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INVENTION
Patent of the Russian Federation RU2207394
ALLOYS BASED ON SILVER
Applicant's name: Kaliningrad State Technical University
The name of the inventor: Savchenko AN; Tilipalov V.N.
The name of the patent holder: Kaliningrad State Technical University
Address for correspondence: 236000, Kaliningrad, Sovetskiy pr., 1, Technical University, Head of the Department. Patent Department, Pat. P. L.A. Odintsum, registration number 423
The effective date of the patent: 2001.11.06
The invention relates to the jewelry industry, in particular to silver based alloys, and can be used in artistic casting, as well as in electrical engineering and instrument engineering. The invention is aimed at enhancing the technological capabilities of the alloy and reducing rejection. A technology for the production of a silver-based alloy containing copper, nickel, and additionally tin, titanium and boron is developed with the following ratio of components, by weight: silver 92.5-93.0; Copper 5.8-6.8; Nickel 0,3-0,5; Tin 0.5-0.9; Titanium: 0.015-0.025; Boron 0,025-0,035.
DESCRIPTION OF THE INVENTION
The invention relates to silver based alloys and is intended for use in the jewelry industry, but can also be used in electrical engineering and instrument engineering, as well as for artistic casting.
A silver alloy of 925 ° is known containing copper at the following component ratio, %: Silver - 92.2-92.8; Copper - 7,2-7,8 (GOST 6836-80), the lack of which are relatively low strength and plastic characteristics, which adversely affects the quality of both cast and stamped products and parts and complicates the technology of their manufacture.
The most close to the proposed by the technical essence and achieved result is a silver-based alloy containing copper and nickel with the following ratio of the components of mass%: silver - 92.5-93.0; Copper - 5.3-6.2; Nickel - 1,3-1,7 (the patent of the Russian Federation 2049136, 27.11.95) .
An essential disadvantage of this alloy is its low foundry properties, in particular, fluidity, which limits its application to the production of mainly pressed and pressed products, as well as castings of a relatively simple shape, for example rings. Obtaining more complex castings, for example full-ring rings with castes, is not possible due to the poor fillability of the mold by the melt because of its low fluidity, as noted above. In addition, the production of castings from this alloy is accompanied by a high percentage of rejects: up to 12% for non-impurities and non-sandwiches, for gas-shrinkage defects - up to 15%.
The task, which is addressed by the proposed technical solution, is the expansion of the technological capabilities of the alloy, in particular, the achievement of the technical result, consisting in the possibility of obtaining from it complex products, for example cast-iron rings with nastes, and reducing casting defects.
The technical result is achieved by the fact that the proposed silver-based alloy containing copper and nickel further contains tin, titanium and boron at the following component ratio, by weight:
- Silver - 92,5-93,0
- Copper - 5,8-6,8
- Nickel - 0,3-0,5
- Tin - 0,5-0,9
- Titanium 0.015-0.025
- Boron - 0.025-0.035
Moreover, the addition of tin, titanium and boron to the alloy, and the upper and lower limits of the content of elements in the alloy are due to the following considerations.
1. When the content of nickel exceeds 0.5% in the alloy, the temperature of melting and pouring increases, and if the content exceeds 1%, nickel becomes a harmful impurity, since it does not dissolve in silver, impairs machinability by cutting (see E. Brepol, Theory And the practice of jewelry, 4th ed., Leningrad, 1982, p. 27).
2. Tin, even in small amounts, significantly reduces the melting temperature of the alloy, reduces its viscosity and increases fluidity. The content in a tin alloy of more than 1% makes the alloy dull, soft and plastic; The hardness and strength of products decreases (ibid., P. 26-28).
3. Titanium and boron are modifiers of the first and second kind, they refine the grain and increase the physical and mechanical characteristics of the alloy, in particular strength and plasticity, and boron is also an effective deoxidizer.
However, the introduction of titanium in an amount exceeding 0.025%, and boron - more than 0.035%, raises the melting temperature of the casting of the alloy, increases segregation, reduces the fluidity of the alloy, and increases the fragility of articles (see AV Kurdyumov et al., Foundry of Non-Ferrous and Rare Metals , Moscow, 1982, p. 78). The content in the alloy of the elements introduced below the lower limit reduces the effectiveness of their action.
The technology of preparation of the claimed alloy is developed taking into account the fact that nickel, titanium and boron in silver are insoluble, so first it is necessary to prepare a copper-tin-titanium-boron ligature and then, with the help of this ligation, to prepare the above silver-based alloy .
Ligature was prepared as follows. The crucible of the induction vacuum melting furnace was heated to a temperature of 1090-1100 ° C and the calculated amount of copper was loaded therein. After melting the copper in the crucible, the required amount of tin was charged and allowed to stand for 2 minutes. Then the melt was thoroughly mixed and consistently introduced into it the refractory components of the charge - nickel, titanium and boron. After 2 minutes, the melt was thoroughly mixed and its temperature was adjusted to 1030-1050 ° C. After 3 minutes, the melt was mixed and poured into molds, in which ingots (pigs) of ligature were obtained.
Example
The claimed silver-based alloy was prepared as follows. In the crucible of the induction vacuum furnace, the calculated amount (92.7% of the total mass of the charge) of the silver was melted. After melting of silver, crucible "copper-nickel-tin-titanium-boron" was loaded into the crucible by 7.3% of the total mass of the charge.
After melting of the master alloy, the melt was thoroughly mixed and poured into ceramic molds made from fusible models in which cast-iron castings were obtained.
Previously, these products were received in two stages: first cast the ring preform, then the casting blank, after which they were joined together by soldering or welding.
Such a technology, as noted above, was due to the low fluidity of the alloy taken for the prototype, and the high percentage of rejects of the castings.
The carried out experimental work showed that from the claimed alloy it is easy to produce cast products, including cast-iron "ring with caste" products, which were previously obtained from the standard 925 o alloy, and it was almost impossible to obtain from the alloy taken as a prototype for these Above reasons.
The use of the proposed alloy, along with the principal possibility of obtaining solid cast complex moldings, has made it possible to sharply reduce the percentage of reject castings: from gas-shrinkage defects from 15 to 2-3%, and for defects "impenetrable" and "non-plots" - from 12 to 1-2% .
This was made possible by the fact that the presence of tin in the alloy, as noted above, significantly improved the fillability of the molds by the melt due to the increase in its fluidity, and the use of the "copper-nickel-tin-titanium-boron" alloy to make the alloy allowed to lower the casting Forms from 1030 to 1000-1005 o C, the temperature of the flask - from 680 to 630-620 o C, which significantly reduced the volumetric shrinkage of the alloy, reduced the time of casting the molds with metal and created the conditions for directional crystallization of the alloy, which in turn allowed a sharp Reduce the number of defects in castings by the gas-shrinkage porosity.
It should be noted that the positive features of the alloy are achieved without compromising its strength and plastic characteristics, which is explained by the modifying action of nickel, titanium and boron.
From the above example of the specific embodiment, it can be seen that the process for obtaining the alloy does not require a fundamentally new equipment or beyond the capabilities of the conventional technology of casting silver alloys.
The process can easily be reproduced many times in production conditions.
CLAIM
A silver based alloy containing copper and nickel, characterized in that it additionally contains tin, titanium and boron at the following component ratio, by weight:
- Silver - 92,5-93,0
- Copper - 5,8-6,8
- Nickel - 0,3-0,5
- Tin - 0,5-0,9
- Titanium 0.015-0.025
- Boron - 0.025-0.035o
print version
Date of publication 02.01.2007гг
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