JPS6012766B2 - Manufacturing method of magnetic head core material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a Fe-N-S alloy known as Sendust alloy.
The present invention relates to a method of manufacturing a magnetic head core material made of an i-based alloy magnetic material by casting.

Conventional casting methods for producing magnetic head cores made of Sendust alloy have generally been carried out under normal atmospheric pressure.

However, during casting of sendust alloy Rakuyo, the solidification shrinkage is extremely large, usually reaching 10 to 15%, so when conventional casting methods are used, a large amount of shrinkage cavities and voids occur, resulting in a significantly low density of the casting. . If a low-density Sendust alloy casting containing shrinkage cavities and voids is used as it is as a magnetic head core, the magnetic properties will be low, and the wear resistance on the contact surface with the magnetic tape will not be sufficient.
Furthermore, chipping occurs from the voids during the final finishing process, and therefore it is practically impossible to cast a casting close to the shape of the magnetic head core and finish it into a product using only the final finishing process. Therefore, in the past, it was usual to cast a coin coin that was significantly larger than the product shape, select a good part of the coin coin that did not contain shrinkage holes or voids, and carve out that part to make the product. However, such conventional manufacturing methods not only have a significantly low material yield, but also have the following problems due to the unique properties of Sendust alloy. That is, since Sendust alloy is extremely hard, it is difficult to cut or grind it, and therefore it is extremely difficult to cut it out from a mirror block to obtain a product as described above.

For this reason, in the past, machining required an extremely long time, resulting in extremely low productivity, and the cutting tools were also severely worn out, resulting in an increase in manufacturing costs. Furthermore, even if a good part is selected from a mirror block, it is difficult to avoid the presence of a certain amount of voids, etc., and therefore it is not always possible to obtain sufficient magnetic properties and wear resistance. ) could not completely avoid the occurrence of defective products. As mentioned above, in order to eliminate the need for difficult cutting and grinding processes for sendust alloys, it is considered to prepare a mold in the shape of the product, pour molten metal into the mold, and directly cast the product shape. It will be done.

However, as mentioned above, shrinkage cavities and voids occur in molten sendust alloy when it solidifies, so it is impossible to directly obtain a cast product shape. In the past, it was considered difficult to simultaneously solve both the problem of lower density and the ever-increasing problem of low density. In addition to the main elements of conventional Sendust alloys, such as Fe, Si, and Si, it has also been proposed to add yttrium, titanium, etc. to prevent shrinkage cavities and voids. On the contrary, there was a problem in that the magnetic properties deteriorated due to the influence, ``as a result, it was difficult to put it into practical use.''

This invention has been made in view of the above circumstances, and it solves the above-mentioned conflicting problems all at once when producing magnetic head core material made of Sendust alloy by casting, and solves the problem of low density during casting. To provide a method for manufacturing a magnetic head core material that eliminates the problems of shrinkage cavities and voids, and at the same time, substantially eliminates the need for cutting and allows the production of a magnetic head core material having excellent magnetic properties at high efficiency and low cost. The purpose is to

That is, the manufacturing method of the present invention uses a mold having a cavity corresponding to a deformed columnar body whose cross-sectional shape is the planar shape of a magnetic head core half, and the mold is aligned in the radial direction with respect to a predetermined axis. Arrange it like this,
The mold is rotated around the axis to apply centrifugal force to the molten metal in the mold, solidifying the molten metal, thereby directly casting an irregularly shaped columnar body having a cross-sectional shape of the magnetic head core halves. This is a summary. This invention will be explained in detail below.

It is desirable that the melted raw materials of Fe, AI, and Sj used in the present invention have a purity higher than that of the raw materials used in the production of conventional sendust alloy magnetic head core materials.

For example, in the manufacture of Sendust alloy magnetic head core materials by powder metallurgy, the purity of the material is Si98.0.
~99.0%, AI99.8%, Fe99.8%, so the raw materials used in this invention have a purity of Si99.0% or more, AI99.9% or more, Fe99.
It is desirable that the purity is 8% or more, and the more optimal purity is Si
99.9-99.99%, AI99.99% or more, Fe
It is about 99.8 to 99.9%. The high purity of the dissolved raw material means that the amount of impurities such as oxide complexes contained in the dissolved raw material is extremely low. Therefore, the use of high-purity melted raw materials contributes to improving the melt flowability when the pillar is damaged, as will be described later, and also contributes to improving the magnetic properties of the product. The high-purity melted raw material as described above is a Fe-AI-Si based sendust alloy whose main components are 3 to 8% M (by weight, same hereinafter), 3 to 12% Si, and the balance Fe. It is blended accordingly. Of these compositional elements, the amount of Si has a large effect on the magnetic properties of the product, especially at 9.7%.
Since the magnetic properties are good in , the Si composition is 9.7.
%±0.2% is desirable. Also, Si9.7
%, it is desirable that AI be 5.8% and Fe be 84.5%. The sendust alloy targeted by this invention is basically a ternary alloy of Fe, AI, and Si as mentioned above, and preferably does not contain other trace components, but in some cases, it may be necessary to prevent rust of the product. For Cr, N
i, etc. may be contained in a total amount of less than 1.0%, preferably less than 0.1%. It is desirable that the above-mentioned molten raw material be melted in a high vacuum, and in this case, the degree of vacuum in the external space in contact with the molten metal is preferably about 10-3 to 10-5 Ton.

In other words, in conventional so-called normal vacuum melting, the degree of vacuum is about 10-ohm, so it is desirable to increase the degree of vacuum even higher than this. By melting in a high vacuum in this manner, oxidation of the raw materials and molten metal is prevented during the heating process up to the melting temperature and at the melting temperature, and almost no new oxide complexes are formed. Therefore, in combination with the use of high-purity melted raw materials as described above, impurities such as oxide complexes are extremely reduced in the molten metal, resulting in extremely good flowability. Next, the molten metal is poured into the mold, and the mold is rotated to solidify the molten metal while applying acceleration due to centrifugal force to the molten metal.

In this casting process, an elongated irregular columnar body 3 (see FIG. 2) whose cross-sectional shape is the planar shape of the half body 2 of the magnetic head core 1 to be finally obtained as shown in FIG. 1 is cast.

That is, as a mold, a precision mold 5 such as a ceramic mold having a cavity 4 corresponding to the irregularly shaped columnar body 3 is used as shown in FIG. The irregularly shaped columnar body 5 cast by the mold 5 is cut into thin pieces using a wire saw or the like to form the head core half body 2 (see the imaginary line in FIG. 2). Note that FIGS. 1 and 3 also show representative dimensions (unit side) of the magnetic head core half body 2 and the mold 5. Furthermore, the precision mold 5 may be molded by a lost wax method or the like similar to the conventional precision mold manufacturing method. When rotating the mold 5 for casting irregularly shaped columnar bodies as described above, the mold 5 is arranged along the radial direction of the axis of rotation. That is, the cavity 4 whose cross-sectional shape is the planar shape of the t-magnetic head core half body 2 is arranged so that the length direction thereof is along the radial direction of the rotation axis.
For example, as shown in FIG. 4, a plurality of elongated molds 5 for casting the irregularly shaped columnar bodies are arranged horizontally and radially with respect to the rotational center axis of the mold holding frame 6 in a rotatable mold holding frame 6, and at appropriate vertical positions. It's fine if you overlap. By arranging the mold 5 in this manner and applying rotation to the mold 5, pressure due to centrifugal force is effectively applied to the molten metal in the mold 5, the molten metal is densified, and the rotation is continued until solidification. This effectively prevents shrinkage cavities and voids from forming in the casting.
The inside of the casting becomes highly dense. In addition, by applying pressure to Rakuyo using the centrifugal force as described above, the molten metal flows into every corner of the mold cavity, thereby making it possible to precisely cast a small, irregularly shaped columnar body with a shape that corresponds to the mold cavity. In particular, in the method of the present invention, a mold having a cavity corresponding to the irregularly shaped columnar body for the magnetic head core halves is arranged radially with respect to the axis of rotation, so that the centrifugal force is applied in the longitudinal direction of the cavity corresponding to the irregularly shaped columnar body. Since the centrifugal force is aligned along the direction of the line of action, the action of centrifugal force as described above is extremely effective. Therefore, as a cast product, a product with extremely few internal defects such as shrinkage cavities and voids and whose shape is faithful to the shape of the cavity can be obtained, and as a result, cutting of the product after casting is almost unnecessary. Note that as a means for pressurizing the molten metal, a method of pressurizing the molten metal using a pressurizing piston has also been considered.

However, when using a pressurized piston, it is difficult to avoid leakage of molten metal from the small gap between the mold and the piston, but the columnar body for the magnetic head core halves is extremely small, as shown in the example of dimensions in Figure 1. Since it has an irregular cross section, even a small amount of melt leakage has a large effect, and therefore even if a piston is used, it is not possible to apply an effective pressing force. In practice, it is impossible to obtain a piston that is compressed with high accuracy due to its shape and dimensions. Therefore, it is only possible to directly cast a columnar body for a magnetic head core having a small size and an irregular cross section by applying centrifugal force by rotating the mold. In addition, when distributing the molds 5 horizontally and radially as shown in FIG. 4, each mold 5 has a portion 58 (see FIG. 3) that forms the tape rubbing portion IA (see FIG. 1) of the head core 1. It is desirable to locate it on the bottom side.

In addition to centrifugal force due to rotation, a large amount of gravity acts on this portion 5B, so that voids are extremely reduced. Therefore, it is possible to obtain a head core 1 with particularly few pores in the tape rinsing moat portion IA. Since the tape-rubbed lacquer portion IA is usually subjected to precise grinding and polishing, the problem of chipping is likely to occur, but the above-mentioned method can effectively prevent the occurrence of chipping of the tape-rubbed portion IA. The rotational speed of the mold 5 is 50 to 360 ratio. p. It shall be within the range of m.

Although centrifugal force varies depending on the distance from the center of rotation,
When the mold 5 with the dimensions shown in the figure is placed at an appropriate position, that is, with the sprue 5A located at a distance of 100 to 20 mm from the center of rotation, the rotation speed will be 5 ratios. p. If it is less than 360 m, sufficient centrifugal force cannot be obtained to prevent the occurrence of shrinkage cavities or pores. p. If it exceeds m, it becomes difficult to use ordinary ceramic materials etc. from the viewpoint of mold strength. However, within the above range, especially 1000 to 180. A value of about p■ is desirable. In the above-mentioned casting process, it is desirable to use a high vacuum of about 10-3 to 10-5 Tom, similar to the melting process.

By adopting such vacuum casting, oxidation of the falling sun during casting is also prevented, and together with the use of high-purity melting raw materials and vacuum melting, the flow of the total molten metal during casting is extremely good. Become. In addition, in this case, since the external space in contact with the molten metal is a vacuum, air bubbles in the setting sun can easily escape to the outside, and as a result, the generation of voids is effectively prevented, and a product with higher density can be obtained.
In particular, when casting irregularly shaped columnar bodies corresponding to magnetic head core halves as in the present invention, the mold cavity is long and narrow and the external closed area is small, so there is a risk that bubbles in the molten metal will be difficult to escape under atmospheric pressure. As mentioned above, by casting in a vacuum, the air bubbles in the flaw can be easily escaped due to the effect of far zero force, and it is possible to obtain a high-density product.For molds such as ceramic molds, It is desirable to heat the water before pouring it.

By pre-heating the mold, moisture, organic matter, gas, etc. adsorbed on the inner wall of the mold can be removed, and it is therefore possible to prevent water vapor and gas from being generated from the inner wall of the mold during Western hot water and from creating voids due to this gas. The magnetic properties of the magnetic head core can be improved. Furthermore, by preheating the mold, the flow of the molten metal during pouring becomes better, which facilitates smooth pouring into the precision mold. Note that the preheating temperature is desirably 50 oo or higher in order to effectively remove moisture and improve the flowability of the melt. Furthermore, if the preheat temperature is too high, there is a problem that the molten metal may stick to the inner wall of the mold, so the upper limit of the preheat temperature is determined depending on the material of the mold. For example, when casting using a deep D force using a ceramic mold, the preheating temperature is desirably 400 oo or less. The magnetic properties of the magnetic head core material obtained by the method of the present invention as described above and the magnetic properties of the magnetic head core material obtained by the subordinate method were judged as follows.

That is, the magnetization strength M at a constant weight of each of the magnetic material obtained according to the method of the present invention and the magnetic material obtained by the secondary method (ordinary casting method under atmospheric pressure) was measured. outer diameter 10 side from the magnetic material of
Cut out a ring-shaped test piece with a thickness of 1.0 ribs on the inner diameter 6 side, measure the maximum saturation magnetic flux density Bs of this O-ring test piece, and calculate the value of 4mpM (where p is the specific gravity of the magnetic material) as shown in the following formula. The ratio r between the value and the value of Bs was determined.

r: Tametei M Here, the saturation magnetic flux density of the ring-shaped test piece is not affected by voids or some impurities in the material, so the value of the ratio r is 1 in an ideal state where there are no pods or impurities.

However, in the material obtained by the method of this invention, the ratio r
The value of is 0.99 or more, whereas there are few materials obtained by conventional methods that have a value of 0499 or more, and most of them have a value of 0.98 or less. From this, it is clear that increasing the density by casting with the addition of centrifugal force contributes to improving the magnetic properties. Next, the present invention will be explained using examples.

Example 1 A molten metal of Fe-AI-Si alloy having the following composition was
At 500 mm, the shape shown in FIGS. 1 and 4,
Casting was carried out using a mold 5 of the same size and a rotatable mold holding frame 6 while applying centrifugal force.

Beat 5.8%Si
9.7%Fe
The relationship between the rotational speed of the mold holding frame 6 and the product yield of the obtained casting was investigated.

The results are shown in Table 1. Table 1 *Due to insufficient strength of the mold made of ceramic material, it could not withstand far zero force, resulting in poor cutting speed of the casting.

From Table 1, the number of revolutions of the mold is 5. p. If it is less than 360 m, a casting can be obtained, but the yield is poor due to shrinkage cavities and voids, and it is industrially disadvantageous. p. If m is exceeded, restrictions arise from the viewpoint of the mold material.

Example 2 A molten Fe-AI-Si alloy having a composition of 5.8% N, 9.7% Si, the balance of Fe, and impurities was heated at 1500°C.
Casting was performed using the same casting apparatus as in Example 1.

The rotation speed at that time was 80. p. m, the preheating temperature of the ceramic mold was 100 qo, the indoor pressure was 10-5Ton, and the purity of the material was as shown in Table 2. Table 2 The relationship between the material purity and the quality of the cast product was investigated.

The results are shown in Table 3. Table 3 From these results, it can be seen that in the method of the present invention, the casting cutting yield can be improved by increasing the purity of the material.

This is because in casting methods that apply centrifugal force, if low-density raw materials are used, the centrifugal force may cause the particles to solidify inside the flaws, reducing the cutting yield. I think that the. Example 3 A molten Fe-N-Si alloy having a composition of 5.8% AI, 9.7% Si, and the balance of Fe was heated at 1500 pm.
Using the same casting apparatus as in Example 1, casting was carried out by changing the pressure in the melting and casting chambers, and the relationship between pressure and product roll was investigated.

The results are shown in Table 4. The rotation speed of the mold was 80 melons. p. m, and the preheating temperature of the ceramic mold is 100°C. From the results shown in Table 4, it can be seen that in the case of the method of the present invention, the walking crab changes significantly depending on the atmospheric pressure inside the casting chamber.

This is because when the pressure decreases, the components of the molten metal undergo compound oxidation due to the high temperature, which clogs the sprue, making the degassing effect of the raw molten metal insufficient, resulting in the generation of pods in the casting and a decrease in yield. Seem. This phenomenon is particularly likely to occur when the rotational speed is small and the effect of centrifugal force is small, which is why the limit on the rotational speed is regulated. Example 4 A Fe-AI-Si alloy having a composition of 5.8% N, 9.7% Si, the balance of Fe, and impurities was cast by the conventional method and the manufacturing method of the present invention under the conditions shown in Table 5, and a test piece was prepared. Fig. 5 and Fig. 6 show the results of examining the magnetic properties of the magnetic material.

Table 5 *Centrifugal force during casting is approximately 100G Magnetic materials manufactured by the method of the present invention are
According to the figure, it can be seen that the magnetic flux density and magnetic permeability are improved.

Example 5 A molten Fe-1-Si alloy having a composition of 5.8% AI, 9.7% Si, and the balance of Fe was cast at 1500° C. by changing the rotational speed of the mold holding frame 6 in the same manner as in Example 1. A head core half body 2 was obtained from the obtained casting.

A magnetic head core was manufactured from this half body 2, and the amount of wear of this magnetic head core was examined. The magnetic tape used was an ordinary product made of gamma hematite as a magnetic material. The results are shown in FIG. As is clear from Figure 7, magnetic head cores formed from castings obtained by rotating the mold and solidifying the molten metal while applying a zero force to the molten metal have less wear compared to those that do not rotate. It can be seen that the degree of decrease in the amount of wear increases as the number increases. This seems to be because the application of centrifugal force reduces the number of voids in the casting, resulting in higher density. As is clear from the above description, according to the manufacturing method of the present invention, the columnar body having a cross section corresponding to the planar shape of the magnetic head core half body can be made without reducing the density, that is, shrinkage cavities and voids are generated. Sendust, which is particularly difficult to machine, can be obtained directly in a high-density state without any process, resulting in significantly improved material yields compared to conventional methods. With alloys, it is possible to significantly improve work efficiency and significantly reduce wear and tear on cutting tools, and therefore, the manufacturing cost of magnetic head cores can be significantly reduced compared to conventional methods.

Furthermore, since the magnetic head core material obtained by the method of the present invention has an extremely high density as described above, a magnetic head core with extremely good magnetic properties can be obtained, and the high density and the high density of the Sendust alloy itself are compatible. As a result, a highly durable magnetic head core with extremely high abrasion resistance and extremely low wear on the lacquered surface of the magnetic tape can be obtained, and furthermore, it is possible to obtain a highly durable magnetic head core with extremely high abrasion resistance and minimal wear on the lacquered surface of the magnetic tape. The risk of chipping occurring and producing defective magnetic head cores is also reduced. Brief description of the drawings Figure 1 is a plan view showing an example of a magnetic head core, Figure 2 is a plan view showing an example of a magnetic head core.
The figure is a perspective view showing an example of an irregularly shaped columnar body as a magnetic head core material manufactured according to the present invention, FIG. 3 is a perspective view showing an example of a mold for casting the irregularly shaped columnar body of FIG. 2, and FIG.
The figure is a schematic longitudinal sectional perspective view showing an example of an apparatus for performing centrifugal casting according to the method of the present invention, and FIGS. 5 and 6 show the magnetic properties of magnetic materials produced by the production method of the present invention and the conventional production method. In the graphs, Fig. 5 shows the DC magnetic characteristics, Fig. 6 shows the AC magnetic characteristics, and Fig. 7 shows the wear resistance of the magnetic head core obtained by the manufacturing method of the present invention and the conventional manufacturing method. It is a graph shown by changing the rotation speed.

1...Magnetic head core, IA...Tape sliding part, 2...Magnetic head core half body, 3...
・Irregular columnar body, 4...Cavity, 5...
template.

Figure 1 Figure 2 Figure 3 Diagram Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A mold having a cavity corresponding to a modified columnar body whose cross-sectional shape is the planar shape of a magnetic head core half body is arranged along the radial direction of a predetermined axis, and the mold A molten metal of Fe-Al-Si based magnetic material is poured into the cavity, and the mold is placed at a height of 50 to 360 degrees centering on the axis.
0r. p. A magnetic head core material characterized in that it is rotated at a rotational speed of m and solidified while applying centrifugal force to the molten metal, thereby casting an irregularly shaped columnar body whose cross-sectional shape is the planar shape of a magnetic head core half body. manufacturing method. 2. In the method for manufacturing a magnetic head core material according to claim 1, the purity of the material is 99.0% or more of Si,
A manufacturing method characterized by containing 99.9% or more of Al and 99.8% or more of Fe. 3. In the method for manufacturing a magnetic head core material according to claim 1 or 2, the pressure is 10^-^3~
A manufacturing method characterized by casting in a room at 10^-^5 Torr. 4. A method for manufacturing a magnetic head core material according to any one of claims 1 to 3, characterized in that the mold is preheated to 50 to 400°C during pouring. 5. In the method for manufacturing a magnetic head core material according to any one of claims 1 to 4, the mold is arranged horizontally with the axis being vertical, and a tape rubbing portion of the magnetic head core is formed. A manufacturing method characterized by arranging the mold so that the part is located on the bottom side.