DE2443071C2 - Process for the production of a cast, copper-hardened permanent magnetic alloy - Google Patents

Description

The invention relates to a method for producing a cast, copper-hardened permanent magnetic Alloy according to the preamble of claim 1.

From DE-OS 19 15 358 cast copper-hardened permanent magnetic alloys are made 30 already known from the components cobalt, samarium, cerium and copper, among other things. The one from this Grain sizes given in the publication refer to the powdered state. With these Alloys hardening with the non-magnetic copper reduces wall movements of the magnetic domains, so that an increasing proportion of the component copper leads to an increasing Koerzltlvfeld strength leads. The magnetic component cobalt, on the other hand, improves with increasing proportion 35 the remanence.

The quantitatively described alloys (Co ₁ Cu) _x Sm or (Co, Cu) _x Ce, where 5 £ χ ^ 8.5, only show high values for x = 5 and then only after heat treatment has been carried out Coercive field strength H _c with moderate values for the remanence B. This is useless for many applications, since good values for coercive field strength, remanence and also energy product are required at the same time. At the same time, however, the magnet should also be as inexpensive as possible, which is always a problem with alloys with χ = 5, i.e. a <* Tn high samarium content because of the high price of samarium.

Another copper-hardened permanent magnetic alloy is known from Japan. J. App !. Phys. 1973, 761. Alloys with the formula (Sm, Ce,. ,, (Co ,. _x _, Fe _x Cu,) ₂ with 5 <, ζ <, 8.5 are described. The alloys are melted, finely ground, pressed in a magnetic field and sintered at temperatures around 1200 ° C 45, then either furnace or rapid cooling. These known alloys also only achieve moderate magnetic values. In addition, the production is undesirable because of the many components and the technologically complex fine grinding process The reference to the independence of the Koerzltlvfeld strength from the grain size relates to the technology described there.

Similar alloys are known from Z.f. Metallkunde 1970, 461, 468 Tab. There is z. B. a composition of the formula Sm Cojj Cu, _J5 Fe _0-4 = Sm (Co _0-66 Cu _0-2 ; Fe ₀ ^ ₁ ) S brushed. This alloy P also only achieves moderate magnetic values, which are significantly below those of pure SmCo _s compounds.

; - ^:: . It is also known from this publication that magnetic hardening takes the form of "precipitation hardening"

$ | can take place by means of the weakly magnetic phase in the finest distribution with correct heat treatment,

f '] and precise control of the cooling rate is important.

| e | 55 It is the object of the invention to improve a method of the type mentioned in such a way that the; ^Vv ; The alloy produced has a coercive field strength of up to 20 kOe, a remanence of up to 10 kCr and a

Ui Encrgle product has from more than 9 MGOe up to 20 MGOe. The alloy should also be cheaper and

ν; ' be technically easier to manufacture than fine particle magnets.

! In a method of the type specified at the beginning, this task is carried out by the identification of the

. 60 claim 1 specified features solved.

ι ·; The copper-hardened permanent magnetic alloys produced according to the invention have unexpected

It has high values of coercive field strength and remanence. For Samar umiegierung H _c - or B, -

G; Values of up to 20 kOe or 10 kG and energy products of over 20 MGOe are determined. This result is so

Wi more surprising than the person skilled in DE-OS 19 15 358 and the publication by EA Nesbltt, RH

f. 65 Willens, RC Sherwood, E. Buehler and JH Wernlck In Appl. Phys. Letters 12, June 1968, p. 361 ff. Enteh-Ϊ; it had to be that r.ur (Co ₁ Cu) ₅ Sm alloys permanent-magnetic materials with good magnetic properties

:.: ■ shafts are and it is also well known to the person skilled in the art that only the SmCo ₅ alloy, but not

! : the SmCo ₆ or the SmCo _{8 5} alloy has good magnetic properties. They also recommend

known publications expressly the use of high cooling speeds so that the values the coercive field strength increase.

However, the alloys produced according to the invention not only have excellent magnetic properties on. Because of the comparatively low proportion of expensive rare earth metal and the unnecessary The fine grinding process can also significantly reduce manufacturing costs and sources of technological error be reduced.

The alloys are statistically distributed through a coarse-grained structure of garbage to centimeter-sized Grains, possibly marked with a directionally solidified structure, each grain being a perfectly aligned one Permanent magnet is. Heat treatment of the alloys does not result in any significant Improvements in magnetic properties achieved.

The invention is explained below with reference to exemplary embodiments shown in the drawings. Here shows

Fig. 1 _c, the dependence of Koerzitlvfeldstärke H and the remanence B _r of samarium in the alloy series of Sm (Co .75Cu _{0 0} J ₅₎ ^ _x,

2 shows the dependence of the coercive field strength H _c and the remanence B, on the copper content in the alloy relhe Sm (Coi_ _v Cu,) ₆ , and

3 shows the dependence of the coercive field strength H _c and the remanence B _r on the annealing temperature T, with an annealing time of approximately two hours for the alloy Sm (Co _0-7 SCu _{0 α2} ) β

All samples of the copper-hardened permanent magnetic alloys given below were produced by melting the elements cobalt, copper and samarium in an induction furnace. The starting materials used were 99.9% pure samarium, 99.99% pure cobalt and low-oxygen 99.999% pure electrolyte copper, roughly crushed into a boron nitride crucible and melted under pure argon at a temperature of approx. 1400 ° C and the melt in situ , at a cooling rate of less than 50 ° C / min., solidified. The resulting material has a structure consisting of 3-5 mm large grains. In which each grain represents an almost completely aligned permanent magnet. The crystallographic and thus also magnetic preferred directions of these grains are statistically distributed over the material. Spherical, monocrystalline samples approx. 2 mm in diameter were ground out of the grains of this material in a ball mill. The demagnetization curves of these spherical single crystals were recorded with the aid of a vibration magnetometer at a maximum field of 23 kOe, from which the coercive field strength H ₁ . and the remanence B were taken. The compositions were determined wet-chemically to an accuracy of 1%.

In the following table the measurement data of some alloys according to the invention are given.

alloy

Composition in% by weight coercive remanence

field strength

Sm Co Cu H _c (k0e) Br (KG)

Sm ₀ , 143Coo.657Cuo.20 Δ Sm (COo.77Cu ₀ .23) 6

Δ Sm (Coo.7iCuo.29 / 6 Smo.143coo.557cuo.30

Δ Sm (COo.65CUoj5) 6

Δ Sm (COo.75CUo.25) 6.l2

Smo.l35coo.645cuo.22

Δ SmiCOo.75CUo.25) 6.4

Smo.13coo.65cuo.22

Δ Sm (COo.75CUo.25) 6.7

Smo.125coo.75cuo.125 Δ Sm (Coo.86Cu _0. , ₄ ) 7

Smo. 128C00.73CU0.142 Δ Sm (COo.84CUo, 16) 6.85

29.46 53.11 17.43 7.4 6.8

29.36 48.92 21.72 14.3 6.8

29.27 44.75 25.98 19.6 5.3

28.94 51.85 19.22 14.3 7.1

28.08 52.58 19.34 16 6.5

27.21 53.33 19.46 10.8 7.4

26.49 62.30 11.20 3.2 9.7

26.95 60.37 12.68 5.3 9.1

In the Flg. 1 and 2 are the coercive field strengths and the remanences of some of these samples. Alloy relays Sm (CO ₀₇₅ CUo ₂ S) ^ x ^and Sm (Co ^ Cu, ^. For the alloy series Sm (Co ₀ J ₅ CUoJs) ₆ ** remains the remanence due to the constant Co content in the OSxSI range is almost the same, whereas the coercive field strength at the limits of this range increases to surprisingly high values in the middle of this range. By changing the copper content, the magnetic properties can be improved even further This can be seen from Fig. 2. In which the Koerzltlvfeld strengthunci remanence values of the alloy series Sm (COi ^ CUj) ₆ are plotted as a function of the copper content y . As can be seen, the remanence decreases with increasing copper content, since the copper atom in contrast to Cobalt has no magnetic moment, while on the other hand the coercive field strength between >> = 0.15

ίο and y = 0, S5 increases very much. A material in which both the coercive force and the remanence have high values, i.e. approximately the range >> = 0.2 to y = 0.3 in FIG. 2, is particularly suitable as a magnetic material.

The energy product of almost all samples was above 9 MGOc and reached a maximum value of approx. 20 MGOe _{with the alloy Sm (Co 084} Cu ₀ , I _{6 Vj 5).}

In Flg. 3 is shown using the example of the alloy Sm (Co ₀₇ , Cu ₀ J ₂ Depending on the dependence of the magnetic properties on the annealing temperature T after a heat treatment lasting about 2 hours. It can be seen that after a heat treatment at 450 ° there is a slight improvement in the coercive field strength The coercive field strength also improves somewhat at 650 ° C, but at this temperature the alloy is decomposed after several hours into a mixture consisting of two phases.

In order to obtain any size from the coarse-grained permanent magnetic material obtained from the melt There are two ways of producing magnetic bodies. Through directional solidification you can either Large single crystals pulled or by grinding the coarse-grained material, by aligning, pressing and sintering the powder, sufficiently large magnetic bodies can be produced. With the powder metallurgy Process for the production of the magnetic body, it proves to be particularly advantageous that the particle size of the Powder obtained by the grinding process is not critical, as the magnetic properties of the materlallen are obtained according to the invention by precipitation hardening and no longer by domain formation and domain wall relocations can be changed.

For this purpose 2 sheets of drawings

Claims (6)

Patent claims: 1. Process for the production of a cast copper-hardened permanent magnetic alloy from Cobalt, copper and samarium with a composition of the formula ⁵ Sm (Co,., Cu ^, with <χ <1 and
0.15 <y <0.35 and a coercive field strength of up to 20 kOe, a remanence of up to 10 kCr, and an energy product 10 from more than 9 MGOe to 20 MGOe, characterized in that the composition of the Alloy corresponding components cobalt, copper and samarium weighed stochrometrically, mixed, melted at approx. 1400 ° C and then cooled at a rate of at most 50 ° C / min are in such a way that-the structure of rubbish-sized, randomly oriented magnetic single crystal grains consists. 15th 2. The method according to claim 1, characterized in that χ approximately at zero, and y approximately at 0.25. 3. The method according to claim 1, characterized in that the structure has 3 to 5 mm large grains. 4. The method according to claim 1, characterized in that the alloy between approx. 450 ° C and approx. 650 ° C is heat treated for about 2 hours. 20th 5. The method according to claim 1 or 4, characterized in that the alloy obtained is pulverized. Aligned in a magnetic field, pressed and subsequently solidified by sintering. 6. The method according to claim 1 or 4, characterized in that for the production of large magnetic bodies large single crystals are pulled by directional solidification.