A method for preparing aluminum-scandium master alloy by electrolysis of molten salt of chloride salt oxide system

Abstract

A method for preparing aluminum-scandium master alloy by electrolysis of molten salt of chloride salt oxide system, using scandium oxide as raw material, in NaCl-CaCl 2 or KCl‑CaCl 2 In the chloride molten salt electrolyte composed of CaO or MgO, and the electrolytic raw material Sc 2 o 3 Composition of chloride-oxide mixed molten salt electrolyte, with liquid aluminum as the cathode and graphite as the anode, electrolyzed by direct current at a temperature of 670-780°C, and the anode current density is 0.5-1.5A / cm 2 , the electrolysis time is 4-10 hours, and the liquid aluminum-scandium master alloy is obtained at the cathode at the bottom of the electrolytic cell. The invention has the advantages of simple process, low production cost, high product purity, easy continuous production, and no need for reducing agent; at the same time, during the electrolysis process, the cathode at the bottom of the electrolytic cell obtains a liquid aluminum-scandium master alloy, and the anode emits CO 2 , no other harmful gases are produced, effectively reducing serious pollution to the environment.

Description

technical field [0001] The invention relates to the technical field of preparation of an aluminum-scandium master alloy, in particular to a method for preparing an aluminum-scandium master alloy by electrolysis of a molten salt of a chloride oxide system. Background technique [0002] Scandium is a rare earth element, and it is the strongest modifier for the grain structure of cast aluminum alloys and the most effective recrystallization inhibitor for processed semi-finished products. Grain refinement, inhibit recrystallization, significantly improve the strength, toughness, welding and corrosion resistance of aluminum alloy. Scandium-containing aluminum alloys are widely used in aerospace industry, military industry, civil industry and other fields because they can greatly improve the comprehensive performance of traditional aluminum alloys. However, because scandium has the highest electronegativity among rare earth metals, its chemical activity is extremely high, and its...

AI Technical Summary

Problems solved by technology

However, because scandium has the highest electronegativity among rare earth metals, its chemical activity is extremely high, and its melting point is as high as 1541°C, which is quite different from the melting point of aluminum at 660°C. It is not easy to mix evenly when directly melting aluminum-scandium alloys, and the formed aluminum-scandium compound crystals Coarse particles and severe segregation; in the production process of industrial aluminum-scandium alloys, scandium must be added in the form of aluminum-scandium master alloys, so aluminum-scandium master alloys are key raw materials for the production of industrial aluminum-scandium alloys

[0003] The preparation methods of aluminum-scandium master alloy include pair mixing method, metallothermic reduction method and molten salt electrolysis method. Among them, molten salt electrolysis method has the advantages of simple process, low production cost, easy continuous production, and no need for reducing agent, etc., but it is difficult to be used. It is used to produce pure metals with a melting point higher than 1000°C. When liquid metal Al, Mg or Zn is used as the cathode, the corresponding alloy can be prepared by depositing alloy elements on the cathode.

In the fluoride molten salt system, with Sc 2 o 3 When the Al-Sc master alloy is prepared as raw material, the temperature of the fluoride molten salt electrolyte is usually high, which seriously corrodes the equipment and electrodes, and the Sc 2 o 3 Low solubility in the electrolyte is not conducive to the smooth and efficient operation of the electrolysis process for a long time

At present, the electrolyte composition used in the electrolysis of aluminum-scandium master alloys in the chloride molten salt system is mainly LiCl / NaCl-KCl-ScCl 3 , in the process of electrolysis, control the appropriate conditions, so that Sc 3+ It is reduced to a simple metal on the cathode and alloyed at the same time to obtain an aluminum-scandium intermediate alloy. Since the electrolytic raw material is scandium chloride, Cl on the anode - It is oxidized to generate chlorine gas, because there is no good way to use the generated chlorine gas, it is easy to cause serious pollution to the environment, and the raw material ScCl 3 The preparation process is long, the equipment is complicated, and the production cost is high