CA1171306A - Magnetic elements for magnetically actuated devices and processes for their production - Google Patents
Magnetic elements for magnetically actuated devices and processes for their productionInfo
- Publication number
- CA1171306A CA1171306A CA000368776A CA368776A CA1171306A CA 1171306 A CA1171306 A CA 1171306A CA 000368776 A CA000368776 A CA 000368776A CA 368776 A CA368776 A CA 368776A CA 1171306 A CA1171306 A CA 1171306A
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Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/02—Contacts characterised by the material thereof
- H01H1/0201—Materials for reed contacts
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
- C21D8/1233—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
- C21D8/1266—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest between cold rolling steps
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
- C21D8/1272—Final recrystallisation annealing
Abstract
Abstract Magnetically actuated devices such as, e.g., switches and synchronizers typically comprise a magnetically semihard component having a square B-H hysteresis loop and high remanent induction. Among alloys having such properties are Co-Fe-V, Co-Fe-Nb, and Co-Fe-Ni-Al-Ti alloys which, however, contain undesirably large amounts of cobalt.
According to the invention, devices are equipped with a magnetically semihard, high-remanence Fe-Mn alloy which contains Mn in a preferred amounts in the range of 3-25 weight percent whose remanence Br (gauss) typically is greater than or equal to 20,000-500 ? (weight percent Mn), and whose squareness Br/Bs typically is greater than 0.95.
Magnets made from alloys of the invention may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.
Preparation of alloys of the invention may be by a treatment of initial deformation, aging, deformation, and final aging.
According to the invention, devices are equipped with a magnetically semihard, high-remanence Fe-Mn alloy which contains Mn in a preferred amounts in the range of 3-25 weight percent whose remanence Br (gauss) typically is greater than or equal to 20,000-500 ? (weight percent Mn), and whose squareness Br/Bs typically is greater than 0.95.
Magnets made from alloys of the invention may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.
Preparation of alloys of the invention may be by a treatment of initial deformation, aging, deformation, and final aging.
Description
3~
MAGNETIC ELEMENTS FOR MAGNETICALIY ACTUATED DEVICES
AND PROCFSSES FOR THEIR PRODUCTION
Technical Field The invention is concerned with magnetic elements for magnetically actuated devices and processes for their production.
~ackground of the Invention l~agnetically actuated devices may be designed for a variety of purposes sucll as, e.g., electrical switc~ing, position sensing, synchronization, flow measurement, and stirring. Particularly important among such devices are so-called reed switches as described, e.g., in the book by L. ~ osko~itz, _rrnanent Magnet Design and Application Handbook, Cahners Books, 1976, pp. 211-220, in U. S.
~atent 3,624,568, issued November 30, 1~71 to K. M. Olsen et al., and in the paper by ~. R. Pinnel, "Magnetic Materials for ~ry Reed Contacts", _EEE Trans. Mag., Vol. MAG-12, ~o. 6, November 1975, pp. 789-794. Reed switches comprise flexible metallic reeds which are made of a material having semihard magnetic properties as characterixed by an essentially square B-H hysteresis loop and high relDanent inductiorl Br; during operation reeds bend elastically so as to make or break electrical contact in response to changes in a rDagrletic field.
Among established alloys having semihard magnetic properties are Co-Ea-V alloys known as Vicalloy*and Remendur, Co-Ee-~b alloys known as Nibcolloy* and Co-E`e-i~ Ti alloys !inown as Vacozet. These alloy~
possess adequate magnetic properties; however, they contain su~stantial amounts of cobalt whose rising cost in world narkets causes concerrl. ~oreover, high cobalt alloys 1:end to be brittle, i.e., to lack sufficient cold formabili~y for shaping, e.g., by cold drawing, rolling, bendirlg, or flatterling.
*Trade Mark , .
:1 ~'7~
Relevant with respect to the invention are the book by M. Hansen, Constitution of Binary Alloys, 2nd edition, McGraw-Hill, 1958, pp. 664-667; the book by R.M.
Bozorth, Ferromagnetism, Van Nostrand, 1951, pp. 234-236 and pp. 418-419; the paper by M.J. Roberts, "Effect of TransEormation Substructure on the Strength and Toughness of Fe-Mn Alloys", Met. Trans., Vol. 1, December 1970, pp.
3287-3294, the paper by F.M. Walters, Jr., "Transformations and Heterogeneity in the Binary Alloys of Iron and Manganese", Trans. American Soc. for Steel Treating, Vol.
21, No. 10, 1933, pp. 1002-1015, and the paper by G.M.
Fedash, "Study of Coercivity of Cold-Worked and Annealed Iron Alloys", The Physics of Metals and Metallography, Vol. 4, No. 2, 1957, pp. 50-55. These references discuss phase transformations, mechanical properties, and coerciv-ity of iron-rich Fe-Mn alloys. Semihard magnetic proper-ties of Fe-Mn ternary and quaternary alloys are disclosed by W~ Jellinghaus, "Kaltverformter Manganstahl als neuer Magnetwerkstoff", Archiv fur das ~isenhuttenwesen, Vol. 15, ~0 No. 2, August 1941, pp. 99-102, by H. Kaneko et al., "Cold Worked Fe-Mn Semihard Magnet Alloy", Journal of the Japanese Institute of Metals, Vol 34, No. 4, 1970, pp.
441-445, and by K. Ogawa, "Semihard Magnetic Material of the ~e-Cu-Mn Systems", J. App. Phys., Vol. 44, No. 4, April 1973 pp. 1810-1812.
According to one aspect of the invention there is provided a magnetic element, especially applicable for use in magnetically actuated devices, which comprises a body of metallic alloy having a magnetic squareness ratio which is greater than 0.7 and a remanent magnetic induction which is greater than 7000 gauss (0.7T), and an amount of at least 98 weight percent of said alloy consisting of Fe and Mn, with Mn being in the range of 3-25 weight percent of said amount, characterized in that said alloy has an anisotropic two-phase or multiphase microstructure and an anisotropic ~;;
.r~
- 2a -grain structure, and, as a result of uniaxial deformation, the particle aspect ratio in said microstructure being equal to or greater than 8, and the magnetic squareness ratio of said alloy being equal to or greater than 0.95.
S According to the invention semihard magnetic properties are reali%ed in Fe-Mn alloys which preferably comprise Fe and Mn in a combined amount of at least 98 weight percent and Mn in an amount in the range of 3-25 weight percent of such combined amount. Remanent magnetic induction Br (gauss) of alloys of the invention is typically greater than or equal to a value of BR (gauss) =
20,000 ~ 500 x (weight percent Mn) {BR(Tesla)=[20,000 -500 x(wt. percent Mn)lxlO 4} and their squareness ratio Br/BS is greater than 0.7 and typically greater than or equal to 0.95.
, Alloys of the invention characteristically exhibit an anisotropic t~o-phase or m~lltiphase microstruc~ure, particles and grains being elongated to have preferred ~spect ratio o~ at least 8 and pre-ferably at least 30. Preferred particle diameter or thickness is less than 8000 Angstrom (800 Nanometers) and pre:Eerably less than 2000 Angstrom (200 Nc~nometers).
Magnets made from such alloys may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.
Preparation of alloys of the invention may be by a treatment of initial deformation, aging, deformation, and final aging. Aging steps are preferaoly carried out at temperatures at which an alloy is in a two-phase or m~ltiphas2 state. The second deformation step is preferably a step of uniaxial deformation.
Brief ~escription o~ the Drawing FI5. l shows phases as a function of temperature and manganese contents of Fe-Mn alloys;
FIG. 2 shows ma~netic properties of an Fe-8~n alloy as a function of a first aging temperature;
FIG. 3 shows magnetic properties of an Fe-8~n alloy as a function of cross-sectional area reduction by wire drawing;
~ FIG. 4 shows rnagnetic properties of an Ee-12~n alloy as a function of cross-sectional area reduction by wire drawing; and FIG. 5 shows a reed switch assembly comprising Ye-~n reeds.
Detailed Description In accordance with the invention, it has been realized that Fe-Mn alloys which preferably comprise Fe and Mn in a combined amount of at least 98 weight percent ; 35 and Mn in an amount in the range of 3-25 weight percent of such combined amount, can be produced to have desirable sernihard ~agnet properties. Such semihard magnet ,, ~
properties are conveniently defined by remanent magnetic induction Br greater than 7000 gauss (0.7T) and squareness ratio Br/Bs greater than 0.7. Alloys having such properties are suited for use in magnetically actuated devices which may be conveniently characterized in that tlley comprise a component whose position is dependent on strength, direction, or presence of a magnetic field and further in that they comprise means sucl~ as, e.g., an electrical contact for sensing the position of such component. Alloys of the invention may comprise small amoun~s of additives such as, e.g., Cr for the sake of enhanced corrosion resistance, or Co for the sake of enharlced magnetic properties; however, excessive aMounts of Cr may be detrimental to maanetic properties. Other elements such as, e.g., iii, Si, Al, Cu, Mo, V, Ti, Nb, Zr, ra, ~f, and W may be present as impurities in individual amounts preferably less than 0.2 weight percent and in a combined atnount preferably less than 1 weigllt percent~
Similarly, elements C, N, S, P, B, ~, and O are preferably kept below 0.1 weight percent individually and below 0.5 weight percent in combination. ~inimization of impurities is in the interest of maintaining alloy formability for development of anisotropic structure as well as for shaping into desired form. Excessive a~nounts of elements mentioned may also lead to inferior magnetic pro3!erties.
Magnetic alloys of the invention possess anisotropic multiphase grain and rnicrostructure in which particles and grains have a preferred aspect ratio of at 3~ least 8 and preferably at least 3Q. As~ect ratio may conveniently be defined as length-to-diameter ratio when deformation is uniaxial such as, e.g., by wire dra~ing, and as lengtll-to-thickness ratio when defor~nation is planar such as, e.g., by rolling. Preferred ~article size is less 3S than 8000 Angstrom (800 Nanometers) and preferably less than 2000 Angstrom (200 Nanometers). Submicron structure may be con-veniently determined, e.g., by electron microscopy.
~' , :~ ~ '7~ 3~
~ emanent magnetic induction Br of alloys of the invention is approximately linearly dependent on Mn content of alloys. Specifically, remanent magnetic incluction Br of al]oys of the invention equals ~r exceeds a valuel~hich may be expressed ~y the approximate ~ormula Br~gauss) = 20,000 - 500 x t~eight percent Mn) {Br~Tesla)-[20,000 - 500 x (~t. percent Mn)] x 10 ~}. Squareness ratio Br/BS of alloys of the invention is typically greater than or equal to 0.95 and magnetic coercivity is in the range of from 1 to 500 oersted (-~rom 79.6 to 39.7~9 ~eres per meter).
Alloys of the invention may be prepared, e.g., by casting from a melt of constituent elements Fe and Mn in a crucible or furnace such as, e.g., an induction furnace;
alternatively, a metallic body having a composition within the specified range may be prepared by powder metallurgy.
Preparation oE an alloy and, in particular, preparation by casting from a melt calls for care to guard against inclusion of excessive amounts of impurities as may originate from raw materials, from the furnace, or from the atmosphere above the melt. To minimiæe oxidation or excessive inclusion of nitrogen, it is desirable to prepare a melt with slag protection, in a vacuum, or in an inert atmosphere .
Cast ingots of an alloy of the invention may typically be processed by hot working, cold working, and solution annealing for purposes such as homogenization, grain refining, shaping, or the development of desirable mechanical properties.
Processing to achieve desirable anisotropic structure such as elongated grains and crystallographic texture may be carried out by various combinations of sequential processing steps. A particularly effective exemplary processing sequence may be speciEied by reference to FIG. 1 and comprises processing at temperatures corresponding to a two-phase region in the phase diagram by (1) initial plastic deformation, t2) initial aging, resulting in essentially two-phase decomposition, (3) plastic deformation, and (4) final aging.
-~'7~ 3 Initial plastic deformation preferably is by an amount corresponding to at least 50 percent area reduction and may be at temperatures in the range of from -196 degrees C (the temperature of liquid nitrogen) to 600 degrees C. Such deformation may se~ve several purposes and, in particular, it may help in transforming undesirable nollmagnetic gamma or epsilon phases to a magnetic alpha-prime phase especially for high Mn alloys. Also, initial plastic deformation may enhance the kinetics o initial two-phase alpha-plus-gamrna decomposition and help to produce uniform, fine scale, isotropic two-phase structure.
At this pOi]lt, particle size may typically be in the neighbor-hood o~`3j000 to 10,000 Angstrom (300-1000 Nanometers). Initial deformation may be uniaxial as, e.g., by rod rolling, extrusion, wire drawing, or swaging; alternatively, deformation may be by methods such as, e.g., cross rolling or cold rollinq. If deformation is carried out at a temperature above room temperature, the alloy may subsequently be air cooled or water quenched.
Heat treatment after initial deformation is preferably effected at ternperatures corresponding to an alpha-plus-gamma two-phase state of the alloy.
Particularly suited, according to ~IG. 2, are temperatures in the general range of 400-600 degrees C. Duration of such heat treatment is preferably at least 30 minutes.
Subsequent cooling to a temperature near or below room temperature l~ay result in transformation of gamma phase - partially or totally to alpha prime phase or epsilon phase.
Isotropic grains and fine scale structure -produced upon two-phase decomposition are subsequently deformed, preferably uniaxially such as, e.g., by wire drawing, rod drawing, s~"aging, or extruding. As compared with swaging, wire drawing was found to result in superior magnetic l~roperties. Planar deformation such as, e.g., by rollin~ is not precluded. Deformation may be effected at room temperature or at any temperature in the range from -196 to 600 degrees C. Preferred amounts oE deforsnation 1'7~3~
correspond to an area reduction of at least 80 percent and preferably at least 95 percent, ductility adequate for such deformation being assured by liMiting ~he presence of impurities and, in particular, of elements of groups 4b and 5b of the periodic table, such as Ti, Zr, Hf, V, ~b, and Ta. A~ter de~o~natlon, saturation magnetization Ps of the alloy is typically greater than or equal to a value o~ Bs(gauss) = 20,000 -500 x (weight percent~) {Bs (Tesl~) = [ 20,000 - 500 x ~eight percent Mn)] x 10 4}.
Ultimate magnetic properties improve as the amount of deformation is increased; this is illustrated in FIG. 3 for an Fe-Mn alloy comprising 8 weight percent Mn and in FIG. ~ for an Fe-Mn alloy comprising 12 weight percent Mn. Calculated aspect ratio shown in r'IG. 3 and 4 is defined as grain length divided by grain di~meter.
Alloys of the invention remain hi<7hly ductile evan after severe deformation such as, e.g., by cold wire drawing resulting in 95 percent area reduction. Such deformed alloys may be Eurther shaped, e.g., by bending or flattening without risk of splitting or cracking. Bending may produce a change of direction of up to 30 degrees with bend radius equal to or greater than thickness. For bending through larger angles, safe bend radius may increase linearly to a value of 4 times thickness for a change of direction of 90 degrees. Flattening may produce a change of ~idth-to-thickness ratio of at least a factor of 2.
Higll formability in the wire-drawn state is of particular advantaye in the manufacture of devices such as reed switciies exemplified in PI~. 5 which shows reeds l and 2 made of an Fe-Mn alloy and e~tending through glass encapsulation 3 which is inside magnetic coils 4 and 5.
Formability is enhanced by minimization of the presence of impurities and, in particular, of elements of groups 4b and 5b of the periodic table such as Ti, Zr, Hf, V, ~b and 'l'a.
- After plastic deformation of a multi2hase structure, a final low temperature aging heat treatment within an alpha-plus-gamma two-phase region is given.
Typical agin~ temperatures are in the range of 350-500 degrees C depending on ~In contents, and aging time is preferably in the ranye of from 10 minutes to 4 hours.
E`inal aging enhances squareness Br/BS of the B-H loop as may be attributed to one or several of metallurgical effects such as, e.g, relief of internal stress caused by deforlnation. Squareness may also be enhanced by partial or total reverse martensitic transformation of an Mn-rich phase which was formed during initial isothermal decomposition in an alpha-plus-gamma region and which subsequently was transformed partially or fully to magnetic lS alpha-prime phase in the course of final deformation.
Eurthermore, enhanced squareness may be due to the presence of nonmagnetic or weakly magnetic gamma or epsilon phases that may serve as a desirable barrier for the demagnetization process, or to formation of a thin layer of nonmagnetic or weakly magnetic gamma phase having higher ~n content along the grain boundaries of the elongated two-phase structure. Rate of cooling to room temperature after annealing or aging heat treatments is not critical;
either air cooling or water quenching may be used.
~mong benefits of Fe-Mn semihard alloys according to the invention are the following: tl) high magne-tic squareness as is desirable in switching and other magnetically actuated devices, (2) abundance and low cost of constituent elements Fe and l~nl (3) ease of processing and forming due to high formability, (4) low magnetostriction as may be specified by a saturation magnetostriction coefficient not exceeding 5xlO-~ and preferably not exceeding 2xl~ 5 as may be desirable, e.g., to prevent sticking of reed contacts, (5~ simplicity of binary composition resulting in ease of meeting magnet tolerances such as, e.g., nominal coercivityJ and (6) ease of plating with contact metal such as gold.
.
13~
iYagnetic properties realized in the .ollowing alloys of the invention are showil in Table I.
~xample 1. An Fe-3Mn alloy was hot rolled, cold rolled, cold shaped into a 0.21 inch ~0.53 cm.) diameter rod, annealed at 900 degrees C for 1 hour, and air cooled~ The sample was cold worked (90 ~ercent area recluction) into 0.067 inch (0.17 cm.) diameter wire and given an initial aging treatment at 500 degrees C for 3.5 hours resulting in two-phase alpha-plus-gamma decomposition and recrystallization. The decomposed isotropic grain size was uniformly fine and average grain size was smaller than 1 micrometer in diameter. The sample was then drawn (95 percent area reduction) to 15 mil (0.038 crn.) diarneter wire~ was given a final aging heat treatment at 450 degrees C for 3 hours, and was air cooled. Magnet-ostriction of this sample was determined to be approximately 1.3 x 10-6.
Example 2. A 0.067 inch (0.17 crn.) diameter wire s~nple of ~e-3Mn alloy was prepared and cold worked as in Example 1, given an initial aging heat treatment at 550 degrees C for 3.5 hours resultiny in alpha-plus-garnma two-phase decornposition, wire drawn (95 percent area reduction), given a final aging heat treatment at 400 degrees C for 40 minutes, and air cooled.
Example 3. ~n Fe-7.5Mn alloy sample was prepared and processed as in Exarmple 1.
Example 4. An Fe~12Mn alloy sample was hot rolled, cold rolled, cold shaped into 0.210 inch (0.53 crn.) diarneter rod, annealed at 930 degrees C for 1 hour~ and water cooled. The sample was further cold drawn (90 uercent area reduction) into 0.067 inch ~0.-17 cm.) diameter wire and w~s given an ir~itial a~ing heat treatrnent at 550 degrees C for 3.5 hours causing two-phase alpha-plus-gamr,la decomposition and recrystallization. The isotropically grained, suhmicron fine two-phase ~tructure was then drawn (95 percent area reduction) to 15 mil (0.038 cm.) diarneter wire, was givén a final aging heat treatmen~ at 450 de~rees C for 40 minutes, and was air cooled.
Example 5. An Fe-12Mn alloy sample was prepared as in Example 4, except that final aging was at 400 degrees C for 40 minutes.
Example 6. An Fe-12Mn alloy sample was prepared as in Example 4, except that i~itial aging was performed at 500 degrees C for 3.5 hours and final aging at 450 degrees C for 10 minutes. ~lagnetic energy product of this sample was determined to be approximately 0.96 MGOe.
Example 7. An Fe-12Mn alloy sample was prepared as in Example 4, except tnat initial aging was conducted at 450 degrees C for 16 hours and final aging at 450 degrees C
for 40 minutes. ~agnetic energy product of this sample was determined to be approximately 1.05 MGOe.
Example 8. An Fe-12Mn alloy sample was prepared as in Example 7, except that the amount of final wire drawing resulted in 90 percent area reduction.
Table I. ~aynet_ Properties of Square-Loop,_ ~ligh ~emanence, Fe-Mn Semiha_d Magnet Alloys.
Example Br Br/BS Hc (gauss) (oersted) ; 20 1 17200 0.94 28
MAGNETIC ELEMENTS FOR MAGNETICALIY ACTUATED DEVICES
AND PROCFSSES FOR THEIR PRODUCTION
Technical Field The invention is concerned with magnetic elements for magnetically actuated devices and processes for their production.
~ackground of the Invention l~agnetically actuated devices may be designed for a variety of purposes sucll as, e.g., electrical switc~ing, position sensing, synchronization, flow measurement, and stirring. Particularly important among such devices are so-called reed switches as described, e.g., in the book by L. ~ osko~itz, _rrnanent Magnet Design and Application Handbook, Cahners Books, 1976, pp. 211-220, in U. S.
~atent 3,624,568, issued November 30, 1~71 to K. M. Olsen et al., and in the paper by ~. R. Pinnel, "Magnetic Materials for ~ry Reed Contacts", _EEE Trans. Mag., Vol. MAG-12, ~o. 6, November 1975, pp. 789-794. Reed switches comprise flexible metallic reeds which are made of a material having semihard magnetic properties as characterixed by an essentially square B-H hysteresis loop and high relDanent inductiorl Br; during operation reeds bend elastically so as to make or break electrical contact in response to changes in a rDagrletic field.
Among established alloys having semihard magnetic properties are Co-Ea-V alloys known as Vicalloy*and Remendur, Co-Ee-~b alloys known as Nibcolloy* and Co-E`e-i~ Ti alloys !inown as Vacozet. These alloy~
possess adequate magnetic properties; however, they contain su~stantial amounts of cobalt whose rising cost in world narkets causes concerrl. ~oreover, high cobalt alloys 1:end to be brittle, i.e., to lack sufficient cold formabili~y for shaping, e.g., by cold drawing, rolling, bendirlg, or flatterling.
*Trade Mark , .
:1 ~'7~
Relevant with respect to the invention are the book by M. Hansen, Constitution of Binary Alloys, 2nd edition, McGraw-Hill, 1958, pp. 664-667; the book by R.M.
Bozorth, Ferromagnetism, Van Nostrand, 1951, pp. 234-236 and pp. 418-419; the paper by M.J. Roberts, "Effect of TransEormation Substructure on the Strength and Toughness of Fe-Mn Alloys", Met. Trans., Vol. 1, December 1970, pp.
3287-3294, the paper by F.M. Walters, Jr., "Transformations and Heterogeneity in the Binary Alloys of Iron and Manganese", Trans. American Soc. for Steel Treating, Vol.
21, No. 10, 1933, pp. 1002-1015, and the paper by G.M.
Fedash, "Study of Coercivity of Cold-Worked and Annealed Iron Alloys", The Physics of Metals and Metallography, Vol. 4, No. 2, 1957, pp. 50-55. These references discuss phase transformations, mechanical properties, and coerciv-ity of iron-rich Fe-Mn alloys. Semihard magnetic proper-ties of Fe-Mn ternary and quaternary alloys are disclosed by W~ Jellinghaus, "Kaltverformter Manganstahl als neuer Magnetwerkstoff", Archiv fur das ~isenhuttenwesen, Vol. 15, ~0 No. 2, August 1941, pp. 99-102, by H. Kaneko et al., "Cold Worked Fe-Mn Semihard Magnet Alloy", Journal of the Japanese Institute of Metals, Vol 34, No. 4, 1970, pp.
441-445, and by K. Ogawa, "Semihard Magnetic Material of the ~e-Cu-Mn Systems", J. App. Phys., Vol. 44, No. 4, April 1973 pp. 1810-1812.
According to one aspect of the invention there is provided a magnetic element, especially applicable for use in magnetically actuated devices, which comprises a body of metallic alloy having a magnetic squareness ratio which is greater than 0.7 and a remanent magnetic induction which is greater than 7000 gauss (0.7T), and an amount of at least 98 weight percent of said alloy consisting of Fe and Mn, with Mn being in the range of 3-25 weight percent of said amount, characterized in that said alloy has an anisotropic two-phase or multiphase microstructure and an anisotropic ~;;
.r~
- 2a -grain structure, and, as a result of uniaxial deformation, the particle aspect ratio in said microstructure being equal to or greater than 8, and the magnetic squareness ratio of said alloy being equal to or greater than 0.95.
S According to the invention semihard magnetic properties are reali%ed in Fe-Mn alloys which preferably comprise Fe and Mn in a combined amount of at least 98 weight percent and Mn in an amount in the range of 3-25 weight percent of such combined amount. Remanent magnetic induction Br (gauss) of alloys of the invention is typically greater than or equal to a value of BR (gauss) =
20,000 ~ 500 x (weight percent Mn) {BR(Tesla)=[20,000 -500 x(wt. percent Mn)lxlO 4} and their squareness ratio Br/BS is greater than 0.7 and typically greater than or equal to 0.95.
, Alloys of the invention characteristically exhibit an anisotropic t~o-phase or m~lltiphase microstruc~ure, particles and grains being elongated to have preferred ~spect ratio o~ at least 8 and pre-ferably at least 30. Preferred particle diameter or thickness is less than 8000 Angstrom (800 Nanometers) and pre:Eerably less than 2000 Angstrom (200 Nc~nometers).
Magnets made from such alloys may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.
Preparation of alloys of the invention may be by a treatment of initial deformation, aging, deformation, and final aging. Aging steps are preferaoly carried out at temperatures at which an alloy is in a two-phase or m~ltiphas2 state. The second deformation step is preferably a step of uniaxial deformation.
Brief ~escription o~ the Drawing FI5. l shows phases as a function of temperature and manganese contents of Fe-Mn alloys;
FIG. 2 shows ma~netic properties of an Fe-8~n alloy as a function of a first aging temperature;
FIG. 3 shows magnetic properties of an Fe-8~n alloy as a function of cross-sectional area reduction by wire drawing;
~ FIG. 4 shows rnagnetic properties of an Ee-12~n alloy as a function of cross-sectional area reduction by wire drawing; and FIG. 5 shows a reed switch assembly comprising Ye-~n reeds.
Detailed Description In accordance with the invention, it has been realized that Fe-Mn alloys which preferably comprise Fe and Mn in a combined amount of at least 98 weight percent ; 35 and Mn in an amount in the range of 3-25 weight percent of such combined amount, can be produced to have desirable sernihard ~agnet properties. Such semihard magnet ,, ~
properties are conveniently defined by remanent magnetic induction Br greater than 7000 gauss (0.7T) and squareness ratio Br/Bs greater than 0.7. Alloys having such properties are suited for use in magnetically actuated devices which may be conveniently characterized in that tlley comprise a component whose position is dependent on strength, direction, or presence of a magnetic field and further in that they comprise means sucl~ as, e.g., an electrical contact for sensing the position of such component. Alloys of the invention may comprise small amoun~s of additives such as, e.g., Cr for the sake of enhanced corrosion resistance, or Co for the sake of enharlced magnetic properties; however, excessive aMounts of Cr may be detrimental to maanetic properties. Other elements such as, e.g., iii, Si, Al, Cu, Mo, V, Ti, Nb, Zr, ra, ~f, and W may be present as impurities in individual amounts preferably less than 0.2 weight percent and in a combined atnount preferably less than 1 weigllt percent~
Similarly, elements C, N, S, P, B, ~, and O are preferably kept below 0.1 weight percent individually and below 0.5 weight percent in combination. ~inimization of impurities is in the interest of maintaining alloy formability for development of anisotropic structure as well as for shaping into desired form. Excessive a~nounts of elements mentioned may also lead to inferior magnetic pro3!erties.
Magnetic alloys of the invention possess anisotropic multiphase grain and rnicrostructure in which particles and grains have a preferred aspect ratio of at 3~ least 8 and preferably at least 3Q. As~ect ratio may conveniently be defined as length-to-diameter ratio when deformation is uniaxial such as, e.g., by wire dra~ing, and as lengtll-to-thickness ratio when defor~nation is planar such as, e.g., by rolling. Preferred ~article size is less 3S than 8000 Angstrom (800 Nanometers) and preferably less than 2000 Angstrom (200 Nanometers). Submicron structure may be con-veniently determined, e.g., by electron microscopy.
~' , :~ ~ '7~ 3~
~ emanent magnetic induction Br of alloys of the invention is approximately linearly dependent on Mn content of alloys. Specifically, remanent magnetic incluction Br of al]oys of the invention equals ~r exceeds a valuel~hich may be expressed ~y the approximate ~ormula Br~gauss) = 20,000 - 500 x t~eight percent Mn) {Br~Tesla)-[20,000 - 500 x (~t. percent Mn)] x 10 ~}. Squareness ratio Br/BS of alloys of the invention is typically greater than or equal to 0.95 and magnetic coercivity is in the range of from 1 to 500 oersted (-~rom 79.6 to 39.7~9 ~eres per meter).
Alloys of the invention may be prepared, e.g., by casting from a melt of constituent elements Fe and Mn in a crucible or furnace such as, e.g., an induction furnace;
alternatively, a metallic body having a composition within the specified range may be prepared by powder metallurgy.
Preparation oE an alloy and, in particular, preparation by casting from a melt calls for care to guard against inclusion of excessive amounts of impurities as may originate from raw materials, from the furnace, or from the atmosphere above the melt. To minimiæe oxidation or excessive inclusion of nitrogen, it is desirable to prepare a melt with slag protection, in a vacuum, or in an inert atmosphere .
Cast ingots of an alloy of the invention may typically be processed by hot working, cold working, and solution annealing for purposes such as homogenization, grain refining, shaping, or the development of desirable mechanical properties.
Processing to achieve desirable anisotropic structure such as elongated grains and crystallographic texture may be carried out by various combinations of sequential processing steps. A particularly effective exemplary processing sequence may be speciEied by reference to FIG. 1 and comprises processing at temperatures corresponding to a two-phase region in the phase diagram by (1) initial plastic deformation, t2) initial aging, resulting in essentially two-phase decomposition, (3) plastic deformation, and (4) final aging.
-~'7~ 3 Initial plastic deformation preferably is by an amount corresponding to at least 50 percent area reduction and may be at temperatures in the range of from -196 degrees C (the temperature of liquid nitrogen) to 600 degrees C. Such deformation may se~ve several purposes and, in particular, it may help in transforming undesirable nollmagnetic gamma or epsilon phases to a magnetic alpha-prime phase especially for high Mn alloys. Also, initial plastic deformation may enhance the kinetics o initial two-phase alpha-plus-gamrna decomposition and help to produce uniform, fine scale, isotropic two-phase structure.
At this pOi]lt, particle size may typically be in the neighbor-hood o~`3j000 to 10,000 Angstrom (300-1000 Nanometers). Initial deformation may be uniaxial as, e.g., by rod rolling, extrusion, wire drawing, or swaging; alternatively, deformation may be by methods such as, e.g., cross rolling or cold rollinq. If deformation is carried out at a temperature above room temperature, the alloy may subsequently be air cooled or water quenched.
Heat treatment after initial deformation is preferably effected at ternperatures corresponding to an alpha-plus-gamma two-phase state of the alloy.
Particularly suited, according to ~IG. 2, are temperatures in the general range of 400-600 degrees C. Duration of such heat treatment is preferably at least 30 minutes.
Subsequent cooling to a temperature near or below room temperature l~ay result in transformation of gamma phase - partially or totally to alpha prime phase or epsilon phase.
Isotropic grains and fine scale structure -produced upon two-phase decomposition are subsequently deformed, preferably uniaxially such as, e.g., by wire drawing, rod drawing, s~"aging, or extruding. As compared with swaging, wire drawing was found to result in superior magnetic l~roperties. Planar deformation such as, e.g., by rollin~ is not precluded. Deformation may be effected at room temperature or at any temperature in the range from -196 to 600 degrees C. Preferred amounts oE deforsnation 1'7~3~
correspond to an area reduction of at least 80 percent and preferably at least 95 percent, ductility adequate for such deformation being assured by liMiting ~he presence of impurities and, in particular, of elements of groups 4b and 5b of the periodic table, such as Ti, Zr, Hf, V, ~b, and Ta. A~ter de~o~natlon, saturation magnetization Ps of the alloy is typically greater than or equal to a value o~ Bs(gauss) = 20,000 -500 x (weight percent~) {Bs (Tesl~) = [ 20,000 - 500 x ~eight percent Mn)] x 10 4}.
Ultimate magnetic properties improve as the amount of deformation is increased; this is illustrated in FIG. 3 for an Fe-Mn alloy comprising 8 weight percent Mn and in FIG. ~ for an Fe-Mn alloy comprising 12 weight percent Mn. Calculated aspect ratio shown in r'IG. 3 and 4 is defined as grain length divided by grain di~meter.
Alloys of the invention remain hi<7hly ductile evan after severe deformation such as, e.g., by cold wire drawing resulting in 95 percent area reduction. Such deformed alloys may be Eurther shaped, e.g., by bending or flattening without risk of splitting or cracking. Bending may produce a change of direction of up to 30 degrees with bend radius equal to or greater than thickness. For bending through larger angles, safe bend radius may increase linearly to a value of 4 times thickness for a change of direction of 90 degrees. Flattening may produce a change of ~idth-to-thickness ratio of at least a factor of 2.
Higll formability in the wire-drawn state is of particular advantaye in the manufacture of devices such as reed switciies exemplified in PI~. 5 which shows reeds l and 2 made of an Fe-Mn alloy and e~tending through glass encapsulation 3 which is inside magnetic coils 4 and 5.
Formability is enhanced by minimization of the presence of impurities and, in particular, of elements of groups 4b and 5b of the periodic table such as Ti, Zr, Hf, V, ~b and 'l'a.
- After plastic deformation of a multi2hase structure, a final low temperature aging heat treatment within an alpha-plus-gamma two-phase region is given.
Typical agin~ temperatures are in the range of 350-500 degrees C depending on ~In contents, and aging time is preferably in the ranye of from 10 minutes to 4 hours.
E`inal aging enhances squareness Br/BS of the B-H loop as may be attributed to one or several of metallurgical effects such as, e.g, relief of internal stress caused by deforlnation. Squareness may also be enhanced by partial or total reverse martensitic transformation of an Mn-rich phase which was formed during initial isothermal decomposition in an alpha-plus-gamma region and which subsequently was transformed partially or fully to magnetic lS alpha-prime phase in the course of final deformation.
Eurthermore, enhanced squareness may be due to the presence of nonmagnetic or weakly magnetic gamma or epsilon phases that may serve as a desirable barrier for the demagnetization process, or to formation of a thin layer of nonmagnetic or weakly magnetic gamma phase having higher ~n content along the grain boundaries of the elongated two-phase structure. Rate of cooling to room temperature after annealing or aging heat treatments is not critical;
either air cooling or water quenching may be used.
~mong benefits of Fe-Mn semihard alloys according to the invention are the following: tl) high magne-tic squareness as is desirable in switching and other magnetically actuated devices, (2) abundance and low cost of constituent elements Fe and l~nl (3) ease of processing and forming due to high formability, (4) low magnetostriction as may be specified by a saturation magnetostriction coefficient not exceeding 5xlO-~ and preferably not exceeding 2xl~ 5 as may be desirable, e.g., to prevent sticking of reed contacts, (5~ simplicity of binary composition resulting in ease of meeting magnet tolerances such as, e.g., nominal coercivityJ and (6) ease of plating with contact metal such as gold.
.
13~
iYagnetic properties realized in the .ollowing alloys of the invention are showil in Table I.
~xample 1. An Fe-3Mn alloy was hot rolled, cold rolled, cold shaped into a 0.21 inch ~0.53 cm.) diameter rod, annealed at 900 degrees C for 1 hour, and air cooled~ The sample was cold worked (90 ~ercent area recluction) into 0.067 inch (0.17 cm.) diameter wire and given an initial aging treatment at 500 degrees C for 3.5 hours resulting in two-phase alpha-plus-gamma decomposition and recrystallization. The decomposed isotropic grain size was uniformly fine and average grain size was smaller than 1 micrometer in diameter. The sample was then drawn (95 percent area reduction) to 15 mil (0.038 crn.) diarneter wire~ was given a final aging heat treatment at 450 degrees C for 3 hours, and was air cooled. Magnet-ostriction of this sample was determined to be approximately 1.3 x 10-6.
Example 2. A 0.067 inch (0.17 crn.) diameter wire s~nple of ~e-3Mn alloy was prepared and cold worked as in Example 1, given an initial aging heat treatment at 550 degrees C for 3.5 hours resultiny in alpha-plus-garnma two-phase decornposition, wire drawn (95 percent area reduction), given a final aging heat treatment at 400 degrees C for 40 minutes, and air cooled.
Example 3. ~n Fe-7.5Mn alloy sample was prepared and processed as in Exarmple 1.
Example 4. An Fe~12Mn alloy sample was hot rolled, cold rolled, cold shaped into 0.210 inch (0.53 crn.) diarneter rod, annealed at 930 degrees C for 1 hour~ and water cooled. The sample was further cold drawn (90 uercent area reduction) into 0.067 inch ~0.-17 cm.) diameter wire and w~s given an ir~itial a~ing heat treatrnent at 550 degrees C for 3.5 hours causing two-phase alpha-plus-gamr,la decomposition and recrystallization. The isotropically grained, suhmicron fine two-phase ~tructure was then drawn (95 percent area reduction) to 15 mil (0.038 cm.) diarneter wire, was givén a final aging heat treatmen~ at 450 de~rees C for 40 minutes, and was air cooled.
Example 5. An Fe-12Mn alloy sample was prepared as in Example 4, except that final aging was at 400 degrees C for 40 minutes.
Example 6. An Fe-12Mn alloy sample was prepared as in Example 4, except that i~itial aging was performed at 500 degrees C for 3.5 hours and final aging at 450 degrees C for 10 minutes. ~lagnetic energy product of this sample was determined to be approximately 0.96 MGOe.
Example 7. An Fe-12Mn alloy sample was prepared as in Example 4, except tnat initial aging was conducted at 450 degrees C for 16 hours and final aging at 450 degrees C
for 40 minutes. ~agnetic energy product of this sample was determined to be approximately 1.05 MGOe.
Example 8. An Fe-12Mn alloy sample was prepared as in Example 7, except that the amount of final wire drawing resulted in 90 percent area reduction.
Table I. ~aynet_ Properties of Square-Loop,_ ~ligh ~emanence, Fe-Mn Semiha_d Magnet Alloys.
Example Br Br/BS Hc (gauss) (oersted) ; 20 1 17200 0.94 28
2 17300 0.90 26
3 18100 0.96 25
4 15200 0.997 67 15700 0.968 53 6 15400 0~992 87 7 15300 0.989 85 ~ 15800 0.95~ 60 ,,
Claims (16)
1. A magnetic element, especially applicable for use in magnetically actuated devices, which comprises a body of metallic alloy having a magnetic squareness ratio which is greater than 0.7 and a remanent magnetic induction which is greater than 7000 gauss (0.7T), and an amount of at least 98 weight percent of said alloy consisting of Fe and Mn, with Mn being in the range of 3-25 weight percent of said amount, characterized in that said alloy has an anisotropic two-phase or multiphase microstructure and an anisotropic grain structure, and, as a result of uniaxial deformation, the particle aspect ratio in said microstructure being equal to or greater than 8, and the magnetic squareness ratio of said alloy being equal to or greater than 0.95.
2. An element according to claim 1, wherein said alloy has a microstructure in which the particle diameter is less than 8000 Angstrom (800 nanometers).
3. An element according to claim 1, wherein said alloy has a magnetostriction coefficient less than or equal to 5x10-6.
4. An element according to claim 1, wherein said alloy has a particle aspect ratio equal to or greater than 30.
5. An element according to claim 1, wherein said alloy has a microstructure in which the particle diameter is less than 2000 Angstrom (200 nanometers).
6. An element according to claim 1, wherein the alloy has a magnetostriction coefficient of less than or equal to 2x10
7. An element according to claim 1, wherein at least 99 weight percent of said alloy consists of Fe and Mn.
8. An element according to claim 1, wherein said alloy has a remanent magnetic induction Br greater than or equal to a value which depends on the weight percent Mn comprised in said amount, said value being defined by the approximate formula Br (gauss) = 20,000 - 500 x (weight percent Mn) (Br (Tesla) = [20,000 - 500 x (wt. percent Mn)] x 10 }.
9. An element according to claim 1 wherein the presence in the alloy of any one of first elements Ni, Si, Al, Cu, Mo, V, Ti, Nb, Zr, Ta, Hf and W is restricted to less than 0.2 weight percent individually and to less than a total of 1.0 weight percent of any combination of five or more of these elements, and the presence of any one of second elements, Cn, N, S, P, B, H and O is restricted to less than 0.1 weight percent individually and to less than a total of 0.5 weight percent of any combination of five or more of the second elements.
10. An element according to claim 1 wherein at least a portion of the surface of said body is gold plated.
11. A method for making a magnetic element comprising a body of a metallic alloy having a magnetic squareness ratio which is greater than 0.7 and having a remanent magnetic induction which is greater than 7000 gauss (0.7 Tesla), which comprises:
the steps of (1) preparing a body consisting essentially of an alloy comprising an amount of at least 98 weight percent Fe and Mn, with Mn being in the range of 3-25 weight percent of said amount, (2) plastically deform-ing said body at a temperature in the range of -196 to 600 degrees C, by an amount corresponding to an area reduction which is greater than or equal to 50 percent, and (3) aging said body at a temperature corresponding to an essentially two-phase state of said alloy, characterized by additionally (4) plastically deforming uniaxially said body at a temperature in the range of -196 to 600 degrees C
by an amount corresponding to an area reduction which is greater than or equal to 80 percent, and (5) aging said body at a temperature corresponding to an essentially two-phase state of said alloy.
the steps of (1) preparing a body consisting essentially of an alloy comprising an amount of at least 98 weight percent Fe and Mn, with Mn being in the range of 3-25 weight percent of said amount, (2) plastically deform-ing said body at a temperature in the range of -196 to 600 degrees C, by an amount corresponding to an area reduction which is greater than or equal to 50 percent, and (3) aging said body at a temperature corresponding to an essentially two-phase state of said alloy, characterized by additionally (4) plastically deforming uniaxially said body at a temperature in the range of -196 to 600 degrees C
by an amount corresponding to an area reduction which is greater than or equal to 80 percent, and (5) aging said body at a temperature corresponding to an essentially two-phase state of said alloy.
12. Method according to claim 11, which comprises:
effecting step (4) by plastically deforming uniaxially by an amount corresponding to at least 95 percent area reduction.
effecting step (4) by plastically deforming uniaxially by an amount corresponding to at least 95 percent area reduction.
13. Method according to claim 11 which comprises;
effecting step (5) by aging at a temperature in the range of 350 to 500 degrees C for a time of at least 10 minutes.
effecting step (5) by aging at a temperature in the range of 350 to 500 degrees C for a time of at least 10 minutes.
14. Method according to claim 11 which comprises:
effecting step (2) by plastically deforming at a temperature which is higher than room temperature, followed by a cooling said body.
effecting step (2) by plastically deforming at a temperature which is higher than room temperature, followed by a cooling said body.
150 Method according to claim 11 which comprises:
effecting step (3) by aging at a temperature in the range of 400 to 600 degrees C for a duration of at least 30 minutes.
effecting step (3) by aging at a temperature in the range of 400 to 600 degrees C for a duration of at least 30 minutes.
16. Method according to claim 11 which comprises:
restricting the presence in the alloy of any one of first elements Ni, Si, Al, Cu, Mo, V, Ti, Nb, Zr, Ta, Hf and W to less than 0.2 weight percent individually and to less than a total of 1.0 weight percent of any combination of five or more of these elements, and the presence of any one of second elements C, N, S, P, B, H and O to less than 0.1 weight percent individually and to less than a total of 0.5 weight percent of any combination of five or more of the second elements.
restricting the presence in the alloy of any one of first elements Ni, Si, Al, Cu, Mo, V, Ti, Nb, Zr, Ta, Hf and W to less than 0.2 weight percent individually and to less than a total of 1.0 weight percent of any combination of five or more of these elements, and the presence of any one of second elements C, N, S, P, B, H and O to less than 0.1 weight percent individually and to less than a total of 0.5 weight percent of any combination of five or more of the second elements.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11675980A | 1980-01-30 | 1980-01-30 | |
| US116,759 | 1980-01-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171306A true CA1171306A (en) | 1984-07-24 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368776A Expired CA1171306A (en) | 1980-01-30 | 1981-01-19 | Magnetic elements for magnetically actuated devices and processes for their production |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS56120107A (en) |
| CA (1) | CA1171306A (en) |
| DE (1) | DE3103000A1 (en) |
| FR (1) | FR2474747B1 (en) |
| GB (1) | GB2070061B (en) |
| NL (1) | NL8100435A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5716460A (en) * | 1996-05-08 | 1998-02-10 | The Arnold Engineering Company | Methods for making magnetic strips |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE896359C (en) * | 1940-07-23 | 1953-11-12 | Eisen & Stahlind Ag | Iron alloy for permanent magnets |
| US2961360A (en) * | 1958-12-01 | 1960-11-22 | Gen Electric | Magnets having one easy direction of magnetization |
| FR2014806A1 (en) * | 1969-07-31 | 1970-04-17 | Nippon Musical Instruments Mfg | Semi-hard magnetic alloys - magnetism imparted by a series of stepwise heating cycles below the curie pt. |
| DE2144560C2 (en) * | 1970-09-11 | 1983-11-03 | Akai Electric Co. Ltd., Tokyo | Method for manufacturing iron-manganese sintered magnets |
-
1981
- 1981-01-19 CA CA000368776A patent/CA1171306A/en not_active Expired
- 1981-01-26 GB GB8102336A patent/GB2070061B/en not_active Expired
- 1981-01-26 FR FR8101355A patent/FR2474747B1/en not_active Expired
- 1981-01-29 NL NL8100435A patent/NL8100435A/en not_active Application Discontinuation
- 1981-01-29 DE DE19813103000 patent/DE3103000A1/en not_active Withdrawn
- 1981-01-30 JP JP1172381A patent/JPS56120107A/en active Pending
Also Published As
| Publication number | Publication date |
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| FR2474747B1 (en) | 1987-06-26 |
| GB2070061B (en) | 1984-05-31 |
| GB2070061A (en) | 1981-09-03 |
| NL8100435A (en) | 1981-09-01 |
| FR2474747A1 (en) | 1981-07-31 |
| JPS56120107A (en) | 1981-09-21 |
| DE3103000A1 (en) | 1982-01-14 |
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