JPH0366375B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a lanthanide-containing alloy, and particularly to a method for producing a highly clean lanthanide-containing alloy useful as a target alloy for magneto-optical disks. [Prior art] 15 rare earth elements La, Ce, Pr, Nd, Pm, ranging from lanthanum with atomic number 57 to lutetium with atomic number 71.
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,
Regarding Lu, that is, lanthanoids, in recent years, studies have been conducted in a wide range of fields on the addition of lanthanoids to alloy systems that take advantage of the unique properties of each element, and they are being applied in various industrial fields. For example, LaNi ₅ , SmCo ₅ , other Mitsushi metal (Mm)-Ni alloys, such as MmNi _4.5 Al _0.5 ,
MmNi _4.5 Mn _0.5 , MmNi _4.7 Al _0.3 Zr _0.1 , etc. are used as hydrogen storage alloys because they can easily store large amounts of hydrogen. Also, SmCo ₅ (Sm36%), Sm ₂ Co ₁₇ , Ce−Co
(Ce20%), ( _Sm1 -x-Prx) _Co5 , Nd-Fe
(Nd20~25%), _Sm2 (FeCuZrCo) ₁₇ (Sm25%,
Co50%), Nd _8~30 B _2~28 balance Fe (e.g.
Nd ₁₅ B ₈ Fe ₇₇ ) exhibits extremely strong magnetism due to the magnetic properties of lanthanides, so it is widely used as a permanent magnet in small motors and the like. As a magnet, (Fe _0.82 B _0.18 ) _0.9 Tb _0.05 La _0.05 amorphous magnet has also been developed. Furthermore, as magnetic recording materials, GdCo, GdFe,
DyFe, GdTeFe, TbFeCo, TbDyFe, GdTbFe
Or Fe group containing Gd, Tb, Dy such as GdTeCo,
Co-based and Ni-based amorphous alloy films are magnetic films with good squareness, have excellent magnetization and erasability, are capable of high-density recording, and have little change over time, so there are great expectations for their research and development. ing. Others: Yb-Al, Yb-Zr-Al, Mm-Zr-
Al is used as a large-capacity Al electric wire with improved heat resistance.
TiGd (Gd5%) is used as a strong light alloy, MgNd as a creep-resistant Mg alloy, and NiCrLa and FeCrLa as heat-resistant alloys that are resistant to high temperature oxidation. As the most important use of lanthanide-containing alloys, research and development have recently been conducted on the application to magneto-optical disks, and attempts have been made to put them into practical use. Currently, amorphous magnetic films that combine rare earth metals (RE) such as Gd, Tb, and Dy with transition metals (TM) such as Fe, Co, and Ni have been developed as magneto-optical disk memory media. There is. Gd−Tb−Fe, Gd−Te−Co, Tb−Fe−Co, Tb−Dy−Fe, Gd−Tb−Fe−Ge, Gd−Co, Tb−Fe, Gd−Fe, Fe−Co−Tb− Gd, Tb-Dy-Fe-Co, Dy-Fe, Gd-Fe-Bi Of these, Co-Gd, Gd-Fe, and Tb-Fe systems initially attracted attention as magneto-optical disk materials, and later Tb-Fe due to composition sensitivity, recording density, etc.
-Co, Gd-Tbi-Co systems, etc. These RE-TM magnetic films have the following characteristics as magneto-optical memory media, and are expected to be put to practical use. Since the Kyrie point is relatively low and compensation point recording is possible, the recording/erasing sensitivity is high. Recording and erasing can be performed using a semiconductor laser (LD). Since it is amorphous, there is little media noise. The Kerr rotation angle is also relatively large, ranging from 0.2 to 0.35°. Therefore, the SN ratio of the reproduced signal is large. Since it is a perpendicularly magnetized film, it can perform high-density recording, and it also has strong magneto-optical effects such as the polar Kerr effect.
You can use the Faraday effect. Large-area films can be created on various substrates. The composition ratio can be adjusted continuously, and various elements can be mixed relatively freely. Conventionally, these lanthanide-containing alloys have been manufactured by melting and casting using a crucible made of alumina or the like. [Problems to be solved by the invention] However, lanthanoids have extremely high reaction activity and react very well with oxygen (O), sulfur (S), and nitrogen (N), so in the past, lanthanoids have been difficult to solve in normal crucible melting. In particular, it was not possible to prevent the mixing of oxygen and sulfur into the molten metal. Furthermore, due to the high activity of lanthanoids, problems such as alloy contamination by refractory furnace materials that come into contact with the molten metal, formation of lanthanide-based oxides, decrease in lanthanide content, and, in severe cases, damage to the refractory furnace materials occur. For example, the molten metal is contaminated by the alumina refractory material due to the following reaction. Note that Ln represents a lanthanide element. Al ₂ O ₃ +2Ln→2Al+Ln ₂ O ₃ or Al ₂ O ₃ +3Ln→2Al+3LnO As described above, lanthanide-containing alloys cannot be melted in a normal refractory container with good cleanliness. On the other hand, it is currently extremely difficult to obtain a homogeneous alloy using methods such as arc melting, plasma melting, and electron beam melting that use a high heat source using a water-cooled copper crucible. In general, magneto-optical disks are required to have high characteristics in terms of recording, reproducing and erasing sensitivity, recording density, perpendicular magnetic anisotropy, Kerr rotation angle, lifespan, etc.
The properties of this material are greatly influenced by the purity and homogeneity of the target alloy for magneto-optical disks. However, as mentioned above, it is not possible to produce lanthanide-containing alloys with high purity and homogeneity using conventional methods. There are many problems that need to be improved in the manufacture of products containing about % by weight, as they are susceptible to contamination of the molten metal due to oxygen contamination and are also very susceptible to cracking. [Means for Solving the Problems] In view of the above-mentioned conventional circumstances, the present invention provides an industrially extremely advantageous method for producing lanthanide-containing alloys, which comprises alloys containing 10% by weight or more of lanthanides. When melting, the inner surface has a CaO content of 95% or more by weight,
Using a container made of calcia refractory material containing 1% by weight or less of CaF ₂ and 0.5% by weight or less of CaCl ₂ , the molten metal of the lanthanide-containing alloy is heated to a temperature 50 to 200°C higher than the melting point of the alloy in an inert gas atmosphere. A method for producing a lanthanide-containing alloy characterized by maintaining the temperature at . The present invention will be explained in detail below. In addition, in this specification, "%" represents "weight %". In the present invention, the lanthanide-containing alloy is
La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Td,
It is an alloy containing 10% or more of one or more lanthanoid elements of Dy, Ho, Er, Tm, Yb, and Lu. This lanthanoid-containing alloy includes, for example, 10 to 50% lanthanoid elements and Al, Cr, Fe,
Mn, Ni, Cu, V, Li, Co, Ti, Ta, W, Sn,
Examples include alloys with one or more of Zr, Mo, Mg, Ga, Nb, Si, Bi, and the like. The following examples are known as lanthanide-containing alloys. Nd-Mg, 20-25% Nd-Fe, Nd _8-30 -B _2-28 -Fe,
_SmCo5 , _Sm2CO17 , (Sm1 _{-x- Prx} ) _Co5 , _LaNi5 , _MmNi5 , Gd-Fe, Gd-Te-Fe, Gd-Te-Co, Gd-Co, 20%Ce-Co , Dy-Fe, Y-Zn-Al, Mm-Zr-Al, Y-Al, La-Ni-Cr, La-Fe-Cr, (Fe _0.82 B _0.18 ) _0.9 Tb _0.05 La _0.05 , Tb-Fe-Co , Tb-Dy-Fe, Sc-Mg-Al, _{Sc -} Li-Al, _Sc5Ga3 , 20-30% Mm-Mg, _Mm -Co, _MmNi4.5Al0.5 , _{MmNi4.5 Mm0.5} , _MmNi4.5Al0.3 Zr _0.1 In particular, the method of the present invention can contain lanthanide elements from 10 to
These alloys, which are effective for producing target alloys for magneto-optical disks containing 50% of the same, include the following. GdCo, GdFe, TbFe, Gd ₁₃ Tb ₁₃ Fe ₇₄ , TbDyFe, GdTbDyFe, Gd ₂₆
(Fe ₈₁ Co ₁₉ ) ₇₄ [(GdTb) ₂₇ Fe ₇₃ ] ₉₆ Ge ₄ Tb ₂₁ (Fe ₈₅ Co ₁₅ ) ₇₉ , (GdTb) ₂₃ Co ₇₇ , (Gd ₅₀ Tb ₅₀ ) _1-a (Fe ₈₅ Co ₁₅ ) _a (Gd ₂₀ Co ₈₀ ) ₅₀ (Tb ₂₁ Te _{79 50} (Gd ₃₃ Tb ₆₇ ) ₃₇ (Fe ₅₃ Co _{47 63} −Sm (Gd ₂₆ Fe ₇₄ ) ₉₆ Bi ₇ , (Gd ₂₆ Co ₇₄ ) ₉₃ Bi ₄ (Gd ₂₆ (Fe ₇₀ Co ₃₀ ) ₇₄ ) ₉₁ Bi ₉ In the present invention, such a lanthanide-containing alloy is used such that the inner surface has a CaO content of 95% or more and a CaF ₂ 1% content.
Hereinafter, using a container made of a calcia refractory containing 0.5% or less of CaCl ₂ , the alloy is heated and melted under an inert gas atmosphere using a conventional method such as high-frequency or low-frequency induction heating, and the melting point is lower than the melting point of the alloy. The molten alloy is held at a temperature 50 to 200°C higher and melted. In the present invention, the CaO refractory material constituting the inner surface of the container used for melting the lanthanoid-containing alloy includes calcia (CaO), CaO-enriched dolomite, and coexisting oxides such as ZrO ₂ , Y ₂ O ₃ , Examples include CaO-based refractory materials containing lanthanide-based oxides. As CaO, fused calcia is extremely suitable because it is dense. Further, calcia (CaO) obtained by burning quicklime, limestone, or slaked lime is also suitable. The higher the CaO content in such a CaO-based refractory material, the less impurities will be generated, and the contamination of the molten metal will be more reliably prevented. In the present invention, the CaO content is
A container made of 95% or more CaO refractory material, preferably 98% or more is used. Further, the content of CaF ₂ , CaCl _{2 ,} etc. in the CaO refractory material is preferably as low as possible, with CaF ₂ being 1% or less and CaCl ₂ 0.5 or less. When melting a lanthanide alloy in a container made of such a CaO refractory material, the melting atmosphere is preferably an inert gas atmosphere such as argon or helium, and the pressure is preferably 10 torr or more. In addition, the melting temperature is 50 to
The temperature will be 200℃ higher. If the holding time is too long, there is a risk of molten metal contamination, so it is preferably about 5 to 10 minutes. The molten metal of the lanthanide-containing alloy obtained by the method of the present invention is then poured into a mold of a desired shape to form an ingot. At this time, during solidification and cooling, a preheated mold is used. It is preferable to cool slowly at a rate of 1° C./min or less. According to the method of the present invention, it is possible to obtain a molten metal in which the amount of oxygen mixed in is significantly reduced, and remelting is also possible by appropriately controlling and adjusting the molten metal. [Effect] CaO has extremely high stability against molten alloys containing highly active metals, and is also stable against molten alloys containing lanthanides. Also, unlike Al ₂ O ₃ , it is less likely to react with lanthanoids to produce lanthanoid oxides. Therefore, the lanthanoid content in the lanthanide-containing alloy melt is not reduced, and the melt is not contaminated with impurities. Also, in particular, according to the method of the invention, the amount of oxygen in the lanthanide-containing alloy is significantly reduced, for example from 2000 to 3000 ppm.
Even if the Gd or Tb alloy contains a certain amount of oxygen, the oxygen content can be reduced to about 150 to 500 ppm by alloying or remelting according to the melting method of the present invention. This is because refractories containing 95% or more of CaO, 1% or less of CaF ₂ , and 0.5% or less of CaCl ₂ tend to react with oxides in the molten metal on the furnace wall.
This is thought to be because lanthanide oxides such as GdO ₂ and TbO ₂ in the molten metal react with the furnace wall and are absorbed as nRxOy; mCaO = n・RxOy・mCaO (in the formula, R represents a lanthanide element). It will be done. Similarly, sulfides in the molten lanthanoid-containing alloy are also absorbed by the furnace wall, and the amount of oxides and sulfides present can be significantly reduced, making it possible to obtain a highly pure lanthanide-containing alloy. Therefore, by using a container whose inner surface is made of such a CaO-grade furnace material, there is no contamination of the molten metal by the refractory material, and it is possible to melt a highly clean lanthanide-containing alloy with low oxygen and sulfur content. . [Examples] The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1, Comparative Example 1 The lanthanoids shown in Table 1 were put into a CaO crucible and an Al ₂ O ₃ crucible with the compositions shown in Table 2 below, respectively, and were heated in an internal heating type induction furnace with an output of 10 kW and a frequency of 50 kHz. The alloy was placed in a furnace and held for 10 minutes after melting under an argon atmosphere. The O and S contents of the obtained alloy were analyzed by chemical analysis and fluorescent X-rays. Table 1 shows the results. From Table 1, it is clear that with the CaO crucible, a lanthanide-containing alloy with low O and S content and high purity can be obtained. In addition, in a dissolution experiment conducted in an Al ₂ O ₃ crucible as a comparative example, contamination of Al was observed.
Residues of 0.1 to 0.05% were observed for each.

【table】

[Table] Example 2, Comparative Example 2 Using a crucible with the composition shown in Table 4, argon
Melting was carried out in the same manner as in Example 1 at 25 torr,
Alloying of 30%Fe-30%Co-20%Gd-20%Tb alloy was carried out. Table 3 shows the results of chemical analysis and fluorescent X-ray analysis of the O and S contents of the obtained alloy. From Table 3, the CaO content is particularly high, CaF ₂ ,
It is clear that a CaO crucible containing less CaCl ₂ provides a lanthanide-containing alloy with less O and S and with high purity.

【table】

[Table] Example 3 Using a CaO crucible with the composition shown in Table 2, it was placed in an internal heating induction furnace with an output of 10 kW and a frequency of 50 kHz.
40%Gd-
A 60% Fe alloy (melting point 1220℃) was remelted. Table 5 shows the results of chemical analysis and fluorescent X-ray analysis of the O and S contents of the obtained alloy. From Table 5, it is clear that when the temperature is maintained at 50 to 200° C. higher than the melting point of the alloy for 5 to 10 minutes, a highly pure lanthanide-containing alloy with extremely low O and S content can be obtained.

【table】

[Table] Example 4 Using a CaO crucible with the composition shown in Table 2, it was placed in an internal heating induction furnace with an output of 10 kW and a frequency of 50 kHz.
50 ~ than the melting point of the alloy under argon 25torr atmosphere
After melting at a temperature higher than 200℃, hold for 5 to 10 minutes,
A 40%Tb-30%Fe-30%Co alloy was produced. The obtained molten metal was placed in a preheated mold and slowly cooled at the cooling rate shown in Table 6 to obtain an ingot. Table 6 shows the results of chemical analysis and fluorescent X-ray analysis of the O and S contents of the obtained alloy. From Table 6, it is clear that by slow cooling at a rate of 1° C./min or less, a lanthanide-containing alloy with extremely low O and S content and high purity can be obtained.

[Table] [Effects of the Invention] As detailed above, according to the method for producing a lanthanide-containing alloy of the present invention, it is possible to obtain a lanthanide-containing alloy with high purity. According to the method of the present invention, a lanthanide-containing alloy that is low in oxygen, low in sulfur, and free from contamination from refractory materials can be easily obtained. In particular, the amount of oxygen is significantly reduced. Therefore, the obtained alloy has excellent magnetic properties, corrosion resistance, heat resistance, etc., and has extremely high properties. The mechanical strength of the alloy is also improved. The refractory material is not eroded and damaged by the lanthanoids, and melting can be carried out continuously over a long period of time. An alloy of extremely homogeneous composition is obtained. Easily remelts and casts lanthanide-containing alloys. Therefore, scrap can be used effectively. Various effects such as these are achieved, and it is extremely advantageous industrially. In particular, the method of the present invention allows Gd, Tb, Dy, etc.
The alloy obtained by the present invention is effective in producing target alloys for magneto-optical disks containing at least 1% of the total amount of carbon dioxide, and the alloy obtained by the present invention solves the problem of cracking, making it possible to provide high-performance magneto-optical disks. Furthermore, the present invention can be successfully applied to melting return material containing lanthanoids.

Claims (1)

[Claims] 1. Calcia refractory whose inner surface has a CaO content of 95% by weight or more, 1% by weight or less of CaF ₂ , and 0.5% by weight or less of CaCl ₂ when melting an alloy containing 10% by weight or more of lanthanoids. 1. A method for melting a lanthanide-containing alloy, which comprises maintaining a molten metal of a lanthanide-containing alloy at a temperature 50 to 200° C. higher than the melting point of the alloy in an inert gas atmosphere using a container constructed of the above. 2. When producing a magneto-optical disk target alloy containing 10% by weight or more of lanthanoids, the inner surface must be made of calcia refractory with a CaO content of 95% by weight or more, CaF ₂ 1% or less, and CaCl ₂ 0.5% by weight or less. Argon gas atmosphere using a container configured
2. The melting method according to claim 1, wherein the molten metal of the alloy is held at a temperature of 50 to 200° C. higher than the melting point of the alloy for 3 to 10 minutes at 10 torr or more.