Method for manufacturing components for magnetic heads of increased abrasion resistance

The present invention relates to a method for manufacturing components for magnetic heads, and more particularly relates to improvements in the method for manufacturing components such as a core and a shield casing for magnetic heads used for magnetic sound or video recording and reproducing.
The material used for the above-described components is in general required to have, in addition to high magnetic properties, high mechanical properties, in particular high abrasion resistance since they are usually subjected to hard and frequent frictional contact with running magnetic tapes.
Permalloy alloys are conventionally and generally used for such components but unable to sufficiently suffice such requirement for high abrasion resistance, thereby causing relatively low durability of these components for magnetic heads. It is proposed to add a particular element or elements to permalloy alloys. Such addition, however, is still unable to raise abrasion resistance of the component to an appreciable extent, and liable to lower magnetic characteristics of the product. It is proposed also to add a hard material or materials such as metal oxide to permalloy alloy. This addition, however, is accompanied with difficulty in uniform dispersion of the added material into the base alloy even in molten state. Biased presence of the added material in the base alloy naturally causes biased mechanical and/or magnetic properties of the product.
In view of the above-described state of the art, the inventors of the present invention has tried to greatly raise abrasion resistance of the components used for magnetic heads by improving their manufacturing method.
In conventional manufacturing of a laminated head core, for example, a cast block is reformed into laminae by rolling. Basically, the present invention proposes to introduce the art of powder metallurgy into the above-described manufacturing in order to obtain permalloy alloy blocks to be subsequently subjected to rolling. It is admitted that mere manufacturing of permalloy alloy block by powder metallurgy itself is an established art well known to public. However, permalloy alloy blocks manufactured by powder metallurgy only have very poor abrasion resistance. Further, presence of numerous fine air voids in the block disables easy application of fine cutting to the block and deteriorates magnetic properties of the product.
It is the basic object of the present invention to provide a method for manufacturing components for magnetic heads which have, in addition to high magnetic properties, sufficient mechanical properties, in particular high abrasion resistance.
In accordance with the basic aspect of the present invention, material powder is blended so as to substantially have a permalloy alloy composition, the blended material powder is subjected to compaction to obtain a compressed block, and the compressed block is subjected to rolling after application of sintering.
In more detail, blending of the material powder is carried out by mixing Fe powder with Ni powder. As a substitute, Fe-Ni alloy powder may be used as the base material with addition of a proper material or materials for improving any property of the product.
So-called 78 permalloy may be used for the permalloy alloy in the present invention. 78-permalloy includes, as the base material, a mixture of 60 to 90% by weight of Ni with 5 to 20% by weight of Fe. In addition to the base material, it may include, depending on requirement in use of the product, at least one of 0.5 to 14% by weight of Mo, 0.1 to 20% by weight of Cu, 0.1 to 10% by weight of Cr, 0.1 to 15% by weight of Nb, 0.1 to 10% by weight of Ti, 0.1 to 8% by weight of V, 0.1 to 8% by weight of Si, 0.01 to 5% by weight of Al, 0.1 to 8% by weight of W, 0.1 to 15% by weight of Ta, 0.01 to 15% by weight of Mn, 0.1 to 5 % by weight of Co, 0.005 to 5% by weight of Y, 0.005 to 5% by weight of Ce, 0.005 to 5% by weight of La and 0.005 to 5% by weight of Sm.
So-called 45-permalloy may be usable also, which includes, as the base material, a mixture of 35 to 55% by weight of Ni, with 35 to 55% by weight of Fe, and, as the additive, at least one of the above-described materials.
After complete blending, the material powder is placed, for example, in a rubber casing for compaction by, for example, hydrostatic compaction. When hydrostatic compaction is employed, the compaction pressure should preferably be in a range from 4,000 to 20,000 kg/cm.sup.2 and the compaction time in a range from 2 to 300 sec.
The compressed block obtained by the compaction is then subjected to high temperature sintering within a vacuum, reducing gas or inert gas atmosphere.
In the case of sintering within a vacuum atmosphere, the degree of vacuum should preferably be 10.sup.-2 Torr or lower. Any degree of vacuum above limit tends to cause oxidation of the material powder, thereby deteriorating magnetic properties of the product.
In the case of sintering within a reducing or inert gas atmosphere, the dew point of the gas should preferably be -20.degree. C. or lower. Any dew point exceeding this value may also cause oxidation of the material powder, thereby lowering magnetic properties of the product.
The sintering temperature should preferably be in a range from 900.degree. to 1,430.degree. C. No effective sintering starts at a temperature below 900.degree. C. whereas any temperature above 1.430.degree. C. may cause melting of the material powder.
The sintering time should preferably be in a range from 1 to 20 hours. No sufficient sintering effect is obtained when heating lasts shorter than 1 hour whereas no remarkable rise in sintering effect is expected when heating time exceeds 20 hours.
Finally, the sintered block is rolled into a lamina of, for example, about 0.3 mm thickness. This rolling preferably includes alternate application of 30 to 70% of cold rollings and annealings at 750.degree. to 850.degree. C.
The lamina so obtained is then cut into laminae of a prescribed pattern. In the case of a laminated head core, such laminae are superposed upon each other and bonded together by suitable resin. In the case of a shield casing, the lamina is subjected to pressure shaping.
In the case of the method of the basic aspect of the present invention, permalloy powder metallurgy is used in combination with the later-staged rolling, thereby successfully raising abrasion resistance of the product. This success accrues from the fact that application of the rolling smashes hard oxidized shells formed on powder particles during the initial blending, compaction and sintering and the smashed pieces disperse uniformly into the body of the rolled lamina.
That is, the first aspect of the present invention tactfully makes use of formation of oxidized shells on powder particles during processes preceding the final rolling. It has been confirmed, however, by the inventors of the present invention, that one cannot always expect sufficient and constant formation of such oxidized shells during manufacturing of the sintered blocks. Consequently, the method of the basic aspect of the present invention cannot always assure successful provision of sufficiently high abrasion resistance.
It is another object of the present invention to enable constant manufacturing of permalloy components for magnetic heads with sufficiently high abrasion resistance.
In accordance with another aspect of the present invention, an easily oxidizable element or elements are added to the base material for permalloy alloy, i.e. mixture of Fe with Ni, and preparation of the material powder includes atomization. Like the method of the basic aspect, the blended material powder is then subjected to compaction, sintering and rolling.
In more detail, the above-described easily oxidizable element or elements are chosen from a group consisting of Al, Ti, Mg, Ca, Ce and Be. The base material of permalloy alloy composition and the easily oxidizable element or elements are blended together by atomization in order to cause formation of oxidized shells on the powder particles. In particular, it was confirmed that remarkable effect can be obtained when Al, Ti, Mg and/or Ca is added to the base material.
The preferable contents for the above-described easily oxidizable elements are as follows;
Al: 0.005 to 2% by weight
Ti: 0.005 to 1.5% by weight
Mg: 0.01 to 2% by weight
Ca: 0.01 to 2% by weight
Ce: 0.005 to 1.0% by weight
Be: 0.001 to 1.0% by weight
When the content of an added element falls short of its lower limit, no sufficient rise in abrasion resistance of the resultant product can be expected. The content of an added element exceeding its upper limit tends to lower magnetic properties of the product obtained. When two or more easily oxidizable elements are used in combination, the total content of such elements should preferably be in a range from 0.005 to 2.0% by weight.
In addition to the above-described easily oxidizable elements, the material powder may contain elements listed in connection with the basic aspect of the present invention.
It is necessary in this aspect of the present invention that at least the material powder containing the easily oxidizable element or elements is prepared by atomization. That is, when only alloy powder having the ultimate composition is used as the base material powder, the molten alloy has to be powdered by atomization. When a part of the ultimate composition is used as the master alloy containing the easily oxidizable element or elements and each remnant is added individually, at least the master alloy has to be powdered by atomization. Further, when any single easily oxidizable element is added, at least the element has to be powdered by atomization.
The atomization used for the present invention may take the form of hydro-atomization in which a substance in molten state is powdered by jet flow of water. It may further take the form of gas-atomization in which a substance in molten state is powdered by flow of compressed gas such as air. A great deal of oxidized shells are formed on the powder particles by use of atomization in blending of the material powder containing easily oxidizable element or elements.
During the last staged rolling, the shells on the powder particles are smashed into fine pieces which then disperse uniformly into the body of the rolled lamina. Concurrently, fine air voids in the sintered block disappear. Such a combined effect greatly raises abrasion resistance of the product.
In the case of the above-described aspect of the present invention, at least one easily oxidizable element is added to the material powder and atomization is used for preparation of the material powder. Use of atomization, however, has its merits with demerits. That is, presence of the oxidized shells on powder particles blocks smooth dispersion of the powder particles and lowers inter-particle bonding. Low inter-particle bond may cause separation of particles from the product depending on the strength of the frictional contact, thereby deteriorating abrasion resistance of the product.
It is the other object of the present invention to provide a method for fortifying the inter-particle bond of the product whilst allowing formation of the oxidized shells on powder particles in preparation of the material powder for components used for magnetic heads.
Thus, in accordance with the other aspect of the present invention, the material powder including at least one easily oxidizable element is subjected to annealing within a reducing atmosphere after preparation including atomization. By this annealing, oxides of easily reducible elements such as Fe and Ni contained in the material powder are reduced in advance of the compaction, sintering and rolling,
The above-described reducing atmosphere should preferably be either hydrogen reducing atmosphere having a dew point of -30.degree. C. or lower or vacuum atmosphere of 10.sup.-2 Torr or higher. The annealing temperature should preferably be in a range from 200.degree. to 800.degree. C. The annealing time should preferably be in a range from 0.5 to 20 hours.
No sufficient reduction is obtained when annealing is carried out within a hydrogen reducing atmosphere having a dew point higher than -30.degree. C. or a vacuum atmosphere lower than 10.sup.-2 Torr. No reduction starts at any temperature lower than 200.degree. C. whereas sintering starts during annealing when the temperature exceeds 800.degree. C. No sufficient reduction can be completed within 0.5 hours whereas no further development in reduction can be expected even when annealing lasts longer than 20 hours.
Due to such reduction during annealing, oxides formed on the powder particles by atomization are partly reduced. That is, among the oxides in the oxidized shells, those originated from easily oxidizable elements such as Al remain almost unchanged during the annealing. In contrast to this, those originated from easily reducible elements such as Ni and Fe are reduced to their original elements during the annealing.
During the sintering to be carried out after the compaction of the material powder, presence of the reduced elements such as Ni and Fe on the powder particles enables smooth inter-particle dispersion, thereby producing sintered blocks with high inter-particle bond.
Such a high inter-particle bond well prevents undesirable fall of particles from the products which is otherwise caused by frictional contact with running tapes.

The invention will hereinafter be explained in more detail in reference to the accompanying drawings, in which
FIG. 1 is a top view of a magnetic head core test piece used for measurement of abrasion resistance in the following examples of the present invention.
FIG. 2 is a side view of the above-described test piece,
FIG. 3 is a side sectional view of the tape contacting face of the sample No. 1 (present invention) in Example 1,
FIG. 4 is a side sectional view of the tape contacting face of the sample No. 9 (conventional) in Example 2, and
FIG. 5 is a perspective view of the shield casing test pieces used in Example 5, and
FIGS. 6 through 17 are graphs for showing results obtained in Examples 9 and 10.

The following examples are illustrative of the present invention but not to be construed as limiting the same.
EXAMPLE 1
Following powders were selectively used for preparation of the material powder;
Fe--Carbonyl iron powder
Ni--Carbonyl nickel powder
Mo--Molybdenum powder
Cu--Electrolytic copper powder
Cr--Electrolytic chromium powder
Nb--Nickel-niobium alloy powder
Ti--Titanium halide powder
V--Ferro-vanadium alloy powder
Si--Ferro-silicon alloy powder
Al--Ferror-alluminum alloy powder
W--Ferro-tungsten alloy powder
Ta--Nickel-tantalum alloy powder
Mn--Ferro-manganese alloy powder
Co--Electrolytic cobalt powder
Using these powders, eight material powder samples No. 1 to No. 8 of different compositions were prepared as shown in Table 1.
TABLE 1______________________________________Sample No Composition (in % by weight)INVEN- CONVEN-TION TIONAL Ni Fe Mo Cu Nb Ti Si Cr______________________________________1 (17) 9 79.0 16.5 4.52 (18) 10 78.5 13.0 4.0 5.03 (19) 11 81.5 10.0 1.5 7.04 (20) 12 83.0 12.0 3.0 2.05 (21) 13 84.0 11.8 4.26 (22) 14 50.0 50.07 (23) 15 45.0 53.0 2.08 (24) 16 39.0 51.0 10.0______________________________________
Each material powder sample was mixed from 0.5 to 4 hours within a V-type mixer and placed within a rubber container for hydrostatic compaction at 15.000 kg/cm.sup.2 for about 200 sec. A compressed block of 50.times.50.times.100 mm. was obtained. The compressed block was then sintered at 1,300.degree. C. for about 15 hours within a vacuum atmosphere of 10.sup.-2 Torr. or lower. The sintered block was subjected to alternate application of cold rolling of 50% and interim annealing at 800.degree. C. for 2 hours until a lamina of 0.3 mm was obtained.
An O-ring shaped test piece was stamped out of the permalloy alloy lamina. The outer diameter was 10 mm, and the innner diameter was 6 mm. The test piece was subjected to annealing at 1,100.degree. C. for 2 hours within a hydrogen atmosphere. Magnetic properties and hardness of the resultant test piece were measured.
Separately, a number of pieces of the pattern shown in FIG. 1 were stamped out of the above-described permalloy alloy lamina, the pattern being to the transverse cross sectional profile of an ordinary magnetic head core. 25 sheets of pieces were superposed and bonded together by means of suitable resin in order to obtain a magnetic head core test piece such as shown in FIG. 2. The dimension of this test piece was as follows;
______________________________________Length 1 = 11.5 mm.Width w = 10 mm.Radius of curvature ofthe tape contacting face A R = 10 mm.Thickness d = 7 mm.______________________________________
In the abrasion test, the test piece was mounted to an auto-reverse type cassette deck and a gamma hematite tape was used, which is generally known to cause maximum abrasion. Running of the tape was continued for 100 hours and the maximum value Dmax of the abrasion depth D in the tape contacting face A of the test piece was measued. The abrasion test was carried out in an atmosphere of 20.degree..+-.2.degree. C. temperature and 40 to 50% humidity. The results of the measurements are shown in Table 2. Abrasion in the tape contacting face A of the test piece No. 1 is shown in FIG. 3.
TABLE 2__________________________________________________________________________Magnetic properties Initial Saturated Maximum magnetic Coercive magnetic flux Hard- abrasionSample permeabi- force density B.sub.10 ness depth D.sub.maxNO. lity (.mu..sub.o) Hc (A/m) (T) (Hv) (.mu.m) category__________________________________________________________________________1 70,000 1.2 0.76 156 1.2 present2 80,000 1.6 0.70 132 1.9 invention3 100,000 0.8 0.60 205 0.24 50,000 2.0 0.57 220 0.25 45,000 2.0 0.55 220 0.356 2,500 8 1.40 130 0.87 5,000 6.0 1.35 140 0.48 2,500 6.8 0.55 130 0.39 90,000 0.88 0.76 140 13 conventional10 70,000 1.44 0.71 115 2011 120,000 0.64 0.61 192 312 60,000 1.6 0.58 210 2.513 40,000 2.48 0.53 208 4.514 2,000 8 1.40 110 1215 5,000 6.4 1.35 120 916 3,000 6.4 0.55 115 6__________________________________________________________________________
EXAMPLE 2
Permalloy alloy powder prepared by carbonyl process was used as the base material while including 75% by weight of Ni and remaining amount of Fe. Carbonyl iron powder and carbonyl nickel powder were added to this base material. Further materials were added in order to obtain eight material powder samples No. 17 to 24 as shown in Table 1. Each material powder sample was subjected to compaction, sintering and rolling in order to obtain a permalloy lamina under conditions same as those employed in Example 1. The test piece so obtained were subjected to measurements of magnetic properties, hardness and abrasion resistance. Results are shown in Table 3.
For comparison, permalloy alloy blocks were prepared in accordance with the conventional casting process and were formed into permalloy alloy laminae in a manner the same as preparation of the laminae in accordance with the present invention. Similar measurements were applied to samples No. 9 to No. 16 and the condition of the tape contacting face of the sample No. 9 after abrasion test is shown in FIG. 4. The compositions of the conventional samples No. 9 to 16 are equal to those of the samples No. 1 to 8 in accordance with the present invention.
TABLE 3__________________________________________________________________________Magnetic properties Initial Saturated Maximum magnetic Coercive magnetic flux Hard- abrasionSample permeabi- force density B.sub.10 ness depth D.sub.maxNO. lity (.mu..sub.o) Hc (A/m) (T) (Hv) (.mu.m) Category__________________________________________________________________________17 80,000 0.8 0.74 156 1.3 Present18 80,000 1.2 0.70 140 1.7 invention19 120,000 0.8 0.59 210 0.120 50,000 2.0 0.57 200 0.221 30,000 3.2 0.51 230 0.2522 2,000 9.6 1.35 140 0.923 4,000 7.2 1.28 150 0.424 2,000 8 0.53 130 0.4__________________________________________________________________________
The results given in Table 2 clearly indicate that employment of the present invention in manufacturing of magnetic head cores results in surprising rise in abrasion resistance. Under same condition of abrasion, the maximum abrasion depth for the samples of the present invention is one-tenth or smaller than that for the samples of the conventional art. Even in the case of sample No. 6 which contains no additional component for improvement of properties, its abrasion resistance is by far higher than the conventional samples containing such an additional component or components. No particular lowering in magnetic properties is recognized. High abrasion resistance could be obtained either when Ni and Fe metallic powders were used (Example 1) or when Ni-Fe alloy powder was used (Example 2).
The above-described improvement in abrasion resistance is believed to accrue from the fact that surfaces of powder particles are a bit oxidized to form shells during compaction and sintering, and the oxidized shells are smashed into fine pieces during rolling of the sintered block which are uniformly dispersed into the body of the lamina and contributes to improvement in abrasion resistance. Due to this internal dispersion, the fine pieces of metal oxides are not reduced during annealing within a hydrogen atmosphere to be applied after stamping of the lamina.
EXAMPLE 3
Each of the alloys having the compositions shown in Table 4 was molten by means of vacuum melting process and powdered by means of hydro-atomization within a mixture of air with argon gass.
TABLE 4______________________________________Sample Composition (in % by weight)NO. Ni Fe Mo Cu Al Ti Mg Ca Ce Be______________________________________25 78 13 4.0 4.5 0.526 78 13 3.5 4.0 1.527 78 13 4.0 4.9 0.128 78 13 3.0 4.0 2.029 78 13 4.0 4.9 0.130 78 13 3.0 4.0 2.031 78 13 4.0 4.9 0.0132 78 13 3.0 4.0 2.033 78 13 4.0 4.9 0.134 78 13 3.0 4.0 1.035 78 13 4.0 5.0 0.00136 78 13 4.0 4.0 1.037 78 13 4.0 4.97 0.05 0.0238 78 13 4.0 4.899 0.05 0.05 0.00139 78 13 4.0 4.97 0.02 0.0540 45 53 2.041 45 53 1.98 0.0242 45 52 2.0 1.043 45 53 1.98 0.0244 45 52 2.0 1.0______________________________________
Each material powder was then placed within a rubber casing for hydrostatic compaction at about 15,000 kg/cm.sup.2 for about 200 sec, thereby obtaining a compressed block of 50.times.50.times.100 mm. The compressed block was subjected to sintering at 1,300.degree. C. for 5 hours within a vacuum atmosphere and the sintered block was subjected to alternate application of cold rolling of 50% and interim annealing at 800.degree. C. for 2 hours until a permalloy alloy lumina of 0.3 mm thickness is obtained.
Test pieces and magnetic head core samples were prepared and measurements were carried out as in Example 1. The results of the measurements are given in Table 5.
TABLE 5______________________________________Magnetic properties Initial magnetic Coercive SaturatedSample permeability force magnetic flux AbrasionNO. .mu..sub.o Hc (A/m) density B.sub.10 (T) .mu. m______________________________________25 15,000 1.84 0.61 1126 11,000 2.08 0.55 927 38,000 1.92 0.56 1228 10,000 3.12 0.48 7.229 54,000 2.00 0.68 1030 8,000 3.28 0.56 7.131 42,000 0.96 0.71 2132 6,000 3.04 0.61 5.633 18,000 3.2 0.60 1334 6,000 4.0 0.50 5.535 38,000 1.92 0.59 1236 10,000 4.0 0.53 7.237 43,000 1.76 0.69 9.338 32,000 1.92 0.69 8.639 21,000 1.44 0.69 10.340 4,000 8.8 13.3 4.141 2,500 12 13.3 3.542 1,200 14.4 13.0 2.843 3,000 12 13.0 4.044 1,800 16 12.6 3.9______________________________________
For comparison, material powder samples No. 45 to 64 having compositions same as those of samples No. 25 to 44, respectively in the listed order, were formed into permalloy alloy cast blocks by means of conventional vacuum melting process. Each cast block was rolled into a permalloy alloy lamina of 0.3 mm thickness which was then subjected to tests similar to those applied to samples No. 25 to 44. The results are given in Table 6.
The extent of oxidization by the above-described atomization applied to samples No. 25 to 44 was from 200 to 3,000 ppm. for each.
TABLE 6______________________________________Magnetic properties Coercive SaturatedSample Initial magnetic force magnetic flux AbrasionNO. permeability Hc (A/m) density B.sub.10 (T) .mu. m______________________________________45 20,000 1.6 0.62 6946 15,000 2.4 0.58 6347 41,000 1.44 0.56 7148 13,000 2.8 0.49 3249 70,000 1.6 0.68 6550 14,000 3.04 0.59 4151 85,000 0.72 0.72 8552 13,000 2.64 0.64 5553 21,000 2.8 0.62 7354 12,000 3.6 0.52 4255 51,000 1.68 0.61 8156 12,000 3.52 0.54 6257 52,000 0.96 0.70 7258 55,000 0.88 0.69 7159 61,000 0.9 0.71 8260 5,000 8.0 1.35 4361 3,000 9.6 1.33 4162 1,500 12 1.30 3563 4,000 10.4 1.33 4664 2,100 14.4 1.28 32______________________________________
The results given in Tables 5 and 6 clearly indicate that addition of an easily oxidizable element or elements in combination with preparation of the material powder by means of atomization greatly improves abrasion resistance of the product.
EXAMPLE 4
Each of the nine material powder samples No. 65 to 73 having compositions shown in Table 7 was molten by vacuum melting process and powdered by means of hydro-atomization within a mixture of air with argon gass.
TABLE 7______________________________________Sample Composition (in % by weight)NO. Ni Fe Mo Cu Al Ti Mg Ca Be______________________________________65 78 13 4 4.5 0.566 78 13 4 4.9 0.167 78 13 3.0 4.0 2.068 78 13 4 4.9 0.0169 78 13 3.0 4.0 2.070 78 13 4 5.0 0.00171 78 13 4 4.889 0.05 0.05 0.00172 78 13 4 4.97 0.02 0.0573 45 52 2.0 1.0______________________________________
Each material powder was then subjected to reduction at 400.degree. C. for 10 hours within a hydrogen atmosphere of -70.degree. C. dew point. Ring shaped test piece and a head core sample was prepared in a manner similar to that in Example 1. Measurements of various properties were also carried out just like in Example 1. The obtained results are given in Table 8.
The amounts of oxygen possessed by each atomized material powder before and after the reduction were measured and the results are given in Table 10.
TABLE 8______________________________________Magnetic properties Coercive SaturatedSample Initial magnetic force magnetic flux AbrasionNO. permeability Hc (A/m) density B.sub.10 (T) .mu.m______________________________________65 20,000 1.20 0.60 1366 40,000 1.60 0.56 1667 13,500 2.88 0.48 8.068 61,000 0.80 0.72 2369 11,000 2.80 0.63 6.270 48,000 1.76 0.59 1471 50,000 1.12 0.69 9.472 46,000 1.08 0.70 12.673 2,100 14.4 1.26 4.0______________________________________
For comparison, material powder samples No. 74 to 82 having compositions same as those of samples 65 to 74, respectively in the listed order, were formed into permalloy alloy cast blocks by means of conventional vacuum melting process.
Each cast was rolled into a permalloy alloy lamina of 0.3 mm thickness which was then subjected to tests similar to those applied to samples No. 65 to 73. The results are give in Table 9.
TABLE 9______________________________________magnetic properties Initial magnetic Coercive SaturatedSample permeability force magnetic flux AbrasionNO. .mu..sub.o Hc (A/m) density B.sub.10 (T) .mu.m______________________________________74 20,000 1.60 0.62 6975 41,000 1.44 0.56 7176 13,000 2.8 0.49 3277 85,000 0.72 0.72 8578 13,000 2.64 0.64 5579 51,000 1.68 0.61 8180 55,000 0.88 0.69 7181 61,000 0.9 0.71 8282 2,100 14.4 1.28 32______________________________________
TABLE 10______________________________________ Amount of oxygen in ppm.Sample After atomizationNO. (before reduction) After reduction______________________________________65 2,100 60066 1,600 40067 2,600 48068 800 30069 3,000 80070 860 26071 1,100 34072 1,200 41073 2,100 1,00______________________________________
The results given in Tables 8 and 9 clearly indicate that introduction of the annealing within a reducing atmosphere into preparation of the material powders greatly contributes to improvement in abrasion resistance of the products. Further, the results given in Table 10 indicate remarkable decrease in content of oxygen which resulted from annealing in a reducing atmosphere.
EXAMPLE 5
Permalloy alloy laminae were prepared in a manner same as that in Example 1 while using the material powder samples No. 1 to 8. Ring-shaped test pieces were stamped out of the laminae. Likewise shield casing test pieces such as shown in FIG. 5 were formed of the laminae. They were all subjected to tests and measurements substantially similar to those employed in Example 1. The results are given in Table 11.
TABLE 11______________________________________Sample Maximum abrasionNO. depth D.sub.max in .mu.m Category______________________________________1 1.1 Present2 1.8 invention3 0.24 0.25 0.46 0.87 0.38 0.39 14 Conventional10 1911 312 313 514 1115 1016 6______________________________________
For comparison, like shield casing test pieces were prepared using the material powder samples No. 9 to 16 in Example 1 by means of the conventional melt casting process and subjected to similar tests and measurements. The results obtained are given in Table 11, also.
EXAMPLE 6
Like shield casing test pieces were prepared in a manner same as that in Example 2 while using the material powder samples No. 17 to 24. Test pieces were all subjected to tests and measurements substantially similar to those employed in Example 5. The results obtained are given in Table 12.
TABLE 12______________________________________ Maximum abrasion Sample depth D.sub.max in No. .mu.m______________________________________ 17 1.2 18 1.7 19 0.1 20 0.2 21 0.2 22 1.0 23 0.5 24 0.4______________________________________
The results given in the Tables clearly indicate advantages accruing from the present invention.
EXAMPLE 7
Like shield casing test pieces were prepared in a manner same as that in Example 3 while using the material powder samples No. 25 to 44 (see Table 4). Test pieces were all subjected to tests and measurements substantially similar to those employed in Example 5. The results obtained are given in Table 13.
For comparison, like shield casing test pieces were prepared by means of the conventional process described in Example 3 whilst using the material powder samples having compositions same as those of samples No. 25 to 44. The results of the tests and measurements are given in Table 13.
TABLE 13______________________________________ maximum abrasion depthSample D.sub.max in .mu.mNO. Present invention Conventional______________________________________25 12 7126 9 6427 12 7328 8 3229 11 6430 7 4231 20 8732 5.2 5733 12 7234 5.2 4135 13 8236 7.4 6437 9.1 7238 8.8 7239 11 8440 4.2 4341 3.7 4042 2.8 3643 4.2 4644 3.8 33______________________________________
It is clearly noted from the results given in Table 13 that employment of the present invention greatly improves abrasion resistance of the products.
EXAMPLE 8
Like shield casing test pieces were prepared in a manner same as that in Example 4 whilst using the material powder samples No. 65 to 74 (see Table 7). Test pieces were all subjected to tests and measurements substantially similar to those employed in Example 5. The results obtained are given in Table 14.
For comparison, like shield casing test pieces were prepared by means of the conventional process described in Example 4 while using the material powder samples having compositions same as those of samples 65 to 73. The results of the tests and measurements are given in Table 14.
TABLE 14______________________________________ Maximum abrasion depthSample D.sub.max in .mu.mNO. Present invention Conventional______________________________________65 12 7166 15 7367 8.0 3268 22 8769 6.3 5770 13 8271 9.2 7272 12.2 8473 4.1 33______________________________________
The results given in Table 14 clearly indicates advantage of the present invention over the conventional method.
EXAMPLE 9
Material powder sample No. 83 to 101 having the compositions shown in Table 15 were used while preparation of test pieces and measurement of their properties were carried out just as in Example 3. The results obtained are shown in Table 16 and FIGS. 6 through 11.
In FIG. 6, change in initial magnetic permeability .mu..sub.o (on the ordinate) is shown relative to change in total content in % by weight of the easily oxidizable element or elements (on the abscissa). Values are given in logarithm scale.
TABLE 15______________________________________Sam-ple Content (% by weight)No. Ni Fe Mo Cu Al Ti Mg Ca Ce Be______________________________________83 78 13 4.0 4.995 0.00584 78 13 4.0 4.99 0.0185 78 13 4.0 4.9 0.186 78 13 4.0 4.995 0.00587 78 13 4.0 4.99 0.0188 78 13 3.5 4.0 1.589 78 13 4.0 4.99 0.0190 78 12.5 3.0 4.0 2.591 78 13 4.0 4.993 0.00792 78 13 4.0 4.9 0.193 78 12.0 3.0 4.0 3.094 78 13 4.0 4.995 0.002 0.00395 78 13 4.0 4.995 0.003 0.00296 78 13 4.0 4.99 0.005 0.00597 78 13 4.0 4.99 0.005 0.00598 78 13 4.0 4.95 0.025 0.02599 78 13 4.0 4.95 0.025 0.025100 78 13 3.0 4.0 0.5 0.5 0.5 0.5101 78 13 3.0 4.0 0.5 0.5 0.5 0.5______________________________________
TABLE 16______________________________________ Saturated maximum Initial mag- Coercive magnetic flux abrasionSample netic permea- force Hc density B.sub.10 depth D.sub.maxNo. bility (.mu..sub. o) (A/m) (T) (.mu.m)______________________________________83 57,500 0.88 0.70 27.284 44,500 1.02 0.66 22.385 23,000 1.44 0.63 15.086 72,000 1.00 0.70 26.287 70,000 1.02 0.62 20.288 10,000 2.22 0.54 7.289 65,500 1.20 0.70 21.390 6,500 3.55 0.54 7.091 52,000 0.81 0.72 25.192 19,000 2.20 0.65 11.393 5,000 4.10 0.58 5.394 120,000 0.80 0.72 24.095 77,000 0.82 0.70 19.896 98,000 0.82 0.69 16.597 64,000 0.92 0.69 14.098 15,500 2.30 0.60 5.899 13,000 2.20 0.62 5.0100 11,000 2.56 0.61 4.0101 8,000 3.11 0.59 3.0______________________________________
FIG. 7 shows like change in maximum abrasion depth in .mu.m. Increase in content of the easily oxidizable element or elements clearly contributes to fortification of the products.
Changes in initial magnetic permeability (solid curve) and maximum abrasion depth (dotted curve) are shown in FIG. 8 with respect to change in content of Ca. Like changes are shown in FIGS. 9, 10 and 11 for Mg, Ti and Al, respectively.
EXAMPLE 10
The material powder samples No. 83 to 86, 92 and 93 used in Example 9 and material samples No. 102 to 114 having the compositions shown in Table 17 were used while preparation of test pieces and measurement of their properties were carried out just as in Example 4. The results obtained are shown in Table 18 and FIGS. 12 to 17, respectively.
TABLE 17______________________________________Sample Content (% by weight)No. Ni Fe Mo Cu Al Ti Mg Ca Ce Be______________________________________102 78 13 3.0 4.0 2.0103 78 13 4.0 4.98 0.02104 78 13 4.0 4.5 0.5105 78 13 4.0 4.995 0.05106 78 13 4.0 4.0 1.0107 78 13 4.0 4.99 0.01108 78 13 4.0 4.9 0.10109 78 13 4.0 4.0 1.0110 78 13 3.0 4.0 2.0111 78 13 4.0 4.994 0.003 0.003112 78 13 4.0 4.98 0.005 0.005 0.005 0.005113 78 13 4.0 4.0 0.5 0.2 0.5 0.3114 78 13 3.0 4.0 1.0 0.5 1.0 0.5______________________________________
TABLE 18______________________________________ Saturated maximum Initial mag- Coercive magnetic flux abrasionSample netic permea- force Hc density B.sub.10 depth D.sub.maxNo. bility (.mu..sub. o) (A/m) (T) (.mu.m)______________________________________83 65,000 0.92 0.70 27.384 58,000 0.92 0.70 21.585 31,500 1.10 0.62 13.486 70,000 0.82 0.72 25.392 40,000 1.12 0.68 12.793 7,500 3.20 0.60 4.0102 12,500 1.51 0.60 10.0103 67,500 1.20 0.70 21.8104 32,500 2.20 0.54 9.0105 67,000 0.80 0.72 30.0106 16,000 2.10 0.65 8.1107 70,000 0.81 0.70 20.5108 65,000 0.92 0.68 9.5109 42,000 1.21 0.65 5.5110 18,000 2.10 0.61 5.0111 100,000 0.76 0.71 22.3112 75,000 0.85 0.70 15.0113 8,000 2.25 0.65 6.5114 6,000 2.41 0.58 3.0______________________________________
In FIG. 12, change in initial magnetic permeability .mu.o (on the ordinate) is shown relative to change in total content in % by weight of the easily oxidizable element or elements (on the abscissa). Values are given in logarithm scale.
FIG. 13 shows like change in maximum abrasion depth in .mu.m. Increase in content of the easily oxidizable element or elements clearly fortifies product against abrasion.
Changes in initial magnetic permeability (solid curve) and maximum abrasion depth (dotted curve) are shown in FIG. 14 with respect to change in content of Ca. Like changes are shown in FIGS. 15, 16 and 17 for Mg, Ti and Al, respectively.

Number	Date	Country
54-64819	May 1979	JPX
54-98317	Jul 1979	JPX
54-98555	Aug 1979	JPX
54-159092	Dec 1979	JPX

Number	Name	Date
3728111	Stromblad et al.	Apr 1973
3814598	Gabriel	Jun 1974
4029475	Hamai et al.	Jun 1977
4029501	Moss	Jun 1977
4209326	Klein	Jun 1980

Method for manufacturing components for magnetic heads of increased abrasion resistance

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