JP5073452B2 - Machining method of powder solidified compact - Google Patents

Description

  The present invention relates to machining of a molded body obtained by filling a metal container with raw material powder and hot-solidifying and forming, and particularly relates to a machining method of a sputtering target material.

  Conventionally, when manufacturing high-melting-point materials that are difficult to manufacture by melting methods or high-carbon tool steels that have large solidification segregation, a metal container is filled with raw material powder and solidified and molded hot. Method and upset method are used. The solidified molded body by these methods is machined into a predetermined shape by a band saw, wire cutting, cutting, polishing, or the like.

  However, in recent years, Zr, Hf, Nb, Ta, B, etc. (amorphous promoting elements) have been added to Co, Fe, Ni (ferromagnetic elements) used for soft magnetic layer formation of perpendicular magnetic recording media. When processing a brittle solidified molded body such as a sputtering target material, cracks or chips are generated at the ends of the solidified molded body, or in the extreme case, cracks occur throughout the solidified molded body. In some cases, the yield of the product is greatly affected, and the establishment of a stable manufacturing method has been an issue.

For example, in Examples of Japanese Patent Application Laid-Open No. 2002-212607 (Patent Document 1) and Japanese Patent Application Laid-Open No. 11-217668 (Patent Document 2), after solidification molding, a stainless steel container or a carbon steel capsule which is a metal container is used. After the removal, the sputtering target material is produced by machining, and the cracking and chipping of the sputtering target material is improved by increasing the density, improving the microstructure, and improving the strength of the molding method. On the other hand, JP-A-8-143370 (Patent Document 3) proposes to use a foil as a capsule against such a crack.
JP 2002-212607 A JP 11-217668 A JP-A-8-143370

  However, some cracks occur even in the method by densification and microstructure improvement, and it cannot be said that the product yield is sufficiently high. The method using foil capsules is not suitable for large-sized molded products such as sputtering target materials. It cannot be used. In particular, the upset method has a high incidence of cracks, and a stable machining method has been strongly demanded. Thus, the actual state is that no conventional example is known in which the generation of cracks is suppressed by improving the machining method.

  As a result of intensive investigations on such problems, the inventors have found that these cracks and chips can be significantly suppressed by defining the removal processing sequence and method of the metallic container covering the solidified molded body. . That is, the present invention provides a processing method for suppressing the generation of cracks in a metal container removing process after solidification molding in a powder compact that is filled with a powder as a raw material and solidified hot.

The gist of the invention is that
(1) In a powder compact billet obtained by filling a powder metal billet filled with raw material powder into a cylindrical metal container and degassing and encapsulating it, the outer cylinder can on the side surface of the metal container is thickened. With at least 0.5 mm remaining, cut the lid of at least one end face of the metal container to 2 mm or less, and then wire cut to a thickness of 15 mm or less from the end where the lid was cut to 2 mm or less A method for machining a powder solidified molded body, comprising a step of slicing.

(2) The method for machining a powder solidified molded body according to (1), wherein the powder solidified molded body is solidified by an upset method.
(3) The ingredient of the raw material powder described in (1) or (2) is at. %, One or more of Fe, Co and Ni are 80 to 95% in total, and one or more of Zr, Hf, Nb, Ta, B, Si, C and P are 5 to 5 in total The present invention resides in a machining method for a powder-solidified molded product, characterized in that 20% and one or two of Al and Cr are 5% or less in total.

  As described above, according to the present invention, the powder as a raw material is filled in a metal container, and by optimizing the procedure of removing the metal container after solidification molding in a powder compact that is solidified hot, It is possible to greatly suppress the occurrence of cracks during processing, and to achieve an extremely excellent effect of improving the product yield.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view showing a part of a metal container according to the present invention. As shown in FIG. 1, a metal container 1 is mainly composed of a side outer cylindrical can 3, and is composed of a lid 2 on an upper end surface and a lid 4 on a lower end surface of the outer cylindrical can 3 on the side surface. In such a configuration, the reason why the lid of at least one end face of the metal container is cut to 2 mm or less with the outer cylinder can on the side surface of the metal container remaining in a thickness of 0.5 mm or more is as follows. . Metallic containers used for the HIP method and the upset method need to withstand high temperatures and high pressures for both the outer can and the lids at both ends, so SS, SC, low alloy, Stainless steel is used.

  When removing these metallic containers by machining, if the outer cylinder can is removed by cutting or wire cutting to less than 0.5 mm while leaving the thickness of the end cover over 2 mm, it becomes a powder compact. Since a large number of cracks are generated, therefore, at least one end face lid is cut to 2 mm or less in a state where the outer cylinder can on the side surface remains 0.5 mm or more. There is no restriction | limiting in particular in the upper limit of the thickness which the outer cylinder can of a side surface leaves, and although it does not matter as thickness of the outer cylinder can to be used, it is usually 10 mm or less. The lower limit of the thickness of the lid on the end face to be cut is not particularly limited, and may be completely removed.

  In addition, the reason for limiting to the step of slicing to a thickness of 15 mm or less by wire cutting is that the present invention mainly relates to a method for producing a sputtering target material, and most of the shape is a disk shape having a thickness of 10 mm or less. Yes, if the slice is excessively thick, the thickness is reduced by subsequent cutting and polishing, and the product yield is lowered. Therefore, the slice is 15 mm or less. The lower limit of the slice thickness varies depending on the shape of the product, but it is desirable to set the thickness of the product plus about 1 mm as the finishing margin.

  The reason for limiting the solidification by the upset method is that the effect of reducing the crack occurrence rate by applying the machining method in the present invention is particularly remarkable in the upset method. . Further, the ingredients of the raw powder are at. %, One or more of Fe, Co and Ni are 80 to 95% in total, and one or more of Zr, Hf, Nb, Ta, B, Si, C and P are 5 to 5 in total The reason why 20% and one or two of Al and Cr are limited to 5% or less in total is that the sputtering target material having the above composition used for generating a soft magnetic film of a perpendicular magnetic recording medium is As can be inferred from the figure, since a very brittle compound is formed by the ferromagnetic element and the amorphous promoting element, cracks are likely to occur. For this reason, it is because the effect of crack generation rate reduction by applying the machining method in the present invention is particularly remarkable.

  There are no particular limitations on the upper and lower limits of the solidification molding temperature and pressure, but as a common-sense temperature and pressure range, the HIP method is about 500 to 2000 ° C. and about 50 to 200 MPa, the upset method is 700 to 1300 ° C., and 100 to 1000 MPa. It doesn't matter. In addition, it is necessary to suppress the temperature to not exceed the melting point of the raw material powder and the outer can.

  The reason why the occurrence of cracks in the powder molded body can be suppressed by removing the metal container by the order and method of the present invention can be estimated as follows. The metal container and the powder molded body are metals having different compositions and have different thermal expansion and thermal shrinkage rates. Due to this difference, a residual stress is generated at the interface between the metal container and the powder molded body during shrinkage while being solidified and molded to hot and then cooled to room temperature. It is considered that cracks are generated in the relatively brittle powder compact at the time of removal.

  Therefore, it is considered that this crack is suppressed because the residual stress is released relatively slowly by optimizing the procedure for removing the metallic container. In particular, since the residual stress at the interface between the end cover and the powder compact is large, it is estimated that a method of cutting the end cover to 2 mm or less with the outer cylinder can remaining 0.5 mm or more is considered effective. . In particular, in the case of the upset method, since the pressurization is unidirectional and high pressure, it is considered that cracks are more likely to occur compared to HIP, which is relatively low pressure and weeping pressure. Is unknown.

  The thickness of the outer can on the side of the metal container can be left as long as it is 0.5 mm or more when the end cover is cut to 2 mm or less. Since a discharge failure may occur in the portion, it is preferable to cut the metal surface so that the metal surface comes out before slicing by wire cutting.

  By processing according to the method of the present invention, it can be confirmed that the rate of occurrence of cracks is greatly reduced. In particular, in the case of the upset method and at.%, One or two of Fe, Co and Ni are used. Species or more is 80 to 95% in total, Zr, Hf, Nb, Ta, B, Si, C and P are one or more of 5 to 20% in total, Al and Cr are one or two kinds It was confirmed that the effect was remarkable in the alloy system containing 0 to 5% in total.

Hereinafter, the present invention will be specifically described with reference to examples.
A powder-filled billet obtained by degassing and encapsulating the raw material powder shown in Table 1 in SS, SC, and SUS304 metal containers was solidified and molded by the HIP method and the upset method at 500 to 1350 ° C., and in the order shown in the table The metal container was removed to the remaining thickness by cutting on a lathe. Thereafter, the slice was cut by wire cutting at a thickness of 15 mm to obtain a disk-shaped material.

(1) For deaeration and sealing, the raw material powder is made of a metal outer can with an outer diameter of 205 mm, an inner diameter of 190 mm (single wall thickness: 7.5 mm), and a length of 300 mm, and a metal lid that is 8 mm thick. The container was deaerated and sealed. The degree of vacuum at the time of deaeration was about 1.3 × 10 ⁻² Pa (about 1 × 10 ⁻⁴ Torr).

(2) As HIP processing conditions, the above powder-filled billet was HIP molded at 500 to 1350 ° C. and 147 MPa.
(3) As an upset method, the above powder-filled billet was heated to 900 to 1200 ° C., then inserted into a constraining container having an inner diameter of 215 mm, and molded at a pressure of 500 MPa.

As an evaluation item and method, the crack occurrence rate of the powder compact was evaluated based on the rate of occurrence of cracks among the 10 disk-shaped materials obtained as described above.
Moreover, the raw material powder composition shown in Table 1 is at%, Co + W, W + V, Al + Si, and Cr + Ti of the raw material powder are Co powder and W powder, W powder and V powder, Al powder and Si powder, Cr powder and Ti powder. Each represents a mixed powder (mixing ratio is 50% by mass), GA is produced by gas atomization, and US is an upset method. Further, the remaining thickness by machining is a designed thickness. However, the remaining 0 mm was visually confirmed.

表１に示す、Ｎｏ．１〜９は本発明例であり、Ｎｏ．１０〜１８は比較例である。

No. 1 shown in Table 1. 1 to 9 are examples of the present invention. 10-18 are comparative examples.

  As shown in Table 1, Comparative Example No. Nos. 10 to 15 and 17 are in a state where the thickness of the side outer cylinder can is less than 0.5 mm. Nos. 16 and 18 are obtained by cutting the end cover to a thickness exceeding 2 mm, and both of them have a high crack generation rate. On the other hand, the present invention example No. Since all of Nos. 1 to 9 satisfy the conditions of the present invention, it can be seen that the crack generation rate is 0 or extremely low.

  As described above, since the residual stress is released relatively slowly by optimizing the procedure for removing the metal container, this crack is suppressed, and in particular, the residual stress at the interface between the end face lid and the powder compact. Therefore, a method of cutting the end surface lid to 2 mm or less with the outer cylinder can remaining 0.5 mm or more is effective.

It is explanatory drawing which shows the site | part of the metal container which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal container 2 Lid of upper end surface 3 Outer cylinder can of side 4 Lid of lower end surface


Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (3)

In a powder compact billet in which a powder-filled billet filled with raw material powder and degassed and encapsulated in a cylindrical metal container is solidified hot, the outer cylinder can on the side of the metal container has a thickness of 0.5 mm In the state left above, the step of cutting the lid of at least one end face of the metal container to 2 mm or less, and then slicing to a thickness of 15 mm or less by wire cutting from the end on which the lid is cut to 2 mm or less A method for machining a powder-solidified molded product, comprising: 2. The method for machining a powder solidified molded body according to claim 1, wherein the powder solidified molded body is solidified by an upset method. The ingredient of the raw material powder according to claim 1 or 2, wherein at. %, One or more of Fe, Co and Ni are 80 to 95% in total, and one or more of Zr, Hf, Nb, Ta, B, Si, C and P are 5 to 5 in total A machining method for a powder solidified molded body, characterized in that 20% and one or two of Al and Cr are 5% or less in total.

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