JP6339719B1 - Aluminum alloy plate for magnetic disk, aluminum alloy blank for magnetic disk and aluminum alloy substrate for magnetic disk - Google Patents

Abstract

An aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and a magnetic disk capable of forming a plated film having high rigidity and smoothness on the surface while having high proof stress. Provide aluminum alloy substrate. An aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk are composed of Si: 0.10% by mass or less, Fe: 0.50% by mass to 1.50% by mass. Mn: 0.50% by mass or more and 1.50% by mass or less, Ni: 1.00% by mass or more and less than 2.00% by mass, Cu: 0.05% by mass or more and 1.00% by mass or less, and the balance Consists of Al and inevitable impurities. [Selection figure] None

Description

  The present invention relates to an aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk.

  As a recording medium for a hard disk drive (HDD) provided in a computer or the like, a magnetic disk made of aluminum alloy is frequently used. The aluminum alloy magnetic disk substrate is made by blanking an aluminum alloy plate punched into an annular shape to produce a blank, then cutting and grinding the blank to produce a substrate, and then subjecting the substrate to a surface treatment. It is manufactured by applying.

  In many cases, the substrate is sequentially subjected to a degreasing process, an acid etching process, a desmut process, a 1st zincate process, a nitric acid stripping process, a 2nd zincate process, and an electroless Ni-P plating process. And a magnetic layer, a protective film, etc. are formed in the surface of the plating film formed by the electroless Ni-P plating process, and the magnetic disk in a readable / writable state is manufactured.

  In recent years, the transfer speed of recorded data has been increased, and accordingly, the rotational speed of the magnetic disk has also been increased. The higher the rotational speed of the magnetic disk during operation, and the thinner and lighter the magnetic disk, the more difficult it is to read and write accurately due to vibration caused by resonance. Therefore, the substrate of the magnetic disk is required to have high rigidity that can withstand vibration. Rigidity that can withstand vibration can be secured by increasing the thickness of the substrate. However, with the technique of increasing the thickness of the substrate, the magnetic disk cannot be reduced in weight, and the number of sheets mounted on the recording device is limited. For this reason, regarding the substrate of the magnetic disk, high rigidity is required for the material itself.

For example, Patent Document 1 describes a lightweight high-rigidity aluminum alloy plate for a magnetic disk substrate in which at least one of ceramic particles or ceramic fibers is dispersed in an aluminum alloy matrix by 5 to 50% by volume. In Patent Document 1, pure Al particles obtained by an atomization method and Al ₂ O ₃ particles are mixed, and the mixture is subjected to HIP treatment near the melting temperature, and then hot-rolled to obtain an aluminum alloy sheet. Yes.

JP 63-183146 A

The lightweight high-rigidity aluminum alloy plate for a magnetic disk substrate described in Patent Document 1 is a HIP process for a mixture of pure Al particles used as matrix particles and ceramic particles or ceramic fibers such as Al ₂ O ₃ particles. Therefore, it is difficult to increase the adhesion between particles and fibers. Therefore, when an electroless Ni—P plating film is formed on the surface, particles and the like are dropped and irregularities are generated on the surface, and there is a high possibility that an electroless Ni—P plating film with high smoothness will not be formed. In addition, the lightweight high-rigidity aluminum alloy plate for a magnetic disk substrate described in Patent Document 1 requires a HIP process for each plate, and thus has a problem of high production cost, and high adhesion cannot be obtained. May decrease.

  The present invention has been made in view of the above problems, and is capable of forming a plating film having high rigidity and high smoothness on the surface, and can also have high proof stress, and can also have high proof stress. It is an object to provide a plate, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk.

As a result of diligent research, the present inventor has increased the rigidity of the magnetic disk substrate itself by appropriately increasing the volume ratio of the intermetallic compound exhibiting a high Young's modulus, and smoothing the plating film as the intermetallic compound increases. The present inventors have found a method that achieves both good rigidity and high plating strength as well as high rigidity, while suppressing deterioration in durability and yield strength. That is, a chemical composition to which Fe, Mn, Ni, or the like is added is employed, and an intermetallic compound is appropriately generated in the aluminum alloy, thereby increasing the rigidity of the magnetic disk substrate itself. Further, the Si content was reduced to reduce simple Si, Mg ₂ Si, etc., on which no electroless Ni—P plating film was formed. In addition, the ratio of Fe, Mn and Ni is limited, and Al—Fe—Ni intermetallic compounds grow coarsely, or Al—Mn—Fe intermetallic compounds concentrate and crystallize during casting. It was supposed to suppress this. In addition, it has been confirmed that the Al—Mn—Fe-based intermetallic compound crystallized in a concentrated manner causes streak defects in the rolled plate due to a sparse distribution during rolling. That is, by reducing coarse intermetallic compounds and intermetallic compounds that cause streak defects, and preventing unevenness due to the dropping of intermetallic compounds and non-uniform surface treatment reactions, an electroless Ni-P plating film Improved smoothness. Then, when casting an aluminum alloy having such a chemical composition, it has been newly discovered that hot water leakage is likely to occur due to the narrowness of the solid-liquid coexistence region on the phase diagram, and Cu, Mg, Zn The present invention has been completed by conceiving measures for lowering the solidus temperature by adding the above.

  In order to solve the above problems, an aluminum alloy plate for a magnetic disk according to the present invention has Si: 0.10% by mass or less, Fe: 0.50% by mass to 1.50% by mass, Mn: 0.50% by mass. 1.50% by mass or less, Ni: 1.00% by mass or more and less than 2.00% by mass, Cu: 0.05% by mass or more and 1.00% by mass or less, with the balance being Al and inevitable impurities It was decided.

  According to such an aluminum alloy plate for a magnetic disk, since Si, Fe, Mn, and Ni are contained within a predetermined content range, the magnetic disk substrate itself has high rigidity and has a smooth surface. It has good plating properties that can form a high plating film and high proof stress. Moreover, in such a chemical composition, since Cu is added within a predetermined content range, leakage of molten metal during casting is reduced. In general, when an aluminum alloy is cast by a semi-continuous casting method (DC (direct chill) casting method) or the like, the cooling ingot is thermally contracted, and a gap is generated between the surface of the ingot and the mold, and heat is generated. Transmission is reduced. A normal aluminum alloy containing only Fe, Mn, Ni, etc. has a narrow solid-liquid coexistence region surrounded by the liquidus and solidus on the phase diagram, and the temperature difference between the liquidus and solidus temperatures. Therefore, when the heat transfer is reduced in this way, the solidified shell is easily remelted, and there is a high possibility of causing a hot water leak. On the other hand, since the solidus temperature is lowered when the chemical composition is added with Cu, the frequency of occurrence of hot water leakage is reduced. Therefore, using this as a raw material, it is possible to provide an aluminum alloy substrate for a magnetic disk that can form a plated film having high rigidity and high smoothness on the surface, but can also have high proof stress. .

  The aluminum alloy plate for a magnetic disk according to the present invention has Si: 0.10% by mass or less, Fe: 0.50% by mass to 1.50% by mass, Mn: 0.50% by mass to 1.50% by mass Ni: 1.00 mass% or more and less than 2.00 mass%, Cu: 0.05 mass% or more and less than 1.00 mass%, Mg: 0.05 mass% or more and less than 1.00 mass%, and Zn : 0.05% by mass or more and less than 1.00% by mass, further containing one or both, wherein the total amount of Cu, Mg and Zn is 1.00% by mass or less, the balance being Al and inevitable It may be made of a general impurity.

  According to such an aluminum alloy plate for a magnetic disk, Si, Fe, Mn, and Ni are contained within a predetermined content range, so that high rigidity is provided, and good plating properties and high yield strength are provided. . Moreover, in such a chemical composition, since Mg and Zn are added within a predetermined content range together with Cu, molten metal leakage during casting is reduced without greatly depending on the Cu content. Therefore, using this as a raw material, it is possible to provide an aluminum alloy substrate for a magnetic disk that can form a plated film having high rigidity and high smoothness on the surface, but can also have high proof stress. .

  The aluminum alloy plate for magnetic disks according to the present invention may further contain Cr: 0.05 mass% or more and 0.23 mass% or less in the chemical composition of the magnetic disk aluminum alloy sheet.

  According to such an aluminum alloy plate for a magnetic disk, since Cr is further contained in a predetermined content range, the crystallized material is further refined, and the strength and proof stress are improved by precipitation strengthening.

  In the aluminum alloy plate for magnetic disk according to the present invention, in the chemical composition of the aluminum alloy plate for magnetic disk, the total amount of Fe, Mn and Ni is 4.20% by mass or less, and the content of Fe The ratio between the amount and the Ni content may be 0.40 to 1.00, and the ratio between the Mn content and the Ni content may be 0.30 to 0.90.

  According to such an aluminum alloy plate for a magnetic disk, the total amount of Fe, Mn, and Ni is limited to a predetermined range, so that coarse intermetallic compounds are reduced. In particular, since the Ni content relative to the Fe content is limited to a predetermined range, the number of Al—Fe—Ni intermetallic compounds that are likely to be coarsened is reduced. In addition, since the Ni content relative to the Mn content is limited to a predetermined ratio, the number of Al—Mn—Fe intermetallic compounds that cause streak defects in the rolled sheet is reduced. As a result, the intermetallic compounds do not fall off and the smoothness of the base of the plating film is not greatly impaired, the smoothness of the electroless Ni-P plating film is increased, and the fine structure has a high yield strength. Provided.

  In the aluminum alloy plate for a magnetic disk according to the present invention, the absolute maximum length of the intermetallic compound on the surface is preferably 20 μm or less.

  According to such an aluminum alloy plate for a magnetic disk, coarse intermetallic compounds are excluded, and the intermetallic compounds exposed on the surface may fall off, and the smoothness of the base of the plating film may be greatly impaired. Disappear. Therefore, the smoothness of the electroless Ni—P plating film is increased, and a high strength is provided by a fine structure.

  The aluminum alloy blank for magnetic disks according to the present invention is made of the above-described aluminum alloy plate for magnetic disks.

  According to such an aluminum alloy blank for magnetic disk, since Si, Fe, Mn and Ni are contained within a predetermined content range, the magnetic disk substrate itself has high rigidity and the surface is smooth. It has good plating properties that can form a high plating film and high proof stress. Moreover, in such a chemical composition, since Cu is added in the range of a predetermined content, molten metal leakage at the time of casting is reduced and stable production can be achieved. Therefore, using this as a raw material, it is possible to provide an aluminum alloy substrate for a magnetic disk that can form a plated film having high rigidity and high smoothness on the surface, but can also have high proof stress. .

  The aluminum alloy blank for a magnetic disk according to the present invention preferably has a Young's modulus of 75 GPa or more and a proof stress of 90 MPa or more.

  According to such an aluminum alloy blank for a magnetic disk, it is possible to provide an aluminum alloy substrate for a magnetic disk having rigidity, impact resistance and the like desired for a magnetic disk application.

  The aluminum alloy substrate for magnetic disks according to the present invention is made of the above-described aluminum alloy blank for magnetic disks.

  According to such an aluminum alloy substrate for a magnetic disk, since Si, Fe, Mn and Ni are contained within a predetermined content range, the magnetic disk substrate itself has high rigidity and has a smooth surface. However, it has good plating properties that can form a high plating film and high proof stress. Moreover, in such a chemical composition, since Cu is added in the range of a predetermined content, molten metal leakage at the time of casting is reduced and stable production can be achieved.

  The aluminum alloy plate for a magnetic disk and the aluminum alloy blank for a magnetic disk according to the present invention can form a plating film having high rigidity and high smoothness on the surface, but can also have high proof stress. An aluminum alloy substrate for disks can be provided. Moreover, the aluminum alloy substrate for magnetic disks according to the present invention has high rigidity, good plating property capable of forming a plating film having high smoothness on the surface, and high proof stress.

  Hereinafter, an aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk according to an embodiment of the present invention will be described. In the following description, each of the aluminum alloy plate for magnetic disk, the aluminum alloy blank for magnetic disk, and the aluminum alloy substrate for magnetic disk according to the present embodiment is simply referred to as “aluminum alloy plate”, “blank”, Sometimes called “substrate”.

[Aluminum alloy plate]
The aluminum alloy plate according to the present embodiment is made of an aluminum alloy containing Si, Fe, Mn, Ni, and Cu within a predetermined content range. The chemical composition of the aluminum alloy plate contains Si, Fe, Mn, Ni and Cu within a predetermined content range, and further contains one or both of Mg and Zn within a predetermined content range. The total content of Cu, Mg and Zn may be limited to a predetermined range. In addition, the chemical composition of the aluminum alloy plate is limited to a predetermined range for the total content of Fe, Mn, and Ni, the value of the ratio between the Fe content and the Ni content, and the Mn content The value of the ratio between the amount and the Ni content may also be limited to a predetermined value range.

  However, the aluminum alloy plate contains Si, Fe, Mn, Ni, and Cu, and in addition to these, further contains Cr in a predetermined content range, and the balance is Al and inevitable impurities. It may be said. Hereinafter, the content of each component contained in the aluminum alloy plate and the reason for limiting the content will be described.

(Si: 0.10 mass% or less)
Si is usually mixed in the aluminum alloy as an inevitable impurity in the metal and forms simple Si, Al—Fe—Si intermetallic compounds, and the like. If the Si content exceeds 0.10 mass%, the amount of simple Si increases, and the smoothness of the electroless Ni—P plating film decreases. Therefore, the content of Si is set to 0.10% by mass or less. In addition, it is more preferable that the content of Si is 0.05% by mass or less from the viewpoint of suppressing the generation of simple Si and the like. The lower the Si content, the better. Even if it is 0% by mass, the characteristics of the present invention are not impaired. However, since high-purity raw materials (such as Al metal and intermediate alloy metal) are required, the cost increases. Therefore, it is industrially preferable that the Si content is 0.004% by mass or more.

(Fe: 0.50 mass% or more and 1.50 mass% or less)
Fe contributes to improvement of strength and Young's modulus. If the Fe content is less than 0.50% by mass, the intermetallic compounds are reduced, the Young's modulus is lowered, and high rigidity may not be obtained. On the other hand, if the Fe content exceeds 1.50% by mass, the crystallized product becomes coarse and high yield strength may not be obtained. In addition, the Al-Fe-Ni intermetallic compound is coarsened, or the Al-Mn-Fe intermetallic compound is coarsened or a streak defect is generated in the rolled plate. There is a possibility that the smoothness of the Ni-P plating film is lowered. Therefore, the content of Fe is set to 0.50 mass% or more and 1.50 mass% or less. The Fe content is more preferably 0.80% by mass or more from the viewpoint of increasing the rigidity. Further, the content of Fe is more preferably set to 1.30% by mass or less from the viewpoint of preventing hot water leakage and suppressing the coarsening of intermetallic compounds and streak defects.

(Mn: 0.50 mass% or more and 1.50 mass% or less)
Mn contributes to improvement of strength and Young's modulus. If the Mn content is less than 0.50% by mass, the intermetallic compound is decreased, the Young's modulus is lowered, and high rigidity may not be obtained. Further, the crystallized product is not refined, and there is a possibility that high yield strength cannot be obtained. On the other hand, if the content of Mn exceeds 1.50% by mass, the crystallized product becomes coarse and high yield strength may not be obtained. Moreover, since the Al—Mn—Fe intermetallic compound is coarsened or a streak defect is generated in the rolled plate, the proof stress and the smoothness of the electroless Ni—P plating film formed on the surface may be lowered. is there. Therefore, the content of Mn is set to 0.50 mass% or more and 1.50 mass% or less. The Mn content is more preferably 0.80% by mass or more from the viewpoint of increasing the rigidity. Further, the content of Mn is more preferably 1.30% by mass or less from the viewpoint of preventing the leakage of hot water and the suppression of coarsening of intermetallic compounds and generation of streak defects.

(Ni: 1.00% by mass or more and less than 2.00% by mass)
Ni contributes to the improvement of strength and Young's modulus. If the Ni content is less than 1.00% by mass, the intermetallic compound is reduced, the Young's modulus is lowered, and high rigidity may not be obtained. Further, the crystallized product is not refined, and there is a possibility that high yield strength cannot be obtained. On the other hand, if the Ni content is 2.00% by mass or more, the crystallized product is coarsened and high yield strength may not be obtained. Moreover, there is a possibility that the Al—Fe—Ni intermetallic compound becomes coarse and the proof stress and the smoothness of the electroless Ni—P plating film formed on the surface are lowered. Therefore, the Ni content is set to 1.00% by mass or more and less than 2.00% by mass. The Ni content is more preferably 1.50% by mass or more from the viewpoint of increasing the rigidity. Further, the Ni content is more preferably 1.95% by mass or less from the viewpoint of preventing hot water leakage and suppressing the coarsening of the intermetallic compound.

(Cu: 0.05 mass% or more and less than 1.00 mass%)
Cu exhibits a low equilibrium partition coefficient and greatly reduces the solidus temperature of the aluminum alloy. Therefore, Cu has the effect of widening the solid-liquid coexistence region on the phase diagram and reducing the occurrence frequency of hot water leakage during casting. When the Cu content is less than 0.05% by mass, the solidus temperature is not sufficiently lowered, and the solid-liquid coexistence region on the phase diagram remains narrow, so that it is difficult to prevent leakage of hot water. On the other hand, when the Cu content is 1.00% by mass or more, the solid-liquid coexistence region on the phase diagram becomes excessively wide. As a result, the Al-Mn-Fe intermetallic compound is likely to be coarsened, or it is likely to cause streak defects in the rolled plate, so that the required proof stress may not be obtained, and the electroless formed on the surface There is a possibility that the smoothness of the Ni-P plating film is lowered. On the other hand, since it becomes difficult to produce an Al—Fe—Ni-based intermetallic compound, the Young's modulus is lowered and high rigidity may not be obtained. Therefore, the Cu content is set to 0.05% by mass or more and less than 1.00% by mass. The Cu content is more preferably 0.20% by mass or more from the viewpoint of preventing hot water leakage. Further, the Cu content is more preferably 0.60% by mass or less from the viewpoint of ensuring necessary proof stress, Young's modulus, smoothness of the plating film, and the like.

(Mg: 0.05 mass% or more and less than 1.00 mass%)
Mg contributes to improvement in yield strength when properly dissolved. However, if the Mg content is high, the Young's modulus of Mg is low, so the Young's modulus may be low. Further, Mg has an effect of widening the solid-liquid coexistence region on the phase diagram and reducing the frequency of occurrence of hot water leakage during casting. If the Mg content is less than 0.05% by mass, the effect of adding Mg cannot be sufficiently obtained. On the other hand, if the Mg content is 1.00% by mass or more, a necessary Young's modulus may not be obtained, or plating properties and proof stress may be reduced due to the formation of Mg-Si intermetallic compounds. . Therefore, when adding Mg, content of Mg shall be 0.05 mass% or more and less than 1.00 mass%. The Mg content is more preferably 0.30% by mass or less from the viewpoint of securing necessary proof stress, Young's modulus, and the like, and the viewpoint of exhibiting the effect of Cu.

(Zn: 0.05 mass% or more and less than 1.00 mass%)
Zn has the effect of widening the solid-liquid coexistence region on the phase diagram and reducing the frequency of hot water leakage during casting. If the Zn content is less than 0.05% by mass, the effect of adding Zn cannot be sufficiently obtained. On the other hand, if the Zn content is 1.00% by mass or more, the intermetallic compound may be reduced and the Young's modulus may be lowered. Therefore, when adding Zn, content of Zn shall be 0.05 mass% or more and less than 1.00 mass%. The Zn content is more preferably 0.30% by mass or less from the viewpoint of securing necessary Young's modulus and the like and the viewpoint of exhibiting the effect of Cu.

(Cr: 0.05 mass% or more and 0.23 mass% or less)
Cr has the effect of refining the primary crystal and distributing the intermetallic compound uniformly, and contributes to the improvement of strength and proof stress. When the content of Cr is less than 0.05% by mass, the primary crystals are not sufficiently refined, and the effect of improving the strength and proof stress due to the addition of Cr cannot be sufficiently obtained. On the other hand, if the Cr content exceeds 0.23% by mass, the intermetallic compound tends to be coarsened, and the proof stress and the smoothness of the electroless Ni—P plating film formed on the surface may be lowered. Therefore, when adding Cr, content of Cr shall be 0.05 mass% or more and 0.23 mass% or less. The Cr content is more preferably 0.10% by mass or more from the viewpoint of improving strength and proof stress.

(Cu + Mg + Zn: 1.00% by mass or less)
The total amount of Cu, Mg and Zn is preferably 1.00% by mass or less. When the total amount of Cu, Mg and Zn exceeds 1.00% by mass, the solid-liquid coexistence region on the phase diagram becomes excessively wide. As a result, the Al-Mn-Fe intermetallic compound is likely to be coarsened, or it is likely to cause streak defects in the rolled plate, so that the required proof stress may not be obtained, and the electroless formed on the surface There is a possibility that the smoothness of the Ni-P plating film is lowered. On the other hand, since it becomes difficult to produce an Al—Fe—Ni-based intermetallic compound, the Young's modulus is lowered and high rigidity may not be obtained. Further, since the specific gravity of the aluminum alloy becomes excessive, the vibration resistance of the magnetic disk may be lowered. If the total amount of Cu, Mg and Zn is in the above range, it is possible to achieve both high Young's modulus and smoothness of the plating film and necessary proof stress. The total amount of Cu, Mg and Zn is more preferably 0.60% by mass or less from the viewpoint of reducing the specific gravity while increasing the Young's modulus, the smoothness of the plating film, and the proof stress.

(Fe + Mn + Ni: 5.00% by mass or less)
The total amount of Fe, Mn and Ni is 5.00% by mass or less. If the total amount of Fe, Mn and Ni exceeds 5.00% by mass, the intermetallic compound is likely to be coarsened, or the intermetallic compound is liable to cause streak defects on the rolled sheet, so that the necessary proof stress is There is a high possibility that it will not be obtained, and the smoothness of the electroless Ni—P plating film formed on the surface will be low. The total amount of Fe, Mn and Ni is more preferably 4.20% by mass or less from the viewpoint of increasing the smoothness of the electroless Ni—P plating film, and from the viewpoint of preventing streak defects. More preferably, it is 4.00 mass% or less. The total amount of Fe, Mn and Ni is more preferably 2.50% by mass or more from the viewpoint of securing a Young's modulus of 75 GPa or more.

(Fe / Ni: 0.40 to 1.00)
Ratio of Fe content to Ni content (Fe content / Ni content), that is, the ratio of Fe content to Ni content should be 0.40 to 1.00. preferable. If the ratio of Fe content to Ni content is 0.40 or more, the proportion of Fe is high, and Al-Mn-Fe intermetallic compounds are easily crystallized, so the Young's modulus is increased. It becomes easy. Moreover, since there is little Ni and it becomes difficult to coarsen an Al-Fe-Ni type intermetallic compound, a possibility that a yield strength and the smoothness of an electroless Ni-P plating film will fall becomes low. On the other hand, if the ratio of the Fe content to the Ni content is 1.00 or less, the Fe ratio is low, and streak defects due to the Al—Mn—Fe intermetallic compound are less likely to occur. The possibility that the smoothness of the formed electroless Ni-P plating film is lowered is reduced. Moreover, since there is much Ni and it becomes easy to form an Al-Fe-Ni type intermetallic compound, it becomes easy to make a Young's modulus high. If the ratio of the Fe content to the Ni content is in the above range, the Al—Mn—Fe intermetallic compound is appropriately crystallized, and the Al—Fe—Ni intermetallic compound also grows moderately. Both high rigidity and plating properties can be achieved.

(Mn / Ni: 0.30-0.90)
The ratio of the Mn content to the Ni content (Mn content / Ni content), that is, the ratio of the Mn content to the Ni content should be 0.30 to 0.90. preferable. If the ratio of the Mn content to the Ni content is 0.30 or more, the ratio of Mn is high and the Al—Mn—Fe intermetallic compound is easily crystallized, so the Young's modulus is increased. It becomes easy. Moreover, since there is little Ni and a yield strength and an Al-Fe-Ni type intermetallic compound become difficult to coarsen, the possibility that the smoothness of an electroless Ni-P plating film will fall becomes low. On the other hand, if the ratio of the Mn content to the Ni content is 0.90 or less, the Mn ratio is low, and streak defects due to Al-Mn-Fe intermetallic compounds are less likely to occur. The possibility that the smoothness of the formed electroless Ni-P plating film is lowered is reduced. Moreover, since there is much Ni and it becomes easy to form an Al-Fe-Ni type intermetallic compound, it becomes easy to make a Young's modulus high. If the ratio of the Mn content to the Ni content is in the above range, the Al—Mn—Fe intermetallic compound is appropriately crystallized, and the Al—Fe—Ni intermetallic compound also grows moderately. Both high rigidity and plating properties can be achieved.

(Inevitable impurities)
Inevitable impurities are impurities that are inevitably mixed in the manufacturing process, and are allowed to be contained within a range that does not impair various characteristics. Examples of inevitable impurities include Ti, Zr, V, B, Na, K, Ca, and Sr. Inevitable impurities do not significantly impair the effects of the present invention as long as the content of each element is 0.005 mass% or less and the total is 0.015 mass% or less. Moreover, if content is the said range, the said element added positively will not inhibit the effect of this invention largely. Therefore, in the present invention, other elements other than the element to be positively added and the element of unavoidable impurities may be positively contained within a content range that does not impair the effects of the present invention. In addition, when setting it as the chemical composition which does not add Cr, if the content of Cr is 0.005 mass% or less, it is permitted to contain. The content of inevitable impurities can be reduced, for example, by using a bullion refined by a three-layer electrolysis method or by removing it using a segregation method.

(Absolute maximum length of intermetallic compound on the surface)
There is a possibility that a coarse intermetallic compound having a long absolute maximum length is generated in the parent phase of the aluminum alloy. When the coarse intermetallic compound is excluded from the matrix and the absolute maximum length of the intermetallic compound on the easily observable surface is reduced, good plating properties and high proof strength can be obtained. The “absolute maximum length” means the maximum value of the distance between any two points located on the particle outline. If the absolute maximum length of the intermetallic compound on the surface exceeds 20 μm, the crystal grains in the matrix phase are not sufficiently refined, so that high proof stress may not be obtained. In addition, since the intermetallic compound exposed on the surface is coarse, it is possible to form an electroless Ni-P plating film with high smoothness due to dropout of particles, reduction in uniformity of acid etching treatment and zincate treatment. It can be difficult. Therefore, the absolute maximum length of the intermetallic compound on the surface is preferably 20 μm or less. The absolute maximum length of the intermetallic compound on the surface is more preferably 15 μm or less from the viewpoint of increasing the yield strength and the smoothness of the electroless Ni—P plating film.

  The absolute maximum length of the intermetallic compound on the surface can be adjusted by adjusting the chemical composition. Examples of the intermetallic compound include Al-Fe-Si, Al-Fe-Ni, Al-Mn-Fe, other Al-Fe, Al-Mn, and Al-Ni. And intermetallic compounds such as Al—Cr—Al—Fe—Mn—Ni. In obtaining the absolute maximum length of the intermetallic compound on the surface, the surface is observed with at least 20 fields of view with a microscope with a magnification of 200 times, and the calculation is performed by treating the single Si occupying the surface in the same manner as the intermetallic compound. .

  The absolute maximum length of the intermetallic compound on the surface can be determined as follows. For example, an FE-SEM (Field Emission Scanning Electron Microscope, model JSM-7001F) manufactured by JEOL Ltd. is used and an acceleration voltage is set to 15 kV to obtain a composition image. And, using the attached analysis system “Analysis Station 3, 8, 0, 31” and the particle analysis software “EX-35110 particle analysis software Ver. 3.84”, it can be recognized on the composition image obtained by FE-SEM. Measure the absolute maximum length of the intermetallic compound.

[Method for producing aluminum alloy sheet]
The aluminum alloy plate according to the present embodiment can be manufactured by a general manufacturing method and equipment for manufacturing a magnetic disk substrate. For example, a casting process in which a raw material is melted to cast an ingot adjusted to a predetermined chemical composition, a homogenization heat treatment process in which the cast ingot is subjected to a homogeneous heat treatment, and a casting in which the homogenization heat treatment has been performed. By a manufacturing method comprising in this order a hot rolling step for hot rolling the ingot to obtain a hot rolled plate and a cold rolling step for cold rolling the hot rolled plate to obtain a cold rolled plate, aluminum Alloy plates can be manufactured. If necessary, intermediate annealing may be performed before the cold rolling process or during the cold rolling process.

  The casting process is preferably performed by melting the raw material at 700 to 800 ° C and casting at 700 to 800 ° C. The cast ingot is preferably chamfered, and the chamfering amount can be 2 to 40 mm / single side, for example.

  The homogenization heat treatment step can be performed, for example, at 400 to 600 ° C. for 4 to 48 hours.

  In the hot rolling step, for example, the hot rolling start temperature can be set to 510 ° C. or higher. Moreover, the completion | finish temperature of hot rolling can be 300-350 degreeC. About the temperature range from 520 degreeC to 400 degreeC, it is preferable to finish hot rolling within 3 hours. Moreover, the plate | board thickness of the hot rolled sheet obtained by hot rolling can be 3 mm, for example.

  In the cold rolling step, the thickness of the cold rolled sheet obtained by cold rolling is preferably set to 0.5 to 1.3 mm, for example.

[blank]
The blank according to this embodiment is made of the aluminum alloy plate and has a perforated disk shape. The blank is made of an aluminum alloy containing Si, Fe, Mn, Ni, and Cu in a predetermined content range, and preferably one or both of Mg and Zn are determined in the same manner as the aluminum alloy plate. In addition, it has a chemical composition in which the total content of Cu, Mg and Zn is limited to a predetermined range. More preferably, the total content of Fe, Mn and Ni is also limited to a predetermined range, the ratio value of the Fe content and the Ni content, and the Mn content and the Ni content. Each value of the ratio to the content also has a chemical composition limited to a predetermined value range.

  The absolute maximum length of the intermetallic compound on the surface for the blank is equivalent to that for the aluminum alloy plate. On the other hand, the characteristic values such as Young's modulus and yield strength of the blank are measured for a blank that has undergone a straightening annealing process described later, or an aluminum alloy sheet that has been subjected to heat treatment under the same conditions as the straightening annealing process described later.

(Young's modulus)
The Young's modulus of the blank is preferably 75 GPa or more. If the Young's modulus is 75 GPa or more, the material itself has high rigidity, so that vibration during operation of the magnetic disk can be sufficiently reduced without making the blank excessively thick. The Young's modulus of the blank is more preferably 80 GPa or more from the viewpoint of suppressing vibration during operation of the magnetic disk.

  The Young's modulus is prepared, for example, according to JIS Z 2280: 1993 (high temperature Young's modulus test method for metal materials), and a test piece having a thickness of 60 mm × 10 mm × 1 mm with the rolling direction as the longitudinal direction is prepared. And can be measured by a free resonance method at room temperature in an air atmosphere. As the test apparatus, for example, JE-RT type manufactured by Nippon Techno-Plus can be used.

(Strength)
The proof stress of the blank is preferably 90 MPa or more. From the viewpoint of further improving the mechanical properties of the magnetic disk, the proof stress of the blank is preferably 100 MPa or more, and more preferably 120 MPa or more.

  The yield strength can be measured, for example, by preparing a JIS No. 5 test piece with the rolling direction as the longitudinal direction and conducting a tensile test in accordance with JIS Z 2241: 2011 (metal material tensile test method). In addition, you may measure with the test piece which resembled JIS5 and the dimension was reduced.

[Blank manufacturing method]
The blank according to this embodiment can be manufactured by a manufacturing method and equipment under general conditions for manufacturing a substrate for a magnetic disk. For example, a blank can be manufactured by a manufacturing method including, in this order, a punching process of punching an aluminum alloy plate obtained by cold rolling in an annular shape and a straightening annealing process of performing straightening annealing on the punched substrate. it can.

  In the punching process, a substrate obtained by punching is applied to, for example, a substrate for 3.5 inch HDD having an inner diameter of 24 mm and an outer diameter of 96 mm, or a substrate for 2.5 inch HDD having an inner diameter of 19 mm and an outer diameter of 66 mm. Can do.

  In the straightening annealing step, it is preferable that the substrate is sandwiched between spacers having high flatness and then annealed while applying a load to the substrate. The annealing temperature can be 300 to 500 ° C., and the holding time can be 3 hours, for example. The temperature increase rate in annealing can be set to 80 ° C./hour, for example, and the temperature decrease rate can be set to 80 ° C./hour, for example.

[substrate]
The substrate which concerns on this embodiment consists of said blank, and has the external shape by which the end surface of the blank was cut and the main surface was ground. The substrate is made of an aluminum alloy containing Si, Fe, Mn, Ni, and Cu in a predetermined content range, preferably the one or both of Mg and Zn, like the aluminum alloy plate. It further contains in a predetermined content range, and has a chemical composition in which the total content of Cu, Mg and Zn is limited to the predetermined range. More preferably, the total content of Fe, Mn and Ni is also limited to a predetermined range, the ratio value of the Fe content and the Ni content, and the Mn content and the Ni content. Each value of the ratio to the content also has a chemical composition limited to a predetermined value range.

  The characteristic values of the substrate, such as the absolute maximum length of the intermetallic compound on the surface, the Young's modulus, and the proof stress, are the same as those of the blank. The characteristic value obtained for the blank can be regarded as the characteristic value for the substrate, and the characteristic value obtained for the substrate can also be regarded as the characteristic value for the blank.

[Substrate manufacturing method]
The substrate according to the present embodiment can be manufactured by a manufacturing method and equipment under general conditions for manufacturing a substrate for a magnetic disk. For example, the substrate can be manufactured by a manufacturing method including an end surface processing step for cutting the end surface of the blank and a grinding step for grinding the main surface of the blank in this order.

[Method of manufacturing magnetic disk]
The magnetic disk can be manufactured by a manufacturing method and equipment under general conditions for manufacturing a magnetic disk. For example, the surface of the substrate is acid-etched to form an electroless Ni—P plating film, and then the surface of the electroless Ni—P plating film is polished. Next, a magnetic disk can be manufactured by forming an underlayer, a magnetic layer, a protective film, and the like on the surface of the substrate.

  Details of manufacturing conditions such as blanks and substrates are described in, for example, Japanese Patent No. 3471557 and Japanese Patent No. 5199714. Manufacture of a blank, a substrate, etc. can be performed with reference to these documents.

  Hereinafter, the present invention will be specifically described with reference to examples of the present invention. However, the technical scope of the present invention is not limited to this.

  Using an aluminum alloy having the chemical composition shown in Table 1, no. Substrates 1 to 38 were produced as follows. "-" Regarding each component in Table 1 indicates that the corresponding component is not added and the content of the component is less than the detection limit value. In Table 1, “Cu + Mg + Zn” is the total content of Cu, Mg and Zn, “Fe + Mn + Ni” is the total content of Fe, Mn and Ni, and “Fe / Ni” is the content of Fe and Ni The value of the ratio to the content of “Mn / Ni” indicates the value of the ratio of the content of Mn to the content of Ni.

  The substrate was manufactured by performing a casting process, a homogenizing heat treatment process, a hot rolling process, a cold rolling process, a punching process, a straightening annealing process, an end face processing process, and a grinding process process in this order. Specific conditions for each step are as follows.

  The casting process was performed by melting the raw material at 750 ° C. The resulting ingot was chamfered at 2 mm / single side.

  The homogenizing heat treatment step was performed at 540 ° C. for 8 hours. In addition, hot rolling was started within 5 minutes after taking out the ingot subjected to the homogenization heat treatment from the furnace.

  The hot rolling step was performed such that the starting temperature was 520 to 540 ° C., the ending temperature was 300 to 330 ° C., and the plate thickness after hot rolling was 3 mm.

  The cold rolling process was performed so that the plate thickness after cold rolling was 1 mm.

  The punching step was performed by punching a cold rolled plate into an annular shape having an inner diameter of 24 mm and an outer diameter of 96 mm.

  The straightening annealing step was performed with an annealing temperature of 400 ° C. and an annealing time of 3 hours. The rate of temperature increase was 80 ° C./hour, and the rate of temperature decrease was 80 ° C./hour.

  The end face processing step was performed by cutting the inner diameter and the outer diameter of the blank by 1 mm each.

  In the grinding process, a blank with end face processing is set in a carrier pocket set in advance on a double-side grinding machine, and grinding is performed with a PVA grinding wheel (Nippon Nenken Co., Ltd. No. 4000) until the target thickness is reached. Processing was performed.

  About each manufactured substrate, Young's modulus, yield strength, the smoothness of the electroless Ni-P plating film formed on the surface, and the risk of hot water leakage during casting were evaluated as follows. Moreover, the absolute maximum length of the intermetallic compound on the surface was also evaluated as a reference value.

(Absolute maximum length of intermetallic compound on the surface)
The absolute maximum length of the intermetallic compound was measured as follows. Using an FE-SEM (Field Emission Scanning Electron Microscope, model JSM-7001F) manufactured by JEOL Ltd., an acceleration voltage was set to 15 kV, and composition images of 20 fields of view were taken at 200 times. Using the attached analysis system “Analysis Station 3, 8, 0, 31” and the particle analysis software “EX-35110 particle analysis software Ver. 3.84”, it can be recognized on the composition image obtained by FE-SEM. The absolute maximum length of the intermetallic compound was measured. Those having an absolute maximum length of 15 μm or less were evaluated as “◎”, those exceeding 15 μm and 20 μm or less were evaluated as “◯”, and those exceeding 20 μm were evaluated as “Δ”. It was determined that Δ was slightly inferior, ○ was excellent, and ◎ was more excellent.

(Young's modulus)
The Young's modulus was prepared in accordance with JIS Z 2280: 1993 (high temperature Young's modulus test method for metal materials), and a test piece having a thickness of 60 mm × 10 mm × 1 mm with the rolling direction as the longitudinal direction was prepared. The measurement was performed by the free resonance method at room temperature in an air atmosphere. As a test device, JE-RT type manufactured by Nippon Techno-Plus was used. Those having a Young's modulus of 80 GPa or higher were evaluated as “◎”, those having 75 GPa or more and less than 80 GPa were evaluated as “◯”, and those having a Young's modulus of less than 75 GPa were evaluated as “X”. ◎ and ○ were determined to be acceptable, and × was determined to be unacceptable.

(Strength)
Yield strength is JIS Z 2241: 2011 (metal material tensile test method) after cutting out a part of the cold rolled sheet obtained in the cold rolling process and annealing at 400 ° C. for 3 hours corresponding to straightening annealing. Based on this, a JIS No. 5 test piece with the rolling direction as the longitudinal direction was prepared and measured by conducting a tensile test. Those with a yield strength of 120 MPa or more were evaluated as “◎”, those with 90 MPa or more and less than 120 MPa were evaluated as “◯”, and those with a yield strength of less than 90 MPa were evaluated as “x”. ◎ and ○ were determined to be acceptable, and × was determined to be unacceptable.

(Smoothness of electroless Ni-P plating film formed on the surface)
The manufactured substrate was degreased at 70 ° C. for 5 minutes using an alkaline cleaner (AD-68F, manufactured by Uemura Kogyo Co., Ltd.) and washed with pure water. Next, an acid etching treatment at 68 ° C. for 2 minutes was performed using a soft etching agent (AD-101F, manufactured by Uemura Kogyo Co., Ltd.), and washed with pure water. Then, desmut treatment was performed with 30% nitric acid, and subsequently, zincate treatment was performed at 20 ° C. for 30 seconds using a zincate treatment solution (AD-301F-3X manufactured by Uemura Kogyo Co., Ltd.). Then, after dissolving zinc once with 30% nitric acid, it was again subjected to a zincate treatment at 20 ° C. for 15 seconds using a zincate treatment solution (AD-301F-3X manufactured by Uemura Kogyo Co., Ltd.). Then, using an Ni-P plating solution (Nimden (registered trademark) HDX manufactured by Uemura Kogyo Co., Ltd.), an electroless Ni-P plating treatment is performed at 90 ° C. for 2 hours, and an electroless Ni— having a thickness of about 10 μm. A P plating film was formed. The plating surface of the substrate on which the electroless Ni-P plating film is formed is made by using Bruker's ContourGT X3 (non-contact 3D optical interference type surface shape roughness meter), objective lens x 50, FOV x 1, VSI mode Measured with On the surface of the plated film, the density of pits having a width of 3 μm or more and a depth of 1 μm or more is “◎” when the density is 0 to 4 / mm ² , “◯” is 5 to 20 / mm ² , and 21 / mm ^Two or more were evaluated as “x”. ◎ and ○ were determined to be acceptable, and × was determined to be unacceptable. In addition, the plating surface of the substrate on which the electroless Ni—P plating film is formed is made of a colloidal silica-based slurry (DISKLITE Z5601A manufactured by Fujimi Incorporated Co., Ltd.) and a pad (manufactured by Kanebo Co., Ltd. (currently Aion Co., Ltd.)). N0058 72D), and the surface was measured, the same evaluation as in the case of not polishing was obtained.

(Risk of hot water leak)
The risk of hot water leakage was evaluated by using the size of the solid-liquid coexistence area of aluminum alloy as an index. The width of the solid-liquid coexistence region was determined by measuring the temperature change in the process of solidifying by cooling after melting the aluminum alloy with a thermocouple. In addition, using Thermo-Calc Sotware AB's thermodynamic calculation system (Thermocalc: Thermo-calc ver. 3.0) and Thermotech's thermodynamic database (Al-DATA ver.8), Table 1 A phase diagram of the chemical component shown was derived, and was determined as a temperature difference between the solid phase point and the liquid phase point on the phase diagram. “◎” indicates that the temperature difference between the solid phase point and the liquid phase point is 20 ° C. or higher, and there is almost no risk of hot water leakage, “○” indicates that the temperature difference is 10 ° C. or higher and lower than 20 ° C. Those having a temperature of less than ° C. were evaluated as “×” because there was a risk of leaking water. ◎ and ○ were determined to be acceptable, and × was determined to be unacceptable.

  Table 1 shows the results of evaluation of the absolute maximum length of the intermetallic compound on the surface, Young's modulus, proof stress, smoothness of the electroless Ni-P plating film formed on the surface, and the risk of hot water leakage during casting.

  As shown in Table 1, no. In Nos. 1 to 20, since the contents of Si, Fe, Mn, and Ni are appropriately controlled within a predetermined range, a high Young's modulus, a high yield strength, and a good plating property are provided. Moreover, the solid-liquid coexistence area is wide, and the risk of hot water leakage during casting is low.

  In particular, no. In Nos. 6 to 8, since Mg and Zn are added, the solid-liquid coexistence region becomes wider regardless of the Cu content alone, and the risk of hot water leakage during casting is further reduced. No. In Nos. 9 to 12, since Cr is also added, the structure is refined, and the Young's modulus and proof stress are further improved.

  Furthermore, no. In Nos. 13 to 16, since the total amount and ratio of Fe, Mn and Ni are also controlled, coarse intermetallic compounds are excluded, and the smoothness and proof stress of the plating film are higher. No. In Nos. 17 to 20, since Cr is also added, the structure is refined, and the smoothness and proof stress of the plating film are further improved.

  In contrast, no. In No. 21, since the Fe content was less than 0.50% by mass, a high Young's modulus was not obtained.

  No. In No. 22, since the Fe content exceeded 1.50% by mass, a coarse Al—Fe—Ni intermetallic compound was produced, and the yield strength was low.

  No. In No. 23, since the Mn content was less than 0.50% by mass, high Young's modulus and yield strength were not obtained.

  No. 24, since the Mn content exceeded 1.50% by mass, the Al—Mn—Fe intermetallic compound was coarsened or streak-like defects were generated, and the proof stress and the smoothness of the electroless Ni—P plating film were increased. The nature became low.

  No. In No. 25, since the Ni content was less than 1.00% by mass, high Young's modulus and yield strength were not obtained.

  No. In No. 26, since the Ni content exceeded 2.00 mass%, a coarse Al—Fe—Ni intermetallic compound was produced, and the yield strength was low.

  No. In No. 27, since the Si content exceeded 0.10% by mass, elemental Si and the like were generated, and the smoothness of the electroless Ni—P plating film was lowered.

  No. In Nos. 28 to 33, since the Cu content was less than 0.50 mass%, the solid-liquid coexistence region was narrow, and the risk of hot water leakage during casting remained high. In particular, no. Since Cr is also added to 31-33, the structure is refined and Young's modulus and proof stress are further improved, but the risk of hot water leakage during casting remained high.

  No. 34, since the Cu content was 1.00% by mass or more, the solid-liquid coexistence region was wide, the Al—Mn—Fe intermetallic compound was coarsened or a streak defect was generated, and a high Young's modulus or Yield strength was not obtained.

  No. In No. 35, since the Cr content exceeded 0.23% by mass, the yield strength and the smoothness of the electroless Ni—P plating film were lowered.

  No. In No. 36, the Mg content was 1.00% by mass or more, so the solid-liquid coexistence region was wide, the Al—Mn—Fe intermetallic compound was coarsened or streak-like defects occurred, and Al—Fe -The amount of Ni-based intermetallic compounds was reduced, and high Young's modulus and yield strength were not obtained.

  No. In No. 37, the Zn content was 1.00% by mass or more, so the solid-liquid coexistence region was wide, the Al—Fe—Ni intermetallic compound decreased, and a high Young's modulus was not obtained.

  No. In No. 38, since the total amount of Cu, Mg and Zn exceeded 1.00% by mass, the solid-liquid coexistence region was wide, the Al—Fe—Ni intermetallic compound decreased, and a high Young's modulus was not obtained.

Claims (8)

Si: 0.10% by mass or less,
Fe: 0.50% by mass or more and 1.50% by mass or less,
Mn: 0.50% by mass or more and 1.50% by mass or less,
Ni: 1.00% by mass or more and less than 2.00% by mass,
Cu: 0.05 mass% or more and 1.00 mass% or less are contained,
An aluminum alloy plate for a magnetic disk, the balance being Al and inevitable impurities. Si: 0.10% by mass or less,
Fe: 0.50% by mass or more and 1.50% by mass or less,
Mn: 0.50% by mass or more and 1.50% by mass or less,
Ni: 1.00% by mass or more and less than 2.00% by mass,
Cu: 0.05 mass% or more and less than 1.00 mass%,
One or both of Mg: 0.05 mass% or more and less than 1.00 mass% and Zn: 0.05 mass% or more and less than 1.00 mass% are further contained,
The total amount of Cu, Mg and Zn is 1.00% by mass or less,
An aluminum alloy plate for a magnetic disk, the balance being Al and inevitable impurities. In the chemical composition of the aluminum alloy plate for magnetic disks according to claim 1 or 2,
A magnetic alloy aluminum alloy plate further containing Cr: 0.05 mass% or more and 0.23 mass% or less. In the chemical composition of the aluminum alloy plate for magnetic disks according to any one of claims 1 to 3,
The total amount of Fe, Mn and Ni is 4.20% by mass or less,
The ratio of the Fe content and the Ni content is 0.40 to 1.00,
An aluminum alloy plate for a magnetic disk, wherein a ratio of the Mn content to the Ni content is 0.30 to 0.90.   5. The aluminum alloy plate for a magnetic disk according to claim 1, wherein the absolute maximum length of the intermetallic compound on the surface is 20 μm or less.   The aluminum alloy blank for magnetic discs which consists of an aluminum alloy plate for magnetic discs as described in any one of Claims 1-5.   The aluminum alloy blank for magnetic disks according to claim 6, wherein the Young's modulus is 75 GPa or more and the proof stress is 90 MPa or more.   An aluminum alloy substrate for a magnetic disk comprising the aluminum alloy blank for a magnetic disk according to claim 6 or 7.