An alloy of tin and lead is called. Tin and lead alloys. Group of special alloys

Tin and lead are ductile, low-melting metals, with increased resistance to corrosion in atmospheric and some acidic conditions.

Lead is a metal with a face-centered cubic lattice; it does not experience allotropic transformations in the solid state. The melting point of lead is 327 ºС.

Tin can be in two crystalline modifications: a-Sn (grey tin) with a diamond lattice - below +13 ºС and b-Sn (white tin) with a body-centered tetragonal lattice. In frost, plastic b-tin crumbles into a gray a-Sn powder. This phenomenon is called tin plague . The melting point of tin is 232 ºС.

Calculation of the temperature threshold of recrystallization in accordance with the rule of A.A. Bochvara (T p = 0.4 T pl) gives the figures -123 and -147 ºС, i.e. the temperature threshold of recrystallization lies well below 0 ºС. Thus, the plastic deformation of lead and tin at room temperature is a hot deformation. Hardening with such deformation is not observed in these metals.

The main area of ​​application of pure tin is tin tinning. Pure lead is used for the lining of sulfuric acid plants and hydrochloric acid containers. Lead is also used for cable sheaths to protect them from soil corrosion.

An important area of ​​application for lead and tin are solders, as well as alloys for typographic fonts, anatomical casts, and fuses. These alloys contain, in addition to lead and tin, bismuth and cadmium. In pairs, all these elements form systems with low-melting eutectics without intermediate phases and chemical compounds, i.e. form simple eutectic systems (Figure 8.8). In ternary systems, ternary eutectics are formed between these elements, which are even more fusible than binary ones. The melting temperature of these eutectics is 90-100 ºС. In the quaternary system of these components, a quaternary eutectic is formed with a melting point of 70 ºС. Practically used Wood's alloy is close to eutectic in its composition (50% Bi, 25% Pb, 12.5% ​​Sn and 12.5% ​​Cd).

To obtain even more low-melting alloys, mercury is introduced into them, for example, an alloy with a content of Bi-36%; Pb-28%; Cd-6% and Hg - 30% has a melting point of 48 ºС.

As solders for soldering copper, steel and many other products, both pure tin and lead-tin alloys containing tin from 3 to 90% and a small amount of antimony (up to 2% Sb) are used.

The melting point of solders depends on the tin content and can be roughly determined from the Pb-Sn double diagram. The most fusible solder is an alloy with 61% Sn, marked POS 61. There are alloys POS 18, POS-40, POS-61, POS 90, etc. Lead alloys with antimony and arsenic (10-16% Sb and 1-4% As) are used for typographic fonts.

The invention relates to non-ferrous metallurgy and can be used in the refining of lead-tin alloys. Lead-tin alloys are treated with zinc. After the introduction of zinc, the alloys are treated with elemental sulfur in an amount of 1–5% by weight of the alloy, which ensures the formation of sulfide zinc-silver removal. The method makes it possible to ensure the extraction of silver from lead-tin alloys up to 99% and, without involving an additional amount of precious metals, to organize the production of silver solders. 3 tab.

The invention relates to non-ferrous metallurgy, in particular to the production technology of lead-tin solders, and can be used in the refining of lead-tin alloys. Known methods of extracting silver from black lead by extraction at temperatures of 330-350 o C metallic zinc. The use of these methods for the extraction of silver from lead-tin alloys does not give positive results, because. in the presence of tin, the lead-tin-zinc system has no areas of delamination. With regard to lead-based tin-containing alloys, methods have been proposed that involve treatment at temperatures of 750-950 o C with melts of chlorides and sulfates of alkali, alkaline earth metals. The disadvantages of these methods are the low extraction of silver (30-40%), the impossibility of carrying out the process in known refining apparatuses and the need to organize hydrochemical processing of silver-containing slags. As a prototype, a method for processing zinc alloys, known as the Parkess process, was adopted. Zinc metal or lead-zinc ligature is mixed into the lead-containing melt at a temperature of 330-350 o C. In this case, zinc-silver intermetallic compounds are formed, which, due to delamination of the lead-zinc-silver system, pass into the surface layer of lead in the form of the so-called silvery foam. The foam is removed from the surface and sent for recycling. However, the prototype method does not provide the extraction of significant amounts of silver from lead-tin alloys. This is due to the fact that in the presence of 5% or more tin in lead, the lead-tin-zinc-silver system does not delaminate. The problem is aggravated by the fact that in real lead-tin alloys (solders) produced, for example, at the Ryaztsvetmet plant, the silver content does not exceed 400 g/t, i.e. an order of magnitude less than in black lead. Thus, the prototype method cannot be used to extract silver from lead-tin alloys (solders). The objective of the present invention is to convert silver into refining stocks during the treatment of lead-tin alloys with zinc. This task is achieved by the fact that in the known method of extracting silver from lead-tin alloys, including their treatment with zinc, according to the invention, after the introduction of zinc, the alloys are treated with elemental sulfur in an amount of 1-5% by weight of the alloy. The method is carried out as follows. In the lead-tin alloy, which is at a temperature of 330-600 o C in the refining boiler, interfere with metallic zinc or lead-zinc ligature. The amount of zinc introduced is 1-5% by weight of the alloy. During this operation, the melt acquires microheterogeneity caused by the formation of zinc-silver microgroups. However, the presence of tin in the alloy does not allow the silver-containing zinc phase to separate as an independent product. After the dissolution of zinc, the alloy is treated with elemental sulfur in an amount of 1-5%, i.e. sufficient to bind zinc to zinc sulfide. At this stage, not only the sulfiding of the zinc introduced into the lead-tin alloy and the silver associated with it occurs, but also the separation into an independent phase immiscible with the alloy - crystalline sulfide zinc-silver removal. Silver removal is removed from the surface of the lead-tin alloy mechanically or by centrifugation. In the latter case, the alloy, after the introduction of sulfur, is passed through a centrifuge, in which the crystalline material is separated from the liquid lead-tin alloy. A certain amount of lead and tin passes into sulfide zinc-silver removal. The content of silver in zinc-silver removal is 20-30 times higher than in the original alloy. Silver from scraps can be extracted by one of the known methods, for example, redox melting on silver solder. In the process of redox smelting, sulfur is removed in the form of sulfur dioxide, zinc, and partially lead and tin. Due to this, the solder formed during melting is enriched with silver. New in the proposed technical solution is the subsequent treatment of the alloy with elemental sulfur after the introduction of zinc, which ensures the formation of sulfide zinc-silver removal. A distinctive feature of the proposed solution is the sequential treatment of the lead-tin alloy with zinc and elemental sulfur and the separation of silver-containing zinc-sulfide removal. Techniques for the sequential treatment of alloys with zinc and sulfur and the removal of zinc-sulfide removals were not found by us in the patent and scientific and technical literature. The proposed method has been tested and verified in laboratory conditions. Example 1. In 500 g of a draft lead-tin alloy containing 25.0% tin, 0.5% copper, 3% antimony, 0.1% nickel, 0.6% iron, 320 g / t silver, the rest is lead , by stirring and at a temperature of 350-400 o C introduced from 5 to 20 g (ie from 1 to 4 wt.%) metallic zinc. The duration of zinc dissolution is 35-65 minutes. After the dissolution of zinc, there was no delamination and the formation of silver-containing removal - silvery foam. Then, at the same temperature, the resulting zinc-containing alloy was treated with 15-25 g (3-5% of the weight of the alloy) of elemental sulfur, which was mixed into the melt for 20-40 minutes. After treatment of the alloy with sulfur, a dry zinc-silver sulfide removal was formed on the surface of the alloy. The output of the removal was from 2 to 6% by weight of the original crude lead-tin alloy. The silver content in the removals is 0.32-0.60%. The recovery of silver for removal depended on the consumption of zinc and sulfur (Table 1) and at the indicated costs amounted to 53-70%. Example 2. In a lead-tin alloy (500 g) (20-25% tin, 310-340 g / t silver), previously refined from copper, iron and other impurities, 1-4% by weight of the zinc alloy is introduced in the form of lead- zinc alloy. The introduction is carried out at a temperature of 500 o C and continuous stirring of the melt for 24-40 minutes. As in example 1, the introduction of zinc did not provide the formation of silver-containing removal. After the introduction of the lead-zinc ligature, the temperature of the melt was lowered to 350 o C and treated with elemental sulfur by mixing it into a silver-containing lead-tin melt for 45-60 minutes. The consumption of elemental sulfur for processing the alloy is 3-5% by weight of the original alloy. As a result of this treatment, dry removal was formed on the surface of the melt, which contained from 0.38 to 0.7% of silver. The yield of removals was 2.6-5.0% by weight of the original alloy. The extraction of silver depended on the amount of zinc introduced and sulfur supplied for processing, and when indicated in table. 2 expenses amounted to 57-63%. The removals obtained in experiments 1-12 (table. 2) were subjected to oxidative firing at a temperature of 750-950 o C in air. The resulting calcine was mixed with silica (20%), calcium oxide (10%), iron oxide (7%), coke (5% by weight of the removals) and melted at a temperature of 1250 o C for 30 minutes. As a result of this treatment, a lead-tin alloy was obtained, which contained 1.25% silver, 35% tin, and the rest lead. According to the content of silver and other metals, the alloy met GOST 19738-74 for silver solder grade PSR-1.0. Example 3. A lead-tin alloy refined from impurities containing 315 g/t of silver is alloyed with metallic zinc, the consumption of which is 1-4% by weight of the alloy. Fusion temperature 600 o C. Then the melt was treated with 3-5 wt.% elemental sulfur. The treatment was carried out by bubbling with a mixture of powdered sulfur and argon. Sulfur consumption was 1-5% of the weight of the removals. As a result of such operations, we received (Tab. 3) silver-containing removal, in which the concentration of silver was from 0.4 to 0.8%. Extraction of silver in eat - 53-62%. The removals were directly redox melted onto silver solder. To do this, the removals (100 g) were mixed with sodium sulfate (15%), pyrolusite (10%), quartz (15% by weight of the removals) and heated to a temperature of 1150 o C. The resulting melt was loaded with a reducing agent - coke in an amount of 10% of mass removals and melting continued for 60 minutes. As a result of melting, solder grade PSR-1.5 and slag were obtained, in which the silver content was less than 5 g/t. Thus, the recovery from silver removals into PSR-1.5 solder was at least 99%. The results given in examples 1-3 testify to the high efficiency of the extraction of silver from lead-tin alloys and the possibility of implementing the method on well-known and mastered in the industry equipment. The implementation of the proposed method will ensure the extraction of silver from lead-tin alloys and will allow, without involving an additional amount of precious metals, to organize, for example, at the Ryaztsvetmet plant, the production of silver solders of grades PSR-1.0-1.5. Sources of information 1. Loskutov F.M. Metallurgy of lead. - M.: Metallurgy, 1965. 2. Copyright certificate 431249. "Method of lead refining, authors A.M.Ustimov and N.N. Kubyshev, BI N 21 dated 05.06.74. 3. Abdeev M.A. , Geukin L.S. and others. Modern ways processing of lead-zinc ores and concentrates. - M.: Metallurgy, 1964, p. 218-220.

Claim

A method for extracting silver from lead-tin alloys, including treating them with zinc, characterized in that after the introduction of zinc, lead-tin alloys are treated with elemental sulfur in an amount of 1-5% by weight of the alloy.

Tin is a soft and ductile shiny metal of a silvery-white color. It is characterized by good corrosion resistance in atmospheric conditions, soluble in dilute strong acids and concentrated alkalis. Tin is used for coating (tinning), obtaining alloys and solders for soldering, as well as alloying additives.

Tin alloys are tin-antimony-copper and tin-antimony-lead systems, which contain from 3 to 90% tin. They are used as antifriction alloys - babbits for pouring bearings and as solders. The use of lead reduces the cost of solder, and the introduction of antimony increases the strength of the weld.

Lead

Lead is a soft malleable ductile metal of light gray color with a bluish tinge. Much softer than tin, cut with a knife and scratched with a fingernail, easily rolled into thin sheets. Lead is resistant to corrosion and a number of chemicals, especially sulfuric acid. Lead smelting was one of the first metallurgical processes. It is widely used in the chemical industry to protect equipment from corrosion. Sheaths are made from lead to protect electrical cables, shot, paint and lead batteries.

lead alloys

Lead alloys have high density and low mechanical strength. They are fusible and resistant to corrosion. Lead-dominated alloys are much cheaper than those based on tin. They are used as anti-friction alloys - babbits, as printing alloys and solders. Lead with additions of tin and antimony becomes much harder.

pewter

rocky shoal

Small rocky island devoid of vegetation

water stone

Long rocky shoal

G. shiny pillowcase, thin layer on what, sheath, half-day, watering, enamel; dullness on the eye, whitish darkening of the transparent shell of the eye. Star. headband, probably light, shiny. Star. outerwear, cloak, mantle. Luda is worn with gold. Perm. silty, cold, gray soil, blue clay; hard soil. Vologda. perm. oatmeal with milk, esp. used during field work. Ryaz. zavara, salamata. Keremet, the goddess of Votyatsk. Lud m. old. crazy, stupid, crazy. Lud, lud. arch. dazzling brilliance, whiteness. Luda Sev. mara or trouble, averting the eyes. Ludu let, fool, let the fog. Luda arch. flagstone river bottom, natural flooring; arch. underwater or surface flat stones, shallows; granite patches. Herring and roots are caught on the ludah. Psk. * unrequited, annoying person. Ludoga petersburg whitefish, from Ptina Nose, on Lake Ladoga. Ludik m. ludyak vyat. perm. gray, silty soil, hardening in the sun, luda. Ludik eats the ground. Ludan m. star. damask fabric, or damask genus. Psk. silk thing, like a scarf, apron. Ludan, ludan penz. silk. Ludushka or ludka, ludushka. arch. olon. luda, in the meaning shallow, stone, and old. floodplain, often diarrheic islet. Tin something, cover it with half-milk, molten tin; tin copper dishes, iron sheets, turning them into tin or white iron. To deceive, to cheat. - Xia, be crazy. Hatch the pot, tin them all, again. Puddle Wed ludka about. action by value vb. To tinker, to tinker with someone, jokingly. beat, beat, set a brawl. Ludilny, related to tin. Tinkering master. Tinning workshop, where they tinker. Tinker m. who tins dishes. Ludila, fighter, bully. -shchikov, belonging to him.; - shchichiy, referring to him in general. Lude, blind with brilliance, whiteness, shine, mirror. Snow puffs up in the sun. Silver ludeet in the forge

Stoneman. island

Stoneman. shallow

rocky island

stone from water

Stone protruding from the water; coastal shoals

Small rocky and bare island

Small rocky island

Alloy for the tinker

tinning alloy

rocky shoal

Rosin

Long rocky shoal

Coastal rocky shoal

And alloys of this material have certain properties that are due to their initial state.

General description of tin

It is important to note here that two types of this raw material are distinguished. The first type is called white tin, and it is the β-modification of this substance. The second type is the α modification, which is better known as tin gray. When moving from one modification to another, namely from white to gray, there is a strong change in the volume of the substance, since a process such as the scattering of metal into powder occurs. This property is usually called. Here it is also important to note that one of the most negative properties of tin is its tendency to frost. In other words, at temperatures from -20 to +30 degrees Celsius, a spontaneous transition from one state to another can begin. In addition, the transition will continue even if the temperature is increased, but after the process has begun. Because of this, raw materials have to be stored in places with a rather high temperature.

Properties of tin and lead

It is worth saying that tin, lead and alloys of these materials have quite a few common properties. For example, the purer the tin, the higher the chance that it will be affected by the plague. Lead, in turn, does not experience allotropic transformations at all.

However, it should also be noted that additional substances are used to slow down this kind of transformation in tin. Best of all, materials such as bismuth and antimony showed themselves. The addition of these substances in a volume of 0.5% will reduce the rate of allotropic transformation to almost 0, which means that white tin can be considered completely stable. It can also be noted here that to a lesser extent, but still, an alloy of tin and lead is used for the same purpose.

If we talk about the properties of lead, then it has a higher melting point - 327 degrees Celsius than tin - 232 degrees. The density of lead at room temperature is 11.34 g/cm 3 .

Characteristics of tin and lead

It is worth starting with the fact that the recrystallization of work-hardened tin, lead and alloys occurs at a temperature that is considered to be below room temperature. For this reason, the process of their processing is of the hot type.

The general indicator was the resistance to corrosion under atmospheric conditions. However, a slight difference lies in the resistance to corrosion under the influence of minor substances. For example, lead manifests itself best when interacting with concentrated compositions of certain acids - sulfuric, phosphoric, etc. Tin, in turn, is best resistant to solutions from food acids. The scope of these substances separately is also different. Tin is widely used for tinning tin, while lead has found its application for lining equipment for sulfuric acid production.

Alloy systems

It is important to start here with the fact that an alloy of tin and lead is an even more fusible material than separately. Such mixtures are most widely used as solders, for the manufacture of typographic fonts, for casting fuses, etc. Such a system as "tin - lead" belongs to the group of the eutectic type. An important property of all materials belonging to this category is that their melting temperature is in the region of 120 to 190 degrees Celsius. In addition, there are groups of ternary eutectics. An example is the tin-lead-zinc alloy system. The melting temperature of such materials drops even lower, and its limit is 92-96 degrees Celsius. If you add a fourth component to the alloy, then the melting temperature will drop to 70 degrees. If we talk about the use of an alloy of tin with lead as a solder, then most often up to 2% of a substance such as antimony is introduced into their composition. This is done in order to improve the flow of the solder. It is worth noting here that the melting temperature can be controlled by the "tin/lead" ratio. The most fusible raw materials melt at a rate of 190 degrees.

babbits

We have already figured out the name of the alloy of tin and lead - this is a eutectic. This group of substances with such a composition is most widely used in the production of bearing alloys, which are called "babbits". This material is used as a fill for bearing shells. The most important thing here is to choose the right material so that it can easily run in to the shaft. At first glance, it seems that the mass of tin and lead alloys with various solders is an excellent way out. However, in reality this is not entirely true. Such materials turned out to be too soft, and the coefficient of friction between the shaft and such an insert was high. In other words, during operation, they heated up too much, because of this, low-melting metals began to "stick" to the shaft. To avoid this shortcoming, a small amount of more solids began to be added. In this way, a material was obtained that is both soft and hard at the same time.

The composition of the substance

In order to achieve such a substance, which has directly opposite characteristics, the following substances were used. The most important thing is that they lie immediately in the two-phase region α + β. Crystals of the β-phase are enriched with solder such as antimony. They act as solid brittle substances. The α-phase crystals, in turn, are a soft and plastic base. In order to avoid such shortcomings as the melting of solid crystals and their ascent, another component is added to the mixture - copper. Thus, from a piece of an alloy of lead and tin with the addition of some other substances, it is possible to create a babbit bearing material that combines two opposite qualities - hardness and softness. Babbit B83 became the classic and most common product of this brand. The composition of this alloy is as follows: 83% Sn; 11% Sb; 6% Cu.

Alternative

It is worth mentioning that, from the point of view of economy, tin-based babbits are very disadvantageous, since this material costs quite a lot. In addition, tin itself is considered a scarce substance. For these two reasons, alternative bearings have been developed based on lead, antimony and copper. In this composition, antimony crystals act as a solid base. The soft base is a direct alloy of lead and antimony. Copper is used here in the same way as lead in the previous composition, that is, to prevent solid base crystals from floating up.

However, here it is worth mentioning the shortcomings. The lead/antimony eutectic is not as ductile as the tin phase. Therefore, parts made in this way suffer from rapid wear. To level this shortcoming, you still have to add some tin. The use of ternary eutectics is not very common.