KR20090035683A - Casting gold alloy - Google Patents

Abstract

Disclosed is a casting gold alloy for use in a dental therapy or an accessory, which can show an enriched gold color and is reduced in thermal deformation. Specifically disclosed is a gold alloy comprising the following components: Au: 83.0-90.0 mass%; Pt: 8.0-10 mass%; In: 1.0-2.0 mass%; and Co: 0.1-1.5 mass%.

Description

Casting Gold Alloy {CASTING GOLD ALLOY}

The present invention relates to a gold alloy for casting.

Casting gold alloys used in dental restorations in dental treatment can give the desired shape by precision casting and have the advantage of excellent fit with teeth. There is a drawback of being aesthetically inferior to ceramic materials.

In order to make up for the drawbacks in the aesthetics of cast gold alloys, metal ceramic restorations are generally used. Metal ceramic restoration is a method of accumulating the dental ceramic material which consists of ceramic powder on a casting frame, drying and baking, and forming a fine ceramic layer on a metal surface. At this time, before accumulating the dental porcelain, the cast body undergoes a heat treatment called degassing to form an oxide layer on the surface, thereby ensuring the bonding with the dental porcelain. Since the ceramic layer made of a dental ceramic material has a color tone close to that of natural teeth, it is possible to produce a restoration excellent in aesthetics even if a metal is used.

The metal frame becomes the base of the ceramic layer, and the color tone is reflected in the color tone of the ceramic layer. If the metal is platinum, the color tone of the ceramic layer becomes dark, which is not aesthetically desirable. In addition, when the restoration is a crown or a bridge, the underlying metal may be exposed along the circumference, and it is not aesthetically desirable if the metal is platinum. For these reasons, a strong golden metal is very preferred.

As an example of the prior art which meets this request, there is a casting gold alloy disclosed in Japanese Unexamined Patent Publication No. Hei 1-32728. This alloy is composed of Au 75 to 98%, Pt 0.1 to 15%, Fe 0.1 to 10%, In 0.1 to 3%, W 0.05 to 5%, and has a golden color.

As another conventional technique, there is a casting gold alloy disclosed in Japanese Laid-Open Patent Publication No. 2002-129252. According to Claim 2 of this document, Ta, Sn is made into 82.0-84.0% of Au, 8.9-10.9% of Pt, 4.0-6.0% of Pd, 0.2-0.5% of Ag, 1.5-2.5% of Zn, 0.2% of Fe, and 0.1% of Ir. It is a gold alloy for casting.

Disclosure of the Invention

Problems to be Solved by the Invention

In the alloy system disclosed in Japanese Laid-Open Patent Publication No. Hei 1-32728, the metal structure of the cast body consists of platinum crystallized particles and Au-rich golden matrix two phases. This is because, in the solidification process during casting, Fe and W, which are hardly dissolved in Au, are crystallized as Pt-Fe-W-based high melting point intermetallic compounds, and the concentration of Pt, Fe, and W in the matrix decreases, so that the concentration of Au is relatively high. Because it increases. Therefore, apparently strong golden color appears.

On the other hand, in order to reproduce the natural color tone of a natural tooth, metal ceramic restoration is very generally performed by repeatedly accumulating and baking ceramic materials of a different color tone, and expressing a complex color tone. Since the firing of ceramic materials usually reaches a high temperature of about 900 ° C, there is a problem that thermal deformation occurs in this alloy system. This is because most of Pt, Fe, and W are crystallized as coarse particles, and the matrix becomes an Au rich phase having low strength and low melting point. Since this alloy system cannot ensure compatibility with teeth by heat deformation, it is difficult to use this alloy for restoration of a large bridge or the like.

Since the alloy system disclosed by Unexamined-Japanese-Patent No. 2002-129252 has a large amount of Zn addition, since the intensity | strength at normal temperature is high and it contains Pd, a liquidus point can be made high. However, since the alloy structure is a solid solution of Zn, Pd, Pt and Au, the Au concentration is relatively lower than that of the alloy-based Au rich phase disclosed in Japanese Patent Laid-Open No. 1-32728, and the hue is diluted with rich golden color unique to Au. It becomes pale yellow. On the other hand, since it contains a lot of Zn in order to increase the hardness at normal temperature, melting | fusing point of an alloy falls, and intensity | strength falls by high temperature at the time of baking a ceramic material, and big thermal deformation is produced. As described above, the gold alloy for casting represented by this alloy system is insufficient in color tone due to insufficient color.

As described above, the demand for the gold alloy for casting is still not sufficiently satisfactory. A high quality cast alloy with a high Au content can be obtained a number of products in addition to the above two examples, but these conventional techniques, as represented by the two examples above, have problems in thermal deformation even if the color tone is excellent. The color tone is faint and the heat deflection is concentrated.

In view of the problems of the prior art, an object of the present invention is to provide a casting gold alloy which exhibits a strong golden color and is excellent in heat deformation resistance.

Means to solve the problem

This invention is the casting gold alloy which consists of Au: 83.0-90.0 mass%, Pt: 8.0-10.0 mass%, In: 1.0-2.0 mass%, and Co: 0.1-1.5 mass%. Here, the casting gold alloy is a gold alloy which is cast and gives a shape, and is not limited to the dental field, and of course, it can also be used for jewelry and other uses.

This invention is a gold alloy for casting characterized by containing 0.1-0.5 mass% of at least 1 type of elements of Fe, Cr, Mn, and Mo.

This invention is a gold alloy for casting characterized by containing 0.02-1.0 mass% of at least 1 type of element among Ir, Rh, Ru, W, and Re.

The present invention is a casting gold alloy, which is used for dental metal ceramic restorations.

Effects of the Invention

According to the present invention, it is possible to provide a casting gold alloy exhibiting a strong golden color and excellent in heat deformation resistance. Next, the reason is described.

The gold color of the gold alloy is darkened with increasing Au content, but if the Au content is too large, practical strength cannot be obtained. Therefore, it is a general design technique of gold alloy to examine addition element. In the prior art, additional elements such as Fe, W, Pt, Pd, and Zn have been selected, and as described above, strong golden color and heat deformation resistance were not compatible.

This invention is the casting gold alloy which consists of Au: 83.0-90.0 mass%, Pt: 8.0-10.0 mass%, In: 1.0-2.0 mass%, and Co: 0.1-1.5 mass%. In the gold alloy of the present invention, Au concentration of the matrix increases by crystallization of a fine Pt-Co dispersed phase, thereby obtaining a rich golden color. The matrix can maintain practical strength by solid solution strengthening of Au, In, and Co. In addition, thermal deformation can be suppressed by strengthening the solid solution of the matrix and enhancing the dispersion by the Pt-Co dispersion phase.

Au is required at least 83% for rich golden expression. When content of Au exceeds 90%, heat deformation will become large and practical strength will not be obtained. Preferably it is 87-90% of addition.

Pt raises melting | fusing point of a gold alloy by 8% or more of addition, and improves heat deformation resistance. However, since the effect of thinning the golden color with a solid solution with Au is large, the upper limit should be 10%. In is dissolved in Au and has an effect of improving strength. If it is less than 1%, the effect is inadequate, and if it exceeds 2%, melting | fusing point will fall remarkably and it will make golden color thin.

In the present invention, the role of Co is specific. As a result of the intensive studies, it was found that the following effects were obtained. Firstly, the Pt-Co intermetallic compound is crystallized during the solidification process of the gold alloy, and secondly, it is dissolved in an Au rich matrix to strengthen the matrix. In order to express these effects and obtain a gold alloy which is rich in golden color and excellent in heat deformation resistance, the amount of Co added is preferably 0.1 to 1.5%. This is because when the amount of Co is less than 0.1%, crystallization of Pt-Co is insufficient, and neither solid solution strengthening nor dispersion strengthening is sufficiently expressed. When the content of Co exceeds 1.5%, the amount of Co dissolved in the matrix increases.

Furthermore, by adding 0.1-0.5% of at least one element of Fe, Cr, Mn, and Mo to the said gold alloy, the function which promotes crystallization of Pt further and increases a golden color is acquired. If the addition amount is less than 0.1%, the effect is not obtained. If the addition amount is more than 0.5%, it is dissolved in the matrix to make the golden color too light.

In addition, by adding 0.02 to 1.0% of at least one element of Ir, Rh, Ru, W, and Re to the gold alloy, crystallization of Pt can be further promoted, and an effect of increasing golden color can be obtained. Since these elements are remarkably high in melting point and are not dissolved in Au, they are known as grain refining elements. However, when these elements are less than 0.02%, the effect is not obtained. The effect is lost, and the thermal deformation becomes excessive.

Moreover, the said gold alloy is suitable for using it for metal ceramic restoration as a dental metal. However, it is also very suitable for use in fields requiring color tone and heat resistance, for example, jewelry and the like, and does not limit the field of application to dentistry.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the color difference ((DELTA) E ^* ) and heating displacement (D) of the gold alloy shown in an Example and a comparative example.

2 is an example of the cross-sectional structure of the gold alloy of the present invention.

Table 1 shows the compositions of Examples of the present invention and Table 2 shows the compositions of Comparative Examples.

(Production of gold alloy)

The gold alloy for casting of the composition shown in Example 1 was obtained by the following method. Au and Pt were melt | dissolved by the arc melting furnace first, and the other additional element was added and the solvent was dissolved. The button-shaped alloy after melting rolled to thickness 1mm, and was cut out.

The gold alloy for casting of the composition shown to Examples 2-5 and Comparative Examples 4-5 was obtained by the method similar to Example 1.

The casting gold alloys of the compositions shown in Examples 6 to 9 and Comparative Examples 1 to 3 were prepared in advance of Example 1 except that a mother alloy of Ir, W, Re, Mn, or Cr and Pt was produced in advance and added later. Obtained in the same way.

(Production of test piece)

The test piece for color tone evaluation and heat distortion evaluation of an Example and a comparative example was produced with the following method. Casting followed the general roast wax method as the precision casting method of the jewelry industry and dental perforation.

The test piece for color tone evaluation produced the wax pattern of diameter 12mm and thickness 1.2mm, and was made to embed | pour and bake with a phosphate-type investing material, and cast using the reverse pressure casting machine. Next, the investment material is removed from the casting, the sprue is cut, one side is polished in sequence with water-resistant abrasive paper of # 100, # 240, # 600, and # 1000, buffed with diamond paste, and the mirror test piece is Got it.

The test piece for thermal deformation evaluation was cast by the square bar of 2 mm in width and 50 mm in length by the casting method similar to the above, and heat-processed in air | atmosphere for 10 minutes at 1000 degreeC assuming degassing. In addition, four surfaces except the cross section of each rod were polished in order by # 100, # 240, # 600 water-resistant polishing paper, and it finished with # 1000 water-resistant polishing paper.

(Evaluation of the hue)

The color tone of the casting gold alloy of the Example and the comparative example was evaluated by the color difference ((DELTA) E ^* ) with pure gold.

Color difference (ΔE ^* ) is a value defined by the square root of the sum of squares of the difference (ΔL ^* , Δa ^* and Δb ^* ) of brightness L ^* , saturation a ^* and saturation b ^* between two colors in the CIELab color system. It is an index indicating quantitatively the difference of the color tone which is difficult to determine.

The larger the color difference ΔE ^* , the larger the difference between the two colors, indicating that the color tone is different.

ΔL ^* , Δa ^*, and Δb ^* of the pure gold mirror surface and the test specimen mirror surface prepared by the above method were measured with a color difference meter (Bikgardner Co., Color Guide) to obtain a color difference (ΔE ^* ).

The results are shown in Table 1 and Table 2.

(Evaluation of heat deformation)

The heat deformation of the casting gold alloy of the Example and the comparative example measured and evaluated the heating displacement (D). When the metal is heated, the strength is generally lowered, which causes thermal deformation due to its own weight. In order to evaluate the degree, one end of the metal rod was fixed and heated in a cantilever state kept horizontally, and the amount of vertical displacement was measured. The test piece used what was produced by the said method, heating conditions shall be 10 minutes in 1000 degreeC Ar gas, and heating displacement (D) measures the vertical displacement of about 40 mm from the fixed end with the height gauge of 0.05 mm precision. It was obtained. According to this evaluation method, the thermal deformation due to its own weight can be obtained quantitatively with good reproducibility by eliminating error factors by the test piece having a simple shape and heating in a non-oxidizing atmosphere.

The results are shown in Table 1 and Table 2.

(result)

The gold alloy for casting shown in Examples 1-4 is a gold alloy of Claim 1. The heating displacement D was 1.8 mm or less, and the color difference ΔE ^* was 23 or less.

The gold alloy for castings shown in Examples 5 and 6 was the gold alloy according to claim 2, wherein D was 1.4 mm or less and ΔE ^* was 22 or less. The same was true even if Mn and Mo were added in addition to Fe and Cr.

In the casting gold alloys shown in Examples 7 and 9, D was 1.8 mm or less and ΔE ^* was 21 or less as the gold alloy of Claim 3. The same was true even if Rh, Ru, and W were added in addition to Ir and Re.

In Comparative Example 1, Comparative Example 4 and Comparative Example 5, ΔE ^* was 23 or less, which was still excellent golden color. However, in these comparative examples, D was 2.3 mm or more, and the heat deformation resistance was not sufficient.

Comparative Example 2 and Comparative Example 3 are examples of commercially available gold alloys. ΔE ^* was 25, and the color was not dark but pale yellow. Moreover, D became 2.7 mm or more, and heat deformation resistance was inadequate.

1 is a relationship between D and ΔE ^* in Examples and Comparative Examples. D was 1.8 mm or less in all the gold alloys shown in the Example of this invention, and D was 2.3 mm or more in all the gold alloys shown in the comparative example. As for the gold alloy shown in the Example, thermal deformation is sufficiently smaller than a comparative example, the fit of a restoration and a tooth are ensured, the circumferential blockade can be improved, and secondary cavities can be suppressed effectively. In addition, all the gold alloys shown in the Example had a color difference (ΔE ^* ) of 23 or less, and had a strong golden color.

2 is a cross-sectional structure of the gold alloy shown in Example 2. FIG. As a result of elemental analysis by EDS, a matrix composed of a fine dispersed phase composed mainly of Pt and Co and a solid solution phase mainly composed of Au, In, and Co was identified. In other examples, the same structure was used. The dispersed phase was also observed in the gold alloys shown in Comparative Example 1, Comparative Example 4 and Comparative Example 5, but the heating displacement was large and the effect of dispersion strengthening was not observed.

By the above-described experimental verification, the casting gold alloy of the composition shown in the present invention has a heat displacement of 1.8 mm or less, a color difference from pure gold of 23 or less, and exhibits a strong golden color compared with the prior art, and is excellent in heat deformation resistance. It became clear.

INDUSTRIAL APPLICABILITY The present invention can be used in the industrial field of casting gold alloys used for dental treatments and jewelry.

Claims (4)

Au: 83.0-90.0 mass%, Pt: 8.0-10.0 mass%, In: 1.0-2.0 mass%, Co: 0.1-1.5 mass%, The casting gold alloy characterized by the above-mentioned. The method of claim 1, 0.1-0.5 mass% of at least 1 type of elements among Cr, Mn, Fe, and Mo, The casting gold alloy characterized by the above-mentioned. The method according to claim 1 or 2, A casting gold alloy characterized by containing 0.02-1.0 mass% of at least 1 type of element among Ir, Rh, Ru, W, and Re. The method according to any one of claims 1 to 3, A casting gold alloy, used for dental metal ceramic restorations.

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