EP0024686A2

EP0024686A2 - Article comprising a magnetic component consisting essentially of an alloy comprising Fe, Cr and Co

Info

Publication number: EP0024686A2
Application number: EP80104952A
Authority: EP
Inventors: Sungho Jin
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1979-08-24
Filing date: 1980-08-20
Publication date: 1981-03-11
Also published as: JPS56501051A; WO1981000643A1; EP0024686A3; KR830003786A; ES494412A0; PL226314A1; ES8106181A1

Abstract

This invention relates to magnetic Fe-Cr-Co alloys which additionally contain Cu. Disclosed are permanent magnet Fe-Cr-Co-Cu alloys which preferably contain 22-38 weight percent Cr, 3-30 weight percent Co, 0.2-5 weight percent Cu, and remainder essentially iron. Presence of limited amounts of other elements such as, e.g., ferrite stabilizing elements or rare earth elements is not precluded. The new alloys have superior magnet properties such as, typically, remanence B, in a range of 8000-14000 gauss, coercive force H_c in a range of 200-1500 oersted (15,920-119,400 A/m), and energy product (BH)_max in a range of 1.0-15.0 million gauss-oersted (79.6-1194 MG' A m). Alloys of the invention may be processed to yield either isotropic or anisotropic magnet properties

Description

Technical Field

The invention is concerned with magnetic materials containing Fe-Cr-Co.

Background of the Invention

Magnetic materials suitable for use in relays, ringers, and electroacoustic transducers such as loudspeakers and telephone receivers characteristically exhibit high values of magnetic coercivity, remanence, and energy product.
Among established alloys having suitable magnetic properties are Al-Ni-Co-Fe and Cu-Ni-Fe alloys which are members of a group of alloys considered to undergo spinodal 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. Specifically, certain ternary Fe-Cr-Co alloys are disclosed in H. Kaneko et al., "New Ductile Permanent Magnet of Fe-Cr-Co Systems", AIP Conference Proceedings, No. 5, 1972, 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 disclosed in U. S. patent 3,954,519 "Iron-Chromium-Cobalt Spinodal Decomposition Type Magnetic Alloy Comprising Niobium and/or Tantalum", U. S. patent 3,989,556 "Semihard Magnetic Alloy and a Process for the Production Thereof", U. S. patent 3,982,972 "Semihard Magnetic Alloy and a Process for the Production Thereof", and U. S. patent 4,075,437 "Composition, Processing, and Devices Including Magnetic Alloy", in the paper by G. Y. Chin et al., "New Ductile Cr-Co-Fe Permanent Magnet Alloys for Telephone Receiver Applications", Journal Applied Physics, Volume 49, No. 3, 1978, p. 2046, the paper by H. Kaneko et al., "Effect of V and V+Ti Additions on the Structure and Properties of Fe-Cr-Co Ductile Magnet Alloys", IEEE Trans. Mag., Volume MAG _-2, No. 6, 1976, p. 977, and the paper by H. Kaneko et al., "Fe_-Cr-Co Ductile Magnet with (BH)_max=8 MGOe", AIP Conf. Proc., No. 29, 1976, p. 620. Fe-Cr-Co alloys containing rare earth additions are disclosed in U. S. patent 4,120,704, issued October 17, 1978 in the name of Richard L. Anderson.
Further development of Fe-Cr-Co alloys and alloy processing is disclosed in pending U. S,. patent applications Serial No. 924,137, now U. S. patent no. 4,174,983 Serial No. 924,138, now Belgian patent no. 877,631 and Serial No. 016,115 (Jin, S. 3). Fe-Cr-Co alloys containing nickel and having enhanced kinetics of aging are disclosed in copending U. S. patent application Serial No. 069,277 (S. Jin 5).

Summary of the Invention

The invention is an Fe-Cr-Co-Cu magnetic alloy which may also contain limited amounts of other elements. The alloy preferably contains 22-38 weight percent Cr, 3-30 weight percent Co, 0.2-5 weight percent Cu, remainder essentially iron, and may contain one or several elements such as, e.g., Si, Al, Zr, Ti, Mo, V. Nb, Ta, W and Mn, preferably in a combined amount not exceeding 5 weight percent. Y, La, and the elements comprising the lanthanide series may be present, preferably ina combined amount not exceeding 0.5 weight percent. Typical magnetic properties of such Cu-containing alloys are remanence Br of 8000- 14000 gauss, coercive force H_c of 200-1500 oersted (15,920-119400 A/m), and energy product (BB)_max of 1.0-15.0 million gauss-oersted (79.6-1194 MG. A/m). Alloys of the invention may be processed to yield either isotropic or anisotropic magnet properties.
Magnets made from Fe-Cr-Co_-Cu alloys may be used, e.g., in electroacoustic transducers such as loudspeakers and telephone receivers, relays, and ringers.

Brief Description of the Drawing

FIG. 1 shows demagnetization curves of two Fe-Cr-Co magnets and one Fe-Cr-Co-Cu magnet, all processed by deformation aging.
FIG. 2 shows magnetic properties as a function of weight percent cobalt for Fe-Cr-Co-Cu alloys containing 33 weight percent Cr, 2 weight percent Cu, remainder Fe; and Fe-Cr-Co alloys containing 33 weight percent Cr and remainder Fe. Alloys were processed by deformation aging.

Detailed Description

In accordance with the invention it has been realized that Fe-Cr-Co-Cu alloys which contain Cr in a preferred range of 22-38 weight percent, Co in a preferred range of 3-30 weight percent, and Cu in a preferred range of 0.2-5 weight percent and remainder essentially Fe can be produced to have desirable magnetic properties. Typical properties are remanence B_r in a range of 8000-14000 gauss, coercivity H_c in a range of 200-1500 oersted (15,920-119,400 A/m), and energy product (BH) _max in a range of 1.0-15.0 million gauss-oersted (79.6-1194 MG' A/m). In addition to Fe, Cr, Co, and Cu, alloys may contain one or several additional elements such as, e.g., Si, A1, Zr, Ti, Mo, V, Nb, Ta, W and Mn, preferably in a combined amount not exceeding 5 weight percent, and Y, La, and lanthanide series elements, preferably in a combined amount not exceeding 0.5 weight percent.
Alloys of the invention may be prepared, e.g., by casting from a melt of constituent elements Fe, Cr, Co, and Cu or their alloys 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 of 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 atmosphere above the melt.
If such care is taken and, in particular, if sufficient care is taken to minimize the presence of impurities such as, e.g., nitrogen, addition of ferrite forming elements may be 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 percent C, 0.05 weight percent N, 0.5 weight percent _Mg, 0.5 weight percent Ca, 0.1 wieght percent S, and 0.05 weight percent O. ,
While the alloys of the present invention can be directly cast into final shape prior to heat treatment, ingots cast from a melt may be processed by additional steps such as, e.g., hot working, cold working, and solution annealing for purposes such as grain refining, shaping, or the development of desirable mechanical properties in the alloy. Additional processing steps such as, e.g., forming into final magnet shape, or machining may also be included during or after the preliminary processing. Such additional steps may also be carried out before or after aging heat treatment.
Aging heat treatment to produce a desirable spinodally decomposed multi-phase structure may be carried out by several previously disclosed methods as described, e.g., in U. S. patent 4,075,437, U. S. patent application Serial No. 924,137, filed July 13, 1978, now U. S. patent no. 4,174,983, U. S. patent application Serial No. 924,138, filed July 13,-1978, now Belgian Patent no. 877,631 or U. S. patent application Serial No. 016,115, (Jin, S. 3) filed February 28, 1979. Isotropic magnet properties are obtained in the alloys of the invention by aging heat treatment in the absence of a magnetic field and without intermediate deformation. Anisotropic, high energy magnet properties are obtained by using magnetic field heat treatment or intermediate deformation.
An advantage realized by the new alloys is illustrated in FIG. 1 which shows superior squareness of B-H hysteresis loop for an alloy of the invention containing 2 weight percent Cu as compared with two prior art alloys. Another advantage is illustrated in FIG. 2 which shows a superior magnetic energy product for an alloy of the invention as compared with a prior art alloy. Such advantages of the new alloys are significant in view of the lower cost of copper as compared with cobalt and further in view of slower kinetics of spinodal decomposition when Cu is substituted for a corresponding amount of Co, slower kinetics being particularly desirable in the processing of heavy section rods. Excessive amount of Cu addition such as, e.g., above 5 weight percent is not desirable in the interest of minimizing chemical segregation in cast ingots and cracking during hot working.
The following examples are of various Fe-Cr-Co and Fe-Cr-Co-Cu alloy compositions which were processed by a variety of processing methods to yield isotropic or anisotropic magnetic properties. Samples were prepared by vacuum induction melting or elemental alloy constituents, casting, hot rolling at temperatures in the range of 1100-1200 degrees C, cold working, and solution annealing for 30 minutes at a temperature of approximately 950 degrees C. Subsequent processing was as described for individual examples. Sample diameter was 65 mil (0.1651 centimeter). Ultimate magnetic properties are shown in Table 1.
Example 1 (prior art). A sample of Fe-Cr-Co alloy containing 33 weight percent Cr and 7 weight percent Co was heated to a temperature of 650 degrees C, cooled at a rate of 4 degrees per hour to a temperature of 595 degrees C, water quenched, cold drawn 67 percent area reduction, reheated to a temperature of 585 degrees C, cooled at a rate of 8 degrees C per hour to a temperature of 540 degrees C, and further cooled at a rate of 4 degrees C per hour to 500 degrees C.
Example 2 (prior art). A sample of an Fe-Cr-Co alloy containing 33 weight percent Cr and 9 weight percent Co was heated to a temperature of 650 degrees C, cooled at a rate of 7 degrees C per hour to a temperature of 595 degrees C, water quenched, cold drawn 67 percent area reduction, reheated to a temperature of 585 degrees C, and cooled at a rate of 8 degrees C per hour to a temperature of 480 degrees C.
' Example 3 (new). A sample of an Fe-Cr-Co-Cu alloy containing 33 weight percent Cr, 7 weight percent Co, and 2 weight percent Cu was treated as described in Example 1.
Example 4 (new). A sample of an Fe-Cr-Co-Cu alloy containing 33 weight percent Cr, 10 weight percent Co, and 2 weight percent Cu was heated to a temperature of approximately 650-670 degrees C, cooled at a rate of 25 degrees C per hour to a temperature of 600 degrees C, water quenched, cold drawn with 70 percent area reduction reheated to a temperature of 590 degrees C, cooled at a rate of 10 degrees C per hour to a temperature of 540 degrees C, and further cooled at a rate of 4 degrees C per hour to a temperature of 480 degrees C.
Example 5 (new). A sample of an Fe-Cr-Co-Cu alloy containing 33 weight percent Cr, 16 weight percent Co, and 2 weight percent Cu was heated to a temperature of 639 degrees C, cooled at a rate of 25 degrees C per hour to a temperature of 615 degrees C, water quenched, cold drawn 70 percent area reduction, reheated to 600 degrees C, and cooled at a rate of 33 degrees C per hour to a temperature of 500 degrees C.
Example 6 (new). A sample of an Fe-Cr-Co-Cu alloy containing 33 weight percent_'Cr, 20 weight percent Co, and 2 weight percent Cu was heated to a temperature of 647 degrees C, cooled at a rate of 40 degrees C, water quenched, wire drawn 70 percent area reduction, reheated to a temperature of 605 degrees C, and cooled at a rate of 40 degrees C per hour to a temperature of 500 degrees C.

Claims

1. An article of manufacture comprising a magnetic component which consists essentially of an alloy comprising Fe, Cr, Co and at least one additional element,
CHARACTERIZED IN THAT
said at least one additional element is Cu, an aggregate of at least 94.5 weight percent of the alloy consisting of Fe, Cr, Co and Cu, with Cr being present in said alloy in an amount in the range of 22-38 weight percent of said aggregate, Co being present in said alloy in an amount in the range of 3-30 weight percent of said aggregate, and Cu being present in said alloy in an amount in the range of 0.2-5 weight percent of said aggregate, said alloy, after having been subjected to plastic deformation, having a magnetic squareness ratio B_r/B_s equal to or greater than 0.98.

2. Article according to claim 1, CHARACTERIZED IN THAT
said alloy may additionally comprise Si, Al, Zr, Ti, Mo, V, Nb, Ta, W and Mn in a combined amount not exceeding 5 weight percent of said alloy.

3. Article according to claim 1, CHARACTERIZED IN THAT
said alloy may additionally comprise at least one of Y, La and elements of the lanthanide series in a combined amount not exceeding 0.5 weight percent of said alloy.

4. Article according to claim 1, CHARACTERIZED IN THAT
said alloy has been treated to selectively yield magnetically isotropic or magnetically anisotropic properties.

5. Article according to claim 4, CHARACTERIZED IN THAT
said alloy has been heat treated in a magnetic field to yield magnetically anisotropic properties.

6. Article according to claim 4, CHARACTERIZED IN THAT
said component has been deformed and heat treated, or heat treated and deformed, or heat treated and deformed and heat treated.

7. Article according to any 'one of preceding claims 1-6,
CHARACTERIZED IN THAT
said magnetic component has a remanence ranging from 8000-14000 gauss, a coercivity ranging from 200-1500 oersted (from 15,920 to 119,400 A/m) and an energy product ranging from 1.0 to 15.0 million gauss-oersted (from 79.6 to 1194 MG·A/m) .