JP4520944B2 - Method for producing white noble metal alloy - Google Patents

Description

The present invention relates to a method for producing a white noble metal alloy for use in ornaments such as rings, necklaces, brooches, earrings and tie pins, watch frames, watch bands, lighters, writing tools, and glasses frames.

  Conventionally, as jewelry, there are chromatic products (yellow gold, pink gold, etc.) mainly composed of gold and achromatic products based on white. Platinum (Pt) alloy, white gold, etc. are used for the achromatic product.

  Recently, white-based precious metal alloys based on white have become popular, and the marriage ring market has come to occupy nearly 90%.

  As the white noble metal alloy, platinum alloy and white gold are used, both of which have the following drawbacks.

  As platinum and platinum alloys for jewelry, there are Pt1000, Pt950, Pt900, Pt850, etc., but palladium (Pd) excellent in castability and workability is frequently used as the split. Moreover, cheap base metals, such as copper (Cu) and cobalt (Co), are used from a cost side. Since Pd has low hardness and insufficient mechanical properties, it has defects such as being easily scratched and easily deformed. On the other hand, Cu, Co, and the like have low costs, but have disadvantages such as poor castability and easy oxidation.

  As a solution to this problem, there are platinum alloys disclosed in Patent Document 1 (Japanese Patent Publication No. 2-42895) and Patent Document 2 (Japanese Patent No. 2923932).

  However, the former platinum alloy has a disadvantage that it is more expensive than a normal platinum alloy because platinum is 80% or more and expensive gold is used as a split. The latter platinum alloy also has the disadvantage that it is expensive with platinum (Pt1000) with improved mechanical properties.

  On the other hand, since platinum is expensive, an alloy called white gold based on gold (Au) is known as a substitute alloy thereof. Generally, white gold is nickel (Ni) in gold of 20K (carat) or less. ) Or palladium (Pd).

  However, white gold using nickel as an additive element has a problem of metal allergy, and white gold using palladium as an additive element has a problem of insufficient mechanical properties.

  A platinum-gold binary alloy that can be used as a substitute for platinum, maintains a high-grade feeling with 100% precious metal, provides practical hardness, and is inexpensive. If possible, it is estimated that more demand is expected. However, various bullions sold as white gold materials have large variations in whiteness (saturation), making it difficult to quantify the color tone required for use as a substitute for platinum. For this reason, the color tone evaluation is largely dependent on individual senses, and even if it is white, there is a difference in individual senses.

The present invention has been made in view of the above circumstances, and by quantifying the color tone required for use as a substitute for platinum, it can be said to be truly white, harder and less expensive platinum-gold. An object of the present invention is to provide a method for producing a binary white noble metal alloy.

In order to solve the above problems, the present inventor first established a method for objectively quantifying the color measurement of a metal color, and then performed the color measurement by the established color measurement method and investigated the hardness. As a result, the inventors have developed a white noble metal alloy that has a color tone as a platinum substitute , is excellent in hardness, and has a higher quality than conventional white gold. In other words, the present invention has been established for the first time by establishing a colorimetric method for quantifying metal colorimetry, which has been difficult to quantify with low reproducibility in the past, with such a colorimetric method.

  More specifically, the inventor of the binary alloy of Pt (platinum) and Au (gold) has a color tone as a platinum substitute, and is a less expensive white noble metal that has no practical problem. An alloy was developed.

The present invention includes a white noble metal alloy containing 50 to 65% by mass of Pt, the balance being Au and unavoidable impurities, and used in any of ornaments, watch frames, watch bands, lighters, writing tools, and glasses frames. In the manufacturing method, the white noble metal alloy is subjected to a timely forming process after annealing, then heated to 1250 to 1300 ° C., and then subjected to high-temperature heat treatment that is water-cooled, and then subjected to an aging treatment in a temperature range of 550 to 600 ° C. It is characterized by that.

As described above, according to the present invention, a platinum-gold binary system which has a color tone and excellent hardness necessary for use as a substitute for platinum, maintains a high-class feeling with 100% precious metal, and is cheaper. A white noble metal alloy can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the L * a * b * color system and the L * C * h color system conforming to JIS Z 8729 are used for the digitization of colors in this embodiment.

[Color measurement method]
First, the color measurement method in the present invention will be described.

In general, in order to feel color, three elements of (1) vision, (2) light source, and (3) object are necessary.

(1) Since there are individual differences in sight and it is difficult to quantify by visual observation, a spectrocolorimeter is used as a device for replacing the visual part with a sensor and digitizing it.

  Several color measurement methods have been proposed by JIS, and a color measurement method (illumination light receiving optical system: geometry) suitable for the sample can be selected.

(2) The light source can be optimized by specifying the color measurement conditions such as the light source itself, the optical path (angle, etc.), the visual field, and the treatment of specularly reflected light.

(1) and (2) depend on the spectrocolorimeter and can be solved by optimizing the measuring machine and the colorimetric conditions. Specifically, the colorimetry method (Geometry), the absolute value accuracy of the colorimeter, the device error, etc. are important.

  Therefore, for this color measurement, a spectrocolorimeter (CM-3600d) manufactured by Minolta Co., Ltd. is used, Geometry (geometry); diffuse illumination 8 ° (d / 8 °) light reception (including regular reflection light), Measurement conditions: 10 ° field of view, D65 light source.

  The absolute value accuracy is an inherent performance of the measuring instrument, and the absolute value accuracy published by the manufacturer of CM-3600d (manufactured by Minolta) used this time is priced by NPL (National Physical Laboratory: United Kingdom). The color difference ΔE * ab in each of the 22 colors of the color tile is 0.33 on average and Max 0.94 (when regular reflection light is included). The instrument error is within ΔE * ab 0.15.

  Therefore, if there is no fluctuation in the measurement object and the measurement environment is constant, the absolute value accuracy of CM-3600d should be considered as ΔE * ab <0.48 on the average and ΔE * ab <1.09 at the maximum. Can do.

(3) When the object is a metal, if it is systematically uniform on the measurement scale, the spectral reflection characteristics are considered to converge to a substantially constant value depending on the composition.

  However, even if the colorimetric conditions are determined, the colorimetric results and visual appearance differ depending on the surface condition of the sample. It is important to make the surface condition the same for reproducibility.

  In order to eliminate the influence of the light source angle and the viewing angle as much as possible, the rough surface roughened so that the surface is diffusely reflected has better visual stability than the mirror surface. However, when quantifying numerically, it is difficult to roughen the surface with good reproducibility. Therefore, the surface roughness is eliminated as much as possible, and the color measurement with high numerical reproducibility can be performed by measuring the color with the highly accurate mirror surface and the optimized color measurement conditions. The level of the measurement mirror surface was an average surface roughness of about 30 nm, and a stable result was obtained by measuring the color within 60 minutes after the generation of the new surface as much as possible. The temperature at the time of measurement was 23 ° C. ± 2 ° C.

  Table 1 shows the color measurement results obtained by the above color measurement method.

Gold and copper are metals that have a unique color among metals, and are high in saturation (C * value).
When the metal color measurement surface is finished to a mirror surface of 30 nm level, if the structure is uniform, a standard deviation worse than the gold and copper levels is not shown. By measuring the color with a mirror surface of 30 nm level, the color of the metal can be measured with good reproducibility.

  The level of the colorimetry technique adopted this time is ΔE * ab when the standard deviation is used as the color difference, and the absolute value error is 0.63 on average and 1.34 at maximum when machine errors are included.

  According to the color handbook, levels 0.6 to 1.1 are first-class (strict color differences), and are defined as practical tolerance limits when various errors are considered. Therefore, the measurement error can be considered as a level that does not cause a problem as a practical color difference.

  By aligning the colorimetric conditions and the colorimetric environment disclosed here, anyone can always measure the metal color stably with the accuracy indicated by the statistical error.

  Next, Example Samples 1 to 8 of the present invention and Comparative Samples 1 to 3 will be listed to clarify the features of the present invention.

(Sample preparation)
As Example Samples 1 to 8, specifically, Au having a purity of 99.99% or more and Pt having a purity of 99.95% or more were put into a high-frequency melting furnace and dissolved, and Au (70 mass%)-Pt (30 Mass%), Au (65 mass%)-Pt (35 mass%), Au (60 mass%)-Pt (40 mass%), Au (55 mass%)-Pt (45 mass%), Au (50 mass%) %)-Pt (50 mass%), Au (45 mass%)-Pt (55 mass%), Au (40 mass%)-Pt (60 mass%), Au (35 mass%)-Pt (65 mass%) 8 level casting material was produced.

  In the above sample, the content of unavoidable impurities is small (maximum 0.06% by mass) and is ignored.

Further, as Comparative Samples 1 to 3, Au having a purity of 99.99% or more and Pt having a purity of 99.95% or more were placed in a high-frequency melting furnace and dissolved, and Au (75 mass%)-Pt (25 mass%) ), Au (30% by mass) -Pt (70% by mass), and Au (25% by mass) -Pt (75% by mass) were produced.
(Saturation measurement method)
About the said Example sample and the comparative example sample, after 70% rolling, it annealed and processed into the board, Then, the sample of colorimetric surface diameter (phi) 6mm was produced.

  Further, after the annealing, a sample having a colorimetric surface diameter of φ6 mm was prepared after high temperature treatment at 1150 ° C. and aging treatment at 500 ° C. for 10 hours.

Next, mirror finishing was performed until the sample surface roughness of each sample was about 30 nm.
Next, color measurement was performed on the mirror-finished sample surface. For colorimetry, as described above, a spectrocolorimeter (CM-3600d) manufactured by Minolta Co. is used, Geometry (geometry); diffuse illumination 8 ° (d / 8 °) light reception (including regular reflection light), Measurement conditions: 10 ° visual field, D65 light source was used.

The results are shown in Table 2.
As shown in Table 2, there is no great difference in the saturation (C *) between the annealed material and the aging material, but it was recognized that the saturation was slightly improved by aging treatment.

(About the regulation of saturation)
As a result of measuring the saturation (C * value) by the above-described colorimetric method for several types of gold alloys currently available as white gold materials, the saturation was 4.9 to 22.5. Next, several samples with different saturations were prepared, and a sensory test was performed to pick up what the subject considered to be a white noble metal.

  Specifically, several samples with saturation between 5.2 and 13.7 are shown to 150 subjects, and the value obtained by dividing the number of people recognized as white noble metals by the total number is expressed as a percentage. Indicated.

  The result is shown in FIG. 1 as a white certified power distribution.

The white certified power distribution shown in FIG. 1 is a diagram in which the horizontal axis represents saturation (C *) and the vertical axis represents frequency (%), and is a curve approximated to a frequency cumulative normal distribution. From FIG. 1, when the saturation is 5.0 or less, 95% of the people recognized as a white noble metal (result of visual sensory test).
(Saturation evaluation)
As shown in Table 2, it was found that Pt is required to be 30% by mass or more in order to achieve a saturation of 5.0 or less by the above colorimetric method. That is, by quantifying the visual sensory test result of saturation, the minimum necessary mass% of Pt could be specified.
(Hardness measurement method)
In addition, the hardness of the material after annealing (annealed material), the hardness after the high-temperature heat treatment, and the hardness of the example sample and the comparative example sample subjected to the aging treatment after the high-temperature heat treatment in the example sample and the comparative sample are measured. It was. The hardness was measured using a Vickers hardness tester under the conditions of a test load of 200 g (1.96 N) and a holding time of 15 seconds.
(Effect of high temperature heat treatment temperature on hardness)
Example Samples and Comparative Samples were rolled 70%, heated at 900 ° C. and held for 60 minutes, annealed by annealing, and then subjected to intermediate processing, 1000 ° C., 1050 ° C., 1100 ° C., 1150 ° C., 1200 After carrying out high temperature heat treatment of 8 levels of water cooling after holding at 1250 ° C., 1300 ° C., 1350 ° C. for 20 minutes, a hardness test was conducted for each. The results are shown in Table 3.

For quality assessment,
☆: Good rough skin, good workability, hardness: Hv300 or more, saturation: 5.0 or less ◎: Good rough skin, good workability, hardness: Hv200 or more, saturation: 5.0 or less ○ (A): Good rough skin, Good workability, hardness: Hv120 or more, saturation: 5.0 or less ○ (B): Partial rough skin, good workability, hardness: Hv120 or more, saturation: 5.0 or less ○ (C): Good skin roughness, processing Possible: Hardness: Hv120 or more, Saturation: 5.0 or less Δ: Good skin roughness, good workability, Hardness: Hv100 to less than 120, Saturation: 5.0 or less × (A): Whole surface roughness × (B): Whole surface Crack (including: crack during finishing)
X (C): Hardness: less than Hv100, saturation: more than 5.0 x: melting

  As shown in Tables 2 and 3, when the Pt is 25% by mass or less, the hardness is Hv100 or less and the saturation exceeds 5.0, and a preferable quality as a white jewelry or the like cannot be obtained. On the other hand, when Pt is 70% by mass or more, cracks are likely to occur during finishing, and the production is impossible.

  Further, if the high temperature heat treatment is performed at 1350 ° C. or higher, the whole or part of the Pt is not more than 60% by mass and cannot be manufactured. When high-temperature heat treatment is performed at 1300 ° C., the surface roughness and workability may be inferior in part, but it can be manufactured as a product.

When Pt is 45 to 65% by mass, high-temperature treatment at 1200 to 1250 ° C. is preferable because the rough surface is good at Hv200 or higher, and workability is good. It is more preferable because of its good properties.
(Effect of aging treatment time on hardness)
Au (65 mass%)-Pt (35 mass%), Au (60 mass%)-Pt (40 mass%), Au (55 mass%)-Pt (45 mass%), Au (50 mass%)-Pt (50 mass%), Au (45 mass%)-Pt (55 mass%), Au (40 mass%)-Pt (60 mass%), Au (35 mass%)-Pt (65 mass%) About the material (annealed material) which annealed the cast material of this, hardness was measured with respect to the hardness after high temperature heat processing, and the sample age-treated after high temperature heat processing, respectively. The hardness was measured using a Vickers hardness tester under the conditions of a test load of 200 g (1.96 N) and a holding time of 15 seconds. In addition, the average value of the hardness measured by each test was used for the hardness of an annealing material and the hardness after a high temperature process.

The results are shown in Tables 4-7 .
Evaluation is as follows: ☆: Hv value increased by 100 or more, ◎: Hv value increased by less than 50 to 100, ○: Hv value increased by less than 10-50, Δ: Change of Hv value less than −10, less than 10; The Hv value was −10 or less or the Hv value was 100 or less.

Table 4 shows a high temperature heat treatment that is held at 1250 ° C. for 20 minutes and then cooled with water, and then aged at 550 ° C. for 15 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, 300 minutes, and 600 minutes. The result of having measured the hardness after a process is shown.

As shown in Table 4 , remarkable age hardening was recognized in the composition range of all 7 levels.

Table 5 shows high-temperature heat treatment that is held at 1250 ° C. for 20 minutes and then water-cooled, and then aged at 600 ° C. for 15 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, 300 minutes, and 600 minutes. The result of having measured the hardness after a process is shown.

As shown in Table 5 , age hardening was recognized by adjusting the aging time as appropriate in all the composition ranges of 7 levels.

Table 6 shows a high temperature heat treatment which is held at 1300 ° C. for 20 minutes and then cooled with water, and then aged at 550 ° C. for 15 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, 300 minutes and 600 minutes. The result of having measured the hardness after a process is shown.

As shown in Table 6 , age hardening was observed in the composition range of all seven levels.

Table 7 shows a high temperature heat treatment which is held at 1300 ° C. for 20 minutes and then cooled with water, and then aged at 600 ° C. for 15 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, 300 minutes and 600 minutes. The result of having measured the hardness after a process is shown.

As shown in Table 7 , age hardening was recognized by adjusting the aging time as appropriate in all 7 composition ranges.

  The Pt—Au alloy produced as described above can be used not only as a noble metal for decoration, but also as a nib (tip of a writing instrument) such as a fountain pen nib.

  The fountain pen nib made with this alloy could be finished with a precious metal 100% precious metal fountain pen nib compared to the conventional 14K white gold pen and 18K white gold pen.

  Since the ballpoint pen tip made of this alloy is made of 100% precious metal, it has excellent corrosion resistance that can be applied to all inks such as current water-based, oil-based and gel inks.

  In addition, since the ballpoint pen tip made of this alloy has no elution of the tip component due to ink corrosion, it is not necessary to add a rust inhibitor or the like to the ink, and the degree of freedom in ink design is expanded.

  In the future, we have created a basis for creating new value by building a system that can collect and recycle chips, along with long-distance writing, in consideration of the environment and effective use of resources.

  In addition, the manufacturing method of the white noble metal alloy according to the present invention is not limited to that of the above-described embodiment. For example, the white noble metal alloy may be manufactured simply by casting, or after casting, high temperature heat treatment, high temperature heat treatment + An aging heat treatment may be performed.

  Moreover, after high temperature heat processing, you may rework and you may further age-process after rework.

  The present invention can be used in the manufacturing industry, processing industry, sales industry, etc. of ornaments such as rings, necklaces, brooches, earrings, tie pins, clock frames, watch bands, lighters, writing tools, and glasses frames.

FIG. 1 is a diagram showing a white recognition frequency distribution.

Claims (1)

This is a method for producing a white noble metal alloy containing Pt in an amount of 50 to 65% by mass, the balance being Au and inevitable impurities, and used in any of ornaments, watch frames, watch bands, lighters, writing tools, and glasses frames. And
  The white noble metal alloy is annealed in a temperature range of 550 to 600 ° C. after being subjected to high-temperature heat treatment that is heated to 1250 to 1300 ° C. and then water-cooled after being timely formed after annealing. Of manufacturing a precious metal alloy.

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