JP2002069601A - Manufacturing method for alloyed platinum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of freely manufacturing materials having characteristics suitable for use such as those attaching importance to workability, hardness, or the like for a highly purified hard alloyed plutinum. SOLUTION: The manufacturing method for an alloyed platinum is characterized in that the method for the alloyed platinum containing 0.05-0.14 wt.% Si as an additive element comprises a process (a) for heating up to 700-1100 deg.C and rapid cooling after melting and casting the alloyed platinum, a process (b) for cold working, and a process (c) for heating up to 500-950 deg.C. In this case, the alloyed platinum can be made more workable by heating up to 500-700 deg.C in the process (c). Meanwhile, it can be made harder and more flexible to a certain extent so as not to crack in the process of working when the heating temperature is increased up to 700-950 in the process (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hard platinum alloy containing a small amount of silicon as an additional element.
More specifically, the present invention relates to a method for producing a hard platinum alloy having a step of appropriately adjusting the hardness and workability of the hard platinum alloy.

[0002]

2. Description of the Related Art Platinum is used as a constituent material of crucibles and glass manufacturing equipment because of its good heat resistance, and is also used as a supporting metal for various catalysts because of its high catalytic activity. This material is widely used for industrial purposes. On the other hand, platinum has a neat shine, has a decorative effect, and is rare. Therefore, platinum is widely used as a decorative material for rings, necklaces, watches and the like.

Conventionally, as platinum for decorative materials, platinum such as palladium, nickel, copper or the like is used in an amount of 5 to 15% by weight.
Platinum alloys added and alloyed are generally used (hole marks (grade marks for precious metal products provided by the Mint) as "Pt950" and "Pt90".
0 "and" Pt850 ". ). This is because platinum has a low hardness and is soft in a pure metal state, and therefore, when pure platinum is applied to a wearable object such as a decorative article, scratches are likely to occur. These platinum alloys compensate for the lack of hardness when this pure metal is applied.

[0004] However, since decorative materials often require an asset value as well as a decorative effect, use of a platinum alloy having a high platinum content (which satisfies the certification criteria of the hall mark "1000") is used. Is particularly required in recent years.
In order to meet such demands, various hard platinum alloys containing a small amount of calcium, titanium, and boron, mainly silicon, have been developed as alloy elements that can be made into a platinum alloy having a high platinum content and high hardness. . These hard platinum alloys contain one or more of the above-mentioned alloying elements, and their total amount is only a very small amount of about 0.1 to 0.01% by weight. A remarkable increase in hardness is observed as compared with pure metal, and even when applied to decorative articles, the occurrence of scratches is small and a long-lasting aesthetic appearance can be maintained.

[0005]

However, although these conventional hard platinum alloys have a sufficient hardness, they have a problem that they are too hard, have poor toughness, and are susceptible to cracking or breakage during working, resulting in poor workability. is there. On the other hand, since decorative articles often have complicated shapes and are often subjected to stretching and bending, the use of such a material having poor workability is preferred from the viewpoint of processing cost or product yield. It is not desirable.

On the other hand, in the process of manufacturing decorative articles, in addition to the above-mentioned plastic working process, joining work such as brazing is often performed. For example, a necklace and a clasp of a watch band are often joined and assembled by brazing. When performing such a joining process, it is considered that the vicinity of the joined portion is heated, and the material is softened by annealing. Therefore, the decorative material is required to have not only ease of plastic working but also hardness enough to maintain a certain hardness even when subjected to heat history.

[0007] As described above, the decorative material is not just a material having a high hardness in consideration of only the properties when used as a product, but is considered to be various in consideration of a manufacturing process when the material is used as a decorative product. Characteristics are required. That is, when producing a decorative material, it is necessary to selectively use materials having different properties, such as a soft material having good workability and a material capable of maintaining a certain hardness even at high temperatures. In addition, such a use is not one in which a plurality of types (a plurality of types of materials) are separately manufactured, but is more efficient in the case of manufacturing a material of one composition and adjusting the characteristics according to the application. it is conceivable that.

The present invention has been made in view of the above background, and has a high purity hard platinum alloy having characteristics according to its use, such as a material that emphasizes workability and a material that emphasizes hardness. It is an object of the present invention to provide a method capable of freely manufacturing a material.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied the characteristics of conventional hard platinum alloys and made intensive studies. As a result, they have found that this hard platinum alloy has the following interesting characteristics by performing a predetermined working heat treatment after melting and casting.

That is, many metal materials tend to soften when heated regardless of the presence or absence of post-casting processing, and their hardness decreases and softens as the heating temperature increases. On the other hand, the hard platinum alloy targeted by the present invention, when subjected to a solution treatment and a cold working treatment after melting and casting, is further heated in a predetermined temperature range to be different from the general metal material described above. Behave differently.

Specifically, this hard platinum alloy is subjected to solution treatment and further cold work to cause work hardening and increase in hardness. However, by heating this to a relatively low temperature of 500 ° C. or less, age hardening is performed. (Precipitation hardening) occurs and a further increase in hardness is observed. Further, as a more interesting phenomenon, when heated at a temperature higher than the temperature at which this age hardening occurs, a two-stage hardness change is exhibited. When heated in a temperature range of 500 to 700 ° C., the hardness is reduced and softened. ° C
On the other hand, when heating is performed in the above temperature range, the hardness increases and becomes harder. In hard platinum alloys, the reason why such a unique change is exhibited by heat treatment after work hardening is not always clear, but the present inventor has taken advantage of such properties to obtain platinum having properties according to the application. It was thought that an alloy could be manufactured, and the present invention was completed.

The invention according to claim 1 of the present application is characterized in that a method for producing a platinum alloy containing 0.05 to 0.14 wt% of silicon as an additional element includes the following steps (a) to (c). This is a method for producing a platinum alloy.

(A) After melting and casting a platinum alloy having the above composition,
Step of heating to a temperature of 700 to 1100 ° C. and quenching (b) Step of cold working (c) Step of heat treatment at a temperature of 500 to 950 ° C.

Hereinafter, the present invention will be described in detail. still,
The hard platinum alloy targeted by the present invention is a platinum alloy containing 0.05 to 0.14% by weight of silicon as an additional element. Silicon is an element that improves the mechanical properties, particularly the strength, of platinum alloys. To secure the desired hardness, at least 0.05% by weight is required, while 0.14% or more is required. Is not suitable in view of the fact that the present invention is directed to an alloy containing a large amount of a platinum component. The present invention is also effective when other elements for improving the characteristics of the platinum alloy besides silicon are added. For example, in the case of a hard platinum alloy, a small amount of indium or calcium may be added as an additional element in order to improve castability and prevent casting cracks. However, such a platinum alloy to which a small amount of indium or the like is added is also useful. In addition, the same applies to the case where titanium or boron is added as an alloy element in order to secure the hardness by the precipitation effect. However, when other additive elements are added in addition to silicon as described above, the addition amount is preferably less than 0.15% including silicon.

In the present invention, a solution treatment and a cold working are first performed on the platinum alloy after melting and casting. Here, the method of melting and casting the alloy before the solution treatment is not particularly limited, but the platinum alloy targeted by the present invention has an extremely low concentration of added elements such as silicon. In order to make adjustments, a platinum alloy having a higher additive element concentration than the target additive element concentration is manufactured as a master alloy, and the mother alloy is redissolved and platinum is added to adjust the additive element concentration. Is preferred.

[0016] The heating temperature in the solution treatment is 700 to 1100 ° C. The heating time at this time is not particularly limited, and is not particularly limited as long as the inside of the alloy to be processed is sufficiently heated, but is preferably about 0.5 to 1 hour.

On the other hand, as a form of working in the cold working treatment after the solution treatment, various cold workings such as rolling, drawing and drawing are performed. There is no particular limitation on the processing rate at this time, and the effects of the present invention can be obtained with any processing rate. However, the working ratio at this time affects the hardness after the subsequent heat treatment, and when the working ratio is high, the hardness after the working becomes higher due to work hardening, and the hardness after the heat treatment tends to become higher. Therefore, a preferable processing rate is 60 to 90%. In addition, since the hardness of the platinum alloy after the solution treatment is reduced and the workability is improved, this cold working step also has a role as a primary working process before the final working.

The platinum alloy that has been subjected to the above-mentioned solution treatment and cold working treatment is made of 5%
Heat treatment is performed at 00 to 950 ° C. Here, the reason for setting the heat treatment temperature to this range is that age-hardening (precipitation hardening) occurs when heating is performed at 500 ° C. or less, so that the hardness of the platinum alloy after the treatment becomes too high. 950 ° C
If the heat treatment is performed as described above, the platinum alloy is significantly softened, so that a hard platinum alloy cannot be obtained. Note that the heating time in this heat treatment is preferably about 0.5 to 1 hour from the viewpoint of preventing crystal grains from becoming coarse.

Furthermore, as described above, the platinum alloy heated in this temperature range has a different tendency of hardness change in the two temperature ranges. Therefore, a platinum alloy having desired product characteristics can be obtained by selecting any one of these temperature regions and performing heat treatment. That is, heating temperature 500 ~
Since the hardness tends to decrease in the temperature range of 700 ° C., heat treatment in this temperature range makes it possible to obtain a platinum alloy having a relatively low hardness but a very good workability.

On the other hand, when the heating temperature is in the range of 700 to 950 ° C., the hardness of the alloy tends to increase. The hardness at this time is not as high as the hardness immediately after the cold working before the heat treatment, and the alloy has an appropriate hardness without brittleness. Therefore, by performing heat treatment in this temperature range, it is possible to obtain a hard platinum alloy which can be processed while having appropriately high hardness and resiliency.

In the present invention, the cold working performed before the heat treatment for adjusting the characteristics also has a role as the primary working before the final working. As described above, this utilizes the fact that the platinum alloy which is the object of the present invention is softened by the solution treatment and the workability is improved. Here, the number of times the series of steps including the solution treatment and the cold working are performed is not limited to one time, and the hardness can be adjusted by the subsequent heat treatment even if the steps are performed a plurality of times. . Therefore, when the working ratio is insufficient as the primary working by only one cold working, for example, when it is necessary to produce a foil-like product and also when sufficient hardness is required, the solution treatment and the cold working are performed. By repeating the inter-working process a plurality of times and then performing heat treatment to adjust the characteristics, a platinum product having a desired shape and characteristics can be manufactured.

[0022]

Preferred embodiments of the present invention will be described below with reference to the drawings.

First Embodiment : A Si pipe 1.5 is mounted on a platinum pipe (outer diameter 8 mm, inner diameter 6 mm) having a purity of 99.95% by weight.
g of Pt-5% Si mother alloy was manufactured by melting and casting in an argon arc melting furnace. Then, a material obtained by further adding platinum to this master alloy is melted and cast in a high-frequency vacuum melting furnace, and 1000 g of a Pt-Si alloy ingot (length 80 mm, width 60 mm, thickness 10 m)
m) was prepared. When the composition of this alloy ingot was analyzed by X-ray fluorescence analysis, the concentration of Si was 0.13% by weight.
Met. When the hardness of this alloy ingot was measured with a Vickers hardness meter (load: 0.2 kg), Hv
Values between 200 and 210 were obtained.

Next, this ingot was placed in the atmosphere at 800 ° C.
For 1 hour, followed by solution cooling treatment by rapid water cooling. Then, the alloy after the solution treatment was cold-rolled at a processing rate of 85% to obtain a sheet material having a thickness of 15 mm. During the cold rolling, the sheet material did not crack or break. The hardness of the alloy after the solution treatment and after the cold rolling was such that the hardness after the solution treatment was Hv150 and 25% softened as compared with the hardness before the treatment, but the hardness after the cold working was Hv293 and the hardness was Hv293. It was confirmed that the hardness was increased by the processing.

The platinum alloy sheet having a thickness of 15 mm by the cold working is heated at 800 ° C. for 30 minutes and then water-cooled, again subjected to a solution treatment, and then cold-rolled at a working ratio of 70%. A 0.45 mm plate material was used. Then, in order to examine the change in hardness due to the heat treatment temperature of the platinum alloy after the solution treatment and the cold working treatment, a test piece (width 10 mm, length 50 mm) was cut out from this plate material, and 100 ° C to 1 ° C.
After heating to a temperature of 100 ° C. for 30 minutes, the hardness of the platinum alloy after heating was measured. The hardness was measured using a Vickers hardness meter and the load was set to 0.2 kg.

FIG. 1 shows the hardness values of the platinum alloy after the solution treatment and the cold working treatment heated at each temperature. From FIG. 1, the platinum alloy heat-treated at a temperature of 500 ° C. or less after cold working has a high Hv of 300 or more, and particularly, the alloy heat-treated at around 350 ° C. has a very high hardness of about Hv 370. This is considered to be due to the precipitation hardening phenomenon due to aging in the heat treatment at a relatively low temperature. Then, it was confirmed that when the heat treatment temperature exceeded about 500 ° C., the hardness decreased, and at about 600 ° C., the hardness softened to Hv140. On the other hand, when heat treatment was performed at a temperature equal to or higher than the maximum softening temperature, it was confirmed that the hardness increased again, and after a second peak of Hv270 was shown at around 900 ° C., the softening was observed.

Furthermore, a bending test (bending radius: 0.45 mm) was performed on these platinum alloys, and the outer surface of the bent portion was observed. Although no break occurred,
Wrinkles were formed on the outer surface of the bent portion. Also, with respect to a platinum alloy having a low hardness which was heat-treated at 1000 ° C. or higher, bending was relatively easy, but the surface of the bent portion was rough, and a so-called orange peel surface morphology due to coarsening of crystal grains was observed. Was. On the other hand, no remarkable defects were found on the bent surface of the platinum alloy heat-treated at 500 to 900 ° C, and particularly, the surface of the platinum alloy heat-treated at 600 ° C showing the lowest hardness was smooth and glossy. There was a very smooth surface condition.

Conventional Example : As a comparative example to this embodiment, the workability and hardness of a conventional platinum alloy as melted and cast were measured. Similarly to the present embodiment, platinum was added to a Pt-5% Si master alloy to produce a Pt-Si alloy ingot having the same composition and size as the present embodiment.

Then, the ingot is processed at a reduction ratio of 20% by a cold rolling mill with a target of 4% per reduction.
%, It was confirmed that cracks were generated on the side surfaces and the surface of the processed alloy sheet material. Therefore, no further processing could be performed. The hardness of the plate after rolling was 270 Hv.

From the above test results, the hard platinum alloy which is the object of the present invention has poor workability as it is after casting, as shown in the comparative example, and is processed at a processing rate of about several percent. It was confirmed that cracking occurred only by repeating this several times. On the other hand, from the results of this embodiment, it was confirmed that the workability of this hard platinum alloy was improved by performing a solution treatment after casting and a predetermined heat treatment after cold working. In particular, from the viewpoint of workability, by setting the heat treatment temperature after cold working to about 500 to 700 ° C., a material having excellent workability that maintains a favorable surface state even for bending can be obtained. . In terms of hardness, by setting the heat treatment temperature to 700 to 900 ° C., the hardness can be made equal to the hardness in the state of only casting, and the material has a certain degree of flexibility and generates cracks even when processed. I will not do it. Therefore, according to the present invention, it is possible to confirm that a hard platinum alloy having a composition of 1 can produce a material having properties according to its use, from those having good workability to those having high hardness. Was.

[0031]

As described above, the present invention has a process of performing a predetermined thermomechanical treatment on a hard platinum alloy, which was conventionally considered to be hard and brittle and thus difficult to process, to adjust its characteristics. It is. ADVANTAGE OF THE INVENTION According to this invention, the hardness can be adjusted about the hard platinum alloy which only had high hardness, and a material with favorable workability and spring property can be manufactured according to the use. The method for producing a hard platinum alloy according to the present invention is suitable for producing decorative materials produced by various production steps and processing methods.

[Brief description of the drawings]

FIG. 1 is a diagram showing hardness when a hard platinum alloy (Pt-0.13 wt% Si) after solution treatment and cold working is heated at various temperatures.

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Claims (4)

[Claims] 1. The method according to claim 1, wherein silicon is added in an amount of 0.05 to 0.1 as an additive element.
A method for producing a platinum alloy containing 14 wt%, comprising the following steps (a) to (c). (A) After melting and casting a platinum alloy having the above composition, 700 to 11
Step of heating to a temperature of 00 ° C. and quenching (b) Step of cold working (c) Step of heating at a temperature of 500 to 950 ° C. 2. The heating temperature in the step (c) is 500 to 700 ° C.
The method for producing a platinum alloy according to claim 1, wherein 3. The heating temperature in the step (c) is 700 to 950 ° C.
The method for producing a platinum alloy according to claim 1, wherein 4. The method according to claim 1, wherein the steps (b) and (c) are performed in at least one step.
The method for producing a platinum alloy according to claim 1, wherein the method is repeated twice.