CN110205652B - A kind of preparation method and application of copper-scandium master alloy - Google Patents

Abstract

The invention discloses a preparation method of a copper-scandium intermediate alloy. In a molten salt electrolyte containing scandium, a metal copper electrode is used as a consumable cathode, and graphite is used as an anode, and the copper-scandium intermediate alloy is prepared by molten salt electrolysis; the above method prepares The copper-scandium master alloy is used to prepare scandium-containing aluminum alloys or other scandium-containing alloys. The preparation method provided by the invention has the advantages of simple process, no pollution and low production cost, the content of scandium in the prepared copper-scandium intermediate alloy can reach 10-75%, and can be used for the preparation of various scandium-containing alloys.

Description

A kind of preparation method and application of copper-scandium master alloy

technical field

The invention relates to the technical field of alloy preparation, in particular to a preparation method and application of a copper-scandium master alloy.

Background technique

The atomic number of scandium is 21. In the periodic table, it belongs to the III subgroup with the lanthanide rare earth metals, and belongs to the 3d-type transition metal with titanium, vanadium, and chromium. Scandium metal is an excellent modifier for cast aluminum alloys and an excellent modifier for iron. At present, metal scandium is widely used in the preparation of aluminum-scandium alloys. Adding a small amount of metal scandium (0.1-0.4%) to the aluminum alloy can refine the grains of the alloy and significantly improve the strength, plasticity, toughness, high temperature resistance and resistance of the aluminum alloy. Corrosion properties, etc. The comprehensive performance of scandium-containing aluminum alloy is obviously better than that of traditional aluminum alloy, and it is widely used in cutting-edge scientific and technological fields such as aerospace and military industry.

Due to the active chemical properties of elemental scandium and its high melting point (1541°C), which is quite different from the melting point of aluminum (660°C), it is difficult to prepare scandium-containing aluminum alloys by direct melting and casting. During the production of aluminum-scandium alloys in the industry, scandium is usually added to the alloy in the form of a master alloy. At present, the preparation methods of Al-scandium master alloy mainly include counter-doping method, metallothermic reduction method and molten salt electrolysis method.

The counter-doping method uses high-purity metal scandium and pure aluminum as raw materials. In an argon protective atmosphere, a specific proportion of metal scandium is wrapped with aluminum foil and added to the aluminum melt, fully stirred, and kept for a sufficient time before casting. An aluminum-scandium master alloy was prepared. The Al-scandium master alloy with scandium content of 2-4% can be prepared by the counter-doping method, and the process is simple, but the counter-doping method needs to use high-purity metal scandium as the raw material, and the cost is high; the alloy loses a lot and the recovery rate is low; and the scandium , The melting point of aluminum has a large difference, the distribution of components in the alloy is uneven, and the quality is poor.

The metallothermic reduction method is mainly based on the vacuum aluminothermic reduction method of scandium fluoride. Scandium fluoride is used as raw material, and metal aluminum is used as reducing agent, and the aluminum-scandium master alloy is prepared by reduction under vacuum. The content of scandium in the master alloy prepared by this method can reach 30%, but the preparation process of the scandium fluoride raw material is complicated, the process cannot be continuously produced, and the yield is low.

The molten salt electrolysis method mainly uses scandium oxide or scandium chloride as raw materials, and conducts electrolysis in a chloride salt system or a fluoride salt system. Among them, when scandium chloride is used as raw material, NaCl–KCl–ScCl ₃ and LiCl–KCl–ScCl ₃ are mostly used as electrolytes, and liquid metal aluminum is used as cathode. Instead of alloying, ^Cl- is oxidized at the anode to form chlorine. It should be pointed out that scandium chloride is easy to absorb moisture, difficult to transport and store, and the production of chlorine in the electrolysis process pollutes the environment, so it is less used in industrial production. When scandium oxide is used as raw material, the electrolyte used is NaF·AlF ₃ -Sc ₂ O ₃ -ScF ₃ -NaCl, NaF-Sc ₂ O ₃ -ScF ₃ , CaCl ₂ -Sc ₂ O ₃ or LiF-Sc ₂ O ₃ -ScF ₃ , mostly using liquid metal aluminum as the cathode or adding Al ₂ O ₃ to the molten salt to generate liquid aluminum at the cathode during electrolysis. During the electrolysis process, scandium ions are deposited at the cathode and form an intermediate alloy with aluminum. Compared with the counter-doping method and the metallothermic reduction method, the aluminum-scandium master alloy prepared by the molten salt electrolysis method has the advantages of uniform composition, low production cost, easy continuous production, and no reducing agent. In the research on the preparation of scandium master alloy by molten salt electrolysis, the aluminum-scandium alloy is basically the target product, and liquid aluminum is used to capture scandium, but the melting points of aluminum and scandium are very different. , the aluminum melt requires a high degree of superheat, and the diffusion of scandium in aluminum is slow, it is difficult to form a high-concentration scandium-containing alloy composition with uniform composition, and the content of scandium in the master alloy is low.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is the problem of low scandium content during the preparation of scandium master alloy by molten salt electrolysis, and provides a method for preparing a copper-scandium master alloy with high scandium content by electrolysis using a copper consumable cathode.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A method for preparing a copper-scandium intermediate alloy. In a molten salt electrolyte containing scandium, a metal copper electrode is used as a consumable cathode, and graphite is used as an anode, and the copper-scandium intermediate alloy is prepared by molten salt electrolysis.

Further, the molten salt electrolyte includes, in parts by mass: 20-70 parts of LiF, 5-60 parts of ScF ₃ , 0-55 parts of MCl or/and MF, wherein M is one of alkali metal elements and alkaline earth metal elements species or multiple species.

Further, raw material Sc ₂ O ₃ is added to the molten salt electrolyte, and the added mass of Sc ₂ O ₃ is 0-30% of the mass of the molten salt.

Further, the molten salt electrolysis temperature is 875-1100°C.

Further, in the molten salt electrolysis, the cathode current density is controlled to be 0.5-40 A/cm ² .

Further, a receiving crucible is placed under the copper cathode to collect the copper-scandium intermediate alloy product, and the receiving crucible is a molybdenum crucible, a tungsten crucible, a tantalum crucible or a graphite crucible.

The copper-scandium master alloy prepared by the above method is used to prepare scandium-containing alloys of other metals.

The preparation method of the copper-scandium master alloy provided by the invention has the advantages of simple process, no pollution, wide source of raw materials and low production cost; in the prepared copper-scandium master alloy, the impurity content is relatively low, and the content of scandium can be adjusted according to the amount of the substance. It can be used in the preparation of various scandium-containing alloys, and can significantly improve the mechanical properties, strength, plastic toughness, high temperature resistance, corrosion resistance and other properties of the alloy.

Detailed ways

A method for preparing a copper-scandium intermediate alloy. In a molten salt electrolyte containing scandium, a metal copper electrode is used as a consumable cathode, and graphite is used as an anode, and the copper-scandium intermediate alloy is prepared by molten salt electrolysis.

The composition of the molten salt electrolyte is LiF-ScF ₃ -MCl/MF, M is one or more of alkali metal elements and alkaline earth metal elements, and the molten salt electrolyte includes 20-70 parts by mass of LiF, 5-60 parts of ScF ₃ , 0-55 parts of MCl or/and MF. The raw material Sc ₂ O ₃ is added to the molten salt electrolyte, and the added mass of Sc ₂ O ₃ is 0-30% of the mass of the molten salt.

Specifically, a method for preparing a copper-scandium master alloy is to mix Sc ₂ O ₃ and a molten salt electrolyte evenly, use a graphite crucible as an anode, insert a copper rod into the molten molten salt as a cathode, and use the graphite crucible as an anode. A receiving crucible is placed under the rod for collecting cathode products, the receiving crucible is insulated from the graphite crucible, and the copper-scandium intermediate alloy is prepared by molten salt electrolysis.

The molten salt electrolysis temperature is 875-1100°C, and the cathode current density is controlled to be 0.5-40A/cm ²

The receiving crucible is a molybdenum crucible, a tungsten crucible, a tantalum crucible or a graphite crucible. .

The copper-scandium master alloy prepared by the above method is used to prepare a scandium-containing alloy. It is added to other metals in the form of master alloys to prepare scandium-containing alloys.

The melting point difference between copper and scandium is smaller than that of aluminum and scandium. According to the Cu–Sc phase diagram, the liquidus is relatively flat. Scandium and copper can form 13% scandium (the ratio of substances) at 865 °C, respectively, and form at 875 °C. A Cu-Sc alloy containing scandium 30% or 71% (in substance ratio) was formed at 890° C. with scandium content of 36.5% (in substance ratio). Therefore, the present invention proposes to use scandium fluoride or scandium oxide as raw material, use copper consumable cathode in fluoride or chloride molten salt electrolyte, and use graphite as anode for electrolysis to prepare copper-scandium master alloy products with high scandium content. During the electrolysis process, the scandium ion Sc ³⁺ migrates to the cathode and is reduced to metal scandium on the copper cathode. The metal scandium and copper form a Cu-Sc alloy. The electrolysis temperature is lower than the melting point of copper, but higher than the melting point of the Cu-Sc alloy. The obtained liquid alloy is separated from the copper cathode and sinks into the receiving crucible below the cathode, and the copper cathode exposes a new surface to continue electrolysis. As electrolysis progresses, the copper cathode is continuously consumed to form an alloy. By adjusting the electrolysis temperature and current density, copper-scandium intermediate alloys with different scandium contents can be obtained, and the Cu-Sc alloy in the crucible is poured and cooled to obtain a Cu-Sc alloy ingot.

The inventive step of the present invention is summarized as follows:

1. The cathode of the present invention is a consumable cathode, and the cathode product is liquid, with respect to the solid product, the impurity content is low, and the subsequent processing is convenient;

2. Compared with the use of liquid cathode aluminum molten salt electrolysis to produce aluminum-scandium alloy, the scandium content of the present invention is significantly increased, and as the intermediate alloy prepared by aluminum-scandium alloy, it is not only convenient to use, but also can greatly reduce the production scale of scandium alloy, saving equipment investment and cost. Scandium alloy production cost;

3. The production equipment and models of rare earth-ferroalloys such as dysprosium iron and terbium iron can be used for reference, and there is no need to develop special scandium alloy electrolysis equipment, and the technology is highly mature.

Embodiment 1 A kind of preparation method of copper-scandium master alloy

Mix 500g of molten salt and 150g of Sc ₂ O ₃ evenly and put it into a graphite crucible with a diameter of 80 mm, wherein, according to the mass percentage, the molten salt electrolyte system is 60 parts of ScF ₃ , 20 parts of LiF and 10 parts of NaF; A molybdenum crucible with a diameter of 50mm that has been insulated from graphite is placed in the center of the bottom of the graphite crucible as a receiving crucible; then the graphite crucible is placed in a furnace and heated to 875°C. After the molten salt is melted, a copper rod with a diameter of 20mm is placed. Insert molten salt, the immersion depth is 30mm; take graphite crucible as anode, copper rod as cathode for electrolysis, current density is ^40A /cm The scandium master alloy liquid is poured into the mold to make a copper scandium master alloy ingot. After testing, the alloy composition according to the material ratio is: copper 25%, scandium 75%.

Embodiment 2 A kind of preparation method of copper-scandium master alloy

Mix 500g of molten salt and 100g of Sc ₂ O ₃ evenly and put it into a graphite crucible with a diameter of 80mm, wherein, according to the mass percentage, the molten salt electrolyte system is 5 parts of ScF ₃ and 70 parts of LiF; the center of the bottom of the graphite crucible is placed There is a molybdenum crucible with a diameter of 50mm that has been insulated with graphite as the receiving crucible; then put the graphite crucible into the furnace and heat it to 1100 ° C. After the molten salt is melted, insert a copper rod with a diameter of 20mm into the molten salt and immerse it in the molten salt. The depth is 30mm; the graphite crucible is used as the anode, and the copper rod is used as the cathode for electrolysis, and the current density is 10A/cm ² ; after the electrolysis for 2h, the molybdenum crucible is taken out with the crucible tongs, and the copper-scandium intermediate alloy liquid collected therein is cast. into a mold to make a copper-scandium master alloy ingot. After testing, the alloy composition according to the material ratio is: copper 80%, scandium 20%.

Embodiment 3 A kind of preparation method of copper-scandium master alloy

Put 500g of molten salt into a graphite crucible with a diameter of 80mm, wherein, according to the mass percentage, the molten salt electrolyte system is 5 parts of ScF ₃ , 70 parts of LiF and 55 parts of MgCl; the center of the bottom of the graphite crucible is placed with graphite insulation. The treated molybdenum crucible with a diameter of 50mm is used as the receiving crucible; then the graphite crucible is put into the furnace and heated to 1000°C. After the molten salt is melted, a copper rod with a diameter of 20mm is inserted into the molten salt, and the immersion depth is 30mm; The graphite crucible was used as the anode, and the copper rod was used as the cathode for electrolysis, and the current density was 0.5A/cm ² ; after 2 hours of electrolysis, the molybdenum crucible was taken out with crucible tongs, and the copper-scandium intermediate alloy liquid collected therein was cast into the mold , made into copper-scandium master alloy ingots. After testing, the alloy composition according to the material ratio is: copper 90%, scandium 10%.

Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent substitutions without departing from the spirit and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims (4)

1. a preparation method of copper-scandium master alloy, it is characterized in that: in the molten salt electrolyte containing scandium, take metal copper electrode as consumable cathode, take graphite as anode, prepare copper-scandium master alloy by molten salt electrolysis; Described molten salt electrolyte comprises by mass fraction: 20～70 parts of LiF, 5～60 parts of ScF ₃ , 0～55 parts of MCl or/and MF, wherein M is one or more of alkali metal elements and alkaline earth metal elements The temperature of the molten salt electrolysis is 875°C, the cathode current density of the molten salt electrolysis is 40 A/cm ² , and the copper-scandium master alloy with a scandium content material ratio of 75% is prepared; or: the molten salt electrolysis temperature is 1100 ℃, the cathode current density of the molten salt electrolysis is 10 A/cm ² , and the copper-scandium master alloy with a scandium content material ratio of 20% is prepared; or: the molten salt electrolysis temperature is 1000 ℃, the molten salt The salt electrolysis cathode current density was 0.5A/cm ² , and the copper-scandium master alloy was prepared with a scandium content-substance ratio of 10%. 2 . The preparation method according to claim 1 , wherein the raw material Sc ₂ O ₃ is added to the molten salt electrolyte, and the added mass of Sc ₂ O ₃ is 0-30% of the mass of the molten salt. 3 . 3. The preparation method as claimed in claim 1, characterized in that: a receiving crucible is placed below the copper cathode to collect the copper-scandium intermediate alloy product, and the receiving crucible is a molybdenum crucible, a tungsten crucible, a tantalum crucible or a graphite crucible. 4. The copper-scandium master alloy prepared by any one of claims 1 to 3 is used to prepare the scandium-containing alloy of other metals.