JP2004330274A - Manufacturing method of cobalt pellet material for forming vapor-deposited film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of cobalt pellet material for forming a vapor-deposited film, which can form a layer of magnetic material with superior magnetic properties without causing heavy splashing during formation of the vapor-deposited film. <P>SOLUTION: When the cobalt pellet material for forming the vapor-deposited film is produced from an ingot which is made through vacuum melting and casting of the cobalt material, the vacuum melting is applied for only one time without remelting and the ingot is cast in the size weighing not less than 2 tons. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a Co pellet material for forming a deposited film for forming a Co thin film by vapor deposition.
[0002]
BACKGROUND OF THE INVENTION
Conventionally, as a material for forming a magnetic recording medium, specifically, a Co—Ni alloy containing pure Co or Ni (for example, a Ni—Co alloy containing 5 to 25% by weight) as a material for forming a magnetic layer on the base layer Alloy) is used.
A vapor deposition method is used as a method of forming a magnetic layer on a base layer such as a resin tape using such a Co material.
[0003]
In this film formation by vapor deposition, for example, an electron beam from an electron gun is applied to a Co pellet material made of the Co material supplied to a crucible in a vacuum processing chamber to heat and melt the same, and the vapor passes through the vacuum processing chamber. It is carried out by adhering to a base layer such as a resin tape and crystallizing by cooling. Thus, a Co magnetic layer is formed on the base layer.
[0004]
At this time, that is, when the Co pellet material is melted by the electron beam, a splash may be generated. If such a splash is generated, a crystal disorder is generated in the deposited film (Co magnetic layer), and the magnetic properties of the same portion are reduced. Is worsened, or in the worst case, the magnetic layer is missing.
[0005]
Although the cause of the occurrence of the splash is not always clear, it is considered that the splash involves the inclusions contained in the Co pellet material.
Specifically, when an electron beam is applied to inclusions contained in the Co pellet material, particularly oxide-based inclusions, the inclusions are decomposed into oxygen and metal, and the oxygen generated by the decomposition is contained in the Co pellet material. It is considered that the CO gas reacts with the carbon remaining in the CO to generate CO gas, and the CO gas bursts to generate a splash.
[0006]
As a solution to the problem of forming a film by vacuum-depositing a Co material on an upper layer of a base layer, for example, one disclosed in Patent Document 1 below is known.
In Patent Document 1, when a Co—Ni alloy containing 5 to 25% by weight of Ni is used as a material for vapor deposition, and this is melted and vaporized by irradiation with an electron beam to form a vapor deposited film on the base layer. , N ₂ , O _{2, and} other gases are generated to generate unevenness in the thickness of the deposited film, that is, the magnetic layer, and pinholes. It is proposed to perform the dissolution, ie, two dissolutions.
[0007]
However, when the present inventors performed this, it was found that a sufficient effect was not obtained in suppressing the splash, which is considered to be caused by inclusions.
[0008]
The present invention has been made to solve such a problem.
In order to solve the problems at the time of vacuum deposition, there is one disclosed in Patent Document 2 below, and the one disclosed in Patent Document 2 also discloses a gas such as N ₂ or O _{2 at} the time of vacuum deposition. The purpose of the present invention is to suppress the occurrence of the problem, and the present invention is different from the present invention in the problem to be solved and the means for solving the problem.
[0009]
[Patent Document 1]
JP-A-9-227968 [Patent Document 2]
JP-A-7-252565
[Means for Solving the Problems]
In order to solve the above problems, a method for producing a Co pellet material for forming a deposited film according to the present invention devised to solve the above-mentioned problem is to obtain an ingot by vacuum melting and casting a Co raw material, and then to form a Co pellet for forming a deposited film from the ingot. In obtaining the material, the vacuum melting is performed only once without re-melting, and the ingot is cast in a large lump of 2t or more (claim 1).
[0011]
Further, claim 2 is characterized in that the Co pellet material is a pure Co material in claim 1, and claim 3 is that in any one of claims 1 and 2, the vacuum melting is vacuum induction melting. Features.
[0012]
[Action and effect of the invention]
As described above, according to the present invention, the vacuum melting is performed only once without re-melting, and the ingot is cast in a large lump of 2 ton or more. The present invention is based on the following knowledge. It is.
That is, the present inventors have focused on the size of the inclusions (oxides) contained in the Co pellet material. If the inclusions are small, even if a splash occurs when the Co pellet material is melted by the electron beam, the splash is reduced. I thought it was a small one with little momentum.
[0013]
A small inclusion means that the amount of oxygen contained therein is small, so even if CO gas is generated, the amount is small and the momentum of the splash is weak. We thought that it would not significantly disturb the crystal arrangement of the deposited film.
[0014]
Conversely, if the inclusions are large, the amount of oxygen generated by electron beam irradiation also increases, so the amount of CO gas generated also increases, and the splash momentum increases, which is considered to greatly disturb the crystal arrangement of the deposited film. .
[0015]
Therefore, the present inventors consider that if the inclusions contained in the Co pellet material are reduced, the inclusions can be rendered harmless during vapor deposition, and the size of the ingot at the time of casting was increased to 2t or more. However, it was confirmed that the size of the inclusions in the Co pellet material obtained from the ingot can be reduced and reduced.
[0016]
This is because by increasing the size of the ingot, the time required for solidification becomes longer, during which the inclusions can be floated and separated sufficiently due to the difference in specific gravity, and the separation efficiency of inclusions has dramatically increased It is thought to be due to.
[0017]
Another feature of the present invention is that the vacuum melting is performed only once without re-melting.
The conventional idea is that if melting is performed twice, the number of inclusions can be reduced accordingly and the vapor deposition material can be further cleaned. However, when the present inventors actually melted twice, the number of inclusions was reduced. However, it was recognized that the inclusions grew and grew harmfully by performing the dissolution twice, and rather harmful large inclusions were formed.
That is, it was confirmed that in order to reduce the size of the inclusions and render the inclusions harmless, it is more effective to dissolve the deposition twice, which is conventionally performed for cleaning the vapor deposition material, and to dissolve the inclusions only once.
The present invention has been made based on such findings.
[0018]
Thus, according to the present invention, when a film is formed by vacuum evaporation using a Co pellet material, harmful and intense splash can be suppressed well, and the magnetic layer of a magnetic tape or the like is partially magnetically treated. Satisfactorily can be formed without causing deterioration of
[0019]
The present invention is suitable as a method for producing a Co pellet material made of a pure Co material (Claim 2), and vacuum induction melting can be suitably used as vacuum melting (Claim 3).
[0020]
【Example】
Next, examples of the present invention will be described below.
The Co raw material is vacuum induction-melted in a vacuum chamber 12 using a vacuum induction melting furnace 10 shown in FIG. 1A to obtain a pure Co molten metal, and then the pure Co molten metal is poured into a mold 14 in the same vacuum chamber 12. Hot water was obtained to obtain 2.5 t of pure Co ingot.
In FIG. 1A, reference numerals 16 and 18 indicate a refractory crucible and an induction coil, respectively.
[0021]
Next, after the ingot was externally milled, slab rolling was performed, and thereafter, wire rod rolling was performed while hot to form a wire rod having a diameter of 10 mm. Subsequently, scale removal of the surface was performed. It was cut into a Co pellet material 20 made of a pure Co material having a size of 26 mmL (length), and then subjected to barrel polishing and ultrasonic cleaning to remove surface dirt and oil.
[0022]
The Co pellet material 20 thus obtained was further cut, and observed microscopically for an area (area) S having a cross section of 8 × 20 mm ² shown in FIG. 2 (B), and the size and number of inclusions were further analyzed by image analysis. investigated.
The result is shown in FIG.
[0023]
However, the results in FIG. 3 (a) show the results for a total area of 1280 mm ² (8 × 20 mm ² × 8) of the eight Co pellets 20, and the vertical axis in the figure indicates the number of inclusions And the abscissa represents the size of inclusions (particle size: μm).
[0024]
In addition, for comparison, a Co raw material was subjected to vacuum induction melting and casting using a vacuum induction melting furnace 10 shown in FIG. 1 (A) to obtain a 1-ton pure Co ingot. A Co pellet material 20 made of a pure Co material having the size shown in FIG. 2A was manufactured, and the inclusions were investigated in the same manner as described above.
The results are shown in FIG.
[0025]
Similarly, for comparison, the Co raw material was vacuum induction-melted using a vacuum induction melting furnace 10 shown in FIG. 1A, and then a vacuum arc was melted again using a vacuum arc melting furnace 22 shown in FIG. After melting, a Co pellet material 20 made of a pure Co material was obtained from the obtained int of pure Co having a size of 1 t in the same manner as described above, and inclusions were investigated in the same manner as above. .
The result is shown in FIG.
In FIG. 1B, reference numeral 24 denotes an electrode, 26 denotes a water-cooled copper mold, and 28 denotes a Co mass.
[0026]
As shown in the results of FIG. 3C, when the size of the pure Co ingot was set to 1 t and remelting was performed, although the number of inclusions was reduced, the inclusions due to the twice melting were reduced. Although the number of large inclusions of 10 μm or more, which is considered to be harmful during vacuum deposition due to coagulation growth, has increased, even if pure Co ingots have the same size of 1 t, remelting is not performed. In the case of melting only once, the number of inclusions is larger than that of melting twice (c) as shown in FIG. The number of large inclusions of 10 μm or more, which are considered as objects, is rather small.
[0027]
On the other hand, in the case of this embodiment in which the size of the pure Co ingot is set to 2.5 t and the melting is performed only once without re-melting, as shown in FIG. The number of large inclusions of 10 μm or more is 0, and the number of inclusions is smaller than that of the ingot having the size of 1t shown in FIG.
[0028]
Then, when vacuum deposition was performed using the Co pellet material 20 of the present example having the number of inclusions and the particle size distribution of inclusions shown in FIG. 3A, the generation of splash was suppressed, and A Co magnetic material layer was successfully formed on the upper layer.
[0029]
The above is an example in the case where the size of the pure Co ingot is set to the size of 2.5t, but the same good result is obtained when the size of the ingot is set to the size of 2t.
[0030]
The embodiment of the present invention has been described in detail above, but this is merely an example.
For example, the present invention can be applied to the production of a Co pellet material for forming a vapor deposition film made of a Ni-containing Co-Ni alloy. is there.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a vacuum induction melting furnace used in an embodiment of the present invention together with a vacuum arc melting furnace.
FIG. 2 is a diagram showing a shape of a Co pellet material obtained in an example of the present invention, together with a survey area for inclusions.
FIG. 3 is a diagram showing a particle size distribution of inclusions in a Co pellet material obtained in an example of the present invention, together with that of a comparative example.
[Explanation of symbols]
20 Co pellet material (pure Co material)

Claims (3)

After obtaining the ingot by vacuum melting and casting the Co raw material, when obtaining a Co pellet material for forming a deposited film from the ingot,
A method for producing a Co pellet material for forming a deposited film, wherein the vacuum melting is performed only once without performing re-melting, and the ingot is cast in a large lump of 2t or more. 2. The method according to claim 1, wherein the Co pellet material is a pure Co material. 4. The method according to claim 1, wherein the vacuum melting is vacuum induction melting.

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