CA1130179A - Fe-cr-co permanent magnet alloy and alloy processing - Google Patents
Fe-cr-co permanent magnet alloy and alloy processingInfo
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- CA1130179A CA1130179A CA328,510A CA328510A CA1130179A CA 1130179 A CA1130179 A CA 1130179A CA 328510 A CA328510 A CA 328510A CA 1130179 A CA1130179 A CA 1130179A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
-
- 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
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- Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
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- Organic Chemistry (AREA)
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- Soft Magnetic Materials (AREA)
Abstract
1 JIN, S. 2 Fe-Cr-Co PERMANENT MAGNET ALLOY AND ALLOY PROCESSING
Abstract of the Disclosure Fine-grained Fe-Cr-Co magnetic alloys are disclosed which have desirable magnetic properties such as, in particular, a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a maximum energy product in the range of 1-6 MGOe.
Disclosed alloys consist essentially of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder iron;
processing of disclosed alloys may typically include low-temperature solution annealing, cold shaping, and an aging heat treatment. Disclosed magnetic alloys may be used, e.g., in the manufacture of ringers, relays, and electro-acoustic transducers.
Abstract of the Disclosure Fine-grained Fe-Cr-Co magnetic alloys are disclosed which have desirable magnetic properties such as, in particular, a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a maximum energy product in the range of 1-6 MGOe.
Disclosed alloys consist essentially of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder iron;
processing of disclosed alloys may typically include low-temperature solution annealing, cold shaping, and an aging heat treatment. Disclosed magnetic alloys may be used, e.g., in the manufacture of ringers, relays, and electro-acoustic transducers.
Description
7~
1 JIN, S. 2 Fe~Cr-Co PERMANENT r1AGNErr ALLOY AND Al.LOY PROCESSJNG
T hnical Field_ The invention is concerned with Fe-Cr-Co 5 magnetic materials.
Background of the Invention ________ ~ agnetic materials suitable for use in relays, ringers, and electro-acoustic transducers such as loudspeakers and telephone receivers characteristically 10 exhibit high values of magnetic coercivity, remanence, and energy product.
Among established alloys having suitable magnetic properties are Al-Wi-Co-~e and Cu-Ni-Fe alloys which are members of a group of alloys considered to undergo spinodal 15 decomposition resulting in a fine-scale two~phase microstructure. Recently, alloys containing Fe) Cr and Co have been investigated with regard to potential suitability in the manufacture of permanent magnets. SpeciEically, certain ternary Fe-Cr-Co alloys are disclosed in H. Kaneko
1 JIN, S. 2 Fe~Cr-Co PERMANENT r1AGNErr ALLOY AND Al.LOY PROCESSJNG
T hnical Field_ The invention is concerned with Fe-Cr-Co 5 magnetic materials.
Background of the Invention ________ ~ agnetic materials suitable for use in relays, ringers, and electro-acoustic transducers such as loudspeakers and telephone receivers characteristically 10 exhibit high values of magnetic coercivity, remanence, and energy product.
Among established alloys having suitable magnetic properties are Al-Wi-Co-~e and Cu-Ni-Fe alloys which are members of a group of alloys considered to undergo spinodal 15 decomposition resulting in a fine-scale two~phase microstructure. Recently, alloys containing Fe) Cr and Co have been investigated with regard to potential suitability in the manufacture of permanent magnets. SpeciEically, certain ternary Fe-Cr-Co alloys are disclosed in H. Kaneko
2~ et al, "New Ductile Permanent Magnet of Fe-Cr-Co Systems", AIP Conference Proceedin~s No. 5, 197~, p. 1088, and in U. S. patent 3,806,336, "Magnetic Alloys". Quaternary alloys containing ferrite forming elements such as, e.g., Ti, Al, Si, Nb or Ta in addition to Fe, Cr and Co are 25 disclosed in U. S. patent 3,954,519, "Iron-Chromium-Cobalt Spinodal Decomposition Type Magnetic Alloy Comprising Niobium and/or Tantalum", in U. S. patent 3,989,556, "Semihard Magnetic Alloy and a Process for the Production Thereof", in U. S. patent 3,982,972, "Semihard Magnetic 30 Alloy and a Process for the Production Thereof", and in U. S. patent 4,075,437, "Composition, Processing, and Devices Including Magnetic Alloy".
The use of ferrite forming elements such as, e.g., Ti, Al, Si, Nb or Ta in quaternary alloys has been 35 advocated, especially at higher Co levels or in the presence of impurities such as, e.g., C, N or O, to facilitate production of a preliminary fine-grained alpha phase structure by low-temperature annealing.
iL7 Summary of the Invention According to one aspect o~ the invention there is provided a method for producing a magnetic element compris-ing a body of an alloy consisting of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder essentially Fe characterized in that said method comprises the steps of (1) subjecting said body to an annealing temperature which does not exceed 1000 degrees C and which is in the range of 650-950 degrees C when said alloy contains 25 weight percent Cr and 7 weight percent Co, in the range of 650-375 degrees C when said alloy contains 25 weight percent Cr, and 12 weight percent Co, in the range of 650-1100 degrees C when said alloy contains 29 weight percent Cr and 7 weight percent Co, in the range of 650-975 degrees C when said alloy contains 29 weight percent Cr and 12 weight percent Co, and in a range whose limits are obtained by approximate linear interpolation at intermediate levels of Cr and Co, whereby an average grain size not exceeding 70 micrometers is obtained in said alloy, (2) forming said body into a desired shape at a temperature not exceeding 100 degrees C either by wire drawing or deep drawing by an amount corresponding to a cross-sectional area reduc-tion of at least 50 percent or by deep drawing or bending so as to result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is proportional to the change in direction, which for a 30 degree change in direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent, and
The use of ferrite forming elements such as, e.g., Ti, Al, Si, Nb or Ta in quaternary alloys has been 35 advocated, especially at higher Co levels or in the presence of impurities such as, e.g., C, N or O, to facilitate production of a preliminary fine-grained alpha phase structure by low-temperature annealing.
iL7 Summary of the Invention According to one aspect o~ the invention there is provided a method for producing a magnetic element compris-ing a body of an alloy consisting of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder essentially Fe characterized in that said method comprises the steps of (1) subjecting said body to an annealing temperature which does not exceed 1000 degrees C and which is in the range of 650-950 degrees C when said alloy contains 25 weight percent Cr and 7 weight percent Co, in the range of 650-375 degrees C when said alloy contains 25 weight percent Cr, and 12 weight percent Co, in the range of 650-1100 degrees C when said alloy contains 29 weight percent Cr and 7 weight percent Co, in the range of 650-975 degrees C when said alloy contains 29 weight percent Cr and 12 weight percent Co, and in a range whose limits are obtained by approximate linear interpolation at intermediate levels of Cr and Co, whereby an average grain size not exceeding 70 micrometers is obtained in said alloy, (2) forming said body into a desired shape at a temperature not exceeding 100 degrees C either by wire drawing or deep drawing by an amount corresponding to a cross-sectional area reduc-tion of at least 50 percent or by deep drawing or bending so as to result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is proportional to the change in direction, which for a 30 degree change in direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent, and
(3) aging said alloy.
In accordance with another aspect of the invention there is provided an article of manufacture comprising a body of a magnetic alloy consisting of 25-29 weight per-cent Cr, 7-12 weight percent Co, and remainder essentially C~
.
. .
Fe and having at least 3000 grains per mm3 and a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a magnetic energy product in the range ~f 1-6 MGOe.
The invention is an essentially ternary Fe-Cr-Co magnetic alloy whose grain size is suf~iciently fine to result in at least 3000 grains per mm3 and which has a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a maximum magnetic energy product in the range of 1-6 MGOe. Thus, the alloy consists essentially of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder Fe and may be conveniently produced, e.g., by a process involving solution annealing at a temperature in the range of 650-1000 degrees C to produce a fine-grained, essentially single phase alpha structure, followed by cold forming and aging. Magnets made from such alloys may be used, e.g., in electro-acoustic transducers such as loudspeakers and telephone receivers, in relays, and in ringers.
Brief Description of the Drawing In the drawing:
FIG. l shows phase diagrams of two Fe-Cr-Co alloy systems containing 9 weight percent Co and ll weight percent Coj respectively;
FIG. 2 is a photomicrograph showing grain struc-ture, magnifie~ 100 times, of an Fe-Cr-Co magnetic alloy ; containing 28 percent Cr and ll weight percent Co which was solution annealed at 900 degrees C; and FIG. 3 is a photomicrograph showing grain -structure, magnified 100 times, of an Fe-Cr-Co magnetic alloy containing 28 weight percent Cr and~ll weight ` percent Co which was solution annealed at 1300 degrees C.
~ ~ ;
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2b Detailed Description In accordance with the invention it has been realized that Fe-Cr-Co alloys containing Cr in a preferred range of 25-29 weight percent, Co in a preferred range of 7-12 weight percent, and remainder essentially Fe can be produced so as to simultaneously have a maximum energy product in the range of 1-6 MGOe and a grain size corresponding to at least 3000 grans per mm3, such grain structure being particularly beneficial when the alloy is : ~ . . . . . : .
- ~ ~ 3~3~.t7~
3 JIN, S 2 to be cold shaped. A more narrow range of Cr content may be preferred and, specifically, in the interest of optimizing alloy formability, an upper limit of 28 weight percent and, in the interest of optimizing magnetic 5 properties, a lower limit of 26 weight percent Cr may be preferred.
Alloys of the invention may be prepared, e.g., by casting from a melt of constituent elements Fe, Cr and Co or their alloys in a crucible or furnace such as, e.g., an 10 induction furnace. Alternatively, a metallic body having a composition within the specified range may be prepared by powder metallurgy. Preparation of an alloy and, in particular, preparation by casting from a melt calls for care to guard against inclusion of excessive amounts of 15 impurities as may originate from raw materials, from the furnace, or from the atmosphere above the melt. If such care is taken and, in particular, if sufficient care is taken to minimize the presence of impu~ities such as, e.g., nitrogen, addition of ferrite forming elements may be ~0 dispensed with. To minimize oxidation or excessive inclusion of nitrogen, it is desirable to prepare a melt with slag protection, in a vacuum, or in an inert atmosphere such as, e.g., an argon atmosphere. Levels of specific impurities are preferably kept below 0.05 weight 25 percent C, ~.05 weight percent N, 0.2 weight percent Si, 0.5 weight percent Mg, 0.1 weight percent Ti, 0.5 weight percent Ca, 0.1 weight percent Al, 0.5 weight percent Pln, a. 05 weight percent S, and 0.05 weight percent O.
Typical processing of the alloy after casting is 30 as follows. The alloy is soaked at a temperature at which the allo~ is in a two-phase, alpha plus gamma state for a period of 1-10 hours, temperatures in the range of 1100-1300 degrees C being generally appropriate for this purpose. More specific preferred limits on such 35 temperature corresponding to alloys containing~
respectively, 9 weight percent Co and 11 weight percent Co can be obtained from FIG. 1. The alloy is then hot worked in such two-phase state, e.g., by hot rolling, forging, or ... . . .......... ~ , ~ --7~
~ JIN, S. 2 extruding to break down the as-cast structure and, if desired, the alloy may be shaped by cold working. In order to develop a uniformly fine grain structure, the alloy is then solution annealed at a temperature at which the alloy is in an essentially single-phase alpha state and which generally is in the range of 650-1000 degrees C. Preferred upper limits on annealing temperature for specific alloys may be conveniently obtained by approximate linear interpolation between the following values: 950 degrees C
for an alloy containing 25 weight percent Cr and 7 weight percent Co, a75 degrees C for an alloy containing 25 weight percent Cr and 12 weight percent Co, 1100 degrees C for an alloy containing 29 weight percent Cr, and 7 weight percent Co, and 975 degrees C for an alloy containing 29 weight percent Cr and 12 weight percent Co and are further required not to exceed 1000 degrees C in the interest of minimization of grain growth. In the interest of improved kinetics, a lower limit of 800 degrees C is preferred and, in the interest of minimizing gamma phase, preferred upper limits are obtained by approximate linear interpolation between respective values of 925 degrees C, 850 degrees C, }075 degrees C, and 950 degrees C and also under the further provision that annealing temperature not exceed 1000 degrees C.
If the alloy has been cold worked, solution annealing so as to substantially recrystallize and homogenize the alloy may take from 10 minutes to 2 hours depending on annealing temperature and size of ingot. ~ore typically, time required is in the range of 30-90 minutes.
Solution annealing may be performed in air or, in the interest of minimizing surface oxidation, under exclusion of oxygen~
Solution annealing is terminated by rapid quenching, e.g., by water or brine quenching, or, in the case of thin strips, by air quenching and preferably so as to result in a cooling rate of at least 1000 degrees C/min.
throughout the alloy. At this point, the alloy is at or near room temperature, i.e., at a temperature which does 7~
JI~, S. 2 not exceed 100 degrees C, and has an essentially unifo mly fine grain size not exceeding 70 micrometers (corresponding to at least 3000 grains per mm3). Such grain structure is lllustrated by FIG. 2 and may be contrasted with the coarse 5 structure obtained by annealing at elevated temperature as illustrated by ~IG. 3.
At a temperature not exceeding 100 degrees C, the alloy may then be cold formed, e.g., by bending, wire drawing, deep drawing, or swagging. Particular benefits 10 are derived from the fine-grained structure if the alloy is to be cold formed by wire drawing, deep drawing, or bending, i.e., by a technique which causes at least local tensile deformation. On account of the uniformly fine grain structure of the alloy as annealed and quenched, 15 drawing may be by an amount corresponding to an essentially cross-sectional area reduction of at least 50 percent.
Similarly, bending may result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is 20 proportional to the change in direction, which for a 30 degree change of direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent.
Processing as described above characteristically comprises a step of maintaining the alloy at a temperature corresponding to an essentially single phase alpha state.
Alternate processing so characterized may be, e.g., by hot working with finishing temperature in an essentially single 30 phase alpha range, cooling, and forming. Moreover, forming may be carried out in stages with intermediary additional solution anneàling and quenching. Additional processing steps such as e.g., machining by drilling, turning, or milling before or after forming are not precluded.
The shaped alloy is finally subjected to an aging treatment to develop magnetic hardening. Such aging treatment may follow any of a variety of schedules, for example as disclosed in U.S~ patent No. 4,075,437~
f . _ 3~
and in U.S. Patent 4,174,983 issued November 20, 1979, which allows the production of magnets having magnetic remanence of 8000-13000 Gauss, magnetic coercivity of 300-600 Oersted, and magnetic energy product o~ million Gauss-Oersted.
Accordingly, such alloys may serve, upon magnetization in a magnetic field, as magnets in relays, ringers, and electro-acoustic transducers such as loudspeakers and telephone receivers.
In the following examples, phase structure and grain size were determined by X-ray dif~raction analysis, hardness measurements, and metallographic analysis of microstructure after solution annealing and quenching, but before cold shaping. Average grain size was in the range of 25-40 micrometers as shown in Table I. Also shown in Table I are magnetic remanence Br, coercivity H3, and energy product (BH)maX determined after aging oE the alloys.
Example _ An ingot of an alloy containing 26.8 weight percent Cr, 9.4 weight percent Co, and balance essentially Fe was cast from a melt. Ingot dimensions were a thickness of 1.25 inches (31.8 mm.), a width of 5 inches (127 mm.), and a length of 12 inches (304.8 mm.). The cast ingot was heated to a temperature of 1250 degrees C, hot rolled into a quarter inch (6.4 mm.) plate, and water cooled. Sections of the plate were cold rolled at room temperature into strips having a thickness of 0.1 inches 12.5 mm.) and width of 0.625 inches~
(15.9 mm.). The strips were annealed at 900 degrees C for 30 minutes and water cooled. The strips were reheated to 630 degrees C, maintained at this temperature for 1 hour, cooled at an essentially constant rate of 15 degrees C/h to a temperature of 555 degreec C, maintained at 540 degrees C
for 3 hours, and maintained at 525 degrees C for 4 hours.
Example 2 Strips of an alloy containing 27.7 weight percent Cr, 10.9 weight percent Co, and balance essentially Fe were prepared by casti~ng, hot working, quenching, solution ?-~
" . ~ ` ~` `
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~` ` ``` ` ` " ` " .. :, `` ` ~- `. ` ` ` ` `: `
` . - ` ` ` ` . . .. .
3L~IL3~
annealing, cooling, and rolling as described in Example lo The strips were reheated to 635 degrees C, maintained at this temperature for 3 minutes, cooled at an essentially constant rate of 15 degrees C/h to 555 degrees C, maintained at 540 degrees C for 3 hours ancl maintained at 525 degrees C
for 4 hours.
Example 3 Strips of an alloy containing 27.3 weight percent Cr, 7.2 weight percent Co, and balance essentially Fe, were prepared as described in Example 1. The strips were reheated to 620 degrees C, maintained at this temperature for 1 hour, cooled at an essentially constant rate of 15 degrees C/h to 555 degrees C, maintained at 555 degrees C for 2 hours, at 540 degrees C for 3 hours, and at 525 degrees C for 16 hours.
Example 4 Strips of an alloy containing 26.8 weight percent Cr, 10.6 weight percent Co, and balance essentially Fe were prepared as described in Example 1. The strips were soft and ductile and could readily be bent in any direction by 90 degrees over a sharp edge having a radius of curvature of 1/32 of an inch (0.08 mm.) or drawn so as to result in 99 percent area reduction. Strips were aged according to a schedule disclosed in U.S. Patent 4,174,983 by maintaining the alloy at a temperature of 680 degrees C for 30 minutes, rapidly cooling at a first rate of 140 degrees C/h to 615 degrees C, and then cooling at exponentially decreasing rates of from 20 to 2 degrees C/h to a temperature of from 525 degrees C.
Example 5 0.7 inch (17.8 mm.) diameter rods of an alloy containing 27.9 weight percent Cr, 10.7 weight percent Co, and balance Fe were prepared by casting, hot working, solution annealing, and quenching. The rods were cold drawn to 0.07 inch (1.78 mm.~ diameter wire ~having 99 percent reduced cross-sectional area), solution annealed at 930 degrees C for 30 minutes, and cooled to room ,; :
~, , . .
~L3i~7~
-8 JIN, S 2 temperature. An aging heat treatment was carried out by maintaining the drawn wire for 30 minutes at 700 degrees C, cooling to 615 degrees C at a rate of 30 degrees C/h in a magnetic field of 1000 Oersted, and cooling to a 5 temperature of 480 degrees C at exponentially decreasing rates of from 20 to 2 degrees C/h"
TABLE I
Grain Br Hc (BH) Cr Co Size Ex. ~t.~ Wt.~ ~m G Oe MGOe _ _ _, _ _ _ _ 15 1 26.8 9.4 30 10010 380 1.55 227.7 10.9 25 9750 400 1.72 327.3 7.2 40 9280 300 1.10 426.8 10.6 40 10010 370 1.76 527.9 10.7 30 12750 570 5.03 .. . . . . . - . , .
In accordance with another aspect of the invention there is provided an article of manufacture comprising a body of a magnetic alloy consisting of 25-29 weight per-cent Cr, 7-12 weight percent Co, and remainder essentially C~
.
. .
Fe and having at least 3000 grains per mm3 and a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a magnetic energy product in the range ~f 1-6 MGOe.
The invention is an essentially ternary Fe-Cr-Co magnetic alloy whose grain size is suf~iciently fine to result in at least 3000 grains per mm3 and which has a coercive force in the range of 300-600 Oersted, a remanence in the range of 8000-13000 Gauss, and a maximum magnetic energy product in the range of 1-6 MGOe. Thus, the alloy consists essentially of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder Fe and may be conveniently produced, e.g., by a process involving solution annealing at a temperature in the range of 650-1000 degrees C to produce a fine-grained, essentially single phase alpha structure, followed by cold forming and aging. Magnets made from such alloys may be used, e.g., in electro-acoustic transducers such as loudspeakers and telephone receivers, in relays, and in ringers.
Brief Description of the Drawing In the drawing:
FIG. l shows phase diagrams of two Fe-Cr-Co alloy systems containing 9 weight percent Co and ll weight percent Coj respectively;
FIG. 2 is a photomicrograph showing grain struc-ture, magnifie~ 100 times, of an Fe-Cr-Co magnetic alloy ; containing 28 percent Cr and ll weight percent Co which was solution annealed at 900 degrees C; and FIG. 3 is a photomicrograph showing grain -structure, magnified 100 times, of an Fe-Cr-Co magnetic alloy containing 28 weight percent Cr and~ll weight ` percent Co which was solution annealed at 1300 degrees C.
~ ~ ;
1~3~7~
2b Detailed Description In accordance with the invention it has been realized that Fe-Cr-Co alloys containing Cr in a preferred range of 25-29 weight percent, Co in a preferred range of 7-12 weight percent, and remainder essentially Fe can be produced so as to simultaneously have a maximum energy product in the range of 1-6 MGOe and a grain size corresponding to at least 3000 grans per mm3, such grain structure being particularly beneficial when the alloy is : ~ . . . . . : .
- ~ ~ 3~3~.t7~
3 JIN, S 2 to be cold shaped. A more narrow range of Cr content may be preferred and, specifically, in the interest of optimizing alloy formability, an upper limit of 28 weight percent and, in the interest of optimizing magnetic 5 properties, a lower limit of 26 weight percent Cr may be preferred.
Alloys of the invention may be prepared, e.g., by casting from a melt of constituent elements Fe, Cr and Co or their alloys in a crucible or furnace such as, e.g., an 10 induction furnace. Alternatively, a metallic body having a composition within the specified range may be prepared by powder metallurgy. Preparation of an alloy and, in particular, preparation by casting from a melt calls for care to guard against inclusion of excessive amounts of 15 impurities as may originate from raw materials, from the furnace, or from the atmosphere above the melt. If such care is taken and, in particular, if sufficient care is taken to minimize the presence of impu~ities such as, e.g., nitrogen, addition of ferrite forming elements may be ~0 dispensed with. To minimize oxidation or excessive inclusion of nitrogen, it is desirable to prepare a melt with slag protection, in a vacuum, or in an inert atmosphere such as, e.g., an argon atmosphere. Levels of specific impurities are preferably kept below 0.05 weight 25 percent C, ~.05 weight percent N, 0.2 weight percent Si, 0.5 weight percent Mg, 0.1 weight percent Ti, 0.5 weight percent Ca, 0.1 weight percent Al, 0.5 weight percent Pln, a. 05 weight percent S, and 0.05 weight percent O.
Typical processing of the alloy after casting is 30 as follows. The alloy is soaked at a temperature at which the allo~ is in a two-phase, alpha plus gamma state for a period of 1-10 hours, temperatures in the range of 1100-1300 degrees C being generally appropriate for this purpose. More specific preferred limits on such 35 temperature corresponding to alloys containing~
respectively, 9 weight percent Co and 11 weight percent Co can be obtained from FIG. 1. The alloy is then hot worked in such two-phase state, e.g., by hot rolling, forging, or ... . . .......... ~ , ~ --7~
~ JIN, S. 2 extruding to break down the as-cast structure and, if desired, the alloy may be shaped by cold working. In order to develop a uniformly fine grain structure, the alloy is then solution annealed at a temperature at which the alloy is in an essentially single-phase alpha state and which generally is in the range of 650-1000 degrees C. Preferred upper limits on annealing temperature for specific alloys may be conveniently obtained by approximate linear interpolation between the following values: 950 degrees C
for an alloy containing 25 weight percent Cr and 7 weight percent Co, a75 degrees C for an alloy containing 25 weight percent Cr and 12 weight percent Co, 1100 degrees C for an alloy containing 29 weight percent Cr, and 7 weight percent Co, and 975 degrees C for an alloy containing 29 weight percent Cr and 12 weight percent Co and are further required not to exceed 1000 degrees C in the interest of minimization of grain growth. In the interest of improved kinetics, a lower limit of 800 degrees C is preferred and, in the interest of minimizing gamma phase, preferred upper limits are obtained by approximate linear interpolation between respective values of 925 degrees C, 850 degrees C, }075 degrees C, and 950 degrees C and also under the further provision that annealing temperature not exceed 1000 degrees C.
If the alloy has been cold worked, solution annealing so as to substantially recrystallize and homogenize the alloy may take from 10 minutes to 2 hours depending on annealing temperature and size of ingot. ~ore typically, time required is in the range of 30-90 minutes.
Solution annealing may be performed in air or, in the interest of minimizing surface oxidation, under exclusion of oxygen~
Solution annealing is terminated by rapid quenching, e.g., by water or brine quenching, or, in the case of thin strips, by air quenching and preferably so as to result in a cooling rate of at least 1000 degrees C/min.
throughout the alloy. At this point, the alloy is at or near room temperature, i.e., at a temperature which does 7~
JI~, S. 2 not exceed 100 degrees C, and has an essentially unifo mly fine grain size not exceeding 70 micrometers (corresponding to at least 3000 grains per mm3). Such grain structure is lllustrated by FIG. 2 and may be contrasted with the coarse 5 structure obtained by annealing at elevated temperature as illustrated by ~IG. 3.
At a temperature not exceeding 100 degrees C, the alloy may then be cold formed, e.g., by bending, wire drawing, deep drawing, or swagging. Particular benefits 10 are derived from the fine-grained structure if the alloy is to be cold formed by wire drawing, deep drawing, or bending, i.e., by a technique which causes at least local tensile deformation. On account of the uniformly fine grain structure of the alloy as annealed and quenched, 15 drawing may be by an amount corresponding to an essentially cross-sectional area reduction of at least 50 percent.
Similarly, bending may result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is 20 proportional to the change in direction, which for a 30 degree change of direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent.
Processing as described above characteristically comprises a step of maintaining the alloy at a temperature corresponding to an essentially single phase alpha state.
Alternate processing so characterized may be, e.g., by hot working with finishing temperature in an essentially single 30 phase alpha range, cooling, and forming. Moreover, forming may be carried out in stages with intermediary additional solution anneàling and quenching. Additional processing steps such as e.g., machining by drilling, turning, or milling before or after forming are not precluded.
The shaped alloy is finally subjected to an aging treatment to develop magnetic hardening. Such aging treatment may follow any of a variety of schedules, for example as disclosed in U.S~ patent No. 4,075,437~
f . _ 3~
and in U.S. Patent 4,174,983 issued November 20, 1979, which allows the production of magnets having magnetic remanence of 8000-13000 Gauss, magnetic coercivity of 300-600 Oersted, and magnetic energy product o~ million Gauss-Oersted.
Accordingly, such alloys may serve, upon magnetization in a magnetic field, as magnets in relays, ringers, and electro-acoustic transducers such as loudspeakers and telephone receivers.
In the following examples, phase structure and grain size were determined by X-ray dif~raction analysis, hardness measurements, and metallographic analysis of microstructure after solution annealing and quenching, but before cold shaping. Average grain size was in the range of 25-40 micrometers as shown in Table I. Also shown in Table I are magnetic remanence Br, coercivity H3, and energy product (BH)maX determined after aging oE the alloys.
Example _ An ingot of an alloy containing 26.8 weight percent Cr, 9.4 weight percent Co, and balance essentially Fe was cast from a melt. Ingot dimensions were a thickness of 1.25 inches (31.8 mm.), a width of 5 inches (127 mm.), and a length of 12 inches (304.8 mm.). The cast ingot was heated to a temperature of 1250 degrees C, hot rolled into a quarter inch (6.4 mm.) plate, and water cooled. Sections of the plate were cold rolled at room temperature into strips having a thickness of 0.1 inches 12.5 mm.) and width of 0.625 inches~
(15.9 mm.). The strips were annealed at 900 degrees C for 30 minutes and water cooled. The strips were reheated to 630 degrees C, maintained at this temperature for 1 hour, cooled at an essentially constant rate of 15 degrees C/h to a temperature of 555 degreec C, maintained at 540 degrees C
for 3 hours, and maintained at 525 degrees C for 4 hours.
Example 2 Strips of an alloy containing 27.7 weight percent Cr, 10.9 weight percent Co, and balance essentially Fe were prepared by casti~ng, hot working, quenching, solution ?-~
" . ~ ` ~` `
-," `
~` ` ``` ` ` " ` " .. :, `` ` ~- `. ` ` ` ` `: `
` . - ` ` ` ` . . .. .
3L~IL3~
annealing, cooling, and rolling as described in Example lo The strips were reheated to 635 degrees C, maintained at this temperature for 3 minutes, cooled at an essentially constant rate of 15 degrees C/h to 555 degrees C, maintained at 540 degrees C for 3 hours ancl maintained at 525 degrees C
for 4 hours.
Example 3 Strips of an alloy containing 27.3 weight percent Cr, 7.2 weight percent Co, and balance essentially Fe, were prepared as described in Example 1. The strips were reheated to 620 degrees C, maintained at this temperature for 1 hour, cooled at an essentially constant rate of 15 degrees C/h to 555 degrees C, maintained at 555 degrees C for 2 hours, at 540 degrees C for 3 hours, and at 525 degrees C for 16 hours.
Example 4 Strips of an alloy containing 26.8 weight percent Cr, 10.6 weight percent Co, and balance essentially Fe were prepared as described in Example 1. The strips were soft and ductile and could readily be bent in any direction by 90 degrees over a sharp edge having a radius of curvature of 1/32 of an inch (0.08 mm.) or drawn so as to result in 99 percent area reduction. Strips were aged according to a schedule disclosed in U.S. Patent 4,174,983 by maintaining the alloy at a temperature of 680 degrees C for 30 minutes, rapidly cooling at a first rate of 140 degrees C/h to 615 degrees C, and then cooling at exponentially decreasing rates of from 20 to 2 degrees C/h to a temperature of from 525 degrees C.
Example 5 0.7 inch (17.8 mm.) diameter rods of an alloy containing 27.9 weight percent Cr, 10.7 weight percent Co, and balance Fe were prepared by casting, hot working, solution annealing, and quenching. The rods were cold drawn to 0.07 inch (1.78 mm.~ diameter wire ~having 99 percent reduced cross-sectional area), solution annealed at 930 degrees C for 30 minutes, and cooled to room ,; :
~, , . .
~L3i~7~
-8 JIN, S 2 temperature. An aging heat treatment was carried out by maintaining the drawn wire for 30 minutes at 700 degrees C, cooling to 615 degrees C at a rate of 30 degrees C/h in a magnetic field of 1000 Oersted, and cooling to a 5 temperature of 480 degrees C at exponentially decreasing rates of from 20 to 2 degrees C/h"
TABLE I
Grain Br Hc (BH) Cr Co Size Ex. ~t.~ Wt.~ ~m G Oe MGOe _ _ _, _ _ _ _ 15 1 26.8 9.4 30 10010 380 1.55 227.7 10.9 25 9750 400 1.72 327.3 7.2 40 9280 300 1.10 426.8 10.6 40 10010 370 1.76 527.9 10.7 30 12750 570 5.03 .. . . . . . - . , .
Claims (19)
1. Method for producing a magnetic element comprising a body of an alloy consisting of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder essentially Fe CHARACTERIZED IN THAT said method comprises the steps of (1) subjecting said body to an annealing temperature which does not exceed 1000 degrees C and which is in the range of 650-950 degrees C when said alloy contains 25 weight percent Cr and 7 weight percent Co, in the range of 650-875 degrees C when said alloy contains 25 weight percent Cr, and 12 weight percent Co, in the range of 650-1000 degrees C when said alloy contains 29 weight percent Cr and 7 weight percent Co, in the range of 650-975 degrees C when said alloy contains 29 weight percent Cr and 12 weight percent Co, and in a range whose limits are obtained by approximate linear interpolation at intermediate levels of Cr and Co, whereby an average grain size not exceeding 70 micrometers is obtained in said alloy, (2) forming said body into a desired shape at a temperature not exceeding 100 degrees C either by wire drawing or deep drawing by an amount corresponding to a cross-sectional area reduction of at least 50 percent or by deep drawing or bending so as to result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is proportional to the change in direction, which for a 30 degree change in direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent, and (3) aging said alloy.
2. Method of claim 1 in which step (1) is effected by solution annealing.
3. Method of claim 1 in which step (1) is effected by hot working terminating at said annealing temperature.
4. Method of claim 1 in which said annealing temperature is in the range of 800-925 degrees C, 800-850 degrees C, 800-1075 degrees C, and 800-950 degrees C
for respective alloys.
for respective alloys.
5. Method of claim 1 in which said alloy is prepared from a melt.
6. Method of claim 5 in which said melt is prepared in a vacuum or in an inert atmosphere or under slag protection.
7. Method of claim 1 in which said alloy, prior to step (1), is soaked at a temperature in the range of 1100-1300 degrees C.
8. Method of claim 7 in which said alloy, after soaking and prior to step (1), is hot worked at a temperature in the range of 1100-1300 degrees C.
9. Method of claim 8 in which said alloy, after hot working and prior to step (1), is cold worked.
10. Method of claim 1 in which forming is carried out in stages with additional intermediate solution annealing and quenching.
11. Method of claim 1 in which aging is by cooling at an essentially constant rate.
12. Method of claim 1 in which aging is by cooling at a first, rapid average rate followed by cooling at a second, slower average rate.
13. Method of claim 1 in which aging is carried out in the presence of a magnetic field.
14. Method of claim 1 in which said body is machined after step (1) and prior to step (2).
15. Method of claim 1 in which said body is machined after step (2) and prior to step (3).
16. Article of manufacture comprising a body of a magnetic alloy consisting of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder essentially Fe and having at least 3000 grains per mm3 and a coercive force in the range of 300-600 Oerstad, a remanence in the range of 8000-13000 Gauss, and a magnetic energy product in the range of 1-6 MGOe.
17. Article of claim 16 in which said alloy contains less than 0.05 weight percent C, 0.05 weight percent N, 0.2 weight percent Si, 0.5 weight percent Mg, 0.1 weight percent Ti, 0.5 weight percent Ca, 0.1 weight percent Al, 0.5 weight percent Mn, 0.05 weight percent S, and 0.05 weight percent 0.
18. Article of claim 16 in which said alloy contains 26-28 weight percent Cr.
19. Method for producing a magnetic element compris-ing a body of an alloy consisting of 25-29 weight percent Cr, 7-12 weight percent Co, and remainder Fe characterized in that said method comprises the steps of (1) subjecting said body to an annealing temperature which is such that, (a) said annealing temperature is greater than or equal to 650 degrees C., (b) said annealing temperature is less than or equal to a temperature which is obtained by approximate linear interpol-ation between a temperature of 950 degrees C, corresponding to an alloy comprising 25 weight percent Cr and 7 weight per-cent Co, a temperature of 875 degrees C. corresponding to an alloy comprising 25 weight percent Cr and 12 weight percent Co, a temperature of 1100 degrees C. corresponding to an alloy comprising 29 weight percent Cr and 7 weight percent Co and a temperature of 975 degrees C. corresponding to an alloy comprising 29 weight percent Cr and 12 weight percent Co, (c) said annealing temperature is less than or equal to 1000 degrees C. whereby an average grain size not exceeding 70 micrometers is obtained in said alloy, (2) forming said body into a desired shape at a temperature not exceeding 100 degrees C. either by wire drawing or deep drawing by an amount corresponding to a cross-sectional area reduction of at least 50 percent or by deep drawing or bending so as to result in a change of direction of at least 30 degrees, the resulting radius of curvature being such that it does not exceed a value which is proportional to change in direction, which for a 30 degree change in direction is equal to the thickness of the part being bent, and which for a 90 degree change of direction is equal to 4 times the thickness of the part being bent, and (3) aging said alloy.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US92413878A | 1978-07-13 | 1978-07-13 | |
| US924,138 | 1978-07-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1130179A true CA1130179A (en) | 1982-08-24 |
Family
ID=25449766
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA328,510A Expired CA1130179A (en) | 1978-07-13 | 1979-05-28 | Fe-cr-co permanent magnet alloy and alloy processing |
Country Status (17)
| Country | Link |
|---|---|
| JP (1) | JPS5541987A (en) |
| KR (1) | KR830001327B1 (en) |
| AT (1) | AT369434B (en) |
| AU (1) | AU529656B2 (en) |
| BE (1) | BE877631A (en) |
| CA (1) | CA1130179A (en) |
| CH (1) | CH645924A5 (en) |
| DE (1) | DE2928059A1 (en) |
| ES (1) | ES482453A1 (en) |
| FR (1) | FR2434466A1 (en) |
| GB (1) | GB2025460B (en) |
| HK (1) | HK69084A (en) |
| IT (1) | IT1162561B (en) |
| NL (1) | NL178016C (en) |
| PL (1) | PL118488B1 (en) |
| SE (1) | SE446990B (en) |
| SG (1) | SG34684G (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3069509D1 (en) * | 1979-08-16 | 1984-11-29 | Inoue Japax Res | Manufacture and use of magnetic scale systems |
| JPS57149456A (en) * | 1981-03-10 | 1982-09-16 | Sumitomo Special Metals Co Ltd | Dendritic fe-cr-co magnet alloy |
| DE3135661A1 (en) * | 1981-09-09 | 1983-03-17 | Sumitomo Special Metals Co., Ltd., Osaka | Sintered magnetic alloy of the Fe-Cr-Co type and process for producing articles with such an alloy |
| JPS59159929A (en) * | 1983-02-28 | 1984-09-10 | Nippon Gakki Seizo Kk | Production of magnet material |
| NL8302276A (en) * | 1983-06-28 | 1985-01-16 | Philips Nv | CATHODE JET TUBE WITH AN FE-CO-CR SHADOW MASK AND METHOD FOR MANUFACTURING SUCH SHADOW MASK. |
| JPS61110715A (en) * | 1984-11-01 | 1986-05-29 | Nippon Gakki Seizo Kk | Manufacture of fe-cr-co alloy magnet |
| JP2681048B2 (en) * | 1985-07-04 | 1997-11-19 | 株式会社ソキア | Magnetic scale material |
| DE19611461C2 (en) * | 1996-03-22 | 1999-05-12 | Dresden Ev Inst Festkoerper | Use an iron-chromium-cobalt-based alloy |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5536059B2 (en) * | 1974-05-02 | 1980-09-18 | ||
| GB1500794A (en) * | 1975-03-21 | 1978-02-08 | Hitachi Metals Ltd | Semihard magnetic alloy and a process for the production thereof |
| US3982972A (en) * | 1975-03-21 | 1976-09-28 | Hitachi Metals, Ltd. | Semihard magnetic alloy and a process for the production thereof |
| US3989556A (en) * | 1975-03-21 | 1976-11-02 | Hitachi Metals, Ltd. | Semihard magnetic alloy and a process for the production thereof |
| US4008105A (en) * | 1975-04-22 | 1977-02-15 | Warabi Special Steel Co., Ltd. | Magnetic materials |
| US4075437A (en) * | 1976-07-16 | 1978-02-21 | Bell Telephone Laboratories, Incorporated | Composition, processing and devices including magnetic alloy |
| JPS5933644B2 (en) * | 1977-02-10 | 1984-08-17 | 日立金属株式会社 | Fe-Cr-Co permanent magnet and its manufacturing method |
| US4174983A (en) * | 1978-07-13 | 1979-11-20 | Bell Telephone Laboratories, Incorporated | Fe-Cr-Co magnetic alloy processing |
-
1979
- 1979-05-28 CA CA328,510A patent/CA1130179A/en not_active Expired
- 1979-07-03 SE SE7905817A patent/SE446990B/en not_active IP Right Cessation
- 1979-07-06 NL NLAANVRAGE7905311,A patent/NL178016C/en not_active IP Right Cessation
- 1979-07-09 AU AU48760/79A patent/AU529656B2/en not_active Ceased
- 1979-07-10 FR FR7917864A patent/FR2434466A1/en active Granted
- 1979-07-11 DE DE19792928059 patent/DE2928059A1/en active Granted
- 1979-07-11 IT IT24303/79A patent/IT1162561B/en active
- 1979-07-11 BE BE0/196247A patent/BE877631A/en not_active IP Right Cessation
- 1979-07-11 PL PL1979217026A patent/PL118488B1/en unknown
- 1979-07-11 GB GB7924154A patent/GB2025460B/en not_active Expired
- 1979-07-12 KR KR1019790002316A patent/KR830001327B1/en active
- 1979-07-12 ES ES482453A patent/ES482453A1/en not_active Expired
- 1979-07-12 AT AT0487179A patent/AT369434B/en not_active IP Right Cessation
- 1979-07-12 CH CH651779A patent/CH645924A5/en not_active IP Right Cessation
- 1979-07-13 JP JP8834179A patent/JPS5541987A/en active Granted
-
1984
- 1984-05-04 SG SG346/84A patent/SG34684G/en unknown
- 1984-09-06 HK HK690/84A patent/HK69084A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NL178016B (en) | 1985-08-01 |
| BE877631A (en) | 1979-11-05 |
| IT7924303A0 (en) | 1979-07-11 |
| IT1162561B (en) | 1987-04-01 |
| FR2434466B1 (en) | 1984-01-20 |
| HK69084A (en) | 1984-09-14 |
| SE446990B (en) | 1986-10-20 |
| PL118488B1 (en) | 1981-10-31 |
| JPS5541987A (en) | 1980-03-25 |
| KR830001327B1 (en) | 1983-07-09 |
| FR2434466A1 (en) | 1980-03-21 |
| AT369434B (en) | 1982-12-27 |
| ATA487179A (en) | 1982-05-15 |
| GB2025460A (en) | 1980-01-23 |
| JPS6312936B2 (en) | 1988-03-23 |
| NL7905311A (en) | 1980-01-15 |
| DE2928059C2 (en) | 1988-01-28 |
| KR830001401A (en) | 1983-04-30 |
| NL178016C (en) | 1986-01-02 |
| SE7905817L (en) | 1980-01-14 |
| GB2025460B (en) | 1983-02-02 |
| AU529656B2 (en) | 1983-06-16 |
| PL217026A1 (en) | 1980-06-02 |
| DE2928059A1 (en) | 1980-01-24 |
| AU4876079A (en) | 1980-01-17 |
| CH645924A5 (en) | 1984-10-31 |
| ES482453A1 (en) | 1980-04-01 |
| SG34684G (en) | 1985-02-08 |
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