JP4965696B2 - Method for producing oxide dispersion strengthened platinum alloy - Google Patents

Description

  The present invention relates to a method for producing an oxide dispersion strengthened platinum alloy in which an oxide is dispersed in platinum or a platinum alloy. In particular, the present invention relates to a method with less contamination that can be mixed in the manufacturing process.

  An oxide-dispersed platinum material in which an oxide such as zirconium oxide (zirconia) or yttrium oxide (yttria) is finely dispersed in platinum or a platinum alloy is also called reinforced platinum. Since it is excellent, it is utilized as a structural material for a glass manufacturing apparatus used in a high temperature environment. For this oxide dispersion strengthened platinum alloy, various improvements have been made so far for the purpose of improving the high-temperature strength, etc., and many reports of effectively dispersing the dispersed oxide by improving the manufacturing process, etc. have been reported. (Patent Documents 1 and 2)

Patent No. 4094959 Japanese Patent No. 4280215

  Here, a powder metallurgy method is generally used as a method for producing an oxide dispersion strengthened platinum alloy. In this method, first, an alloy powder of platinum and zirconium is manufactured, and this is subjected to an oxidation treatment to internally oxidize zirconium in the alloy powder to obtain zirconium oxide, thereby obtaining platinum powder in which zirconium oxide is finely dispersed. Then, this is pulverized by a pulverizing means such as an attritor or a ball mill, and this is sintered and processed to obtain a platinum material. In the invention described in Patent Document 1, the manufacturing conditions are adjusted based on this manufacturing method. Moreover, in the said patent document 2, after manufacturing the alloy powder of platinum and zirconium, without oxidizing this, it grind | pulverizes in water with an attritor and oxidizes zirconium with water, oxide formation and Powders are pulverized at the same time and then sintered, but they are common in that they are based on powder metallurgy.

  The conventional methods for producing an oxide dispersion strengthened platinum alloy are intended to disperse oxide particles in a suitable state, and can all be said to be useful in that respect. However, in any of the methods, a defect may occur in the manufactured platinum alloy. This defect is not limited to the fact that the strength of the alloy is insufficient, but the hardness of the alloy is higher than expected (design) and may hinder processing. The problem of processing due to the increase in hardness is pointed out that, for example, the surface of the workpiece is too high during the chamfering process for forming and the processed surface becomes scaly.

  The occurrence of defective products as described above is not a problem of the manufacturing method itself, and is a sudden occurrence even if the management of the quality of raw materials is performed stably. The present invention provides a method capable of stably producing a high quality oxide dispersion strengthened platinum alloy together with investigation of the cause of this problem.

  In order to solve the above-mentioned problems, the present inventors examined each step in the conventional method for producing an oxide dispersion strengthened platinum alloy and investigated the properties of the platinum alloy in which the problem occurred. As a result, it was confirmed that in the platinum alloy that is considered to be problematic, zirconium oxide having a relatively large variation in particle size is dispersed. Then, the factor of such a large particle size zirconia mixture was examined, and it paid attention to the constituent material of the crushing apparatus in a crushing process.

  A grinding device such as an attritor or a ball mill includes a container (pot) for storing a material to be ground, a grinding medium (ball, beads), and a stirring rod (agitator). And the grinding | pulverization apparatus at the time of manufacturing an oxide dispersion strengthened platinum alloy often applies a zirconia from a hardness surface as a grinding | pulverization medium. Here, the oxide dispersion strengthened platinum alloy is a dispersion of oxide such as zirconia, and even if zirconia of the grinding medium is mixed, it is not necessary to regard it as a contaminant on the composition. Until now, the contamination has not been regarded as a problem.

  On the other hand, the inventors of the present application thought that there was a problem with zirconia contamination during pulverization, which had been ignored so far. This is because although zirconia can act as a dispersion strengthening material for oxide dispersion strengthened platinum alloys, it is not possible to disperse oxides with a larger particle size than the original dispersion material irregularly due to the principle of dispersion strengthening. The material strength may be different from the design value. The movement of the grinding medium during the grinding operation is not completely predictable, and the amount of wear and the size of the small pieces that are worn away and cannot be controlled. Therefore, it is considered that sometimes undesirable zirconia is mixed. Therefore, the present inventors have found the present invention in order to perform the pulverization operation while suppressing zirconia contamination during the pulverization step.

  That is, the present invention relates to a method for producing an oxide dispersion strengthened platinum alloy comprising a step of pulverizing an object to be crushed comprising a platinum alloy in a solvent by a pulverizer comprising a container, a pulverizing medium, and a stirring rod. The dispersion of the oxide is characterized in that the contact surface of the grinding medium and the stirring bar at least with the material to be ground is composed of platinum or a platinum alloy, and the hydrogen peroxide solution is added to the solvent for grinding. It is a manufacturing method of a type platinum alloy.

  In the method according to the present invention, the container, the grinding medium, and the stirring rod, which are constituent materials of the grinding device in the grinding process, are all made of platinum or a platinum alloy (hereinafter referred to as a platinum-based material). In some cases). Thus, by using a platinum-based material for the contact surface with the object to be crushed, zirconia can be inevitably avoided.

  The present invention is not limited to simply changing the material of the constituent material of the pulverizer. When the object to be pulverized and the pulverizing apparatus are made of a platinum-based material as in the present invention, there is a high possibility that the object to be pulverized adheres to the stirring rod and the wall surface of the container and joins and the pulverization does not proceed. In particular, such a phenomenon is likely to occur in a high energy ball mill such as an attritor. In the present invention, in consideration of this point, hydrogen peroxide is added to the solvent in the container. Addition of hydrogen peroxide causes foaming in the solvent, and the foam acts as a buffer material to suppress adhesion between platinum and the like, thereby enabling a smooth grinding operation.

  Hereinafter, the present invention will be described in more detail. In the method according to the present invention, the steps before and after the pulverizing step of the platinum alloy powder basically conform to the conventional method for producing an oxide dispersion strengthened platinum alloy. The adjustment of the platinum alloy powder before the pulverization process is also performed in accordance with the conventional method. For example, as in Patent Document 1, the platinum alloy powder is internally oxidized to adjust the platinum alloy powder in which zirconia or the like is dispersed, or as in Patent Document 2. Any step may be performed such as adjusting the platinum alloy powder not containing oxide without performing oxidation treatment.

  For the pulverization step, the present invention applies a pulverization apparatus in which the contact surface of the container, the pulverization medium, and the stirring rod with the object to be crushed is composed of platinum or a platinum alloy. Here, platinum or a platinum alloy may be applied at least as long as it is a contact surface with the object to be pulverized. It may be what was done. For example, as the container, a container whose inner surface is clad with platinum or a small-sized container made of platinum inserted into a container such as stainless steel can be used. Also, the stirring rod may be manufactured from a bulk material such as platinum, but a rod clad with platinum may be used. Here, as platinum or a platinum alloy constituting the contact surface with the object to be crushed, reinforced platinum (oxide dispersion strengthened platinum alloy) as well as pure platinum, platinum alloy (platinum-rhodium alloy, platinum-gold alloy, etc.) ) Is applicable. Note that reinforced platinum contains oxides such as zirconia, but its absolute amount is too small. Since there is no problem, it is possible to use reinforced platinum.

  The pulverization step is wet pulverization using a solvent. This is for appropriately dispersing the material to be crushed. As this solvent, in addition to pure water, organic solvents such as heptane and alcohol, or a mixed solution thereof can be applied. However, when a platinum alloy powder that has not been oxidized as in Patent Document 2 is oxidized in the pulverization step, it is preferable to use water (pure water).

  The hydrogen peroxide charged into the solvent is preferably added so that the hydrogen peroxide concentration is 0.2 to 1% with respect to the solvent used. If the content is less than 0.2%, foaming is small and the effect is poor. If the content exceeds 1%, foaming becomes conversely difficult to control. The hydrogen peroxide solution is preferably added in the form of an aqueous solution, but the concentration and addition amount of the aqueous solution are adjusted in consideration of the concentration with respect to the solvent. In addition, the total amount of hydrogen peroxide may be input once at the start of pulverization, but may be divided and added multiple times during pulverization.

  About the grinding | pulverization conditions (time, temperature) of a grinding | pulverization process, it can set similarly to the conventional method. The same applies to the rotation speed of the stirring rod.

  The alloy powder after the pulverization step can be formed and solidified to form a bulk alloy as in the conventional method. This molding and solidification treatment is preferably a method of sintering while applying pressure as in a hot press. Moreover, about the alloy after a shaping | molding solidification process, a compactness can be improved by a forge process. Furthermore, plastic working such as rolling, extruding, and drawing can be performed in order to form into a predetermined shape.

  According to the present invention, it is possible to prevent zirconia from being mixed into a material to be crushed, which has conventionally occurred in the pulverization step, and to make the manufactured oxide dispersion strengthened platinum alloy free of coarse zirconia. it can. As a result, it is possible to obtain a reinforced platinum alloy with good workability and no unexpected strength fluctuation.

  Further, according to the present invention, by using a platinum-based material as a grinding medium, it is possible to achieve a finer and highly dispersed oxide to be dispersed. This is because a platinum-based material that is a dispersion medium is heavier (high specific gravity) than conventionally used zirconia, and therefore has a larger kinetic energy at the time of pulverization than that of the prior art, thereby improving the pulverization ability. The present invention also leads to an improvement in the quality of the platinum alloy from this point.

The figure explaining the structure of the crusher (attritor) used by this embodiment

  Hereinafter, preferred embodiments of the present invention will be described. In this embodiment, first, a platinum alloy (platinum-0.1 wt% zirconium alloy) powder was manufactured. The platinum alloy powder was produced by vacuum melting an ingot of platinum-0.1 wt% zirconium alloy, and using this as an electrode, a platinum alloy powder was obtained by a rotating electrode gas atomization method (EIGA method). This platinum alloy powder had an average particle size of 80 μm (particle size width of 1 to 300 μm).

  Next, 4000 g of the alloy powder was put into an attritor shown in FIG. The attritor used in this embodiment is a pot (inner diameter φ195 × height 175 mm × thickness 2 mm, weight 5) made of reinforced platinum (trade name: GTH, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) manufactured by the method of Patent Document 1. .8 kg) inserted into a stainless steel pot, a stirrer bar made of reinforced platinum (GTH) (stirring blade φ16 × 160 mm × 4, weight 14 kg), a reinforced platinum ball (φ5 mm, total 14 kg as a grinding medium) ).

  Then, 2 L of pure water was added to the attritor, and the hydrogen peroxide aqueous solution was further adjusted to 0.5% with respect to the pure water.

  In the pulverization step, the platinum alloy powder was pulverized by rotating the stirring bar of the attritor at 340 rpm for 5 hours after the above preparation. In this embodiment, the platinum alloy powder is oxidized simultaneously with pure water.

  After the pulverization step, the platinum alloy powder was separated and dried by sieve selection. When the platinum alloy powder after drying was weighed, it was 4002.7 g, which was 2.7 g higher than before pulverization. Moreover, when the weight of each component of the attritor after the pulverization step was measured, 1.5 g, 1.0 g, and 0.2 g of weight loss of the ball, the stirring rod, and the pot were found, respectively. The increase in the weight of the platinum alloy powder is because the platinum alloy was mixed into the platinum alloy powder by pulverization.

The platinum alloy powder after the pulverization step is placed in a carbon mold (dimensions: 70 × 70 × 100 (mm)), degassed in a vacuum furnace (1200 ° C. × 3 hours), and then 1100 ° C., 20 MPa. And pressure sintering. The dimensions of the sintered platinum alloy were about 70 mm × 70 mm × 48.4 mm and a density of 16.9 g / cm ³ . Next, this platinum alloy ingot was hot forged (1300 ° C.) a plurality of times to obtain a density of 21.4 g / cm ³ (dense density 100%). The dimension at this time was about 75 mm × 100 mm × 25 mm. Then, both sides of this platinum alloy ingot are chamfered with a shaper, cold-rolled (100 mm × 310 mm × 6 mm), annealed (1250 ° C., 30 minutes), cold-rolled again by changing the rolling direction by 90 degrees. The plate material was 600 mm × 300 mm × 1 mm. A test piece for a creep test described later was punched out from the plate material.

Comparative Example : For comparison, a platinum alloy was manufactured by applying a conventional grinding process. The platinum alloy powder used is the same as in this embodiment. The attritor used in the pulverization process is a pot made of zirconia (inner diameter φ200 × height 165 mm, capacity 5 L), a stainless steel stirring rod (a zirconia cap connected to the tip of the stirring blade, dimensions and shape are the same as in the embodiment), pulverization A medium equipped with a YZT zirconia ball (φ5 mm, 7 kg in total) was used. In the pulverization step, 4000 g of platinum alloy powder and 2 L of pure water were put into an attritor and pulverized under the same conditions as in this embodiment.

  When the platinum alloy powder after pulverization and drying was weighed, it was 4005.7 g, which was 5.7 g more than before pulverization. Moreover, when the weight loss of the zirconia ball | bowl of the attritor after a grinding | pulverization process was measured, the weight loss of 5.7g was seen.

  The crushed platinum alloy powder was sintered into an ingot in the same process as in this embodiment, and then processed into a plate material through hot forging and rolling. Creep specimens were also collected.

  As described above, the oxide dispersion strengthened platinum alloys manufactured in the present embodiment and the comparative example were subjected to the quantitative analysis of the zirconium content in the alloy and the creep test. In the creep test, the fracture time was measured at a test temperature of 1400 ° C. and a stress of 15 MPa and 20 MPa using five test pieces. These results are shown in Table 1.

  From Table 1, the platinum alloy of this embodiment has a zirconium content of 0.1% by weight, which is equal to the zirconium content of the platinum alloy powder that is the raw material before pulverization. This indicates that zirconia contamination in the pulverization process is suppressed. On the other hand, in the comparative example, the zirconium content of the manufactured platinum alloy was increased by 0.11% by weight, indicating zirconia contamination during the pulverization process. This can also be seen from the fact that the weight of the grinding media (zirconia balls) decreased after the grinding process.

  And it turns out that the platinum alloy of this embodiment has favorable high temperature strength from the result of a creep test. That is, it can be seen from Table 1 that the platinum alloy of the present embodiment has an extension effect several times as long with respect to the breaking time as compared with the comparative example.

  In addition, the effect of this embodiment appeared also in the manufacturing process of said platinum alloy board | plate material. This is because when the both sides of the hot forged ingot are chamfered, in this embodiment, the entire surface exhibited a smooth glossy surface after processing, whereas in the comparative examples, there were some scale-like surfaces. . From this, it is considered that the method of the present embodiment that avoids zirconia contamination also contributes to improvement of the workability of the platinum alloy.

  Further, in this embodiment, due to the change in the weight of the platinum alloy powder before and after pulverization and the change in the weight of the pulverization medium (reinforced platinum balls), in this embodiment, the platinum alloy powder is slightly mixed during the pulverization process. It can be said that there was. However, from the results of the creep test, it cannot be said that this deteriorates the properties of the platinum alloy. Also, from the analysis result of the zirconium content, the composition ratio in the oxide dispersion strengthened platinum alloy of this embodiment is not changed, and it is considered that the strengthening action is not reduced.

  As described above, the method for producing an oxide dispersion strengthened platinum alloy according to the present invention is a method capable of producing a higher quality platinum alloy than the conventional method.

Claims (2)

In a method for producing an oxide dispersion strengthened platinum alloy comprising a step of pulverizing a material to be crushed comprising a platinum alloy in a solvent by a pulverizer equipped with a container, a pulverizing medium, and a stirring rod,
The contact surface of the container, the grinding medium, and the stirring rod with at least the object to be ground is composed of platinum or a platinum alloy,
A method for producing an oxide dispersion strengthened platinum alloy, wherein a hydrogen peroxide solution is charged into the solvent and pulverized. The method for producing an oxide dispersion strengthened platinum alloy according to claim 1, wherein the hydrogen peroxide solution is added so that the hydrogen peroxide concentration is 0.2 to 1 mass% with respect to the solvent in the container.

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