EP0443647A1 - Aimants de terre rare-fer-carbone façonnés à chaud - Google Patents

Aimants de terre rare-fer-carbone façonnés à chaud Download PDF

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Publication number
EP0443647A1
EP0443647A1 EP91200208A EP91200208A EP0443647A1 EP 0443647 A1 EP0443647 A1 EP 0443647A1 EP 91200208 A EP91200208 A EP 91200208A EP 91200208 A EP91200208 A EP 91200208A EP 0443647 A1 EP0443647 A1 EP 0443647A1
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EP
European Patent Office
Prior art keywords
percent
hot
iron
neodymium
carbon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP91200208A
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German (de)
English (en)
Inventor
Carlton Dwight Fuerst
Earl George Brewer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motors Liquidation Co
Original Assignee
Motors Liquidation Co
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Filing date
Publication date
Priority claimed from US07/622,690 external-priority patent/US5085716A/en
Application filed by Motors Liquidation Co filed Critical Motors Liquidation Co
Publication of EP0443647A1 publication Critical patent/EP0443647A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C22C1/0441—Alloys based on intermetallic compounds of the type rare earth - Co, Ni
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/058—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IVa elements, e.g. Gd2Fe14C

Definitions

  • This invention relates to permanent magnets based on rare earth elements and iron. More particularly, this invention relates to permanent magnets based on iron, neodymium and/or praseodymium and carbon as specified in the preamble of claim 1, for example, as disclosed in US-A-4,849,035.
  • Permanent magnets based on the RE2Fe14B-type structure have gained wide commercial acceptance. Such magnets can be made by a sintering practice, and they can be made by rapidly solidifying a melt of suitable composition and producing bonded magnets or hot-pressed magnets or hot-pressed and hot-worked magnets from the quenched material.
  • rare earth-iron-carbon compositions have been formed in a RE2Fe14C structure which is analogous to the above-mentioned iron-rare earth-boron structure.
  • Stadelmaier and Liu, c.f., US-A-4,849,035 cast iron-dysprosium-carbon compositions and iron-dysprosium-neodymium-carbon-boron compositions in the form of ingots and through a prolonged annealing cycle at 900°C produced the magnetically-hard tetragonal 2-14-1 structure.
  • the casting displayed permanent magnet properties as did comminuted particles produced from the casting.
  • the comminuted particles were disclosed as suitable for use in a bonded magnet. Whilst such materials displayed appreciable magnetic coercivity, they displayed relatively low magnetic remanence.
  • An anisotropic permanent magnet according to the present invention is characterised by the features specificied in the characterising portion of claim 1.
  • a melt comprising neodymium and/or praseodymium, iron and carbon, or carbon and boron, that is suitable, upon hot-working, for forming the 2-14-1 type structure with a minor portion of one or more second phases.
  • This molten composition is very rapidly solidified, such as by melt-spinning, to produce an amorphous composition or a composition of very fine grain size, for example, no greater than about 40 nm in average grain size.
  • the melt-spun material is initially in the form of friable, magnetically-isotropic ribbon fragments which may be readily broken into a powder suitable for hot-pressing and/or other hot-working in a die cavity.
  • Such powder particles are amorphous or contain many very fine, substantially spherical grains.
  • the particles are magnetically isotropic. They are hot-pressed at a suitable elevated temperature of about, e.g., 700°C to 900°C for a period from 20 to 30 seconds to a few minutes to form a fully-dense, fine-grain Nd2Fe14C-type tetragonal crystal structure.
  • the hot-pressed body may then be further hot-worked at an elevated temperature, e.g., 750°C to 900°C, to promote the growth of platelet-like grains and to plastically deform the body to align the platelets such that their c-axes are generally parallel and the resultant body is magnetically anisotropic.
  • the body is still fine-grained although the grains are flattened and aligned and its preferred direction of magnetization is in the direction of pressing, i.e., perpendicular to the direction of material flow during hot-working.
  • the largest average dimension of the flat grains be no more than about 1000 nm and that they be no more than 200 nm thick.
  • the microstructure of the hot-worked material is characterized by a predominance of these flattened 2-14-1 grains with one or more minor phases of intergranular material that is typically composed of iron and the rare earth element(s) present.
  • Iron is preferably the transition metal element used although mixtures of iron and cobalt may also be employed.
  • Neodymium and/or praseodymium is preferably used as the rare earth element although up to 40 percent of the total rare earth content may include other rare earth elements.
  • Carbon or mixtures of carbon and boron is preferred for the third constituent of the 2-14-1 structure.
  • the proportions of iron (or iron and cobalt), rare earth elements and carbon must be balanced so that the predominant crystalline phase formed is the 2-14-1 tetragonal structure. If this crystal structure is not formed, the hot-worked product will have low magnetic coercivity or no permanent magnetic characteristics at all.
  • Figure 1 consists of two scanning electron microscope (SEM) photographs [Figure 1(a) and Figure 1(b)] from the fracture surface of a die-upset Nd 13.75 Fe 80.25 C6 magnet.
  • the press direction lies vertically in the photographs. Two magnifications of the same region are provided.
  • Figure 2 consists of three graphs of process parameters measured during the hot-pressing of melt-spun ribbons with the composition Nd16Fe78C9.
  • Figure 3 consists of three graphs of process parameters measured during the die-upsetting of a hot-pressed precursor with the composition Nd16Fe78C9.
  • Figure 4 consists of demagnetization curves for hot-pressed and die-upset magnets. The compositions are indicated in each panel under the respective curves.
  • the product of the present invention is a permanent magnet. It has a coercivity greater than 1000 Oersteds.
  • An ingot was prepared whose composition on an atomic percent basis was neodymium, 13.75 percent; iron, 80.25 percent; and carbon, 6 percent.
  • This material was re-melted by induction melting in a quartz crucible under argon atmosphere at a super-atmospheric pressure of 6.89 - 20.68 kPa (1-3 psi) and melt-spun by ejecting the molten material through a 0.65 mm orifice at the bottom of the crucible onto the perimeter of a 254 mm (10 inch) diameter chromium-plated copper wheel rotating at a speed of 28 meters per second.
  • the ejected molten stream was instantaneously quenched as it hit the rim of the spinning wheel and thrown off as ribbon fragments.
  • the resulting hot-pressed body had a density of about 7.74 g/cc and contained the Nd2Fe14C tetragonal crystal phase with small amounts of intergranular phases of uncertain composition believed to be largely neodymium and iron.
  • the magnetic properties of this hot-pressed body were derived from a demagnetization curve measured with a hysteresisgraph. The body displayed magnetic anisotropy.
  • a hot-pressed cylinder from Example 1 was pressed a second time in the same direction in vacuum using an oversized (19.05 mm (0.75 inch) internal diameter) graphite die that permitted the cylinder to plastically deform at a die temperature of 750°C to 800°C to about 40 percent of its original height.
  • the resulting die-upset, flat cylindrical magnet was sectioned with a high-speed diamond saw to produce a 2 mm cube for measurement of its magnetic properties in a vibrating sample magnetometer. The cube was cut so that two opposite faces were perpendicular to the direction of pressing and die-upsetting, and the other four faces were parallel to the direction of pressing and die-upsetting.
  • This magnetic anisotropy is indicative of the alignment of the c-axis of the individual die-upset grains along the press direction.
  • the magnetic coercivity of the sample in the press direction was 2.8 kOe.
  • Figures 1(a) and 1(b) are two SEM photographs at different magnifications of the same region of a fracture surface of this die-upset specimen.
  • the grains of the Nd2Fe14B tetragonal crystals are seen to be aligned flat platelets.
  • the grains are about 100 nm thick and up to about 700 to 800 nm in their largest dimension.
  • the short dimension of the grains, the c-axis, the preferred direction of magnetization, lies along the direction of applied stress.
  • a family of four alloys was prepared so as to be composed as follows: Nd 13.75 Fe 80.25 (B 1-x C x )6 where x in the four samples was respectively 0.2, 0.4, 0.6 and 0.8.
  • Example 1 The four samples were individually melt-spun to form amorphous ribbon fragments as in Example 1.
  • the four lots of ribbon fragments were pulverized and hot-pressed into cylindrical bodies in accordance with the practice of Example 1. They contained fine grains of the tetragonal phase Nd2Fe14C x B 1-x where the values of x were as indicated above.
  • the densities and the magnetic properties of the cylindrical magnetic bodies were as follows:
  • Typical process parameters used for hot-pressing these Nd-Fe-r ribbons are shown in Figure 2.
  • the ribbons were heated to 650°C in about 5.75 minutes, at which point the pressure was applied (see panels A and B of Figure 2).
  • the time interval required to reach full (or nearly full) density was between 1 and 2 minutes at maximum pressure (about 65 MPa), as the lower two panels in Figure 2 show.
  • the final hot-press temperature was around 850°C for the hot-pressed carbide magnets, compared to about 800°C for Nd-Fe-B magnets.
  • the hot-pressed magnets were removed from the die and cooled to room temperature. Magnetic measurements were then made as described below. The data is reported in Table I below. Some of the hot-pressed magnets were then re-heated and die-upset in a larger die as described in Example 2.
  • An initial die-upsetting pressure of about 15 MPa was applied at about 800°C (see Figure 3). This pressure was maintained until the sample height had decreased at least by about 5 percent, at which point the pressure was increased to 20 to 25 MPa. Starting with 15 MPa ensured that deformation could be induced without cracking the precursor; however, the strain rate at 15 MPa was too slow. Increasing the pressure to 20 to 25 MPa enhanced the strain rate to levels comparable to those observed for Nd-Fe-B alloys (about 1 min - 1). Higher temperatures were required to produce fully die-upset carbide magnets; the final temperature (about 900°C) was 50 to 100 degrees higher than that used for die-upsetting boride magnets. All die-upset magnets discussed here were reduced to 45 percent of their original height (i.e., 55 percent die-upset).
  • the magnetic coercivity of the hot-pressed magnets decreased sharply compared to similar boride compositions.
  • the magnetic coercivity apparently vanishes altogether at Nd16Fe78C6 due to the formation of the phase Nd2Fe17.
  • the major diffraction peaks are easily accounted for when compared to the calculated pattern for the 2-17 phase. It is quite possible that the observed 2-17 phase contained dissolved carbon, as reported by others studying annealed ingots.
  • phase such as ⁇ -Fe and 2-17 in these alloys was made more apparent by adjusting the neodymium concentration whilst maintaining high carbon levels of 9 percent and 10 percent.
  • Increasing the neodymium levels above 16 percent (up to about 17 percent) reduced the magnetic coercivity in these hot-pressed magnets, and again the X-ray diffraction patterns of the annealed ribbons revealed the presence of the 2-17 phase.
  • the three hot-pressed magnets with the highest magnetic coercivities were die-upset using the process parameters already described (see Table II for compositions). Demagnetization curves for the three die-upset magnets and their hot-pressed precursors appear in Figure 4; in each case, die-upsetting increased the magnetic remanence by just over 40 percent. More importantly, the magnetic coercivity of these die-upset magnets was sufficient to permit much higher energy products (about 18 MGOe to about 22 MGOe) than those observed with lower neodymium and carbon concentrations (see Example 2).
  • rapidly-solidified compositions of rare earth elements, iron (or iron and cobalt) and carbon (or carbon and boron) are hot-worked to form fully-densified, fine-grained bodies in which the fine grains are wrought into magnetic alignment such that the body is magnetically anisotropic.
  • hot-working is meant a process such as hot-pressing, hot die-upsetting, extrusion, hot-isostatic compaction, or rolling, so long as the specified resultant hot-worked microstructure is attained.
  • the hot-working process comprises more than one step, such as the combination of hot-pressing and die-upsetting, all steps can be carried out without an intervening cooling step.
  • compositions selected, the rapid solidification practice and the practice of rapid solidification and hot-working are controlled and carried out so that the microstructure of the resultant body consists essentially of the magnetic phase Re2TM14C x B 1-x together with a minor portion of intergranular material.
  • the hot-working aligns the fine platelet-like grains of the principal phase such that the c-axes of the grains are aligned and the resultant body is magnetically anisotropic.
  • the melt-spun (rapidly solidified) material is preferably amorphous or suitably extremely fine-grained such that the average grain size is no greater than about 40 nm. Following severe hot-working, flattened grains are obtained and it is preferred that, on the average, their greatest dimension be no greater than about 1000 nm.
  • the overall composition of the anisotropic magnets of the invention comprise on an atomic percent basis 50 to 90 percent iron, 6 to 20 percent neodymium and/or praseodymium, and 0.5 to 18 percent carbon or carbon and boron.
  • Neodymium and/or praseodymium contents of 13 to 17 atomic percent and a carbon content of 6 to 12 atomic percent are especially preferred.
  • RE is neodymium and/or praseodymium or mixtures of these rare earths with other rare earths provided that the other rare earths make up no more than about 40 percent of the total rare earth content
  • TM is iron or mixtures of iron with cobalt
  • x has a value in the range of 0.2 to 1.0.
  • Cobalt may make up about half of the TM content of the alloy.
  • the hot-worked, anisotropic magnets of the invention can be comminuted to an anisotropic magnetic powder for use in bonded magnets.
  • the pulverized powder is mixed with an epoxy resin or other suitable bonding material, magnetically aligned, and pressed or moulded. This resin is cured by heating, if appropriate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Power Engineering (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Hard Magnetic Materials (AREA)
EP91200208A 1990-02-20 1991-02-04 Aimants de terre rare-fer-carbone façonnés à chaud Withdrawn EP0443647A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US622690 1984-06-20
US48212490A 1990-02-20 1990-02-20
US07/622,690 US5085716A (en) 1990-02-20 1990-12-05 Hot worked rare earth-iron-carbon magnets
US482124 2000-01-11

Publications (1)

Publication Number Publication Date
EP0443647A1 true EP0443647A1 (fr) 1991-08-28

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EP (1) EP0443647A1 (fr)
JP (1) JPH05152119A (fr)
CA (1) CA2034632C (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0704264A1 (fr) * 1994-09-30 1996-04-03 Ykk Corporation Poudre très fine composite ainsi que sa préparation
US5803992A (en) * 1994-04-25 1998-09-08 Iowa State University Research Foundation, Inc. Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109695001B (zh) * 2017-10-20 2020-09-29 鞍钢股份有限公司 一种新型稀土热作模具钢及其制备方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0320063A1 (fr) * 1987-12-11 1989-06-14 Koninklijke Philips Electronics N.V. Matériau magnétique dur exempt de bore contenant une phase tétragonale magnétique

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0320063A1 (fr) * 1987-12-11 1989-06-14 Koninklijke Philips Electronics N.V. Matériau magnétique dur exempt de bore contenant une phase tétragonale magnétique

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF APPLIED PHYSICS. vol. 65, no. 2, 15 January 1989, NEW YORK US pages 704 - 709; R.Coehoorn et Al.: "Permanent magnetic materials based on Nd2Fe14C prepared by melt spinning" *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 2 (E-700)(3350) 06 January 1989, & JP-A-63 213315 (TDK CORP.) 06 September 1988, *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5803992A (en) * 1994-04-25 1998-09-08 Iowa State University Research Foundation, Inc. Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making
EP0704264A1 (fr) * 1994-09-30 1996-04-03 Ykk Corporation Poudre très fine composite ainsi que sa préparation

Also Published As

Publication number Publication date
JPH0584043B2 (fr) 1993-11-30
JPH05152119A (ja) 1993-06-18
CA2034632A1 (fr) 1991-08-21
CA2034632C (fr) 1997-05-13

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