Method for producing reinforced platinum material

Abstract

[Problems]Providing a strengthened platinum material with the use of melt-sprayed platinum alloy powder and through a simpler working process, which ensures strength of weld and is excellent in high temperature creep property. [Means for Solving the Problems]In a method for producing a strengthened platinum material, comprising the steps of: adding an organic solvent and wet-milling a platinum alloy powder obtained by melt-spray; degassing the milled platinum alloy fine powder by heating; sintering the fine powder; and forging the fine powder, wherein the method further comprises subjecting a sintered body formed by the sintering to oxidation treatment; and subjecting the sintered body to compression molding.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a strengthened platinum material, and especially to a technology of producing a strengthened platinum material with the use of a platinum alloy powder obtained through melt-spray. BACKGROUND ART [0002] Regarding a strengthened platinum material acting as a structural material used in handling a glass material or ceramic material, such as an optical glass and an optical fiber, in a molten state, various producing methods have been conventionally proposed. The strengthened platinum material is required to have such properties as a high creep strength and no occurrence of blisters. [0003] As producing methods of a strengthened platinum material having high temperature strength properties, for example to improve a high creep strength at 1400° C., a method is known in which the metal oxide such as zirconium oxide is finely and uniformly dispersed in a platinum base metal of the strengthened platinum material. ...

AI Technical Summary

Benefits of technology

[0012] The present invention was made against a background of the above situation, and it is an object to improve the present-inventor's proposed method of producing a strengthened platinum material with the use of a platinum alloy powder obtained through melt-spray, and provide a method of producing a strengthened platinum material which requires more simplified operation, does not cause various problems arising from forging, namely voids and splashes during welding, and ensures weld strength.

[0015] Since an oxidation treatment of a sintered body having low denseness in the method for producing a strengthened platinum material according to the present invention enables oxidation of zirconium to advance through to the center of the sintered body, and by subjecting the oxidation-treated sintered body to compression molding, the sintered body having low denseness is formed a compact having a predetermined shape to allow the subsequent forging to be readily and promptly conducted. That is to say, by subjecting a sintered body having an essentially empty state (i.e. very porous state) of denseness as low as 35%, the sintered body is allowed to be oxidized progressively to the center thereof in a short period of time, and subsequent compression molding can prevent heat from being let out from a sintered body during forging and the sintered body from crumbling, thereby preventing costly platinum base metal from getting scattered and lost, and improving production yield. Consequently, minor adjustment of striking power at an initial stage of forging can be eliminated, and reduction in forging time can be conspired, which is an epoch-making effect.

[0018] It is preferable if the compression molding according to the present invention is carried out with hot pressing (hot press molding). The hot pressing enables compression molding from top and bottom under vacuum reduced pressure, so that degassing treatment can be conducted simultaneously with pressing treatment, thereby providing a high-density compact. It is preferable if the temperature of the hot pressing ranges from 20° C. to 1200° C. If the temperature of the hot pressing exceeds 1200° C., hot pressing carried out in a vacuum atmosphere easily causes reductive reaction, thereby reducing an oxide-dispersion component (for example, zirconium oxide) contained in a platinum alloy, and decomposed oxygen will become gasified to generate bubbles, which contributes to blisters of materials and voids during welding. This phenomenon tends to be especially remarkable when a later-described carbon sheet is used. In contrast, the reason why the temperature of hot pressing is extended to 20° C. as the lower limit, so-called room temperature is that the present inventor's research revealed hot pressing carried out at room temperature in a vacuum atmosphere will hardly cause a phenomenon of trapping of air, can make a sintered body of low-denseness a compact of high-denseness, thereby subsequent forging will be readily and promptly carried out.

[0020] With respect to the heat resistant container used in a degassing treatment in the present invention, it is preferable to provide the container with a carbon sheet onto which wet-milled platinum alloy fine powder is injected, and with respect to the hot press molding used in hot pressing, it is desirable to provide the molding with a carbon sheet and to arrange a sintered body on the press molding. Thus, a carbon sheet can effectively prevent a platinum base metal from adhering to a heat resistant container and a hot press molding, so that maintenance operations of a heat resistant container and a hot press molding can be eliminated. It is preferable if the thickness of the carbon sheet ranges from 0.03 to 0.5 mm. If the thickness is smaller than 0.03 mm, such a sheet will be no elastic, be deteriorated in shape-keeping capability, and be easily broken, thereby is impractical. In contrast, if the thickness exceeds 0.5 mm, such a sheet will be poor in flexibility, easily crack up, thereby is impractical. In the present invention, it is possible to use a heat resistant container per se or a press molding per se formed with carbon and to adopt a process in which no carbon sheet is used, however taking production costs and strength thereof into consideration, it is deemed more practical to use a carbon sheet.

[0024] As described above, according to the present invention, it is possible to produce a strengthened platinum material with the use of melt-sprayed platinum alloy powder and through a simpler working process, which will not cause problems due to a forging treatment, such as voids and splash during a welding process, ensures strength of weld and is excellent in high temperature creep property.

Problems solved by technology

Thus, the present inventors' proposed manufacturing method, which involves the above-described oxidation treatment caused prolonged manufacturing time associated with increased steps and loss of platinum bare metal associated with adhesion of platinum to an alumina tray, thereby suffering from a defect that manufacturing yield cannot be improved.

Since the platinum bare metal is adhered to the heat-resistant container during the degassing, troublesome maintenances including shaving off the adhered matters with the use of a knife or spatular material are required.

Further in forging, an agglomeration of platinum alloy powder, namely an ingot tends to crumble very easily.

Additionally, a bond strength of platinum particles immediately after sintering is so weak that an ingot crumble very easily.

Even if forging can be carried out under ideal conditions, some platinum tends to crumble from porous portions of a surface of an ingot.

Thus, it has been an inherent problem that costly platinum base metal will get scattered and lost, thereby production yield cannot be improved.

Plate materials of platinum alloy obtained through rolling after forging tend to cause, during welding, voids and splashes (phenomenon in which fine molten metals splash and spatter during welding of a strengthened platinum material).

However, only a small proportion of air and gaseous component remaining in the ingot are trapped among sintered platinum grains, which will lead to voids and splashes during welding.

Oxide-dispersion-strengthened platinum materials are known to have an extremely deteriorated strength of weld thereof compared with that of a base material.

Consequently, strengthened platinum materials, which often cause voids and splashes, will cause deteriorated weld strength and are likely to cause damages such as breakage of a glass melting tank.

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