JPS6133048B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for refining molten non-ferrous metals and non-ferrous alloys that prevents the contamination of moisture, and more specifically, the present invention relates to a method for refining molten non-ferrous metals and non-ferrous alloys that prevents moisture from entering the molten metal. This invention relates to a molten metal refining method for nonferrous metals and nonferrous alloys that eliminates the adverse effects of moisture on metals and prevents moisture from entering. In general, molten nonferrous metals and nonferrous alloys are contaminated by raw materials charged or mixed into the melting process, or by newly generated oxides, gases inhaled from the atmosphere, etc., and then processed during subsequent processing such as rolling. Products subjected to this process may have various defects such as linear defects and pinholes. Therefore, in order to prevent such various defects in products, impurity inclusions in the molten metal are conventionally transported by transporting flux using an inert gas and injecting it into the molten metal of nonferrous metals and nonferrous alloys at the same time. Molten metal refining methods to remove gases and gases have been implemented. However, in the molten metal refining method using the simultaneous injection of flux and inert gas, it is known from experience that degassing does not progress as much as the theoretical reaction value in actual operation. As a result of repeated experimental research by the present inventor as to the reason why the degassing reaction does not proceed in the molten metal, it was discovered that the reason lies in the moisture contained in the flux and inert gas. That is, inert gas (nitrogen,
For example, high-purity nitrogen gas contains 1 to 4 mg of moisture due to the influence of the container used, and industrial nitrogen gas contains approximately 13 mg of moisture due to the influence of piping, etc. If nitrogen gas containing a large amount of water is used as a transportation medium for flux in molten metal refining, H ₂ generated by decomposition of H ₂ O will be absorbed into the molten metal after refining, reducing the degassing effect. . Furthermore, O ₂ generated by decomposition of H ₂ O produces oxides in the molten metal, reducing the refining effect. Therefore, in the refining process in which flux is simultaneously injected into the molten metal using an inert gas containing a relatively large amount of water as a transport medium, the degassing effect is insufficient due to the moisture content, and the deoxidizing effect is also insufficient. You can say that. The above explanation deals with the case where the moisture contained in the inert gas directly affects the molten metal and causes a deterioration in the quality of the molten metal, but it also has an adverse effect indirectly.
In other words, a flux that generates chlorine gas (Cl ₂ , fluorine-containing gas), which is said to have an excellent effect on refining molten non-ferrous metals (alloy-containing), such as aluminum, is blended, but the flux is thermally decomposed. Just before the molten aluminum, the chlorine gas immediately reacts with moisture in the inert gas to become hydrogen chloride gas, and the molten aluminum is blown with hydrogen chloride gas, and some of this hydrogen chloride gas is decomposes to generate _H2 ,
Similarly to the above, it causes molten metal contamination. Also,
According to the inventor's experiments, it is clear that the amount of chlorine gas effective for refining in the flux + inert gas immediately before molten aluminum is extremely small, about 1/500 to 5000 of the amount of hydrogen chloride. This proves that a reaction is occurring. Above, we have explained the moisture contained in the inert gas, but we can also explain the moisture contained in the flux that is simultaneously blown into the molten metal by the inert gas.
The decomposition of this water has the same effect on the molten metal as the adverse effect of water in an inert gas. Therefore, the adverse effect of moisture on the molten metal is that the moisture contained in the inert gas and the moisture contained in the flux are brushed, and the influence on the quality of the molten metal is enormous. In view of the numerous problems encountered in the conventional refining of molten non-ferrous metals and non-ferrous alloys by simultaneous injection of flux and inert gas as explained above, and the knowledge of the results of the research conducted by the present inventor, In order to improve the respective effects of degassing the molten metal and removing inclusions, the moisture content in the inert gas and the moisture content of the flux in the flux-inert gas simultaneous injection method as a molten metal refining method are extremely low. It has been found that it is effective to prevent H ₂ and O ₂ generated by the thermal decomposition of water from entering the molten metal directly and indirectly as described above. The present invention has been made based on the prior art described above and the knowledge of the inventor, and is based on the refining reactivity when using a flux-inert gas simultaneous injection method in molten metal refining of non-ferrous metals and non-ferrous alloys. The purpose is to improve the quality of molten non-ferrous metals and non-ferrous alloys. Total of moisture content in flux and moisture content in inert gas, per flux/inert gas mixture
The purpose is to remove it so that it is 3.4mg/or less and then inject it. The method for refining molten nonferrous metals and alloys that prevents moisture from entering according to the present invention (hereinafter sometimes referred to as the refining method according to the present invention) will be specifically described below. The following description will be made using aluminum as the non-ferrous metal and alloy, and nitrogen among nitrogen, helium, argon, etc. as the inert gas. In the refining method according to the present invention, the total moisture content of the flux and nitrogen that are simultaneously blown into the molten aluminum is added per flux/nitrogen gas mixture.
The reason why it should be 3.4mg/or less is as mentioned above, but the water contained in the flux and nitrogen decomposes into H ₂ O → H ₂ + O ₂ , and the chlorine (fluorine) in the flux is decomposed into Cl ₂ +H ₂ O→HCl+O ₂ reaction occurs, and in the molten metal it decomposes into HCl+O ₂ →H ₂ +Cl ₂ +O ₂ HCl→H ₂ +Cl ₂ HCl+Al→AlCl ₃ +H ₂ , and H ₂ and Exists as _O2 ,
O ₂ generates oxides by reaction with molten metal. Figure 1 shows the relationship between the amount of water contained in the flux and nitrogen, and the amount of _H2 in the molten metal after completion of refining. The conditions in this case are as follows. Molten metal type: 5052, 20t Flux: JDR946B 20Kg Injection conditions: Molten metal temperature 760℃ Injection rate 1Kg/min Gas rate 500/min ( _H2 amount was measured using the telegas method.) It is clear from Fig. 1 that: Flux+
When the total moisture content of nitrogen is less than 3.4 mg/1 flux/nitrogen mixture, the amount of _H2 in the molten metal hardly decreases and remains almost constant, that is, 0.2 cc/100 gA.
It is becoming. In addition, regarding the influence of O ₂ , after refining using fluxes with different H ₂ O contents and nitrogen, the molten metal is made into an ingot, which is then rolled to produce a plate.
The results of investigating the occurrence of oxide defects existing on the plate surface are shown in Figure 2. The refining conditions in this case are the same as those described in FIG. In addition, the rolling conditions are hot rolling and cold rolling for 400mmt.
mmt. As is clear from Fig _{. 2, the H 2 O} content in flux + nitrogen also increases with respect to oxide defects, as in the case of H 2 described above.
It can be seen that a dose of 3.4mg or less shows extremely excellent effects. As explained above, in the refining method according to the present invention, it is clear that effective refining results cannot be obtained unless the total water content of flux + nitrogen that is simultaneously blown into the molten metal is 3.4 mg/or less. Next, the removal of moisture between the flux and nitrogen used in the refining method according to the present invention will be explained. Therefore, there are cases where the moisture of flux and nitrogen are dehumidified separately and then mixed before being blown into the molten metal, and cases where a mixture of flux and nitrogen is simultaneously dehumidified and blown into the molten metal. A case where nitrogen and nitrogen are dehumidified separately and a case where (flux + nitrogen) are dehumidified simultaneously will be explained. First, dehumidification methods include (1) a method in which H 2 O is removed as a liquid by lowering the temperature of nitrogen, flux, and nitrogen + flux and increasing relative humidity; (2) a method that removes H ₂ O as a liquid by lowering the temperature of nitrogen, flux, and nitrogen + flux; There is a method of removing moisture using a chemical compound. In the method (1) above, in order to reduce the moisture content to 3.4 mg or less per flux/nitrogen mixture, the temperature must be kept at -59°C or lower, and commercially available refrigerators for dehumidifying gases such as air need to be heated to -20°C. Since the _limit is around Preferably, O ₅ , Mg(ClO ₄ ) ₂ , KOH, Al ₂ O ₃ , MgO, etc. are used. Furthermore, these two methods (1) and (2) may be combined, and the use of two or more types of desiccant is also effective. In both of these methods, it is desirable to have a sufficiently wide contact area with the nitrogen and flux to be dehumidified, and to make the contact time as long as possible. (1) Method for removing moisture from nitrogen (a) To reduce the temperature to below -59℃, use ethyl alcohol + dry ice (-72℃) or ethyl ether + dry ice (-77℃) as a gaseous material. uses liquid nitrogen. That is, nitrogen with a moisture content of 10 mg/cm2 was added to a heat exchange tube installed in a cryogen containing 1 ethyl alcohol + 0.3 dry ice (volume of each) at a pressure of 0.2 kg/ ^cm2 .
0.01mg after dehumidification when passed at a flow rate of /min.
The amount of H ₂ O was below. The generated drain may be extracted as appropriate. (b) Use a compound with excellent hygroscopicity, that is, increase the contact area of the desiccant with nitrogen and reduce the resistance to nitrogen to provide good air permeability, and use P ₂ as the desiccant. Nitrogen with a water content of 10 mg using O ₅ at a flow rate of 50/min and pressure
When nitrogen is introduced at 0.2Kg/cm ² , after dehumidification H ₂ O is
It was below 0.01mg. (2) Method for removing moisture from flux (a) Dehumidify in a sealed container containing a desiccant in advance, and then heat to a temperature of 100°C or higher and lower than the decomposition starting temperature of the flux. (b) Dehumidify in an airtight container containing desiccant in advance. (c) Dehumidify by heating to 100℃ or higher and lower than the decomposition temperature of the flux. By these methods, the H ₂ O content can be reduced to 1% or less. (3) Method for removing moisture from (flux + nitrogen) mixture. The desiccant is dehumidified by passing through a space having a dehumidifying function, for example, a blowing pipe after the flux tank. By the dehumidification method described above, the moisture content in nitrogen, flux, and nitrogen + flux is reduced to 3.4 mg/or less per flux/nitrogen mixture when flux and nitrogen are blown simultaneously. An embodiment of the refining method according to the present invention will be explained in comparison with a conventional method. Example After the total moisture content of the flux + nitrogen was reduced to 3.4 mg/or less per flux/nitrogen mixture by the dehumidification method described above, molten aluminum was refined by the simultaneous injection method of flux + inert gas. . The following table shows the implementation conditions and results. FIG. 3 shows the total water content (flux+nitrogen) and the judgment of the examples and comparative examples, and it can be seen that the refining method according to the present invention is superior.

[Table] Compared to the conventional method, the refining method according to the present invention has a higher water content in flux + nitrogen, and
It can be seen that the amount of H ₂ in the molten metal is extremely small since it is 3.4 mg/or less per nitrogen mixture, and that it has excellent effects in that the quality is also good. As explained above, the method for refining molten nonferrous metals and alloys thereof that prevents moisture from entering according to the present invention,
Since it has the above structure, H ₂ in the molten metal is extremely low, which improves the quality of the molten metal.Furthermore, the subsequent vacuum degassing process time can be shortened, and the filter process can be simplified and the product can be improved. This has the excellent effect of improving quality.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the total amount of moisture (flux + nitrogen) and the amount of _H2 in the molten metal. Figure 2 shows the total amount of moisture (flux + nitrogen) and defects per unit area of the product. Figure 3 The figure is a diagram showing the relationship between the total amount of water (flux+nitrogen) and the determination for the refining method according to the present invention and a comparative example.

Claims (1)

[Claims] 1. When refining flux containing halides by injecting it into molten nonferrous metals and nonferrous alloys using inert gas, the sum of the moisture content of the flux containing halides and the moisture content of the inert gas is per inert gas mixture
A molten metal refining method for non-ferrous metals and non-ferrous alloys that prevents the incorporation of moisture, which is characterized by blowing after removing the metal to a concentration of 3.4 mg/min or less.