CN111411372A - Preparation method of rare earth iron alloy - Google Patents

Abstract

The invention discloses a preparation method of rare earth iron alloy. The crucible under the cathode is used as a receiver; in the rare earth fluoride and lithium fluoride molten salt electrolyte system, rare earth oxide and iron are used as raw materials, and direct current electrolysis is passed through, and the rare earth iron intermediate alloy is collected in the receiver; The alloy and iron are put into the crucible as raw materials, and the rare earth iron intermediate alloy is further smelted by the melting method in the intermediate frequency induction furnace to obtain the rare earth iron alloy. The rare earth iron alloy obtained by the invention has uniform and stable composition, low content of impurity elements, density and melting point close to those of steel, and is easy to be added into steel; the rare earth iron alloy can fundamentally solve the problem of effective addition of rare earth to steel, and can accurately control the concentration of rare earth in steel. rare earth content.

Description

Preparation method of rare earth iron alloy

technical field

The invention relates to a production technology of rare earth iron alloy, in particular to a preparation method of rare earth iron alloy by adopting non-consumable cathode electrolysis and intermediate frequency furnace composition regulation double method.

Background technique

At present, steel is the largest metal structural material and is widely used in construction, energy, transportation, aerospace and other fields. The application and research of rare earths in steel have also developed rapidly. The addition of rare earths to molten steel can play the role of desulfurization, deoxidation, and change the shape of inclusions, which can improve the plasticity, stamping performance, wear resistance and welding performance of steel. Various rare earth steels, such as rare earth steel plates for automobiles, die steels, rails, etc., have been widely used.

In the production process of rare earth steel, the method of adding rare earth has always been the focus of scientific research. The existing adding methods include wire feeding method, cored wire, rare earth iron master alloy and other forms. At present, the most obvious effect is the rare earth iron intermediate alloy. Alloy addition method. The technology for preparing rare earth iron master alloy mainly includes the following categories:

(1) Miscibility method.

The miscibility method, also known as the counter-doping method, mainly uses an electric arc furnace or an intermediate frequency induction furnace to mix rare earth metals and iron to obtain an alloy. This method is a commonly used method at present, and its process technology is simple, and it can prepare multi-component master alloys or application alloys, but it also has shortcomings: 1) the local concentration of rare earth metals in molten iron is easily too high, resulting in segregation; 2) this method The raw materials used are rare earth metals, especially for medium and heavy rare earth metals, the preparation process is complicated and the cost is high; 3) The smelting temperature is high, since rare earth metals and pure iron are used as raw materials, the smelting temperature is required to be high.

(2) Molten salt electrolysis method.

The preparation of rare earth iron master alloy by molten salt electrolysis mainly adopts iron consumable cathode method. For example, Chinese patent CN1827860 discloses a process and equipment for producing dysprosium-iron alloy by molten salt electrolysis. It is proposed that under high temperature conditions, dysprosium oxide melted in a fluoride solution is ionized, and under the action of a DC electric field, dysprosium ions are precipitated on the surface of the iron cathode, It is reduced to metal dysprosium, and dysprosium is alloyed with iron to form dysprosium-iron alloy. This method has low production cost and simple process, but also has the following defects: the distribution of rare earth and iron in the alloy fluctuates greatly, which is difficult to control, and the distribution error is as high as 3%-5%, which affects product consistency.

Magnesium oxide crucibles are commonly used in the production of rare earth steels. According to the literature "Research on Carbon Deoxidation in Vacuum Induction Melting" (Steel, Vol. 38, No. 6, P275-278, 2003), it is shown that the use of magnesium oxide crucibles in the process of smelting rare earth ferroalloys will increase The oxygen content in the alloy affects the yield and effect of rare earth added to the steel. In addition, in the process of smelting rare earth metals and alloys using magnesium oxide, aluminum oxide or calcium oxide crucibles, rare earth metals will react with the crucible, adding impurities to the alloy. It can be seen that it is obviously not enough to control the content of impurities through the selection of raw materials, and the selection of crucibles in the smelting process is also an important link.

However, the rare earth iron alloy prepared by the miscibility method and the molten salt electrolysis method has a relatively high oxygen content. After being added to the ladle, the generated inclusions are prone to the problem of nozzle blockage, which affects the normal tapping. When the miscibility method and the molten salt electrolysis method are used to prepare rare earth iron alloys, the precise control of rare earth elements cannot be achieved. The currently used crucibles still bring in impurities when smelting rare earth metals and their alloys.

SUMMARY OF THE INVENTION

The technical problem solved by the invention is to provide a preparation method of rare earth iron alloy, which adopts non-consumable cathode electrolysis and intermediate frequency furnace composition control double method to prepare, and the obtained rare earth iron alloy has uniform and stable composition, low impurity element content, and close density and melting point. Due to the density and melting point of steel, it is easy to add to steel, which can fundamentally solve the problem of effective addition of rare earths in steel, accurately control the content of rare earths in steel, and reduce the cost of applying rare earths in steel.

The technical solution is as follows:

A preparation method of rare earth iron alloy, comprising:

Non-consumable cathode electrolysis to prepare rare earth iron master alloy; put electrolyte in the electrolytic cell, use graphite carbon plate as anode, tungsten or molybdenum material as cathode, oxidize tungsten-molybdenum crucible, alkaline earth oxide crucible or alkali metal under the cathode The metal crucible is used as the receiver; in the rare earth fluoride and lithium fluoride molten salt electrolyte system, the rare earth oxide and iron are used as raw materials, and direct current electrolysis is passed through, and the rare earth iron intermediate alloy is collected in the receiver;

The rare earth iron master alloy and iron are used as raw materials into an alkaline earth oxide crucible or an alkali metal oxide crucible, and the rare earth iron master alloy is further smelted by melting method in an intermediate frequency induction furnace to obtain a rare earth iron alloy that meets the requirements.

Further, the iron used in the molten salt electrolysis process is in the form of blocks, wires, rods, powders or chips, the rare earth content in the prepared rare earth iron master alloy is greater than 60wt%, and the control accuracy of the rare earth content in the rare earth iron master alloy is ±2wt%; The mixing process is carried out under vacuum conditions or a protective atmosphere. In the rare earth iron alloy, the rare earth content is less than 60wt%, the control accuracy of the rare earth content in the rare earth iron alloy is ±1wt%, the oxygen in the rare earth iron alloy≤0.01wt%, the carbon≤0.01wt%, Phosphorus≤0.01wt%, sulfur≤0.005wt%.

Further, in the electrolysis process, the anode current density is 0.5-2.0A/cm ² , the cathode current density is 5-15A/cm ² ; the temperature is 1050±50°C, and the current intensity is 100-15000A.

Further, during the melting process, the temperature is controlled at 1500±100°C, and the protective gas is argon, nitrogen or mixed inert gas.

Further, the preparation method of the alkaline earth (alkali metal) oxide crucible containing rare earth oxyfluoride coating, comprising:

Coating ingredients, mix rare earth oxide, rare earth fluoride and polyvinyl alcohol uniformly according to the weight ratio of 100:0.2-50:5-15;

The coating ingredients are pressed on the inner wall of the alkaline earth (alkali metal) oxide crucible, and the coating and the crucible are pressed together on a press to form, and the pressure is controlled at 270-500Mpa; then dried and roasted to obtain a rare earth-containing oxyfluoride coating. layer of alkaline earth (alkali metal) oxide crucibles.

Further, after the coating ingredients are pressed, they are put into a drying kiln for natural drying for 72-120 hours, and then roasted according to the following process: at room temperature, the temperature is raised to 150 ℃ and kept for 2-3 hours, and the heating rate does not exceed 5 ℃ per minute; Keep the temperature at 1000°C for 5-6 hours, and the heating rate does not exceed 10°C per minute; heat up to 1350-1400°C for 10-11 hours, and the heating rate does not exceed 10°C per minute; Cool down to below 100°C with the furnace and take it out for use.

Further, the alkaline earth oxide or alkali metal oxide is selected from magnesium oxide, aluminum oxide or calcium oxide, the density of the coating is 3-8 g/cm ³ , and the porosity of the coating is 5-20%.

Further, the density of the coating is 3-7.5 g/cm ³ or 6-8 g/cm ³ .

Further, rare earth oxides are selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, bait oxide, thulium oxide, ytterbium oxide, lutetium oxide, and yttrium oxide. , one or more of scandium oxide; rare earth fluoride is selected from lanthanum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, One or more of holmium fluoride, bait fluoride, thulium fluoride, ytterbium fluoride, lutetium fluoride, yttrium fluoride or scandium fluoride; rare earth oxides and rare earth fluorides use the same rare earth elements.

The technical effects of the present invention include:

1. The present invention adopts non-consumable cathode electrolysis and intermediate frequency furnace composition control double method to prepare rare earth iron alloy. The rare earth iron alloy has uniform and stable composition, small segregation and low impurity content.

In the invention, the rare earth content in the rare earth iron alloy can be controlled twice by the melting method, the rare earth content in the rare earth iron alloy can be precisely controlled, the composition of the rare earth iron alloy is uniform, and the rare earth content in the rare earth iron alloy can be controlled within ±1wt%. Due to the smelting under vacuum or inert atmosphere, the rare earth burning loss is small, the yield is high, and the product quality is high.

2. The density and melting point of rare earth iron alloys are close to those of steel, so they are easy to be added to steel and have high rare earth yield when applied to rare earth steel. Rare earth ferroalloys can fundamentally solve the problem of effective addition of rare earths in steel, can accurately control the content of rare earths in steel, reduce the cost of applying rare earths in steel, have no pollution, have remarkable effects, and are suitable for large-scale industrial production.

The application of rare earth iron alloy in steel can greatly improve the product quality and comprehensive performance of rare earth steel, improve and improve the plasticity, low temperature impact toughness, thickness direction performance and corrosion resistance of steel.

3. The rare earth iron alloy provided by the present invention uses rare earth oxides as raw materials, and the smelting crucible is also the oxide crucible of the same name rare earth, so the rare earth iron alloy introduces less impurities.

4. The application of rare earth iron alloys in steel can significantly improve the yield of rare earths, realize deep purification of molten steel, significantly improve the yield of rare earth elements when smelting rare earth steel, and improve and improve the plasticity, low temperature impact toughness and thickness direction of steel. performance and corrosion resistance, reducing production costs.

5. The rare earth elements in the rare earth iron alloy proposed in the present invention exist in the form of a compound state, with good oxidation resistance and high thermal stability; the rare earth elements in the alloy are uniform and stable in composition, low in segregation, and contain impurities such as O, S, P, and C. At the same time, the rare earth elements added through the rare earth iron master alloy expand the application field of rare earth in steel through dispersion strengthening, especially rare earth is used in some high-tech fields.

6. The present invention is provided with a rare earth oxide coating on the inner wall of the alkaline earth (alkali metal) oxide crucible, which can avoid bringing in impurities when smelting rare earth metals and their alloys, and is suitable for smelting rare earth metals and their alloys, and the process is simple, low cost.

(1) The rare earth oxide coating has high density, low porosity, and strong resistance to metal or alloy liquid erosion;

(2) The alkaline earth (alkali metal) oxide crucible uses rare earth oxide as the coating. In the process of smelting rare earth metal, rare earth iron master alloy and rare earth iron alloy, since the metal liquid of rare earth oxide and rare earth iron alloy is the same material, it will not be Bring in impurities.

7. In the present invention, the cathode material adopts the non-consumable cathode electrolysis method of tungsten or molybdenum to prepare the rare earth iron alloy, which can reduce the difficulty of controlling the cathode. Compared with the consumable iron cathode electrolysis method, the amount of slag is small, the current efficiency is high, and the alloy composition can be Precise control and small component segregation.

8. The present invention is also applicable to the preparation of rare earth copper, rare earth nickel, rare earth magnesium aluminum alloy and rare earth zinc alloy.

Description of drawings

Fig. 1 is the structural representation of equipment for preparing rare earth iron master alloy in the present invention;

Fig. 2 is a flow chart of the method for preparing rare earth iron alloy from a non-consumable cathode in the present invention.

Detailed ways

The following descriptions sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice and reproduce them.

As shown in FIG. 1 , it is a schematic structural diagram of the equipment for preparing rare earth iron master alloy in the present invention.

The equipment for preparing rare earth iron intermediate alloy includes: refractory brick 1, iron sleeve 2, receiver 3, rare earth iron intermediate alloy 4, graphite carbon anode plate 5, cathode 6 made of tungsten or molybdenum, electrolyte 7, electrolytic cell 8, insulation layer 9. Carbon stamping layer 10.

The electrolytic cell 8 is a graphite cell, and the outer side of the graphite cell body is sequentially covered with a carbon ramming layer 10, a thermal insulation layer 9, a refractory brick 1, and an iron sleeve 2; a cathode 6 made of tungsten or molybdenum is arranged in the middle of the graphite cell; in the graphite cell A graphite carbon anode plate 5 is arranged around the cathode 6 ; a receiver 3 is arranged at the bottom center of the graphite tank, and the receiver 3 is located below the cathode 6 .

When in use, rare earth oxide, electrolyte 7, iron (iron block, scrap steel, iron powder, etc.) are loaded into the graphite tank, and electrolyte 7 adopts rare earth fluoride and lithium fluoride molten salt electrolyte, and the rare earth iron alloy melt generated after electrolysis After being enriched from the cathode 6, it flows into the receiver 3.

As shown in FIG. 2, it is a flow chart of the preparation method of rare earth iron alloy in the present invention.

The preparation method of rare earth iron alloy adopts non-consumable cathode electrolysis and intermediate frequency furnace composition control double method, and the specific steps include:

Step 1: non-consumable cathode electrolysis to prepare rare earth iron intermediate alloy; electrolyte is loaded into the electrolytic cell, graphite carbon plate 5 is used as anode, tungsten or molybdenum material is used as cathode 6, and rare earth-containing oxyfluoride coating under cathode 6 is used The alkaline earth metal oxide crucible, alkali metal oxide crucible or tungsten-molybdenum crucible are used as receiver 3; in the rare earth fluoride and lithium fluoride molten salt electrolyte system, rare earth oxide and iron are used as raw materials, and direct current electrolysis is passed into the receiver. The device 3 receives the rare earth iron master alloy 4;

The rare earth iron master alloy is enriched and melted on the cathode 6 and falls into the receiver 3 below. The form of iron used in the molten salt electrolysis process can be blocks, wires, rods, chips, etc. In the prepared rare earth iron master alloy, the rare earth content is greater than 60wt%, and the control accuracy of the rare earth content in the alloy is ±2wt%.

During the electrolysis process, the anode current density is 0.5-2.0A/cm ² , the cathode current density is 5-15A/cm ² ; the temperature is 1050±50°C, and the current intensity is 100-15000A. The use of tungsten or molybdenum non-consumable cathodic electrolysis to prepare rare earth iron alloys can reduce the difficulty of cathode control. Compared with consumable iron cathodic electrolysis, the amount of slag is small, the current efficiency is high, the alloy composition can be precisely controlled, and the composition segregation is small.

Step 2: Put rare earth iron master alloy and iron as raw materials into an alkaline earth (alkali metal) oxide crucible containing rare earth oxyfluoride coating, and further smelt the rare earth iron master alloy by melting method in an intermediate frequency induction furnace , to obtain rare earth iron alloys that meet the requirements.

The temperature in the smelting process is controlled at 1500±100°C, and the protective gas can be inert gas such as argon, nitrogen or a mixture thereof.

The melting process is carried out under vacuum conditions or protective atmosphere. In rare earth iron alloy, the content of rare earth is less than 60wt%, the control accuracy of rare earth content in rare earth iron alloy is ±1wt%, oxygen in rare earth iron alloy≤0.01wt%, carbon≤0.01wt% , phosphorus≤0.01wt%, sulfur≤0.005wt%.

The alkaline earth (alkali metal) oxide crucible is provided with a rare earth oxide coating on the inner wall, and the alkaline earth oxide is selected from magnesium oxide, aluminum oxide or calcium oxide. Its parameters are as follows: Density of the coating: 3-8 g/cm ³ ; Porosity 5-20%. Preferably 3-7.5 g/cm ³ or 6-8 g/cm ³ . The rare earth oxide is used as the coating. Since the metal liquid of the rare earth iron alloy is of the same name, it will not bring in impurities.

A preparation method of an alkaline earth (alkali metal) oxide crucible containing rare earth oxyfluoride coating, comprising:

1. For coating ingredients, mix rare earth oxide, rare earth fluoride and polyvinyl alcohol uniformly according to the weight ratio of 100:0.2-50:5-15;

The rare earth oxide of the coating corresponds to the rare earth element of the rare earth fluoride, that is, the same rare earth element is used in the rare earth oxide and the rare earth fluoride.

Rare earth oxides are selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, bait oxide, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide, oxide One or more of scandium.

Rare earth fluorides are selected from lanthanum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, bait fluoride, fluoride fluoride One or more of thulium, ytterbium fluoride, lutetium fluoride, yttrium fluoride or scandium fluoride.

2. Coat the ingredients on the inner wall of the crucible, press the coating together with the crucible on a press (the pressure is controlled at 270-500Mpa) to form, then dry and bake to obtain an alkaline earth (alkali earth) containing rare earth oxyfluoride coating. ) oxide crucible.

After the coating is pressed, it is put into a drying kiln for natural drying for 72-120 hours, and then fired according to the following process:

(1), heat up at room temperature (the rate of temperature increase does not exceed 5°C per minute) to 150°C for 2-3 hours;

The temperature rise in this section is mainly to ensure that the moisture in the material is fully evaporated.

(2), heat up (the heating rate does not exceed 10°C per minute) to 1000°C for 5-6 hours;

The temperature rise in this section is mainly to ensure the sufficient escape of impurities with low melting point and low boiling point in the material, and at the same time, the temperature cannot be raised too fast.

(3), heat up to 1350-1400 ℃ (the heating rate does not exceed 10 ℃ per minute) and keep it for 10-11 hours;

The main control speed of heating in this section should be slow to ensure that the crucible is intact and not broken, and at the same time, it can ensure that the mixed rare earth oxide coating has high density, low porosity, and strong resistance to metal or alloy liquid erosion. The high temperature section allows the rare earth oxide and the rare earth fluoride to fully react to form a high melting point rare earth oxyfluoride, which has a good bonding force with the crucible matrix.

(4), cooling to below 100 DEG C with the furnace and taking out for use to obtain an alkaline earth (alkali) oxide crucible containing rare earth oxyfluoride coating.

The rare earth oxyfluoride coating formed by rare earth oxide, rare earth fluoride and polyvinyl alcohol at high temperature has the characteristics of high melting point (melting point 2000-3000 ° C) and corrosion resistance.

Metal detection is based on national standards such as GB/T18115.1-2006, and is tested by ICP-MS; C is detected according to GB/T12690.13-1990, and is tested by high-frequency combustion-infrared method; O is tested according to GB/T12690.4 -2003, tested by inert gas pulse-infrared method. The standard deviation S of the chemical composition is calculated by the following formula:

Wherein X _i is the chemical composition of the sample; the average value of X is the average value of the chemical composition at n points of the sample, and n=20 in the present invention.

Example 1

The electrolytic cell 8 adopts a circular graphite electrolytic cell of Φ650 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; the lanthanum fluoride in the electrolyte is 80wt%, and the lithium fluoride is 20wt%; the cathode 6 is made of tungsten, with a diameter of 70mm , the average current intensity is 3500A, the anode current density is 0.7-1.0A/cm ² , the cathode current density is 7-9A/cm ² , the electrolysis temperature is maintained at 1000-1050 ℃, the continuous electrolysis is 150 hours, and the consumption of lanthanum oxide is 923kg to obtain lanthanum iron The master alloy is 857kg, the average lanthanum content is 90%, the current efficiency is 85%, and the lanthanum yield is 98%. The alloy composition results are shown in Table 1.

Table 1 Analysis results of composition of lanthanum iron master alloy/wt%

La Fe C O P S Si Mn 90.0 9.85 0.0085 0.0094 <0.01 <0.005 0.012 <0.005

Using the prepared lanthanum-iron master alloy as a raw material, taking 3.33kg of lanthanum-iron master alloy, adding 11.67kg of iron, and smelting in a 30kg medium-frequency vacuum induction furnace, the protective gas is argon, and after smelting, it is obtained in a lanthanum oxide-coated crucible. The composition of lanthanum-iron alloy is shown in Table 2.

Table 2 Lanthanum-iron alloy composition analysis results/wt%

RE Fe C O P S Si Mn 20.11 79.73 0.0080 0.0095 <0.01 <0.005 0.008 <0.005

Example 2

The electrolytic cell 8 adopts a circular graphite electrolytic cell with a diameter of 600 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; the cerium fluoride in the electrolyte is 90wt% and the lithium fluoride is 10wt%; the cathode 6 is made of tungsten, with a diameter of 75mm , the average current intensity is 4000A, the anode current density is 0.8-1.2A/cm ² , the cathode current density is 6-8A/cm ² , the electrolysis temperature is maintained at 1000-1050 ° C, the continuous electrolysis is 720 hours, the consumption of cerium oxide is 4051kg, and the iron cerium is obtained. The master alloy is 3764kg, the average cerium content is 85%, the current efficiency is 85%, and the cerium yield is 97%. The alloy composition results are shown in Table 3.

Table 3 Analysis results of composition of ferric cerium master alloy/wt%

Ce Fe C O P S Si Mn 84.91 14.93 0.0097 0.0074 <0.01 <0.005 0.013 <0.005

Using the prepared ferric cerium master alloy as a raw material, take 1.76 kg of ferric cerium master alloy, add 13.24 kg of iron, and carry out smelting in a 30 kg intermediate frequency vacuum induction furnace. The protective gas is argon, and the obtained smelting cerium oxide coating crucible is obtained. The composition of cerium-iron alloy is shown in Table 4.

Table 4 Analysis results of cerium-iron alloy composition/wt%

Ce Fe C O P S Si Mn 9.96 89.93 0.0080 0.0096 <0.01 <0.005 0.009 <0.005

Example 3

The electrolytic cell 8 adopts a circular graphite electrolytic cell with a diameter of 620 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; in the electrolyte, neodymium fluoride is 85wt% and lithium fluoride is 15wt%; the cathode 6 is made of tungsten, with a diameter of 80mm , the average current intensity is 5000A, the anode current density is 0.7-1.1A/cm ² , the cathode current density is 7-9A/cm ² , the electrolysis temperature is maintained at 1020-1070 ℃, the continuous electrolysis is 480 hours, the consumption of neodymium oxide is 4720kg, and the neodymium iron is obtained. The master alloy is 4843kg, the average neodymium content is 80%, the current efficiency is 90%, and the neodymium yield is 98%. The alloy composition results are shown in Table 5.

Table 5 Analysis results of NdFe master alloy composition/wt%

Nd Fe C O P S Si Mn 80.06 19.89 0.011 0.0084 <0.01 <0.005 0.011 <0.005

Using the prepared Nd-Fe master alloy as a raw material, take 3kg of Nd-Fe master alloy, add 13kg of iron, smelt in a 30kg intermediate frequency vacuum induction furnace, the protective gas is argon, and the Nd-Fe alloy obtained in the neodymium oxide coating crucible after smelting The ingredients are shown in Table 6.

Table 6 Analysis results of NdFe alloy composition/wt%

Nd Fe C O P S Si Mn 14.99 85.94 0.0091 0.0097 <0.01 <0.005 0.010 <0.005

Example 4

The electrolytic cell 8 adopts a circular graphite electrolytic cell of Φ400mm, and the graphite carbon anode plate 5 is composed of four graphite plates; the praseodymium fluoride in the electrolyte is 85wt%, and the lithium fluoride is 15wt%; the cathode 6 is made of tungsten, with a diameter of 40mm , the average current intensity is 2000A, the anode current density is 0.7-1.1A/cm ² , the cathode current density is 7-9A/cm ² , the electrolysis temperature is maintained at 1010-1060 ° C, the continuous electrolysis is 100 hours, the consumption of praseodymium oxide is 313kg, and the praseodymium iron is obtained The master alloy is 302 kg, the average praseodymium content is 85%, the current efficiency is 88%, and the praseodymium yield is 97%. The alloy composition results are shown in Table 7.

Table 7 Analysis results of praseodymium iron master alloy composition/wt%

Pr Fe C O P S Si Mn 84.95 15.02 0.010 0.0093 <0.01 <0.005 0.012 <0.005

Using the prepared praseodymium iron master alloy as a raw material, take 3.3kg of praseodymium iron master alloy, add 10.7kg of iron, smelt in a 30kg medium frequency vacuum induction furnace, the protective gas is argon, and the praseodymium oxide coating crucible obtained after smelting is obtained. The composition of praseodymium iron alloy is shown in Table 8.

Table 8 Analysis results of praseodymium-iron alloy composition/wt%

Pr Fe C O P S Si Mn 20.04 79.91 0.0091 0.0097 <0.01 <0.005 0.010 <0.005

Example 5

The electrolytic cell 8 adopts a circular graphite electrolytic cell with a diameter of 500 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; Lithium is 18wt%; the cathode 6 is made of molybdenum, the diameter is 60mm, the average current intensity is 3000A, the anode current density is 0.7-1.2A/cm ² , the cathode current density is 6-10A/cm ² , and the electrolysis temperature is maintained at 1050-1080 ℃, Continuous electrolysis for 300 hours consumes 1452 kg of lanthanum cerium oxide (lanthanum oxide: cerium oxide = 35:65) to obtain 1792 kg of praseodymium neodymium (lanthanum: cerium = 35:65) iron master alloy, the average rare earth content is 65%, and the neodymium content is 85%, the current efficiency is 89%, the rare earth yield is 97%, and the alloy composition results are shown in Table 9.

Table 9 Lanthanum-cerium-iron master alloy composition analysis results/wt%

La Ce Fe C O P S Si Mn 22.76 42.27 34.91 0.011 0.010 <0.01 <0.005 0.013 <0.005

Using the prepared lanthanum-cerium-iron master alloy as a raw material, take 3.5kg of the lanthanum-cerium-iron master alloy, add 11.5kg of iron, and smelt in a 30kg medium-frequency vacuum induction furnace, the protective gas is argon, and the lanthanum-cerium oxide-coated crucible is smelted. The composition of the lanthanum-cerium-iron alloy obtained in Table 10.

Table 10 Lanthanum-cerium-iron alloy composition analysis results/wt%

La Ce Fe C O P S Si Mn 5.26 9.78 84.89 0.0091 0.0097 <0.01 <0.005 0.010 <0.005

Example 6

The electrolytic cell 8 adopts a circular graphite electrolytic cell of Φ650 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; in the electrolyte, praseodymium fluoride (praseodymium fluoride: neodymium fluoride=25:75) is 86wt%, fluoride fluoride Lithium is 14wt%; the cathode 6 is made of tungsten, with a diameter of 80mm, an average current intensity of 6000A, an anode current density of 0.6-1.2A/cm ² , a cathode current density of 6-9A/cm ² , and the electrolysis temperature is maintained at 1020-1070°C, Continuous electrolysis for 720 hours consumes 7765 kg of praseodymium neodymium oxide (praseodymium oxide: neodymium oxide = 25:75) to obtain 8570 kg of praseodymium neodymium (praseodymium: neodymium = 25:75) iron master alloy, with an average content of praseodymium neodymium of 75%, and the current efficiency 87%, the yield of praseodymium neodymium is 98%, and the alloy composition results are shown in Table 11.

Table 11 Composition analysis results of praseodymium neodymium iron master alloy/wt%

Pr Nd Fe C O P S Si Mn 18.77 56.29 24.90 0.012 0.0099 <0.01 <0.005 0.011 <0.005

Using the prepared praseodymium neodymium iron master alloy as a raw material, take 2kg of praseodymium neodymium iron master alloy, add 13kg of iron, smelt in a 30kg medium frequency vacuum induction furnace, the protective gas is argon, and obtain in the praseodymium oxide neodymium oxide coating crucible after smelting. The composition of the praseodymium neodymium iron alloy is shown in Table 12.

Table 12 Analysis results of praseodymium neodymium iron alloy composition/wt%

Pr Nd Fe C O P S Si Mn 2.46 7.48 90.01 0.0091 0.0097 <0.01 <0.005 0.010 <0.005

Example 7

The electrolytic cell 8 adopts a circular graphite electrolytic cell of Φ320 mm, and the graphite carbon anode plate 5 is composed of four graphite plates; 55:32:3:10) is 82wt%, lithium fluoride is 18wt%; the material of cathode 6 is tungsten, the diameter is 30mm, the average current intensity is 1000A, the anode current density is 0.6-1.0A/cm ² , the cathode current density is 6- 8A/cm ² , the electrolysis temperature was maintained at 1000-1050°C, continuous electrolysis was carried out for 120 hours, and 193 kg of mixed rare earth oxides (lanthanum oxide: cerium oxide: praseodymium oxide: neodymium oxide = 28:52:5:15) were consumed to obtain lanthanum Cerium praseodymium neodymium (lanthanum:cerium:praseodymium:neodymium=28:52:5:15) iron master alloy 219kg, average rare earth content 70%, current efficiency 85%, rare earth yield 96%, alloy composition results are shown in Table 13.

Table 13 Analysis results of composition of Lanthanum, Cerium, Praseodymium, NdFe, and Fe master alloys/wt%

La Ce Pr Nd Fe C O P S Si Mn 19.54 36.36 3.51 10.44 30.08 0.012 0.0099 <0.01 <0.005 0.011 <0.005

The prepared lanthanum, cerium, praseodymium, neodymium-iron master alloy was used as a raw material, and 6.43 kg of lanthanum, cerium, praseodymium, neodymium-iron master alloy was taken, and 8.57 kg of iron was added. The smelting was carried out in a 30 kg medium-frequency vacuum induction furnace. The protective gas was argon. After smelting, lanthanum oxide was used. The composition of the lanthanum cerium praseodymium neodymium iron alloy obtained in the cerium praseodymium neodymium coating crucible is shown in Table 14.

Table 14 Analysis results of composition of lanthanum cerium praseodymium neodymium iron alloy/wt%

La Ce Pr Nd Fe C O P S Si Mn 8.41 15.61 1.51 4.50 69.92 0.012 0.0099 <0.01 <0.005 0.011 <0.005

The terms used in the present invention are terms of description and illustration, not limitation. Since the invention can be embodied in many forms without departing from the spirit or spirit of the invention, it is to be understood that the above-described embodiments are not limited to any of the foregoing details, but are to be construed broadly within the spirit and scope defined by the appended claims Therefore, all changes and modifications that come within the scope of the claims or their equivalents should be covered by the appended claims.

Claims (9)

1. A method for preparing a rare earth ferroalloy, comprising:

Preparing rare-earth iron intermediate alloy by non-consumable cathode electrolysis; electrolyte is filled in an electrolytic tank, a graphite carbon plate is used as an anode, tungsten or molybdenum material is used as a cathode, and a tungsten molybdenum crucible, an alkaline earth oxide crucible or an alkali metal oxide crucible below the cathode is used as a receiver; in a fused salt electrolyte system of rare earth fluoride and lithium fluoride, rare earth oxide and iron are used as raw materials, direct current is introduced for electrolysis, and rare earth iron intermediate alloy is obtained in a receiver;

The rare earth iron intermediate alloy and iron are used as raw materials and put into an alkaline earth oxide crucible or an alkali metal oxide crucible, and the rare earth iron intermediate alloy is further smelted in a medium-frequency induction furnace by adopting a melting method to obtain the rare earth iron alloy.

2. The method of claim 1, wherein the form of the iron used in the molten salt electrolysis process is block, wire, rod, powder or scrap, the rare earth content in the prepared rare earth iron intermediate alloy is more than 60 wt%, and the control precision of the rare earth content in the rare earth iron intermediate alloy is ± 2 wt%; the melting process is carried out under vacuum condition or protective atmosphere, the content of rare earth in the rare earth ferroalloy is less than 60 wt%, the control precision of the content of rare earth in the rare earth ferroalloy is +/-1 wt%, the content of oxygen in the rare earth ferroalloy is less than or equal to 0.01 wt%, the content of carbon is less than or equal to 0.01 wt%, the content of phosphorus is less than or equal to 0.01 wt%, and the content of sulfur is less than or equal to 0.005 wt%.

3. The method for producing the rare-earth iron alloy as claimed in claim 1, wherein the anode current density in the electrolysis is 0.5 to 2.0A/cm ²The cathode current density is 5-15A/cm ²(ii) a The temperature is 1050 + -50 ℃, and the current intensity is 100-15000A.

4. The method of claim 1, wherein the temperature is controlled to 1500 ± 100 ℃ during the melting process, and the protective gas is argon, nitrogen or mixed inert gas.

5. The method of making the rare earth-iron alloy of claim 1, wherein the method of making the rare earth oxyfluoride coated alkaline earth metal oxide or alkali metal oxide crucible comprises:

Coating ingredients, namely mixing rare earth oxide, rare earth fluoride and polyvinyl alcohol according to the weight ratio of 100: 0.2-50: 5-15, mixing uniformly;

Pressing the coating material on the inner wall of a crucible of alkaline earth metal oxide or alkali metal oxide, and pressing the coating and the crucible together on a press to form, wherein the pressure is controlled at 270-500 Mpa; and then drying and roasting to obtain the alkaline earth metal oxide or alkali metal oxide crucible containing the rare earth oxyfluoride coating.

6. The method for preparing the rare-earth ferroalloy as claimed in claim 5, wherein the coating material is pressed, put into a drying kiln for natural drying for 72-120 hours, and then roasted according to the following process: heating to 150 deg.C at room temperature, and maintaining for 2-3 hr at a heating rate of no more than 5 deg.C per minute; heating to 1000 deg.C, and maintaining for 5-6 hr at a heating rate of 10 deg.C/min; heating to 1350-1400 deg.c for 10-11 hr at the speed of not more than 10 deg.c per minute; cooling to below 100 deg.c with the furnace and taking out for further use.

7. The method for preparing the rare-earth ferroalloy as claimed in claim 5, wherein the alkaline earth metal oxide or the alkali metal oxide is selected from magnesium oxide, aluminum oxide or calcium oxide, and the density of the coating is 3 to 8g/cm ³The porosity of the coating is 5-20%.

8. The method of claim 7, wherein the coating has a density of 3 to 7.5g/cm ³Or 6-8g/cm ³。

9. The method for preparing a rare-earth iron alloy as claimed in any one of claims 5 to 8, wherein the rare-earth oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide, scandium oxide; the rare earth fluoride is one or more of lanthanum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, bait, thulium fluoride, ytterbium fluoride, lutetium fluoride, yttrium fluoride or scandium fluoride; the rare earth oxide and the rare earth fluoride use the same rare earth elements.

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