CN111411372B - Preparation method of rare earth iron alloy - Google Patents
Preparation method of rare earth iron alloy Download PDFInfo
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- CN111411372B CN111411372B CN201910853695.0A CN201910853695A CN111411372B CN 111411372 B CN111411372 B CN 111411372B CN 201910853695 A CN201910853695 A CN 201910853695A CN 111411372 B CN111411372 B CN 111411372B
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- C22C1/03—Making non-ferrous alloys by melting using master alloys
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Abstract
The invention discloses a preparation method of rare earth ferroalloy, which comprises the following steps: preparing rare-earth iron intermediate alloy by non-consumable cathode electrolysis; electrolyte is filled in the electrolytic tank, a graphite carbon plate is used as an anode, tungsten or molybdenum material is used as a cathode, and a crucible below the tungsten-molybdenum 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; rare earth iron intermediate alloy and iron are taken as raw materials and put into a 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. The rare earth ferroalloy obtained by the invention has uniform and stable components and low content of impurity elements, has density and melting point close to those of steel, and is easy to add into the steel; the rare earth ferroalloy can fundamentally solve the problem of effective addition of rare earth in steel, and can accurately control the content of the rare earth in the steel.
Description
Technical Field
The invention relates to a rare earth ferroalloy production technology, in particular to a preparation method of rare earth ferroalloy by adopting a non-consumable cathode electrolysis and intermediate frequency furnace component regulation and control duplex method.
Background
At present, steel is the first major metal structural material and is widely applied to the fields of buildings, energy sources, transportation, aerospace and the like. The application and research of rare earth in steel are also rapidly developed, and the rare earth added into molten steel can play roles in desulfurization, deoxidation, inclusion form change and the like, and can improve the plasticity, stamping property, wear resistance and welding property of steel. Various rare earth steels such as rare earth steel plates for automobiles, die steel, steel rails and the like are widely applied.
The method for adding rare earth in the process of producing rare earth steel is always the key point of research, the existing adding method comprises various forms such as a wire feeding method, a core-spun wire, a rare earth iron intermediate alloy and the like, and the existing adding method has obvious effect. The technology for preparing the rare-earth-iron intermediate alloy mainly comprises the following steps:
(1) a mixed dissolution method.
The mixing and dissolving method is also called as a counter-doping method, and mainly utilizes an electric arc furnace or an intermediate frequency induction furnace to mix and dissolve rare earth metals and iron to prepare alloy. The method is a commonly adopted method at present, has simple process technology, can prepare multi-element intermediate alloy or application alloy, but has the following defects: 1) the local concentration of rare earth metal in the molten iron is easy to be too high, and segregation is generated; 2) the raw materials adopted by the method are rare earth metals, particularly medium and heavy rare earth metals, the preparation process is complex, and the cost is high; 3) the smelting temperature is high, and the requirement on the smelting temperature is high due to the fact that rare earth metal and pure iron are used as raw materials.
(2) Molten salt electrolysis.
The molten salt electrolysis method for preparing the rare earth iron intermediate alloy mainly adopts an iron consumable cathode method. For example, chinese patent CN1827860 discloses a process and equipment for producing dysprosium-iron alloy by molten salt electrolysis, which proposes that under the condition of high temperature, dysprosium oxide dissolved in fluoride solution is ionized, dysprosium ions are precipitated on the surface of an iron cathode under the action of a direct current electric field and reduced into metal dysprosium, and dysprosium is alloyed with iron to form dysprosium-iron alloy. The method has low production cost and simple process, but also has the following defects: the rare earth and iron in the alloy have large distribution fluctuation and are difficult to control, and the distribution error is up to 3-5 percent, thereby influencing the consistency of products.
Magnesium oxide crucibles are commonly used in rare earth steel production, and according to research on vacuum induction melting carbon deoxidation research (iron and steel, vol. 38, No. 6, 2003, P275-278), the magnesium oxide crucibles are used for smelting rare earth ferroalloys, so that the oxygen content in the alloys is increased, and the yield and the effect of the rare earth added into steel are influenced. In addition, during the process of smelting rare earth metal and alloy by using a magnesia, alumina or calcium oxide crucible, the rare earth metal can react with the crucible, so that impurities are added to the alloy. Therefore, the aim of controlling the impurity content by closely selecting raw materials is obviously insufficient, and the selection of the crucible in the smelting process is also an important link.
However, rare earth ferroalloys prepared by the mixed solution method and the molten salt electrolysis method have high oxygen content, and after the rare earth ferroalloys are added into a ladle, generated inclusions easily cause the problem of nozzle blockage, thereby influencing normal tapping. When the rare earth ferroalloy is prepared by a mixed solution method and a molten salt electrolysis method, the accurate control of rare earth elements cannot be realized. Impurities are still brought into the crucible used at present when rare earth metals and alloys thereof are smelted.
Disclosure of Invention
The invention solves the technical problem of providing a preparation method of rare earth ferroalloy, which adopts a double-process preparation of non-consumable cathode electrolysis and medium frequency furnace component regulation, the obtained rare earth ferroalloy has uniform and stable components and low content of impurity elements, the density and the melting point are close to those of steel, the rare earth ferroalloy is easy to be added into the steel, the problem of effective addition of rare earth in the steel can be fundamentally solved, the content of the rare earth in the steel is accurately controlled, and the cost of applying the rare earth in the steel is reduced.
The technical scheme is as follows:
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 meeting the requirements.
Furthermore, the form of 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%.
Further, the current density of the anode in the electrolysis process is 0.5-2.0A/cm2The cathode current density is 5-15A/cm2(ii) a The temperature is 1050 + -50 ℃, and the current intensity is 100-.
Furthermore, in the melting process, the temperature is controlled to be 1500 +/-100 ℃, and the protective gas is argon, nitrogen or mixed inert gas.
Further, a method of making an alkaline earth (alkali metal) oxide crucible containing a rare earth oxyfluoride coating, comprising:
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 an alkaline earth (alkali metal) oxide crucible, and pressing and molding the coating and the crucible together on a press, wherein the pressure is controlled at 270-500 MPa; and then drying and roasting to obtain the alkaline earth (alkali metal) oxide crucible containing the rare earth oxyfluoride coating.
Further, after the coating ingredients are pressed, the mixture is put into a drying kiln to be naturally dried for 72 to 120 hours and then is 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-; cooling to below 100 deg.c with the furnace and taking out for further use.
Further, the alkaline earth oxide or alkali metal oxide is selected from magnesium oxide, aluminum oxide or calcium oxide, and the density of the coating is 3-8g/cm3The porosity of the coating is 5-20%.
Further, the density of the coating is 3 to 7.5g/cm3Or 6-8g/cm3。
Further, the rare earth oxide is one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, bait, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide and 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.
The invention has the technical effects that:
1. the rare earth ferroalloy is prepared by adopting a non-consumable cathode electrolysis and intermediate frequency furnace component regulation and control duplex method, and has uniform and stable components, small segregation and low impurity content.
The invention adopts the melting method to carry out secondary regulation and control on the content of the rare earth in the rare earth ferroalloy, the content of the rare earth in the rare earth ferroalloy can be accurately controlled, the components of the rare earth ferroalloy are uniform, and the content of the rare earth in the rare earth ferroalloy can be controlled to be +/-1 wt%. Because the smelting is carried out in 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 the rare earth ferroalloy are close to those of steel, the rare earth ferroalloy is easy to add into the steel, and the rare earth yield is high when the rare earth ferroalloy is applied to the rare earth steel. The rare earth ferroalloy can fundamentally solve the problem of effective addition of rare earth in steel, can accurately control the content of the rare earth in the steel, reduces the cost of applying the rare earth in the steel, has no pollution and obvious effect, and is suitable for large-scale industrial production.
The rare earth ferroalloy is applied to steel, so that the product quality and the comprehensive performance of the rare earth steel can be greatly improved, and the plasticity, the low-temperature impact toughness, the thickness direction performance and the corrosion resistance of steel can be improved and enhanced.
3. The rare earth ferroalloy provided by the invention adopts rare earth oxide as a raw material, and the smelting crucible is also an oxide crucible of the same name of rare earth, so that the rare earth ferroalloy has less introduced impurity content.
4. The rare earth ferroalloy can be applied to steel to obviously improve the yield of rare earth, realize the deep purification of molten steel, obviously improve the yield of rare earth elements when smelting rare earth steel, improve and improve the plasticity, low-temperature impact toughness, thickness direction performance and corrosion resistance of steel and reduce the production cost.
5. The rare earth elements in the rare earth ferroalloy exist in a compound state, so that the rare earth ferroalloy has good oxidation resistance and high thermal stability; the rare earth elements in the alloy have uniform and stable components and low segregation, and the content of O, S, P, C and other impurities is low; meanwhile, the application field of the rare earth in steel is expanded by the rare earth element added into the rare earth iron intermediate alloy through dispersion strengthening, and particularly the rare earth is applied to some high-end technical fields.
6. The rare earth oxide coating is arranged on the inner wall of the alkaline earth (alkali metal) oxide crucible, so that impurities can be prevented from being brought in during smelting of rare earth metals and alloys thereof, the method is suitable for smelting of the rare earth metals and the alloys thereof, and the method is simple in process and low in cost.
(1) The rare earth oxide coating has high density, low porosity and strong metal or alloy liquid corrosion resistance;
(2) the alkaline earth (alkali metal) oxide crucible adopts rare earth oxide as a coating, and in the process of smelting rare earth metal, rare earth iron intermediate alloy and rare earth iron alloy, because the metal liquid of the rare earth oxide and the rare earth iron alloy is the same material, impurities can not be brought in.
7. In the invention, the cathode material adopts tungsten or molybdenum non-consumable cathode electrolysis to prepare the rare earth iron alloy, which can reduce the control difficulty of the cathode.
8. The invention is also suitable for preparing rare earth copper, rare earth nickel, rare earth magnesium-aluminum alloy and rare earth zinc alloy.
Drawings
FIG. 1 is a schematic structural view of an apparatus for preparing a rare-earth iron master alloy in accordance with the present invention;
FIG. 2 is a flow chart of a method of making a rare earth ferroalloy with a non-consumable cathode of the present invention.
Detailed Description
The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce it.
FIG. 1 is a schematic structural view of an apparatus for preparing a rare-earth-iron master alloy according to the present invention.
The equipment for preparing the rare-earth iron intermediate alloy comprises: the device comprises a refractory brick 1, an iron sleeve 2, a receiver 3, a rare earth iron intermediate alloy 4, a graphite carbon anode plate 5, a tungsten or molybdenum cathode 6, an electrolyte 7, an electrolytic bath 8, a heat insulation layer 9 and a carbon tamping layer 10.
The electrolytic bath 8 is a graphite bath, and the outer side of the graphite bath body is sequentially coated with a carbon tamping layer 10, a heat 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 tank; a graphite carbon anode plate 5 is arranged around the cathode 6 in the graphite groove; a receiver 3 is arranged at the center of the bottom of the graphite tank, and the receiver 3 is positioned below the cathode 6.
When in use, rare earth oxide, electrolyte 7 and iron (iron blocks, scrap steel, iron powder and the like) are filled in the graphite tank, the electrolyte 7 adopts rare earth fluoride and lithium fluoride molten salt electrolyte, and rare earth ferroalloy melt generated after electrolysis flows into the receiver 3 after being enriched from the cathode 6.
FIG. 2 is a flow chart showing the method for preparing the rare earth iron alloy of the present invention.
The preparation method of the rare earth ferroalloy adopts a non-consumable cathode electrolysis and intermediate frequency furnace component regulation and control duplex method, and comprises the following specific steps:
step 1: preparing rare-earth iron intermediate alloy by non-consumable cathode electrolysis; electrolyte is filled in an electrolytic tank, a graphite carbon plate 5 is used as an anode, tungsten or molybdenum material is used as a cathode 6, and an alkaline earth metal oxide crucible, an alkali metal oxide crucible or a tungsten-molybdenum crucible containing a rare earth oxyfluoride coating below the cathode 6 is used as a receiver 3; 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 a rare earth iron intermediate alloy 4 is obtained at a receiver 3;
the rare earth iron master alloy enriches and melts on the cathode 6 and falls into the receiver 3 below. The form of the iron used in the molten salt electrolysis process can be blocks, wires, rods, scraps and the like, the content of the rare earth in the prepared rare earth iron intermediate alloy is more than 60 wt%, and the control precision of the content of the rare earth in the alloy is +/-2 wt%.
The current density of the anode in the electrolysis process is 0.5-2.0A/cm2The cathode current density is 5-15A/cm2(ii) a The temperature is 1050 + -50 ℃, and the current intensity is 100-. The rare earth iron alloy is prepared by adopting a tungsten or molybdenum non-consumable cathode electrolytic method, the control difficulty of the cathode can be reduced, and compared with a consumable iron cathode electrolytic method, the rare earth iron alloy has the advantages of small slag amount, high current efficiency, accurately controllable alloy components and small component segregation.
Step 2: the rare earth iron intermediate alloy and iron are used as raw materials and put into an alkaline earth (alkali metal) oxide crucible containing a rare earth oxyfluoride coating, 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 meeting the requirements.
The temperature in the smelting process is controlled at 1500 +/-100 ℃, and the protective gas can be argon, nitrogen or the mixture of the argon and the nitrogen.
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%.
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. The parameters are as follows: density of the coating: 3-8g/cm3(ii) a The porosity is 5-20%. Preferably 3 to 7.5g/cm3Or 6-8g/cm3. The rare earth oxide is used as the coating, and the rare earth oxide and the metal liquid of the rare earth iron alloy are of the same name, so that impurities cannot be brought in.
A method of making an alkaline earth (alkali metal) oxide crucible containing a rare earth oxyfluoride coating, comprising:
1. 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;
the rare earth oxide of the coating corresponds to the rare earth element of the rare earth fluoride, namely the same rare earth element is used in the rare earth oxide and the rare earth fluoride.
The rare earth oxide is one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, bait, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide and 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.
2. The ingredients are coated on the inner wall of the crucible, the coating and the crucible are pressed together on a press (the pressure is controlled at 270-500Mpa) for molding, and then the molding is dried and roasted to obtain the alkaline earth (alkali) oxide crucible containing the rare earth oxyfluoride coating.
After the coating is pressed, the coating is put into a drying kiln to be naturally dried for 72 to 120 hours and then is roasted according to the following process:
(1) heating up (the heating rate is not more than 5 ℃ per minute) to 150 ℃ at room temperature, and keeping the temperature for 2-3 hours;
the temperature rise in the section is mainly to ensure that the moisture in the materials is fully evaporated.
(2) Heating (the heating rate is not more than 10 ℃ per minute) to 1000 ℃ and preserving the heat for 5-6 hours;
the temperature rise in the section is mainly to ensure that impurities with low melting point and low boiling point in the material are fully escaped, and simultaneously the temperature rise cannot be too fast, the escape speed of the impurities with low boiling point is mainly controlled to be slow, and the crucible is ensured to be intact and not to break.
(3) Heating to 1350-;
the temperature rise of the section is mainly controlled at a low speed, so that the crucible is ensured to be intact and not to crack, and meanwhile, the mixed rare earth oxide coating is ensured to have high density, low porosity and strong metal or alloy liquid corrosion resistance. The high temperature section allows the rare earth oxide and the rare earth fluoride to fully react to form the rare earth oxyfluoride with high melting point, and the rare earth oxyfluoride has good binding force with the crucible matrix.
(4) And cooling to below 100 ℃ along with the furnace, taking out for later use, and obtaining the alkaline earth (alkali) oxide crucible containing the rare earth oxyfluoride coating.
The rare earth oxyfluoride coating formed by the rare earth oxide, the rare earth fluoride and the polyvinyl alcohol at high temperature has the characteristics of high melting point (the melting point is 2000-.
The metal detection adopts ICP-MS test according to national standards such as GB/T18115.1-2006 and the like; the detection of C is tested by a high-frequency combustion-infrared method according to GB/T12690.13-1990; the test of O is carried out according to GB/T12690.4-2003 by using an inert gas pulse-infrared method. The standard deviation S of the chemical composition is calculated by the following formula:
wherein XiIs the chemical composition of the sample; the average value of X is the average value of chemical components of n points of the sample, and n is 20 in the invention.
Example 1
The electrolytic tank 8 adopts a circular graphite electrolytic tank with the diameter of 650mm, and the graphite carbon anode plate 5 consists of four graphite plates; 80 wt% of lanthanum fluoride and 20 wt% of lithium fluoride in the electrolyte; the cathode 6 is made of tungsten with a diameter of 70mm, an average current intensity of 3500A and an anode current density of 0.7-1.0A-cm2Cathode current density of 7-9A/cm2The electrolysis temperature is maintained at 1050 ℃ of 1000-.
TABLE 1 composition analysis 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 |
Taking 3.33kg of the prepared lanthanum-iron intermediate alloy as a raw material, adding 11.67kg of iron, smelting in a 30kg medium-frequency vacuum induction furnace, wherein the protective gas is argon, and the components of the lanthanum-iron alloy obtained in the lanthanum oxide coating crucible after smelting are shown in Table 2.
TABLE 2 composition analysis of lanthanum-iron alloy/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 tank 8 adopts a circular graphite electrolytic tank with phi of 600mm,the graphite carbon anode plate 5 consists of four graphite plates; the electrolyte contains 90 wt% of cerium fluoride and 10 wt% of lithium fluoride; the cathode 6 is made of tungsten with a diameter of 75mm, an average current intensity of 4000A and an anode current density of 0.8-1.2A/cm2Cathode current density of 6-8A/cm2The electrolysis temperature is maintained at 1050 ℃ of 1000-.
TABLE 3 composition analysis results in cerium-iron 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 |
The prepared cerium-iron intermediate alloy is taken as a raw material, 1.76kg of the cerium-iron intermediate alloy is taken, 13.24kg of iron is added, smelting is carried out in a 30kg medium-frequency vacuum induction furnace, the protective gas is argon, and the components of the cerium-iron alloy obtained in a cerium oxide coating crucible after smelting are shown in Table 4.
TABLE 4 composition analysis results in wt% of Ce-Fe alloy
| 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 tank 8 adopts a round graphite electrolytic tank with phi of 620mm, and the graphite carbon anode plate 5 consists of four graphite plates; the electrolyte contains 85 wt% of neodymium fluoride and 15 wt% of lithium fluoride; the cathode 6 is made of tungsten with a diameter of 80mm, an average current intensity of 5000A and an anode current density of 0.7-1.1A/cm2Cathode current density of 7-9A/cm2The electrolysis temperature was maintained at 1020 ℃ and 1070 ℃ for 480 hours, 4720kg of neodymium oxide was consumed by continuous electrolysis to obtain 4843kg of neodymium-iron master alloy, the average neodymium content was 80%, the current efficiency was 90%, the neodymium yield was 98%, and the results of the alloy compositions are shown in Table 5.
TABLE 5 analysis of the composition of the neodymium-iron master alloys in% by weight
| Nd | Fe | C | O | P | S | Si | Mn |
| 80.06 | 19.89 | 0.011 | 0.0084 | ＜0.01 | ＜0.005 | 0.011 | ＜0.005 |
The prepared neodymium-iron intermediate alloy is used as a raw material, 3kg of the neodymium-iron intermediate alloy is taken and added with 13kg of iron, smelting is carried out in a 30kg medium-frequency vacuum induction furnace, the protective gas is argon, and the components of the neodymium-iron alloy obtained in a neodymium oxide coating crucible after smelting are shown in Table 6.
TABLE 6 analysis of Nd-Fe alloy composition in% by weight
| 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 tank 8 adopts a circular graphite electrolytic tank with the diameter of 400mm, and the graphite carbon anode plate 5 consists of four graphite plates; the electrolyte contains 85 wt% of praseodymium fluoride and 15 wt% of lithium fluoride; the cathode 6 is made of tungsten with a diameter of 40mm, an average current intensity of 2000A and an anode current density of 0.7-1.1A/cm2Cathode current density of 7-9A/cm2The electrolysis temperature is maintained at 1010-1060 ℃, the electrolysis is continuously carried out for 100 hours, 313kg of praseodymium oxide is consumed, 302kg of praseodymium-iron intermediate alloy is prepared, the average praseodymium content is 85 percent, the current efficiency is 88 percent, the praseodymium yield is 97 percent, and the alloy composition results are shown in Table 7.
TABLE 7 composition analysis results/wt% of praseodymium-iron intermediate alloy
| Pr | Fe | C | O | P | S | Si | Mn |
| 84.95 | 15.02 | 0.010 | 0.0093 | ＜0.01 | ＜0.005 | 0.012 | ＜0.005 |
Taking 3.3kg of the prepared praseodymium-iron intermediate alloy as a raw material, adding 10.7kg of iron, smelting in a 30kg medium-frequency vacuum induction furnace, wherein the protective gas is argon, and the components of the praseodymium-iron alloy obtained in the praseodymium oxide coating crucible after smelting are shown in Table 8.
TABLE 8 praseodymium ferroalloy composition analysis result/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 tank 8 adopts a circular graphite electrolytic tank with the diameter phi of 500mm, and the graphite carbon anode plate 5 consists of four graphite plates; 82 wt% of lanthanum cerium fluoride (lanthanum fluoride: cerium fluoride: 55: 45) and 18 wt% of lithium fluoride in the electrolyte; the cathode 6 is made of molybdenum with a diameter of 60mm, an average current intensity of 3000A and an anode current density of 0.7-1.2A/cm2Cathode current density of 6-10A/cm2The electrolysis temperature was maintained at 1050-.
TABLE 9 analysis result of lanthanum cerium iron master alloy composition/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 |
The prepared lanthanum-cerium-iron intermediate alloy is used as a raw material, 3.5kg of the lanthanum-cerium-iron intermediate alloy is taken, 11.5kg of iron is added, smelting is carried out in a 30kg medium-frequency vacuum induction furnace, argon is used as protective gas, and the components of the lanthanum-cerium-iron alloy obtained in a lanthanum-cerium coating crucible are oxidized after smelting are shown in a table 10.
TABLE 10 analysis result of lanthanum cerium iron alloy composition/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 tank 8 adopts a circular graphite electrolytic tank with the diameter of 650mm, and the graphite carbon anode plate 5 consists of four graphite plates; the electrolyte contains 86 wt% of praseodymium neodymium fluoride (praseodymium fluoride: neodymium fluoride: 25:75) and 14 wt% of lithium fluoride; the cathode 6 is made of tungsten with a diameter of 80mm, an average current intensity of 6000A and an anode current density of 0.6-1.2A/cm2Cathode current density of 6-9A/cm2The electrolysis temperature was maintained at 1020 + 1070 ℃ and the electrolysis was continued for 720 hours, with 7765kg of praseodymium-neodymium oxide (praseodymium oxide: neodymium oxide: 25:75) being consumed, 8570kg of praseodymium-neodymium (praseodymium: neodymium oxide: 25:75) iron intermediate alloy was produced, the average praseodymium-neodymium content was 75%, the current efficiency was 87%, the praseodymium-neodymium yield was 98%, and the results of the alloy components are shown in Table 11.
TABLE 11 praseodymium neodymium iron intermediate alloy composition analysis results/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 |
The prepared praseodymium-neodymium-iron intermediate alloy is taken as a raw material, 2kg of praseodymium-neodymium-iron intermediate alloy is taken, 13kg of iron is added, smelting is carried out in a 30kg medium-frequency vacuum induction furnace, the protective gas is argon, and the components of the praseodymium-neodymium-iron alloy obtained in the praseodymium-neodymium oxide coating crucible after smelting are shown in table 12.
TABLE 12 analysis result/wt.% of praseodymium-neodymium-iron alloy component
| 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 tank 8 adopts a circular graphite electrolytic tank with the diameter phi of 320mm, and the graphite carbon anode plate 5 consists of four graphite plates; in the electrolyte, 82 wt% of lanthanum-cerium-praseodymium-neodymium fluoride (lanthanum fluoride: cerium fluoride: praseodymium fluoride: neodymium fluoride: 55:32:3:10) and 18 wt% of lithium fluoridewt%; the cathode 6 is made of tungsten with a diameter of 30mm, an average current intensity of 1000A and an anode current density of 0.6-1.0A/cm2Cathode current density of 6-8A/cm2The electrolysis temperature was maintained at 1000 ℃ and 1050 ℃, the mixed rare earth oxide (lanthanum oxide: cerium oxide: praseodymium oxide: neodymium oxide: 28:52:5:15) was continuously electrolyzed for 120 hours, 193kg of lanthanum cerium praseodymium neodymium (lanthanum: cerium: praseodymium: neodymium: 28:52:5:15) iron intermediate alloy was produced, 219kg of lanthanum cerium praseodymium neodymium (lanthanum: cerium: praseodymium: neodymium) iron intermediate alloy, the average rare earth content was 70%, the current efficiency was 85%, the rare earth yield was 96%, and the results of the alloy components are shown in table 13.
TABLE 13 analysis of the composition of lanthanum cerium praseodymium neodymium iron master alloy in 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 intermediate alloy is used as a raw material, 6.43kg of the lanthanum-cerium-praseodymium-neodymium-iron intermediate alloy is taken, 8.57kg of iron is added, smelting is carried out in a 30kg medium-frequency vacuum induction furnace, argon is used as protective gas, and the components of the lanthanum-cerium-praseodymium-neodymium-iron alloy obtained in a lanthanum-cerium-praseodymium-neodymium coated crucible are oxidized after smelting are shown in Table 14.
TABLE 14 analysis results of lanthanum cerium praseodymium neodymium iron alloy composition in 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 terminology used herein is for the purpose of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.
Claims (6)
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 the 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 or an alkaline earth 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;
placing the rare earth iron intermediate alloy and iron as raw materials into an alkaline earth metal oxide crucible, and further smelting the rare earth iron intermediate alloy in a medium-frequency induction furnace by adopting a melting method to obtain rare earth iron alloy; the form of 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%;
the preparation method of the alkaline earth metal oxide crucible containing the rare earth oxyfluoride coating comprises the following steps:
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 ingredients on the inner wall of the alkaline earth metal oxide crucible, and pressing and forming the coating and the crucible together on a press, wherein the pressure is controlled at 270-500 MPa;
after the coating ingredients are pressed, the mixture is put into a drying kiln to be naturally dried for 72 to 120 hours, and then is dried and roasted, and the roasting is carried out 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-; cooling to below 100 ℃ along with the furnace, taking out for later use, and obtaining the alkaline earth metal oxide crucible containing the rare earth oxyfluoride coating.
2. 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/cm2And the cathode current density is 5-15A/cm2(ii) a The temperature is 1050 + -50 ℃, and the current intensity is 100-.
3. 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.
4. The method for preparing the rare-earth ferroalloy as claimed in claim 1, wherein the material of the alkaline-earth metal oxide crucible is selected from magnesium oxide or calcium oxide, and the rare-earth oxyfluoride-containing coating has a density of 3 to 8g/cm3The porosity of the rare earth-containing oxyfluoride coating is 5-20%.
5. The method of claim 4, wherein the coating has a density of 3 to 7.5g/cm3Or 6-8g/cm3。
6. The method for preparing a rare-earth iron alloy as claimed in any one of claims 1, 4 or 5, 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 and 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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| CN115389283A (en) * | 2022-06-24 | 2022-11-25 | 赣州艾科锐检测技术有限公司 | Internal control sample in rare earth metal or alloy detection, preparation method and application |
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