widely used as an outer plate material and can material for products. The manufacturing process for obtaining these Al alloy products is as follows. Melting raw materials (metals, scraps, etc.) → Melting and refining → Slag →
Casting → Soaking → Hot working → Cold working → Heat treatment → Surface treatment → Inspection → Shipping

In the melting / refining process, oxides (alumite, etc.) on the surface of the smelting raw material and oxides generated in the melting / refining process float up on the surface of the molten metal as slag. This slag is a mixture of non-metal components mainly consisting of oxides and metal components (Al alloy). If this slag is left as it is, the non-metal components will mix into the Al alloy molten metal and cause contamination of the molten metal. Not only does it occur, but it adheres and deposits on the furnace wall and furnace bottom after tapping, which reduces the volume of the melting furnace and adversely affects productivity.

Therefore, it is necessary to remove slag from the surface of the molten metal as soon as possible after melting and refining. However, since this slag contains a large amount of metal as described above and has a high affinity with the molten metal, it is difficult to separate the slag, and if you try to forcefully remove it from the surface of the slag, a large amount of metal will accompany it. Since it is discharged, the yield of the molten Al alloy is significantly reduced.
Therefore what is currently widely used as means for increasing the skimming properties, for example, KCl-AlF ₃ chloride or boiling products such as such as sparging with flux mainly or halogen-based gas (Cl _2,, six (Ethanol chloride, Freon, etc.) is blown into the slag, and the entire slag layer is heated by igniting and burning part of the metal components in the slag, melting the metal components mixed in the solid state A method is adopted in which the oxide and the like are changed to oxides that are more stable and have poor wettability with the molten metal to improve the separation of the molten metal and then remove the slag.

By the way, in order to effectively bring out the effect of adding such a refining agent, it is necessary to thoroughly mix the refining agent into the entire slag layer floating on the entire surface of the molten metal. It is surprisingly difficult to mix the refining agent uniformly throughout the slag layer in a processing furnace where the surface of the molten metal fluctuates considerably with respect to the volume of the molten metal, such as a reverberatory furnace. The return and removal of the molten metal from the slag become partially insufficient, and the metal loss during slag removal cannot be reduced sufficiently.

[0006]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and an object thereof is to perform melting and refining of an Al alloy raw material using a reverberatory furnace.
An object of the present invention is to provide a method capable of efficiently removing slag while returning the metal content in the slag layer formed on the molten metal surface to the molten metal well. Another object of the present invention is to provide a method capable of efficiently separating and recovering a metal content from a slag discharged with a large amount of metal content.

[0007]

The constitution of the slag removal method according to the present invention which has been able to solve the above-mentioned problems is Al or Al.
In melting the alloy raw material in the melting furnace, it is a method of removing the slag on the surface of the molten metal prior to casting, and has the gist of removing the slag after applying stirring force in the entire thickness direction of the slag layer. is there. Here, for stirring the slag layer, it is advantageous to use a rotary blade that rotates in a direction substantially perpendicular to the slag layer, and to remove the slag while stirring the slag by rotating this in the slag direction, In addition, an inclined surface with a downward slope is provided on the lower surface of the slag discharge port of the melting furnace, and the slag is discharged while rotating the rotary blade in a direction orthogonal to this inclined surface. Since the metal content in the separated slag flows down along the inclined surface toward the inside of the furnace, the metal loss can be further reduced.

Further, in this slag removal process, the return of the metal content in the slag layer in the direction of the molten metal can be promoted only by mechanical stirring by the rotary blade, but as described above, the heating of the slag layer by the addition of the refining agent is promoted. When used together, the metal loss can be further reduced and the slag removal performance can be enhanced. The rotary blade may be made of any material as long as it has corrosion resistance and heat resistance with respect to the main components of slag, alumina and metal components, but cast iron and ceramics are particularly preferable. A rotary blade made of graphite or graphite.

Further, in the present invention, the metal content in the slag is removed by applying a stirring force to the slag discharged from the melting furnace together with a large amount of the metal content with a rotary blade that rotates in a substantially vertical direction. It can be efficiently separated and collected.

[0010]

The present inventors pay attention to the fact that a large amount of metal components are discharged together with the slag in the slag removal process, and the existence form of the metal components in the slag layer does not significantly affect metal loss. With that in mind, the existence form of metal was investigated. As a result, in the slag layer, the metal component is encapsulated by the oxide film, and there are innumerable states as if the water was wrapped in the vinyl bag, and the oxide, which is the main slag component, is removed. If you try to do this, the metal content wrapped in the oxide film will be discharged at the same time, which is a major cause of increasing metal loss,
They found that if the slag layer was mechanically agitated to destroy the oxide film and let out the metal content inside, the metal loss could be greatly reduced without using a refining agent.

Further, the effect of improving the slag removal effect obtained by adding the refining agent is exhibited by the exothermic reaction between the metal component contained in the slag and the refining agent as described above. Since most of the minute part is encapsulated by the oxide film as described above, the added refining agent does not react sufficiently with the metal part, and the effect of the refining agent is effectively exerted to improve the slag removal property. It is possible that it has not been done. However, if the slag layer to which the refining agent is added is mechanically agitated, the reaction with the refining agent is promoted by the outflow of the metal component due to the destruction of the oxide film as described above, and the mixing effect of the agitation is combined with the refining agent. The reaction with the metal content is enhanced, and the effect of improving the slag removal property by adding the refining agent is further enhanced.

As a stirring means in the slag, a method of stirring the slag layer in the horizontal direction and a method of stirring the slag layer in the vertical direction (the thickness direction of the slag layer) can be considered. However, with the method of horizontally stirring the slag layer, it is difficult to sufficiently stir the molten metal near the boundary between the slag layer and the molten metal because it is necessary to control the swelling of the molten metal surface and control the contamination of the molten metal by the slag. hand,
Since only the upper part of the slag layer is stirred, for example, as shown in FIG. 1, an unstirred slag layer 2b is formed between the molten metal 1 and the stirred slag layer 2a. In the unstirred slag layer 2b, the oxide film is not destroyed, so that the metal component is not discharged, and the metal component 3 flowing out from the upper stirred slag layer 2a is not stirred. Since the metal components 3 accumulated on the layer 2b cannot return to the molten metal 1 and these metal components 3 are discharged together with the unstirred slag layer 2b, the metal loss reduction effect by stirring cannot be effectively exhibited.

On the other hand, when the method of stirring the slag layer 2 in the thickness direction (vertical direction) by using the rotary blade 4 or the like as shown in FIG. 2 is adopted, the height position of the rotary blade 4 can be adjusted well. Thus, the molten metal 1 can be sufficiently agitated to the deep portion of the slag layer 2 without causing almost any waviness. As a result, the oxide film on the entire slag layer 2 is efficiently destroyed to cause the metal to flow out, and the metal content 3 that has flowed out quickly returns to the molten metal 1. As a result, not only the metal content in the slag layer after the stirring treatment is significantly reduced, but also the difference in specific gravity between the slag 2 and the molten metal 1 is expanded due to the reduction of the metal content, and the viscosity of the slag 2 is also reduced. It also improves the ability to remove hot water and enhances slag removal. In this case, it is preferable to rotate the rotary blade in the slag discharge direction because the slag layer can be stirred and the slag can be transferred in the discharge direction.

By the way, it is very difficult in terms of equipment to dispose the stirrer equipped with the above rotary blades over the entire surface of the melting furnace to stir the entire slag layer. Therefore, in putting the present invention into practical use, for example, as shown in FIG. 3, the rotary blade 4 which rotates in the slag direction is disposed along the lower surface 5a of the slag port 5 of the melting furnace, and the slag port 5 is rotated. It is preferable that the lower surface 5a is provided with a downward slope toward the inside of the melting furnace, and the rotary blade 4 is rotated to remove the slag while stirring the slag 2.

That is, when this method is adopted, the slag 2 is stirred at the position of the discharge port to elute the metal component 3 due to the destruction of the oxide film, and the eluted metal component 3 is stored in the melting furnace along the inclined surface. While being returned to the molten metal 1, the slag 2 is sequentially discharged out of the furnace. The slag on the surface of the molten metal is attracted toward the slag outlet 5 along with this slag, and the elution separation and slag of the metal component 3 are sequentially performed, so that the work can be performed extremely efficiently.

At this time, when the refining agent is used, it may be sprayed over the entire surface of the slag layer on the surface of the molten metal, or may be continuously sprayed in the vicinity of the slag outlet 5 to remove the slag. The latter method is more preferable for more effectively exerting the effect of improving the sludge removal property by adding the refining agent. The constituent material of the rotary blade is not particularly limited, but the most common material is cast iron, ceramics, or graphite having both excellent corrosion resistance and heat resistance against alumina and metal components (Al alloy).

In the above description, an example in which the slag is stirred in the melting furnace or in the vicinity of the slag outlet has been shown, but as described above, the characteristics of the oxide film being destroyed by the stirring and the elution and separation of the metal component are effective. As another means for exhibiting the slag, for example, the slag 2 discharged from the melting furnace is put in a funnel-shaped slag stopper 6 as shown in FIG. 4, and the slag 2 is used by a rotary blade 4 with / without using a refining agent. The oxide film is destroyed by stirring in the vertical direction, and the eluted metal component 3 is taken into the recovered metal reservoir 7, and the remaining slag is sequentially taken out from the slag outlet. Also in this case, if necessary, a refining agent may be added to the slag reservoir 6 to cause a heating reaction to accelerate the elution and separation of the metal component 3.

[0018]

EFFECTS OF THE INVENTION The present invention is configured as described above, and a metal component incorporated in the slag layer in a form encapsulated in an oxide is obtained by stirring the slag layer by applying a vertical stirring force. It is possible to efficiently elute and separate the slag, and it is possible to improve the separation of the slag component mainly containing oxides from the molten metal, and to improve the slag removal efficiency while reducing metal loss.

[0019]

EXAMPLES Hereinafter, the effects of the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and is within a range applicable to the gist of the preceding and following. It is also possible to make changes and carry out,
All of them are included in the technical scope of the present invention.

Example 1 (Example of agitation in a melting furnace) When smelting, smelting and slag were carried out under the following conditions and the combination of the smelting condition and the slag condition was changed, the slag and molten metal were separated and the slag was removed. We compared the metal loss associated with. (Smelting conditions): Melting furnace ... Heavy oil-fired 20 ton reverberatory furnace Melting raw material ... JIS5056 series Al alloy, 18 tons Melting temperature ... 720 ° C Melting atmosphere ... Atmosphere (Refining conditions): Blowing refining gas ... Chlorine gas, per ton of molten metal 400N liter injection Refining flux addition ... Chloride-Fluoride-Sulfate-Al
Add 0.005% of powder and molten metal weight to the surface of slag layer (remove slag): Stir the slag layer in the thickness direction using a stirrer equipped with an arc type rotary blade, and discharge it to the outside of the furnace with a rake.

The results are shown in Table 1, and the conventional slag removal method using the refining agent significantly improved the slag removal property,
Further, although the metal loss is also reduced to 4%, it can be seen that the slag removal property is further improved and the metal loss can be further reduced by vertically stirring the slag layer according to the present invention.

[0022]

[Table 1]

Example 2 (Example of agitation at slag outlet) The same melting and refining conditions as those employed in Example 1 above were adopted and an arc type rotary blade was rotated along the lower surface of the slag outlet. Remove slag with stirring. At this time, the slag removal performance and metal loss were compared between the case where the bottom surface of the slag outlet was provided with the slope and the case where the slope was not provided.

The results are shown in Table 2, and even when the lower surface of the slag outlet was not inclined, the slag removal performance was enhanced by vertically stirring the slag at the slag outlet portion, and the metal loss was reduced. Significantly reduced. However, it can be seen that a more excellent effect can be obtained by providing a slope on the lower surface of the slag outlet.

[0025]

[Table 2]

Example 3 (Example of recovering metal after slag) Rake slag was removed by a conventional method without using a refining agent (blown with Cl ₂ ) and stirring with a rotary blade.
800 kg of slag at 50 ° C. was placed in a slag reservoir as shown in FIG. 4, and this slag was stirred vertically by an arc type rotary blade at 20 ppm for 20 minutes, and then the weight of metal recovered in the metal reservoir was measured. As a result, 560 kg (70% of the amount of slag) of metal was recovered. On the other hand, when stirring with a rotary blade was omitted and the weight of the metal recovered in the metal reservoir was checked only by natural flow, it was only 120 kg (15% of the amount of slag).

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a separation state of a metal component when a slag layer is horizontally stirred.

FIG. 2 is a conceptual diagram showing a state of separation of metal components when a slag layer is stirred in a thickness direction by a rotary blade.

FIG. 3 is a conceptual diagram showing a state of separation of a metal component when a slag is stirred at a slag outlet position.

FIG. 4 is a conceptual diagram showing a situation in which a slag is collected in a slag pool and then a metal component is collected.

[Explanation of symbols]

 1 molten aluminum alloy 2, 2a, 2b slag layer 3 metal component 4 rotary blade 5 slag outlet 6 slag reservoir 7 metal reservoir

Front page continued (72) Inventor Ryukichi Ikeda 14-1 Nagafu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works, Ltd. Chofu Works (72) Inventor Osamu Domoto 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel, Ltd. (72) Inventor Takayuki Kitano 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works, Ltd. Chofu Factory

Claims (7)

[Claims] 1. A method of removing slag on the surface of the molten metal prior to casting when melting Al or Al alloy raw material in a melting furnace, wherein stirring force is applied in the entire thickness direction of the slag layer, and then the slag is removed. A method for removing slag from an Al or Al alloy melt. 2. The slag according to claim 1, wherein a rotary blade that rotates in a direction substantially perpendicular to the slag layer is used to stir the slag layer, and the rotary blade is rotated while rotating in the slag discharge direction. Slag method. 3. A slag is provided on the lower surface of the slag discharge port in the melting furnace, with an inclined surface having a downward slope toward the inside of the melting furnace, and the rotary blade is rotated while rotating in a direction substantially orthogonal to the inclined surface. The slag method according to 1 or 2. 4. The slag method according to claim 1, wherein a rotary blade made of cast iron, ceramics or graphite is used. 5. The refining agent is added to the slag layer in the slag removal step, a part of the metal content in the slag is burned, the slag is heated by the heat of combustion, and then the slag is removed. The slag method described in crab. 6. When melting an Al or Al alloy raw material, the slag discharged from the melting furnace is stirred outside the melting furnace in the thickness direction of the slag layer, so that the metal component in the slag layer flows down and is separated. A method for recovering metal from slag, which is characterized by the fact that 7. A refining agent is added to the slag to burn a part of the metal content in the slag to heat the slag by the heat of combustion, and the slag layer is agitated in the thickness direction so that the metal content in the slag layer is increased. The method for recovering a metal component from a slag according to claim 6, wherein the metal is allowed to flow downward and separated.