JPS6237329A - Method for refining aluminum and aluminum alloy - Google Patents

Abstract

PURPOSE:To facilitate the removal of slag and to reduce erosion by adding a compound which produces gaseous O2 and SO2 by decomposition to a refining agent so as to cover the surface of molten metal with gaseous SO2. CONSTITUTION:About 20wt% compound which produces gaseous O2 and SO2 by decomposition, e.g., potassium sulfate is added to chloride, fluoride or a mixture thereof used as a refining agent during the refining of Al or an Al alloy in a furnace. The surface of the molten metal is covered with generated gaseous SO2 to insulate the molten metal from the atmosphere in the furnace, so the excessive acceleration of reaction is prevented. The irreducible minimum extent of reaction is carried out with oxygen produced from the refining agent.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for scouring aluminum and aluminum alloys.

<Conventional technology> As a refining method for aluminum and aluminum alloys,
For example, it is common to use a halogen gas such as C12t, or a refining agent containing at least a halogen compound, to carry out degassing and removal of inclusions. In this case, in order to easily remove the sludge from the inclusions that have risen to the surface of the molten metal during refining, a portion of the molten metal that coexists with the inclusions is burned at a high temperature, so that the bulk specific gravity is small and the wettability with the molten metal is low. Usually, it is changed to oxides with bad properties.

<Problems to be solved by the invention> If the above-mentioned combustion treatment is performed to facilitate slag removal, the molten metal will change into oxides etc. that cannot be recycled.
There is a problem that so-called melting loss occurs and the loss of old material becomes large.

The present invention has focused on this point, and an object of the present invention has been to provide a material that has good sludge removal properties and reduces melting loss, thereby satisfying both the sludge removal properties and melting loss.

Means for Solving the Problems> In order to achieve the above-mentioned problems, the method for refining aluminum and aluminum alloys of the present invention uses a refining agent containing a component that generates oxygen and sulfur dioxide gas by decomposition, and the surface of the molten metal is heated. The smelting process is done while covering with sulfur dioxide gas.

Effect> Sulfur dioxide gas is heavier than air and covers the surface of the molten metal, cutting off contact between the molten metal and the air. Moreover, it hardly reacts with the molten metal even at high temperatures, so it does not interact with the molten metal and oxygen, nitrogen, etc. in the furnace atmosphere. reaction is hindered.

It is also presumed that the oxygen generated by the decomposition acts as a molten metal combustion agent and changes the floating inclusions into oxides with low bulk specific gravity and poor wettability with the molten metal. That is,
In order to satisfy the two demands of improving slag removal and reducing melting loss, it is sufficient to obtain the minimum necessary combustion state, but oxygen and nitrogen in the furnace atmosphere may cause reactions to occur more than necessary. sulfur dioxide gas prevents the
The minimum necessary reaction is carried out by the oxygen generated from the refining agent.

<Example> Examples of the present invention will be described below.

If the molten metal that coexists with inclusions is combusted with oxygen in the furnace atmosphere, it will be difficult to control the reaction and increase melting loss. , oxygen is supplied from a refining agent. Therefore,
A compound containing oxygen is used as a component of the refining agent, and examples of such compounds include carbonates, nitrates, and sulfates.

After studying these compounds, the inventors found through experiments that carbonates cause defects if they remain in the molten metal, and that it is desirable to avoid their use. Furthermore, due to its chemical properties, nitrates pose a risk of explosion depending on the blending ratio, so it is better to avoid using them. When we investigated sulfates, we found that they did not have the above-mentioned problems and did not pose any new technical problems, so we concluded that it would be appropriate to use sulfates as an oxygen supply source for molten metal combustion. A conclusion has been reached.

Furthermore, after examining the cost, reactivity, etc. of several types of sulfates, it was found that potassium sulfate (K, So,) was the most suitable, so specifically, it was decided to use SO4. The study results are shown in Table 1.

[table! ] Next, in the present invention, as a means to cut off contact between the molten metal and the atmosphere in the furnace, the surface of the molten metal is covered with a specific gas for shielding. Therefore, we investigated the suitability of various gases in terms of density, reactivity with molten metal, etc., and found that sulfur dioxide (S
It was found that 0 was optimal. The study results are shown in Table 2.

[As a result of Table 2 and above, SO2 determined to be optimal can be generated by decomposing K 2 SO-, which was determined to be optimal as an oxygen supply source. Therefore, SO was added to chlorides, fluorides, or mixtures thereof, which are commonly used as refining agents for aluminum and aluminum alloys, and heated to 900°C in an inert gas atmosphere to cause the decomposition reaction of the refining agent. Examined. As a result, it was confirmed that S Ot gas was generated at a constant temperature regardless of the type of scouring agent. In addition, we conducted the tests shown in Table 3 to confirm the sludge removal performance and erosion reduction effect, and found that K2S0. The effect of

Next, the relationship between the blending ratio of SO in the refining agent, deslag removal performance, and erosion loss was confirmed while changing the blending ratio. Table 4 shows the test conditions and results.

[Table 4] (a) Test conditions Molten metal type JIS 5056 Refining agent KCρ (50vt%)-A (IF Ba 50-
awt%) K2SOa (awt%) Amount of refining agent used: 0.15wt% of 7A amount Refining method N
, Simultaneous injection of gas into the molten metal Refining time: 15 minutes Refining temperature: 730°C ± 5° As a result, in this refining agent system, K and SO4 are 2 to 20% by weight.
It was found that the sludge removal property is good when this is the case, and it is also effective in reducing the erosion rate. Similarly, when we tested other refining agent systems with different ingredients while changing the blending ratio, the results were the same! So.

It was confirmed that a blending ratio of 2 to 20% by weight was effective in improving sludge removal performance and reducing erosion loss.

Next, Table 5 shows the results obtained when SO was added to a commonly used refining agent system for various alloy systems. In any case! In the case of containing So, the sludge removal performance was improved and the melting loss was reduced, and the effect was confirmed.

[Table 5 (a) Test conditions K t S O - blending ratio in the scouring agent 10wt% Refining conditions Simultaneous injection of N and gas Temperature 730°C ± 5°C Molten metal amount 15 Amount of refining agent used 1,5 kg ( b) Results <Effects of the Invention> As stated above, the present invention is for refining using a refining agent containing a component that generates oxygen and SO2, and the oxygen generated by decomposition is present on the surface of the molten metal. While contributing to the combustion of the molten metal coexisting with inclusions, the SO generated by decomposition
The t-gas does not contribute to combustion, but covers the molten metal surface and shields it from the furnace atmosphere.

Since molten aluminum and aluminum alloy hardly reacts with SO and gas even at high temperatures, it is presumed that the minimum reaction is carried out by oxygen supplied from the refining agent. As a result, the reaction can be carried out properly without excess or deficiency, making it possible to satisfy the two demands of improving sludge removal and reducing melting loss.

Claims (2)

[Claims] (1) A method for refining aluminum and aluminum alloys, which is characterized by using a refining agent containing a component that generates oxygen and sulfur dioxide gas by decomposition, and performing refining while covering the surface of the molten metal with sulfur dioxide gas. (2) In the method for refining aluminum and aluminum alloys as set forth in claim 1, aluminum and aluminum are used in which 20% by weight or less of potassium sulfate is added to the refining agent as a component that generates oxygen and sulfur dioxide gas by decomposition. Aluminum alloy refining method.