The master alloys for permanent magnets based on rare earth metals

 

(57) Abstract:

The invention relates to the production of master alloys for permanent magnets on the basis of the metals. The master alloys for permanent magnets based on rare-earth metals contains, wt%: one or more rare-earth metals selected from the group of rare-earth metals containing neodymium, praseodymium, dysprosium, terbium 72 - 78, iron and/or cobalt - rest. The corrosion resistance of the alloys provided an opportunity for their long term storage in plastic containers, and the fragility of this material has simplified its use for the determination of the charge upon receipt of high-energy magnets based on rare-earth metals type REM2Fe14B. 1 table.

The invention relates to the field of metallurgy, in particular the production of alloys of rare earth and transition metals of the iron subgroup for the issuance of these alloys and high-energy permanent magnets.

The production of permanent magnets based on rare-earth metals involves receiving at the first stage base alloys doped or undoped. The alloys used for the manufacture of permanent magnets must have the following structure: the amount of REM (neodymium, praseodymium, dysprosium, terbium) 30-36 wt.%, if this is real Fe. Alloys of this composition can be prepared by the joint recovery of fluorides of rare-earth metals with FeF2, FeF3or their mixture, with the addition to the mixture FeB, powder metal iron and alloying elements [1]. In one of the patents is proposed to use as a component of the charge of iron in the form of trichloride [2]. In both cases, the recovery is carried out chips of metallic calcium. Due to differences in the raw materials and the conditions of the melt is not always possible to obtain an alloy of a given composition.

There is a method of making permanent magnets from alloys obtained by fusing the individual components [3, 4]. The alloys are prepared by fusing the individual components of neodymium, terbium, dysprosium, iron, ferroboron, and alloying additives. For the preparation of an alloy of a given composition the estimated number of individual substances (REE, Fe, FeB, alloying additives) is melted in a crucible of alumina in induction furnaces, after which the melt is poured into the mould.

The advantage of the method of producing alloys of the individual components is convenience in their synthesis and the possibility of obtaining alloys specified composition.

However, for alloys the data metallotrejderskogo recovery anhydrous individual fluoride in an induction furnace in an argon atmosphere. Reductive smelting is carried out in the niobium or tantalum crucibles. To remove excess calcium individual REE (Nd, Pr, Dy, Tb) re-melt in vacuum in tantalum crucibles [5, 6]. Individual REE are characterized by high ductility and corrosion activity; therefore, to reduce losses during storage they are covered with a layer of paraffin and placed in a sealed package. The high plasticity of individual REE hampers their compartmentalisation in the air to catch the weight of material loaded for melting the composition of the charge.

The disadvantages of the method of obtaining an individual REMS include the following:

the use of expensive crucibles for the production of metals and their melting;

the difficulty of storing and dividing into parts in the preparation of the charge for making alloys of a given composition;

significant power consumption for the heating system when the furnace metallothermic obtaining metal REM (Nd, Pr, Dy, Tb) and their subsequent remelting removal of slag and impurities including metal calcium [7].

All of these factors significantly increases the cost price of the alloys obtained from individual REE.

The closest analogue to the claimed izobreteniya, and as a rare earth metal samarium in the following ratio, wt.%:

Iron - 8-10

Cobalt - 20-35

Samarium - Rest

The alloy is used as alloys for permanent magnets [8].

The difference between the claimed invention from the closest is that the ligature as REM contains at least one rare-earth metals selected from the group consisting of neodymium, praseodymium, dysprosium, terbium, as well as transition metals such as iron and/or cobalt in the following ratio, wt. %: at least one rare-earth metals selected from the group consisting of neodymium, praseodymium, dysprosium, terbium 72-78, iron and/or cobalt - rest.

The problem solved by the invention was the development of the composition of the alloys to produce alloys used for the manufacture of permanent magnets, with the fragility and corrosion resistance in the air higher than the individual rare earths.

The solution of this problem is provided by the fact that the proposed alloys based on rare-earth metals contains one or more rare-earth metals selected from the group consisting of neodymium, praseodymium, dysprosium, terbium, and jelly is - 72-78

Iron and/or cobalt - 100

The presence of ligatures REM number 72-78 wt.% provide for its high fragility and better corrosion resistance due to the formation of intermetallic compounds and low concentrations of free REE. The use of cheaper material ligatures REM-iron (cobalt) instead of individual REE provides for remelting obtaining alloy of a given composition.

Retrieving ligature is illustrated by the following example:

Getting ligatures composition 72 Nd - 28% (wt.) Fe.

For the manufacture 2000 ligatures used TRIFLUORIDE REE concentration of neodymium 69,8% (wt. ) and praseodymium 2,2% (wt.), TRIFLUORIDE iron with iron concentration of 50% (wt.). An excess of metallic calcium to restore metal fluoride amounted to 20% of the stoichiometric quantity.

The excess of neodymium in the original mixture to obtain the required ligatures composition is 8%, so theoretical mass of the ingot is increased to 2115,2, From the calculated amount of iron in the composition of the alloy (560 g) 35% in the mixture introduced in the form of a powder of metallic iron (196 g) and 65% in TRIFLUORIDE, the amount of which amounted to 728, After calculation, we obtain the charge for in the Naya weight of the charge - 4231,

The components of the mixture after weighing mix in the mixer, is loaded into a crucible, which is installed in the device recovery, and carry out the restoration. The apparatus of the recovery vacuum, filled with argon gas and electric blasting initiate the reaction of recovery. At the moment of passage of the reaction devices fix the elevated pressure and temperature. After rehabilitation melting apparatus is cooled to room temperature (18-30oC), then open and raise the crucible. From the crucible remove the ingot and slag, after which the ingot cleaned from slag inclusions and weighed. Weighing got a lot of ingot ligatures, equal 1980.3 g, which corresponds to the output 93,6%. From ingot was selected sample.

Chemical analysis of the ingot showed the following results: Nd 70,1%, Pr Of 2.1%, Ca to 0.15%, Cu and 0.09%, Ni of 0.07%, Fe rest (wt.%).

Chemical compositions and properties of the proposed ligatures are presented in the table.

Offer ligatures these compositions synthesized at the Siberian Chemical combine. The corrosion resistance of the alloys provided an opportunity for their long term storage in plastic containers, and the fragility of this material has simplified its use for selection is energy magnets based on rare-earth metals type P3M2Fe14B. Proposed by the authors ligatures are used as substitutes for individual REE induction smelting magnetic alloys of any composition.

Sources of information taken into account in the preparation of the description:

1. US 4612047 A, C, 22 C 33/00, 1986.

2. FR 8666948 A1, C 22 C 23/06, 1988.

3. US 4756775 A, H 01 F 1/04, 1988.

4. Cecala I. B. , Samarin A. B. Physical metallurgy precision alloys. Alloys with special magnetic properties. - M: metallurgy, 1989, S. 458.

5. Handbook of rare metals. Edited by ivy C. E. - M.: Publishing house "Mir" 1965, S. 585.

6. Zelikman A. N. Metallurgy of rare earths, thorium and uranium. - M: GNTI 1961, S. 192.

7. EN 2066269 C1, H 01 F 1/053, 3/08, 1996.

8. SU 384922 A, C, 22 C 28/00, 29.05.1973.

The master alloys for permanent magnets based on rare earth metals containing rare-earth metals and transition metals, characterized in that as REM it contains at least one rare-earth metals selected from the group consisting of neodymium, praseodymium, dysprosium, terbium, and as the transition metals iron and/or cobalt in the following ratio, wt.%:

At least one rare-earth metals selected from the group consisting of neodymium

 

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