DE2303519A1 - CASTING COMPOSITION FOR THE PRODUCTION OF GOLD ALLOYS - Google Patents

Description

Applicant:

Williams Gold Refining Company Incorporated, 2978 Main Street, Buffalo, New York 14214, USA

Casting composition for producing gold alloys

The invention relates to preventing the formation of oxide coatings during the casting of gold alloys. The invention refers in particular to the use of aluminum and / or silicon in dental and jewelry gold alloys, in which copper, iron, tin, indium or mixtures of tin and indium are used as the hard metal. According to the invention a small amount of silicon and / or aluminum is also added to the casting composition to make it glassy coating on the surface of the cast adjacent to the mold Product.

In dental and jewelry gold alloys, the common hardness element consists of copper. In some cases, however, iron, Tin, indium, or mixtures of tin and indium are used as the hardness element. When these alloys are cast to For example, in investment casting molds using the lost wax process, part of the alloy is made during the melting and casting processes partially oxidized. In particular, it appears that at least a portion of the hardness component is oxidized. The education for example, copper oxide creates a black deposit on the surface of the resulting casting which is removed must, for example by pickling liquor, grinding or sandblasting. After the oxide coating has been removed, the dull surface then buffed to give a on the product

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to maintain a metallic sheen. ■

To improve the casting process and the problems mentioned above To eliminate, many attempts have been made to provide casting compositions or casting processes in which the cast or otherwise molded product does not have an oxide coating. For example, according to the American patent 3,613,209 an oxidation preventing metal inert gas and injection molding used to make a gold alloy to produce, which has no oxide coating after molding. However, the above method requires complicated and costly operations such as injection molding under high pressure and the use of an inert gas around the molten alloy.

In the case of casting processes, oxygen scavenging agents such as Example zinc and indium. However, neither zinc nor indium eliminates the dissolved oxides and none of them has an appreciable effect on the oxide coating of the casting.

Another method that has been used to minimize the oxide coating on casting is that Casting under vacuum. However, the use of high vacuum is a ■ relatively expensive operation and not very successful. Various fluxes have also been used, to prevent the formation of oxides during casting, but these usually remain in the crucible and set therefore are not effective means of preventing oxidation during the solidification and cooling of the alloy in the mold. As a result graphite in the mold has been used to protect the casting during solidification and cooling, and the same is at least somewhat effective. A difficulty arises, however, in removing some or all of the graphite from the investment mold is burned out during removal of the casting using the lost wax technique.

A common practice is to keep oxide levels in the cast metal to a minimum Decrease is to melt an element

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add, which has a higher oxidation potential than the element that is to be protected from oxidation. this will referred to as deoxidation of the melt, and the oxide is mainly found in the slag on the surface of the melt. This slag consists of intentionally oxidized metals, of accidentally oxidized metals, and of those forming the slag Fluxes. However, if such deoxidation is used by including, for example, zinc and / or indium in Ede Intet al alloys, there is a reduction in the oxide content of the cast alloy, but the surface oxide is still always present, except when the amount of additive used is so great that the properties of the alloy change drastically will. The surface oxide must therefore still be removed before polishing.

One of the objects of the invention is therefore to protect the casting from surface oxidation during the critical period the solidification and cooling of the alloy in the investment casting mold.

Another object of the invention is to further enhance the inclusion and / or dissolution of copper oxide in the melt reduce to a minimum.

Another object of the invention is to reduce the loss of copper or other hardness elements during melting and Pour the product to a minimum.

Yet another object of the invention is to provide a simple process which is essential, if not essential allows complete elimination of the oxide coating from the surface of the cast product.

Yet another object of the invention is to produce a Alloy that, when cast, has a shiny gold surface which can be used without polishing.

The invention therefore relates to an improved casting composition

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for a gold alloy in which aluminum and / or silicon used in an amount sufficient to produce a shiny, oxidation-resistant material during and after casting To form surface coating, as well as the casting process using these components and the cast Product, a deoxidizer can also be used will.

The above and other objects will be apparent from the description below.

According to the invention, a gold alloy, which for example contains up to 50% by weight of copper or other hardness elements, a quantity of silicon and / or aluminum is added in the molten state in order to obtain a surface coating on the finished cast product to obtain. The casting is carried out, for example, according to the lost wax process in an investment casting mold, after which the product is cooled and removed. The resulting Product has a vitreous surface coating that has a glossy appearance.

When casting dental or jewelry gold alloys according to the invention, an alloy containing a hardness element is, for example, up to 50% by weight copper, preferably more than about 5% by weight copper, as well as other known additives such as Silver, zinc, etc., additionally silicon and / or aluminum added in an amount sufficient to produce the shiny, cast product according to the invention. The amount of aluminum and / or silicon required varies with the surface area of the mold. For example, when a spherical part or a tooth is formed, there is less surface area present than when, for example, a lattice structure is formed. More of the additive is therefore required to produce the glossy surface according to the invention on a lattice structure. In general, however, about O ₄ oil to 2 wt. on the basis of the total aluminum, silicon or both content of the alloy »Preferably, about 0.04 to 0.5 wt.

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Although any conventional hardness element can be used, the preferred group includes copper, iron, tin, indium, and mixtures of tin and indium. When copper is used, the same in amounts up to 50 wt -.% Of the alloy may be present, preferably more than about 5 Gew.-Ϊ. If iron is used, the same should in amounts up to about 1 wt -.% To be present, preferably about 0.25 to 0.75 wt ?. If tin and / or indium are used, should the total amount of hardening element, either separately if one is used, or combined if both be used, be up to 7% by weight? be, preferably about 3 to 6 wt .- ?.

In addition, other common elements, such as silver, Palladium and even platinum can be used. Silver is most common in alloys and is common in amounts up to to about 30 wt. present, preferably about 5 to 25 wt.

The aluminum or silicon can be added to the melt or to a mixture of metals, if the same either in are melted in their pure form or as mother alloys, for example alloyed with silver, the alloy according to the invention can also be obtained, for example, in bar form, by casting it beforehand and, if necessary, rolling it out. In this case the original casting has the coating and the subsequent casting also has a coating. If a mother alloy is used, it is in any case the timing of the addition of the mother alloy is not important. All components for the desired alloy can for example placed in a crucible or other heating device and melted, they can be melted individually and mixed, or in a crucible in any one Order to be melted. However, when aluminum and / or silicon are added in their unalloyed form, it is it is preferred that the silicon and / or aluminum be added last will.

The alloy melt is then poured using normal methods, for example by pouring into an investment mold

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and cooling by usual methods. The temperature of the melt depends on the composition of the alloy and is the same under normal conditions. In general, however, temperatures of from about 8L6 to 1,371 ° C, preferably from about 899 to 1,2OiI ⁰ C is used. The mold is maintained at conventional temperatures during the period prior to casting, usually about 482 to 871 ° C, and preferably about 593 to 816 ° C. It should be noted, however, that more of the additive according to the invention is required as the mold temperature is increased "·. The cooling of the casting is done again by normal procedures. The mold can be air-cooled or quenched, or it can be air-cooled to a certain extent and then quenched.

The following particular uses of alloys according to the invention are contemplated: Alloys according to the invention for dental use are, for example, those which are about 9 to 18 wt. Contain copper, as is common practice. For jewelry, big changes are the norm when casting Gold alloys possible, that is, normal jewelry alloys contain about 92 to 60 wt. or less gold, though too other changes are possible. 18 carat gold contains about 75 wt. 2 gold and 10 to 20 wt. Silver in combination with 5 up to 15 percent by weight copper, while 14 carat gold for dental purposes is usually 63 percent by weight? Gold, 30 wt. Silver and 12 wt. Contains copper. However, the method according to the invention is not dependent on the different alloy compositions, to obtain the product according to the invention, but the criterion of the invention consists in the addition of enough silicon and or. Aluminum to obtain the vitreous coating on the surface of the molded product and thereby the shiny product to create*

Furthermore, other additional components, namely deoxidizers, such as zinc, magnesium and barium can be used.

When using the method according to the invention to produce

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The vitreous surface coating is obtained with the gold alloy according to the invention, which is shiny in the cast state. Microscopic Studies using a scanning electron microscope have shown that a vitreous coating is formed on the surface of the molded product in the area in contact with the mold. Further is the surface not oxidized, but if the same is abraded or otherwise rubbed to remove the surface coating, and then subjected to oxidizing conditions, the oxidation will only occur in the area in which the abrasion occurs was effected. The vitreous nature of the coating seems to be the best way of describing it, although for the time being its actual character is not known. It schelrfc However, to be a certain form of silicon or aluminum containing material. When the silicon or aluminum oxidizes as the oxidation potential indicates, silica or aluminum hydroxide would be produced. These connections however, melt at around 1,135 ° C or »2,010 ° C, depending on the temperature on their structure, and therefore it appears that no liquid form of silica or aluminum hydroxide is produced. However, a vitreous coating can be formed at the time of the oxidation reaction. Furthermore, a certain form of the Eutectic are formed. The exact nature of the coating is therefore not known, but it can be seen from the experimental results described below that by the addition Substantial improvements of the present additives in the specified amounts and that a coating of one Texture is created which is not subject to oxidation.

The invention is hereinafter described by the following examples.

EXAMPLE · I

If an attempt is made to obtain a melt that does not oxidize, ps is common, the free energy of oxide formation as a measure in which the elements are effective. These

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free energy of formation of oxides can be removed from the usual publications such as the Handbook of Chemistry and Physics, the WUR published by the Chemical Rubber Co. _T de. For example, free energies based on individual oxygen atoms are as follows:

Table I.

Element 25 ° C 1,350 ° Kelvin

Calcium - 144.4 - 101.6

Aluminum - 125.6 - 99.0

Copper. - 35.0 - 17.8

Silver - 4.8 +12.4

From these figures it can be seen that both calcium and aluminum in their oxide form are in a much lower energy state reside as copper in its oxide form, it can therefore be expected to oppose both calcium and aluminum Preferably oxidize copper and thus form good deoxidizing agents.

However, if a dental alloy containing 9 * 5 wt % copper as the sole hardening agent (the alloy contains 25 wt% Si silver and 3 wt% palladium in addition to the copper and gold), about 0.04 wt%. -? Calcium is added and poured into an investment mold which is burned out at 593 ° C, the resulting product will be gold in color but not have a metallic sheen,

On the other hand, if about 0.04 wt % aluminum is added in place of calcium to the same alloy containing 9.5 wt.% Copper and cast by the same method, the resulting alloy will have a gold color and be in the area in contact with the form shiny.

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EXAMPLE II

A dental alloy containing 9 wt -.% Copper, 12 wt -.% Silver and 4 wt -.% Palladium includes, after the addition of 0.02 wt -.% Of lithium to the melt cast by pouring into a Investmentgußform, in which the temperature is 593 ° C. The resulting casting has no black copper oxide on its surface but has no metallic luster.

EXAMPLE III

A dental alloy that is 9.5 wt. Copper (like the alloy of Example I) and 0.64 wt. Containing titanium is melted and poured as in Example II. The one during solidification and surface in contact with the air is blue-black, while that during solidification and cooling Cooling surface in contact with the investment form has a gold color, but has no metallic luster.

EXAMPLE IV

An alloy with the same composition as in Example III, with the exception that instead of titanium 0.16 wt Tantalum added is cast in the same manner as in Example III and the results are the same.

EXAMPLE V

Another alloy according to Example III, instead of Titanium 0.04 wt -.% Chromium are added, is poured. Of the surface of this alloy in contact with the air, only 75 % are gray and 25 % gold, but without a metallic sheen. The surface in contact with the investment form has a gold color, but no sheen.

EXAMPLE VI

Three casts of the alloy, the 9.5 wt. Contains copper,

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as in Example I, but with a content of 0.04, 0.08 and
0.228 wt. Barium, are poured. In all three cases the resulting alloy has a gold color in the area in contact with the investment form, but no luster,

EXAMPLE

VII

Numerous castings are made with the results given in the table below. The castings, which 9
Weight? and 9.5 wt. Containing copper are the same as
indicated above, with the exception of the aluminum or silicon content. The casting, which is 18 wt.? Contains copper
also 13 wt.? Silver and 5 wt. Palladium, while the rest
is made of gold.

TABLE II

Copper content

9 %

9 %

9 %

9 %

9 %

9 %

9 %

9 %

9 %

9.5 % 9.5 %

9.5 %
9.5 %

Added
element

Al
Al
Al
Al
Al
Si
Si
Si
Si

Al
Al

9.5 % Al

Al
Si

9.5 % Si

Si

Al Al

Weight?

0.01
0.02
0.04
0.08
0.16
0.08
0.16
0.40
0.84

0.04
0.08

Results

Casting

Gold-no shine

Shiny gold

Shiny gold

Shiny gold

Shiny gold

Shiny gold

Gold-no shine

Shiny gold

Shiny gold

Gold Shiny Gold Shiny

0.16 gold shiny

0.32 shiny gold 0.44 shiny gold, some black spots 0.48 shiny gold

0.56 shiny gold

0.06 gold shiny

50 % black

0.08 gold shiny

Part in contact with air

black

75? Black Gold-Shiny Gold-Shiny Gold-Shiny Gold + Black Gold-no shine gold-no shine gold-shiny

black
Shiny gold

+ 10? Black shiny gold

+ 10? Gray gold-shining gold-no shine,

50? Gray

Shiny gold,

20? black spots

Shiny gold, gray areas

black

Glossy + 10? black

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Trains
put it
element Weight? TABLE II Results Casting With the air in
Touch standing
part Al
Si
Si
Si
Si 0.16
0.16
0.32
0.80
0.90 (Continuation) Shiny gold
Gold-no shine
Shiny gold
+ Black
Shiny gold
+ no shine
Gold-no shine Shiny gold
black
80 % black
50 % black
black copper
salary 18 %
18 %
18 %
18 %
18 %

It can be seen from the examples that aluminum and silicon, when used separately, produce alloys which in cast Condition are shiny when very small amounts of each component are used. If further a more limited area is used by quantities, the casting has a shiny appearance not only in the area in contact with the mold Surface, but the casting also has a shiny surface in the area not in contact with the mold on. For example, when 0.04 to 0.15 wt. Si aluminum in a 9 wt. Gold alloy containing copper are used, is the resulting casting both in the area in contact with the mold and in the area in contact with the air standing area shiny. Furthermore, it appears that the castings according to the invention are not only shiny, but can also be more easily extracted from the investment form. That is, there does not appear to be any adhesion between the mold and the metal to pass so that the extraction is fairly easy. This is possible due to the lack of coverage of the investment form the molten alloy, although the reasons for this are currently unknown.

EXAMPLE VIII

A metal alloy containing 18% by weight copper as in Example VII, which has 5 different aluminum / silicon contents is cast. The contents of the five different attempts are

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given in Table III below.

attempt

TABLE III amounts Components 0.12 % Al 0.20 % Si 0.10 % Al 0.10 % Si 0.03 % Al 0.05 % Si 0.02 % Al 0.10 % Si ' 0.02 2 Al 0.05 % Si

B C

In all of the above cases, the casting has a metallic luster where it is in contact with the investment mold, as well as varying degrees of blackness, where it is cooled in contact with air. From the above experiments it can be seen that that if 0.08 wt .- ί aluminum are required to the to produce shiny casting, and a perfectly shiny casting is not produced while using silicon only 0.02 to 0.05 wt. 3 »silicon produce a perfectly shiny casting with the exception of the surface which is in contact frozen with the air. It appears, therefore, that aluminum and silicon are more than a mere additive in their effects.

EXAMPLE IX

In dental gold alloys, which, in addition to gold, are three percent by weight palladium and eight percent by weight platinum less as one percent by weight of indium and tin, as well as 0.25 wt, - * Containing iron as the hardening agent, a dark oxide coating is usually formed when the lost wax process is used for the Pouring is applied. In accordance with the invention, however, varying amounts of aluminum are added to the cast iron pins with different results added. When 0.01, 0.02 and 0.04 parts by weight of aluminum are three

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are added to various casting compositions, the resulting Product a bit shiny, but the investment form sticks to the surface of the poured product. But when 0.08, 0.16 and 0.32 wt .-> ί aluminum are added, that is Product glossy and can be easily removed from the investment form,

EXAMPLE X

If castings are made according to Example IX, but silicon is used instead of aluminum, 0.02 wt .- 5t silicon is required to obtain a casting with low gloss, but only 0.08% by weight of silicon are required to obtain the full metallic luster,

EXAMPLE XI

Other dental cast alloys are made according to Example IX using tin and / or indium as that Hardener, the casting composition is modified with aluminum in amounts of 0.04 to 0.32 wt. The resulting castings are shiny, but the form of investment seeks to stick.

EXAMPLE XII

Alloys with the same composition as in Example XI are made in the same manner, with the exception that in each of the alloys aluminum is replaced by silicon. A casting that contains 0.04 wt. -5 tons of silicon has a low gloss, but all other castings that contain up to 0.32 Contain 56 wt. Silicon, have a high gloss and can can easily be taken from the investment form.

EXAMPLE XIII

A 9.5 carat jewelry alloy (38.5% gold, 50% by weight copper and 11.5% by weight silver) is mixed with aluminum with the following formula:

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modified result:

Weight? aluminum

Casting results

0.02 black and dull 0.04 black and dull 0.06 shiny with black spots 0.08 glittering EXAMPLE XIV

Silicon is used to make the casting composition of the example XIII with the following results:

Weight? Silicon

Casting results

0.02 black and dull 0.04 black and dull 0.06 shiny with black spots 0.08 glittering EXAMPLE XV

From the photomicrographs of the scanning electron microscope it can be seen that the addition of silicon and aluminum to a melt gives a cast product that is one for oxygen impermeable coating or a layer on the surface of the casting. This layer is continuous, when there is enough additive, but discontinuously when the additive is insufficient (e.g. 0.06 wt% aluminum or silicon in Examples XIII and XIV). The requirements for the amount of additive in terms of surface area can be seen from the results according to which the above-mentioned dental alloy containing 18 wt.? Contains copper, with 0.04 wt. Aluminum, 0.06 wt. Silicon, 0.03 wt. Chromium and 0.01 wt. Yttrium is modified. With the alloy composition Two types of castings are made, one of which is a sphere and the other is a grid. the spherical structure obviously has a considerably small

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has a larger surface area per unit volume than the grid and is glossy. The grille, however, although it is quite shiny, shows small black spots that are visible when magnified. The appearance of the surface coating according to the invention is therefore shown and the requirements for sufficient amounts of aluminum and / or silicon to form this surface coating can be seen.

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Claims (1)

¹ J, A composition according to claim 6, characterized in that copper I3T present in an amount of at least 5 wt £. 8. A method for casting gold-containing alloys which contain a hardening element, characterized in that a material selected from the group consisting of aluminum, silicon, and mixtures thereof, the casting composition is added in an amount sufficient to provide a glossy surface on the resulting cast product obtain. 9. The method according to claim 8, characterized in that the hardening element is selected from the group consisting of copper, Contains iron, tin, indium, and mixtures of tin and indium. 10. The method according to claim 8, characterized in that the The hardening element is made of copper. 11. The method according to claim 8, characterized in that the Material is present in an amount from 0.01 to 2% by weight. 12. The method according to claim 11, characterized in that the material in an amount of 0.04 to 0.5 wt. is available. 13. The method according to claim 10, characterized in that copper in an amount up to 50 wt -% is present.. 14. The method of claim 13 'characterized in that copper in an amount of at least 5 wt - is present.%. 15. Shiny, cast, gold-containing alloy, which is a hardening element contains, characterized in that the hardness element is selected from the group consisting of copper, iron, tin, indium and mixtures of tin and indium, and that about 0.01 to 2% by weight of a material is added which consists of is selected from the group that contains aluminum, silicon and mixtures thereof » 309832/0907 Applicant: Williams Gold Refining Company Incorporated, Main Street, Buffalo, New York 14214, USA PATENT CLAIMS 1 »Casting composition for producing gold alloys, in which a hardening element is used, characterized in that sufficient quantities of a material are used for the casting composition selected from the group consisting of aluminum, silicon and mixtures thereof are added to to obtain a glossy surface coating on the product cast from the composition, 2. Composition according to claim 1, characterized in that the hardness element is selected from the group consisting of copper, iron, tin, indium and mixtures of tin and indium. 3 .. Composition according to claim 2, characterized in that the hardness element consists of copper. 4. Composition according to claim 1, characterized in that 0.01 to 2% by weight of the material are added, 5. Composition according to claim 4, characterized in that 0.04 to 0.5 wt-i of the material are added, 6. Composition according to claim 3, characterized in that Copper is present in an amount up to 50% by weight. 309832/0907 16. Alloy according to claim 15, characterized in that the hardening element consists of copper. 17. Alloy according to claim 16, characterized in that copper is present in an amount of up to 50 % by weight . 18. Alloy according to claim 17, characterized in that copper is present in an amount of at least 5% by weight of Si. 19. Alloy according to claim 15, characterized in that the material is present in an amount of 0.04 to 0.5 % by weight 309832/0907