RU2538065C1 - Tin alloy for art casting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: tin alloy containing tin, stibium and copper is added with indium. The alloy contains the following, wt %: tin 95-77; stibium 4-10; copper 0.5-4; indium 0.5-9.0.

EFFECT: increasing the strength, hardness, corrosive resistance and gloss value.

1 tbl, 1 ex

Description

The invention relates to metallurgy, and in particular to alloys for the production of art or decorative casting, and can be used in the manufacture of small plastic products in the form of body jewelry, all kinds of decor and cabinet art castings from tin alloys.

Tin alloys for art casting have not been specifically studied previously. Industrial antifriction tin alloys for the production of sliding bearings, as well as tin alloys, lead-free solders, are much more famous.

Known tin antifriction alloys containing indium:

- tin-based alloy containing copper, antimony, zinc, silicon, characterized in that it additionally contains gallium and indium in the following ratio of components, wt.%: copper 6.0-8.0; antimony 8.0-9.0; zinc 0.5-1.5; silicon 0.2-0.3; gallium 0.01-0.03; indium 0.03-0.05; tin - the rest [Pat. 2352661 Russian Federation, IPC C22C 13/02. Tin-based alloy / Yu.A. Shchepochkina; applicant and patent holder Yu.A. Shchepochkina; No. 2007143927/02; Declared 26.11.2007];

- tin-based alloy containing antimony, copper, characterized in that it additionally contains indium and germanium in the following ratio of components, wt.%: antimony 7.5-8.5; copper 7.5-8.5; indium 0.2-0.5; germanium 0.1-0.2, tin - the rest [Pat. 2389815 Russian Federation, IPC C22C 13/00. Tin-based alloy / Yu.A. Shchepochkina; applicant and patent holder Yu.A. Shchepochkina; No. 2009127416/0; declared 07/16/2009].

Known tin lead-free solders:

- for low-temperature brazing in microelectronics from 76-96 wt.% Sn, 0.2-0.5 wt.% Cu, 2.5-4.5 wt.% Ag,> 0-12 wt.% In, 0, 5-5.0 wt.% Bi and 0.01-2 wt.% Sb [US Pat. 2254971 Russian Federation, IPC B23K 35/24, C22C 13/02. Lead-Free Solder / MEDL Alan Lenard, UON Jenny S., Guo Shenfen; applicant and patent holder SINGAPORE ASAHI KEMIKAL AND SOULDER INDUSTRIES PTE. LTD .; No. 2003114304/02; declared 11.16.2000];

- solder containing 91.39% tin, 4.1% silver, 4.0% indium, 0.5% copper and 0.01% phosphorus [US Pat. 2268126 Russian Federation, IPC B23K 35/26, C22C 13/00. Solder, essentially free of lead, and method for its production / CHU Kai Hua, PAN Wei Chih; applicants and patent holders SINGAPORE ASAHI KEMIKAL AND SOLDER INDUSTRIES Pi-Ti LTD., KUONTUM CHEMICAL TECHNOLOGIES S 'POR Pi-Ti LTD .; No. 2004103629/02; declared 01/22/2002].

The disadvantage of these alloys is that they are not intended for the manufacture of thin artistic castings and do not have the necessary complex of casting properties. In addition, having high wear resistance or high physico-chemical properties, they do not have the necessary strength and hardness.

Closest to the offer is a white alloy called "British metal", which has come into general use since 1850 in England for the production of mainly dishes: spoons, teapots, sugar bowls, milk jugs, candlesticks, composition: 85-93% tin, up to 10% antimony, additionally containing small amounts of copper, zinc, and sometimes arsenic [Encyclopedic Dictionary / Ed. I.E. Andreyevsky, K.K. Arsenyev, F.F. Petrushevsky; Ed. F. Brockhaus [Leipzig], I.A. Efron [St. Petersburg]. - SPb .: Semenovskaya Tipo-Lithography I.A. Efron, 1890-1907]. Since this alloy was originally used for the manufacture of dishes, in Europe and Russia it became known as "utensil tin", in another way - "pewter". At present, tin alloys with other metals: copper, antimony, bismuth, or lead, are referred to as computers, for example:

- (1) an alloy consisting of 97-98% tin and 2-3% lead, and the lead content can vary from 2 to 50% [Pyuter, utensil tin, British metal [Electronic resource]. Access mode: http://drunemeton.itersuum.ru/pewter.htm, free. - Zagl. from the screen (Date of access: 08/12/2013)];

- (2) an alloy for the manufacture of art products containing 90-95% tin, 2-8% antimony and / or copper and sometimes 1-2% bismuth [Pyuter, utensil tin, British metal [Electronic resource]. Access mode: http://drunemeton.itersuum.ru/pewter.htm , free. - Zagl. from the screen (Date of access: 08/12/2013)].

Note: lead is sometimes introduced into tin alloys to increase the casting properties, lower the melting temperature and partially harden the solid solution, as well as reduce the cost of the solution. Lead significantly hardens the solid solution, but reduces gloss, promotes rapid tarnishing (oxidation) and is an environmentally harmful impurity in tin alloys used for art casting. Alloys containing lead cannot be used at all for the manufacture of art products directly in contact with the human body, since they can cause undesirable allergic reactions.

The main disadvantages of these computer alloys are low strength and hardness, as well as insufficient corrosion resistance. These shortcomings significantly reduce the operational (consumer) properties of the alloys: cast products from them quickly fade, easily bend, scratch and break. It is this circumstance that basically impedes the widespread development of the technology for the production of art products from tin alloys and their mass distribution. In addition, the known alloys do not possess the luster, desirable for jewelry and necessary, in particular, for the manufacture of decor for products from crystal, wood, fabrics, etc.

The aim of the invention is to increase the strength, hardness, corrosion resistance, as well as gloss.

To achieve this goal, the tin alloy additionally contains indium in the following ratio of components, wt.%:

Tin 95-77 Antimony 4-10 Copper 0.5-4 Indium 0.5-9.0

The addition of indium to tin bearing alloys increases their strength, hardness, and corrosion resistance [Element Properties: Ref. ed. / Ed. Dritsa M.E. - M.: Metallurgy, 1985. - 672 p.]. Indium enters the crystal lattice of the tin matrix as atoms of a substitution solution, helps to strengthen the solid solution and increase the ability to prevent fatigue fracture. It is known that indium additives linearly increase the strength of tin alloys up to concentrations of 8-12%. In this regard, the introduction of an indium additive of less than 0.5% does not give a significant effect, and an increase in the concentration of indium in the alloy of more than 9.0% is not economical and not advisable, since, on the one hand, the alloy is significantly more expensive, and on the other it does not contribute the desired increase in the strength of the solution and is spent on the formation of excess γ-phase.

Antimony and copper additives also lead to an increase in the strength of tin alloys. Copper and antimony form intermetallic compounds with tin. Copper forms Cu ₃ Sn, Cu ₆ Sn ₅ particles, and antimony forms SnSb particles. These intermetallic particles themselves are much stronger than the tin matrix and, in addition, effectively block the propagation of the fatigue crack. Moreover, the formation of multi-intermetallic particles contributes to finer grinding of the granular structure of the solid solution. Particles of solid intermetallic compounds in a tin plastic matrix extend the fatigue life of alloys. From experience in the production of tin bearing alloys, it is known that the optimum antimony content in tin (lead-free) alloys, providing the maximum value of the strength of alloys, is 6-8%. An analysis of a significant number of our own experimental data showed that antimony additives of less than 4% do not lead to significant hardening of tin alloys, and an increase in antimony concentration of more than 10% is not advisable, since they contribute to a significant increase in the melting temperature of alloys and complicate the technological process of casting production. Particles of intermetallic compounds Cu ₆ Sn ₅ not only contribute to additional hardening of tin alloys, they form a continuous skeleton - a grid in a hardened alloy, which prevents sedimentation of lighter SnSb particles and stratification of the alloy in the casting. SnSb crystals grow on the branches of the skeleton, as on the branches of a tree and do not float [Bochvar A.A. Metallurgy. Fifth revised and enlarged edition. - M .: State scientific and technical publishing house for ferrous and non-ferrous metallurgy, 1956. - 495 p.]. According to [Melting and casting of non-ferrous metals and alloys. / Ed. A.J. Murphy, trans. from English - M .: State scientific and technical publishing house for ferrous and non-ferrous metallurgy, 1959. - 646 p.] This is one of the main reasons for the introduction of copper in tin alloys. A copper additive of less than 0.5% is not able to significantly affect either the strength of tin alloys or the sedimentation stability of SnSb particles, and an increase in copper concentration of more than 4% is not advisable, since it does not contribute to an effective increase in the properties of alloys, and together with antimony leads to a significant increase in their melting points.

Example. The tin alloys for art casting, known by the proposed invention, were prepared in a resistance furnace of the SCHOL type in graphite crucibles according to the following technology: after melting and overheating of tin to a temperature of 500-550 ° C, alloying elements were sequentially introduced into it, with vigorous stirring: copper , antimony and indium. After that, the melts were overheated in an oven to temperatures of 700-720 ° C, held for 20-30 minutes for homogenization, and cooled to the pouring temperature. Pouring was carried out in cast iron forms (without heating, t _f = 18-20 ° C) at a temperature 70-100 ° C higher than the liquidus temperature of the alloy. Samples were cast in the form of rods with a diameter of 7 mm and a length of 100 mm for measuring the strength of alloys, as well as samples with a diameter of 18 mm and a length of 100 mm to determine the hardness and corrosion resistance of the alloys. Before testing, the last samples were cut in height into glazing beads with a height of 18–20 mm. Brinell hardness was measured using an HBRV-187.5 instrument with an indenter diameter of 5 mm.

Atmospheric corrosion research methods are long-term (10-15 years). To accelerate the tests, a standard method for studying corrosion processes in an electrolyte was used. Prepared glazing beads were suspended on a nylon string and placed in a container with electrolyte, which was used as a salt solution of the following composition: NaCl - 5%, water - the rest. The test duration is 15 days. An indicator of corrosion was the change in the mass of the sample, referred to a surface unit per unit time. To assess the corrosion rate, the samples were weighed on an Adventurer AR2140 electronic balance.

The gloss of alloy samples was determined in the cast state, without the use of special processing. At present, there is no test procedure that allows quantitatively evaluating the brilliance of metals and alloys. Therefore, the gloss of the samples was determined visually using a representative sample of a group of 20 people who evaluated the gloss of the collection of cast samples by their own sensations in points, on a ten-point scale. The readings taken were then averaged.

The results of comparative tests are presented in table 1.

Table 1

The results of comparative tests of samples of tin alloys.

No. Alloy Chemical composition, % Strength,
MPa Hardness,
HB Speed Corr.,
g / m ² per day Liquidus temperature, ° С Shine, points Sn Sb Cu In Proposed: one Lower level 95.0 4.0 0.5 0.5 41 124 0.0095 252 9.2 2 Average level 86.0 7.0 2.0 5,0 58 174 0.0068 264 9.7 3 Upper level 77.0 10.0 4.0 9.0 38 115 0.0060 317 9.9 Beyond the boundaries of the proposed alloy: four beyond the bottom line 96.6 3.0 0.2 0.2 37 112 0.0101 241 8.2 5 beyond the upper bound 73.5 11.5 5,0 10.0 34 104 0.0062 323 9.9 6 Famous (1) 97.0 Pb 3.0 - 22 68 0.0121 226 2,4 7 Famous (2) 88.0 6.0 6.0 - 38 116 0.0107 289 5.8

As follows from the presented data, the considered properties of the proposed tin alloy are higher in comparison with the known alloy compositions:

- strength and hardness 1.2-2.0 times;

- corrosion resistance 1.3-2.0 times;

- Gloss indicators 1.7-4.0 times.

In comparison with alloys whose chemical composition lies beyond the boundaries of the proposed composition:

- the alloy (4) does not have sufficient hardness and corrosion resistance while reducing the gloss value by 1.2 times;

- alloy (5), having sufficient corrosion resistance and a high gloss value, has a low hardness and a higher melting point. In addition, the cost of the alloy in comparison with the upper limit of the proposed alloy composition increases by 380 rubles / kg.

Claims (1)

Tin alloy for art casting containing tin, antimony and copper, characterized in that it additionally contains indium in the following ratio of components, wt.%:
Tin 95-77 Antimony 4-10 Copper 0.5-4 Indium 0.5-9.0