JP2008024988A - Casting gold alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting gold alloy which is used for dental care and accessories, shows a full gold color and inhibits thermal deformation. <P>SOLUTION: The gold alloy comprises, by mass%, 83.0 to 90.0% Au, 8.0 to 10.0% Pt, 1.0 to 2.0% In and 0.1 to 1.5% Co. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gold alloy for casting.

  The casting gold alloy used for the preparation of restorations in dental treatment can give a desired shape by precision casting, and has the advantage of being excellent in conformity with the teeth, but the color tone is metallic, so a white resin material or Compared to all-ceramic materials, it has the disadvantage of being less aesthetic.

  In order to compensate for the shortcomings in the aesthetics of casting gold alloys, metal ceramic restoration is generally used. Metal ceramic restoration is a technique in which a dental ceramic material made of ceramic powder is built up on a casting frame, dried and fired to form a dense ceramic layer on the metal surface. At this time, before the dental porcelain is built up, the cast body is subjected to a heat treatment called degassing to form an oxide layer on the surface to ensure the bonding with the dental porcelain. Since the ceramic layer made of dental porcelain has a color tone close to that of natural teeth, a restoration with excellent aesthetics can be produced even if a metal is used.

  The metal frame serves as a base for the ceramic layer, and its color tone is reflected in the color tone of the ceramic layer. When the metal is platinum color, the color tone of the ceramic layer becomes dark, which is not aesthetically pleasing. Furthermore, when the restoration is a crown or a bridge, the underlying metal may be exposed along the edge, and it is not aesthetically pleasing that the metal is platinum color. For these reasons, strong golden metals are highly preferred.

As an example of the prior art that meets this need, there is a casting gold alloy disclosed in Patent Document 1. 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. is there.
As another conventional technique, there is a gold alloy for casting disclosed in Patent Document 2. According to claim 2 of this document, Au 82.0-84.0%, Pt 8.9-10.9%, Pd 4.0-6.0%, Ag 0.2-0.5%, Zn 1.5- It is a gold alloy for casting containing Ta and Sn in 2.5%, Fe 0.2% and Ir 0.1%.
Japanese Patent Laid-Open No. 1-132728 JP 2002-129252 A

In the alloy system disclosed in Patent Document 1, the metal structure of the cast body is composed of two phases of platinum-colored crystallized particles and Au-rich golden matrix phase. This is because Fe and W, which are hard to dissolve with Au in the solidification process at the time of casting, crystallize as Pt—Fe—W refractory intermetallic compounds, and the Pt, Fe, W concentration of the matrix decreases. This is because the Au concentration is relatively increased. For that reason, it has a strong golden color in appearance.
On the other hand, in metal ceramic restoration, in order to reproduce the natural color of natural teeth, it is very common to express complex colors by repeatedly building and firing different color porcelain. . Since firing of porcelain usually reaches a high temperature of around 900 ° C., this alloy system has a problem of causing thermal deformation. This is because most of Pt, Fe, and W crystallize as coarse particles, and the matrix becomes an Au-rich phase with low strength and low melting point. This alloy system is difficult to be used for restoration of a large bridge or the like because it cannot ensure conformity with a tooth due to thermal deformation.

  Since the alloy system disclosed in Patent Document 2 has a large amount of Zn added, it has a high strength at room temperature and can contain a Pd, so that the liquidus point can be increased. However, since the alloy structure is a solid solution of Zn, Pd, Pt, and Au, the Au concentration is relatively lower than the Au-rich phase of the alloy system disclosed in Patent Document 1, and the color tone is a rich golden color unique to Au. Becomes diluted pale yellow. On the other hand, since a large amount of Zn is contained in order to increase the hardness at room temperature, the melting point of the alloy is lowered, and when the porcelain is fired, the strength is lowered due to the high temperature, so that a large thermal deformation occurs. Thus, the gold alloy for casting represented by this alloy system has an insufficient color tone, and is also concerned about conformity.

  As described above, the need for a gold alloy for casting has not been sufficiently satisfied. Many high-grade gold alloys for casting with high Au content are available in addition to the above two examples, but these conventional techniques are excellent in color tone as represented by the above two examples. They are summarized into those that have problems with thermal deformation and those that have a pale color tone and problems with thermal deformation.

  An object of the present invention is to provide a gold alloy for casting excellent in heat distortion resistance while exhibiting a strong golden color in view of the problems of the prior art.

  In the present invention, Au: 83.0 to 90.0 mass%, Pt: 8.0 to 10.0 mass%, In: 1.0 to 2.0 mass%, and Co: 0.1 to 1.5 mass% It is a gold alloy for casting consisting of%. Here, the gold alloy for casting is a gold alloy that is cast to give a form, and can of course be used not only in the dental field but also for jewelry and other applications.

  The present invention is a gold alloy for casting characterized by containing 0.1 to 0.5% by mass of at least one element of Fe, Cr, Mn, and Mo.

  The present invention is a gold alloy for casting characterized by containing 0.02 to 1.0% by mass of at least one element selected from Ir, Rh, Ru, W, and Re.

  The present invention is a gold alloy for casting characterized by being used for dental metal ceramic restoration.

  ADVANTAGE OF THE INVENTION According to this invention, the gold alloy for casting which exhibits a strong golden color and was excellent in heat-resistant deformation property can be provided. The reason is described below.

  The golden color of the gold alloy becomes darker as the Au content increases, but if the Au content is too high, a practical strength cannot be obtained. Therefore, it is a general design method for gold alloys that examines additive elements. In the prior art, additive elements such as Fe, W, Pt, Pd, and Zn have been selected, and as described above, it has been impossible to achieve both a strong golden color and heat distortion resistance.

  In the present invention, Au: 83.0 to 90.0 mass%, Pt: 8.0 to 10.0 mass%, In: 1.0 to 2.0 mass%, and Co: 0.1 to 1.5 mass% It is a gold alloy for casting consisting of%. In the gold alloy of the present invention, the Au concentration in the matrix is increased by the crystallization of the fine Pt—Co dispersed phase, and a rich golden color is obtained. The matrix can maintain a practical strength by solid solution strengthening of Au, In, and Co. Furthermore, thermal deformation can be suppressed by solid solution strengthening of the matrix and dispersion strengthening by the Pt—Co dispersed phase.

  Au is required at least 83% for rich golden expression. When the content of Au exceeds 90%, thermal deformation increases and practical strength cannot be obtained. Desirably, 87-90% of addition is good.

  Addition of 8% or more of Pt increases the melting point of the gold alloy and improves the heat distortion resistance. However, since the effect of thinly dissolving with Au and thinning the golden color is strong, the upper limit must be 10%. In has an effect of improving the strength by dissolving in Au. If it is less than 1%, the effect is insufficient, and if it exceeds 2%, the melting point is remarkably lowered and the golden color is diluted.

  In the present invention, the role of Co is specific. After intensive research, it was found that the following effects were exhibited. The first is the effect of crystallizing the Pt—Co intermetallic compound during the solidification process of the gold alloy, and the second is the effect of strengthening the matrix by solid solution in the Au-rich matrix. In order to obtain these effects and to obtain a gold alloy having a rich golden color and excellent heat resistance, the amount of Co added is preferably 0.1 to 1.5%. If Co is less than 0.1%, crystallization of Pt-Co is insufficient, and solid solution strengthening and dispersion strengthening are not fully expressed. If it exceeds 1.5%, Co dissolved in the matrix increases. This is because the golden color is diluted.

  By adding 0.1 to 0.5% of at least one element of Fe, Cr, Mn, and Mo to the gold alloy, it is possible to further promote the crystallization of Pt and increase the golden color. . If the addition amount is less than 0.1%, the effect cannot be obtained. If the addition amount exceeds 0.5%, the golden color is excessively diluted by dissolving in the matrix.

  Furthermore, by adding 0.02 to 1.0% of at least one element of Ir, Rh, Ru, W, and Re to the gold alloy, it further promotes crystallization of Pt and increases the golden color. can get. Since these elements have a remarkably high melting point and do not dissolve in Au, they are known as crystal grain refining elements. However, if the content is less than 0.02%, the effect cannot be obtained. Coarse particles are crystallized, the effect of dispersion strengthening is lost, and thermal deformation becomes excessive.

  The gold alloy is suitable for use in metal ceramic restoration as a dental metal. However, it is also suitable for use in fields where color tone and heat distortion resistance are required, for example, accessories, and the application field is not limited to dentistry.

  Hereinafter, specific examples of the present invention will be described.

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

(Production of gold alloy)
The gold alloy for casting having the composition shown in Example 1 was obtained by the following method. Au and Pt were first melted by an arc melting furnace and further added with other additive elements to be melted. The melted button-like alloy was rolled to a thickness of 1 mm and cut.
The casting gold alloys having the compositions shown in Examples 2 to 5 and Comparative Examples 4 to 5 were obtained in the same manner as in Example 1.
The casting gold alloys having the compositions shown in Examples 6 to 9 and Comparative Examples 1 to 3 were prepared in advance by preparing a master alloy of Ir, W, Re, Mn or Cr and Pt, and adding this later. Obtained in the same manner as in Example 1.

(Preparation of test piece)
Test pieces for color tone evaluation and thermal deformation evaluation of Examples and Comparative Examples were prepared by the following method. Casting was based on the lost wax method, which is a common precision casting method for the jewelry industry and dental technicians.

  The test piece for color tone evaluation was prepared by forming a wax pattern having a diameter of 12 mm and a thickness of 1.2 mm, burying and firing with a phosphate-based investing material, and then casting using a reverse pressure casting machine. Next, the investment material is removed from the cast body, the sprue is cut, one side is polished sequentially with water resistant abrasive paper of # 100, # 240, # 600, # 1000, buffed with diamond paste, and the mirror surface is polished. A specimen was obtained.

  The test piece for thermal deformation evaluation was cast into a 2 mm square and 50 mm long square bar by the same casting method as described above, and heat treated in the atmosphere at 1000 ° C. for 10 minutes assuming degassing. Further, the four surfaces except for the end face of the square bar were polished in order with # 100, # 240 and # 600 water-resistant abrasive paper, and finished with # 1000 water-resistant abrasive paper.

(Evaluation of color tone)
The color tone of the casting gold alloys of the examples and the comparative examples was evaluated by a color difference ΔE ^{* with} respect to pure gold.
The color difference ΔE ^* is defined as the square root of the square sum of the differences (ΔL ^* , Δa ^*, and Δb ^* ) of the lightness L ^* , saturation a ^*, and saturation b ^* between the two colors in the CIELab color system. This is an index that quantitatively represents a difference in color tone that is difficult to determine with the naked eye.
The larger the color difference ΔE ^* , the greater the separation between the two colors, indicating that the color tone is different.

ΔL ^* , Δa ^* and Δb ^* between the pure gold mirror surface and the mirror surface of the test piece prepared by the above method were measured with a color difference meter (Big Gardner Co., Color Guide) to obtain a color difference ΔE ^* .
The results are shown in Tables 1 and 2.

(Evaluation of thermal deformation)
The thermal deformation of the casting gold alloys of Examples and Comparative Examples was evaluated by measuring the heating displacement D. When a metal is heated, the strength generally decreases and the metal is thermally deformed by its own weight. In order to evaluate the degree, the vertical displacement was measured by heating one end of the metal bar in a cantilever state in which one end was fixed and held horizontally. The test piece prepared by the above method is used, the heating condition is 10 minutes in Ar gas at 1000 ° C., and the heating displacement D is a vertical displacement amount of about 40 mm from the fixed end with a height gauge with an accuracy of 0.05 mm. Measured and determined. According to this evaluation method, thermal deformation due to its own weight can be obtained quantitatively with good reproducibility by eliminating the cause of error by using a simple-shaped test piece and heating in a non-oxidizing atmosphere.
The results are shown in Tables 1 and 2.

(result)
The gold alloy for casting shown in Examples 1 to 4 is the gold alloy according to 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 casting shown in Example 5 and Example 6 is the gold alloy according to claim 2, wherein D is 1.4 mm or less and ΔE ^* is 22 or less. The same was true when Mn and Mo were added in addition to Fe and Cr.
The gold alloy for casting shown in Example 7 and Example 9 is the gold alloy according to claim 3, wherein D is 1.8 mm or less and ΔE ^* is 21 or less. The same was true when 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 also excellent golden color. However, in these comparative examples, D was 2.3 mm or more, and the heat distortion resistance was not sufficient.
Comparative Example 2 and Comparative Example 3 are examples of commercially available gold alloys, but ΔE ^* was 25, the golden color was light, and the color was pale yellow. Furthermore, D was 2.7 mm or more, and the heat distortion resistance was insufficient.

FIG. 1 shows the relationship between D and ΔE ^{* in} Examples and Comparative Examples. In all the gold alloys shown in the examples of the present invention, D was 1.8 mm or less, and in all the gold alloys shown in the comparative examples, D was 2.3 mm or more. The gold alloy shown in the examples has a thermal deformation that is sufficiently smaller than that of the comparative example, ensures that the restoration and the tooth are properly fitted, can improve the marginal sealing performance, and effectively suppress secondary caries. Can do. Further, all the gold alloys shown in the examples had a strong golden color with a color difference ΔE ^* of 23 or less.

  FIG. 2 is a cross-sectional structure of the gold alloy shown in Example 2. As a result of elemental analysis by EDS, a fine dispersed phase composed of a phase mainly composed of Pt and Co and a matrix composed of a solid solution phase mainly composed of Au, In and Co were confirmed. The other examples also had the same structure. A 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 recognized.

  As a result of the above experimental verification, the gold alloy for casting having the composition shown in the present invention has a heat displacement of 1.8 mm or less and a color difference of 23 or less from pure gold, and exhibits a strong golden color compared to the prior art. However, it was revealed that it has excellent heat distortion resistance.

It is a figure showing the relationship between the color difference (DELTA ⁾ E ^* and the heating displacement D of the gold alloy shown to an Example and a comparative example. It is an example of the cross-sectional structure of the gold alloy of the present invention.

Claims (4)

  Au: 83.0-90.0% by mass, Pt: 8.0-10.0% by mass, In: 1.0-2.0% by mass, and Co: 0.1-1.5% by mass A gold alloy for casting featuring   The gold alloy for casting according to claim 1, wherein the alloy contains 0.1 to 0.5% by mass of at least one element selected from Cr, Mn, Fe, and Mo.   3. The gold alloy for casting according to claim 1, comprising 0.02 to 1.0 mass% of at least one element selected from Ir, Rh, Ru, W, and Re. The gold alloy for casting according to any one of claims 1 to 3, which is used for dental metal ceramic restoration.