JPH08104974A - Method for hardening platinum or platinum alloy and method for hardening palladium or palladium alloy - Google Patents

Abstract

PURPOSE: To impart high hardness to the surface of Pt or Pt alloy without roughening the surface. CONSTITUTION: A mixture of 40% B4 C with 20% borax (Na2 B4 O7 ) is prepd., 20% NaCl and 20% KCl are added to the mixture and they are mixed in a crucible. Platinum of 99.95% purity cast into a hexagonal-round ring is put in the resultant mixture and heated at 800 deg.C for 4hr in an electric furnace. Boron in the mixture penetrates into the surface of the Pt ring to harden the surface. The Vickers hardness Hv of the surface of the Pt ring is 350. The surface of the hardened ring is hardly roughened and is comparable to the surface of an unhardened Pt ring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of hardening platinum or a platinum alloy, which is a precious metal material used as jewelry, and palladium or a palladium alloy.

[0002]

2. Description of the Related Art Platinum (Pt), a precious metal material used as jewelry, is soft and easily scratched. For example, if the content of pure platinum is 99.95% or more, the Vickers hardness (Hv) when annealed is only about 50 to 55, easily scratched, and may be deformed by a light impact. In this state, it is not actually usable as jewelry.

For this reason, platinum is processed into jewelry or the like in a cured state. How to cure platinum
Alloying with other metals, processing such as rolling and forging, or plating is common.

Similarly, palladium, which is a metal of a white metal element, or an alloy of palladium with gold, silver, etc., is also soft and easily scratched.

Platinum (Pt) usually has a purity of 99.
If it is 8% or more, it is called pure platinum. In such pure platinum, it has been attempted to increase the hardness by adding a trace amount of various metal elements of about 0.1%. However, in the case of pure platinum, only Vickers hardness (Hv) of about 80 to 90 can be obtained in consideration of cracks, cavities and the like during casting.

On the other hand, in the platinum alloys containing 95%, 90% and 85% of platinum (Pt), palladium (Pd), cobalt (Co), tungsten (W), copper (Cu), Hardness can be increased by adding a metal such as iridium (Ir) or ruthenium (Ru). However, if the hardness is high, the castability is reduced, shrinkage cavities due to solidification shrinkage, pinholes due to gas absorption, cracks, etc. may occur during casting, and the flowability is poor and the products cannot be cast into a predetermined shape. There is a risk.

For example, a platinum alloy in which 10% of palladium (Pd) is mixed with 90% of platinum (Pt) has good castability, but has a Vickers hardness (Hv) of 70.
It is about 75, and the hardness is insufficient for use as jewelry.

[0008] Also, for 90% platinum (Pt),
Palladium (Pt) 5%, Tungsten (W) 5%
The blended platinum alloy has a high Vickers hardness (Hv) of about 230 even when annealed, but it is almost impossible to cast into a predetermined shape because tungsten is oxidized, and it becomes brittle when cast. There is a problem of becoming.

In addition, 90% platinum (Pt), 7% palladium (Pt), 3 cobalt (Co)
%, The platinum alloy has good castability, but has a Vickers hardness (Hv) of about 120, which is liable to be damaged as a jewelery product, and is easily deformed.

Such a platinum alloy can be used as a decorative article if its thickness, thickness and the like are increased in order to prevent deformation. However, ornaments with increased thickness, thickness, etc. are not only expensive because they require a large amount of metal, but also are heavy, and when worn directly on the body such as rings and earrings. Can cause stiff shoulders. In addition, a brooch that is directly attached to clothes has a problem that the clothes are easily damaged.

In the work hardening method in which the hardness is increased by forming into a predetermined shape by rolling or forging, it is impossible to form a fine shape like the casting method which is a usual jewelery forming method. There are restrictions on the design.
The hardness of the platinum alloy can also be increased by forming by a spatula process, but there is a problem in that uniform hardness cannot be obtained over the entire area, and moreover, it takes a lot of time and labor. A ring with a simple structure such as a marriage ring can be manufactured by molding, grinding, and polishing by mechanical processing after increasing hardness by rolling or forging instead of casting, but it is manufactured by casting. It cannot be processed into an elaborate design, shape, etc.

Thus, platinum or platinum alloy formed by rolling or forging has a problem that it is not easy to form it into a complicated shape as a jewelry.
Moreover, the tableware such as knives and forks manufactured by rolling or forging cannot be practically used with platinum or platinum alloy, and are not in practical use at present.

When the surface of a platinum alloy processed into a predetermined shape by casting is plated, the hardness of the surface increases, but a metal of a different type from the base material of the platinum alloy is adhered to the surface. Therefore, there is a risk of peeling over time.

Since the same problem occurs in the case of palladium and alloys containing palladium such as gold and silver, the range of use of palladium and alloys containing palladium is limited as jewelry and the like.

Japanese Unexamined Patent Publication (Kokai) No. 6-346222 discloses an article in which the surfaces of platinum and palladium are hardened with boron, and a method for producing the article. The method disclosed in this publication is specifically a mixture of boron and potassium borofluoride, or a mixture of this mixture with polyproisobutylene and light benzene, or a mixture of these with aluminum oxide, platinum, etc. By heating at a temperature of 750 ° C or higher,
The surface of platinum etc. is hardened.

[0016]

However, although such a curing method can cure the surface of platinum or the like, the surface of the surface is so rough that polishing work for giving a luster as jewelry is required. There is a problem that it is not easy.

Further, when a fluoride is used, since it may have an adverse effect on the environment, it is necessary to purify wastewater after curing platinum or the like, and equipment therefor. There is a problem that is needed.

The present invention solves such a problem and can remarkably improve hardness, and further,
It is an object of the present invention to provide a method for curing platinum or a platinum alloy and a method for curing palladium and an alloy containing palladium, which has less rough skin and can very easily obtain the luster required for jewelry.

[0019]

In order to achieve the above object, the present invention provides platinum or a platinum alloy, or palladium or a palladium alloy with a mixture of boron carbide, borax and salts for a predetermined time. It is characterized by heating to a temperature.

As the salt, a mixture of sodium chloride and potassium chloride is preferable.

In this case, specifically, the mixing ratio of boron carbide and borax to sodium chloride and potassium chloride may be 10:90 to 50:50 by weight, and more specifically. The mixing ratio of boron carbide and borax is 95: 5 to 60:40 by weight%, and the mixing ratio of sodium chloride and potassium chloride is by weight%.
It may be 40:60 to 60:40.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

Platinum or a platinum alloy, or palladium or an alloy containing palladium is heated at a temperature of 600 ° C. to 800 ° C. for about 30 minutes to 4 hours together with boron carbide, borax, salts of sodium chloride and potassium chloride. . This brings boron into the surface of platinum or a platinum alloy, or palladium or a palladium alloy, and the surface hardness of platinum or a platinum alloy, or palladium or an alloy containing palladium is significantly improved. Moreover, the platinum or platinum alloy, or the surface of the palladium or palladium surface is less rough, and the polishing work for obtaining the gloss required for jewelry is significantly reduced.

The mixture of boron carbide and borax that is heated with platinum or a platinum alloy, or palladium or an alloy containing palladium, the higher their amount and the longer the heating time, the platinum or platinum alloy surface, or The amount of boron penetrating the surface of palladium or an alloy containing palladium increases, and the surface hardness increases.

Further, by using salts with boron and borax, platinum or a platinum alloy,
Or while promoting the hardening of palladium or an alloy containing palladium, platinum or a platinum alloy,
Alternatively, roughening of the surface of palladium or an alloy containing palladium is suppressed. As the salt, a mixture of sodium chloride (NaCl) and potassium chloride (KCl) is particularly preferable, but sodium chloride (NaCl) or potassium chloride (KCl) may be used alone, or other salts may be used individually. Alternatively, multiple can be used simultaneously.

It is considered that the boron carbide and the borax are turned into liquid by heating with salts, and the surface roughness of platinum or a platinum alloy, or palladium or an alloy containing palladium is suppressed.

Platinum or a platinum alloy heated with a mixture of boron carbide, borax and salts, or palladium or an alloy containing palladium, is a platinum or platinum alloy or palladium which has almost no surface roughening and is not hardened. Or it is almost comparable to the surface condition of the alloy containing palladium. Therefore, by performing simple barrel polishing, buffing, and the like, excellent gloss that can be used as jewelry is obtained, and the polishing work is significantly reduced.

Platinum or a platinum alloy, or palladium or an alloy containing palladium may be cast in a predetermined shape in advance, or may be forged or rolled into a predetermined shape. The surface of cast platinum or platinum alloys, or palladium or alloys containing palladium, when the boron or boron compound is platinum or platinum alloys or alloys containing palladium or palladium, even when shaped into complex shapes such as ornaments Hardness is increased over the entire surface due to penetration throughout. Platinum or a platinum alloy previously formed into a plate shape by forging or rolling, or palladium or an alloy containing palladium has a hardness that can prevent deformation, and therefore is practically used as a tableware such as a knife or a fork. Can be used.

As the alloy containing palladium, not only an alloy mainly containing palladium but also a gold alloy, a silver alloy, a copper alloy having a palladium addition rate of half or less, without roughening the surface, Hardening of the surface is observed.

[0030]

Embodiments of the present invention will be described below.

<Example 1> Boron carbide (B ₄ C) 36
%, Borax (Na ₂ B ₄ O ₇ ) 4%, sodium chloride (NaCl) 30%, potassium chloride (KCl) 30%
Were mixed in a crucible made of stainless steel, and a plate material of platinum (Pt) 99.95% and an instep ring were embedded in the mixed powder. The plate material is 10 mm square and has a thickness of 1.
It is 2 mm. Then, the crucible was housed in an electric furnace while being covered with a stainless plate, and heated at 750 ° C. for 3 hours. After the heating was completed, the plate and the instep round ring were taken out from the crucible and washed with hot water to remove the mixture of boron carbide and the like adhering to the surface of the plate.

The Vickers hardness (Hv) of the surface of the plate material thus obtained was 50 before the treatment but 167 after the treatment.

The surface roughness of the obtained plate material was measured by a surface roughness measuring machine (trade name "Circoph 5 manufactured by Tosei Engineering Co., Ltd."
50A "), the center line average roughness Ra is 0.
It was 16 μm. The measurement graph of the surface roughness is shown in FIG.

Further, a micrograph (100 times) of the surface of the obtained Komaru ring is shown in FIG. The surface of this round ring had almost no rough skin. The results are shown in Table 1.

<Example 2> Purity 9 in Example 1
Platinum (Pt) 90 instead of 9.95% platinum
%, Palladium (Pd) 10% platinum alloy, 10 mm square, 1.2 mm thick plate material and instep ring were used. Other than that, the curing treatment was performed under the same conditions as in Example 1. The Vickers hardness (Hv) of the surface of the cured plate material was 70 before the treatment, but became 230 after the treatment.

The center line average roughness Ra of the obtained plate material is
It was 0.10 μm. The measurement graph of the surface roughness is shown in FIG. Further, a micrograph (100 times) of the surface of the obtained Komaru ring is shown in FIG. For comparison, a photomicrograph (100 times) of the surface of the round ring before hardening treatment is shown in FIG. The surface of the Komaru ring had almost no rough skin. The results are also shown in Table 1.

<Example 3> Boron carbide (B ₄ C) 21
%, Borax (Na ₂ B ₄ O ₇ ) 9%, sodium chloride (NaCl) 35%, potassium chloride (KCl) 35%
Was mixed in a stainless crucible, and a plate material of 99.95% platinum (Pt) similar to that in Example 1 and an instep round ring were embedded in the mixed powder, and the same as in Example 1, It heated at 750 degreeC in the electric furnace for 3 hours.

The Vickers hardness (Hv) of the surface of the obtained plate material and the surface of the round ring was 50 before the treatment, but became 156 after the treatment.

The center line average roughness Ra of the obtained plate material is
It was 0.40 μm. The measurement graph of the surface roughness is shown in FIG.

FIG. 7 shows a micrograph (100 times) of the surface of the obtained Komaru ring. The surface of this round ring had almost no rough skin. The results are also shown in Table 1.

<Example 4> In Example 3, the purity was 9
Platinum (Pt) 90 instead of 9.95% platinum
%, Palladium (Pd) 10%, a 10 mm square, 1.2 mm thick plate material and instep ring made of a platinum alloy of 10% were used. Other than that, the curing treatment was performed under the same conditions as in Example 3. The Vickers hardness (Hv) of the surface of the cured plate material was 70 before the treatment, but became 313 after the treatment.

The center line average roughness Ra of the obtained plate material is
It was 0.29 μm. The measurement graph of the surface roughness is shown in FIG. Further, a micrograph (100 times) of the surface of the obtained Komaru ring is shown in FIG. The surface of the Komaru ring had almost no rough skin. The results are also shown in Table 1.

Example 5 Boron Carbide (B ₄ C) 40
%, Borax (Na ₂ B ₄ O ₇ ) 20%, sodium chloride (NaCl) 20%, and potassium chloride (KCl) 20% are put into a stainless crucible and mixed, and a purity of 99. 95% platinum (Pt) was cast into a round ring and put in. Then, the crucible was placed in an electric furnace and heated at 800 ° C. for 4 hours. After the heating was completed, the ring was taken out from the crucible and washed with hot water to remove the mixture such as boron carbide adhered to the ring surface.

The Vickers hardness (Hv) of the surface of the ring thus obtained was 350, and there was almost no surface roughness. When the obtained ring was buffed, which is a usual ring finishing step, it became a glossy ring in a short time. The results are also shown in Table 1.

<Example 6> In Example 5, the purity was 9
Platinum (Pt) 90 instead of 9.95% platinum
%, Platinum (Pd) 10% platinum alloy was used by casting in a round ring. Otherwise, Example 1
Curing treatment was carried out under the same conditions as above. The Vickers hardness (Hv) of the cured ring was 560, and the surface of the obtained ring had almost no surface roughness. The results are also shown in Table 1.

Example 7 Boron Carbide (B ₄ C) 7%,
Borax (Na ₂ B ₄ O ₇ ) 3%, sodium chloride (Na
Cl) 45% and potassium chloride (KCl) 45% are mixed in a crucible made of stainless steel, and platinum (P) having a purity of 99.95% cast on a standing claw ring is mixed in the mixture.
t) was added. Then, place the crucible in an electric furnace at 80
Heat at 0 ° C. for 4 hours. After the heating was completed, the ring was taken out from the crucible and washed with hot water to remove the mixture such as boron carbide adhered to the ring surface.

The surface of the ring thus obtained had a Vickers hardness (Hv) of 172, and almost no rough skin was observed. When the obtained standing nail ring was buffed, which is a usual finishing process, a glossy ring was obtained in a short time. When stones were attached to the standing claw ring, the stones were firmly fixed as compared with the conventional standing claw ring, and the gloss was also the same as the conventional one. The results are also shown in Table 1.

<Example 8> In Example 7, instead of platinum having a purity of 99.95% cast on the standing claw ring,
A platinum alloy of 90% platinum (Pt) and 10% palladium (Pd) was cast into a standing nail ring and used. Other than that, the curing treatment was performed under the same conditions as in Example 7. The hardened standing nail ring had a Vickers hardness (Hv) of 157, and the surface of the ring as a product showed almost no rough surface. Also, the ring was firmly stone-fastened. The results are also shown in Table 1.

Example 9 Boron Carbide (B ₄ C) 34
%, Borax (Na ₂ B ₄ O ₇ ) 16%, sodium chloride (NaCl) 25%, potassium chloride (KCl) 25%
Were mixed in a stainless crucible, and the mixture was mixed with platinum (Pt) 90% and palladium (Pd) 5
%, Tungsten (W) 5% platinum alloy was pressed into a clip-type earring using a leaf spring and introduced. Then, place the crucible in an electric furnace at 800 ° C for 30 minutes.
Heated for minutes. After the heat treatment was completed, the earrings were taken out from the crucible and washed with hot water to remove the mixture adhering to the earrings.

The Vickers hardness (Hv) of the surface of the earring thus obtained was 424, and the surface was not roughened. The platinum alloy of this example has a Vickers hardness (Hv) of 23 before press working.
0, the Vickers hardness (Hv) at the time of press working was about 360, and the hardness was remarkably improved by the curing treatment for 30 minutes. When the obtained earrings were buffed, which is a usual finishing step for products, they became glossy earrings in a short time. Further, the clip has a pressing pressure of 35.4 gf because the plate material constituting the leaf spring has a high hardness, which is remarkably against the pressing pressure of the earring clip of 25.2 gf when it is not cured. It was getting higher. The results are also shown in Table 1.

Example 10 Boron Carbide (B ₄ C) 34
%, Borax (Na ₂ B ₄ O ₇ ) 16%, sodium chloride (NaCl) 25%, potassium chloride (KCl) 25%
Were mixed in a stainless crucible, and a plate material obtained by casting platinum with a purity of 99.95% was put into the mixture. Then, place the crucible in an electric furnace at 80
Heat at 0 ° C. for 4 hours. After the heat treatment was completed, the platinum alloy plate was taken out from the crucible and washed with hot water to remove the mixture of boron carbide and the like adhering to the surface of the platinum alloy plate.

The surface of the platinum plate material thus obtained had a Vickers hardness (Hv) of 50 before being hardened.
However, Vickers hardness (H
v) It was 367. In addition, there was almost no surface roughness. The results are also shown in Table 1.

<Example 11> In Example 10, when the plate material was subjected to a hardening treatment by forging before the hardening treatment,
The Vickers hardness (Hv) became 144. After that, when heat treatment was performed together with the boron compound under the same conditions as in Example 11, the Vickers hardness (H
v) became 346. In addition, there was almost no surface roughness. The results are also shown in Table 1.

<Example 12> In Example 10, platinum (Pt) 9 was used instead of platinum having a purity of 99.95%.
A cast plate made of a platinum alloy containing 0% and 10% palladium (Pd) was used. Other than that, the curing treatment was performed under the same conditions as in Example 10. The Vickers hardness (Hv) before the curing treatment was 70, but the Vickers hardness (Hv) of the cured plate material was 495. In addition, there was almost no surface roughness. The results are also shown in Table 1.

<Example 13> In Example 12, the plate material was subjected to a hardening treatment by forging before the hardening treatment.
The Vickers hardness (Hv) became 156. Then, when heat treatment was performed together with the boron compound under the same conditions as in Example 10, the Vickers hardness (Hv) of the platinum alloy plate material became 508. In addition, there was almost no surface roughness. The results are also shown in Table 1.

Example 14 In Example 10, a cast plate material of a platinum alloy of 90% platinum (Pt), 7% palladium (Pd) and 3% cobalt (Co) was used. Other than that, the curing treatment was performed under the same conditions as in Example 10. The Vickers hardness (Hv) of the platinum alloy plate material before the hardening treatment was 112, but the Vickers hardness (Hv) of the hardened platinum alloy plate material was 327. In addition, there was almost no surface roughness. The results are also shown in Table 1.

<Example 15> In Example 14, when the platinum alloy plate was hardened by forging before the hardening treatment, the Vickers hardness (Hv) became 248. After that, when heat treatment was performed together with the boron compound under the same conditions as in Example 13, the Vickers hardness (Hv) of the platinum alloy plate material became 314. In addition, there was almost no surface roughness. The results are also shown in Table 1.

Example 16 Boron carbide (B ₄ C) 40
%, Borax (Na ₂ B ₄ O ₇ ) 20%, sodium chloride (NaCl) 20%, potassium chloride (KCl) 20%
Were mixed in a stainless crucible, and a plate material of 10 mm square and 1 mm thick palladium (Pd) was put into the mixture. Then, place the crucible in an electric furnace at 80
Heated at a temperature of 0 ° C. for 4 hours. After the heat treatment was completed, the palladium plate material was taken out from the crucible and washed with hot water to remove the mixture of boron carbide and the like adhering to the surface of the plate material.

The palladium (P
The surface of the plate material of d) had Vickers hardness (Hv) 254. In addition, there was almost no surface roughness. The results are also shown in Table 1.

Example 17 In Example 16, instead of palladium (Pd), 18% gold of palladium white gold containing 75% gold (Au), 11% palladium, 10% copper, and 4% silver was used. Other than that, the curing treatment was performed under the same conditions as in Example 16. Palladium white gold 1
8 gold is Vickers hardness (Hv) 1 before hardening treatment
Although it was 30, the Vickers hardness (Hv) became 163 after the curing treatment. In addition, there was almost no surface roughness. The results are also shown in Table 1.

Example 18 In Example 16, 18% gold of palladium white gold containing 75% gold (Au) and 25% palladium was used. Other than that, Example 16
Curing treatment was carried out under the same conditions as above. Palladium white gold 18K should be Vickers hardness (H
v) 89, the Vickers hardness (Hv) became 222 after the curing treatment. In addition, there was almost no surface roughness. The results are also shown in Table 1.

<Comparative Example 1> For comparison, Japanese Patent Laid-Open No. 6-3
Platinum (Pt) 99.95 used in Example 1 by the method described in Example 1 of 46222.
% Plate and Komaru ring were treated. That is, a mixture of 85% of boron (B) and 15% of potassium borofluoride (KBF ₄ ) was put into a crucible, the plate material and the Komaru ring were embedded in the mixture, and the mixture was heated in an electric furnace at a temperature of 750 ° C. Heated over time.

The center line average roughness Ra of the obtained plate material is
It was 1.58. The measurement graph of the surface roughness is shown in FIG.

A microscopic photograph of the surface of the Komaru ring (1
00 times) is shown in FIG. As described above, the surface of the Komaru ring was rough and the gloss was poor. Table 2 shows the results.

<Comparative Example 2> Purity of 9 in Comparative Example 1
Platinum (Pt) 90 instead of 9.95% platinum
%, Palladium (Pd) 10% platinum alloy, 10 mm square, 1.2 mm thick plate material and instep ring were used. Other than that, the curing treatment was performed under the same conditions as in Comparative Example 1.

The center line average roughness Ra of the obtained plate material is
It was 1.21 μm. Figure 12 shows the measurement graph of surface roughness.
Shown in Further, a micrograph (100 times) of the surface of the obtained Komaru ring is shown in FIG. As described above, the surface of the Komaru ring was rough and the gloss was poor. The results are also shown in Table 2.

<Comparative Example 3> By the method described in Example 8 of Japanese Patent Application Laid-Open No. 6-346222, the same plate material and instep ring as 99.95% platinum (Pt) used in Example 1 were used. Plates and Komaru rings were processed. That is, boron (B) 20%, boron carbide (B ₄ C) 4
A mixture of 0%, boron nitride (BN) 30% and potassium borofluoride (KBF ₄ ) 10% was put into a crucible, the plate material and the Komaru ring were embedded in the mixture, and the temperature was raised to 750 ° C. in an electric furnace. Heated for 3 hours.

The center line average roughness Ra of the obtained plate material is
It was 2.48. The measurement graph of the surface roughness is shown in FIG.

A microscopic photograph of the surface of the Komaru ring (1
00 times) is shown in FIG. As described above, the surface of the Komaru ring was rough and the gloss was poor. The results are also shown in Table 2.

<Comparative Example 4> In Comparative Example 3, the purity was 9
Platinum (Pt) 90 instead of 9.95% platinum
%, Palladium (Pd) 10% platinum alloy, 10 mm square, 1.2 mm thick plate material and instep ring were used. Other than that, the curing treatment was performed under the same conditions as in Comparative Example 3.

The center line average roughness Ra of the obtained plate material is
It was 1.04 μm. Figure 16 shows the measurement graph of surface roughness.
Shown in In addition, a micrograph (100 times) of the surface of the obtained Komaru ring is shown in FIG. As described above, the surface of the Komaru ring was rough and the gloss was poor. The results are also shown in Table 2.

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

As described above, the method for hardening platinum or a platinum alloy and the method for hardening palladium or an alloy containing palladium according to the present invention are such that boron penetrates the entire surface of platinum or a platinum alloy, palladium or an alloy containing palladium. As a result, the hardness of the surface is remarkably improved, and the surface is hardly roughened. Therefore, the polishing work for obtaining the gloss as a jewelry is remarkably reduced.

[Brief description of drawings]

FIG. 1 is a graph showing a measurement result of surface roughness of a plate material obtained by a curing method in Example 1 of the present invention.

FIG. 2 is a micrograph (magnification: 100) of the surface of an instep round ring obtained by the curing method in Example 1 of the present invention.

FIG. 3 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Example 2 of the present invention.

FIG. 4 is a micrograph (magnification of 100) of the surface of an instep round ring in Example 2 of the present invention.

FIG. 5 is a micrograph (magnification: 100) of the surface of an instep round ring before hardening treatment in Example 1 of the present invention.

FIG. 6 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Example 3 of the present invention.

FIG. 7 is a micrograph (magnification: 100) of the surface of an instep round ring in Example 3 of the present invention.

FIG. 8 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Example 4 of the present invention.

FIG. 9 is a micrograph (magnification: 100) of the surface of an instep round ring in Example 4 of the present invention.

FIG. 10 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Comparative Example 1.

FIG. 11 is a micrograph (magnification: 100) of the surface of an instep round ring obtained by the curing method in Comparative Example 1.

12 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Comparative Example 2. FIG.

FIG. 13 is a micrograph (magnification: 100) of the surface of a round ring in Comparative Example 2.

FIG. 14 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Comparative Example 3.

FIG. 15 is a micrograph (magnification of 100) of the surface of a round ring in Comparative Example 3.

16 is a graph showing the measurement results of the surface roughness of the plate material obtained by the curing method in Comparative Example 4. FIG.

FIG. 17 is a micrograph (magnification of 100) of the surface of the Komaru ring in Comparative Example 4.

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[Submission date] October 6, 1995

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Claims (8)

[Claims] 1. A method for hardening platinum or a platinum alloy, comprising heating platinum or a platinum alloy together with a mixture of boron carbide, borax and salts to a predetermined temperature for a predetermined time. 2. The method for hardening platinum or a platinum alloy according to claim 1, wherein the salt is a mixture of sodium chloride and potassium chloride. 3. The mixing ratio of boron carbide and borax to sodium chloride and potassium chloride is 1% by weight.
The method for hardening platinum or a platinum alloy according to claim 2, wherein the method is 0:90 to 50:50. 4. The mixing ratio of boron carbide and borax is 95: 5 to 60:40 by weight, and the mixing ratio of sodium chloride and potassium chloride is 40:60 by weight.
The method for hardening platinum or a platinum alloy according to claim 3, wherein the method is 60:40. 5. A method for curing palladium or a palladium alloy, which comprises heating palladium or a palladium alloy together with a mixture of boron carbide, borax and salts to a predetermined temperature for a predetermined time. 6. The method of hardening palladium or a palladium alloy according to claim 5, wherein the salt is a mixture of sodium chloride and potassium chloride. 7. The mixing ratio of boron carbide and borax to sodium chloride and potassium chloride is 1% by weight.
The method for curing palladium or palladium alloy according to claim 6, wherein the method is 0:90 to 50:50. 8. The mixing ratio of boron carbide and borax is 95: 5 to 60:40 by weight%, and the mixing ratio of sodium chloride and potassium chloride is 40:60 by weight%.
The method for hardening palladium or palladium alloy according to claim 7, wherein the method is 60:40.